Water regime–nitrogen fertilizer–straw incorporation interaction: Field study on nitrous oxide emissions from a rice agroecosystem in Nanjing, China

The comprehensive impacts of agricultural management on nitrous oxide (N2O) emissions are not well documented. Field experiments with 23 factorial designs were conducted to investigate the influence of water regimes, nitrogen fertilizer, and straw incorporation on N2O emissions from rice paddies in Nanjing, China. In addition to the main factorial design, three single factor designs were included: water regime, N rate, and mid-season drainage duration, each with three levels. The results demonstrate that there were significant differences in the responses of soil N2O emissions to water regime, nitrogen fertilizer, and straw amendment as well as interaction between straw and nitrogen fertilizer. The cumulative seasonal N2O emissions from the treatments with mid-season drainage averaged 0.41 kg N ha−1, ranging from 0.20 to 0.73 kg N ha−1. These emissions were higher than those from continuously flooded treatments, which averaged 0.28 kg N ha−1 and ranged from 0.13 to 0.55 kg N ha−1. The integrated application of straw and nitrogen fertilizer mitigated N2O emissions by approximately 50% under both water regimes. N2O emissions were mainly promoted by the transition period from the upland crop season to the flooded rice season, by nitrogen application, and by depression with straw amendment. Three groups were formed according to a polynomial relationship between seasonal N2O emissions and rice production. The results of this study suggest that the integrated application of straw and nitrogen fertilizer can mitigate N2O emissions from rice agriculture without a decrease in rice production.