Impacts of rice varieties and management on yield-scaled greenhouse gas emissions from rice fields in China: A meta-analysis

Abstract. Increasing numbers of studies have suggested that a comprehensive assessment of the impacts of cropping practices on greenhouse gas (GHG) emissions per unit yield (yield-scaled), rather than by land area (area-scaled), is needed to inform trade-off decisions to increase yields and reduce GHG emissions. We conducted a meta-analysis to quantify impacts of rice varieties on the global warming potential (GWP) of GHG emissions at the yield scale in China. Our results showed that significantly higher yield-scaled GWP occurred with indica rice varieties (1101.72 kg CO₂ equiv. Mg⁻¹) than japonica rice varieties (711.38 kg CO₂ equiv. Mg⁻¹). Lower yield-scaled GHG emissions occurred within 120–130 days of growth duration after transplanting (GDAT; 613.66 kg CO₂ equiv. Mg⁻¹), followed by 90–100 days of GDAT (749.72 kg CO₂ equiv. Mg⁻¹, 100–110 days of GDAT (794.29 kg CO₂ equiv. Mg⁻¹), and 70–80 days of GDAT (800.85 kg CO₂ equiv. Mg⁻¹). The fertilizer rate of 150–200 kg N ha⁻¹ resulted in the lowest yield-scaled GWP. Consequently, appropriate cultivar choice and pairs were of vital importance in the rice cropping system. A further life cycle assessment of GHG emissions among rice varieties at the yield scale is urgently needed to develop win–win policies for rice production to achieve higher yield with lower emissions.