Influence of Soil-Water Potential on the Water Relationships of Honey Mesquite

Abstract

Thermocouple psychrometry was used to measure soil and plant water potentials of honey mesquite growing under irrigated and nonirrigated field conditions. The trees growing on the irrigated area experienced more internal stress (average minimum water potential, -30.9 bars) than trees growing under nonirrigated conditions (average minimum water potential, -19.4 bars). The water potential in the trees and transpiration rates adhered to a very distinct daily pattern. Minimum water potential occurred about noon in the trees growing on both sites. During the growing season, the average transpiration rate of the trees on the irrigated area was 9.59 X 10^-5 g cm-2 min-1, while the average transpiration rate for those trees growing on the nonirrigated area was 7.15 X 10^-5 g cm-2 min-1. The trees growing under irrigation produced 2 times more foliage than the trees growing without irrigation. Consequently, the greatest amount of soil water depletion occurred under irrigation. The results of this study indicated that water loss via transpiration in honey mesquite growing in shallow soils or on upland sites (relatively dry situations) is not as great as the amount lost from trees growing on bottomland and on riparian sites.