Abstract
A petrochemical soil conditioner (Hydro-grow 400) was incorporated in a sandy soil and an examination of water movement was carried out under saturated as well as unsaturated conditions. The conditioned saturated soil created a gain in stored water budget as a result of minimizing both gravitional and evaporation water losses. Moreover, soil conditioner increased water movement in the unsaturated condition. The magnitude of the change in the water movement was found to be dependent on the application rate of the conditioner as well as water tension.
It was found that the 0.75% application rate was the optimum rate for water conservation and the maintainance of an adequate supply of soil water for plant growth in sandy soils. This recommended rate reduced water movement under saturated condition by -79.2% and water loss from evaporation by -30.0%. Moreover, this rate resulted in a maximum increase in water movement under unsaturated conditions, especially under high water tensions. On the other hand, the highest application rate (1.0%) seems to seal the soil pores, and this reflected itself directly on the values of K(s) and K(theta). Increasing application rate of soil conditioner and the subsequent swelling of the conditioner particles resulted in linear decreases in K(s) (r = -0.935), K(theta) at 0.01 MPa tension (r = -0.972), water loss by evaporation (r = -0.981) and drainable pores in the soil (> 30 mum and 9-30 mum, r = 0.984 and -0.870, respectively).