Soil Aggregate Stability Index Research Articles

Influence of cover crops on soil aggregate stability, size distribution and related factors in a no-till field

Soil aggregation plays an essential role in maintaining soil structure. A three-year field experiment was undertaken to explore the effects of cover crops on soil aggregate stability indices (mean weight diameter, water-stable aggregates greater than 0.25 mm, and soil erodibility factor), size distribution and their correlations with nine soil physical and chemical properties (soil bulk density, pH, organic carbon, total nitrogen, C/N, calcium, phosphorus, potassium, and cation exchange capacity) at 0–5 and 5–10 cm depths in a Marietta silt loam soil in a no-till field, Northeastern Mississippi. The cover crop treatments included elbon rye (Secale cereale L.), daikon radish (Raphanus sativus ssp. acanthiformis), Austrian winter field peas (Lathyrus hirsutus), and their mixture. The samples were wet-sieved to five size classes of aggregates (> 2, 2–1, 1–0.5, 0.5–0.25, and < 0.25 mm). Results showed that the < 0.25 mm aggregates dominated (50.95–78.02 %) soil aggregate size distribution at 0–5 and 5–10 cm depths. The rye plot soil displayed the greatest values for mean weight diameter (0.58 mm) in the two soil depths. Soil water-stable aggregates greater than 0.25 mm value under peas was significantly higher by 68.61 % compared to the no cover crop treatment at 0–5 cm depth, while soil erodibility factor did not change significantly. Mean weight diameter, water-stable aggregates greater than 0.25 mm, soil erodibility factor, 1–0.5 mm aggregates, and < 0.25 mm aggregates were significantly correlated with soil organic carbon, pH, bulk density, phosphorus, and potassium. The dominant factors driving changes in three aggregate stability indices and size fractions (excluding 2–1 mm aggregates) were bulk density and pH. Furthermore, high pH restricted soil aggregate stability and size distribution. This study demonstrated the positive impact of cover crops, specifically peas and rye, on soil aggregate stability and size distribution. This study will provide valuable information for future research on soil stabilization in crop production management systems.

Effects of Straw Returning on Soil Aggregates and Its Organic Carbon and Nitrogen Retention under Different Mechanized Tillage Modes in Typical Hilly Regions of Southwest China

Tillage modes and straw returning influence soil aggregate stability and the distribution of organic carbon (C) and nitrogen (N) in aggregates of different particle sizes. In the typical hilly regions of southwest China, the predominant soil type is purple soil, characterized by heavy texture and high stickiness, with relatively lower soil fertility compared to other soil types. The improper use of fertilizers and field management practices further exacerbates soil compaction. However, abundant straw resources in the region provide an opportunity for comprehensive straw utilization. The effective utilization of straw resources is of significant importance for stabilizing agricultural ecological balance, improving resource utilization efficiency, and alleviating ecological pressure. Previously, most studies have focused on the impact of different mechanized tillage systems on the physical and chemical properties of soil in hilly areas, while research on the preservation of water-stable aggregates’ organic C and N content remains limited. In this study, the soil properties of fields under a winter pea–summer corn rotation for two years were studied with regards to the effects of straw returning on its water-stable aggregate distribution, macroaggregate content (R0.25), mean weight diameter (MWD), geometric mean diameter (GMD), and the organic C and N content in soil aggregates of different particle sizes and at different depths. The effects of five different tillage modes were assessed, namely rotary tillage with straw mixed retention (RTM), conventional tillage with straw burial retention (CTB), no-tillage with straw covered retention (NTC), subsoiling with straw covered retention (STC), and no-tillage without straw retention (NT). Based on the study results, under different tillage modes, straw returning effectively enhanced the soil organic carbon (SOC) and total nitrogen (TN) reserves at the plow layer (0–30 cm), SOC increased by 17.2% to 88%, and TN increased by 8.6% to 85.9%. At the same time, the content of 0.25–2 mm aggregates increased under the straw-return treatments under different tillage patterns. The NT treatment had the lowest R0.25 and MWD and GMD values for soil aggregates at different depths, which were significantly different (p &lt; 0.05) from the other treatment modes. The correlation coefficients between SOC and soil aggregate stability indices ranged from 0.68 to 0.90, with most of them showing highly significant positive correlations (p &lt; 0.01). In conclusion, straw returning under different tillage systems has improved soil aggregate stability and promoted soil structure stability. Specifically, the STC treatment has shown more pronounced effects on soil improvement in the upper soil layer of the hilly regions in southwest China, while the RTM treatment is beneficial for improving the lower soil layer. Therefore, the comprehensive experimental results indicate that the combination of STC and RTM treatments represents the most promising mechanized tillage and straw returning practices for the hilly regions in southwest China.

Nutrient addition affects stability of soil organic matter and aggregate by altering chemical composition and exchangeable cations in desert steppe in northern China

AbstractNitrogen and phosphorus can influence the stability of soil organic matter (SOM) and aggregate, which are important for ecosystem functions. However, understanding remains limited regarding the impact of nutrient addition on soil aggregate stability, aggregate‐relevant organic matter and nutrients in desert steppe. Here, we studied the variation of soil aggregate stability, nutrients, and the exchangeable cations distribution characteristics, and the chemical composition and thermal stability of SOM were analyzed using thermogravimetric (TG) and Fourier transformed infrared spectroscopy. Samples of soil were collected under four conditions, phosphorus addition (P), nitrogen addition (N), combined phosphorus and nitrogen addition (NP), and no addition (CK), from 0 to 10 cm depth over 4‐year experiments in desert steppe in northern China. The percentage of micro‐aggregates (0.25–0.053 mm) and large macroaggregates (&gt;2 mm) dramatically increased by 34.2% and 18.1%, respectively, under the N treatment condition compared to the CK treatment, and micro‐aggregate content significantly increased under the P treatment, respectively. Nitrogen addition significantly increased the soil aggregate stability index, but the P addition reduced their value. The both macro‐aggregates (&gt;0.25 mm) and silt‐clay (&lt;0.053 mm) were preferentially enriched with soil nutrients and the exchangeable cations. The N and P addition was beneficial to nutrients accumulating in macro‐aggregates, and enhanced the aliphatic‐C and aromatic‐C abundances respectively. The TG‐T50 value (i.e., temperature when 50% of SOM is lost) increased after nutrient addition, indicating that the SOM has higher thermal stability, especially in the micro‐aggregates. The addition of N may have potentially a greater influence on aggregate stability through their influence exchangeable polyvalent cations (Ca2+ and Mg2+), and stability of SOM was influenced by chemical composition and exchangeable K+, Na+, Ca2+ contents in desert steppe. Overall, nutrient addition effects stability of SOM and aggregate by altering chemical composition and exchangeable cations in desert steppe in northern China.

The impact of the long-term application of mineral nitrogen and sewage sludge fertilizers on the quality of soil organic matter

BackgroundSoil fertility is substantially influenced by soil organic matter quality and quantity. Much attention has also been given to glomalin content as one of the qualitative parameters of soil fertility. Glomalin content is considered an indicator of soil fertility due to its positive correlation with soil organic carbon.AimThis study aim to (i) determine the influence of different fertilization systems on maize yield and soil organic matter quality parameters, (ii) ensure that changes in total glomalin content (TG) and easily extractable glomalin (EEG) content are sensitive enough to reflect changes in the SOM quality resulting from long-term fertilization, and (iii) determine whether both forms of glomalin must be determined or if the easily extractable glomalin (EEG) content is sufficient, even for a fertile chernozem.Materials and methodsLong-term field experiments with silage maize monocultures were used to study relationships under different rates of mineral nitrogen and sewage sludge fertilization. The trials comprised 5 treatments: (i) no fertilization control (Con), (ii) and (iii) two different calcium ammonium nitrate rates (N120 and N240 at doses of 120 and 240 kg N ha−1 year−1, respectively), and iv) and v) two different sewage sludge rates (S120 and S240 corresponding to mineral N doses). Topsoil (0–30 cm) analysis was performed 28 years after the onset of the experiment to determine soil organic carbon, the fractions of humic substances, potentially mineralizable carbon and dissolved organic carbon, the potential wettability index, soil aggregate stability, EEG, and total glomalin (TG).ResultsThe control treatment, which did not include fertilization, showed significantly lower average yields (9.76 t DM ha−1 year−1) than the fertilization treatments (on average 12.3 DM ha−1 year−1). Significant differences in yields were not found between the fertilization treatments. A positive correlation between glomalin (EEG, TG) content and soil organic matter carbon content was observed. A periodic application of sewage sludge increased the content of glomalin. However, the highest quality of SOM was found in the control treatment (nonfertilized). This treatment had the highest values for the humic/fulvic acid ratio and the highest contents of humic acids and potentially mineralizable carbon. Furthermore, the Con treatment showed the highest soil aggregate stability and potential wettability index. Mineral N fertilization significantly reduced soil aggregate stability values.ConclusionsThe unfertilized control showed the highest SOM quality but the lowest yields. The data on glomalin content can be used to study soil organic matter quality. Because the EEG extraction method is easy to apply, uses lower quantities of chemicals and consumes less time, it presents a better option than TG extraction. The sensitivity of the methods for SOM quality determination decreases with increasing SOM content.Graphical

Effects of Poplar Shelterbelt Plantations on Soil Aggregate Distribution and Organic Carbon in Northeastern China

This study aimed to determine the distribution, stability, and soil organic carbon (SOC) of aggregates, and the contribution of soil aggregate proportion, stability index, and aggregate-associated SOC to the total SOC. Three hundred and sixty soil samples were gathered from shelterbelts and neighboring farmlands in five layers of 1 m profiles in Songnen Plain, northeastern China. The shelterbelt plantations were found to increase by 69.5% and 103.8% in &gt;2 mm and 0.25–2 mm soil aggregates, respectively, and their R0.25, mean weight diameter (MWD), and geometric mean diameter (GMD) were enhanced by 96.3%, 33.2%, and 40.0%, respectively, compared to those of farmlands in soil layers at 0–20 cm depth (p &lt; 0.05). The total SOC content increased by 13.3% at 0–20 cm soil depth, and the SOC content and stock in &gt;2 mm aggregates increased by 21.5% and 18.7% in the 20–40 cm layer (p &lt; 0.05), respectively. The SOC content and stock in total soil had a significantly positive relationship with the proportion of &gt;2 mm soil aggregates and a negative relationship with the value of fractal dimension (D). The enhancement in the SOC of the total soil was dependent on the increase in aggregate-associated SOC, with larger-particle aggregates having a greater contribution. Based on the study results, afforestation improved soil stability and the structure of soil aggregates, and SOC accumulation in the total soil was not only governed by SOC concentration and stock within the aggregate size class, but also the proportion of &gt;2 mm soil aggregates and the value of the fractal dimension.

Changes in physical and chemical properties of saline soil amended with municipal solid waste compost and chemical fertilizers in a mustard–pearl millet cropping system

AbstractSoil salinity is a severe threat in arid and semiarid agro‐ecosystem of India, and it is directly influenced by soil physical properties. Therefore, understanding the dynamic nature of salinity is the key to implementing suitable management options for re‐builing the fertility of saline soils. In this context, we conducted field experiments in saline soil, comprising five treatments (1‐5 following) and a control (C). These are: C) no amendments and chemical fertilizer; T1) recommended dose nitrogen, phosphorus, and potassium (N‐P‐K) fertilizers @60:30:30 kg ha−1; T2) 100% recommended dose of chemical fertilizers (RDF).; T3) rice straw compost (RSC) @14 Mg ha−1; T4) gypsum enriched compost (GEC) @14 Mg ha−1; and T5) municipal solid waste compost @16 Mg ha−1 (MSWC) applied for three consecutive years (2012 to 2015). Our results revealed that compost and chemical fertilizer had significant effect on soil organic carbon, soil aggregate stability indices, soil water retention, transmission characteristics, and pore size distribution. This improvement in soil physical properties imparted into better soil physical environment and significant reduction in soil salinity (75%) was apparent with application of MSWC. Multivariate analysis indicated that mean weight diameter (MWD) and retension pores (RP) were the two main soil physical properties that help to reduce soil salinity. Our results revealed that, MWD increased by 49.1% in MSWC and 37.7% in GEC over control (C) (0.53 mm). Improvement in soil environment under composted soil produced significantly higher grain yield of mustard (2.22 Mg ha−1) and pearl millet (2.29 Mg ha−1) with MSWC as compared to control (C). Organic amendments significantly improved the soil physical environment.

The Changes in Soil Microorganisms and Soil Chemical Properties Affect the Heterogeneity and Stability of Soil Aggregates before and after Grassland Conversion

The conversion of grasslands to croplands is common in the agro-pastoral ecotone and brings potential risks to soil health and environmental safety. As the forming unit of soil structure, the status of soil aggregates determines soil health and is affected by multiple factors. This study investigated the changes in soil aggregate and main related factors in conversion grasslands with different managed years. Grassland conversion ages were selected as experimental treatments, which included unmanaged grassland, 3 years, 10 years, 30 years, and 50 years since grassland conversion. After grassland conversion, the proportion of large macro-aggregates with a particle size of &gt;2 mm in the 0–10 cm soil layer decreased, small macro-aggregates with a particle size of 2–0.25 mm and micro-aggregates with a particle size of 0.25–0.053 mm increased, while aggregates with a particle size of &lt;0.053 mm had no significant change. Soil chemical properties, most microorganisms and the soil aggregate stability indices MWD and GMD decreased at the early stage (&lt;30 years) of the managed grasslands. After about 50 years of cultivation, soil chemical properties and microorganisms returned to equal or higher levels compared to unmanaged grasslands. However, the stability of aggregates (mean weight diameter (MWD) and geometric mean diameter (GMD)) did not recover to the initial state. MWD and GMD were positively correlated with most bacterial factors (total phospholipid fatty acids (PLFAs), bacteria, Gram-positive bacteria, Gram-negative bacteria, actinomycetes and arbuscular mycorrhizal fungi (AMF)) and some soil chemical properties (carbon, nitrogen and polysaccharides). According to the partial least square structural equation model, soil organic carbon, total nitrogen and phosphorus in the 0–10 cm soil layer explained 33.0% of the variance in MWD by influencing microorganisms. These results indicated that the stability of aggregates was directly driven by microorganisms and indirectly affected by soil organic carbon, total nitrogen and phosphorus.

Caragana korshinskii Kom. plantation reduced soil aggregate stability and aggregate-associated organic carbon on desert steppe.

BackgroundAfter implementing of the “Grain-for-Green” project, Caragana korshinskii Kom. has been widely planted in China’s arid regions. Although natural restoration grassland and artificial Caragana plantations measures have long been focuses in carbon research, the combined influence of natural restoration grassland and artificial Caragana plantation measures on aggregate stability and the aggregate-associated organic carbon (OC) remains unclear.MethodWe selected natural grassland (NG) and three different densities of Caragana plantations (high planting density, HG; middle planting density, MD; low planting density, LD) on desert steppe. The soil aggregate distribution and stability index such as fractal dimension (D), mean weight diameter (MWD), geometric mean diameter (GMD), percentage of aggregation destruction (PAD), as well as aggregate-associated OC concentration and stock were measured.ResultsResults shows that the soil aggregates were primarily macroaggregates (>2 mm) and mesoaggregates (0.25–2 mm) under dry sieving while microaggregates (<0.25 mm) were preponderant under wet sieving (more than 57%). Overall, compared with Caragana plantations, the MWD (4.43 and 4.51 mm) and GMD (1.72 and 1.83 mm) were both highest in two soil layers under the NG and the D (2.77 and 2.71) was lowest. Compared with the NG, the aggregate-associated OC stocks in the 0–40 cm depths in the LD, MD, and HD decreased by 41.54%, 46.93%, and 42.03%, respectively. SOC stock was mainly concentrated in the soil aggregate with sizes of >2 mm and <0.25 mm. These results suggested that natural grassland restoration measures could improve the soil aggregate stability and aggregate-associated OC concentration better than Caragana plantation restoration measures, which NG may be optimal for increasing carbon sequestration and stabilizing soil aggregates on desert steppe.

The relative contributions of soil hydrophilicity and raindrop impact to soil aggregate breakdown for a series of textured soils

Soil aggregate breakdown is the first key factor that causes soil erosion. At present, research on the mechanisms of soil aggregate breakdown during rainfall is common. However, the research to on quantifying the relative contributions of internal and external forces to aggregate breakdown remains limited. This paper was conducted to analyse the relative contribution of internal and external forces to aggregate disintegration and the factors affecting aggregate stability during rainfall. Soil aggregates with a series of textures were selected as test soil samples; deionized water was employed as the soaking solution and rainfall material in static disintegration experiments and rainfall simulation tests. The effect of internal force (soil hydrophilicity) on aggregate disintegration was analysed by the static disintegration method, and the combined effects of internal force (soil hydrophilicity) and external force (raindrop impact) on soil aggregate breakdown were analysed by rainfall simulation experiments. The results indicated that external force caused more severe soil aggregate breakdown than internal force, and the crushed aggregate was mainly distributed in the range of 2–0.25 mm. With increasing rainfall kinetic energy, the degree of aggregate breakdown increased gradually, and the degree of aggregation of the soil particles decreased gradually. Furthermore, soil aggregates with a high clay content (> 30%) were more stable than medium-clay (20–30%) and low-clay (< 20%) soil aggregates, and the correlation coefficient provided a good representation of the relationship between the clay content and soil aggregate stability index (ASI). Therefore, external force contributed more to soil aggregate breakdown than internal force during rainfall, and clay plays an important role in aggregate stability. The results of this study are of great significance for elaborating the mechanism and factors affecting aggregate breakdown.

Kajian Biofisik Lahan Untuk Tanaman Porang Sebagai Anasir Konservasi Pada Sistem Agroforestri Di Pulau Lombok

Agricultural land in North Lombok is dominated by a typology of sub-optimal land, physically, chemically and biologically. These properties make it vulnerable to degradation. In such land, agroforestry system is highly recommended, where the porang plant can be included as a component. Nowdays, porang is gaining popularity as a commodity with economic value, and is suitable as an intercropping plant. It is easy to grow on almost all types of soil, and is resistant to shade, making it adaptive to agroforestry systems as non-timber under standing plants in community forest systems. It is believed that this will provide multiple benefits economicly and environmentaly, if it accompanied by the principles of soil and water conservation. The role of porang as a conservative agent has been investigated through a scientific approach as the basis for the domistication of porang in agroforestry systems. The results showed that agroforestry with porang could help improve the stability of the soil aggregates as indicated by the soil aggregate stability index 59 which means rather stable. Soil moisture of wilting point in agroforestry system with porang increased from 3.0% (without porang) to 5.4%. In addition, the soil organic matter content increased to 3.94% (quite high) on the system with porang because the stems and leaves of porang plant are quickly weathered. The ground cover is relatively tight, so it can prevent soil erosion. Porang also play a role in increasing water infiltration due to the presence of porang’s roots and tubers. Thus the domistication of porang fulfills the requirements as an agent of soil conservation, as non-timber plant in the agroforestry system, if it is cultivated according to the principles of soil and water conservation on the typology of sub-optimal land in North Lombok.

Spatial prediction of soil aggregate stability and soil organic carbon in aggregate fractions using machine learning algorithms and environmental variables

Knowledge about the spatial variability of soil aggregate stability indices, soil organic carbon (SOC) in various aggregate sizes, and aggregation across the landscape is crucial for sustainable land use planning and management practices. Direct traditional measurements for the target variables, as mentioned above, are time-consuming and expensive. Thus, this study attempts to spatially predict the soil aggregate stability indices, including mean weight diameter-MWD, geometric mean diameter-GMD, water-stable aggregates-WSA, and SOC in various aggregate fractions using digital soil mapping and machine learning models using the environmental covariates as the time and cost-effective approaches. Thus, a total of 100 soil surface samples (0–10 cm depth) were collected from the natural forest, tea plantation, and paddy rice field land uses, and soil aggregate stability indices were determined following laboratory analyses. The machine learning models, including random forest (RF), k-nearest neighbors (kNN), support vector machine (SVM), artificial neural network (ANN), and the ensemble of four single models, were trained using the repeated 10-fold cross-validation method. The models were evaluated by the root mean square error (RMSE), mean absolute error (MAE), coefficient of determination (R2), and normalized RMSE (nRMSE). The modeling results demonstrated that the RF model outperformed for MWD (R2 = 0.74, nRMSE = 24.28), GMD (R2 = 0.75, nRMSE = 12.72), and WSA (R2 = 0.58, nRMSE = 10.40), while kNN and SVM models resulted in the best prediction of SOC in (meso and micro-aggregates (RMSE = 1.03 and 0.88)) and macroaggregates (RMSE = 1.49), respectively. However, the ensemble model increased the prediction accuracies for all soil targets (RI ≥ 15.78%). Moreover, the variable importance analysis showed that soil properties such as soil organic matter (SOM) and remote sense-data mainly explained the variation of soil aggregate stability indices and SOC in various aggregate fractions. Overall, the results revealed that the machine learning-based models could accurately predict the soil aggregate stability and associated SOC, and the produced maps can be a baseline map for land use planning and decision making.

Potential of visible-near infrared spectroscopy for the determination of three soil aggregate stability indices

Aggregate stability (AS) is an important parameter to evaluate soil resistance to erosion. The conventional determination methods to measure AS are time consuming, difficult and labour intensive. Visible (vis) and near infrared (NIR) spectroscopy could be a better alternative to the conventional determination methods of AS. This study explored the possibilities of estimating three AS indices, reflecting stability upon slow wetting (SW), fast wetting (FW) and mechanical breakdown (MB), using vis-NIR spectra data on some air-dried, non-sieved soils of the Belgian loam belt. Partial least squares regression (PLSR) was used to build calibration models for the three stability indices, using a calibration set accounting for 70% and a validation set of 30% of the total samples. Results showed that all three AS indices can be predicted to appreciable accuracies from vis-NIR-PLSR models [coefficient of determination (R2) = 0.72–0.80, residual prediction deviation (RPD) = 1.93–2.27, ratio of performance to interquartile range (RPIQ) = 2.23–4.09 and root mean square error (RMSE) = 0.29–0.52 mm]. The prediction results suggest that omission of sample pre-treatment by sieving or grinding may have very limited impact on the prediction accuracy. This opens up opportunities for the in-situ deployment of vis-NIR spectroscopy, provided that problems associated with variable soil moisture contents can be overcome.

Soil aggregate stability index and particulate organic matter in response to differently afforested lands in the temperate regions of Iran

Aggregate Stability Index (ASI) and particulate organic matter (POM) are strongly influenced by land use and management. This work illustrates the effects of plantations on ASI and POM-C and POM-N in northern Iran. Three plantations of P. deltoides (PD), T. distichum (TD), A. subcordata (AS), and a fourth site ‒ adjacent abandoned lands (BL, as control) were selected. Soil samples were taken within 16 quadrats of each plantation and BL from the two depths of 0–15 cm and 15–30 cm during the summer. Soil C was significantly higher under TD (2.10%) than under BL (2.02%) &amp;gt; PD (1.61%) &amp;gt; AS (1.30%). Soil N was found in ranked order of AS (8.99%) &amp;gt; TD (7.82%) &amp;gt; PD (5.30%) &amp;gt; BL (3.68%) (P &amp;lt; 0.019). The significantly higher ASI was found under TD (57.49) in comparison with PD (53.10), BL (51.23), and AS (36.57). The POM-C was as follows: TD (0.209%) &amp;gt; PD (0.141%) &amp;gt; AS (0.139%) &amp;gt; BL (0.075%) (P = 0.020). The highest POM-N was found under TD (0.035), followed by AS (0.0284%), PD (0.0288%), and BL (0.007%). The results indicate the positive effect of afforestation on soil ASI and POM-C and POM-N, especially in the surface layers of soil.

Data fusion of visible near-infrared and mid-infrared spectroscopy for rapid estimation of soil aggregate stability indices

Soil aggregate stability (AS) is a crucial soil physical property for sustainable agricultural and environmental land management practices. Yet, its conventional laboratory methods are fastidious and time consuming thereby restricting high-density sampling and large-scale estimation. Therefore, the potential of fusing visible near-infrared (vis-NIR) and mid-infrared (MIR) spectroscopy to enhance the prediction of three AS indices, namely, fast wetting (FW), slow wetting (SW) and mechanical breakdown (MB) on some Belgian Retisol, Cambisol and Luvisol topsoils was evaluated. Partial least squares regression (PLSR) was used to build calibration models for the three AS indices using the vis-NIR spectra, MIR spectra and the fusion of both spectra (SF). Another data fusion approach (i.e. model output averaging, MOA) included the use of four averaging algorithms. Results showed that MIR models outperformed the vis-NIR models for all three indices. The SF approach showed an improved prediction performance over both individual sensor techniques for the FW index only. MOA models outperformed the individual and SF models and yielded the best prediction accuracy for SW and MB indices. Data fusion modelling thus enhanced the accuracy of FW, SW and MB predictions, although the selection of the best data fusion approach is dependent on the nature of the dataset and the stability index to be assessed.

Application of soil amendments as a strategy for water holding capacity in sandy soils

Global warming will affect the pattern of precipitation, evaporation, water run-off, soil moisture, and climate variations so that it can threaten food production. High evaporation and unpredictable precipitation will cause drought. Sandy soils have low water holding capacity, high infiltration, and high runoff. The application of soil amendments able to improve the soil’s physical properties through increasing the water holding capacity to increase crop productivity. The research aimed to determine the effect of the application of soil amendments to water holding capacity in sandy soils. The method used was a randomized complete design with one single factor, the type of soil amendments consisting of 7 treatments: P0 (control/without amendment), P1 (cow dung 60 tons ha-1), P2 (rice husk biochar 10 tons ha-1), P3 (clay-soils 10 tons ha-1), P4 (cow dung 60 tons ha-1+ rice husk biochar 10 tons ha-1), P5 (cow dung 60 tons ha-1+ clay-soils 10 tons ha-1), P6 (rice husk biochar 10 tons ha-1+ clay-soils 10 tons ha-1). The results showed that the interaction of rice husk biochar 10 tons ha-1+ clay-soils 10 tons ha-1 significant to increase soil moisture and decrease soil permeability. Combination of cow dung 60 tons ha-1 rice husk biochar 10 tons ha-1 more increase soil aggregate stability index up to 1.87 times than control.

INDEKS STABILITAS AGREGAT TANAH PADA PERKEBUNAN TEH BERBASIS SLOPE DAN UMUR TANAMAN DI KECAMATAN GUNUNG TALANG KABUPATEN SOLOK

Land-use change from the forest into tea plantation in Solok Regency in 1983 has decreased the area of forests in Gunung Talang District. Clearing up the forest at the beginning for tea plantation could worsen the physical and chemical conditions of the soil. One of which is soil aggregate stability that is very dynamic and can influence other soil physical properties. This study was aimed to determine soil Aggregate Stability Index (ASI) at tea plantations. Soil samples was taken at a depth of 0-20 cm from five different slopes (0-8% (A), 8-15% (B), 15-25% (C), 25-45% (D), and&gt; 45% (E)) and at two crop ages (10 and 35 years old). The results showed that the soil aggregate stability index at tea plantations ranged from stable to very stable. It tended to decrease by increasing slope percentage at each of crop age, Between the ages, it showed higher ASI at 35 years old crop age under relatively flat (0-8%) and very steep (&gt;45%) areas.

Arbuscular mycorrhizal fungi and soil aggregation in a no‐tillage system with crop rotation

AbstractCrop rotation adoption in no‐tillage systems (NTS) has been recommended to increase the biological activity and soil aggregation, suppress soil and plant pathogens, and increase the productivity aiming at the sustainability of agricultural areas. In this context, this study aimed to assess the effect of crop rotation on the arbuscular mycorrhizal fungi (AMF) community and soil aggregation in a soil cultivated for nine years under NTS. Treatments consisted of combinations of three summer crop sequences and seven winter crops. Summer crop sequences consisted of corn (Zea mays L.) monoculture, soybean (Glycine max L. Merrill) monoculture, and soybean–corn rotation. Winter crops consisted of corn, sorghum (Sorghum bicolor (L.) Moench), sunflower (Helianthus annuus L.), sunn hemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan (L.) Millsp.), oilseed radish (Raphanus sativus L.), and millet (Pennisetum americanum (L.) Leeke). Soil samples were collected at a depth of 0–0.10 m for analyses of soil chemical, physical, and biological attributes. Spore abundance, total glomalin, and soil aggregate stability index were higher in the soil under corn monoculture. The highest values of aggregate mean weight diameter were observed in the soybean–corn rotation (3.78 mm) and corn monoculture (3.70 mm), both differing from soybean monoculture (3.15 mm), while winter crops showed significant differences only between sorghum (3.96 mm) and pigeon pea (3.25 mm). Two processes were identified in the soil under summer crop sequences. The first process was observed in PC1 (spore abundance, total glomalin, easily extractable glomalin, pH, P, and Mg2+) and was related to AMF; the second process occurred in PC2 (aggregate mean weight diameter, soil aggregate stability index, K+, and organic matter) and was related to soil aggregation. The nine‐year no‐tillage system under the same crop rotation adoption influenced AMF abundance in the soil, especially with corn cultivation in the summer crop sequence, which promoted an increased total external mycelium length and number of spores of AMF. In addition, it favored an increased soil organic matter content, which is directly related to the formation and stability of soil aggregates in these managements.

Artificial soil nutrient, aggregate stability and soil quality index of restored cut slopes along altitude gradient in southwest China.

In the subalpine mountainous region of southwest China, the artificial soil properties of restored cut slopes along the altitude gradient were studied, including available nitrogen (AN), available phosphorus (AP), available potassium (AK), urease (UR), sucrase (SC), protease (PR), catalase (CAT), texture, and aggregate stability of soil. Soil aggregatet stability by mean weight diameter (MWD), geometric mean diameter (GMD), structure failure rate (P), index of unstable aggregates (IUA) and area difference of dry and wet sieve cumulative distribution curve (ΔS) were measured and analyzed. It was found that available soil nutrients, UR, and CAT activities increased initially and then decreased, but the texture of soil was finer, and aggregate structure tended to be more stable along with an increase in the altitude gradient. The soil aggregate stability index that MWD, GMD, P, IUA, and ΔS indicated that the higher the altitude, the stability of soil aggregates was better. Principal component analysis (PCA) was used to determine the soil quality index (SQI). The obtained results from this study showed that the artificial soil quality of the cut slopes was better at a higher altitude compared to a lower altitude. These results provide a reference for the improvement of artificial soil properties of cut slopes and their quality in the future. It is necessary to pay attention to the soil quality management at a low-altitude area and reform the soil nutrients, enzyme activities, and soil structure for the restored cut slopes in the mountainous subalpine highway of southwest China.

Interrelationship between soil depth and soil properties of Pieniny National Park forest (Poland)

The purpose of this research was to investigate the relationship between soil biota such as microbial activity, soil fauna (e.g., earthworms and enchytraeids), and soil physical and chemical properties. The study area was located in Pieniny National Park (PNP) in the Carpathian Mountains in southern Poland. Soil samples were collected from six forest monitoring areas of PNP from two soil layers (at 0–15 cm and 15–30 cm down, respectively). The investigated soils were classified to eutric cambisols and had silt or silt loam soil texture. Upon analysis, soil aggregate stability index was connected with other physical, chemical, and biological soil properties. It was noted that the stability index of 3 mm to 5 mm soil aggregates influenced pH and dissolved organic carbon. The stability index of 2 mm to 3 mm soil aggregates was positively correlated with dissolved organic carbon, soil moisture, microbial biomass carbon, total organic carbon, total nitrogen, and enchytraeid density, and negatively correlated with bulk density, particle density, porosity, and permanent wilting point. The stability index of 1 mm to 2 mm soil aggregates was positively correlated with total nitrogen, enchytraeid and earthworm density and negatively correlated with particle density, porosity, and permanent wilting point. The study has shown what factors create a stable soil structure in the forest soils of PNP.

Spatial analysis of soil aggregate stability in a small catchment of the Loess Plateau, China: II. Spatial prediction

As indicators of soil degradation vulnerability, soil aggregate stability indices play important roles in representing soil resistance to water erosion, and their spatial variability provides both agriculturally and environmentally important information. The spatial variability of aggregate stability indices is synergistically affected by the soil, topography, vegetation, and human factors. To understand the formation processes of aggregates by a spatial analysis, a prediction model combining soil properties with natural and human factors should be developed to improve the accuracy of the spatial interpolation of soil aggregate stability indices. In this study, the mean weight-diameter (MWD, mm), water-stable aggregates greater than 0.25 mm (WSA>0.25, %) and soil erodibility factor (K factor) were satisfactorily predicted by multiple stepwise regression (MSR) and regression kriging (RK) based on soil properties and natural and human factors (0.436≤ R2 ≤0.578). In addition, spatial variability and prediction modeling of aggregate stability indices were highly dependent on the quantification of land use type and landscape structure (the spatial structure of landscape elements and the connections between the different ecosystem types or landscape elements). It has received little attention in previous studies. The exclusion of all soil variables did not affect the predictions of K factor, and for MWD and WSA>0.25, even though the performance of the models may appear relatively low, but also significant (0.183≤ R2 ≤0.312), indicating that the prediction of the spatial distributions of aggregate stability indices with easily available auxiliary data is practicable and effective. Residual maps showed that high residuals are distributed around built-up land (transportation land and residential land) or farmland, indicating that anthropogenic factors increase the uncertainty of the models. The spatial distribution maps of MWD, WSA>0.25 and K factor can be useful in landscape planning and decision making to minimize water erosion risks.