Abstract:
Abstract: Greenhouse gas emissions from paddy field in China have aroused widespread attention. Northeast China is the most important marketable grain base in China, and the paddy fields acreage of northeast China is increasing rapidly in nearly a decade. It has only scattered reports in regard to paddy greenhouse gas emissions in the northeast cold region. The winter of northeast is very cold and long, and organic matter of farmland soil is relatively high. Nitrous oxide (N2O) emissions from fields in cold region of northeast China may play an role in climate change. In this study, a field experiment was conducted to investigate the N2O emissions from rice paddy field in cold region under different irrigation modes and its response to environmental factors. The experiment was set up in Rice Irrigation Experimental Center of Heilongjiang located in Heping town of Qing'an county in 2014 with four treatments including control irrigation, wet irrigation, intermittent irrigation and flood irrigation. The For all the treatments, drainage and drying were conducted in the lateral tillering stage and yellow ripe stage. In addition, under the control irrigation system, the soil water content was controlled at 0.7 or 0.8 times of saturated moisture content except for seeding establishment when water layer was 0-30 mm; Under the intermittent irrigation system, water layer was arranged at 0-30 or 0-40 mm for stages other than the lateral tillering stage and yellow ripe stage; Under the wet irrigation system, water layer was arranged at 0-20 or 0-30 mm for stages other than the lateral tillering stage and yellow ripe stage; Under the flood irrigation, most of stages had water layer of 0-40 mm. Each treatment was repeated three times. During the experiment, the N2O emission was measured at 10:00-14:00 using the method of static chamber-gas chromatographic techniques. Additionally, rice yield was determined at harvest. The results showed that the N2O emissions fluxes had same trend in the seasonal variation under different treatments. The peak of emissions appeared in the stage when water alteration was frequent. The N2O emission was low in the early stage of rice growth and small amounts of N2O emissions occurred in steeping field stage. Compare to flood irrigation, the total amount of N2O emissions under intermittent irrigation increased by 47.3%, but that of control and wet irrigation treatments reduced by 40.7% and 39.6%. The N2O emission flux from cold rice paddies was closely related to soil NO3-N content and soil 10-cm temperature (P<0.05). The N2O emission from rice yield would increase with soil temperature and NO3-N content. For rice yield, the treatment of wet irrigation was worse than the others and the other treatments had no significant difference. The N2O emissions per unit yield of control and wet irrigation were 40% and 30% lower than the flood irrigation. However, the rice yield of control irrigation treatment was significantly higher than wet irrigation. Therefore, the control irrigation was best irrigation mode to increase rice yield and reduce N2O emission among the four treatments. It should be heavily emphasized in future in the cold regions of China. The results can provide valuable information for selection of water-saving irrigation method in Heilongjiang cold region.