Effects of irrigation, fertilization and crop straw management on nitrous oxide and nitric oxide emissions from a wheat-maize rotation field in northern China

摘要

a- We investigated the crop yield and N2O/NO fluxes for different management practice. a- The improved irrigation, fertilization and crop straw management increased crop yield. a- The improved management also reduced water and fertilizer inputs and N2O/NO emissions. One-year winter wheat-summer maize rotation is the most popular double cropping system in north-central China, and this highly productive system is an important source of nitrous oxide (N2O) and nitric oxide (NO) emissions due to the high fertilizer N and irrigation water inputs. To sustain the high crop production and mitigate the detrimental impacts of N2O and NO emissions, improved management practices are extensively applied. The aim of this study is therefore to evaluate the effects of an improved management practice of irrigation, fertilization and crop straw on grain yield and N2O and NO emissions for a wheat-maize rotation field in northern China. Using automated and manual chamber measuring systems, we monitored N2O and NO fluxes for the conventional (CT, 2007-2008), improved (IT, 2007-2008), straw-amended (WS, 2008-2009), straw-not-amended (NS, 2008-2009), and no N-fertilizer treatments (WS-NN, 2008-2009), respectively, for one rotation-year. The grain yields were determined for CT and IT for three rotation-years (2005-2008) and for WS, NS and WS-NN for one rotation-year (2008-2009). The improved management of irrigation and fertilization reduced the annual N fertilization rate and irrigation amount by 17% and 30%, respectively; increased the maize yield by 7-14%; and significantly decreased the N2O and NO emissions by 7% (p <0.05) and 29% (p <0.01), respectively. The incorporation of wheat straw increased the cumulative N2O and NO emissions in the following maize season by 58% (p <0.01) and 13%, respectively, whereas the effects of maize straw application were not remarkable. The N2O and NO emission factors of applied N were 2.32A plus or minus 2.32% and 0.42A plus or minus 1.69% for wheat straw and 0.67A plus or minus 0.23% and 0.54A plus or minus 0.15% for chemical N-fertilizers, respectively. Compared to conventional management practices using high application rates of irrigation water and chemical N-fertilizer as well as the field burning of crop straw, the improved management strategy presented here has obvious environmentally positive effects on grain yield and mitigation of N2O and NO emissions.