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Rill erosion, mostly affecting steep and long hillslopes, is one of the most severe effects of deforestation and wildfires in natural ecosystems. Specific monitoring and accurate but simple models are needed to assess the impacts of these forest disturbances on the rill detachment process. To address this need, this study has simulated the rill detachment capacity (Dc) through flume experiments on samples of soils collected in hillslopes after deforestation and severe burning. The associations between Dc and organic matter (OM) and the aggregate stability of soil (WSA), two key parameters influencing the rill detachment process, have also been explored under the two soil conditions (deforested and burned soils) using multivariate statistical techniques. Finally, linear regression models to predict Dc from these soil parameters or the hydraulic and morphological variables (water flow rate, WFR, and soil slope, S), set in the flume experiments, have been proposed for both soil conditions. Higher Dc in samples from deforested sites compared to the burned soils (+35%) was measured. This Dc increase was associated with parallel decreases in OM (−15%) and WSA (−34%) after deforestation compared to the wildfire-affected sites. However, the discrimination in those soil properties between the two soil conditions was not sharp. Accurate linear equations (r2 > 0.76) interpolating Dc and the shear stress (τ) have been set to estimate the rill erodibility (Kr) to evaluate soil resistance in erosion models to be applied in deforested or burned sites. [ABSTRACT FROM AUTHOR]

Soil aggregate formation and stability are crucial in safeguarding soil carbon pools, as they form the basic unit of soil structure in terrestrial ecosystems. The impact of different land uses on soil aggregation pattern has widely been studied but is limited under tropical dry climate conditions. This study aimed to determine the soil aggregation pattern at two soil depths (0-15 cm and 15-30cm) in three different plantations (Peltophorum pterocarpum, Eucalyptus globulus, and Acacia nilotica) established in degraded land under tropical dry climate. The soil aggregates were categorized into microaggregate, mesoaggregate and macroaggregate based on their size fractions which were determined by the wet sieving method. The percent of macroaggregate, mesoaggregate, and microaggregate fractions at 0-15 cm depth ranged from 62.2 - 82.6%, 31.6 - 36.7%, and 1.1 - 4.9 % respectively whereas at 15-30 cm depth, it ranged from 69.7 - 81.7%, 17.1 - 31.6%, and 1.2 - 2.8%. The mean weight diameter values at 0-15 cm and 15-30 cm soil depth ranged from 2.27-3.37mm and 2.85-3.35 mm respectively. The higher percentage of macroaggregate fractions in Peltophorum pterocarpum plantation compared to Eucalyptus globulus, and Acacia nilotica plantations indicated that the Peltophorum pterocarpum plantation has slightly more potential to improve aggregate formation and soil structure in the degraded lands under tropical dry climate. In addition, appropriate land use practices can increase soil aggregate stability in the study area. [ABSTRACT FROM AUTHOR]

Soil aggregate stability is an important index that reflects soil quality and anti-erosion ability and strongly affects soil processes and functions. Bedrock strata dips (dip and anti-dip slopes) and land use types primarily influence soil aggregate stability, whereas the detailed mechanisms are unclear in karst trough valley. Therefore, to explore the effects of bedrock strata dip and land use type on soil aggregate stability in karst trough valleys, soils were collected from five major land use types (abandoned land, grassland, pepper fields, corn fields and forest) on dip and anti-dip slopes. The soil was fractionated into macroaggregates and microaggrates using dry and wet sieving analysis. The soil particle size distributions in the macroaggregates and microaggregates were measured in conventional laboratories. The results showed significant differences in soil aggregate stability among different bedrock strata dips, slope positions, and land use types (P 0.25 mm water-stable aggregates (85.31%) and mean weight diameter (2.67 mm) on the upper slope compared to that in the other slope positions of the dip slope. In addition, the dip slope had a higher percentage of aggregate destruction (35.57%) than the anti-dip slope (29.81%), and the soil erodibility factor value of the natural forest of the dip/anti-dip slope was significantly lower than that of the other land use types (P

Microplastics (MPs) pollution has become a global pollution problem, potentially affecting soil carbon cycling and structure stability in agricultural systems. However, the effects of MPs pollution on soil organic carbon fractions/transformation and soil aggregate stability remain unknown. Thus, a combination of one-year pot and short-term mineralized incubation experiments that involved a reference (CK, with no MPs), different concentrations (0.1, 1, and 2 w/w % polyethylene (PE)), and types (0.1 w/w % PE, polypropylene (PP), and polyvinyl chloride (PVC)) of MPs were carried out to investigate the effects on the soil aggregate stability and organic carbon mineralization after one year of adding MPs. The results showed that the size distribution of the soil partial aggregates varied significantly as affected by the MP concentration and type (p ˂ 0.05). Compared with 0.1% PE, significant increases in the MWD (mean weight diameter) and GMD (geometric mean diameter) of 2% PE of 27.22% and 32.73%, respectively, were detected. In addition, high concentrations (>1%) of PE significantly decreased the dissolved organic carbon (DOC) (p ˂ 0.05), whereas they significantly increased the stable carbon fractions including the particulate organic carbon (POC) and mineral-bound organic carbon (MOC) (p ˂ 0.01). Meanwhile, compared with the CK, both MP types and doses significantly decreased the soil organic carbon mineralization rate (SOCMR) and cumulative mineralization amount (CM) (p ˂ 0.001). Moreover, the MPs significantly increased the total PLFA (phospholipid fatty acid) by 261.9–438.8% (p ˂ 0.01), and the soil pH and total PLFA were the dominant factors that affected the SOCMR as affected by MPs. Thus, a high concentration (>1%) of PE significantly decreased the SOCMR by influencing the soil pH, TN, and macroaggregate (R>0.25) content and microbial community composition. This study provided evidence of the feedback of MPs pollution on soil C dynamic and aggregates in cultivated soil in South China. [ABSTRACT FROM AUTHOR]

Enhancing soil structure and soil nitrogen availability is the key to sustainable agricultural development in global cropping systems. Straw return can affect soil aggregation, but the results of recent studies on the influence of straw return on soil aggregation are not consistent, and the distribution and availability of straw‐derived nitrogen in soils are still unclear. Here, a meta‐analysis of the effects of straw return on soil aggregation was conducted based on 57 studies published in China over the past 10 years. Moreover, combined with a pot experiment, the distribution and transfer characteristics of the two main wheat (Triticum aestivum L.)‐preceding crops, corn (Zea mays L.) and soybean (Glycine max L.) straw‐derived nitrogen in the soils were studied by using the 15N‐tracer method in the main wheat‐producing areas of China. 15N‐labeled straw was introduced into soils in pots at rates of 0.3% and 0.5% of the soil dry mass and incubated 60%–70% of the field water capacity throughout the entire growth period of wheat (220 days). A meta‐analysis revealed that straw return significantly improved the mass ratio of large macro‐aggregates (LM%) and small macro‐aggregates (SM%) but significantly decreased the mass ratio of micro‐aggregates (MI%) and silt plus clay‐size particles (CS%), with mean effect sizes of 36.27%, 9.06%, −8.26%, and −21.32%, respectively. The mean weight diameter (MWD) and geometric mean diameter (GMD) also increased by 21.48% and 15.64%, respectively. Compared with SM%, LM% made a greater contribution to the stability of soil aggregates. Moreover, only LM% showed a significant positive correlation with the corresponding aggregate‐associated nitrogen content, which was an important reason for the improvement in soil nitrogen availability after straw return. The positive effect of straw return on soil aggregation was greatest when the soil pH was close to 6.5–7.5, the average annual temperature was greater than 15°C, and the average annual rainfall was close to 800–1000 mm. The results of the pot experiment revealed that the proportions of straw‐derived nitrogen in >2 mm aggregates were 1.21–1.28, 1.50–2.23, and 1.34–1.74 times greater than those in 0.25–2, 0.053–0.25, and <0.053 mm aggregates, respectively. Moreover, the proportion of straw‐derived nitrogen content of aggregates of different particle sizes showed that the proportion of straw used to reach 0.5% of the soil dry weight was greater than 0.3%, which was 1.09–1.66 times greater, and that of soybean straw was significantly greater than that of corn straw, which was 1.50–2.28 times greater. At application rates of 60 g pot−1 and 100 g pot−1 straw, the absorption of soybean straw‐derived nitrogen by wheat was 1.83 and 2.15 times greater than that of corn straw‐derived nitrogen, respectively. In conclusion, straw return effectively improved soil aggregate stability and nitrogen availability, which was closely related to the increase in soil LM%. Soybean straw can stabilize soil aggregates better than corn straw, and its straw‐derived nitrogen is an important nitrogen source for subsequent wheat crops. [ABSTRACT FROM AUTHOR]

Processes of water retention and movement and the hydraulic conductivity are altered in the rhizosphere. The aim of this study was to investigate the physical-hydric properties of soil aggregates in the rhizosphere of annual ryegrass (Lolium multiflorum) cropped in a Kandiudalfic Eutrudox, taking into account aspects related to soil aggregate stability. Soil aggregates from rhizosphere soil (RZS) and soil between plant rows (SBP) were used to determine soil water retention curves (SWRCs) and saturated hydraulic conductivity (Ksat). In addition, properties related to soil aggregate stability, such as water-dispersible clay, soil organic carbon (SOC), and microbial activity, were also assessed. The higher microbial activity observed in the RZS was facilitated by increased SOC and microbial activity, resulting in improved soil aggregation (less water-dispersible clay). For nearly all measured matric potentials, RZS had a higher water content than SBP. This was attributed to the stability of aggregates, increase in SOC content, and the root exudates, which improved soil water retention. The increase in total porosity in RZS was associated with improved soil aggregation, which prevents deterioration of the soil pore space and results in higher Ksat and hydraulic conductivity as a function of the effective relative saturation in RZS compared to SBP. [ABSTRACT FROM AUTHOR]

In the southern Xinjiang region of China, developing efficient irrigation and fertilization strategies to enhance resource utilization and prevent desertification is of critical importance. This study focuses on jujubes in Xinjiang, China, and involves a three-year field experiment aimed at exploring the optimal application strategy of magnetically treated water combined with microbial organic fertilizer to provide scientific support for high-quality jujube production. The experiment included a control group (using only fresh water, denoted as CK) and combinations of magnetically treated water drip irrigation with varying amounts of microbial organic fertilizer: in 2021, treatments included M0 (only irrigating with magnetically treated water), M6 (0.6 t/ha), M12 (1.2 t/ha), M18 (1.8 t/ha), and M24 (2.4 t/ha); in 2022 and 2023, treatments included M0, M6 (0.6 t/ha), M12 (1.2 t/ha), M24 (2.4 t/ha), and M48 (4.8 t/ha). This study investigated the effects of magnetically treated water drip irrigation combined with microbial organic fertilizer on soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality. The application of microbial organic fertilizer significantly reduced the soil bulk density by 3.07% to 11.04% and increased soil porosity by 1.97% to 14.75%. Soil saturated hydraulic conductivity gradually decreased with the increasing amount of microbial organic fertilizer, with a reduction range of 5.95% to 13.69%, while the water-holding capacity significantly improved (from 0.217 cm3/cm3 to 0.264 cm3/cm3). Additionally, microbial organic fertilizer significantly enhanced the activities of urease, catalase, and sucrase in the soil and significantly increased the proportion of large soil aggregates. Jujube yield increased by 3.66% to 21.38%, and the quality significantly improved, as evidenced by the increase in soluble sugar and flavonoid content. The Gauss model calculation results recommended 3.09 t·hm2 as the optimal amount of microbial organic fertilizer for comprehensively improving jujube yield and quality. These findings indicate that magnetically treated water drip irrigation combined with high amounts of microbial organic fertilizer significantly improved soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality, providing scientific evidence for desert soil improvement and agricultural production. [ABSTRACT FROM AUTHOR]

Idaho's Magic Valley is a highly productive agricultural region in the United States due to irrigation. The soils in this region are prone to crusting, have low organic matter, and are high in calcium carbonates, making them susceptible to erosion and water runoff. Soils need to be better managed to enhance aggregate stability to enable increased infiltration of irrigation water and decreased soil erosion in nearby waterways. However, to make management recommendations, the identification of appropriate measurements of aggregate stability needs to be identified, and few relevant studies exist. Thus, the overall goal of this project was to identify appropriate methods for the assessment of soil aggregate stability in the study region. The study sites were located in Southern Idaho and set up using common cropping rotations and agricultural management practices for the region using a variety of nutrient sources, tillage types, and cover cropping. Three methods were used to measure soil aggregate stability: wet sieving, simulated rainfall using a Cornell Sprinkle Infiltrometer (sprinkler height: 30, 90, and 150 cm), and the SLAKES mobile application. No differences in soil aggregate stability were found when the wet sieving or SLAKES methods were used at the three study sites, either due to the method or a general lack of differences between treatments. When using the Cornell Sprinkle Infiltrometer, no treatment differences were found at LT-Manure or GRACEnet; however, differences were observed between treatments at the Cover Crop study site at sprinkler heights of 30 and 90 cm. At a sprinkler height of 30 cm, the average mean weight diameter was the highest when winter forage crops (WFC) and solid dairy manure (SDM) were applied (3.73 mm) and the lowest in the control (3.12 mm). At a sprinkler height of 90 cm, the average mean weight diameter was the highest when WFC and SDM were applied (3.54 mm) and the lowest in the WFC Only treatment (2.46 mm). These results not only have implications for which methods are best for assessing progress but also for what management practices can be utilized to decrease soil erosion from irrigated cropland. This study highlighted that under these soils and management practices, simply increasing soil carbon does not increase aggregate stability, especially when root crops are included in the crop rotation with intensive tillage. In arid and semi-arid regions, the Cornell Sprinkle Infiltrometer may be a more sensitive method of measuring soil aggregate stability compared to traditional wet sieving. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The poor soil structure caused by salinization is a major factor affecting crop growth and soil structure will further affect hydrological function. Biochar is widely used to improve soil physical structure because of its special porous material. However, the mechanism of soil pore structure on hydrological function (e.g., soil saturated hydraulic conductivity, plant available water, least limiting water range) after biochar incorporation in saline soil remains unclear. Therefore, the present study examined the response of soil structural properties of different biochar addition in saline clay loam, and subsequently assessed how the pore structure influence soil hydrological function. The study involved four treatments: CK (Control)、C1 (7.5 t ha−1 biochar)、C2 (15 t ha−1 biochar)、C3 (30 t ha−1 biochar). Soil aggregate stability increased from 15 % to 30 % when the amount of biochar addition increased from 7.5 t ha−1 to 30 t ha−1. The highest connectivity index (2.36) and the highest fractal dimension (2.56) were found at the biochar addition of 30 t ha−1. Biochar addition reduced the proportion of small pores (300 µm pore size). Biochar amendment reduced the soil penetration resistance, with the soil saturated hydraulic conductivity, plant available water and the least limiting water range were measured 46 %, 27 % and 40 % greater in rate of 30 t ha−1 biochar addition as compared with those of the CK, respectively. Pearson’s correlation analysis and redundancy analysis revealed that the soil saturated hydraulic conductivity was positively correlated with large pores (diameter >300 μm) and pore connectivity (p < 0.05). The lowest least limiting water range of the CK was primarily constrained by a relatively higher penetration resistance. The improved pore connectivity and elongated pore structures were the key responsible for the reduced penetration resistance in biochar-amended soil, which subsequently increased the least limiting water range. These quantitative estimates highlight the positive effects of biochar amendment-induced soil pore structure alternations towards improving soil hydrological functionalities. These findings are essential for devising effective strategies to enhance sustainable agriculture in saline soils.

Glomalin-related soil protein (GRSP) is a potential byproduct of arbuscular mycorrhizal fungi (AMF) and a major contributor to the passive soil organic carbon (SOC) pool. Despite its crucial role in SOC storage, we know little about the response of GRSP to anthropogenic global change factors (GCFs). Here, using 530 observations from 107 primary studies, we conducted a global meta-analysis to unravel the effects of multiple GCFs (climate change, plant invasion (PI), wildfire, urbanization, land-use change (LUC), and nutrient addition (nitrogen; N, phosphorus; P, and potassium; K) on two functional GRSP fractions (easily extractable- (EE-) and total- (T-) GRSPs) in terrestrial ecosystems. We found that elevated carbon-dioxide increased T-GRSP by 28%, combined NP addition by 39.9%, and NPK addition by 29.5%. Climate warming and alone N addition increased EE-GRSP solely by 2.4% and 13.6%, respectively, but did not influence T-GRSP. However, urbanization and drought decreased T-GRSP by 26% and 15%, respectively. The LUC from natural ecosystems to cropland decreased T-GRSP by 40%, while afforestation in croplands increased it by 32%. Other GCFs (PI, wildfire, and P) had non-significant effects on GRSP probably because of (i) minor changes in AMF activity and (ii) the counterbalancing of effects by opposite processes. GCF impacts were robust when applied at higher intensities for medium-to-long durations (3–10＋ years) in humid conditions and clay-rich soils. The sandy soils experienced greater T-GRSP losses during LUC. Increases in T-GRSP were positively correlated with AMF-root colonization, soil mean-weight diameter, and SOC content. Further, our structure equation model confirmed that GCFs directly influence SOC by altering AMF-GRSP production and indirectly affecting soil aggregate formation and protection, suggesting that optimizing GRSP production can enhance SOC sequestration.

Soil aggregate stability measurement is essential to determine soil health status under various conditions. The Mean Weight Diameter (MWD) is the most applied index to express aggregate stability particularly for wet and dry sieving. However, the MWD could generally present results affected by pre-stress aggregate size distribution when remained aggregates after stress are considered for calculation. Therefore, the objective of the present study was to eliminate the similarities between the MWD results and pre-stress aggregate size distribution, which largely affects treatments differentiation. Samples from 145-160 m (lower), 160–169 m (middle), and 169–175 m (upper) elevations differently affected by the Water Level Fluctuation in Three Gorges Reservoir (TGR) and control (>175 m) were exposed to wet shaking stress. Aggregates remained at each sieve opening, aggregates disintegrated/passed through the sieve opening, and small macroaggregates and microaggregates accumulated were recorded. These aggregates were used to determine and compare two indexes (1) using remained aggregates (MWD) and (2) using disintegrated/accumulated aggregates (MWDd/a) based on the differences among treatments. The results for both pre-stress aggregates and remained aggregates after stress were showed consistent significant differences (p

Aims: Film mulching has been widely used for increasing crop yields in semiarid areas, but its long-term impact on crop performance and soil quality remains poor. This study aims at investigating the long-term effects of different mulching methods on the crop root growth and soil aggregates stability. Methods: A continuous experiment for eight years was set to assess the effects on the soil aggregates stability, root traits, and yield under five different treatments: (i) control method comprising flat planting without mulching (CK), (ii) flat planting with half film mulching (P), (iii) film mulching on ridges and planting in narrow furrows (S), (iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R). Results: The soil quality improved significantly after continuous film mulching for eight years. Compared with CK, mulching decreased the soil bulk density, and increased the soil porosity, soil macroaggregate content (7.39%-22.92% by dry-sieving, and 8.49%-21.67% by wet-sieving), and soil aggregate stability, especially under S and D. Mulching could promote the root growth (root length, root diameter, root surface area, and root volume) distinctly, while S and D increased the average root biomass by 17.27% compared with R and P. The improved soil structure and root traits under mulching increased the yield (29.98–63.96%), and the average yield under S was 1.32%, 25.7%, and 26.14% higher than those under D, R, and P, respectively. Conclusions: In general, the best improved soil aggregate fractions and stability was found under film mulching on ridges and planting in narrow furrows (S), which was significantly associated with the root traits improvement, and thus increasing the crop yield. Therefore, it can be considered an effective mulching pattern for increasing and stabilizing the crop yield in the Loess Plateau region of China. [ABSTRACT FROM AUTHOR]

Soil aggregate is the basic structural unit of soil, which is the foundation for supporting ecosystem functions, while its composition and stability is significantly affected by the external environment. This study was conducted to explore the effect of external environment (wetting-drying cycles and acidic conditions) on the soil aggregate distribution and stability and identify the key soil physicochemical factors that affect the soil aggregate stability. The yellow-brow soil from the Three Gorges Reservoir area (TGRA) was used, and 8 wetting-drying conditions (0, 1, 2, 3, 4, 5, 10 and 15 cycles) were simulated under 4 acidic conditions (pH = 3, 4, 5 and 7). The particle size distribution and soil aggregate stability were determined by wet sieving method, the contribution of environmental factors (acid condition, wetting-drying cycle and their combined action) to the soil aggregate stability was clarified and the key soil physicochemical factors that affect the soil aggregate stability under wetting-drying cycles and acidic conditions were determined by using the Pearson's correlation analysis, Partial least squares path modeling (PLS–PM) and multiple linear regression analysis. The results indicate that wetting-drying cycles and acidic conditions have significant effects on the stability of soil aggregates, the soil aggregate stability gradually decreases with increasing number of wetting-drying cycles and it obviously decreases with the increase of acidity. Moreover, the combination of wetting-drying cycles and acidic conditions aggravate the reduction in the soil aggregate stability. The wetting-drying cycles, acidic conditions and their combined effect imposes significant impact on the soil aggregate stability, and the wetting-drying cycles exert the greatest influence. The soil aggregate stability is significantly correlated with the pH, Ca2+, Mg2+, maximum disintegration index (MDI) and soil bulk density (SBD). The PLS–PM and multiple linear regression analysis further reveal that the soil aggregate stability is primarily influenced by SBD, Ca2+, and MDI. These results offer a scientific basis for understanding the soil aggregate breakdown mechanism and are helpful for clarifying the coupled effect of wetting-drying cycles and acid rain on terrestrial ecosystems in the TGRA. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land use changes modify soil properties, including aggregate structure, and thus, profoundly affect soil quality and health. However, the effects of land use changes originating from alpine grassland on soil aggregates and aggregate-associated organic carbon have received little attention. Soil aggregate fraction, aggregate-associated organic carbon and relevant influencing factors were determined at 0–20, 20–40 cm soil layers for alpine grassland, cropland and abandoned land in the eastern Qinghai–Tibet Plateau (QTP), and their relationships were analyzed by partial least square regression (PLSR). Results showed the following: (1) conversion from alpine grassland to cropland resulted in a significant decline macroaggregate fraction (R0.25), mean weight diameter (MWD), mean weight diameter (GMD), soil organic carbon (SOC), and microaggregate-associated SOC; (2) almost all aggregate stability indexes, SOC, and aggregate-associated SOCs were significantly positively correlated with silt and glomalin, suggesting that the binding of fine particles (silt) with the organic cementing agent (glomalin) was probably a key mechanism of SOC formation and aggregate stability in the studied region; (3) compared with biotic factors such as SOC, glomalin and root biomass, abiotic factors including silt and sand can better predict aggregate stability and SOC fraction using the PLSR model. The above results indicated that the conversion of alpine grassland to other land use types in high altitude areas would destroy soil structure and decrease soil organic carbon content, and then reduce soil quality. [ABSTRACT FROM AUTHOR]

The world's natural wetlands, which have important ecological functions, are being lost at an alarming rate. The erosion and deposition of soil on wetlands is a major cause of wetland conversion to agriculture. An urgent problem to be solved is how to slow down the erosion and deposition of wetlands resulting from land use. Land use patterns affect soil properties, thereby affecting soil aggregate stability and erodibility. Evaluating the effects of land use patterns on soil aggregate stability and erodibility in small watersheds of wetland ecosystems of karst plateau is of great importance. Thus, we compared the soil properties, aggregate stability indicators and soil erodibility of shrubland, grassland, artificial forest land and sloping farmland for evaluating the impact of various land use patterns on soil aggregate stability and erodibility in typical karst plateau wetland ecosystems. Our results showed that the mass fraction of soil aggregates > 0.25 mm was the main component in the four land uses, with greater variation in aggregates > 5 mm; overall, MWD, GMD and WSA0.25 were higher in grassland and shrubland than in sloping farmland and artificial forest land, while K values, PAD and SCAI showed the opposite trend. Correlation analysis showed that effective soil nutrients had a positive effect on soil aggregate stability. In conclusion, the stability of soil aggregates and resistance to soil erosion were strongest under the influence of shrubland. Our study showed that shrubland can better improve soil aggregate stability and erosion resistance, which may provide a guide for protecting and restoring karst plateau wetland ecosystems. [ABSTRACT FROM AUTHOR]

The wetting–drying (WD) cycles, caused by natural or anthropogenic processes such as rainfall or irrigation, can affect many soil properties. Among these properties, soil aggregate stability has been introduced as a convenient soil health indicator because of its relation to the soil’s primary particles (sand, silt, and clay) and organic matter content (OM). However, previous studies have shown erratic effects depending on soil type and WD cycle setup when measuring aggregate stability. Therefore, this study aimed to characterize the soil primary particles composition and organic matter (OM) content of macroaggregates and measure the effects of WD cycles on aggregate stability. A series of soils with distinctive properties, such as OM and clay contents from five different USDA textural classes (loam, sandy loam, silty clay loam, silty loam, and clay loam) were used. Particle size distribution, OM, and mass fraction were measured in three aggregate size classes (2–1 mm, 1–0.5 mm, and 0.5–0.25 mm), and isolated aggregates were exposed to 3, 6, and 12 wetting and drying cycles. The main results indicate that soils with a high OM content have macroaggregates with finer particles, and the OM in soils is linearly related to the macroaggregate OM content. For 2–1 mm aggregates, a statistically significant reduction (p

We studied changes in the concentrations of aggregate-cementing agents after different reclamation times and with different fertilization regimes, as well as the formation mechanism of aggregates in reclaimed soil, to provide a theoretical basis for rapid reclamation of soil fertility in the subsidence area of coal mines in Shanxi Province, China. In this study, soil samples of 0–20 cm depth were collected from four fertilization treatments of a long-term experiment started in 2008: no fertilizer (CK), inorganic fertilizer (NPK), chicken manure compost (M), and 50% inorganic fertilizer plus 50% chicken manure compost (MNPK). The concentrations of cementing agents and changes in soil aggregate size distribution and stability were analysed. The results showed that the formation of >2 mm aggregates, the aggregate mean weight diameter (MWD), and the proportion of >0.25 mm water-stable aggregates (WR0.25) increased significantly after 6 and 11 years of reclamation. The concentration of organic cementing agents tended to increase with reclamation time, whereas free iron oxide (Fed) and free aluminium oxide (Ald) concentrations initially increased but then decreased. In general, the MNPK treatment significantly increased the concentrations of organic cementing agents and CaCO3, and CaCO3 increased by 60.4% at 11 years after reclamation. Additionally, CaCO3 had the greatest effect on the stability of aggregates, promoting the formation of >0.25 mm aggregates and accounting for 54.4% of the variance in the proportion and stability of the aggregates. It was concluded that long-term reclamation is beneficial for improving soil structure. The MNPK treatment was the most effective measure for increasing maize grain yield and concentration of organic cementing agents and CaCO3.

Soil organic carbon (SOC) and aggregate stability are the critical factors in evaluate soil quality and carbon sinks in agricultural soils. Especially in complex saline soils containing larges amount of sodium and calcium ions. To quantitatively estimate the importance of salinity factors, SOC fractions, and soil aggregate fractions on SOC contents and the mean weight diameter (MWD), as well as to reveal the transformation mechanism of SOC under the interactions between salinity and straw, a laboratory experiment was conducted on three soils with different salinity, with and without straw addition. The results showed that straw and salinity interactions significantly increased the proportion of large macro‐aggregate fractions and the MWD, decreased micro‐aggregate fractions, but promoted the conversion of SOC fractions to mineral‐associated organic carbon (MAOC) of micro‐aggregates in moderately saline soils. The responses of SOC contents and MWD to electrical conductivity (EC1:5) were nonlinear. The exchangeable sodium to calcium ions ratio (E‐Na/E‐Ca) (%IncMSE = 11.4, p < 0.01), and MAOC contents (%IncMSE = 17.0, p < 0.01) provided the best explanations of SOC contents, while the MWD was more explained by calcium carbonate (CaCO3) contents (%IncMSE = 9.6, p < 0.01), and MAOC/SOC (%IncMSE = 10.5, p < 0.01). The proportion of micro‐aggregate fractions was significant drivers of both SOC contents and MWD. The increased MAOC contents was mainly caused by improving the binding sensitivity of aliphatic compounds to salt‐related compounds, and the contents of C–C/C–H and C=O functional groups. The findings offer new perspectives into the mechanism of SOC sequestration and sustainable development of moderately saline soils under straw returning in the Hetao area. [ABSTRACT FROM AUTHOR]

Purpose: Soil aggregates regulate soil water and temperature, soil fertilizer, and leaf gas exchange. In desert steppes, precipitation restricts the growth and development of plants, and it affects the availability of soil carbon and nitrogen, thereby influencing soil aggregate stability. However, studies on precipitation influence on the stability of aggregates are limited. Materials and methods: Here, we conducted a 2-year field experiment in a desert steppe of Siziwang Banner, Inner Mongolia, to test the effect of a changing precipitation gradient "reducing precipitation by 50% (W-50%), natural precipitation (W), increasing precipitation by 50% (W+50%), and increasing precipitation by 100% (W+100%)" on the depth distribution, stability of soil aggregates and aggregate-associated organic carbon content (OC), and total nitrogen (TN) contents. We used a wet sieving method yielding silt and clay (SCA, < 0.053 mm), microaggregates (MIA, 0.053–0.25 mm), small macroaggregates (SMA, 0.25–2 mm), and large macroaggregates (LMA, > 2 mm). Results and discussion: Our results indicated that the topsoil (0–30 cm) was dominated by SCA and MIA. Increasing precipitation increased soil aggregate stability and reduced soil erodibility by increasing water-stable aggregates (WSA, > 0.25 mm). In this study, the comprehensive soil aggregate stability score was the highest at W+100%. Although LMA serve as the main carriers of SOC and TN, MIA-associated OC and TN had the highest contribution rate to SOC and TN. This study revealed that bulk soil properties including MBN, BD, MBC, and pH significantly influenced aggregate stability. Additionally, WSA-associated OC were found to be the most crucial contributors to soil aggregate stability. Conclusions: Overall, our study indicates that increasing precipitation is beneficial to WSA accumulation and highlighted the vital role of microbial biomass and WSA-associated OC on maintaining soil aggregate stability under precipitation change. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to investigate the effects of different land use patterns on the distribution characteristics and stability of soil aggregate on the Qinghai-Tibet Plateau, and to provide a scientific basis for improving soil quality in alpine regions. [Methods] Five different land use patterns(farmland, plantation, wetland, shrubland, and bareland) were selected as the study samples on the Tibetan Plateau. Soil aggregate size distribution and soil organic carbon(SOC), total carbon(TC), total nitrogen(TN), and pH were determined by dry and wet sieving methods. ＞0.25 mm soil aggregates weight percentage(DR＞0.25, WR＞0.25), the percentage of aggregate destruction(PAD), the mean weight diameter(MWD), and the geometric mean diameter(GMD) of soil aggregates were determined, and the composition and stability characteristics of soil aggregates under different land use patterns in the alpine region were studied. [Results] Compared with mechanically stable aggregates, soil water-stable aggregates were more susceptible to the influence of land use patterns and better reflected the structural stability of soil aggregations in Tibet. Farmland cultivation increased the content of soil macroaggregates with mechanical stability, but not with water stability. Soil aggregates in plantations and wetlands had high water stability characteristics. Correlation analysis showed that the MWD of soil aggregates was positively correlated with SOC and TN contents. For machine-stable aggregates, 1 mm is the critical size of positive and negative correlation, and for water-stable aggregates, 0.25 mm is the critical size of positive and negative correlation. [Conclusion] Agricultural cultivation in alpine areas can only improve the mechanical stability of soil aggregates, while wetlands and planted forests have a positive effect on the stability of aggregates, and it is recommended that reasonable vegetation cover should be carried out to improve soil quality in alpine areas in the future. [ABSTRACT FROM AUTHOR]

Intercropping is an effective measure to increase crop yield and improve soil structure. The soil aggregate is the basic unit of soil structure, and its stability is affected by intercropping system. To study the effects of intercropping system on soil aggregate stability, the particle size distribution and stability characteristics of soil aggregates under three planting patterns of maize only (SM), peanut only (SP) and maize intercropped with peanut (M-P) were evaluated by dry sieving (mainly used to determine the mechanical stability of soil aggregates), wet sieving (mainly used to determine the water stability of soil aggregates) and Le Bissonnais (mainly used to distinguish different decomposition mechanisms of soil aggregates) (including slow wetting (SW), wet stirring (WS) and fast wetting (FW) tests) methods. The results showed that the particle size distribution of soil aggregates was mainly the >2 mm fraction in the dry sieving test, the 1-0.5 mm and <0.053 mm fractions in the wet sieving test, the >2 mm fraction in the SW test, the >2 mm and 2-1 mm fractions in the WS test and the 1-0.5 mm and 0.5-0.25 mm fractions in the FW test. The mean weight diameter (MWD), geometric mean diameter (GMD) and R0.25 of soil aggregates in the three determination methods were all ranked as SP < SM < M-P, indicating that intercropping could increase the proportion of large aggregates and improve the stability of soil aggregates. In the three tests using the Le Bissonnais method, the MWD order was FW < WS < SW, indicating that the soil aggregates in this area were the most sensitive to slaking effects and the least sensitive to mechanical breakdown, and intercropping could reduce the sensitivity of soil aggregates to slaking effects and mechanical breakdown. In addition, the MWD of dry sieving was significantly positively correlated with the MWD of SW and WS, and the MWD of wet sieving was significantly positively correlated with the MWD of FW. The results of this study could provide a reference for better understanding of farmland soil structure and aggregate stability under intercropping system in the North China Plain. [ABSTRACT FROM AUTHOR]

Crop productivity under intensive agriculture depends on the maintenance of fertility and soil structure. Chemical fertilizers are effective in supplying nutrients for crops but eventually lead to loss of the soil organic carbon that is important in supporting soil structure. Biogas slurry is an alternative to chemical fertilizers that potentially can both provide nutrients and promote organic carbon content. A field experiment was conducted to compare the effects of applying biogas slurry (BS), chemical fertilizer (CF) or a combination of both with 50% of nitrogen derived from each (BSCF) and no fertilizer application control (CK) to a fluvo-aquic soil of the North China Plain. All fertilizer application treatments had equal nutrient supply and were continuously applied over 4 years. Annual yields of wheat and maize were determined. Water-stable aggregates in size classes >5 mm, 2-5 mm, 0.25-2 mm, 0.053-0.25 mm and <0.053 mm in the topsoil of 20 cm were separated by wet sieving; mean weight diameter (MWD), geometric mean diameter (GMD), percentage of aggregates destruction (PAD) and fractal dimension (D) were derived. The concentrations of organic carbon associated with the aggregates were measured, and the distribution of soil organic carbon (SOC) was quantified. Fertilizer application treatments enhanced total crop yield by 49.1%-75.0%. Fertilizer application also increased the mass proportions of water-stable macro-aggregates by 81.6%-164.4%, MWD by 100.0%-264.3%, GMD by 54.5%-227.3%, while decreasing PAD by 15.4%-47.8% and D by 1.0%-3.8% (all relative to CK). The highest proportions of macro-aggregates, the greatest aggregate stability and the greatest crop yield all resulted from BSCF. All fertilizer application treatments substantially increased the SOC content of water-stable aggregates, with greater relative contribution in macro-aggregates. Increased SOC in macro-aggregates was mainly attributable to mass proportion changes rather than changes in their SOC concentrations. However, SOC concentration tended to account for a larger proportion of the total changes in micro-aggregates. BSCF also produced the highest total soil organic carbon stocks in aggregates (40.3% and 57.3% greater than CF and CK, respectively). Our work demonstrates that half substitution of chemical fertilizer with biogas slurry is a practical management to enhance soil aggregation and its stability that is associated with a higher crop yield than either treatment individually. It also promotes organic carbon accumulation in soil aggregates, which will support sustainable agricultural development in fluvo-aquic soil. [ABSTRACT FROM AUTHOR]

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Acacia decurrens plantations in the Timble-Faguita-Lekma watershed are being actively expanded to accommodate various land uses, mainly to produce charcoal and construction. This study aimed to investigate the effects of various land-use types on the hydrology of a watershed and the physicochemical characteristics of soils. Experiments comprised soil depth (0-15 cm and 15-30 cm) and land cover type (arable land, pasture, 0, 2, and 4-year stand). A 5*2 factorial array of randomized complete block designs (RCBD) with 4 replicates made up the design. The physicochemical parameters of the selected soils were investigated using 40 (5*2*4) composite soil samples. A semi-structured questionnaire and a two-way analysis of variance (ANOVA) were used to investigate selected farmers' perceptions of watershed hydrology. The results revealed that soil particle size (sand, silt, clay) and SOC concentration differed significantly across all land-use types and soil depths studied. Soil pH did not alter with depth (p

Microplastics (MPs) pollution has become a global pollution problem, potentially affecting soil carbon cycling and structure stability in agricultural systems. However, the effects of MPs pollution on soil organic carbon fractions/transformation and soil aggregate stability remain unknown. Thus, a combination of one-year pot and short-term mineralized incubation experiments that involved a reference (CK, with no MPs), different concentrations (0.1, 1, and 2 w/w % polyethylene (PE)), and types (0.1 w/w % PE, polypropylene (PP), and polyvinyl chloride (PVC)) of MPs were carried out to investigate the effects on the soil aggregate stability and organic carbon mineralization after one year of adding MPs. The results showed that the size distribution of the soil partial aggregates varied significantly as affected by the MP concentration and type (p ˂ 0.05). Compared with 0.1% PE, significant increases in the MWD (mean weight diameter) and GMD (geometric mean diameter) of 2% PE of 27.22% and 32.73%, respectively, were detected. In addition, high concentrations (>1%) of PE significantly decreased the dissolved organic carbon (DOC) (p ˂ 0.05), whereas they significantly increased the stable carbon fractions including the particulate organic carbon (POC) and mineral-bound organic carbon (MOC) (p ˂ 0.01). Meanwhile, compared with the CK, both MP types and doses significantly decreased the soil organic carbon mineralization rate (SOCMR) and cumulative mineralization amount (CM) (p ˂ 0.001). Moreover, the MPs significantly increased the total PLFA (phospholipid fatty acid) by 261.9–438.8% (p ˂ 0.01), and the soil pH and total PLFA were the dominant factors that affected the SOCMR as affected by MPs. Thus, a high concentration (>1%) of PE significantly decreased the SOCMR by influencing the soil pH, TN, and macroaggregate (R>0.25) content and microbial community composition. This study provided evidence of the feedback of MPs pollution on soil C dynamic and aggregates in cultivated soil in South China.

In the southern Xinjiang region of China, developing efficient irrigation and fertilization strategies to enhance resource utilization and prevent desertification is of critical importance. This study focuses on jujubes in Xinjiang, China, and involves a three-year field experiment aimed at exploring the optimal application strategy of magnetically treated water combined with microbial organic fertilizer to provide scientific support for high-quality jujube production. The experiment included a control group (using only fresh water, denoted as CK) and combinations of magnetically treated water drip irrigation with varying amounts of microbial organic fertilizer: in 2021, treatments included M0 (only irrigating with magnetically treated water), M6 (0.6 t/ha), M12 (1.2 t/ha), M18 (1.8 t/ha), and M24 (2.4 t/ha); in 2022 and 2023, treatments included M0, M6 (0.6 t/ha), M12 (1.2 t/ha), M24 (2.4 t/ha), and M48 (4.8 t/ha). This study investigated the effects of magnetically treated water drip irrigation combined with microbial organic fertilizer on soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality. The application of microbial organic fertilizer significantly reduced the soil bulk density by 3.07% to 11.04% and increased soil porosity by 1.97% to 14.75%. Soil saturated hydraulic conductivity gradually decreased with the increasing amount of microbial organic fertilizer, with a reduction range of 5.95% to 13.69%, while the water-holding capacity significantly improved (from 0.217 cm3/cm3 to 0.264 cm3/cm3). Additionally, microbial organic fertilizer significantly enhanced the activities of urease, catalase, and sucrase in the soil and significantly increased the proportion of large soil aggregates. Jujube yield increased by 3.66% to 21.38%, and the quality significantly improved, as evidenced by the increase in soluble sugar and flavonoid content. The Gauss model calculation results recommended 3.09 t·hm2 as the optimal amount of microbial organic fertilizer for comprehensively improving jujube yield and quality. These findings indicate that magnetically treated water drip irrigation combined with high amounts of microbial organic fertilizer significantly improved soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality, providing scientific evidence for desert soil improvement and agricultural production.

The aims of this study are to clarify the main factors affecting the stability of water stable aggregates, and provide the scientific and technological support for the comprehensive management of red soil slope farmland in Yunnan Province. [Methods] Three treatments of maize monoculture, potato monoculture and maize and potato intercropping were set up to analyze the effects of intercropping on crop rhizosphere soil nutrient content. enzyme activity, glomalin-related soil protein (GRSP) content, aggregate composition and stability, as well as the agronomic traits and yield of crops. [Results] (1) Compared with monoculture, intercropping of maize and potato not only significantly increased the content of organic matter and available phosphorus in the rhizosphere soil of potato by 13.53% and 46.53% (p<0.05), respectively. but also increased the contents of total glomalin-related soil protein (T-GRSP) and easily extractable glomalin-related soil protein (EE-GRSP) in rhizosphere soil of two crops, and the difference of maize reached a significant level (p<0.05). (2) Compared with monoculture, maize and potato intercropping could significantly increase the activities of urease, acid phosphatase and catalase in the rhizosphere soil of the two crops, as well as the content of >0.25 mm water-stable aggregates (R0.25) and mean mass diameter (MWD) of soil. The increase rates were 17.63%~41.29% for maize and 10.81%~34.79% for potato. (3) Compared with monoculture, intercropping of maize and potato significantly increased the shoot and root dry weights of both crops (p<0.05). The land equivalent ratio of maize and potato was 1.81>1, which had the advantage of intercropping yield. (4) Correlation analysis showed that EE-GRSP, T-GRSP, urease, acid phosphatase and catalase were significantly positively correlated with R0.25 and MWD (p<0.05). Redundancy analysis showed that the effects of each index on aggregate indexes followed the order: catalase >urease >EE-GRSP> acid phosphatase >T-GRSP, among which catalase was the main factor affecting the composition and stability of soil aggregates. [Conclusion] Intercropping of maize and potato can not only promote the material circulation of rhizosphere soil of two crops, increase the large size content and stability of aggregates, but also promote the growth of aboveground and root of two crops, which is of great significance for the selection of reasonable intercropping crops in red soil sloping farmland in Yunnan Province. [ABSTRACT FROM AUTHOR]

In order to investigate the characteristics of soil structural stability and the factors influencing it under typical land use types in the karst region of western Hubei, soil samples were collected from five land use types (natural mixed forest [NF], cypress forest [CF], stone dike terrace [ST], stone dike forest [SF], and abandoned land [AL]) in Xialaoxi to analyze the particle size distribution of aggregates, structural stability, and the distribution characteristics of carbon, nitrogen, and extracellular enzyme contents. The results showed that the aggregates of NF, CF, SF, and AL were dominated by >2‐mm aggregates, while ST showed mostly 2–0.25‐mm aggregates. The mean weight diameter (EMWD) and the geometric mean diameter (EGMD) of mechanical aggregates showed a trend of CF > NF > SF > AL > ST, whereas the erodibility factor K showed an opposite trend. The total organic carbon (TOC), labile organic carbon (LOC), and total nitrogen (TN) contents of aggregates of each particle size were significantly higher in NF and CF than in ST and AL under the five land types. The content of available nitrogen (AN) was highest in NF and ST. The content of carbon and nitrogen and extracellular hydrolases (β‐glucosidase [BG], cellulose disaccharide hydrolase [CBH], β‐N‐acetyl‐aminoglucosidase [NAG], and leucine aminopeptidase [LAP]) in soil aggregates were mainly concentrated in <0.25–0.053‐mm aggregates. The variation in carbon and nitrogen abundance of each particle size agglomerate mainly originated from the LAP content of that particle size agglomerate and showed significant correlation. The partial least squares path models (PLS‐PM) showed that the main influences on the stability of soil aggregates in small watersheds were land use types, soil physical properties, carbon and nitrogen abundance, and extracellular enzyme activity. In conclusion, the structural stability of soil aggregates in Xialaoxi watershed is the result of the interaction between human disturbance and soil nutrient self‐cycling. In general, NF and CF have better soil aggregate stability and are conducive to soil carbon and nitrogen accumulation, whereas for later development and management of SF, ST, and AL sample plots, scientific cultivation means should be adopted, and attention should be paid to long‐term carbon and nitrogen accumulation and conservation. [ABSTRACT FROM AUTHOR]

A long-term field experiment has been ongoing since 1999 at the Experimental Station of Vytautas Magnus University's Agriculture Academy. According to the latest edition of the International Soil Classification System, the soil in the experimental field can be classified as Planosol, with a silty medium-loam texture at a depth of 0–20 cm and a silty light-loam texture at a depth of 20–40 cm. Studies were carried out on winter wheat crops in 2014, 2017, and 2023. This research aimed to assess how different long-term tillage systems impact soil shear strength and aggregate stability, their interconnection, and the effect of crop residues on soil stability. The treatments were arranged using a split-plot design. In a two-factor field experiment, straw was removed from one part of the experimental field, while the entire straw yield was chopped and spread at harvest in the other part (Factor A). The subplot factor (Factor B) included three different tillage systems: conventional deep ploughing, cover cropping for green manure with no tillage, and no tillage. The soil samples were analyzed at the Laboratory of Agrobiology at Vytautas Magnus University's Agriculture Academy. The findings indicated that the long-term application of reduced tillage significantly increased the soil shear strength. Shallower tillage depths led to a higher soil shear strength, while the effect of spreading plant residues was relatively lower. The long-term tillage of different intensities, spreading plant residues, and catch crop cultivation for green manure did not significantly affect the soil structure. However, the soil structural stability was found to be highly dependent on soil tillage. Cover cropping for green manure with no tillage and no tillage alone positively affected the soil aggregate stability in the upper 0–10 cm and 10–25 cm layers. The correlation–regression analysis showed that, in the top 0–10 cm and 10–25 soil layers, there were moderate to strong correlations between the soil structural stability, soil shear strength, and the effect of crop residues on soil stability. [ABSTRACT FROM AUTHOR]

【Objective】 Restoring coal mining waste dumps is a way to alleviate their detrimental impact on environment. In this paper, we present the results of an experimental study on distribution and stability of soil aggregates in a reclaimed coal mining overburden dump. 【Method】 The experiment was carried out at a reclaimed coal mine dump site in a grassland region in northern China. We measured the development of fissures from Zone I (GF) to Zone three (GFIII) in the fissure zone. The composition and distribution soil aggregates in these zones were determined using dry-wet sieve method. Aggregate stability and its relationship with the fissures was analyzed. 【Result】 The content of the >0.25 mm air-dried aggregates over the fissure zones was 23.02%~42.70%, and content of the >0.25 mm water-stable soil aggregates was 16.9%~29.52%. There was no significant difference between air-dried aggregates and water-stable aggregates. The content of the >0.25 mm water-stable soil aggregates in the 0~60 cm soil layer in GF, GFⅡ and GF Ⅲ was 25.26%, 26.57%, 23.62%, respectively, while the percentage of aggregate destruction in the three fissure zones was 20.77%~36.17%, 20.52%~25.00%, and 26.58%~40.56%, respectively. The percentage of aggregate destruction in 0~10, 10~20, 20~30, 30~40, 40~50, and 50~60 cm soil layers was 28.81%, 29.96%, 26.19%, 23.50%, 24.91%, and 29.38%, respectively. The fractal dimension of air-dried and water-stable soil aggregates was 2.847~2.919 and 2.898~2.942, respectively. Small aggregates and fine particles are the dominant aggregates. The mean mass diameter (MWD) and geometric mean diameter (GMD) of the air-dried aggregates in three fissure zones were 1.11, 1.05, 1.28 mm, and 0.45, 0.44, 0.49 mm, respectively. The MWD and GMD of water-stable soil aggregates in the three fissure zones were 0.67, 0.73, 0.72 mm, and 0.36, 0.38, 0.37 mm, respectively. Soil in GFⅡ had good structure and aggregate stability. Most of water-stable soil aggregates in the fissure zones were unstable due to the formation and development of fissures. 【Conclusion】 The formation and development of fissures in the reclaimed coal mining overburden dump reduced the stability of soil aggregates, thereby resulting in aggregate segmentation. The larger and wider the fissures were, the less stable the soil aggregates were.

Land use changes modify soil properties, including aggregate structure, and thus, profoundly affect soil quality and health. However, the effects of land use changes originating from alpine grassland on soil aggregates and aggregate-associated organic carbon have received little attention. Soil aggregate fraction, aggregate-associated organic carbon and relevant influencing factors were determined at 0–20, 20–40 cm soil layers for alpine grassland, cropland and abandoned land in the eastern Qinghai–Tibet Plateau (QTP), and their relationships were analyzed by partial least square regression (PLSR). Results showed the following: (1) conversion from alpine grassland to cropland resulted in a significant decline macroaggregate fraction (R0.25), mean weight diameter (MWD), mean weight diameter (GMD), soil organic carbon (SOC), and microaggregate-associated SOC; (2) almost all aggregate stability indexes, SOC, and aggregate-associated SOCs were significantly positively correlated with silt and glomalin, suggesting that the binding of fine particles (silt) with the organic cementing agent (glomalin) was probably a key mechanism of SOC formation and aggregate stability in the studied region; (3) compared with biotic factors such as SOC, glomalin and root biomass, abiotic factors including silt and sand can better predict aggregate stability and SOC fraction using the PLSR model. The above results indicated that the conversion of alpine grassland to other land use types in high altitude areas would destroy soil structure and decrease soil organic carbon content, and then reduce soil quality.

Abstract In order to investigate the characteristics of soil structural stability and the factors influencing it under typical land use types in the karst region of western Hubei, soil samples were collected from five land use types (natural mixed forest [NF], cypress forest [CF], stone dike terrace [ST], stone dike forest [SF], and abandoned land [AL]) in Xialaoxi to analyze the particle size distribution of aggregates, structural stability, and the distribution characteristics of carbon, nitrogen, and extracellular enzyme contents. The results showed that the aggregates of NF, CF, SF, and AL were dominated by >2‐mm aggregates, while ST showed mostly 2–0.25‐mm aggregates. The mean weight diameter (EMWD) and the geometric mean diameter (EGMD) of mechanical aggregates showed a trend of CF > NF > SF > AL > ST, whereas the erodibility factor K showed an opposite trend. The total organic carbon (TOC), labile organic carbon (LOC), and total nitrogen (TN) contents of aggregates of each particle size were significantly higher in NF and CF than in ST and AL under the five land types. The content of available nitrogen (AN) was highest in NF and ST. The content of carbon and nitrogen and extracellular hydrolases (β‐glucosidase [BG], cellulose disaccharide hydrolase [CBH], β‐N‐acetyl‐aminoglucosidase [NAG], and leucine aminopeptidase [LAP]) in soil aggregates were mainly concentrated in

Soil stoichiometric characteristics and aggregate stability are affected by vegetation restoration in degraded land. Yet, it is not known that how the aggregate stability is related to soil stoichiometric characteristics under different vegetation restorations. A 5-year in situ experiment was conducted to investigate the effects of vegetation restoration on the composition, stability and stoichiometric properties of soil aggregates. In the northwest part of Beijing, Bromus inermis Leyss. and Medicago sativa L. were planted in a typical area of desertification, and natural restoration was used as control. Boosted regression trees (BRTs) were applied to partition the factors that control aggregate stability. The results showed that the mean weight diameter (MWD) of soil water-stable aggregates under natural restoration (CK) and Medicago sativa L. sowing treatments (AF) was significantly higher than that under the restoration of the Bromus inermis Leyss. sowing treatments (SB). Compared with CK, AF significantly increased the geometric mean diameter (GMD) water stable aggregates, while SB showed the opposite result. AF significantly increased the proportion of soil aggregates >2 mm compared with CK. AF could improve the stability of soil aggregates by increasing the proportion of large aggregates. For the stoichiometric characteristics of the aggregates, AF increased significantly the value of C/P in 0.053−0.125 mm particle size aggregates in all soil layers. The MBC/MBN ratio aggregates at depths of 0–10 cm and 10–20 cm was also significantly increased in the treatment of AF. The BRTs indicated that stoichiometric ratio is the main factor driving the stability of soil aggregates rather than microbial community characteristics and soil nutrients. The C/P is the main driving factor affecting the MWD, in which the overall stoichiometric influence accounts for 46%, followed by the microbial influence of 36%. For the GMD, MBC/MBN is the main driving factor, and the stoichiometric influence accounts for 94%. Our findings indicate that AF is beneficial to the stability of deep soil aggregates, and their stoichiometric characteristics of soil are the key factors affecting the stability of soil aggregates.

Purpose: Digestates from anaerobic digestion are increasingly used in agriculture. There is thus a need for better understanding of digestates' value as organic soil amendments, and how this varies depending on the process parameters and post-treatments applied. Methods: A range of fifteen digestates (raw, solid, phase separated, and composted digestates), originating from farm and centralised anaerobic digestion sites were characterised. Carbon mineralisation and soil aggregate stability (AS) dynamics following the addition of the digestates to soil were monitored over a 182-day incubation period at 20 °C. Results: The mineralisation of carbon varied significantly between digestates, with the lowest percentage of carbon lost at 11.45% for composted digestate, and the highest at 49.27% for a solid batch digestate. Using hierarchical clustering of soil AS analysis at several sample dates, digestates were classified into four groups: those inducing (1) rapid but transient improvement of AS, (2) slower, temporary improvement of AS, (3) immediate improvement followed by a longer-lasting increase in AS, (4) minor or non-significant improvement in AS. Conclusion: Phase separation and composting of digestates were found to have more impact than other process parameters in determining the rate of mineralisation and dynamics in AS. Impact: Characterising and classifying digestates by their potential impact on soil structure would help to improve decision making for digestate production and sustainable use in agriculture. [ABSTRACT FROM AUTHOR]

Soil aggregate stability and soil erodibility (k) are crucial indicators of soil quality that exhibit high sensitivity to changes in soil function. Therefore, it is of great significance to explore the quantitative relationship between these indicators and soil quality for effective ecosystem monitoring and assessment. In this study, soil samples were collected from eight altitude gradients in a karst mountainous area; we analyzed 11 soil physical, chemical, and biological properties, and assessed soil quality using the minimum data set (MDS) method. The results revealed that soil aggregate stability, bulk density (BD), pH, and fungal community diversity exhibited a unimodal altitudinal pattern, whereas the soil organic carbon (SOC), total nitrogen (TN), and C:N ratio showed an increasing trend. Among the factors considered, SOC, BD, soil pH, mechanical composition, and fungal community diversity were found to explain the most variation in soil aggregate stability and soil erodibility (k). Principal component analysis (PCA) identified soil fungal community diversity, C:N ratio, coarse sand, and macro-aggregate (MA) content as highly weighted indicators for MDS. The integrated soil quality index (SQI) values, ranging from 0.30 to 0.62 across the eight altitude gradients, also exhibited a unimodal altitudinal pattern. The analysis indicated a significant linear relationship between the fractal dimension (D) and soil erodibility of the EPIC model (Kepic) with SQI, suggesting that D and Kepic can serve as alternative indicators for soil quality. These findings further enhance our understanding of the response of soil properties to altitude changes, and provide a novel method for assessing and monitoring soil quality in karst mountainous areas. [ABSTRACT FROM AUTHOR]

Surface vegetation has a substantial impact on soil aggregate stability, which is an important indicator of soil quality. However, there is still limited research on the response of soil aggregate stability indicators and the organic carbon, total nitrogen, and total phosphorus content in soil aggregates for different vegetation patterns in rocky desertification fragile ecological areas. Therefore, in order to study the effects of different vegetation restoration models on soil aggregate stability and aggregate related nutrient content and their promoting relationships in the karst rocky desertification areas in southwest China, soil samples under three artificial restoration vegetation measures (Juglans regia L.-Rosa roxburghii Tratt., Rosa roxburghii Tratt.-Lolium perenne L., Juglans regia L.-Lolium perenne L.) were collected in 0–10 cm and 10–20 cm soil, and the traditional farmland (Zea mays L.) was used as the control, combined with dry and wet sieving experiments for the research and analysis. The results showed that there were significant differences in the distribution of aggregates and soil nutrients among the four types of plots. Compared with traditional agricultural land, artificial afforestation increased the content of soil large macroaggregates (LMAs) and decreased the proportion of microaggregates (MIAs) and silt+clay (SCA), which enhanced the soil aggregate stability and reduced the soil fragmentation and erodibility. The afforestation restoration increased the content of soil aggregate-related SOC, TN, and TP, and increased with the decrease in the aggregate particle size. Research has found that soil aggregate stability indicators are significantly influenced by the particle size distribution of soil aggregates. In the positive succession process of vegetation types, soil nutrient accumulation is controlled by changes in the soil aggregate particle size, which affects the soil aggregate stability and reduces soil erodibility, thereby protecting the soil nutrient loss. The composite management of forest and irrigation in degraded ecological areas has certain reference and indicative significance for ecological restoration in rocky desertification areas. [ABSTRACT FROM AUTHOR]

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Soil erosion and surface pollution near reservoirs can adversely affect water quality and safety. Soil aggregate stability is an important predictor of soil water loss and erosion resistance that is strongly influenced by land use. This study therefore aimed to identify factors affecting soil aggregate stability near reservoirs to provide empirical and theoretical insights that could guide the development of management measures to increase land quality, optimize land use, and maximize sustainability. This study focuses on the land around the Shitoukoumen Reservoir in China and examines the effects of six land use types, eleven soil physicochemical properties, and five environmental factors. Ninety-four sets of soil samples were collected in 2021 for analysis of soil aggregates and properties. Particle size classification of soil aggregates was carried out using the wet sieve method and four indicators were calculated to evaluate the effects of land use, soil physicochemical properties, and environmental factors on soil aggregate stability: water stable aggregates (WSA), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D). Descriptive statistics and geostatistics were used to explore the spatial distributions of soil aggregate stability around the reservoir and the influence of soil properties was studied using correlation analysis and path analysis. The conclusion indicates that land use type significantly affects aggregate stability. The most stable aggregates were found in paddy fields (WSA = 0.77, MWD = 0.76, GMD = 0.57) and forests (WSA = 0.75, MWD = 0.76, GMD = 0.55), followed by an orchard, irrigated land, and grassland. Aggregate stability was worst in upland sites (WSA = 0.61, D = 2.28), where soil aggregates were highly fragmented. There were clear spatial correlations between all four stability indicators. The environmental factors and soil physicochemical characteristics with the strongest influence on aggregate stability were soil organic matter, pH, soil clay content, total nitrogen, and temperature changes. Path analysis revealed that some soil properties affect aggregate stability indirectly, with particularly complex relationships between clay, soil organic matter, and pH. In conclusion, land use type, soil organic matter, pH, soil clay content, total nitrogen, these soil physicochemical properties, and environmental factors, especially temperature, significantly affect soil aggregate stability around reservoirs. In the future, it is necessary to appropriately change upland into paddy land, increase forest land, and appropriately add organic fertilizer to improve soil quality. [ABSTRACT FROM AUTHOR]

The article discusses research which evaluated the effect of conservation tillage and agricultural land management practices on soil physical properties in different sequence cropping systems under rainfed conditions. The plot field experiment examined soil physical properties including aggregate stability, bulk density, total porosity, maximum water holding capacity and penetration resistance at plough depth. It compared the effectiveness of conventional tillage with and without crop residues.

Soils formed on limestones occupy large area in Serbia, but there is not a lot of information about their properties. This paper presents physical and chemical properties of the Brownized Calcomelanosols and Moderately-deep Calcocambisols of the Ozren Mountain. Brownized Calcomelanosols under natural grassy vegetation were investigated at the Vlasina pass, whereas Calcocambisols under mixed forests were investigated near the site "Ozrenske livade". Soil profiles were excavated up to the parent material, and disturbed and undisturbed soil samples were collected from soil genetic horizons. Following soil characteristics were determined: particle size distribution, soil structure and water resistance of structural aggregates, bulk density, total porosity, air capacity, water-holding capacity, water conductivity, pH, content of humus, available phosphorus (P2O5) and potassium (K2O), hydrolytic acidity, cation exchange capacity (CEC), sum of exchangeable base cations, and base saturation. Humus-accumulative horizon (Amo) of the Brownized Calcomelanosols has silty clay texture, whereas the cambic (B)rz horizon of both soils has a clay texture. The Amo horizon of Calcomelanosols is characterized by fine to medium granular structure (0.5-5 mm) of very high water resistance. The total porosity, air capacity and water permeability of both soils is high. Their water-holding capacity is high. Amo horizon of Calcomelanosols is characterized by a high humus content (>10%). Soil reaction in water of Amo horizon is neutral, whereas in (B)rz horizons both soils are moderately acid. Both soils have high CEC (>58 cmol kg-1 ) and base saturatation (>95%). Brownized Calcomelanosol is moderately to highly supplied with available K2O, whereas Calcocambisol is moderately supplied; while both soils are very poor in available P2O5. Since this study presents quite favorable physical and chemical properties of the investigated soils due to the conservation of natural forests and grasslands, the results can help in a deeper understanding of soil ecology and the preservation of natural plant cover.

Background: In areas prone to water erosion, crop selection strategies should be based on assessment of their effects on soil structural properties. Aims: The present study compared the effects of the cultivation of forage maize (Zea mays L.) and forage oat (Avena sativa L.) and their cultivars on soil aggregation relative to potato (Solanum tuberosum L.) or wheat (Triticum aestivum L.) at a hydrothermally limited site on the Loess Plateau, China. Methods: The water‐stable aggregate (WSA) distribution in soil was measured under three cultivars in each of maize, oat, wheat, and potato (a total of 12 cultivars from four crops) in their flowering stage of three cropping seasons, when root biomass was largest. Results: In each year, the water‐stable macroaggregates (>0.25 mm) content and mean weight diameter (MWD) of WSAs in the top 20 cm of soil did not differ between tested cultivars of every crop but increased under maize and oat, compared with those under wheat or potato. The increased soil aggregation under maize and oat, compared with wheat or potato, was consistent with the pattern of change in root biomass but was not consistent with the changes in root length density, root surface area, or root mean diameter across the crops. The water‐stable macroaggregates content and MWD of soil was positively correlated with root biomass across cultivars and crop species within each cropping season. Conclusions: We suggest that increased root biomass under maize and oat relative to potato or wheat resulted in increased soil aggregation in maize and oat cultivated soils. It is demonstrated that, in areas prone to soil water erosion, planting high‐biomass‐yielding crops such as maize and oat is more beneficial for increasing soil aggregation and stability, compared with low‐biomass‐yielding crops such as wheat or potato. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil aggregation plays a critical role in the maintenance of soil structure and crop productivity. Fertilization influences soil aggregation, especially by regulating soil organic carbon (SOC) and total nitrogen (TN) contents in aggregate fractions. Here, we conducted a fixed-site field experiment to quantify the effect of five N application rates: 0, 75, 150, 225, and 300 kg·N·ha−1, denoted as N0, N75, N150, N225, and N300, respectively, on soil aggregate stability, aggregate-associated SOC and TN sequestration and crop productivity. Soil aggregates were divided into >0.25 (>5, 5–2, 2–1, 1–0.5, 0.5–0.25) and <0.25 mm through wet and dry sieving methods. The results showed that long-term fertilization increased the proportion of macro-aggregates (>0.25 mm), decreased the proportion of micro-aggregates (<0.25 mm), and improved the aggregates stability. Compared with N0, the proportion of micro-aggregates in N225 was significantly decreased by 66.45% under wet sieving, while the proportion of >5 mm macro-aggregates in N225 was significantly increased by 19.24% under dry sieving (p < 0.05). With the increase in N application rate, the bulk SOC and TN contents first increased and then decreased, and the SOC and TN of N225 were significantly increased by 17.75% and 72.33% compared with N0 (p < 0.05). More specifically, fertilization promoted the distribution and enrichment of SOC and TN in macro-aggregates and reduced the C/N of the micro-aggregates and the contribution of SOC and TN in the micro-aggregates. Compared with N0, the contribution rate of macro-aggregates to SOC and TN of N225 under wet sieving was significantly increased by 84.13 and 17.18%, respectively, while the C/N of micro-aggregates of N225 under wet and dry sieving methods was significantly decreased by 45.95 and 31.74%, respectively (p < 0.05). Moreover, fertilization improved the yield, and N225 significantly increased the total yield by 80.68% compared with N0 (p < 0.05). In conclusion, N225 was the suitable N application for improving soil aggregate stability, carbon and nitrogen sequestration, and crop productivity on the Loess Plateau, China. [ABSTRACT FROM AUTHOR]

Tillage practices significantly influence soil nutrient retention, soil structure, and stability. However, the impact of tillage practices on soil stability and erosion resistance through the perturbation approach of soil structure remains unclear. This study aimed to establish universal principles across slope surface and soil profile scales. We evaluated the effects of various tillage practices, including conventional tillage (CT), soil compaction (CM), subsoil tillage (ST), no tillage (NT), and subsoil tillage and soil compaction (SCM) on soil stability and erosion resistance in China's red soil hilly region. Soil stability, erosion resistance, and other soil properties were quantified using field surveys and laboratory experiments. We discovered significant variations in soil aggregate stability (SAS), wet aggregate stability (WAS), soil mechanical stability (SMS), and soil erodibility (SE) among the five tillage methods. The K factor's average value indicated that the 0–40 cm soil layer was more erodible for CT (0.472) than for other methods, with NT (0.26) being the least erodible. NT (0.43) was the most effective treatment for reducing SE, while SCM (0.41) enhanced soil fertility, controlled SE, and mitigated machinery-induced soil compaction risks. CM (0.38) maintained soil stability without improving the soil nutrient storage, while ST (0.33) improved the soil stability such as alleviating the soil hardening caused by CM. The results provide reference parameter values for selecting appropriate tillage methods to decrease soil degradation and erosion while enhancing the soil productivity in a red soil hilly region. [ABSTRACT FROM AUTHOR]

It is of great significance to determine soil aggregate stability in predicting agricultural production conditions and soil erosion risk. However, the problem exposed in the process of evaluating soil aggregate stability cannot be ignored: Can the effects of different mechanisms on the degree of soil aggregate breakdown be distinguished by selecting ethanol and water as dispersion media? Based on this question, natural soils with a gradient in soil textures of silty loam to loamy clay were used as the test materials. Deionized water, ethanol and hexane were employed as soaking solutions to quantitatively analyze the extent to which the aggregates were dispersed in static disintegration experiments. The results suggested that the soil hydrophilicity (SH) of six soils with a texture gradient were >1 by comparing the aggregate breakdown index (ABI) of soils undergoing ethanol and hexane dispersion. This indicated that the hydrophilic group (-OH) contained in ethanol interacted with the hydrophilic surfaces of the soil particles. Therefore, the soil hydrophilicity (hydration) should be determined by comparing the ABI values undergoing hexane and water dispersion. From silty loam to loamy clay, the average contribution of hydration to aggregate fragmentation decreases, and the process of aggregate breakdown with different textures is characterized by size selectivity. When the soil aggregates were fragmented into 2–0.25 mm aggregate fractions, for silty loam and sandy clay loam, 0.002–0.02 mm and <0.002 mm particles were preferentially moved; for clay loam and loamy clay, >0.002 mm particles were preferentially moved. When the soil aggregates were fragmented into <0.25 mm aggregate fractions for soils with different textures, the 0.002–0.02 mm and <0.002 mm particles all exhibited preferential migration characteristics. This work provides an idea for improving the methods of aggregate stability measurements in the future. [ABSTRACT FROM AUTHOR]

Aims: In order to better understand the changes of soil carbon sequestration capacity in forest after forest mixing, the effects of broadleaf tree invasion on soil aggregate stability and carbon sequestration were studied. Methods: In northern China, the pure Larix principis-rupprechtii plantations and the Larix principis-rupprechtii plantations invaded by Betula platyphylla at various degrees with the same site conditions were selected (Betula platyphylla had mixed degrees of 0.2 and 0.4). The distribution and stability of soil aggregates were analyzed, and soil organic carbon and active carbon components were determined. Results: The distribution of soil macroaggregates (> 0.25 mm) increased with the increase in the mixed degree of Betula platyphylla. The mixture of Betula platyphylla could effectively increased SOC, EOC, DOC and MBC of the original soil and soil aggregates of different diameter classes. The invasion of Betula platyphylla had a positive indirect impact on soil carbon sequestration by affecting the soil physical and chemical properties and the aggregate stability. Conclusion: The invasion of Betula platyphylla had significant positive effects on soil aggregate stability, erosion resistance and soil nutrient status in Larix principis-rupprechtii plantation. Maybe the selection of suitable broadleaf mixed species can improve the soil quality and soil organic carbon sequestration of the Larix principis-rupprechtii plantation in this area. [ABSTRACT FROM AUTHOR]