Soil N₂ O emissions from specialty crop systems: A global estimation and meta-analysis

Nitrous oxide (N₂ O) exacerbates the greenhouse effect and thus global warming. Agricultural management practices, especially the use of nitrogen (N) fertilizers and irrigation, increase soil N₂ O emissions. As a vital sector of global agriculture, specialty crop systems usually require intensive input and management. However, soil N₂ O emissions from global specialty crop systems have not been comprehensively evaluated. Here, we synthesized 1137 observations from 114 published studies, conducted a meta-analysis to evaluate the effects of agricultural management and environmental factors on soil N₂ O emissions, and estimated global soil N₂ O emissions from specialty crop systems. The estimated global N₂ O emission from specialty crop soils was 1.5 Tg N₂ O-N year^-1 , ranging from 0.5 to 4.5 Tg N₂ O-N year^-1 . Globally, soil N₂ O emissions exponentially increased with N fertilizer rates. The effect size of N fertilizer on soil N₂ O emissions generally increased with mean annual temperature, mean annual precipitation, and soil organic carbon concentration but decreased with soil pH. Global climate change will further intensify the effect of N fertilizer on soil N₂ O emissions. Drip irrigation, fertigation, and reduced tillage can be used as essential strategies to reduce soil N₂ O emissions and increase crop yields. Deficit irrigation and non-legume cover crop can reduce soil N₂ O emissions but may also lower crop yields. Biochar may have a relatively limited effect on reducing soil N₂ O emissions but be effective in increasing crop yields. Our study points toward effective management strategies that have substantial potential for reducing N₂ O emissions from global agricultural soils.