ESTIMATION OF CITRUS EVAPOTRANSPIRATION BY SOIL WATER MASS BALANCE1

Abstract

Evapotranspiration (ET) is a major component of soil water mass balance. An improved understanding of citrus tree ET can be used to enhance the precision of irrigation scheduling aimed at minimizing leaching of water and nutrients below the root zone and to avoid any potential water stress. EnviroSCAN® capacitance probes were used in this study to measure the soil water content continuously within and below the rootzone of young nonbearing Hamlin orange trees (Citrus sinensis (L.) Osb.) on Swingle citrumelo (Citrus paradisi Macf. X Poncirus trifoliata L. Raf.) rootstock grown in a Candler fine sand (hyperthermic, uncoated Typic Quartzipsamments). Continuous measurements of the soil water content below the rootzone was used to determine water losses below the root zone. Deep percolation data, used along with a soil water balance model, were used to calculate daily, monthly, and yearly citrus ET and water leached below the root zone for 1996. The daily ET followed a seasonal pattern, with the lowest values during the month of December and the highest values in July. The ET values in this study were close to those reported for citrus trees of similar ages grown in lysimeters but were slightly lower than the ET reported for mature grapefruit and orange trees.