Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield

Straw mulching is widely used to conserve soil water and increase crop yields. The effects of wheat straw mulching rate and method on dryland soil water storage, winter wheat (Triticum aestivum L.) growth and yield, and water-use efficiency (WUE) were examined from 2008 to 2015 in the Loess Plateau of China. Treatments included wheat straw mulching at a high rate of 9000 kg ha(-1) (HSM) and low rate of 4500 kg ha(-1) (LSM) throughout the year, straw mulching at a rate of 9000 kg ha(-1) during summer fallow (FSM), and no mulching (CK). Soil water storage at wheat planting and precipitation-storage efficiency (PSE) were greater with straw mulching than without. Soil water storage at harvest was greater with HSM than CK and FSM. Wheat yield components such as number of wheat seedling, plant, tiller, and spike and thousand-grain weight varied with treatments and years, but wheat aboveground biomass and grain yields were usually greater with mulching than without during years with below-average precipitation. Harvest index and WUE were lower with ISM and HSM than other treatments in most years, but evapotranspiration did not vary with treatments. Overall, the increased PSE due to straw mulching did not increase yield and WUE, and straw mulching could sustain dryland wheat grain yield only in dry years.