Nitrous oxide and methane emissions from soil-plant systems

The closed chamber method was used to measure the N2O and CH4 emissions from rice, maize, soybean and spring wheat fields in Northeast China. Rice field almost did not emit or deposit N2O in total during flooding period, whereas N2O was substantially emitted during non-flooding period. The annual emission amount of N2O was 1.70 kg N2O ha(-1), but that in flooding period was only 0.04 kg N2O ha(-1). Daily average and seasonal total CH4 emission in rice field were 0.07 and 7.40 g CH(4)m(-2), respectively. A trade-off between N2O and CH4 emissions from rice field was found. The growth of Azolla in rice field greatly stimulated both N2O and CH4 emissions. Total N2O emissions (270 days) from maize and soybean fields were 7.10 and 3.12 kg N2O ha(-1), respectively. The sink function of the uplands monitored as the atmospheric CH4 was not significant.