Effects Of Conservation Tillage On Crop Growth, Soil Physical And Chemical Properties For Summer Sowing Soybean In Loess Plateau

The effects of different tillage practice on system of summer sowing soybean (Glucine max CYFeng Shoul2) including soil temperature, soil water and nutrients as well as biomass dynamic with different phonological stage were examined at Xifeng loess plateau, Gansu province. The main results were summarized as follows:1. Straw mulching reduced fluctuation of soil temperature, especially on the top soil. The soil temperature fluctuation under no-tillage + straw mulching was l.64癈, 1.99癈 respectively lower than without straw mulching, that under conventional tillage +straw mulching was 1.00癈, 1.33癈 respectively less than conventional tillage and no-tillage practice.2. The practice of no-tillage and straw mulching not only reduced efficiently evaporation of surface water but also enhanced the earth moisture. All of no-tillage -i-straw mulching, conventional tillage +straw mulching and no-tillage had ability to keep soil water content The effect of no-tillage + straw mulching was very well, and was 17.8% higher than that of conventional tillage.3. No-tillage could improve the fertility of soil. Total N and organic matter ofno-tillage were 5.6% and 2.3% respectively more than that of conservation tillage in 0-1 Ocm soil layer. Total N, organic matter and total P of no-tillage were 10.9%, 16% and 3.8% respectively more than that of conservation tillage in 10-3 Ocm soil layer. The result is consistent with usual effects of no-tillage.4. Straw mulching could provide favorable condition of water and fertility for soybean, and promote soybean early growing. Above-ground biomass of straw mulching was higher than that of no-tillage and conservation tillage at different stage. Seed yield of summer sowing soybean from no-tillage was remarkably higher than that of conservation tillage. Straw mulching significantly increased the thousand grain weight (P<0.05).5. The photosynthesis of summer sowing soybean appeared a descending tendency within the season. The peak value came in early stage. This physiological and ecological character of summer soybean was related to sun-shine hour and PAR (photosynthesis available radiation)condition locally. Straw mulching enhanced the Pn of summer sowing soybean that was highly correlated to soil water content. The practice of conservation tillage also improved the WUE (water use efficiency) of summer sowing soybean.