=146. Seeds and Seed Residues.=—The proteid matters in seeds and seed
residues, after the extraction of the oil, are highly prized as sources
of nitrogenous fertilizers either for direct application or for mixing.
Typical of this class of substances is cottonseed-meal, the residue
left after the extraction of the oil which is accomplished at the
present time mostly by hydraulic pressure. The residual cakes contain
still some oil but nearly half their weight consists of nitrogenous
compounds. The following table gives the composition of a sample of
cottonseed-meal:
Ash 7.60 per cent.
Fiber 4.90 “
Oil 10.01 “
Protein 51.12 “
Digestible carbohydrates, etc. 26.37 “
While the above shows the composition of a single sample of the meal
it should be remembered that there may be wide variations from this
standard due either to natural composition or to different degrees of
the extraction of the oil.
The composition of the ash is given below:
Phosphoric acid, P₂O₅ 31.01 per cent.
Potash, K₂O 35.50 “
Soda, Na₂O 0.57 “
Lime, CaO 5.68 “
Magnesia, MgO 15.19 “
Sulfuric acid, SO₃ 3.90 “
Insoluble, 0.69 “
Carbon dioxid and undetermined, 7.46 “
The cakes left after the expression of the oil from flaxseed and
other oily seeds are also very rich in nitrogenous matters; but these
residues are chiefly used for cattle-feeding and only the undigested
portions of them pass into the manure. Cottonseed cake-meal is not so
well suited for cattle-feeding as the others mentioned, because of the
cholin and betaïn which it contains; often in sufficient quantities
to render its use dangerous to young animals. The danger in feeding
increases as the total quantity of the two bases and also as the
relative quantity of cholin to betaïn, the former base being more
poisonous than the latter. In a sample of the mixed bases prepared in
this laboratory from cottonseed cake-meal the cholin amounted to 17.5
and the betaïn to 82.5 per cent of the whole.[125]
The nitrogen contained in these bases is also included in the total
nitrogen found in the meal. The actual proteid value of the numbers
obtained for nitrogen is therefore less than that obtained for the
whole of the nitrogen by the quantity present as nitrogenous bases.
In the United States cottonseed cake-meal is used in large quantities
as a direct fertilizer but not so extensively for mixing as some of
the other sources of nitrogen. Its delicate yellow color serves to
distinguish it at once from the other bodies used for similar purposes.
No special mention need be made of other oil-cake residues. They are
quite similar in their composition and uses, and manner of treatment
and analysis to the cottonseed product.
=147. Fish Scrap.=—Certain species of fish, such as the menhaden, are
valued more highly for their oil and refuse than for food purposes.
But even where fish in large quantities are prepared for human food,
there is a considerable quantity of waste matter which is valuable for
fertilizing purposes. The residue of fish from which the fat and oil
have been extracted, is dried and ground for fertilizing uses. The fish
scrap thus obtained is used extensively, especially on the Atlantic
border of the United States, for furnishing the nitrogenous ingredient
in mixed fertilizers, and also for direct application to the fields. In
fish flesh deprived of oil and water, the content of phosphoric acid is
about two and one-half per cent, while the proteid matter may amount to
three-quarters of the whole.[126]
The use of fish for fertilizing purposes is not new. As early as 1621
the settlers at Plymouth were taught to fertilize their maize fields by
Squanto, an Indian. According to Goode, the value of nitrogen derived
from the menhaden alone was two million dollars in 1875.[127] In 1878
it is estimated that 200,000 tons of these fish were captured between
Cape Henry and the Bay of Fundy. The use of fish scrap for nitrogenous
fertilizing has, since then, become an established industry, and the
analyst may well examine his samples for this source of nitrogen when
they are manufactured at points on the Atlantic coast, in proximity to
great fishing centers.
=148. Dried Blood and Tankage.=—The blood and débris from abattoirs
afford abundant sources of nitrogen in a form easily oxidized by the
microorganisms of the soil. Blood is prepared for use by simple drying
and grinding. The intestines, scraps, and fragments of flesh resulting
from trimming and cutting, are placed in tanks and steamed under
pressure to remove the fat. The residue is dried and ground, forming
the tankage of commerce. Dried blood is richer in proteid matter than
any other substance in common use for fertilizing purposes. When in a
perfectly dry state, it may contain as much as fourteen per cent of
nitrogen, equivalent to nearly eighty-eight per cent of proteid or
albuminoid matter. Tankage is less rich in nitrogen than dried blood,
but still contains enough to make it a highly desirable constituent of
manures. Naturally, it would vary more in its nitrogen content than
dried blood.
=149. Horn, Hoof, and Hair.=—These bodies, although quite rich in
nitrogen, are not well suited to fertilizing purposes on account
of the extreme slowness of their decomposition. Their presence,
therefore, should be regarded in the nature of a fraud, because by the
usual methods of analysis they show a high percentage of nitrogen,
and therefore acquire a fictitious value. The relative value of the
nitrogen in these bodies as compared with the more desirable forms, is
given in paragraph =5=.
=150. Ammoniacal Nitrogen.=—In ammonia compounds, nitrogen is used
chiefly for fertilizing purposes as sulfate. The ideal nitrogenous
fertilizer would be a combination of the ammoniacal and nitric nitrogen
found in ammonium nitrate. The high cost of this substance excludes its
use except for experimental purposes.
=151. Nitrogen in Guanos.=—The nitrogen in guanos may be found partly
as organic, partly as ammoniacal, and partly as nitric nitrogen. The
high manurial value of guanos and bat deposits in caves, is due not
only to their phosphoric acid, but also to the fact that part of the
nitrogen is immediately available, while a part becomes assimilable
by nitrification during the growing season. The content of nitrogen
in guanos is extremely variable, and depends largely on the climatic
conditions to which the deposit has been subjected. The state in which
it exists is also a variable one, but with a constant tendency to
assume finally the nitric condition.
The well-known habits of birds in congregating in rookeries during
the nights, and at certain seasons of the year, tend to bring into a
common receptacle the nitrogenous matters which they have gathered
and which are deposited in their excrement and in the decay of their
bodies. The feathers of birds are particularly rich in nitrogen, and
the nitrogenous content of the flesh of fowls is also high. The decay
therefore, of remains of birds, especially if it take place largely
excluded from the leaching of water, tends to accumulate vast deposits
of nitrogenous matter. If the conditions in such deposits be favorable
to the processes of nitrification, the whole of the nitrogen, or at
least the larger part of it, which has been collected in this débris,
becomes finally converted into nitric acid, and is found combined
with appropriate bases as deposits of nitrates. The nitrates of the
guano deposits, and of the deposits in caves, arise in this way. If
these deposits be subject to moderate leaching, the nitrate may become
infiltered into the surrounding soil, making it very rich in this form
of nitrogen. The beds and surrounding soils of caves are often found
highly impregnated with nitrates.
While for our purpose, deposits of nitrates only are to be considered
which are of sufficient value to bear transportation, yet much interest
attaches to the formation of nitrates in the soil even when they are
not of commercial importance.
In many soils of tropical regions not subject to heavy rainfalls, the
accumulation of these nitrates is very great. Müntz and Marcano[128]
have investigated many of these soils, to which attention was called
first by Humboldt and Boussingault. They state that these soils are
incomparably more rich in nitrates than the most fertile soils of
Europe. The samples which they examined were collected from different
parts of Venezuela and from the valleys of the Orinoco, as well as on
the shore of the Sea of Antilles. The nitrated soils are very abundant
in this region of South America, where they cover large surfaces. Their
composition is variable, but in all of them calcium carbonate and
phosphate are met with, and organic nitrogenous material. The nitric
acid is found always combined with lime. In some of the soils as high
as thirty per cent of calcium nitrate have been found. Nitrification
of organic material takes place very rapidly the year round in this
tropical region. These nitrated soils are everywhere abundant around
caves, as described by Humboldt, which serve as the refuge of birds and
bats. The nitrogenous matters, which come from the decay of the remains
of these animals, form true deposits of guano, which are gradually
spread around, and which, in contact with the limestone and with access
of air, suffer complete nitrification with the fixation of the nitric
acid by the lime.
Large quantities of this guano are also due to the débris of insects,
fragments of elytra, scales of the wings of butterflies, etc., which
are brought together in those places by the millions of cubic meters.
The nitrification, which takes place in these deposits, has been found
to extend its products to a distance of several kilometers through the
soil. In some places the quantity of calcium nitrate is so great in the
soils that they are converted into a plastic paste by this deliquescent
salt.
=152. Nitric Nitrogen.=—In its purer forms, and suited to manurial
purposes, nitric acid exists in combination with sodium as a compound
commonly known as Chile saltpeter.
The existence of these nitrate deposits has long been known.[129] The
old Indian laws originally prohibited the collection of the salt, but
nevertheless it was secretly collected and sold. Up to the year 1821,
soda saltpeter was not known in Europe except as a laboratory product.
About this time the naturalist, Mariano de Rivero, found on the Pacific
coast, in the Province of Tarapacà, immense new deposits of the salt.
Later the salt was found in equal abundance in the Territory of
Antofagasta, and further to the south in the desert of Atacama, which
forms the Department of Taltal.
At the present time the collection and export of saltpeter from Chile
is a business of great importance. The largest export which has ever
taken place in one year was in 1890, when the amount exported was
927,290,430 kilograms; of this quantity 642,506,985 kilograms were
sent to England and 86,124,870 kilograms to the United States. Since
that time the imports of this salt into the United States have largely
increased.
According to Pissis[130] these deposits are of very ancient origin.
This geologist is of the opinion that the nitrate deposits are the
result of the decomposition of feldspathic rocks, the bases thus
produced gradually becoming united with the nitric acid provided from
the air.
According to the theory of Nöllner[131] the deposits are of more modern
origin, and due to the decomposition of marine vegetation. Continuous
solution of soils beneath the sea gives rise to the formation of great
lakes of saturated water, in which occurs the development of much
marine vegetation. On the evaporation of this water, due to geologic
isolation, the decomposition of nitrogenous organic matter causes
generation of nitric acid, which, coming in contact with the calcareous
rocks, attacks them, forming calcium nitrate, which, in presence of
sodium sulfate, gives rise to a double decomposition into sodium
nitrate and calcium sulfate.
The fact that iodin is found in greater or less quantity in Chile
saltpeter is one of the chief supports of this hypothesis of marine
origin, inasmuch as iodin is always found in sea plants, and not
in terrestrial plants. Further than this, it must be taken into
consideration that these deposits of sodium nitrate contain neither
shells nor fossils, nor do they contain any calcium phosphate. The
theory, therefore, that they are due to animal origin is scarcely
tenable.
Lately extensive nitrate deposits have been discovered in the U.
S. of Columbia.[132] These deposits have been found extending over
thirty square miles and vary in thickness from one to ten feet. The
visible supply is estimated at 7,372,800,000 tons, containing from
1.0 to 13.5 percent of nitrate. The deposits consist of a mixture of
sodium nitrate, sodium chlorid, calcium sulfate, aluminum sulfate, and
insoluble silica. It is thought that the amount of these deposits will
almost equal those in Chile and Peru.