Roles of Soil, Climate and Management In Regulating Crop Water Use Efficiency: Observations and Modeling.

In semiarid environments, water is the most limiting factor to crop growth. Water use efficiency (WUE) of crops relies on several factors, including the amount and timing of available water (rainfall and irrigation), the ability of soil to capture and store water, the ability of crops to access soil water, to convert water into biomass and biomass to grain. This presentation focuses on the roles of soil, climate and management strategies in regulating crop water use efficiency, illustrated using soil-plant systems modelling. We will further present examples of how measurement and modelling are combined together to benchmark WUE and to explore management strategies for increasing WUE in dryland cropping systems in the Murray-Darling Basin (MDB) of Australia and in irrigated wheat-maize double cropping system in the North China Plain (NCP). Options in MDB include better managing previous crops and fallows and improving soil conditions to increase soil water storage, reducing evaporative losses from soil surface, synchronising crop growing season with rainfall pattern using optimal cultivar and sowing time, and maximizing crop water extraction from soil. Examples in NCP include changing partition of irrigation water into wheat and maize seasons, optimising irrigation amount and timing, reduced irrigation and intercropping.