Water use efficiency of dryland wheat in the Loess Plateau in response to soil and crop management

Improvement of wheat water use efficiency (WUE= grain yield per unit seasonal evapotranspiration) in the dryland area of Loess Plateau of China is an imperative imposed by the critical situation of water resources, as well as by the demographic pressure. The aims of this study were (i) assessing WUE of dryland wheat in the Loess Plateau, and (ii) identifying management practices returning higher efficiencies. We compiled a data base of 39 sets of experiments spanning 20 years, where conventional practice was compared with alternatives including NT, no tillage without straw mulching; RT, reduced tillage without straw mulching; NTS, no tillage with straw mulching; SS, subsoiling with straw mulching; CTS, conventional tillage with straw mulching; PM, plastic film mulching 100%; RM, ridge mulched with plastic film + bare furrow; RMS, ridge mulched with plastic film + furrow mulched with crop straw. Yield ranged from 818 to 7900 kg ha(-1) and WUE from 3.4 to 23.4 kg ha(-1) mm(-1); the maximum yield and WUE were achieved under RM and RMS and the minimum under NT/RT. Practices had small and inconsistent effect on seasonal evapotranspiration, hence variation in both yield and WUE were attributable to changes in the contribution of soil evaporation to total evapotranspiration, and the partitioning of seasonal water use before and after anthesis. The yield-evapotranspiration relationship indicated that present yields are limited by environmental (e.g. seasonal distribution of rainfall) and management factors. The range of WUE is very large for the same or various practices, and thus offers tremendous opportunities for maintaining or increasing WUE. Implications for crop management and further improvement in yield and WUE are discussed. (C) 2013 Elsevier B.V. All rights reserved.