Reducing greenhouse gas emissions while maintaining yield in the croplands of Huang-Huai-Hai Plain, China

Agroecosystems face double pressures of producing more food to feed growing global population and reducing greenhouse gas (GHG) emissions to mitigate climate change. The Huang-Huai-Hai (HHH) plain produces similar to 1/3 wheat and maize of China with very high resource inputs, particularly synthetic nitrogen (N) fertilizers since the 1980 s. Although fertilizer input has substantially increased crop yield and enhanced biomass carbon (C) input to the soil and thus stimulating soil C sequestration, GHG emissions (e.g., nitrous oxide (N2O)) relating to the fertilizers have been also dramatically increased. Yet, a systematic regional assessment on the trade-offs between crop yield, soil C sequestration and N2O emissions as impacted by management practices and environmental conditions is lacking. Here we calibrated a fanning system model to conduct comprehensive assessment on crop yield and GHG emissions (soil CO2 and N2O emissions) during the period 1981-2010 across the HHH plain at the resolution of 10 km. We found that soil in HHH plain was a C sink with an annual C sequestration rate of 1.53 CO2-eq ha(-1) yr(-1) (0-30 cm soil layer) during the period under current typical agricultural practices, but this sink could only offset about 68% of global warming potential from contemporary N2O emissions. By reducing the annual N input rate (from current more than 300 to similar to 250 kg N ha(-1) yr(-1)) and enhancing crop residue retention rate (from current 30% to 100%), the HHH plain could act as a net sink of GHG without sacrificing grain yield. Apart from management, the effects of three key environmental factors, i.e., mean annual rainfall and temperature and initial soil organic carbon stock on dynamics of crop yield, soil CO2 and N2O emissions were also studied. The results will have important implications for the development of management strategies to maintain yield while reducing GHG emissions.