Estimation of greenhouse gas mitigation potential through optimized application of synthetic N, P and K fertilizer to major cereal crops: A case study from China

Food security and climate warming are urgent challenges facing humans. The production and application of nitrogen (N), phosphate (P) and potash (K) synthetic fertilizers are directly related to several greenhouse gas (GHG) processes. As the largest fertilizer consumer and CO2 emitter, China must determine its fertilization status and the overall impact of optimized fertilization on GHG emissions, considering different fertilizer-related processes. Based on a national-scale survey, we investigated the status of synthetic fertilizer application to rice, wheat and corn in 2011 in China. In addition, we built the “carbon accounting and net mitigation for synthetic fertilizer application (CANM-SFA)” framework, which comprehensively evaluates the emissions from fertilizer production and the influences of fertilization on non-CO2 GHG emissions from cropland and soil carbon sequestration. Using the CANM-SFA framework, we estimated the net mitigation potential (NMP) of GHGs under optimized fertilization in accordance with national fertilization recommendations (the “Recommendation”). Our results indicated that overuse and unbalanced fertilization are common in China. Compared to fertilization in 2011, the fertilizer use in the Recommendation could be reduced by 37%, 43% and 44% for N, P and K fertilizer in China, respectively. The Recommendation could mitigate 5.2, 5.9 and 7.6 Tg Ce from fertilizer production for rice, wheat and corn, respectively. For rice, the CH4 emissions changed from 30.5 Tg Ce in 2011 to 34.1 Tg Ce under the Recommendation. In addition, the N2O emissions decreased from 4.8 Tg Ce to 3.6 Tg Ce. For both wheat and corn, the N2O emissions were 2.5 Tg Ce under the Recommendation. In summary, the NMP was 0.8, 5.3 and 6.5 Tg Ce at rates of 26, 219 and 195 kg Ce ha−1 yr−1 for rice, wheat and corn, respectively. The national NMP, as the sum of 14.5, −1.4 and −0.4 Tg Ce from the N-, P- and K- optimized fertilization adjustments, respectively, could offset 5.8% of China's CO2 emissions from fuel combustion in 2011. Therefore, the implementation of the Recommendation, especially for N fertilization, throughout the country has great potential for mitigating GHG emissions.