Infiltration in a calcareous sandy soil as affected by water-soluble polymers

Deep percolation loss of irrigation water is one of the main limitations in most agricultural soils of Saudi Arabia. Some synthetic polymers proved to be effective in mitigating this constraint. The present study was undertaken to investigate the changes in cumulative infiltration (D) and advance of the wetting front (Z) under ponded irrigation water using water-soluble polymers. Three different polyacryalmide (PAM) polymers, one nonionic (2J), and two anionic (21J and 40J) were used in this study at concentrations of 0, 10, 20, 30, 40, and 50 mg L- to determine D and Z in a calcareous sandy soil (Typic Torripsamments). The results showed that for the three polymers at a given time, both D and Z decreased with increase in concentration. The decrease in D was slight, whereas that in Z was pronounced. The time required for Z to reach a given value was in the order 40J > 21J > 2J. This order is mainly attributed to the viscosity of the polymer solutions. The results also showed that the polymers at concentrations from 250 to 1000 mg L- displaped non-Newtonian poly. The viscosity of 2J, 21J, and 40J at 250 mg L- were 7.78, 10.56, and 9.90 mPa.s at a shear rate of 245 s(-1). Since these water-soluble polymers affect the wetting front mainly through their effects on viscosity, the potential of using them for soil erosion control is good, but their use for increasing water availability in the soil is not good.