Crop water use efficiency at multiple scales

Food security is an issue of global concern, which is tightly linked with water supply issues as regional demands for water are dominated by agricultural water use. This special issue of Agricultural Water Management focuses on crop–water use in China, especially in the North China Plain (NCP) and Loess Plateau and surrounding areas, where intensive agriculture (e.g., wheat–maize double cropping) with limited water is practiced to meet the large demand for grains. Such intensive agriculture raises concerns for agricultural sustainability due to limited water supply and effects on water quality, which may be aggravated by projected climate change and its variability across the region and over time. Addressing these issues requires basic understanding of crop–water relationships in water-limited agricultural systems, methods to quantify water demand and actual crop–water use over multiple scales, and strategies to improve water use efficiency (WUE, or water productivity). Advances in crop breeding (selection) and agronomic management, such as irrigation and nutrient management, and tools to assess and improve WUE at multiple scales are addressed for a range of cropping systems in China. Water supplies within a basin (regional scale) must be managed in view of the patterns of water demand in space and time determined by soil and climatic conditions.