Decomposition Characteristics Of Returned Crop Straw In Soil And Its Effect On Soil Fertility And Crop Yield

Excess of crop straw and its burning phenomenon is increasingly serious at present, so research of straw resource utilization is concerned. Although there are many ways of straw resource utilization, but straw returning is the most straight and effective path of utilization straw resource. The decomposition characteristics of returned straw and its effect were conducted on soil physical and chemical properties, crop yield and benefit based on field experiment and pot experiment. The results showed that:1、The decomposition ratio of rapeseed straw and rice straw increased fast in the early stage, and then increased slow, while the decomposition rate decreased gradually. The straw decomposition ratio was about50%at90d after straw-returning, and the straw decomposition rate of0-15d was3-5times of decomposition rate of90-120d.2、In the mode of rice cultivation, the rapeseed straw decomposition rate was shown as:The rate of0cm deep returned> the rate of20cm deep returned> the rate of10cm deep returned, the rate of with decomposing bacteria> the rate of without decomposing bacteria. In the mode of rapeseed planting, the rice straw decomposition rate was shown as:The rate of5cm deep returned> the rate of10cm deep returned> the rate of0cm deep returned, the straw decomposition rate of farming conditions> the straw decomposition rate of no-tillage conditions.3、In the mode of rice cultivation, the release quantity of carbon and nitrogen from rapeseed straw in the early stage was more than that in the late stage. The ratio of carbon and nitrogen changed little with time and had the downward trend in volatility.4、The returned straw changed several soil basic properties. At120d after straw-returning, not only soil bulk density decreased, but also the content of soil organic matter, nitrogen, phosphorus and potassium all increased. When rapeseed harvest, the soil bulk density of the whole amount and1/2whole amount of rice straw returned10cm depths was respectively1.37g/cm3and1.39g/cm3, which was reduced by0.05g/cm3and 0.03g/cm3than that of the control treatment (1.42g/cm3), While the content of soil organic matter was respectively20.13g/kg and18.38g/kg, which was increased by2.82g/kg and1.07g/kg than that of the control treatment (17.31g/kg). When rice harvest, the soil bulk density of rapeseed straw returned0cm depths and10cm depths of farming conditions was respectively1.25g/cm3and1.28g/cm3, which was reduced by0.07g/cm3and0.04g/cm3than that of the control treatment (1.32g/cm3), While the content of soil organic matter was respectively18.14g/kg and19.21g/kg, which was increased by1.86g/kg and2.93g/kg than that of the control treatment (16.28g/kg). The content of soil nitrogen, phosphorus, potassium all increased in a certain extent, but the regularity of improving was not obvious.5、Straw returning not only improved crop yields but also increased the economic benefit of crop planting. In the mode of rice cultivation, through rapeseed straw returning the rice average yield was8812.5kg/hm2, which was improved by1087.5kg/hm2than that of the control treatment (7725kg/hm2), so that the economic benefit was increased2718.75yuan/hm2and the increasing range was14.08%. In the mode of rapeseed cultivation, through rice straw returning the rapeseed average yield was2702.18kg/hm2, which was improved by334.73kg/hm2than that of the control treatment (2367.45kg/hm2), so that the economic benefit was increased1673.63yuan/hm2and the increasing range was14.14%. In the no-tillage conditions of rice straw returning, the rapeseed average yield was2581.35kg/hm2, which was improved by440.4kg/hm2than that of the control treatment (2140.95kg/hm2), so that the economic benefit was increased2202yuan/hm2and the increasing range was20.57%.