The Effects Of No Tillage And Straw Returning Continuously On Soil Nutrient Content And Rice Yield

No-tillage and straw returning is a new type of cultivation pattern, it changes the agricultural soil environment, affecting the growth and development of rice. This study based on the experimental location platform of protective tillage of wheat/rice cropping system for 13 years, during the one rice growing season of 2013 and 2014.Nanjing 9108 was the rice variety used in this study. The study was arranged in a randomized block design with eight treatments with three replicates. The eight treatments included no-tillage and straw returning (NTS), no-tillage and high stubble returning (NTH), no-tillage in wheat and convention tillage in rice (RNT), convention tillage in wheat and no-tillage in rice (RCT), convention tillage and full straw returning (CTS1), convention tillage and half-amount straw returning (CTS2), convention tillage and straw burning (CTB), and convention tillage (CT). The effects of these eight treatments on soil fertility, nutrition absorption and growth of rice plants were studied. The main results were as follows.1 Straw returning, this increased the content of organic matter in soil cultivation layer. Especially CTS1 and CTS2, the content of soil organic matter was maintained at a high level both before rice sowing and after rice harvest. The dynamic trend of total nitrogen content was similar to that of organic matter. Although the treatments of CTS1 and CTS2 increased the content of total nitrogen so that the amount of applied fertilizer may be appropriate to be reduced. No-tillage and straw returning didn’t produce significant effects on the content of available phosphorus NTS and NTH enriched the content of available potassium in soil surface area. The treatments of CST1 and CST2 increased the content of available potassium in all the soil layers.2 The height of rice was lower and dry matter accumulation was decreased, because of no seedling and the interference of wheat stubble in NTS. Rice grew rapidly in the later stages in treatments with straw returning, which increased the danger of rice lodging, and influenced the accumulation of dry matter. The rice plants in NTS, RNT, CTS1, and CTS2 treatments were inhibitions in early growth stages because they penetrated the cover of straw.CTSl and CTS2 delaying leaves senescence, so that photosynthetic rate increased and the high yield of rice could also be realized. With the advance of the growth period, content of plant nitrogen except that the plant potassium content increased in tillering stage. Continuous no-tillage significantly decreased the absorption amount of nitrogen and phosphorus in rice plants and slightly decreased the absorption of potassium. Rice yield is lower in CTB than that in CTS1 and CTS2.3 Rice yield was higher in treatments with straw returning, but was lower in continuous no-tillage treatments so convention tillage or rotation tillage should be taken after a long period of no-tillage. Rice yield was lower in no-tillage treatments than that in tillage treatments, as the same straw mulching was taken. CTB wasn’t significant increase in rice production...