Modeling soil water and salt dynamics in cotton-sugarbeet intercropping and their monocultures with biochar application

Managing soil salinity in arid areas is a challenging task that is becoming increasingly difficult. Various management practices include using salt-tolerant crops like cotton and sugarbeet, plastic-mulched drip irrigation, intercropping, and biochar. However, studying the effectiveness of these practices can be difficult, costly, and time-consuming, as obtaining information on soil water and salt dynamics can be challenging. Numerical simulations show promise, but have limited application in simulating complex field experiments, such as adding ameliorants and intercropping systems. This study aimed to use a simulation model called HYDRUS-2D to simulate soil water and salt dynamics and root water uptake (RWU) in cotton and sugarbeet monocultures and intercropping with biochar application in an arid climate to minimize soil water losses through optimal irrigation under plastic-mulched drip irrigation systems. The results of a three-year field experiment were used to calibrate and validate the HYDRUS-2D model. The soil water and salt dynamics were measured in fields with biochar applied at three different rates [0 t ha^–1 (CK), 10 t ha^–1 (B10), and 25 t ha^–1 (B25)]. The R², RRMSE and NSE showed that the soil hydraulic and solute transport parameters optimized in HYDRUS-2D satisfied simulation accuracy requirements. The simulation results showed that biochar application increased soil water and salt storage. Simulated RWU ranked as B10>B25>CK, consistent with soil water storage and yield. The B10 treatment showed promising application potential in RWU enhancement, evaporation and water drainage reduction, irrigation water conservation and farmers’ income increment. This study provides a useful reference for agricultural production and social benefits in arid and semiarid areas.