Net global warming potential and greenhouse gas intensity from the double rice system with integrated soil-crop system management: A three-year field study

The impact of integrated soil-crop system management (ISSM) on net global warming potential (GWP) and greenhouse gas intensity (GHGI) is poorly documented though crucial for food security and nitrogen fertilizer use efficiency (NUE). Using local farming practices (FP) and no nitrogen (NN) as the controls, three ISSM practices at different N rates were established in 2009 in a double rice system in Hunan Province, China. Soil organic carbon sequestration rates (SOCSR) were estimated by changes in SOC between 2009 and 2014. Field measurements of methane (CH4) and nitrous oxide (N2O) fluxes, grain yield and NUE of early and late rice were measured from April 2011 through April 2014. The net GWP of the annual CH4 and N2O emissions and SOCSR and the GHGI over the three years in the FP was 15.35 t CO2 eq ha(-1) year(-1) and 1.00 kg CO2 eq kg(-1) grain. The ISSM (N-2) treatment increased annual rice yield by 23%, NUE by 76% and SOCSR by 129%, with similar sizes of net GWP and GHGI under the same N input relative to the FP. A second ISSM (N1) treatment in which annual fertilizer N input was decreased by 20% also showed the potential to lower net GWP and GHGI and increase SOCSR and significantly increased annual rice grain yield by 8.6% and NUE by 59%. The third ISSM (N3) in which fertilizer N input was 20% greater than in FP, significantly increased annual rice yield by 26%, NUE by 57% and SOCSR by 98% but notably increased the CH4 and N2O emissions. Our findings show that the ISSM strategies are promising and feasible in sustainable rice agriculture for food security and GHGs mitigation. (C) 2015 Elsevier Ltd. All rights reserved.