A Meta‐Analysis of Nitric Oxide Emissions From Chinese Cropland

ABSTRACT Cropland is a significant source of nitric oxide (NO) in rural areas. We extracted field measurement data from peer‐reviewed publications and conducted a pairwise meta‐analysis, with major objectives (1) to quantify the variations of NO emissions and direct emission factors (EF d s) across Chinese cropland, and (2) to evaluate the impacts of various mitigation strategies on NO emissions and EF d s. Cropping systems included paddy rice–winter wheat, vegetables, maize–winter wheat, orchards, and tea plantations. The dataset comprised 650 and 427 records of NO emissions and EF d s, respectively, from 71 publications (2006–2026). Mean seasonal NO emissions were 0.49, 2.23, and 1.71 kg N ha −1 for paddy rice, winter wheat, and vegetables, respectively. Mean annual NO emissions were 1.33, 1.78, and 5.89 kg N ha −1 for maize–winter wheat, orchards, and tea plantations, respectively. Mean EF d s were 0.16%, 0.70%, 0.79%, 0.31%, 0.17%, and 1.47% for paddy rice, winter wheat, vegetables, maize–winter wheat, orchards, and tea plantations, respectively. Tea plantations and vegetable systems were identified as major sources of NO emissions. Reducing nitrogen input rates significantly decreased NO emissions by 33% on average, but had nonsignificant effects on EF d s. Organic amendments, straw retention, and the application of biochar or enhanced‐efficiency fertilizers reduced NO emissions (ranging from −37% to −16%) and EF d s (ranging from −49% to −13%). These findings provide a basis for effectively mitigating NO emissions from Chinese cropland.