The Effects Of No Tillage And Straw Returning Continuously On Soil Fertility And Wheat Yield

To investigate the effects of continuous no-tillage and straw returning on soil fertility and wheat grain yield, a field study was conducted on the experimental location platform of protective tillage of wheat/rice cropping system during the two wheat growing seasons of 2012-2013 and 2013-2014. Yangmai 13 was the wheat 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 wheat plants were studied. The main results were as follows.1.Straw returning, especially CTS1 and CTS2, increased the content of organic matter in soil cultivation layer. The content of soil organic matter was maintained at a high level both before wheat sowing and after wheat harvest. The effects on the content of organic matter were mainly decided by many factors, such as the original content of organic matter, the amount of straw returning, and tillage methods. 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, there was no significant relationship between the amount of straw returning and the content of total nitrogen when the amount of straw returning ranged from 3000 to 4500 kg/hm2. NTS and NTH increased the content of alkali-hydrolysable nitrogen in soil surface area. Straw returning increased the content of alkali-hydrolysable nitrogen in all the soil layers (0-21 cm). No-tillage and straw returning didn’t produce significant effects on the content of available phosphorus, but significantly increased the content of available potassium. NTS and NTH enriched the content of available potassium in soil surface area (0-7 cm). The treatments of CST1 and CST2 increased the content of available potassium in all the soil layers.2.The wheat plants in the NTS, RNT, CTS1, and CTS2 treatments were long and slim at the early growth stages because they penetrated the cover of straw. At the late growth stages, wheat plants were high, which increased the risk of lodging. The height of wheat plant in the treatments of no-tillage (NTS, NTH, and RNT) was small, which was beneficial to improving the lodging resistance of wheat plants. The treatments of no-tillage and straw returning increased the area of the three leaves on the upper part of wheat plant, which created favorable conditions for increasing grain yield. Straw returning also promoted the translocation of nitrogen in leaves at the late growth stages and thus the photosynthesis of the three leaves on the upper part of wheat plant. CST1 increased the photosynthesis of flag leaf. At the early growth stages, the content of nitrogen and phosphorus was low in the plants of the treatments of no-tillage and straw returning. The nitrogen content in the wheat plants of the treatments of no-tillage and straw returning was increased at the late growth stages. CST2 increased the amount of nitrogen and phosphorus absorption. Continuous no-tillage significantly decreased the absorption amount of nitrogen and phosphorus in wheat plants and slightly decreased the absorption of potassium.3.No-tillage and straw returning increased the number of spike per hectare and the number of grain per spike. The 1000-grain-weight varied differently in the no-tillage treatments in the two growing seasons. There was a decreasing trend in the 1000-grain-weight in the straw returning treatments. The grain yield was higher in the treatments of no-tillage and straw returning as compared CT. The grain yield was higher in RNT than in continuous no-tillage treatments. The grain yield was higher in CTS2 than in CTS1. During the consecutive 10 years, the highest and the lowest grain yield were recorded in the treatments of RNT and CT, with an increase ranging from 0.45-5.37%. Compared with CT, RNT, RCT, CTS1 and CTS2 increased grain yield. RNT and CTS2 produced a stable increase in grain yield as compared with RCT and CTS1.