Zhang Chong, Song Xiaotong, Zhang Yaqian, Wang Dan, Rees Robert M, Ju Xiaotang
College of Tropical Crops, Hainan University, Haikou, China.
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
Glob Chang Biol. 2022 Jul;28(14):4409-4422. doi: 10.1111/gcb.16198. Epub 2022 Apr 27.
Ammonia (NH ) and nitrous oxide (N O) are two important air pollutants that have major impacts on climate change and biodiversity losses. Agriculture represents their largest source and effective mitigation measures of individual gases have been well studied. However, the interactions and trade-offs between NH and N O emissions remain uncertain. Here, we report the results of a two-year field experiment in a wheat-maize rotation in the North China Plain (NCP), a global hotspot of reactive N emissions. Our analysis is supported by a literature synthesis of global croplands, to understand the interactions between NH and N O emissions and to develop the most effective approaches to jointly mitigate NH and N O emissions. Field results indicated that deep placement of urea with nitrification inhibitors (NIs) reduced both emissions of NH by 67% to 90% and N O by 73% to 100%, respectively, in comparison with surface broadcast urea which is the common farmers' practice. But, deep placement of urea, surface broadcast urea with NIs, and application of urea with urease inhibitors probably led to trade-offs between the two gases, with a mitigation potential of -201% to 101% for NH and -112% to 89% for N O. The literature synthesis showed that deep placement of urea with NIs had an emission factor of 1.53%-4.02% for NH and 0.22%-0.36% for N O, which were much lower than other fertilization regimes and the default values recommended by IPCC guidelines. This would translate to a reduction of 3.86-5.47 Tg N yr of NH and 0.41-0.50 Tg N yr of N O emissions, respectively, when adopting deep placement of urea with NIs (relative to current practice) in global croplands. We conclude that the combination of NIs and deep placement of urea can successfully tackle the trade-offs between NH and N O emissions, therefore avoiding N pollution swapping in global croplands.
氨（NH₃）和一氧化二氮（N₂O）是两种重要的空气污染物，对气候变化和生物多样性丧失有重大影响。农业是它们的最大来源，针对单一气体的有效减排措施已得到充分研究。然而，NH₃和N₂O排放之间的相互作用和权衡仍不明确。在此，我们报告了在中国华北平原（NCP）冬小麦-夏玉米轮作体系中进行的为期两年的田间试验结果，华北平原是全球活性氮排放的热点地区。我们的分析得到了全球农田文献综述的支持，以了解NH₃和N₂O排放之间的相互作用，并制定联合减排NH₃和N₂O的最有效方法。田间试验结果表明，与农民常用的地表撒施尿素相比，尿素与硝化抑制剂（NIs）深施分别使NH₃排放量降低了67%至90%，N₂O排放量降低了73%至100%。但是，尿素深施、地表撒施含NIs的尿素以及施用含脲酶抑制剂的尿素可能导致两种气体之间的权衡，NH₃的减排潜力为-201%至101%，N₂O的减排潜力为-112%至89%。文献综述表明，尿素与NIs深施时，NH₃的排放因子为1.53%-4.02%，N₂O的排放因子为0.22%-0.36%，远低于其他施肥方式以及IPCC指南推荐的默认值。在全球农田中采用尿素与NIs深施（相对于当前做法），这将分别减少3.86-5.47 Tg N yr的NH₃排放和0.41-0.50 Tg N yr的N₂O排放。我们得出结论，NIs与尿素深施相结合可以成功解决NH₃和N₂O排放之间的权衡问题，从而避免全球农田中的氮污染交换。
