=1. Introduction.=—In the first volume the principal plant foods
occurring in soils have been named and the methods of estimating them
described. As fertilizers are classed those materials which are added
to soils to supply supposed deficiencies in plant foods, or to render
more available the stores already present. There is little difference
between the terms fertilizer and manure. In common language the former
is applied to goods prepared for the farmer by the manufacturer or
mixer, while the latter is applied to the stores accumulated about the
stables or made elsewhere on the farm. Thus it is common to speak of a
barnyard or stall manure and of a commercial fertilizer.
One of the objects of the analysis of soils, as described in the first
volume of this work, is to determine the character of the fertilizer
which should be added to a field in order to secure its maximum
fertility.
One purpose of the present part is to determine the fitness of offered
fertilizing material to supply the deficiencies which may be revealed
by a proper study of the needs of the soil.
=2. Natural Fertilizers.=—In the succession of geologic epochs which
has marked the natural history of the earth there have been brought
together in deposits of greater or less magnitude the stores of
plant food unused by growing crops or which may once have been part
of vegetable and animal organisms. Some of these deposits have been
mentioned in the first volume, paragraphs =11, 12=, and =18=.
For a full description of the extent and origin of these deposits the
reader is referred to works on economic geology. These deposits are
the chief sources of the commercial fertilizers which are offered to
the farmers of to-day and to which the agricultural analyst is called
upon to devote much of his time and labor. The methods of determining
the chemical composition and agricultural value of these deposits, as
practiced by the leading chemists of this country and Europe, will be
fully set forth in the following pages.
=3. Waste Matters as Fertilizing Materials.=—In addition to the natural
products just mentioned the analyst will be called on also to deal with
a great variety of waste materials which, in the last few years, have
been saved from the débris of factories and abattoirs, and prepared for
use on the farm. Among these waste matters may be mentioned, bones,
horns, hoofs, hair, tankage, dried blood, fish scrap, oil cakes, ashes,
sewage, and sewage precipitates, offal of all kinds, leather scraps,
and organic débris in general.
It is important, before beginning an analysis, to know the origin of
the substances to be determined. As has already been pointed out in
volume first the process which would be accurate with a substance of
a mineral origin might lead to error if applied to the same element
in organic combination. This is particularly true of phosphorus and
potash. A simple microscopic examination will usually enable the
analyst to determine the nature of the sample. In this manner, in the
case of a phosphate, it would at once be determined whether it was
bone, mineral, or basic slag. The odor, color, and general consistence
will also aid in the determination.
=4. Valuation of Fertilizing Ingredients.=—Perhaps there are no more
numerous and perplexing questions propounded to the analyst than those
which relate to the value of fertilizing materials. There is none
harder to answer. As a rule these questions are asked by the farmer,
and refer to the fertilizers put down on his fields. In such cases
the cost of transportation is an important factor in the answer. The
farther the farmer is removed from the place of fertilizer manufacture
the greater, as a rule, will be the cost. Whether the transportation is
over land or by water also plays an important part in the final cost.
The discovery of new stores of fertilizing materials has also much to
do with the price. This fact is especially noticeable in this country,
where the price of crude phosphates at the mines has fallen in a few
years from nearly six dollars to three dollars and forty-three cents
per ton[1]. This decrease has been largely due to discoveries of vast
beds of phosphatic deposits in Florida, North Carolina, Tennessee, and
Virginia. The state of trade, magnitude of crops, and the vigor of
commerce also affect, in a marked degree, the cost of the raw materials
of commercial fertilizers.
=5. Trade Values of Fertilizing Ingredients in Raw Materials and
Chemicals.=—The values proposed by the Massachusetts Experiment Station
are given below.[2]
Cents per
pound.
Nitrogen in ammonia salts, 19
“ “ nitrates, 14½
Organic nitrogen in dry and fine-ground fish, meat, blood,
and in high-grade mixed fertilizers, 18½
“ “ “ cottonseed meal, linseed meal, and
castor pomace, 15
“ “ “ fine-ground bone and tankage, 16½
“ “ “ fine-ground medium bone and tankage, 15
“ “ “ medium bone and tankage, 12
“ “ “ coarse bone and tankage, 7
“ “ “ hair, horn shavings, and coarse
fish scraps, 7
Phosphoric acid soluble in water, 6
“ “ soluble in ammonium citrate, 5½
“ “ in fine bone and tankage, 5½
“ “ in fine medium bone and tankage, 4½
“ “ in medium bone and tankage, 3
“ “ in coarse bone and tankage, 2
“ “ in fine-ground fish, cottonseed meal,
linseed meal, castor pomace, and wood-ashes, 5
“ “ insoluble (in ammonium citrate) in
mixed fertilizers, 2
Potash as high-grade sulfate, and in mixtures free from
muriate, 5
“ “ muriate, 4½
The manurial constituents contained in feed stuffs are
valued as follows:
Organic nitrogen, 15
Phosphoric acid, 5
Potash, 5
The organic nitrogen in superphosphates, special manures, and mixed
fertilizers of a high grade is usually valued at the highest figures
laid down in the trade values of fertilizing ingredients in raw
materials; namely, eighteen and one-half cents per pound, it being
assumed that the organic nitrogen is derived from the best sources;
_viz._, animal matter, as meat, blood, bones, or other equally good
forms, and not from leather, shoddy, hair, or any low-priced, inferior
form of vegetable matter, unless the contrary is evident. In such
materials the insoluble phosphoric acid is valued at two cents a pound.
These values change as the markets vary.
The scheme of valuation prepared by the Massachusetts station does not
include phosphoric acid in basic slags. By many experimenters the value
of the acid in this combination, tetracalcium phosphate, is fully equal
to that in superphosphates soluble in water and ammonium citrate. It
would perhaps be safe to assign that value to all the phosphoric acid
in basic slags soluble in a five per cent citric acid solution.
Untreated fine-ground phosphates, especially of the soft variety, so
abundant in many parts of Florida, have also a high manurial value when
applied to soils of an acid nature or rich in humus. On other soils
of a sandy nature, or rich in calcium carbonate, such a fertilizer
would have little value. The analyst in giving an opinion respecting
the commercial value of a fertilizer, must be guided not only by the
source of the material, its fineness or state of decomposition, and its
general physical qualities, but also by the nature of the crop which it
is to nourish and the kind of soil to which it is to be applied.