Researches On Greenhouse Gases Emission Under Different Tillage From Dryland Farming

Based on different tillage experiment was implemented in Lijiabu town of Dingxi from Gansu province, an experiment was conducted to study the soil respiration rate , CH₄ and N₂O flux emission rules and influence factors under different tillage measures with rotation in 2010, and attempt to provided a scientific basis to reduce greenhouse gas on dryland farming. The examined tillage treatments were T (Conventional tillage with no straw) , NT(No-till with no straw cover),NTS(No-till with straw cover),TS(Conventional tillage with straw incorpo), and the rotation sequence was spring wheat (w) followed by field pea(p).The main results showed as follows:1. Growth period variation of soil respiration in dryland farmingThe soil respiration for spring wheat under conventional tillage with no straw(T) and the soil respiration rate for field pea under no-till with straw cover(NTS) were lower than others, which could significantly decrease the soil respiration. The mean values of soil respiration were NTS>TS>NT>T under different tillage in spring wheat, the highest was NTS, the value was 0.2418μmol·m^-2·s^-1,the lowest was T, the value was 0.2036μmol·m^-2·s^-1.In field pea, the mean values of soil respiration were NTS<TS<NT<T, the highest was T, the value was 0.2736μmol·m^-2·s^-1,the lowest was NTS, the value was 0.2181μmol·m^-2·s^-1.2. Growth period variation of CH₄ flux in dryland farmingSpring wheat and field pea were overall atmospheric CH₄ sink under different tillage's during the growth period, No-till with no straw cover(NT) and No-till with straw cover(NTS) were beneficial for the absorption of CH₄, especially in spring wheat. CH₄ flux under different tillage were NTS>NT>TS>T in spring wheat, the highest was NTS, the value was 0.0818 mg.m^-2.h^-1,the lowest was T, the value was 0.0416 mg.m^-2.h^-1.In field pea, CH₄ flux under different tillage were NT>NTS>T>TS, the highest was NT, the value was 0.0737 mg.m^-2.h^-1,the lowest was TS, the value was 0.0416 mg.m^-2.h^-1.3. Growth period variation of N₂O flux in dryland farmingSpring wheat and field pea were overall atmospheric N₂O source under different tillage's during the growth period , No-till with no straw cove(NT), No-till with straw cover(NTS) and Conventional tillage with straw incorpo(TS) could significantly reduce N₂O emissions. In spring wheat, N₂O efflux under different tillage were T>NT>TS>NTS under different tillage, the highest is T, the value was 0.0891 mg.m^-2.h^-1,the lowest was NTS, the value was 0.0461 mg.m^-2.h^-1.In field pea, N₂O efflux were T>NT>NTS>TS under different tillage, the highest was T, the value was 0.1234 mg.m^-2.h^-1,the lowest was TS, the value was 0.0350 mg.m^-2.h^-1.4. Influences factors of greenhouse gas emissions in dryland farmingIn spring wheat, with the increased of the means of soil moisture content and temperature, the soil respiration rate and CH₄ fluxes enlarged, and soil respiration rate were very significantly positive correlation with Soil moisture content in filed pea. And the N₂O emission was positively correlated to soil temperature, especially in field pea.5. Greenhouse Effect on different tillage's during growth period in dryland farmingTotal Greenhouse Effect in spring wheat showed that: NTS>TS>NT>T,and field pea showed that: NTS<TS<NT<T. The relative effect between CO2 and N₂O showed positive effect, CH₄ showed a negative effect, and greenhouse effect mainly showed that CO2'greenhouse effect.