Evaluation and improvement of crop root-water-uptake and transpiration in AquaCrop

The AquaCrop model has been extensively utilized to simulate the growth and yield of various crops across diverse environments, with transpiration-driven water consumption serving as a critical variable. While AquaCrop's treatment of root water uptake (RWU) and transpiration are relatively simplistic, improvement has recently been proposed via the inclusion of the effects of previous water stress, nonlinear characteristics of root distribution, and the relative distribution between soil water and roots. The objectives of this study were to compare and assess the RWU model utilized in AquaCrop (RWU-AC) against a revised RWU model (RWU-RE) using data from two greenhouse column experiments on winter wheat, and to integrate the revised RWU model into AquaCrop and assess its performance relative to the original model in simulating soil-plant water dynamics and crop growth. The column experiments encompassed loam and sandy soils, surface and subsurface irrigation, and different irrigation levels. Compared to the RWU-AC model, the RWU-RE model significantly improved the simulation accuracy of transpiration and soil water dynamics under various water supply conditions in a soil-wheat system, with 44 % and 57 % average increase of determination coefficient ( R 2 ), and 62 % and 71 % average decrease of normalized root mean squared error (NRMSE), respectively. The RWU-RE model was subsequently incorporated into AquaCrop to investigate its simulation performance using data from a two-year field experiment on spring maize. Results indicated that the revised AquaCrop markedly improved the accuracy of the simulation for soil water distribution, transpiration, canopy cover, aboveground biomass, and grain yield, with R ² increased by 87 %, 18 %, 27 %, 7 %, and 10 %, and NRMSE reduced by 66 %, 52 %, 49 %, 44 %, and 69 %, respectively. The incorporation of the improvements in root-water-uptake and transpiration in AquaCrop makes it a more reliable tool for studying a wide range of crop responses to water, and hence helpful for optimizing irrigation strategies. • Root-water-uptake (RWU) and transpiration in AquaCrop were evaluated and improved. • Improvement was implemented by incorporating a recently proposed RWU model. • Root distribution characteristics and RWU hysteresis effect were considered. • Improved AquaCrop performed well in simulating soil water flow and crop growth.