Soil Root Zone Available Water Capacity

The Root Zone Available Water Capacity (RZAWC) is determined by multiplying available water capacity by the thickness of all layers in the root zone. It approximates the volume of water that is held in the root zone that can be used by crop plants and reflects important physical soil properties. The RZAWC soil is calculated from the surface to the beginning of the first root-restrictive soil layer, such as bedrock or a very dense layer, or to a depth of 150 centimeters. The importance of RZAWC varies geographically because the capacity to hold water during key parts of the growing season is more critical in some climates than in others. Available water in the surface layer is critical to establish plants, but the amount of available water stored throughout the root zone usually determines the most productive soils for the entire growing season.

Courtesy of Natural Resources Conservation Service, U.S. Department of Agriculture.