Application of superabsorbent polymers is a suitable method to enhance water use efficiency in agricultural soil. The polymers improve soil hydraulic properties such as water holding capacity, plant available water, and hydraulic conductivity of soil. Superabsorbent polymers absorb high amount of water and release it gradually as soil dries out. In this research, the effect of two superabsorbents (Geohumus and Hydrogel) on soil hydraulic properties and plant growth was evaluated. This research was done in two stages. The first stage was conducted as completely randomized design in which treatments were different levels of superabsorbents (0, 5, 10 and 20g Geohumus/kg soil and 0, 4, 6 and 8 g Hydrogel/kg soil). The aim of this stage was to determine effect of superabsorbents on soil physical and hydraulic properties. The second stage was a greenhouse trial, conducted as completely randomized factorial design in which the treatments were 4 levels of superabsorbents (the same with first stage) and three irrigation regimes consisting 50, 70 and 100 percent of field capacity. The objectives of this stage were evaluation of superabsorbents on growth indices and yield of cucumber ( Cucumis sativa var. Danito ), under reduced irrigation regimes. The results showed that using of Geohumus leads to significant increase in amount of water in FC and PWP and uptake of N, K and Fe by plant but there was a significant decrease in soil hydraulic conductivity and available water content of the soil. But the changes on bulk density, particle density, MWD and Zn and P uptake by plant were not significant. A significant increase in height, fresh weight and dry weight of cucumber plants were observed in the 5 g Geohumus per kg soil but there was a significant decrease in these growth indices by increasing the Geohumus levels. Using of Superab A200 leads to significant increase in amount of FC and PWP water, MWD, water availability, fresh and dry weight of plant but it leads to significant decrease in soil hydraulic conductivity. No significant difference was observed in bulk density, particle density and fruit weight. Also, No special trends were found in nutrient uptakes by plant in Hydrogel treatments. Increasing of water regimes to 100% of FC leads to significant increase in fruit weight and all growth indices of plant.
