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Pomological Paragraphs 



Recently it was suggested that we add to the fertilizer table for 

 blueberries another column giving costs. This would be a good idea if the 

 value of fertilizer could be judged by cost alone. Of course, it can't. 

 There is a quality factor which is more important than actual price per 

 ton. The cost per unit of nitrogen or phosphorus, or potash, or a combin- 

 ation of these, is more important than the cost per ton. In general, high 

 analysis fertilizers are the least expensive per unit. It is good business 

 to buy fertility as cheaply as possible. Buying the cheapest fertilizer 

 may not yield the c heapest fertility . 



---J. S. Bailey 



I I I I I I I I I I I I I I I I 



PREVENTING FROST DAMAGE TO STRAWBERRIES 



Late spring frosts have caused considerable damage to strawberry crops in a 

 single night. Growers that irrigate for frost protection report that irrigation 

 means the difference between a good strawberry crop and a near failure. 



Frosts generally occur when the earth and surrounding objects reach the 

 temperature of 32° F. or lower. Frosts are usually accompanied by deposition of 

 ice crystals, but temperatures below 32° may occur without formation of ice 

 crystals. 



The principle by which water is able to prevent frost injury is based on the 

 latent heat which is released when water is changed to ice. Some heat is re- 

 leased as water is cooled to 32° F., but the main effect is produced when water 

 is changed to ice. When 1,000 gallons of water is changed to ice as much 

 heat is released as when 800 gallons of boiling water is cooled to 32° F. The 

 temperature of any object remains near 32° F. as long as water is freezing on 

 it. VJhen an irrigation system is used for frost protection, water is con- 

 tinuously sprayed on the plants and soil. As the water starts to freeze on 

 the plants, it gives off heat to the strawberry plant leaves and blossoms 

 and to the air and soil. Unless the air temperature is very low or the heat 

 is rapidly removed by a cold wind, the head absorbed by the plants is 

 sufficient to keep the temperature above freezing. The water should be 

 applied before the air temperature reaches 32° and continuously as long as 

 the air temperature remains below freezing. If sprinkling stops before 

 thawing takes place, the temperature of the wet strawberry blossoms drops 

 rapidly and they will be killed. 



A Massachusetts grovjer reports that irrigation gave complete protection 

 of strawberry plants in 1956 when air temperature dropped to 22 degrees. Reports 

 from other states indicates that growers have been able to protect strawberry 

 plants against temperature as low as 12 degrees. 



It was reported in the 84th Annual Report of the State Horticultural 

 Society of Michigan that some Michigan strawberry growers assume that the 

 start of ice crystals is the time to start applying water and that these 



