Meta-analysis of yield and nitrous oxide outcomes for nitrogen management in agriculture

Improved nitrogen (N) use is key to future food security and environmental sustainability. While many regions still experience N shortagesagriculture is the leading global emitter of N2O due to losses exacerbated by N surpluses in other regions. In order to sustainably maintain or increase food productionfarmers and their advisors need a comprehensive and actionable understanding of how nutrient management affects both yield and N2O emissionsparticularly in tropical and subtropical agroecosystems. We performed a meta-analysis to determine the effect of N management and other factors on N2O emissionsplant N uptakeand yield. Our analysis demonstrates that performance indicators—partial N balance and partial factor productivity—predicted N2O emissions as well as or better than N rate. While we observed consistent production and environmental benefits with enhanced-efficiency fertilizerswe noted potential trade-offs between yield and N2O emissions for fertilizer placement. Furthermorewe observed confounding effects due to management dynamics that co-vary with nutrient application practicesthus challenging the interpretation of the effect of specific practices such as fertilization frequency. Thereforerather than providing universally prescriptive management for N2O emission reductionour evidence supports mitigation strategies based upon tailored nutrient management approaches that keep N balances within safe limitsso as to minimize N2O emissions while still achieving high crop yields. The limited evidence available suggests that these relationships hold for temperatetropicaland subtropical regionsbut given the potential for expansion of N use in crop productionfurther N2O data collection should be prioritized in under-represented regions such as Sub-Saharan Africa.