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Dryland agriculture is fundamental to global crop production and vital to food security. Conservation tillage is extensively practiced in USA wheat cultivation. Meanwhile, the adoption of conservation tillage by Chinese farmers is limited. This meta-analysis compared the yield and nitrogen use efficiency (NUE) between conservation tillage and conventional tillage (CT) with different types of cropping systems, mulching methods, levels of nitrogen fertilizer (NF), and addition of manure. The meta-analysis presented that conservation tillage at high-NF enhanced the yield and NUE, and reduced the yield and NUE at low-NF, compared to CT. The interaction of conservation tillage with leguminous cover crops (LCC) and manure application increased the yield and NUE at low-NF, compared to CT. Non-leguminous cover crops (NLCC) increased the yield and NUE under high-NF than low-NF. The interaction of conservation tillage with management practices showed that the no-tillage (NT) with leguminous cover crops (LCC) significantly increased wheat yield by 58% and NUE by 47% under low-NF compared to CT. However, increasing the rate of NF did not increase the yield under such interaction. Cropping systems, mulching types, and manure application mainly determined the effects of conservation tillage on wheat yield and NUE. The adverse impact of CT on yield and NUE could be alleviated with the application of LCC and manure under moderate NF. We demonstrate that adding LCC and manure have a generally substitutive relationship with N fertilizer, resulting in a significant increase in wheat yield and NUE at low-NF doses as at high N fertilizer dosages. Therefore, based on the obtained results, moderate NF with LCC and manure application is recommended for growing winter wheat in dryland regions of the USA and China., (© 2024. The Author(s).)

Waste-to-energy systems can provide a functional demonstration of the economic and environmental benefits of circularity, innovation, and reimagining existing systems. This study offers a robust quantification of the greenhouse gas (GHG) emission reduction potential of the adoption of anaerobic digestion (AD) technology on applicable large-scale dairy farms in the contiguous United States. GHG reduction estimates were developed through a robust life cycle modeling framework paired with sensitivity and uncertainty analyses. Twenty dairy configurations were modeled to capture important differences in housing and manure management practices, applicable AD technologies, regional climates, storage cleanout schedules, and methods of land application. Monte Carlo results for the 90% confidence interval illustrate the potential for AD adoption to reduce GHG emissions from the large-scale dairy industry by 2.45-3.52 MMT of CO 2 -eq per year considering biogas use only in renewable natural gas programs and as much as 4.53-6.46 MMT of CO 2 -eq per year with combined heat and power as an additional biogas use case. At the farm level, AD technology may reduce GHG emissions from manure management systems by 58.1-79.8% depending on the region. Discussion focuses on regional differences in GHG emissions from manure management strategies and the challenges and opportunities surrounding AD adoption.

Reactive nitrogen (N) fluxes have increased tenfold over the last century, driven by increases in population, shifting diets, and increased use of commercial N fertilizers. Runoff of excess N from intensively managed landscapes threatens drinking water quality and disrupts aquatic ecosystems. Excess N is also a major source of greenhouse gas emissions from agricultural soils. While N emissions from agricultural landscapes are known to originate from not only current‐year N input but also legacy N accumulation in soils and groundwater, there has been limited access to fine‐scale, long‐term data regarding N inputs and outputs over decades of intensive agricultural land use. In the present work, we synthesize population, agricultural, and atmospheric deposition data to develop a comprehensive, 88‐year (1930–2017) data set of county‐scale components of the N mass balance across the contiguous United States (Trajectories Nutrient Dataset for nitrogen [TREND‐nitrogen]). Using a machine‐learning algorithm, we also develop spatially explicit typologies for components of the N mass balance. Our results indicate a large range of N trajectory behaviors across the United States due to differences in land use and management and particularly due to the very different drivers of N dynamics in densely populated urban areas compared with intensively managed agricultural zones. Our analysis of N trajectories also demonstrates a widespread functional homogenization of agricultural landscapes. This newly developed typology of N trajectories improves our understanding of long‐term N dynamics, and the underlying data set provides a powerful tool for modeling the impacts of legacy N on past, present, and future water quality. Plain Language Summary: Over the last century, people have increasingly used nitrogen fertilizer to increase crop yields. The nitrogen not taken up by crops in agricultural areas runs off of the land and pollutes rivers, lakes, and coastal areas. This excess nitrogen also forms a powerful greenhouse gas that contributes to climate change. Excess nitrogen can build up in the environment over time and pollute our water for decades. It is therefore necessary for us to know how much extra nitrogen has been applied over many decades to better understand current risks to the environment. In our study, we have used multiple data sources to calculate how much nitrogen has been added to the landscape, how much nitrogen has been removed through crop production, and how much human waste is produced, for every county in the contiguous United States from 1930 to 2017. We show that the main sources of nitrogen can be different in different areas of the country. We also show that high levels of nitrogen use can make landscapes in very different climates look very similar. This new data set will be very important for creating models that can predict how decades of high nitrogen inputs impact water quality and future changes in climate. Key Points: A county‐scale data set for components of the nitrogen (N) mass balance (TREND‐nitrogen) was developed for the contiguous United States, 1930–2017Cluster analysis was used to identify 10 clusters with unique N surplus trajectoriesSimilar nitrogen trajectories across diverse geographic regions indicate widespread functional homogenization of human‐dominated landscapes [ABSTRACT FROM AUTHOR]

Manures allow for nitrogen (N) and phosphorus (P) recycling but low N:P ratios result in P over-fertilization when applying manures to meet crop N demand. Such stoichiometric imbalances can result in inefficient use of non-renewable P resources as well as aquatic eutrophication. On average, P surpluses in wheat (Triticum aestivum L.) and corn (Zea mays L.) systems of the United States vary between 1.4 and 3.1 kg P per kg of plant-available nitrogen (PAN) applied. Hybrid systems combining manures and biological N2-fixation from cover crops can limit P over-fertilization and reduce synthetic N fertilizer inputs. On average, about 40–48% of corn and 69–75% of wheat crop N demand could be met by manures and legume cover crops in the United States. However, the range of their possible N contribution to a specific system is wide given the variability in nutrient concentrations/availability and transfer to a subsequent crop. The adoption of hybrid systems is also limited by other constraints, most notably the spatial decoupling between animal and crop production. [ABSTRACT FROM AUTHOR]

Winter rye (Secale cereale L.) is a popular cover crop in North Central United States for preventing soil erosion and nutrient losses, among other agronomic and ecosystem benefits. Winter rye can also be a high-quality spring forage option when double-cropped with corn silage (Zea mays L.), thus adding diversity to monocrop rotations. However, these sustainability-promoting benefits have potential trade-offs including soil nutrient immobilization and decreased corn yields. We hypothesized that winter rye would promote sustainable intensification of corn silage, as substantiated by decreased nitrogen budget and soil nitrate without yield loss. We also predicted that winter rye double-cropped and harvested as a forage would maintain total production (corn silage + rye harvest) compared to corn silage alone. This five-season study is representative of continuous corn silage systems in North Central United States, and Wisconsin specifically, distinguished by fall liquid dairy manure applications. Corn was planted after rye termination or harvest, and varying rates of nitrogen were applied to corn. As predicted, rye cover reduced preplant soil nitrate without affecting corn silage yield. Rye harvested as a forage crop reduced preplant and in-season soil nitrate, and total production equaled or exceeded corn silage yields without rye, despite a 13% decrease in corn silage yield. The 5-year nitrogen balance demonstrated almost 40% reduction in excess nitrogen in the rye forage system. This novel study demonstrated no cumulative or single-year agronomic limitations to winter rye implementation in manured, corn silage systems characteristic of North Central United States over a range of seasonal weather conditions. Furthermore, the dual use of rye as a cover crop conservation practice or harvested as a forage double-crop makes it agronomically advantageous and demonstrate potential for sustainable intensification in this system. This research is the first to show that sustainable intensification through double cropping dairy-based systems can increase high-quality biomass production while reducing nitrogen losses to the environment. [ABSTRACT FROM AUTHOR]

Using food waste (FW) as a co-substrate in anaerobic digestion (AD) results in increased energy production, decreases in greenhouse gas emissions, and recycles the FW nutrients back to the land for producing crops. This research investigated food waste AD systems in the United States (US) and Germany (DE) that co-digested FW with dairy manure at the lab and full-scale. In DE, the post-consumer FW had 32–49% more CH 4 potential (477–499 mL CH4 /g VS) than maize and grass silage (368 and 331 mL CH4 /g VS) and solid and liquid manure (243 and 91 mL CH4 /g VS). Methane production in the full-scale DE system with 66% FW (by volume) was 882 m3 CH4 /d, which was 37% higher than the laboratory results due to the 86-day retention and 42 °C AD conditions in the field. The pre-consumer FW in the US had a similar CH 4 potential (264–553 mL CH4 /g VS), but due to the lack of heating in the full-scale system, 62% less CH 4 was produced than the lab-based potential. While DE requires pasteurization of FW for AD and bans FW bans to landfills, the US does not have specific requirements for FW treatment in AD or federal FW landfill policies, with a few forthcoming FW bans in some municipalities and states. As FW diversion and utilization in AD systems is expected to grow, it is important to understand the effect of FW in biogas production and nutrient content, comparisons between lab and field-scale results, and the effect of policy on FW utilization. [ABSTRACT FROM AUTHOR]

• Biochar has the potential to improve animal waste composting process. • It can extend the thermophilic phase and lower pH. • It can also reduce NH 3 , CH 4 , and N 2 O emissions. • Feedstock and pyrolysis conditions affect the performance of biochar. • More studies that focus on biochar use in animal mortality composting are needed. The animal production industry in the United States is currently undergoing a phase of growth; however, such growth brings certain challenges. One of the most prominent concerns in this regard is the increasing amounts of animal waste produced as a natural consequence of stock population growth. For decades, composting, including that of manure and animal mortalities, has been utilized to manage animal waste. Recently, in an effort to enhance the composting process, biochar has been proposed for use as a compost amendment, and over the last few years, an increasing number of papers on composting with biochar have been published. However, although there have been a few review papers that have summarized the literature regarding biochar use in composting, none of these has focused on animal waste composting. Accordingly, the purpose of this review is to critically analyze the role of biochar in livestock and poultry waste composting, identify gaps in our current knowledge, and propose future research directions. On the basis of the studies analyzed, biochar has the potential to improve animal waste composting processes at application rates of 5–10%. Biochar can extend the thermophilic phase of the composting process, lower the pH of compost material, prevent leachate formation, and reduce ammonia, methane, and nitrous oxide emissions. Given that the feedstock used to produce biochar and the pyrolysis conditions employed in its production affect the performance of biochar, it is important to report the physicochemical properties of the biochars used to enable comparison of the results of different studies. Moreover, there is a need for further research to gain a better understanding of the impact of biochar regarding the elimination of antibiotic-resistant genes and animal mortality composting. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) emissions from dairy liquid storage systems can be a source of reactive nitrogen (N) released to the environment, with a potential to adversely affect sensitive ecosystems and human health. However, little on-farm research has been conducted to estimate these emissions and determine the factors that may affect these emissions. Six lagoons in south-central Idaho were monitored for one year using open-path Fourier transform spectrometry, with NH3 emissions estimated using inverse dispersion modeling (WindTrax software). Lagoon physicochemical characteristics thought to contribute to NH3 emissions were also monitored over this period. Average total emissions from the lagoons ranged from 12 to 43 kg NH3 ha-1 d-1, or 5.4 to 85 kg NH3 d-1. Emissions from the settling basin on one dairy were 30% of the total emissions from the liquid storage system, indicating that basins are important sources of on-farm NH3 emissions. Emissions generally trended greater during the summer, when temperatures were greater. High wind events and agitation of the lagoons created temporary increases in NH3 emissions irrespective of temperature. Lagoon physicochemical characteristics, such as total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN), were highly correlated with emissions (r = 0.52 and 0.55, respectively). Regression models were developed to predict on-farm NH3 emissions and indicated that TKN, TAN, wind speed, air temperature, and pH were the main drivers of these emissions. An on-farm N balance suggested that lagoon NH3-N losses represented 9% of total N lost from the facility, 65% of total lagoon N, and 5% of dairy herd N intake. A process-based model (Integrated Farm System Model) estimated values for N excretion and NH3-N loss from the lagoon within 5% of that measured on-farm. More on-farm research is needed to better refine both process-based models and emission factor estimates to more accurately predict NH3 emissions from lagoons on dairies in the western U.S. [ABSTRACT FROM AUTHOR]

In recent decades, the importance of managing the earth's dwindling phosphorus (P) has grown exponentially, as have efforts to develop a circular economy. Livestock manure represents a P-rich waste product, so recycling P from livestock manure has garnered the attention of scholars worldwide. Based on a global database from 1978 to 2021, this study presents the current status of recycling P from livestock manure and proposes strategies for efficient P utilization. Unlike traditional review articles, this work establishes a visual collaborative network on P recycling from livestock manure of research areas, countries, institutions, and authors through a bibliometric analysis using Citespace and VOSviewer software. The co-citation analysis of literature revealed the development of the main research content in this field, and further clustering analysis illustrated the current key research directions. Keyword co-occurrence analysis identified the hotspots and new frontiers of research in this field. According to the results, the United States was the most influential and actively contributing nation, and China was the country with the tightest international ties. The most popular research area was environmental science, and the Bioresource Technology published the largest number of papers in this area. The research priority was the technologies development of P recycling from livestock manure, of which the most used method was struvite precipitation and biochar adsorption. Subsequently, evaluation is also essential, including the economic benefits and environmental impacts of the recycling process by life cycle assessment and substance flow analysis, as well as the agronomic efficiency of the recycled products. New directions for technological innovation in recycling P from livestock manure and potential risks in the recycling process are explored. The results of this study may provide a framework for understanding the mechanisms of P utilization in livestock manure, and support the overall popularization of P recycling technology from livestock manure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Manure management on farms presents potential risks to human health and safety, including infectious, chemical, and physical exposures that may result in injury or fatality. Toxic gases and confined spaces are among the most common hazards. These hazards are especially salient for the Upper Midwest of the United States. This study characterizes the occupational health and safety practices and experiences of manure applicators in Minnesota. This cross-sectional study surveyed 162 commercial manure applicators about their work characteristics, safety practices, and health and safety experiences. Respondents reported an average of 17 hours per day applying manure during the busy season, which typically occurs several weeks each year. One hundred and thirty-one (90%) of 145 respondents did not regularly use gas monitors during application. Thirty-three (37%) of 90 respondents reported at least one symptom of gas exposure during manure application work. Those that worked with swine manure were more likely to report symptoms of gas exposure than those who did not work with swine (OR 9.5; CI: 2.0, 89.0). Those that had entered confined spaces were more likely to report symptoms of gas exposure than those who had not entered confined spaces (OR 4.4; CI: 0.1, 1.1). Fourteen (9%) of 150 respondents reported being injured when applying manure. Manure work can be hazardous and may be associated with injury and gas exposure. These findings offer a starting point for future research and intervention to protect and improve the health and safety of applicators.

The ability of both regulators and farmers themselves to monitor the impact of environmental practices may be an issue with nonpoint source pollution. Effects that can be perceived via direct sensory evidence provide information at low cost. Results from a survey of livestock farmers suggest that a practice that has more obvious effects on water quality, manure application setbacks, is more likely to be adopted than a more complicated one with less visible effects, manure testing. Farmers’ perceptions of the profitability of the two practices were similar. The importance of observability and complexity has implications for educational programs. [ABSTRACT FROM PUBLISHER]

Livestock manure management accounts for almost 10% of greenhouse gas emissions from agriculture globally, and contributes an equal proportion to the US methane emission inventory. Current emissions inventories use emissions factors determined from small-scale laboratory experiments that have not been compared to field-scale measurements. We compiled published data on field-scale measurements of greenhouse gas emissions from working and research dairies and compared these to rates predicted by the IPCC Tier 2 modeling approach. Anaerobic lagoons were the largest source of methane (368 ± 193 kg CH4 hd−1 yr−1), more than three times that from enteric fermentation (~120 kg CH4 hd−1 yr−1). Corrals and solid manure piles were large sources of nitrous oxide (1.5 ± 0.8 and 1.1 ± 0.7 kg N2O hd−1 yr−1, respectively). Nitrous oxide emissions from anaerobic lagoons (0.9 ± 0.5 kg N2O hd−1 yr−1) and barns (10 ± 6 kg N2O hd−1 yr−1) were unexpectedly large. Modeled methane emissions underestimated field measurement means for most manure management practices. Modeled nitrous oxide emissions underestimated field measurement means for anaerobic lagoons and manure piles, but overestimated emissions from slurry storage. Revised emissions factors nearly doubled slurry CH4 emissions for Europe and increased N2O emissions from solid piles and lagoons in the United States by an order of magnitude. Our results suggest that current greenhouse gas emission factors generally underestimate emissions from dairy manure and highlight liquid manure systems as promising target areas for greenhouse gas mitigation. [ABSTRACT FROM AUTHOR]

Little is known regarding hormone export from tile-drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile-drained fields were quantified. Before and during the 17-month study period (January 2009 - May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β- and 17α-estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β- and 17α-trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17-month study period were in ranges of 16-58 mg/ha for total estrogens, 6.8-19 mg/ha for natural androgens, and 4.2-44 mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9-26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high-flow events occur must be targeted. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the prevalence and risk factors for work-related respiratory conditions (asthma, farmer's lung, sinusitis, rhinitis, and environmental allergies, diagnosed by a physician) among farm and ranch operators in the central US. A survey was conducted by the Central States Center for Agricultural Safety and Health (CS-CASH) in 2018, focusing on work-related injuries, illnesses, exposures, and preventive measures in a seven-state region (Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, and South Dakota). Farms and ranches (n = 16,818) with an email address and annual sales exceeding $5,000 were randomly selected for the survey. Agricultural production and weather data were merged with survey responses. The relationship between exposures and respiratory conditions was analyzed using generalized estimating equations. We received responses from 3,268 agricultural operations (19% response rate) containing information on 4,064 individual operators. The life-time prevalence of (any) respiratory conditions among farm/ranch operators was 18%. Risk factors for respiratory conditions included exposures to grain/hay/feed dust (OR 2.41), animal confinement dust (OR 1.57), field/road dust (OR 2.11), manure/silage gasses (OR 1.66), anhydrous ammonia (OR 1.51), fuels/solvents/paints (OR 1.92), older age group >70 vs. <43 (OR 1.40), female gender (OR 1.82), and being primary vs. third operator (OR 1.61). Farmers and ranchers have a high prevalence of respiratory conditions associated with dust and gas exposures at work. More effective protective measures are needed using the hierarchy of controls, including improved use of respiratory protection.

Abstract: Anaerobic digestion (AD) is an economically viable manure treatment option for large dairies (>500 cows) in the U.S. However, roughly 90% of U.S. dairies have less than 200 cows, making this technology economically inaccessible to the vast majority of U.S. dairies. While there have been case studies of individual small dairies with anaerobic digesters, there are no comparative studies using cost data from these systems. The objectives of this study were to (1) determine the economic viability of small-scale U.S. digesters using cost data from nine existing 100 to 250-cow dairies and seven theoretical systems and (2) reevaluate the minimum size dairy farm needed for economically feasible AD in the U.S. Cash flow analysis results showed that total capital costs, capital costs per cow, and net costs per cow generally decreased with increasing herd size in existing systems. Among existing revenue streams, use of digested solids for bedding generated the highest revenue ($100cow−1 year−1), followed by biogas use for heating and/or electrical generation ($47 to $70cow−1 year−1) and CO2 credits ($7cow−1 year−1). No system had a positive cash flow under the assumed conditions (8% discount rate, 20-year term). However, six of the 16 systems had positive cash flows when 50% cost sharing was included in the analysis. Our results suggest that, with cost sharing, economically viable AD systems are possible on 250-cow dairies. Additional revenue streams, such as tipping fees for food waste, may reduce the minimum size to 100-cow dairies. [Copyright &y& Elsevier]

Abstract: Spatial concerns are growing in many rural regions in the United States. Exurban sprawl and residential development can often surge past urban boundaries and encroach on historically rural areas. These emerging “co-existence” problems affect both farms and non-farming rural residents. One area of particular concern has been zoning and land use regulation laws associated with livestock waste handling. In this research, we develop an agent based simulation/case example of a representative county in rural Vermont to illustrate how the proximity of non-farm rural residents (NFRRs) to existing dairy farms in the region can curtail potential farm expansion, primarily through laws governing livestock waste disposal and pit location. The disposal problem is further exacerbated by certain physical land features as many NFRR homes are located on escarpments, as well as other physical features which tend to run diagonally, the latter situation being one that further complicates field manure disposal traffic patterns. Thus, the co-existence issue in dairy farming in much of rural America has an important spatial dimension. [Copyright &y& Elsevier]

The manureshed represents cropland needed to safely assimilate manure nutrients from an animal feeding operation. Dairy manuresheds can be contained on-farm but may need to involve additional farms that can assimilate excess nutrients. We present case studies reviewing challenges and opportunities to manureshed management in four major dairy-producing states using available information on local manuresheds. Additionally, geographic information system software was used with data from regulated Minnesota dairies to assess cropland assimilative capacities and transport needs surrounding large dairies. Manureshed requirements vary across regions, but increased import of feed and soil phosphorus accumulation constrain on-farm manure utilization across the United States. In Minnesota, a growing proportion of Jersey cattle and differences in continuous corn (Zea mays L.) vs. corn-alfafa (Medicago sativa L.) rotations contribute to the amount of land needed to absorb dairy manure nutrients. Farm-gate budgets reveal that N-based manuresheds can be contained within Idaho dairies, but P-based manuresheds extend beyond the farm. In New Mexico, relocation of surplus manure nutrients off the farm is common via informal networks, but incentives to strengthen these networks could ensure sustainable manureshed management. Evaluation of manureshed requirements in Pennsylvania is often complicated by the need for additional nutrient management planning and greater understanding of nutrient balances on the preponderance of small dairies. Nutrient imbalances with highly concentrated dairy production often lead to the need for manure transport off-farm. However, advances in herd and cropland management offer opportunities to improve on-farm nutrient efficiencies, and emerging networks and technologies promise to facilitate manure export when needed., (© 2022 The Authors. Journal of Environmental Quality © 2022 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Nutrient circularity can help supply chain participants meet sustainability targets. Across the segmented beef supply chain, opportunity exists to reinforce and introduce nutrient circularity by recycling surplus manure nutrients from cattle feedlots to lands where cattle feed is produced. We describe four datasets developed to evaluate options in U.S. and Canadian beef systems. The datasets delineate three "circular manuresheds," each encompassing a hay-grazing landscape where beef cattle are raised on grazingland and supplemented with hay grown nearby, and the distant feedlots where those cattle produce manure nutrients for potential import back to the hayfields. We selected the hay-grazing landscapes of New Mexico, USA; Florida, USA; and western Canada (Manitoba, Saskatchewan, Alberta, British Columbia) because of their significant grazingland production and potential to substitute feedlot manure for commercial fertilizer on hayfields. In each circular manureshed, the manure nutrients from major feedlot destinations could supply a considerable proportion of the P used by hay for grazing cattle: 34% of the P requirements in New Mexico, 36% in Florida, and 6% in western Canada. The average distance to return the resource was 647 km for New Mexico, 1,884 km for Florida, and 1,587 km for western Canada. These magnitudes and distances suggest that the New Mexico circular manureshed may be the most economically viable in the current agri-food system, but this reflects only part of a greater, multi-factor assessment of tradeoffs. The circular manureshed concept provides a platform for simultaneous consideration of competing factors for sustainability via circularity., (© 2022 Her Majesty the Queen in Right of Canada. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Manure generated by livestock operations can cause negative impacts on the environment if there is no control of its storage, transport or application. Manure emits greenhouse gases into the atmosphere, and micro and macro nutrients accumulate in soil and bodies of surface water. Today, in the USA specific legislation exists for management and deposition of animal excreta that impact bodies of water, the soil and the atmosphere, which is supervised and certified by the Environmental Protection Agency (EPA). In Canada the regulations for management and deposition of animal manure are no less rigorous. In Argentina, Chile, Colombia and México regulation and government vigilance of the use and management of animal mature is scarce and confusing, specifying only certain norms for discharges of pollutants into water, while giving less importance to emissions into the atmosphere and soil, and there are no clear specifications related to animal manure. [ABSTRACT FROM AUTHOR]

Abstract: Changes in the ratio of volatile N to non-volatile specific minerals or total ash in manure can potentially be used to estimate losses of N from manure. The aim of this study was to evaluate the accuracy of using specific minerals (P, K, Ca, Mg, and Na) or total ash as markers to estimate volatile N losses from incubated manure slurries. Holstein cows were fed diets with the forage as predominantly corn silage (CS) or alfalfa silage (AS) or a diet identical to the CS diet except 5g/kg urea was added (CSU). Total output of urine and feces were measured and used to prepare two types of slurry mixtures (all slurry mixtures contained 1200g of manure per tray): (1) as excreted (AsEx) and (2) AsEx+sand (SAND). The SAND slurry was designed to mimic manure from barns that used sand as a bedding material. Feces and urine were mixed in the same proportion as excreted by the cows for both slurry types and 240g of sand were added to the SAND slurries. Initial and final (3d incubation period) slurry weights and concentrations of N, ash, and specific minerals were measured to calculate loss of volatile N. Losses of volatile N from the slurries were estimated as: (N intake−N milk)−[N/ash×(ash intake−ash milk)], where N and ash intake=g/d consumed by the cow; N and ash milk=g/d secreted in milk; and N/ash=ratio of N and ash concentrations in slurry samples at 3d. To evaluate specific minerals as markers, the same equation was used except that Ca, K, Mg, Na or P replaced the ash term. Measured N losses from the AsEx slurries were 0.44, 0.62, and 1.03g/3d for the AS, CS, and CSU treatments and estimated N losses (using N/ash) were 0.29, 0.49, and 1.14g/3d. Estimated losses were less than measured losses for cows with negative N balance and greater than measured losses for cows in positive N balance. For AsEx slurries, the use of N to specific mineral ratios was generally less accurate than using the N/ash ratio. Estimated N losses from SAND slurries were extremely inaccurate for all markers. The use of the N/ash ratio to estimate N volatilization from manure shows promise but markers that are in appreciable concentrations in bedding material will not be accurate. [Copyright &y& Elsevier]

Abstract: As dairy operations continue to intensify world-wide, with greater nitrogen (N) inputs contributing to increasing productivity, the reliance on N recycling is decreasing, leading to larger N surpluses and environmental losses. We investigated feed N use efficiency (FNUE) and milk urea N concentrations (MUN) of the lactating herd, and manure management practices on 29 grazing and confinement-based commercial dairy farms in Victoria, Australia and Wisconsin, USA, to assess opportunities to increase N efficiency and reduce N losses. There was a similar variation in FNUE on dairy farms in Victoria and Wisconsin, ranging from 15 to 35%. FNUE and MUN levels demonstrated opportunities to improve diet management and reduce N intakes on many farms in both regions. In summer, Victorian dairy farms were significantly (P <0.001) less efficient in converting feed N into milk, even though low N intakes were determined on 7 farms. Grazing-based systems had between 51 and 89% of excreted N directly deposited on to pasture soils, while on confinement-based farms between 57 and 100% of excreted N was deposited in areas with routine collection, which was reapplied to cropped land. Irrespective of the production system, only a small proportion of available land was used to apply collected manure. On a large number of farms in both regions, substantial amounts of excreted N were deposited in non-productive areas with no collection, potentially increasing the risk of N losses in surface runoff. We suggest that simple on-farm assessments can be used in contrasting dairy production operations internationally to assess feed and manure N management practices, which will assist in developing appropriate industry benchmarks and benefit productivity and environmental outcomes. [Copyright &y& Elsevier]

Each year, over 16 million tons of poultry litter is produced in the United States. Federal and state regulations now limit the amount of poultry litter that can be land-applied, making it difficult to store and dispose of poultry litter. The objective of this study was to evaluate composted poultry litter (CPL) as a fertilizer source for bedding plants at various rates in comparison with commercially available inorganic fertilizers in regard to plant growth and nutrient leaching. Two experiments were conducted to evaluate use of CPL as fertilizer for landscape annual bedding plants. Petunia spp. 'Celebrity Red' and Verbena hybrida 'Quartz Scarlet' were planted in raised beds simulating an urban landscape. Before planting, 10 inorganic fertilizer or CPL treatments were incorporated into the raised beds, including Peafowl® brand garden-grade fertilizer 13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m² and 9.8 g N/m², Polyon®13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m² and 9.8 g N/ m², and CPL at rates of 4.9 g N/m²,9.8 g N/m²,19.6 g N/m²,29.4 g N/m²,39.2 g N/m², and 49 g N/m². Use of CPL incorporated into landscape planting beds as a fertilizer source resulted in plants equal to or larger than plants grown with conventional inorganic fertilizers. Nitrate (NO3) and ammonia (NH4) levels in leachates from plots amended with CPL were comparable with plots amended with commercial inorganic fertilizers and nitrogen (N) levels were in most cases less in plots fertilized with CPL when compared with inorganic fertilizers when the same N rate was applied. Composted poultry litter may not be able to fully replace inorganic fertilizers, but it can reduce inorganic fertilizer requirements and provide an environmentally sound alternative to poultry waste disposal as well as provide beneficial aspects for plant growth in annual bedding plants. [ABSTRACT FROM AUTHOR]

Abstract: Pollution from concentrated animal feeding operations (CAFOs) in the United States is impairing water quality. CAFOs have been designated as point sources of pollutants, so under the Clean Water Act, they need a permit before they discharge pollutants into federal waters. Federal regulations known as the CAFO Rule delineate particulars about which CAFOs need permits and details about how CAFOs must minimize discharges of pollutants. The provisions of the CAFO Rule have been controversial. Revisions in 2003 and 2008 were challenged by agricultural and environmental groups for not complying with the requirements set forth by federal law. Agricultural groups feel the rule imposes too many costs and that some of the regulatory provisions are invalid because they not pursuant to any statutory authority. Environmentalists feel that the rule does not provide sufficient requirements to prevent discharges of pollutants. The analysis of five major issues illuminates the challenges faced by governments as they make efforts to limit contamination of water resources. [Copyright &y& Elsevier]

Abstract: Effectiveness of surface-applied unincorporated broiler litter as a fertilizer relative to conventional inorganic fertilizers under no-till or conventional-till cotton (Gossypium hirsutum L.) production systems in the upland soils of the southern and southeastern USA is not well documented. The objectives of this research were to (1) test if broiler litter improves plant macronutrient (N, P, K, and Mg) nutrition of cotton above that of cotton fertilized with conventional inorganic fertilizers and (2) determine if lack of incorporating litter into the soil reduces macronutrient concentration in cotton plant parts in an upland soil considered marginal for cotton. Six treatments consisting of an unfertilized control, a fertilized standard (STD), two litter-only, and two litter plus inorganic N as urea–ammonium nitrate solution (UAN) were tested in two adjacent fields, one under no-till (NT) and the other under conventional-till (CT) systems. Litter alone, UAN, or a combination of litter plus UAN were applied to supply 101kgha−1 plant available N assuming nearly all of the UAN-N and 50% of the total litter N becomes plant available during the cotton growing season. Concentration of N, P, K, and Mg were measured in leaves, stems, and reproductive parts on three or four dates between early flowering and maturity. Cotton fertilized with the litter-only treatments always had less N concentration but greater P and K concentration in leaves, stems, and reproductive parts than cotton that received the STD treatment. Leaf and stem Mg concentration seems to depend on the N concentration in these plant parts. Lack of incorporating litter into the soil reduced N concentration in nearly all plant parts at all growth stages, suggesting some amount of the litter-derived N is lost due to lack of incorporation. Lack of incorporation also reduced leaf and stem Mg concentration, which seemed to be due to its reducing effect on N concentration. Unlike N and Mg, lack of incorporation did not consistently affect concentrations of P and K in all plant parts. Regardless of the incorporation treatment, fertilization with the litter-only treatments increased tissue P and K concentration and supported lint yield exceeding that of the STD without increasing tissue N concentration. [Copyright &y& Elsevier]

The article presents a study which examines the effects of agricultural sources and transformations on nitrogen stable isotopes in streams in the U.S. Primary consumer invertebrates from streams in agricultural settings in Wisconsin were collected to evaluate the relative influence of animal manure, inorganic fertilizer and denitrification on biotic δ15nitrogen. According to the findings, inorganic fertilizer is more likely than manure to drive variability in biotic δ15nitrogen and to cause excessive nitrogen concentrations in streams.

In an effort to save regulatory resources, the US Environmental Protection Agency and individual states have interpreted the Clean Water Act in a manner that authorizes discharges from concentrated animal feeding operations without the review of nutrient management plans. Environmental groups have objected to the abbreviated regulatory procedures, and courts have ruled that permitting agencies must review substantive documentation of effluent limitations contained in nutrient management plans. Proposed new federal regulations prescribing the requirement of a meaningful review of appropriate documentation by the permitting agency respond to the judicial mandates. To facilitate regulatory approval, regulators might use a state certification program to achieve the obligatory meaningful review. Independent certifiers would ensure that an operation's land application of manure meets federal water quality requirements. [ABSTRACT FROM AUTHOR]

Abstract: Non-native plant species pose a serious ecological and economic threat to managed and natural ecosystems; therefore, there is a great need to identify sources for the introduction of non-native species and develop management plans to reduce or eliminate their introduction. Horses have been suggested to be an important source for the introduction of non-native plant species along trails, but the conclusions were based on anecdotal evidence. In this study, horse hay, manure, and hoof debris samples were collected from 12 to 24 horses at five endurance ride events in North Carolina, Kentucky, Illinois, Wisconsin, and Michigan. One sub-sample of each material from each horse was sown in pots and grown under ideal conditions to determine if horse hay, manure, and hoof debris samples contained seeds from non-native species. A second sub-sample of each material from each horse was placed back on their respective trail to determine what plants would germinate and establish on the trail. Vegetation surveys were also conducted along 50m transects perpendicular to horse and hiking (horses not permitted) trails at three of the five sites to compare species composition of native and non-native plant species. On average, non-native plant species germinated in 5.2% of the hay samples in the pots, but non-native species did not germinate from the manure or hoof debris samples. Only 3 of the 288 (≈1% of total samples) hay, manure, and hoof debris plots established on horse trails at the five sites contained plants, all of which were native plants, at the end of the first growing season and no plants were observed at the end of the second growing season. Non-native species composition and percent of total plants species did not differ significantly (p =0.56) between horse and non-horse trails, and non-native plant species were only found within 2m of the trail. The results of this and another study [Campbell, J.E., Gibson, D.J., 2001. The effect of seeds of exotic species transported vie horse dung on vegetation along trail corridors. Plant Ecology 157, 23–35] demonstrate that horse hay and manure does contain seeds of non-native plant species, but native and non-native plant species rarely become established on horse trails because of the harsh environmental conditions. Management and policy implication of this study are discussed. [Copyright &y& Elsevier]

Federal and state regulations are being promulgated under the Clean Air Act to reduce hazardous air emissions from livestock operations. Although much is known about air emissions from livestock operations in Europe, few data are available on emissions from livestock facilities in the United States and the management practices that may minimize these emissions. The objective of this study was to measure seasonal and diet effects on ammonia emissions from experimental tie-stall dairy barns located in central Wisconsin. Four experimental chambers each housed 4 lactating Holstein dairy cows for three 28-d trial periods corresponding to spring, early fall, and winter. A 4 x 4 Latin square statistical design was used to evaluate 4 diets [corn silage (CS)- or alfalfa silage (AS)-based diets at low or high crude protein] in each chamber for a 4-d ammonia monitoring period. Partially due to higher crude protein levels, average ammonia-N emissions during spring (18.8 g/cow per d) were approximately twice the emissions recorded during early fall (8.4 g/cow per d) and 3 times greater than emissions during winter (6.7 g/cow per d). Ammonia-N emissions accounted for approximately 1 to 3% of consumed feed N, 2 to 5% of excreted manure N, and 4 to 11% of manure ammonical N. Night-time ammonia emissions were on average 30% lower than daytime emissions. Forage type did not affect ammonia emissions during winter or early fall. Only during early spring were ammonia emissions lower from chambers containing cows fed low-CP diets than from cows fed high-CP diets. Of the total chamber N inputs (feed and bedding), 93, 91, and 95% were recovered in N outputs (milk, manure, body weight change, and ammonia N) during spring, early fall, and winter trials, respectively. Confidence in the accuracy of ammonia emission results was gained by the relatively high chamber N balances and favorable comparisons of study data with published relationships among the variables of feed N intake, milk urea N, manure N, and urine N excretion, and ammonia emissions. [ABSTRACT FROM AUTHOR]

Most estimates of carbonaceous gas emissions from manure treatment lagoons are based on biogas production from anaerobic digesters, gases collected over covered lagoons, or the CH4 production potential of animal waste. More data from direct measurements are necessary for evaluating mitigation strategies. Researchers at Oklahoma State University have successfully operated a pilot-scale bioreactor consisting of four 270 L columns that recreate environmental conditions found in anaerobic lagoons as indicated by color, temperature, pH, and electrical conductivity (EC). The columns were loaded at a surface organic loading rate similar to lagoons treating manure from commercial swine farms in the state of Oklahoma (935 kg VS/ha-day). The simulated mid-to-late summer CH4 emission rate was determined to range between 200 and 300 kg/ha-day, and the CO2 emission rate ranged between 380 and 580 kg/ha-day. Approximately 65% of the total carbon applied to the surface of the lagoon simulator was recovered as CH4 and CO2 gases; however, lagoon methane production was greater than expected using chemical oxygen demand (COD) as a predictive standard. The daily patterns of gaseous emissions and volatile organic acid concentrations in the liquid suggest that CH4 production takes place across the entire depth of the reactor. Easily digestible organic matter is converted in the upper layers; more slowly digested material settles and is converted at the sludge layer. Data on day versus night emissions show that biogas had a higher proportion of CO2 during the day than during the night. [ABSTRACT FROM AUTHOR]

To provide locally-determined field data for extension and environmental management purposes, gaseous N losses were measured following cattle slurry application to an arable silty-loam soil in the mid-Atlantic region of the USA. The field had been cropped to no-till maize. NH3 volatilization was measured with the micro-meteorological, integrated horizontal flux (IHF) method, and denitrification with a core incubation method using acetylene inhibition. An early-winter surface application (5 December 1996; 88 m3 ha-1 supplying 91 kg NH-N ha-1) was either unincorporated or immediately incorporated. NH3 volatilization was measured from the unincorporated application, and denitrification from both slurry treatments and appropriate control soils. Total NH3 loss from the unincorporated slurry application was 19% of applied NH-N; temperatures were cool (4-6 °C), and 25 mm of rain fell within 24 h of application. For 3 months, enhanced denitrification occurred from the two slurry treatments, with generally higher rates from the incorporated slurry. Total net denitrification loss from the surface-applied and incorporated slurry treatments was, respectively, 11 and 17% of applied NH-N. Denitrification loss over the winter/early-spring period was appreciable but not substantial, even where NH3 volatilization was restricted by immediate incorporation. From the spring application (30 April 1997, 39 m3 ha-1 supplying 51 kg NH-N ha-1), total NH3 loss was 71% of applied NH-N. These NH3 volatilization loss data and the similarity of climate suggest that NH3 loss factors from recent NW European work are likely to be generally applicable in the mid-Atlantic region. NH3 volatilization from the spring application was also measured using the Z-instrument (ZINST) approach, and with a system of small wind tunnels. A comparative assessment of the three methods is reported. [ABSTRACT FROM AUTHOR]

Abstract The response of a long-term, mixed-species hayfield in Maine, USA, to commercial fertilizers and liquid dairy manure was evaluated over a 6-year period, including the effects on yield, nutrient concentration and cycling, forage species composition and soil nutrient levels. Nutrient treatments included an unamended control, N fertilizer, NPK fertilizer and liquid dairy manure (LDM). The application rates of plant-available N, P, and K were constant across treatments. Application of nutrients in any form increased forage yield, generally by 2–4 t dry matter (DM) ha-1 year-1 . Yield from NPK fertilizer was 0·05–0·25 higher than from LDM, due to differences in N availability. Yield responses to P and K were minimal and there appeared to be no difference between P and K in fertilizer and manure. The forage sward became increasingly dominated by grass species as the experiment progressed; application of P and K in fertilizer or LDM allowed Agropyron repens to increase at the expense of Poa pratensis . Forage nutrient removal accounted for all applied N and K, and nearly all applied P, throughout the study period, demonstrating the important role these forages can play in whole-farm nutrient management. [ABSTRACT FROM AUTHOR]

California''s dairies are the largest confined animal industry in the state. A major portion of these dairies, which have an average herd size of nearly 1000 animal units, are located in low-relief valleys and basins. Large amounts of liquid manure are generated and stored in these dairies. In the semi-arid climate, liquid manure is frequently applied via flood or furrow irrigation to forage crops that are grown almost year-round. Little is known about the impact of manure management practices on water quality of the extensive alluvial aquifers underlying these basins. The objective of this work is to assess nitrate and salt leaching to shallow groundwater in a relatively vulnerable hydrogeologic region and to quantify the impact from individual sources on dairies. The complex array of potential point and nonpoint sources was divided into three major source areas representing farm management units: (1) manure water lagoons (ponds); (2) feedlot or exercise yard, dry manure, and feed storage areas (corrals); and (3) manure irrigated forage fields (fields). An extensive shallow groundwater-monitoring network (44 wells) was installed in five representative dairy operations in the northeastern San Joaquin Valley, CA. Water quality (electrical conductivity, nitrate-nitrogen, total Kjehldahl nitrogen) was observed over a 4-year period. Nitrate-N, reduced nitrogen and electrical conductivity (EC, salinity) were subject to large spatial and temporal variability. The range of observed nitrate-N and salinity levels was similar on all five dairies. Average shallow groundwater nitrate-N concentrations within the dairies were 64 mg/l compared to 24 mg/l in shallow wells immediately upgradient of these dairies. Average EC levels were 1.9 mS/cm within the dairies and 0.8 mS/cm immediately upgradient. Within the dairies, nitrate-N levels did not significantly vary across dairy management units. However, EC levels were significantly higher in corral and pond areas (2.3 mS/cm) than in field areas (1.6 mS/cm) indicating leaching from those management units. Pond leaching was further inferred from the presence of reduced nitrogen in three of four wells located immediately downgradient of pond berms. The estimated minimum average annual groundwater nitrate-N and salt loading from manure-treated forage fields were 280 and 4300 kg/ha, respectively. Leaching rates for ponds are estimated to be on the order of 0.8 m/year, at least locally. Since manure-treated fields represent by far the largest land area of the dairy, proper nutrient management will be a key to protecting groundwater quality in dairy regions overlying alluvial aquifers. [Copyright &y& Elsevier]

Abstract Development of sustainable agricultural management systems will depend, in part, on the ability to better use renewable resources, such as animal manure, and to synchronize the levels of soil available N with crop plant needs during the growing season. This study was conducted at the US Meat Animal Research Center in the central USA to determine whether differences in electromagnetic (EM) soil conductivity and available N levels over a growing season can be linked to feedlot manure/compost application and use of a green winter cover crop. A series of soil conductivity maps of a research cornfield were generated using global positioning system (GPS) and EM induction methods. The study site was treated over a 7-year period with manure and compost at rates matching either the phosphorus or the nitrogen requirements of silage corn (Zea mays L.). The plot was split for sub-treatments of a rye (Secale cereale L.) winter cover crop and no cover crop. Image processing techniques were used to establish electrical conductivity (EC) treatment means for each of the growing season surveys. Sequential measurement of profile weighted soil electrical conductivity (EC a) was effective in identifying the dynamic changes in available soil N, as affected by animal manure and N fertilizer treatments, during the corn-growing season. This method also clearly identified the effectiveness of cover crops in minimizing levels of available soil N before and after the corn-growing season, when soluble N is most subject to loss. The EM method for assessing soil condition provides insights into the dynamics of available N transformations that are supported by soil chemical analyses. This real-time monitoring approach could also be useful to farmers in enhancing N use efficiencies of cropping management systems and in minimizing N losses to the environment. [ABSTRACT FROM AUTHOR]

It is estimated that enteric methane (CH 4 ) contributes about 70% of all livestock greenhouse gas (GHG) emissions. Several studies indicated that feed additives such as 3-nitrooxypropanol (3-NOP) and nitrate have great potential to reduce enteric emissions. The objective of this study was to determine the net effects of 3-NOP and nitrate on farmgate milk carbon footprint across various regions of the United States and to determine the variability of carbon footprint. A cradle-to-farmgate life cycle assessment was performed to determine regional and national carbon footprint to produce 1 kg of fat- and protein-corrected milk (FPCM). Records from 1,355 farms across 37 states included information on herd structure, milk production and composition, cattle diets, manure management, and farm energy. Enteric CH 4 , manure CH 4 , and nitrous oxide were calculated with either the widely used Intergovernmental Panel on Climate Change Tier 2 or region-specific equations available in the literature. Emissions were allocated between milk and meat using a biophysical allocation method. Impacts of nitrate and 3-NOP on baseline regional and national carbon footprint were accounted for using equations adjusted for dry matter intake and neutral detergent fiber. Uncertainty analysis of carbon footprint was performed using Monte Carlo simulations to capture variability due to inputs data. Overall, the milk carbon footprint for the baseline, nitrate, and 3-NOP scenarios were 1.14, 1.09 (4.8% reduction), and 1.01 (12% reduction) kg of CO 2 -equivalents (CO 2 -eq)/kg of FPCM across US regions. The greatest carbon footprint for the baseline scenario was in the Southeast (1.26 kg of CO 2 -eq/kg of FPCM) and lowest for the West region (1.02 kg of CO 2 -eq/kg of FPCM). Enteric CH 4 reductions were 12.4 and 31.0% for the nitrate and 3-NOP scenarios, respectively. The uncertainty analysis showed that carbon footprint values ranged widely (0.88-1.52 and 0.56-1.84 kg of CO 2 -eq/kg of FPCM within 1 and 2 standard deviations, respectively), suggesting the importance of site-specific estimates of carbon footprint. Considering that 101 billion kilograms of milk was produced by the US dairy industry in 2020, the potential net reductions of GHG from the baseline 117 billion kilograms of CO 2 -eq were 5.6 and 13.9 billion kilograms of CO 2 -eq for the nitrate and 3-NOP scenarios, respectively., (© 2022, The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

• Historic manure applications can enhance phosphorus (P) loss to surface waters. • Decrease in soil P levels below environmental thresholds can take decades. • Sufficient soil P was available for crop uptake after no P applications for 15 years. • Water-extractable P and P saturation are good indicators for P loss in soils. • Enhanced nutrient management practices are needed to curb P loss from soils. Manure applications exceeding crop phosphorus (P) requirements have historically occurred in intensive animal agriculture areas because of a lack of options to sustainably utilize manure. We investigated the legacy impacts of manure application on agronomic (Mehlich 3-P, M3-P) and environmental (water-extractable P, WEP; M3-P saturation ratio, M3-PSR) soil P pools after manure applications were ceased. Three field sites located in the coastal plain soils of northeastern United States received manure applications for four years, equivalent to 0, 100, 200, 300, and 400 kg total P ha−1 yr-1. Then, no manure or fertilizer P was applied for 15 years. The soil WEP (1:10 soil to water ratio) in manure treatments declined significantly (0.7–2.5 mg kg-1 yr-1) for the first 9 years, but did not significantly decline (0.2–0.4 mg kg-1 yr-1) between 9 and 15 years after cessation of manure application. Over the 15 years, the M3-P across manure treatments declined steadily at 7.7–15.3 mg kg-1 yr-1. Despite the decline, P pools in soils remained above agronomic (92 mg kg-1 M3-P) and environmental (8.6 mg kg-1 WEP, M3-PSR >0.15) thresholds in the highest manure treatments. Percent decline in soil P pools (60–71 % for WEP; 41–53 % for M3-P) was similar across all manure treatments despite a larger absolute WEP and M3-P decline for higher manure treatments. We conclude that in fields with a legacy of manure application, M3-P may decline 5.4–6.3% per year after cessation of P applications, while sufficient P will persist for decades as indicated by the abundance of agronomic and environmental P pools. [ABSTRACT FROM AUTHOR]

Objective: Manure storage, handling, and transport facilities and equipment have been associated with life threatening hazards on many livestock farms. These hazards have been documented in prior research as including 1) exposure to toxic manure gases or lack of adequate oxygen in enclosed structures, which can be fatal to both humans and livestock; 2) below and above ground liquid manure storage structures that have the potential risk for drowning and falling; and 3) mechanical hazards associated with manure handling and transport equipment, including entanglement, road collisions, runover, and equipment failure. Methods: Over the past 40 years, Purdue University's Agricultural Safety and Health Program (PUASHP) has collected, documented, and maintained data regarding agricultural-related injuries and fatalities associated with agricultural confined spaces in the United States. As part of ongoing surveillance, a total of 369 fatal and non-fatal cases relating to manure storage, handling and transport equipment, and facilities have been documented. Of these, 89 have involved children, youth, and young farm workers ages (birth-21) documented between 1975 and 2019. The purpose of this study was to summarize these 89 documented cases to better understand contributing factors and to develop recommendations for evidence-based strategies to reduce the frequency and severity of these incidents. Though recognized as not comprehensive for all incidents of this type, the data represent the largest data set known to exist, providing insight into previously unstudied hazards facing children and youth living and working on, and visiting farms as non-workers. Results: Findings in this study include: there has been an increase in the documented frequency of these incidents, which may be due, at least partially, to enhanced or more aggressive surveillance efforts; 57% of the cases were fatal; incidents involving underground or inground manure storage facilities were the most frequent type; incidents involving manure transport vehicles were higher than expected; 33% of the victims were five years of age and younger; and July was the month with the most documented incidents. Conclusions: Recommendations for future injury prevention strategies include incorporation of information on manure-related hazards in curricula targeting children and youth, more aggressive enforcement of child labor laws that currently prohibit the employment of youth to work in manure storage structures or to be involved in their operations, and greater use of physical and administrative controls, including safety signage, fencing, gates, and covers to restrict access to manure storage structures.

In the 1930s, erosion caused storms of dust to hurtle across the American Great Plains and Midwest. While agricultural conservation methods helped remediate this landscape, recent studies suggest the region is contending with a new type of particle cloud: desiccated fecal dust that renders the vitalities of factory farms airborne, potentially exposing those in their surrounds to various forms of illness while spreading antibiotic resistance genes. Thinking alongside these findings, and based on research within corporate hog farms, this article develops an ethnography of excrement by tracing the practices and knowledge of people who live and labor in proximity to late industrial lifeforms, such as confined pigs and resistance genes, and who are tasked with intimately shaping this unruly waste that has the potential to affect broader populations. In so doing, it analyzes the maintenance of American animals' toxic health alongside the politics of labor with complex anthropogenic materials., (© 2019 by the American Anthropological Association.)

Untreated biological soil amendments of animal origin (BSAAO), such as manure, are commonly used to fertilize soils for growing fruit and vegetable crops and can contain enteric bacterial foodborne pathogens. Little is known about the comparative longitudinal survival of pathogens in agricultural fields containing different types of BSAAO, and field data may be useful to determine intervals between manure application and harvest of produce intended for human consumption to minimize foodborne illness. This study generated 324 survival profiles from 12 different field trials at three different sites (UMES, PA, and BARC) in the Mid-Atlantic United States from 2011 to 2015 of inoculated nonpathogenic Escherichia coli (gEc) and attenuated O157 E. coli (attO157) in soils which were unamended (UN) or amended with untreated poultry litter (PL), horse manure (HM), or dairy manure solids (DMS) or liquids (DML). Site, season, inoculum level (low/high), amendment type, management (organic/conventional), and depth (surface/tilled) all significantly ( P  < 0.0001) influenced survival duration (dpi100mort). Spatiotemporal factors (site, year, and season) in which the field trial was conducted influenced survival durations of gEc and attO157 to a greater extent than weather effects (average daily temperature and rainfall). Initial soil moisture content was the individual factor that accounted for the greatest percentage of variability in survival duration. PL supported greater survival durations of gEc and attO157, followed by HM, UN, and DMS in amended soils. The majority of survival profiles for gEc and attO157 which survived for more than 90 days came from a specific year (i.e., 2013). The effect of management and depth on dpi100mort were dependent on the amendment type evaluated. IMPORTANCE Current language in the Food Safety Modernization Act Produce Safety Rule states no objection to a 90- or 120-day interval between application of untreated BSAAO and harvest of crops to minimize transfer of pathogens to produce intended for human consumption with the intent to limit potential cases of foodborne illness. This regional multiple season, multiple location field trial determined survival durations of Escherichia coli in soils amended with manure to determine whether this interval is appropriate. Spatiotemporal factors influence survival durations of E. coli more than amendment type, total amount of E. coli present, organic or conventional soil management, and depth of manure application. Overall, these data show poultry litter may support extended survival of E. coli compared to horse manure or dairy manure, but spatiotemporal factors like site and season may have more influence than manure type in supporting survival of E. coli beyond 90 days in amended soils in the Mid-Atlantic United States.

Reported estimates of CH 4 emissions from ruminants and manure management are up to 2 times higher in atmospheric top-down calculations than in bottom-up (BU) inventories. We explored this discrepancy by estimating CH 4 emissions of 2 dairy facilities in California with US Environmental Protection Agency (US EPA) methodology, which is used for BU inventories, and 3 independent measurement techniques: (1) open-path measurements with inverse dispersion modeling (hereafter open-path), (2) vehicle measurements with tracer flux ratio method, and (3) aircraft measurements with the closed-path method. All 3 techniques were used to estimate whole-facility CH 4 emissions during 3 to 6 d per farm in the summer of 2016. In addition, open-path was used to estimate whole-facility CH 4 emissions over 13 to 14 d per farm in the winter of 2017. Our objectives were to (1) compare whole-facility CH 4 measurements utilizing the different measurement techniques, (2) compare whole-facility CH 4 measurements to US EPA inventory methodology estimates, and (3) compare CH 4 emissions between 2 dairies. Whole-facility CH 4 estimates were similar among measurement techniques. No seasonality was detected for CH 4 emissions from animal housing, but CH 4 emissions from liquid manure storage were 3 to 6 times greater during the summer than during the winter measurement periods. The findings confirm previous studies showing that whole-facility CH 4 emissions need to be measured throughout the year to estimate and evaluate annual inventories. Open-path measurements for liquid manure storage emissions were similar to monthly US EPA estimates during the summer, but not during the winter measurement periods. However, the numerical difference was relatively small considering yearly emission estimates. Manure CH 4 emissions contributed 69 to 79% and 26 to 47% of whole-facility CH 4 emissions during the summer and winter measurement periods, respectively. Methane yields from animal housing were similar between farms (on average 20.9 g of CH 4 /kg of dry matter intake), but CH 4 emissions normalized by volatile solids (VS) loading from liquid manure storage (g of CH 4 per day/kg of VS produced by all cattle per day) at 1 dairy were 1.7 and 3.5 times greater than at the other during the summer (234 vs. 137 g of CH 4 /kg of VS) and winter measurement periods (78 vs. 22 g of CH 4 /kg of VS), respectively. We attributed much of this difference to the proportion of manure stored in liquid (anaerobic) form, and suggest that manure management practices that reduce the amount of manure solids stored in liquid form could significantly reduce dairy CH 4 emissions., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Nutrient management on US dairy farms must balance an array of priorities, some of which conflict. To illustrate nutrient management challenges and opportunities across the US dairy industry, the USDA Agricultural Research Service Dairy Agroecosystems Working Group (DAWG) modeled 8 confinement and 2 grazing operations in the 7 largest US dairy-producing states using the Integrated Farm System Model (IFSM). Opportunities existed across all of the dairies studied to increase on-farm feed production and lower purchased feed bills, most notably on large dairies (>1,000 cows) with the highest herd densities. Purchased feed accounted for 18 to 44% of large dairies' total operating costs compared with 7 to 14% on small dairies (<300 milk cows) due to lower stocking rates. For dairies with larger land bases, in addition to a reduction in environmental impact, financial incentives exist to promote prudent nutrient management practices by substituting manure nutrients or legume nutrients for purchased fertilizers. Environmental priorities varied regionally and were principally tied to facility management for dry-lot dairies of the semi-arid western United States (ammonia-N emissions), to manure handling and application for humid midwestern and eastern US dairies (nitrate-N leaching and P runoff), and pasture management for dairies with significant grazing components (nitrous oxide emissions). Many of the nutrient management challenges identified by DAWG are beyond slight modifications in management and require coordinated solutions to ensure an environmentally and economically sustainable US dairy industry., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).)

To lessen soil erosion due to high animal stocking rates on small Georgia dairies, the Natural Resources Conservation Service (NRCS) recommends a system that utilizes geotextile material covered with crusher run gravel as a soil cover in high animal traffic areas. Our objective was to determine the runoff and leachate characteristics of a typical system. At a 60-cow dairy in Oglethorpe County, Georgia, a loafing lot was constructed on a Pacolet sandy loam soil (clayey, kaolinitic, thermic, Typic Kanhapludult). Tile drains were installed at 0.65 m (26 in) depth on 7.5 m (25 ft) spacing. Approximately 18 percent of the rainfall became surface runoff. Surface runoff water typically contained levels of NH4-N and PO4-P that exceeded the Environmental Protection Agency (EPA) guidelines for surface water. Approximately 32 percent of the rainfall became drainage water that moved below the top 1.5 m (60 in) soil profile and had nitrate levels ranging from 10 to 40 mg NO3-N L-1. Our results indicate that surface water running off of these sites should be impounded in a lagoon or similar structure and these systems should not be located in areas where groundwater contamination is a concern. [ABSTRACT FROM AUTHOR]

Animal manure has become a major focal point of conservation efforts. A shift in the industry over the past decade towards fewer, larger operations has resulted in concerns over the utilization and disposal of animal manure. Land application of manure, a preferred disposal method, may be difficult and costly to implement on larger operations if restrictions on land disposal increase the amount of land required for spreading. The hog sector provides an example of how restrictions on manure application rates can affect the need for land. Using data from the 1998 Hog Agricultural Resource Management Survey we found that most confined hog operations would need to increase the land receiving manure to meet the needs of a nitrogen-based (N-based) or phosphorus-based (P-based) nutrient management plan. Both are possible under proposed Clean Water Act regulations by the Environmental Protection Agency (EPA) and program goals for the U.S. Department of Agriculture. Smaller operations tended to have adequate land on the operation to meet the needs of a N-based plan in most regions. Larger operations generally had inadequate land for N-based plans. All large operations would need to find substantial amounts of additional land to meet the needs of a P-based plan. [ABSTRACT FROM AUTHOR]

A mail survey of 1,200 farms across 16 states was conducted to identify the number, type, and size of manure storages per farm, as well as safety-related behaviors or actions related to entry into confined-space manure storage and handling facilities. Respondents provided data on 297 storage units and facilities, with approximately 75% reporting up to three storages per farm operation. Dimensions were provided for 254 manure pits: nearly 66% were less than or equal to 100 feet long, 75% were less than or equal to 40 feet wide, and 75% were less than or equal to 10 feet deep. Almost 14% of the reported storages were over 300 feet long, seven were wider than 100 feet, and 17 were more than 20 feet deep. Survey results suggest that most farm operations with confined-space manure storages do not follow best safety practices regarding their manure storages, including using gas detection equipment before entering a manure pit, using rescue lines when entering storages, or developing a written confined-space safety policy or plan. Survey results also suggest that few farmers post warning signs around their storages, post recommended ventilation times before entry, or conduct training for workers who enter confined-space manure storages. This article provides a benchmark against which the effectiveness of educational programs and design tools for confined-space manure pit ventilation systems and other confined-space manure pit safety interventions can be measured.

Animal manures, used as a nitrogen source for crop production, are often associated with negative impacts on nutrient levels in surface water. The concentrations of estrogens in streams from these manures also are of concern due to potential endocrine disruption in aquatic species. Streams associated with livestock operations were sampled by discrete samples (n = 38) or by time-integrated polar organic chemical integrative samplers (POCIS, n = 19). Samples were analyzed for estrogens by gas chromatography-tandem mass spectrometry (GC-MS(2)) and estrogenic activity was assessed by three bioassays: Yeast Estrogen Screen (YES), T47D-KBluc Assay, MCF-7 Estrogenicity Screen (E-Screen). Samples were collected from 19 streams within small (≈ 1-30 km(2)) watersheds in 12 U.S. states representing a range of hydrogeologic conditions, dominated by: dairy (3), grazing beef (3), feedlot cattle (1); swine (5); poultry (3); and 4 areas where no livestock were raised or manure was applied. Water samples were consistently below the United Kingdom proposed Lowest Observable Effect Concentration for 17β-estradiol in fish (10 ng/L) in all watersheds, regardless of land use. Estrogenic activity was often higher in samples during runoff conditions following a period of manure application. Estrone was the most commonly detected estrogen (13 of 38 water samples, mean 1.9, maximum 8.3 ng/L). Because of the T47D-KBluc assay's sensitivity towards estrone (1.4 times 17β-estradiol) it was the most sensitive method for detecting estrogens, followed by the E-Screen, GC-MS(2), and YES. POCIS resulted in more frequent detections of estrogens than discrete water samples across all sites, even when applying the less-sensitive YES bioassay to the POCIS extracts., (Published by Elsevier Ltd.)

Agriculture is among the most hazardous sectors for workers globally, and dairy farming has been associated with a high risk of injury among workers in several countries. The purpose of this paper is to provide an update on what is known about modern dairy farms and related injuries and fatalities in different regions of the world. As in other sectors of agriculture, fatalities appear to be associated with heavy equipment usage, whereas injuries occur at higher rates with animal production, specifically cattle and milk production. Dairy farming is associated with higher rates of injury as compared with other industrial sectors, but a lack of work-related injury reporting continues to be an issue in several countries. Worker fatality associated with heavy equipment use is not a new observation (e.g., tractors); however, manure-handling systems, livestock handling, and quad bike operation continue to be associated with worker injuries and fatalities on modern farms. Opportunities exist for improvement of safety-related equipment to reduce injury and fatality risk during worker interactions with large animals and farm equipment.