Proceedings - Soil Science Society of America最新文献

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.

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.

Hodges, R. C., Boettinger, J. L., & Deenik, J. L. (2025). Pedogenesis of a coastal climosequence and a volcanic ash-influenced elevational transect of western Haleakalā, Maui. Soil Science Society of America Journal, 89, e70119. https://doi.org/10.1002/saj2.70119

In the Funding Information section, “Utah Agricultural Experiment Station, Utah State University, Grant/Award Number 9824” has been updated to “Utah Agricultural Experiment Station, Utah State University, Project Number: UTA 1532.”

In addition, the following statement was added to the Acknowledgements section: “This research was partially supported by the Utah Agricultural Experiment Station, Utah State University, and approved as journal paper number 9824.”

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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.

Potassium (K) deficiency is a common yield-limiting factor in cotton (Gossypium hirsutum L.) production, requiring effective management to minimize yield losses and maintain fiber quality. We evaluated how K availability influences cotton lint yield and fiber quality. Ten fertilizer-K rate (0–187 kg K ha⁻¹) trials were conducted on silt loam soils with soil-test K (STK) ranging from very low to above optimum during the 2023 and 2024 growing seasons. Cotton was planted in raised beds and furrow-irrigated, and lint yield, turnout, and fiber quality (i.e., fiber length, micronaire, uniformity, strength, and elongation) were measured at maturity. Cotton lint yield was positively affected by fertilizer-K rates (p ≤ 0.10) at STK ≤ 114 mg K kg⁻¹. Yields were maximized at responsive sites with applications of 56 kg K ha⁻¹ in long-term trials and 37, 75, or 112 kg K ha⁻¹ in single-site-year trials, showing yield increases of 20%, 53%, 47%, and 70% compared to the no-K control, respectively. Lint turnout and fiber quality were affected by K availability. Overall, at yield-maximizing fertilizer-K rates, lint turnout was 2.4% greater across cultivars in relation to the control. Similarly, fiber elongation increased by 0.35%. At sites with Very Low STK, as little as 37 kg K ha⁻¹ increased lint uniformity and strength up to 0.67% and 1.84 g tex⁻¹. Micronaire increased on average by 0.50, with greatest values occurring with 112 kg K ha⁻¹ application. These findings suggest adequate K management is key to maximizing both cotton yield potential and fiber quality.

The preservation of soil fertility is essential for ecosystem sustainability, particularly in tropical regions where agricultural intensification often leads to rapid degradation. This study evaluated the impact of different land-use systems on soil organic matter (SOM), enzymatic activities, and soybean productivity in tropical sandy soils. Five land-use systems were analyzed: integrated crop–livestock–forest (ICLF), no-tillage (NT), conventional tillage (CT), degraded pasture (PA), and native vegetation (NV). Soil samples were collected at multiple depths (0–40 cm), and chemical, biological, and physiological parameters (gas exchange and yield) were assessed. The ICLF, NT, and NV systems exhibited significantly higher soil organic carbon (SOC), total nitrogen, SOM concentrations, and enzymatic activities compared to CT and PA, with improvements largely confined to the surface layer (0–10 cm). In the 0–5 cm layer, ICLF increased SOC by 35% and SOM by 32% compared to CT, whereas NT increased SOC and SOM by 28% and 26%, respectively. β-Glucosidase activity was 62% higher in ICLF and 55% higher in NT relative to CT. Soybean yield was 3.8-fold higher under ICLF (3900 kg ha⁻¹) and 3.5-fold higher under NT (3600 kg ha⁻¹) compared to CT (1000 kg ha⁻¹). Moreover, both yield and physiological performance were consistently enhanced in ICLF and NT. These findings demonstrate that conservation-based systems can rapidly improve soil health indicators even in sandy tropical soils, supporting sustainable agricultural intensification and aligning with global efforts to promote soil conservation and food security. Remarkably, such improvements were observed within only 2 years of experimentation.

Traditional laboratory analyses of soil texture and soil organic matter (SOM) are time consuming and labor-intensive, so they are impractical to be measured at the same scale as routine nutrient testing. The objective of this study was to determine soil clay, sand, and SOM across a large number of samples by improving mixed-land-use predictive models proposed by Drescher et al. in 2024, creating a rice (Oryza sativa L.)-specific set of models that integrates soil pH, Mehlich-3 extractable nutrients, and estimated cation exchange capacity (EstCEC). With a clustering analysis, a soil dataset containing 179 samples from major rice producing states in the United States was split into a training set (80%) for rice model development and a testing set (20%) for validation. Another dataset of 111 samples from Arkansas was used to compare the performance of rice models with mixed-land-use models. After validation, a high-accuracy clay model (R² = 0.84; RMSE = 68.14 g kg⁻¹) was obtained using pH, phosphorous (P), potassium (K), calcium (Ca), and magnesium (Mg). The sand model containing pH, Ca, Mg, and EstCEC fit with moderate accuracy (R² = 0.36; RMSE = 89.94 g kg⁻¹). The best SOM model relied on pH, P, K, Mg, and EstCEC (R² = 0.80; RMSE = 4.28 g kg⁻¹). The Arkansas rice soil dataset showed that rice models enhanced SOM prediction (R² increased from 0.78 to 0.81), and they improved the overall soil textural classification accuracy to 70% versus 58% by mixed-land-use models. While our models are suitable for clay and silt-dominated classes, such as clay, silt loam, clay loam, and silty clay loam, they may not be for several sand-dominated classes. This study provides a tool by which to efficiently and inexpensively estimate key soil physicochemical properties for agricultural decision-making but the overall utility of our models for rice soil textural classification is limited at present.

Enhanced rock weathering through the application of crushed silicate rock powder has been suggested as an effective CO₂ sequestration strategy for agricultural systems. However, its effects on soil physical properties and CO₂ dynamics remain poorly understood, particularly under field conditions, where soil structure and moisture dynamics play critical roles in regulating gas exchange. This study investigates the effects of applying 150 t ha⁻¹ (15 kg m⁻²) of basalt amendments to a fluvisol with clay loam texture, focusing on changes in soil physical properties, soil water and temperature, and CO₂ dynamics, based on field monitoring in a soybean [Glycine max (L.) Merr.] field in Hokkaido, Japan. The results showed that basalt application significantly increased soil bulk density by 9.27% and increased the trend of water retention while reducing total porosity at 10-cm depth. The calculated CO₂ flux near the soil surface was higher in basalt-treated soils, likely driven by increased microbial respiration under elevated pH (5.48–5.86 at 10-cm depth). Basalt application amplified the rainfall-driven CO₂ efflux, leading efflux pulses immediately after rainfall events. These findings highlight the need for further research on the interactions between soil structure, microbial activity, and long-term basalt weathering in agricultural systems.

The specific role of each fraction of soil C (i.e., particulate [POC] or mineral-associated organic carbon [MAOC]) in each soil strength mechanism remains unexplored. We investigated the relationships of total organic C and its physical fractions with soil strength of two tropical soils (sandy clay loam [SCL_soil] and sandy clay [SC_soil]). We measured soil strength indicators from oven-dry aggregates [tensile strength (σ_t)] and some related to soil compaction [precompression stress (σ_p), compression index (λ), and penetration resistance (SPR) at constant matric potential (−100 hPa)]. These soil strength indicators were used as response variables in path analyses to determine direct effects of C, MAOC, and POC mediated by key physical strength inducers (bulk density or water content). Results suggest a C role conferring soil strength verified by positive correlation with tensile strength and SPR increase, positively influenced by MAOC in SCL_soil and C/POC/MAOC in SC_soil. For SPR, the C effect was mediated by water content or bulk density (i.e., indirect contribution for correlation). Organic C, in turn, showed limited effect on soil compressibility. These findings indicate that increases in soil carbon that enhance aggregate mechanical strength and penetration resistance do not result in reduced soil compressibility (i.e., resistance to compaction). In sandy clay loam soils, MAOC plays a key role in increasing soil strength, whereas all carbon fractions contribute to strength gains with increasing clay content. Thus, while organic carbon can promote beneficial structural stability in the long term, it may also increase SPR, which affects root growth.

This 3-year field study evaluated the effects of winter cover crop treatments, including no cover crop (control), elbon rye (Secale cereale L.), daikon radish (Raphanus sativus ssp. acanthiformis), Austrian winter field peas (Lathyrus hirsutus), and their mixture, on topsoil (0–10 cm) aggregate size distribution and stability, as well as soil organic carbon (SOC) and total nitrogen (TN) stocks in bulk soil and aggregate fractions under a no-till dryland cotton–corn rotation. Results revealed the <0.25 mm aggregates were the most dominant (63.6%–74.8%), exhibited the highest C and N preservation capacity due to their high aggregate content, and contributed the most to SOC and TN stocks, accounting for 40.8%–65.9% and 36.1%–65.1%, respectively. No significant differences in aggregate size distribution or stability were found among treatments. The treatment with radish, peas, and rye planted sequentially over 3 years exhibited the highest SOC stock (28.2 Mg ha⁻¹), while the peas treatment had the highest TN stock (3.1 Mg ha⁻¹) in bulk soil. The radish-radish-mixed (peas + radish + rye) sequence increased the proportion of SOC (38.8%) and TN (42.8%) within the 2–1 mm and 1–0.5 mm aggregate fractions. In the <0.25 mm aggregates, the peas treatment had the highest SOC (11.2 Mg ha⁻¹), and the treatment with 2 years of radish followed by a mixed species of peas, radish, and rye had the highest TN (0.8 Mg ha⁻¹). The main factors influencing bulk SOC stock were the C preservation capacity and SOC stock of the 0.5–0.25 mm aggregates, while bulk TN stock was primarily driven by the N preservation capacity and TN stock of the >2 mm aggregates. The findings suggest that cover crop strategies involving peas and species diversification, such as sequential planting of radish, peas, and rye, can enhance SOC and TN accumulation, particularly in the <0.25 mm aggregates, thereby improving soil health in no-till dryland systems.