Water Use Efficiency of Cultivated Crops

Abstract

Abstract The concept of crop water use efficiency (WUE), determined by the ratio between the marketable yield and the seasonal values of actual evapotranspiration, has become a suitable tool for analysing the strategies that allow attaining the best use of water in agriculture. Crop WUE is easy to quantify from field measurements, but it is a complex indicator because wide differences can be observed for the WUE values of the same species cultivated under the same site. In this article, the major causes of the large range of WUE values are identified and analysed. The authors demonstrate that the WUE variability can be ascribed mainly to three factors: agro‐techniques (water regime, mineral supply and water quality), crop (species, varieties and sensitivity of the growth stage to the stress) and environment (climate, atmospheric pollution, soil texture and climate change). Understanding and taking into consideration the WUE variability are primary conditions for advanced studies on WUE. The paths for further research and management programmes, allowing to valorise the water in agriculture, can be drawn from the analysis reported here. Key Concepts: To ameliorate the efficiency of water used by cultivated crops is one of the three possible strategies for increasing water sustainability in agriculture. To attain this objective, ecophysiological and agronomical approaches can be used. The ecophysiological approach refers to values of carbon assimilation and transpiration rates per leaf unit area. It helps in understanding global results obtained from the agronomical approach. In the agronomic approach, the concept of crop use water efficiency (WUE) refers to final yield and to total water consumed by crops, under field conditions. They are key data to manage the crop production. Crop WUE is easy to quantify from field measurements, but it is a complex indicator because of its intrinsic variability. The major causes of WUE variability are identified and analysed in this review: crop, environment and agro‐techniques. If the causes of such variability are known and taken in the right consideration, the concept of WUE can represent an interesting tool for studying how to valorise the water in agriculture.