Comparison of Unsaturated Hydraulic Conductivity Calculated by Jackson Equation and Van Genuchten Equation for Three Different Soils in Their Gypsum Content and Treated with Polymer and Peatmoss

Abstract An experiment was conducted to compare the unsaturated hydraulic conductivity (K) calculated by Jackson equation and van Genuchten for soils different in gypsum content treated with some soil conditioners. Two were used, gypsiferous (410 gm kg-1gypsium) clayey (435 kg-1 clay), mixed three levels 0, 50, 100%. The peat moss 0 and1%, polymer,0,1.and 2% without addition. Then, packed into plastic tubes 5 cm diameter 25 height at bulk density of 1.3 Mg m-3 exposed wetting / drying cycles. from (Jackson equation, equation. results showed good agreement between K values measu dy using RETC program. relationship θ percentages is a positive ψ an inverse relationship. value increased 81.7 cm. day-1 137.8 when percentage 46 410 g consecutively conditioners within minor tension limits approaching zero. decreased peatmoss polymer, most effective treatment reducing mixture (2% polymer + 1% peatmoss). remained close zero medium high tensions also low , it did not increase degree except approached its upper tensions, exponential these ranges.