A case study on water use efficiency in extreme water-saving cultivation of tomato plants

Abstract

In horticulture, the definition of water use efficiency (WUE) is context-dependent, which causes confusions in the studies of deficit irrigation. This paper focuses on the precise relationship between individual crop growth and water absorption, aiming to experimentally verify WUE analysis based on actual crop water absorption from micro soil water dynamics in the crop rooting zone and to provide a case study of WUE assessment when crop water absorption was extremely low. In this paper, water consumption of tomato plants was observed and analyzed using a high-resolution soil moisture sensor matrix method. The experiment system was placed in an enclosed, climate-controlled environment. The system created an extreme water-saving condition by controlling moisture in the crop rooting zone to ensure a small level of crop growth. Irrigation water volume in the rooting zone was manually determined by measuring soil moisture dynamics. Relationship between WUE and root water uptake was analyzed based on the rooting zone moisture dynamics. WUE was finally determined as the ratio of crop yield to total water absorption. Comparisons were made to previous, high-efficiency crop production under different irrigation conditions. In this study, the crops showed extremely low WUE under the extreme water-saving condition. The experiment verified the feasibility of using micro soil water dynamics to analyze crop WUE and using WUE as an index of crop physiological characteristics under severe survival conditions. We propose using WUE as an index throughout the cultivation process to assess the effectiveness of irrigation management in response to crop water absorption.