soil moisture

1) Water stored in soils. 2) One of the most important elements involved in pedological processes and plant growth. There are three basic forms: a) water adhering in thin films by molecular attraction to the surface of soil particles and not available for plants is termed hygroscopic water. b) Water forming thicker films and occupying the smaller pore spaces is termed capillary water. Since it is held against the force of gravity it is permanently available for plant growth and it is this type of soil water which contains plant nutrients in solution. c) Water in excess of hygroscopic and capillary water is termed gravitational water, which is of a transitory nature because it flows away under the influence of gravity. When the excess has drained away the amount of water retained in the soil is termed its field capacity, when some of its pore spaces are still free of water. (Source: LANDY / DUNSTE)