Eastern North Carolina has been subjected to widespread water quality degradation for decades, notably throughout the Cape Fear River Watershed, owing largely to the magnitude of concentrated animal feeding operations (CAFOs) in the region. Long-term nutrient monitoring data from numerous locations throughout southeastern North Carolina have shown significantly elevated organic nitrogen (Org-N) concentrations starting around the year 2000-a concerning development, as labile Org-N can stimulate algal blooms and subsequent bacterial production, thus enhancing eutrophication in freshwater systems. By measuring the stable isotope signatures (δC, δN) of particulate organic matter sampled from a range of southeastern North Carolina waters, the predominant sources to the observed Org-N loadings were elucidated. Isotope data from across the Cape Fear River watershed indicated a large gradient of livestock waste-N contributions, with hog waste-N contributions consistently higher in the Northeast Cape Fear River watershed and with fertilizer-N contributions higher in the Black River watershed-findings that are consistent with each sub-basin's land usage. %N sediment content was positively correlated with hog waste-N contributions in the Black River watershed, indicating that sediments in CAFO-dense regions are reservoirs for agricultural nutrient pollution. Hog waste-N source contributions and %N sample contents for Black River sediments were strongly correlated with regional swine and poultry CAFO densities, establishing a strong connection between industrial animal production and stream sediment nutrient loads. Collectively, these findings suggest a major role of livestock waste, as well as human sewage, in driving the long-term Org-N increase in eastern North Carolina water bodies.

Phosphorus (P) loss from soils can contribute significantly toward P enrichment in water bodies, impairing water quality. Application of soil amendments is a viable strategy to decrease soluble P in surface soils. Since soluble P is reduced through different mechanisms that are amendment-specific, blended amendments could be a better approach than single amendment applications; however, very little information is available on blended amendment effects in reducing P loss from soils. We compared the effectiveness of gypsum (CaSO·2HO), Epsom salt (MgSO·7HO), and alum [Al(SO)·18HO] applied singly or blended in different ratios in reducing water-extractable P (WEP) and Mehlich-3 P of two soils (0- to 15-cm depth) with contrasting P status (Mehlich-3 P of 7.1 mg kg and 202 mg kg) from the Red River Valley region in MB, Canada. Ten treatments used for the laboratory incubation study were unamended control, gypsum or Epsom salt at 2.5 or 5 Mg ha, alum at 2.5 Mg ha, and four blended treatments of gypsum: alum or Epsom salt: alum at 1:1 or 2:1. Treated soils were saturated and incubated for 2 weeks and analyzed for WEP (an indicator of risk of P loss) and Mehlich-3 P (plant-available P) concentrations. All amendments significantly reduced the WEP concentrations compared to control in both soils. The blended amendments, particularly gypsum-alum blends, performed better than unblended amendments in reducing the potential risk of P loss. Mehlich-3 P concentration was not influenced by amended treatments, suggesting no significant decrease in plant-available P with amendments in both soils.

Atmospheric nitrous oxide (NO) is a potent greenhouse gas, with long atmospheric residence time and a global warming potential 273 times higher than CO. NO emissions are mainly produced from soils and are influenced by biotic and abiotic factors that can be substantially altered by anthropogenic activities, such as land uses, especially when unmanaged natural ecosystems are replaced by croplands or other uses. In this study, we evaluated the spatial variability of NO emissions from croplands (maize, soybean, wheat, and sugar cane crops), paired with the natural grasslands or forests that they replaced across a wide environmental gradient in Argentina, and identified the key drivers governing the spatial variability of NO emissions using structural equation modeling. We conducted on-farm field measurements over 2 years at nine different sites, including a wide environmental gradient (mean rainfall from 679 to 1090 mm year and mean temperatures from 13.8°C to 21.3°C), with diverse plant species life forms, and ecosystems, from the Semiarid Chaco forests in the Northwest of Argentina to the Pampas grasslands in the Southeast. On average, agricultural systems emitted more than twice NO (+120%), had higher soil water content (+9%), higher soil temperatures (+3%), higher soil nitrate content (+19%) but lower ammonium (-33%) than natural ecosystems. We found that land use was the main driver of NO emissions by directly affecting soil NO contents in both natural ecosystems and croplands. Urgent management practices aimed at reducing NO emissions from croplands are needed to mitigate their contributions to global climate change.

Ephemeral streams are important pollutant conduits, but the mechanisms that control nutrient transport to these systems remain unclear. In the US Virgin Islands (USVI), where most streams flow ephemerally, a lack of continuous hydrologic and water quality data limits our understanding of streamflow behavior and its influence on water quality. We therefore assessed the impact of soil moisture and hydrometeorological conditions on nitrogen (N) concentrations within an ephemeral stream on St. Croix, USVI. Stream N concentrations were usually highest during initial flow events, after prolonged dryness, and declined thereafter. Nitrogen increased with shallow antecedent soil moisture and rainfall intensity and decreased with deep soil moisture and baseflow emergence, indicating it was predominantly exported to the stream via surface runoff, as opposed to subsurface leaching. Our results are the first of their kind for the USVI and could be used to improve water quality of freshwater and marine systems.

Evaluating how weather, farm management, and soil conditions impact phosphorus (P) loss from agricultural sites is essential for improving our waterways in agricultural watersheds. In this study, rainfall characteristics, manure application timing, tillage, surface condition, and soil test phosphorus (STP) were analyzed to determine their effects on total phosphorus (TP) and dissolved phosphorus (DP) loss using 125 site-years of runoff data collected by the University of Wisconsin Discovery Farms and Discovery Farms Minnesota. Three linear mixed models (LMMs) were then used to evaluate the influence of those factors on TP and DP losses: (1) a model that included all runoff events, (2) manured sites only, and (3) precipitation events only. Results show that the timing of manure application relative to the timing of a runoff event only had a marginal association with P loads and concentrations, although the majority of the runoff events were collected after 10 days of manure application. Tillage was as influential factor, with greater DP loads and concentrations associated with no-till, especially during frozen conditions. Fields in this study had high STP values, but the model results only showed positive associations between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth. The precipitation event LMM (which included precipitation characteristics) was the model that resulted in the largest R value. While the predictive capacity of the LMMs was low, they did illuminate the relative importance of management and environmental variables on P loss, and can be used to guide future research on P loss in this region.

Soil ecophysiology is adversely affected by various environmental hazards, particularly in mining regions. While there has been substantial research on the effects of coal, mica, copper (Cu), and manganese (Mn) mining on soil quality, the impact of bauxite mining operations on nearby soils has largely been overlooked in the literature. Therefore, this study aims to investigate how microbial activity and dynamics are influenced by soil stressors, such as acidity and heavy metals, in areas adjacent to active bauxite mines. Soil samples were collected from three adjacent locations of an active bauxite mine area at distances of <100 m (S1), 100-500 m (S2), and >500 m (S3). The samples contained chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), manganese (Mn), and cadmium (Cd), as well as elevated acidity and aluminum (Al). These conditions adversely affected the soil microbial indicators, including fluorescein diacetate (FDA), microbial biomass carbon (MBC), and enzyme activity. The highest concentrations of labile metals (i.e., water-soluble and exchangeable) were found in soil mixed with mining waste (S1), whereas acidity and Al were highest in sparsely vegetated soil (S3). Total acidity, total potential acidity, pH-dependent acidity, and Al were significantly positively correlated. Moreover, the significant positive correlation among organic carbon (OC), acidity, Al, and microbial properties (FDA, MBC, and microbial enzymes) suggests a potential effect of OC in mitigating acidity in S3. The ratios of microbial properties with OC depicted a significant negative correlation with acidity and Al fraction, denoting that acidity and Al posed a deleterious effect on soil microbial health. The similarity percentage analysis identified acid phosphatase as the key enzyme accounting for ∼78% of the observed differences in enzyme composition across the sites. Visual MINTEQ modeling revealed that the sites were saturated with different Al-bearing minerals. Pollution load index (PI) and the geo-accumulation index (I) values identified the region as heavily contaminated (PI > 1). Finally, the health risk analysis revealed that Ni posed a potential carcinogenic risk for both adults and children.

Agricultural researchers are increasingly encouraged to engage with stakeholders to improve the usefulness of their projects, but iterative research on the design and assessment of stakeholder engagement is scarce. The USDA Long-Term Agroecosystem Research (LTAR) Network recognizes the importance of effective engagement in increasing the utility of information and technologies for future agriculture. Diverse stakeholders and researchers at the Kellogg Biological Station (KBS) LTAR site co-designed the KBS LTAR Aspirational Cropping System Experiment, a process that provides a testing ground and interdisciplinary collaborations to develop theory-driven assessment protocols for continuous stakeholder engagement. Informed by prior work, we designed an assessment protocol that aims to measure participant preferences, experiences, and perceived benefits at various stages of this long-term project. Two online surveys were conducted in 2021 and 2022 among participants of LTAR engagement events at KBS, using a pre-post design, resulting in 125 total responses. Survey respondents had positive perceptions of the collaboratively designed research experiment. They had a strong expectation that the research would generate conservation and environmental advances while also informing policy and programs. Respondents also indicated a desire to network with other stakeholders. The research team noted the significant role of a long-term stakeholder engagement specialist in inviting participants from diverse backgrounds and creating an open and engaging experience. Overall, results highlight an interdisciplinary path of intentional and iterative engagement and evaluation to build a program that is adaptive and responsive to stakeholder needs.

The Eastern Corn Belt (ECB) node of the Long-Term Agroecosystem Research (LTAR) network is representative of row crop agricultural production systems in the poorly drained, humid regions of the US Midwest and a significant focus for addressing water quantity and quality concerns affecting Lake Erie and the Gulf of Mexico. The objectives of this paper were to (1) present relevant background information and collection methodology, (2) provide summary analyses of measured data, and (3) provide details for accessing the dataset and discuss potential database applications. The ECB-water quality (ECB-WQ) database is comprised of hydrology and water quality data from three privately owned farms in Northwest Ohio and Northeast Indiana and is available for download through the United States Department of Agriculture Ag Data Commons. The dataset includes information on site characteristics (drainage area and soil type), field management (fertilizer application, planting rate, and yield), and daily discharge and measured nutrient concentrations from surface and subsurface tile drainage outlets. Discharge and water quality vary widely across the ECB and are paramount to developing innovative management strategies that balance crop production goals with environmental targets. Discharge is generally greater from subsurface tile drainage compared to surface runoff. Phosphorus concentrations are typically greater in the surface runoff compared to tile drainage, while nitrogen concentrations are greater in subsurface tile drainage. The ECB-WQ database was developed to better facilitate understanding of water quantity and quality within this unique, systematic, artificially tile-drained region and is critical for understanding implications of field management practices, quantifying environmental and production processes, constraining hydrology/water quality models, and informing future water quality policies.

Population growth in coastal areas increases nitrogen inputs to receiving waterways and degrades water quality. Wetland habitats, including floodplain forests and marshes, can be effective nitrogen sinks; however, little is known about the effects of chronic point source nutrient enrichment on sediment nitrogen removal in tidally influenced coastal systems. This study characterizes enrichment patterns in two tidal systems affected by wastewater treatment facility (WWTF) effluent and assesses the impact on habitat nitrogen removal via denitrification. We collected intact sediment cores from prevalent habitats in a tidal freshwater river (TFZ; swamp forest) and a tidal estuarine creek system (EST; salt marsh) upstream and downstream of a WWTF outfall, and quantified dissolved gas fluxes across the sediment-water interface during wet conditions in early summer and dry conditions in late summer. Data collected during two synoptic water quality monitoring campaigns complimented laboratory experiments to provide environmental context for biogeochemical processing. The two systems exhibited different enrichment patterns such that the river-dominated TFZ system was characterized by consistently elevated nitrate + nitrite concentrations downstream of the WWTF, whereas precipitation and tidal influence affected nutrient distributions in the EST creek. Downstream sediments in TFZ exhibit an apparent saturation response, while upstream rates may be limited by other factors, such as labile organic matter availability. In contrast, downstream sediments in EST denitrify at higher rates than upstream during wet conditions that may enhance transport of effluent. This work provides information on ecosystem functioning in human-influenced environments and can be of use in developing nature-based solutions, such as water treatment wetlands, for nitrogen removal.

Maintaining yield goals while reducing nitrate-nitrogen (NO-N) leaching to groundwater is a challenge for potato (Solanum tuberosum) production in the Wisconsin Central Sands as well as across the United States. The objectives of this study were to quantify the effect of conventional and enhanced efficiency nitrogen (N) fertilizers on NO-N leaching, crop yield, and N uptake in potatoes. We compared five N treatments, which include a 0 N control and 280 kg ha as ammonium sulfate and ammonium nitrate (AS/AN), polymer-coated urea (PCU), urea with a urease inhibitor (Urea+UI), or urea with a UI and a nitrification inhibitor (Urea+UI+NI). The study occurred on grower fields during the 2009, 2010, and 2011 growing seasons, and NO-N leaching was measured with equilibrium tension lysimeters. PCU resulted in a reduction in NO-N leaching and an increase in yield compared to AS/AN in a year with large early-season rainfall; Urea+UI also reduced NO-N leaching in this year. In 2010, large plot-to-plot variation and 250 kg ha of additional N applied by the grower masked our ability to see differences among fertilized treatments. In 2011, a year with less intense rainfall events, no differences among treatments were observed. Collectively, these results show a potential benefit to PCU, but these benefits are only realized under specific seasonal weather conditions. Overall, the percentage of applied N lost to leaching during the growing season and removed in biomass was relatively low, suggesting substantial amounts of NO-N leaching outside of the growing season.

Nutrient losses via subsurface tile cause environmental degradation of aquatic ecosystems. Various management practices are primarily aimed at reduction of nitrate leaching in tile discharge; however, studies on leaching of other nutrients are limited. A replicated plot experiment was initiated in 2016 as part of the Long-Term Agroecosystem Research (LTAR) network Croplands Common Experiment to quantify the effectiveness of management practices on leaching of NO-N, total P, K, and S from drained soils. Corn (Zea mays L.) and soybean (Glycine max L. Merr.) were grown under five different treatments: (1) BP: basic practice with fall chisel plow; (2) NT: no-till crop production; (3) RC: no-till with a winter rye (Secale cereale L.) cover crop; (4) DW: no-till with woodchip denitrification walls parallel to both sides of the tile; and (5) ZN: zero N; no-till without N fertilization. Compared to BP, both RC and DW treatments reduced NO-N load by 63% and 47%, respectively; 15.5, 5.8, and 8.2 kg N ha year, while omitting N fertilization did not impact N loads (12 kg N ha year). The DW resulted in greater K loss compared to BP, presumably due to decomposing woodchips. No-till practices increased drainage flow and K and P loads compared to conventionally tilled BP plots but had no impact on other nutrients. The BP produced the highest corn yield, whereas soybean yields were not affected by treatments. These findings indicate that while some conservation practices are effective in reducing nutrient leaching, others are likely to increase their loss and reduce crop yields.

Although ecosystem management and restoration are known to enhance carbon storage, limited knowledge of ecosystem-specific soil organic carbon (SOC) stocks and processes hinders the development of climate-ready, biodiversity-focused policies. Baseline SOC stocks data for specific ecosystems is essential. This paper aims to: (i) examine SOC stock variability across major grassy ecosystems in Brazil and (ii) discuss data limitations and applications. We compiled the Grassland Synthesis Working Group dataset, which comprehensively aggregates SOC stocks data from published studies on main Brazil's grassy ecosystems. Our dataset results from systematic literature review and regional soil sampling datasets. The dataset provides spatially explicit SOC stocks, physical soil properties, and ancillary information from 182 studies (1996-2021) across 803 sites, spanning 35° latitude and 28° longitude. The dataset, structured in relational tables, reports soil C stocks and ancillary soil parameters at depths up to 100 cm. SOC stocks vary by grassy ecosystem types and sampling depth, with subtropical grasslands (Campos Gerais, South Brazilian highland grasslands, and Pampa) showing the highest SOC stocks across all depth layers (SOC 0-30 cm: 64.5-162.8 Mg C ha; SOC 0-100 cm: 137.6-224.7 Mg C ha). The tropical Cerrado and Amazon grassy ecosystems exhibit high SOC stocks, particularly in subsurface layers (SOC 0-30 cm: 53.6 and 38.3 Mg C ha; SOC 0-100 cm: 109.8 and 121.4 Mg C ha, respectively). Our data analysis shows high carbon stocks in natural/seminatural ecosystems, but some ecosystems are undersampled. The dataset on SOC stocks in grassy ecosystems could greatly aid Brazil's national greenhouse gas inventory.

Legacy phosphorus (P) is a concept advanced by Dr. Andrew Sharpley and colleagues that was originally applied to the persistence of anthropogenic signatures in watersheds, and it has since been adopted in a diversity of settings to help guide the science and management of P. Following Sharpley's example to develop consensus-based science, we considered contrasting perspectives on legacy P and defined legacy P as those stores within the environment that arise from historic human activity excluding "natural" or "background" geogenic sources. Legacy P is not restricted to one system or setting; it may reside in soils, sediments, biota, and water bodies. Legacy P has been estimated by fluxes (inputs minus outputs of P to a system) or, equivalently, by mass stocks (total minus geogenic). Because the origin of P in the environment cannot currently be directly quantified, we recommend that researchers report "total P" to track wider watershed P stocks and fluxes of P that include legacy P. We recognize that the definition of legacy P will continue to evolve as we continue to work toward consensus. Ultimately, the final definition of legacy P has consequences for the implementation and success of regulatory and voluntary strategies for legacy P management in agricultural systems. We support continued progress toward a consensus-backed, research-grounded definition for legacy P that is widely applicable yet useful for guiding management and policy.

The evolution and spread of antibiotic resistance are problems with important consequences for bacterial disease treatment. Antibiotic use in animal production and the subsequent export of antibiotic resistance elements in animal manure to soil is a concern. Recent reports suggest that exposure of pathogenic bacteria to glyphosate increases antibiotic resistance. We review these reports and identify soil processes likely to affect the persistence of glyphosate, antibiotic resistance elements, and their interactions. The herbicide molecular target of glyphosate is not shared by antibiotics, indicating that target-site cross-resistance cannot account for increased antibiotic resistance. The mechanisms of bacterial resistance to glyphosate and antibiotics differ, and bacterial tolerance or resistance to glyphosate does not coincide with increased resistance to antibiotics. Glyphosate in the presence of antibiotics can increase the activity of efflux pumps, which confer tolerance to glyphosate, allowing for an increased frequency of mutation for antibiotic resistance. Such effects are not unique to glyphosate, as other herbicides and chemical pollutants can have the same effect, although glyphosate is used in much larger quantities on agricultural soils than most other chemicals. Most evidence indicates that glyphosate is not mutagenic in bacteria. Some studies suggest that glyphosate enhances genetic exchange of antibiotic-resistance elements through effects on membrane permeability. Glyphosate and antibiotics are often present together in manure-treated soil for at least part of the crop-growing season, and initial studies indicate that glyphosate may increase abundance of antibiotic resistance genes in soil, but longer term investigations under realistic field conditions are needed. Although there are demonstratable interactions among glyphosate, bacteria, and antibiotic resistance, there is limited evidence that normal use of glyphosate poses a substantial risk for increased occurrence of antibiotic-resistant, bacterial pathogens. Longer term field studies using environmentally relevant concentrations of glyphosate and antibiotics are needed.

Phosphorus (P) loading from tile-drained agricultural lands is linked to water quality and aquatic ecosystem degradation. The RZWQM2-P model was developed to simulate the fate and transport of P in soil-water-plant systems, especially in tile-drained croplands. Comprehensive evaluation and application of RZWQM2-P, however, remains limited. This study evaluates RZWQM2-P in simulating P dynamics using extensive data and assesses the potential of management practices for mitigating P losses. Subsurface drainage and surface runoff flows were monitored at a tile-drained site from 2017 to 2020 in Ohio, and the water flow and P loss data were summarized on a daily basis. RZWQM2-P was calibrated and validated using those observed data and was subsequently used to assess the effectiveness of controlled drainage (CD) and winter cover crops (CC) in reducing P losses. The model satisfactorily simulated dissolved reactive P (DRP) loss from tile drainage on daily and monthly bases (Nash-Sutcliffe efficiency [NSE] = 0.50, R= 0.52, index of agreement [IoA] = 0.84 for daily; NSE = 0.73, R= 0.78, IoA = 0.94 for monthly) and total P (TP) loss on a monthly basis (NSE = 0.64, R= 0.65, IoA = 0.88), but the daily TP simulation was less accurate (NSE = 0.30, R= 0.30, IoA = 0.59). Simulations showed that winter rye CC reduced DRP by 16% and TP by 4% compared to the base scenario, whereas CD increased DRP (60%-129%) and TP (5%-17%) losses at three tested outlet elevations compared to free drainage. RZWQM2-P can capture P dynamics in tile-drained cropland and is a promising tool for effective P management.

Hydrologic alterations associated with urbanization can weaken connections between riparian zones, streams, and uplands, leading to negative effects on the ability of riparian zones to intercept pollutants carried by surface water runoff and groundwater flow such as nitrate (NO ) and phosphate (PO ). We analyzed the monthly water table as an indicator of riparian connectivity, along with groundwater NO and PO concentrations, at four riparian sites within and near the Gwynns Falls Watershed in Baltimore, MD, from 1998 to 2018. The sites included one forested reference site (Oregon Ridge), two suburban riparian sites (Glyndon and Gwynnbrook), and one urban riparian site (Cahill) with at least two locations and four monitoring wells, located 5 m from the center of the stream, at each site. Results show an increase in connectivity as indicated by shallower water tables at two of the four sites studied: Glyndon and Cahill. This change in connectivity was associated with decreases in NO at Glyndon and increases in PO at Glyndon, Gwynnbrook, and Cahill. These changes are consistent with previous studies showing that shallower water table depths increase anaerobic conditions, which increase NO consumption by denitrification and decrease PO retention. The absence of change in the forested reference site, where climate would be expected to be the key driver, suggests that other drivers, including best management practices and stream restoration projects, could be affecting riparian water tables at the two suburban sites and the one urban site. Further research into the mechanisms behind these changes and site-specific dynamics is needed.

Residential lawn management often includes fertilizer application to encourage healthy plant growth and support the aesthetic preferences of homeowners and communities. These inputs may negatively impact the environment by increasing nutrient export to aquatic ecosystems via surface runoff or leaching through soil into groundwater. Fertilizer management and nutrient export are of particular concern in karst areas like North-Central Florida, where the underlying karst geology leads to rapid, direct connections between surface and groundwater ecosystems. We quantified nitrogen (N) and phosphorus (P) leaching from residential landscapes in North-Central Florida. We investigated nutrient leaching from landscapes spanning a real estate gradient and across different fertility treatments (no N fertilizer, synthetic mineral fertilizer, biosolids-based organic mineral fertilizer, compost topdressing, natural areas). We measured leachate from these landscapes weekly for 1 year. All residential landscapes, including control yards that received no N fertilizer, leached >10x more nitrate than natural areas, and landscapes treated with synthetic fertilizer exhibited an >80x increase in nitrate leaching. Fertilizer treatments also appeared to alter the N leaching composition, with a greater proportion of total dissolved N leaching coming from nitrate in fertilized treatments (synthetic and organic) compared to natural, control, or compost-treated landscapes. These results show that landscape management and human actions are important drivers of nutrient leaching in residential landscapes. While all residential lawns leached more N than natural areas, less leaching was associated with certain management approaches. When implemented at larger scales, these approaches may reduce the likelihood of negative impacts of residential landscapes on regional water quality.

Sustainable reuse of biosolids as fertilizers is being threatened by the presence of per- and polyfluoroalkyl substances (PFAS) in our waste stream warranting research on strategies that will minimize PFAS mobility from land-applied biosolids. Here, we evaluated the ability of waste-derived sorbents aluminum chlorohydrate water treatment residuals (ACH-WTRs, 1 wt%) and biosolids-based biochar (1.5 wt%) to reduce mobility of PFAS in columns with 3 wt% biosolids-amended soils with and without sorbent layered on top of soil only and operated under transient unsaturated conditions. Cycles of simulated rain events of approximately three pore volumes distributed over a 4-day period followed by 3 days of drying were imposed for 6 months. Total PFAS concentrations in collected leachates were lower in the sorbent-treated columns compared to the control columns. Biochar outperformed the ACH-WTR with 41% versus 32% lower total PFAS in leachate, respectively, compared to the control. The most significant mitigation effect was observed with PFOS (perfluorooctane sulfonate) with 68% and 62% less PFOS in the leachates from the columns treated with ACH-WTR or biochar compared to the control, respectively. These results provide a first-of-its-kind assessment of the potential benefit of co-applying WTRs or biochar with biosolids to reduce PFAS mobility in biosolids-amended soils.

Simple models can help reduce nitrogen (N) loss from land and protect water quality. However, the complexity of primary production systems may impair the accuracy of simple models. A tool was developed that assessed the risk of N loss as the product of N source inputs and relative transport by leaching and runoff. A dynamic process-based model was used to estimate the long-term monthly N loss risk by leaching and runoff in response to the interaction of static biophysical factors like soil type, slope, and long-term climate. Source inputs included dung and urine (from livestock), fertilizer, crop residues, and soil erosion. Estimates of the rank of N loss risk were related (r = 0.69, p < 0.001) to 96 observations of N loss (kg ha year) across nine land uses; all but two of the observations fell within 95% prediction intervals. Across land uses, leaching accounted for 84% of N loss risk. Additional observations are needed to determine if N loss risk is representative of short-rotation vegetables and to account for potential lag times between calculated and measured losses. The good performance of the tool suggests that when displayed spatially, the tool can be used to target high-risk areas with actions to reduce the risk of N loss and the likelihood of water quality impairment.

Land application of biosolids to pastures confers multiple agronomic and environmental benefits, particularly in coarse-textured soils with low nutrient and organic matter levels. However, concerns over potential water quality have led to more stringent regulations that will limit beneficial reuse of biosolids in Florida. This 3-year field study evaluated the impacts of biosolids application strategies on N and P leaching losses, and soil P availability in an established bahiagrass (Paspalum notatum Flueggé) pasture. Treatments consisted of 2 P sources (biosolids and inorganic fertilizer) applied at 0, 20, 40, and 60 kg total P ha. Inorganic fertilizer treatments received the same N loads as the corresponding biosolids treatments. Biosolids and inorganic fertilizer increased in situ soil P availability and pore-water P concentrations relative to the control. Pore-water P concentrations increased linearly with P rate with the greatest values generally associated with inorganic fertilizer. Relatively low leachate P concentrations (below the detection limit of 0.025 mg L in 596 out of 777 samples) observed in the current study indicates minimum P offsite movement risk regardless of the P management strategy. Annual P mass leached was not affected by treatments; however, inorganic fertilizer resulted in modest but significant greater annual NO-N mass leached than the other treatments. Lack of biosolids application rate effect on P and N leaching losses indicates that reduction in biosolids imposed by new state regulation will likely have no positive impact on water quality. Data demonstrated that, when properly managed, biosolids can be an environmentally sound fertilizer source for pastures.

Concerns regarding per- and polyfluoroalkyl substances (PFAS) and their precursors have driven increased research into their sources, impacts, and mitigation strategies, aiming to reduce their prevalence in the environment. While much of this research has centered on known large sources of PFAS (e.g., military bases, airports, fire training sites, and some manufacturing facilities), there has been increased interest in evaluating the inadvertent introduction of PFAS into agroecosystems from beneficial reuse of treated domestic wastewater for irrigation and land application of biosolids and composts derived from food waste. Additional sources to agricultural fields include the use of PFAS-containing pesticides. These activities raise questions regarding the potential impacts of PFAS introduced to agricultural systems on rural water supplies, soil health, and food safety. This special section contains papers that fall into three categories: (i) source assessment of PFAS in water and wastewater residuals destined for beneficial reuse in agroecosystems, (ii) improved understanding of PFAS fate and transport in agroecosystems following land application of PFAS-containing materials, and (iii) small-scale assessment of techniques that demonstrate promise for mitigating PFAS mobilization in agroecosystems. The work contained in this special section can be used to help guide future decisions related to PFAS guidelines, policies, and regulations in agroecosystems intended to protect human and ecological health.