Effects of Chitosan and Arabic Gum Biopolymers on Some Physical Properties of Swelling Soils

Tillage operations in swelling soils comprise some difficulties due to the fact that they are sticky during wet periods and hard in dry conditions. Applying soil conditioners is one of the solutions for managing these soils. In this study, a completely randomized (CRD) factorial experiment with two factors including type (Arabic gum and Chitosan) and amounts (zero, 5, and 10 grams per kilogram) of two soil conditioners with three replications was carried out to investigate the effect of these natural biopolymers on the improvement of the physical quality of these soils. Several soil characteristics were examined after three weeks of incubation time. The results showed that the use of Arabic gum and Chitosan increased saturated hydraulic conductivity (Ks) (approximately twice) and wet-aggregate stability (WAS) (approximately 3-4 times). The mean weight dimeter (MWD) index increased around twice as a result of the treatment of soil by Arabic gum and decreased around half due to soil treatment by Chitosan. Regarding soil water storage, Arabic gum retained more water in soil exposing to evaporation force. The swelling volume of the examined soils decreased around half as a result of the application of both above-mentioned biopolymers. Therefore, the above-mentioned biopolymers can be used to treat swelling soils hoping a considerable reduction in their swelling and shrinkage characteristics.