Soil Water and Salinity Distribution under Different Treatments of Drip Irrigation

In this study, field experiments and numerical simulations for different drip irrigation treatments in a sandy loam soil were conducted to investigate soil water and salinity distribution as well as dye infiltration patterns. Three treatments, surface drip irrigation without and with plastic mulch (T-1 and T-2, respectively) and subsurface drip irrigation (T-3), were used. Daily and bi-weekly irrigation regimes were used for each treatment. After completion of each irrigation treatment, horizontal soil sections were dug with 10 cm intervals. Dye patterns were photographed using a digital camera and soil water and pore water electric conductivity were measured by a WET-sensor. Experimental results revealed that maximum dye infiltration depth and maximum dye coverage volume occurred during the bi-weekly irrigation regime and in T-3. Daily irrigation regime kept the top soil layer moist with adequate amount of soil water as compared to the bi-weekly irrigation. Moreover, T-2 provided higher soil water content within the soil domain as compared to other treatments. The simulation results demonstrated that model prediction for soil moisture distribution within the flow domain was excellent. Furthermore, T-2 and daily irrigation showed lower salinity levels in the flow domain as compared to other irrigation treatments and regimes. In sum, mulching treatment with daily irrigation regime is recommended for arid areas over other drip irrigation treatments and regimes. In addition, HYDRUS-2D/3D can be used as a fast and cost effective assessment tool for water flow and salt movement for sites having similar soil conditions.