Journal of environmental quality最新文献

Eutrophication enhances emissions of greenhouse gases (GHGs) from surface waters. Policies designed to ameliorate eutrophication by limiting nutrient loadings to surface waters can reduce these GHG emissions and, in turn, reduce future climate damages (e.g., from heat stress, sea-level rise, etc.)—yet this benefit has not been considered in benefit-cost analyses of water quality policies. We address this gap by using a set of linked watershed, lake, and aquatic GHG models to estimate emission reductions from a large-scale nutrient management program in the America's largest estuary, the Chesapeake Bay. The modeling system predicts reductions in chlorophyll-a, total phosphorus, and GHG emission rates in waterbodies throughout the watershed, but those in the southern portion of the watershed are predicted to exhibit greater reductions than those in the north, likely due to strong climate (e.g., ice-cover duration) and land-cover gradients across the domain. We estimate climate benefits from changes in GHG emissions from these water bodies of over $300 million over the first 50 years of the program (2025–2075)—similar in magnitude to commonly quantified categories of water quality benefits. We then extrapolate our results to the third largest drainage basin in the world—the Mississippi-Atchafalaya River Basin—to estimate climate benefits of reduced GHG emissions from lakes and reservoirs in the basin resulting from a similarly stringent nutrient management policy. Our findings suggest that reductions in GHG emissions from nutrient management programs should not be overlooked when evaluating the societal benefits of such policies.

Separation and pyrolysis of the solid fractions of biogas digestate and animal slurry offer potential solutions to environmental and logistical challenges associated with direct slurry application as fertilizer. However, thermochemical transformations during pyrolysis typically reduce P availability. This study evaluated biochars produced at 400°C, 500°C, and 600°C from the solid fractions of biogas digestate (BDF) and pig manure (PMF) for their P-fertilization effects using a pot experiment with perennial ryegrass (Lolium perenne var. Soriento) and the ³³P dilution approach. The ryegrass biomass across two harvests remained similar for all biochar treatments but was significantly lower than for the mineral fertilizer (KH₂PO₄) treatment. Significant differences were evident in P contribution from biochars and raw feedstocks, as well as in total P uptake rates between treatments. The readily available P contents of biochar and P-recovery rates in plant shoots were negatively correlated with pyrolysis temperature, which was especially pronounced for digestate-derived biochars. All materials except high-temperature biochar (600°C) had mineral fertilizer replacement values exceeding 50%, indicating substantial P-recycling potential. Biochars produced at 400°C and 500°C had a similar fertilizer value as their original feedstocks. Therefore, low-temperature pyrolysis of separated solid fractions represents a promising approach that preserves the P fertilizer value while providing climate benefits through soil C sequestration and reduced energy requirements for transport.

Practices such as no-tillage, cover crops, or diversification of crop rotation are thought to be capable of addressing climate change challenges while ensuring food security. Public and private sectors at national and international levels are currently incentivizing farmers to adopt these practices to increase soil carbon (C) levels, thus helping to mitigate climate change. However, increasing soil C levels with an expectation of mitigating and adapting to climate change needs further evaluation. Reduced soil disturbance, retention of crop residues, planting cover crops, or diversification of crop rotations with perennials are indeed effective, especially in the long term (>10 years), in improving soil properties that enhance climate change adaptation, but not so much climate change mitigation. However, planting of cover crops, considered to be one example that represents conservation agriculture, is currently practiced on only 4.7% of cropland in the United States. Further, we question whether current programs that pay for C stored in soil are sufficient to incentivize farmers to change their operations due to the high cost to test soil C to validate their efforts. We propose that to promote wider adoption of sustainable conservation agricultural practices, and to make large-scale positive impacts through their use, farmers should be paid to “do the right thing” instead of paying them based on soil C accrual. The literature indicates that doing the right thing includes (1) continuous no- or minimum-soil disturbance, (2) permanent biomass soil cover, (3) biodiversity in crop rotations, and (4) applying or practicing these three principles on a continuous year-after-year basis. Paying farmers to “do the right thing” versus paying farmers for C credits will lead to much higher adoption rates of sustainable conservation agricultural practices by farmers. This will in turn lead to improved crop production and soil and environmental quality.

To help envision the desired futures for agricultural systems in urbanized landscapes over the next 25 years, we assess the support of agricultural and nonagricultural residents for scenarios that propose alternative approaches to achieve long-term economic and environmental sustainability for agriculture in the Chesapeake Bay Watershed (CBW). The scenarios include (1) business as usual—or maintaining current trends, (2) providing incentives (e.g., public funds) that help agricultural producers engage in best management practices, (3) preserving farmland, (4) increasing farm profitability through enhanced local food efforts and strengthening rural and urban relationships, and (5) encouraging a societal shift from consumption of meat to vegetable-based proteins. We draw upon data from an online panel of 955 residents and a mail/online survey of 365 producers across the southern part of the CBW (Maryland, Delaware, and Virginia) in 2021 and 2022, respectively. Our results indicate that nonagricultural residents mostly supported Scenarios 3 and 4, while agricultural residents mostly supported Scenarios 2 and 3. The least supported scenarios from both groups were Scenarios 1 and 5. Residents' level of education, income, other sources of income, political identity, family farm ownership, age, and gender are related to support of the top scenarios. This information can help stakeholders and policymakers understand the broader landscape of perceptions and help with state or regional planning efforts.

Andrew Sharpley was one of the first scientists to point out that the effects of best management practices (BMPs) on improving water quality are often slower, smaller, and shorter-lived than expected due to legacy phosphorus (P). One BMP for reducing P runoff and ammonia (NH₃) volatilization that has been widely adopted is treating poultry litter with aluminum sulfate (alum). Because of the economic benefits of improved poultry production and reduced propane use, alum is now used to grow >40% of the broiler chickens in the United States. The objective of this study was to determine the legacy effects of alum treatment of poultry litter on P runoff. A 30-year study was conducted using paired watersheds, which were fertilized with untreated or alum-treated litter for 21 years and were not fertilized for the following 9 years. During the fertilization period (1995–2015) when incidental P losses were occurring, the annual P loads from untreated litter (2.0 kg P ha⁻¹) were 2.4 times higher than alum-treated litter (0.84 kg P ha⁻¹). Phosphorus losses during the unfertilized period (legacy P) from 2016 to 2024 were much lower, as would be expected; annual P loads in runoff from the watershed that had received untreated litter (0.64 kg P ha⁻¹) were almost twice as high as that from alum-treated litter (0.34 kg P ha⁻¹), which was due to lower water-soluble P in the soil. This study demonstrated that treating manure with alum has a long-lasting effect on P runoff from pastures, even after fertilization has ceased, providing further evidence that this is a sustainable BMP.

The expression of an organism's genes determines its own characteristics in any given environment. In this study, we demonstrate that the phenotypic traits of genetically modified transgenic Arabidopsis thaliana plants, designed for nutrient efficiency and enhanced yield, can be naturally and readily transferred to neighboring wild-type plants. Our findings reveal that the transgenic plants significantly influence the populational, compositional, and functional traits of their root-associated microbiome (RAM), resulting in a larger population, with distinct composition and high functional potential compared to wild-type plants, regardless of soil type. This phenomenon appears to stem from altered metabolite exudation patterns, which enhance root recruitment. Notably, the RAM plays a dual role: it not only contributes to the robust phenotype of the transgenic plants but also facilitates the transfer of these traits to adjacent wild-type plants. Upon transplanting wild-type plants into the presence of transgenics, we observed the induction of transgenic-like phenotypes. Metagenomic and compositional analyses indicate that this transfer is linked to an increase in 2,3-butanediol (2,3-BD) fermenting bacteria. Furthermore, exposure to 2,3-BD alone was sufficient to elicit transgenic phenotypes in wild-type plants. These results suggest that factors external to plant tissues, such as root-associated bacteria and their volatile metabolic products, play a crucial role in the transferability of plant phenotypes to neighboring plants. Our findings underscore the importance of evaluating microbiome interactions in the context of transgenic organisms and open new avenues for alternative agricultural practices that may reduce reliance on genetic modification.

Agricultural runoff is the major contributor to eutrophication. To address this problem, some have advocated for nutrient recovery from agricultural waste. We have previously reported phosphorus recovery from poultry litter using a sequencing batch reactor with CO₂-assisted nutrient extraction and NaOH-based precipitation of the slow-release struvite and potassium struvite fertilizers. In our patented process, US Patent US11104617B2, the process effluent was recycled to generate the slurry for the next batch. Pilot-scale studies suggested that precipitated particles were being recirculated during reuse of the process effluent, reducing overall recovery. The objective of this work was to improve struvite settling through the addition of natural coagulants and flocculant aids. Jar tests were conducted with liquid extracts generated from 20 g L⁻¹ poultry litter slurries. The solution pH was adjusted to 9.0 to precipitate struvite, and then variable chitosan and bentonite concentrations were dosed into the jars under rapid mix conditions at 120 rpm for 3 min. The particle size distributions showed that chitosan and bentonite formed larger particles. The 50th percentile struvite particle size increased from 0.07 µm without coagulant and flocculant aids to ∼400 µm with 100 mg L⁻¹ of chitosan and bentonite. When 500–1000 mg L⁻¹ of chitosan and bentonite were added, large, uniform flocs formed and settled within 1 h. The chitosan–bentonite system had optimal performance with 25 mg L⁻¹ chitosan and 10 mg L⁻¹ bentonite and 50 mg L⁻¹ chitosan and 50 mg L⁻¹ bentonite. The chitosan–alginate system generated larger flocs with 75 mg L⁻¹ alginate, but the addition of chitosan diminished performance. Alginate-only systems were most effective at aggregating fine struvite particles produced from poultry litter extracts and have the added benefit of providing an environmentally friendly alternative to conventional coagulants as a soil amendment that provides controlled nutrient release.

A case study was launched to quantify potential water quality benefits attainable through practical and realistic conservation implementation targets. The Lake Michigan Basin was selected because of its importance as a dairy, grain, and oilseed production region that supports a range of ecosystems and endangered species. The objective was to build a framework, implementing a widely accessible tool that could be applied by local conservation staff to set practical, watershed-level, clean water targets. The US Environmental Protection Agency's Pollutant Load Estimation Tool, which is free and provides a user-friendly web interface, was applied to quantify phosphorus and sediment load reduction from six conservation scenarios in each Hydrologic Unit Code-8 watershed. Conservation scenarios included rotational grazing, cover crops, conservation tillage, nutrient management, prairie strips, and a combination of the practices referred to as “regenerative agriculture.” Each scenario was compared to a baseline of current cover crop and conservation tillage adoption rates, established using remote sensing data. The model estimated that implementing the regenerative agriculture scenario, which would require an additional 2640 km² of conservation and $260 million in investment, could reduce phosphorus loads by 21% and sediment loads by 10% compared to current loading. Results confirm that conservation investments by multiple stakeholders at the federal, state, and local levels can result in meaningful impacts to achieve water quality goals. This framework can be applied to other regions with minimal data inputs, making it a scalable approach to guide collective action toward water quality conservation targets.

Nitrous oxide emissions from semiarid, irrigated cropping systems are strongly influenced by tillage, nutrient source, and cover cropping, yet their long-term interactive effects remain underexplored. We quantified N₂O emissions from a continuous silage corn (Zea mays) system under factorial combinations of tillage (conventional vs. reduced), nitrogen source (dairy manure vs. synthetic fertilizer), and winter cover cropping (triticale vs. fallow) over 3 years (2021–2023) following 6 years of prior treatment implementation. Dairy manure solids were applied annually in the fall from 2015 through 2020. No further manure applications were made, and from spring 2021 onward, N₂O fluxes were monitored to assess legacy effects. Fluxes were monitored weekly using vented, nonsteady-state chambers. Emissions were episodic, with peak emissions occurring after irrigation onset and during winter months. In 2021, reduced tillage plots produced 25% greater cumulative emissions than CT (3.3 vs. 2.7 kg N₂O-N ha⁻¹; p = 0.030), though no tillage differences were observed in subsequent years following a field-wide moldboard plowing in spring 2022. Manure-treated plots consistently produced the highest emissions, exceeding synthetic fertilizer treatments by 723%, 267%, and 147% in 2021, 2022, and 2023, respectively (p < 0.0001). Winter cover cropping lowered preplant soil nitrate but did not reduce N₂O losses in manured soils, likely due to continued in-season mineralization. These results show that manure legacy effects persist after applications end and that tillage impacts on emissions are short-lived. Optimizing nutrient use and reducing emissions in semiarid irrigated systems will require integrated management of manure, tillage, and irrigation.

Model projections predict increasing temperatures and precipitation change in many locations in the Central United States. To provide perspective on what these trends might bring relative to what has already happened, we compared historical temperature and precipitation change with what models from the Coupled Model Intercomparison Project (CMIP6) predict. The analysis focuses on regions represented by five long-term agroecosystem research sites along a latitudinal transect from Michigan to Iowa, Missouri, Oklahoma, and Mississippi. We analyzed trends in long-term records (≥50 years) of precipitation and temperature data at annual and monthly scales using indicators that characterize extreme and average temperature and rainfall amounts. Results show that temperatures have changed from 1900 to 2020, more for minimum (0.1°C–0.3°C decade⁻¹) than maximum (−0.1°C–0.2°C decade⁻¹), more for winter (−0.1°C–0.3°C decade⁻¹) than summer (−0.1°C–0.1°C decade⁻¹), and more often in the north than in the south. Except in Mississippi, annual precipitation has increased at rates of 25 mm decade⁻¹ or greater over 1950–2020, but monthly trends were inconsistent. Projected trends suggest continued temperature increases, highlighting the urgent need for research on management systems that are resilient to such increases.