ORCHARD HEATING 43 



with labor, etc., because if labor is hired and oil is burned the 

 crop must be saved to pay for these. Unless the horticultural 

 business is on a prosperous basis and a thorough preparation is 

 made and carried out orchard heating will not be profitable. 



SUMMARY 



1. Approximately one-fifth, or twenty per cent, of the fruit 

 on Utah farms is destroyed and considerable damage is done to 

 general farm crops by frosts. 



2. In the case of fruit, elimination of this waste has been 

 attempted by delaying the time of flowering until the danger 

 of frost was over, by soil treatments such as irrigating", sand- 

 ing, and cultivating, by smudging with smoke, water vapor, and 

 carbon dioxide, or by covering the plants or trees with cloth or 

 straw. The most important method is by applying heat and 

 smudge simultaneously through burning coal or oil in the 

 orchard. 



3. Professor Cox olf the U. S. Weather Bureau has shown 

 that by decreasing the heat capacity of the cranberry bogs of 

 Wisconsin through draining, sanding and cultivating, the mini- 

 mum temperature of the air directly above the ground was 7o F. 

 higher than that over the untreated bogs. This difference in 

 temperature disappeared at a height of three feet above the 

 ground. Many farmers report the successful protection of crops, 

 such as alfalfa and even fruit, by irrigating during the night of 

 the 'frost. 



4. Frost usually occurs on clear nights because of the absence 

 of a cloud blanket, which blanket prevents the upward escape of 

 heat. Smud|g;es are to supply an artificial cloud or blanket of 

 gas or smoke which is not transparent but rather absorbs well 

 the heat and prevents its upward escape. Carbon dioxide, water 

 vapor, and unburned carbon (which are the products of ordinary 

 combustion), ammonia, gaseous hydrocarbons, dust, and smoke 

 are the best materials for smudge because their diathermancy is 

 small. 



5. Ninety-six pounds of carbon dioxide were liberated dur- 

 ing the night on an acre in an hour and one-half. The treated 

 area cooled just as fast as the adjoining untreated area. 



6. An area of ten by fifty feet surrounded by brick walls 

 with no roof was supplied with carbon dioxide as fast as it would 

 run out olf a tank, the neck of which was kept warm with hot 



