Legume-based rotations are key to enhancing soil carbon (C) storage in stable forms such as mineral-associated organic matter (MAOM), improving soil health, and helping maintain long-term C stock. This study investigates how plant inputs and tillage practices influence the distribution, composition, and persistence of MAOM in wheat cropping systems when legumes are incorporated into the rotation. Soil samples were collected from Walla Walla silty loam of northeast Oregon, including conventional tillage (CT) and no-till (NT) treatments in a long-term dryland winter wheat (Triticum aestivum L.) and spring pea (Pisum sativum L.) rotation experiment, with an adjacent grass pasture (GP) plot serving as the baseline. Bulk soil, particulate organic matter (POM), and MAOM fractions were scanned using mid-infrared (Mid-IR) spectroscopy and analyzed for total C and nitrogen (N) as well as radiocarbon age, aggregate stability, and mineralizable C. In WP systems, NT promoted greater C accumulation and stabilization in MAOM than CT, reaching levels similar to those under native GP conditions. Furthermore, our findings indicate that decades of continuous legume-based rotation were insufficient to restore total bulk C content to levels observed in the undisturbed reference site (GP) in the 0-30 cm layer, with increases limited to the surface layer. The Mid-IR data provided insights into how cultivation may alter the chemical composition of MAOM. An increase in amide bands was observed in GP, while legume-based rotation systems favored an abundance of aliphatic (C-H) components in the MAOM fraction. In cultivated soils, C in MAOM exhibited longer residence times under arable conditions than in grassland, while POM remained an actively cycled pool across all treatments. Despite variations in the chemical composition of MAOM across treatments, mineralizable C emissions from MAOM fractions remained statistically unchanged during the 96-hour incubation period. Our findings suggest that soil physical protection, enhanced by reduced tillage, is the primary factor influencing MAOM cycling.

Intensive cropping and long-term ammoniacal nitrogen (N) fertilization have degraded soil health in eastern Oregon dryland wheat systems, leading to soil acidification and declining soil organic carbon (SOC) stocks, which poses a critical threat to sustainability. This study assessed the impacts of a one-time biochar application on soil acidity, SOC sequestration, and nutrient dynamics over 10 years in a winter wheat–spring pea rotation. Biochar, derived from forest waste and applied only once in 2013 at rates of 11.2, 22.4, and 44.8 t ha−1, was evaluated against both non-amended control plots and plots receiving nitrogen fertilizer alone. Key soil properties, including pH, SOC, labile carbon (POXC), cation exchange capacity (CEC), electrical conductivity (EC), nutrient concentrations, and mineralization rates, were measured. Results showed biochar significantly increased soil pH by up to 0.9 units, with improvements persisting for a decade, particularly at higher rates. Elevated pH positively correlated with improved CEC, indicating enhanced nutrient retention and better macro/micronutrient availability (Zn, Ca, Mg, K), reducing Fe solubility. Biochar instantly increased SOC stocks by 95–207% and maintained the stocks for more than 10 years, demonstrating long-term persistence, particularly at higher application rates. Biochar effectively maintained a higher labile carbon content (POXC), although a declining POXC/SOC ratio suggested a shift to more stabilized carbon pools. Mineralization changes were moderate, with non-significant increases in CO2 efflux at higher biochar rates and no consistent net N mineralization trends, suggesting limited direct stimulation of microbial N cycling. Overall, a single alkaline biochar application provided sustained, long-term benefits, playing a dual role in mitigating acidity and enhancing carbon sequestration, thereby supporting a sustainable strategy for restoring soil fertility and ecosystem function and strengthening dryland agroecosystem resilience.

Management of soilborne diseases is challenging in the winter wheat production system of the inland Pacific Northwest due to the lack of effective management options and increased adoption of no-till practices. To determine whether cover crops (CCs) could be a viable management tool for winter wheat soilborne disease in no-till dryland winter wheat systems, a 4-site-year study was conducted in northeastern Oregon under low and intermediate annual precipitation regimes. The treatments included three fall-planted CCs (winter lentil, winter pea, and fall mix), six spring-planted CCs (common vetch, phacelia, spring barley, tillage radish, yellow mustard, and spring mix), and a fallow control. The abundance of soilborne pathogens was quantified during the winter wheat phase following a single-year CC rotation. The abundance of soilborne pathogens varied between study sites. The CCs influenced the abundance of Fusarium pseudograminearum and Pythium clade F in crop year 2022/2023, but none significantly reduced the pathogen abundance compared with fallow. Most CCs increased Pythium clade F abundance in crop year 2022/2023 compared with fallow. There was no effect of CC on any pathogen in crop year 2021/2022. Overall, the results suggest that short-term, single-year CC rotations do not reduce the abundance of soilborne pathogens of winter wheat compared with fallow. This study highlights the need for longer-term CC studies to better understand their impacts on soilborne diseases of wheat.Copyright (c) 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The potential for increasing soil carbon (C) storage in dryland croplands is still under debate, and there is a lack of comprehensive data regarding storage capacity under conservation management practices. In this study, we analyze the potential for sequestration and stabilization by soil minerals in agricultural land in Eastern Oregon when legume-based rotations are incorporated into cereal cropping systems. This study encompasses long-term experiments that compare the traditional conventional tillage (CT) with winter wheat-summer fallow (WW-SF) cropping system to winter wheat (Triticum aestivum L.) (WW) - spring pea (Pisum sativum L.) (SP) rotation (WW-SP) under both CT and no-till (NT). Soil C sequestration rates were estimated by analyzing mid-infrared spectral data in archived soil samples from the WW-SP and WW-SF systems. Partial least squares (PLS) models were trained to predict different properties in archived soil samples, such as total C and nitrogen (N) in bulk soil and C in mineral-associated organic matter (MAOM). Our findings show that over nearly 60 years in the WW-SP cropping system, soil C in the top 30 cm depth profile increased annually by at least 0.16 t C per hectare under CT and 0.25 t C per hectare under NT following conversion from WW-SF systems. The WW-SF cropping system was highly susceptible to C losses in the MAOM fraction, while the NT cereal legume-based rotation showed significantly higher C levels in this fraction. Furthermore, the NT WW-SP resulted in a 60% increase in C sequestration in this fraction following the incorporation of cereal-legume systems. Although the studied sub-basin represents less than 1% of the state's croplands, we estimate that incorporating legumes into the WW-SF system could sequester enough C to offset approximately 0.20% of Oregon's annual agricultural CO₂ emissions. Our findings indicate that incorporating legumes into arable WW-SF systems can effectively increase C stock and stabilize eastern Oregon's dryland farms, promising to offset GHG emissions.

Cover cropping in the fallow phase of winter wheat ( Triticum aestivum L.)–fallow systems of the semiarid Pacific Northwest has been identified as an opportunity to build resilience and enhance farm profitability. Nine fall‐ and spring‐sown cover crops (CCs) grown during the traditional fallow period were evaluated at sites in the low and intermediate precipitation zones of the region in a 2‐year study (2021 and 2022). The fall‐sown CCs included winter pea ( Pisum sativum L.), winter lentil ( Lens culinaris Medik.), and fall species mix; and the spring‐sown CCs included common vetch, yellow mustard, lacy phacelia, tillage radish ( Raphanus sativus L.), spring barley ( Hordeum vulgare L.), and a spring species mix. CCs were evaluated for biomass production and impacts on soil water and weeds. CC growth was dependent on location, year, planting timing, and CC species. Fall‐sown CCs generally produced more biomass than spring‐sown CCs across site‐years, with winter peas and the fall species mix being most productive. Following a year of greater than average precipitation, no negative effects of CCs on fall soil moisture were observed at the intermediate precipitation site, while fall‐sown CCs reduced soil moisture at the low precipitation site. The suppressive effect of CCs on weeds ranged from null to moderate, depending on site, year, and CC seeding time. Fall‐sown CCs more consistently suppressed weeds than spring‐sown CCs. Additionally, fall‐sown CCs were terminated in the spring before weeds set viable seeds, saving a herbicide application and reducing herbicide pressure without exacerbating future weed issues. Overall, select fall‐sown CCs showed promise to enhance ecosystem services during the traditional fallow period.

Interest in soil organic carbon (SOC) levels is focused on both soil quality and sequestering carbon from the atmosphere. Farmers have developed minimum tillage systems and no-till systems. This study carefully measured SOC at three sites where long-term, randomized, replicated studies compared minimum tillage and no-till ro-tations in the low-precipitation inland Pacific Northwest, USA. To overcome seasonal, annual, and rotational effects, a soil sample was taken from each plot monthly for three years. The top 250 kg m-2 dry soil mass (representing the 0-to 20-cm depth) from each core was analyzed for SOC. Averages of monthly samples revealed the tilled treatment had 7.21 g kg-1 of SOC compared to 7.04 for the no-till treatment (p < 0.004). Examining variation month-to-month, 93% of sample variation was due to sample date, and 7% due to blocks (replications) within sites. Of 77 individual site-by-date samples, only six produced significant t-tests (p < 0.05) but SOC differences were 46-31 in favor of tillage and those 46 had larger differences. Power calculations estimated 34-100 samples would be required to detect a relative difference of 5% given the data's standard deviation. Soil water and soil temperature to 30 cm was measured at the time of sampling, and while no-till more often had greater water, temperature differences were inconsistent. We conclude that no-till did not result in more soil carbon in these systems and judicious tillage is an option for sustainable production.

Purpose Currently, several soil health testing approaches are available to assess soil health such as comprehensive assessment of soil health (CASH) and Haney soil health test (HSHT). However, suitability and interpretation of these tests vary considerably across regions due to inherent soil and climatic variability. Although CASH and HSHT have shown promise in their respective region of origin, suitability of these methods for inland Pacific Northwest region is unknown. Therefore, this study was conducted to evaluate suitability of CASH and HSHT in dryland wheat systems. Methods This study was conducted with samples collected during the Soil Health Institute’s North American Project to Evaluate Soil Health Measurements (NAPESHM). Soil samples were collected from multiple long-term grass pastures (GP), crop residue management under wheat-fallow (CR), tillage management under wheat-fallow (WT), and wheat-pea (WP) systems, which include treatments like tillage intensity, organic amendments, nitrogen (N) rates, and stubble burning. Samples were analyzed for indicators of CASH and HSHT methods. Results Among field studies, soil health scores for CASH and HSHT were greater under GP than other treatments and showed overall trend of GP > WP > CR > WT. Although most CASH and HSHT scores and indicators varied under treatments across field studies, there were only a few significant differences among treatments within any study. Both CASH and HSHT did not discern among soil health of any treatment within any study, except CR. Conclusions The lack of sensitivity of CASH and HSHT for management-induced soil health changes within field studies highlights the need for further extensive evaluation and/or calibration before regional adoption.

Soil organic carbon (SOC) is considered a significant contributor to soil water retention. However, generalizations about the role of SOC in available water-holding capacity (AWHC) may have inaccurately portrayed this relationship. We aim to reexamine the relationship between SOC and water retention using the National Cooperative Soil Survey (NCSS) Database. We focus on regional soil groups within the Pacific Northwest wheat production region, including Haploxerolls, Argixerolls, Haplocambids, and Durixerolls. We evaluated 77 sites based on SOC, total nitrogen (TN), pH, texture, bulk density (BD), field capacity (FC), permanent wilting point (PWP), and AWHC. Our findings indicate that texture and BD were the most significant contributors to AWHC variation, while SOC played a secondary role in explaining this variation. Mid-infrared (MIR) spectroscopy coupled with a random forest (RF) algorithm was used to evaluate the importance of spectral bands in determining changes in FC and PWP. This analysis identified mineral bands related to inner-surface hydroxyl groups in kaolinite (3700 cm −1) and Si-O-Si overtones (1870 cm −1) as the most important spectral contributors to PWP. The water retention at FC was associated with organic absorbances relevant to soil aggregation, such as polysaccharide C–O (~1035 cm −1), while mineral bands were relatively less influential. This study highlights the need to reexamine the impact of SOC as well as the interaction between soil texture and compaction on soil water retention to elucidate the underlying mechanisms responsible for AWHC, thus providing insight into future drought adaptation strategies.

Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and beta-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confi-dence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.

Cover crops are widely advocated for increasing soil organic carbon (SOC) levels, thereby benefiting soil health improvement and climate change mitigation. Few regional-scale studies have robustly explored SOC stocks under cover cropping, due to limited long-term experiments. We used the unique experimental data from the North American Project to Evaluate Soil Health Measurements conducted in 2019 to address this issue. This study included 19 agricultural research sites with 36 pairs of cover cropping established between 1896 and 2014. Explanatory variables related to site-specific environmental conditions and management practices were collected to identify and prioritize contributing factors that affect SOC stocks with cover crops, by coupling the Boruta algorithm and structural equation modeling. Overall, cover crops significantly (P < 0.05) improved several indicators of soil health, including greater SOC (concentration: +8%; stock: +7%), total nitrogen (+8%), waterstable aggregates (+15%), and potential carbon mineralization (+34%), on average, compared to no cover crop control. Likewise, on average, cover crops sequestered SOC 3.55 Mg C ha-1 (0-15 cm depth), with a sequestration rate of 0.24 Mg C ha-1 yr-1. In addition, we found climate (Hargreaves climatic moisture deficit) was important in explaining the variation of SOC stocks with cover crops, followed by soil properties (e.g., soil clay content). In terms of management practices, cover crop type had a significant positive (0.36) effect on SOC stocks, with non-legumes showing a greater impact, compared to legumes and mixtures. Crop rotational diversity also had a positive (0.28) effect on SOC accumulation. Our findings suggested that integrating non-legume cover crops into diverse crop rotation is likely to be a promising strategy to maximize SOC stocks with cover crops across North America.

Soil microbes play a crucial role in soil organic matter decomposition and nutrient cycling and are influenced by management practices. Therefore, quantifying the impacts of various agricultural management practices on soil microbiomes and their activity is crucial for making informed management decisions. This study aimed to assess the impact of various management systems on soil bacterial abundance and diversity, soil enzyme activities and carbon mineralization potential in wheat-based systems. To accomplish this, soil samples from 0 to 15 cm depth were collected from ongoing long-term field trials in eastern Oregon region under wheat ( Triticum aestivum L.)-fallow (WF), WF with different tillage (WT), wheat-pea ( Pisum sativum L.) (WP), WF under different crop residue management (CR) and natural undisturbed/unmanaged grassland pasture (GP). These trials consisted of an array of treatments like tillage intensities, nitrogen rates, organic amendments, and seasonal residue burning. This study was a part of the Soil Health Institute’s North American Project to Evaluate Soil Health measurements (NAPESHM). Bacterial community structure was determined using amplicon sequencing of the V4 region of 16SrRNA genes and followed the protocols of the Earth Microbiome Project. In addition, extracellular enzyme activities, and carbon mineralization potential (1d-CO 2 ) were measured. Among different trials, 1d-CO 2 in WT, WP, and CR studies averaged 53%, 51% and 87% lower than GP systems, respectively. Enzyme activities were significantly greater in GP compared to the other managements and followed similar trend as respiration. We observed higher evenness in GP and higher richness in spring residue burning treatment of CR study. Our results indicated that species evenness is perhaps a better indicator of soil health in comparison to other indices in dryland wheat systems.

Abstract Tillage and nitrogen (N) application influence soil‐chemical properties and crop productivity. In a long‐term (76‐yr) wheat (Triticum aestivum L.)–fallow system in northeast Oregon, we assessed the effects of tillage (subsurface‐sweep, sweep; offset‐disk, disk; and moldboard plow, plow) and N application rates (0, 90, and 180 kg N ha−1) on soil organic matter (SOM), soil‐chemical properties in 0‐to‐30‐cm soil profile, and wheat yields. Sweep and disk exhibited more pronounced vertical gradient in soil chemical properties within the 0‐to‐30‐cm soil profile than plow due to shallow soil mixing. Across N rates, at 0‐to‐10‐cm depth, sweep and disk had lower pH (0.60), calcium (Ca; 0.32 g kg−1), magnesium (Mg; 83 mg kg−1), and estimated cation exchange capacity (CECe; 1.8 cmol kg−1), but higher SOM (9 g kg−1) and aluminum (Al; 26 mg kg−1) than plow. Below 10 cm, plow had lower pH (0.67–0.83), Ca (0.29–0.31 g kg−1), and CECe (1.7–1.8 cmol kg−1), but higher Al (13–16 mg kg−1) than disk and/or sweep. Across tillage treatments and depths, pH, Ca, Mg, and CECe generally decreased, whereas phosphorus, potassium, and Al increased with increasing N rates. Wheat yields increased by 14% from N application but did not differ between 90 and 180 kg N ha−1. Sweep and disk produced 9% less wheat yield than plow. Long‐term N application and grain removal of basic cations resulted in surface soil acidification under sweep and disk, which if not remedied, can decrease wheat productivity in this region.

Farmers, scientists, and other soil health stakeholders require interpretable indicators of soil hydraulic function. Determining which indicators to use has been difficult because of measurement disconformity, spatial and temporal variability, recently established treatments, and the effect of site characteristics on management practice differences. The North American Project to Evaluate Soil Health Measurements includes 124 sites uniformly sampled across a range of soil health management practices in North America in 2019. We compare and recommend indicators of hydraulic function that best characterize soil health. We assessed the relationship of each indicator to a suite of soil inherent properties and climate variables, the response of each indicator to soil health management practices, the effect that soil inherent properties (clay content, sand content, and pH) and climatic variables (10-yr mean annual precipitation and temperature) had on response to management practices, and the relationship among the responses of the indicators to soil health management practices. Field capacity measured on intact cores (theta(FC_INTACT)) was the best measure of soil hydraulic function, because it responded to management, represents a direct measure of soil hydraulic function, is proximal to stakeholder values, and its response to management was not significantly influenced by inherent and climatic variables. Other suitable indicators are bulk density, soil organic carbon (SOC), and aggregate stability, which are not direct measures of soil hydraulic function but do respond to management and may be practical in situations in which measuring theta(FC_INTACT) is not. This study informs selection of soil health indicators to measure soil hydraulic function.

Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (theta(AWHC)), while some studies show the ability to substantially increase theta(AWHC) through management. The Soil Health Institute's North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (theta(FC)) and permanent wilting point (theta(PWP)). New pedotransfer functions had predictions of theta(AWHC) that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on theta(AWHC). For an increase in SOC of 10 g kg(-1) (1%) in noncalcareous soils, an average increase in theta(AWHC) of 3.0 mm 100 mm(-1) soil (0.03 m(3) m(-3)) on average across all soil texture classes was found. This SOC related increase in theta(AWHC) is about double previous estimates. Calcareous soils had an increase in theta(AWHC) of 1.2 mm 100 mm(-1) soil associated with a 10 g kg(-1) increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience.

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity.

A two‐year winter wheat–fallow system in the Pacific Northwest is practiced in areas with annual precipitation <16 inches. Wheat is planted in the fall and harvested in the summer, followed by 13 to 14 months of fallow. The summer fallowing often involves different types of tillage practices to facilitate water storage and weed control, which can influence vertical distribution of soil acidity and nutrients in the profile, possibly affecting crop yields. Long‐term studies could help us understand soil nutrients and yield responses across different tillage and N rate applications. Earn 0.5 CEUs in Soil & Water Management by reading the article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses .

The global increases in the surface and groundwater nitrate (NO3 - ) concentrations due to synthetic fertilizer input have emerged as major sustainability threats to terrestrial and aquatic ecosystems. Cover crops can reportedly reduce nitrate leaching from croplands. However, the underlying mechanisms and the effectiveness of cover crops in reducing nitrate leaching across species, soil types, agronomic management, and climates remain elusive. We conducted a global meta-analysis to evaluate the effects of cover crops on nitrate leaching and water drainage. A random-effects analysis was established to investigate seven moderating variables in 41 articles. Results showed that globally, cover crops reduced nitrate leaching by 69% compared with fallow while demonstrating no effect on water drainage. Overall, cover crops from Brassicaceae and Poaceae families showed the greatest effect with 75% and 52% reduction in nitrate leaching, respectively. Cover cropping on Ultisols, Histosols, and Inceptisols resulted in the greatest reduction in nitrate leaching (77%, 78%, and 77%, respectively). Greater efficacy of cover crops at reducing nitrate leaching was evident with increasing soil sand content. In general, cover crops appeared to perform better to reduce nitrate leaching in vegetable systems compared to field crops. Cover cropping on conventional tillage resulted in a 63% reduction in nitrate leaching compared with no-tillage (50%) and reduced tillage (38%) systems. The impact of cover crops on water drainage was nonsignificant which implies that nitrate leaching control by cover crops is unlikely exerted through reducing water drainage. This study brings further insight into the intrinsic factors affecting cover crop efficacy and management practices that enhance cover crop potential in reducing nitrate leaching from agricultural systems.

Growth in demand for organic small grains, coupled with persistently low prices in the conventional small grains market, has increased interest in producing certified organic crops in the semiarid Western U.S. The region is well-suited for organic small grains production due to the strong demand for organic food products exists on the U.S.'s West Coast, the climatic conditions that tend to produce high quality grains relative to wetter, more humid areas, and the benefits that certified organic practices can have for soil and environmental conservation in a region at high risk of damage from degradative conventional farming practices coupled with climate change. However, many producers encounter significant and persistent challenges with weed control and especially maintaining adequate nitrogen fertility due to poor legume performance and low access to manure-based organic amendments. In this paper, we present a review of the newly growing body of research literature working to expand certified organic agriculture in the semiarid West where small grains are the predominant cash crop, irrigation is rare, and soils are fertile but highly susceptible to erosion and degradation. We highlight progress made on market development; identification of crop rotations, fertility, and weed management practices that optimize productivity; and finally, highlighting pioneering work on new ecological management systems, including semiarid organic reduced tillage methods and intercropping. Our review reinforces the environmental- and economic-based need to grow organic small grains production in the semiarid West, while also identifying remaining challenges and research/development priorities.

Aggregate stability is a commonly used indicator of soil health because improvements in aggregate stability are related to reduced erodibility and improved soil-water dynamics. During the past 80 to 90 years, numerous methods have been developed to assess aggregate stability. Limited comparisons among the methods have resulted in varied magnitudes of response to soil health management practices and varied influences of inherent soil properties and climate. It is not clear whether selection of a specific method creates any advantage to the investigator. This study assessed four commonly used methods of measuring aggregate stability using data collected as part of the North American Project to Evaluate Soil Health Measurements. The methods included water stable aggregates using the Cornell Rainfall Simulator (WSACASH), wet sieved water stable aggregates (WSAARS), slaking captured and adapted from SLAKES smart-phone image recognition software (STAB10), and the mean weight diameter of water stable aggregates (MWD). Influence of climate and inherent soil prop-erties at the continental scale were analyzed in addition to method responses to rotation diversity, cash crop count, residue management, organic nutrient amendments, cover crops, and tillage. The four methods were moderately correlated with each other. All methods were sensitive to differences in climate and inherent soil properties between sites, although to different degrees. None measured significant effects from rotation diversity or crop count, but all methods detected significant increases in aggregate stability resulting from reduced tillage. Significant increases or positive trends were observed for all methods in relation to cover cropping, increased residue retention, and organic amendments, except for STAB10, which expressed a slightly negative response to organic amendments. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Therefore, secondary considerations (e.g., cost, method availability, increased sensitivity to a specific management practice, or minimal within-treatment variability) driven by the needs of the investigator, should determine the most suitable method.

Crop residue management strategies have exhibited significant effects on crop growth and soil properties, which in turn may influence soil phosphorus (P) transformation and availability. In this study, the effect of long-term (83-year) crop residue management treatments (straw plus 45 or 90 kg N ha−1; straw burning in fall or spring; straw plus manure) on soil P availability and storage capacity in the surface (0–0.3 m) and subsurface (0.3–0.6 m) were investigated relative to straw incorporated into soil (control) in a wheat-fallow rotation in the Pacific Northwest. Compared to the control, N application significantly decreased soil available P by 37–49%, measured as Olsen-P, due to the higher P removal by the wheat crop. The significant decrease in NaOH-extractable inorganic P (Pi) by 31–42% and Oxalate-extractable Fe by 20–27% suggests N application induced Fe associated-Pi release to supply crop growth. Straw burning had no significant effect on soil P balance but decreased available P by 20–36%, which can be attributed to the transformation of labile Pi and/or moderately labile Pi to stable Pi and P downward transport due to the increased pH of 0.4–0.9 and the loss of organic carbon. Fall burning appeared to have a greater effect on soil properties and P chemistry than spring burning. Manure application significantly increased soil available P by 245% in surface soil in 2014 while resulted in obvious negative soil P storage capacity (− 103 mg P kg−1) and high potential of P downward transport due to long-term positive P surplus together with the increase in soil pH of 1.2.