Agricultural Water Management (Oct 2023)
Quantifying water and salt movement in a soil-plant system of a corn field using HYDRUS (2D/3D) and the stable isotope method
Abstract
Brackish water has been increasingly used worldwide for irrigation to relieve crop water stress. However, crop yield reductions inevitably occur under uncontrolled irrigation with saline waters, especially in areas with shallow and saline groundwater. It is essential to quantify the movement of soil water and salts in a soil-plant system and to optimize irrigation patterns with brackish water to alleviate the harm of salt stress on crop growth. Therefore, a two-year cornfield experiment was carried out during 2020–2021 to evaluate differences in soil water and salt movement under different irrigation regimes: a) brackish water irrigation with high (HB), medium (MB), and low (LB) irrigation depths, and b) freshwater irrigation with medium irrigation depths (MF). Moreover, the HYDRUS (2D/3D) model was used to evaluate soil water contents (SWC), electrical conductivities of the saturation paste extract (ECe), and fluxes, distributions, and mass balances of soil water and salts for the HB, MB, LB, and MF regimes. Meanwhile, oxygen isotope (18O) was used to calibrate and verify the simulation accuracy of the HYDRUS (2D/3D) model by determining the proportion of water and salt sources in a soil-plant system.The results showed that HYDRUS (2D/3D) could precisely capture SWC and ECe under different irrigation treatments, with the root mean square error (RMSE) of 0.004–0.017 cm3 cm−3 and 0.023–0.372 dS m−1 for SWC and ECe, respectively. The highest differences in SWCs and ECe in plots under brackish water and freshwater irrigations occurred in the 0–20 cm soil layer. The stress areas in the soil profile due to water and salt stresses under MB decreased and increased by 1.8 cm2 and 2010.0 cm2, respectively, compared with MF, accounting for 0.04% and 40.2% of the root zone. However, average root water uptake (RWU) in both years under MB decreased by 1.9% compared to MF. Additionally, RWU showed a nonlinear relationship with irrigation depth when brackish water was used for irrigation. The highest RWU occurred under MB, where the average RWU in both years increased by 7.7% and 12.4% compared with HB and LB, respectively. Therefore, the MB treatment could be recommended to increase crop yield and alleviate the freshwater shortage in agricultural production. Moreover, the findings of this study improve our understanding of the mechanisms of soil water and salt movement and groundwater contributions in a system under brackish water irrigation with different irrigation depths.
