Improving soil health in dairy forage systems is crucial to making dairy more sustainable. This study evaluated four key soil health indicators from commercial dairy farms under a range of management practices across dairyproducing regions of the U.S., including New York, Wisconsin, Texas, New Mexico, and Idaho. The selected soil health indicators included soil organic carbon (SOC), aggregate stability, carbon (C) mineralization potential (Cmin), and available water-holding capacity (AWHC). To account for environmental variability when assessing management effects, we used an ANCOVA to incorporate climatic, topographic, and edaphic covariates. Dairy forage soils in humid continental climates, particularly in New York and Wisconsin Driftless region, had higher SOC concentrations (20.4-35.8 g C kg- 1) compared to drier regions of northwestern Texas and northeastern New Mexico (SOC 7.3-12.6 g C kg-1) and southcentral Idaho (SOC 15.8-18.8 g C kg- 1). Similarly, aggregate stability and Cmin were generally higher in humid continental climates. Soils under grazed and hayed pastures consistently had higher soil health indicators than those under row crop systems in the surface 15 cm. In semi-arid regions, irrigated systems had higher SOC concentrations, Cmin, and AWHC than dryland systems in Texas and New Mexico. The effects of reduced tillage on soil health were inconclusive in New York and Wisconsin, perhaps because of differences in tillage implements and soil compaction from heavy manure and harvesting equipment. Our results help establish soil health conditions in dairy forage soils and highlight the importance of considering environmental covariates when assessing management effects. These findings provide a foundation for tracking soil health trends in dairy systems and informing the calibration of biophysical models to enhance their accuracy in predicting soil dynamics in dairy forage systems.

The US dairy industry has committed to advancing environmental sustainability by reducing greenhouse gas (GHG) emissions, enhancing water use efficiency, and improving water quality. Feed production accounts for approximately 12% of GHG emissions and 99% of consumptive water use from dairy operations, making it a focus area for potential resource use and overall efficiency improvements. However, few studies report changes to GHG emissions or water quantity and quality outcomes from adopting soil health management systems and use of novel manure products for dairy feed production. The Dairy Soil and Water Regeneration (DSWR) project is exploring whether soil health management systems and novel manure products can help advance environmental sustainability outcomes across major dairy-producing regions in the United States. Through a suite of coordinated studies, including regional soil benchmarking and large-plot- to field-scale experiments, DSWR is evaluating the performance and scalability of reduced tillage, cover crops, and novel manure products applied to row crop feed production systems. By integrating high-resolution data on soil, water, GHG emissions, and crop production, this project is generating actionable insights to support decision-making for farmers, farm managers, dairy cooperatives, retailers, and consumer packaged goods companies. We introduce the project by summarizing its purpose, the conceptual framework guiding its design and implementation, and its approaches to hypothesis testing about soil health, hydrology, and yield responses.

Improving sustainability on US dairy farms has become a critical focus across the industry. As dairy farms continue to consolidate, there is a growing need to identify scalable, implementable soil health management practices that enhance environmental sustainability in the fields managed by the dairy. This paper examines the constraints on dairy forage operations, summarizes key findings from research station experiments comparing soil health management practices in these systems, and synthesizes findings from on-farm research projects that track environmental outcomes after practice adoption. We discuss the knowledge gaps related to soil health management practices and forage production, highlighting the need for long-term, actionable research that is applicable to the diversity of dairy operations across the United States. To drive meaningful improvements in environmental sustainability, it is crucial to integrate region-specific soil health practices, supported by technical and financial support. We conclude that the current body of literature is not adequate to support the widespread adoption of locally appropriate practices, underscoring the urgent need for comprehensive research and support systems to ensure the environmental and economic sustainability of the US dairy industry. Finally, we propose future research directions to address the knowledge gaps and region-specific challenges through an integrated systems approach, focusing on the farm-scale impacts of soil health practices across diverse climates and production systems.

Semiarid rangelands constitute nearly 30 % of the world's grassland ecosystems and livestock grazing is the most widespread land use in these ecosystems. These semiarid rangelands provide a variety of ecosystem goods and services, many of which may depend on soil health. While advances have been made with indicators of soil health for croplands, similar efforts for rangelands are lacking. The North American Project to Evaluate Soil Health Measurements (NAPESHM) sampled soils to 15 cm from long-term (>= 40 years) grazing treatments spanning a range of grazing intensity (ungrazed to heavy grazing) in two semiarid rangelands, shortgrass steppe (SGS) and northern mixed-grass prairie (NMP), in fall 2019. Soils were analyzed for chemical (permanganate oxidizable carbon [POXC] and soil organic carbon [SOC]), biological (mineralizable soil carbon [MinC], phospholipid fatty acids [PLFA], ACE protein, and beta-glucosidase enzyme activity [BG]), and physical (saturated hydraulic conductivity [SHC], available water capacity [AWC], and aggregate stability) indicators of soil health. Light particulate organic carbon and mineral associated organic carbon fractions were also analyzed at the SGS. Additionally, annual net primary productivity and the relative production of warm-vs cool-season grasses were evaluated from 2010 to 2019. Soil health responses to grazing intensity treatments in these two semiarid rangeland ecosystems were generally inconsistent across and within chemical, biological, and physical indicators. For instance, POXC and SOC differed between the two rangeland ecosystems, but neither soil health response within a site was significantly affected by grazing intensity. MinC and saturated hydraulic conductivity consistently decreased as grazing intensity increased in both rangeland ecosystems, while all other biological and chemical indicators were either 1) solely influenced by rangeland ecosystem type, 2) the interaction between rangeland ecosystem and grazing intensity, or 3) unaffected by rangeland ecosystem or grazing intensity. At SGS, delta 13 C values of both organic carbon fractions became less negative as grazing intensity increased, consistent with a greater proportion of warm-season perennial grasses and lower proportion of cool-season grasses. Our results suggest that generalizations about the effects of multi-decadal grazing intensity gradients in western Great Plains semiarid rangelands in North America on chemical, biological, and physical indicators of soil health remain elusive.

Biosolids are municipal wastewater products (sewage sludge) that have undergone additional treatment to meet EPA requirements to be land applied to crop land as a nutrient and organic matter (OM) source. In semi-arid dryland systems, biosolids may be beneficial for improving soil physical, chemical, and biological attributes. The objective of this study was to determine how agronomically relevant biosolids application rates at two long-term (20+ year) field trials affected soil health properties in semi-arid dryland systems. Soil samples were collected (0-15 cm) from (1) a 26-year trial in central Washington (WA) in a grain-fallow rotation, with three biosolids application rates applied every four years compared to synthetic fertilizer and unfertilized controls, and (2) a 23-year trial in central-eastern Colorado (CO) comparing biosolids to synthetic fertilizer in both a wheat-corn-fallow (WCF) and wheat-fallow (WF) rotation. At the WA site, increasing biosolids applications increased soil carbon (C) and nitrogen (N) pools, potential activity of N-acetyl β-glucosaminidase (NAG) and phosphomonoesterase (PME) enzymes, and available water holding capacity, while decreasing bulk density. At both sites, biosolids increased microbial biomass as measured by phospholipid fatty acids (PLFA) and Mehlich-3 extractable soil P. Overall, biosolids had a greater influence at the WA site, likely due to soil texture and higher cumulative biosolids inputs. In CO, most biosolids effects were seen across both crop rotations but were numerically greater in the WCF rotation, which received greater cumulative biosolids applications than the WF rotation. This study shows that biosolids can improve key soil health functions of C accumulation, nutrient cycling, and water storage in semi-arid dryland cropping systems.

Anoxic microsites are potentially important but unresolved contributors to soil organic carbon (C) storage. How anoxic microsites vary with soil management and the degree to which anoxic microsites contribute to soil C stabilization remain unknown. Sampling from four long-term agricultural experiments in the central United States, we examined how anoxic microsites varied with management (e.g., cultivation, tillage, and manure amendments) and whether anoxic microsites determine soil C concentration in surface (0-15 cm) soils. We used a novel approach to track anaerobe habitat space and, hence, anoxic microsites using DNA copies of anaerobic functional genes over a confined volume of soil. No-till practices inconsistently increased anoxic microsite extent compared to conventionally tilled soils, and within one site organic matter amendments increased anaerobe abundance in no-till soils. Across all long-term tillage trials, uncultivated soils had ∼2-4 times more copies of anaerobic functional genes than their cropland counterparts. Finally, anaerobe abundance was positively correlated to soil C concentration. Even when accounting for other soil C protection mechanisms, anaerobe abundance, our proxy for anoxic microsites, explained 41% of the variance and 5% of the unique variance in soil C concentration in cropland soils, making anoxic microsites the strongest management-responsive predictor of soil C concentration. Our results suggest that careful management of anoxic microsites may be a promising strategy to increase soil C storage within agricultural soils.

The concept of soil health is appropriately receiving increased attention from governments, producers, corporations, and other stakeholders because of the many functions of soil that support ecosystem services and farm profitability. With this interest, there is growing need to verify and monitor changes in soil health that result from how agricultural soil is managed. There are many indicators of soil health and, although this benefits the scientific community, it complicates interpretation across studies. The North American Project to Evaluate Soil Health Measurements (NAPESHM) assessed over 30 available measurements on 124 long-term agricultural research sites with replicated soil health treatments and created new pedotransfer functions. This analysis draws on findings from NAPESHM to identify a minimum suite of effective indicators of soil health for the North American Continent. The criteria for a minimum suite of effective indicators are that they (1) primarily reflect soil health rather than inherent soil properties or fertility, (2) are responsive to agricultural management practices that exemplify soil health principles, (3) are conducive to measuring soil health at scale in terms of cost and availability, and (4) are not redundant with regard to linking different soil functions to ecosystem services. Many indicators were determined effective for use in soil health studies and based on this analysis, soil organic C concentration, aggregate stability, and 24 h C mineralization potential were selected for the minimum suite of indicators. Using this minimum suite, as few as three laboratory measurements can be made to assess and track improvement in soil functioning as a result of soil management changes. These indicators may be supplemented with new pedotransfer functions to also estimate changes in available water holding capacity. This minimal suite of soil health measurements is recommended for scaling up soil health assessments across North America, and possibly beyond.

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.

Soil health lies at the core of a sustainable food production system. A comprehensive evaluation of different agronomic practices and their effect on soil health is essential to determine the best practices that support soil ecosystem services. However, it may take years or decades to observe measurable changes in soil health under varying management practices. The objective of this experiment was to evaluate the effects of long-term (>77 years) manure and inorganic nitrogen (N) fertilizer on soil health and determine the interrelationship among the measured soil bio-physicochemical indicators. The study also aims to understand the sustainability of the monocropping maize production system under long-term manure and inorganic N fertilizer management. The experiment site is the historic Knorr-Holden Plot, established in 1910 and continued till today. Over the years, the treatments were constant, with manure as the main factor and N rates as the sub-plot factor. Aligning with advancements in agronomic management, the rates of fertilizer and manure have been revised from time to time. Analysis of soil health indicators showed a significant effect of manure on different labile carbon (C) & N fractions, soil enzymes, and soil organic matter (SOM). Manure treatment improved C stabilization and reached a C equilibrium for management. Water holding capacity was significantly improved at wilting point and field capacity for manure treatment. Nitrogen treatments only affected soil pH, cationic exchange capacity (CEC), and phosphorus. Analysis of the interrelationship among soil health indicators showed SOM was determinative for C & N fractions and CEC. Soil organic carbon can be used as a proxy for soil total N (R2 = 0.98). Water extractable fractions of C and N were interrelated and can be used as determinative factors for each other. The results inform that a sustainable monocropping system can be maintained using long-term manure application, where soil health and organic carbon improve over time. The results also indicate that soil health measurement can be minimized to a few key indicators based on the functional interrelationship, which can broaden the adoption of soil health monitoring and measurement.

This is the second article in our series on soil health and greenhouse gas emissions on U.S. dairies associated with crop production. This article will focus on the first objective of the Dairy Soil and Water Regeneration (DSWR) project, which is to benchmark soil health and soil carbon stocks in dairy forage production systems. Earn 1 CEU in Sustainability by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses .

Measuring carbon dioxide (CO2) produced after re-wetting previously dried soil is an increasingly popular soil health assay, but there is disagreement on the optimal soil drying temperature. We tested whether soil drying temperature impacts water-extractable organic carbon (WEOC) and soil CO2 emissions following rewetting. Soils were collected from corn/soybean croplands and adjacent perennial vegetation at four sites in Iowa, USA. Soil replicates were dried at 22 & DEG;C, 35 & DEG;C, 55 & DEG;C, 85 & DEG;C, and rewetted for incubation at 22 & DEG;C. Soil WEOC and CO2 emissions after re-wetting increased nonlinearly with drying temperature. Effects on CO2 were largest after four days of incubation, but cumulative differences persisted even after 42 days. Responses of CO2 and its stable isotope ratio (& delta;13C) to increased drying temperature varied among sites and vegetation types, indicating shifts in C sources. Soil health assays performed with different soil drying temperatures may not be directly comparable, effects of drying temperature may vary idiosyncratically among samples, and drying at 22 & DEG;C or 35 & DEG;C as opposed to higher temperatures may be preferable to avoid increasing C availability.

Phospholipid fatty acid analysis (PLFA) provides an easy to use and robust measure of changing soil microbial condition. The method provides data on both the quantity and composition of the soil microbial community- critical knowledge because the community is an important component of soil health. However, it is challenging for new researchers to know how to process data, how to interpret the results, and to know its effectiveness in evaluating soil health management. We set out to address these challenges using the North American Project to Evaluate Soil Health Measurements PLFA dataset. The dataset is comprised of results of over 1800 agricultural soil samples from a range of environmental regions and management practices. Using this dataset, we identified that quantifying soil PLFA biomass through summing the biomarkers from C14:0 to C20:0 yielded greater biomass results than summing specific biomarkers and was almost identical to summing C9:0 to C20:0. We utilized microbial biomass with common and novel biomarker ratios to evaluate the response of the soil microbial community to changes in the environment or changes in management practice. These ratios were based on commonly used genotypic categorization (e.g., Gram-positive to Gram-negative) or based on chemical structure with chemical ratios of either universal characteristics (e.g., unsaturated to saturated) or targeted phenotypic biomarkers known to shift with changing growth conditions (e.g., a15:0 and a17:0 to i15:0 and i17:0). One novel phenotypic ratio, the adaptation response ratio (ARR), significantly correlated with mean annual temperature and soil pH across grassland reference plots, a wheat climate transect, an intensive vegetable agricultural dataset, and a wheat-corn dataset from Mexico. Neither the common genotypic ratio nor ratios based on chemical structure demonstrated clear and consistent trends with environmental conditions. Targeted phenotypic biomarker ratios and microbial biomass also detected significant differences with soil health management practices of decreased tillage, cover crops, organic nutrients, residue retention, and rotation diversity. Therefore, with standardized microbial biomass and biomarker calculations that significantly vary with environmental conditions and management practices, these results support a wider understanding and adoption of the PLFA method in soil health management.

Canada's interest in agricultural lands has changed with time from a desire of crop yields at Confederation through to discussions in the Senate on adaptation and resilience in 2018. Long-term research experiments (LTRs) have been present and utilized by federal and university researchers to provide answers throughout. Here we highlight the importance of LTRs by identifying the historical context of LTRs and soil health research in Canada. We then briefly describe the history and key results from select LTRs and illustrate the wealth of information collected from the North American Project to Evaluate Soil Health Measurements cross-country point-in-time soil sampling from these LTRs. We discuss the LTRs, and the knowledge gained from them, with the hope that by showing the distinctive narratives associated with each of these study sites, researchers will be inspired to use them to address their research questions and make sound predictions to facilitate the adaptation of Canadian agroecosystems to climate challenges. Through identifying the value generated by these unique LTRs, we hope that the importance of these sites will inspire not only their continued maintenance but also the next generation of LTRs.

Atmospheric deposition of dissolved organic carbon (DOC) to terrestrial ecosystems is a small, but rarely studied component of the global carbon (C) cycle. Emissions of volatile organic compounds (VOC) and organic particulates are the sources of atmospheric C and deposition represents a major pathway for the removal of organic C from the atmosphere. Here, we evaluate the spatial and temporal patterns of DOC deposition using 70 data sets at least one year in length ranging from 40° south to 66° north latitude. Globally, the median DOC concentration in bulk deposition was 1.7 mg L −1 . The DOC concentrations were significantly higher in tropical (<25°) latitudes compared to temperate (>25°) latitudes. DOC deposition was significantly higher in the tropics because of both higher DOC concentrations and precipitation. Using the global median or latitudinal specific DOC concentrations leads to a calculated global deposition of 202 or 295 Tg C yr −1 respectively. Many sites exhibited seasonal variability in DOC concentration. At temperate sites, DOC concentrations were higher during the growing season; at tropical sites, DOC concentrations were higher during the dry season. Thirteen of the thirty‐four long‐term (>10 years) data sets showed significant declines in DOC concentration over time with the others showing no significant change. Based on the magnitude and timing of the various sources of organic C to the atmosphere, biogenic VOCs likely explain the latitudinal pattern and the seasonal pattern at temperate latitudes while decreases in anthropogenic emissions are the most likely explanation for the declines in DOC concentration.

Nitrogen is an important and limiting nutrient for crop production, but its role as a soil health indicator relating to most soil properties and crop production needs further exploration. Our objectives were to examine the sensitivity of soil N fractions to management practices and their relationships to 60 soil physical, chemical, biological, and biochemical properties and mean crop yields in two long-term (14- and 36-year-old) experiments under dryland cropping systems in the northern Great Plains, USA. Nitrogen fractions were soil total N (STN), potential N mineralization (PNM), water-extractable N (WEN), autoclaved citrate-extractable protein (ACEP), NH4-N, and NO3-N. Management practices were no-till and tilled crop rotations of spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), pea (Pisum sativum L.), and fallow with and without N fertilization. Soil properties were analyzed from samples collected before farm operations in April 2019 and crop yields determined. Nitrogen fractions, except NH4-N and NO3-N, were greater with continuous cropping than crop-fallow. A principal component analysis (PCA) showed that PNM and ACEP were associated with most soil properties, followed by STN, WEN, NO3-N, and NH4-N. PNM, ACEP, and STN were more strongly related to mean crop yields across years in coarse- than medium-textured soil and other N fractions were weakly related. Because of its sensitivity to management practices, stronger relationships to most soil properties and crop yields, and rapid measurement, ACEP may be used as a promising N indicator of soil health in coarse- than medium-textured soil in dryland cropping systems in semiarid regions.

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.

Soil chemical properties have often been related to some other soil properties and crop yields, but extensive evaluation of the relationships of soil chemical properties with other properties and long-term crop yields under dryland cropping systems is lacking. We related six soil chemical properties (pH, electrical conductivity [EC], cation exchange capacity [CEC], and inorganic P [IP], K, and Al concentrations) with 62 other soil physical, chemical, biological, and biochemical properties and crop yields at two long-term (14- and 36-year old) dryland farming sites in the northern Great Plain, United States. Treatments were rotations of no-tillage and conventional tillage spring wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), pea ( Pisum sativum L.), and fallow with or without N fertilization. Soil samples collected to a depth of 0–15 cm in April 2019 were analyzed for soil properties and long-term crop yields were determined. Soil chemical properties were mostly correlated to each other at the short-term than at the long-term site. Based on the principal component analysis, EC, CEC, and IP, and K concentrations were associated with most of the physical, chemical, biological, and biochemical properties at both sites. The CEC, IP, and K concentrations were related to mean crop yields across years at individual or combined sites, but other chemical properties were not related to yields. We conclude that CEC, IP, and K concentrations may be used as potential chemical indicators of soil health that were related to most soil properties and crop yields under dryland cropping systems in the semiarid region.