Soil Structural Quality Research Articles

Effects of Terracing on Soil Aggregate Stability and Erodibility in Sloped Farmland in Black Soil (Mollisols) Region of China

Soil aggregates are important indicators of soil structure stability and quality. The black soil region of northeast China, known for its high agricultural productivity, faces significant challenges due to soil erosion. This study investigates the impact of terracing on the stability and erodibility characteristics of soil aggregates in sloped farmlands, which is crucial for this important agricultural area. Three research sites with the same basic management modes were selected along a latitudinal gradient, from the mid-temperate zone to the cold temperate zone, in the black soil region of northeast China. The Savinov method was used to analyze the differences in soil aggregate size distribution, stability characteristics, and soil erodibility between terraced and non-terraced slopes at each research site. The results showed that terracing increased the content of large soil aggregates (>0.25 mm) by 5.38–6.35%, with the increase becoming more pronounced from north to south. The improvement in soil structure varied by location and slope position, with the most significant improvement at the middle slope position. Terracing enhanced soil aggregate stability, reduced soil erodibility, and improved soil structure by increasing clay and soil organic matter (SOM) content and reducing soil bulk density (BD), promoting the conversion of small aggregates to large aggregates. Soil stability indicators such as water-stable aggregates (WSAs), mean weight diameter (MWD), and geometric mean diameter (GMD) were dominated by aggregates > 5 mm, while erodibility indicators such as fractal dimensions (Ds) and the soil erodibility factor (K values) were mainly influenced by aggregates < 0.25 mm. Terraces can improve the soil structure and stability of sloping farmland by increasing the content of large soil aggregates and enhancing overall soil quality. The benefits of these improvements increase with latitude. These findings provide critical insights for determining effective management practices for sloped farmlands in the black soil region under various site conditions. They offer scientific evidence for preventing soil erosion and improving soil quality, thus supporting the sustainable development strategy for protecting black soil and ensuring long-term agricultural productivity.

The added value of CoreVESS score and penetration resistance in predicting the soil–water retention curve

Soil hydraulic properties, such as the soil–water retention curve (SWRC), play a crucial role in simulating water transport within the vadose zone. They can be directly measured in the laboratory or field, or indirectly predicted by using Pedotransfer Functions (PTFs). It has been advocated that accounting for soil structure could marginally improve the prediction accuracy of PTFs in its wet range. The aim of this study was to test whether the use of an easy-to-determine soil structure-related variable could effectively increase the prediction accuracy of water retention curve PTFs. Additionally, we explored whether including soil strength, another soil property that is easy and quickly to determine in the field in many replicates, could improve PTF performance. Our investigation involved extensive sampling of 252 soil horizons across 42 cropped fields, each exhibiting within-field variations in soil structural degradation. Soil structure was represented by a soil structural quality score (Sq) taken from a semi-quantitative visual soil assessment (CoreVESS), which was included in the PTFs as predictor variable or as discriminator (Sq) for data grouping in addition to or instead of ‘classical’ predictors such as soil organic carbon content, clay and sand content, bulk density and soil layer. Penetration resistance (PR) was taken as a variable for soil strength. Various regression methods from classical regression to machine learning were evaluated on Train and Test subdatasets. To evaluate the effect of data grouping, the dataset was split in two based on structure and on texture. Both point and parametric PTFs were developed, with the latter predicting the parameters of the Van Genuchten (VG) water retention equation. Overall, the k-nearest neighbors PTFs (KNN-PTFs) achieved the best performance showing the highest R2 and lowest RMSE values. Moreover, the point PTFs showed much better and more stable predictive ability than parametric PTFs. The inclusion of PR as an additional predictor variable slightly improved the prediction performance in the wet range of the SWRC. Interestingly, Sq proved beneficial when substituted for bulk density but not when used in addition to it. Grouping data based on texture and structure improved the prediction accuracy of the PTFs, particularly evident in textural grouping and MLR, but not in KNN.

Assessment of Soil Structural Quality Under Area Closure and Open Grazing Land in Hidabu Abote District, North Shewa Zone, Oromia Regional State, Ethiopia

The experiment was conducted at Sire Morise kebele, Hidabu Abote district, to assess soil structural quality of different land management system (area closure and open grazing land). In this study, area closure land management practice was compared with open grazing land management practice in similar slope positions for soil structural quality build up. Soil samples were collected from both land management system at three slope position with three times replication. Totally 36 undisturbed soil blocks were collected from both land management system at 10 and 20 cm sampling depths. The finding of the study showed that the average value of volumetric moisture content and saturated hydraulic conductivity of soil were greater at area closure than open grazing land management system and also higher at bottom slope position than middle and upper slope position. The mean value of air-filled porosity and bulk density were lower at both area closure management practices and bottom slope position. Bulk density, volumetric soil moisture content and saturated hydraulic conductivity at 20 cm sampling depth were shows significantly different with respect to management practices. According to visual assessment in the field, soil physical quality was unfavourable in open grazing land management system and upper part of landscape position soils and the visual assessment scores showed that the soils under area closure had a good soil structural quality. There were strong relations among the three visual field assessment methods and also between visual assessment methods and laboratory determined soil properties of both land management system. In general, the result of the study showed that physical and structural quality of soil in area closure was improved due to good land management system. Based on the result of study it can be conclude that area closure improves soil physical and soil structural qualities and from the technical point of view, open grazing lands in hilly area should be changed to area closure before soil properties and soil nutrient contents are exhausted more.

Mapping Topsoil Behavior to Compaction at National Scale from an Analysis of Field Observations

Soil compaction is one of the most important and readily mitigated threats to soil health. Digital Soil Mapping (DSM) has emerged as an efficient method to provide broad-scale maps by combining soil information with environmental covariates. Until now, soil information input to DSM has been mainly composed of point-based quantitative measurements of soil properties and/or of soil type/horizon classes derived from laboratory analysis, point observations, or soil maps. In this study, we used field estimates of soil compaction to map soil behavior to compaction at a national scale. The results from a previous study enabled clustering of six different behaviors using the in situ field observations. Mapping potential responses to soil compaction is an effective land management tool for preventing future compaction. Random forest was used to make spatial predictions of soil behavior to compaction over cultivated soils of mainland France (about 210,000 km2). Modeling was performed at 90 m resolution. The map enabled us to spatially identify clusters of possible responses to compaction. Most clusters were consistent with known geographic distributions of some soil types and properties. This consistency was checked by comparing maps with both national and local-scale external sources of soil information. The best spatial predictors were available digital maps of soil properties (clay, silt, sand, organic carbon (SOC) content, and pH), some indicators of soil structural quality using SOC and clay content, and environmental covariates (T °C and relief-related covariates). Predicted maps were interpretable to support management recommendations to mitigate soil compactness at the soil–scape scale. Simple observational field data that are usually collected by soil surveyors, then stored and available in soil databases, provide valuable input data for digital mapping of soil behavior to compaction and assessment of inherent soil sensitivity to compaction.

Traffic induced compaction and physical quality of grassland soil under different soil moisture deficits

Soil compaction is widely recognised as one of the key contributors to soil degradation in Europe. Information is needed for farmers and land managers to guide management decisions and prevent traffic-induced soil compaction. Predicted soil moisture deficit (SMD) from the hybrid SMD model may provide information on when soil conditions are suitable for machinery trafficking. The objective of this study was to investigate the relationship between soil water content and traffic induced soil compaction and if a predicted SMD threshold level could be identified, above which soils can be trafficked without significant soil compaction occurring. The study also evaluated the capacity of selected soil physical indicators such as soil bulk density and water stable aggregates to indicate soil physical degradation across a range of soil water contents. The experiment was carried out on grassland with moderately drained soil, located in Wexford, Ireland. Machinery trafficking of the soil with a tractor equipped with a fully loaded slurry tanker, was assessed in the field across the four seasons of the year. Traffic was imposed at target predicted SMD + 10 mm (relatively dry soil), 0 mm (relatively moist soil), and −10 mm (relatively wet soil). After each traffic event, samples were taken in the middle of the wheel track at three depths (0–10, 10–20 and 20–30 cm) to assess soil bulk density. Water aggregate stability was evaluated at the same three depths following the fourth traffic event. Results showed that when planning field machinery operations, especially repeated trafficking events, soil becomes prone to physical degradation when predicted SMD ≤ 0 mm. Traffic on soil at predicted SMD 0 mm (close to field capacity) lead to compaction after two traffic events. However, when predicted SMD was −10 mm, soil bulk density indicated no significant difference from the non-trafficked soil. When water-stable aggregates were measured on the predicted SMD 0 mm and −10 mm trafficked soils, it indicated physical degradation of soil. Hence, bulk density alone did not give an accurate indication of soil structural quality when soils where trafficked under relatively wet or saturated conditions (SMD −10 mm). These results indicate that avoiding machinery trafficking of grassland soils at predicted SMD ≤ 0 mm will help protect soil physical structure. On soils where multiple machinery operations are likely to occur over the year, trafficking when the predicted SMD > 0 mm is recommended to minimise loss of soil physical quality.

Conservative farming systems and their effects on soil organic carbon and structural quality

Pesticides-free integrated farming systems emerge as a viable option to promote environmental protection, due to the diversification of the agroecosystem, making the soil productive and resilient. However, there is a lack of information about the influence of integration farming systems on the relationship between soil physical quality and organic matter. The objective was to determine soil organic carbon fractions, and soil structural attributes in conservative single and integrated farming systems, to verify the potential of these farming systems to increase soil organic carbon stocks and improve soil structural quality. The experiment was carried out at a pesticide-free agricultural systems. Soil samples were collected in three layers (0–0.05, 0.05–0.10, and 0.10–0.20 m) of five farming systems (Cropland - C, Livestock - L, Forestry - F, Livestock-Forestry – LF, and Crop-Livestock-Forestry - CLF) in the randomized block design. Sampling was carried out in two transects of 25 m each, collecting five samples per transect, totaling 10 samples per layer. The following soil attributes were determined: soil organic carbon (SOC), particulate organic carbon (POC), mineral-associated organic carbon (MAOC), soil organic carbon stocks (Cst), visual evaluation of soil structure (VESS), tensile strength of aggregates (TS), soil friability, weighted mean diameter (WMD), geometric mean diameter (GMD) and the aggregate stability index (ASI). At 0–0.05 m, the SOC content was up to 12% higher in the Cropland system compared to other farming systems, while at 0.05–0.10 m and 0.10–0.20 m of depth, the difference was higher, around 27% between Cropland and other farming systems. For the VESS, Cropland had the lowest score (1.35), while the higher scores were in the Forestry, and CLF systems (2.25, 2.24, respectively). Both soil organic carbon and soil physical quality were greater in all farming systems. The particulate organic carbon and weighted mean diameter were efficiently to promote changes in soil carbon inputs and structural changes. The single and integrated farming systems promoted an increase in soil organic carbon, by a rate of 3.02, 1.81, 2.17, 1.78, and 2.01 Mg ha−1 yr−1, respectively for Cropland, Livestock, Forestry, LF, and CLF. The pesticide-free farming systems, under conservative practices, were very promising in showing the increase of SOC, POC and MAOC, supporting the soil physical quality, and cooperating with the soil health.

Long-term soil quality and C stock effects of tillage and cover cropping in a conservation agriculture system

Conservation and regenerative agriculture are widely considered as approaches aiming at addressing challenges in relation to climate change and soil quality. In that respect, no tillage (NT) and use of cover crops (CCs) are seen as key elements in achieving the sustainability goals of these approaches, but the long-term individual and interactive effects of these elements remain unknown. We examined the impact of tillage (NT and mouldboard ploughing) combined with a fodder radish CC in continuous cereal cropping. Soil was sampled in the 0–10 and 10–20 cm layer after two decades of treatments in the CENTS experiment at AU Viborg (Denmark) situated on a sandy loam with 9% clay. We assessed soil structural quality, SOC stocks, clay dispersibility (CD), wet stability of aggregates (WSA) and soil pore characteristics. Neither tillage nor cover cropping affected the SOC stock in the 0–20 cm soil layer. No tillage improved CD, WSA and plant available water capacity in 0–10 cm depth as compared to ploughing. The marked improvement in CD and WSA of NT soils could not be explained by SOC per se, but rather positive effects ascribed to absence of disturbance. In contrast, soil porosity, especially in 10–20 cm depth, the fraction of soil volume represented by >30 µm pores and gas diffusivity decreased, and NT soils resulted in a less good soil structural quality. The inclusion of CCs improved soil structural quality and the functionality of the soil macropore system. Hence, CCs have the potential to alleviate negative effects of NT on pore characteristics at macroscale. Furthermore, we found that the positive effects of NT on CD and WSA and of CCs on pore characteristics at macroscale were much more pronounced after long- (20 yrs NT; 13 yrs CC) than after medium-term (10 yrs NT; 5 yrs CC) underlining the value of long-term conservation agriculture experiments.

Soil organic matter thermal pools as influenced by depth, tillage, and soil texture – A Rock-Eval® analysis study on the cropland soils of the Swiss Plateau

This study investigated the relationships between the soil organic matter content (SOM), SOM thermal pools, soil properties, and tillage practices, on cropland soils of the central plateau of Switzerland. Soil samples were collected in 45 no-till and conventional tillage fields in five layers from 0 to 40 cm depth. Soil organic carbon content (SOC) and hydrocarbon compound (HC) pools were analysed with Rock-Eval® thermal analysis. In addition, the clay content was determined by sedimentation.The SOM contents were highest in 0–5 cm of no-till soils and the plough pan of tilled soils. SOM was less oxygenated and showed lower degradation under conventional tillage then no-tillage. The proportion of the thermo-stable pool was mainly explained by the SOC:clay ratio, regardless of tillage practices. Below a SOC:clay ratio of 0.08, all pools were decreasing nearly equally with decreasing SOC. Above this ratio, thermo-stable pools increased only slightly, while thermo-labile pools increased linearly with SOC:clay on the full SOC:clay range. The 0.08 SOC:clay threshold in the thermo-stable pools content corresponded to the lower threshold of structure stability determined for Swiss and UK soils, below which, on average, severely degraded structures are observed in the field. These findings suggest that a large proportion of thermo-labile pool is necessary for acceptable to high soil structure quality, to protect the thermo-stable forms from degradation, and to reach the carbon sequestration potential of the soil.

The organic carbon‐to‐clay ratio as an indicator of soil structure vulnerability, a metric focused on the condition of soil structure

AbstractThe soil organic carbon to clay ratio (SOC:clay) is a metric used in soil quality management. In Switzerland and the United Kingdom, for example, threshold values for SOC:clay ratios have been determined to indicate very good (>1:8) to degraded (<1:13) soil structures. A recent article in Soil Use and Management by Poeplau and Don, however, suggested that this metric is ‘strongly biased and misleading’, based on their observation that German sandy soils and heavy clay soils tend to show very high and very low SOC:clay ratios, respectively. An alternative metric was proposed based on the ratio of actual SOC to expected SOC level for a considered area. We offer a commentary on the proposal, arguing that because soil structure quality is overlooked by the approach, it fails to provide appropriate SOC levels for soil health and could lead to soils with highly depleted SOC being classified ‘good’. The SOC:clay ratio, on the other hand, does address soil structure condition, providing a structure vulnerability index, a key function independent of local soil management conditions. When soils are found to have high structure vulnerability, as indicated by the SOC:clay ratio, the cropping practices at the site should be investigated and ways to increase the SOC content considered. Structure condition threshold values may only need to be reassessed if it is shown that the average structure quality observed is not in conformity with the present thresholds, which would be expected for some soils, such as Andosols.

Soil physical quality response to management systems in a long‐term sugarcane trial

AbstractIn order to support sugarcane growth for biofuel production without compromising the environmental sustainability, this work aims to assess the physical quality of soils cultivated under different long‐term tillage and management systems to identify the system that most contributes for a sustainable sugarcane production. Visual assessments and soil sampling to determine physical soil quality indicators were performed in sugarcane plots managed with no‐tillage (NT) and conventional tillage (CT) with 0 (CT0–NT0) and 4 (CT4–NT4) Mg ha−1 of lime and in an adjoining area with native forest. In general, the results from traditional indicators showed no statistical difference between the different sugarcane cultivation systems and the different depths, so were not sensitive to identify the best tillage and management system in relation to soil physical quality for soils cultivated with sugarcane. However, even without statistical difference, three indicators presented limiting values for plant growth and development (Bd, ASW, and S index) in at least two sugarcane cultivation systems and one depth. Although all the systems showed a good soil structural quality in surface, the visual assessments suggest a poor and unsatisfactory soil structural quality in the subsurface of CT0, CT4, and NT0 (3.7 ± 0.2, 3.3 ± 0.6, and 3.7 ± 0.7 in Visual Evaluation of Soil Structure [VESS] and 2.2 ± 0.3, 3.1 ± 1.0, and 3.6 ± 1.1 in Rapid Diagnosis of Soil Structure [DRES], respectively), requiring immediate management changes, while structural quality in NT4 (2.6 ± 0.9 and 3.9 ± 0.7, in VESS and DRES, respectively) was considered good. Thus, NT4 is suggested as the tillage and management system that least compromises structural quality of soils cultivated with sugarcane, and it is considered a viable alternative to promote soil conservation, as well as environmental and economical sustainability for sugarcane cultivation, as this system corrects soil acidity, minimally disturbs the soil, and maintains the soil cover, thus delivering ecosystem services.

Assessing soil structural quality as an indicator of productivity under semi-arid climate

A near real-time evaluation of the management system's impact on soil conditions requires a quick and straightforward framework to help farmers with a reliable on-farm assessment. The visual soil evaluation methods can potentially be used as a reliable on-farm approach for assessing soil physical quality. This research aims to better understand the importance of visual soil evaluation for productivity in semi-arid climates. The objectives were to evaluate the ability of Visual Evaluation of Soil Structure (VESS) and Double Spade (DS) under agricultural systems in a semi-arid region and to assess the relationship between soil structural quality and crop yield. Forty arable sites under rain-fed and irrigated farming with crop rotation and mono-cropping systems were studied, and twenty-one physical and bio-chemical soil properties were determined at two depths (0–20 cm and 20–40 cm). VESS and DS were conducted at each farm. The reliability of visual approaches was evaluated using measured soil properties and their capability to detect the impact of management systems. Soil quantitative measurements and crop yield information were deployed to assess soil productivity and its relationship with soil physical quality. The overall assessment of soil properties indicated a better soil condition for irrigated farming with crop rotation. The visual scores were in a range of 1.5–3.4 for VESS and a range of 1.9–3.5 for DS. The mean scores of VESS and DS were different between rain-fed and irrigated farms (P < 0.05), and visual methods were able to differentiate between mono-cropping and crop rotation (P < 0.05). The best soil structural quality was associated with the highest level of crop yield, and visual approaches were able to detect the differences in wheat yield levels (P < 0.05). The scores of VESS and DS were significantly correlated with soil properties (r > 0.6). Both VESS and DS indicated good efficiency for a practical on-farm assessment of soil conditions under agricultural management in northwest Iran and similar ecosystems. A close relationship between crop yield and soil structural quality was obtained, which indicated that the optimum soil structural condition plays an important role in the sustainability of crop production in semi-arid cultivation.

Visual evaluation of soil structure in low‐intensity land use systems of steppe zone of Ukraine

AbstractThe network of natural forests and shelterbelts is a crucial element of agroforestry systems for the efficient and environmentally sustainable land use in Ukraine. From 2016 to 2021, we studied the quality of black soils structure under steppe wildland herbaceous vegetation, man‐made tree plantations of Robinia pseudoacacia L. and Quercus robur L., and native forest vegetation of ravines and floodplains in the steppe zone of Ukraine. According to the visual evaluation of soil structure (VESS) scores, the content of the agronomically valuable fraction (AVF), soil organic carbon (SOC) and earthworm casts, native forest soils (Chernozems and Phaeozems) had a significantly (p &lt; .05) higher soil structural quality in 0–25 cm layer as compared with the Chernozems under the steppe vegetation and shelterbelt plantations. In the conditions of steppe landscapes, VESS methods were shown to provide efficient diagnostics to differentiate the black soil structural quality of low‐intensity land use systems, that is steppe wildlands, shelterbelts, native forests: VESS indicators significantly (p &lt; .05) correlated with quantitative characteristics of soil structure. The most significant dependence was found between VESS parameters and earthworm casts content. The need to improve VESS method was demonstrated, that is to assign higher weight to the earthworm bioturbation process as one of the key indicators of soil structural quality.

Unearthing Soil Structure Dynamics under Long-Term No-Tillage System in Clayey Soils

Soil structure is a sensitive and dynamic soil physical property that responds rapidly to different tillage systems, and thus it requires constant monitoring and evaluation. The visual evaluation of soil structure (VESS) and subsoil visual evaluation of soil structure (SubVESS) methods were used to assess the soil structure quality of clayey soils subjected to different tillage systems. The tillage systems were no-tillage (NT) and conventional tillage (CT), with virgin fields (VGs) used as controls. The study was conducted at Tshivhilwi and Dzingahe in Thohoyandou, Vhembe District, Limpopo Province, South Africa. The soil structure quality at Tshivhilwi, as determined by VESS and SubVESS, was found to be poor. However, at Dzingahe, both the VESS and SubVESS scores responded to the impact of tillage. VESS showed a fair (Sq = 2.25) soil structural quality in the NT system, poor quality (Sq = 3.57) in the CT system and moderately poor quality (Sq = 3.05) in the VG. Similarly, at the same location, the SubVESS scores were moderately good in the NT system, moderately poor for the CT system and fair in the VG. The differences in the responses of VESS and SubVESS at the two locations were attributed to differences in the duration of the NT system. The VESS and SubVESS results were supported by selected measured soil physico-chemical properties such as bulk density and porosity. In conclusion, the findings of this study showed that VESS and SubVESS were able to effectively differentiate between the impacts of tillage systems on soil structural quality. The soil structure quality was better under NT than CT at Tshivhilwi and Dzingahe.

English

Millets are becoming popular due to special features of high nutrition, low inputs, and climate resiliency. While major crops like wheat, rice &amp; maize are exhaustive, resource-loving, and susceptible. There is a need for crop diversification &amp; potential millets to be adapted for sustainability. Faisalabad is the grain belt of Punjab, Pakistan, but only one millet crop, pearl millet, is being cultivated for grain purposes. An alternate crop, foxtail millet study was designed, and 200 exotic accessions of different origins were acquired from the USDA. Germination behavior at optimal controlled temperatures (18 °C, 25°C, 32°C, and 39 °C) was tested, best germination was observed at 32 °C, and 135 out of 200 accessions germinated at ≥80%. These accessions were initially screened for germination strength (G%, G50, MGT, U, GI, Z, and CVG), seedling vigor (SL, RL, SFW, SDW), and preliminary yield tests in the greenhouse, then evaluated under three different field locations of varied soil environments. Principle component analysis (PCA) was performed, and 14 clusters of accessions were sorted out using hierarchical clustering. The high-yielding accessions were selected from each cluster and sown at three different locations/soil environments in the Faisalabad, i.e., 1- ARA, UAF (fertile, low irrigated), 2= DFP, UAF (salt-affected soil), 3= JKA, CJF (fertile, well-irrigated). Results were statistically analyzed &amp; graphically represented using project R for statistical computing. Accessions A73-IN and A101-IN produced the highest grain yield of 3504 kg ha-1 and 2667 kg ha-1 respectively, and a biomass accumulation of 8 t ha-1 at the location JKA, CJF. Yield-related results under low irrigation &amp; saline soil were also significant, however, overall, 69% of yield was reduced in the saline and 67% in low irrigated fields. It was concluded that accessions of Indian origin may be adapted under Faisalabad climate and an additional inquiry into abiotic stresses is required to discover suitable genotypes

Estimation of generalized soil structure index based on differential spectra of different orders by multivariate assessment

Better soil structure promotes extension of plant roots thereby improving plant growth and yield. Differences in soil structure can be determined by changes in the three phases of soil, which in turn affect soil function and fertility levels. To compare the quality of soil structure under different conditions, we used Generalized Soil Structure Index (GSSI) as an indicator to determine the relationship between the “input” of soil three phases and the “output” of soil structure. To achieve optimum monitoring of comprehensive indicators, we used Successive Projections Algorithm (SPA) for differential processing based on 0.0–2.0 fractional orders and 3.0–10.0 integer orders and select important wavelengths to process soil spectral data. In addition, we also applied multivariate regression learning models including Gaussian Process Regression (GPR) and Artificial Neural Network (ANN), exploring potential capabilities of hyperspectral in predicting GSSI. The results showed that spectral reflection, mainly contributed by long-wave near-infrared radiation had an inverse relationship with GSSI values. The wavelengths between 404-418 nm and 2193–2400 nm were important GSSI wavelengths in fractional differential spectroscopy data, while those ranging from 543 to 999 nm were important GSSI wavelengths in integer differential spectroscopy data. Also, non-linear models were more accurate than linear models. In addition, wide neural networks were best suited for establishing fractional-order differentiation and second-order differentiation models, while fine Gaussian support vector machines were best suited for establishing first-order differentiation models. In terms of preprocessing, a differential order of 0.9 was found as the best choice. From the results, we propose that when constructing optimal prediction models, it is necessary to consider indicators, differential orders, and model adaptability. Above all, this study provided a new method for an in-depth analyses of generalized soil structure. This also fills the gap limiting the detection of soil three phases structural characteristics and their dynamic changes and provides a technical references for quantitative and rapid evaluation of soil structure, function, and quality.

Greening and browning of urban lawns in Geneva (Switzerland) as influenced by soil properties

Urban green spaces with healthy vegetation play a key role in improving the quality of life in cities. However, urban soils, the basis of the urban greenery, are under strong anthropogenic influence and can considerably differ from natural soils. In this study, we observed short-term greening and browning of lawns during one vegetation period in urban parks of Geneva (Switzerland). We related the temporal trajectory of seasonal Normalized Difference Vegetation Index (NDVI) (8 days median) as a proxy of vegetation condition at different test sites to the physical soil properties (soil depth, coarse material, bulk density, conditioned air and water content) and Soil Organic Carbon (SOC). Strong drops of NDVI during dry periods in summer were related to shallow soil depths (<40 cm) and a high amount of coarse material (>10%) as well as lower SOC. Bulk density of the fine earth and the soil structure quality (expressed by air and water content of soil cores conditioned at a soil water potential of −100 hPa) had a significant influence on grass growth in spring but not in summer. Dense soils with conditioned air content closer to the trigger value of degraded soil structure resulted in lower NDVI values in spring. Our approach of using Earth Observation (EO) data for observing short-term greening and browning patterns, in this case the rise and decline of NDVI values, revealed that the role of the soil properties changed with the season. This approach may contribute to digital soil mapping and the assessment of soil ecosystem services in urban contexts. Urban planners are advised to save natural soils from over-building and keep them for green spaces. If soil has to be restored to create new green spaces, it should be deep and should not contain much coarse material, even for grassy vegetation.

Structural soil quality and system fertilization efficiency in integrated crop-livestock system

The nutrient use efficiency in integrated crop-livestock systems under system fertilization may be related to soil structural variations caused by grazing. These hypothetical cause-effect relationships are not known, which reflects a limited understanding of the underlying processes. This study evaluated the association between soil structural quality and system fertilization efficiency of phosphorus and potassium in an integrated crop-livestock system and a pure crop system. The treatments were two fertilization strategies (system fertilization and crop fertilization) in a factorial scheme with two production systems (an integrated crop-livestock system and a pure crop system) distributed in a randomized block design with four replicates. In the pure crop system, soybean was grown followed by Italian ryegrass as a non-grazed cover crop. In the integrated crop-livestock system, the ryegrass was grazed by sheep. In the crop fertilization strategy, phosphorus and potassium were applied at the soybean planting, and nitrogen in the ryegrass establishment. In the system fertilization strategy, nitrogen, phosphorus, and potassium were applied during the establishment of ryegrass. Soil physical quality indices were calculated for the beginning, middle, and end of the pasture phase (2020) and at the soybean harvest (2021). Forage and soybean production were also evaluated. Based on the soil physical quality index, the soil’s ability to perform its physical functions decreased from 94% under an integrated crop-livestock system to 89% under a pure crop system. The results indicated higher total forage production (36%) and soybean yield (13%) in the system fertilization strategy as compared to the crop fertilization strategy. Moreover, the integrated crop-livestock system produced more forage (31%) and soybean grains (15%) than the pure crop system. The study provides the first evidence that higher structural quality of soils in an integrated crop-livestock system favors crop yields at all stages of production. However, the nutrient use efficiency in system fertilization is only partially explained by the soil’s physical quality.

Grassland Ecosystem Progress: A Review and Bibliometric Analysis Based on Research Publication over the Last Three Decades

Understanding the grassland ecosystem is crucial for improving grassland ecosystem functions and services such as climate regulation, water and soil conservation, carbon sequestration, and biodiversity and gene pool maintenance. However, a systematic and comprehensive review of the relevant literature is still unclear and lacking. The VOSviewer software and cluster analysis were used to visually analyze and perform dimension reduction classification on the 27,778 studies related to grassland ecosystem research based on the Web of Science database. The number of publications targeting grassland ecosystem increased rapidly from 2006 to 2021. Ecology, agronomy, and environmental science were the most popular research categories, and the top journal sources were Remote Sensing, Journal of Ecology, and Ecology and Evolution. The leading publishing countries were the United States, China, and Germany. The top three institutions were the Chinese Academy of Sciences, the University of Chinese Academy of Sciences, and Colorado State University. Cooperation between different countries and institutions had increased. Keyword co-occurrence network analysis showed that Biodiversity, Vegetation and Conservation were the most popular study areas, grassland management, climate change, land use pattern, and ecosystem impact were the hot research topics. All studies could be divided into three categories by cluster analysis: grassland ecological characteristics including basic physicochemical properties, vegetation community characteristics, aboveground and belowground biomass, and soil structural quality of grassland; driving mechanisms that demonstrated effects of human activities and climate change on grassland ecosystem function; and grassland ecosystem services that focused the influences of different grassland management strategies on ecological services, animal welfare and human well-being. The three topic categories of reviewed studies were interrelated and consistent with each other, and the performances were progressive. This paper reviewed the trend evolution through keyword hotspots and analyzed the future research directions to provide an important reference for scientists to better respond to the balance of herbage and sustainable utilization of grassland and maintenance of ecological security.

Soil organic carbon content and soil structure quality of clayey cropland soils: A large‐scale study in the Swiss Jura region

AbstractSoil organic carbon (SOC) fashions soil structure, which is a key factor of soil fertility. Existing SOC content recommendations are based on SOC:clay ratio thresholds of &gt;1:10. However, the corresponding SOC content might be considered hard to reach in clayey soils, whose structure degradation risk is assumed to be high. Here, we analysed the SOC content and soil structure quality of soils under similar cropping practices with clay contents ranging from 16% to 52%. Five undisturbed soil cores (5–10 cm layer) were collected from 96 fields at 58 farms in the Swiss Jura region. We assessed the soil structure quality visually using the CoreVESS method. Gravimetric air content and water content, and bulk density at −100 hPa were also measured, and the soil structure degradation index was calculated. We found that the relationship between SOC and clay content held over the clay content range, suggesting that reaching an acceptable SOC:clay ratio is not limited by large clay contents. This suggests that the 1:10 SOC:clay ratio may remain useful for clayey soils. In contrast to what was expected, it is not more challenging to reach this ratio in clayey soils even if it implies reaching very large SOC contents. SOC content explained the considered physical properties better than clay content. From a soil management point of view, these findings suggest that the soil texture determines a potential SOC content, while the SOC:clay ratio is determined by farming practices regardless of the clay content.

Soil structural quality and development of second-crop corn intercropping with forage grasses under no-tillage

Soil structural quality and development of second-crop corn intercropping with forage grasses under no-tillage