Clay deposits for water management of sandy soils

Water management practices in conserving water for arid lands are crucial in sustaining agriculture and food production. Sandy soils (Typic Torrripsamments] are practically important land resources in many Middle Eastern countries. In a laboratory experiment, five naturally occurring clay deposits were applied at different rates to sandy calcareous soil in order to evaluate their effect on relative swelling, infiltration and water conservation. Relative swelling index (RSI), cumulative infiltration (D), and advance of wetting front (Z) were measured in the laboratory for untreated and treated soil samples mixed with 1, 2, 3, and 5% of the clay deposits. Results indicated that addition of natural deposits significantly increased RSI. The differences in RSI values between natural deposits at any rate of application were significant and related to clay content and presence of smectite type clay. RSI values for each clay deposit fitted to the following exponential function with the application rate x (RSI=aebx}. Results of D indicated that increasing natural deposit rate significantly increased the time required for the wetting front to reach 40cm. There was a significant difference between the clay deposits at 5% rate and the difference was related to the type of clay and clay content in each deposit. The presence of CaCO3, dominance of kaolinite type clay and low clay content in the deposits enhanced water movement while dominance of smectite clay and high clay content decreased D. Advance of wetting front was markedly affected by the type and the rates of clay deposit applied. Z decreased with increasing rates of clay deposits. Soil water distribution profile was characterized by three zones based on the type and the rate of applied clay deposit to the soil