Modelling long-term soil salinity dynamics using SaltMod in Hetao Irrigation District, China

Soil salinity is considered the most serious factor that limits food security and sustainable development of irrigated agriculture productivity, especially in arid and semi-arid regions. Irrigation and drainage management play a critical role in soil water dynamics, soil desalinization, and crop growth and yield. This study was conducted to determine the changes caused by salinization on cultivated lands and salt wastelands in the long term given the present irrigation and drainage practices and under the different water management scenarios. Moreover, this study was aimed at developing appropriate management strategies to decrease the salt accumulation based on long-term simulation results. A SaltMod model was calibrated and validated using data from 2010 to 2016. Leaching efficiencies of Flr = 0.85 and Flx = 0.65 in the root and transition zones and natural drainage of 0.10 m/year were determined, thereby providing the optimal match between the observed and simulated values. Prediction results showed that the salinity of the cultivated land would exhibit slight decrease in the next 10 years under the current irrigation and drainage conditions. The proposed irrigation schemes were analyzed to improve the soil desalination effect in the long-term. Results indicated that autumn irrigation water was increased by approximately 10%–20%, and summer irrigation water was decreased by approximately 15% in the prospective 10 years (2016–2026) based on the present irrigation conditions. Furthermore, the soil salinity will decrease by approximately 1.06%–10.92%, and the total irrigation water will decrease by approximately 50–295 m3/ha, thereby possibly contributing to improved water saving and soil desalination.