The Influence Of Different Drainage Measures In Winter Wheat Fields On Methane And Nitrous Oxide Emissions From Rice Paddy

CH4 and N2O are two important greenhouse gases and rice paddy is a major emission source of CH4 and N2O. The single cropping rice in the plain area of the middle and lower Yangtze River is an important rice production field in China, but researches on it are rare that the influence of different drainage measures in winter wheat fields on CH4 and N2O emissions in rice fields, though there have been a lot of research about CH4 and N2O emission flux and its seasonal variation in rice growth period in this region.This experiment mainly study in the single paddy fields, a typical rice-wheat rotation cropping systems in the plain area of the middle and lower Yangtze River, which is located in Chaohu, Hefei, Anhui province. It uses static chamber-gas chromatograph technique to monitor CH4 and N2O emissions in rice growth period. The purpose of this study is to explore the influence of different drainage measures in winter wheat fields on CH4 and N2O emissions in rice fields. The test is divided into two stages. Firstly we set of 4 kinds of processing in winter wheat season including Conventional water-fertilizer managing (I), Conventional water-fertilizer managing (Ⅱ), Conventional water-fertilizer managing&Shallow ditch (Ⅲ) and Conventional water-fertilizer managing&Deep ditch (IV). Then, in rice-growing season, other 4 treatments were set on the basis of the treatments in wheat-growing season. There was (I)&No-fertilizer (CK), (Ⅱ) &Conventional water-fertilizer managing (CG), (Ⅲ)&Conventional water-fertilizer managing (CQ) and (IV)&Conventional water-fertilizer managing (CS)Through field monitoring, we can reach a conclusion as follows:1. Different drainage measures in winter crop season had a significant impact on CH4 and N2O emission from single rice paddy fields. There have a highly significant difference (P<0.01) of CH4 emission were observed between different drainage measures. Different drainage measure in winter wheat significantly reduced the soil CH4 emissions during the following flooded and rice-growing season. The soil CH4 emissions of CQ, CS treatments reduced by 43.1%,39.9% compared with CK treatment and reduced by 58.1%and 55.7% compared with CG treatment. The distributive law of time of soil CH4 emissions rice-growing season was changed due to the different drainage measure in winter wheat. There was a important emission fountain of soil CH4 emissions during the following flooded and accounted for 65.2%,65.7% of the total amount respectively in no drainage treatments such as CK and CG.which were almost no significant difference. This showed that there were not effective enough for nitrate fertilizer application effecting on the soil CH4 emissions rice-growing season. There was a important emission fountain of soil CH4 emissions before the sunning land and accounted for 53.5%,54.1% of the total amount respectively in drainage treatments such as CQ and CS, which were also almost no significant difference.; but there have a highly significant difference of CH4 emission were observed between CK,CG and CQ,CS measures. Because CH4 emissions reduction during the following flooded, CQ CS total emissions are greatly reduced.2. Soil CH4 emission from rice paddies has a remarkable correlation to 5cm soil temperature (p<0.01) in all rice growing period. The relationship of soil CH4 emission from rice paddies and 5cm soil temperature were basically identical before the sunning land period and CH4 emission less affected by 5 cm soil temperature in the sunning land period, but CH4 emission closed relation with 5 cm soil temperature during the following flooded period. CH4 emissions of single the single paddy fields have a significant negative correlation with soil Eh. The correlation of CK, CG with Eh is distinct better than of CQ, CS with Eh, especially in the following flooded period among them. The soil Eh from CQ, CS and CK, CG were all under-150mv, but CH4 emission flux of CQ, CS obviously under of CQ, CS, due to the relationship between soil Eh and CH4 emission flux weakening significantly.3. Different drainage measure in winter wheat slightly reduced the soil N2O emissions during the following flooded and rice-growing season. The soil N2O emissions of CQ, CS treatments reduced by 22.61%,14.63% respectively compared with CG treatment and the difference of the two is slight. The accumulation of N2O emission of CQ and CS treatments are 51.46 mg·m-2,56.77 mg·m-2 respectively and there is no significant difference in both, but the accumulation of N2O emission showed major differences between the CG,CQ, CS treatments and CK treatment and increased by 70.79%,62.26% and 65.79% respectively. This showed that the nitrogen supplying from the soil are the main factor of affecting N2O emissions. N2O emission from paddy fields only has significant correlation with the temperature variation after soil drying. The drainage measure in winter-crop season increased the utilization rate of fertilizers and soil N2O emission from CQ, CS by urea have reduced by 32.3%,21.3% respectively compared with CK method.4. Considering the global warming potential (GWP) from greenhouse gases, both CQ and CS treatments reduced the farmland greenhouse gas emissions under the condition of no affecting rice yields. In conclusion, soil drainage in winter-crop seasons is an effective measure to reduce greenhouse gas emissions in the plain area of the middle and lower Yangtze River and among soil drainage measures, the reduction effect about emission of CQ treatment is better than that of CS treatment.