To meet minimum spring flows, water managementdistricts in Florida sought to make both agriculture and urban landscapes waterefficient, which includes tree farms. Quercusvirginiana, commonly known as live oak trees, is endemic to Central Florida and among the mostpopular landscape trees for their gracefulness and spreading shade. To providea basis for irrigation allocations both during production and in landscapes,daily actual evapotranspiration (ETA) in liters for three live oaktrees was measured with weighing lysimeters over five years, beginning withseedlings and continuing until trees averaged 7.2 meters in height. Empiricalmodels were derived to calculate ETA based on crown horizontal projected area (PCA) or trunkcaliper (TCSA), adjusted daily by changes in evapotranspiration (ETO).Average ETA to produce these live oaks was 62,218 L cumulative over5.5 years. Effectively transpiring leaf, tree water use volume divided by ETO,was closely related to PCA over five years with the slope of this relationshipbeing equivalent to a Plant Factor of 0.93. The product of ETO andthis Plant Factor can be used to estimate depth of live oak water demand inurban landscapes. Also, this Plant Factor can estimate water demand volume innurseries and landscapes when combined with PCA, and similarly the slopes forTCSA can be used to estimate ETA water volume from measured trunkdiameter.
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