Effect of deep-plow and mulching during fallow period on soil water and wheat water use efficiency in dryland

Dryland wheat is very critical in China's wheat production. But as water is a major limiting factor of dryland wheat production, high water use efficiency is an important issue in dryland wheat production. Currently, a significant progress has been made in rainwater harvesting and soil water retention in dryland wheat fields. The deep-plow, sub-soiling and mulching cultivation techniques have been vital water retention practices for increased dryland wheat production. However, precipitation during fallow season, which accounts for about 60% of the annual precipitation, has been largely ignored. Thus this study combined mulching and water retention cultivation technique to use fallow period rainfall, improve soil water retention capacity and ensure adequate soil water for spring wheat cultivation. A field experiment was carried out to study the effects of deep-plow at 15 d (15 DAH) or 45 d (45 DAH) after harvest and the applications of WPM (water permeability plastic film mulching) and LFM (liquid film mulching) immediately after deep-plow on soil water and wheat water use efficiency. The results showed that compared with 15 DAH, deep-plow at 45 DAH significantly improved soil water storage capacity during the 65 d (fallow period) and 316 d (booting stage of next crop of wheat) after harvest, 120 300 cm soil water storage before wheat sowing and also wheat water use efficiency. Deep-plow and mulching during fallow period also significantly improved soil water storage capacity at 65 d and 316 d after harvest, 0 300 cm soil storage capacity before sowing and wheat water use efficiency. Soil moisture condition was best under deep-plow with WPM. Also compared with 15 DAH, deep-plow at 45 DAH significantly reduced soil dry-up rate of 60 300 cm layer during sowing to jointing stage, 0 60 cm and 120 240 cm layer during jointing to anthesis stage, and 180 300 cm layer during anthesis to maturity stage. Soil moisture regulation effect of WPM after deep-plow was best during jointing to anthesis stage. Thus deep-plow after rain in fallow period improved soil water storage and wheat water use efficiency. Soil moisture regulation effect was best under WPM after deep-plow. The study therefore recommended deep-plow and WPM after rainfall during fallow period (about late July to early August), to ensure soil water conservation in dryland wheat fields and to preserve high, stable yields and water use efficiency of dryland wheat.