الملخص الإنجليزي
Information on the effectiveness of soil conditioners over a prolonged period is scarce. experiment was undertaken to evaluate the effectiveness of a polyacrylamide (Broadleaf P4) soil conditioner on the physical properties of sandy soil subjected to wetting and drying cycles. Four concentrations Broadleaf P4 0. 0.2. 0.4 and 0.6% on dry weight basis were uniformly mixed with a calcareous sandy soil. Addition of Broadleat P4 to sandy soil increased the water holding capacity, decreased the bulk density, and increased the porosity and void ratio at 0 and 16 wetting and drying cycles. The coefficient of linear extensibility increased considerably with increasing concentrations of the polymer. The addition of polymer at 0 and 16 cycles increased considerably the retention and availability of water in sandy soil. Saturated hydraulic conductivity decreased with increasing concentrations of Broadleat P4 whereas unsaturated hydraulic conductivity at 0 and 16 cycles showed an increase with increasing soil moisture contents. After 16 wetting and drying cycles, the capacity of the soil to hold water was lost on average by 15.8% when compared to the 0 wetting and drying cycle. The effectiveness of the soil conditioner on bulk density, coefficient of linear extensibility, available water and saturated hydraulic conductivity was reduced on average by 14.1, 24.5. 21.1 and 53.7%. respectively. The significant changes in soil properties between 0 and 16 cycles suggested that the effectiveness of the conditioner decreased with the application of wetting and drying cycles. However, its effect was still considerable when compared to untreated soil under laboratory conditions.
