PRESS BULLETIN 138
Florida Agricullural Experimeni Slallon
FERTILIZING CONSTITUENTS REMOVED IN AN ORANGE CROP
By S. E. Collison
In order that we may fertilize intelligently we should know the amounts
of the fertilizing elements which are removed from our soils in the fruit
we send away. A further knowledge of the nature and behavior of our
soils is required to guide us in this respect. Finally we should make due
allowance for the plant food that is lost through leaching.
Fertilizing Constituents in an Average Orange Crop
We find that in an average crop of 300 boxes of 80 pounds each, per
acre, there are removed from the soil 34.4 pounds of ammonia (equal to
28.3 pounds of nitrogen), 12.7 pounds of phosphoric acid, and 70.3 pounds
This loss could just be supplied by 138 pounds of sulphate of ammonia
(analyzing 25 per cent.), 79.5 pounds of acid phosphate (analyzing 16 per
cent.), and 143.5 pounds of high-grade sulphate of potash (analyzing 49
Other Losses of Fertilizing Ingredients
The fertilizing constituents removed in the fruit do not represent the
total loss of plant food from the soil. We must take into consideration two
other sources of loss: the. material used in the production of new wood,
leaves, and roots; and that lost from the soil by leaching.
The following are the numbers of pounds of ammonia, phosphoric acid,
and potash, in 1000 pounds of leaves and 1000 pounds of wood. In the
leaves are 8.5 pounds of ammonia, 1 pound of phosphoric acid, and 4 pounds
of potash; in the wood there are 8.5 pounds of ammonia, 5 pounds of phos-
phoric acid, and 7 pounds of potash. As may be seen, the tree draws
most heavily upon the ammonia and potash. However after the tree reaches
maturity the loss of plant food from the soil due to formation of leaves
and wood would be relatively small.
The loss by leaching falls most heavily on the ammonia, and is greatest
when applications of nitrate of soda are followed by heavy rains. In open
sandy soils the loss of phosphoric acid and potash must also be considerable.
January 15, 1910
Should we have a continuous heavy rainfall-say 4 to 6 inches-soon after
fertilizers have been applied, much more of the plant food would be leached
out, and carried beyond the reach of the roots, than if this same amount
of rain had been distributed over a period-of several weeks. On groves
where we have a cover crop established during the rainy season, the loss
would not be so great as it would where clean culture is the rule; since the
network of roots would tend to check the downward movement of the
It is impossible to form an accurate estimate of the loss from the last
two causes; but that more or less loss is sustained is evident, and it must
be taken into consideration when we decide upon the quantity of fertilizers
to be applied. Nn doubt in many cases this loss could be reduced without
harm to the crop by a judicious use of more humus-forming materials, and
thus the cost of fertilizing would be lessened.
Comparison With Cotton
An average crop of cotton consisting of 300 pounds of lint and 654
Pounds of seed per acre would remove from the soil 25.3 pounds of am-
monia, 6.8 pounds of phosphoric acid, and 9.9 pounds of potash. Nearly
all this is in the cotton seeds, there being only 3.3 pounds of fertilizing in-
gredients in 300 pounds of lint. It is assumed that the body of the plant is
returned to the soil. It is apparent that the orange crop draws much more
Heavily upon the soil than does the cotton crop.
Analyses of Oranges
Analyses of eleven varieties of Florida oranges show that every 10
boxes, of 80. pounds each, contain 1.2 pounds of ammonia, (equal to .96
pounds of nitrogen),.4 pounds of phosphoric acid, and 2.32 pounds of potash.
With these figures at hand it is easy for us to calculate the amount of
fertilizing constituents removed per acre in a crop of any size.
State papers please copy.