[Effects of cropping systems on nitrous oxide emissions from paddy soils during the rice-growing season]

Cropping systems influence nitrous oxide (N2O) emissions from agricultural soils. Effects of 3 rice-based cropping systems on N2O emissions from paddy soils in pot experiment were investigated with closed chambers in triplicate. The results demonstrated that the seasonal N2O emission rate of the rice pot under rice-wheat cropping system was obviously higher than that of the early rice pot under double rice-wheat system, being 4.21 and 2.17 kg.hm-2, respectively. No distinct difference was observed between the seasonal average fluxes, which were 116.9 and 117.6 micrograms.m-2.h-1 respectively. Both of above mentioned seasonal average fluxes were greatly higher than that of the late rice pot under early rice-late rice-wheat cropping system and of rice pot under rice-flooding fallow system, being 67.0 and 42.1 micrograms.m-2.h-1 respectively. More than 91% of the seasonal emission was focused on the first half growing period both in the rice season in rice-wheat system and in the early rice season in double rice-wheat system in which the previous cropping was upland wheat. 91% of the seasonal emission was focused on the water drainage period including the mid-season aeration and final drainage in the late rice season in double rice-wheat system in which the previous cropping was lowland rice. The results implied that cropping system and water status of previous cropping impacted N2O emission from paddy soil.