How to model plant available water

How to model plant available water

Plant available water made simple

Both the amount and the availability of water (plant available water) in soil is important to plant roots and soil-dwelling organisms. To describe the amount of water in the soil, we use the term water content. To describe plant available water, we talk of water potential. In thermodynamics, the water content would be referred to as the extensive variable and the water potential as the intensive variable. Both are needed to correctly describe the state of water in soil and plants. In addition to describing the state of water in the soil, it also may be necessary to know how fast water will move in the soil. For this, we need to know the hydraulic conductivity. Other important soil parameters are the total pore space, the drained upper limit for soil water, and the lower limit of available water in a soil. Since these properties vary widely among soils, it would be helpful to establish correlations between these very useful parameters and easily measured properties such as soil texture and bulk density.

In this article word-renowned scientist, Dr. Gaylon S. Campbell presents the information needed for simple models of soil water processes. Learn about:

  • Water content and bulk density
  • How water potential indicates plant available water
  • Hydraulic properties and soil texture
  • Calculations for these parameters
  • Field capacity and permanent wilting point
  • Predicting permanent wilting point from field capacity
  • Obtaining hydraulic properties from soil survey data


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