Improving water use efficiency of irrigated crops in the North China Plain - measurements and modelling

High crop productivity in the North China Plain (NCP) relies on irrigation. However, as a result of rapid regional development in the last two decades the competition for water has become very acute. This presents a serious problem for the sustainable agriculture in the region. This work examines relationships between irrigation, evapotranspiration (ET), crop growth and water use efficiency (WUE) of a corn-wheat rotation common in the region. During the period of 1984-1996 field experiments were conducted at Luancheng Agricultural Ecosystem Station in the North China Plain to measure water and energy balance components and crop growth of corn and wheat. A process-based model (WAVES) was used to analyse the measurements and to simulate the effect of irrigation management on crop growth. The summer dominant rainfall of the region means that irrigation is required during the winter wheat growing season when the difference between rainfall and evapotranspiration is large, while corn grows during summer, some irrigation is still required. Soil evaporation (E,) is a significant proportion of total evapotranspiration especially when leaf area index (LAI) is low and on average E under a wheat canopy accounted for 30% of ET. Mulching reduced soil evaporation by up to 50% and saved about 80 mm of water during a wheat growth season. Current irrigation schemes in the area can be improved by reducing irrigation frequency and amount. (C) 2001 Elsevier Science B.V. All rights reserved.