Soil Water Potential

Potential refers to the energy status of water in soil, as it relates to water in other regions of soil. The total (net) potential in a soil region is composed of several component potentials:

A difference in soil water potential between 2 points in space is a soil water potential gradient, the driving force for all soil water movement. Water moves from regions of more positive (or less negative) to regions of more negative potential.

Before we discuss some of the components of soil water potential, a word about word usage. Soil water potentials may be positive or negative, but the greatest magnitudes found in the field are generally negative. This may result in confusion when certain relative references (e.g. "higher potential") are made. To reduce ambiguity, we use the terms "less negative" or "more negative" although both potentials may be either positive or negative. For example, -10 kPa is less negative than -100kPa, and water will flow from a region at -10 kPa to a region at -100 kPa.