Nitrous oxide emissions from paddy soil in three rice-based cropping systems in China

Rice-flooding fallow, rice-wheat, and double rice-wheat systems were adopted in pot experiment in an annual rotation to investigate the effects of cropping system on N2O emission from rice-based cropping systems. The annual N2O emission from the rice-wheat and the double rice-wheat cropping systems were 4.3 kg N ha−1 and 3.9 kg N ha−1, respectively, higher than that from rice-flooding fallow cropping system, 1.4 kg N ha−1. The average N2O flux was 115 and 118 μg N m−2 h−1 for rice season in rice-wheat system and early rice season in double rice-wheat system, respectively, 68.6 and 35.3 μg N m−2 h−1 for the late rice season in double rice-wheat system and rice season in rice-flooding fallow, respectively, and only 3.1–5.3 μg N m−2 h−1 for winter wheat or flooding fallow season. Temporal variations of N2O emission during rice growing seasons differed and high N2O emission occurred when soil conditions changed from upland crop to flooded rice.