Effect Of Conservation Tillage On Fluxes Of Greenhouse Gases Of Arable Soil In The Arid And Semiarid Regions

Soil are also the important source or sink of the greenhouse gas, which role agricultural soil plays depend on the agricultural land use models and management methods. It is estimated that around 20% of CO2, 70% of CH4 and 90% of N2O in atmosphere come from agricultural activities and land use change process. Therefore, it is an essential measure to mitigate global warming trend by controlling the of greenhouse gas emissions in agricultural soil.In recent years, a amount of arable land degradated in China, especially in the arid and semiarid regions of China where soil erosion are very serious. The deterioration of the ecological environment has gone through a long historical process. But from the point of view of reality, the traditional farming systems and practice methods which expose soil surface, loose soil, increase strong evaporation result in the heavy water and wind erosion. Therefore, the traditional farming practice needs to convert to a new, sustainable pattern of farming. Conservation tillage is a feasible farming techniques charactered with drought-resistant water-saving, nutrients-saving, and increasing-income. As the technique with high-yield, high efficiency, low consumption, environmental protection, conservation tillage can be viewed as an effective solution to the negative effects caused by the traditional farming. This study focuses on the effect of conservation tillage on fluxes of greenhouse gases of arable soil in the arid and semiarid regions in northwestern China.This study was conducted in Dingxi and Wuwei experimental sites located in the arid and semiarid region of Gansu province. Each experimental site included a series of tillage practice (traditional and conservation tillage). The result show that the CO2 flux in Dingxi is aroundly increasing with the study time, the value of CO2 flux range from 10 mg m-2 h-1 in lower and 400 mg m-2 h-1 in higher. In the early trial period, the CO2 flux in two no-tillage treatments with no-mulched (NTd and NTPd) are lower comparing to other treatments. While the CO2 flux of NTPd rise up in the mid-end of the study, that of NTd is still retain a lower level. The CO2 flux are not significantly defferent among the other three treamtments (Td, NTSd and TPd) on the May 31, June 15 and June 30. In Wuwei experimental site, while the flux of CO2 of TISw is still at the highest level compared with other treatments in the same site, that of NTw is at the lowest level. Both of the relationships in Wuwei are same with that in Dingxi. No-tillage treatment has the lowest CO2 flux, and traditional tillage treatment with stubble integrated into soil has the highest CO2 emission potential.In Dingxi and Wuwei, CH4 fluxes are not significantly different between treatments and sampling dates.In two experimental sites, N2O flux increase with the temperature increasing. In Dingxi, six treatments can generally be divided into three groups. The first group includes two treatments (TSd and TPd) in which N2O flux in the whole period of experiment are at a relatively highet level; the second group included Td and NTSd, N2O Flux has the middle value in the six treatments; the other two treatments NTd and NTPd has the lowest value in the experimental site. In Wuwei, the result of N2O flux trend is same with that in Dingxi. The traditional tillage soil releases more N2O, and no-tillage (NTw and NTp) will reduce N2O flux; the no-tillage with stubble integrated in soil will increase the N2O emission.In both sites, the relationship between N2O and CO2 flux is high positive correlativity, and in Wuwei the correlativity is higher than in Dingxi. The correlativity of CO2 and CH4 flux is low, the R2 value are only 0.024 and 0.032, respectively. And the correlativities are different. In Dingxi the relationship is negative correlation, while in Wuwei is a positive correlation. But the correlativities between N2O and CH4 flux are not significantly in both experimental sites.Surface soil moisture content has different impacts on greenhouse gas fluxes. The more evident relationship can be observed in CO2 and the soil water content. The correlativities of 0-5cm & 5-10 cm soil moisture and CO2 flux are tight. The correlation coefficients R2 are 0.593 and 0.207, respectively. And the relationship is negative between the soil moisture and CO2 flux. However, the relationships between surface soil moisture content and NH4 & N2O are relatively low, moreover, the the relationship is not clear. The higher correlation coefficient among these relationship is only 0.213.The relationship between greenhouse gases and the soil organic carbon content are not clear, except the correlation coefficient between SOC in 0-5 cm and CO2 flux, 0.443, is relative high, others is around lower than 0.01.The correlativities between the greenhouse gases and surface soil bulk density and the saturated hydraulic conductivity generally are showed positive. But the the correlation coefficients are very low. Although the correlativities of CO2 flux and saturated hydraulic conductivity is highest in these gases, R2 value only is 0.266.