Research on Emissions of Greenhouse Gases from Different Soils beneath Fluctuated Kinds of Moisture Systems, China

Greenhouse gases emissions have increased during the last century due to human activities such as agricultural practices, fossil fuel burning and industrial practices. The formation of greenhouse gases, in particular N2O or CO2 is strongly controlled by both soil temperature and soil humidity. Laboratory experiment was conducted to assess the response of grassland and arable soils with regard to N2O and CO2 flows and mineral nitrogen concentration; soils were exposed to various drying rewetting cycles at different gravimetric water contents (?wt) under controlled conditions. In total, four treatmentswere conducted: soils under continuously moist control at 30% ?wt soils receiving short drying rewetting cycles (SDWC) between 30% to 21% (?wt), soils exposed tomedium drying rewetting cycles (MDWC) at 30-18% (?wt) and a treatment with long drying rewetting cycles (LDWC) 30-5% (?wt). The results indicated that both soils reduced N2O-N flow in the long dryingrewetting treatments. For the CO2-C flow, soils showed differing patterns, at which the shortly dried-rewetted cycle treatment of grass soils yielded highest (128 ?g/kg) cumulative flow that was 24% higher than LDWC. There was no effect of drying-rewetting cycles (DWC) on grass soils. The stressed treatments emitted only 18 % higher CO2-C flow than the control. The treatment with 4% ?wt successfully reduced N2O-N flow in grassland and arable soils. This study shows that the soil net nitrogen mineralization and nitrification rates of arable soil were significantly higher in arable soil compared to grass soil.