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In the U.S., spray irrigation is the most common method used in agriculture and supplementing with animal wastewater has the potential to reduce water demands. However, this could expose individuals to respiratory pathogens such as Legionella pneumophila and nontuberculosis Mycobacteria (NTM). Disinfection with methods like anaerobic digestion is an option but can increase concentrations of cytotoxic ammonia (personal communication). Our study aimed to model the annual risks of infection from these bacterial pathogens and the air concentrations of ammonia and determine if anaerobically digesting this wastewater is a safe option. Air dispersion modeling, conducted in AERMOD, generated air concentrations of water during the irrigation season (May–September) for the years 2013–2018. These values fed into the quantitative microbial risk assessments for the bacteria and allowed calculation of ammonia air concentrations. The outputs of these models were compared to the safety thresholds of 10−4 infections/year and 0.5 mg/m3, respectively, to determine their potential for negative health outcomes. It was determined that infection from NTM was not a concern for individuals near active spray irrigators, but that infection with L. pneumophila could be a concern, with a maximum predicted annual risk of infection of 3.5 × 10−3 infections/year and 25.2% of parameter combinations exceeding the established threshold. Ammonia posed a minor risk, with 1.5% of parameter combinations surpassing the risk threshold of 0.5 mg/m3. These findings suggest that animal wastewater should be anaerobically digested prior to use in irrigation to remove harmful pathogens. [ABSTRACT FROM AUTHOR]

In the U.S., spray irrigation is the most common method used in agriculture and supplementing with animal wastewater has the potential to reduce water demands. However, this could expose individuals to respiratory pathogens such as Legionella pneumophila and nontuberculosis Mycobacteria (NTM). Disinfection with methods like anaerobic digestion is an option but can increase concentrations of cytotoxic ammonia (personal communication). Our study aimed to model the annual risks of infection from these bacterial pathogens and the air concentrations of ammonia and determine if anaerobically digesting this wastewater is a safe option. Air dispersion modeling, conducted in AERMOD, generated air concentrations of water during the irrigation season (May-September) for the years 2013-2018. These values fed into the quantitative microbial risk assessments for the bacteria and allowed calculation of ammonia air concentrations. The outputs of these models were compared to the safety thresholds of 10 -4 infections/year and 0.5 mg/m 3 , respectively, to determine their potential for negative health outcomes. It was determined that infection from NTM was not a concern for individuals near active spray irrigators, but that infection with L. pneumophila could be a concern, with a maximum predicted annual risk of infection of 3.5 × 10 -3 infections/year and 25.2% of parameter combinations exceeding the established threshold. Ammonia posed a minor risk, with 1.5% of parameter combinations surpassing the risk threshold of 0.5 mg/m 3 . These findings suggest that animal wastewater should be anaerobically digested prior to use in irrigation to remove harmful pathogens., (© 2020 Society for Risk Analysis.)

Cover cropping is beneficial for reducing soil erosion and nutrient losses, but there are conflicting reports on how cover cropping affects emissions of nitrous oxide (N 2 O), a potent greenhouse gas. In this study, we measured N 2 O fluxes over a full year in Illinois corn plots with and without rye cover crop. We compared these year-round measurements to N 2 O emissions predicted by the Intergovernmental Panel on Climate Change (IPCC) Tier 1 equation and the Denitrification-Decomposition (DNDC) model. In addition, we measured potential denitrification and N 2 O production rates. The field measurements showed typical N 2 O peaks shortly after fertilizer application, as well as a significant late-winter peak. Cover cropping significantly reduced all peak N 2 O fluxes, with decreases ranging from 39 to 95%. Neither model was able to accurately predict annual N 2 O fluxes or the decrease in N 2 O emissions from cover-cropped fields. In contrast to field measurements, lab assays found that cover cropping significantly increased potential denitrification by 90-127% and potential N 2 O production by 54-106%. The rye cover-cropped plots had lower soil nitrate and higher soil carbon. When limiting nitrate and excess carbon were provided in lab assays, the proportion of N 2 O resulting from denitrification decreased. These results suggest that the discrepancy between the observed decrease in field N 2 O emissions and the increase in denitrification potential may be due to the difference in available nutrients between the field and laboratory measurements. Overall, these results suggest the importance of late-winter peaks in N 2 O emissions and the potential of rye cover cropping to reduce N 2 O emissions from agricultural fields., 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 © 2020 Elsevier B.V. All rights reserved.)

Due to the contributions of nitrous oxide (N 2 O) to global climate change and stratospheric ozone destruction, it is important to understand how climate and agricultural management affect N 2 O emissions. Although the process-based Denitrification Decomposition (DNDC) model is often used for quantifying emissions of N 2 O, the accuracy of these predictions remains in question, and it is not clear which input variables, environmental or field management, have the greatest effect on model performance. In this study, DNDC was evaluated for prediction of N 2 O fluxes from two climatically-different corn-field sites in the United States (a Colorado irrigated field and a Minnesota rainfed field). Besides climate, these sites offer the additional advantage that measurements are available for multiple field management practices, including fertilizer application, tillage, and crop rotation. This evaluation found that DNDC did not consistently, correctly predict daily-scale N 2 O fluxes. Cumulative growing season N 2 O fluxes were significantly under-predicted in Colorado and were both under- and over-predicted in Minnesota. Model calibration of four soil input parameters did not significantly improve N 2 O emission predictions at either site or time scale. Modeled and measured N 2 O fluxes and model error were all strongly correlated with precipitation. Over-predictions of N 2 O fluxes were associated with heavy precipitation and high modeled denitrification. Based on our results, model improvements to decrease model error for corn cropping systems in temperate climate zones should focus on better accounting for the effects of precipitation on denitrification. Despite discrepancies in daily and cumulative growing season N 2 O fluxes, DNDC correctly identified the only field management (fertilizer application rate) that significantly influenced the measured N 2 O fluxes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

China's rapid urbanization, large population, and increasing consumption of calorie-and meat-intensive diets, have resulted in China becoming the world's largest source of ammonia (NH 3 ) emissions from livestock production. This is the first study to use provincial, condition-specific emission factors based on most recently available studies on Chinese manure management and environmental conditions. The estimated NH 3 emission temporal trends and spatial patterns are interpreted in relation to government policies affecting livestock production. Scenario analysis is used to project emissions and estimate mitigation potential of NH 3 emissions, to year 2030. We produce a 1km×1km gridded NH 3 emission inventory for 2008 based on county-level activity data, which can help identify locations of highest NH 3 emissions. The total NH 3 emissions from manure generated by livestock production in 2008 were 7.3TgNH 3 ·yr -1 (interquartile range from 6.1 to 8.6TgNH 3 ·yr -1 ), and the major sources were poultry (29.9%), pigs (28.4%), other cattle (27.9%), and dairy cattle (7.0%), while sheep and goats (3.6%), donkeys (1.3%), horses (1.2%), and mules (0.7%) had smaller contributions. From 1978 to 2008, annual NH 3 emissions fluctuated with two peaks (1996 and 2006), and total emissions increased from 2.2 to 7.3Tg·yr -1 increasing on average 4.4%·yr -1 . Under a business-as-usual (BAU) scenario, NH 3 emissions in 2030 are expected to be 13.9TgNH 3 ·yr -1 (11.5-16.3TgNH 3 ·yr -1 ). Under mitigation scenarios, the projected emissions could be reduced by 18.9-37.3% compared to 2030 BAU emissions. This study improves our understanding of NH 3 emissions from livestock production, which is needed to guide stakeholders and policymakers to make well informed mitigation decisions for NH 3 emissions from livestock production at the country and regional levels., (Copyright © 2017 Elsevier B.V. All rights reserved.)