SIMULATION OF SOIL WATER AND SALINITY DISTRIBUTION UNDER SURFACE DRIP IRRIGATION

ABSTRACT Higher crop production and better water use efficiency are usually achieved with surface drip irrigation as compared to traditional surface irrigation methods. Increasing competition for fresh water also means a greater use of brackish water in agriculture. For this reason, the effects of soil hydraulic properties, initial soil moisture content (θi), and irrigation regime on soil water and salinity distribution under surface drip irrigation (DI) with brackish irrigation water were investigated. Model simulations were performed using the HYDRUS‐2D/3D model assuming tomato crop in saline soil. Simulation scenarios were conducted including sand, loamy sand, and sandy loam soils, together with daily and alternate‐day irrigation regimes. Two θi values were considered in the simulations. Results revealed that the effect of the irrigation regime on wetting patterns differed according to the soil's hydraulic properties, while the effect of the initial soil moisture content disappeared after a few days. The irrigation regime and θi value did not display any significant effect on soil salinity distribution. Higher soil salinity occurred along the soil surface by the end of the simulation period. The higher soil salinity was more close to the emitter in sand as compared to loamy sand and sandy loam. Water balance calculations showed that as the initial soil moisture content increased, the free drainage component increased. However, the irrigation regime and initial soil moisture content did not affect the evaporation rate and root water uptake rate. Copyright © 2013 John Wiley & Sons, Ltd.