The Effects Of Soil Managements Affecting The Greenhouse Gas Emitted From Cropland

Cropland and carbon sink where greenhouse gas emitted from are two cores on modern agricultural ecological system study. Rice-wheat rotation is a main planting pattern in the middle-lower Yangtze area. Which together make study on the mechanism and effect of greenhouse gas emitted from cropland and carbon cycle affected by soil management has the theory and practice significances for reasonable management of farmland ecosystem in high yield grain areas. This paper took long-term fertilization test and different tillage depths test in Su Zhou academy of agricultural science as research background. It was used to study not only the characteristics of CO2, CH4and N2O emitted from rice-wheat rotation field but also the effects of carbon fixation of soil under the conditions of long-term different combined application of fertilizer (N, P, K), manure and different tillage depths. And on the basis of the field experiment, we built cropland management database and used DNDC model to simulate the observed data. The following items are the main conclusion of this paper:1. Different fertilizers combined with application of long-term fertilization has a significant impact on greenhouse gas emissions and carbon fixation effects. Compared with single fertilizer, the application combined with organic manure fertilizer can increase CO2, CH4and N2O emissions, which increased42.9%,59.1%and14.9%respectively. At the same time, the results show organic carbon density of the surface soil can significantly increase by15.4%. Long-term application of NP and NPK may improve CO2emissions; while the combined application of N, P and K has no effect on CH4emissions, the combined application of manure and N, NP can obviously increase N2O emissions. Organic manure fertilizer will increase organic carbon density on the surface soil and solid carbon fixation, but it has nothing to do with the combined application of N, P and K. And its GWP is obviously higher than single fertilizer’s. Considered from the greenhouse gas emissions reduction and carbon sinks improvent, not organic fertilizer for farmland is the rational fertilization system of Taihu Lake region.2. Different tillage depths can also affect greenhouse gas emissions and carbon fixation effects. Deep tillage in wheat season will lead to the highest CO2emissions and reduce CH4emissions of the next paddy field; and9cm tillage depth of wheat season may improve N2O annual emissions. Appropriate deep tillage in wheat season is good for the effects of carbon fixation in middle and upper soil layer. And different tillage depths in rice season have different influences to greenhouse gas emissions and carbon fixation effects. During the whole rotation cycle, different tillage depths of rice and wheat seasons have different CO2, CH4and N2O emissions.4cm tillage depth of wheat season and17-18cm tillage depth of rice season have the highest carbon fixation in arable soil layers, which reaches13182g.9cm tillage depth in both rice and wheat season is not good for the effects of carbon fixation. Overall, in the short or long time scale,17-18cm tillage depth of rice and wheat seasons has the highest GWP. Shallow tillage in the whole rotation cycle, especially in the rice season, has good influences on greenhouse gas emissions reduction and greenhouse effect mitigation. Considered from the greenhouse gas emissions reduction and carbon sinks improvent,4cm tillage depth of wheat season and17-18cm tillage depth of rice season is the rational tillage system of Taihu Lake region.3. DNDC model can be applied to the research of CO2, CH4and N2O emitted from rice field in Tai Lake region, but it is need to strengthen and improve the simulation of CH4and N2O emitted from wheat field.