A conceptual framework for the improvement of crop water productivity at different spatial scales

Total food crop production still needs to increase to feed a growing world population, and this increase needs to be accomplished under increasing scarcity of water. This challenge has lead to the notion that crop water productivity (WP) needs to be increased. The debate on how to increase WP is confounded by different definitions and scale levels of analysis. Moreover, improvements in WP do not necessarily mean the production of more food. A systematic framework built on generic principles for the analysis of WP can help to identify interventions that can contribute to the dual goal of increasing food production and saving water. In this paper, a conceptual framework with four principles is proposed that can be applied at different scales: (1) increase transpirational crop water productivity, (2) increase the storage size for water in time or space, (3) increase the proportion of non-irrigation water inflows to the storage pool, and (4) decrease the non-transpirational water outflows of the storage pool. These principles can be applied to the improvement of genetic resources and to the improvement of natural resource management. The framework is illustrated with examples at the plant, field and (small) agricultural landscape level, for cropping systems found in semi-arid areas to flooded rice in monsoon climates.