Florida Agricultural Experiment Station


may be located near the brow of the slope, and in other cases,
near the base; whereas the trees on the higher and more nearly
level ground will be wholly unaffected.
 DIEBACK AND FERTILIZERS
 Perhaps most of the cases of dieback, which have been classed
as acute, can be attributed to the effect of ammonia fertilizers
added to the soil. The use of excessive quantities of ammonia
from organic sources often leads to the development of dieback.


FIG. 9.-Dieback marked, or ammoniated grapefruit


The amounts of these which will prove excessive vary consider-
ably and are dependent on soil conditions and the kind of citrus
tree. These sources can be used much more freely upon clay soils
than upon the sandy soils. They can be used much more freely
upon the dry sandy soil lacking in humus than upon the low
moist soil well supplied with organic matter. In fact, their use
should be avoided almost entirely upon the latter class of soils.
 Citrus trees differ in their fertilizer requirements. Grape-
fruit and tangerine trees are heavier feeders than orange trees.
The quantities of ammonia from organic sources which can be