A novel water use efficiency model based on stomata coupling crop growth and farmland water cycle processes in arid area

Abstract

Water use efficiency (WUE) determined by water-carbon coupling process is important to evaluate the relationship between crop growth and water consumption. Aiming to provide a novel WUE dynamic evaluating method at field scale, we developed a crop WUE model based on stomata, which coupled the processes of crop growth and farmland water cycle. In previous work, we developed a stomatal conductance model in which crop stomatal conductance could be described by its relationship to meteorological factors, soil water and salinity. In this study, we coupled crop transpiration and photosynthesis based on stomata. Furthermore, the model described the daily crop growth and hydrological processes. As a result, the developed model could simulate the dynamic changes of crop canopy evapotranspiration (ET), canopy photosynthesis, dry matter accumulation and assimilation distribution, soil water movement, soil salt transport and WUE of farmland ecosystems on a daily scale. Three years field experimental data were used to calibrate the developed model. The results showed that the model could simulate the variation of agricultural hydrology processes properly in sunflower field on the daily scale, with determination coefficient (R2) and Nash-Sutcliffe efficiency coefficient (NSE) of ET, transpiration and WUE all close to 0.60. R2 and NSE of net ecosystem productivity above 0.74 and 0.68, respectively. And the coupling model had a good performance in simulating the dynamic change process of soil moisture and salt with the R2 and NSE above 0.71 and 0.61, respectively. Sensitivity analysis of model parameters showed that the selection of the extinction coefficient had a great influence on the accuracy of the model and the accurate description of soil resistance parameters played a crucial role in the accurate quantification of ET. The developed field WUE model can provide novel method to evaluate daily hydrological processes, agricultural productivity and WUE dynamics.