Ammonia emissions from paddy fields are underestimated in China.

Excessive nitrogen (N) fertilizers are often used in China, and a large proportion of the N can be lost as ammonia (NH3). However, quantifying the NH3 emission from paddy fields is always affected by large uncertainties due to different measuring methods and other factors such as climate. In this study, using a standardized method, we measured the NH3 emissions in three typical annual rice cropping systems: single rice, double rice and rotation with other crops. The measurements were conducted for 2 years with a total of 3131 observations across China. Results showed that NH3 emissions accounted for 17.7% (14.4-21.0%) of the N applied under current farm practice, which was 33.1% (10.6-52.6%) higher than previous estimates. Nitrogen application rate was the dominant factor influencing NH3 emission rate, which exponentially increased with the N fertilizer rate (p < .001). Total NH3 emissions from paddy fields were estimated at 1.7 Tg N yr-1 in 2013 in China, several times the amount of N lost through leaching or runoff. This suggests that mitigation measures for non-point source pollution from cropland should take into account not only the N lost to water, but also to air, thereby improving air quality.

[1]  Yongjun Zeng,et al.  Effects of fertilizer management practices on yield-scaled ammonia emissions from croplands in China: A meta-analysis , 2016 .

[2]  Carolien Kroeze,et al.  An inventory of the emission of ammonia from agricultural fertilizer application in China for 2010 and its high-resolution spatial distribution , 2015 .

[3]  J. Schjoerring,et al.  Ammonia Emission from Mineral Fertilizers and Fertilized Crops , 2004 .

[4]  Xin-ping Chen,et al.  Reducing environmental risk by improving N management in intensive Chinese agricultural systems , 2009, Proceedings of the National Academy of Sciences.

[5]  L. Cárdenas,et al.  Effect of slurry and ammonium nitrate application on greenhouse gas fluxes of a grassland soil under atypical South West England weather conditions , 2013 .

[6]  P. Vitousek,et al.  Significant Acidification in Major Chinese Croplands , 2010, Science.

[7]  Ammonia volatilization in Chinese double rice-cropping systems: a 3-year field measurement in long-term fertilizer experiments , 2014, Biology and Fertility of Soils.

[8]  C. M. Groenestein,et al.  A model for inventory of ammonia emissions from agriculture in the Netherlands , 2012 .

[9]  Rajasekhar Balasubramanian,et al.  Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies , 2013, Environmental Science and Pollution Research.

[10]  H. Cantarella,et al.  Ammonia volatilization losses from surface-applied urea with urease and nitrification inhibitors , 2012 .

[11]  Wang Jinping,et al.  Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China , 2011 .

[12]  Yan-lin Zhang,et al.  Fine particulate matter (PM2.5) in China at a city level , 2015, Scientific Reports.

[13]  Feng Zhou,et al.  Quantifying nitrogen leaching response to fertilizer additions in China's cropland. , 2016, Environmental pollution.

[14]  Rong Yang,et al.  Nitrogen budget and riverine nitrogen output in a rice paddy dominated agricultural watershed in eastern China , 2011 .

[15]  NH3 volatilization, soil concentration and soil pH following subsurface banding of urea at increasing rates , 2013 .

[16]  K. Hayashi,et al.  Limited ammonia volatilization loss from upland fields of Andosols following fertilizer applications , 2011 .

[17]  J. Barrett,et al.  Substrate and nutrient limitation of ammonia-oxidizing bacteria and archaea in temperate forest soil , 2014 .

[18]  H. Akimoto,et al.  Estimation of nitrous oxide, nitric oxide and ammonia emissions from croplands in East, Southeast and South Asia , 2003 .

[19]  A. Deng,et al.  Nonlinear response of soil ammonia emissions to fertilizer nitrogen , 2017, Biology and Fertility of Soils.

[20]  E. Larson,et al.  A high-resolution emission inventory for eastern China in 2000 and three scenarios for 2020 , 2005 .

[21]  Dejun Li.  Emissions of NO and NH3 from a Typical Vegetable-Land Soil after the Application of Chemical N Fertilizers in the Pearl River Delta , 2013, PloS one.

[22]  Effects of Temperature and Soil Type on Ammonia Volatilization from Slow-Release Nitrogen Fertilizers , 2011 .

[23]  David G. Streets,et al.  Projections of SO2, NOx, NH3 and VOC Emissions in East Asia Up to 2030 , 2001 .

[24]  Z. Xiong,et al.  Mitigating gaseous nitrogen emissions intensity from a Chinese rice cropping system through an improved management practice aimed to close the yield gap , 2015 .

[25]  S. Yue,et al.  Closing the N-use efficiency gap to achieve food and environmental security. , 2014, Environmental science & technology.

[26]  Stefan Reis,et al.  PM2.5 pollution is substantially affected by ammonia emissions in China. , 2016, Environmental pollution.

[27]  Jiabao Zhang,et al.  An inverse dispersion technique for the determination of ammonia emissions from urea-applied farmland , 2013 .

[28]  D. R. Jackson,et al.  Emission factors for ammonia and nitrous oxide emissions following immediate manure incorporation on two contrasting soil types , 2014 .

[29]  S. Yue,et al.  Closing the yield gap could reduce projected greenhouse gas emissions: a case study of maize production in China , 2013, Global change biology.

[30]  W. Shi,et al.  Higher rates of nitrogen fertilization decrease soil enzyme activities, microbial functional diversity and nitrification capacity in a Chinese polytunnel greenhouse vegetable land , 2010, Plant and Soil.

[31]  Anqiang Chen,et al.  Characteristics of ammonia volatilization on rice grown under different nitrogen application rates and its quantitative predictions in Erhai Lake Watershed, China , 2014, Nutrient Cycling in Agroecosystems.

[32]  Toshimasa Ohara,et al.  Regional-specific emission inventory for NH3, N2O, and CH4 via animal farming in South, Southeast, and East Asia , 2004 .

[33]  Huijing Hou,et al.  Nitrogen and phosphorus leaching losses from paddy fields with different water and nitrogen managements , 2011, Paddy and Water Environment.

[34]  C. Place,et al.  Modelling the spatial distribution of ammonia emissions in the UK. , 2008, Environmental pollution.

[35]  Jörg Richter,et al.  Calibration of a simple method for determining ammonia volatilization in the field – comparative measurements in Henan Province, China , 2006, Nutrient Cycling in Agroecosystems.

[36]  C. Müller,et al.  Mechanisms for the retention of inorganic N in acidic forest soils of southern China , 2013, Scientific Reports.

[37]  Jianliang Huang,et al.  Strategies for overcoming low agronomic nitrogen use efficiency in irrigated rice systems in China , 2006 .

[38]  Philippe Rochette,et al.  NH3 volatilization, soil concentration and soil pH following subsurface banding of urea at increasing rates , 2013, Canadian Journal of Soil Science.

[39]  Bo Zhu,et al.  Modeling nitrogen loading in a small watershed in southwest China using a DNDC model with hydrological enhancements , 2011 .

[40]  Jianliang Huang,et al.  Producing more grain with lower environmental costs , 2014, Nature.

[41]  A. Dikshit,et al.  Burden of disease attributed to ambient PM2.5 and PM10 exposure in 190 cities in China , 2017, Environmental Science and Pollution Research.

[42]  W. Shi,et al.  Nitrogen Balance in a Highly Fertilized Rice–Wheat Double-Cropping System in Southern China , 2012 .

[43]  P. Coheur,et al.  Ammonia Emissions May Be Substantially Underestimated in China. , 2017, Environmental science & technology.

[44]  Zhao-liang Zhu,et al.  Assessment of ammonia volatilization from paddy fields under crop management practices aimed to increase grain yield and N efficiency , 2013 .

[45]  Yiqi Luo,et al.  Ammonia volatilization from synthetic fertilizers and its mitigation strategies: A global synthesis , 2016 .

[46]  Hailin Zhang,et al.  Do high nitrogen use efficiency rice cultivars reduce nitrogen losses from paddy fields , 2015 .

[47]  Sheng Zhou,et al.  Ammonia Emissions from Anaerobically-digested Slurry and Chemical Fertilizer Applied to Flooded Forage Rice , 2007 .

[48]  B. Fu,et al.  Spatial patterns of nitrogen runoff from Chinese paddy fields , 2016 .

[49]  Jie Chang,et al.  Agricultural ammonia emissions contribute to China's urban air pollution , 2014 .

[50]  Weiguang Wang,et al.  Ammonia volatilization losses from a rice paddy with different irrigation and nitrogen managements , 2012 .

[51]  Effect of nitrogen fertilization and residue management practices on ammonia emissions from subtropical sugarcane production , 2016 .

[52]  Philippe Ciais,et al.  Re-estimating NH3 Emissions from Chinese Cropland by a New Nonlinear Model. , 2016, Environmental science & technology.

[53]  R. Follett,et al.  Nitrogen Source Effects on Ammonia Volatilization as Measured with Semi-Static Chambers , 2012 .