Study on yield and quality of double cropping rice in different straw return approaches

The localization field experiments were conducted to study on yields and quality characteristics of rice in different straw incorporation ways at double cropping rice seasons of 2010-2011. There were six treatments, total rice straw incorporation and chemical fertilizers(NPK+S), rice straw incineration and chemical fertilizers (NPK+SI), rice straw noincorporation with only chemical fertilizers (NPK) and the others three compared treatments with no chemical fertilizers. The results show that NPK+S could increase the number of early rices tillers, the form rate of tillers, leaf area index at the middle and late growing seasons and aboveground dry matter, promote chlorophyll content (SPAD value) and the number of effective panicles in unit area, and delay the senescence trend under the conditions of equal nitrogen, phosphorus and potassium nutrient. However the effects are not obvious for late rice. Compared with the NPK and NPK+SI treatments, NPK+S could enhance significantly the grain yield of early rice, and the average yield of the two years are increased by 3.78%-8.77%. As the time of rice straw incorporation prolonged, late rice yields under the NPK+S and NPK+SI treatments are not significantly different, and the yield are increased significantly by 5.66%-7.32% compared with the NPK treatment. However, the effects of CK+S on early and late rices growth and yields are obviously greater than those of CK+SI and CK in the plots of no chemical fertilizers. Moreover, NPK+S could improve flavor quality of early and late rice, but lower the external and nutrition quality, which are not benefited for improving the processed quality of late rice. Ultimately, it suggests that there is significance for promoting rice yields in the double cropping rice.