Net global warming potential and greenhouse gas intensity in rice agriculture driven by high yields and nitrogen use eficiency: a 5 year field study.

Our understanding of how net global warming potential (NGWP) and greenhouse gas intensity (GHGI) is affected by management practices aimed at food security with respect to rice agriculture remains limited. In the present study, a 5 year field experiment was conducted in China to evaluate the effects of integrated soil-crop system management (ISSM) on NGWP and GHGI after accounting for carbon dioxide (CO₂) emissions from all sources (methane, CH₄, and nitrous oxide, N₂O, emissions, agrochemical inputs, Ei, and farm operations, Eo) and sinks (i.e., soil organic carbon, SOC, sequestration). For the improvement of rice yield and agronomic nitrogen use efficiency (NUE), four ISSM scenarios consisting of different nitrogen (N) fertilization rates relative to the local farmers' practice (FP) rate were carried out, namely, N1 (25% reduction), N2 (10% reduction), N3 (FP rate) and N4 (25% increase). The results showed that compared with the FP, the four ISSM scenarios, i.e., N1, N2, N3 and N4, significantly increased the rice yields by 10, 16, 28 and 41% and the agronomic NUE by 75, 67, 86 and 82%, respectively. In addition, compared with the FP, the N1 and N2 scenarios significantly reduced the GHGI by 14 and 18%, respectively, despite similar NGWPs. The N3 and N4 scenarios remarkably increased the NGWP and GHGI by an average of 67 and 36%, respectively. In conclusion, the ISSM strategies are promising for both food security and environmental protection, and the ISSM scenario of N2 is the optimal strategy to realize high yields and high NUE together with low environmental impacts for this agricultural rice field. [ABSTRACT FROM AUTHOR]