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Show Conditions Must Be Right To Assure Good Fruit Crop Like bears in hibernation, fruit trees must get their winter rest, afterwards they must accumulate a specific amount of solar energy. Both are necessary to develop the buds and blossoms. If both of these happen before the last killing frost in the springs, POWI Much, if not all of the fruit crop is lost! That's the way nature works. But engineers, climatologists, and plant scientists with the Agricultural Experiment Station at Utah State University have found a way to thwart nature and greatly reduce the chances of spring frost damage to the fruit crop. When enough "chill units" have accumulated for the trees to complete their winter's slumber, the researchers apply evaporative cooling using an overhead sprinkler. This prevents or slows down the radiant energy from the sun accumulating in the trees as it does naturally whenever the temperature rises above about 45 degrees F. Simple? Not quite. It takes a lot of climatological data fed into computers to tell when the rest period has been completed in the various kinds and varieties of fruit. Also, it takes some knowledgable engineering to get effective, efficient cooling of the trees at the right time using overhead sprinkling. The ideal, they say, is a sprinkling system that will turn on automatically when the temperature rises above 45 degrees, will spray intermittently with just enough water to wet all the branches and buds, continue the evaporation, and will shut off and drain automatically when temperatures fall below 45 degrees to prevent freezing of the system. Under controlled research conditions, 27 days of bloom delay has been achieved. Regular overhead sprinkling irrigation systems have been adapted and used in some commercial orchard situations to achieve two weeks delay. A longer delay could be obtained by making sure to start early ' enough, as soon as temperatures start going above 45 degrees, and then sprinkle whenever the temperature is above that point, day or night. Of course you don't want to delay blossoming too long or your crop won't mature. How much delay you want in your fruit trees depends on the risk you are willing to take with that last killing frost. This concept affecting the temperature of the trees to alter development, is receiving notice worldwide. USU plant scientists have been invited to Europe to explain it there in international meetings. The research team members are being asked to explain the details of it at various meetings and research stations in the U.S. and Canada. Most interesting, the USU researchers have even been engaged to help set up a research project on peaches in Florida. Only there the problem is not frost, it's insufficient winter rest. The aim is to hold the tree temperature down through evaporative cooling so the trees will get a long enough period of winter rest, accumulating the necessary number of "chill units" to break dormancy. Through this modification of the trees, natural slumber patterns, they expect to be able to produce some of the sweeter, more desirable varieties that presently will not bear fruit in that climate. By engineering to control the effects of weather in these ways, USU scientists are adding to the world's ability to produce fruit and other foods to meet the needs of today and the future. |