Soil N2O emissions from specialty crop systems: A global estimation and meta-analysis

Abstract

Nitrous oxide (N2O) exacerbates the greenhouse effect and thus global warming. Agricultural management practices, especially the use of nitrogen (N) fertilizers and irrigation, increase soil N2O emissions. As a vital sector of global agriculture, specialty crop systems usually require intensive input and management. However, soil N2O 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 N2O emissions, and estimated global soil N2O emissions from specialty crop systems. The estimated global N2O emission from specialty crop soils was 1.5 Tg N2O-N year−1, ranging from 0.5 to 4.5 Tg N2O-N year−1. Globally, soil N2O emissions exponentially increased with N fertilizer rates. The effect size of N fertilizer on soil N2O 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 N2O emissions. Drip irrigation, fertigation, and reduced tillage can be used as essential strategies to reduce soil N2O emissions and increase crop yields. Deficit irrigation and non-legume cover crop can reduce soil N2O emissions but may also lower crop yields. Biochar may have a relatively limited effect on reducing soil N2O emissions but be effective in increasing crop yields. Our study points toward effective management strategies that have substantial potential for reducing N2O emissions from global agricultural soils.