Plant available water capacity (PAWC)

A growing crop relies greatly on water that has been stored in the soil during periods of fallow or reduced cropping activity; the capacity to store this water depends on the soil's physical characteristics such as structure and depth.

The maximum water available is known as the Plant Available Water Capacity (PAWC); it varies with soil type and crop. button.jpg (845 bytes)

PAWC is the difference between the upper water storage limit of the soil and the lower extraction limit of a crop over the depth of rooting (Godwin et al. 1984; Ratliff et al. 1983; Gardner 1985). (Formulae 1 and 2)

In many seasons, the maximum water storage capacity is not reached for reasons including insufficient rainfall, fallow weeds, run-off and evaporation. In these cases, the actual water present is described in terms of the PAWC, that is, how full is the bucket.