SOIL PHYSICS AND IRRIGATION - TAPPING THE POTENTIAL FOR DRIP

Soil physical knowledge has contributed substantially to the understanding of how much water to apply to re-wet the soil and of how water is distributed away from points of application. However, the development of drip irrigation requires that water applied to a limited soil volume should be freely available enough to enable maximal growth but not contribute to drainage. The physical bases for estimating the quantity of water to apply, and for calculating the movement of water in soils are reviewed and the problems of using them in drip irrigation discussed. Rooting depth and distribution contribute to the actual rate at which water is utilised and the preferential wetting of limited soil volumes can modify these features. In practice, then, biological knowledge is essential to quantify water use, water distribution and response to irrigation. © 1990.