Study On Conservation Tillage Of Rape Following Rice

The experiments about straw mulching with different tillages, nitrogen managements, were carried out on rape following rice on the experimental farm of the university of Yangzhou, along Yangtse River, and ecological garden of Heheng of Jiangyan, Lixiahe areas province. The main results showed as follows:1.The rape yield of rotary tillage was obviously superior to the non-tillage in the clay soil. there was no difference in yield between two tillage methods in sandy soil. Under two tillage methods the straw mulching can improve potential yield in the both clay and sandy soil, among them, non-tillage combine with straw mulching in the sandy soil can largely increase yield.With straw mulching, the available N in the top layer of soil was reduced in earlier stage, and increased in later stage. The available K was increased obviously in the top layer of soil, and the available P was not changed obviously. The content of organic matter was increased obviously. As compared to ck, the organic matter in the layer of soil 0-10cm increased by 0.52g/kg and 0.73g/kg individually, As compared to the the initial stage, the organic matter of the layer 0-10cm increased by 0.16g/kg and 0.26g/kg.2. The effect on rape under the different nitrogen management with straw mulching shows that, as a result of negative effects of"capturing for the nitrogen"in earlier stage, the nitrogen regime, base:seedling:elongation=5:2:3, was adopted in order to ensure enough nitrogen in earlier stage, and postpone the nitrogen fertilize in elongation stage can reduce many ineffective branch and increase the proportion of highly efficient branch and the nitrogen use efficiency. 3. The straw mulching has obvious regulating the temperature of the 0-5cm soil layer in winter, and the influence under the 10cm soil layer is very small. In the low-temperature period of winter, straw mulching can increase 2.3～2.5℃of the surface temperature, increase 1.4～1.5℃of the 5cm soil layer. This kind of effect of keeping warm by straw mulching is mainly a kind of buffer function. The power of its effect largely depends on the variation of temperature, and has little to do with the level of absolute temperature. With the continuation of the low temperature, the power of keeping warm is dropping down. The straw mulching may decrease the soil temperature in the rise stage of temperature.4. The straw decomposition process can be divided into three stages during 7 months of rape growth. The first is faster decomposition stage, which is affected mainly by condition of the moisture, and about 30% of straw is dissolved. The second is stagnant stage, which is affected mainly by temperature condition, and about 10% of straw is dissolved. The last is steady stage, which is affected mainly by the indissoluble proportion of the straw, and about 30% of straw is dissolved. Though the difference exists at the speed of resolving of the different levels in different periods, but the final resolving amount is very close,70%. The remaining straw,30%, is the part most difficult to dissolve,but it's impact on following crop is very limited.