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.

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.

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 beginning from 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 resulted 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 ·kg-1 after 6-10 years of reclamation. The average annual decline rate was 1.41 ·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 ·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 m·kg-1. This indicated 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】 This 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.

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.

Abstract:ObjectiveThis study aimed to reveal the characteristics of soil nitrogen (N) transformation in different clonal Chinese fir plantations in Yangkou National Forest Farm of Fujian. This study provided theoretical basis for artificial nitrogen management and improved seed breeding of different clones of Chinese fir plantations.MethodAn incubation experiment was carried out with 7 different kinds of 15-year old third-generation excellent culture materials and seedlings (Y003, Y008, Y020, Y061, Y062, Ysec and Ymix) as the research objects, and the basic physical and chemical properties, net N mineralization and nitrification rate of soil of different clones were evaluated.ResultThe results showed that the net rates of N mineralization and nitrification were significantly affected by different clonal Chinese fir plantations. Specifically, the net mineralization rate and net nitrification rate were -0.09-0.118 mg·kg-1·d-1 and -0.021-0.051 mg·kg-1·d-1, respectively. During the whole incubation period, the average net soil N mineralization rate of Y061 was 0.117 mg kg-1 d-1, which was significantly higher than that of other clones and followed by Ymix (0.046 mg·kg-1·d-1) and Y062(0.033 mg·kg-1·d-1). In contrast, the average net N mineralization rates of the other four clones were negative, indicating the occurrence of net N immobilization. The average net soil nitrification rate of the Y008 clone was the highest, which was 0.051 mg kg-1 d-1, followed by Ymix (0.003 mg·kg-1·d-1) and Y020 clone (0.007 mg·kg-1·d-1). There were no significant differences in soil pH, ammonium nitrogen, C/N and the composition of silt and sand, but there were significant differences in soil nitrate nitrogen, organic matter, total nitrogen and clay composition. The results showed that ammonium nitrogen, nitrate nitrogen, pH and total nitrogen in soil were the main factors affecting the net nitrification rate and were all positively correlated, In contrast, the average net nitrification rate of the other four clones was negative, indicating the occurrence of net immobilization of nitrate. There were no significant differences in soil pH and carbon (C)/N among different clones, but significant differences in soil particle size composition, organic matter and total N content. Soil pH and total N were positively correlated with net mineralization and net nitrification rate, while soil C/N was negatively correlated with sand content.ConclusionThe results showed that the soil N supply capacity and N retention capacity of Y061 and Y062 clones were significantly higher than those of other clones, and the risk of N loss such as leaching in Y008 clones was higher than that of other clones. Therefore, the clone species should be rationally selected to ensure the soil fertility supply in actual planting. This study provides a theoretical basis for artificial nitrogen management and improved seed breeding of different clones of Chinese fir plantations.

Abstract:ObjectiveBt toxins released from Bt plants and Bt biopesticides are potential exogenous pollutants in the environment with biocidal activity. The environmental behavior and ecological effects of Bt toxins are the focus of safety risk assessment of transgenic plants and transgenic microorganisms. Fungus is an important component of soil microbes and plays a key role in maintaining soil ecosystem stability, but the dynamic response of soil fungal communities and potential functions to exogenous Bt toxins remains unclear.MethodIn this study, the retention dynamics of Bt toxins in soils incorporated with different concentrations of Bt toxins were analyzed, and high-throughput sequencing technology of fungal 18S rRNA gene was used to analyze the effects of Bt toxins application on the soil fungal community and functional diversity.ResultThe results showed that the concentration of water-dissolved Bt toxins in soil decreased significantly with the prolongation of soil incubation time, and the amounts of water-dissolved Bt toxins in soil with initial Bt toxins concentrations of 50, 100 and 500 ng·g-1 decreased to those of control soil on the 100th day. Both the application of Bt toxins and incubation time could significantly affect the composition of the soil fungal community, and with an increase of initial Bt toxins concentration and prolongation of soil incubation time, the difference in soil fungal community gradually widened. The application of Bt toxins increased the Shannon index of the soil fungal community, the negative correlation and modules of the association network, and thus it did not adversely affect the diversity and stability of the soil fungal community.ConclusionThe results indicate that the initial concentration of Bt toxins and its long-term effects should be of concern when assessing the environmental behavior and micro-ecological effects of Bt toxins. With the increase of Bt toxins concentration, the relative abundances of Phymatotrichopsis, Homalogastra, Geosmithia and Apiotrichum increased significantly, as well as functional genes encoding enzymes involved in protein degradation, carbon metabolism and phosphorus metabolism. It is speculated that the above-mentioned fungal taxa and potential functions were involved in the degradation and transformation process of Bt toxins in the soil. This study provides a scientific reference and theoretical basis for the ecological safety risk assessment of Bt plants, Bt recombinant biopesticides and Bt toxins.

Abstract:【Objective】Little or no research has been done on the carbon footprint and economic benefits of different rice planting patterns at the provincial level. Thus, a systematic analysis of the carbon footprint and economic benefits of different rice planting patterns is of great significance for carbon emission reduction of rice production and the development of low-carbon agriculture.【Method】Based on the survey data of rice farming in Jiangsu Province, the carbon footprint and economic benefits of different rice planting patterns in Jiangsu Province were quantitatively analyzed by using the life cycle assessment method.【Result】The results showed that from 2016 to 2020, the carbon footprint per unit area, the carbon footprint per unit yield, and the carbon footprint per unit value were 11.28-14.39 t·hm–2,, 1.30-1.52 kg·kg–1 and 0.49-0.58 kg·yuan–1, respectively. The carbon footprint per unit area, per unit yield and per unit output value of different rice production and planting patterns were in order of broadcasted seeding rice or manual transplanting rice, mechanical transplanting rice, direct seeding rice. The carbon footprint per unit area of mechanical transplanting rice and manual transplanting rice production showed a decreased trend with the increase of years. Also, the carbon footprint per unit yield of mechanical transplanting rice, manual transplanting rice, and direct seeding rice production showed a decreased trend with the increase of years. Methane emissions from rice fields accounted for the largest proportion, followed by carbon footprints caused by nitrogen fertilization, nitrous oxide emissions from rice fields and carbon footprints caused by irrigation electricity. Nitrogen fertilizer and irrigation electricity were the main driving factors affecting the regional differences in the carbon footprint of different rice planting patterns. The total income of different rice planting patterns was between 2.51×103- 2.75×103 yuan·hm–2, the resource input cost was 1.88×103- 1.99×103 yuan·hm–2, the carbon emission cost was 0.20×103- 0.25×103 yuan·hm–2, and the net income (NI-CO2) considering carbon emissions was 0.39×103- 0.64×103 yuan·hm–2. The NI-CO2 of mechanical transplanting rice was lower than that of manual transplanting rice, broadcasted seeding rice and direct seeding rice. This was mainly caused by the higher total income and the lower resource input cost and carbon emission cost of mechanical transplanting rice.【Conclusion】In conclusion, direct seeding rice was the lowest carbon emission rice planting pattern. Considering the carbon emission and economic benefits, machinal transplanting rice was superior to manual transplanting rice, direct seeding rice and broadcasted seeding rice.

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.

Abstract:【Objtctive】 Tropospheric ozone (O3) is one of the most severe plant toxic air pollutants, it poses a serious threat to food production and security. Ethylenediurea (EDU) can effectively mitigate O3-induced crop yield loss. However the effects of elevated O3, EDU, and their interaction on the rhizospheric bacterial community of wheat plant remains unclear.【Method】 Triticum aestivum L. Nongmai88 was grown in China O3 Free-Air Concentration Enrichment (O3-FACE) platform under either ambient atmospheric O3 (A treatment) or 1.5 times ambient atmospheric O3 (E treatment), and the foliage sprayed with 450 mg·L-1 EDU or equal mount of water every ten days. The rhizospheric bacterial communitites under different treatments were analyzed by MiSeq sequencing of bacterial 16S rRNA genes in combination with redundancy analysis (RDA).【Result】 It was found that EDU increased wheat root biomass by 8%-58% and decreased soil pH by 4%-10%, both of which reached significant levels under A treatment. The elevated O3, EDU foliar spray, and their interaction did not significantly affect the alpha diversity indices of rhizospheric bacterial communities, but the elevated O3 caused significant variation in the whole bacterial community structure. In addition, the effect of EDU on the structure of the bacterial community in A treatment was more significant than that under E treatment. Proteobacteria (with a relative abundance ratio of 28%-39%), Bacteroidota (11%-20%), and Acidobacteriota (7%-11%) were the most dominant phyla in all treatments of the rhizosphere soil. Both the elevated O3 and EDU foliar spray significantly reduced the relative abundance of Alphaproteobacteria but increased the relative abundance of Chloroflexi. E treatment increased the relative abundance of Nitrospirota by 71% to 164%, while EDU treatment increased the relative abundance of Planctomycota by 23% to 70%. Based on the results of RDA, it was found that the content of available postassium (AK) and pH were the main drivers, explaining 21% and 16% of the variation in bacterial community structure, respectively (P<0.005). Furthermore, the Spearman correlation analysis results showed that the content of AK in rhizospheric soil was significantly negatively correlated with the relative abundance of the Chloroflexi and Nitrospirota phyla(r=-0.846 - -0.586), while it was significantly positively correlated with the relative abundance of the Alphaproteobacteria subphyla (r=0.604).【Conclusion】 In summary, wheat may improve its adaptability to increased O3 concentration by reducing the abundance of copiotrophic bacteria and increasing the relative abundance of oligotrophic bacteria, while foliar spraying with EDU may also alleviate wheat O3 stress in wheat through this way.

Abstract:Controlled by soil forming factors, the origination and development of earth soil had been experiencing contrasting environmental changes and corresponding processes. Previous studies have shown that the earliest weathering regolith appeared during the Archean Eon, with evolution of the Earth, biological forcing had been involved in soil formation and soils as defined by the modern concept got appeared during the Cambrian period. Over the geological periods soils formed and developed in episodic changing environments while the formation of soil and the establishment of soil cover (pedosphere) gave feedback to landscape evolution, topography, ecosystem and atmospheric system, therefore substantially changing atmospheric composition and altering global biogeochemical cycling. The formation of pedosphere is a prerequisite of the inhabitable earth.