Effects Of Conservation Tillage On The Emissions Of Greenhouse Gases At Dry Farmland During Fallow Period

The emissions of greenhouse gases from agricultural soil has become a hot research field for many experts. The study of the emissions of greenhouse gases in dry farmland during plant growth period is more than that during fallow period at home and abroad , and the study about reduction of the emissions of greenhouse gases is focus on how to ameliorate agricultural management, but been paid less attention to comparative study on different conservation tillage measures. By taking the dryland in two phases rotation system with Spring Wheat and Field Pea under different conservation tillage measures as the research object, the dynamics of CO₂ and N₂O fluxes during fallow period were measured by static chamber-gas chromatographic techniques. The main results showed as follows:1. The farmlands of two phases rotation system with Spring Wheat and Field Pea under different conservation tillage measures during fallow period are the "source" of CO₂ emissions. There is a dramatic decrease of CO₂ emissions into fallow period and decreased slowly afterwards .CO₂ average emissions and total emissions of the farmlands in two phases rotation system under different conservation tillage measures were shown as: no-tillage with no straw mulch (NT) 2 average emissions between under NTS and TS in two phases rotation system during fallow period. It can be reduced the emissions of CO₂ under NT comparative to other three treatments,and increased the emissions of CO₂ under TS comparative to other three treatments.The farmlands of two phases rotation system under different conservation tillagemeasures during fallow period are the weak "source" of N₂O emissions. N₂O averageemissions and total emissions of the farmlands of two phases rotation system underdifferent conservation tillage measures were shown as: no-tillage with no straw mulch(NT) 2O under different tillage measures is consistent with each other, all of them increased a little then decreased slowly. Straw returning could increase the emission of N₂O, the emission of N₂O from Field Pea farmlands is higher than that from Spring Wheat farmlands.2. In the rotation sequence of P→W,the order of soil organic carbon content at the soil layer of 0～30cm is NT2 and N₂O emission. The fluxes of CO₂ and N₂O were significant related to soil temperature at different depths in two phases rotation system under different tillage measures during fallow period. The fluxes of CO₂ and N₂O were extremely significant related to topsoil temperature, soil temperature at the depth of 5cm. The fluxes of the two kinds of Greenhouse gases showed negative correlations with soil water content at different soil layers.4. The fluxes of CO₂ in two phases rotation system under different tillage measures showed extremely positive correlations with organic carbon content and ratio of carbon to nitrogen, also showed significant positive correlations with soil total nitrogen contents, but there were significant correlation with soil bulk density; The fluxes of N₂O in two phases rotation system under different tillage measures showed extremely positive correlations with soil organic carbon content, soil total nitrogen contents and ratio of carbon to nitrogen, showed negative .correlations with ammonium nitrogen contents and soil bulk density.5. Total Greenhouse Effect in two phases rotation system with Spring Wheat and Field Pea under different tillage measures both showed:TS> T>NTS>NT. The Greenhouse Effect at farmland of Spring Wheat under different tillage measures higher than that of Field Pea under different tillage measures. The relative effect between N₂O and CO₂ showed positive effect, which increased the Greenhouse Effect. The Greenhouse Effect of farmland under different tillage measures appears as the effect of CO₂.6. The Greenhouse Effect under NT lower than other three tillage measures during fallow period, but there was not significant difference about the Greenhouse Effect between NT and NTS. No-tillage is good for reducing the emissions of CO₂ and N₂O, and it can bring better environmental benefit. The total Greenhouse Effect of unit yield under NTS lower than other tillage measures, there was significant difference about the total Greenhouse Effect of unit yield under different tillage measures. Agriculture study should focus on achieving Win-Win Relationships between production benefit and environmental benefit in the future. The Implementation of No-tillage with straw covered is good for reducing the emissions of greenhouse gases in arid planting area in western Loess plateau, and also can promote the virtuous circle of farmland ecosystem.