Effects of tillage practices on grain yield formation of wheat and the physiological mechanism in rainfed areas

Although the effect of tillage practices on crops has been well studied, the systematic effect of these practices on the yield formation process of wheat in rainfed regions is often poorly reported. Here, four tillage practices, namely, strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage (R) and rotary tillage after subsoiling (RS), were performed during 3 wheat–growing seasons to study the effect of tillage practices on the yield formation process and the physiological mechanism in rainfed wheat. SRS and SR reduced the tiller numbers but increased the percentage of earring tillers. SRS and SR produced the spike numbers similar to those produced by RS and R but increased the grain numbers per spike by increasing the number of grains per spikelet. SRS reduced the evapotranspiration (ET) during the early–filling stage and increased the ET and water consumption ratio during the mid– and late–filling stages. Because of increased water consumption, the flag leaf water potential by SRS was improved during the late–filling stage; photosynthetic rate and superoxide dismutase activity also improved. Accompanied by the improvement in physiological characteristics, the post–anthesis dry matter accumulation by SRS increased significantly. The average grain yield by SRS in the three growing seasons was 6.0 %, 13.4 % and 7.0 % higher than those by SR, R and RS, respectively. The yield–increasing effect of subsoiling once could last for 3 years but the growth rate on the third year decreased from 8.6 % to 3.2 % in SRS, and decreased from 6.0 %–4.2 % in RS.