Yield Increasing Mechanism Of Conservation Tillage Practices In Rainfed Wheat Production Of Middle Shandong Province

Field experiments were conducted in Xuhe village, Zhangqiu county, Shandong Province in2009-2010and2010-2011wheat growing seasons to determine the effects of rainfed conservation tillage practices on soil properties and wheat characteristics, and to study the mechanisms of grain yield increasing. During the2growing seasons, Yannong19were used as experimental material. Four soil tillage treatments were set in the experiment:Plough tillage with straw removing (T1, CK), Plough tillage with straw returning (T2), Rotary tillage with straw returning (T3) and Seedbed strip tillage with straw mulching (T4), respectively. The results are as follows:1. Effects of rainfed conversation tillage on soil propertiesShort-term tillage treatments have little effects on soil bulk density and soil porosity. The rank of soil bulk density were T4>T1>T2>T3at sowing period, while the bulk densities of T1, T2and T3became higher than sowing period, but T4get lower slightly, but T4still has the highest value than the other treatments.Conservation tillage can obviously improve soil organic matter content and available potassium content in0-20cm soil profile, but available phosphorus and available nitrogen content have no apparent changes.The main characteristic of tillage effects on soil temperature is that conservation tillage has a significant’decrease temperature effect’ in high temperature and’less increase temperature effect’ in low temperature condition. By which, the soil temperature fluctuation range lower than that of conventional tillage.Among the4tillage treatments, T4had the highest water contents in the0-100cm soil profile through the whole growing season, while T1has the lowest water content along the growing season.2. Effects of rainfed conversation tillage on photosynthetic abilitiesDuring jointing period, the LAI between different treatments has no significant differences, but T4with the lowest. Since then, the LAI was increasing dramatically, and all of the treatments got to their highest LAI value at anthesis stage, in which, T4has the highest LAI. After anthesis, the LAI begin decline, T4has the lowest rate in the procedure. Since anthesis, T4has the highest LAI. The LAI of T4was12.44%higher than that of T1at anthesis in2010-2011wheat growing season.Compared with the3other treatments, T4has the highest photosynthesis rate (Pn) since booting stage, and keeping this sustained trend to mature stage. The photosynthesis rates of T4were10.03μmol m-2s-1and9.20μmol m-2s-1at20d after anthesis in2009-2010and2010-2011growing seasons, respectively, and were38.7%and24.89%higher than that of T1. The change of SPAD and Tr have the same trend like Pn among the treatments. The dry matter amount of T4was lower before jointing stage and was the highest at mature stage. The dry matter amount of T4was10333.3kg hm-2and9045.0kg hm-2, and was8.75%and16.66%higher over T1.Rainfed conversation tillage could increase grain yield. The grain yields of T1were only4202.3kg hm-2and3358.8kg hm-2, respectively, in2009-2010and2010-2011wheat growing seasons. While T4were4794.7kg hm-2and3988.1kg hm-2, respectively, at the same time. Compared with T1, T4were14.10%and18.74%higher than Tlin the2seasons, respectively.The increasing yields of T4were attributed to the increasing of spike No. per unit area, grain No. per spike and1000-grain weight, in which, spike No. and1000-grain weight are the main facts for the increasing yield. There are significant differences between T4and T1. And the HI of T4is also higher than T1in2009-2010and2010-2011wheat growing seasons.3. Effects of rainfed conversation tillage on water use efficiency (WUE)Compared with the3other treatments, T4had the highest total water consumption amount, but lowest soil water consumption amount before jointing stage. Compared with T4, T1consumed almost the same amount of T4, but soil water consumption amount was higher than T4before jointing stage. From jointing stage to mature, T4consumed the highest soil water among the4tillage treatments, but got the highest grain yield, makes the T4have the highest WUE among the4treatments. The WUE of T4was16.25kg mm-1hm-2and17.90kg mm-1hm-2in2009-2010and2010-2011growing seasons, respectively. That is13.46%and24.93%higher than that of T1, respectively.The yield increasing effect of conservation tillage was due to the improvement of soil properties, such as soil structure, soil water, soil nutrient, soil temperature.