Heat, moisture, and salt transport in the soil profile under surface and subsurface drip irrigation methods in the presence of shallow saline groundwater

Reducing evaporation and wastage of soil water and controlling soil salinity from shallow saline groundwater are important for increasing agricultural production in arid and semiarid regions. This study was conducted to (a) evaluate the transfer of heat, moisture, and salinity in the soil profile under surface and subsurface drip irrigation methods in the presence of shallow saline groundwater and (b) estimate evaporation using the energy balance method. This experiment was performed in field conditions and drainage lysimeters filled with loam soil (bulk density 1.45 g cm −3 ), and the water table was fixed at 60 cm (salinity of 10 dS m −1 ). Then, it was irrigated by surface drip irrigation (DI), and subsurface drip irrigation (SDI). The results showed that most energy fluctuations occurred on the soil surface. The highest amount of energy transfer took place at 45 to 70% in thermal conductivity due to the temperature gradient. The vapor flux increased as soil moisture diminished, and 97% of the vapor transfer occurred due to the temperature gradient. Furthermore, the results revealed that salinity had no noticeable effect on vapor flux in the soil profile. The calculated evaporation using energy balance methods had a high correlation with the measured values by the lysimeter method. The amount of evaporation in DI was 23% more than in SDI. SDI by increasing the downward and decreasing the upward fluxes reduced the transfer of water and salts from the underground source to the upper soil layers. It can be concluded that, in the presence of a shallow and saline groundwater table level, SDI is an efficient method to control salinity in the root zone.