Simultaneous Effect of Soil Salinity and Matric Suction on Evaporation and Redistribution of Moisture and Salinity in Two Soils with Different Textures

Daily increasing salinity is one of the main problems of agricultural lands, especially in arid and semi-arid regions, with high evapotranspiration rates. The purpose of this research was to investigate the simultaneous effect of salinity at five levels 2, 4, 8, 16 and 20 dSm-1 for wheat and 0.7, 2, 4, 6 and 8 dSm-1 for bean and matric suction at four levels 2, 6, 10 and 33 kPa, on evaporation rate and redistribution of moisture and salinity in the soil profiles of sandy loam and clay loam. This study was conducted in greenhouse conditions in pots by compeletly randomized factorial desigh with 3 replicates.  It was found that evaporation rate decreased by time in the saline and water stress treatments, especially in the clay loam soils, and this reduction was more in the high suction and salinity levels. The lowest evaporation reduction was observed in treatments with the highest soil moisture content. Because, water availability reduced the salinity effect on evaporation. As, at the 2kPa matric suction, the evaporation rate was approximately the same at all levels of salinity and the highest throughout the day after treatment. In the 15th day after treatment and at the 33kPa suction, different salinity levels (from 0.7 to 20 dSm-1) reduced the evaporation rate by 19% in both soils. Also, the results showed that the ECe of the drained soils with 10kPa constant suction increased exponentially with moisture reduction. This trend was more in the clay loam soils. Because the evaporation/drainage ratio of the clay loam soil is more than the one in the sandy loam soil. The salinity redistribution in the both soil profiles and for the two plants were almost constant over time. Also, moisture reduction over the time was higher in the clay loam soil than the one in the sandy loam soil, especially under low salinities.