266 NEBRASKA STATE HORTICULTURAL SOCIETY. 



from frost by turning water into the irrigation ditches during 

 the night. 



SMUDGING. 



In European countries, particuhirly in France, it has long 

 been a custom to fight expected frosts bj creating a dense 

 smoke which was allowed to float over the vineyards. This 

 method of frost protection is known as smudging. A smudge 

 fire may serve a double purpose. Owing to the fact that on 

 cloudy nights radiation from the earth is so reduced as to pre- 

 vent the formation of frost, it was thought that an artificial 

 obscuration of the sky b}' means of dense smoke would be a 

 successful means of protection. 



Besides preventing the radiation at night, of the heat ab- 

 sorbed by the earth during the day, a smudge, if made of damp 

 material, may add considerable quantities of moisture to the 

 air. Such smudges are made by burning a mixture of damp 

 straw and stable manure, sacks of manure alone, bales of wet 

 straw or excelsior, the prunings from trees and vines, etc. 

 Smudges of this kind are said to be better than those made of 

 tar, crude petroleum, and other dry materials for the reason 

 that, in addition to creating a dense smoke, they add to the 

 atmosphere a considerable amount of evaporated water, 

 which, though invisible, serves to retard the radiation of the 

 heat. 



In making th(^ dry smudges for the value of the dense 

 smoke alone, the citrus fruit growers of California used burn- 

 ing coal extensively. The fuel was placed in wire baskets and 

 fired by various devices. Crude petroleum was used for the 

 same purpose. About ten years ago they discovered that by 

 using from 20 to 50 coal burners per acre enough heat could 

 be generated to actually raise the temperature in the orchard 

 from 2 to 5 degrees, which was sufficient to save the crop. 



This discovery marked the real beginning of practical or- 

 chard heating. The California growers found that to equip 

 an orchard with 50 baskets per acre represented an outlay of 



