Aggregate Stability Index Research Articles

Aggregate stability in rainfall‐induced soil physical crusts on the Loess Plateau, Northwest China

AbstractComprehensive insights into the aggregate stability of physical crusts enhance the understanding of erosional processes and transport mechanisms. This study evaluated the erosion resistance and aggregate stability in structural and sedimentary crusts of a Lou soil induced by simulated rainfall. A runoff plot (200 cm long × 100 cm wide × 50 cm high) with a slope of 5° was set up to simulate contour tillage (20 cm in ridges, 30 cm in furrows). A single rainfall intensity (60 mm h−1) was applied over six durations (5, 10, 15, 20, 25, and 30 min) to obtain structural and sedimentary crusts. With an increase in rainfall duration, bulk density of structural and sedimentary crusts increased from 1.26 g cm−3 (soil before rainfall) to 1.56 and 1.58 g cm−3, respectively. Macroaggregate contents in structural crust changed slightly (from 7.5 to 7.4%); however, a marked increase (from 9.0 to 18.6%) was observed in sedimentary crust with increased rainfall duration. The mean weight diameter and geometric mean diameter (i.e., the inverse of erodibility factor) in structural crusts were lower than sedimentary crusts developed from all rainfall conditions. The aggregate stability index of structural and sedimentary crusts initially increased from 2.12 and 2.07 with the increase in rainfall duration, respectively, and then leveled off at 2.42 and 2.48. Soil aggregate stability of sedimentary crust, which conferred greater resistance against external erosive forces, was stronger than that of structural crust.

Effects of Organic Agriculture in Structure and Organic Carbon Adsorption at Colloidal Scale in Marginal Olive Groves, Characterized by the Extended DLVO Model

Relationship between macroscopic and microscopic behavior of soils is a difficult issue, especially when dealing with complex properties such as structure or carbon sequestration, but it is necessary for a suitable understanding of the agricultural soil quality. In this work, we used the extended-DLVO theory to compute total energy of interaction between particles (kT), of three soils over granodiorites. This parameter allows predicting the tendency to aggregate formation at the colloidal scale, being the basis of soil structure. Furthermore, we characterized the mechanism and adsorption capacity of humic molecules on mineral surfaces, and its influence in the interaction energy, by means of the adsorption isotherms. The aim was to compare first the effects of organic farming on conventionally managed soils and, second, to compare these with a non-cultivated forest soil under Mediterranean climate. When total energies are negative (particle attraction), or positive (particle repulsion) but near 0 kT (<100 kT), then particle flocculation occurs and the structure at colloidal scale can be developed. Total energy was less in the forest sample and greater in the soil of conventional groves, with intermediate values in organic farming soil. This indicates a tendency toward particle flocculation and more stability of the structure at colloidal scale in less disturbed soils, agreeing with other soil physical properties such as the total porosity (50, 41 and 37% in forest, organic and conventional plots, respectively) or the aggregate stability index (0.94, 0.73 and 0.66, respectively), which followed the same trend. Of the three components of the total energy of interaction, the acid-base force was a key factor. This component, related with the electron-donor component of surface free energy, γ−, yielded a strong attractive force (−150 kT at 3 nm) when calcium solutions were analyzed for the forest soil. This indicates a clear hydrophobic character of this sample. Because the mineralogical composition of the samples is quite similar, hydrophobicity should be attributed to the organic carbon content of the forest soil, which is much higher than that of the cultivated ones (12.03 vs. 1.44% and 0.88% in organic and conventional farms, respectively), proving to be an essential element for the development of the structure at the colloidal level.

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 >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 <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 (<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.

Fertilizer combination effects on aggregate stability and distribution of aluminum and iron oxides#

AbstractBackgroundOne main anthropogenic activity through which aggregate stability and elements are impacted in soils is through fertilization. Inputs of phosphate fertilizers to soils, for instance, have direct impacts on other elements in soils. Organic fertilizer sources are also known to markedly influence the availability of microelements. However, the extent to which different combination ratios of organic and chemical fertilizers affect the availability of these microelements in paddy soil aggregates is not clear.AimTherefore, this study examined aggregate stability and the distribution pattern of various extractable aluminum, and iron oxides as influenced by a long‐term varied combinations of pig manure with chemical nitrogen, phosphorus, and potassium (NPK) fertilizer in a rice‐managed paddy.MethodMehlich 3, dithionite, oxalate, and pyrophosphate solutions were used to extract oxides of Al and Fe in bulk soil, and aggregates under long‐term fertilizer combinations, which included unfertilized CK (control), chemical NPK, 30% chemical NPK + 70% pig manure, 50% chemical NPK + 50% pig manure, and 70% chemical NPK + 30% pig manure in a randomly complete block design.ResultsThe highest manure treatment (70% manure) markedly increased total organic carbon (TOC), and total nitrogen (TN) in contrast to other treatments. Soil pH was higher in all manure‐treated fertilizers than in chemical NPK fertilizer likely because organic matter (OM) neutralized the protons. Additionally, the highest manure treatment led to the creation of more macroaggregates (2–0.25 mm), which translated into higher aggregate stability indices such as mean weight diameter (MWD), and geometric mean diameter (GMD) compared to other treatments. It was also noted that the 70% manure treatment in comparison with other treatments, was associated with higher concentrations of extractable Al and Fe oxides. It was, however, not clear if the changes in extractable metals detected in this treatment resulted from OM‐driven redistribution of metals or if the manure contained some Al and Fe itself.ConclusionThe 70% manure treatment increased TOC, TN, pH, and aggregate stability indices (higher MWD and GMD). This fertilizer treatment was also associated with more extractable Al and Fe oxides. For more sustainable rice‐managed paddies, the 70% manure treatment should be considered over the other fertilizer combinations.

Do fallow in the off-season and crop succession promote differences in soil aggregation in no-tillage systems?

The no-tillage (NT) system is an agricultural practice that stands out the most within conservation agriculture. Conservation agriculture is based on three principles: soil tillage that is limited to the sowing row, crop rotation, and soil surface cover throughout the year (>30%). Despite these principles, the maintenance of soil cover throughout the year and crop rotation are commonly neglected, which can promote changes in soil aggregation. The aim of this study was to evaluate the effects of fallow in the off-season, and two crop successions (grass/grass and grass/legume), on soil aggregation in NT systems. The study was conducted in five fields with different land uses for more than 10 years in southeastern Brazil. Three land uses under NT, all sown with maize within the season, were used, yielding three groups: NT with fallow in the off-season (NT-f), NT with legumes (brown hemp) in the off-season (NT-l), and NT with maize in the off-season (NT-g). For comparison, we considered forest land (F) as a conservation reference for soil aggregation and land being used under conventional tillage (CT) as a low-conservation system. The soil variable that contributed the most to the separation of land use was the mineral-associated organic carbon content. The absence of soil surface cover throughout the year in an NT system is as harmful to soil aggregation as a CT system. Moreover, succession promotes differences in soil aggregation, with grass-grass succession (NT-g) leading to higher particulate organic carbon content and aggregate stability index in some soil layers compared to the NT-l. Here, we demonstrate that conservation agriculture practices, such as NT, require a system-centered approach to improve soil conditions. We also found that fallow in the off-season promotes an NT system with low soil conservation.

Forest expansion on cropland on China’s Loess Plateau facilitates C sequestration by increasing microbial-derived but not plant-derived carbohydrates

Conversion of cropland to forest affects the microbial transformation of plant-derived organic substances and the accumulation of microbially synthesized products in soil. Labile litter represents the major source for soil microbial products, which promote soil aggregation and long-term carbon (C) stabilization. The present study investigated the changes in carbohydrate monosaccharides and their origins (i.e., microbial-derived or plant-derived carbohydrates) following the afforestation of cropland in the Loess Plateau region by Robinia pseudoacacia. Carbohydrate monosaccharides were determined in the soil fractions and plant organs in cropland and four R. pseudoacacia forests aged 5, 12, 25, and 32 years. The distributions of the soil aggregates and their stability were also measured. Forest expansion on cropland significantly increased the total organic C in the 0–10 cm soil layer by 31.8%. Glucose was the dominant monosaccharide in the plants and all soil fractions from all R. pseudoacacia forests, followed by galactose, xylose, and mannose. Following 32 years of afforestation, the ratios of microbial-derived carbohydrates relative to plant-derived carbohydrates (such as R(Rhamnose + Fucose)/(Arabinose + Xylose)) significantly increased by 131%, 149%, and 86% in the particulate organic matter, stable aggregate, and silt and clay fractions, respectively. Significant and positive correlations were found between the aggregate stability indexes and microbial-derived monosaccharides, thereby indicating that microbial-derived monosaccharides may play key roles in the stabilization of soil aggregates. These results suggest that following forest expansion on cropland, the increasing amounts of microbially-derived compounds corresponding to the increased allocation of soil C to stable aggregates may promote soil aggregation.

陇东雨养苹果覆膜对土壤团聚体结构稳定性与细根分布的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 陇东雨养苹果覆膜对土壤团聚体结构稳定性与细根分布的影响 DOI: 10.5846/stxb202102190468 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31760555）；财政部和农业农村部：国家现代农业产业技术体系（GARS-27）；农业农村部西北地区果树科学观测实验站（S-10-18） Effects of film mulching on soil aggregate structure stability and fine root distribution of rain-fed apple in eastern Gansu Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:不同的果园管理方式可影响果树根系生长、分布与土壤团聚体稳定性、有机碳固存，进而改变"根-土"复合体响应关系。对西北陇东旱塬不同覆膜年限（2 a、4 a和6 a）苹果园表层土壤（0-20 cm）细根生长进行调查，并采用干筛法和湿筛法相结合的方式对土壤团聚体进行分级（>2 mm，0.5-2 mm，0.25-0.5 mm和<0.25 mm）。计算团聚体稳定性参数[> 0.25 mm机械稳定性团聚体含量（DR0.25）、> 0.25 mm水稳性团聚体含量（WR0.25）、平均重量直径（MWD）、平均几何直径（GMD）、团聚体破坏率（PAD）、水稳系数（WSC）]和团聚体有机碳含量。分析细根生长与土壤物理结构对长期覆膜的响应，探明土壤团聚体稳定性与有机碳固持关系，揭示黄绵土物理结构稳定机制。结果表明：6 a处理通过增加表层土壤黏粒和物理性黏粒比例，改变孔隙结构，抑制细根生长，其根量、根长和根表面积仅为对照（CK）的20.97%、24.66%和41.25%；降低表层土壤团聚体力稳性，其DR0.25、机械稳定性团聚体MWD和GMD仅为CK的82.2%、74.02%和59.38%；对水稳性团聚体的保护作用低于短期覆膜（2 a），其PAD和WSC为2 a处理的121.17%和54.56%。2 a处理可提高土壤团聚体的力稳性、水稳性和土壤团聚程度，使土壤结构得到改善。同时对机械稳定性、水稳性团聚体有机碳提升效果优于6 a处理，为6 a处理的115.66%和116.6%。大团聚体固持有机碳能力高于微团聚体，但由于长期覆膜团聚体稳定性的下降，6 a处理的DR0.25为CK的82.2%，不利于对有机碳的保护，使土壤有机碳水平对团聚体稳定性变异决定性仅为29.55%。连续覆膜引发的频繁干湿交替增加了黏粒对土壤结构稳定性的影响权重，促使表土"隐形"退化，抑制苹果细根在表层土壤中的生长、分布。2 a处理对土壤团聚体结构有良好的保护作用，促进土壤有机碳累积。 Abstract:Different orchard management methods can affect the growth and distribution of fruit roots, the stability of soil aggregates and the ability of organic carbon storage, and then change the response relationship of root-soil complex. The fine root growth of apple orchard surface soil (0-20 cm) with different plastic film mulching years (2 a, 4 a, and 6 a) was investigated in the dry tableland of Longdong, Northwest China. The combination of dry and wet screening methods was used to classify soil aggregates (>2 mm, 0.5-2 mm, 0.25-0.5 mm, and <0.25 mm). The aggregate stability index, including > 0.25 mm Mechanical stability aggregates content (DR0.25), > 0.25 mm water-stabled aggregates content (WR0.25), Mean weight diameter (MWD), geometric mean diameter (GMD), percentage of aggregate destruction rate (PAD), water stability coefficient (WSC), and the content of organic carbon were calculated. The response of soil physical structure and fine root growth to long-term film mulching was analyzed, the relationship between soil aggregate stability and organic carbon sequestration was explored, and the stability mechanism of physical structure of loess soil was revealed. The results showed that film-mulching six years inhibited fine root growth by increasing soil clay, the proportion of physical clay and changing pore structure, and the root weight, root length and root surface area were only 20.97%, 24.66% and 41.25% of conventional tillage (CK); The DR0.25, MWD and GMD of surface soil aggregates were 82.2%, 74.02% and 59.38% of CK; The protective effect of PAD and WSC were 121.17% and 54.56% of film-mulching two years, compared with that of short-term film mulching. Film-mulching two years improved the force stability and water stability of soil aggregates as well as the degree of soil aggregates, and improved the soil structure. At the same time, the organic carbon improvement effect of mechanical stability and water stability aggregates was better than that of film-mulching six years, which was 115.66% and 116.6% of film-mulching six years. Although the ability of large aggregates to hold organic carbon was higher than that of micro aggregates, due to the long-term stability decline of coated aggregates, the DR0.25 of film-mulching six years was only 82.2% of CK, which was not conducive to the protection of organic carbon, so that the decisive effect of soil organic carbon level on the stability variation of aggregates was only 29.55%. The frequent dry-wet alternation caused by continuous film mulching increased the influence weight of clay particles on soil structural stability, promoted the invisible degradation of the topsoil, and inhibited the growth and distribution of fine roots of apple in the topsoil. Film-mulching two years had a good protective effect on soil aggregate structure and promoted soil organic carbon accumulation. 参考文献 相似文献 引证文献

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.

Effects of biochar and straw application on the soil structure and water-holding and gas transport capacities in seasonally frozen soil areas

To explore the effects of different regulation modes on the soil structure and gas transport characteristics in seasonal permafrost regions, freeze-thaw cycles (FTCs) were used as boundary conditions and three typical soils on the Songnen Plain were used: black soil, baijiang soil and meadow soil. Four treatments were established: biochar addition (B1), straw addition (S1), biochar combined with straw addition (B1S1) and an untreated control (CK). The changes in the proportion of soil water-stable aggregates, total soil porosity (TP), soil water characteristic curves (SWRCs), soil dissolved organic carbon (DOC) and soil air permeability (PL) were analyzed. The results showed that biochar and straw influenced the structure of the three soil types. The proportions of large (2–0.5 mm) and medium (0.5–0.25 mm) aggregates increased significantly. The soil aggregate stability indexes of the treated soils were better than those of the CK, and the three-phase ratios of the treated soils were closer to ideal. The different treatments had particularly obvious effects on the black soil; the generalized soil structure index (GSSI) values reached 95.59, 94.36 and 98.74 in the B1, S1 and B1S1 treatments, respectively. An interaction effect was observed between biochar and straw. B1S1 had a stronger effect than the other treatments, and the soil water holding capacity was significantly improved (FC = 0.317 cm3 cm−3). Under the B1S1 treatment, the DOC contents in black soil, baijiang soil and meadow soil were 160.78 mg/kg, 272.828 mg/kg and 271.912 mg/kg, respectively. Moreover, biochar and straw combined effectively reduced PL fluctuations under FTCs and improved the long-term stability of the soil structure. These results can aid in rational straw and biochar use to achieve comprehensive agricultural waste utilization.

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.

Why has the Brazilian economy stagnated in the 2010s? A Minskyan analysis of the behavior of non-financial companies in a financialized economy.

The Brazilian economy entered a deep recession in 2015–2016 and since then has shown a sluggish recovery. In this paper, we offer an interpretation for the slow growth based on Minsky’s financial instability hypothesis and recent literature on financialization and growth. We analyze the balance sheet of large non-financial companies over the period 2012–2019, a period that comprises the positive investment cycle—initiated during the commodities boom which lasted from the second half of the 2000s until 2014—the 2015–2016 recession, and the period preceding the shock of the COVID-19 pandemic. Based on Minsky’s taxonomy of financial profiles, we map a proxy for financial instability at the firm level based on Davis et al. (2019). We also propose an aggregate financial stability index. We conclude that after the 2015–2016 recession, companies have been restructuring their debt profile and adopting a defensive behavior, increasing their liquidity preference. Our analysis supports the interpretation that, even with the sharp fall in domestic real interest rates, the degree of confidence on expectations to recover investment in productive assets is low. This corroborates with the thesis that agents’ decisions do not respond only to supply stimulus, but are guided by expectations of future returns, which fundamentally depend on the performance of aggregate demand. Since 2015, Brazilian economic policy has been driven by fiscal consolidation, which has proven ineffective in increasing economic growth.

Soil Densification Effect on The Seismic Response of Structures Taking into Consideration Soil-Structure Interaction

Soil compaction is a considerable construction activity to ensure safety and durability, notably in the transportation industry. This technique of compaction increases soil bulk density and soil strength, while decreases porosity, aggregate stability index, soil hydraulic conductivity, and nutrient availability, thus reduces soil health. Consequently, it lowers crop performance via stunted aboveground growth coupled with reduced root growth. Therefore, if the characteristics of the soil are changed, it will affect the response of the structures. In this work, the effect of improving soil characteristics by compaction techniques on the dynamic response of foundations and structures, taking into consideration the effect of soil-structure interaction was determined. The dynamic response of foundations is presented by the impedances functions, which are determined numerically by the CONAN program, based on the cone method. In addition, the response of the structure will be presented according to the lateral displacement in each level of it. This motion vector is a function of the forces in each level; for this, the equivalent static method was applied, which allows to calculate the seismic force at the base and its distribution on the height of the structure. The results obtained show the efficiency of soil densification on the seismic response of MDOF frames.

Soil health indicators and crop yield in response to long-term cropping sequence and nitrogen fertilization

There is a need for including soil physical and biological properties along with chemical properties to accurately measure soil health and relate to crop yields. The objective of this study was to determine a suite of soil health indicators that were sensitive to cropping systems and N fertilization and relate to soil properties and dryland crop yield in a 14-yr-old cropping sequence and N fertilization study in eastern Montana, USA. Main-plot (cropping sequence) treatments were conventional till barley (Hordeum vulgaris L.)/spring wheat (Triticum aestivum L.)-fallow (CTWF), no-till continuous barley/spring wheat (NTCW), no-till barley/spring wheat-fallow (NTWF), and no-till barley/spring wheat-pea (Pisum sativum L.) (NTWP) and split-plot (N fertilization) treatments were 0 (N0) and 80/100 kg N ha−1 (N1) applied to barley and spring wheat. Barley was grown for the first six years that was replaced by spring wheat for the last eight years. The NTCW increased aggregate stability, wet aggregate stability index, average slake aggregate, P concentration, KMNO4-extractable C, CO2 flush (1 d incubation), potentially mineralizable N, and N-acetyl β-glucosaminidase (NAG), but reduced NO3-N concentration compared to other treatments. Water-stable aggregation, macro-porosity, volumetric water content at water saturation, and Mg concentration were greater with N0, but water-extractable total N and NO3-N concentration were greater with N1. Mean crop (barley/spring wheat) yield from 2006 to 2019 were greater in NTCW with N1 than other treatments. Multivariate analysis showed that phospholipid-derived fatty acid (PLFA) and CO2 flush at 4-d incubation were negatively related to Ca and Al concentrations, but positively to crop yield. Microbial abundance and activity can be used as important soil health indicators that were enhanced by no-tillage with increased cropping intensity and related to crop yield.

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.

Accumulation and relationship of metals in different soil aggregate fractions along soil profiles

Different aggregates vary in their ability to retain or adsorb metals in soil. Five soil profiles were sampled from different soil horizons and grouped, and the concentrations of Al, Mg, Ca, Fe, Mn, Cd, Cu and Pb were determined in six sizes of aggregates (> 2, 2-1, 1-0.6, 0.6-0.25, 0.25-0.053, < 0.053 mm). Significantly high (p < 0.05) structural stability indexes (SSI) and aggregate stability indexes (ASI) were recorded in the topsoil horizon, which may be attributed to the high soil organic matter (SOM) content in aggregates from topsoil. In addition, ASI and SSI were positively correlated (r = 0.569, p < 0.05) with each other, which indicated that the stability of soil aggregates could contribute to the structural stability of bulk soil. Moreover, accumulation factors (AF), principal component analysis (PCA) and Pearson's correlation coefficients were used for metal element assessment. The results indicated that SOM was not a key factor affecting the accumulation of Ca, Mg, Al, Fe, Mn, Pb, Cd and Cu in soil aggregates. In general, AF values for metal elements in microaggregates (< 0.25 mm) were high, which showed that metals preferred to accumulate in fine soil aggregates. The PCA and Pearson's correlation coefficients indicated that soil parent materials primarily controlled the distribution of Al, Ca, Fe, Mg and Mn, while materials derived from technogenic sources have important impacts on the distribution of Cd, Cu and Pb in soil aggregates along the soil profile.

Soil Sensitivity to Wind and Water Erosion as Affected by Land Use in Southern Iran

Land degradation by soil erosion is one of the most severe environmental issues that is greatly dependent on land use management. In this study, the effects of long-term land use management (including annual cultivated field (ACF), fallow field (FF), rangeland (R), and orchard field (OF)), soil depth (0–10 and 10–20 cm), and soil organic matter content (SOM) on wind- and water-erosion indices were investigated in calcareous soils of southern Iran. Soil samples were collected from four above-mentioned land-use types, and some soil properties and erosion indices were measured. Results showed that the most of soil aggregates stability indices in the surface layer (0–10 cm) of OF were higher than those in ACF, FF, and R, respectively, by nearly 39%, 32%, and 47% for dry mean weight diameter of aggregates (MWDdry); 10%, 10%, and 48% for dry geometric mean weight diameter of aggregates (GMDdry); 21%, 17%, and 15% for water-stable aggregates (WSA); and 11%, 16%, and 31% for aggregate stability index (ASI). Moreover, the mean of the soil wind erosion indicators in OF (0–10 cm) were lower than those in ACF, FF, and R, respectively, by nearly 18%, 24%, and 26%, for wind-erodible fraction (EF); 43%, 38%, and 49% for soil erodibility to wind erosion (K); and 36%, 32%, and 41% for wind erosion rate (ER). In ACF, despite the high clay content, some aggregate stability indices such as MWøDdry and WSA were the lowest among studied land-use types which showed the negative effects of conventional tillage practices. Depth factor had only a significant effect on dust emission potential (DEP) in ACF, FF, and OF. In addition, there were significant and strong correlations between SOM and MWDdry (r = 0.79), WSA (r = 0.77), EF (r = −0.85), K (r = 0.74), and ER (r = 0.74) in all datasets.

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.