Soil N 2 O emissions from specialty crop systems: A global estimation and meta-analysis.

Nitrous oxide (N 2 O) exacerbates the greenhouse effect and thus global warming. Agricultural management practices, especially the use of nitrogen (N) fertilizers and irrigation, increase soil N 2 O emissions. As a vital sector of global agriculture, specialty crop systems usually require intensive input and management. However, soil N 2 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 N 2 O emissions, and estimated global soil N 2 O emissions from specialty crop systems. The estimated global N 2 O emission from specialty crop soils was 1.5 Tg N 2 O-N year -1 , ranging from 0.5 to 4.5 Tg N 2 O-N year -1 . Globally, soil N 2 O emissions exponentially increased with N fertilizer rates. The effect size of N fertilizer on soil N 2 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 N 2 O emissions. Drip irrigation, fertigation, and reduced tillage can be used as essential strategies to reduce soil N 2 O emissions and increase crop yields. Deficit irrigation and non-legume cover crop can reduce soil N 2 O emissions but may also lower crop yields. Biochar may have a relatively limited effect on reducing soil N 2 O emissions but be effective in increasing crop yields. Our study points toward effective management strategies that have substantial potential for reducing N 2 O emissions from global agricultural soils.