Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality.

Summary Hydrophilic polymers can swell by absorbing huge volumes of water or aqueous solutions. This property has led to many practical applications of these new materials, particularly in arid regions for improving water retention in sandy soils and the water supply to plants grown on them. The effects of two hydrophilic polymers, carboxymethylcellulose (RF) and isopropyl acrylamide (BF) on the water holding capacity and saturated hydraulic conductivity ( K S ) of a sandy soil at varying soil temperature and water quality were evaluated. The RF was less efficient in absorbing water than BF, but the efficiency of BF in retaining water was negatively affected by its thermo-sensitivity and the quality of water. The temperature dependence of the water absorption was not clear for the soils treated with RF, whereas, the efficiency of BF treatment in absorbing water decreased significantly ( P K S on soil temperature differed with the type of hydrophilic polymer used. The K S of the control soil remained nearly constant as the soil temperature increased. The K S of the BF treated soil increased significantly ( P 3  cm −3 for 0.1% and from 0.27 to 0.12 cm 3  cm −3 for 0.2%, as the soil temperature increased from 15 to 35 °C. This implies that the soil–BF absorbent mixtures would release some moisture as the soil temperature would increase from 15 to 35 °C, and this water could be lost by percolation or taken up by plant. It was found that available water content increased up to four times with RF as compared to control soil whereas it increased up to five times with BF treatment. At high temperature, the difference was much reduced except for RF at 0.2%. This understanding of the characteristics of the absorbents and the interactions among absorbents, soil, and temperature would be of help in water management in sandy soil.