| To explore the transport of water and salts of underground pipe drainage under mulch-drip irrigation system,we conducted an experiment with underground pipe drainage system of a 1 m deep and 4 m spacing pipes. The dynamic changes of soil moisture and salinity were measured during irrigation and leaching, and the transport was analyzed and verified with HYDRUS numerical model under the condition of subsurface drainage. The results showed that after three times of irrigation and washing, the salt content decreased to 2 g·kg-1 in 0~20 cm soil layer, reaching the level of non-salinized soil. The effect on upper layer desalination was greater than that on lower layer soil of 20~60 cm, and the total salt content was less than 8 g·kg-1.Through verification of the measured and simulated values, the maximum RMSE of soil salinity and moisture were 0.632 and 1.324, and the minimum values of R2 were 0.992 and 0.906, respectively, which indicated the simulation results were in good agreement with the measured results.The HYDRUS model was more reliable to simulate the transport of water and salt in the subsurface drainage system.The dynamic characteristics of water and salt in different depths of soil layer under the subsurface drainage after irrigation for 6 times (90 days) were simulated by the model.The simulation results showed that the salt content was decreased to 2 g·kg-1 in 0~40 cm soil layer, reaching the level of non-saline soil.The salt content in 40~80 cm was decreased to 4 g·kg-1, which basically reached the level of slight salinization. The salt content in the soil profile fluctuated with distances from the pipe. The greater the distance from the pipe, the greater the salt content in the soil and the salt content varied within the range of 0~8 g·kg-1. |