170 



1916 ANNUAL REPORT 



has been generally adopted for citrus. Broadly speaking the application 

 of commercial fertilizers deriving their elements of plant food from 

 wholly chemical sources has not proven successful. In many instances, 

 through lack of more difinite information, growers have given their 

 avocados the same fertilizers which they have used on their citrus trees. 

 Where the formulae have been those most frequently applied to citrus, 

 with nitrogen derived from sulphate of ammonia or nitrate of soda, 

 potash from sulphate of potash, and phosphoric acid from acid phosphate, 

 the results with the avocado have been generally unsatisfactory. How- 

 ever, when the formula used has been of the tji)e known as "young tree" 

 fertilizer, carrying a proportionately higher percentage of ammonia, 

 largely derived from organic sources, better effects have been obtained. 



Many isolated avocado trees are to be found throughout the Southern 

 part of Florida, chance seedlings usually of unknown origin, and it has 

 been commonly observed that such of these trees as are located in the 

 vicinity of cow pens, chicken yards or where kitchen slops are thrown 

 out, are almost invariably lusty growers and heavy bearers. This has 

 given ground for the theory that the avocado is partial to a food supply 

 derived from organic sources and chance applications of such fertilizers as 

 cottonseed meal, tankage or stable manure have borne out the same idea. 



During the past few years the wi'iter has done more or less experi- 

 mental work in an effort to arrive at formulae best suited to the avocado 

 and also to determine the frequency and approximate seasons of the year 

 at which to apply the fertilizers. Along these lines several problems must 

 be solved and the probabilities are the same solutions will not fit the 

 West Indian, Guatemalan and Mexican types equally well. 



Avocado trees of the West Indian types, when in good condition of 

 grovirth, are prone to put on a tremendous bloom from which a setting of 

 fruit is apt to result so heavy as to be entirely beyond the carrjang 

 capacity of the tree. Following this abnormal effort there is often a 

 period of apparent exhaustion during which the tree seems to realize that 

 it has "bitten off more than it can chew", and to be seeking the best 

 method to recoup from its over exertion. This is a critical time in the 

 life history of the tree and calls for intelligent handling on the part 

 of the grower. If left to its own devices the tree will endeavor to carry 

 the over crop, draining upon its reserves until its vitality has been 

 seriously impaired. Evidences of this condition are usually very apparent. 

 The tree drops a large portion of its leaves, the younger branches change 

 in color from a dark green to a saffron yellow and no new gro-^^i^h is put 

 on. Lack of sufficient foliage to provide proper shade often results in 

 serious sun-burning of the more tender branches, and the low state of 

 vitality lays the tree particularly liable to the inroads of disease, especially 

 the anthracnose fungus which seldom loses such an opportunity for mak- 

 ing an attack. Finally the tree is compelled to drop practically its entire 

 crop of fruit and is left in a condition which means, at the very best, a 

 set-back of two seasons in its development and not infrequently results in 

 its actual death. 



To obviate overblooming, particularly in the case of young trees, is 

 very difficult, for the better the cultural condition of the tree, the more 



