Under- and Overtree Microsprinkler Irrigation for Frost Protection of Peaches

in HortTechnology
Author: Mark Rieger1
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  • 1 Department of Horticulture, University of Georgia, Athens. GA 30602

Spring frost events reduce fruit production in the southeastern United States more than any other factor, with some losses occurring in 5 out of 7 years. Orchard heaters, wind machines, and overhead irrigation are sound methods of reducing losses, but their relatively high cost is a major deterrent for fruit growers (Castaldi, 1990). A potentially leas-costly and more water- efficient approach to frost protection is overtree microsprinkling. Microsprinkler irrigation was applied either beneath or onto canopies of 4-year-old `Loring' peach [Prunus persica (L.)] trees at a rate of 38 liters/h per tree to evaluate the relative efficacy of low-volume undertree and overtree microsprinkling for frost protection. Overtree microsprinkling maintained flower bud temperatures 2C during a calm, radiative frost on 20-21 Mar. 1990 (minimum air temperature -4.4C), whereas undertree sprinkling provided 0.5C of air temperature elevation at a comparable height in trees (2 m). Twelve days later, fruit set was lower for nonirrigated and undertree-irrigated trees (none to one fruit/m of shoot length) than for trees irrigated with overtree microsprinklers (eight to nine fruit/m of shoot length). Economic analysis showed that capital costs of overtree microsprinkler systems increased annual costs of peach production by 8% to 13%, which required increased yield (or price per unit yield) of 17% to 20% before profits exceeded those of nonirrigated orchards, assuming all else equal. The estimated 1% increase in annual production costs of overtree microsprinkling compared to undertree microsprinkling appears to be justified by the increased efficacy of the overtree system.

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