Abstract The intensification of global agriculture has led to excessive fertilizer use, posing significant challenges to sustainable agricultural development. Organic fertilizers, rich in organic matter, improve soil structure by enhancing aeration and water retention, making them widely adopted for cultivating economic crops such as tobacco. Despite the rich organic matter content of tobacco stalks, their natural decomposition can contribute to long‐term soil acidification, resulting in their underutilization as organic fertilizers. Here, the present study conducted field experiments to assess the feasibility of using composted tobacco ( Nicotiana tabacum L. ‘CB‐1′) stalks to enhance tobacco production. The analysis focused on soil nutrient levels, plant agronomic traits, microbial community composition and function, and associated production costs, offering a comprehensive evaluation of this approach's potential to improve sustainability in tobacco cultivation. As a results, tobacco stalk compost (T2) significantly elevated soil pH and nitrogen levels compared to traditional organic fertilizers (T1). Agronomic assessments revealed superior growth performance in T2, with single‐leaf area increasing by 11.0% compared to T1, respectively. Economic output value analysis indicated that T2 achieved 13.5% higher profitability than T1. Microbial community analysis showed enhanced diversity and stability under compost treatment, accompanied by proliferation of unique taxa and increased abundance of microbiome involved in nitrogen and sulfur cycling. Additionally, T2 exhibited greater cost‐effectiveness, reducing production costs by 171.1 Chinese yuan (RMB)/t compared to T1. Overall, our findings demonstrate that T2 not only improves soil ecological health and crop productivity but also serves as an economically viable alternative to T1.

Abstract Soil detachment capacity ( D c ) is a key parameter for characterizing the soil erosion process. Polyacrylamide (PAM) mitigates soil erosion, but the mechanism by which it acts on soil–rock mixtures is unclear. This study investigated the impact of applying PAM on detachment of soil–rock mixtures and predicted D c using machine learning models. Small‐sample scouring tests were conducted in a flume with a 30° slope, under flow discharges of 4, 8, 12, 16, and 24 L·min −1 ; gravel content of 0%, 10%, 30%, 50%, and 70%; and PAM (anionic type, molecular weight 12 million, degree of hydrolysis 20%) application rates of 0, 1, 2, 3, 4, and 5 g·m − 2 . When flow discharge was lower than 16 L·min −1 , the best D c inhibition effect was achieved by applying 4 g·m −2 PAM rate. From 16–24 L·min −1 , the optimal application rate of PAM for D c inhibition varied according to gravel content: 3 g·m −2 for gravel content of <50% and 4 g·m −2 for gravel content of 50%–70%. PAM primarily influenced D c indirectly by enhancing shear strength, but as gravel content increased, PAM effect on shear strength reduced. At 30% gravel content, the soil–rock mixture was more stable, and D c remained consistently low. The extreme gradient boosting model trained using four parameters (PAM application rate, gravel content, shear strength, and stream power) outperformed multiple regression equations when used to predict D c .

Abstract In the karst region of southwestern China, limited land resources and intense human‐land conflict pose challenges to sugarcane ( Saccharum officinarum L.) cultivation, a key economic crop. Sloping farmland is particularly vulnerable to water erosion, causing soil, water, and nutrient losses that hinder sustainable agriculture. Results show that runoff and sediment production vary significantly ( p < 0.05) with rainfall intensity and sugarcane growth stages. Compared to conventional downslope tillage, contour tillage combined with straw mulching and trenching reduced runoff and sediment yield by 39.90% and 88.32%, respectively. Nutrient loss was mainly driven by sediment transport, with nutrient retention varying among tillage methods. Contour tillage with straw mulching and trenching effectively retained soil organic carbon, total phosphorus, alkali‐hydrolyzable nitrogen, available phosphorus, and available potassium, while contour deep tillage with biochar was more effective in preserving total nitrogen and total potassium. Path analysis revealed that sediment yield had stronger correlations and path coefficients with nutrient losses than with runoff. These findings provide a scientific basis for soil and water conservation strategies and the selection of sustainable tillage practices for sloping farmland in karst regions.

Abstract Tillage and cover cropping are known to affect soil water dynamics and crop evapotranspiration (ET), and consequently, water footprint (WF) of crop production and economic return. In this study, two tillage practices (conventional tillage [CT] and no‐tillage [NT]) and cover crop (CC) treatments (Austrian winter pea [ Pisum sativum ] CC and no‐CC [NC]) were investigated to quantify soil water balance, ET, and WF of yield and revenue for cotton ( Gossypium hirsutum ) and sorghum ( Sorghum bicolor ) production. Soil volumetric water content was measured from 0‐ to 120‐cm depth from May to October in 2020 and 2021. Runoff, deep percolation, and ET were modeled using the root zone water quality model (RZWQM2), and WF was determined as m 3 of water consumed per kg of yield or unit revenue. The RZWQM2 performance was acceptable, validated by low residual errors. Pooled across years, CT treatments depleted soil water storage by 9% and 7% over the season in cotton and sorghum, respectively, which was 6% and 7% for NT. No‐till reduced the runoff by 31% over CT when averaged across years and cash crops. The NTCC (no‐tillage, cover crop) minimized ET, compared to NTNC (no‐tillage, no cover crop) and CT treatments, particularly in sorghum. Tillage increased the WF of yield and revenue for cotton by 7% and 6% over NT treatments, respectively. In sorghum, neither tillage nor cover cropping altered the WF outcomes. Overall, cover cropping and conservation tillage could be used to complement each other to minimize the WF of cotton and sorghum production in the humid Lower Mississippi River Basin.

Abstract Direct measurements of free‐living nitrogen fixation (FLNF) using 15 N‐labeled dinitrogen ( 15 N 2 ) have been complicated by a lack of standardization regarding soil sampling and storage, and because key incubation parameters have yet to be systematically optimized. With the aim of developing a standardized protocol for laboratory assay of carbon (C)‐stimulated FLNF, studies with four Illinois soils were conducted with respect to sampling depth, storage condition and period, surface exposure, moisture content, C source and pH, phosphorus (P) amendment, and incubation period. Among the major findings, diazotrophic activity was greatest with surface (0−7.5 cm) sampling, and storage effects were minimized when field‐moist samples were kept at room temperature (25°C) or in a refrigerator (5°C) for ≤1 day with or without sieving (<2 mm). In the presence of exogenous C (4 mg C g −1 dry soil), the rate of 15 N 2 fixation was maximized at ≥200% water‐holding capacity, with a 3‐day incubation period, and by increasing atmospheric exposure with the use of a shallow soil container. A simulated corn ( Zea mays L.) root exudate was identified as the optimal C source, regardless of a divergent preference observed for soil samples collected before and after a 6‐month interval. By standardizing several key parameters pertinent to the measurement of C‐stimulated FLNF, the work reported can help facilitate research to define the ecological importance and agricultural potential of a process that has largely been unexplored in the soil N cycle.

Abstract Particle size is a key factor in shaping water and air retention properties and drainage capacity of growing media. Thus, manufactured growing media are made of screened, crushed, or sieved raw materials whose particle sizes are adapted to cropping objectives. The relationships between the particle size distribution of the growing media constituents and the resulting structure are, however, not well known, which requires better understanding of particle arrangement and its change with water upon shrinkage. A proper characterization of the structure would help to guide substrate manufacturing, which is inherently complex due to the use of various materials made up of heterogeneous particles in terms of size and shape. To this aim, we analyzed the shrinkage of white and black peats, coir, pine bark and wood fiber, raw material, and derived particle size fractions extracted by sieving. Hyprop systems coupled to linear vertical displacement transducers were used to determine the shrinkage curves. The dual porosity shrinkage XP model (XP model) was used to analyze the hydrostructural behavior of the different growing media constituents. The possible distinction of interparticle and intraparticle pores, based on the dual pore system assumption of the shrinkage model, was discussed. Interparticle porosity volume represented the major part of the total porosity, whatever the materials and particle size fractions. Greater volume shrinkage of interparticle porosity was observed for the smaller particle size fractions of materials. Conversely, intraparticle porosity volume shrinkage is of the same magnitude for all particle size fractions. The use of the XP model to study growing media is relevant, although no residual domain on the shrinkage curves was observed. This work revealed that particle arrangement and physical behaviors during drying of materials depend on the nature of constituents but also highly on particle size fraction. These results provide a complementary approach for characterizing the pore functional properties of growing media.

Abstract Soil health underpins ecosystem services and sustainable agriculture. This study compared soil health properties among three long‐term land‐use systems in Trans Nzoia, western Kenya: biointensive agriculture (BIA), natural shrubland reserve, and conventional maize monocropping. Soil health was assessed primarily through chemical and biological indicators, with bulk density (BD) included as the measured physical property. Soil texture was also determined across sites, providing context as an inherent and potentially management‐influenced property. Soil samples (from 0‐ to 5‐cm, 5‐ to 15‐cm, 15‐ to 30‐cm, 30‐ to 60‐cm, and 60‐ to 100‐cm depths) were analyzed for microbial biomass carbon and nitrogen (MBC), dissolved organic C, total dissolved N (TDN), potential mineralizable C and N, total N (TN), total C (TC), TN stocks, TC stocks, bulk density, and soil texture. Several soil health indicators were higher in BIA and shrubland than in maize, especially at 0–5 cm. At this depth, MBC (BIA vs. maize: +117%) and TDN (nature reserve vs. maize: +141%) were greater. TC (BIA vs. maize: +69%) and TN (shrubland vs. maize: +58%) stocks were also higher. BIA had the lowest BD (1.07 g cm −3 at 0–5 cm) compared to maize (1.27 g cm −3 ), consistent with better aeration and root penetration. While recognizing that observed differences reflect the combined influence of management history and inherent site properties, these case comparisons suggest that BIA management is associated with higher C and N stocks, enhanced microbial biomass, and reduced compaction. Adopting BIA could help mitigate soil degradation and support agricultural sustainability in smallholder systems.

Abstract Organic inputs are vital to sustainable agriculture because of their capacity to improve soil nutrients and nourish soil microbial communities. However, it is still not well known how organic inputs modify soil microbial functions. Here, we studied the effects of cover crop inclusion and manure compost amendment on maicrobial communities in sandy soils under organic vegetable production. Two manure composts (with and without) and four cover crop treatments, that is, cereal rye ( Secale cereale L.), hairy vetch ( Vicia villosa ), the mixture of the two, and no cover crop control, were fully crossed and established in the fields in 2020. After 2 years of repeated treatments, soils were collected for biogeochemical and microbial analyses in 2022. We found limited treatment effects on microbial alpha diversity, but both manure compost application and cover crop inclusion altered microbial community structure, in which cereal rye and hairy vetch had distinct effects. In addition, hairy vetch and cereal rye increased the abundances of dominant soil bacterial and fungal taxa, respectively. Organic inputs altered C and N‐cycling extracellular enzyme activities (EA), which correlated with soil biogeochemical properties and microbial diversity. The changes in predicted microbial functions are likely to have a significant impact on long‐term soil fertility.

Abstract Soil structure is an important feature that facilitates water infiltration, storage, and transport into the profile, as well as affecting soil organic matter storage, habitat for soil organisms, and nutrient cycling. How land use and grassland management affect soil structural characteristics in the warm, humid region of the southeastern US remains poorly described. A cross‐sectional study from 308 grassland fields and 29 woodlots was sampled at 0‐ to 10‐cm depth in North Carolina. Soils were mostly Ultisols (90%) and included some Alfisols, Inceptisols, and Entisols. Soil texture classes included sand (6%), loamy sand (7%), sandy loam (21%), sandy clay loam (27%), loam (17%), clay loam (13%), silt loam (7%), and silty clay loam (1%). Overall, soil bulk density was greater under grassland than under woodland (1.26 vs. 1.06 Mg m −3 , respectively) but the difference narrowed with finer soil texture. Mean‐weight diameter of water‐stable aggregation was greater under grassland than under woodland in fine‐textured soils but not in other soils. Soil stability index was not different between grassland and woodland, possibly due to high levels (>90%) in both land uses. Several grassland management factors influenced soil structural characteristics, including prior land‐use history, pasture age, stocking density, and forage utilization. Soil structural characteristics were strongly negatively associated with sand concentration and positively associated with soil‐test biological activity. Older pastures with moderate grazing pressure exhibited the strongest soil structural characteristics on medium‐ and fine‐textured soils, thereby delivering vital ecosystem services from this widely prevalent land use in the eastern United States.