Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Plant Available Soil Water

Author
item Tolk, Judy

Submitted to: Encyclopedia of Water Science
Publication Type: Book / Chapter
Publication Acceptance Date: September 26, 2001
Publication Date: August 1, 2003
Citation: TOLK, J.A. PLANT AVAILABLE SOIL WATER. STEWART, B.A., HOWELL, T.A., EDITORS. MARCEL-DEKKER, INC., NEW YORK, NY. ENCYCLOPEDIA OF WATER SCIENCE. 2003. P. 669-672.

Interpretive Summary: Plant available water (PAW) is the amount of water in the soil that the plant can absorb readily through its roots to sustain its life. It is defined as the region bounded by the upper and lower soil water contents over which water, oxygen, and mechanical resistance are not limiting to plant growth. Determination of these boundaries is difficult, because they ywill vary with such factors as plant rooting characteristics, how much water the soil can hold, how easily the water moves through the soil to the roots, and environmental conditions. Many procedures exist to determine PAW, but increased accuracy requires specialized equipment and an extensive number of measurements.

Technical Abstract: Knowledge of the amount of water available to the plant, or plant available water (PAW), is needed to determine the agricultural and ecological potential of soils, and is used in many agronomic applications, such as irrigation scheduling programs or crop production models. It is defined as the region bounded by the upper and lower soil water contents over which water, oxygen, and mechanical resistance are not limiting to plant growth. Factors which determine PAW include rooting characteristics, soil hydraulic conductivity, leaf and root resistances to water flow through the plant, and environmental conditions. Many procedures exist to determine PAW, which increased accuracy requiring specialized equipment and an extensive number of measurements.

Last Modified: 11/28/2014
Footer Content Back to Top of Page