Effects of limited irrigation on yield and water use ef®ciency of winter wheat in the Loess Plateau of China Shaozhong Kang a,b,* , Lu Zhang c , Yinli Liang b , Xiaotao Hu a , Huanjie Cai a , Binjie Gu d a Key Lab for Agricultural Soil and Water Engineering in Arid and Semi-arid Areas of Ministry of Education, Northwest Sci-Tec University of Agriculture and Forestry, Yangling, Shaanxi 712100, PR China b Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, PR China c CSIRO Land and Water, Canberra 2601, ACT, Australia d Department of Irrigation and Drainage, Ministry of Water Resources, Beijing 100053, PR China Accepted 3 September 2001 Abstract On the Loess Plateau of China crop yields are mainly limited by available water. A ®eld experiment was conducted for winter wheat Triticum aestivum L.) during the period 1995±1998 to evaluate the effects of limited irrigation on yield and water use ef®ciency. A controlled soil water de®cit,eithermildorsevere,wasappliedatdifferentstagesofcropgrowth.Photosynthesisrate,soil water content, and root and shoot dry mass accumulation were measured. Final grain yields and total water consumption were recorded, and the water use ef®ciency and harvest index were calculated. The results showed that, in different growing periods, evapotranspiration, grain yield, biomass, water use ef®ciency WUE), and harvest index depended on the controlled ranges of soil water content. Grain yield response to irrigation varied considerably due to differences in soil moisture contents and irrigation scheduling between seasons. Evapotranspiration was largest in the high soil moisture treatment, and so was the biomass, but this treatment did not produce the highest grain yield and WUE was relatively low. WUE increased linearly with harvest index HI) and improvement in the latter gave better WUE under limited irrigation conditions. Appropriately controlled soil water contents can improve the grain yield, WUE, and harvest index. Consistently high values of grain yield, WUE, and harvest index were produced under conditions of mild water de®cit at the seedling and start of regrowth to stem-elongation stages, in addition to a further soil water depletion at the physiological maturity to harvest stage. We therefore suggest that periods of mild soil water depletion in the early vegetative growth period together with severe soil water Agricultural Water Management 55 2002) 203±216 * Corresponding author. Tel.: 86-29-7092129; fax: 86-29-7092559. E-mail address: kangshaozhong@163.net S. Kang). 0378-3774/02/$ ± see front matter # 2002 Published by Elsevier Science B.V. PII:S0378-377401)00180-9