PRESS BULLETIN No. 73. November 25, 1907.
Florida AgPicullural Experiment Stlalon.
SOME SOURCES OF NITROGEN.
(a) TWO ORGANIC FORMS.
(b) TWO INORGANIC FORMS.
BY A. W. BLAIR.
Nitrogen is the most expensive of the fertilizing materials, and for this
reason especial care should be exercised in purchasing materials contain-
ing this element.
(a) COTTON SEED MEAL AND DRIED BLOOD.
Two organic forms very much used in Florida are cotton-seed meal and
dried blood. If we judge cotton-seed meal solely by its nitrogen content
(about 6.6 per cent, on the average for bright meal), its present high price
would place it at a great disadvantage when compared with such materials
as nitrate of soda and sulphate of ammonia. It should be remembered, how-
ever, that the meal contains also some phosphoric acid and potash. Jenkins
and Street (Cotton-seed Meal as a Fertilizer. Conn. Expt. Sta. Bulletin No.
156), have pointed out that the average of 349 samples showed 2.97 per cent.
phosphoric acid, and 1.90 per cent. potash. Now, if we accept 20 cents a pound
as the price of nitrogen, 5 cents for phosphoric acid, and 5 cents for potash,
then for a ton of cotton-seed meal analyzing 6.6 per cent. nitrogen, 2.97 per
cent. phosphoric acid, and 1.90 per cent. potash, the calculated value would
be as follows:
Nitrogen ...................................... .. .. $26.40
Phosphoric Acid ......... r........................... 2.97
'Potash .......................... ................. 1.90
Total ................................... ......... $31.27
Bright cotton-seed meal is now quoted on this market at $31.60, and it
will thus be seen that the calculated and market price are practically the
same. If we assign the same value to the nitrogen in nitrate of soda,
namely, 20 cents per pound, then nitrate of soda analyzing 15 per cent.
nitrogen would be worth $60.00 per ton. Nitrate of soda is quoted on this
market at $59.60 per ton, so that We see here again the prices as calculated
and as quoted, running very close together. Thus it would appear that
when we take into consideration all the plant food elements, cotton-seed
meal is but little, if any, more expensive, proportionately, than nitrate of
soda. Should we adopt some other figure as the price of nitrogen, 17c for
example, tie same relationship would hold true, that is, the ratio of the cal-
culated to the market price of cotton-seed meal would be practically the
same as the ratio of the calculated to the market price of nitrate of soda.
It may be noted that the fertilizing elements in cotton-seed meal become
available rather slowly, and on this account are not lost by leaching to such
an extent as nitrate of soda or sulphate of ammonia would be. Hence,
for crops that remain in the ground over long periods of time, as the pine.
apple, citrus, and other trees, this form of nitrogen would seem especially
Dried Blood is considered one of the best sources of organic nitrogen.
It contains from 13 to 14 per cent. of nitrogen, and decays rapidly when
placed in the ground. Organic materials, such as cotton-seed meal and
dried blood, must undergo, in the soil, natural processes known as nitrifi-
cation, before their nitrogen can be assimilated by the plant. These nitri-
fication processes are dependent upon minute organisms known as nitrify-
ing bacteria, and these in turn require a certain degree of warmth and
moisture. Fortunately for the farmer, these organisms are almost univer-
sally present in soils that have been properly cultivated and drained. This
fact is well illustrated by the rapid disappearance of animal excreta or
meat scraps after being buried in good soil. Nitrification does not take
place so rapidly at the surface as it does a few inches beneath the surface;
and furthermore, the loss of nitrogen by escape of ammonia into the air
will be greater if these changes take place at the surface. Hence the import-
ance of placing organic fertilizers slightly beneath the surface of the soil.
(b) NITRATE OF SODA, AND SULPHATE OF AMMONIA.
Nitrate of Soda is very soluble in water, and when thus dissolved, can
be taken up by the plant directly without further change. The ease with
which this material dissolves, makes it an expensive source of nitrogen to
use during rainy periods. For use during periods of drought, and for quick-
growing crops, it is especially adapted. It contains about 15 per cent. of
Sulphate of Ammonia contains about 19 to 22 per cent. of nitrogen, and
is also readily soluble in water. Much of it, however, is probably not taken
up by the plant until it is converted, by bacterial action, into the' form of
nitrate. It is regarded by some as unsuited to soils having an acid tend-
ency. It should not be used directly with lime, as in this case the lime
would be likely to liberate ammonia. Lime does not, however, have this ef-
fect upon nitrate of soda.
State papers please copy.