AGRO 2051 Lecture Notes - Lecture 4: Soil Structure, Transpiration, Potential Gradient
Document Summary
Polarity results in hydration of dissolved ions and water adsorption onto polar surfaces. H-bonding accounts for strong adhesion of to solid surfaces and cohesion among water molecules. Surface tension is force per unit length that opposes expansion of the surface area. It can be shown that the pressure difference across a curved air-water is interface directly related tension and to surface inversely related to the radius of curvature of the interface. Thus, when a capillary tube is dipped in water, the reduced pressure at the curved interface is offset by the positive pressure caused by rise of a column of water in the capillary. A relation between the height of rise and radius of the capillary can be derived, h = 2t / rgd where. T is surface tension r is radius of curvature (= capillary tube radius for 0 contact angle) g is acceleration due to gravity. Capillarity and capillary bundle model for soil water content and movement.
