Regolith Particle Size Controls Deep Nitrate Accumulation in a Typical Arid Region
Source-Route-Receptor-Based Spatial Zoning Study on Soil Heavy Metals Pollution Risk
Effects of Long-term Straw Burying and Nitrogen Fertilizer Application on Soil Bacterial Community Characteristics
Isolation and Application of Rhizosphere Core Strains to Improve Salt Tolerance of Rice
Dry-wet Alternation Regulate Soil Active Bacterial Communities and Potential Functions in Paddy Fields
- Regolith Particle Size Controls Deep Nitrate Accumulation in a Typical Arid Region
- Source-Route-Receptor-Based Spatial Zoning Study on Soil Heavy Metals Pollution Risk
- Effects of Long-term Straw Burying and Nitrogen Fertilizer Application on Soil Bacterial Community Characteristics
- Isolation and Application of Rhizosphere Core Strains to Improve Salt Tolerance of Rice
- Dry-wet Alternation Regulate Soil Active Bacterial Communities and Potential Functions in Paddy Fields
- Current Discuss
- First Published
- Album Paper
- Browser
-
Pollution Risk and Regulation of Organochlorine in Soil: From the Perspective of Multi-process Coupling
HE Yan, SU Xin, LI Shuyao, CHENG Jie, YANG Xueling, DOU Jibo, XU Jianming
2024,61(5):1179-1187, DOI: 10.11766/trxb202312010504
Abstract:
Traditional and emerging organochlorine pollutants (OCPs) are prone to form persistent sources of pollution, which adversely affect human health and the ecological environment. Although the usage of OCPs has been banned for many years, these pollutants could still be detected in soils, sediments and other environments where they have never been applied. Numerous studies have confirmed that anaerobic reduction dechlorination, the most efficient pathway for the complete removal of OCPs from soil, is essentially a process mediated by the metabolic activity of dechlorination bacteria. Under anaerobic conditions, the environmental fate of OCPs in the soil is abiotically and biotically attributed to biogeochemical redox processes, which are significantly influenced by the cycling of biogenic elements mediated by microbial-extracellular-respiration-initiated electron transfer. A better understanding of the microbial and geochemical interactions that occur during the environmental transformation of OCPs in anaerobic soils is required for improving soil pollution control and remediation. Owing to the global demand for “One Health”, it is quite necessary to illuminate the potential soil health risks of residual OCPs from the perspective of multi-process coupling. As such, this paper aims to briefly comb the research progress and current status of residual OCPs in soil in the past 42 years, and clarify the state-of-the-art research findings and academic frontiers. On this basis, the potential relationship between the reduction and dechlorination of OCPs and the biochemical cycle process of key elements like C, N, Fe and S in the soil is sorted out, to provide a new understanding of the ecological and health risks of underground environment polluted by residual OCPs. Finally, this paper puts forward suggestions and prospects for the future research direction of soil health risk in China, providing research ideas for facilitating pollution reduction of soil polluted by OCPs, thereby supporting the improvement of soil health theory.
-
Research Progress and Prospects of Human Health Risk Assessment of Heavy Metal Pollution in Farmland Soils of China
LONG Xinxian, LIU Wenjing, QIU Rongliang
2024,61(5):1188-1200, DOI: 10.11766/trxb202306130229
Abstract:
Heavy metal contamination of agricultural soils poses a great threat to food safety and human health. Heavy metals enter the human body mainly through exposure pathways such as direct ingestion of soil, inhalation of soil particles, dermal exposure and food chain ingestion, with direct ingestion of heavy metal-contaminated soil and eating agricultural products being the main exposure route. Human health risk assessment plays an important role in the classification of agricultural soil quality categories and environmental risk management. Therefore, this paper reviews the development of human health risk assessment of heavy metal contamination in agricultural soils in China, introduces the basic process and assessment techniques of human health risk assessment, and discusses the main factors affecting the accuracy of human health risk assessment and the optimization measures. The research indicates that in the health risk assessment of heavy metals in farmland soil, the coupled pollution source identification technology should be strengthened while the exposure route of food consumption needs more attention. Also, the exposure parameters of different sensitive receptors should be accurately identified, and the exposure parameters of localized sensitive receptors, and the bioavailability of heavy metals should be included to improve the accuracy of health risk assessment of heavy metals in farmland soil. In the future, the health risk assessment of heavy metals in farmland soil can be deepened from many aspects, such as strengthening technical methods to deal with the uncertainty of the health risk assessment process and considering the exposure pathways of various diets. This will help with establishing localized heavy metal toxicity standard data to promote the development of the theory and technology of human health risk assessment of heavy metals in agricultural soils of China.
-
Research Advances on Mechanisms and Preventions of Soil-borne Diseases Exacerbated by Root Exudates in Continuous Cropping Systems
YOU Chuan, YANG Tianjie, ZHOU Xingang, WANG Xiaofang, XU Yangchun, SHEN Qirong, WEI Zhong
2024,61(5):1201-1211, DOI: 10.11766/trxb202307180281
Abstract:
The rhizosphere microbial communities play a crucial role in assisting plants in dealing with soil-borne pathogens. When plants encounter specific soil pathogen invasions, they adapt the composition and quantity of root exudates to recruit beneficial microorganisms that can utilize these substances to resist soil pathogen infections. However, recent studies have revealed that certain root exudates can promote the occurrence of soil-borne diseases. This paper aims to provide a comprehensive review and summary of existing evidence regarding the role of root exudates in continuous cropping systems, which contribute to the occurrence and outbreaks of soil-borne diseases. The paper begins by presenting observations of soil-borne diseases exacerbated by continuous cropping and the accumulation of key root exudates. Subsequently, it summarizes the potential mechanisms through which some root exudates in continuous cropping promote the invasion of soil-borne pathogens. Considering the process of soil-borne pathogens causing plant diseases in continuous cropping involves introduction (soil to the rhizosphere), colonization (rhizosphere to root surface), and infection(root surface to root interior), the substances exacerbating soil-borne pathogen invasion in each stage are categorized into the following three groups based on their functions: 1)substances that facilitate the migration, proliferation, and pathogenicity of soil-borne pathogens from soil to the rhizosphere (“enriching pathogens”); 2)substances that disrupt the defense line of beneficial microbial communities in the rhizosphere (“suppressing beneficial microbes”); and 3) substances that hinder the root immune system (“self-toxic”). Subsequently, the paper explores the mechanisms of diversified cropping systems such as rotation, grafting, row intercropping, relay intercropping, and companion planting in alleviating soil-borne diseases from the perspective of root exudates. These mechanisms include: 1) enhancing the diversity of root exudates; 2) reducing the secretion of self-toxic substances by main crops; 3) secreting root exudates that suppress pathogens; 4) promoting the formation of a protective rhizosphere microbial community to enhance plant disease resistance and 5) regulating the synthesis pathways of metabolites to reduce the production of self-toxic substances. Finally, the paper outlines several green, efficient, safe, and comprehensive control strategies for soil-borne diseases. These strategies include: 1) identification of “enriching pathogens”, “suppressing beneficial microbes” and “self-toxic” root exudates; 2) application of diversified planting, rootstock grafting, biochar, and organic fertilizer to regulate root exudates, improve soil microbial community structure, enhance plant growth, and reduce diseases; and 3) establishment of biodegradation technologies for identifying, isolating, and culturing bacterial and fungal strains capable of decomposing the “enriching pathogens”, “suppressing beneficial microbes” and “self-toxic” plant root exudates.
-
The Multifractal and Relative Entropy Characteristics of Pore Structure of CT Images in Biochar-amended Saline Soils
2024,61(5):1212-1223, DOI: 10.11766/trxb202304070130
Abstract:
【Objective】Soil structure is the key to understanding physical, chemical, and biological processes that play a vital role in biodiversity and agricultural productivity. However, due to the mutual influence and simultaneous progress of these process, soil structure evolution has become irregular, unstable, and highly complex. With the development of computer technology on CT scanning images, different scaling and descriptive statistical analysis allow for a better study of soil pore structure or architecture. 【Method】Inthis study, the saline/sodic soil in the coastal reclamation area of JiangsuProvince was taken as the object of investigation. Based on multifractal and relative entropy theory, combined with Micro-CT technology, the scaling features of the pore structure of biochar-amended saline soil were revealed. 【Result】In this study, the surface soils (0-20 cm) were amended by thoroughly mixing with biochar atthree application rates (0%, 2% and 5% by mass of soil) in a completely randomized design. This experiment lasted for four years from 2017 to 2020. To reveal the scaling characteristics of CT pores, two methods were applied: multifractal analysis (MFA) and relative entropy (E). The results showed that different theoretical methods should be used to analyze the complex scaling behavior of soil pores. The multifractal method was suitable for grey images, while the relative entropy method was suitable for binary images. The pore complexity of all treatments increased from one year to the next. Also, the addition of biochar accelerated the developments of soil pore structure and induced a faster rate of increase in pore complexity. Among different biochar treatments, the pore complexity of 2% biochar treatment was the highest (Δα=0.061, RangeΔE=0.436)and the improvement effect was the best. The addition of high biochar(5% biochar treatment)reduced the pore complexity(Δα=0.045, RangeΔE=0.531), reducing the improvement effect of biochar. 【Conclusion】This study can provide a theoretical basis for the use of biochar to improve pore structure from a microscopic point of view.
-
Simulation of Lucerne and Vetiver Hydroponic Root Exudates to Alleviate Clayey Red Soil Penetration Resistance
HE Yangbo, DONG Junqi, ZENG Hui, LIU Siyu, WANG Faming, YANG Mingxuan, GUO Zaihua
2024,61(5):1224-1235, DOI: 10.11766/trxb202304190155
Abstract:
【Objective】The objective of this study was to investigate the influence of fibrous and taproot plant root exudates, in terms of their relative composition and application rate, on soil penetration resistance (SPR) under specific compaction conditions (compaction, and compaction followed by wetting/drying), in order to evaluate the adverse effects of SPR on crop growth in clayey red soil.【Method】Fibrous root vetiver and taproot lucerne were selected to collect hydroponic secretions. These secretions were then analyzed to determine the root exudate composition, which was subsequently freeze-dried to obtain the original dry exudates. Clayey red soils (0～20 cm) were amended with different rates of dry root exudate materials (0, 0.02, 0.2, and 1 mg·g-1, dry root exudates wt/soil wt), and left to equilibrate for one week in a 4℃ refrigerator. Soils amended with varying rates of dry root exudates were then compacted into steel cores (d= 5 cm and h= 5.1 cm) and subjected to two types of compaction. One subset of core samples was wetted to -33 kPa and compacted to 200 kPa stress (compaction), and another subset underwent 200 kPa stress followed by one cycle of saturation and drainage back to -33 kPa (compaction+w/d). The SPR, soil water content (SWC), aggregate properties, and bulk density (Bd) were determined. 【Result】 The results showed that: (1) The relative content of aromatic carbon, alkoxy carbon, and carbonyl carbon in the root exudates was higher in lucerne (3.23%, 6.83%, 55.09%) than that in vetiver (1.64%, 4.12%, 45.78%), whereas the ratio of hydrophobic to hydrophilic substances showed an opposite trend(0.52 for Lucerne and 0.86 for vetiver). (2) The SPR decreased as the exudate rate increased, with a significant decrease observed only when the root exudate application rate exceeded 0.2 mg·g-1. For example, compared to the control, 0.2 mg·g-1root exudates application from lucerne and vetiver resulted in reductions of 29.4% and 11.4% in SPR, respectively. (3) At the same root exudate application rate, lucerne showed a higher degree of SPR reduction than vetiver under both compaction conditions. (4) The SWC increased with increasing exudate rate compared to the control. For example, compared to the control, the application of 1 mg·g-1root exudates resulted in an increase in SWC by 7.98% (compaction) and 21.65% (compaction + w/d) for lucerne, and 13.07% (compaction) and 11.15% (compaction + w/d) for vetiver. Furthermore, the aggregate mean weight diameter (MWD) also increased after root exudate treatments compared to the control. Correlation and regression analysis confirmed that a low ratio of hydrophobic to hydrophilic substances, a high proportion of alkoxy carbon, and a high exudate rate resulted in a low SPR value by improving SWC and aggregate MWD. 【Conclusion】In conclusion, taproot plants showed a more apparent effect in alleviating SPR than fibrous roots in clayey red soil. Therefore, selecting appropriate taproot green manure has the potential to effectively reduce SPR in clay red soil by improving SWC and aggregate MWD.
-
Regolith Particle Size Controls Deep Nitrate Accumulation in a Typical Arid Region
DONG Xuetao, WU Huayong, SONG Xiaodong, ZHANG Ganlin, PAN Jie
2024,61(5):1236-1246, DOI: 10.11766/trxb202303290119
Abstract:
【Objective】 Overuse of Nitrogen (N) fertilizer results in a low N use efficiency and intensive soil nitrate accumulation in arid farmland critical zone of China, which threatens eco-environmental safety. Elucidating characteristics of soil nitrate accumulation and its influencing factors can provide scientific reference for integrated management of water and fertilizers. 【Method】 The Aksu region, a typical arid region, was selected as the study area. Regolith core samples were collected from three drilling sites including XJ1 (40°36′48.7″N, 80°48′14.2″E), XJ2 (41°16′16.2″N, 80°19′9.1″E), and XJ3 (41°20′37.6″N, 80°17′11.0″E) along a topographic sequence from south to north, with depths of 7.75 m, 10.52 m, and 9.91 m, respectively. The drilling sites were located in a 60-year-old cotton field, a 32-year-old apple orchard, and a 15-year-old apple orchard, respectively. Key soil properties were measured and their relationship to soil nitrate concentration accumulation was analyzed using linear and nonlinear correlations. 【Result】 Significant accumulation of soil nitrate concentration was found under cotton fields with a low altitude and apple orchards with different planting years and a high altitude. Soil nitrate concentrations at depth can reach 44 mg·kg-1 and soil nitrate accumulation occurs deeper than 10 m. Key soil properties including soil water content and soil particle (gravel, sand, silt and clay fractions) sizes could explain about 50% variations of soil nitrate concentrations with depth. Among key soil properties, soil water content and soil particle sizes were found to be the main factors determining soil nitrate accumulation at depth. Soil nitrate concentration was generally accumulated under conditions with a high soil water content and a fine soil particle. Notable denitrification below the groundwater table at a depth of 4 m occurred under cotton fields and led to a low nitrate concentration below 1 mg·kg-1. Notable denitrification was not observed below 10 m under apple orchards with a deep groundwater table and soil nitrate concentration was intensively accumulated beyond the root zone deeper than 5 m. 【Conclusion】 Soil water content was found to be the below-ground direct factor determining soil nitrate accumulation at depth. Soil particle sizes were found to be the fundamental factor determining soil nitrate accumulation via controlling soil water content variations.
-
Experimental Study on Carbon Mineralization of Different Sizes Particle in Forest Soils
MA Hongliang, CHEN Chanchan, YIN Yunfeng, GAO Ren
2024,61(5):1247-1259, DOI: 10.11766/trxb202303140102
Abstract:
【Objective】Soil is composed of different size particles, and the properties of each particle and their spatial position in the soil are different. However, prior studies focused on a small range of different aggregates or particle sizes. Thus, this study aimed to investigate different carbon changes in each particle with a wide range and evaluate the role of the turnover and stability of soil carbon for each particle in bulk soil. 【Method】After collecting soil samples from subtropical broad-leaved forest, the soil particles (> 2 000, 2 000-250, 250-53, < 53, 53-20, 20-2, < 2 μm) were obtained by physical fractionation. Moreover, the mineralization experiment was carried out with the same soil weight for each particle and bulk soil to study the difference in mineralization amount, carbon change trend and their relationship. Furthermore, after the dimension reduction of seventeen variables, a composite characteristic index was considered for each soil particle by principal component analysis. 【Result】 Although all soil particles were provided as the same amount for incubation to study their different carbon mineralization, their proportion in bulk soil was used to simulate their summation and compare them with bulk soil. The calculated sum values in cumulative CO2 emissions, total carbon, C/N, aromatic index, and free oxide iron content for all soil particles according to the proportion of each particle in bulk soil are 95.0%-101.8% of the bulk soil. In addition, it was 132.6% and 116.7% for the calculated sum values of the proportion of specific surface area and total pore volume in bulk soil. It was also observed that the cumulative CO2 emissions of <2 μm and 20-2 μm particles were significantly higher than those of other particles and bulk soil. The correlation analysis showed that the cumulative CO2 emissions of bulk soil or particles were positively correlated with specific surface area, total pore volume, total carbon, DOC, MBC, readily oxidized carbon, and free iron oxide, but negatively correlated with C/N. Moreover, this correlation analysis would be altered when soil particles were considered as size group analysis rather than including all. The factor analysis of sixteen indexes for each particle showed that the composite characteristic index was the highest for < 2 μm and 20-2 μm particles, which means they have the most role in bulk soil. 【Conclusion】Physical fractionation of bulk soil facilitates the study by isolating the individual particle, but also amplifies the role of the individual, especially for < 2 μm and 20-2 μm. These different results in soil particles and bulk soil suggest that the carbon change in bulk soil can be traced back to the different changes in carbon in each particle and their relationships. The encapsulation of small-size particles (<2 μm and 20-2 μm) by large-size particles or aggregation might be one mechanism for reducing carbon mineralization, which is conducive to maintaining soil carbon stability or storage.
-
Driving Mechanism of Soil Organic Carbon Response to Increase Hydrothermal Conditions in Different Climatic Regimes
HUANG Weigen, NI Haowei, HUANG Ruilin, WANG Xiaoyue, SUN Bo, LIANG Yuting
2024,61(5):1260-1270, DOI: 10.11766/trxb202305220077
Abstract:
The Mollisol in north-eastern China is rich in organic matter, which supports high crop yields and agricultural production. Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems, which responds to climate change directly affects the global carbon cycle. Understanding the response of SOC to increased hydrothermal conditions is important for soil conservation in the context of global climate change. 【Objective】This study aimed to analyze the response of SOC to long-term increasing hydrothermal conditions and their driving factors. 【Method】Based on a soil transplantation experiment, large transects of Mollisol in a cold temperate region (Hailun, HL) were translocated to warm temperate (Fengqiu, FQ) and mid-subtropical (Yingtan, YT) regions to simulate the increasing conditions of MAT and MAP. The experiment was started in 2005, soil samples were collected in August 2013. The SOC and microbial necromass C (MNC) were measured to investigate the changes and drivers of SOC after 8 years of increasing hydrothermal conditions.【Results】The results showed that the increased hydrothermal conditions increased plant biomass, litter C/N, and potential activities of hydrolytic enzymes while decreasing the content of SOC, MNC and soil activity minerals. Moreover, the contribution of MNC to SOC also decreased as hydrothermal conditions increased. The ratio of
DMNC and DSOC was calculated to characterize the change in microbial necromass C per unit decrease in SOC, which could be considered a quantitative representation of necromass loss efficiency. DMNC/ DSOC increased with increasing hydrothermal activity, with values of 72.50% ± 9.35% in FQ and 82.67% ± 2.37% in YT. The correlation and Random forest analysis showed that DMNC/ DSOC positively correlated with the changes in MAT, MAP, α-D-Glucosidase, β-N-Acetyl Glucosaminidase, plant biomass and Straw C/N, while negatively correlated with the changes in pH, poorly crystalline Fe and Al oxyhydroxides, organically complexed Fe and Al, and exchangeable Ca. Structural equation modeling (SEM) indicated that DMNC/ DSOC increased with increasing hydrothermal conditions, while decreased with soil mineral protection, with standardized coefficients of 0.64 and -0.24, respectively. It was confirmed in the variance partitioning analysis (VPA), which showed that hydrothermal conditions together with changes in soil mineral protection explained 83.69% of the variance in DMNC/ DSOC. The above results indicate that hydrothermal conditions and soil mineral protection play decisive role in regulating DMNC/ DSOC. 【Conclusion】In conclusion, long-term increases in hydrothermal conditions reduce the protection of MNC by soil minerals and/or stimulate the utilization of MNC by soil microorganisms. As evidenced by increased soil N limitation that allowed microbes to decompose more MNC and weakened the conservation capacity of minerals for MNC, contributing to the significant loss of SOC by reducing MNC. -
Study on the Effects of Counter Tillage on Runoff and Sediment Yield and Process of Nitrogen and Phosphorus Nutrient Loss on Sloping Farmland
LU Shuning, LI Rongrong, YAO Chong, WU Faqi
2024,61(5):1271-1283, DOI: 10.11766/trxb202305040172
Abstract:
Counter tillage is a common soil and water conservation tillage practice, which can influence the soil erosion process by increasing storage and infiltration capacity on sloping farmland. However, studies about the effects of counter tillage on nutrient losses during soil erosion processes on sloping farmland are still limited. 【 Objective】 Therefore, this study aimed to reveal the characteristics of nutrient loss on sloping farmland. 【 Method】 In this study, the rainfall simulation was conducted with a rainfall intensity of 90 mm·hh–1, five slope gradients (3°, 5°, 10°, 15°, 20°) and two types of slope treatments (counter tillage and flat slope) on runoff plots with projection length 4.5 m and projection width 1.5 m to explore the effects of counter tillage on the characteristics of soil erosion and nitrogen and phosphorus nutrient losses on sloping farmland of different slope gradient. 【 Result】 The results showed that: (1) When the slope gradient was less than 20°, counter tillage significantly reduced the amount of runoff and sediment on the sloping farmland and the amount of runoff and sediment reduced by a maximum of 95% and 99% respectively. When the slope gradient increased to 20°, a break in the ridge occurred on the counter tillage and the control effect on the runoff and sediment was gradually weakened. Also, the amount of runoff and sediment was close to or greater than that of the flat slope. (2) The effect of counter tillage on the concentration of nutrient loss was small, but it had a significant effect on the nutrient losses. When the slope gradient was less than 20°, the counter tillage had a better effect on controlling the nutrient losses on the sloping farmland. However, when the slope gradient increased to 20°, the effect of counter tillage on controlling nutrient losses was weakened. Additionally, TN losses were always greater than TP losses in runoff; except for the 10° slope gradient on CT, while TP losses were greater than TN in sediment. (3) The nutrient losses were mainly determined by the amount of runoff and sediment, while the nutrient loss rate and runoff rate or sediment production rate satisfied a linear positive correlation. In addition, the reduction benefits of nutrient losses on counter tillage in runoff and sediment can reach 45% to 100% and 59% to 100%, respectively. 【 Conclusion】 Our results show that counter tillage is an effective tillage practice to control soil erosion and nutrient losses.
-
Distinguishing Features and Influential Factors of Soil Iron Oxide in a Representative Karst Watershed in Guizhou Province
XU Zuliang, LU Xiaohui, ZENG Hailian, ZOU Yufeng
2024,61(5):1284-1298, DOI: 10.11766/trxb202305040171
Abstract:
【Objective】 Understanding the characteristics and differentiation of soil iron oxide in subtropical karst basins is crucial for comprehending the occurrence, development, and type evolution of soil in this unique regional complex. 【Method】 This study focused on 53 typical soil profiles in the Houzhai River Basin, Puding County, Guizhou Province. The research involved measuring the content of various forms of iron oxides in diagnostic surface and subsurface horizons, calculating their weathering indexes, and analyzing the characteristics and differentiation of soil iron oxides. Additionally, the study explored the impacts of soil-forming environments and soil attributes on the characteristic differentiation of iron oxides.【Result】The results revealed an increasing trend in the content of total iron and free iron from diagnostic surface to subsurface horizons, with average increments of 25.54% and 39.63%, respectively. Iron oxides exhibited enrichment in diagnostic subsurface horizons. The activation degree of iron in the diagnostic surface layer surpassed that in subsurface horizons, while free iron and the iron crystal gel rate showed an opposite trend. Most tested diagnostic tables' subsoil had over 30 g·kg-1 of free iron, over 50% iron dissociation degree, and less than 30% iron activation degree, indicating that the soil was in the aluminization stage during the middle phase of desilication. Factors such as parent rock, land use, watershed position, organic matter, pH, clay CEC7, and texture types significantly influenced the iron oxide content and weathering index of various soil forms. Geographical detector analysis highlighted the significant explanatory power of parent rock and organic matter on iron oxide index differences (excluding free iron degree), with the highest Q value observed in their interaction (total iron 41.9%, free iron 39.8%, amorphous iron 40.1%, iron activity 41%, iron crystal gel ratio 52.5%).【Conclusion】Apparently, parent rock and organic matter are the primary factors influencing the differentiation of soil iron oxide characteristics in subtropical karst watersheds.
-
Alleviating Effects of Bone Meal Biochars on Acidic Soil
ZHAO Wenrui, KONG Qunfang, ZHANG Wenjuan, HU Chengkai, LIN Yuxin, TAO Bingjiao, WANG Guoxing, Peng Kerui, WANG Cong, ZHAO Kuan
2024,61(5):1299-1309, DOI: 10.11766/trxb202309150379
Abstract:
【Objective】The purpose of this study was to explore the optimum preparation conditions of bone biochars, their improvement effects on acid soil, and the influence on Al forms from the perspective of soil solid phase and liquid phase.【Method】The anaerobic pyrolysis of pig, chicken, ox, and sheep bone meals were used as raw materials to produce biochars(bone biochars)as ameliorants and three typical acid soils were used.【Result】The results showed that the bone biochars prepared by high-temperature anaerobic pyrolysis were rich in CaO, CaCO3, and Ca5(PO4)3(OH), contained alkaline substances such as NaO and MgO and characterized by many functional groups including -OH. Nevertheless, the alkali content of bone biochar was greatly affected by the pyrolysis temperature. The alkali content was close to the peak value and remained stable at 800 ℃ for chicken and cow bones, and the same at 900 ℃ for pig and sheep bones. Interestingly, the alkali content of these bone biochars was about 90% of the quicklime, which is the best preparation temperature. Also, the biochars effectively increased the pH of acidic red soils from Anhui, Jiangxi, and Guangdong with an original pH of lower than 6. The alkaline substances in bone biochars mainly existed in the form of H+ buffers and the magnitude of the increase in soil pH was inversely proportional to the initial soil pH. After adding 5 g·kg-1 pig, chicken, sheep, and ox bone biochars to the red soils with pH = 4.40, the Al concentration in soil solution decreased by 33%, 34%, 47%, and 41%, respectively, compared with the control, and the content of organically bound Al in solid phase had no significant change(P > 0.05). Bone biochars increased the cation exchange capacity of acidic soil and reduced the content of soil solution Al and exchange Al by promoting the conversion of active Al to adsorbed hydroxyl Al and more stable Al in the soil solid phase.【Conclusion】Bone biochars are rich in nutrients required for plant growth, has the dual characteristics of inorganic and organic amendments, and are high-quality materials that can replace traditional lime as soil amendments for acidic farmlands.
-
Study on the Anaerobic Dechlorination of Hexachlorobenzene in Hydragric Acrisols Promoted by Nano-Fe3O4/Biochar
LIU Cuiying, YU Lixin, YANG Chao, FAN Jianling, SONG Yang
2024,61(5):1310-1322, DOI: 10.11766/trxb202303290120
Abstract:
【Objective】 Reductive dechlorination is a key pathway for the degradation of hexachlorobenzene (HCB) which is a persistent organic pollutant. In anaerobic paddy soils, magnetite (Fe3O4) can enhance the direct dechlorination under the action of iron-reducing bacteria and their interacting microorganisms which have a dechlorination function. The process is characterized by an increased electron transfer rate and enhanced chemical reductive dechlorination of organic chlorinated pollutants by an acceleration in the production of adsorbed Fe(Ⅱ), which is an effective electron donor. To improve the dispersity of Fe3O4, this study attempted to load nano-Fe3O4 onto biochar and then clarified the effect of nano-Fe3O4/biochar composite material on the reductive dechlorination of HCB in anaerobic paddy soil and their possible mechanisms. 【Method】 First, nano-Fe3O4, biochar and nano-Fe3O4/biochar composite materials were prepared, and their surface morphologies, crystal structures, and characteristic functional groups were characterized. Then, the anaerobic incubation experiment was conducted in slurry systems with Hydragric Acrisols as the tested soil. The internal relationships between pH, Eh, adsorbed or dissolved Fe(Ⅱ), and the HCB dechlorination process in the reaction systems were analyzed. 【Result】 Results showed that the dechlorination degradation of HCB was negligible for the sterilized control treatment, indicating that the reductive dechlorination of HCB was mainly completed by microorganisms. The addition of single biochar accelerated the reductive dechlorination of HCB by increasing soil pH, enhancing the reducibility of the reaction system, and promoting the formation of adsorbed Fe(Ⅱ). The addition of exclusive nano-Fe3O4 presented a stronger effect on promoting the reductive dechlorination of HCB than the addition of biochar alone. This was mainly because nano-Fe3O4 could significantly enhance the production of adsorbed Fe(Ⅱ) through dissimilatory Fe reduction and adsorbed Fe(Ⅱ) as an effective electron donor to accelerate the chemical reductive dechlorination of HCB. Also, the application of nano-Fe3O4/biochar composite material presented a stronger effect on promoting the reductive dechlorination of HCB than the single nano-Fe3O4. This was attributed to the larger specific surface area of nano-Fe3O4/biochar composite material and better dispersity of nano-Fe3O4 on the biochar surface. This was more beneficial for the electron transfer process in the reaction system relative to the exclusive nano-Fe3O4 application. 【Conclusion】 In conclusion, the nano-Fe3O4/biochar composite material was a more efficient remediation additive for HCB-contaminated soil compared with single nano-Fe3O4 and biochar. In the future, the nano-Fe3O4/biochar composite material can be promoted and applied in the remediation and treatment of polychlorinated organic pollutants.
-
Source-Route-Receptor-Based Spatial Zoning Study on Soil Heavy Metals Pollution Risk
YI Shiyi, LI Xiaonuo, CHEN Xinyue, CHEN Weiping
2024,61(5):1323-1338, DOI: 10.11766/trxb202303220112
Abstract:
【Objective】The establishment of a spatial zoning system of soil pollution risk management indicates the concrete implementation of “classification, division and phased soil environmental management” claimed in Soil Pollution Prevention and Control Law. The high-resolution risk spatial mapping can undoubtedly provide scientific and effective decision-making guidance not only for delineating prior areas for soil pollution risk management but also for facilitating the overall deployment of soil pollution prevention and control works at a large scale.【Method】This study first adopted positive matrix factorization (PMF) model to identify emission sources and the corresponding contribution rate of Cr, Cu, As, Cd, Pb, Ni, Sb and Hg in an industrial agglomeration area in Ningbo City, Zhejiang Province. Then, a spatial zoning technical system for risk management on soil heavy metals pollution was developed based on the source-route-receptor relationship and mass balance theory.【Result】The results showed that: (1) the spatial distribution of soil heavy metals presented a significant heterogeneity and five factors were primarily determined as the emission sources of soil heavy metals including coal-fired power generation source(17.08%), other industrial sources(17.94%), natural source(28.61%), agricultural source(26.07%), and traffic source(10.31%); (2) five risk levels were clustered using the established spatial zoning technical system, including extremely high-, high-, medium-, low- and extremely low-risk accounting for 8.64%, 17.28%, 18.27%, 22.92%, and 32.89% of the total area, respectively. 【Conclusion】The quantification of the regional risk stress levels can effectively map high-risk hotspots to apply prior measures for precise soil pollution management.
-
Input and Output Balance of Heavy Metals (Cd, Cu, Pb) in Arable Soils in Atmospheric Deposition Area of Typical Smelter
MI Yazhu, LIANG Jiani, ZHOU Jun, LIU Mengli, KOU Leyong, XIA Ruizhi, TIAN Ruiyun, SHI Ying, SHU Tiancai, SHU Wuxing, ZHOU Jing
2024,61(5):1339-1348, DOI: 10.11766/trxb202302180064
Abstract:
【Objective】This study aimed to investigate the input and output characteristics of cadmium (Cd), copper (Cu), and lead (Pb) in different atmospheric deposition areas.【Method】The arable soils (0-20 cm) of Guixi Smelter with main wind direction at 34 km (background site), 6 km (moderate deposition site) and 1 km (high deposition site) were selected as the research objects. The main input (atmospheric deposition, irrigation water, pesticides, and fertilizers) and output pathways (surface runoff, leaching water, and grain harvest) were monitored and quantitatively analyzed for three years by using the chemical mass balance (CMB) method.【Result】The results showed that the average annual input fluxes of Cd in the background, moderate, and high deposition sites by atmospheric deposition were 0.84, 2.26, 9.01 mg·m-2·a-1, accounting for 43.18%, 38.33%, and 100%, while the average annual input fluxes of Cu were 17.62, 99.68, 747.6 mg·m-2·a-1, accounting for 80.76%, 86.24%, 100%, respectively. Also, the average annual input fluxes of Pb were 13.93, 27.43, 73.17 mg·m-2·a-1, accounting for 97.75%, 92.36%, and 100%, respectively. Specifically, the average annual input fluxes of Cd in the background and moderate deposition sites due to irrigation water were 1.05 and 3.60 mg·m-2·a-1 and accounted for 54.62% and 60.82%, respectively, whereas the annual heavy metal input fluxes by pesticides and fertilizers accounted for less than 5%, which could be ignored. The main output pathways of arable soil in different atmospheric deposition areas were surface runoff and leaching water, with the output ratio ranging from 86.66% to 100%, and the output ratio of the grain harvest ranging from 2.88% to 13.34%. From 2019 to 2021, the average annual net input fluxes of Cd, Cu, and Pb were all greater than 0 in the background site, moderate deposition site, and high deposition site. For example, the average annual net input fluxes of Cd were 1.54, 1.96, and 4.38 mg·m-2·a-1, for Cu were 12.72, 28.02, and 184.0 mg·m-2·a-1, and for Pb were 13.03, 21.31, 55.04 mg·m-2·a-1 in the background site, moderate deposition site, and high deposition site, respectively. 【Conclusion】In general, it is advisable to strengthen the long-term supervision of atmospheric pollution sources and irrigation water quality in the study area and avoid the direct return of straw to the field. This study provided theoretical support for the remediation of heavy metal pollution and the protection of environmental quality in regional arable soils.
-
Phytoextraction of the Soils from the East of Yunnan Province with a High Cadmium Geological Background and Its Effect on Rice Cadmium Uptake
WU Tuozheng, ZHAN Juan, ZHOU Jiawen, ZHOU Tong, LI Zhu, HU Pengjie, HUANG Huagang, LI Tingxuan, ZHANG Xizhou, LUO Yongming
2024,61(5):1349-1359, DOI: 10.11766/trxb202303060092
Abstract:
【Objective】Yunnan Province is one of the typical high geological background regions in China. However, a few studies have focused on the phytoextraction of high geological soils for safe agricultural production. 【Method】This research was conducted to investigate cadmium (Cd) phytoextraction efficiency of the high geological background soils from Shilin, Fuyuan, and Luoping in Yunnan Province by the Cd/zinc (Zn) hyperaccumulator Sedum plumbizincicola and its effect on plant growth and Cd uptake by rice (Oryza sativa) through pot experiments. 【Result】After triple-cropping of S. plumbizincicola, the total Cd and available Cd concentrations in soils showed a substantial decrease, with the total Cd decreasing to 24.8%, 30.9%, and 58.8% of the original values for soils from Shilin, Fuyuan, and Luoping, respectively. S. plumbizincicola showed better growth when grown in soils from Fuyuan developed from basalt with more soil nutrients but presented a greater Cd phytoextraction efficiency when grown in soils from Shilin developed from limestone with higher soil pH, thereby greater Cd mobilization capacity. These significant differences indicated that plant growth and heavy metal accumulation of hyperaccumulators were affected by the comprehensive effects of soil parent materials, soil nutrients, and heavy metal availability in soils. After a triple-cropping of S. plumbizincicola, Cd concentration in brown rice and rice straw was significantly decreased under flooding conditions through the whole growth period, resulting in a Cd-safe production. However, the rice grain possessed a high Cd pollution risk without phytoextraction when grown under a dry cultivation system. 【Conclusion】The phytoextraction of high geological background soils by S. plumbizincicola combing with water management measures benefits greatly the safe production of rice crops, thereby providing a theoretical basis and technical support for the safe production of the high geological background soils.
-
Effects of Application of Straw and Organic-inorganic Fertilizers on Soil Quality and Wheat Yield in Different Texture Fluvo-aquic Soils
GUO Wei, LI Dandan, XU Jisheng, ZHOU Yunpeng, WANG Qingxia, ZHOU Tantan, ZHAO Bingzi
2024,61(5):1360-1373, DOI: 10.11766/trxb202306120228
Abstract:
【Objective】The combined application of crop straw with chemical fertilizers and manure is an effective measure to improve soil quality, but its effect on wheat yield and its mechanism in the different textures of fluvo-aquic soils are still unclear. 【Method】Here, we examined shifts in soil quality and wheat grain yield when three soil textures (sandy, loam and clay) were subjected to different management strategies and through a 7-year field experiment at the Fengqiu Agro-Ecological Experimental Station of the Chinese Academy of Sciences. Five different treatments were used: no fertilizer or crop straw returning(N0S0), crop straw returning(N0S), traditional chemical fertilization(NS0), crop straw returning with chemical fertilizer(NS), and crop straw returning with chemical fertilizer and the nitrogen was substituted 20% by chicken manure(NSM). 【Result】The results showed that compared with the N0S0 treatment, the grain yield under the NS treatment was increased by 611.56%, 440.00%, and 403.55% while under the NSM treatment, it was increased by 676.56%, 546.67% and 492.86%, respectively. In sandy, loam, and clay soils, compared with the N0S0 treatment, the soil quality index(SQI) under the N0S and NS0 treatments was significantly increased, with that under the NS treatment being more significant. In sandy soil, the SQI of the NSM treatment was better than that of the NS treatment, but in loam and clay soils, the SQI of the NSM and NS treatments showed no significant differences. Random forest analysis indicated that in sandy soil, grain yield was significantly affected by pH, alkali-hydrolyzable nitrogen(AHN), dissolved organic nitrogen(DON), available phosphorus(AP), soil organic carbon(SOC), and available potassium(AK), in loam soil, it was significantly affected by AP, pH, AK, AHN, microbial biomass carbon(MBC), and SOC, while in clay soil, grain yield was significantly affected by AP, DON, AHN, and pH. The partial least squares path model(PLS-PM) showed that in sandy, loam, and clay soils, the soil properties significantly affecting grain yield were significantly regulated by management strategies, and all of these properties had significant effects on SQI, and SQI had direct significant effects on grain yield. The key soil properties affecting grain yield could be used as indicators to monitor the changes in soil quality and grain yield to select management strategies. In addition, in loam soil, SQI also indirectly affected the grain yield by affecting wheat yield components. 【Conclusion】The combined application of crop straw with chemical fertilizers and chicken manure improved soil quality and directly or indirectly affected grain yield through different action modes in the different textures of fluvo-aquic soils.
-
Effects of Long-term Straw Burying and Nitrogen Fertilizer Application on Soil Bacterial Community Characteristics
LIU Mingfeng, ZHOU Guixiang, ZHANG Jiabao, ZHANG Congzhi, XUE Zaiqi, ZHAO Zhanhui
2024,61(5):1374-1385, DOI: 10.11766/trxb202303090096
Abstract:
【Objective】In order to reveal the response mechanism of microbial community and ecological network to straw returning process in typical fluvo-aquic soil, we experimented with different straw-returning treatments under long-term wheat-maize rotation.【Method】The high-throughput sequencing and ecological network methods were utilized to analyze the soil bacterial community composition, bacterial network co-occurrence and their relationships with soil nutrient concentrations.【Result】The results indicated that compared to straw removal and no nitrogen fertilizer treatment, straw returning with conventional fertilization treatments significantly reduced soil pH, while increasing the content of TN, SOC, AP, AK and NO3--N(P < 0.05). The treatments of straw burying with nitrogen fertilizers were beneficial for increasing soil nutrient content. Moreover, no significant difference in bacterial alpha diversity was observed between different straw-returning methods and different amounts of nitrogen fertilizers, but a significant difference was observed in bacterial community structure. Factors such as pH, SOC, and TN drove variations in bacterial community structure.Also, Acidobacteriota, Proteobacteria, Bacteroidota and Chloroflexi were the dominant phyla in the fluvo-aquic soil. Furthermore, co-occurrence network analysis revealed four main ecological clusters that were significantly correlated with soil nutrients. The abundances of taxa in module 1 were found to be inversely correlated with SOC, TN, TP, NO3--N, AP and AK(P < 0.001), and positively correlated with pH(P < 0.001). Conversely, the abundances of taxa in module 2 and module 3 were significantly positively correlated with most nutrient content, and negatively related to pH.【Conclusion】Therefore, it can be concluded that straw burying combined with nitrogen fertilizers can improve soil nutrient by regulating ecological relationships of microorganisms. The findings of this study can provide a scientific basis for the efficient utilization of straw and the efficient management of soil fertilization.
-
Organic Matter Compensation Scheme and Preliminary Mechanism for Remediation of Soil Productivity Decline in Continuous Cropping Garlic
HONG Huayang, WEI Tianqi, ZHOU Hongmei, REN Yanyun, MA Longchuan, SU Yanhua, ZHANG Huanchao
2024,61(5):1386-1397, DOI: 10.11766/trxb202303140101
Abstract:
【Objective】This study aimed to use different proportions of organic fertilizer instead of chemical fertilizer as organic matter compensation schemes to study their effects on garlic yield attenuation in long-term continuous cropping garlic fields in the main garlic-producing area of Jinxiang County, Shandong Province. 【Method】The representative fields with more than 25 years of continuous cropping history were selected in this experiment. The wheat field without garlic planting was used as the non-continuous cropping field control. Four treatments were set up : conventional chemical fertilizer fertilization (CF) and organic fertilizer to replace chemical fertilizer with 25% (M25), 50% (M50) and 100% ( M100) based on nitrogen (N).【Result】The results showed that in the long-term garlic continuous cropping soil, organic fertilizer instead of chemical fertilizer treatment had a significant effect on the increase(20%)of garlic yield in the current season. Also, the content of N in continuous cropping soil and the proportion of soil > 2 mm aggregates were increased, and the N nutrient supply status and soil aggregate structure in the soil were improved. Among the treatments, 25% organic fertilizer instead of chemical fertilizer treatment( N )had the best yield and economic benefit of garlic, and also had a better repair effect on the decline of soil productivity of continuously cropping garlic. However, in non-continuous cropping soil without organic matter deficit, organic substitution treatment did not have a direct effect on increasing production. 【Conclusion】This study clarified that the application of organic fertilizer(partial organic fertilizer instead of chemical fertilizer treatment)based on chemical fertilizer application can only promote the formation of large-grained soil aggregates and enhance the holding capacity of soil available nutrients during the whole growth period in the continuous cropping garlic soil with obvious deficiency of soil organic matter. It also has a significant restoration effect on the degradation of continuously cropping garlic soil productivity. This study provides a useful reference for alleviating similar soil degradation problems and maintaining the sustainability of soil productivity in continuous cropping systems.
-
Relative Contribution of Ammonia-oxidizing Microorganisms to Nitrous Oxide Emissions in Upland Agricultural Soils
YANG Yu, ZHAO Yongjian, SONG Xiaotong, ZHANG Limei, JU Xiaotang
2024,61(5):1398-1409, DOI: 10.11766/trxb202303250115
Abstract:
【Objective】Ammonia oxidizers make an important contribution to N2O emissions. However, the composition of their relative contribution to N2O emission in different soils and agricultural management systems has not been systematically studied.【Method】We studied the contributions of AOB, AOA + comammox and heterotrophic nitrifiers to the potential nitrification rate, net nitrification rate and N2O emission in typical upland surface soils (fluvo-aquic soil, black soil, latosol, red soil), and in latosols from soil profile under organic fertilizer amendment.【Result】In the surface fluvo-aquic soil, black soil, latosol and red soil, potential nitrification rate significantly increased with soil pH (P < 0.05), and was 32.5, 6.6, 4.8 and 2.3 mg·kg-1·d-1, respectively. AOB dominated the potential nitrification rate in the above surface soils, with contributions ranging 58%-100%. Further analyses of the fluvo-aquic soil, black soil and latosol indicated that net nitrification rate and N2O emission both significantly increased with soil pH (P < 0.05), which were consistent with potential nitrification rate. For the net nitrification rate, AOB and AOA + comammox contributed equally (30%-40%) in the fluvo-aquic soil and latosol, while AOB dominated in the black soil (72%). N2O emissions from the fluvo-aquic soil, black soil and latosol were all dominated by AOB (58%-92%). For soils from the organic fertilizer-amended latosol profile, pH, potential nitrification rate, net nitrification rate and N2O emission significantly increased from the subsurface to surface layer (P < 0.05). The increase in potential nitrification rate and net nitrification rate was dominated by AOA + comammox (contributing 63% and 54%) and the increase in N2O emission was dominated by AOB (contributing 54%).【Conclusion】This study provides new evidence for developing reduction measures of N2O emissions that match the soil ammonia oxidation characteristics and soil properties.
-
Isolation and Application of Rhizosphere Core Strains to Improve Salt Tolerance of Rice
MA Aiyuan, REN Yi, WANG Jiao, YAN He, SHI Chenyu, SHEN Qirong, ZHANG Ruifu, XUN Weibing
2024,61(5):1410-1420, DOI: 10.11766/trxb202302190069
Abstract:
【Objective】Rhizosphere beneficial microorganisms can enhance plant salt stress tolerance through multiple pathways, including re-establishing ion and osmotic homeostasis, preventing damage to plant cells, and resuming plant growth in saline soil. This study aimed to obtain plant growth-promoting rhizobacteria that can improve salt tolerance of rice and to explore its application effects.【Method】Two rice cultivars were used in this study, of which one is salt-tolerant cultivar Hunanxian and the other is salt-sensitive cultivar Nanjing 46. The physiological characteristics of rice seedlings were compared after planting in sterile and non-sterile saline soils. Then, the key rhizobacterial groups associated with salt tolerance, which were enriched in the rhizosphere of salt-tolerant rice cultivars, were identified by compositional differences and co-occurrence network analyses based on the 16S rRNA gene amplicon sequencing. Subsequently, the culturable strains of the key rhizobacterial groups were isolated through the high-throughput cultivation and identification method of rhizobacteria. Finally, pot experiments were conducted to evaluate the beneficial effects of the strains on enhancing the salt tolerance of salt-sensitive rice cultivar.【Result】The height of shoot and root length of salt-tolerant rice were significantly higher while the content of proline was significantly lower when cultivated in non-sterile soil than in sterile soil under salt stress. This indicates that the rhizosphere microbial community of salt-tolerant rice cultivars may play a crucial role in enhancing the salt tolerance of the host plant. Amplicon sequencing results demonstrated that the composition of the rhizosphere microbial communities of salt-tolerant and salt-sensitive rice cultivars was significantly different. The bacterial families of Flavobacteriaceae and Pseudomonadaceae were the key rhizobacterial groups that were both enriched in the rhizosphere of the salt-tolerant rice. Several bacterial strains affiliated with Flavobacteriaceae and Pseudomonadaceae were isolated, in which two strains of Pseudomonas punonensis P34 from Pseudomonadaceae and Chryseobacterium taeanense C18 from Flavobacteriaceae were screened to be the most efficient strains in improving the salt tolerance of rice by germination and hydroponics tests using salt-sensitive rice under salt stress. Finally, the efficient strains of C18 and P34 were applied as direct inoculants and seed-coating agents in pot experiments, and the results demonstrated that they were able to promote the growth of salt-sensitive rice under salt stress. 【Conclusion】Two rhizobacterial strains of C18 and P34 showed great capacity to enhance the salt tolerance of rice and they could be developed as bacteriological agents for seed coating or microbial fertilizer for application in saline lands.
-
Dry-wet Alternation Regulate Soil Active Bacterial Communities and Potential Functions in Paddy Fields
DING Chenxiao, LIU Yaowei, LIU Haiyang, YE Xinzhe, CHEN Yawen, YE Jing, DI Hongjie, XU Jianming, LI Yong
2024,61(5):1421-1431, DOI: 10.11766/trxb202302180065
Abstract:
【Objective】A large number of studies have found that changing from dry to wet significantly affects soil microbial communities and greenhouse gas emissions. However, the transient dynamic of active microorganisms and greenhouse gas emissions of soils under dry to wet fluctuations are still unclear. 【Method】In this study, the dynamic of bacterial communities and greenhouse gas emissions under dry, wet, and dry-wet changes conditions in paddy soil were investigated. The diversity, assembly, and potential functions of active bacterial communities under dry-wet change conditions were further revealed by combining 18O-based DNA stable isotope probing technology (DNA-SIP) and high-throughput sequencing. 【Result】Dry-wet change treatment significantly promoted emissions of carbon dioxide and contained significantly higher relative abundances of Actinobacteria and planctomycetes compared with those in the dry and/or wet treatments. The relative abundances of Proteobacteria, Actinobacteria, and planctomycetes increased significantly along with the incubation. DNA-SIP experiment showed that the alpha diversity of active bacteria in the dry-wet change treatment decreased significantly along with the incubation. Proteobacteria and Actinobacteria dominated the active bacterial communities, and the relative abundance of Myxococcales in Proteobacteria increased significantly along with the incubation. The assembly of active bacteria was dominated by determinism, and the contribution of determinism was increased along with the incubation. Functional prediction of active bacteria further found that carbohydrate metabolic potential decreased significantly during the incubation. 【Conclusion】In conclusion, the dry-wet change treatment significantly changed the soil bacterial community and promoted carbon dioxide emission in paddy soil. The active bacteria in the dry-wet change treatment were dominated by Proteobacteria and Actinobacteria, and their assembly was dominated by a deterministic process.
-
Analysis of the Differences and Causes in Microbial Biomass Carbon Metabolism Characteristics of Forest Soils Developed from Two Types of Rocks
FU Ruitong, WAN Xiangyu, YANG Xinyi, LI Dejun, HU Peilei, DUAN Pengpeng, ZHANG Yuling
2024,61(5):1432-1443, DOI: 10.11766/trxb202302210071
Abstract:
【Objective】Microbial biomass carbon(C)metabolism is vital in the formation and stabilization of organic C in soil, constituting a critical parameter in the models of terrestrial ecosystems. Yet, the variances in the microbial C metabolism indices in soils developed from different lithological origins remain undefined. 【Method】To address the scientific gap in the characteristics and driving factors of microbial biomass C metabolism in soils developed from different rocks, we sampled forest soils developed from limestone and clastic rocks as research objects. Using 18O-H2O labeling, we measured the microbial growth rate, respiration rate, carbon use efficiency (CUE), and turnover time. Combined with soil physicochemical properties, soil organic matter mineral protection characteristics, soil enzyme activity, and microbial biomass and community composition, we clarified the influencing mechanism of lithology on forest soil microbial biomass C metabolism. 【Result】The findings indicate that the pH and the 0.002～0.05 mm particle content in limestone-derived soils surpass those in clastic rock-derived soils, whereas soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon(DOC), C: P and N: P ratios were lower in limestone-derived soils (P<0.05). The limestone-developed soils had a higher content of exchangeable calcium and magnesium (Ca/Mg) and free iron and aluminum ((Fe+Al)d) than the clastic rock-developed soils, but the content of amorphous iron and aluminum((Fe+Al)o)was lower than that in the clastic rock-developed soils. Furthermore, the enzyme activity related to C, N, and P cycling in limestone-developed soils was significantly lower than that in clastic rock-developed soils (P< 0.05). In addition, the microbial biomass phosphorus (MBP) in limestone-developed soils was higher than that in clastic rock-developed soils, but microbial biomass carbon(MBC), fungi: bacteria ratio (F: B), and Gram-positive to Gram-negative bacteria ratio (G+: G-)were significantly lower than those in clastic rock-developed soils (P<0.05). The microbial growth rate and turnover rate in limestone-derived soils were significantly higher than in clastic rock-derived soils (P<0.05), but there was no significant difference in the microbial respiration rate and CUE between the two types of soils. Correlation analysis revealed that the soil microbial growth rate and turnover rate were significantly positively correlated with soil pH, (Ca+Mg): (Fe+Al)o, (Ca+Mg): SOC, (Fe+Al)d: SOC, and Gram-negative bacteria(P<0.05), and significantly negatively related to DOC, organic C bound to iron and aluminum, enzyme activity, MBC: MBN, F: B, and G+: G- ratio(P<0.05). The soil CUE was significantly negatively correlated with MBC and MBC: MBN (P<0.05) while microbial respiration rate was only significantly negatively correlated with phenol oxidase activity (P<0.05). In summary, the higher pH, weaker amorphous iron-aluminum mineral protection, lower microbial resource limitation, and larger bacterial biomass (especially Gram-negative bacteria) in limestone-derived soils may lead to greater microbial motility in these soils and stronger substrate availability, resulting in larger microbial growth and turnover rates. However, there was no difference in the soil microbial biomass CUE between the two rock types, which may be due to the similar soil C: N ratio. 【Conclusion】The microbial biomass C metabolism of forest soils developed from two types of rocks is controlled by biological and non-biological factors. These research results provide a new mechanism for explaining the differences in organic carbon pools in forest soils developed from different rocks.
-
A Meta-Analysis of Soil Microbial Necromass Accumulation in Response to Climate Warming
2024,61(5):1444-1454, DOI: 10.11766/trxb202303200109
Abstract:
【Objective】The effect of warming on the accumulation dynamics of microbial necromass is of great significance to the balance of soil carbon(C)pool. However, the impact of climate warming on microbial necromass is poorly understood. Thus, the objective of this study was to evaluate the responses of microbial necromass to climate warming and the main factors controlling this feedback.【Method】In this study, a meta-analysis was conducted to reveal general patterns of climate warming on amino sugars (microbial necromass biomarkers) in soils under grasslands, forests, and croplands. Here, 12 published publications from international and domestic journals were collected and extracted independent observations that met our criteria (29 for total amino sugars, 35 for glucosamine, 39 for muramic acid, and 25 for galactosamine).【Result】The results showed that the overall effects of warming could promote the accumulation of microbial necromass. However, warming effect sizes on microbial necromass were not consistent across different ecosystems, with the most sensitive responses occurring in cropland. The response of fungal and bacterial necromass differed under climate warming. Specifically, warming significantly increased the content of galactosamine and muramic acid, with an increase of 10.3% and 5.0%, respectively. Together with the significant decline in the ratio of glucosamine to muramic acid, the results suggested that warming benefited the accumulation of bacterial necromass compared to fungi. Also warming significantly increased the proportion of bacterial necromass to soil organic carbon (SOC), while the contribution of fungal and total necromass to SOC did not change significantly, suggesting that the contribution of fungal-derived C to SOC was weakened under warming scenarios. Warming magnitude was a key factor affecting the accumulation of microbial necromass. For instance, the accumulation of microbial necromass increased by 2.7%-14.6%, when the warming magnitude was less than or equal to 2℃ relative to unwarmed control. However, when the warming amplitude was greater than 2℃, the accumulation of microbial necromass was decreased by 8.0%-14.3%. Interestingly, the duration of warming was an important factor affecting the accumulation of microbial necromass.【Conclusion】The results demonstrate that warming has significant effects on the accumulation dynamics of microbial necromass and their contribution SOC pool. The intensity and direction of the warming impact are largely dependent upon ecosystem type and soil depth, in which warming amplitude, warming duration, and mean annual precipitation are important factors controlling the sequestration of the microbial-derived C under global climate warming.
-
Effect of Vegetation Type on Rhizosphere Microorganisms of Reclaimed Soils in Coal Mining Areas
LI Houchun, LI Junjian, ZHANG Hong, ZHANG Xiujuan, NING Yuewei, LIU Yong
2024,61(5):1455-1465, DOI: 10.11766/trxb202303140100
Abstract:
【Objective】Long-term mining activities have caused serious damage to the ecological environment in the mining area. Soils near mining areas have reduced quality, decreased vegetation cover, and changed microbial habitats. Stripped soil and coal gangue are mixed to form hillocks and the exposed surface of the hillocks is highly susceptible to wind and water erosion, which has resulted in increasingly severe damage to the ecosystems, including changes in plant species composition and community structure, reduced biodiversity and productivity, deterioration of soil and microenvironment, and changes in the relationships between organisms. Hence, the ecological restoration of the coal mines is an urgent task. Interestingly, vegetation types may affect the composition and diversity of microbial communities in rhizosphere soil owing to the growth conditions, vegetation cover, root turnover rates, and the chemical composition of root exudates. Therefore, it is important to explore the response of microbial community composition and diversity under different vegetation types in mining ecological restoration areas.【Method】The rhizosphere soils of five vegetation types (Platycladus orientalis, Picea asperata, Pinus sylvestris, Pinus tabuliformis, and Sabina chinensis) were collected in this study to detect the soil physicochemical properties, enzyme activities, and bacterial community structure. Also, we identified key environmental factors affecting rhizosphere bacterial communities using redundancy analysis and conducted a mantel-test analysis between dominant bacterial phyla and environmental factors. Structural equation models were established to explore the interactions between plants, soil, and microbes. Furthermore, the soil-integrated fertility index was calculated to analyze the ecological restoration effectiveness of different vegetation types.【Result】Vegetation types had significant effects on soil physicochemical properties, enzyme activities, bacterial community composition, and diversity. The P. sylvestris field had significantly higher total carbon content, total nitrogen contents, bacterial abundance, and diversity, while soil alkaline phosphatase and soil urease activities were significantly higher in the P. asperata field. The Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes were the dominant phyla of soil bacterial communities. Also, the dominant genera were RB41, Streptomyces, MND1, Ferruginibacter, and Variovorax. Total sulfur, soil bulk density, and soil alkaline protease were the key factors affecting the structure of rhizosphere soil bacterial communities. Our analysis revealed that vegetation types can directly affect soil physicochemical properties, soil enzyme activities, and bacterial community structure, as well as indirectly affect rhizosphere soil bacterial community structure through soil physicochemical properties and soil enzyme activities. Soil integrated fertility index indicated that P. sylvestris and P. asperata were superior to other vegetation in the ecological restoration of mining areas.【Conclusion】Vegetation types have significant effects on soil physicochemical properties, soil enzyme activity, and bacterial community in the rhizosphere. P. sylvestris and P. asperata can improve the rhizosphere soil bacterial diversity and soil fertility, which is beneficial to the ecological restoration of the coal mine reclamation area. This study provides a scientific basis for vegetation selection for ecological restoration of coal mine reclamation areas in semiarid regions.
Insights and Perspectives
Reviews and Comments
Research Articles
-
Spatial Distribution Pattern of Soil Microbiota Stoichiometry and the Influencing Factors in the Northwest Sichuan Alpine Meadow
CHEN Danyang, WANG Changting, DING Luming, LIAO Xiaoqin, QIAO Fusheng, SUONAN Jiangcai
DOI: 10.11766/trxb202401290049
Abstract:
【Objective】 As indicators reflecting soil fertility and biological activity, the soil microbial community plays key roles in global biogeochemical cycles by participating in litter decomposition and nutrient mineralization. The soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) are labile and available nutrients for plants, and important for maintaining ecosystem functions. However, there is still a lack of information on the spatial distribution of the soil microbial biomass and the potential key drivers affecting it in the alpine meadows of Northwest Sichuan Province. Therefore, the current study aims to investigate the spatial heterogeneity of soil microbial biomass in the alpine meadows of Northwest Sichuan and its influencing factors based on the Second Comprehensive Scientific Expedition to the Qinghai-Tibet Plateau project.【Method】The typical alpine meadows in Northwestern Sichuan were investigated in this study to determine soil MBC, MBN and MBP by chloroform fumigation method. Soil pH, water content, total carbon, total nitrogen and total phosphorous were also measured.【Result】The results showed that (1) The content of MBC and MBN showed a decreasing trend from South to North alpine meadow in the Northwest Sichuan Province. Conversely, the MBP content showed an increasing trend from South to North while the MBC:MBN ratio showed a decreasing trend from Northeast to Southwest. Nevertheless, the MBC:MBP ratio was more complex and showed an overall decreasing trend from South to North while the MBN:MBP ratio showed an increasing trend from West to East.; (2) Random forest modeling results showed that mean annual temperature (MAT), mean annual precipitation (MAP), soil pH, and soil moisture (SMC) were important factors that positively affected soil microbial biomass and its stoichiometric ratio. The structural equation modeling (SEM) results further showed that soil pH and soil bulk density (BD) had direct negative effects on the changes of soil microbial carbon, nitrogen and phosphorous biomass whereas the stoichiometric ratio and soil total carbon (TC) had direct positive effects on them. MAT and MAP indirectly and negatively affected soil MBC, MBN, MBP, and the stoichiometric ratio, which was mainly attributed to the effects of MAT and MAP on soil physicochemical properties. Specifically, MAT and MAP increased both MBC and MBP mainly by lowering soil pH, and MAT also directly decreased TC, which increases MBN as well as decreased MBP ; (3) Generally, the soil nutrients are limited in the alpine meadows of Northwest Sichuan Province, and showed the following trend: carbon > nitrogen > phosphorus.【Conclusion】Soil pH, BD, and TC had direct effects on the alteration of soil microbial biomass and its stoichiometric ratios in the alpine meadows of Northwest Sichuan Province, while MAT and MAP indirectly affected the soil microbial biomass and its stoichiometric ratios. In addition, the latitude and longitude showed effects on the spatial distribution pattern of nutrient limitation in the study area.
-
Dynamics and Influencing Factors of Transpiration of Pinus sylvestris in the Sandy Region of Yulin in Northern Shaanxi Province
WANG Xuanzhen, DUAN Yizhong, HUANG Laiming, PEI Yanwu, WANG Ziwei
DOI: 10.11766/trxb202403120106
Abstract:
Pinus sylvestris var. mongholica is one of the major vegetation restoration trees in the northern sand-prevention belt of China, which plays a vital role in the sheltering of wind and sand fixation, regulating regional microclimate, and maintaining ecosystem stability. 【Objective】This study seeks to clarify the dynamics and controlling factors of transpiration in P. sylvestris plantations in water-limited sandy regions and provide a scientific basis for the reasonable construction and sustainable management of artificial plants. 【Method】This study used the thermal dissipation probes, soil moisture sensor, automatic weather station, and groundwater level monitor to continuously observe the sap flow density, soil moisture content, meteorological parameters, and groundwater level in the sandy region of Yulin City, northern Shaanxi Province. With this design, we aimed to reveal the characteristics and controlling factors of transpiration water consumption of P. sylvestris. 【Result】Results showed that: (1) The sap flow density of P. sylvestris increased initially and then decreased during the monitored period (May 2021 to October 2021). On a sunny day, the sap flow density displayed an unimodal curve and had a relatively high peak value; however, on cloudy and rainy days, the sap flow density varied irregularly and had relatively low peak values. (2) The sap flow density was most sensitive to the changes in wind speed and air temperature, followed by groundwater level fluctuation. (3) The average daily transpiration rate of P. sylvestris was 0.67 mm·d-1, and the total transpiration water consumption in the growing season was 147 mm. 【Discussion】The seasonal variations of meteorological parameters (vapour pressure deficiency, wind speed, air temperture, photosynthetically active radiation) and groundwater level and the associated changes in soil water content were the main factors controlling the dynamics of transpiration water consumption of P. sylvestris. The study results can provide theoretical guidance for high efficient use of water resources and sustainable management of sand-fixing plants in the sandy region.
-
The Synergistic Effect of a Phage-Probiotic Combination on Suppressing Bacterial Wilt Disease
XI Ningbo, WANG Shuo, LI Tingting, WANG Xiaofang, XU Yangchun, SHEN Qirong, WEI Zhong
DOI: 10.11766/trxb202405160200
Abstract:
【Objective】Bacterial wilt disease, caused by soil-borne Ralstonia solanacearum, has led to significant yield reductions or even crop failures in tomatoes, potatoes, and tobacco, severely limiting the safe supply of agricultural products. Rhizosphere microorganisms play a crucial role in mitigating soil biotic impediments. Probiotics can inhibit pathogens through antagonism or nutrient competition, while phages can target pathogens through specific infections. However, the single use of either probiotics or phages often results in unstable effects, and the high-density fermentation cost of these strains is considerable. 【Method】To establish an efficient and stable technology for reducing soil biotic impediments, this study constructed combinations of antagonistic-competitive and nutrient-competitive beneficial bacteria with phages. It explored their synergistic effects in reducing soil wilt disease through in vitro microplate and greenhouse pot experiments. The potential mechanisms of synergy between probiotics and phages were also investigated. 【Result】 The results showed that most combinations of phages and probiotics exhibited synergistic effects, significantly enhancing the inhibition of pathogenic R. solanacearum growth and the reduction of bacterial wilt disease. Notably, the combination of the antagonistic-competitive beneficial bacterium T-5 with phages resulted in an 89.19% reduction in pathogenic bacterial growth compared to the control. Greenhouse experiments indicated that the synergistic effect reduced the disease index by an average of 58.18%, with the combination of the nutrient-competitive beneficial bacterium WR21 and phages significantly reducing the disease index by 67.28%. Further studies revealed that even at lower concentrations of beneficial bacteria, the phage-bacteria synergy remained effective. At a concentration of 104 CFU?g-1 substrate, the combination of T-5 with phages reduced the disease index by 21.56% and the number of rhizosphere pathogenic bacteria by 19.21% compared to the application of beneficial bacteria alone, demonstrating a strong synergistic effect. Additionally, the study explored the impact of phage-beneficial bacteria combinations on the characteristics of pathogenic R. solanacearum. The results showed that the phage-nutrient-competitive beneficial bacteria combination significantly reduced the pathogen""s carbon source utilization ability, with the WR21 and phage combination reducing the number of carbon sources utilized by the pathogen by 87.9%. Furthermore, under the dual stress of phages and antagonistic-competitive beneficial bacteria, the sensitivity of the pathogen to the antagonistic substances produced by T-5 increased by 64.10%. 【Conclusion】This study highlights the potential of phage-beneficial bacteria combinations in mitigating bacterial wilt disease and preliminarily elucidates the potential mechanisms behind their synergistic effects. These findings provide theoretical and technical support for the development of efficient soil biological obstacle reduction techniques.
-
Study on Gross Nitrogen Transformation Rates of Soils Under Different Land Use Types in Caohai Nature Reserve
LANG Man, NIE Hao, ZHU Sixi, LI Ping
DOI: 10.11766/trxb202403110102
Abstract:
【Objective】 To understand the effects of land use type change on soil N cycle and eco-environment, this study aimed to elucidate the gross N transformation rates in soils under different land use types. 【Method】 A laboratory incubation experiment was conducted using a 15N labeled technique and the numerical FLUAZ model to study the difference of gross N transformation rates among soils under different land use types such as wetland, dryland, vegetable land, and forest land in the Caohai nature reserve located in the Yunnan-Guizhou Plateau. 【Result】 The results showed that land use type significantly affected gross N transformation rates in the soils. Wetland soil had the highest rates of gross N mineralization (11.95 mg∙kg−1∙d−1) and immobilization (6.13 mg∙kg−1∙d−1) while the forest soil had the lowest gross N mineralization rate (2.39 mg∙kg−1∙d−1), but the gross N immobilization rate (2.09 mg∙kg−1∙d−1) was comparable to that of dryland soil and vegetable soil (2.29 and 1.52 mg∙kg−1∙d−1, respectively). The gross nitrification rate of forest soil (0.77 mg∙kg−1∙d−1) was significantly lower than that of wetland soil, dryland soil, and vegetable soil (2.68, 6.33 and 5.39 mg∙kg−1∙d−1, respectively). The ratios of gross nitrification to NH4+ immobilization and gross N mineralization to the immobilization of dryland soil and vegetable soil were both >1, whereas the ratio of gross nitrification to NH4+ immobilization rate was <1 in wetland soil and forest soil, and the ratio of gross N mineralization to the immobilization rate was close to 1 in forest soil. The gross N mineralization rate was significantly positively correlated with soil organic carbon (SOC), total nitrogen (TN), C/N ratio, and soil pH, and significantly negatively correlated with silt content. Also, the gross N immobilization rate and ammonium immobilization rate were significantly positively correlated with SOC, TN, water-soluble organic C (SOCw), and soil pH, and significantly negatively correlated with silt content. The gross nitrification rate was significantly negatively correlated with SOCw and clay content and significantly positively correlated with sand content. 【Conclusion】 The results indicate that in comparison with the wetland soil, dryland soil, and vegetable soil, the mineralization and immobilization processes in forest soil were more tightly coupled, thereby decreasing the occurrence of nitrification and subsequent NO3- loss to the environment. The results of this study can provide a scientific basis for the rational layout of land use and the evaluation of the environmental effects of ecological restoration projects within the Caohai Nature Reserve.
-
Impacts of Simulated Erosion and Fertilization on Soil Quality and Corn Yield in Northeastern Black Soil Region
WANG Zhiqiang, LI Yangyang, ZHANG Xiaoping
DOI: 10.11766/trxb202401220038
Abstract:
【Objective】Soil erosion is a major factor causing soil degradation and crop productivity reduction in the northeast black soil region. However, the in situ systematic and quantitative assessment of the effects of erosion on soil quality and crop productivity remains unclear. 【Method】A long-term field experiment on erosion-productivity relation was set up at Heshan Farm, Heilongjiang Province in 2005 based on comprehensive effects of erosion and tillage on soil profile. The experiment was a two-factor completely randomized block design with simulated erosion depth (8 levels of 0, 10, 20, 30, 40, 50, 60, and 70 cm) and fertilization (no fertilization and fertilization), totaling 16 treatments with 3 replications per treatment. In 2022, a series of soil physicochemical properties [bulk density (BD), soil water content (SWC), clay content, pH, soil organic C (SOC), alkali-hydrolyzed N (AN), Olsen-P (AP) and available K (AK)] and biological properties [microbial biomass C and N (MBC, MBN), catalase, urease, ?-glucosidase, cellulase activity] in 0-20 cm soil layer and corn yield were measured after 18 years of the setup. 【Result】1) Soil clay content, SOC, AN, AP, MBC and cellulase activities decreased significantly with the increase of simulated erosion depth, while soil BD and AK increased significantly. Also, fertilization significantly decreased soil BD, pH, AK, and catalase activity, but increased clay content, SOC, AN, AP, and the activities of urease, ?-glucosidase, and cellulase. Interestingly, fertilization weakened the correlation between soil urease activity, BD and other physicochemical properties. 2) Simulated erosion resulted in significant reductions in soil quality and corn yield, the decrease mainly occurred before the erosion depth of 40 cm. Soil quality index decreased by 28.1% for the unfertilized treatment and 26.7% for the fertilized treatment, and yield loss was 45.8% for the unfertilized treatment and 11.7% for the fertilized treatment at 40 cm of erosion depth. Additionally, fertilization increased the soil quality index by 7.0% and corn yield by 3.0 fold. 3) The main factors affecting soil quality under simulated erosion were cellulase activity, MBC and AN for the unfertilized treatment, and cellulase activity, MBC, AP for the fertilized treatment. Also, the main factors affecting corn yield under long-term simulated erosion were AN for the unfertilized treatment and AP for the fertilized treatment. 【Conclusion】These results quantified the degree of soil erosion on soil quality and productivity and clarified the major factors affecting soil quality and productivity in black soil, and can serve as reference for the restoration of degraded black soil.
-
Amelioration of Acidic Purple Soil with Calcareous Purple Mudstones
CHEN Jingjing, GUO Xinyi, LI Zhongyi, YU Junfeng, WU Wenchun, ZHOU Jia
DOI: 10.11766/trxb202403170116
Abstract:
【Objective】 Extensive regions of purple soil are afflicted by acidification, whereas calcareous purple mudstones, distinguished by their alkaline pH, abundant mineral composition, and low heavy metal content, are theoretically well-suited to ameliorating acidic purple soil in their vicinity. 【Method】An 80-day laboratory incubation experiment was conducted to evaluate the effectiveness of calcareous purple mudstones in ameliorating acidic purple soil. The geological ages of the two parent rocks were the Jurassic Shaximiao Formation (J2s) and the Jurassic Suining Formation (J3sn). 【Result】The findings revealed that both purple mudstones effectively neutralized soil acidity, enhanced soil potassium content and, increased potassium bioavailability, and reduced the bioavailability of heavy metals. These mudstones offer a promising solution for improving acidic purple soil, thereby promoting soil health and fertility. Compared to J2s mudstone, J3sn mudstone exhibited a superior overall improvement effect on acidic purple soil due to its richer calcium content. (1) When J2s mudstone was added to acidic purple soil at rates of 2%, 5%, and 10%, the soil pH increased gradually from 4.73 to 4.93, 5.30, and 6.27, respectively. Concurrently, the soil exchangeable acidity decreased from 2.84 cmol·kg-1 to 2.79, 1.40, and 0.70 cmol·kg-1, respectively. Differently, when J3sn mudstone was added at the same rates, the pH of the acidic purple soil increased significantly to 7.20, 7.87, and 8.00, achieving neutral to alkaline levels. Notably, no exchangeable H+ or Al3+ was detected in the soil after the addition of J3sn mudstone. Additionally, the addition of both mudstones resulted in an increase in soil exchangeable Ca2+, effective cation exchange capacity, and base saturation. (2) Overall, the addition of both J2s and J3sn mudstones to acidic purple soil resulted in a gradual increase in the contents of rapidly available potassium (K), slowly available K, and total K. Specifically, after an 80-day incubation period, the proportion of soil available K to total K increased from 1.58% to 1.76%, 1.88%, and 2.08% with the addition of 2%, 5%, and 10% J2s mudstone, respectively. In comparison, the addition of J3sn mudstone at the same rates led to a more significant increase in the proportion of available K to total K, reaching 1.91%, 2.01%, and 2.24%, respectively. (3) The addition of purple mudstones did not significantly increase the content of total heavy metals (Cu, Zn, Ni, Pb, Cd) in soil, but it significantly decreased the available heavy metal content in proportion to the total content. This reduction was more pronounced with the addition of J3sn mudstone compared to J2s mudstone, indicating its superior passivation effects on heavy metals in acidic purple soil. 【Conclusion】Given the widespread availability, cost-effectiveness, ease of crushing, and convenience of application of calcareous purple rocks in regions where purple parent rocks are naturally exposed, they offer a practical solution for improving acidic purple soil. It is recommended that, under field conditions, 15~45 tons per ha of J3sn mudstone or 75~120 tons per ha of J2s mudstone should be applied to ameliorate acidic purple soil. By leveraging these mudstones, farmers and land managers can efficiently ameliorate acidic purple soil, thereby promoting soil health, crop yield, and overall ecosystem resilience.
-
Effects of Changes in Organic Matter Distribution in Lake Sediments on Microbial Community Structure
ZENG Aoqi, NIE Xiaodong, LIAO Wenfei, LIAO Shanshan, RAN Fengwei, LIU Yi, LI Zhongwu
DOI: 10.11766/trxb202311200488
Abstract:
【Objective】Microorganisms play an important role in the biogeochemical cycle of lake ecosystems and are important factors affecting the long-term sequestration of organic carbon in lakes. However, the current understanding of the distribution of sediment microbial communities and their impact on carbon dynamics is still insufficient. 【Method】In this study, we used high-throughput sequencing to analyze the distribution pattern of microbial communities in sediments of west Dongting Lake. Combined with geochemical parameters such as sediment mechanical composition, total organic carbon, and molecular composition of organic matter, we analyzed the influence of environmental factors on microbial community structure and explored the key factors regulating the structure of sediment microbial communities. 【Result】Significant differences in microbial community structures were observed among different sediment layers (Bacteria: R2 = 0.542, P < 0.001; Fungi: R2 = 0.430, P < 0.001). On the one hand, from the shallow layer (0~20 cm) to the deep layer (50~100 cm), the relative abundance of copiotrophic microorganisms (e.g., Proteobacteria) in the sediments significantly decreased while the relative abundance of oligotrophic microorganisms (e.g., Chloroflexi) significantly increased. On the other hand, the abundance of the main functional groups of microorganisms changed significantly with increasing sediment depth. In particular, the functions related to aerobic chemoheterotroph and aerobic ammonia oxidation were significantly more abundant in the shallow sediment than in the subsurface (20~50 cm) and deep layers. The differential distribution of microbial communities in sediments is mainly influenced by changes in organic matter content (Bacteria: R2 = 0.532, P < 0.001; Fungi: R2 = 0.534, P < 0.001). Our result also revealed that the content of total organic carbon significantly affected the abundance changes of various microbial taxa including Proteobacteria, Chloroflexi, Actinobacteria, Basidiomycota, and Glomeromycota, explaining 76.2% (P < 0.001) and 58.2% (P < 0.01) of the variation in bacterial and fungal community structures, respectively. 【Conclusion】The variation in the distribution of organic matter was the main reason for the differences in microbial community structure in different sedimentary layers. Thus, this study reveals the role and feedback mechanism of microorganisms in lake ecosystems and is of great significance for exploring the evolution and stability of lake ecosystems.
-
Effect of Shewanella putrefaciens CN32 and Geobacter sulfurreducens PCA Co-culture on Mercury Transformation Mediated by Dissolved Organic Matter
SONG En, WANG Yuncheng, JIANG Yangzhao, ZHAO Haoyu, HU Dafu, HU Yujie, BIAN Yongrong, YANG Xinglun, YE Mao, JIANG Xin
DOI: 10.11766/trxb202402030060
Abstract:
【Objective】A variety of dissolved organic matter (DOM) and microorganisms affect mercury transformation under anaerobic conditions by mediating biogeochemical cycles. However, it is still unclear how specific organic matter would affect mercury transformation under this condition.【Method】Using batch experiments, the effect of DOM and the co-culture of microorganisms on mercury transformation were investigated. Under simulated the anaerobic environment, three kinds of DOM (cysteine and glutathione containing sulfhydryl and fulvic acid) and two kinds of bacteria (Shewanella putrefaciens CN32 and Geobacter sulfurreducens PCA) were selected to create a reduction environment and methylated mercury, respectively. Batch experiments were carried out to investigate the effect of DOM and the co-culture of microorganisms on mercury transformation.【Result】The results showed that the unit cell adsorption/uptake capacity of G. sulfurreducens PCA for Hg(Ⅱ) was 69.0% of that of S. putrefaciens CN32. Cysteine and glutathione did not alter the proportion of intracellular mercury in G. sulfurreducens PCA, but the proportion of intracellular mercury in S. putrefaciens CN32 was decreased. In the culture of G. sulfurreducens PCA, cysteine promoted mercury reduction and methylation, glutathione promoted mercury reduction, and fulvic acid inhibited mercury reduction and methylation. In the co-culture system of S. putrefaciens CN32 and G. sulfurreducens PCA, the mercury methylation ratio was as high as 18.7%±3.1% after the addition of cysteine complexed mercury, which was mainly attributed to the enhancement of Hg methylation of G. sulfurreducens PCA by microbial co-culture.【Conclusion】The results of this study elucidate the mechanism of DOM and co-culture of microorganisms on mercury species transformation in anaerobic condition, and provide a theoretical basis for the remediation of mercury pollution in flooded paddy field wetland.
-
The Spatial Distribution of Particulate Organic Matter within Aggregates of Shajiang black Soil under Various Straw Return Practices Based on X-ray CT Technology and Machine Learning
DING Tianyu, GUO Zichun, WANG Yuekai, JIANG Fahui, ZHANG Ping, PENG Xinhua
DOI: 10.11766/trxb202401310052
Abstract:
【Objective】 Protection of particulate organic matter (POM) within soil aggregates has been recognized to be one of the principal mechanisms of C sequestration in soil. The low soil organic carbon (SOC) content of Shajiang black soil is a major factor for limiting crop yields in the Huaibei plain. Increasing SOC sequestration by returning crop residues to the field has been recommended. No-tillage (NT), rotary tillage (RT), and deep tillage (DT) with straw return (S) are commonly implemented. The objective of this study was to evaluate the spatial distribution of POM within aggregates in Shajiang black soil under various straw return practices. 【Method】The six-year field experiment was conducted using X-ray CT technology and machine learning. The soil aggregates (6-8 mm in diameter) were collected from depths of 0-10, 10-20, and 20-40 cm. POM is divided into two parts: fresh residue and old POM, based on its morphological characteristics. 【Results】Overall, the POM within aggregates was primarily composed of fresh residues, comprising 76.4% to 87.0% across various soil layers under three different straw return practices. The distribution ratio of fresh residues in connected pores ranged from 0.266 to 0.788, while the distribution ratio of old POM varied between 0.177 and 0.569. There was a substantial quantity of POM was distributed within aggregates under NTS treatment in the 0-10 cm soil layer. Fresh residues and old POM were primarily distributed in the connected pores, with the proportions of 0.788 and 0.569, respectively. In the 20-40 cm soil layer, POM volume density within aggregates was highest under DPS treatment among all the treatments. Specifically, the proportions of fresh residue and aged POM distributed in the connected pores were 0.729 and 0.536, respectively. In comparison to the RTS treatment, the NTS led to a significant change in both the total POM volume density and fresh residue volume density by 54.4% and 56.7% within the 0-10 cm soil layer (P < 0.05), respectively. Additionally, the NTS treatment resulted in a 25.5% increase in the proportion of fresh residues in connected pores and a remarkable 96.4% increase in its volume density (P < 0.05). Furthermore, the DPS treatment resulted in a reduction of 37.4% in total POM and 40.4% in fresh residue volume density within the 0-10 cm soil layer (P < 0.05). However, there were no significant differences observed in the total POM volume density, porosity (>16 μm), or connected porosity of the aggregates among the NTS, RTS and DPS treatments within the 10-20 cm soil layer (P > 0.05). Compared with the RTS, the DPS treatment led to a significant increase in the total POM volume density by 2.78 times within the 20-40 cm soil layer, with the fresh residue and old POM volume density increasing by 3.10 and 1.72 times (P < 0.05), respectively. Additionally, the DPS treatment significantly increased the porosity of aggregates (>16 μm) and connected porosity by 74.2% and 142.8% within the 20-40 cm soil layer (P < 0.05), while it increased the fresh residue volume density and old POM volume density in the connected pores by 9.41 times and 7.96 times (P < 0.05), respectively. 【Conclusion】 The substantial increase in POM volume density within aggregates primarily stems from a significant rise in fresh residue volume density observed in the topsoil (0-10 cm) under no-tillage, as well as in the deeper soil (20-40 cm) following deep ploughing with straw incorporation. Connected pores serve as pivotal reservoirs for the storage and transformation of fresh residue through decomposition processes. Our findings suggest that deep tillage promotes the formation of connected pores and POM accumulation in the deeper soil layers, which is significant for improving agricultural soil quality and soil carbon sequestration in Shajiang black soil.
-
Lettuce Foliar Uptake of Heavy Metals Directly from the Deposition of Atmospheric Particulate Matter Emitted from Coal Combustion
LIU Xin, TONG Xin, CHEN Zhihuai, ZHANG Tingting, GUO Haohua, LUO Xiaosan
DOI: 10.11766/trxb202401290047
Abstract:
【Objective】The combustion of fossil fuels such as coal emits a large amount of particulate matter and heavy metals into the atmosphere, which are then significant sources of input into the agricultural environment by dry and wet deposition. These pollutants will directly influence crop growth and heavy metal accumulation, and indirectly threaten human health through the food chain. Atmospheric particulate matter rich in heavy metals can enter the plant through two pathways: deposition into the soil followed by root absorption or direct foliar uptake of dry deposition on the crop leaf surface. However, the respective proportions and specific mechanisms of these pathways remain elusive. 【Method】An open-side (covered with fine particulate matter filter membranes) transparent chamber was designed for vegetable pot experiments, simulating the actual dry deposition flux of atmospheric particulate matter in diverse coal-burning regions. This quantitative study systematically compared the effects of fly ash from two representative coal-fired power plants in southern and northern China on lettuce (Lactuca sativa L.) growth and the leaf accumulation of typical heavy metals through deposition into soil and leaf surface, respectively. 【Result】The results indicated that atmospheric deposition is a significant source of Cd, Pb, Cr, and As in crops. The heavy metal contents in lettuce leaves increased with the fly ash deposition. The proportion of deposited Cd accumulated by the edible above-ground parts of lettuce through the foliar uptake is 40.9%-84.2% and the proportion of Pb can be 62.3%-85.6%. This indicates that direct foliar uptake is the main pathway for lettuce leaf accumulation of Cd and Pb in atmospheric particulate matter, especially for metals with high content (Pb) or bioavailability (Cd) in particulates, and if the amount of particle deposition does not exceed the foliar uptake capacity. However, when the atmospheric deposition flux is high or the bioavailability is low, heavy metals such as As in particulate matter are mainly accumulated by leaves through the traditional pathway of soil-root migration, absorption, and transport. Because of the higher contents of most heavy metals and stronger bioavailability in the soil-lettuce system, the southern fly ash induced higher accumulation of heavy metals by the leaf, and stronger toxic effects translated to lower photosynthetic activity and less biomass.【Conclusion】Consequently, comprehensive pollution control measures such as source prevention and reduction of heavy metal deposition input from the emissions of atmospheric particulate matter like coal combustion, as well as suppression of leaf dust retention, are of great environmental and health significance for ensuring crop growth and the quality and safety of leafy vegetables in coal burning areas.
-
Role of a Highly-Efficient Plant Growth-Promoting Bacterium in Decreasing Cd Uptake of Wheat Plant in Cd-contaminated Weakly Alkaline Arable Soils
FENG Hai, ZHANG Qiangbing, WANG Qi, WU Hongsheng, CHENG Cheng
DOI: 10.11766/trxb202402170070
Abstract:
【Objective】The safe utilization of farmland with mild to moderate cadmium (Cd) pollution is of great significance for the safety of agricultural products and human health. However, the effects of plant growth-promoting bacteria with the ability to immobilize Cd and regulate Cd-uptake by wheat plant from weakly alkaline farmland soil remains unexploited.【Method】Triticum aestivum L. Yangmai-13 was used as the tested plant, and weakly alkaline heavy metal polluted farmland soil was used as the test soil. Pot experiments were conducted to study the dynamic effects of Pseudomonas taiwanensis WRS8 on wheat growth, Cd content in rhizosphere soil and different parts of wheat, as well as rhizospheric and root endophytic bacterial communities during the jointing, booting, and maturity stages.【Result】The results showed that compared to the control group without inoculation, rhizosphere inoculation with strain WRS8 led to a significant increase in the aboveground biomass, root biomass, and grain weight of Yangmai 13 by 34% - 64%, 60% - 102%, and 10% - 14%, respectively. It decreased the Cd content in shoots, roots, grains, and rhizosphere soil by 55% - 60%, 5% - 8%, 78% - 82%, and 32% - 49%. Moreover, inoculation with strain WRS8 significantly increased the pH value of the rhizosphere soil during the booting and maturity stages. In terms of rhizospheric and root endophytic bacterial communities, inoculation with strain WRS8 only resulted in a significant reduction in the alpha diversity index of endophytic bacterial communities during the booting stage; The principal co-ordinates analysis clustering results showed that both the treatment with live and inactivated bacteria significantly changed the bacterial community structure in the rhizosphere soil and roots, and the bacterial community structure also changed significantly with the extension of the growth period. Inoculating strain WRS8 reduced the relative abundances of Chloroflexi and Proteobacteria in the rhizosphere soil, while increasing the relative abundance of Arthrobacter and Bacillus. Also, strain WRS8 inoculation reduced the relative abundances of Actinobacteria and Chloroflexi phyla of root endophytic bacterial communities, while increasing the relative abundance of Pseudomonas during the jointing and booting stages.【Conclusion】In summary, strain WRS8 not only significantly reduced the absorption of Cd by Yangmai 13 from weakly alkaline farmland soil, but also effectively improves wheat biomass and yield, suggesting its potential to achieve safe utilization of weakly alkaline heavy metal polluted farmland.
-
Effects of Long-term Nitrogen Application on the Soil Ammonifier and Nitrogen Mineralization
LIU Lingzhi, GUO Bingqing, WANG Feng†, MENG Ao, LIANG Minjie, AN Tingting, WANG Jingkuan
DOI: 10.11766/trxb202310310445
Abstract:
【Objective】Ammoniation is the process by which microorganisms convert organic nitrogen into inorganic nitrogen, which can improve soil nitrogen supply. Under different long-term fertilizer application scenarios, soil organic nitrogen undergoes significant changes, which makes comprehension of its ammonification process challenging. 【Method】This study relied on a 29-year long-term targeted fertilization experiment at Shenyang Agricultural University, targeting four different fertilization treatments, including no fertilization (CK), chemical fertilizer (HCF), chemical fertilizer reduction (LCF), and fertilizer reduction combined with organic fertilizer (CMF), considering three soil depths (0-20 cm, 20-40 cm, and 40-60 cm), and three sampling period (pre-planting, maize tasseling stage and post-harvest). Using the real-time fluorescence quantitative PCR (qPCR) method, the abundance, activity, and nitrogen mineralization changes of soil ammonification gene gdh in different soil layers were studied during maize growth period after long-term different fertilization treatments. Also, the effects of fertilization, season, soil depth, and their interactions on ammonifier and soil net nitrogen mineralization rate were evaluated. 【Result】The results showed that: 1) Compared with soil layer and fertilization treatment, the sampling period had the most significant impact on the abundance and activity of gdh genes. During the three sampling periods, the soil gdh gene activity and net nitrogen mineralization rate during the maize tasseling stage were significantly higher than pre-planting and post-harvest (P < 0.05); 2) Compared with no fertilization (CK), long-term application of chemical fertilizers (LCF and HCF) significantly increased soil nitrogen mineralization rate during the tasseling period (P < 0.05) while reduction of fertilizer combined with organic fertilizer (CMF) showed stable or increased soil nitrogen mineralization rate in post-harvest; 3) The abundance and activity of ammonifiers were significantly positively correlated with soil net nitrogen mineralization rate, and the ammonium nitrate ratio was an important factor affecting ammonifiers (P < 0.01). 【Conclusion】In summary, nitrogen application, and crop absorption change the soil ammonium nitrate ratio, causing differences in the abundance and activity of soil ammonifiers. This led to changes in soil nitrogen mineralization rate. Long-term application of LCF and HCF is beneficial for increasing the rate of surface soil nitrogen mineralization in pre-planting and tasseling. CMF can help stabilize the activity of soil ammonifiers in post-harvest and promote the ammonification process of soil organic nitrogen.
-
Effects of Short-term and Long-term Nitrogen and Phosphorus Additions on Microbial Necromass Accumulation Coefficients in Meadow Soils of the Qinghai-Tibet Plateau
LI Yifan, SHI Biwan, YANG Zhiying, GAO Wenjing, MA Tian, ZHU Jianxiao, HE Jinsheng
DOI: 10.11766/trxb202401090018
Abstract:
【Objective】Microbes and their necromass play a key role in the accumulation and long-term sequestration of soil organic carbon (SOC). Moreover, continuous increases in nitrogen (N) and phosphorus (P) inputs can significantly affect microbe-mediated SOC accumulation processes. The microbial necromass accumulation coefficient (NAC), which quantifies the accumulation of microbial necromass per unit of microbial biomass, plays a key role in assessing the efficiency of microbial necromass accumulation. However, the influence of short-term and long-term additions of N and P on this coefficient within meadow ecosystems remains unclear. This study focused on investigating the differential responses of NAC to (1) short-term and long-term N and P additions and (2) additions of N and P across different soil layers. 【Method】To explore the response of NAC to N and P additions, this study analyzed soil samples from the meadow on the Qinghai-Tibet Plateau subjected to 1 year (short-term) and 10 years (long-term) of N and P additions. It was measured the soil microbial necromass carbon (MNC) and the soil microbial biomass carbon (MBC), and calculated the value of NAC. Additionally, considering other environmental factors including soil physical and chemical properties, microbial extracellular enzyme activities, and plant biomass, the main influencing factors of NAC were identified. 【Result】The results showed that after short-term N and P additions, the NAC values in the 0-10 cm and 20-30 cm soil layers were 31.33±2.97 (mean±SE) and 38.12±3.90, respectively, and N and P additions had no significant effect on NAC (P>0.05). After long-term additions of N and P, the NAC values in the 0-10 cm and 20-30 cm soil layers were 14.46±1.12 and 17.49±3.22, respectively; and the additions of N and P significantly reduced the NAC in the 20-30 cm layer (P<0.05). The results of the Random Forest indicated that pH was the most important factor affecting NAC, and the correlation analysis revealed a significant positive relationship between soil pH and NAC. Moreover, the long-term N addition, P addition and simultaneous addition of N and P significantly reduced the pH of the 20-30 cm soil layer. These findings suggest that the decrease in soil pH due to long-term N and P supplementation is the main cause of the reduction in NAC. The lowered soil pH may lead to the dissolution of minerals, thereby reducing the mineral protection of MNC, making it more susceptible to decomposition, ultimately decreasing the NAC of microorganisms. 【Conclusion】In summary, changes in pH resulting from long-term nutrient additions dominated the changes in NAC. In the context of ongoing increases in N and P deposition, it is advisable to closely monitor changes in soil pH and implement timely measures to maintain the stability of SOC. This study explores the differential responses of NAC to N and P additions and their influencing factors, providing data support for understanding microbial-mediated carbon accumulation under the context of increasing N and P deposition.
-
Effects of AM Fungi on Soil Extracellular Enzyme Activities Under the Background of Winter Snow Changes in a Desert Ecosystem
XUE Hui, YANG Rong, QIN Wenhao, DONG Qianqian, JI Zhanquan, JIA Yangyang
DOI: 10.11766/trxb202310300444
Abstract:
【Objective】Soil extracellular enzymes, as the catalysts of soil biochemical reactions, directly drive soil element cycling and energy flow processes and play indispensable roles in the biogeochemical cycling of carbon, nitrogen, and phosphorus in desert ecosystems. Winter snow is a key climatic factor regulating soil element cycling. Soil extracellular enzyme activities respond sensitively to the changes in winter snow cover and the relatively stable hydrothermal conditions highly alter soil extracellular enzyme activities under the winter snow cover. Thus, changes in the winter snow cover will trigger fluctuations in soil extracellular enzyme activities, significantly influencing the nutrient cycling processes in desert ecosystems which are water-scarce and nutrient-poor.【Method】In order to investigate the effects of winter snow cover changes and arbuscular mycorrhiza (AM) fungi on soil enzyme activities in the Gurbantunggut Desert under the background of a “warm and humid” trend, we conducted a long-term field experiment simulating winter snow cover changes and in situ inhibition of AM fungal activities with a split-area randomized block experimental design. The following treatments were adopted; for the primary zone, the control (40 mm water increase, W) and an AM-inhibition treatment (40 mm water increase with the addition of benomyl, BW); for the subplot zone, including three levels, 100 % snow cover increase (+S), natural snowfall (CK), and 100 % snow cover decrease (-S). Soil samples were collected from 0-10 and 10-20 cm soil layers, soil physicochemical properties, and soil enzyme activities which are related to soil carbon, nitrogen, and phosphorus cycling were determined to uncover the effects of AM fungi on soil enzyme activities and microbial metabolism limitation under the background of winter snow cover changes in the desert ecosystem.【Result】(1) AM fungi significantly increased the aboveground net primary productivity of plant community, decreased the content of soil available phosphorus and ammonium nitrogen, but increased the content of soil organic carbon. The activities of soil enzymes related to soil carbon, nitrogen, and phosphorus cyclings were decreased under the natural snow cover and increased snow cover in the AM fungi treatments. In contrast, AM fungi treatments increased the activities of soil enzymes which are related to the soil carbon and nitrogen cyclings under decreased snow cover. (2) Based on the vector analyses, our results indicated that soil microbial activities were co-limited by soil carbon and phosphorus in desert ecosystems. Furthermore, we found that AM fungi decreased soil microbial carbon limitation under the natural snow cover and increased snow cover treatments, but there was no consistent pattern in the effects of AM fungi on soil microbial carbon and phosphorus limitation under the decreased snow cover treatment.【Conclusion】AM fungi play an important role in promoting plant available phosphorus and ammonium nitrogen uptake, enhance soil enzyme activities which are related to soil carbon and nitrogen cyclings, and alleviate soil microbial carbon limitation in desert soils under the background of winter snow cover changes. Importantly, our results revealed the effects of winter snow cover changes and AM fungi on soil extracellular enzyme activities and soil microbial metabolism limitation. This contribution will provide a reference in the understanding of belowground ecological processes and feedbacks, and a scientific basis for the protection and ecological restoration constructions for desert ecosystems in the future.
-
Spatial Distribution of the Buried Depth and Thickness of Albic Soil Albic Layer in Sanjiang Plain and Its Influencing Factors
DONG Fangjin, ZHANG Zhongbin, JIANG Fahui, WANG Jianhao, WANG Qiuju, LI Lujun, PENG Xinhua
DOI: 10.11766/trxb202311070459
Abstract:
【Objective】Albic soil is one of the main soil types with low productivity in Northeast China, mainly distributed in Sanjiang Plain. The soil profile is mainly composed of three layers, the black soil layer, the albic layer, and the illuvial layer. The albic layer has the physical characteristics of high bulk density, high strength, and poor aeration and water permeability, which is easily subjected to drought and waterlogging, thus, limiting crop root growth and yield formation. Its buried depth and thickness are closely related to the penetration depth and growth performance of crop roots, which are the key indexes to quantify the productivity of albic soil. However, little is known about the spatial distribution and driving factors of buried depth and thickness of the albic layer in the albic soil in Sanjiang Plain. The objective of this study was to investigate the spatial distribution pattern and driving factors of the buried depth and thickness of the albic layer in the albic soil in Sanjiang Plain. 【Method】Based on classical statistics and geostatistics, the albic soil in the southeast of Sanjiang Plain ( Jidong County, Mishan City, Hulin City, and Baoqing County ) was selected, and the soil profile of 0-60 cm was excavated. The thickness of the black soil layer and the albic layer was read by visual method, and the soils of the black soil layer, and the albic layer were taken for physical and chemical analysis. In addition, the meteorological, topographic, and parent material data of each sample point were collected. A total of 62 sampling points were obtained from 51 sampling points in the field and 11 points in the literature survey. 【Result】 (1) The average buried depth of the albic layer in the albic soil was 23.7 cm, and it gradually increased from southwest to northeast (13-37 cm). The average thickness was 18.5 cm, which gradually increased from southwest to northeast (8 ~ 35 cm), and the buried depth was opposite to the thickness of the albic layer in some local areas. (2) The burial depth of the albic layer was mainly affected by human tillage methods, and plough tillage increased the burial depth of the albic layer. (3) The thickness of the albic layer was negatively correlated with altitude ( r = -0.355, P < 0.01 ), annual average evaporation ( r = -0.441, P < 0.01 ), annual average temperature ( r = -0.273, P < 0.05 ), and clay mineral montmorillonite ( r = -0.432, P < 0.01 ), but positively correlated with annual average precipitation ( r = 0.463, P < 0.01 ), annual average humidity index ( r= 0.461, P < 0.01 ), coarse mineral hydromica ( r = 0.446, P < 0.01 ), and coarse mineral quartz ( r = 0.321, P < 0.05 ). 【Conclusion】 The buried depth of the albic horizon in the Sanjiang Plain is related to tillage methods. The thickness of the albic horizon is mainly affected by meteorological topographic factors and soil minerals, resulting in a spatial distribution pattern of shallow and thin in the southwest and deep and thick in the northeast.
-
Effects of Different Carbon-nitrogen Ratios of Substrate Addition on the Priming Effect of Purple Soil and Its Regulation Mechanism
Huang Chuanxiong, Yao Zhiyuan, Wang Tao, Huang Qishun
DOI: 10.11766/trxb202311240495
Abstract:
【Objective】Exogenous substrate quality (carbon to nitrogen ratio, C/N) can mediate priming effect (PE). However, the effects and regulation mechanism of priming effect under different C/N ratios of substrate addition is still unclear. 【Method】The effects and regulation mechanism of purple soil which was fertilized by crop straw with synthetic fertilizers were explored through an indoor incubation experiment using glucose and ammonium sulfate. 【Result】Positive priming effect during the incubation period was significantly reduced by 87.4 % and 93.7 % when the material C/N was 10 (CN10) compared to the treatments with a C: N of 50 (CN50) and 100 (CN100). CN100 and CN50 treatments significantly increased soil soluble organic carbon (DOC) and microbial carbon (MBC) content but significantly decreased total soluble nitrogen (TDN) content compared to CN10. After 14 and 43 days of incubation, CN100 treatment significantly elevated the activities of cellobiohydrolase (CBH), β-N-acetylglucosaminoglycosidase (NAG), and leucine aminopeptidase (LAP) compared to CN10. Positive PE in the first two weeks was significantly positively correlated with MBC, CBH, NAG, and LAP, and negatively correlated with TDN, (βG+CBH)/(NAG+LAP) (βG, β-glucosidase), and at the end of the incubation, the positive PE was significantly positively correlated with MBC, βG, CBH, NAG, LAP, and (βG+CBH)/(NAG+LAP) and remained negatively correlated with TDN.【Conclusion】Lower C: N substrate addition significantly reduced the positive PE in purple soils and contributed to efficient soil carbon sequestration; Microorganisms responded to changes in the relative effectiveness of nutrients in the soil environment mainly by adjusting the activities of key enzymes, which in turn regulated the PE. This study can provide a theoretical basis for regional development of fertilizer application programs for efficient carbon sequestration, as well as an in-depth understanding of carbon dynamics in agroecosystems and their microbial-driven mechanisms.
-
Effects of Folsomia candida on Soil Microaggregates Under Different Nitrogen Addition
YOU Lelin, ZHANG Tingting, DAI Wencai, XIAO Naichuan, ZHAO Huan, ZHANG Yarong, XIE Jun
DOI: 10.11766/trxb202404080148
Abstract:
【Objective】This study aimed to investigate the impact of different nitrogen fertilizer application rates on the growth and reproduction of Folsomia candida and their effects on soil micro-aggregates.【Method】Soil samples from field experiments with varying nitrogen application rates (N0: 0 kg·hm-2, N90: 90 kg ·hm-2, N180: 180 kg·hm-2, N270: 270 kg·hm-2, N360: 360 kg·hm-2) were cultivated to examine the differences in Folsomia candida reproduction, total body weight, and their effects on soil micro-aggregates over different cultivation periods (28 d, 42 d, 56 d).【Result】The results indicated that nitrogen application significantly affected soil pH, with the N360 treatment showing a decrease of 0.9 pH units compared to the N0 treatment (P < 0.05). The reproduction of Folsomia candida showed significant differences among the nitrogen treatments as the cultivation period extended. After a 56 d cultivation period, the reproduction number in the N0 treatment was 1.10-1.53 times higher than that in the other treatments (P < 0.05). The total biomass of Folsomia candida larvae generally followed the same trend as the reproduction, with the lowest values observed in the N360 treatment across all cultivation periods. Also, Folsomia candida significantly increased the quantity of 0.05-0.01 mm micro-aggregates by 11.3%-48.4% compared to the untreated soil samples, and significantly decreased the quantity of 2-0.25 mm small aggregates by 27.9%- 60.9%, with more pronounced effects as the cultivation period extended (P < 0.05). The mean weight diameter (MWD) and geometric mean diameter (GWD) of soil under all nitrogen treatments were significantly lower than those of the untreated soil samples (P < 0.05).【Conclusion】The growth and reproduction of Folsomia candida were inhibited by nitrogen fertilization, and high densities of Folsomia candida can increase the content of soil micro-aggregates but destroy small aggregates, leading to reduced soil stability. The results of this study will provide a scientific reference for improving soil structure.
-
Peanut/maize Intercropping Promotes Peanut Soil Organic Carbon Sequestration by Increasing Soil Microbial Activity
LI ShiWen, LU JuMeng, HUANG Geng, SHEN Yi, SUN Bo, ZHANG Qin, CHEN Yan
DOI: 10.11766/trxb202312260540
Abstract:
【Objective】Intercropping is an effective strategy for increasing soil carbon (C) sequestration by utilizing farmland biodiversity. The aim of this study was to investigate the contribution of peanut rhizosphere microbes adjacent to maize to soil organic C (SOC) sequestration in an intercropping system. 【Method】Based on the long-term peanut/maize intercropping experimental platform of Jiangsu Academy of Agricultural Sciences, two rows of peanuts and two rows of maize were planted in strips. Ecological test plate (BIOLOG) and gas chromatography were used to analyze the C metabolic ability of maize to adjacent peanuts rhizosphere microbes and the accumulation of microbial necromass C. 【Result】The results showed that compared with peanuts planted far away from maize, peanuts planted adjacent to the maize decreased rhizosphere polyphenol oxidase activity by 19.0%, soil respiration rate by 18.2%, average color change rate (AWCD) by 22%, rhizosphere microbial metabolism of phenolic acids and amino acids by 149.4% and 16.1%, respectively. The total amino sugar ( TAS ) content of peanut rhizosphere soil adjacent to maize was 6.45% higher than that of peanut planted far away from maize, and the content of bacterial necromass C and fungal necromass C was increased, which eventually led to a 12.9% increase in SOC. 【Conclusion】Our study suggests that adjacent maize does not change the soil respiration rate of the peanut rhizosphere, but reduces the activity of SOC decompositiong enzymes in the peanut rhizosphere and enhances the ability of rhizosphere microbes to metabolize a wider range of organic carbon components, thereby increasing SOC by accumulating bacterial and fungal necromass C.
-
Dynamic Changes of Microbial Community Metabolisms Along Soil Profile in Response to Exogenous Carbon and Nitrogen Addition in Mollisols
HU Yaohua, CAI Yuanfeng, CAO Weiwei, JIA Zhongjun
DOI: 10.11766/trxb202402040062
Abstract:
【Objective】 Soil profile is a model system for deciphering the formation and maturation of organic matter-centric fertility. However, the physiological metabolic potential of the soil profile microbial community and the mechanism of its transformation of labile carbon are not clear.【Method】The metabolic mechanisms of soil microbial communities under exogenous carbon and nitrogen input scenarios were investigated by using 13C-labeled glucose and ammonium nitrate to cultivate soils in the surface (0~10 cm), middle (30~40 cm), and deep (90~100 cm) layers of a typical thin-layered black soil. The insoluble organic carbon (13C-SOC) synthesized by microbial growth and reproduction, 13CO2 produced by heterogeneous metabolism, the priming effect, the efficiency of 13C-carbon utilization, and their nitrogen limitation features were determined.【Result】The increase in soil respiration intensity after exogenous 13C-glucose addition was in the order of surface (3.2-fold), middle (11.3-fold), and deep soil (14.5-fold) compared to the control water treatment; the relative priming effect was 43.5%, 150.5%, and 267.0%; carbon utilization efficiency was 34.9%, 37.3%, and 32.9%, respectively. Approximately 45%~50% of glucose was isomerized and metabolized to 13CO2. Also, the number of soil microorganisms increased by about 85.0% in the surface and middle layers and 1.9 times in the deep layer while the 13C-SOC of insoluble cellular biomass synthesized by microorganisms using glucose was 111.6±11.7 mg kg-1 (surface soil), 119.5±3.4 mg kg-1 (middle soil), and 105.2±21.6 mg kg-1 (deep soil). However, the proportion of the total soil organic carbon, in descending order was 0.98% (surface layer) < 1.70% (middle layer) < 4.76% (deep layer). Interestingly, the 13C-SOC tended to increase after nitrogen addition although it was not statistically differentiated, however, it significantly suppressed the relative priming effect. High-throughput sequencing revealed that surface, middle, and deep soil microbial communities clustered independently regardless of carbon and nitrogen treatments under glucose addition conditions. Micrococcaceae were significantly increased in the surface soil and were probably the main contributor of organic carbon from insoluble microbial sources whereas Nocardioides were the main contributors of organic carbon from microbial sources in the middle and deep soil.【Conclusion】These results suggest that the deep soil, despite its lower diversity and abundance, can utilize exogenous and readily decomposable organic carbon to rapidly colonize and produce insoluble organic carbon of microbial origin and its total new carbon inputs were almost identical to those of the surface soil. Soil microbial communities in black soil profiles developed strong functional plasticity during long-term adaptation to geo-climatic variability, which provides an important basis for the stability of soil ecosystem structures and functions.
-
Phosphorus Speciation Characteristics of Typical Artificial Vegetation Rhizosphere Soil in Mu Us Sandy Land
HAN Chaoqun, WANG Jiao, ZHAO Chunlei, SHAO Ming’an
DOI: 10.11766/trxb202403290141
Abstract:
【Objective】Artificial vegetation plays an important role in the restoration of the ecosystem in Mu Us Sandy Land. Understanding the phosphorus (P) forms in the rhizosphere and bulk soils of typical artificial vegetation can provide a basis for scientific vegetation construction in the area. 【Method】The rhizosphere soil and bulk soil of seven typical artificial vegetations (Pinus sylvestris, Populus simonii, Amygdalus pedunculata, Amorpha fruticosa, Salix psammophila, Sabina vulgaris, and Artemisia ordosica) in Mu Us Sandy Land were collected and the phosphorus content of different forms were subsequently determined using Jiang-Gu phosphorus fractionation method. 【Result】The results showed that 1) The total phosphorus (TP) content of Salix psammophila rhizosphere soil was significantly higher than that of other vegetation types while Populus simonii, Amygdalus pedunculata, and Artemisia ordosica increased available phosphorus (AP) content in rhizosphere soil. This indicates that planting Populus simonii and the other 3 vegetation types was beneficial for P activation. 2) The Ca8-P content in rhizosphere soil of Pinus sylvestris, Amygdalus pedunculata, Amorpha fruticosa, and Salix psammophila was lower than in the bulk soil. The decrease in Al-P and Fe-P in Amorpha fruticose rhizosphere soil was the largest, and the difference in Ca10-P content between rhizosphere and bulk soil was the smallest in Salix psammophila. 【Conclusion】Al-P and Fe-P showed a significant positive correlation with AP in most vegetation rhizosphere soils and were the main forms involved in soil P transformation. This study provides scientific evidence and directives for the management and planting pattern layout of plantations to promote sustainable P management.
-
Effects of Shrub Encroachment on Soil Carbon Pool and Soil Microbial Community Structure in Alpine Grassland
TENZING Droma, MA Wenming, MA Xiangli, MU Xianrun
DOI: 10.11766/trxb202310260437
Abstract:
【Objective】With global climate change and overgrazing, shrub encroachment is extensively occurring in global grasslands. However, relatively little is known about how the structure of bacterial communities shifts with shrub encroachment. Thus, considering the aboveground plant community, soil carbon chemical composition, soil bacterial community structure and network beneath the canopies of three typical shrub species (Potentilla fruticosa, Spiraea alpina, and Caragana microphylla) as well as in adjacent grassland (as a control), the effects of shrub encroachment on the structure of soil bacterial communities and soil carbon pools were explored.【Method】16S rRNA gene sequencing was used to investigate the bacterial communities and co-occurrence features among bacterial taxa while Fourier transform infrared spectroscopy (FTIR) was conducted to assess the soil organic carbon (SOC) chemical composition.【Result】Shrub encroached grasslands (Potentilla fruticosa and Caragana microphylla) showed significant changes in aboveground plant community composition (P < 0.01) while the aboveground plant community diversity and richness remained constant (P > 0.05). The biomass of the three shrub plots was significantly higher than that of grassland (P < 0.05) whereas underground biomass showed no significant difference (P > 0.05). Shrub encroachment had no significant effects on SOC and total nitrogen (TN) contents, but weakened the differences of SOC contents between top- and subsoils, as shown by significantly higher SOC contents in the topsoil of the grassland than in its subsoil (P < 0.05), with no such trend in the three shrub plots.The SOC chemical composition in both top- and subsoils of the three shrublands and grassland was dominated by aromatics (except for deep soil in Caragana microphylla plots), with no significant difference in aromatic content between shrub and grassland plots (P > 0.05). However, the Caragana microphylla plots exhibited a surface-aggregated distribution of aromatics (P < 0.05). Random forest model analysis revealed that the distribution of Acidobacteria and Actinobacteria was the most important predictor of shrub encroachment in top and subsoils (P < 0.01). According to Non-metric multidimensional scaling (NMDS) analysis, the bacterial community composition of alpine grassland was significantly altered by shrub encroachment. Moreover, plant community composition and SOC chemical compositions were the main explanatory factors affecting bacteria community composition in both depths. Functional prediction analysis identified four biological metabolic pathways, including cellular processes, environmental information processing, metabolism, and genetic information processing, with metabolism being enriched in shrub plots (P < 0.05). Based on topological parameters of total links, complexity, and natural connectivity, the results showed that the soil bacterial network of shrublands was more complicated and stabilized than that in grasslands, and mutualism or commensalism may play an important role in establishing the bacterial community structure. 【Conclusion】In summary, the results of this study suggest that shrub encroachment had an important regulatory effect on soil bacterial community structure and soil carbon pool. The results enrich the literature on soil microbial community in alpine grassland and provide a theoretical basis for the effect of soil carbon source and sink in alpine grassland.
-
Isolation, Identification, and Characteristics of Autotrophic Nitrogen-fixing Bacteria in Vegetation Concrete Under Freeze-thaw Conditions
LIU Daxiang, XU Zhihai, GAO Xian, XU Boyang, ZHENG Wei, XIA Dong, XU Wennian, YANG Yueshu
DOI: 10.11766/trxb202312110525
Abstract:
【Objective】This study aimed to isolate and identify autotrophic nitrogen-fixing bacteria in vegetation concrete under freeze-thaw conditions and to investigate their effects on the physical and chemical properties of vegetation concrete and the growth of ryegrass. 【Method】Autotrophic nitrogen-fixing bacteria GDJ-1 and GDJ-2 were isolated from vegetation concrete that had experienced multiple freeze-thaw cycles by selective nitrogen fixation medium. The strains were identified by morphological, physiological, and biochemical characteristics, 16S rDNA, and phylogenetic analysis. The effects of target strains on physicochemical indexes of vegetation concrete and the growth of ryegrass were explored. 【Result】Strain GDJ-1 was identified as Microbacterium proteolyticum, a Gram-positive bacterium with a round yellow colony. The strain GDJ-1 did not produce oxidase but was capable of producing catalase and it could not degrade gelatin or hydrolyze starch. This bacterium exhibited favorable growth under pH levels that ranged from 7 to 9 and in the presence of sodium chloride (NaCl) concentrations between 0.5% and 2%. After treatment with GDJ-1, the aboveground fresh biomass, aboveground dry biomass, belowground fresh biomass, and belowground dry biomass of ryegrass increased by 29.09%, 5.05%, 13.40%, and 16.40%, respectively, compared with the control group. The contents of organic matter, total nitrogen, alkali-hydrolyzed nitrogen, and available phosphorus in vegetation concrete were increased, and the increase of alkali-hydrolyzed nitrogen was 62.95%. Furthermore, strain GDJ-2 was Ralstonia pickettii, a Gram-negative bacterium with a round beige colony. The strain GDJ-2 produced oxidase but did not produce catalase, and was capable of hydrolyzing gelatin and starch. It exhibited favorable growth under conditions with a pH range of 7 to 9 and a sodium chloride (NaCl) concentration of 0.5% to 2%. After treatment with GDJ-2, the aboveground fresh biomass, aboveground dry biomass, belowground fresh biomass, and belowground dry biomass increased by 35.71%, 4.93%, 46.38%, and 13.79%, respectively, compared with the control group. The contents of organic matter, total nitrogen, alkali-hydrolyzed nitrogen, and available phosphorus in vegetation concrete were increased, and the increase of available phosphorus reached 35.73%.【Conclusion】There were great differences in morphology and enzyme metabolism between the two strains, but both were capable of enhancing the nutrient condition of vegetation concrete and promoting the growth of ryegrass. In the ecological restoration of vegetation concrete, autotrophic nitrogen-fixing bacteria GDJ-1 and GDJ-2 displayed application potential. GDJ-1 possessed a robust nitrogen fixation ability, effectively converting nutrients in the soil, which was more suitable for regions where the soil was poor or lacking nutrients. However, GDJ-2 demonstrated superior environmental adaptability, especially exhibiting heightened tolerance to alkaline environments, making it more fitting for regions with stringent conditions such as saline-alkaline soils. Considering the necessity for nutrient balance in actual engineering projects, further research can be conducted on freeze-thaw tolerant indigenous phosphate-solubilizing, potassium-releasing, and cellulose-decomposing bacteria, to develop a composite bio-agent tailored for vegetation concrete ecological restoration in freeze-thaw areas.
-
Effects of Bacterial Residue Organic Fertilizer on Tomato Growth and Soil Antibiotic Resistance Genes Accumulation
CUI Gege, ZHANG Yaozhong, YANG Tianjie†, WANG Shimei, HUANG Yishuo, XU Yangchun, SHEN Qirong
DOI: 10.11766/trxb202402180072
Abstract:
【Objective】Bacterial residue is a solid waste produced during the fermentation process of antibiotic synthesis intermediate (6-aminopenicillanic acid). Improper treatment will endanger environmental safety and increase the risk of the spread of antibiotic resistance genes (ARGs). At present, composting is the main method for treating residues due to its harmless and resourceful characteristics. Thus this study was designed to investigate the effects of composted bacterial residue organic fertilizer on tomato growth and soil ARGs accumulation and to assess the ecological risks of residue organic fertilizer. 【Method】In a field experiment, the tomato plant was used as the research object and the effects of organic fertilizer fermented from bacterial residue of penicillin synthesis intermediates on tomato growth, soil physicochemical properties, bacterial community structure, and the diversity and abundance of antibiotic resistance genes were analyzed【Result】The results showed that the application of residue organic fertilizer can increase the aboveground dry biomass of tomatoes in the field, and continuous application for two seasons can increase the vitamin C content of tomato fruits and soil nitrate nitrogen content. After being treated with organic fertilizer, there was no significant change in the diversity of bacterial communities in the rhizosphere soil. However, compared with conventional fertilization, the abundance of Proteobacteria significantly increased, while the abundance of Chloroflexi significantly decreased. There was no significant change in the diversity of ARGs in tomato soil after the application of residue organic fertilizer, but the amino glycoside resistance gene aada1 and sulfonamide resistance gene sul (II) were significantly higher than those in conventional compound fertilizer treatment. Also Luteimonas sp. was positively correlated with tetracycline, aminoglycoside, and sulfonamide resistance genes. 【Conclusion】After applying microbial residue organic fertilizer in tomato rhizosphere soil, there was no enrichment of β-lactam ARGs. However the risk of accumulation of tetracycline, aminoglycoside, and sulfonamide ARGs in rhizosphere microorganisms needs further evaluation.
-
Mechanisms of Mn-modified Biochar to Mediate Inorganic Arsenic Speciation in the Soil-Solution System
HUANG Qin, TONG Fei, WANG Bo, DU Xiaofei, FAN Guangping, LIU Lizhu, ZHANG Mingchao, QIU Yige, GAO Yan
DOI: 10.11766/trxb202401030007
Abstract:
【Objective】The reductive release of arsenic (As) from paddy soils can be enhanced under waterlogged conditions. This study aimed to investigate the mechanisms of Mn-modified biochar (MBC), with high oxidation and adsorption capacity, on inhibiting As release in the waterlogged paddy soil microcosms and to reveal the potential pathways of mediating As transformation and speciation in soil solution and soil. 【Method】This study determined changes in the basic properties of soil solution, soil, and biochar through mixed or separate incubation of biochar and flooded soil. 【Result】The results showed that, compared with the control and unmodified biochar, MBC significantly promoted the oxidation of As(III) to As(V) in the soil solution, keeping a low concentration of As(III) (0.02-0.88 mg?L-1) throughout the incubation period. The Mn released from MBC into the soil solution was readily precipitated with As(V). Also, the MBC containing rich pore structure and oxygen-containing functional groups would promote its adsorption for more inorganic arsenic (iAs). MBC showed greater affinity for Fe (3.12 mg?g-1 of Fe was adsorbed on MBC after 28 d), leading to a significant decrease of Fe concentrations in the soil solution (P < 0.05) and enhanced the adsorption of iAs on the solid-phase. The reduction of Mn-oxides on MBC increased the pH (0.08-0.22 pH units) of the soil solution, which further promoted the precipitation of Fe on the solid phase thereby strengthening its adsorption for iAs. As a result, the concentration of iAs extracted from the MBC was 12 times higher than that of the unmodified biochar after incubation of 28 d. The high oxidative properties of MBC inhibited the reductive dissolution of Fe minerals, thereby significantly reducing the soil-available Fe and As concentrations (P < 0.05). This led to the transformation of soil available As to iron-manganese bound and residual fraction As. As a result, the soil available As was stabilized under a lower range of concentrations. 【Conclusion】Generally, the addition of MBC to waterlogged paddy soil can inhibit the release of iAs from the solid phase and promote the transformation of mobile iAs into more stable forms in the soil, resulting in a significant reduction in arsenic mobility and toxicity in waterlogged paddy soil.
-
Effect and Mechanism of Food Waste Compost on the Stability of Paddy Soil Aggregates
DOI: 10.11766/trxb202402240077
Abstract:
【Objective】 Food waste composting is one of the potential directions of food waste resource utilization. Food waste compost is rich in organic matter and salt, and its impact on soil aggregates is still unclear. Exploring the influence of food waste compost application on the stability of paddy soil aggregates and its mechanism can provide references for agricultural utilization of food waste compost. 【Method】 Six treatments were set up in this study: No fertilizer (CK), Chemical fertilizer (F), Food waste fresh compost (FC), Food waste aged compost (AC), Chicken manure organic fertilizer (CM), Pig manure organic fertilizer (PM), The effects of these treatments and the influence of food waste compost on the stability of soil aggregates and soil surface electrochemical parameters were investigated. Correlation analysis and redundancy analysis (RDA) were used to investigate the main factors affecting the stability of aggregates. 【Result】 The results showed that: (1) Food waste compost enhanced the water stability of paddy soil aggregates, and reduced the slaking and differential swelling effects. Also, the MWDYoder, MWDLB-fast, and MWDLB-slow of AC were 21.4%, 107.8%, and 49.3% higher than CK, respectively. (2) The electrochemical properties of the soil surface were the main factors affecting the stability of aggregates and the surface charge density of the four organic fertilizers increased by 29.0%-45.2%. (3) Organic matter has a significant correlation with surface charge density, specific surface area, and surface charge number, and the correlation coefficients are 0.67, 0.53, and -0.63, respectively. Furthermore, exchangeable calcium showed a significant positive correlation with organic matter and the correlation coefficient was 0.90. 【Conclusion】 Food waste compost can enhance the surface charge density of soil by increasing soil organic matter, thus increasing the cementation between exchangeable calcium and soil particles and enhancing the stability of soil aggregates.
-
Research on Soil Type Inference Based on Combinatorial Cartography Method
LI Kun, HUANG Wei, FU Peihong, CHEN Yuhao, WANG Ziying
DOI: 10.11766/trxb202402030056
Abstract:
【Objective】For the rational use of land resources, it is important to obtain accurate spatial distribution of soil types using digital soil mapping technologies.【Method】In this study, environmental factors were screened according to the soil parent material type based on field sampling points, and then three different mapping methods, random forest, SoLIM, and KNN, were used to map the zones according to the selected environmental factors, respectively. Each method was used individually to generate zoning maps, providing different reasoning for the spatial distribution of soil types. The zoning mapping results were obtained and combined to form a universal spatial distribution map of soil types, and then, we used the FP-Growth algorithm to effectively mine the internal correlation between environmental factors. By combining these associations with different mapping results obtained previously, the spatial distribution of soil types in the study area was deduced and used to obtain higher quality and precision inference results. 【Result】The mapping results revealed several key findings: (1)The independent mapping of soil type based on the parent material type of soil by three different mapping methods is more effective and accurate than the joint mapping of all parent materials, and the inference of spatial distribution of soil types is also more reasonable. (2) Among the three mapping methods adopted in this study, the method combining random forest and frequent itemset mapping had the highest accuracy of 70.73%. Moreover, the results obtained by this combined method are similar to the spatial distribution of soil types inferred by the other two combined methods. Through comparative analysis, we were able to determine the approximate spatial distribution of soil species in the study area. (3) After the three mapping methods were combined with frequent itemsets, we observed that all methods had different degrees of improvement in accuracy verification and Kappa coefficient. Among them, the KNN method had the most significant improvement effect, the total mapping accuracy increased by 9.76%, and the Kappa coefficient increased by 11.70%. On the contrary, the random forest method had the smallest improvement, wherein, the total mapping accuracy and the Kappa coefficient increased by 4.88%, and 5.85%, respectively. These results validate the effectiveness of the combination method designed in this study. 【Conclusion】The first, aspect of this study aimed to investigate the influence of soil parent material type on environmental factor screening. This aspect had relatively important reference significance for selecting appropriate environmental factors in the process of digital soil mapping. On the other hand, by combining frequent itemsets with the three different mapping methods used, this study not only provides a new method and idea for the exploration and application of digital soil mapping, but also provides a useful reference for the information application of frequent itemsets association.
-
The Influence of Ion Interface Reaction on the Permeability Pressure Characteristics of Typical Granite Benggang Sandy Loam Red Soil Layer in Anxi Country
WU Yunbo, ZHANG Zhi, LI Xiaofei, MAO Xiaohua, ZHANG Yue, JIANG Fangshi, HUANG Yanhe, LIN Jinshi
DOI: 10.11766/trxb202401040012
Abstract:
【Objective】Rainfall can alter the movement of water in the soil of landslide-prone slopes, affecting the types and concentrations of ions in various soil layers, thereby influencing ion-interface reactions on soil particle surfaces. Additionally, moisture accumulation can exert high permeability pressure on the underlying soil layers, making them prone to deformation and instability. Soil with weaker resistance to permeability pressure, when closer to the surface, is more susceptible to soil erosion. Previous research has mainly focused on the influence of soil water stability and mechanical stability on landslide erosion, however, the impact of ion-interface reactions based on ion characteristics on the permeability characteristics of landslides is not well understood. 【Method】This study focused on the red soil layer of a typical landslide in Anxi County and used ion solutions with different valences and concentrations to manipulate ion-interface reactions on the soil particle surfaces and analyzed their effects on the permeability characteristics of the landslide""s red soil layer. 【Result】K+ reduced soil porosity and decreased the soil""s permeability and conductivity, while Mg2+ increased soil porosity and enhanced the soil""s permeability and conductivity. There was a good single exponential increasing relationship between the permeability coefficient and the electrolyte concentration, with the fitting equations for various consolidation pressures expressed as k = ae-x/t + b, R2 > 0.845, P < 0.1. Also, K+ increased the electrostatic repulsion between soil particles, resulting in net repulsion forces between them, while Mg2+ reduced the electrostatic repulsion, leading to net attraction forces between soil particles. Higher electrolyte concentrations have a more significant impact on altering the internal forces within the soil. 【Conclusion】Ion-interface reactions based on differences in ion characteristics can influence the internal forces of the soil, causing some degree of structural changes in landslide-prone soil.
-
Effects of Iron Oxides on the Priming Effect of Topsoil and Subsoil Carbon Decomposition in A Subtropical Forest
ZHANG Yuting, XU Wenhao, WANG Qingkui, TIAN Peng
DOI: 10.11766/trxb202401030009
Abstract:
【Objective】The relationship between soil organic carbon and iron oxides is crucial to the regulation of soil carbon stability. In terrestrial ecosystems, subsoil is an important organic carbon reservoir, which has been paid increasing attention due to its dynamic processes. However, little is known about how carbon inputs affect the interactions between soil minerals and organic carbon, especially in the subsoil.【Method】To address the knowledge gap, this study investigated the effects of two different crystalline forms of iron oxides, goethite and ferrihydrite, on the priming effect of topsoil (0~10 cm) and subsoil (20~40 cm) in subtropical forests. We incubated the soils by adding 13C-labeled glucose to quantify the intensity of the priming effects in a laboratory experiment.【Result】The results show that the priming effects of topsoil and subsoil were 1.63 mg·g−1and 0.61 mg·g−1, respectively, indicating that the priming effects decreased with soil depth. An interactive effect was observed between the type of iron oxides and soil depth on the priming effect of SOC. In topsoil, the addition of goethite significantly decreased the intensity of the priming effect (P < 0.05), while ferrihydrite showed no significant influence on it. In the subsoil, the addition of ferrihydrite significantly increased the intensity of the priming effect (P < 0.05), but the addition of goethite had no significant effect on the priming. In topsoil, after goethite was added, the co-precipitation produced iron-bound organic carbon, which inhibited the mineralization of organic carbon, influenced microbial carbon limitation, and further decreased the intensity of the priming effect. In the subsoil, the intensity of the priming effect was influenced by the limitation of microbial carbon and phosphorus. Glucose acted as an electron shuttle, increasing iron reduction and CO2 production. The reduction and dissolution of ferrihydrite reduced the protective effect of iron oxide on SOC, which in turn enhanced the mineralization of SOC. Iron oxides can increase SOC accumulation and stability through mineral protection and lead to SOC mineralization through redox reaction.【Conclusion】Overall, the priming effects of topsoil and subsoil have different responses to iron oxides, and the influence of iron oxides on organic carbon accumulation is affected by their properties and soil conditions.
-
Dynamic Characteristics of Cynodon Dactylon Root Growth and Its Influence on Soil Pore Evolution
ZHANG Jing, RAN Yiguo, MA Donghao, CHEN Lin, WU Yingbo, HUANG Ping
DOI: 10.11766/trxb202310310446
Abstract:
【 Objective 】 Cynodon dactylon is a commonly used herbaceous plant for ecological greening, soil consolidation and slope protection, vegetation restoration, and soil and water conservation. Its developed root system network and unique growth characteristics have a significant impact on the formation and spatial reorganization of soil pores. Current research has mostly focused on the role of the plant’s roots in soil aggregate formation and stability, however, the dynamic impact of root growth on soil pores remains unclear. 【 Method 】 This study employed a pot experiment, selecting Cynodon dactylon as the model plant and typical purple soil and yellow soil from the mountainous and hilly regions of southwestern China as the culture substrates. Four different treatments were established: purple soil with Cynodon dactylon (G), purple soil control (CK), yellow soil with Cynodon dactylon (YG), and yellow soil control (YCK). The soil profile images under different treatments were continuously collected using the minirhizotron technique. The root traits of Cynodon dactylon and soil pore structure parameters at different stages were quantified through optimized root extraction algorithms and image processing techniques. Combined with statistical analysis, the study explored the dynamic growth of Cynodon dactylon roots and their impacts on the evolution of soil pore structure. 【 Result 】 The results showed that: (1) Cynodon dactylon grew well in both purple and yellow soils, and the root growth rate was higher in purple soil than in yellow soil. The root length, root surface area, and root volume of Cynodon dactylon in purple soil were nearly three times higher than those under yellow soil cultivation conditions; (2) Compared with the unplanted CK and YCK, the growth of Cynodon dactylon significantly reduced the number of pores, porosity, and fractal dimension of purple and yellow soils, and the reduction effect of roots on soil pores continuously increased with root growth; (3) Redundancy analysis indicated that roots explained 40.60% of the variation in soil pore structure, and root length, root surface area, and root volume were the key root traits that reduced soil pore structure parameters. 【 Conclusion 】 In summary, through the optimized minirhizotron technique, continuous observation of plant roots and soil pores was achieved on site. It was found that Cynodon dactylon significantly reduced pore number and other parameters during its growth period, providing methodological support for in-situ, non-destructive, and dynamic studies on root-pore interactions, as well as theoretical support for vegetation restoration and soil and water conservation in ecologically fragile areas.
-
Research Progress on Soil Organic Phosphorus Mineralization and Its Regulation
Zhang Wannian, Yang Zi, Yan Yupeng, Wang Xiaoming, Yin Hui, Xu renkou, Tan Wenfeng, Feng Xionghan
DOI: 10.11766/trxb202404140154
Abstract:
Soil organic phosphorus (P) is an important component of the soil P pool and its mineralization plays an important role in global P cycling. Understanding the mineralization of soil organic P is beneficial for the efficient utilization and management of P in terrestrial ecosystems. In recent years, the application of advanced techniques such as modern spectroscopy, chromatography, and mass spectrometry has provided crucial avenues for a more comprehensive characterization of the composition and structure of organic P. This review summarizes the applications of these technologies in quantifying changes in soil organic P content. Organic P, following mineralization, is converted into inorganic P(Pi), making it available for direct uptake and utilization by plants and microorganisms. Soil organic P mineralization is orchestrated by two primary pathways: enzymatic and mineral-mediated processes. Delving into the mechanisms of biological catalysis and abiological mineral-mediated catalysis is crucial for elucidating the control pathways of organic P. The mechanisms of soil organic P mineralization can be divided into biological mineralization driven by the oxidation of organic matter by microorganisms (phoA, phoD, and phoX) in response to energy demand, and biochemical mineralization driven by the release of Pi nutrients from plants in response to the demand for P nutrients mediated by phosphatases. Recent investigations have underscored the significance of minerals as an abiological mineralization pathway, shedding light on the mechanisms and actions of mineral-mediated catalysis. The surfaces of minerals (such as iron (hydro)oxides, manganese (hydro)oxides, and aluminum (hydro)oxides) provide an enzyme-like environment, facilitating the cleavage of phosphate ester (P-O-C) and terminal phosphoanhydride (P-O-P) bonds, resulting in the hydrolysis of organic P to Pi. In soil ecosystems, the biogenic elements carbon (C) and nitrogen (N) are intimately linked with soil organic P mineralization. From a nutrient factor perspective, elucidating the driving patterns of organic P mineralization can inform strategies to regulate soil P pools. Specifically, C effectively drives microbial mineralization of organic P, whereas N influences enzymatic metabolism, with the interplay between the two elements profoundly influencing the soil organic P mineralization process. The multiple forms of organic P present in soils are susceptible to influences from various external factors, which modulate phosphatase activity and alter organic P content, thereby further affecting the mineralization process. Various factors, including agricultural practices (such as fertilizer application, tillage practices, and biochar application), soil physical and chemical properties (such as pH, temperature, soil water content, and soil aeration status), microbial biomass, soil CO2 concentration, vegetation, and pollutants all impact soil organic P mineralization, resulting in corresponding environmental ecological effects. Therefore, regulating organic P mineralization is crucial for enhancing soil fertility and protecting the environment. Future strategies can focus on enhancing phosphatase activity, altering organic P composition, and increasing the abundance of phosphorus-solubilizing microorganisms to improve soil organic P mineralization. This review summarizes the advances in soil organic P mineralization research, synthesizing the soil processes, influencing factors, and control pathways, and highlighting the existing challenges and prospects.
-
The Influence of Root Zone Fertilization in Combination with Azolla and soil pH on Ammonia Volatilization
ZhuTong, LiHong, zhouyanping, zhengjicheng, YinBin, YaoYuanLin
DOI: 10.11766/trxb202301180026
Abstract:
【Objective】Azolla has a highly biological nitrogen fixation ability, however, the growth of Azolla is sensitive to ammonium nitrogen in water and is easily affected by water pH. Research suggests that root zone fertilization of fertilizers can effectively reduce the concentration of ammonium nitrogen in floodwater. However, it is unknown whether culturing Azolla under root zone fertilization of fertilizers can stably inhibit ammonia volatilization and increase yield for paddy soils with different pH values. This study aimed to determine the effect of root zone fertilization of fertilizers in combination with Azolla on ammonia volatilization and rice yield in paddy soils with different pH values.【Method】A pot experiment was conducted with three types of paddy soil (acid, neutral, alkaline), two methods of fertilization (broadcasting and root zone fertilization of fertilizers), and two modes of rice cultivation (with or without Azolla). The ammonia volatilization potential and grain yields of rice were determined for these 15 treatments. 【Result】The results showed that: (1) Under the same nitrogen application rate, root zone fertilization of fertilizers treatments only volatilized NH3-N 1.0-1.8 kg·hm-2(calculated by nitrogen), which were 96% lower than surface application of nitrogen fertilizer for the three types of paddy soil, and Azolla-rice co-culture treatments lowered the ammonia volatilization by 17%-50% when compared with those of rice mono-culture treatments; (2) Compared with rice mono-culture treatments, Azolla-rice co-culture treatments produced higher rice yield. Moreover, root zone fertilization of fertilizers combined with Azolla reached the highest rice yield in black soil, increased by 41% compared with the grain yield of black soil surface application without Azolla. 【Conclusion】 In conclusion, root zone fertilization of fertilizers can significantly reduce ammonia volatilization for paddy soils with different initial pHs while root zone fertilization of fertilizers combined with Azolla has greater potential for increasing rice yield.
-
Variation of the Increased CH4 Emissions in Paddy Fields with Straw Incorporation across 11 Consecutive Years
YANG Zhengyu, LI Zongming, LI Yanyan, SHEN Jianlin, WU Jinshui
DOI: 10.11766/trxb202402230076
Abstract:
【Objective】 This study aimed to explore the variations of the increased methane (CH4) emissions and its mechanisms in paddy fields with straw incorporation across 11 consecutive years, so as to provide a scientific basis for the accurate assessment of CH4 emissions under long-term straw incorporation.【Method】A typical double-cropping rice field in the subtropical region was selected as the research subject, and the fertilizer only treatment (CON), low amount of straw incorporation treatment (3.0 t?hm-2, LS) and high amount of straw incorporation treatment (6.0 t?hm-2, HS) were set up. The field experiment was conducted for 11 years (2012—2022) with CH4 fluxes and related soil and environmental factors measured in the early and late rice seasons across the 11 years.【Result】The results showed that in the 11th year of straw incorporation, CH4 emissions in both the LS and HS treatments were substantially higher than those in the CON treatment, with the highest emissions recorded in the HS treatment, followed by the LS and then the CON treatment (HS > LS > CON). However, it was noted that the increment in CH4 emissions due to straw incorporation in the 11th year had diminished by 75.1% and 83.5% when compared to the increment in the first year (P < 0.05). In the 11th year, the contents of soil organic carbon (SOC), ammonium nitrogen (NH4+-N), and dissolved organic carbon (DOC) in the LS and HS treatments showed significant increases by 7.90% and 20.8% (LS and HS treatments, the same as below), and 15.0% and 25.7%, 19.5%, and 31.3%, respectively, compared to the CON treatment (P < 0.05). However, the redox potential (Eh) and soil bulk density (BD) exhibited significant reductions of 14.1% and 21.7%, and 10.3% and 7.76%, respectively (P < 0.05). Furthermore, the abundance of the mcrA and pmoA genes, which are instrumental in methanogenesis and methane oxidation processes, respectively, as well as the mcrA/pmoA gene ratio, were significantly enhanced in the LS and HS treatments compared to the CON, which increased by 96.0% and 152%, 12.7% and 34.8%, and 73.9% and 85.8%, respectively (P < 0.05). Through redundancy analysis, it was determined that in the 11th year of straw incorporation, CH4 emissions in the paddy field displayed a significant positive correlation with the abundance of mcrA and the mcrA/pmoA ratio in the soil (P < 0.05). The decrease in BD and the rise in Eh, induced by the increase in SOC content, likely fostered the augmentation in pmoA gene abundance, which might be the principal reason for the undermined increase in CH4 emissions for the straw treatments observed in the later stages of the experiment.【Conclusion】 In the subtropical regions, relative to CON, the increases in CH4 emissions under long-term straw incorporation was reduced by approximately 80% (P < 0.05) compared to the increase under short-term straw incorporation due to the changes in SOC, BD, and Eh. Therefore, the assessment of CH4 emissions from paddy fields with straw incorporation needs to be dynamically adjusted according to the year of duration of straw incorporation.
-
The Decomposition Characteristic of Crop Straws and Their Released Dissolved Organic Matter Properties
DOI: 10.11766/trxb202311130472
Abstract:
【Objective】It is an essential prerequisite to understanding the environmental behavior of straw carbon in farmland soil to understand the decomposition characteristics of crop straw and the properties of dissolved organic matter (DOM) released. However, the information on straw decomposition characteristics obtained from relevant studies needs to be more comprehensive and requires further investigation. 【Method】In this study, the straws of corn, wheat, bean, and rape were laboratory incubated for 69 days. The two-dimensional correlation-Fourier Transform infrared spectroscopy (2D-COS-FTIR), ultraviolet-visible spectroscopy (UV-Vis), three-dimensional Excitation-Emission-Matrix Spectra (3D-EEM), and parallel factor analysis (PARAFAC) were employed to monitor the changes in the components of straw during decomposition (0–69 days), as well as the humification characteristics of their released DOM. 【Result】The results showed a double increase in corn, wheat, and corn straws during their decomposition period, and all four straws reached maturity at 65–69 d. At the end of decomposition, the mass loss rates of the four straws were 56.8 % (rape), 51.1 % (corn), 48.5 % (soybean), and 44.0 % (wheat), respectively. Although the decomposition order of different substances differed in the four straws, the decomposing intensity of functional groups on the surface of the corn, wheat, and rape straw exhibited the same order (C=O > O-H > -CH2 > -COO-) but the bean straw showed a different order. The dissolved organic carbon (DOC) content released by the corn, wheat, bean, and rape straws gradually decreased and was stable at 69 days of decomposition, of which the DOC content was 23.6, 12.2, 17.2, and 10.7 mg·g-1 biomass, respectively. During the decomposition, the SUVA254 value and aromaticity of DOM released from decomposed corn and soybean straws gradually increased, and the E2/E3 value gradually decreased. In contrast, those in wheat and rape straws showed a fluctuating trend. At the end of the decomposition, the aromaticity of DOM released from decomposed corn, wheat, bean, and rape straw was 20.58, 10.55, 17.45, and 8.32, as well as the E2/E3 value being 3.27, 4.29, 3.16, and 5.77. In addition, the aromaticity of maize and soybean straw DOM was higher than that of wheat and rape straw, and the E2/E3 value showed the opposite trend. The 3D-EEM results showed that though the DOM composition in the four crop straws varied, a similar conversion was observed from protein-like substances (I + II) to humic-like and fulvic-like substances (III + V). Four fluorescence components in the straw DOM identified by the parallel factor analysis model showed similar results. Finally, the humic-like substances (C2 and C4) comprised 35.0%–41.9%, and the fulvic-like substances (C1) accounted for 19.9%–42.9%. In contrast, the protein-like substances (C3) only accounted for 10.0%–29.4%. 【Conclusion】Our study revealed that the decomposition of straw and the content of its released DOM were influenced by the type of crop, while the substance degradation strength and transformation pattern remained consistent.
-
Effects of Organic Fertilization on the Phosphorus Solubilizing Bacteria Community and Maize Productivity in Dryland Red Soil
YANG Yeyuping, ZHENG Jie, JIN Lele, PENG Ziyi, WANG Xiaoyue, XU Qinsong, JIANG Yuji
DOI: 10.11766/trxb202311170480
Abstract:
【Objective】Phosphorus solubilizing bacteria (PSB) is an important functional group of the soil microbial community. The changes in the abundance, composition, and diversity of the PSB community in the rhizosphere can affect soil alkaline phosphomonoesterase (ALP) activity and phosphorus (P) cycle dynamics. Here, we explored the mechanism of the abundance, composition, and diversity of the PSB community in regulating maize productivity under different organic fertilization treatments.【Method】In this study, we conducted a long-term field experiment with different organic fertilization treatments at the Yingtan National Agroecosystem Field Experiment Station of the Chinese Academy of Sciences in Jiangxi. The field experiment included four treatments: no manure (M0), low manure (M1), high manure (M2), and high manure with lime addition (M3). Illumina sequencing was used to investigate the abundance, composition, and diversity of the PSB community in the rhizosphere.【Result】Different organic fertilization treatments (M1, M2, and M3) significantly increased pH, soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), abundance of PSB, ALP activity, and maize productivity compared to M0 treatment, with the highest values observed under M3 treatment. Organic fertilizer treatments affected the PSB community composition and diversity in the rhizosphere. Bradyrhizobium, Mesorhizobium, and Pseudomonas were the dominant genera in the PSB community under M2 and M3 treatments. Compared with the M0 treatment, the PSB community diversity was significantly increased under the M1 treatment. The abundance and dominant genera of the rhizosphere PSB community were mainly affected by AP. Correlation analysis and structural equation modeling revealed that AP and TP indirectly affected maize productivity by increasing the abundance and changing the relative abundance of dominant genera of PSB.【Conclusion】Taken together, this study elucidates the promotion mechanisms of the rhizosphere PSB community on the mineralization of soil organic phosphorus and maize productivity. Our findings provide a scientific basis for establishing better organic fertilization practices and enhancing the fertility and health of red soils.
-
Hot Moments and Hot Spots and the Associated Influencing Factors of Denitrification along Farmland Soil Profiles in Southern China
Zhou Han, Wang Xiaomin, Wei Zhijun, Ma Xiaofang, Zhang Yumeng, Shan Jun, Yan Xiaoyuan
DOI: 10.11766/trxb202401020003
Abstract:
【Objective】Denitrification is the primary pathway for removing NO3?-N in agricultural soil profiles, converting NO3?-N into N2, and reducing the risk of NO3?-N accumulation. However, due to methodological limitations, previous studies have mainly focused on the accumulation patterns in soil profiles or the transformation of NO3?-N in the surface soil, with less attention to its removal throughout the entire soil profile. Thus, the rate of denitrification and absolute amount of nitrate removal capacity along the soil profile remain unclear. Furthermore, the existence of “hot moments” and “hot spots” for denitrification in soil profiles is still unknown. 【Method】To evaluate the NO3?-N removal capacity of typical farmland profiles in southern China and to explore the hot moments and hot spots of denitrification, paddy fields (rice-wheat rotation), vegetable fields, and vineyard in the Taihu Lake region were selected for this study. Near in-situ incubation of flooded and non-flooded layers of the soil profile (0-300 cm) of these fields was performed using the Membrane Inlet Mass Spectrometer (MIMS) and Robotized continuous flow incubation system (RoFlow) over a year.【Result】Our results showed that the soil denitrification rate exhibited distinct hot moments and hot spots across the three planting patterns. Denitrification hot moments in rice fields were primarily observed in October during the rice season, with a rate of 17.6±1.0 nmol N g?1 h?1. The denitrification hot moments of vegetable fields and orchards mainly occurred in March, with rates of 44.2±2.5 nmol N g?1 h?1 and 45.3±7.5 nmol N g?1 h?1, respectively. The hot spots of denitrification in the paddy field occurred in the topsoil (0-20 cm) with an average rate of 3.4±0.4 nmol N g?1 h?1. The denitrification hot spots of the vegetable field and orchard mainly occurred at 20-100 cm, with average rates of 11.7±1.3 nmol N g?1 h?1 and 9.4±2.3 nmol N g?1 h?1, respectively. Also, the removal rate of NO3?-N in these denitrification hot spots exceeded 90%, and almost all NO3?-N in the soil profile was removed under the three planting patterns. Correlation analysis results indicated that the soil NO3?-N content was the primary limiting factor for denitrification. 【Conclusion】Our study reveals that the farmland soil profiles under the three planting patterns in the Taihu Lake area exhibit high denitrification rates with distinct denitrification hot moments and hot spots, effectively removing NO3?-N from the soil profile. These findings deepen our understanding of the NO3?-N removal process in farmland soil profiles, holding significant implications for accurately assessing the cumulative risk and removal capacity of NO3?-N in high N input areas of southern China.
-
Environmental Behavior and Terrestrial Ecological Risks of Typical Rubber Antioxidants and Their Derivatives
JiangJinlin, WuHuiyi, WangLei, DongShunan, CaoShaohua
DOI: 10.11766/trxb202308310345
Abstract:
Soil is the main natural resource for human survival and development. In recent years, the aquatic risks of tire rubber antioxidant N-(1, 3-dimethylbutyl-N""-phenyl-p-phenylenediamine (6PPD) and its ozonated product N-(1, 3-dimethylbutyl-N"" -phenyl-p-benzoquinone (6PPD-Q) have attracted global attention, but little is known about their soil environmental behavior and soil biota effects. Research has shown that soil is an important "aggregation" of tire wear particles, and the TWPs entering the environment release various of additives, such as rubber antioxidants, silica, metals, etc. Among them, p-Phenylenediamines(PPDs) are the most widely added rubber antioxidants due to their excellent performance, which can be released as TWPs entered environmental media and produced derivatives such as PPD-Qs. Therefore, studying the fate and ecological environmental risks of 6PPDs and their derivatives in soil is of great significance. This article focuses on soil environmental safety and ecological health, stating the behavioral characteristics of the occurrence, migration, and transformation of 6PPD and 6PPD-Q in the soil environment. For providing a theoretical basis of the ecological risk assessment and prevention and control of 6PPD and 6PPD-Q pollution, this paper introduces the accumulation, transportation, and metabolic mechanisms of 6PPD and 6PPD-Q in soil organisms, and elaborates on their toxic effects and mechanisms on soil organisms.
-
Soil Iron Speciation Transformation and in-Situ Monitoring of Element Bioavailability During the Flooding-drainage in Polluted Paddy Soils
ZHAO Wantong, WANG Yufeng, LIU Zhe, HUANG Qiaoyun, YI Ceng, FENG Xionghan, WANG Xiaoming
DOI: 10.11766/trxb202310210430
Abstract:
【Objective】Paddy soils are extensively polluted by heavy metals (HMs) in China and present significant challenges for safe agricultural use. Thus, this study seeks to address the heavy metal pollution in China""s paddy soils, focusing on polluted soils from the Dabaoshan mining areas in Shaoguan, Guangdong Province.【Method】A flooding-drainage incubation experiment was conducted and combined with chemical extraction, diffusive gradients in thin films (DGT) technology, and correlation analyses. Also, the impact of phosphorus (P) and humic acid (HA) addition on soil Fe speciation and the bioavailability of related elements was evaluated. The selection of P and HA concentrations was based on common agricultural practices to ensure the environmental relevance of this study.【Results】The results revealed that soil pH gradually became neutralized while redox potential (Eh) decreased during the flooding period. The concentrations of acid-soluble Fe2+, amorphous Fe, and Fe activation degrees increased from 1.5 g?kg-1 to 4.8 g?kg-1, 6.6 g?kg-1 to 10.1 g?kg-1, and 21% to 29%, respectively, with a decrease in amorphous Fe content observed in treatments with added P and HA from 2 to 42 days of flooding. After soil drainage, both amorphous Fe (Feox) and Fe activation degree rapidly decreased to 7.4 g?kg-1 and 21.6%. Regarding CaCl2-extractable heavy metals, the lowest values were observed after 14 days of flooding, whereas levels of As, Cd, Cu, and Zn rapidly increased to 0.1, 0.4, 0.3, and 7.0 mg?kg-1, respectively, after drainage. The addition of P and HA in the early flooding stage increased the As content by 80% and 35% compared to the control, respectively, but decreased the contents of Cu, Zn, and Cd, with HA addition, the reduction rates of CaCl2-extractable Cu, Zn and Cd were over 67%. During flooding, DGT-extracted P and Fe content initially increased then decreased, while Zn content gradually reduced. The addition of P and HA significantly reduced the bioavailable Zn content in the early stages of flooding while the bioavailable content of P and As was primarily controlled by bioavailable Fe.【Conclusion】During the soil flooding-drainage incubation, significant changes occurred in soil physicochemical parameters including pH, Eh, and speciation of Fe. The addition of P and HA could regulate the bioavailability of elements such as Fe, P, and HMs. These findings offer valuable insights for the remediation of HMs-polluted soils, highlighting the potential for using P and HA in improving soil quality and ensuring safe agricultural production.
-
Temporal Dynamics and Content of Soil Particulate Organic of Gahai Wetland in Gansu Province During Vegetation Degradation Succession
MA Weiwei, LIU Qiang, LI Guang, CHANG Wenhua
DOI: 10.11766/trxb202309040355
Abstract:
【Objective】Soil particulate organic carbon (POC) is a key player in the transformation and sequestration of soil carbon pools. However, POC content is significantly regulated by changes in soil environment. Therefore, this study was aimed to clarify the change of POC and its influencing factors with vegetation degradation of alpine wetlands, in an attempt to provide certain basic data for further understanding the responses of soil carbon pool dynamics to climate change and human activities in alpine wetland. 【Methods】In this study, the swampy meadow of Gahai wetland in the northeastern edge of the Qinghai-Tibet Plateau (QTP) was taken as the study area. In the typical vegetation growth area around Gahai Lake, the spatial instead of temporal method was used to characterize the degree of degradation. Sample plots were set up by selecting lots with gentle terrain and consistent slope orientation. Different vegetation degradation levels were classified according to the indicators of plant species composition, aboveground biomass, community height and cover. Soil samples were collected from four vegetation degradation levels, including non-degraded (ND), slightly degraded (SD), moderately degraded (MD), and heavily degraded (HD) in swampy meadow at Gahai wetland. The contents of soil POC were investigated in in the growing seasons of 2016-2017 by field sampling and laboratory analysis. Three-factor analysis of variance was used to analyze the effects of vegetation degradation, soil layer, sampling time and their interactions on soil moisture, soil organic carbon (SOC) and POC contents. Redundancy analysis was performed to determine the dominant factors affecting the change of SOC components in each vegetation degradation levels. 【Results】The results showed that vegetation degradation significantly decreased the amount of POC at soil surface layers (0-10 and 10-20 cm), but there was no significant effect on the deep layers (20-40, 40-60, 60-80 and 80-100 cm). As the growing season progresses, the contents of POC at 0-10 and 10-20 cm layers decreased first and then increased in four vegetation degradation levels. However, the contents of POC at the other deep layers did not change significantly. In terms of inter-annual variation, soil POC levels and fluctuations were higher in 2016 than in 2017. Analysis of variance (ANOVA) showed that the sampling time, the vegetation degradation and soil layer had significant effects on the POC content, respectively. Meanwhile, the interaction of sampling time, vegetation degradation and soil layer had a significant effect on soil POC content. To further identify the intrinsic factors affecting changes in POC content. Redundancy analysis was utilized to reveal the differences between the studied factors. The results showed that total nitrogen and below-ground biomass were the main factors driving changes in soil organic carbon fractions. 【Conclusion】In summary, the process of vegetation degradation in alpine wetlands may impair the accumulation of surface soil carbon pools in the wetlands of the QTP. The original POC accumulation is gradually lost with the increasing degree of vegetation degradation. This phenomenon suggests that vegetation degradation may have transformed the QTP wetlands into a new potential carbon source.
-
Effects of Chinese Milk Vetch Incorporation on the Gene Abundance of Ammonia-oxidizing Microorganisms in Red Paddy Soil
SUN Luyuan, LIU Jia, FENG Mengmeng, LIU Han, MA Tingting, CHEN Xiaofen, LIN Yongxin
DOI: 10.11766/trxb202401110021
Abstract:
【Objective】 Nitrification, an important component of nitrogen cycling, has the potential to influence soil nitrogen availability. As a result, it will lead to ecological and environmental issues such as eutrophication, and greenhouse gas (nitrous oxide) emissions. The objective of this study was to explore the effect of Chinese milk vetch incorporation on the gene abundance of ammonia-oxidizing microorganisms in red paddy soil under a rice-Chinese milk vetch planting system. 【Method】 In a field experiment, five fertilization treatments were applied, including Chinese milk vetch incorporation (G), 100% chemical fertilizer (C), Chinese milk vetch incorporation + 100% chemical fertilizer (GC), and Chinese milk vetch incorporation + 20% chemical fertilizer reduction (GCT20), with a no fertilization treatment serving as the control (CK). Real-time quantitative PCR was used to determine the abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox Nitrospira Clade A and Clade B in each treatment. 【Result】 The results showed that Chinese milk vetch incorporation increased soil organic carbon and total nitrogen content compared with CK, while the 100% chemical fertilizer treatment showed no significant effect. There was no significant difference in AOA and Clade B abundance among all the treatments, indicating a weak response to nitrogen inputs from both chemical fertilizers and green manure. However, both the sole application of chemical fertilizer and its combination with Chinese milk vetch incorporation significantly increased the abundance of AOB and Clade A. Additionally, Chinese milk vetch incorporation alone had no significant effect on AOB and Clade A, suggesting their sensitivity to chemical fertilizer, but resistance to green manure nitrogen input. Furthermore, gene abundance of all ammonia-oxidizing microorganisms showed a similar trend across growth stages, with higher abundance observed during the mature stage followed by the booting stage and then the tillering stage. This suggests that growth stage and oxygen concentration are key factors influencing the growth of these microorganisms in paddy soils. 【Conclusion】 Growth stage is a key factor affecting the abundance of ammonia-oxidizing microorganisms in paddy soils. Additionally, Chinese milk vetch incorporation had a weaker promotion effect on AOB and Clade A abundance compared to chemical fertilizer, potentially contributing to nitrogen retention and stability in paddy soils.
-
Environmental Footprint Assessment of in Situ Chemical Oxidation Remediation for Contaminated Aquifer Based on SiteWiseTM Method
LIU Peng, SANG Chunhui, ZHANG Hongzhen, XIAO Meng, MENG Hao, LI Xianglan
DOI: 10.11766/trxb202312090523
Abstract:
【Objective】The environmental footprint assessment of in-situ chemical oxidation remediation technology (ISCO) for polluted sites has important scientific research value and practical significance for promoting green and sustainable remediation. However, its application in chlorinated hydrocarbon-contaminated sites has not received much attention. 【Method】 This study employed the ISCO method to remediate a chlorinated hydrocarbon-contaminated site. The remediation of polluted sites using ISCO is divided into four stages: material consumption, transportation process, remediation process, and sampling testing. SiteWiseTM tool was used to conduct an environmental footprint assessment. 【Result】The results showed that using ISCO technology to remediate 73 800 cubic meters of polluted aquifers resulted in 1 261 tons of greenhouse gas (GHG) emissions, total energy consumption of 16 876 GJ, 4 096 kg of SOx emissions, 2 678 kg of NOx emissions, and 912 kg of particulate matter 10 (PM10) emissions. The environmental footprint mainly came from the use of materials such as sodium persulfate and sodium hydroxide, and the consumption of construction electricity caused higher atmospheric pollutant emissions. The Monte Carlo analysis results indicated that the coefficient of variation of greenhouse gas emissions was less than 10%. Also, the sources of uncertainty in this study mainly included redundant designs from ISCO, as well as significant differences in mechanical efficiency and emission factors between different countries. 【Conclusion】The SiteWiseTM tool has reference value for the environmental footprint assessment of ISCO remediation projects in polluted sites in China and future researchers should update it locally by considering machinery types and efficiencies, emission factors, and units of measurement. These considerations will improve applicability to the environmental footprint assessment of polluted sites in China.
-
Effects of Experimental Warming on Soil Microorganisms: A Meta-Analysis
ZHAO Wenyu, MIAO Run, CHENG Cheng, WANG Qi
DOI: 10.11766/trxb202402180071
Abstract:
【Objective】Microbial community plays an important role in soil ecological activities. It can regulate soil nutrient supply by changing the structure and function of the soil ecosystem. At present, the response of soil microbial community to warming and the main influencing factors are not well understood.【Method】This study collected 1 020 sets of data from 206 published domestic and foreign research literature and synthesized them to evaluate the effects of experimental warming on soil microbial community (microbial biomass, community diversity, and soil enzyme activity) using meta-analysis. The different responses of soil microbial communities to different magnitudes, durations and methods of warming, as well as planting habits and ecosystem types were evaluated and discussed. Also, the relationship between the response of soil microbial communities to warming treatment and environmental factors (annual mean precipitation, annual mean temperature, and mean altitude) was explored.【Result】It was found that experimental warming decreased the soil microbial community diversity by 6.7%, increased the activities of soil antioxidant enzymes, enzymes related to carbon (C), and nitrogen (N) conversion by 7.5%, 10.8%, and 19.7%, respectively. A high magnitude of warming (≥4℃) significantly reduced soil microbial biomass and increased the activities of soil antioxidant enzymes and enzymes related to C conversion. Low- temperature increase (≤2℃) had more significant effects on soil microbial community diversity and soil enzymes related to N and phosphorus (P) conversion. Also, long-term warming (>2 years) had significant effects on soil microbial biomass, community diversity, antioxidant enzymes and enzymes related to C conversion. The responses of enzymes related to N and P conversion to medium-term warming (0.5 to 2 years) were more significant and the response of soil microorganisms to experimental warming was different among different ecosystems. Further analysis revealed that the response of enzyme activities related to P conversion to warming was positively correlated with annual mean temperature and annual precipitation. The response of soil microbial community diversity was negatively correlated with mean annual temperature, annual precipitation and mean altitude.【Conclusion】In summary, the experimental warming significantly reduced the diversity of soil microbial communities while increasing soil enzyme activity. The warming amplitude, warming duration, and ecosystem type all affect the effects of experimental warming on soil microbes.
-
Assessing the Impacts of Extreme High Temperatures and Long-Term Warming on Paddy Soil Organic Carbon based on the DNDC Model-A Case Study in Zhangzhou of Fujian Province
ZHANG Liming, LI Jing, CHEN Weiming, SUN Jiarui, XIE Xilin, ZHANG Hua, SHEN Jinquan, LIAO Wenqiang, XING Shihe
DOI: 10.11766/trxb202402070064
Abstract:
【Objective】 Soil organic carbon (SOC) is an essential indicator of soil health. It not only provides a carbon source for plant growth and maintains the physical structure of soil, but also releases carbon into the atmosphere in the form of greenhouse gases, such as carbon dioxide. Therefore, it plays a critical role in the global carbon balance. Currently, the world is experiencing climate change characterized predominantly by warming and increasing frequency and intensity of extreme weather events. However, the impacts of the changing climate, including long-term warming and extreme weather events on SOC are not entirely the same. Distinguishing and quantifying the effects of extremely high temperatures (EH) and global warming (GW) on SOC is the key to formulating adaptive strategies.【Method】 In this study, we focused on paddy soils in Zhangzhou of Fujian Province, a typical subtropical region of China. Based on a 1:50,000 detailed soil database, we employed the biogeochemical process model (DeNitrification-DeComposition, DNDC) to simulate SOC dynamics under four climate scenarios: de-trended climate base state (CTRL), extreme high temperatures (EXP_EH), long-term warming (EXP_GW), and measured temperatures (EXP_obs).【Result】 The results revealed that the total amount of carbon sequestered by paddy fields in Zhangzhou from 1980 to 2016 under the four different climate scenarios (CTRL, EXP_EH, EXP_GW, and EXP_obs) was 1,032.17, 952.15, 1,045.98 and 966.03 Gg, with the corresponding average annual sequestration rates of 93.98, 86.70, 95.24, and 87.96 kg·hm-2, respectively. The long-term warming led to a net increase of 13.81 Gg of SOC in paddy fields across Zhangzhou, while extremely high temperatures resulted in a net decrease of 80.02 Gg. The combined effect of these two factors was -66.14 Gg in SOC, indicating that long-term warming promoted the sequestration of organic carbon in paddy soils, while extremely high temperatures reduced the soil carbon sink capacity, with extremely high temperatures exerting a dominant negative effect. Also, the variations in annual carbon sequestration rates between different climate scenarios indicated that extremely high temperatures throughout the years from 1980 to 2016 had a negative effect on carbon sequestration in the paddy soils of Zhangzhou, but the long-term warming effect on SOC turned from positive to negative around the year of 2000. This may be related to the diminishing effect of warming on plant growth over time. The results of grey relational analysis-structural equation modeling also indicated that the clay content, bulk density, and organic fertilizer application rate were most closely associated with the carbon sequestration rate in rice fields of Zhangzhou, followed by the annual average temperature, precipitation, and pH levels. At the county level, climate change had the greatest impact on the carbon sequestration of Nanjing County. Additionally, the extremely high temperatures and long-term warming caused -26.23% and 7.27% impacts on its carbon sequestration rate, respectively. Among subclasses of rice soils, acid sulfate paddy soils were most affected, with -23.05% and 8.10% changes in carbon sequestration rate caused by warming and extremely high temperatures, respectively. Furthermore, among different terrain and topographical areas, the carbon sequestration rate of hilly and mountainous areas was significantly affected by extremely high temperatures and long-term warming, with -8.84% and 1.98% changes, respectively. 【Conclusion】 In conclusion, while the paddy soils in Zhangzhou still maintain a strong carbon sequestration capacity in the context of climate change, the increasing extreme high-temperature events in the future may potentially contribute to greater carbon losses to some extent.
-
Characteristics of Natural Humus Modified Materials and Their Growth-promoting Effects on Maize Under Drip Irrigation
CHEN Zhuo, ZHANG Congzhi, ZHANG Jiabao, ZHAO Bingzi, PAN Hui
DOI: 10.11766/trxb202312170531
Abstract:
【Objective】This study aims to analyze the physicochemical properties of two natural humus-modified materials (M1 and M2) produced by different processing methods, compare the differences between the two materials, and investigate their effects at different concentrations on the growth of maize under drip irrigation conditions. The goal is to explore the most suitable application concentration and amount of humus under drip irrigation and provide new perspectives and practical bases for agricultural production. 【Method】The content of humus and its components in M1 (natural humus sand grinding fluid) and M2 (fully water-soluble potassium nitrohumate) was determined and the physical and chemical properties of the materials were analyzed through elemental analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). Then, field experiments were designed to evaluate the effects of applying different concentrations (0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0 g?L-1) and amounts (650, 1 300, 1 950 L?hm-2) of M1 and M2 on the height, biomass, and yield of maize. 【Result】The results showed that: 1) There were significant differences in chemical composition between M1 and M2. M1 had a higher content of humus, larger molecular weight, more complex structure, and stronger stability in soil. On the other hand, M2 had a lower total content of humus, a high content of fulvic acid (FA), a smaller molecular weight, and a lower degree of humification. 2) The microstructure of M1 and M2 differed. M1 had a rough and complex particle surface with uneven particle size while M2 exhibited a smoother and looser sponge-like appearance with no chaotic structure on the particle surface. FTIR analysis showed that M1 may contain more aromatic structures or carboxylate salts and silicate impurities while M2 may contain more carboxyl groups. 3) Although the application of M1 and M2 had little effect on plant height, it significantly increased the biomass and yield of maize. Especially for M2, when its concentration was 1.0 g?L-1 and the amount was 1 300 or 1 950 L?hm-2, the biomass of maize plants increased significantly by 40.11% and 40.74% and the yield increased significantly by 25.75% and 27.45%, respectively.【Conclusion】The application of different concentrations and amounts of M1 and M2 effectively promoted the growth of maize, with M2 exhibiting greater growth potential under the same conditions. This may be attributed to the role of humus in improving soil structure, increasing and retaining soil moisture and nutrient content, activating specific biochemical pathways, and enhancing soil microbial activity, thereby improving the nutrient absorption efficiency and photosynthetic capacity of maize plants. Considering factors such as cost, it is recommended to apply M2 at a concentration of 1.0 g?L-1 and an amount of 1 300 L?hm-2 in the field to fully exploit its effects in promoting maize growth potential and increasing yield. This provides new perspectives and practical bases for the efficient utilization of humus in agriculture.
-
Kinetic Study of Montmorillonite-humus Condensation Induced by Mixed Electrolyte
HE Aizhou, YU Linqiao, LI Hang†
DOI: 10.11766/trxb202311080466
Abstract:
【Objective】Natural soil typically consists of a variety of colloids and multiple electrolytes coexisting simultaneously. However, existing studies on soil colloid coagulation have mostly been conducted under conditions involving a single electrolyte and a single colloid. In this study, the coagulation dynamics of a mixed colloid system comprising montmorillonite and humic acid under mixed electrolyte conditions were systematically investigated attempting to explain the coagulation effect and mechanism of mixed electrolyte on the mineral-organic mixture.【Method】Using dynamic laser scattering (DLS) technique, the coagulation kinetics of montmorillonite colloids and montmorillonite-humic acid mixed colloids under the influence of mixed electrolytes were studied by considering key parameters such as the average coagulation rate, critical coagulation concentration (CCC), and coagulation activation energy.【Result】The results revealed the following key findings: (1) Under mixed electrolyte conditions, whether involving a single colloid or a mixed colloids, there was only one CCC. This indicates that under mixed electrolyte conditions, both the two cations in the mixed electrolyte system play a cooperative role in the coagulation of the colloid. Although both cations collaboratively influenced colloid coagulation, the analysis of colloid coagulation rate, CCC, and coagulation activation energy revealed that the cation with stronger competitive adsorption ability played a decisive role. For example, in the 99% Mont(Montmorillonite) + 1% HA(Humic acid) mixed colloids system, the CCC (97.41 mmol?L-1) of the Na+ + K+ mixed system closely resembled the CCC (94.91 mmol?L-1) of K+ alone system, indicating that the role of Na+ in the coagulation of this mixed colloid was almost negligible. This implies that in the Na+ + K+ mixed system, K+ plays a decisive role in colloid coagulation. (2) Increasing the content of humic acid significantly enhanced the stability of the mixed colloid, resulting in the requirement of a higher electrolyte concentration to induce colloid coagulation. This effect can be attributed to the fact that the addition of humic acid increased the surface charge density of the organic/inorganic composite colloidal particles, thereby strengthening the electrostatic repulsion between particles.【Conclusion】The scientific findings of this study not only provide guiding significance for further unraveling the formation mechanism of soil organic-inorganic complexes, but also shed light on the cooperative role of cations in colloidal coagulation under mixed electrolyte conditions. The results underscore the decisive role of the cation with stronger competitive adsorption ability in colloid coagulation. Furthermore, the study reveals that increasing the content of humic acid significantly enhanced the stability of the mixed colloid, necessitating a higher electrolyte concentration to induce colloid coagulation. These insights contribute to the understanding of the complex interplay between organic and inorganic components in soil, paving the way for future research in this field.
-
Effect of Basal Application of Magnesium Sulfate and Magnesium Chloride on Seed Yield and Quality of Rapeseed
GENG Guotao, YE Xiaolei, YU Xiaohong, CONG Rihuan, LI Xiaokun, ZHANG Yangyang, LU Zhifeng†, LU Jianwei
DOI: 10.11766/trxb202311180483
Abstract:
【Objective】Rapeseed (Brassica napus L.), one of the most important oilseed crops in China, is sensitive to magnesium (Mg) deficiency. The Yangtze River Basin is the main planting area for winter oilseed rape in China, and the climatic characteristics of the region with simultaneous rain and heat, high-intensity planting patterns and long-term unbalanced fertilization have led to serious depletion of soil magnesium. It provides a theoretical basis for the rational application of Mg fertilizers in rapeseed cultivation to investigate the impact of different Mg fertilizers on seed yield and quality of rapeseed in China’s main winter oilseed rape production areas. 【Method】Between 2019 and 2020, 56 field trials were conducted in the main rapeseed-growing regions in China. The trials followed a one-way experimental design, with three distinct Mg fertilizer treatments: no Mg fertilizer (CK), magnesium sulfate at the rate of 45 kg?hm-2 (Calculated as MgO, the same as below) (MgSO4?H2O, referred to as MgSO4), and magnesium chloride, also at the rate of 45 kg?hm-2 (MgCl2, referred to as MgCl2). The response of rapeseed to the two Mg fertilizers was evaluated by analyzing the rapeseed yield, yield components, oil, protein, sulfide content and fatty acid fractions. 【Result】The results revealed that the application of both MgSO4 and MgCl2 significantly increased rapeseed yield by 14.1% and 11.8%, respectively. The increase was primarily attributed to an increase in pod number per plant and seeds per pod. MgSO4 and MgCl2 increased the pod number per plant by 10.2% and 8.2%, and the seeds per pod by 3.9% and 2.4%, respectively. Analyzing the relationship between soil Mg content, sulfur content and yield increase resulting from Mg application indicated that the increase in seed yield was mainly associated with soil Mg content but not soil sulfur. The addition of MgSO4 and MgCl2 resulted in an 11.8% and 8.7% increase in seed Mg content (relative to no Mg application treatment), respectively. However, Mg accumulation was similar in both Mg application treatments. Additionally, the application of Mg fertilizer significantly improved rapeseed quality by increasing oil, oleic acid, and linoleic acid content by 5.5% and 4.8%, 8.3% and 7.7%, 7.8% and 11.4% for MgSO4 and MgCl2, respectively. Meanwhile, stearic acid, palmitic acid, and erucic acid contents were decreased by 4.60% and 26.1%, 7.5% and 13.9%, and 33.2% and 24.1% for MgSO4 and MgCl2, respectively. Although the application of MgSO4 resulted in a significant increase in sulfide, it remained below the national limits for edible rape oil and feed cake meal for double-low oilseed rape. 【Conclusion】In the main winter oilseed rape production areas in China, the application of MgSO4 and MgCl2 can significantly increase rapeseed yield, with MgSO4 having a slightly greater effect compared to MgCl2. Magnesium application also increases the Mg content and improves the oil quality of rapeseed by increasing the content of oleic acid and linoleic acid while reducing stearic acid and palmitic acid contents. These synergistic improvements contribute to both yield and quality enhancement.
-
Evaluation of Improvement Effect and Analysis of Influencing Factors of Different Amendments on Saline-sodic Soils Based on a Meta-analysis
HUANG Guangzhi, HUANG Lihua, LIU Baishun, JIANG Xiaotong, YANG Can, LIANG Yanping, Cai Jinghui
DOI: 10.11766/trxb202309060360
Abstract:
【Objective】 Saline-sodic soils are widely distributed in the western part of the Songnen Plain. A variety of materials or measures have been used to improve soils in the process of long-term saline-sodic land management, and get great improvement effect. However, the improvement effect of these amendments on saline-sodic soils is mostly an assessment of individual factors, thus, the quantitative assessments for the impacts on multiple soil functions of different amendments are still lacking. 【Method】Based on this, Our study used a meta-analysis to obtain 854 sets of relevant data from 589 papers on the improvement of saline-sodic soils in the past 30 years. The improvement effects of gypsum type amendment, biochar, and mixed amendments(combined application of 2 or more amendments) on saline-sodic soil and the factors influencing the improvement effect were quantitatively evaluated and analyzed with a meta-analysis and the Random Forest method.【Result】The results showed that the effects in saline sodic paddy fields of the three amendments on decreasing alkalinity were -29.1%, -38.6%, and -41.1%, respectively, and the effect of improvement was significant, however, the difference in improvement effectiveness between amendments was not significant; Furthermore, biochar (47.7%) had the best effects on improving soil nutrient content, while gypsum-type amendments (26.3%) were relatively the lowest. The three amendments were mostly used for soil amendment at the top soil layer (0~20 cm) of moderate and heavy saline-sodic soils, and there were differences in the application amount and application duration on the effect of soil improvement. Amendment application amount was a significant factor affecting the effectiveness in reducing soil salt/alkali of gypsum type amendments.【Conclusion】The main working principle of gypsum-type amendments is to reduce soil alkali, indirectly enhance soil nutrients and promote crop growth, whereas biochar and mixed amendments have the combined effect of reducing soil alkali and directly promoting soil nutrients. The selection of soil amendments should take into account not only the amount, but also the crop types, the cost of the amendments, the durability of the effect, and environmental safety issues.
-
Effects of High CO2 Concentration on Soil Organic Carbon Mineralization
WANG Ruoyao, LI Yuanyuan, XIA Bin, GAO Zihui, ZHAO Yunge, XU Mingxiang
DOI: 10.11766/trxb202312010505
Abstract:
【Objective】Soil CO2 concentration is often higher than that of the atmosphere. Current studies on soil organic carbon mineralization are mostly conducted under conditions of increasing atmospheric or simulated atmospheric CO2 concentration. This may lead to deviation of the results from the actual organic carbon mineralization process in the soil profile or impose some bias on indoor mineralization incubation experiments towards the "mineralization potential" rather than the actual mineralization rate. How and to what extent soil organic carbon mineralization is affected by high CO2 concentrations in the soil profile? The lack of a clear answer to this question limits the comprehensive understanding of soil organic carbon stability. 【Method】In this paper, an indoor mineralization incubation test was conducted with six CO2 concentration gradients of CK (400 μmol·mol-1, atmospheric level), 800, 2 000, 4 000, 6 000, and 8 000 μmol·mol-1, and three replicates were set for each treatment. The effects of different concentrations of CO2 on the rate of soil organic carbon mineralization, cumulative mineralization, and active organic carbon fractions were investigated, and the extent to which CO2 concentration and other influencing factors explained the cumulative mineralization was analyzed.【Result】The results showed that: 1) High concentration of CO2 (2 000-8 000 μmol·mol-1) in soil significantly inhibited the mineralization of soil organic carbon, with the mineralization rate decreasing by 6.27%-45.61%, and the cumulative amount of mineralization decreased by 1.72%-40.82%; 2) Lower concentration of CO2 (800 μmol·mol-1) in soil significantly promoted the mineralization of soil organic carbon, the mineralization rate increased by 4.38%-12.65%, and the cumulative mineralized amount increased by 17.37%-48.43%; 3) The CO2 concentration in the soil effected the content of active organic carbon fractions. At a range of CO2 concentrations, soil microbial biomass carbon (MBC) content increased significantly and dissolved organic carbon (DOC) content decreased significantly compared to CK. However, the content of easily oxidizable organic carbon (EOC) was not significantly changed; 4) The mineralization characteristics of organic carbon showed a significant negative correlation with CO2 concentration, a significant positive correlation with DOC, a negative correlation with EOC, and no significant correlation with MBC; 5) Under the appropriate conditions of temperature and humidity, the contribution of CO2 concentration to the cumulative mineralization of soil organic carbon reached 22.93%. 【Conclusion】High CO2 concentration significantly inhibited soil organic carbon mineralization by affecting the soil organic carbon readily available carbon source, which may be one of the important factors to maintain soil organic carbon stability.
-
Effects of Facility Cultivation Pattern on Soil Bacterial Community in Ningxia Region
SUN Yinqinqin, YAN Yuanyuan, QU Jisong, ZHANG Lijuan, ZHU Qiannan, ZHAO Jun, ZHANG Jinbo, CAI Zucong, HUANG Xinqi
DOI: 10.11766/trxb202312070519
Abstract:
【Objective】Soil bacterial community characteristics are important indicators of soil quality, however, little is known about the effects of facility cultivation on soil microbiological properties. Thus, clarifying the responses of soil bacterial community and functions to facility cultivation is of significance for the sustainable utilization of facility soil.【Method】To reveal the change of soil bacterial community under intensive cultivation and its main influencing factors, this study collected and analyzed 67 facility-open field paired soil samples in Ningxia region. Based on amplicon sequencing technology, the effects of facility cultivation on soil bacterial community diversity, composition, interspecific interaction, and assembly process were investigated.【Result】The results showed that compared with the open field soil, the number of bacteria, Shannon, ACE, and Pielou indices of the bacterial community increased by 63.3%, 3.20%, 11.4%, and 1.69%, respectively. The facility cultivation significantly changed the soil bacterial community structure. Redundancy analysis (RDA) showed that the content of available phosphorus, pH, and electrical conductivity were the main environmental factors determining bacterial community structure. Physicochemical parameters such as pH and soil available nutrient contents significantly affected the bacterial community composition of the facility soil, and the climatic factors including annual average precipitation and annual average temperature significantly affected the bacterial community composition of the open field soil. At the phylum level, the relative abundances of Planctomycetes and Firmicutes increased significantly, while the relative abundances of Gemmatimonadetes and Myxobacteria decreased significantly in the facility soil. At the genus level, the dominant genera such as Bacillus and Pseudomonas were enriched in the facility soil. Co-occurrence network analysis showed that the edge, average degree, clustering coefficient, and modularization degree of the bacterial network in the open field soil increased by 10.8 times, 11.0 times, 36.8%, and 1.78 times compared to those in the facility soil, respectively. Also, facility cultivation significantly reduced the complexity and modularization degree of the soil bacterial network. Functional prediction using the Functional Annotation of Prokaryotic Taxa (FAPROTAX) database showed that facility cultivation significantly increased the relative abundance of carbon, nitrogen, and other element cycles and bacterial functional groups related to pathogenic bacteria. The distance decay relationship of the bacterial community in the facility soil was weaker than that in the open field soil. The community assembly was greatly affected by the deterministic process and the diffusion limitation was higher in the facility soil compared to that in the open field soil.【Conclusion】Collectively, facility cultivation in Ningxia region significantly changed multiple properties of the soil bacterial community. These results can provide theoretical guidance for the sustainable utilization of local facility soil.
-
Short-term Low Nitrogen Addition Alters the Molecular Composition and Stability of Soil Dissolved Organic Matter in a Pinus taiwanensis Forest
YUAN Xiaochun, ZHANG Xiaoqing, ZHOU Qian, WU Lianzuan, CHEN Junming, ZENG Quanxin, BAI Xinyu, LI Wenzhou, CHEN Yuemin
DOI: 10.11766/trxb202311160476
Abstract:
【Objective】Dissolved organic matter (DOM) is highly sensitive to environmental changes, and its dynamic changes are crucial for understanding regional/global carbon cycling under global change scenarios. However, it is not yet clear how the characteristics of soil DOM molecules change under nitrogen deposition. This study aimed to investigate the response of DOM molecular composition and stability to nitrogen addition. 【Method】In this study, three nitrogen addition levels (0, 40, and 80 kg?hm-2?a-1) were conducted in a Pinus taiwanensis forest by using urea addition to simulate nitrogen deposition in the field. The effect of short-term (three years) nitrogen addition on the molecular composition of DOM and its stability was investigated using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). 【Result】The results of FT-ICR MS analysis revealed that DOM molecules were mainly concentrated in 250-400 Da, and CHO compounds accounted for more than 50% of all compounds. Of the eight types of DOM molecules, lignin-like molecules dominated all soil DOM molecules, followed by tannins and condensed aromatics, with the relative abundance of readily decomposable small molecules (including lipids, proteins, and carbohydrates) being low. There was no statistically significant change in the content and optical properties of DOM under nitrogen addition, but significant changes occurred in the properties and composition of DOM molecules. Compared to high nitrogen treatment, low nitrogen treatment significantly reduced the relative abundance of carbohydrate molecules in DOM by 73.33%. This may be largely attributed to the increase in microbial biomass and hydrolytic enzyme activities. Nitrogen addition did not change the nitrogen-containing compounds in DOM molecules, but reduced the sulfur-containing compounds. Furthermore, the average molecular weight and ratio of double bond equivalent to carbon atom number (DBE/C), modified aromaticity index (AImod), and aromaticity equivalent (Xc) of DOM molecule did not show significant changes under nitrogen addition. However, a significant increase in DBE values was observed under low nitrogen addition, indicating an improvement in the molecular stability of DOM. The improvement of DOM molecular stability may have a potential impact on soil carbon pool stability. Pearson""s correlation analysis revealed that DBE values were significantly negatively correlated with small molecule compounds such as carbohydrates and proteins/amino sugars, while the correlation with large molecules such as lignin and condensed aromatics was not significant. Besides, nitrogen addition did not significantly change the difficult-to-decompose molecules such as lignin and condensed aromatic compounds in DOM. This suggests that the molecular stability of DOM under short-term nitrogen addition may depend on the removal of readily decomposable small molecules, such as carbohydrates, rather than the increment of refractory molecules.【Conclusion】Collectively, this study provides a new perspective at the molecular level for understanding the behavior of soil DOM under nitrogen deposition, and a reference for understanding the potential relationship between DOM molecules and soil carbon stability.
-
A Review of Soil 3D Prediction and Modelling Techniques
XIE Xianli, XIA Chengye, YIN Biao, LI Anbo, LI Kaili, PAN Xianzhang
DOI: 10.11766/trxb202311140473
Abstract:
Soil is a complex with high heterogeneity. The early research on digital soil mapping mainly focused on the lateral variation of soil, with less consideration of the vertical variation and three-dimensional (3D) digital soil mapping. In recent years, the rapid developments of 3D geographic information technology and earth observation and detection technology have greatly promoted research on soil 3D data acquisition, 3D prediction, 3D data modeling, 3D model and visualization. In this paper, we reviewed the existing research on soil prediction and soil model construction in 3D space, to provide suggestions for the application and development of 3D digital soil mapping. We searched the Web of Science database by using 3D soil mapping, 3D GIS, 3D data model, 3D geological modeling, 3D visualization, soil spatial variability, spatial prediction, Kriging interpolation, soil-landscape analysis, depth function, machine learning, geostatistics, random simulation as keywords, and selected the key literatures for analysis based on correlation, citation rate and literature sources. We summarized the popular methodologies for soil spatial variability, 3D spatial soil prediction, soil 3D data model, and 3D model construction, and evaluated the advantages, disadvantages and application scenarios of each method. This review presents the common problems of 3D soil mapping, such as sparse soil profile data, low accuracy of 3D soil prediction, and insufficient information to create the data source for 3D soil modelling, and put forward some feasible research prospects.
-
In situ Dissolution Kinetics of Ammonium Nitrogen Interacting with Precipitated Calcium Phosphate Determined by Atomic Force Microscopy
DOI: 10.11766/trxb202309210395
Abstract:
【Objective】The increase in global food demand and the consumption of phosphorus (P) fertilizer in modern agriculture have caused P accumulation in extensively managed croplands. Most of the accumulated P deposits exist in sparingly soluble or insoluble species, leading to their low availability, which is almost impossible to use directly by plants or microorganisms. Therefore, improving the utilization of soil accumulated P is not only one of the effective ways to enhance the utilization efficiency of P fertilizers but also relieves the increasing tension of P resources. At present, a large number of macroscopic field experiments have revealed the synergistic promoting effect of nitrogen (N) on P activation and uptake. However, in the N and P interaction, in-situ observation of dissolved N interacting with precipitated P has been lacking. 【Method】Herein, Ca-P precipitates with different solubilities, namely sparingly soluble (DCPD) and insoluble (HAP), were selected as test materials. Taking aqueous solution as control, five NH4Cl concentrations (0.5, 5, 50, 500, 1,000 mmol?L-1) were set as N sources. The in-situ dissolution kinetics of DCPD and HAP at different N levels were directly observed by atomic force microscopy (AFM). AFM-based dynamic force spectroscopy (DFS) technique was employed to characterize the interaction between ammonium cations and DCPD/HAP surfaces at the molecular scale. 【Result】The result showed that the surface dissolved immediately, accompanied by the formation of triangular etch pits, following the addition of NH4Cl. When increasing the NH4Cl concentration, the surface dissolution rate of DCPD was significantly promoted. The quantitative results further exhibited the dissolved P mass was significantly increased from 27.00 mg?kg-1 to 145.0 mg?kg-1 with the increase of NH4Cl concentration from 0.5 mmol?L-1 to 1 000 mmol?L-1. By contrast, the surface morphology of HAP almost remained constant without obvious dissolution even if the NH4Cl concentration was up to 1 000 mmol?L-1. The dissolved P mass was 5.00 mg?kg-1, which was not significant compared with the dissolved P mass of 3.00 mg?kg-1 in aqueous solution. AFM-based DFS results showed that the interaction force between ammonium cations and DCPD (230.6 pN) was significantly greater than that between ammonium cations and HAP (154.0 pN). Due to the difference in binding strength of ammonium cations on Ca-P surfaces at the molecular level, the hydration layer of mineral surfaces is destroyed at different degrees. As a result, the surface dissolution kinetics of DCPD and HAP were significantly different when regulated by ammonium cations. 【Conclusion】This research provides method guidance for in-situ observation of nanoscale dissolution kinetics of different Ca-P minerals. It also illustrates the enhanced interface dissolution on negatively charged DCPD induced by ammonium cation to release available P, thus improving the continuous P supply capacity in soils.
-
Characteristics of Spatial Distribution of Soil Organic Carbon in Anhui Province Based on Soil Profile Occurrence Layer and Environmental Variables
GAO Wenjing, XIA Bing, LU Yuanyuan, YING Rongrong, HU Pengjie, LI Yixu, CHEN Hongfeng, QIAN Jiazhong
DOI: 10.11766/trxb202402040063
Abstract:
【Objective】Soil organic carbon (SOC) plays an important role in the global carbon cycle, and extremely small changes in SOC could cause dramatic changes in atmospheric CO2 concentration. Accurately grasping the spatial distribution characteristics of SOC and its main controlling factors is an important requirement for improving soil carbon sequestration potential and coping with climate change. Therefore, this study aimed to analyze the spatial distribution of SOC in the topsoil layer (A genetic horizon), subsoil layer (B genetic horizon), and parent material layer (Parent material) in Anhui Province from the perspective of the soil profile occurrence layer and explore the factors controlling the changes of SOC in different profile occurrence layers.【Method】 In this study, a total of 451 sites were distributed in the study area using the systematic distribution method combined with the judgmental distribution method. The basic soil parameters, such as SOC content, pH, soil texture, and bulk density, were obtained from 451 sites through wild sampling and indoor experiments. Meanwhile, the related environmental variables, such as climatic factors, topographic factors, and normalized difference vegetation index, were also collected. Also, we used geostatistical methods to obtain the best half-variance function model and spatial distribution characteristics of SOC content at different soil profile levels, as well as correlation analysis and random forest regression analysis to explore the influencing factors of spatial differences in SOC content.【Result】The results showed that the average organic carbon content of the soil profile in Anhui Province was 8.47 g?kg-1 and there was a phenomenon of surface aggregation of SOC, whose occurrence in the layer was as follows: A genetic horizon: 15.86 g?kg-1 ＞ B genetic horizon: 5.80 g?kg-1 ＞ Parent material: 3.74 g?kg-1 and all of them had moderate spatial variability. The spatial distribution map of SOC showed that the spatial distribution of organic carbon content in each occurrence layer was generally increasing from north to south. We also found that there were some differences in the driving factors of SOC content in different profiles of the occurrence layer. In the A genetic horizon, soil texture, and bulk density were the most important factors affecting SOC content; as the depth of the soil layer increased, the influence of topographic factors and soil texture gradually strengthened on the accumulation of SOC content in the B genetic horizon. For the Parent material, the influence of soil texture, topographic factors, and bulk density were all more influential on the SOC content.【Conclusion】Soil texture is the main factor driving the spatial distribution characteristics of SOC in Anhui Province, but the effects of topographic factors and bulk density should also be fully considered in the subsequent development of SOC control measures, to provide theoretical support for improving soil quality and coping with climate change.
-
The Microbial Diversity of Reclaimed Soil Drives Its Multifunctional Variation in the Eastern Plain Mining Area
MA Jing, HUA Ziyi, YOU Yunnan, ZHU Yanfeng, ZHNAG Qi, CHEN Fu
DOI: 10.11766/trxb202401010001
Abstract:
【Objective】Land reclamation is a significantly important way to restore soil productivity in high groundwater mining areas. However, most of the reclaimed soil always shows poor functions, such as lower fertility and biodiversity, while the in-depth understanding of microbiological mechanisms underlying the formation and restoration of multifunctional reclaimed soil is still deficient. 【Method】Four reclamation plots including 9 years, 12 years, 15 years, and 18 years of reclamation, and 1 control plot from the Dongtan mining area in Zoucheng City, Shandong Province, were selected as the research objects. A total of 75 surface soil samples were collected, and 18 soil physical, chemical, and biological indicators such as organic carbon were measured to explore the interaction between soil microbial communities and soil multifunctionality, as well as the microbiological mecha-nisms of multifunctionality variation. Moreover, based on the molecular ecological network methods, supplemented by statistical analysis methods, several microbial networks were constructed to investigate the interaction between microbial community di-versity, network structure, and soil multifunctionality. 【Result】 The results showed that: (1) Land reclamation activities and the normal vegetation rotation of the cultivated land have significantly improved soil multifunctionality, with soil multifunctionality almost reaching the undisturbed control level after 18 years of reclamation. Moreover, among the soil properties, soil organic carbon, pH, available phosphorous, and most enzyme activities were important influencing factors for multifunctionality. (2) With the increasing reclamation years, soil microbial diversity significantly increased, while the richness performance of bacteria and fungi was different. The increasing trend of bacteria was not significant after 12 years of reclamation whereas fungi in-creased significantly until 18 years of reclamation. However, the abundance of bacteria and fungi reached normal farmland lev-els after 15 years and 18 years of reclamation, respectively. (3) The analysis results of the microbial co-occurrence network showed that the nodes, edges, average degree, average path length, network density, clustering coefficient, and betweenness centrality in the bacterial community co-occurrence network significantly increased with the increase of reclamation time. More-over, the topological properties of bacterial and fungal subnetworks such as edge, degree, and network density were signifi-cantly positively correlated with soil multifunctional properties. The diversity of microbial communities showed a positive im-pact on the network complexity, enhancing the association between species and thereby enhancing their versatility. Both the complexities of bacterial and fungal community networks presented significant correlations with soil multifunctionality. The impact of bacterial network complexity on soil multifunctionality was not affected by other indicators, whereas the correlation between fungal network complexity and soil multifunctionality was influenced by bacterial richness, soil microbial diversity, and fungal richness. The structural equation model results indicated that microbial diversity can directly and positively regulate soil multifunctionality, or indirectly manipulate soil multifunctionality by positively influencing the network complexity of bacteria and fungi.【Conclusion】 This study has revealed the driving mechanism of multifunctional restoration of reclaimed soil in the eastern plain mining area, which would provide important guidance for the deeper understanding of the development and func-tional succession of reclaimed soil microbiota, as well as soil quality management and protection.
-
Effects of Biochar on Red Soil Nematode Community Characteristics under Chemical Fertilizer Reduction
CHENG Liuzhu, ZHU Baijing, CHENG Yanhong, WAN Bingbing, LIU Ting, TAO Yiheng, CHEN Xiaoyun, HU Feng, LIU Manqiang
DOI: 10.11766/trxb202311120469
Abstract:
[Objective] The approach of reducing chemical fertilizer usage while increasing the application of organic materials is a common strategy for maintaining optimal crop yields and preserving soil ecological functions. Biochar, as a carbon-rich, alkaline, and porous byproduct produced from biomass pyrolysis, has great potential in soil biodiversity restoration and soil health improvement in acidic red soil areas. [Method] This study conducted a 2×3 full factorial interactive design experiment in red soil cultivated with sweet potato-rapeseed in subtropical arid areas. The experiment involved the application of organic materials (control without organic material application, straw, and biochar) and two fertilizer application rates (full dose of NPK fertilizer and reduced dose of 60% NPK fertilizer), totaling six treatments. The aim was to investigate the impact of biochar application on nematode communities in upland red soils and to understand the underlying mechanisms after five years of application. [Result] The results indicated that under full chemical fertilizer application, the use of biochar significantly increased the abundance of bacterivores and the ratio of microbivores to herbivores, reduced the root-to-shoot ratio of sweet potatoes and soil soluble organic carbon, and increased soil mineral nitrogen. Under reduced chemical fertilizer application, compared to the control and straw application, biochar significantly increased the abundance of total nematode, bacterivorous, herbivorous, and omnivorous predators. Simultaneously, it increased the sweet potato root biomass, root-to-shoot ratio, and soil pH but significantly decreased soil mineral nitrogen. By analyzing the relationship between soil nematode communities and plant growth as well as soil properties, it was evident that the application of biochar in combination with reduced chemical fertilizer led to a reduction in soil nutrient availability, thus nutrient limitation prompted plants to allocate more photosynthetic products below ground, resulting in increased crop root biomass and the abundance of herbivores. [Conclusion] This study suggests that under the background of reducing chemical fertilizer and increasing the application of organic materials in China, soil fertilization practices combining biochar application with reduced chemical fertilizer should take into comprehensive consideration the potential adverse effects of nutrient deficiency on crop growth.
-
Effect and Mechanism of Polystyrene on the Co-transport of Copper and Soil Colloids in Saturated Porous Media
GONG Jiaqi, DONG Yanan, XU Shaohui, LIN Qing
DOI: 10.11766/trxb202401150028
Abstract:
【Objective】The ubiquitous colloidal substances in the environment profoundly affect the transport and transformation of pollutants in soil and groundwater. The impact of microplastics, as an emerging pollutant, on the transport of colloids and colloid-associated pollutants is still unclear. 【Method】Therefore, column experiments were conducted in saturated quartz sand, with polystyrene (PS) microplastics as the research object. By combining with sedimentation experiments, Fourier infrared spectroscopy (FTIR), and other methods, the influencing mechanisms of microplastics on soil colloid, copper (Cu2+), and their co-transport were investigated. 【Result】The results showed that PS facilitated the transport of soil colloids through mechanisms involving heterogeneous aggregation with soil colloids, competition for surface sites on quartz sand, and steric hindrance. This promotional effect was more pronounced in the presence of Cu2+. In comparison to soil colloid, the effect of PS on Cu2+ migration was not obvious due to its low concentration as well as low adsorption capacity. In the presence of PS, 83.47% of Cu2+ was transported in dissolved form, while 35.25% of Cu2+ was transported in colloidal form under the effluence of soil colloid. PS enhanced the mobility of soil colloids, but it concurrently reduced the adsorption of Cu2+ and facilitated the transport of dissolved Cu2+ compared to the scenario with only soil colloids. However, PS did not have a significant impact on the effluent concentration of total Cu. Furthermore, the mobility of PS was also influenced by soil colloids and Cu2+. 【Conclusion】 In general, microplastics in the soil environment not only directly interact with Cu2+, but also alter the properties of soil colloids. Changes in colloidal properties may be the primary reason for the impact of microplastics on the environmental behavior of Cu.
-
Methods of Filling in Bulk Density Gaps of Cropland Topsoil in The Sichuan Basin
LI Aiwen, LI Wendan, SONG Liangying, RAN Min, CHEN Dan, CHEN Jinli, QI Haoran, GUO Conghui, LI Qiquan
DOI: 10.11766/trxb202311270498
Abstract:
【Objective】This study aimed to construct a high precision prediction method for soil bulk density to accurately complete the regional soil attribute database.【Method】Based on the data of 2,883 typical cropland samples in the Sichuan Basin (including Sichuan Province and Chongqing Municipality) obtained during the second national soil census, this study used correlation analysis, variance analysis, and regression analysis to reveal the statistical characteristics and main controlling factors of the cropland topsoil bulk density in the Sichuan Basin. The traditional pedotransfer functions (PTFs), multiple linear regression (MLR) models, radial basis function neural network (RBFNN) model, and random forest (RF) models were used to establish a soil bulk density prediction model through three modeling methods: whole region, by river basin and by soil type, to fill the missing value of soil bulk density.【Result】The results show that the cropland topsoil bulk density in the study area ranged from 0.60 to 1.71 g·cm-3, with a mean value of 1.29 g·cm-3. Soil organic matter, soil subgroup, and rainfall in summer were the most important factors influencing bulk density. The RBFNN model constructed by the river basin can better capture the nonlinear relationship between soil bulk density and the influencing factors and the spatial non-stationarity of this relationship. The coefficient of determination (R2) and root mean square error (RMSE) of the 432 independent validation samples were 0.519 and 0.095 g·cm-3, respectively, which were significantly better than those of other methods.【Conclusion】Therefore, the RBFNN prediction model constructed in sub-basin is helpful to improve the imputation accuracy of the missing values of topsoil bulk density in the Sichuan Basin, and also provides a method reference for the imputation of missing values of soil properties in other regions.
-
Screening of Indigenous Microbial Helpers for the Chlorpyrifos-degrading Bacterium Shingopyxis granuli CP-2
LI Mei, WANG Zhongyang, JING Lili, HOU Yugang, MA Liya, SHENG Hongjie, YU Xiangyang†
DOI: 10.11766/trxb202311200486
Abstract:
【Objective】Chlorpyrifos residue poses a significant challenge to food safety. Microbial degradation which is called bioaugmentation is an effective approach for the elimination of such residues. Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined how the interactions between the invaded degrading bacteria and resident microorganisms in the target environment can influence microbial degradation. In this study, chlorpyrifos-degrading bacteria Shingopyxis granuli CP-2 was used as material, from the perspective of microbe-microbe interactions, to select resident bacterial helper of CP-2. 【Method】Soils from the field were first collected, a batch of bacteria from the soil was isolated by continuous dilution method, and identified by full-length sequencing of the 16S rRNA gene. The 16S rRNA gene sequences of all isolates were aligned using MUSCLE. Sequences in the alignment were trimmed at both ends to obtain maximum overlap using the MEGA X software, which was also used to construct taxonomic cladograms. A maximum-likelihood (ML) tree was constructed, using a general time reversible (GTR) + G + I model, which yielded the best fit to our data set. Bootstrapping was carried out with 100 replicates retaining gaps. A taxonomic cladogram was created using the EVOLVIEW web tool (https://evolgenius.info//evolview-v2/). The taxonomic status (phylum) of each rhizobacterial strain was also added as heatmap rings to the outer circle of the tree. The resident bacterial helper which could promote the growth of CP-2 was then screened by supernatant assay from the isolates isolated from soils, and the bioinformatics results of these helpers were analyzed. At last, a bacterial isolate which well promoted the growth of CP-2 was chosen, and its effect on CP-2""s ability to degrade chlorpyrifos was investigated in vitro. 【Result】109 strains of indigenous bacteria were isolated and were classified into four main phyla: Proteobacteria (54.1%), Actinobacteria (14.8%), Firmicutes (15.6%), and Bacteroidetes (15.6%). Among them, 41.3% significantly inhibited the growth of CP-2, 17.4% had no significant effect on CP-2, and 41.3% (45 bacterial strains) significantly enhanced CP-2""s growth and were identified as indigenous bacterial helpers of CP-2. The 45 bacterial strains in the helper bank mainly belong to 3 phyla, 4 classes, 7 orders, 13 families and 20 genera. One strain (B72), which exhibited a strong growth-promoting effect on CP-2 was selected to assess its impact on chlorpyrifos degradation by CP-2. The results demonstrated that both the bacterial strain B72 and its supernatant significantly promoted the chlorpyrifos degrading ability of CP-2. 【Conclusion】Together, the strains identified in this study provide valuable resources for future research and applications involving microbial degradation of soil toxicants such as chlorpyrifos or other pollutants. Furthermore, the indigenous bacterial helper of chlorpyrifos degrading bacterium CP-2 significantly promoted its ability to degrade chlorpyrifos, which offers theoretical guidance and technical support for potential co-inoculation strategies involving both chlorpyrifos-degrading bacteria and indigenous bacterial helpers aimed at pollution remediation.
-
Progress of Survey, Monitoring, and Control Technology of Benggang Erosion in Red Soil Hilly Area
DOI: 10.11766/trxb202312120526
Abstract:
Benggang is aunique type of soil erosion in the south of China, which refers to the erosion phenomenon of collapse and scouring of the hillside damaged by the combined action of hydraulic force and gravity. Bengngang erosion is an advanced stage of gully development and is a permanent gully that cannot be filled in by farming practices. Benggang mainly occurs in the southern granite hill region which is mostly agricultural production, and its harmful effects are serious, destroying land resources, affecting agricultural production, and seriously impeding the coordinated and sustainable socio-economic development. Due to the complexity of the factors involved in the formation of Benggang, the knowledge of the mechanism and the management measures are still being explored. The objective of this study was to identify the current status of soil erosion in the region by outlining the survey methods of Benggang erosion, to obtain basic information on Benggang erosion, and to provide a scientific and theoretical basis for the development of soil and water conservation measures. Specifically, this study detailed the methodology, content, and purpose of individual Benggang surveys, and through this process grasped the basic characteristics of Benggang erosion. Subsequently, the methodology of investigating the regional influencing factors of the Benggang was introduced, which mainly includes the main influencing factors of the Benggang, such as geological geomorphology, climatic conditions, soil parent material, vegetation, and anthropogenic activities. Based on the investigation, this study also compiles the monitoring techniques of the Benggang used in recent years, combining the traditional manual methods with emerging technologies to truly and efficiently grasp the distribution characteristics, influencing factors and erosion development trend. Then, the research progress on the risk assessment and prediction methods of Benggang was reviewed to objectively assess the losses or impacts caused by Benggang disasters and to explore preventive and control measures. Finally, existing measures and models for the prevention and control of Benggang are discussed based on the survey of basic information on Benggang, field monitoring methods and risk assessment and prediction studies. Our investigation shed light on the current situation of erosion and the prediction of the development trend of Benggang, which is of great significance to the prevention and control of erosion in the Benggang region in China. The contents of the review in this study also assist in providing a basis for methods of investigation in the same erosion types, which can be generalized to the research of soil erosion in regions with similar geomorphology.
-
Inhibition Mechanisms of Acidification Induced by Urea Application Using Organic Carbon Sources with Different Availability for Microorganisms in Ultisol
GUAN Peng, WANG Ruhai, SHI Renyong, Li Jiuyu, XU Renkou
DOI: 10.11766/trxb202308140323
Abstract:
【Objective】 This study investigated the mechanism of different organic carbon (C) sources to control fertilizer nitrogen (N) transformation and its induced soil acidification. 【Method】 Four types of organic C sources (glucose, sodium benzoate, cellulose, and lignin) with different availability for microorganisms were selected for a 45-day indoor incubation experiment. It was conducted under the condition that the C/N ratio of C source and fertilizer (urea) was 40. The effects were analyzed for the combined application of organic C source and urea on N transformation and soil acidity in Ultisol. 【Result】 The results showed that intensive nitrification occurred when urea was used solely in Ultisol, resulting in a soil pH decrease of 1.17 pH units at the end of the incubation. Compared with the sole application of urea, the combined application of organic C sources and urea significantly enhanced soil respiration, and decreased soil inorganic N by 17.1%-99.4% and soil NO3--N by 46.1%-99.9%. However, these organic treatments increased soil microbial biomass N and solid organic N (non-extractable N) by 3.0%-14.8%, and increased soil pH by 0.67-3.11 pH units. These findings suggest that the combined application of organic C sources and N fertilizer promoted the immobilization of fertilizer N by soil microorganisms and soil N sequestration, thereby significantly reducing nitrification and soil acidification induced by N fertilizer. Specifically, as a labile organic C source, glucose facilitated the rapid immobilization of fertilizer N by microorganisms in the early stage and the mineralization of organic N in the later stage. It indicated that glucose could play a role in temporary storage and slow release of fertilizer N in the soil. Cellulose was less easily utilized by microorganisms and also promoted microbial immobilization of fertilizer N. Although cellulose was not as fast as glucose, it had strong immobilization capacity and high C use efficiency, which was conducive to the long-term immobilization of fertilizer N in the soil. Lignin, a resistant organic C source, weakly promoted microbial immobilization of fertilizer N but directly inhibited nitrification. The mentioned C sources regulated the N transformation process and increased the soil pH by approximately 0.6 pH units. Sodium benzoate, as a labile organic acid salt, reduced nitrification directly by inhibiting nitrification and indirectly by promoting microbial N immobilization, although the microbial immobilization of fertilizer N was significantly lower than that of glucose and cellulose. Decarboxylation of sodium benzoate rapidly consumed a substantial amount of H+ and significantly increased the soil pH by approximately 3.0 pH units. 【Conclusion】 The chemical properties of organic C sources, including the complexity of their chemical structure, microbial availability, microbial C use efficiency, and microbial toxicity, are the main factors affecting the transformation process of soil C and N, and consequent soil acidification. The findings obtained in this study provide significant theoretical support for the effective and sustainable management of soil nutrients and acidity in cropland.
-
Effects of Dazomet Fumigation and Reductive Soil Disinfestation on Antibiotic Resistance Genes in Farmland Soil
YU Wenhao, LI Shu, LIN Yulan, ZHANG Jingqing, XU Chenwei, LIU Liangliang, ZHANG Jinbo, CAI Zucong, ZHAO Jun
DOI: 10.11766/trxb202309100369
Abstract:
[Objective] The prevalence and dissemination of antibiotics resistance genes (ARGs) in farmland soils have become a major threat to food security and human health. However, there is still no effective method to remediate ARGs-contaminated farmland soil. Chemical fumigation and reductive soil disinfestation (RSD) are widely used to kill soil-borne pathogens in agricultural production, but it is still unknown whether they are capable of reducing the abundance of ARGs in ARGs-enriched soil. [Method] In this study, an ARGs-enriched farmland soil due to long-term application of chicken manure was selected, and soil incubation experiment with seven treatments: CK (control without soil treatment), FCK (maximum water holding capacity treatment), DZ (chemical fumigation with 0.02% dazomet), and RSD with 1% ethanol (ET, TOC: 521.7 g·kg-1), alfalfa (AL, TOC: 454.9 g·kg-1, C/N: 21.2), molasses (MO, TOC: 270.1 g·kg-1, C/N: 12.6) and the mixture of alfalfa and molasses (AM, m/m=1:1), were conducted to investigate the shifts in absolute abundance and relative abundance of ARGs and mobile genetic elements (MGEs) via real-time PCR. The effects of different treatments on soil ARGs and MGEs were evaluated by reduction rate. [Result] Results showed that RSD treatment could decrease the relative abundance of aadA21, msrE, tetG, tetM, and ErmF genes, with the reduction of the aadA21 gene in relative abundance being 50.5%~58.3% in AL-, MO-, and AM-treated soils, while the relative abundances of msrE, tetG and tetM genes were significantly lowered by ET treatment, with the reduction rate being as high as 80.9%, 78.3%, and 66.9%, respectively. Meanwhile, RSD treatment could significantly decrease the relative abundance of MGEs (IS6100 and IS26 gene), with the reduction rate being 67.7%~74.3% and 38.1%~42.6%, respectively. In addition, the relative abundances of ARGs and MGEs were slightly increased in DZ treatment, with the increasing rate of ARGs and IS26 gene being 21.9% and 42.6%, respectively. [Conclusion] Collectively, RSD treatment can decrease soil ARGs contamination by reducing the relative abundance of ARGs and MGEs, limiting the horizontal transfer ability of ARGs, and the reduction effect is related to the type of organic materials used. Moreover, RSD treatment is more effective in reducing the relative abundance of ARGs and MGEs than dazomet fumigation and has the potential for rapid remediation of ARGs-contaminated soil.
-
Characteristics of Soil Organic Carbon Fraction Accumulation and Stability under Different Rice-rape Rotation Measures
SHU Yeqin, PENG Fuxi, LEI Wenshuo, JIANG Tongtong, CHEN Yumei, LIU Weimin, ZHANG Zhenhua, XIA Yinhang
DOI: 10.11766/trxb202311030452
Abstract:
Rape multiple-cropping is an important planting mode to promote grain stabilization and rapeseed increase in South China rice growing area. We explored the influence of soil organic carbon (SOC) accumulation and its stability characteristics under different rice-rape rotation measures with whole-straw returning, which is of great significance for in-depth analysis of soil carbon cycle in paddy fields by making full use of winter fallow fields to plant rape. This study is based on an 8-year yield localization experiment. In contrast with rice-rice-winter fallow, we explored the characteristics of SOC and its fraction accumulation under three rice-rape rotation treatments: rice-rice-rape, rice-rape-tillage, and rice-rape-no tillage. The results indicated that the content of SOC in 0~20 cm soil layer was increased by 5.28%~25.12% under the three rice-rape rotation treatments, especially under the rice-rice-rape treatment. Also, the increasing rate of SOC in 20~40 cm soil layer was 18.48%~43.97%, among which the rice-rape-tillage and the rice-rape-no tillage treatment reached a significant level. Except for rice-rape-tillage treatment in 0~20 cm soil layer, the content of mineral-associated organic carbon (MAOC) from all the rice-rape rotation measures was increased significantly in different soil layers. At the same time, the ratio of particulate organic carbon (POC) to SOC was significantly decreased while the ratio of MAOC to SOC increased in each treatment from both 0~20 cm and 20~40 cm soil layer. The increasing rate of MAOC/SOC were 2.31%~7.49% and 1.56 %~2.66% in the two soil layers, respectively. Possible causes of these results may be that rice-rape rotation increased the activity of organic carbon invertase enzyme (β-glucosidase、β-1,4-glucanase and Laccase) as well as microbial biomass carbon in 0~20 cm soil layer to varying degrees, thereby promoting the conversion of POC to MAOC. In summary, rape multiple-cropping in winter fallow not only promoted the accumulation of SOC in paddy field, but also increased the ratio of MAOC/SOC, ultimately enhancing the stability of soil carbon pool.
-
Effect of Soil Acid Reduction and Fertilizer Cultivation Under Conditioner Application: Meta-analysis Based on Acid Soil Improvement Studies in China
MING Runting, WAN Fang, NA Liping, WU Haicheng, WANG Wei, TAN Wenfeng, WU Yupeng†
DOI: 10.11766/trxb202311050456
Abstract:
【Objective】This study aimed to accurately evaluate the effect of soil conditioner application on acid reduction and fertilizer cultivation of acidic soils in China. 【Method】This study conducted a meta-analysis of 127 published literature, and identified the effects of acid soil conditioner application on soil acidity, soil fertility, and crop yield. 【Result】The results showed that the acid reduction effect of the conditioner in extremely acidic soil (pH≤4.5) was the best. After application, the soil pH increased by 14.39%, and the reduction rates of exchangeable Al and exchangeable acidity reached 68.61% and 69.90%. The pH and basicity of the conditioner itself were the main factors affecting the acid-lowering effect of the conditioner, among which the lime conditioner had the best effect. It was observed that the soil pH increased by 18% and the exchangeable acidity decreased by 75.81% after application. The nutrient content of the conditioner itself and the amount of the conditioner were the main factors affecting the soil fertility after the conditioner application and the application of organic fertilizer had the best effect on the improvement of soil available nitrogen and available phosphorus (60.16%, 135.30% respectively). Also, biochar amendments had the best effect on the improvement of soil-available potassium and organic matter (75.52% and 76.02%). The application of amendments can reduce soil acidity and increase soil fertility to increase production, and biochar amendments had the best effects of increasing production, reaching 78.23%.【Conclusion】For managing acidic soils, it is recommended to apply high pH and high alkalinity amendments such as lime and biochar. For acidic soils with low organic matter content, it is recommended to apply high-alkalinity organic fertilizer, biochar and other amendments while biochar and mineral amendments are recommended for acidic soils with high organic matter content. For weakly acidic soil, it is recommended to apply common organic fertilizer. Nevertheless, it is necessary to further strengthen research on the combined application of inorganic and organic amendments to obtain a better effect on acid soil improvement.
-
Research of Paddy Soil Dissolved Organic Matter Composition and its Binding Process with Cd2+
LIANG Yihao, NI Caiying†, LI Yanliang, XIAO Luochang, JIAN Minfei
DOI: 10.11766/trxb202310180426
Abstract:
【Objective】Cadmium (Cd) is the heavy metal pollutant with the highest over-limit rate in paddy soil in China. The bioavailability and mobility of Cd are affected by dissolved organic matter (DOM) in the soil. Paddy fields are important food production areas in China. As an important ecological agriculture mode in the rice industry, integrated planting and breeding of rice fields is of great significance to rural revitalization. The modification of paddy field environments and fishing can change DOM, but the complexation process between soil DOM and Cd2+ in paddy soil and during integrated planting and breeding of rice field process has not been clearly understood. 【Method】In this study, the complexation process between DOM and Cd2+ in rice-shrimp cultivation (RS) and rice monoculture (CK) systems was investigated using a comprehensive array of analytical techniques, including ultraviolet-visible absorption spectrum (UV-Vis), 3D fluorescence spectroscopy, synchronous fluorescence spectroscopy, parallel factor analysis (PARAFAC), 2D correlation analysis (2D-COS), and the modified Stern-Volmer binding reaction model. Herein, RS was taken as an example of integrated planting and breeding of rice fields.【Result】The PARAFAC analysis showed that soil DOM components of RS and CK were similar, including 1 tryptophan(C1) and 3 humus components (C2, C3, C4). Compared with CK, the proportions of C2 and C4 in soil DOM of RS were lower, while C3 was higher, and C1 was not significantly different. The UV-vis spectrum showed that DOM absorbance in CK was higher than in RS, with the absorption peak mainly located at 200-230 nm. With the increase of Cd2+, the change of UV-vis spectrum and UV254 was significantly different between RS and CK. Synchronous fluorescence spectra and 2D-COS analysis showed that paddy soil DOM fluorescence intensity changed with the increase of Cd2+, three absorption peaks were found by synchronous fluorescence spectra in DOM of paddy soil, which were the peak of tryptophan at 270 nm and the humus peak at 310 nm and 370 nm, respectively. The binding order between soil DOM and Cd2+ in RS was humus (310 nm), tryptophan, and humus (375 nm) , respectively. However, in CK, the binding order was tryptophan, humus (375 nm), humus (310 nm). In the Stern-Volmer binding reaction model, the fluorescence intensity of C1 and C4 decreased with the increase of Cd2+, but the fluorescence intensity of C2 and C3 was unstable, which showed that the complexation of humus components C2 and C3 with Cd2+ had instability. This also led to the failure of fitting C2 and C3 in the model. The complexation constants lgK of C1 and C4 in the soil DOM of RS were 4.25 and 5.03, which were higher than in CK.【Conclusion】The soil DOM in RS and CK mainly consisted of humus and the material composition ratio of soil DOM in RS was different. The complex process of DOM and Cd2+ in paddy soil belonged to static quenching and the aromatic structure affected the stability of DOM and Cd2+ complexation. Also, RS influenced the binding ability of tryptophan and fulvic acid DOM to Cd2+ whereas the instability of the complexation of humus with Cd2+ and the complexation of C4 with Cd2+ can enhance the bioavailability of Cd in soil. The results of this research can provide a scientific reference for the study of soil Cd pollution mechanism and pollution prevention in paddy fields.
-
Effect of Canopy Nitrogen Deposition on Soil Phosphorus Fractions in a Moso Bamboo Forest
WEI Jingwei, XIAO Xiangqian, ZHUO Shoujia, JIANG Wenting, SUN Hongyang, CHEN Youchao, LI Yongfu, YU Bing, CAI Yanjiang†
DOI: 10.11766/trxb202309110372
Abstract:
【Objective】Nitrogen (N) deposition is an important global climate change factor affecting soil phosphorus (P) cycling in forest ecosystems. However, understory N application typically applied directly to the ground, has been widely used to simulate N deposition in forest ecosystems in the past. This simulation method may neglect the retention and adsorption effect of the forest canopy, which cannot truly assess the effect of N deposition on soil P cycling. Moreover, organic N is another important component of atmospheric N deposition, but the ecological effect of the organic N deposition has not been fully studied.【Method】To evaluate the effect of atmospheric N deposition on soil P cycling, a field experiment was conducted involving six treatments: canopy control (CNA-CK), canopy inorganic N addition (CNA-IN), canopy organic N addition (CNA-ON), understory control (UNA-CK), understory inorganic N addition (UNA-IN), and understory organic N addition (UNA-ON) based on the Anji MosoBamboo Ecosystem Research Station of Zhejiang A&F University, in Anji County, Zhejiang Province. The N deposition rate was set at 50 kg·hm-2·a-1 (based on the atomic mass of N, the same as below). IN uses ammonium nitrate while ON uses a mixture of 25 kg·hm-2·a-1 urea and 25 kg·hm-2·a-1 glycine as the N source. The CK treatment involves adding an equal amount of water. Soil P fractions, microbial biomass P, acid phosphatase activity, P cycling functional gene abundance, and some physicochemical properties were measured to investigate the effects of different N deposition simulation approaches and N components on soil P fractions and their driving factors.【Result】The results showed that canopy N addition (CNA) significantly reduced soil total P, occluded P, and labile P concentrations compared to understory N addition (UNA) with the percentage of 15.1%-26.5%, 18.3%-21.5% and 9.7%-38.3%, respectively. However, soil P fractions did not differ significantly between CNA-ON and CNA-IN treatments, whereas UNA-IN treatment significantly reduced resin P and labile P content compared to UNA-ON treatment. Acid phosphatase activity and pH were the main factors affecting soil P fractions, but N deposition did not significantly influence soil P cycling functional gene abundance.【Conclusion】Therefore, it was suggested that simulating N deposition via CNA significantly reduced the contents of total P and P fractions such as occluded P and labile P of Moso bamboo forest soils, whereas simulating N deposition via conventional UNA underestimated this reduction effect. Soil P is closely linked to the cycling of soil carbon and N, which are vital for maintaining a balanced nutrient ecosystem. Consequently, future simulation experiments on N deposition should systematically consider the effects of N deposition simulation approaches and N addition components on soil carbon, N, and P cycling processes.
-
Effects of Single Application of Organic Amendments and Their Combination with Biochar on Microbial Community Composition in a Red Soil
XU Yimeng, ZHANG Lei, BAI Meixia, ZHOU Yan, QIN Hua, XU Qiufang, CHEN Junhui
DOI: 10.11766/trxb202308200332
Abstract:
【Objective】This study aimed to clarify the effects of different return methods of organic matter on the characteristics of soil microbial communities.【Method】The changes of soil microbial community abundance and structure under single application of maize straw, sheep manure and combined application with biochar were analyzed by quantitative PCR and high-throughput sequencing based on two years of field experiments in dry cropland red soil.【Result】The results showed that: (1) Compared with the control (no material), the soil pH and nutrient content of sheep manure alone increased significantly, while the single application of straw had no significant effect on them. Compared with straw and sheep manure alone, soil organic carbon content under the treatment of biochar co-application with straw or sheep manure was significantly increased by 133.5% and 81.47%, respectively. (2) The abundance of bacteria and fungi under the treatment of sheep manure treatment significantly increased by 448.7%and 1 709%, respectively, and the abundance of bacteria under the treatment with biochar was further increased by 35.34%. Straw alone only increased fungal abundance. Single straw application and its combination with biochar significantly reduced bacterial diversity and richness but had no significant effect on fungal diversity. (3) Straw, sheep manure and biochar alone changed the structure of bacterial and fungal communities, and there were significant interaction effects. Functional predictive analysis showed that the combination of biochar and organic materials reduced carbohydrate metabolism and the abundance of potential plant pathogens. Available phosphorus, pH, total nitrogen and available potassium were the main factors affecting the abundance and structure of soil microbial communities.【Conclusion】In summary, the combined application of sheep manure and biochar can effectively improve the fertility of dryland red soil, increase the abundance of soil microorganisms, and reduce the number of potential pathogens. Thus, the combined application of sheep manure and biochar can be used as an effective measure to improve the fertility of dryland red soil and maintain soil health.
-
Properties and Aggregation Characteristics of Humic Acid in Surface Soil Under Two Forest Vegetations of Jinyun Mountain
DOI: 10.11766/trxb202309280403
Abstract:
【Objective】Soil organic carbon (SOC) pool, the largest C pool in terrestrial ecosystems, can achieve long-term C sequestration. SOC plays a vital role in the global C cycle and is a key link in achieving C peaking and C neutrality goals. Humic acid (HA) is one of the most important and more stable components of soil organic matter, representing a more stable soil C pool. The vegetation coverage type of regional soil affects the quantity, quality and composition of HA, and further affects its aggregation characteristics. In this study, HA in surface soil under bamboo forest (Altitude 580 m) and broad-leaved forest (Altitude 280 m) in Jinyun Mountain, Chongqing, was taken as the research object, and then surface properties and aggregation characteristics of these two HA were clarified. 【Method】The structural characteristics were evaluated by element analysis, thermal gravimetric analysis, and Fourier infrared spectroscopy. Combined with dynamic light scattering and zeta potential measurement, the aggregation kinetic characteristics of these two HA colloids induced by Na+, Mg2+ and Ca2+ were studied and compared. 【Result】It was found that HA in bamboo forest soil had higher C/N, C/H, stronger thermal stability and aromatic infrared absorption characteristic spectra, indicating HA in bamboo forest soil had more aromatic functional groups, more complex structure, and higher humification degree. The results of dynamic light scattering showed that the critical coagulation concentrations of Na+, Mg2+, and Ca2+ for the HA colloids of bamboo forest soil were 1 097.9 mmol?L-1, 8.6 mmol?L-1, and 5.1 mmol?L-1, respectively. The HA colloids of broad-leaved forest soil did not aggregate in the Na+ system, and the critical coagulation concentrations in Mg2+ and Ca2+ systems were 80.7 mmol?L-1 and 20.2 mmol?L-1, respectively. The zeta potential of HA in bamboo forest soil was much lower than that in broad-leaved forest soil. The absolute value of the zeta potential of HA in bamboo forest soil was 3.43 times that of HA in broad-leaved forest soil, which could be used to explain the difference in aggregation characteristics between the two. The sensitivity of the HA in bamboo forest soil to three cations is much higher than that of HA in broad-leaved forest soil, which can quickly aggregate and form larger particle sizes. 【Conclusion】The change of coverage vegetation types will cause the corresponding change of HA properties in surface soil. The humification degree of HA in high-altitude bamboo forest soil is higher, and the sensitivity to cations is also higher. The results of this study provide an important reference for understanding the formation and stability of HA after organic matter input into soil.
-
Response mechanisms of soil microbial carbon use efficiencies to cropland management measures
ZHANG Chenyang, SUN Liyang, XU Minggang, LIJianhua, CAI Andong
DOI: 10.11766/trxb202309020351
Abstract:
【Objective】Soil microbial carbon use efficiency (CUE) is an important indicator reflecting the regulation of the soil carbon cycle by microorganisms through their metabolism. However, the response and driving factors of soil microbial CUE to different management measures in cropland ecosystems are still unclear. This hinders a deep understanding of soil organic carbon turnover, rapid improvement of soil fertility, and effective mitigation of climate change.【Method】We collected published literature from around the world, and established 198 paired of relatively independent soil microbial CUE databases under different cropland management measures, including 13C-labeled substrate (CUE13C), 18O-labeled water (CUE18O) and stoichiometric model (CUEST) approaches. We quantitatively evaluated the response of soil microbial CUE to different cropland management measures under specific climate, soil properties, and experimental conditions by meta-analysis, combining Pearson and regression analysis to study the biotic and abiotic factors that control soil microbial CUE variation.【Result】(1) Compared with no biochar addition, biochar addition increased soil microbial CUE13C and CUE18O by 9.40% and 18.22%, respectively, while CUEST decreased by 40.01%. Compared with no fertilization, the application of chemical fertilizers could reduce soil microbial CUE18O (-4.71%), but increased soil microbial CUEST (28.20%), whereas straw amendments led to a decrease in soil microbial CUE18O and CUEST by 14.08% and 28.64%, respectively. Relative to conventional tillage, no or reduced tillage significantly increased soil microbial CUE13C, CUE18O, and CUEST (-2.12%-15.45%). (2) There were significant differences in the effects of cropland management measures on soil microbial CUE under different climates, soil properties and experimental conditions. Cropland management measures in semi-arid and humid areas reduced the soil microbial CUE13C by 8.80% and increased by 4.69%, but the soil microbial CUE18O decreased from 44.57% to -2.31%. When the soil organic carbon content was > 12 g·kg-1, cropland management measures increased the soil microbial CUE13C and CUEST by 7.79% and 12.87%, respectively. In the transition from acidic to alkaline soils, cropland management measures caused the soil microbial CUE13C to decrease from 12.74% to -7.51%. Also, as soil clay content increased, soil microbial CUE13C and CUEST decreased, while soil microbial CUE18O showed an increasing trend. With the increase of soil cation exchange capacity, soil microbial CUE18O and CUEST showed a decreasing trend. When the experimental duration was 3-10 years, cropland management measures increased soil microbial CUE18O by 43.49% while soil microbial CUEST decreased by 23.72%. (3) Soil microbial CUE13C increased with aridity index and decreased with soil pH. Furthermore, the soil microbial CUE18O increased with soil microbial growth rate and soil microbial biomass carbon. Soil organic carbon, β-glucosidase and N-acetyl-glucosaminidase were positively correlated with soil microbial CUEST (P < 0.05) whereas soil clay content was negatively correlated with soil microbial CUEST (P < 0.01). 【Conclusion】Considering climatic factors and soil chemical properties, and the response of microbial activity and function to cropland management measures at a specific site is conducive to adjusting the soil microbial CUE at the microbial community or cell level, thereby effectively promoting soil carbon formation and accumulation in cropland ecosystems.
-
Long-term Observation Effects on Soil Salinity and Fertility in Saline-alkali Land Reclamation Under Drip Irrigation
HUO Weige, PENG Yi, ZHANG Shaomin, LIU Shenglin, BAIDENGSHA Maimaiti, FENG Gu†
DOI: 10.11766/trxb202309080368
Abstract:
【Objective】The submembrane drip irrigation planting mode has been a major factor in the evolution of physicochemical traits after the reclamation of saline-alkali land in inland arid areas, especially the changes in soil salinity and available nutrient content. 【Method】In this study, the gray desert soil of Xinjiang was studied by continuous localization survey and observation of the sample plot. The sample plots of Manas in Xinjiang were selected for land reclamation in different years in 1996, and four surveys were carried out from 2010 to 2020. The dynamic changes of soil salinity and fertility traits of gray desert soil under the condition of submembrane drip irrigation cotton after reclamation were monitored at fixed points, and the differences of several plots after different planting years were compared.【Result】The main results suggest that the soil salinity in the topsoil (0-20 cm) was significantly reduced after the reclamation from uncultivated land to farmland, and the average salinity of various plots decreased to 3.71 g·kg-1 after 6-10 years of reclamation. The average annual decline rate was 1.41 g·kg-1·a-1, reaching the level of mild salinization, then with the continued reclamation (11-25 years), the soil salinity was maintained between 2.06-2.11 g·kg-1, and reaching the non-salinization level. The soil pH in different reclamation years showed a significant downward trend after reclamation. With continued reclamation (11-25 years), the average soil pH remained between 8.2 and 8.5, which was slightly alkaline. With increasing years of reclamation, the soil available phosphorus (P) increased significantly, after 11-25 years of reclamation and planting, the soil average available P level remained between 13.33, and 19.97 mg·kg-1. This indicates that the variation of soil fertility was different with the different reclamation years. The soil organic matter increased significantly after 6-10 years of reclamation while the soil available potassium slowly decreased after 1-5 years of reclamation but slightly increased after 6-10 years. Also, available potassium increased to the original level after 11-16 years and then remained stable. The content of soil inorganic nitrogen increased significantly after 6-15 years of reclamation and remained stable after 16-25 years.【Conclusion】Our study showed that the process of reclamation and utilization of uncultivated land into farmland had a significant effect on the improvement and cultivation of soil P fertility. The uncultivated land reclamation and utilization effectively reduced soil salinity and pH, and it took 6-10 years to change the good land after uncultivated land reclamation. This study provides a theoretical basis for the control of salt content and the improvement of fertilization and farmland productivity during the reclamation process of inland saline-alkali uncultivated land.
-
Mechanism of Degradation of Typical Malodorous Benzene Congeners in Soil by Activated Persulfate with Sulfidized Nano-zero-valent Iron Loaded on Biochar
LI Yanlu, YANG Xinglun, BIAN Yongrong, MA Zhiyong, GU Chenggang, SONG Yang, XIANG Leilei, WANG Fang, JIANG Xin
DOI: 10.11766/trxb202310240433
Abstract:
【Objective】The degradation of organic pollutants in soil by activated persulfate (PS) with nanoscale zero-valent iron (nZVI) or sulfidized nanoscale zero-valent iron (S-nZVI) is currently one of the research hotspots in in-situ chemical oxidation remediation technologies. Benzene, toluene, ethylbenzene, and xylene (BTEX) are typical odorous pollutants in petrochemical-contaminated sites. Thus, the discovery of remediation technologies aimed to achieve efficient removal of BTEX and the elucidation of the degradation mechanism is of great environmental significance.【Method】The study established a persulfate oxidation system using biochar-supported sulfidized nano zero-valent iron (S-nZVI@BC) as the activator, explored the degradation of BTEX under different conditions, and compared its effectiveness with other materials for PS degradation. Moreover, based on chemical probe experiments, electron paramagnetic resonance (EPR) experiments, and purge-and-trap-gas chromatography-mass spectrometry (PT-GC-MS), the degradation pathways of BTEX were indicated.【Result】The results showed that S-nZVI@BC/PS system had the best degradation efficiency on BTEX in the soil at pH = 3, S/Fe = 1/4, Fe/C = 1/2, S-nZVI@BC dosage of 0.01g•g-1soil, and PS concentration of 30 mmol•L-1. The degradation rates of benzene, toluene, ethylbenzene, and ortho-xylene in the S-nZVI@BC/PS system reached 96.7%, 98.5%, 96.9%, and 98.4% within 2 h, respectively. The S-nZVI@BC catalytic system showed the best performance among the five different catalytic systems studied in the order of PS < nZVI/PS < nZVI@BC/PS < S-nZVI/PS < S-nZVI@BC/PS. Also, S-nZVI@BC maintained good reaction activity in a wide range of pH 2-9. There were three active free radicals in the system: SO4˙-, HO˙, and O2˙-, among which SO4˙- was confirmed as the main active substance in the reaction process. Based on main free radicals and intermediates, it is indicated that BTEX may have two degradation pathways: Free radical addition and free radical hydrogen extraction reaction.【Conclusion】Sulfur modification and biochar loading effectively improved the stability of nZVI catalytic performance, and S-nZVI@BC/PS can efficiently degrade BTEX. This study provides theoretical support for the establishment of efficient degradation technology for odorous pollutants in soils.
-
Leaching Characteristics of Residual Fertilizer Nitrogen in the Dryland of Loess Plateau During the Summer Fallow Period
XIA Mengjie, WANG Huimin, LEI Shuang, ZHAO Mengzhen, FENG Hao, ZHOU Jianbin
DOI: 10.11766/trxb202308250340
Abstract:
【Objective】Summer fallow after winter wheat harvest in dryland is a common practice on the Loess Plateau. However, due to bare land and intensive rainfall during summer fallow, the leaching characteristics of residual fertilizer nitrogen (N) after crop harvest deserve attention. This study aimed to reveal that the destination of applied N fertilizer after wheat season and the leaching characteristics of residual N fertilizer during summer fallow in dryland of the Loess Plateau. 【Method】This study was carried out in large lysimeters (3 m×2.2 m×3 m) by the 15N labeled method. 15N labeled urea was applied at the beginning as basal fertilizer with the rate of 150 kg•hm-2. Firstly, the absorption of 15N labeled fertilizer by wheat and the residual N in the soil after wheat harvest were investigated, and subsequently the 15N abundance and content changes of residual 15N labeled fertilizer in the soil profile were measured during the summer fallow of three years (2015—2017). 【Result】The results showed that the average absorption of nitrogen fertilizer by wheat was 53.9% while the amount of 15N fertilizer distributed in the soil (0-100 cm) after wheat harvest was 36.3% of the N application rate, with an average of 40.1% being in nitrate form. In the first year, the residual 15N fertilizer which accumulated in the 0-40 cm soil layer moved downward and accumulated in the 60-80 cm soil layer during the following summer fallow. The 15NO3--N mainly accumulated in the above 80 cm soil layer before summer fallow, but the accumulation peak of 15NO3--N was in the 80-100 cm soil layer at the end of fallow. In the second and third years, the residual 15N fertilizer and 15NO3--N moved downward about 20 cm, respectively, during summer fallow. After the summer fallow, the amount of residual 15N fertilizer in the 0-100 cm soil layer decreased, but the amount of residual 15N fertilizer and 15NO3--N in the 100-200 cm soil layer both increased. Specifically, the amount of residual N in the 100-200 cm soil layer increased by 1.9 and 7.0 kg•hm-2 during the summer fallow of the second and third years, respectively. Also, the amount of 15NO3--N in the 100-200 cm soil layer increased by 2.7 and 7.0 kg•hm-2 during the summer fallow of the second and third years, respectively. 【Conclusion】During the summer fallow, residual N fertilizer leached significantly. Under normal precipitation conditions, the average downward migration rate of residual N fertilizer during a summer fallow was 20 cm. As the age increased, the residual N fertilizer in the 0-100 cm soil decreased; while it increased in the 100-200 cm soil layer, with nitrate as the main leached form. However, the cumulative total loss of residual N fertilizer in the 0-200 cm soil profile during summer fallow was small, indicating that the redistribution of residual N fertilizer nitrogen in the soil profile was the main mechanism.
-
Progress of soil temperature prediction equation
Zhang Jianbin, Gao Zhi Qiu, Tong Bing, Wang Linlin
DOI: 10.11766/trxb202210220581
Abstract:
Soil temperature (especially surface temperature) is a key physical quantity in the interaction between land and atmosphere, and plays a very important role in the earth system. Soil temperature prediction technology has always been the core scientific problem in land surface model, numerical weather prediction and climate prediction. This paper systematically reviews the research progress of soil temperature prediction equation, from the classical heat conduction equation to the heat conduction convection equation that takes into account the physical process of vertical movement of soil moisture, from the single sine wave approximation to the Fourier series approximation of the daily change of surface temperature, from the assumption that the diurnal change of convection parameters is constant to the consideration of its diurnal change, and emphatically summarizes the creation, improvement and solution of the soil heat conduction convection equation. Finally, this paper reviews the application of heat conduction convection equation in the study of surface energy balance, vertical movement of soil moisture, water flux, earthquake and frozen soil heat transfer. At the same time, it is pointed out that the influences of soil water phases and plant roots on the heat conduction-convection equation is warranted for the future research of soil temperature prediction equation.
About
Supervisor： Chinese Academy of Sciences
Sponsor：Soil Science Society of China
Editor-in-Chief：Xu Renkou
Address：71 East Beijing Road, Nanjing 210008, P. R. China
Zip Code：210008
Phone：+86-25-86881237
Email：actapedo@issas.ac.cn
ISSN：0564-3929
Qr Code
-
WeChat