Florida Agricultural Experiment Station


which trees fail to thrive and even cover crops cannot be grown.
Growers must realize that they cannot maintain groves in good
condition indefinitely by reliance on commercial fertilizers alone
when there is a deficiency of organic matter in the soil. Groves
kept clean cultivated continuously and merely supplied with com-
mercial fertilizers are almost certain to fail gradually and to de-
velop a number of nutritional troubles of obscure cause. When
there is at least a moderate amount of organic matter in the soil,
however, the citrus tree is not only enabled to utilize commercial
fertilizers to better advantage but benefits in many other ways.
The dominant problem in the production of quality citrus fruit
on our lighter sandy soils is supplying and conserving organic
matter.
 Fertilization:-It is well known that the kind, amount, and
 method of application of fertilizers exert a considerable influence,
 either directly or indirectly, on certain diseases of citrus trees.
 Well fed trees are more resistant to cold and to the attacks of
 such organisms as the withertip fungus, the Diplodia fungus,
 and others. On the other hand, fertilizers, together with the
 chemical make-up of the soil, have a very important influence
 on the development of mottle-leaf and chlorosis. The ready
 tendency for citrus trees to develop exanthema diebackk) or am-
 moniation of the fruit under certain often poorly understood
 conditions probably is more directly responsible than any other
 one thing for the general finicalness of Florida growers in regard
 to the composition, proportion, and use of fertilizers. The men-
 ace of this disease, through a general misunderstanding and
 lack of knowledge of the causes contributing to its development,
 has created considerable unjustifiable prejudice to the use of
 stable manure and other organic fertilizer materials in past
 years.
 The question of fertilization is further complicated by the
 great diversity of soils, soil moisture conditions, and soil re-
 actions. To further increase the complexity of this situation,
 repeated attempts are made to grow citrus trees on land utterly
 unsuited to them. As a result, the majority of Florida citrus
 growers are in a state of constant turmoil and indecision in re-
 gard to the proper fertilizer practices. Probably with no other
 fruit crop anywhere else in the world is there greater multi-
plicity of opinion relative to fertilization than with citrus in
Florida.