Studies on soil water and salt balances and scenarios simulation using SaltMod in a coastal reclaimed farming area of eastern China

•Slow desalinization trend exists under the condition of rainfed and present drainage.•A more densely designed drainage system than the present one is not necessary.•Shallow drain depth in dry season and deep drain depth in rainy season is recommended.•Irrigation with saline river water is not suggested in view of soil salinity management. The need for understanding water and salt balances of the soil and predicting the impacts of hydrological changes is getting increasingly important because of growing concern about the productivity of salt-affected soils. This study was undertaken to simulate the impact of various drainage scenarios on soil salinity and to develop appropriate management strategies to accelerate soil desalination based on long-term simulation results. The study was conducted in rainfed coastal salt-affected farmland in north Jiangsu Province, China, using the SaltMod model. Data such as drain discharge, soil salinity, water table depth, and soil properties were periodically collected to calibrate SaltMod and investigate the effects of varying drainage and irrigation practices on root zone salinity and water table depth. A leaching efficiency of 0.5 in the root zone and a natural drainage of 0.03m/year gave model results best matching the observed data. Under the rainfed condition and the present drainage system, the soil water salinity in root zone decreases after 10 years from the initial 29.2dS/m to 15.0 (in the 1st season) and 14.0dS/m (in the 2nd season). Different drain depths and spacings had considerable impact on root zone salinity and water table depth. Simulation results of the irrigation scenario showed that the direct irrigation with saline river water is not recommendable. The study suggests that SaltMod can be used with success to predict the effect of varying irrigation and drainage practices on root zone salinity.