Numerical simulation of moisture distribution in different soils affected by mulch and shallow saline groundwater

The aim of this study was to investigate the effect of straw mulch on water content distribution in a soil profile and simulating water flow in soil under shallow saline groundwater using HYDRUS-1D. Lysimetric experiments were conducted in two soil textures (sand and loam) at three water table salinity levels of 5, 10 and 15 dS m-1 mulch and no mulch with three replications in a three-month interval. Soil moisture content was continuously monitored in the depths of 5, 10, 20, 30 and 50 cm. Evaporation was also measured using Marriott bottle technique on a daily basis. The results showed that mulch cover retained soil moisture by 16 % and 20 %, and reduced evaporation by 27 % and 8% in surface layer of loamy and sandy soil, respectively. Our findings highlighted a strong correlation between measured and simulated soil moisture data using HYDRUS-1D with R2 ranging from 0.89 to 0.97 and 0.90 to 0.96 in sand and loamy soils, respectively. The numerical model estimated soil moisture with RMSE of 0.0121- 0.0489 cm3 cm-3 for loamy and 0.0129-0.0521 cm3 cm-3 for sand. The simulation results revealed that HYDRUS-1D overestimates moisture content of layers close to water table.