Reducing agricultural greenhouse gas (GHG) emissions is attracting increasing attention. Balanced fertilization (BF) of cropland has been widely promoted and applied and has great potential to reduce GHG emissions. This study assesses GHG mitigation of BF cropland systems including winter wheat and summer maize double-cropping system (wheat-maize) and winter oilseed rape (Brassica napus) and rice double-cropping system (rape-rice) in Shaanxi province, China. We determined the boundaries, scenarios, leakage, and sources of GHG mitigation and developed a measurement system for GHG mitigation under these cropping systems for BF farmland. In the measurement system, except for the changes in nitrogen fertilizer rates, soil carbon storage, mechanical fuel consumption, and fertilizer management mode (paddy), change in crop yield was recommended as a primary source of GHG mitigation. The BF cropland areas of wheat-maize and rape-rice were 2818.89 ha and 1671.73 ha, respectively. The use of BF reduced the GHG emissions of wheat-maize by 1.15 tCO2 equivalent (CO2e) ha-1 per year and the emissions of rape-rice by 1.05 tCO2e ha-1 per year. The BF cropland produced 5007.6 tCO2e per year. Our results do not only provide a reference for the assessment of GHG mitigation on BF cropland under double-cropping systems, but also will be helpful for improving the methodology of GHG mitigation on BF cropland.
Keywords: Double-cropping system; Farmland; Fertilizer; Greenhouse gas mitigation; The measurement system.