Mean Weight Diameter Of Aggregates Research Articles

Soil Compressibility and Resilience Based on Uniaxial Compression Loading Test in Response to Soil Water Suction and Soil Organic Matter Content in Northeast China

Due to the widespread use of heavy machinery, improper soil tillage practices, and insufficient soil organic materials input, soil compaction has become a major issue affecting soil function in modern agriculture and the sustainability of the environment. The aim of the present study was to evaluate the responses of soil mechanical parameters to soil water content and soil organic matter content (SOM), and to investigate the physical properties of nine disturbed soils in a black soil region in Northeast China. The soil samples were capillary saturated and subjected to 6, 10, 100, 600, and 800 kPa soil water suction (SWS), and pre-compression stress (σp), compression index (Cc), and decompression index (Dc) were measured. SWS and SOM, and their interaction, significantly influenced the mechanical parameters. σp increased with an increase in SWS until 600 kPa, while Dc exhibited an opposite trend with an increase in SWS. Cc had a peak value at SWS of 100 kPa. All mechanical parameter values were higher under high SOM than under low SOM. σp, Cc, and Dc were influenced variably by different soil physicochemical factors. Structural equation modeling results revealed that soil mechanical parameters were directly and indirectly influenced by soil texture and mean weight diameter of aggregates, in addition to SOM and SWS. According to the results of the present study, based on soil mechanical and physical properties, increasing SOM and ensuring suitable soil water content during tillage could be applied as management strategies to minimize further soil compaction and improve soil resilience, and thus promote the sustainable development of agriculture in Northeast China.

The effect of biochars produced from barberry and jujube on erosion, nutrient, and properties of soil in laboratory conditions

The use of biochar can improve the various soil properties and reduce erosion. Also, biochar production has caused the optimal use of agricultural and industrial waste and can convert waste into useful compounds. A large mass of leaves and pruned barberry and jujube branches are abandoned annually without planning to use in South Khorasan. Therefore, in this experiment, the impact of biochars produced from barberry and jujube pruned materials (after six months) on the rate of soil erosion, nutrient, and soil properties were studied in the laboratory conditions at the University of Birjand, Iran, in 2021. Biochar treatments were examined at three 0%, 2%, and 5% levels by weight with four replications. Physicochemical and biological properties and soil nutrients were measured before and after adding biochars and applying erosion. The amount of soil loss was calculated by a standard portable rainfall simulator (a rainfall with an intensity of 160 mm/h for 15 min). The data was investigated using variance analysis and mean comparison (by LSD test and P ≤ 0.05), based on a completely randomized design by JMP13 software. The H/C ratio in the barberry and jujube biochars was about 0.33 and 0.53, respectively. Using the biochars at the 2% and 5% application levels significantly decreased soil erosion and improved soil properties. The 5% barberry biochar treatment caused the greatest reduction in bulk density and soil loss.Moreover, this treatment greatly increased the mean weight diameter of aggregates, saturation moisture, cation exchange capacity, organic matter, microbial biomass carbon, microbial respiration, and substrate-induced respiration of the soil compared to the other treatments. It was also more efficient in increasing and retaining soil nutrients. Using the produced biochars is recommended to improve the soil properties.

Soil quality indicators along a degradation gradient in central Iran: comparison of two regions with contrasting grazing systems

ABSTRACT Soil degradation poses serious environmental problems and requires quantitative assessment. This study aimed to investigate the soil properties in rangelands with different management conditions. Based on the assessment of soil erosion, vegetation cover, vegetation composition, and vegetation vigor, 56 sites were selected in rangelands with moderate, poor, and very poor conditions located in 15 grazing-free areas and one wildlife refuge region. Soil samples (0–10 cm layer) were collected from these sites through a systematic-random method to compare their physical and chemical properties. Results showed that soil organic carbon (OC) and total nitrogen content were significantly different between sites with different range conditions. The mean weight diameter of water-stable aggregates and structural stability index in moderate rangelands were 1.56 mm and 3.98%, respectively, and declined towards more degraded rangeland (i.e. 0.84 mm and 0.83%). Grazing-free rangelands exhibited a relatively larger OC deficit; hence specific management measures and control of grazing are required to enhance the quality of soil in these sites. This study highlighted the role of organic matter in preserving soil structural stability. Increasing protection level of rangelands and decreasing grazing pressure may preserve soil quality and combat desertification in these arid regions.

若尔盖退化高寒草甸土壤团聚体结合有机碳的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 若尔盖退化高寒草甸土壤团聚体结合有机碳的变化 DOI: 10.5846/stxb202011132940 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2019YFC0507701）；国家自然科学基金（U20A2008，31870407）；西南民族大学中央高校基本科研业务费专项资金资助（2020NYBPY06） Changes in soil aggregate-associated organic carbon of degraded alpine meadow in the Zoigê Plateau Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选取若尔盖沼泽化草甸及其不同退化程度为研究对象，利用湿筛法进行团聚体分级，并测定各组分有机碳含量，研究了高寒草甸退化对土壤有机碳（SOC，Soil Organic Carbon）、团聚体以及团聚体结合有机碳（OC，Organic Carbon）的影响，旨在从土壤团聚体及其内部组成的角度去解析SOC的变化特征及机制。结果显示：1）退化使大团聚体比例降低且内部组成改变，团聚体稳定性降低。2）退化使各粒级团聚体及大团聚体内部组分结合OC含量均显著降低。3）大团聚体及其内部粗颗粒有机质中OC储量减少是退化中土壤有机碳流失的主要形式，微团聚体、闭蓄态微团聚体和闭蓄态黏粉粒中OC储量随退化增加。4）退化显著降低了高寒草甸SOC含量和储量，表层（0-10 cm） SOC含量变化主要决定于微团聚体和大团聚体OC含量，亚表层（10-20 cm） SOC含量主要受大团聚体OC含量和团聚体平均重量直径（MWD）影响；对于SOC储量，团聚体MWD是表层SOC储量的最重要影响因素，而亚表层SOC储量取决于团聚体组成、土壤理化性质和大团聚体OC含量的综合作用。研究结果表明，改善土壤团聚体组成和稳定性，增加大团聚体有机碳可能是提高土壤养分供应，提升土壤有机碳水平，从而恢复退化草地生产力和功能的重要途径。 Abstract:Soil aggregate is a basic unit of soil structure. The physical isolation of soil aggregate is the most important mechanism for soil to protect organic carbon from being decomposed by microorganisms. The effects of soil aggregates to maintain the stability of soil organic carbon even exceed the decomposability of organic carbon itself. Meanwhile, the distribution of organic carbon in soil aggregates and the stability of soil aggregate are closely related to the magnitude and stability of soil organic carbon pool, thus they can explain the change in soil organic carbon pool under the changing environment. Zoigê wetland, the most typic plateau wetland in the world, is the birthplace of the Yangtze and Yellow Rivers and stores a large of soil organic carbon. Since the 1960s, the Zoigê wetland has undergone extensive degradation which led to the decomposition of peat and the acceleration of carbon release. However, there are few research on the changes in organic carbon distribution in soil aggregates and its relationship with the changed soil organic carbon pool under alpine meadow degradation. Therefore, we investigated the soil organic carbon (SOC), soil aggregate, and aggregate-associated organic carbon in an alpine meadow and its adjacent degraded sites under the degree of light degradation (LD), moderate degradation (MD), severe degradation (SD), and extreme degradation (ED) in the Zoigê Plateau to explain the mechanism of soil organic carbon pool change and support for the restoration and management of alpine meadow. Wet sieving was used to analyze soil aggregate. The results showed that 1) the aggregate stability and the mass proportion and internal composition of the macroaggregate decreased with degradation, 2) the OC concentration of all size aggregate particles and internal fractions of macroaggregate also decreased with degradation, 3) although the OC stocks in free microaggregate, occluded microaggregate and occluded silt and clay increased with degradation, the decreased SOC was mainly resulted from the decrease of OC stocks in macroaggregate and coarse particulate organic matter, 4) in the surface soil (0-10 cm), the decreased SOC concentration was mainly due to the changes of OC concentration of microaggregate and macroaggregate, while it was the OC concentration of macroaggregate and the aggregate mean weight diameter (MWD) dominating the changes of SOC concentration in the subsurface soil (10-20 cm). Moreover, the SOC stocks in the 0-10 cm soil depth was largely affected by aggregate MWD, but that in the 10-20 cm soil depth was the result of the combination of aggregate structure, soil physicochemical properties and OC concentration of macroaggregate. Overall, improving the composition and stability of soil aggregates and increasing the macroaggregate-associated OC could increase the nutrient supply for plants and the SOC stocks, and ultimately could restore the productivity and function of the degraded alpine meadow. 参考文献 相似文献 引证文献

秦岭天然林凋落物去除对土壤团聚体稳定性及细根分布的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 秦岭天然林凋落物去除对土壤团聚体稳定性及细根分布的影响 DOI: 10.5846/stxb201912272807 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 农业部农业环境重点实验室开放基金(K4030217149);国家林业公益性行业科研专项(201304307) Effects of litter removal on soil aggregate stability and distribution of fine roots in natural forests of Qinling Mountains Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究凋落物去除对秦岭天然林土壤团聚体稳定性及细根分布特征的影响机制,为森林生态治理提供理论依据。结果表明:(1)凋落物去除导致云杉林10-40 cm土层土壤中粒径大于0.25 mm水稳性团聚体含量(WR0.25)较对照显著降低(P<0.05);混交林10-40 cm土层的大于0.25 mm机械稳定性团聚体含量(DR0.25)显著降低(P<0.05);红桦林表层0-10 cm土壤团聚体的平均质量直径(MWD)显著降低(P<0.05);(2)凋落物去除导致三种天然林0-20 cm土层的细根生物量密度(FRBD)较对照显著降低44.18%-57.24%,细根体积(FRV)显著降低24.64%-60.41%;三种天然林中红桦林0-40 cm各土层的FRV最高;(3)凋落物去除导致云杉林0-40 cm土层的土壤容重较对照显著增加5.24%-13.04%,三种天然林0-40 cm土层的土壤有机碳含量显著降低7.92%-25.21%,全氮含量显著降低10.17%-18.10%;(4)相关分析表明,云杉林土壤的团聚体破坏率(PAD)和土壤不稳定团粒指数(ELT)与FRBD、细根根长密度(FRLD)和FRV均呈极显著负相关,混交林土壤的PAD与FRBD呈极显著负相关关系(r=-0.814),红桦林土壤团聚体MWD与FRBD、FRLD和细根比根长(FSRL)均呈显著负相关关系(r=-0.777、-0.771和-0.786)。综上,凋落物去除在总体上降低了天然林土壤团聚体的稳定性及有机碳和全氮含量,并且不利于林木细根的生长。 Abstract:The objective of this study is to investigate the effects of litter removal on the characteristics of soil aggregates stability and fine root distribution so as to provide theoretical bases for vegetation restoration and ecological protection in Qinling Mountains. Results indicated that (1) the litter removal significantly decreased the percentages of >0.25 mm water-stable aggregates (WR0.25) in 10-40 cm soil layer (P<0.05). The percentage of >0.25 mm mechanical-stable aggregates (DR0.25) in 10-40 cm soil layer of mixed forest was also decreased significantly (P<0.05). The mean weight diameter (MWD) of aggregates in 0-10 cm soil layer of Betula albosinensis forest was decreased (P<0.05) by litter removal. (2) By litter removal, the fine root biomass density (FRBD) in 0-20 cm soil layer of the three forests significantly decreased by 44.18%-57.24%; the fine root volume (FRV) significantly decreased by 24.64% to 60.41%. The FRV in 0-40 cm soil layer of Betula albosinensis forest was the highest among the three forests. (3) After 3-year litter removal, the soil bulk density in 0-40 cm soil layer of Picea asperata forest significantly decreased by 5.24%-13.04%. The soil organic carbon contents in 0-40 cm soil layer of the three forests significantly decreased by 7.92%-25.21%, and the contents of total nitrogen significantly decreased by 10.17%-18.10%. (4) The results of correlation analysis showed that percentage of aggregate destruction (PAD) and unstable soil aggregate index (ELT) of Picea asperata forest soil had significantly negative correlations (P<0.01) with FRBD, fine root length density (FRLD), and FRV. The PAD of mixed forest soil showed a significantly negative correlation (P < 0.01) with FRBD (r=-0.814). The aggregate MWD of Betula albosinensis forest soil had significantly negative correlations (P < 0.01) with FRBD, FRLD and fine specific root length (FSRL) (r=-0.777, -0.771 and -0.786). Overall, the litter removal decreased the stability of soil aggregates, the contents of soil organic carbon and total nitrogen in soils of natural forests, which also inhibited the growth of fine roots. 参考文献 相似文献 引证文献

Effects of different vegetation restoration types on soil hydro-physical properties in the hilly region of the Loess Plateau, China

Context Severe soil erosion in the Chinese Loess Plateau and the resulting high sediment yield of the Yellow River have been important research topics. Aims Understanding the impacts of vegetation types on soil hydro-physical properties is essential for understanding regional runoff-sediment changes, soil and water conservation, and revegetation. Methods Three main plantation covers of the study area [natural restoration grassland (NG), artificial Prunus armeniaca forest (AP), and artificial Hippophae rhamnoides shrubland (AH) with 15 years of restoration] and Sorghum bicolor agricultural land as control (CK), were selected to compare their soil hydro-physical properties and infiltration capacity in the soil profile. Key results The bulk density was lower, and soil organic matter (SOM), the proportion of macro-aggregates (&gt;5 mm), mean weight diameter (MWD) of water-stable aggregates, and the initial infiltration and stable infiltration rate were higher in the AH plot compared to CK and the other two plots. The impacts of vegetation restoration on soil properties were mainly in the 0–60 cm layer. Infiltration rates changed mainly within 5 h and basically stabilised within 10 h, with even shorter times to reach stable infiltration in CK. The initial and stable infiltration rates were significant positively correlated (P &lt; 0.05) with macro-aggregate content, MWD, and SOM. Conclusions The AH and AP had greater impacts on soil hydro-properties than NG. The AH had the greatest positive effect on soil hydro-properties and soil and water conservation functions. Implications This study provides practical references for vegetation restoration measures assessment on the Loess Plateau or other similar regions.

Organic Farming Improves Soil Aggregation and Organic Carbon Status in the Rice-Wheat Cropping System in an Inceptisol

The paper deals with the long-term (11 yr.) impact of organic farming on soil aggregates and different forms of organic carbon namely, total, oxidizable and recalcitrant pools, and particulate organic matter-C in rice-wheat (R-W) and rice-wheat-mung bean (R-W-M) rotations in an Inceptisol. Soil aggregate stability (AS) was higher in R-W-M (86%) in the 0-7.5 cm layer than under R-W (83%). Organic nutrients resulted in 88-94% aggregate stability compared to 75% in the control (no nutrient supply). The R-W rotation recorded greater aggregate mean weight diameter (MWD) of 0.50 and 0.52 mm compared to 0.43 and 0.40 mm in R-W-M in 0-7.5 and 7.5-15 cm layer, respectively. The farmyard manure (FYM) with crop residues resulted in the highest total organic carbon (CTOC) content in both layers (1.88-2.05%). Large amounts of particulate organic matter-C (CPOM) were recorded in organic nutrient treatments as 0.4-0.5% in 0-7.5 cm compared to 0.3-0.4% in 7.5-15 cm layer. The MWD of aggregates correlated the best with CPOM (r=0.51) among the C pools, while AS showed the highest correlation with CTOC (r=0.53). The tensile strength of aggregates showed wide variability among the organic treatments and decreased with an increase in CTOC. An overall consideration of the results indicates that crop residue application with vermicompost or FYM has the most potent impact on soil physical condition and soil C status, holding a promise for sustaining the R-W cropping system in Inceptisol.

Planting date and fertilizer type influenced soil quality indices and soybean (Glycine max L.) yields in derived savannah of Nigeria

Soybean is grown in many parts of Northern Nigeria, with little climatic challenges and soil organic matter. There is need to investigate possible influence of planting date of the crop in Southeastern Nigeria, an environment that is rather foreign to the crop. A study was carried out in 2018 and 2019 cropping seasons at Federal College of Agriculture, Ishiagu, Ebonyi State, to evaluate the influence of different planting dates and fertilizer types on selected soil physical and chemical properties, growth and yield of soybean. A split plot in a randomized complete block design was used with planting date (May and June) as the main plots, while six fertilizer types (poultry-droppings manure 5 t ha–1, swine-droppings manure 5 t ha–1, rice-husk dust 5 t ha–1, NPK 15:15:15 at 150 kg ha–1, urea at 100 kg ha–1 and the control) constituted the sub-plots. At crop maturity, some soil quality indices and pod and grain yields (t ha–1) of soybean were assessed. Soil organic carbon (SOC) and total nitrogen contents were significantly (p &lt; 0.05) influenced by both planting date and fertilizer type in 2018 and 2019, while soil pH was improved significantly (p &lt; 0.05) only by fertilizer type in these two cropping seasons. Mean-weight diameter of aggregates, soil bulk density and SOC stock as well as soybean yields were significantly (p &lt; 0.05) influenced by both planting date and fertilizer type in the two seasons. Generally, planting in May improved soil total nitrogen and soybean pod yield whereas planting in June improved the other soil quality indices and soybean grain yield, the best soil amendment in either case being poultry-droppings manure but sometimes parameter-specific. The choice of planting date (May or June) in soybean production in the derived savannah and the soil amendment to use in the enterprise thus has both agronomic and environmental implications. Such a choice would depend on the indices of soil quality and/or the aspects of soybean yields (pod or grain) whose improvements the farmer intends to achieve at crop maturity.

Exchangeable Ca2+ content and soil aggregate stability control the soil organic carbon content in degraded Horqin grassland

Grasslands store 20–30% of global soil organic carbon (SOC) but a majority of grasslands are suffering degradation accompanied by SOC loss. SOC stock is determined by the balance between C input from plants and C output from microbial decomposition, but the relative importance of these factors in controlling SOC and the stabilization mechanisms of SOC are poorly understood. Here, we investigated the main factors influencing SOC loss along a grassland degradation gradient in the Horqin grassland, including non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD) grasslands. The contents of SOC, TN and TP at the ND and LD sites were significantly higher than those at the MD and SD sites. Plant aboveground, belowground and litter biomass significantly decreased with the intensification of degradation. Compared to the ND site, the mean weight diameter of soil aggregates decreased by 8.70%, 17.39% and 26.1% at the LD, MD and SD sites, respectively. Exchangeable Ca2+ and Mg2+ contents also decreased along the degradation gradient. Moreover, the results of structural equation modeling indicated that grassland degradation reduced plant biomass, resulting in an increase in soil available phosphorus content, thus causing less energy losses for microbes through their deployment of extracellular enzymes, eventually leading to an increase in microbial carbon use efficiency. Correlation analysis also confirmed that microbial carbon use efficiency was positively correlated with the ratio of G+/G-. The results of boosted regression tree model suggested that exchangeable Ca2+ and mean weight diameter were the two most influential factors on SOC among the 13 studied variables. Stabilization mechanisms linked to chemical stabilization by polyvalent cations and soil aggregation were the most important controlling factors on SOC content during grassland degradation. In summary, although microorganisms mitigated soil carbon loss to some extent by decreasing their total biomass and increasing their carbon use efficiency, the weakened physical protection of SOC resulted in SOC loss during grassland degradation.

Predicting wind erosion rate using portable wind tunnel combined with machine learning algorithms in calcareous soils, southern Iran

Wind erosion is a critical factor in land degradation worldwide, particularly in arid and semi-arid regions of southern Iran, which have been severely exposed to wind erosion in the recent years due to climate change and land use changes. The main objective of the present study was to predict the wind erosion rate (WER) using easily measurable soil properties combined with some data mining approaches. For this purpose, the WER was measured at 100 locations with different land uses and soil types in the Fars Province, southern Iran using a portable wind tunnel. The WER was predicted by multiple linear regression (MLR), support vector regression (SVR) and decision tree (DT) algorithms using easily measurable soil properties. Results revealed that land use and soil type had significant effect on the WER. The highest mean WER was observed in Entisols with the lowest organic matter (OM), the lowest penetration resistance (PR) and the lowest aggregate mean weight diameter (MWD). Bare lands with the lowest OM and MWD showed the highest WER compared to other land uses. R2 and RMSE of the non-linear regression models developed based on the type of the relationship between the WER and easily measurable soil properties improved by 15% and 12%, respectively, compared to the linear regression model. In both train and test datasets, the SVR and DT models coupled to a genetic algorithm (GA) used for selecting the effective easily measurable soil properties had higher performance than the SVR and DT models using all easily measurable soil properties for predicting WER. With respect to statistical indices, the SVR model with R2 = 0.91 and RMSE = 0.68 g m−2 s−1 outperformed the MLR and DT for predicting the WER. We concluded that combining the SVR with GA could be an applicable and promising method for predicting WER.

Forest floor manipulation effects on the relationship between aggregate stability and ectomycorrhizal fungi

Forest floor and mineral soil manipulations influence the soil biogeochemical properties important for loblolly pine (Pinus taeda L.) tree growth. The impacts of forest floor manipulations on soil aggregate stability and the presence of ectomycorrhizal fungi (EMF), was assessed to elucidate the relationship between EMF abundance and aggregate stability. The study site consists of a 14-year-old loblolly pine plantation managed by Weyerhaeuser Company in the Lower Coastal Plain, approximately 8 miles east of New Bern, North Carolina, USA. The soil samples were collected from the top 7.62 cm of each soil treatment which includes three levels of forest floor retention: removed, control, and doubled and two levels of forest floor mixing with the mineral soil: mixed and unmixed. Ectomycorrhizal fungi abundance was evaluated by ester-linked fatty acid methyl ester analysis and microbial community functionality was assessed by acid-phosphatase activity measurement. Aggregate stability was assessed using the aggregate mean weight diameter approach. Results indicate that the forest floor manipulations had no significant impact on aggregate stability and EMF abundance. However, a positive relationship between EMF abundance and aggregate stability was identified. Removing the forest floor resulted in a soil bulk density increase of 0.18 g cm−3 compared to doubling the forest floor. Our results demonstrate that some mineral soil properties recover relatively quickly from forest floor manipulations. The study informs forest managers interested in how soil responds to forest floor manipulation and the interaction between EMF and aggregate stability.

Effect of integrated nutrient management (INM) practices on soil quality indicators and indices under sorghum (Sorghum bicolor(L.) Moench) + pigeon pea (Cajanus cajan (L.) Millsp.) (4:2) and soybean (Glycine max (L) Merr) + pigeon pea (Cajanus cajan (L.) Millsp.) in rainfed Vertisols of Western India

A field experiment was conducted at the research farm of the All-India Coordinated Research Project for Dryland Agriculture, Parbhani Center, located in Central and Western Maharashtra, India, to study the effect of 7 predominant integrated nutrient management (INM) practices viz., F1: FYM @ 5 t ha-1 ; F2: Gliricidia @ 3t ha-1 (semi dried); F3: Recommended dose of fertilizer (RDF); F4: 25% RDF + FYM @ 2.5 t ha-1 ; F5: 25% RDF + Gliricidia @ 1.5 t ha-1 ; F6: Control with rotation and F7: Absolute control without rotation, on soil quality indicators and indices under two inter-cropping systems viz.,i) sorghum + pigeon pea (4:2), and ii) soybean + pigeon pea (4:2). The effect of INM treatments on soil quality indicators and indices under these cropping systems was studied individually, and the common indicators were also identified among the two cropping systems and mean SQI (Soil Quality Index) and RSQI(Relative Soil Quality Indices) were computed. The common indicators among the two cropping systems emerged for these Vertisol soils were: available S, dehydrogenase assay (DHA), labile carbon (LC) and mean weight diameter (MWD) of soil aggregates. These indicators assume great significance in managing these Vertisol soils. The methodology followed and the results of the present study will be immensely useful to different stakeholders such as researchers, students, farmers, land managers and NGOs in managing and improving soil quality under different inter-cropping systems in Vertisols

Effects of 15-year vegetation restoration on organic carbon in soil aggregates on the Loess Plateau, China

ABSTRACT Effects of 15-year vegetation restoration on organic carbon content of soil aggregates in the Wangmaogou Watershed in China were evaluated. Major land use types include grassland, forestland, shrubland, and sloping cropland. Soils from depths of 0–20, 20–40, and 40–60 cm were collected from each study site. Soil aggregates were divided into macro (5–2 mm), small (2–0.25 mm), and micro (< 0.25 mm) aggregates. Vegetation restoration improved the organic carbon content of soil aggregates, which was positively correlated with soil aggregate stability (R = 0.44 and 0.53 for the mean weight diameter and geometric mean diameter, respectively) and negatively correlated (R = – 0.57) with the soil erosion rate (measured by 137Cs tracer). The levels of macro- and small- aggregates in vegetated lands were more than double than those in sloping cropland. Following vegetation restoration, the dominant soil aggregates in the 0–20 cm soil layer were transformed from micro-aggregates to macro-aggregates. The mean weight diameter and geometric mean diameter of soil aggregates from vegetated land were significantly higher than those of sloping cropland. Vegetation restoration increased the organic carbon content of soil aggregates by improving the stability of soil aggregates and reducing soil erosion.

Forage productivity and soil properties in dual‐purpose cover crop systems

AbstractIntensification of dryland cropping systems with cover crops (CCs) in the semi‐arid central Great Plains could enhance soil health and diversify production when used for forage. This study was conducted from 2015 to 2020 to determine forage mass, nutritive value of CCs, and effects of dual‐purpose CCs on soil properties in a no‐till winter wheat (Triticum aestivum L.)–grain sorghum [Sorghum bicolor (L.) Moench]–fallow cropping system. Treatments were oat (Avena sativa L.)/triticale (× Triticosecale Wittm.) CCs grown in place of fallow, which were hayed, grazed by yearling heifers, or left standing. Forage mass varied across years and averaged 3,546 kg ha−1 for standing CCs. Hayed and grazed CCs removed 73 and 26% of available forage. Soil bulk density was unaffected by haying or grazing compared to standing CCs. Soil organic carbon (SOC) stocks in the 0‐to‐15‐cm depth in 2019 were similar among CC treatments (27.31 Mg ha−1). Stocks with standing and hayed CCs were greater than fallow (24.79 Mg ha−1) which was similar to grazed CCs. However, in 2020, stocks were less with hayed CCs (21.80 Mg ha−1) compared to grazed or standing CCs (24.27 Mg ha−1) and all were similar to fallow. Mean weight diameter of water stable aggregates increased with standing and grazed CCs (2.89 mm) compared to fallow (1.67 mm) in both years but hayed CCs were greater than fallow in 1 yr. Findings suggest CCs can replace fallow to produce high‐quality forage while improving soil health but residue management is critical when CC productivity is low.

Soil aggregate stability and its response to overland flow in successive Eucalyptus plantations in subtropical China

Soil aggregates constitute the basic units of the soil structure, and soil aggregate stability is an important indicator of soil erodibility. Successive planting of fast-growing plantations can change the erosion resistance of the soil under rainfall conditions. Pure Eucalyptus plantations in this study (first- to fourth-generations, i.e., I, II, III, and IV, respectively) were investigated. The stability and abrasion characteristics of soil aggregates were analyzed by the wet sieving method, the Le Bissonnais (LB) method and a slope flow scouring experiment. With an increase in successive generations of Eucalyptus, the soil bulk density increased, and the saturated water content, porosity, organic matter and Iron, Aluminum and Manganese (Fe-Al-Mn) oxide contents decreased. Additionally, the wet sieving results showed that the first- and second-generations had higher macroaggregate content than the fourth generation. The mean weight diameter (MWD) values decreased with the number of planting significantly. Based on fast wetting (FW), slow wetting (SW) and mechanical breakdown by shaking after pre-wetting (WS), the aggregate stability was ranked in a decreasing order as MWDSW > MWDWS > MWDFW. The relative dissipation index (RSI) and mechanical crushing index (RMI) increased with increasing number of planting generations. Aggregate stability was significantly negatively correlated with the soil bulk density and was significantly positively correlated with the organic matter and Fe-Mn oxide contents. The extent of aggregate abrasion (Wr/Wi) values and MWD values decreased with increasing scouring distance and slope gradient during the transport process. The α and Wr/Wi values of the scoured aggregates were significantly correlated with aggregate stability. Hence, with successive planting of Eucalyptus, the soil aggregate stability decreased, and the soil was prone to erosion when subjected to slope flow.

Global meta-analysis suggests that no-tillage favourably changes soil structure and porosity

Role of soil to meet global food security, sustainable intensification and food nutritional quality has got renewed attention with a larger focus on soil physical condition. No-tillage (NT) practice can essentially contribute to develop a sustainable, low carbon and resource efficient agriculture, and encourage the use of crop residues for added soil benefits. Soil aggregation and pore size distribution, two most important soil physical factors controlling the mass and energy transport processes within the soil and between soil and environment, were evaluated under the NT through a global meta-analysis of 5065 pairs of data points from 419 peer-reviewed studies. Compared to conventional tillage (CT), NT increased mean weight diameter of aggregates, water stable aggregates, and macroaggregates by averages (0–30 cm) of 25, 10 and 22%, respectively, although predominantly in 0–10 and/or 10–20 cm layers, with an accompanying reduction in microaggregates. A small but significant 3% decrease in total porosity, a large reduction (20–32%) in macroporosity and a moderate increase (4–7%) in microporosity were realized under NT up to 20 cm soil depth. Bulk density remained stable, although a very large decrease (70% change over CT) in saturated hydraulic conductivity was recorded in 10–20 and >30 cm soil layers. Years of adoption of NT had an additive effect on mean weight diameter and macroaggregates, and the total and macroporosity. Increase in latitudes favoured soil aggregation and micropore volume under NT, while clay content was unfavourable to macro- and water stable aggregate contents. Improvement in structure and water retention properties relate to long-term sustainable development of soils by following no-till practice, which has far-reaching implications beyond the boundaries of agronomy.

Surface soil hydraulic conductivity and macro-pore characteristics as affected by four bamboo species in North-Western Himalaya, India

Soil hydraulic properties are important aspects of the bamboo plantation's eco-hydrological processes as they affect the runoff, soil erosion, and water balance. This study assessed the effect of four commercially important sympodial bamboo species viz., Bambusa vulgaris, Bambusa balcooa, Dendrocalamus hamiltonii, and Dendrocalamus strictus on surface soil saturated and near-saturated hydraulic conductivity (NSHC), macropore characteristics, and the factors influencing the soil hydrological processes. The surface soil hydraulic conductivity at 0, -10, and -30 mm pressure heads and macropore characteristics were estimated from measured steady-state infiltration using a tension (hood) infiltrometer. Soil organic carbon, bulk density, aggregate mean weight diameter (MWD), root biomass, and litterfall was correlated with saturated hydraulic conductivity (SHC) to determine these parameters' relationship with the hydraulic properties. D. hamiltonii showed significantly higher SHC, NSHC, and water-conducting macroporosity than the rest of the species. The correlation analysis revealed that root biomass and soil aggregate MWD were the major determinants of soil hydraulic conductivity characteristics. Bulk density, soil organic carbon, and leaf litter were weakly correlated with SHC. Among the species evaluated, D. hamiltonii was found to be a highly promising species for improvement of soil hydro-physical property and, therefore, can be recommended for increasing infiltration, reducing runoff, controlling soil erosion, and improving groundwater recharge.

Impact of Long-term Application of Organic and Inorganic Nutrient Through Inductive cum Targeted Yield Model on Soil Physical Properties under Pearl Millet [Pennisetum glaucum (L.)] –Wheat [Triticum aestivum (L.)] Cropping System of Semi-arid North-West India

ABSTRACT Sustainability of cereal-based cropping system is important for the livelihood and food security in semi-arid regions. The present study explores the impact of long-term organic and inorganic nutrients and integrated fertilization practices of soil test crop response (STCR) approach of inductive-cum-targeted yield model on soil physical properties and its correlation with soil organic carbon (OC) under pearl millet–wheat in sandy-loam soils of semiarid north-west regions of India. Results showed that OC in the soils significantly increased in farm yard manure (FYM) and integrated treatments up to a maximum of 135% and 148%, respectively, in a period of 8 years over the control in surface soils (0–15 cm). The increase in OC significantly increased the infiltration rate (IR), hydraulic conductivity (HC), soil water retention at all suctions, water stable aggregates (WSA) (> 0.25 mm) and mean weight diameter of the soil aggregates, while decreased the bulk density (BD) and penetration resistance (PR) both at surface and subsurface soil layers. Soil OC also showed a negative correlation with BD (r = −0.955) and PR (r = −0.820). The hydraulic properties of the soil, viz., soil water retention, showed a high positive correlation with field capacity (r = 0.973), 0.922 for permanent wilting point (r = 0.922), HC (r = 0.938), IR (r = 0.973), and WSA (r = 0.979) with OC. Thus, long-term application of organic material in conjunction with NP improved soil physical health, provided better environment to grow crops through improved nutrient concentration and its translocation that ultimately helps to achieve yield target through STCR (Soil Test Crop Response) approach of inductive-cum-targeted yield model.

Microstructure characteristics of aggregates and Cd immobilization performance under a 3–year sepiolite amendment: A field study

Sepiolite is an efficient mineral for the immobilization of Cd in contaminated soils. Here, we conducted a 3–year field experiment to investigate the effect of sepiolite on soil aggregation and porosity, Cd availability, and organic carbon content in the bulk and aggregate soils and Cd accumulation by leafy vegetables. The sepiolite–treated soils showed a 15.4%–53.4% and 5.5%–63.0% reduction in available Cd content in the bulk soil and different particle–size aggregates, respectively. Moreover, the Cd concentrations in the edible parts of Brassica campestris, Lactuca sativa L., and Lactuca sativa var. ramosa Hort. decreased by 5.9%–26.2%, 22.8%–30.1%, and 14.4%–19.1%, respectively, compared with those of the control groups. Treatments with 0.5%–1.5% sepiolite resulted in a significant increase (P < 0.05) in the proportion of 0.25–5.0 mm aggregates, and the increase in the mean weight diameter and geometric mean weight of the soil aggregates indicated that sepiolite treatments enhanced soil aggregate stability. Furthermore, three–dimensional X–ray computed tomography imaging showed that sepiolite treatments resulted in an increase in the total area, average size, and pore perimeter of aggregates, with the maximum values being 1.63–, 1.41–, and 1.401–fold higher than those of the corresponding control groups, respectively. The highest values of soil organic carbon and particulate organic carbon were obtained in 1.5% sepiolite–treated soils and were 2.07– and 1.91–fold higher than those of the control groups, respectively. Additionally, the level of organic carbon functional groups in the bulk soil and different particle–size aggregates generally increased with increasing sepiolite application. Overall, sepiolite, as a soil amendment, not only reduced toxic element bioavailability and uptake by plants but also enhanced soil structure and function.

Effects of tillage method and drainage management on some soil physical properties

Tillage is one of the most important practices affecting soil physical and hydraulic properties. Its effects may vary intensely according to the tillage method. This study aims to evaluate the effects of different tillage methods (moldboard plow+disk harrow, moldboard plow+rotary tiller and chisel plow+disk harrow) and drainage (subsurface drainage and non-drainage) on soil physical properties in a clay loam soil. The experiment was conducted in split-plot in time statistical design. Soil bulk density, aeration porosity, organic matter, aggregate mean weight diameter (MWD) and water infiltration rate were measured after planting and after harvesting of winter-wheat crop. Results revealed that the tillage method had significant effect on organic matter content, such that the lowest (1.18%) and highest (1.35%) values were observed in moldboard plow/disk harrow and chisel treatment, respectively. Tillage effect was significant on saturated moisture content, MWD, aeration porosity and infiltration rate. The effect of time was significant on all investigated factors. The effect of drainage was significant on MWD and infiltration rate. Evaluating the interaction effect of tillage and drainage indicated that the contribution of drainage on changing MWD is higher than the tillage methods. Further, it was concluded that the selection of tillage method had an important role on aeration porosity and MWD in no drainage condition, so that moldboard plow makes much more aeration porosity (25.48% against 17.17%) and less MWD (2.40 against 2.80 mm) compared to chisel. According to the result, the treatment combination including drainage/after planting/moldboard plow and disk harrow had the lowest MWD and also, combined treatment of no drainage/after harvesting/chisel plow) had the highest MWD. The application of chisel is not recommended in no-drained areas having high level of groundwater, because of the highest saturated moisture content and MWD along with the lowest aeration porosity compared to moldboard plow.