This research investigates the improvement of expansive soils by incorporating fly ash, focusing on its impact on soil engineering properties such as plasticity index (PI), swelling potential (SP), California bearing ratio (CBR), maximum dry density (MDD), and unconfined compressive strength (UCS). The different mix proportions comprised of CM (control mix), FSM 1, FSM 2, FSM 3, FSM 4, and FSM 5 (where FSM is fly ash stabilized mix), were subjected to tests after a curing period of 7, 14, and 28 days. Using the experimental result, FSM 4 was determined to be the most effective mix regarding UCS, PI, SP, CBR, and MDD. The response surface methodology (RSM) was used to model the five properties of the most effective mix, producing R-2 values of 0.9331 for UCS, 0.9189 for CBR, 0.9368 for PI, 0.9286 for SP, and 0.9421 for MDD in order to increase prediction accuracy. The hybrid quantum neural network-Krylov subspace optimization model (QNN-KSO) was introduced and proved to be the best out of the RSM, deep neural network-grey wolf optimization, and random forest-artificial bee colony out of all six criteria, as it resulted in more reliable and accurate prediction of UCS, CBR, PI, SP, and MDD. The hybrid QNN-KSO model produced excellent performance while minimizing the root mean squared error while achieving an R-2 value of 0.99 making this an improved modeling technique for soil stabilization.
Understanding potassium (K) speciation in soils is essential for evaluating its availability to plants and guiding sustainable nutrient management. In this study, five distinct soils from Taiwan, representing varying management practices and physicochemical properties-including soils with and without long-term K fertilization, alkaline soil, red soil, and forest soil-were analyzed to determine K speciation. A combination of indirect (sequential chemical extraction) and direct (synchrotron-based X-ray absorption spectroscopy) techniques was employed to comprehensively characterize soil K forms. Wet chemical extraction revealed that >95% of total K resides in the residual fraction, while exchangeable, carbonate-bound, Fe/Mn oxide-bound, and organic-bound forms collectively accounted for <5%. X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses provided insights into the local coordination environment of K, revealing a consistent white line feature at similar to 3615.2 eV across samples, with intensity trends indicating K availability in the order: alkaline soil > long-term fertilized soil > forest soil > red soil > unfertilized soil. Linear combination fitting indicated that illite-smectite is the dominant K-bearing phase, while soluble and organic-associated K forms vary with soil type and management. This study demonstrates the advantages of combining wet chemical and synchrotron-based spectroscopic approaches for an accurate, multiscale understanding of soil K speciation.
This paper establishes standardized terminology and field documentation protocols for cryostructures and cryogenic soil structures in permafrost-affected soils and provides brief guidance on descriptions of ground ice morphology and ice volume estimates. We consolidate permafrost terminology from Russian and North American literature, clarify long-standing ambiguities, and provide explicit guidelines that align with US Department of Agriculture-Natural Resources Conservation Service soil description standards. Our scheme makes critical distinctions between cryostructure, the distribution of ice within soil, and cryogenic soil structure, the morphological structure of soil resulting from ice formation. The scheme organizes cryostructures into three main categories: non-segregated ice, visible segregated ice, and ice matrices. We introduce standardized codes and parameters for field descriptions of ice and soil that enable machine-readable data collection compatible with existing soil information systems. This standardization will significantly enhance the integration of field observations into landscape-scale assessments of permafrost stability, infrastructure vulnerability, and ecosystem response to permafrost thaw, addressing an urgent need for quantitative data to inform modeling and decision-making in rapidly changing Arctic and subarctic environments.
Mountain hay meadows are a high-elevation forage-producing agroecosystem dependent on flood irrigation and nitrogen (N) fertilization to maintain yields, meaning management has great potential to influence greenhouse gas (GHG) emissions. To assess GHG fluxes and inorganic N dynamics in meadows, field monitoring was established at four ranches in Wyoming and Colorado for 24 months from October 2021 through September 2023. At each ranch, three long-term management systems were compared: unirrigated rangeland, irrigated-unfertilized meadow, and irrigated-fertilized meadow. Soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes were measured along with soil samples (0- to 10-cm depth) analyzed for water content, nitrate (NO3-), and ammonium (NH4+). Flood irrigation resulted in 41%-91% increase in annual CO2 emissions compared to rangelands. Flood irrigation combined with fertilization increased CO2 emissions by another 19% in 2023. Both irrigated-fertilized and irrigated-unfertilized meadows emitted CH4 during flooding, while rangeland soils assimilated CH4 throughout the study. Unexpectedly, N2O emissions were highest in rangelands and not influenced by irrigation or fertilization in meadows. Soil NO3- and NH4+ concentrations were low during the growing season and no correlation between inorganic N and N2O emissions was observed. Calculated global warming potential in meadows revealed GHG emissions were driven mainly by CO2, indicating that maintaining photosynthetic carbon (C) sequestration in meadows through optimum agronomic management may be an important strategy to balance GHG emissions.
Soil water retention curves (SWRCs) are traditionally determined in the laboratory, but modern sensors enable their measurement under field conditions. This study compared SWRCs obtained from laboratory and field instrumentation within the same soil volume. A well-aggregated tallgrass prairie soil was instrumented with co-located sensors that measured volumetric water content and matric potential at 3.5-cm depth inside collars that prevented root intrusion, minimized lateral flow, and ensured consistent sensor placement. The field experiment was conducted from June 1 to August 11, 2023, capturing multiple wetting and drying cycles. Afterward, the collars were excavated and analyzed in the laboratory using precision mini-tensiometers and a dewpoint water potential meter. Laboratory-derived SWRCs consistently showed greater water contents near saturation compared to field-derived SWRCs, which were consistent across three drydown periods and collars. The two methods produced nonequivalent SWRCs, likely due to sensor responsiveness, air entrapment, and rapid macropore drainage that limited in situ measurement of near-saturation conditions.
Most irrigation areas in the Yellow River Basin widely use muddy water irrigation, and the sand in the water is the main characteristic that distinguishes muddy water irrigation from clear water irrigation, resulting in a significant difference in its infiltration mechanism compared with clear water. This research aims to determine the influence of muddy water properties on the infiltration process and pore air pressure in the presence of air resistance. Indoor soil column infiltration tests were used to examine the infiltration procedure and the process of pore air pressure change under various muddy water sand contents and sediment particle compositions. The hydraulic conductivity, cumulative infiltration per unit area, and frontal matrix suction in the traditional Green-Ampt (G-A) model were modified, a saturated layer thickness calculation model was introduced, and an improved G-A model considering air resistance based on the layered assumption was established. The research results indicated that the change in pore air pressure over infiltration time may be split into two stages: rapid change and stable change. The sand content and the physical clay content were positively correlated with the pore air pressure and negatively correlated with the saturated hydraulic conductivity. After the wetting front reached 20 cm below the soil surface, compared to the traditional G-A model, the revised model estimated the infiltration time closer to the measured infiltration time. The improved model significantly improves the prediction accuracy and offers theoretical support for the exploration of muddy water infiltration behavior. The higher the sediment concentration and the higher the clay content, the more obvious the superiority of the modified model becomes.
Microwave (MW) soil treatment has proven to have the potential to reduce weeds and enhance soil nutrient availability and crop yields. This study hypothesized similar benefits in newly established pastures. Four treatments (Lucerne and Phalaris, with and without pre-sowing MW soil treatment for 120 s) were tested with four replicate plots (1.5 m 2 each). Three 700 W MW magnetrons, with a frequency of 2.45 GHz, were attached and remotely connected to the controller circuitry of three domestic MW ovens. Soil physio-chemical properties were analyzed, and plots were harvested via mowing three times during the experiment. Pasture samples were assessed for nutritive value. MW treatment increased nitrate, ammonium nitrogen, and potassium in both species plot soil but decreased soil phosphorus. Germination counts significantly increased in MW-treated Lucerne ( p = 0.018) and Phalaris ( p = 0.002), while weed counts decreased ( p = 0.091 and p < 0.001, respectively). MW-treated Phalaris plots had 30% and 26% higher crude protein and metabolizable energy yields compared to controls ( p < 0.05). However, MW treatment did not affect Lucerne's nutrient yields ( p > 0.05). The findings suggest MW soil treatment can enhance nutrient yields in Phalaris but not Lucerne, while also aiding weed control. Further research is needed to explore the interactions between pasture species and MW treatment. This technology has potential as a sustainable tool for improving pasture productivity and weed management.
Basic indicators of soil health that influence water infiltration, root growth, gaseous exchange, and overall agronomic productivity are soil physical properties such as bulk density (BD), total porosity (TP), particle density (PD), and penetration resistance (PR). Agricultural practices, particularly tillage and land use, are known to alter soil physical properties by disrupting soil structure and altering soil organic matter content. Therefore, this study aimed to assess the effects of conservation agriculture practices, meadows, and woodlands on above-mentioned soil properties. This on-farm study was conducted at 41 sites located within five counties that covered five soil series (Blount, Eldean, Pewamo, Spinks, and Warsaw) in Central Ohio. From November 2023 to July 2024, soils (0- to 10-cm depth) were sampled from cropland under conventional tillage, minimum tillage (MT), and no-tillage (NT), as well as from meadows and woodlands, to evaluate BD, PD, and TP. PR was measured in the field. All land management practices had been in place for at least 15 years prior to sampling. Data were analyzed using a linear fixed-effects model to test the effects of land use within each soil series. Soil TP, BD, and PR varied significantly (p < 0.05) across land management practices and soil series, with woodland soils consistently showing lower BD and PR, and higher TP compared to those under cropland independent of tillage practice and those under meadow, whereas PD did not differ among practices. Soil TP, BD, and PR were significantly related (R 2 >= 0.33, p < 0.001) to soil organic carbon (SOC) content, reflecting a moderate influence of SOC on reducing soil compaction. Overall, these findings highlight the lasting positive impact of relatively undisturbed land use (woodlands) on soil physical health, while also suggesting that NT and MT may require longer timeframes (>15 years) to induce improvements in soil structure and compaction. Plain Language SummaryHealthy soil is important for water movement, root growth, air flow, and crop pro-ductivity. Key indicators of good soil health include how tightly packed the soil is(bulk density), how much space is available for air and water (total porosity), theweight of soil particles (particle density), and how hard it is for roots to push throughthe soil (penetration resistance). Farming methods, especially tillage and how theland is used, can affect these soil properties by changing soil structure and organicmatter content. This study evaluated 41 farm sites across five counties in CentralOhio between November 2023 and July 2024. Soil samples were taken from the top10 cm of land used for conventional tillage, minimum tillage, no-tillage, meadows,and woodlands. The goal was to compare soil physical health across these land uses.Results showed that soils under woodland were healthier: they had lower compactionand more total porosity, or the available space for water and air. In contrast, croplandsoils, regardless of tillage method, were more compacted. Soils with more organiccarbon content generally had better physical health. The study suggests that undis-turbed land like woodlands can maintain good soil structure, and while no-tillageor reduced tillage can also be useful, it may take more than 15 years to see majorimprovements.
Enhanced efficiency fertilizers, including urease inhibitors (UIs), nitrification inhibitors (NIs), and dual inhibitors (DIs [UI + NI]), are widely used to reduce nitrogen (N) losses and improve crop nitrogen use efficiency (NUE). However, their relative effectiveness across multiple nitrogen loss pathways remains unclear. This study aimed to address that gap through a 31-day soil column experiment and a 25-day soil incubation study using loamy sand soil. Here we assessed the impact of single and DIs on nitrate (NO3-N) and ammonium (NH4-N) leaching, ammonia (NH3) volatilization, nitrous oxide (N2O) emissions, and residual soil nitrogen. Treatments included UAN alone and UAN with established (Agrotain, Instinct NXTGEN, and Nitrolock) and novel (VLS-UI, VLS-NI, and VLS-UI + NI) inhibitors. The NIs reduced potential NO3--N leaching by up to 20% compared to UAN and outperformed DIs by 10%. In contrast, UIs and DIs did not reduce NO3--N leaching. UI treatments increased NH4+-N leaching, while NIs and DIs had no significant effect. DIs were most effective in reducing NH3 volatilization (82%-89% reduction), surpassing UIs and NIs (68%-75%). N2O emissions did not differ significantly among treatments. NIs significantly reduced nitrification potential, with VLS-NI showing the greatest reduction (22%). Soil pH decline correlated with increased NO3--N leaching and nitrification. Total mineral N leaching accounted for 31% of applied N, and gaseous losses (NH3 + N2O) accounted for up to 9%. Overall, NIs were more effective in reducing NO3--N leaching and nitrification, while DIs were best for controlling NH3 volatilization. These findings highlight the importance of selecting nitrogen stabilizers based on dominant loss pathways and site-specific conditions to optimize NUE and reduce environmental impacts.
Biochar consistently improves soil physicochemical properties and lowers the bioavailability of Cd and Pb, yet the exact mechanisms controlling metal mobility under field-relevant flow conditions remain unresolved. We therefore conducted a leaching column experiment to quantify the vertical migration of Cd and Pb in a sandy-loam paddy soil. The soil was amended with wheat straw biochar and shrub branch and leave-biochar and leached with two concentrations (5 and 10 mM) of citric acid or sodium humate. The results revealed distinct patterns for Cd and Pb in response to biochar treatments. Biochar accelerated the migration of surface layer Cd but simultaneously reduced exchangeable Cd content by 4.5%-10.7% compared to control treatment. In contrast, Pb migration was retarded, and breakthrough was delayed even though the proportion of bioavailable (reducible + oxidizable) Pb increased by 3.1%-4.7%, reflecting ligand-enhanced dissolution that was later re-immobilized along the profile. Organic acid concentration governed the extent of transport. At 5 mM, neither citric acid nor sodium humate appreciably moved Cd or Pb beyond 4 cm. At 10 mM, however, sodium humate doubled leachate velocity and transported both metals to 8-12 cm, enhancing subsoil concentrations and increasing groundwater risk. However, biochar also increased the proportion of residual fractions of both Cd and Pb in the 4- to 8-cm layer, indicating its role in transforming bioavailable forms into stable and non-bioavailable forms. Collectively, the data show that Cd mobility is controlled primarily by leachate ionic strength, whereas Pb transport is driven by the concentration of water-soluble organic ligands. Thus, biochar can be an effective long-term immobilization agent only if coupled with management practices that limit the buildup of strong organic acid solutions in the profile.
Aluminum (Al) is one of the most abundant elements in soils. As poorly crystalline Al hydroxides are reactive toward soil organic matter (SOM), they are thought to be involved in SOM stabilization. This is also inferred from correlations between soil organic carbon contents and those of Al extracted by acid oxalate in darkness (AOD), although it is known that several species release Al by this extraction. We tested the completeness of dissolution by AOD of synthesized poorly crystalline Al hydroxides and models of Al in organic association, which included dissolved organic matter flocculated by Al ions and Al adsorbed on peat. While Al was almost completely extracted from the organic models, all hydroxides were completely dissolved by AOD extraction. A review of the literature revealed frequent misinterpretation of data on the extraction of Al from hydroxides. An approximation of the detection limit of a combination of extractions, X-ray diffractometry, and X-ray fluorescence spectroscopy revealed that unambiguous quantification of oxidic Al in soils of temperate latitudes is not possible because of the low contents. Therefore, we consider statements about the importance of Al hydroxides for stabilizing SOM in these soils to be questionable as long as adequate analytical technology is unavailable to identify and selectively quantify Al in poorly crystalline phases.
Applied Zn undergoes multiple biogeochemical reactions that determine the available Zn concentration in soil. The choice of Zn fertilizer should depend on the chemical reactions it undergoes, namely, adsorption-desorption, precipitation-dissolution, and complexation-dissociation. The treatments included four different Zn fertilizers: ZnO, ZnSO4.7H(2)O (ZnSO4), ZnEDTA, and Zn mix (a new Zn product with 60% ZnO, 36% ZnSO4 & centerdot;7H(2)O, and 4% ZnEDTA by weight). The treatments also included a control (No-Zn) and an ethylenediamine tetraacetic acid (EDTA) treatment (No-Zn + EDTA). The overall objective of this study was to compare the above treatments based on relative Zn diffusion, water extractability, plant biomass, and plant Zn uptake using incubation (soil only) and greenhouse (soil + plant) studies. The X-ray absorption near-edge structure (XANES) spectroscopy was used to evaluate the Zn reaction products in soil. Zinc sulfate and ZnEDTA showed greater diffusion, water extractability, plant concentration, and diethylenetriaminepentaacetic acid extractability of Zn in soil than ZnO and Zn mix treatments. The XANES analysis showed that Zn mainly existed as Zn aluminum nitrate double-layered hydroxide (ZnALDHnitrate)-like species in all treatments except ZnEDTA, complementing our understanding from the incubation and greenhouse studies that Zn gets sorbed quickly to metal oxides or soil surfaces. Plant uptake, Zn concentration, and biomass were comparable between ZnSO4 and ZnEDTA, indicating that both can serve as effective Zn sources under neutral soil conditions. Given its comparable performance and lower cost, ZnSO4 represents a practical alternative to chelated Zn sources such as ZnEDTA.
Woody perennial polycultures (WPPs) can contribute to sequestration of soil organic carbon (SOC). We studied how WPP diversity and density, and landscape features influence SOC change. We quantified SOC, particulate organic matter-carbon and -nitrogen (POM-C and POM-N), potentially mineralizable nitrogen (PMN), and inherent properties in soil collected in 2015 and 2022 using plot- and grid-based sampling approaches. The SOC stocks increased in the top 60 cm in 3- and 4-species (3-Sp and 4-Sp) treatments, double density 3-Sp (3-SpX2), and corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) control (CS). Gains ranked 3-Sp > CS > 3-SpX2 > 4-Sp and ranged from 0.6 to 3.5 Mg C ha(-1) year(-1). Only differences between 3-Sp and 4-Sp were statistically significant. Gains in the CS are attributable to their relatively small plot size (one-fifth that of WPP plots) that reduced erosion and increased deposition. Gains in POM found in the pastured inter-rows drove SOC stock change in the 0- to 30-cm depth. Comparatively, small POM gains in the WPP rows suggest WPP diversity and density were not important drivers of SOC change. Multiple linear regression of grid-based data revealed that SOC gains in the surface were positively related to PMN and negatively related to elevation, and SOC change was less than that seen at the 30-60 cm that was positively related to available P. Net SOC change is the result of plant productivity in the surface and of erosion, deposition, and leaching at depth. The use of both treatment- and spatial-based sampling was needed to understand where and how vegetative inputs and landscape features determined SOC change. Plain Language SummaryWoody Perennial Polycultures (WPPs) are types of agroforestry systems that plantwoody perennial species (trees and bushes). This study evaluated how WPPs influence soil organic carbon sequestration in a 7-year-old study site. It also con-sidered the influence of soil characteristics and landscape factors on soil organiccarbon change. The three WWP treatments evaluated, and the control, gained soilorganic carbon in the top 60 cm of soil. Within the WPP treatments, the greatestgains occurred in the grassy areas between the rows established with woody peren-nial species. This study also revealed that terrain elevation and indicators relatedto soil productivity were as influential as vegetative inputs on soil organic carbonchange. Findings underscore the need to consider sampling approaches that accountfor vegetation as well as soil and landscape characteristics when evaluating carbonsequestration in complex agroforestry systems.
A multi-probe heat pulse (HP) sensor measures in-depth variations of water evaporation rates (E) in subsurface soil layers. A multi-probe HP sensor requires an input source of heating power, a high-frequency data logging system, and computer software for data analysis, which may hinder its adoption for wide use in field applications. This study aims to optimize the measurement configurations via systematic evaluations of vertical probe distributions, heater probe requirements, and thermal property sampling intervals. Field data obtained with an 11-probe HP sensor revealed that 87% of evaporation occurred within the 0- to 23-mm soil layer during drying cycles, requiring the use of only seven temperature probes and two heater probes (root mean square error < 0.02 mm h(-1) vs. full configuration). Thermal property measurement intervals could be extended from 4 to 8 h when timed to capture critical daytime transitions in soil thermal conductivity, maintaining accuracy while reducing the data collection requirement by 38%. Soil thermal gradients accounted for >90% of sensible heat flux values, necessitating +/- 0.3 mm spacing precision for the uppermost probes. These quantified operational thresholds provide sensor manufacturers and field researchers with evidence-based design criteria that balance measurement integrity and system efficiency.
Lettuce (Lactuca sativa) is a widely consumed leafy vegetable with high nutritional value. Enhancing its yield and quality through sustainable practices is crucial. This study aimed to investigate the combined effects of arbuscular mycorrhizal fungi (AMF) and phosphorus nanofertilizer (PNPs) on lettuce growth, productivity, and nutritional traits. A total of eight treatment combinations were established and replicated three times under greenhouse conditions, including the control (no AMF, no PNPs), AMF inoculation at 20 g plant(-1), foliar application of PNPs at 250, 500, and 750 mg L-1, and their respective combinations with AMF, using a randomized complete block design. Results indicated that both AMF and PNPs, particularly when combined at 500 mg L-1, significantly enhanced plant growth (plant height and root dry weight), folded leaf number, plant weight (fresh weight), and total biomass (root and shoot system), nutritional value (ascorbic acid, chlorophyll a and b, carotenoids, and total phenolic content), and mineral content (phosphorus and potassium) compared to the control, the individual applications, and the other combination treatments. The next most effective treatments were AMF with 750 mg L-1 PNPs and 500 mg L-1 PNPs alone. This combined approach enhanced physiological performance and increased the levels of bioactive compounds. These results suggest that combining bio- and nano-fertilizers can synergistically improve lettuce productivity and nutrition, providing a promising method for sustainable crop production. Future studies should explore the long-term and field-scale impacts of these treatments.
Flooded rice ( Oryza sativa L.) systems are critical for global food security but contribute significantly to anthropogenic greenhouse gas (GHG) emissions due to high methane (CH 4 ) emissions from anaerobic soils. Drill-seeding (DS) rice, which in California includes early-season irrigation flushes to establish the rice, has been shown to reduce CH 4 emissions compared to water-seeded (WS) systems. The effect of these early-season flushes on nitrogen (N) fertilizer losses and nitrous oxide (N 2 O) emissions, however, is not well understood. In a 2-year study, we quantitatively compared DS to WS systems with respect to their global warming potential (GWP) (CH 4 + N 2 O in CO 2 eq.), nitrate (NO 3 − ) accumulation during flushes, and crop N-uptake. Despite 0.68 kg ha −1 more N 2 O–N emissions in the DS system, GWP was 3700 CO 2 eq. kg ha −1 , a 42% reduction compared to 6340 CO 2 eq. kg ha −1 in the WS system. This was due to a 46% reduction in CH 4 in the DS (94.5 CH 4 –C kg ha −1 ) relative to the WS (175.7 CH 4 –C kg ha −1 ) system. Nitrate accumulation in the DS system amounted to 26.2 kg NO 3 –N ha −1 , and subsequent N losses via denitrification likely contributed to the 22.4 kg N ha −1 less crop N-uptake in the DS system. These results suggest that DS rice has potential for improved environmental impact via GWP reductions but will require increased N inputs. Future efforts should focus on reducing N losses, which have a negative economic impact for the farmer and contribute to N 2 O emissions.
Microplastics (MPs), recognized as an emerging pollutant, represent a significant threat to terrestrial ecosystems worldwide by compromising soil structure, inhibiting plant growth and the reproduction of soil fauna, and disrupting biogeochemical cycles. The remediation of MP-contaminated soils is essential for sustaining healthy soil, ensuring global food security, and mitigating climate change. This review provides a comprehensive analysis of the current research advancements regarding biochar (BC) as a sustainable approach for the remediation of MP-contaminated soils. BC, an environmentally benign material with multifunctional properties, has been shown to enhance soil characteristics in MP-affected environments by stabilizing soil aggregates, improving porosity and moisture retention, and regulating pH and nutrient levels. The review illustrates that BC promote microbial diversity, increases populations of beneficial bacteria, and creates a favorable environment for the growth and reproduction of plants and soil animals in MP-contaminated soils. The efficacy of BC remediation is influenced by its physicochemical properties (such as surface area, porosity, and functional groups) as well as the specific conditions of the soil (including texture, organic matter content, and pH). This comprehensive evaluation underscores BC as a promising, cost-effective, and environmentally sustainable strategy for the remediation of MP-contaminated soils, bearing significant implications for agricultural sustainability and ecosystem health. However, knowledge gaps persist in the understanding of microscopic interactions between BC and MPs, as well as in the application of BC at the field scale. These gaps should inform and direct future research endeavors.
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.
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.
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 (R-2 = 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 (R-2 = 0.36; RMSE = 89.94 g kg(-1)). The best SOM model relied on pH, P, K, Mg, and EstCEC (R-2 = 0.80; RMSE = 4.28 g kg(-1)). The Arkansas rice soil dataset showed that rice models enhanced SOM prediction (R-2 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.
