Soil hydrophysical properties as affected by kind of added polymer.

Laboratory experiments were carried out to clarify the impact of different types of natural and synthetic polymers on some hydrophysical properties (soil hydraulic parameters) of a sandy soil. Adding 0.5% (w/w) of each treatment to soil significantly increased water retention at saturation, field capacity, total available water and readily available water. This treatment decreased the value of inflection point on water retention curve as result of enhancing water behavior in the soil. The obtained results revealed that soil water storage significantly increased from 0.271 in control treatment (without adding polymer) up to 0.414 in treatment [T10] (Acrylic acid + Xanthan) while, field capacity increased significantly from 0.078 in control up to 0.242 of the abovementioned treatment (T10). Regarding the effects of polymer application in total available water and readily available water, data revealed significant increases in the above mentioned parameters. Total available water increased from 0.044 in control treatment up to 0.153 in T10 and readily available water increased from 0.057in control treatment up to 0.185 in T10. Concerning values of inflection point on soil water retention curve, the obtained results revealed that, inflection point of control treatment (1000 mbar) decreased to 590 mbar, as a result of adding a mixture of polymer acrylic acid + xanthan (T10 ).Soil depletion rate decreased as due to polymer application by 25% up to 75% depending on type of polymer and wether it was added individually or in combination with another polymer. This effect led to significant differences among control treatment (control) and the other treatments. Generally, there were significant effects of all polymers on the concerned hydrophyical properties of the studied sandy soil, i.e. storage capacity of soil water, depletion rate of soil water, soil field capacity , soil available water, readily available water and inflection point on the soil water retention curve. Acrylic acid recorded the best results concerning soil water behavior if it was added individually to the sandy soil (Treatment 2) or in combination with Xanthan (Treatment 10) or with Lignosulphonate (Treatment 11).