title: A meta-analysis of fertilizer-induced soil NO and combined NO+N2O emissions.
abstract: Soils are among the important sources of atmospheric nitric oxide (NO) and nitrous oxide (N2O), acting as a critical role in atmospheric chemistry. Updated data derived from 114 peer-reviewed publications with 520 field measurements were synthesized using meta-analysis procedure to examine the N fertilizer-induced soil NO and the combined NO+N2O emissions across global soils. Besides factors identified in earlier reviews, additional factors responsible for NO fluxes were fertilizer type, soil C/N ratio, crop residue incorporation, tillage, atmospheric carbon dioxide concentration, drought and biomass burning. When averaged across all measurements, soil NO-N fluxes were estimated to be 4.06 kg ha-1yr-1, with the greatest (9.75 kg ha-1yr-1) in vegetable croplands and the lowest (0.11 kg ha-1yr-1) in rice paddies. Soil NO emissions were more enhanced by synthetic N fertilizer (+38%), relative to organic (+20%) or mixed N (+18%) sources. Compared with synthetic N fertilizer alone, synthetic N fertilizer combined with nitrification inhibitors substantially reduced soil NO emissions by 81%. The global mean direct emission factors of N fertilizer for NO (EFNO) and combined NO+N2O (EFc) were estimated to be 1.16% and 2.58%, with 95% confidence intervals of 0.71-1.61% and 1.81-3.35%, respectively. Forests had the greatest EFNO(2.39%). Within the croplands, the EFNO(1.71%) and EFc(4.13%) were the greatest in vegetable cropping fields. Among different chemical N fertilizer varieties, ammonium nitrate had the greatest EFNO(2.93%) and EFc(5.97%). Some options such as organic instead of synthetic N fertilizer, decreasing N fertilizer input rate, nitrification inhibitor and low irrigation frequency could be adopted to mitigate soil NO emissions. More field measurements over multiyears are highly needed to minimize the estimate uncertainties and mitigate soil NO emissions, particularly in forests and vegetable croplands.
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Shuwei
authors: S
authors: Liu
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Feng
authors: F
authors: Lin
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Shuang
authors: S
authors: Wu
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Cheng
authors: C
authors: Ji
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yi
authors: Y
authors: Sun
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yaguo
authors: Y
authors: Jin
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Shuqing
authors: S
authors: Li
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Zhaofu
authors: Z
authors: Li
authors: Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Jianwen
authors: J
authors: Zou
mesh_terms: D018556:Crops, Agricultural; D005308:Fertilizers; D065928:Forests; D009569:Nitric Oxide; D009609:Nitrous Oxide; D012987:Soil / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D012987:Soil; D009569:Nitric Oxide; D009609:Nitrous Oxide
keywords: emission factor; fertilizer; meta-analysis; nitric oxide; nitrous oxide; trace gas