Soil salt leaching under different irrigation regimes: HYDRUS-1D modelling and analysis

 Field irrigation experiments were conducted in the Hetao Irrigation District of Inner Mongolia, China, to study the effects of irrigation regimes on salt leaching in the soil profile. The data were used to calibrate and validate the HYDRUS-1D model. The results demonstrated that the model can accurately simulate the water and salt dynamics in the soil profile. The HYDRUS-1D model was then used to simulate 15 distinct irrigation scenarios. The results of the simulation indicated that irrigation amount did not have a significant effect on soil water storage but that increases in irrigation amount could accelerate salt leaching. However, when the irrigation amount was larger than 20 cm, the acceleration was not obvious. Compared with irrigating only once, intermittent irrigation had a better effect on increasing soil water storage and salt leaching, but excessive irrigation times and intervals did not improve salt leaching. In addition, we found that the irrigation regime of 20 cm, irrigated twice at 1-d intervals, might significantly increase salt leaching in the plough layer and decrease the risks of deep seepage and groundwater contamination.