Issue link: http://read.dmtmag.com/i/105709
TWELVE PRINCIPLES of frost protection overtree sprinkling requires great amounts of water, large pipelines, and big pumps." The irrigation must continue until the ice melts. A ll frost protection methods consist of using one or more of the following principles, according to USDA Agricultural Research Service irrigation specialist Dr. Robert Evans: 11. Good site selection and proper siting of buildings, windbreaks, and fences so cold air drains away 12. Mixing of the air, using wind machines or helicopters, to use heat stored in the atmosphere and to prevent stratification of cold air near the ground 13. Direct heating of the air using heaters or undertree sprinkling with water 14. Radiant heating occurs when heaters are glowing red 15. Release of the latent heat of fusion from water Pump failure The system requires application of at least 70 gallons of water per acre per minute, continuously. A failure of the pump or the water supply can lead to disaster. Trying to stretch the water supply by intermittent application is not a good idea, he said. Growers can expect to raise orchard temperatures at least 4˚F with this method if done correctly. Undertree sprinkling uses half as much water, Evans said, and produces about half the effect—raising the temperature about 2 to 4˚F, depending on the temperature inversion. Most of the increase comes from the cooling of the applied water and not from the heat released as water freezes, he said. Therefore, the warmer the water applied, the better. Applying water heated to about 110˚F—a limit imposed by the softening point of plastic water lines— would give similar results with about half the water requirement. "Research has shown that, depending on water temperatures and flow rates, applications of preheated water with flow-through boiler systems can be economical and only use about 20 percent of the fuel required for heaters for the same heat," he said. Heaters Orchard heating is an ancient method—the Romans burned prunings to heat vineyards 2,000 years ago—but it has fallen into disfavor with the rising price of fuel, the applied to the canopy by overhead or undertree sprinklers and then freezing 16. Release of the latent heat of condensation using humidification, fogs, or sprinklers 17. Radiative heat loss interception using covers or fogs to conserve heat 18. Use of heat stored in bare soil over time 19. Thermal insulation by covering with foams or greenhouses 10. Bloom delay using tree wraps, white paint, or other heat reflective methods 11. Planting cold-tolerant or late blooming varieties 12. Genetic development of cold-resistant plants need for labor to handle the 40 or so heaters needed for every acre, concerns about air pollution, and the fact they don't really add heat very effectively, Evans said. Their use has been totally banned in California and in parts of Washington State, because of air quality concerns. (Continued on page 42) Excellent Control of Mealybugs, Thrips, Grapes · Cucurbits · Vegetables · Potatoes No water condition restrictions · Liquid fertilizer · Tank mixes with fungicides and other insecticides Excellent control in grapes · Controls mealybugs, thrips, · For table, wine, and raisin grapes Innovative liquid formulation · Easily mixes into spray solutions · Increased speed of plant uptake vs. competitive products · Increased speed of translaminar movement within the leaf · Ideally suited for drip, micro sprinkler, and foliar applications Labeled for use on grapes, potatoes, cucurbits and vegetables. 800.883.1844 · www.gowanco.com Scorpion® is a registered trademarks of Gowan Company L.L.C. EPA Reg No. 10163-317 Always read and follow label directions. www.goodfruit.com GOOD FRUIT GROWER FEBRUARY 1, 2013 41