EVAPOTRANSPIRATION AND SOIL WATER MOVEMENT BENEATH THE ROOT ZONE OF IRRIGATED AND NONIRRIGATED MILLET (PANICUM MILIACEUM)

Abstract

A water balance was estimated for irrigated and nonirrigated millet grown in a Varina sandy loam, harvested periodically during the growing season. Evapotranspiration (ET) was calculated using the water balance equation; all elements, except the subsurface drainage, were measured directly. The subsurface drainage was estimated using the Darcy equation, to determine the net soil-water flux into and out of the root zone. The ET calculated from the irrigated plots agreed reasonably well with potential ET values computed using the combination equation. Hydraulic gradient data in nonirrigated plots showed that water moved upward for most of the season. During 1 drought the upward flux accounted for .apprx. 34% of the calculated ET. Although the total amount of water moving upward was small, it provided enough water for the crop to subsist until rainfall was adequate.