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Reducing cropland ammonia (NH 3 ) emissions while improving air quality and food supply is a challenge, particularly in China where there are millions of smallholder farmers. We tested the effectiveness of a tailored nitrogen (N) management strategy applied to wheat-maize cropping systems in 'demonstration squares' across Quzhou County in the North China Plain. The N-management techniques included optimal N rates, deep fertilizer placement and application of urease inhibitors, implemented through cooperation between government, researchers, businesses and smallholders. Compared with conventional local smallholder practice, our NH 3 mitigation campaign reduced NH 3 volatilization from wheat and maize by 49% and 39%, and increased N-use efficiency by 28% and 40% and farmers' profitability by 25% and 19%, respectively, with no detriment to crop yields. County-wide atmospheric NH 3 and fine particulate matter (with aerodynamic diameter <2.5 μm) concentrations decreased by 40% and 8%, respectively. County-wide net benefits were estimated at US$7.0 million. Our demonstration-square approach shows that cropland NH 3 mitigation and improved air quality and farm profitability can be achieved simultaneously by coordinated actions at the county level., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Ammonia (NH 3 ) is an important alkaline reactive nitrogen (Nr) species which is involved in global nitrogen (N) biogeochemical cycling, but which has negative impacts on the environment and human health. In order to better understand and control the NH 3 loss potential in soil-upland crop systems in China, an integrated data analysis including 1302 observations from 236 published articles between 1980 and 2021 was conducted. The typical NH 3 volatilization rate (AVR) and the main factors influencing AVR in the major Chinese upland crops (maize, wheat, openfield vegetables and greenhouse vegetables and others) were estimated and analyzed. The mean AVR for maize, wheat, openfield vegetables and greenhouse vegetables were 7.8%, 5.3%, 8.4% and 1.8%. The most important influencing factors were fertilizer placement, meteorological conditions (especially temperature and rainfall) and soil properties (especially SOM). Subsurface N application produced a significantly lower AVR compared to surface application. High N recovery efficiency and N agronomic efficiency were generally associated with low AVRs. In conclusion, high N application rates, inefficient application methods and the use of loss-prone N fertilizer types are the main factors responsible for high AVRs in major Chinese croplands., 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. Published by Elsevier Ltd.)

Growing population and consumption pose unprecedented demands on food production. However, ammonia emissions mainly from food systems increase oceanic nitrogen deposition contributing to eutrophication. Here, we developed a long-term oceanic nitrogen deposition dataset (1970 to 2018) with updated ammonia emissions from food systems, evaluated the impact of ammonia emissions on oceanic nitrogen deposition patterns, and discussed the potential impact of nitrogen fertilizer overuse. Based on the chemical transport modeling approach, oceanic ammonia-related nitrogen deposition increased by 89% globally between 1970 and 2018, and now, it exceeds oxidized nitrogen deposition by over 20% in coastal regions including China Sea, India Coastal, and Northeastern Atlantic Shelves. Approximately 38% of agricultural nitrogen fertilizer was excessive, which corresponds to 15% of global oceanic ammonia-related nitrogen deposition. Policymakers and water quality managers need to pay increasingly more attention to ammonia associated with food production if the goal of reducing coastal nitrogen pollution is to be achieved for Sustainable Development Goals.

Reducing atmospheric ammonia (NH 3 ) emissions is critical to mitigating poor air quality. However, the contributions of major agricultural and non-agricultural source emissions to NH 3 at receptor sites remain uncertain in many regions, hindering the assessment and implementation of effective NH 3 reduction strategies. This study conducted simultaneous measurements of the monthly concentrations and stable nitrogen isotopes of NH x (gaseous NH 3 plus particulate NH 4 + ) at 16 sites across China. Ambient NH x concentrations averaged 21.7 ± 19.6 μg m -3 at rural sites, slightly higher than those at urban (19.2 ± 6.0 μg m -3 ) and three times of those at background (7.0 ± 6.9 μg m -3 ) sites. Based on revised δ 15 N values of the initial NH 3 , source apportionment results indicated that non-agricultural sources (traffic and waste) and agricultural sources (fertilizer and livestock) contributed 54 and 46% to NH 3 at urban sites, 51 and 49% at rural sites, and 61 and 39% at background sites, respectively. Non-agricultural sources contributed more to NH 3 at rural and background sites in cold than warm seasons, arising from traffic and waste, but were similar across seasons at urban sites. We concluded that non-agricultural sources need to be addressed when reducing ambient NH 3 across China, even in rural regions.

Livestock and crop production are the main sources of ammonia (NH 3 ) emissions, which are known to degrade the air quality. Numerous studies have been conducted to explore the mitigation potential of various approaches, although few have examined the systematic NH 3 emission mitigation potential when considering both crop and livestock systems based on coherent in situ measurement results. Herein, we design an optimal system wherein coupled crop and layer production systems reveal feasible approaches for significant mitigation potential at each stage of the process. Specifically, these measures involve (i) using a low crude protein (LCP) feed, (ii) composting manure with certain additives, and (iii) substituting manure with optimal fertilization in a summer maize-winter wheat cropping system. The results show that (i) LCP feed leads to a 14 % reduction in NH 3 emissions at the housing stage, (ii) introducing additives during the composing stage reduces NH 3 emissions by 16 %-46 %, and (iii) the NH 3 reduction potential reaches 35 %-44 % at the field application stage. In the overall crop-layer system, the optimal system with the improved management strategy applied at every stage results in a 48 % and 56 % reduction in NH 3 emissions for per unit eggs and grain production, respectively, relative to a traditional production system. This study confirms that NH 3 emissions can be cut in half by implementing optimal crop-livestock systems with appropriate mitigation approaches. This is a feasible model that can be promoted and extended in various agricultural areas, which together with technological, policy, and economic support can enable significant mitigation potential for sustainable agriculture development., 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 © 2022 Elsevier B.V. All rights reserved.)

SignificanceAgricultural systems are already major forces of ammonia pollution and environmental degradation. How agricultural ammonia emissions affect the spatio-temporal patterns of nitrogen deposition and where to target future mitigation efforts, remains poorly understood. We develop a substantially complete and coherent agricultural ammonia emissions dataset in nearly recent four decades, and evaluate the relative role of reduced nitrogen in total nitrogen deposition in a spatially explicit way. Global reduced nitrogen deposition has grown rapidly, and will occupy a greater dominant position in total nitrogen deposition without future ammonia regulations. Recognition of agricultural ammonia emissions on nitrogen deposition is critical to formulate effective policies to address ammonia related environmental challenges and protect ecosystems from excessive nitrogen inputs.

Ammonia (NH 3 ) emissions mostly from agriculture result in air pollution and degrade human health. However, a full picture of soil NH 3 emissions and associated abatement in cropping systems are not well understood. Here we present a thorough analysis of cropland NH 3 emissions, discuss mitigation potential and assess associated abatement costs. Global cropland NH 3 emissions account for 26% of total soil nitrogen losses, and are estimated as 22.8-31.2 Tg N yr -1 during 1996-2013 with the increase rate of 1.6% yr -1 . Our results also show that, with no increase in nitrogen fertilizer, climate change can contribute to an additional 10% increase in cropland NH 3 emissions in 2100 compared to the 2010 baseline. Instead, our scenario analysis show, cropland NH 3 emissions will decline by 26% from 2010 to 2100 given a 0.5% yr -1 decrease in N fertilizer (with current technology and agricultural management level), considering the facts stronger control policies are expected to occur worldwide including Western Europe, the United States of America and China. The most ambitious management (with all known mitigation practices) can reduce cropland NH 3 emissions by up (71%, 17.6 Tg N yr -1 ) at an abatement cost of US$524 billion. Our findings indicate that cropland NH 3 emissions can be mitigated through adoption of appropriate human management practices with considerable economic costs, providing a critical reference for the future NH 3 abatement strategies., 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 © 2021 Elsevier B.V. All rights reserved.)

Substantial ammonia (NH3) losses from rice production result in poor nitrogen (N) use efficiency and environmental damage. A data synthesis using the published literature (127 studies with 700 paired observations), combined with an incubation experiment using 50 paddy soils from across China, were conducted to improve the current understanding of the NH3 loss from paddy rice and its drivers. The efficacy of the urease inhibitor Limus® for reducing NH3 losses was also evaluated. The mean loss of N, through NH3 volatilization, was 16.2% of the urea-N applied to paddy rice. The largest losses were from double rice cropping systems, and losses increased with the N application rate, surface application of N, unstable N types (ammonium bicarbonate and urea), and high floodwater pH. Under simulated flooded conditions, urea amended with Limus® reduced NH3 loss by 36.6%, compared to urea alone, but floodwater pH had a significant effect on inhibitor efficacy. Key driving factors were air temperature, N application rate, and floodwater pH. The effectiveness and limitations of the inhibitor in NH3 emission mitigation was examined, as well as its basis as one means of N pollution control in paddy rice cropping systems. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) is the most important alkaline gas in the atmosphere, which has negative effects on biodiversity, ecosystems, soil acidification and human health. China has the largest NH 3 emissions globally, mainly associated with agricultural sources including nitrogen fertilizer and livestock. However, there is still a limited number of ground monitoring sites in China, hindering our understanding of both surface NH 3 concentrations and emissions. In this study, using the polar-orbiting satellite (Infrared Atmospheric Sounding Interferometer – IASI) and Fengyun-4A Geostationary Interferometric Infrared Sounder (GIIRS), we analyzed the changes in hourly NH 3 concentrations and estimated surface NH 3 concentrations and NH 3 emissions in China. GIIRS-derived NH 3 concentrations in the daytime were generally higher than those at night, with high values during 10:00–16:00 local time. Satellite-derived surface NH 3 concentrations were generally consistent with the ground observations, with R -square at 0.72 and slope equal to 1.03. Satellite-based NH 3 emissions ranged from 12.17 to 17.77 Tg N yr -1 during 2008–2019. Spatially, high values of NH 3 emissions mainly occurred in the North China Plain, Northeast China and the Sichuan Basin, while low values were mainly distributed in West China (Qinghai–Tibet Plateau). Our study shows a high predictive power of using satellite data to estimate surface NH 3 concentrations and NH 3 emissions over multiple temporal and spatial scales, which provides an important reference for understanding NH 3 changes over China. [ABSTRACT FROM AUTHOR]

Paddy fields in China contributed to one third of the global cropland ammonia (NH 3) emission inventory, while rice accounted for half of cereal consumption, necessitating exhaustive considerations of the balance between NH 3 emissions abatement and food demand. The concept of yield-scaled emission intensity (emissions per unit crop production) has the potential to guide sustainable intensification strategies, yet its application to NH 3 emissions remains poorly understood. Here, by constructing novel crop-specific models for single rice production and NH 3 emissions in the Middle and Lower Yangtze River Basin (LYRB) as a case study, the relationships between fertilizer N application and yield-scaled NH 3 were estimated. Contrary to our hypothesis of a tipping point, our results showed that yield-scaled NH 3 curves could not directly identify optimal nitrogen (N) rates. However, the benefit of lower N fertilizer rate on NH 3 abatement consistently outweighed the risk of yield loss. The exponential relationships between yield-scaled NH 3 and N surplus allowed us to estimate the N surplus criterion as 15.6 kg N ha−1 (or 190 kg N ha−1 fertilizer N rate) for the LYRB. Under the N surplus criterion, NH 3 emissions can be reduced by 23–27% without severely impacting rice yield, compared to the N rate required for the highest yield. Moreover, five major controlling factors for yield-scaled NH 3 were estimated by random forest models, ranked in order of importance as N rate, total N, K rate, mean annual precipitation, and soil organic carbon. Among the agricultural practices (irrigation, tillage, and fertilizer management), deep placement was the most effective measure to reduce yield-scaled NH 3, showing 48% reduction potential, followed by proper N splitting frequency (43%). Overall, this study highlights the efficacy of N application optimization and targeted farm management in mitigating NH 3 emission while maintaining crop productivity. [Display omitted] • Yield-scaled NH 3 cannot directly guide N rate due to high abatement efficacy. • The Yield-scaled NH 3 –N surplus criterion reduces NH 3 emissions by 23–27%. • Five key factors contributing to spatial variations were unraveled. • Deep placement and optimal splitting frequency perform best in yield-scaled NH 3 mitigation. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is an intensive agricultural area and ammonia (NH 3) emission hotspot in China. Urgent mitigation actions are needed to reduce its environmental impact. A field trial was conducted, and results combined with a synthesis of existing data to assess the NH 3 loss and mitigation potentials in a wheat-maize double-crop rotation, a dominant crop production system in the NCP. Ammonia volatilization losses from N fertilizer applied to summer maize and winter wheat were 9.1% and 5.0%, respectively, based on the data synthesis, and were significantly affected by fertilizer application method and N fertilizer type. From the field trial, optimized reduction in N application rate, compared with conventional practice, had great efficiency for NH 3 mitigation. Despite their high NH 3 reduction potential, the higher input costs associated with the use of controlled-release fertilizers, replacement of urea with calcium ammonium nitrate or inclusion of double inhibitors (urease and nitrification inhibitors) with urea limited their applicability from an economic perspective. The inclusion of a urease inhibitor with urea achieved over 70% reduction in NH 3 emission and also gave a significant improvement in grain yield, net income and N use efficiency. Future adoption of NH 3 mitigation options in the NCP should focus on establishing a reduction target and consider the cost-benefits of simultaneous implementation of multiple mitigation techniques. [Display omitted] • Placement of fertilizer and fertilizer types significantly influence NH 3 emissions. • High cost of fertilizer amendment compromised economic benefits. • Using urease inhibitor showed good economic and environmental performance. [ABSTRACT FROM AUTHOR]

Large uncertainties and challenges remain in the quantification of land-atmosphere exchanges of ammonia (NH 3), mainly due to limitations in measurement techniques. In this study, the eddy covariance (EC) technique based on an open-path quantum cascade laser (QCL) spectrometer was used to measure the NH 3 fluxes at a typical cropland in the North China Plain, one of the global NH 3 hotspots. It is the first attempt of measuring both NH 3 volatilization and deposition fluxes at an agricultural ecosystem using the open-path instrument-based EC technique. During the one-month experimental period, the NH 3 fluxes were characterized by enhanced emissions after fertilizer application and persistent dry depositions after ploughing practice, with the flux magnitude varying from −0.293 to 7.29 (median: −0.042) mg N m−2 h−1. Nearly 93% of the half-hourly fluxes (absolute values) exceeded the mean instrumental flux detection limit of 9.6 μg N m−2 h−1. Nitrogen loss rate from the wheat field through NH 3 volatilization was 0.57–0.71% relative to the applied nitrogen fertilizers. Ammonia deposition dominated the period after the ploughing practice, showing an average deposition rate of 0.014 kg N ha−1 d−1 with a significant diurnal pattern. Both the local emission sources and meteorological conditions influenced the variation of NH 3 dry deposition. The deposition fluxes measured by the EC technique were nearly one third the results modelled by the widely used inferential model method, but the difference needs to be validated by more observations that includes different surface and meteorological conditions. This study suggests that this open-path QCL-based EC instrument is an effective tool for long-term and high-frequency measurements of ecosystem NH 3 exchanges. It also enables cross-validation between different methods to improve the understanding in the atmospheric reactive nitrogen cycling. • The open-path QCL-based eddy covariance instrument can detect small NH 3 fluxes. • Nitrogen loss rate from the wheat field through NH 3 volatilization was 0.57–0.71%. • NH 3 dry deposition averaged to 0.014 kg N ha−1 d−1 with a significant diurnal pattern. • Depositions estimated by inferential model were two times larger than the observed. [ABSTRACT FROM AUTHOR]