274 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



enough oil was retained in the former to allow for relighting them in 

 case of a sudden drop in temperature. 



It was found difficult by many growers to get the right kind of 

 labor and to get the help when needed. The use of larger pots will 

 reduce the amount of night labor needed, and the small ranch of ten 

 acres ought to be handled successfully by two men, if they are vigilant 

 and if their methods are correct. 



Temperature at Which to Fire. The experiences of the past have 

 shown that one of the most necessary precautions to take is to begin 

 heating soon enough. There is general agreement that it is easier to 

 hold a temperature than to raise it after it has gone too low. For 

 this reason some of those who have had most experience in heating 

 are planning to begin lighting for lemons at 31 degrees. With oranges 

 a degree or two lower than this may be risked before beginning 

 operations.* 



It has also proved of advantage to bank extra pots outside of the 

 grove along the windward side. Not only is this necessary in order 

 to protect the outside rows but it makes it much easier to hold the 

 temperature within the orchard. 



Value of Combined Effort. Where large blocks of groves were 

 heated the task of heating was easier than when the heated areas were 

 small and isolated. The effects from the heating on a large acreage 

 were often noticeable at a considerable distance from the groves where 

 the firing was being done. In one section the heating of one hundred 

 acres produced a rise in temperature of from 2 to 3 degrees in groves 

 a mile distant as soon as the smoke reached these groves. The co- 

 operation of growers in the vicinity of Pomona forms a notable ex- 

 ample of the benefit of such combined effort. The co-operation can 

 profitably extend to the employment of special observers, maintenance 

 of special danger calls, employment of labor, purchase and storage of 

 supplies, and the like. 



Causes of Failure. The principal causes of failure in the heating 

 done in 1913 may be briefly stated as follows : 



1. The use of pots which were too small. These burned out quickly 

 and were difficult to refill. 



2. Insufficient number of pots per acre. 



3. Shortage of fuel. 



4. The use of fuel which did not give off enough heat. 



5. Allowing temperatures to go too low before lighting. 



* See article by J. G. McBeth and J. E. Allison, California Citroffraph, Jan., 

 1919, p. 51. 



