Response of N2O emission to straw retention under two contrasting paddy water conditions: a field experiment over rice–rice-fallow rotation

Abstract

Few studies are available on comprehensive impacts of straw retention and water regimes on nitrous oxide (N2O) emission from rice–rice-fallow rotation systems. A field experiment with or without rice straw (5000 kg ha−1 each rice season) retention under two contrasting water regimes (1. continuous flooding; 2. rain-fed with exception flooding irrigation about 15 days after transplanting) was conducted in south China. N2O emission was monitored using the closed chamber method over the entire rice–rice-fallow rotation. The results demonstrate that there were significant differences in the responses of N2O emission to water regime, straw retention, and their interaction. N2O emission was negligible in the continuously flooded treatments, with annual N2O emission of 0.052 kg ha−1 with straw and − 0.008 kg ha−1 without straw, respectively. In contrast, substantial N2O fluxes were observed under rain-fed condition when water layer disappeared, with annual N2O emission of 0.969 kg ha−1 with straw and of 0.618 kg ha−1 without straw, respectively. About 50–60% of annual N2O emission occurred in fallow season under rain-fed treatments. The results indicate that rice straw retention has a potential to accelerate N2O emission depending on paddy water conditions.