| As an important byproduct of agricultural production, crop straw is not only the important resources in agriculture and downstream industry, but also one of the important organic fertilizer source, However, it is also likely to be the pollution sources of rural ecological environment. Straw returning as an effective and direct way of using straw, on the one hand, can solve the pollution problem, on the other hand, it can promote rural nutrient resources recycling and sustainable development of agriculture. The study was selected at rice-wheat rotation system in the lower reaches of Yangtze River. By field plot test, we studied the effect of different amounts of straw returning on yield of rice and wheat, soil microbial properties and soil carbon pool in rice-wheat rotation cropland. The aim of our study was exploring suitable quantity returned straw for local production and ecological conditions. Further straw returning could perfect the local technology, improving soil productivity and protecting the ecological environment. Main conclusion in our study as follows,1. Appropriate amount of straw had obvious effect on crop growth and yiledIn the early growth stage of rice, straw returning had no obvious influence on the number of tillers, plant height and the relative content of chlorophyll. Compared to the control,1500-3000kg·hm-2straw returning treatment significantly increased the number of tillers and keep some more effective tillers.1500-3000kg·hm-2straw returning treatment also significantly increased plant height and the relative content of chlorophyll. After one season wheat straw returning, every straw returning treatment increased the yield of rice.1500kg·hm-2and3000kg·hm-2straw returning treatment significantly increased the actual yield of rice with the increase of8.60%and9.04%, respectively. Straw returning after two seasons of one year, every straw returning treatment increased the yield of wheat. Continuous1500kg·hm-2wheat straw and2250kg·hm-2rice straw to field significantly increased the actual yield of wheat. Continuous3000kg·hm-2wheat straw and4500kg·hm-2rice straw to field had the same effect. This shows that an appropriate amount of straw could effectively the growth of crop and significantly increased crop yields.2. Appropriate amount of straw could improve soil environment and had obvious effect on improving soil fertilityAfter one season wheat straw returning,3000kg·hm-2wheat straw returning significantly enhanced soil microbial biomass-C, N. Compare to the control,3000kg·hm-2wheat straw returning also significantly improved soil Urease, Catalase and Invertase of paddy. Different amount of straw returning all increased the soil nutient in different degrees of paddy.1500-4500kg·hm-2wheat straw returning significantly improved soil total nitrogen and available nitrogen in comparison to the control. Straw returning after two seasons of one year, continuous1500kg·hm-2wheat straw and2250kg·hm-2rice straw to field significantly increased soil microbial biomass-C, N and also significantly improved soil Urease, Catalase and Invertase of catcher. Different amount of straw returning all increased the soil nutient in different degrees of catcher. Continuous3000kg·hm-2wheat straw and4500kg·hm-2rice straw to field significantly increased soil total nitrogen and available nitrogen and effective phosphorus in comparison to the control. This shows that an appropriate amount of straw could significantly increase soil microbes and microbial activity, effectively improve the soil environment, promote straw decomposition release nutrient into the soil and improve soil fertility.3. Appropriate amount of straw could significantly increase the effect of soil carbon sinkContinuous1500kg·hm-2wheat straw and2250kg·hm-2rice straw to field treatment significantly promoted the yield of yearly grain with the increase of9.61%and9.88%.So as the continuous3000kg·hm-2wheat straw and4500kg·hm-2rice straw to field treatment. Straw returning after two seasons of one year could affect the vertical distribution of soil total organic carbon and water soluble organic carbon, all showed by0-7cm>7-14cm>14-20cm. The effect of straw returning treatments on soil total organic carbon at each soil layer is not the same. At0-7cm soil layer and7-14cm soil layer, there were no significant differences between the straw returning treatments and the control on the soil total organic carbon; At7-14cm soil layer and0-20cm soil layer, continuous3000kg·hm-2wheat straw and4500kg·hm-2rice straw to field treatment significantly increased soil total organic carbon in comparison to the control. At every soil layer, different straw returning treatments show the same regulation on active organic carbon:Continuous1500kg·hm-2wheat straw and2250kg·hm-2rice straw to field and continuous3000kg·hm-2wheat straw and4500kg·hm-2rice straw to field treatments significantly increased soil water soluble organic carbon and easily oxide organic carbon compared to the control. Low and medium amounts of straw returning showed obvious advantages to soil labile organic carbon fractions efficiently for different soil layer and carbon management index. This shows that an appropriate amount of straw could significantly increase the effect of soil carbon sink... |
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