Greenhouse Gases Emission Of Farm Soil In Eastern Gansu Loess Plateau

Aagricultural activities is the important source of greenhouse gas emission in China, CH4, CO2 and N2O account for 25%,23% and 52% of the total emissions respectively, and the loess plateau is China’s traditional agricultural areas with a long history. The study was carried out in LongDong loess farming system under rain-fed, we analyzed diurnal/seasonal variations of soil greenhouse gases about the main crops of corn, wheat and alfalfa, as well as environmental factors such as soil moisture, soil temperature, soil nutrient and so on. The research obtained the following results:1. The dry greenhouse gas in agro-ecosystem soil manifest:soil absorbed CH4 and N2O, emitted and absorbed CO2;2. The diurnal variation of mainly farmland soil greenhouse gases CH4, CO2, N2O was singlet curve on overall trends:the maximum appear in 14:00, and occasionally climax at 10:00 am occasionally;3. The seasonal variation of soil greenhouse gas fluxes in dry land was:cornfields CH4 absorption showed a gradually increased trend, the maximum flux in July and September. Wheat land, alfalfa land and grassland all presented increase at first and then decrease, the maximum is in May. Soil CO2 emissions of four treatments also showed the trend of increase at first and then decrease, the maximum appears in the May and June; soil N2O flux was more complex, cornfields obviously emitted N2O.4. The soil surface temperature had a significant influence on diumal variation of soil CH4, N2O absorption, emission of grassland, and soil CO2 emissions of cornfields. It also had a significant influence on seasonal variation of soil CH4 absorption, CO2 emissions, N2O absorption and emission in comfields, and soil N2O absorption and emission in alfalfa fields;5. Soil organic carbon and soil total nitrogen showed positive correlated with the absorb of soil CH4, but negative correlated with the emission of soil CO2;6. Soil available nitrogen and soil available showed phospborus negative correlated with above plant biomass; Plant biomass on the ground showed positive correlated with the absorb of soil CH4 and the emission of soil CO2;7. The grassland site is conductive to slow down the greenhouse gas emission, soil in cornfield and wheat field has a stronger ability of carbon storage.Based on these results, considering the agro-ecosystem greenhouse gas emissions and global warming, on the problem of reasonable utilization of land on LongDong loess plateau, we suggest returning farmland to grassland to the mountain and slope area, planting grass and alfalfa to develop animal husbandry industry, finally to reduce soil CO2 emissions and enhance soil CH4 absorption to slow down the global warming caused by soil greenhouse gas emission on agro-ecosystem.