IN THE CITRUS INDUSTRY 29 



exact science. Each grower has his own ideas on the sub- 

 ject, and they rarely coincide with the views of other 

 growers. Commercial fertilizer is extensively used ; in fact, 

 with the exception of citrus plantations in Florida it is 

 applied more heavily than in any other fruit raising indus- 

 try. Applications are made twice a year, in the fall and 

 spring. One widely followed practice is to give each tree 

 as many pounds of fertilizer annually as the number of 

 years during which the tree has been planted. Thus a 

 twelve year old tree would receive twelve pounds of fer- 

 tilizer. But the condition of the trees and the character 

 of the soil in different groves are so varied that no general 

 rule of fertilization can be stated. The three essentials of 

 suitable fertilizer for citrus trees are nitrogen, phosphoric 

 acid and ptotash, but the proper quantities of each of these 

 elements to apply in order to secure maximum results can 

 be determined only by prolonged and careful experimenta- 

 tion on each grove. Where available, large quantities of 

 barnyard manure are also used, partly for the sake of the 

 chemical elements mentioned above, partly to add humus 

 to the soil. It is applied more or less throughout the entire 

 course of the year. 



Citrus growers probably have more enemies to overcome 

 than any other type of farmer. They must wage incessant 

 warfare against insects and fungous pests, guard against 

 various kinds of mechanic?! injury to the trees and fruit, 

 and strive to minimize troubles attributable directly to nat- 

 ural phenomena, such as sunburn, frost, premature drop- 

 ping, dropping caused by wind, splitting, puffing, or, with 

 Valencias, turning green after once having become yellow. 

 All of these vexations are receiving constant study by in- 

 dividual growers, by the United States Department of Agri- 

 culture and by the Citrus Experiment Station of the State 

 University. Some of the problems are well in hand, others 



