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【Objective】The present paper aimed to study the occurrence form of cadmium (Cd) accumulation in soil aggregates of Cd-contaminated brown calcareous soil matrices of paddy fields in the Karst area of northwestern Guangxi, and to provide data reference for safe rice production in this type of Cd-contaminated paddy fields in the region. 【Method】The sampled soil aggregates were separated into five aggregates as ＞ 2.000 mm, 1.000-2.000 mm, 0.050-1.000 mm, 0.074-0.250 mm and ＜0.074 mm, the composition of soil aggregates particle size, Cd content of different particle size aggregates and their main occurrence patterns from 0-20, 20-30, 30-50 and 50-80 cm depth profiles in the Karst area of northwest Guangxi were studied.【Result】The proportion of 0.250-1.000 mm size aggregates in each profile was stable, above 30.00%, with no significant difference between profiles (P＞0.05), the proportion of ＞2.000 mm size aggregates in the 0-20 cm soil profile (tillage layer) was the largest (40.20%), and as the depth of the profile increased, the proportion of ＞2.000 mm size aggregates decreased rapidly, and the proportion of ＜0.250 mm size aggregates showed a gradual increasing trend. Analysis of the Cd content of agglomerates of different particle sizes showed that, in 0-20, 20-30 and 30-50 cm soil profiles, Cd was mainly enriched in ＞2.000 mm particle size aggregates, with contents as high as 2.22, 1.66 and 0.95 mg/kg, respectively, and in the 50-80 cm soil profile, Cd was mainly enriched in 1.000-2.000 mm particle size aggregates. ＞2.000 mm particle size aggregates contributed most to the whole soil Cd content in the 0-30 cm soil layer. The occurrence form of Cd in the aggregates at different profile depths showed obvious differences, the proportion of Cd in aggregates of all particle sizes in the 0-20 cm profile was mainly in the organic matter binding state, with the smallest proportion of Cd in the exchangeable state (except for ＜0.074 mm particle size aggregates), and the proportion of Cd in the exchangeable state in the aggregates increased greatly with the increase of the depth of the profile, when the profile depth was increased to under 30 cm, the Cd in the aggregates mainly existed in carbonate bound state, and with minimal content in the residue lattice state.【Conclusion】In the typical Cd-contaminated brown calcareous soil matrices of paddy fields in the Karst area of northwestern Guangxi, the Cd is mainly enriched in aggregates of ＞2.000 mm and 1.000-2.000 mm particle size, the Cd in the aggregates of each particle size in the 0-20 cm tillage soil is mainly in the form of organic matter bound state, and with the smallest proportion in the form of exchangeable state. With the increase of the profile depth, the proportion of exchangeable Cd increases greatly, while the proportion of Cd in the stable form decreases significantly. Therefore, in the actual production process, it should focus on improving the content of large particle size soil aggregates and avoiding excessive intensive ploughing and deep tilling, reducing the exchangeable state Cd content in the ploughed soil, and ultimately reducing the risk of excessive Cd in rice during rice production. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to investigate the effects of microplastics on the structure and carbon, nitrogen, phosphorus stoichiometric characteristics of red soil with different levels of iron enrichment, and to provide theoretical basis for guiding the improvement of soil quality and pollution management in red soil areas. [Method] Using subtropical red soil as the research object, low density polyethylene (M0, M1, M2) with 0, 0.1%, 1.0% mass and iron (Fe0, Fe1, Fe2) with 0, 10 and 20 g/kg mass were added through indoor cultivation experiments to simulate the pollution level of microplastics and the degree of iron enrichment in red soil. The distribution characteristics of water stable aggregates and the stoichiometric characteristics of carbon, nitrogen and phosphorus in red soil polluted by microplastics under different iron enrichment conditions were studied. [Result] Under the condition of Fe0o, compared with M0, the aggregate content (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD) of M1 with particle size > 0.25 mm decreased, and the WSA, MWD and GMD of M2 increased significantly; Under Fe0, conditions, there was no significant difference in the stability indicators of aggregates among M0, M1 and M2; Under Fe2 conditions, both M1 and M2 significantly reduced the WSA, MWD and GMD of soil aggregates. In terms of carbon, nitrogen and phosphorus content and their stoichiometric characteristics, M1 and M2 under Fe0 conditions could significantly increase soil organic carbon content (SOC); Under Fe0, and Fe2 conditions, microplastic treatment had no significant effect on SOC. The total nitrogen content (TN) of the soil decreased significantly under Fe0, and Fe1, conditions, while microplastic treatment had no significant effect on TN under Fe2 conditions; The total phosphorus content (TP) of the soil showed M0 > M1 > M2. The changes in soil nutrients ultimately led to a significant increase in C/N, C/P and N/P of all microplastic treatments (except for Fe0, M1, Fe2 M1 and Fe2 M2). [Conclusion] The effects of different treatments on the stability of soil aggregates vary. Under the current existing red soil conditions, low micro plastic pollution can reduce the stability of soil aggregates, while high micro plastic pollution can increase the stability of soil aggregates. Under relatively light iron rich red soil conditions, both low and high microplastic pollution have no significant impact on the stability of soil aggregates. Under relatively high iron rich red soil conditions, both low and high microplastic pollution can reduce the stability of soil aggregates. M0reover, the changes in soil aggregate structure under different treatments led to significant differences in the stoichiometric characteristics of carbon, nitrogen and phosphorus in the soil. Overall, microplastic pollution can significantly improve the C/N, C/P and N/P of red soil. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of vegetation restoration on soil aggregates and organic carbon in severe burning sites in Greater Khingan Mountains, this paper used larch plantations of different stand ages (11, 21 and 32 years) planted on heavy fire sites as the research object, and conducted a study on the stability of soil aggregates and organic carbon characteristics of soil aggregates by measuring the percentage content of each particle size and the organic carbon content of soil aggregates. The results showed that: 1)After vegetation restoration of burned areas, the mechanical stability and water stability of soil aggregates in larch plantations of different stand ages were dominated by the content of >0. 25 mm particle size, accounting for 85. 57%-89. 42% and 62. 86%-83. 19%, respectively. With the increase of stand age, the content of soil mechanical stability aggregates >2 mm particle size in 0-10 cm layer of larch plantation decreased significantly and the content of 0. 25-2 mm particle size increased significantly, while the water stability aggregates showed a trend that the content of >2 mm particle size decreased significantly and the content of 0. 5-2 mm particle size increased significantly (P < 0. 05). 2)32 years of larch plantation soil mechanical stability aggregates mean weight diameter (MWD) and geometric mean diameter (GMD) of the upper soil water-stable aggregates were significantly smaller than 11 years, and the MWD of the upper soil water-stable aggregates was consistent with the characteristics of the mechanically stable aggregates. Water-stable macroaggregate content (WSA 0. 25 ) gradually increased with the increase of restoration years, and the percentage of aggregate destruction (PAD) of the 32 years old larch plantation decreased significantly. 3)With the increase of forest age, the organic carbon content of soil aggregates in larch plantation forest increased, and the increase was more in the upper layer. The organic carbon contribution of large aggregates (>0. 25 mm fraction) dominated. The results could provide scientific basis for vegetation restoration of burned areas in Greater Khingan Mountains. [ABSTRACT FROM AUTHOR]

【Objective】The aims of the present paper is to explore the spatial variation and stability of soil aggregates at different soil depths under different years of the deep turning measure. 【Method】The soil of the deep turning measure（2014） was used as a control, and the soil aggregates of 0-20, 20-40, 40-60 cm soil depths were continuously sampled and monitored based on the years of deep turning（2014-2020）. The changes of soil aggregates, particle size distribution patterns and stability of soil aggregates with the age of deep turning were analyzed. 【Result】 WR0.25 was more sensitive to the response to deep turning than DR0.25, which was significantly lower than DR0.25; WR0.25 generally increased with the age of deep turning and decreased with the increase of soil depth; Under deep flipping, WR0.25 was more sensitive to the response of deep turning than DR0.25, and the content of WR0.25 decreased with the increase of soil depth and increased with the increase of deep turning age; MWD showed no obvious overall change with the increase of deep turning age in 0-20 cm soil layer, 20-40 cm soil layer showed a gradual increase trend with the increase of deep turning age, MWD in 40-60 cm soil layer showed an increasing trend with the increase of deep turning age after 1-5 years of deep turning, and MWD gradually decreased after 6-7 years of deep turning. PAD showed a tendency to increase with the increase of soil depth and decrease with the increase of deep turning age. WR0.25, PAD and MWD showed a significant correlation（P<0.05）, in which WR0.25 showed a significant negative correlation with PAD, the correlation coefficient R was-0.750, WR0.25 showed a significant positive correlation with MWD, the correlation coefficient R was 0.866, and the PAD and MWD showed a significant negative correlation relationship, and the correlation coefficient R was-0.795.【Conclusion】The deep turning measure directly acted on the structure of soil aggregates, and the recombination of aggregate content components led to the hierarchical differentiation of the original tillage soil, which was manifested as two-level differentiation of the surface layer and the bottom layer, and the water stability aggregates had greater variation and more sensitive hierarchical response. The deep turning effect makes the soil surface and bottom layer achieve spatial displacement and mixing, resulting in the homogenization of the original layers of each soil layer, and with the increase of the deep turning age, the distribution pattern of soil aggregates tends to gradually converge and the stability gradually increases. [ABSTRACT FROM AUTHOR]

[ Purpose] The present paper aimed to study the physical properties, soil enzyme activities and their correlation characteristics of wild Bletilla striata soil in different producing areas in Guizhou, so as to provide a theoretical basis for realizing high yield and quality of B. striata artificial cultivation. [ Method] 8 soil sample plots for the wild B. striata were collected in Guizhou province to detect and analyze the soil physical and enzyme activity index characteristics and the correlation between them. [ Result]The soil density was between 2. 06 -2. 55 g/ cm³ with weak variation. The soil texture was mainly clay loam and sandy loam. In most soils, the proportion of the > 0. 25 mm size soil water-stable aggregates reached 70% . The distribution of the soil water-stable aggregates size fraction were different, 2 - 5 mm size fraction was the dominant size fraction in 4 soil plots, < 0. 25 mm size fraction was the dominant size fraction in 3 soil plots. The dominant size fraction of soil micro-aggregate was 0. 25 -0. 05 mm size fraction. The activities of urease, acid phosphatase and sucrase in soil were significantly different with strong variation. The activities of catalase in soil were not significantly different with weak variation. Soil enzyme activity was strongly influenced by the soil density, soil aggregates and microaggregates. There was a significant positive correlation between urease and acid phosphatase, which could promote each other. [Conclusion] Guizhou wild B. striata has strong adaptability to soil environment. It mainly grows in sandy soil or clay with soil clay content less than 25 %, and some wild B. striata can also grow in clay with soil clay content more than 30% ; Soil specific gravity, soil aggregates and micro aggregates are important factors affecting soil enzyme activity of B. striata. The suitable soil specific gravity is 2. 06 - 2. 55 g/ cm³, the dominant particle size is 2 - 5 mm or < 0. 25 mm, and loam is the best soil texture; Urease and acid phosphatase can promote each other. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to explore the impact of different farming methods on soil physical properties in Aksu area.[Method] The soil under five typical farming methods including wheat field, single-cropping jujube orchard, jujube-wheat intercropping garden, wasteland single-cropping jujube orchard, and abandoned land were collected in Aksu area, and the main physical characteristics were studied through field investigation and indoor analysis.[Result] Compared with farmland wheat fields and abandoned land, the soil bulk density of jujube orchard and jujube-wheat intercropping orchard is reduced, and soil porosity, aggregate stability, and soil moisture content are correspondingly improved; soil wet sieve aggregate composition under different farming methods. They are mainly 2-0.25 mm intermediate aggregates, with a content of 38.95%-53.74%.After the farmland was converted into a jujube orchard or a jujube-wheat intercropping orchard, the content of soil aggregates over 0.25 mm increased significantly (P<0.05), and both soil MWD and GMD showed an increase. After the abandoned land was converted into a jujube orchard, the content of soil powder + clay aggregates dropped by 5.25%-43.86%.The content of soil macroaggregates, intermediate aggregates and microaggregates showed an increase, with the increasing range of 9.07%-64.92%, 0.49%-4.19% and 0.72%-20.11%, respectively. [Conclusion] Compared with farmland wheat fields and abandoned land, jujube orchards and jujube-wheat intercropping gardens are beneficial to the stability of soil aggregates and can promote the formation of good soil structure. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to reveal the difference of soil water holding capacity of different forest lands in the loess hilly region and guide the construction and management of water conservation forest system in this area. Based on the field survey and consultation of Chemingyu Forestry Station in Zhongyang County, Shanxi Province, which belongs to the loess hilly area, three typical forest lands of Populus davidiana Dode, Robinia pseudoacacia L. and Pinus tabulaeformis were selected as the research objects and 20 m × 20 m standard plots were set up respectively. Soil sample in 0-10, 10-20 and 20-30 cm soil layers were collected in each standard plot, including soil ring knife samples and soil loose samples. Soil mechanical composition, soil aggregate, soil water content, soil bulk density, soil total porosity and other physical property indexes were measured by laboratory test, and soil physical properties and soil water holding capacity of three typical forest lands were systematically studied. The results indicate that the soil physical properties of three typical forest lands exist differences. Soil water content of the typical forest land in the loess hilly region is Pinus tabulaeformis > Robinia pseudoacacia L. > Populus davidiana Dode. The soil bulk density of Robinia pseudoacacia L. is the largest and Populus davidiana Dode is the smallest, and the difference between each plot is significant. The soil total porosity is Populus davidiana Dode > Pinus tabulaeformis > Robinia pseudoacacia L.. The mean weight diameter and geometric mean diameter of soil aggregates with wet sieves are smaller than those of dry sieves. The mean weight diameter of dry sieve soil aggregate in 0-30 cm soil layer is Robinia pseudoacacia L. > Pinus tabulaeformis > Populus davidiana Dode. The maximum of mean weight diameter with wet sieve soil aggregate is Populus davidiana Dode and which of the minimum is Robinia pseudoacacia L.. That is to say, the soil aggregate stability of Robinia pseudoacacia L. is the worst and which of Populus davidiana Dode is the strongest. There are differences in soil saturated water content, field water capacity, wilting coefficient and soil available water in different plots, but the overall water status of Pinus tabulaeformis is better. The field water capacity and soil available water with different plots are Pinus tabulaeformis > Populus davidiana Dode > Robinia pseudoacacia L., and the wilting coefficient is Populus davidiana Dode > Pinus tabulaeformis > Robinia pseudoacacia L.. [ABSTRACT FROM AUTHOR]

【Objective】 According to the soil quality degradation caused by soil salinization in oasis area in Xinjiang, effect of cottonseed meal on exchange base cation’s distribution in salinization soil aggregates was studied. 【Method】 In the present paper the superior resources of cottonseed meal’s effects on saline soil quality were taken as the starting point, field test plot was adopted, and saline alkali soil conditions with different gradients were simulated, together with the application of a certain amount of cottonseed meal.【Result】Two types of salinization in soil > 0.2+5 large aggregate accounted for about 86%, with > 5 mm total maximum particle size aggregates. In the aggregate, the average content of cation size was Na++> Ca2++ > K++> Mg2++. Sodium chloride type soil exchangeable Ca2++ and sodium carbonate in the soil exchangeable Mg2++ were mainly accumulated in 2+0-40 cm soil layer. Exchangeable Na+ + in the exchangeable soil K+ + and two kinds of salinized soil in the sodium carbonate type soil were mainly distributed in the micro aggregate. The exchangeable Mg2++ was more evenly distributed among the particle size aggregates, and exchangeable K++ and exchangeable Ca2++ were mainly distributed in the large aggregates in the sodium chloride soil. In the same soil in the same concentration and processing of cottonseed meal, > 5 mm and 2+-5 mm of sodium chloride in soil particle size in(Ca2++ + Mg2++ )/（K++ Na++） were higher than the ratio of the content of sodium carbonate in soil, the grain size was on the contrary. The accumulation of two valence base ions and the decrease of monovalent ion promoted the formation of large aggregates in the soil of sodium chloride type, and the aggregation of soil was better. 【Conclusion】 Improvement effect of cottonseed meal on sodium chloride soil is better than that on sodium carbonate soil. [ABSTRACT FROM AUTHOR]

This paper focuses on environmental risk caused by livestock manure disorderly discharged from integrated livestock and poultry industry. 2-year pot experiment was carried out to study the effects of pig manure organic fertilizer on fluvo-aquic soil organic carbon, available nutrient content and soil aggregate distribution, which designed in 5 levels of organic fertilizer application(0, 6.7, 13.3, 26.7, 40.0 g.kg-1 soil). The results showed that the organic carbon, alkali-hydrolyzable nitrogen, available P and available K contents in soil were enhanced with organic fertilizer application increasing, and the indicators of soil were increased significantly in second year, such as organic carbon content was 2.7%~54.0% higher than that of the first year, alkali-hydrolyzable nitrogen content was higher 6.7%~34.6%, available P content was higher 36.8%~ 159.5% and available K content was higher 20.3%~35.7%. There was a significant linear relationship between soil organic carbon content and external organic carbon input. Organic fertilizer application could significantly improve lettuce yield, and it had a significant effect. The soil micro-aggregate contents for 0.053~0.25 mm and <0.053 mm took a larger percentage of total soil aggregates, and showed a decreasing trend with organic fertilizer application increasing, while the contents of 0.25 ~0.5 mm and >0.5 mm soil macro-aggregates were increased with organic fertilizer application increasing. Organic fertilizer application could promote soil macro-aggregates formation, when the pig manure organic fertilizer applied 40.0 g.kg-1 soil, the contents of >0.25 mm soil aggregates reached maximum, and also the mean weight diameter(MJFZ)) and geometric average diameter( GWD) of soil aggregates were higher than that of other treatments, the soil agglomeration became more stronger and the soil structure became more stable. [ABSTRACT FROM AUTHOR]

In this paper, the soils of jasmine plantation from Fuzhou were taken as the study object. Soil aggregate composition, distribution and stability, including mean weight diameter (DMW), geometric mean diameter (DGM) and fractal dimension (N) of 0-50 cm soil layer under common and organic cultivation were measured and analyzed. The results showed that: (1) The soil aggregate in common jasmine cultivation is dominated by micro aggregate (<0.25 mm) in 0-50 cm soil layer, its percentage is 67. 63%, While the soil aggregate of > 1 mm is the lowest, its percentage only is 4. 13% % The content of macro aggregate (R0 25) in 0-20 cm soil layer of organic Jasmine cultivation is majority, and the percentage is up to 59. 30%; In the 20-50 cm soil layer, the percentage of micro aggregates is significant, and the percentage is 53.36%; (2) Compared with common cultivation, the organic cultivation in the 0-50 cm soil layer increases the content of macro aggregate (R 0 25), reached 84. 27%, 126. 85% and 235. 38%, respectively; (3) Compared with common cultivation, mean weight diameters (DMW) and geometrical mean diameters (DGM) of soil aggregates in organic jasmine cultivation are improved in 0-50 cm soil layer. The fractal dimensions numbers of soil aggregates in common and organic cultivation are ranged within 2.84-2.92 and 2.53-2.85, respectively. The fractal dimension numbers of soil aggregates in Organic Jasmine cultivation is relatively lower, which indicates that organic cultivation improves the stability of soil aggregates. [ABSTRACT FROM AUTHOR]