• Volume 57,Issue 6,2020 Table of Contents
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    • >Insights and Perspectives
    • A Review of Researches on Viruses in Soil – Advancement and Challenges

      2020, 57(6):1319-1332. DOI: 10.11766/trxb202004280203

      Abstract (2342) HTML (2930) PDF 1.52 M (4459) Comment (0) Favorites

      Abstract:Viruses are non-cellular biological entities, simple in structure, composed of proteins outside and nucleic acids inside. The total number of virus-like particles (VLPs) in the Earth biosphere was estimated about 4.80×1031, which is overwhelmingly higher than that of organisms with cellular structure therein. Soil is an important reservoir of viruses, consisting mainly of bacteriophages (phages) that are able to infect prokaryotes. Metadata analysis shows that the number of the viruses in soil is closely related to the number of their host cells and certain soil physical and chemical properties. Although researchers in this aspect have realized that the viruses in soil may play an important role in regulating composition of soil microbial communities, thus influencing recycling of soil elements, promoting microbial evolution, and affecting the health of animals and plants, as well as human beings. However, due to high adsorbability of the soil virus particles and heterogeneity of the soil, as well as the limitation of research methods and analysis platforms, the cognition of and the attention paid to the viruses in soil in the current researches lags far behind those in the environments of flowing waterbodies, like river, oceans, etc.. Among the soil viral metagenomes, a huge number of genes remain undetermined in sequence, source and function and hence are sorted into the catalogue of unknown genes. Consequently, viruses in soil are deemed as biological ‘dark matter’ and the largest unexploited gene treasure trove. In this paper, a brief introduction to morphology, abundance, existing form and diversity of the viruses in soil, a review of the methods and their limitations in using molecular marker genes, random amplified polymorphic DNA-PCR and metagenomic analysis techniques to parse diversity of the viruses in soil, and then discussions about validated and potential ecological functions of the viruses were presented. In the end, directions of the researches in future on viruses in soil that should be strengthened were brought forth, stressing the importance of coupling studies on soil viruses and soil microorganisms in future studies to reveal ecological functions of the soil.

    • >Reviews and Comments
    • Research Progress and Perspective of the Multi-medium Interface Process and Regulation Principle of Pollutants in Site Soil-Groundwater

      2020, 57(6):1333-1340. DOI: 10.11766/trxb202004230193

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      Abstract:In recent years, the pollution of heavy metals and organic pollutants in site soil-groundwater in China is very prominent, which has become one of the important problems to be solved urgently. Multi-medium interface is the key to control the environmental behavior of complex pollutants in site system. Therefore, the development of the multi-medium interface process and regulation mechanism of pollutants in site soil-groundwater is very important for understanding the causes of site pollution and remediation. This paper systematically analyzes the research progress and development trend of multi-medium interface process and regulation of pollutants in soil-groundwater at home and abroad, points out the scientific and technical problems to be solved in this field, and puts forward the research ideas and main directions of the multi-medium interface process and regulation mechanism of pollutants in site soil-groundwater in China, which will promote the development of soil and groundwater environmental science and technology in China.

    • Progresses in Research on Sources and Characteristics of Chromium Pollution in Soils and Groundwater of Tannery Sites

      2020, 57(6):1341-1352. DOI: 10.11766/trxb201911120506

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      Abstract:In recent years, the issue of chromium pollution in tannery sites has attracted widespread attention. Through analyzing their tanning process, properties of the wastewater and solid waste discharged from tanning and history and status quo of their disposal, this paper points out that irrational disposal of these chromium-containing wastes and inadvertent dripping and leaking of chromium-containing liquor are the main sources of chromium pollution in tannery sites, and characterizes the chromium pollution in their soils and groundwater. The soils are mainly polluted by trivalent chromium rather than hexavalent chromium. However, the contents of total chromium and hexavalent chromium in some tannery sites far exceed the limit set in the national standards for soil environmental safety. Soil chromium content is characterized by site regional distribution, vertical distribution, and fractionation. Chromium polluted soil is mainly located in sludge disposal sites, workshops, and waste water discharge sites. The content of total chromium is high in the surface soil, and decreases gradually with soil depth. In the soils short in exposure to pollution, the content of available chromium (e.g., water soluble and exchangeable) is higher, while in the soils long in exposure to pollution, stable fractions, such as residue, dominate in content. Total chromium and hexavalent chromium are detected in groundwater, and the content of chromium is affected by factors, such as soil chromium content, time of exposure to pollution, and hydrogeology. As tannery sites are also exposed to organic pollution and acid-base pollution, this paper further elaborates effects of organic pollutants and soil pH on chromium behaviors, such as redox, fractionation, and transport in the soil. This paper points out that researches should be focused on contents and formation mechanism of available chromium and hexavalent chromium. In the end, the paper discusses the main challenges faced and countermeasures to be adopted in preventing the environmental risk of chromium pollution in tannery sites.

    • A Review of Research on Influencing Factors and Sustainability of Ratoon Rice Cultivation in China

      2020, 57(6):1365-1377. DOI: 10.11766/trxb201907170371

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      Abstract:As a special rice cultivation mode, ratoon rice, once planted and harvested twice, is of great significance for increasing grain yield, ensuring national food security and improving rice field utilization efficiency. This paper reviewed development trends of ratoon rice cultivation in China, analyzed their key affecting factors, elucidated high-yield cultivation techniques, and proposed that under the premise of a good first crop, 150 kg·hm-2 of urea be applied as sprout fertilizer 15 days after the heading stage of the first season rice, rice stubbles of a proper height be retained in harvesting, and another 150 kg·hm-2 of urea coupled with P and K fertilizers be applied as seedling prompting fertilizer 3 days after harvesting of the first season rice to ensure balance of soil nutrients for higher yield. In the end, current problems and future directions were discussed. It is considered that researches in future should focus on issues, like industrialization, soil nutrient management, and high yield cultivation techniques for ratoon rice cultivation, quality of ratoon rice, greenhouse gases and water quality in ratoon paddy fields to promote development of ratoon rice cultivation and provide reference for domestic peers in their research.

    • >Research Articles
    • Logic Expression and Retrieval of Soil Taxonomy Based on Pedon

      2020, 57(6):1378-1386. DOI: 10.11766/trxb201904090429

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      Abstract:【Objective】At present, certain progress has been made in the research on a Chinese Soil Taxonomy (CST)-based Soil Type Retrieval System, but the research has come across the following problems: (1) Ignorance of the impact of the coupling of diagnosis object, soil type and retrieval framework (Inference Process) on updating of the system; (2) Lack of consideration of division of the spatial structure of soil information carriers, which is unconducive to management of the soil information; and (3) Scope matching of the soil characteristics always expressed in traditional conditional nested statement and logical relationships between soil characteristics, making retrieval language cumbersome and redundant.【Method】In order to improve the above situations, this study introduced the concept of ontology, set soil geography and CST classification rules as its theoretic bases, analyzed spatial structure of soil entities and their relationship with CST objects (soil types and diagnostic objects) and eventually on such a basis, established an ontological model for relationship between soil entities and CST objects. To standardize the expression of soil characteristics, this paper defined soil attribute models, and divided soil characteristics into two categories, i.e. ordinary soil characteristics and complex soil characteristics. Moreover, this paper also defined corresponding predicate logics to express the relationships between types or models in logic and membership.【Result】This paper used Python language to realize construction of the ontology models and definition of the predicate logics, developed a type retrieval system covering all the four levels (Order, Suborder, group and subgroup), and cited the data of some single pedons representative of the Soil Series of China (Hubei volume) for test. And the test not only helped determine types of the pedons at all the four levels, but also recorded the entire retrieval processes, which facilitated analysis of the result later.【Conclusion】To compare with other existing retrieval models, this ontological model divides the carrier of soil information into four categories, i.e. Horizon, Profile, Pedon, and Polypedon, which facilitates management of the soil information and reduces complexity of the classification rules. Besides, the retrieval model separates the rules from the framework and can be characterized by high cohesion and low coupling, so that the model can better support the retrieval system in updating and expanding. The retrieval framework no longer takes soil characteristics as retrieval object, but encapsulates soil characteristics into soil entities, diagnostic objects, and soil types, thus elevating retrieval objects up to the level of category, which tallies more with human cognition. In brief, a method of constructing a retrieval model is proposed from the perspective of ontology in this paper. It can solve some problems of the existing retrieval models to a certain extent. However, the issue of semantics of soil characteristics and quantification of soil morphological characteristics remains to be a topic to work on. Therefore, to further improve the model, further efforts should be made in the next phase of the research to establish a soil characteristics semantic dictionary with complete metadata and information and introduce uncertain information as system auxiliary information.

    • Particle-size Composition of Erosion Sediment on Granite-derived Red Soil Slope Relative to Erosion Degree

      2020, 57(6):1387-1398. DOI: 10.11766/trxb201907200268

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      Abstract:【Objective】Soil erosion is a main mechanism of land degradation. Much works have been done on sensitivity of coarse-textured soils to erosions different in degree, however, little is known about erosion mechanism of slopes of granite-derived red soil. An indoor simulation experiment was done to characterize runoff and sediment production on steep slopes of granite-derived red soil as affected by rainfall intensity and erosion degree and to explore erosion mechanism of slopes of coarse-textured soils.【Method】The experiment had flumes (3 m long, 1 m wide and 0.45 m high, each) packed with coarse-textured soil to simulate soil slopes different in erosion degree, two treatments in rainfall intensity (90 and 120 mm•h-1) and two in inflow rate (2 and 2.66 L•min-1). Based on field investigations and previous studies, the three slopes were designed to be slight (E1), moderate (E2) and severe (E3) in erosion degree, separately and all 16.7% in gradient, commonly seen in the hilly region in the sub-tropical climate zone of China. Before each run of the experiment, the flume was covered with a gauze to reduce the splashing impact of rain drops and then treated with a rainfall event low in intensity (30 mm•h-1) till runoff appeared at the outlet of flume. Before each run, soil moisture content in the soil slope was determined with a soil moisture meter to ensure it was no more than 30%, and rainfall intensity and inflow rate was calibrated to ensure they were up to the set requirement of the test(±5%).【Result】Results show: (1) both rainfall intensity and flow rate played important roles in runoff formation and soil erosion. Runoff yield rate and soil erosion rate increased with rainfall intensity and inflow rate, and soil erosion varied in characteristic with slope erosion degree. The slope slight in erosion degree (E1) was most affected by rainfall intensity and inflow rate. (2) The slopes varied in erosion characteristics with erosion degree erosion. The slopes exhibited an order of E2 > E1 > E3 in runoff yield rate and an order of E3 > E2 > E1 in soil erosion rate. Multi-factor stepwise regression analysis shows that the higher the bulk density, the lower the runoff yield rate (R2 = 0.8, P< 0.01) and the higher the clay content or the lower the silt content, the lower the soil erosion rate (R2=0.715, P< 0.01). (3) With rising rainfall intensity and scouring strength or inflow rate, gravel and clay contents increased, sand and silt contents decreased and fractal dimension of the sediment increased. (4) Fractal dimension was ultra-significantly and linearly related to the ratio of clay/sand in content.【Conclusion】All the findings in this study may provide a train of thought for evaluation of soil evolution under erosion and contents of the research on soil evolution.

    • Effects of Soil Erosion on Soil Moisture and Infiltration Characteristics of Slope Farmland

      2020, 57(6):1399-1410. DOI: 10.11766/trxb201912270288

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      Abstract:【Objective】Cultivated slopeland in the hilly areas of purple soil is an important erosion inflicted area in the Yangtze River Basin, where soil moisture is not only the main factor governing agricultural productivity of the land and crop growth in the area, but also an important one influencing the erosion process therein. Soil moisture is of great significance to rain-fed agricultural sloping farmlands. This study was to explore impacts of soil erosion on soil moisture and water infiltration in sloping farmlands, in an attempt to provide some parameters as a basis for control of soil water erosion in sloping farmlands in hilly purple soil areas.【Method】For this paper, a soil erosion simulation experiment was carried out on a shoveled plot of land, to explore soil water characteristic curves, water infiltration, soil water pool characteristics and drought resistance of the sloping farmland 0, 5, 10, 15 and 20 cm in depth.【Result】Results show: (1) Aggravation of soil erosion degree reduced volumetric water content of the soil that remained the same in suction, which is detrimental to water storage in the sloping farmland soil, leading to reduced drought resistance of the slopeland. Under the same suction force, soil volumetric moisture content decreased with aggravating soil erosion; when soil erosion occurred in the 0 to 20 cm soil layer, soil volumetric water content decreased by 7.8% ~ 24.32%, or 17.80% on average. With aggravating soil erosion, soil water infiltration rate gradually decreased too in the 0~10 cm soil layer, and at the same time soil water infiltration rate tended to be similar in all soil layers regardless of vertical depth. (2) Soil water pool characteristics varied sharply with the degree of soil erosion. With aggravating soil erosion, the total soil water pool capacity tended to rise firstly, and exhibited an order of S-10 (422.7 t•hm-2 ) > S-5 (413.1 t•hm-2) > S-15 (408.2 t•hm-2) > S-0 (404.9 t•hm-2) > S-20 (403.5 t•hm-2) by layer, and at the same time, ineffective portion of the water pool increased to a varying extent; soil erosion reduced water holding efficiency of the soil, which, however, almost had nothing to do with degree of the erosion. (3) Soil water pool characteristics in the 0~40 cm soil layer did not vary much from slopeland to slopeland different in soil erosion; the maximum water holding capacity accounts for 75% of the saturated water holding capacity in the soil layer the same in depth, regardless of erosion degree. With aggravating soil erosion cumulative water loss from the cultivated layer, under the same suction, increased by a varying degree, and displayed a rising trend on the whole, and a declining order, by layer, of S-10> S-20 > S-15 > S-5 > S-0; This shows that under the same soil suction, the surface soil layer lost the least water and the 0~10 soil layer the most.【Conclusion】Soil erosion causes destruction of soil structure, thus reducing soil water infiltration, water retaining capacity, and drought resistance of sloping farmlands. All the findings in this research may serve as technical parameters for the regulation of soil moisture and drought resistance of farmlands on purple soil slopes on the plot scale.

    • Characteristic of soil aggregate loss on cinnamon soil slope within contour ridge system under different soil surface hydrological conditions

      2020, 57(6):1411-1421. DOI: 10.11766/trxb201908210276

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      Abstract:【Objective】Soil moisture content is one of the major factors determining degrees of soil aggregate breakdown, which alters the distribution of particle sizes in sediment. Soil surface hydrological condition reflects the spatial distribution of soil moisture content at slope, and strongly affects the characteristic of soil aggregate loss. However, previous researches focused on the influence of soil surface hydrological condition on runoff and sediment yield process within flat tillage system, and limited information are available about effect of soil surface hydrological condition on soil aggregate loss, especially under seepage condition in a contour ridge system. While, contour ridge system is an effective soil conservation practice used worldwide.【Method】In this study, simulated rainfall experiment was conducted to determine the lost characteristic of six size soil aggregates(≥5, 2-5, 1-2, 0.5-1, 0.25-0.5, and<0.25 mm) under three soil surface hydrological conditions (free drainage, soil saturation, and seepage) and three rainfall intensities (30, 60, and 90 mm•h-1)for cinnamon soil in a contour ridge system.【Result】Results showed that soil aggregate loss was in order of seepage>soil saturation>free drainage, seepage and soil saturation had 1.44-4.22 and 0.26-3.12 times soil aggregate loss greater than free drainage condition. Contribution rate of the existence of soil saturation and seepage for soil aggregate loss was significantly 2.02-3.71 and 1.28-2.51 times higher than that of water potential difference with the change of rainfall intensity. There was significantly difference in the loss distribution of soil aggregate among soil surface hydrological conditions. Soil saturation and seepage resulted the loss percentage of 2-5, 1-2, and 0.5-1 mm aggregate increased by 46.74%-121.19%, but weakened more than 90% of 0.25-0.5 mm aggregate loss. In addition, soil saturation and seepage increased by 23.77%-215.80% for the enrichment rate of >0.5 mm aggregate, but induced the enrichment rate of 0.25-0.5 mm aggregate decreased by 45.07%-68.90%. Because 0.25-0.5 mm aggregate occurred re-aggregate during erosion process, and the transport capacity of 2-5 mm aggregate was strengthened under the interaction of soil saturation and seepage. For the four characteristic indices of lost soil aggregate (the mean weight diameter, geometric mean diameter, mean weight soil specific area, and fractal dimension), difference in the mean weight diameter was the largest among soil surface hydrological conditions. The mean weight diameter was better indicator characterizing soil aggregate loss under free drainage and soil saturation conditions, while it was fractal dimension under seepage condition. Soil aggregate loss pronouncedly increased with the increase of rainfall intensity under free drainage, soil saturation, and seepage conditions. Among, effect of rainfall intensity on soil aggregate loss was the most pronounced under free drainage condition, and rainfall intensity had the greatest influence on 2-5 mm aggregate.【Conclusion】Soil saturation and seepage significantly enhanced soil aggregate loss, and showed more pronounce influence on the loss of lager size aggregate. These findings enhance our understanding of erosion mechanism for soil surface hydrological condition and contour ridge influence on soil erosion process, and supply guidance for implementing contour ridge system.

    • Synchrotron-based X-ray Tomographic Microscopy Reveals Morphology and Spatial Structure of Intra-aggregate Pores in Red Soils

      2020, 57(6):1422-1429. DOI: 10.11766/trxb201906290122

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      Abstract:[Objective] The pore structure and spatial distribution of intra-aggregates in soils determine many functions of soil aggregates and physical, chemical, and biological processes occurring in aggregate. The objectives of this study were (i) to examine the three dimension (3D) pore characteristics of intra-aggregate pores; (ii) describe the spatial distribution of macropores (>30 ?m) within aggregates, and (iii) to analyze the relation between pore structure and functions of the aggregates. [Method] The 3-5 ?m aggregate of two red soils (named as Q4 and Q12) with different stability were used in this study. Synchrotron radiation X-ray microcomputed tomography (SR-mCT) was used to scan the 3-5 mm aggregate of two red soils. A combination of SR-mCT and image analysis was applied to describe the intra-aggregate pore characteristics and pore spatial distribution within the aggregates. [Result] The SR-mCT images of aggregates indicated a considerable difference in the morphology, pore size, and pore growth direction of intra-aggregate in two soil samples. The soil Q4 was characterized by abundance macropores, multifarious pore growth direction and pore size distribution, whereas soil Q12 by dense micropores, and consistent pore grow direction. They have similar single pore shape, while different interconnected pore shape. The porosities of 5-30, 50-80, and >80 ?m in soil Q4 were significantly higher than those of soil Q12. The abundance of macropores (>30 ?m) within soil Q4 aggregates was relatively larger in the center part of aggregate, while soil Q12 had a uniform spatial pattern with larger in the outer part of aggregate. [Conclusion] The SR-mCT system could clearly describe pore diversity and spatial variation of intra-aggregates without disrupting the aggregate microstructure, which could be effectively to predict the function and physical processes of the aggregates.

    • Soil AerationPorosity in Typical Tobacco-planting Soils and Its Main Controlling Factors in Typical Tobacco-planting Soilin Yunnan Province, China

      2020, 57(6):1430-1438. DOI: 10.11766/trxb201907240386

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      Abstract:Soil air capacity is very important to growth and quality of tobacco. In soils poor in air capacity, tobacco has its leaves expanding slowly at its early growth stage and getting thickened and inadequately expanded at its late growth stage because of continuous nitrogenrelease from the soil, thus seriously affecting quality and flavor of its flue-cured leaves. 【Objective】 This study was oriented toinvestigate soil air capacity of the tobacco-planting areas typical of Yunnan Province, and explore relationshipof soilaeration porosity and soil physical properties with tobacco growth and main factors influencing soilaerationporosity so as to find effective ways to improve quality and yield of the tobacco in Yunnan Province.【Method】For this study, field experiments were laid out in three tobacco planting areastypical of Yunnan Province, i.e. in QinglongTown, NingzhouTown of Huaning County, YuxiCity and ZiwuTown in ChuxiongCity. A total of 38 soil samples were collected from the topsoil and subsoil layers of the experimental tobacco fields for analysis of basic physico-chemical properties, including soil texture, soil bulk density,soil organic matter(SOM) and total nitrogen(TN) contents,pH and so on. Soilaeration porosity of the soil samples was measured with the sand–kaolin box method. Variance analysis and correlation analysis were performed of the obtained data to explore relationshipsof soil aerationporosity with soil physico-chemicalproperties. In the end, a soil aerationporosity prediction model was established based on transfer function of the soil physico- chemicalproperties.【Results】Results show that in line withthe USDA standard for soil texture classification, the soil samples collected from the three areas were dominantly of clayey loam in soil texture, making up about 40% of the total, then of loam and the least of silty loam, which accounted only for 7.9% of the total; bulkdensity of the soils in the three areasvaried from 1.3 to 1.5g• cm-2, a suitable range for tobacco growth in Yunnan Province; soil organic matter (SOM)content and soil nitrogen supply capacity were high enough to meet the nutrient needs of tobacco for growth and to ensure quality and yield of the crop;and soil aeration porosity was found in the range of 5.9%-15.1%, being on the low side as whole for the areas and varied quite much spatially between areas, with the one in Qinlong Town being the highest, at about 15.1%, which was followed by the one in Ningzhou Town and then the one in Ziwu Town, the lowest at about 9.4%, which is obviously inadequate to meet the need for cultivation of high quality tobacco.Correlation analysis shows that aeration porosity in tobacco-planting soils is mainly affected by silt and clay contents and ultra-significantly and positively related to silt content and negatively to clay content. Consequently, soil aeration porosity can be roughly estimated based on silt and clay contents in the soil.【Conclusion】The soils in the tobacco planting areas of Yunnan are mainly of loam and clayey loam in texture, and their soil bulk densities and nutrient contents are suitable for growth of flue-cured tobacco. But their soil aeration porosities are apparently inadequate for healthy growth and flavor development of tobacco.Soil aeration porosity is significantly related to silt and clay contents in the soil. Therefore, it is recommended that tobacco should be cultivation in soils, loam or sandy loam in texture, where high soil air capacity is available for healthy growth of quality tobacco. The findings in this study may serve as reference for local governments in zoning for cultivation of flue-cured tobacco.

    • Effects of Coated Potassium Chloride Containing Mepiquat Chloride on Cotton Yield and Soil Potassium

      2020, 57(6):1439-1448. DOI: 10.11766/trxb201907120286

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      Abstract:【Objective】Potassium is a main nutrient element that affects cotton yield and fiber quality. Repeated application of potassium fertilizer can increase cotton yield, but topdressing not only causes mechanical damage to the crop, but also increases labor cost, thus reducing cotton planting benefits. Mepiquat chloride (MC) is a kind of plant growth regulator characterized by low toxicity and water solubility. It is now widely used in cotton planting countries all over the world to inhibit vegetative growth of the plant and hence to eliminate the traditional labor-costing pruning operations. However, so far little is known about whether MC could increase cotton yield when it is applied into the cotton fields. Therefore, the objective of this study is to investigate effects of coated potassium chloride containing MC on cotton yield, economic benefit and balance of soil potassium.【Method】A field experiment was initiated in 2018 with five treatments different in potassium application pattern and three replicates for each treatment, i.e. Treatment CRKMC (basal application of 180 kg·hm-2 coated potassium chloride containing mepiquat chloride); Treatment 70% CRKMC (reduced potassium dosage (126 kg·hm-2) or 70% of CRKMC); Treatment CRK (basal application of 180 kg·hm-2 common coated potassium chloride); Treatment KCl (split application of 180 kg·hm-2 ordinary potassium chloride, 60% basal and 40% topdressing at the first bloom stage); and CK (no potassium fertilizer used), and in addition foliar spraying of MC was performed three times on each of the latter three treatments.【Result】Treatment CRKMC and CRK increased cotton yield by 8.81% and 9.36%, and economic benefit of the crop by 15.53% and 12.86%, respectively, while Treatment 70%CRKMC increased cotton yield by 6.53% and net income by 13.64%, respectively as compared with Treatment KCl. Treatment CRKMC inhibited cotton plant height before the full-bloom stage, but increased plant height, stem diameter and chlorophyll value at later stages (from the full-bloom stage to maturity stage), and plant biomass by 18.56%~24.98%, as compared with Treatment KCl, enhanced potassium uptake, and also improved apparent K use efficency by 25.06%~38.83%. Release of Potassium and MC in the CRKMC exhibited a trend of “slow – fast – leveling off” in the soil, and peaked during the period between the full bloom stage and the initial boll-opening stage, which significantly increased the content of available potassium in the soil after the squaring stage.【Conclusion】Therefore, application of CRKMC into soil can reasonably regulate the growth potential indices of cotton and meet the demand of cotton for potassium. The application of CRKMC 30% less in potassium dosage can still improve economic benefits of the crop and potassium use efficiency. So CRKMC can realize integrated coordination of MC and K under the same temporal/spatial conditions, which helps reduce fertilization rate, improve crop yield and simplify crop management.

    • Effect of Selenium Application on Soil Physical and Chemical Properties and Quality of Chrysanthemum morifolium cv Hangbai

      2020, 57(6):1449-1457. DOI: 10.11766/trxb201912030593

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      Abstract:【Objective】Effects of selenium application on soil physical and chemical properties, nutrient elements of Chrysanthemum morifolium cv Hangbai, selenium content and yield of the plant, relative to application method were analyzed.【Method】In this experiment, nano-selenium was used as extraneous selenium for exploration of effect of its application on quality of Chrysanthemum morifolium. In terms of application of selenium, this experiment was designed to have four treatments, i.e. Treatment T (applying selenium as fertilizer into the soil (T); Treatment Y (spraying selenium solution onto leaves), Treatment (T+Y) (applying and spraying selenium together), and Treatment CK (no selenium applied as control.【Result】 Results show that as compared with CK, selenium application, regardless of method, did not have much effect on soil bulk density, soil porosity and soil water content and on the activities of soil alkaline phosphatase and soil catalase, either, but did dull the activity of urease and stimulate that of sucrase significantly in the soil, lower the Vc content and increased the contents of flavonoids and chlorogenic acid and the Se content in the inflorescences of the plant. Besides, selenium application increased the number of flowers per plant, the dry biomass per flower and the yield of flowers per mu. The effect was the most significantly in Treatment T+Y.【Conclusion】Based on comprehensive comparison analysis of the effects of the three selenium application methods on soil physical and chemical properties, nutrient contents selenium content and yield of Chrysanthemum morifolium, it could be concluded that selenium application via both fertilization and foliar spraying is the most effective method for selenium application to Chrysanthemum morifolium. All the findings in the experiment may serve as a practical and theoretical basis for the production of Se-enriched Chrysanthemum.

    • Bibliometric-based Analysis of Researches on Soil Microbes at Home and Abroad in the Past 30 Years

      2020, 57(6):1458-1470. DOI: 10.11766/trxb201907270247

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      Abstract:【Objective】Soil microbes are an indispensable active component of soil ecosystems. The research on soil microbes is closely linked to current international hotspot issues such as global change, agricultural production, soil environmental protection, etc. The research in soil microbiology is very fruitful, and of great significance for quantitative analysis of soil microbiology literature and data. The use of traditional literature analysis methods to handle large volumes of relevant literature and information and to track development of the research fields has come across a number of difficulties. This paper was oriented to find out latest research hotspots and development trends in the field of soil microorganisms at home and abroad.【Method】Bibliometric analysis of the soil microbial literature contained in the Science Citation Index Expanded (SCI-EXPANDE) database of 1990-2018 in the Web of Science was carried out by country, research institute, source journal, citation, main research content and hot spot of attention, with the aid of visual analysis software, like VOSviewer and CiteSpace. A diagram of cooperations between countries or between research institutions was drawn with the aid of VOSviewer, and keyword co-occurrence network atlases by time period and by country were with CiteSpace. 【Result】Results show that in this research field, the number of documents in China is growing rapidly, but the total citation is still low; the USA ranks first in number of documents and total citation frequency. The Chinese Academy of Sciences, an important research institution in China, its on the top of the lists of number of documents and total citation frequency in the country, but is still quite low in per-paper citation frequency. The "Applied and Environmental Microbiology", "Soil Biology & Biochemistry" are the main journal sources. Though the journal “Soil Science Society of America Journal” is quite low in influence and in volume of publications, it is high or in the forefront in total citation frequency. The keyword co-occurrence network in China formed quite late, but it develops rapidly, showing a trend of convergence with foreign researches in hotspot. The study object has evolved from a single species to a complex microflora, and the research direction has turned more attention to microbial community composition and diversity. Keywords in the soil microbiology research papers in China are increasing in number and in linkage, forming cross-cutting research hotspots. Soil microbiology researches both at home and abroad focus mainly on the following aspects: soil microbes participating in soil organic matter decomposition, carbon and nitrogen recycling as nutrient; biodegradation of heavy metal or organic pollutants matter and bioremediation of heavy metal or organic compound polluted soils; mechanisms of soil microbial communities responding to global environmental change in structure; and mechanisms of rhizosphere microbes, soil and plants interacting with each other. 【Conclusion】Researchers all over the world in this field have made great progresses in the field of soil microbial community structure, function and diversity. Through co-occurrence analysis of keywords by time periods in China and abroad, this paper has brought to light hotspots and trend of the research on soil microbiology, which may be of some reference value for understanding the context of the overall researches in the field of soil microbe and provide certain theoretical guidance to researchers who have just begun their exploration in the field.

    • Structure and Diversity of Soil Nematode Community in Soil under Tsuga dumosa Forest in Galongla Mountain

      2020, 57(6):1471-1482. DOI: 10.11766/trxb201909270130

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      Abstract:【Objective】In this study, a tract of Tsuga forest typical of the Garongla Mountain, Motuo County, Southeast Tibet was taken as research object. The purpose of this study was to investigate structure and diversity of the soil nematode community in the Tsuga forest ecosystem in this region and their relationships with soil properties, and stability and succession of the ecosystem by analyzing environmental indicators and functions of the soil nematode community. This study is expected to be of important scientific significance in unveiling diversity laws of the soil nematodes in the Tsuga forest ecosystem in Southeast Tibet, discussing interactions and correlations between the evolution processes underground and aboveground, and learning roles of the soil nematode community in subalpine/alpine forest soil ecological processes.【Method】In September 2017, four sample plots were set up different in plant community and topography. Soil sampling points (at least 5 points) were specified in each sample plot randomly in distribution and soil samples were collected from 5 soil layers, 0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm and 20-25 cm, at each sampling point with a soil drill 7 cm in inner diameter, and then blended together into one, separately. Nematodes in the soil samples were separated with the shallow basin method, observed under stereomicroscope for identification till the genus level and characterized by species composition, individual density, diversity index and functional index for analysis of structure and diversity of the soil nematode community. The soil samples were also analyzed for physical and chemical properties with the conventional methods, and redundancy analysis and linear correlation analysis was performed of the data for relationships with the nematode community.【Result】Results show that soil nematodes in the soil under Tsuga dumosa forest in Mt. Galongla could be sorted into 5 orders, 29 families and 34 genera, averaged to be 278 individuals∙100 g-1 dry soil in density and did not vary much between soil layers. In the community Tylencholaimus and Leptonchus were the dominant genera and fungivorous nematodes were the most important nutritional group. Soil organic matter was decomposed mainly by fungi. Redundancy analysis (RDA) and linear correlation analysis shows that readily available potassium, organic matter, total nitrogen and total potassium are the major factors affecting the soil nematode community and its relationship with soil physical and chemical properties, and readily available potassium is the most important one. A significant and positive relationship was found between nematode density and soil water content. Uneven distribution of soil water may be one of the important causes for the variation of soil nematodes community in density with the habitat in the hemlock forest in Mt. Garongla.【Conclusion】Soil organic matter is decomposed mainly by fungi. The Tsuga forest ecosystem in Mt. Garongla is high in maturity and in a relatively stable state. The content of readily available potassium in the soil significantly affects number and diversity of the nematodes in the community. Organic matter, total nitrogen, hydrolyzed nitrogen and available phosphorus are also factors affecting number of the nematodes. Soil water content is one of the important environmental factors that affect species composition of the soil nematode community and number of the nematodes in the soil under Tsuga dumosa Galongla forests.

    • Modes of Uptake and Translocation of NO3- Affecting Growth of Host Plants in Arbuscular Mycorrhizal Symbiosis

      2020, 57(6):1483-1491. DOI: 10.11766/trxb201909090476

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      Abstract:【Objective】Effects of uptake and translocation of NO3- in arbuscular mycorrhizal symbiosis and formation of arginine(Arg) in extraradical mycelium(ERM) and mycorrhizal root when ERM was exposed to NO3-or NH4+, affecting growth of their host plants were studied. 【Method】In this study a dual split culture system was established with Ri T- DNA transformed carrot root and Glomus intraradices(Rhizophagus intraradices) and the 15N/13C isotope tracing technique was used to explore pathways of the uptake and transport of NO3-, and determine how much arginine accumulated in ERM and mycorrhizal root after NO3- or NH4+ was absorbed and translocated in the fungal compartment, and a field experiment was conducted too to address how uptake and translocatiton of NO3-or NH4+ affect growth of the host plants. 【Result】Results show that AM hypha preferred to uptake NH4+ over NO3- when they both were available in the soil. When AM extraradical hypha were exposed to NH415 NO3- for 1 week, though the free amino acids, include Arg, in the extraradical mycelium (ERM) were not labelled by15N, those in the mycorrhizal tissues were, indicating that 15 NO3- in the fungal compartment were transported directly via mycelium into mycorrhizal tissues rather than any new translocation mode; on the contrary, when extraradical hypha were cultured with 15NH4 NO3-, only Arg was 15N-labelled therein, while the form of nitrogen composed of other amino acids in the ERM was 14NO3- translocated mainly from the hypha compartment and hence not labelled. While exposed to 13C6-Glucose for 6 weeks, the ERM was found to have no13C-labelled Arg or protein, which indicates that ERM is unable to utilize glucose. When exposed to 13C1,2-acatate, the ERM was found to have Arg and protein13C labelled up to 8.5%2.3% and 7.6%0.7%, respectively; when exposed to 13C1,2-acatate plus 15NO3-, the ERM increased the concentration of free Arg with increasing N input, up to 54.2%19.3% and 13C labelled Arg and protein up to 57.4%4.8% and 50.3%2.8%, respectively, which indicates that increased C and N inputs in the hypha compartment may promote formation of Arg. In the field experiment, in the field low in P level, addition of KNO3 increased significantly weight of the AM-inoculated sweet corm plants by 12.28%, as compared to the control, but addition of NH4SO4 did not have such an effect and instead decreased biomass of the plants by 8.19%, and addition of urea did by 13.02%; however amendment of organic manure to urea application mitigated the adverse effect.【Conclusion】There are two different modes of AM fungi absorbing and transporting ammonium and nitrate. AM fungi absorb and transport ammonium nitrogen (NH4+ and urea), via GS-GOGAT in ERM, and most of the absorbed nitrogen is integrated into Arg molecules, and the synthesized arginine is intactly transported to the intraradical mycelium by ERM. Meanwhile, NO3-in the AM fungi symbiosis, as revealed by the isotope tracing technique, is adsorbed by ERM and transported via ERM to intraradical mycelium. Application of NO3 may promote growth of the AM fungi-hosted sweet corn, while application of NH4+ may affect the crop reversely.

    • Effects of Copper and Zinc Contamination on Soil Nematode Communities from Natural Woodland and Farmland

      2020, 57(6):1492-1503. DOI: 10.11766//trxb201909020335

      Abstract (1030) HTML (943) PDF 1.89 M (1791) Comment (0) Favorites

      Abstract:【Objective】The relationship between biodiversity and community stability is a fundamental component of soil ecology. To explore effects of pollution on the relationship between soil nematode diversity and community stability, comparisons were made of nematode communities in woodlands vs. those in farmlands that were simulated to be contaminated with copper (Cu) or zinc (Zn) varying in concentration. 【Methods】Cu or Zn was added to fresh soil samples, which were convert to final concentrations of the minerals in dry soil equivalent to 0, 100, 400, and 800 mg•kg-1 . For each treatment had three replicates, a total of 42 subsamples (14 treatments × 3 replicates) were prepared. The soil samples were incubated at 25°C for 23 days before nematodes were collected using the cotton-wool filter method. Comparisons were made in nematode community structure (abundance, diversity and functional indices) between soils different in pollution gradient and between habitats. 【Results】A total of fifty-two taxa of nematodes, belonging to four main trophic groups, were identified, 48 taxa in the woodland soil and 32 in the farmland soil. Bacterivores dominated both the woodland and farmland samples. Herbivores were the second most dominant trophic group in the woodland soil, but bottomed in the farmland soil. Nematode abundance in the woodland soil decreased with rising Cu and/or Zn concentrations. In the farmland soil, however, nematode abundance was lower when Cu and/or Zn concentrations were low and higher when they were medium or high. Bacterivores and the total of nematodes in a similar trend. In the woodland soil, omnivore-carnivore abundance decreased when soil Zn was the highest or low in concentration, and when soil Cu was medium and high in concentration. In the natural woodland soil, the gradient of heavy metal concentration had no significant effect on diversity of nematodes, but in the farmland soil, it reduced Shannon–Wiener (H’) index and increased nematode dominance (λ). High concentration of Cu significantly affected structure index (SI) of the nematodes in the farmland soil. In the woodland soil, basic index (BI) was reduced when soil Zn was low in concentration and increased when it was high. SI was also significantly reduced when soil Zn was high in concentration. In the farmland soil, the effect of soil Zn on nematode functional indices varied displaying a wavy trend. Principal component analysis (PCA) shows that in the woodland soil, nematode communities were similar to those in the control soil in all the treatments, except for treatments medium in Cu and/or Zn concentration and high in Zn concentration. In the farmland soil, as affected by treatments, nematode communities differed from those in the control soil. 【Conclusion】The soil nematode community in the woodland or farmland soil responds differently to the gradient of Cu and/or Zn contamination. In the woodland soil, the response is embodied mainly in overall abundance of nematodes, while in the farmland soil, it is in community structure, diversity, and ecological indices. The nematode community in the natural woodland soil is high in diversity and more able to tolerate Cu and Zn pollution than that in the farmland soil, which is relatively simple in the soil food web.

    • Effects of Inorganic Fertilizer Combined with Organic Manure on Soil Nematode Community under Jackfruit Trees

      2020, 57(6):1504-1513. DOI: 10.11766/trxb201909270245

      Abstract (1296) HTML (643) PDF 2.30 M (1850) Comment (0) Favorites

      Abstract:【Objective】In order to investigate effects of organic manure on soil nematode community under jackfruit trees, a comparison study was conducted using grafted Malaysian No.1 saplings. 【Method】The experiment in the study was designed to have six treatments, i. e., CK (no fertilizer), 100CF (100% chemical fertilizer), 30OM (30% organic manure plus 70% chemical fertilizer), 50OM (50% organic manure plus 50% chemical fertilizer), 70OM (70% organic manure plus 30% chemical fertilizer), 100OM (100% organic manure). 【Result】 Results show that compared with CK and Treatment 100CF, all the other four treatments had varying significant effects of promoting biomass accumulation of the jackfruit saplings and increasing soil pH and organic matter in the soils. With increasing organic manure replacement rate, microbivorous nematodes and omnivores/predators increased in proportion, while plant-parasites decreased, the soil nematodes as a whole increased in diversity (H') and evenness (J') significantly, and the bacteria-dominated decomposition pathways in the soil food web did in proportion, too. β diversity analysis shows that the treatments varied significantly in nematode community structure, except for Treatments 50OM and 100CF, which were quite similar in that field. Dry weight of the shoot of the jackfruit saplings was significantly and positively related to abundance of bacterivores, organic matter and soil pH, while abundance of plant-parasites was negatively related to soil pH, organic matter, alkalyzable nitrogen and abundance of microbivorous ones, and abundance of bacterivores was significantly and positively related to soil organic matter and pH. 【Conclusion】Combined application of chemical fertilizers and organic manure can improve soil nematodes in diversity and evenness, balance the nematodes different in feeding habit in proportion, improve soil fertility and make the soil environment healthier and hence promote growth of the jackfruit saplings.

    • Variation of Stable Isotopes in Soil Water under Cinnamomum Camphora woods in Changsha and Its Influencing Factors

      2020, 57(6):1514-1525. DOI: 10.11766/trxb201905050241

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      Abstract:【Objective】In order to explore temporal variation of stable isotopes in soil water and distribution in soil profile, and to characterize the soil water line (SWL) in the monsoon region, this research project was launched, which was expected to be conducive to a better knowledge of redistribution processes of soil water. 【Method】 In this study, monitoring was carried out of stable isotopes in ground water in the soil profile (0-130 cm), precipitation and groundwater, and relevant environmental factors (including soil water content, soil temperature and meteorological variables), in a Cinnamomum camphora forest in Changsha from March 2017 to February 2019, and the monitoring data were collated and analyzed to determine variation of stable isotopes in soil water and rain water and its influencing factors. 【Result】 Stable isotopic composition of the soil water in the 0-60 cm soil layer varied significantly with the season, and the variation lagged by a varying degree behind that in rain water. The mean monthly maximum hydrogen stable isotope ratios (δ2H) in soil water regardless of soil depth all appeared all in May, and the mean monthly minimum one did in the period from September to December. However, no obvious seasonal variations were observed in the soil water and ground water below 60 cm in depth. All the above findings suggest that rain water may directly affect the soil water in the 0-60 cm soil layer and the soil water in the soil layers below and groundwater may preserve more data of stable isotopes in rain water accumulated from preceding rainfall events. Difference of the δ2H in soil water from the local meteoric water line (LMWL) increased in mean lc (Line-conditioned excess) with soil depth, decreased in standard deviation and gradually leveled off, which suggests that evaporation of soil water gradually decreases with soil depth. Significant and positive relationships were found between lc andδ2H in soil water at all soil depths. That is to say, the higher the δ2H in soil water, the lower the deviation degree of δ2H in soil water from the LMWL, and the weaker the evaporation of soil water; and likewise the lower the δ2H in soil water, the higher the deviation degree of δ2H in soil water from the LMWL, and the stronger the evaporation of soil water. Correlation analyses of lc in soil water at various soil depths with accumulated atmospheric evaporation (∑E) and accumulated atmospheric temperature (∑TA) in the preceding period shows that the latters significantly affected lc in soil water in the 0-60 cm soil layer, but insignificantly in soil layers below 60 cm in depth. Moreover, a certain relationship was found between soil water content (θ) and lc in soil water. The study also shows that relatively low stable isotope ratios in soil water in all soil layers were observed mostly during warm seasons relatively high in ∑E and ∑TA, and during the seasons evaporation enrichment grew stronger, while lc in soil water did lower, thus making scatter points of stable isotopes in soil water deviate further from LMWL; while relatively high stable isotope ratios in soil water in all soil layers appeared mostly during cold seasons, relatively low in ∑E and ∑TA, and relatively weak evaporation enrichment and relatively high lc in soil water during the seasons made scatter points of stable isotopes in soil water close to LMWL. Therefore, the slope of SWL was higher than that of LMWL in all soil layers in this study area. 【Conclusion】Stable isotopes contained in atmospheric precipitation are a direct factor affecting stable isotopes in soil water. Abundance of the stable isotopes in soil water is related to atmospheric heat and humidity in the preceding period. The cause why the slope of SWL is higher than that of LMWL in all soil layers is negatively and seasonally related to stable isotopes in precipitation and evaporation enrichment intensity of stable isotopes in soil water.

    • Carbon Storage of Forested Wetland Ecosystems in the Cold Temperate Permafrost Region, Northeast China

      2020, 57(6):1526-1538. DOI: 10.11766/trxb201910210076

      Abstract (1004) HTML (1285) PDF 2.23 M (1810) Comment (0) Favorites

      Abstract:【Objective】Wetlands play an important role in the global carbon cycle, but in estimating their carbon stocks, a number of uncertainties need to be settled. The aim of this paper is to quantify ecosystem carbon storage and the carbon sequestration capacity of the seven natural wetlands, and explore rules for spatial distribution of the wetlands along the environmental gradient of the permafrost transition zone.【Method】Ecosystem carbon storage (ECS=vegetation C storage and soil organic C storage), net primary productivity(NPP) and annual net carbon sequestration(ANCS) of seven kinds of typical natural wetlands (C: tussock wetland, G: shrub wetland, M: Alnus sibirica wetland, B: Betula platyphylla wetland, LT: Larix gmelinii-Carex schmidtii wetland, LX: Larix gmelinii -Moss wetland, and LN: Larix gmelinii-Sphagnum spp wetland) distributed one by one in an order along the environmental gradient of the transition zone of the Daxing’anling permafrost in the cold temperate zone were measured sychroneously by using relative growth equations and Multi N/C 3100, HT 1300 Solids Module (Analytik Jena AG, Germany).【Result】Results show: (1)VCS of the seven wetlands varied from 3.60 to 62.18 t•hm-2, exhibiting a skewing trend of rising first and then decreasing along the water environmental gradient of the transition from marsh to forest; (2)SOCS of the seven wetlands did from 179.47 to 320.81 t•hm-2, and the SOCSs of the forested wetlands(except Wetland M) and shrub wetlands were significantly or 56.4%-78.8% higher than that of Wetland C by (P<0.05) and 32.0%-50.9%(P<0.05) higher than that of Wetland M; (3)ECS of these wetlands did from 183.07 to 347.14 t•hm-2, and ECS of the forested wetlands (except Wetland M) and shrub wetlands were significantly or 64.0%-89.6% higher than that of Wetland C (P<0.05) and 28.1%-48.1% higher than that of Wetland M(P<0.05), yet the proportion of soil carbon stocks in the forested wetlands (82.1%-96.4%) was lower than that in Wetlands C and G (98.0%-98.3%); (4)NPP and ANCS of the seven wetlands did from 6.76 to 11.22 t•hm-2•a-1 and from 2.97 to 5.37 t•hm-2•a-1, respectively, and NPP and ANCS of the forested wetlands(except Wetland LN) were significantly or 26.9%-61.4% and 30.5%-66.0% higher than their respective ones of Wetland C and 38.6%-77.2% and 41.4%-80.8%(P<0.05) higher than their respective ones of Wetland G.【Conclusion】Therefore, the ECSs of all the types of wetlands in the cold temperate permafrost region were relatively low, reaching only up to 46.9%~89.0% of the bottom value of the peat land carbon reserve (390-1 395 t•hm-2) in North China, and on the whole displayed an increasing trend along the environmental gradient of the transition zone. Carbon sequestration capacity of the forested wetlands (except Wetland LN) was higher than that of the shrub wetlands and tussock wetlands. And the former was slightly higher than the estimated ANCS of the global terrestrial vegetation (4.1 t•hm-2•a-1), the latters were equal only to 3/4 of that.

    • Altitudinal Gradient of Soil Organic Carbon in Forest Soils in the Mid-Subtropical Zone of China

      2020, 57(6):1539-1547. DOI: 10.11766/trxb201909300184

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      Abstract:【Objective】 Forest soil organic carbon (SOC) is an important component of the carbon storage in the forest ecosystem. Accumulation and storage of SOC in the forest soil can directly affect carbon budgeting in the terrestrial ecosystem and global carbon recycling. SOC in mountain forest soils in the transitional climatic zone is sensitive to climatic change. So the subject of variation of SOC along an altitudinal gradient is also a key topic concerning regional carbon dynamics. Hence, the survey of altitudinal gradient of SOC in a transitional climate zone is far more valuable than that in a typical climate zone to predicting variation of regional SOC in response to climate changes. The objective of this study was to investigate effects of altitude on SOC so as to explain how carbon stocks distributes in the subtropical transitional climate zone of East China. 【Method】 A total of 20 soil profiles were prepared along the altitude (179-1 410 m a.s.l.) in Jiangxi Jiulianshan National Nature Reserve, located just in the transitional climate zone from the south-subtropical zone to the mid-subtropical zone. Soil samples were collected separately from five layers (0-10 cm, 10-20 cm, 20-40 cm, 40-60 cm and 60-100 cm) of each of the soil profiles (0-100 cm). After being air-dried, the samples were analyzed for soil organic carbon content with the potassium bichromate oxidation titration method. Soil organic carbon density (SCOD) and soil organic carbon stocks (SOCS) were calculated. Along the altitude, red soil, red-yellow soil, yellow soil and meadow soil was distributed in sequence, so impacts of altitude on SOCC and SBD (soil bulk density) could be explored by analyzing the two parameters in the four types of soils. Soil layer depth and soil type were two factors affecting SOCC and SBD and their impacts were analyzed with two-way Analysis of Variance (two way- ANOVA); impact of soil type on SOCD was with ANOVA; and relationships of altitude with SOCC and SOCD were with Pearson correlation analysis and nonlinear analysis, respectively. 【Result】 Results show: (1) SBD increased dramatically with soil depth, but did not vary much between soil types; soil type and soil layer depth influenced SOCC, with the mountain meadow soil being the highest in SOCC among the four types and varying in the range of 39.72 ± 19.14 g•kg-1; SOC accumulated mainly in the topsoil; SOCC in 0-0 cm was fourfold of that in 60-100cm; and 84.74% of the SOC in the soil were accumulated in the 0-40cm soil layer of the soil profile. (2) Topsoil was more sensitive than the other soil layers to change in altitude, and the effect of altitude on SOCC declined with soil depth; SOCC in the 0- 40 cm topsoil increased with altitude, but in the 40-100 cm subsoil layer, SOCC acted reversely. (3) ANOVA shows that soil type did not contribute much to soil carbon density, so SOCD was estimated at 10.64 ± 0.72 kg•m-2 and SOCS at 1.426 ± 0.096 Pg in the soil of the nature reserve. Pearson correlation analysis and nonlinear analysis shows that the relationship between altitude and SOCD could be expressed as SOCD = 1×10-5 altitude2 - 0.0227 altitude+ 17.928. 【Conclusion】 The findings in the study lead to the conclusion that the effects of altitude on SOC spatial distribution is quite complicated. Soil organic carbon accumulates mostly in the topsoil layer (0- 40 cm) of the soil profiles. Topsoil SOCC increases with altitude, but the trend weakens with soil depth. However, altitude does not have any impact on SOCD.

    • >Research Notes
    • The Multi-Phase Tempo-Spatial Distribution and Variation of Soil Organic Matter in the Qiluhu Basin

      2020, 57(6):1548-1555. DOI: 10.11766/trxb201911110116

      Abstract (1031) HTML (822) PDF 9.30 M (1510) Comment (0) Favorites

      Abstract:Of the data of the sites for the four-round soil sampling, and the data gathered during the field survey of the sample sites and published in the statistical yearbook, ordinary kriging, multiple regression and exploratory regression were performed to predict spatial distribution of SOM in the Qiluhu Basin and to analyze its influential factors. Results show that the exponential model outperformed the spherical model in fitting the spatial variation of SOM in 2008 and 2011, while the spherical model behaved better in 2013 and 2015. In all the four time phases, the distribution of SOM showed a saddle-shaped curve, that is, low, high and low in content, going from the southwest to the center and then to the northeast in the area. Moreover, the peak stayed unchanged in position, while expanding in area year by year. During the first three time phases, the area with SOM keeping on increasing was twice as large as the area with SOM decreasing continuously. Soil subclasses, agricultural facilities and soil textures explained 14.3%, 2.6% and 1.3% of the variability of SOM, respectively. The decline in SOM content could be attributed to the increase in the yield of the cereal and vegetable crops. And the practice of properly reducing the application rate of nitrogen fertilizers and increasing that of compound fertilizers helped maintain or even raise the content of SOM in the area.

    • Impacts of Mulching Plastic Film Residue on Migration of Soil Nitrogen and Growth of Flue-cured Tobacco Roots

      2020, 57(6):1556-1563. DOI: 10.11766/trxb201906030257

      Abstract (1216) HTML (815) PDF 496.28 K (1473) Comment (0) Favorites

      Abstract:To explore impacts of mulching plastic film residue (MPFR) on migration of nitrate nitrogen and ammonium nitrogen in soil and growth of flue-cured tobacco roots. A pot experiment coupled with soil column leaching test and was conducted and had the pots divided into four groups or treatments different in amount of MPFR in the soil, i.e. 0 (CK), 450 kg·hm-2 (T1), 900 kg·hm-2 (T2) and 1 350 kg·hm-2 (T3); contents of soil nitrate nitrogen and ammonium nitrogen in different soil layers were determined, and length, surface area, volume, diameter and number of root tips and dry matter accumulation of flue-cured tobacco were also measured. MPFR in the soil retarded movement of soil nutrient, and hence migration of nitrate nitrogen and ammonium nitrogen in the soil significantly; MPFR inhibited development of flue-cured tobacco roots and affected, morphology parameters of the roots, such as length, surface area and volume, which decreased gradually with increasing amount of MPFR. When MPFR in the soil reached ≥900 kg·hm-2 in amount, it significant impeded growth of the underground and aboveground parts of the flue-cured tobacco. So, it is quite obviously that mulching plastic residues in the fields will inhibit migration of soil nutrients and growth and development of the flue-cured tobacco therein.

    • Effects of Combined Application of Rapeseed-cake as Organic Manure and Chemical Fertilizer on Yield, Quality and Nutrient Use Efficiency of Flue-cured Tobacco

      2020, 57(6):1564-1575. DOI: 10.11766/trxb202003060099

      Abstract (1159) HTML (1252) PDF 496.31 K (1433) Comment (0) Favorites

      Abstract:A field experiment was conducted to explore effects of combined application of organic manure (300 g·kg-1 or 400 g·kg-1 rapeseed cake) and chemical fertilizer on yield, quality and nutrient utilization efficiency of flue-cured tobacco, in an attempt to provide scientific basis for improving utilization efficiency of the rapeseed resources and tobacco quality. Using flue-cured tobacco of cultivar K326 as test material, the experiment was designed to have ten fertilization treatments, i.e. T1 (chemical fertilizer, consisting of 400 kg·hm-2 specialized tobacco fertilizer equal to 60 kg·hm-2 in N nutrient + 362.5 kg·hm-2 superphosphate +160 kg·hm-2 potassium sulfate as control), T2 (OR30 at 400 kg·hm-2, equal to T1 in N rate ), T3 (OR30 at 265 kg·hm-2, equal to T1 in N rate, and 150 kg·hm-2 potassium nitrate,) , T4 (OR30 at 225 kg·hm-2, 10% less than T1 in N rate, and 150 kg·hm-2 potassium nitrate), T5 (OR30 at 440 kg·hm-2, 10% more than T1 in N rate) , T6 (OR40 at 500 kg·hm-2, equal to T1 in N rate), T7 (OR40 at 331.2 kg·hm-2 and 150 kg·hm-2 potassium nitrate, equal to T1 in N rate) , T8 (OR40 at 281.2 kg·hm-2 and 150 kg·hm-2 potassium nitrate, 10% less than T1 in N rate) , T9 (OR40 at 550 kg·hm-2, 10% more than T1 in N rate ) and T10 (neither manure or fertilizer). Results showed that compared with treatment T1, Treatments T2, T3, T5, T7 and T9 significantly improved growth, leaf area and leaf area coefficient of the tobacco plants by 1.74% -4.51% and 4.47%-19.11%, respectively. Compared with treatment T1, Treatments T4, T5, T7 and T9 significantly increased fresh weight, dry weight and root volume of the plants; Treatments T2, T4, T5, T7 and T9 increased by 2.69%-7.46% in yield, increase rate; and Treatments T2, T5 and T9 increased significantly or by 10.99% -13.46% in output. Meanwhile, Treatments T2, T4, T7 and T9 increased contents of total sugar, reducing sugar, potassium oxide and water-soluble chlorine, and decreased the content of total nitrogen and nicotine in the middle position tobacco leaves. Compared with Treatment T1, Treatments T2, T4, T5 ,T7 and T9 were 9.31% -25.17% and 7.67%-22.32% higher to apparent and physiological N use efficiency, respectively; Treatments T2, T4 and T9 were 19.85% -28.05% and 14.71% - 21.39%, respectively higher in apparent and physiological P use efficiency; and Treatments T2, T4, T5 and T9 were 8.55%-17.40% and 9.06% -21.98%, respectively higher in apparent and physiological K use efficiency. In summary, the application of a proper amount of complex organic-inorganic fertilizer in Treatments T5 and T9, and the application plus potassium nitrate in Treatments T4 and T7 can promote growth, yield, output value and quality of the flue-cured tobacco by improving their NPK absorption.

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