These divided themselves into: (a) Natural nitrogenous manures; (b)
imported or manufactured manures.
a. NATURAL NITROGENOUS MANURES
Under this heading come--farm-yard manure; seaweed; refuse cakes and
meals; wool dust and shoddy; hoofs and horns; blood; soot; sewage
sludge.
_Farm-yard Manure._--This is the most important, as well as the most
generally used, of all natural manures. It consists of the solid and
liquid excreta of animals that are fed at the homestead, together with
the material used as litter. The composition of farm-yard manure will
vary greatly according to the conditions under which it is produced.
The principal determining factors are (1) the nature and age of the
animals producing it, (2) the food that is given them, (3) the kind
and quantity of litter used, (4) whether it be made in feeding-boxes,
covered yards or open yards, (5) the length of time and the way in
which it has been stored. The following analysis represents the
general composition of well-made farm-yard manure, in which the litter
used is straw:--
Water 75.42
*Organic matter 16.52
Oxide of iron and alumina .36
Lime 2.28
Magnesia .14
Potash .48
Soda .08
**Phosphoric acid .44
Sulphuric acid .12
Chlorine .02
Carbonic acid, &c. 1.38
Silica 2.76
------
100.00
------
* Containing nitrogen = .59%,
which is equal to ammonia .72%
** Equal to phosphate of lime .96
Put broadly, farm-yard manure will contain from 65 to 80% of water,
from .45 to .65% of nitrogen, from .4 to .8% of potash, and from .2 to
.5% of phosphoric acid.
This analysis shows that farm-yard manure contains all the
constituents, without exception, which are required by cultivated
crops in order to bring them to perfection, and hence it may be called
a "perfect" manure. Dung, it may be observed, contains a great variety
of organic and inorganic compounds of various degrees of solubility,
and this complexity of composition--difficult, if not impossible, to
imitate by art--is one of the circumstances which render farm-yard
manure a perfect as well as a universal manure.
The excrements of different kinds of animals vary in composition, and
those of the same animal will vary according to the nature and
quantity of the food given, the age of the animal, and the way it is
generally treated. Thus, a young animal which is growing, needs food
to produce bone and muscle, and voids poorer dung than one which is
fully grown and only has to keep up its condition. Similarly, a
milking-cow will produce poorer dung than a fattening bullock. Again,
cake-feeding will produce a richer manure than feeding without cake.
Straw is the most general litter used, but peat-moss litter, sawdust,
&c., may be used, and they will affect the quality of the manure to
some extent. Peat-moss is the best absorbent and has a higher manurial
value than straw. Box-fed manure, and that made in covered yards will
suffer much less loss than that made in an open yard. Lastly, manure
kept in a heap covered with earth will be much richer than that left
in an uncovered heap. The solid and liquid excrements differ much in
composition, for, while the former contain principally phosphoric
acid, lime, magnesia, and silica and comparatively little nitrogen,
the urine is almost destitute of phosphoric acid, and abounds in
alkaline salts (including salts of potash) and in nitrogenous organic
matters, among which are urea and uric acid, and which on
decomposition yield ammonia. Unless, therefore, the two kinds of
excrements are mixed, a perfect manure supplying all the needs of the
plant is not obtained; care must accordingly be taken to absorb all
the urine by the litter. Farm-yard manure, it is well known, is much
affected by the length of time and the way in which it has been kept.
Fresh dung is soluble in water only to a limited extent, and, in
consequence, it acts more slowly on vegetation, and the action lasts
longer than when dung is used which has been kept some time; fresh
dung is therefore generally used in autumn or winter, and thoroughly
rotten dung in spring, when an immediate forcing effect is required.
The changes which farm-yard manure undergoes on keeping, have been
made the subject of much inquiry. In Germany, Maercker and
Schneidewind; in France, Muntz and Girard; and in England, Voelcker,
Wood, Russell and others, have investigated these losses, coming to
very similar conclusions concerning them. Perhaps the most complete
set of experiments is one conducted at the Woburn experimental station
and extending over three years (1899-1901). The dung was cake-fed
manure made in feeding-boxes from which no drainage issued, and, after
removal, it was kept in a heap, covered with earth. Hence it was made
under as good conditions as possible; but, even then, the
losses--after deduction for live-weight increase of the animals--were
found to be 15% of the total nitrogen of the food, during the making,
and 34% (or a further 19%) during storing and by the time the manure
came to be put on the land. Accordingly, under ordinary farm
conditions it is quite clear that only about 50% of the nitrogen of
the food given is recovered in the dung that goes on the land. This is
the figure which Lawes and Gilbert suggested in the practical
application of their Tables of Compensation for Unexhausted Manure
Value.
During the fermentation of dung a large proportion of the
non-nitrogenous organic matters disappear in the forms of carbonic
acid and water, while another portion is converted into humic acids
which fix the ammonia gradually produced from the nitrogenous
constituents of the solid and liquid excreta. The mineral matters
remain behind entirely in the rotten dung, if care be taken to prevent
loss by drainage. For proper decomposition, both air and moisture are
requisite, while extreme dryness or too much water will arrest the due
fermentation of the mass.
Well-fermented dung is more concentrated and consequently more
efficacious than fresh farm-yard manure. Neither fresh nor rotten dung
contains any appreciable quantity of volatile ammonia, and there is no
advantage from applying gypsum, dilute acid, superphosphate, kainit,
or other substances recommended as fixers of ammonia. If dung is
carted into the field and spread out at once in thin layers it will
suffer comparatively little loss. But if dung be kept for a length of
time in shallow heaps, or in open straw-yards and exposed to rain, it
loses by drainage a considerable proportion of its most valuable
soluble fertilizing constituents. Experiments with farm-yard manure
kept in an open yard showed that, after twelve months' exposure to the
weather, nearly all the soluble nitrogen and 78.2% of the soluble
mineral matters were lost by drainage (A. Voelcker). To prevent this
loss, farm-yard manure, as had been pointed out, should, whenever
possible, be carted into the field, spread out at once, and ploughed
in at the convenience of the farmer. It is, however, not always
practicable to apply farm-yard manure just at the time it is made,
and, as the manure heap cannot be altogether dispensed with, it is
necessary to see how the manure may best be kept. The best dung is
that made in regular pits or feeding-boxes. In them the urine is
thoroughly absorbed, and, the manure being more compact through the
constant treading, air enters less freely and the decomposition goes
on less rapidly, the volatile matters, in consequence, not being so
readily lost. External agents, such as rain, wind, sun, &c., do not
affect the manure as they would in the case of open yards. Next best
to box-fed manure is that made in covered yards, then that in sheds,
and lastly that in open yards. When removed from the box or yard, the
manure should be put in a heap upon a floor of clay or
well-beaten-down earth, and then be covered with earth. When kept in
an open yard, care should be taken not to let spoutings of buildings
lead on to it, and if there be a liquid-manure tank, this might be
pumped out over the manure again when the latter is too dry.
The advantages of farm-yard manure consist, not only in its supplying
all the constituents of plant food, but also in the improved physical
condition of the soil which results from its application, inasmuch as
the land is thereby kept porous, and air is allowed free access.
While, however, farm-yard manure has these advantages, experience has
shown that artificial manures, properly selected so as to meet the
requirements of the crops intended to be grown on the particular land,
may be employed to greater advantage. In farm-yard manure about
two-thirds of the weight is water and one-third dry matter; a large
bulk thus contains only a small proportion of fertilizing substances,
and expense is incurred for carriage of much useless matter when dung
has to be carted to distant fields. When a plentiful supply of good
farm-yard manure can be produced on the farm or bought at a moderate
price in the immediate neighbourhood, it is economy to use it either
alone or in conjunction with artificial manures; but when food is dear
and fattening does not pay, or farm-yard manure is expensive to buy,
it will be found more economical to use artificial manures. This has
obtained confirmation from the experience of Mr Prout, at
Sawbridgeworth, Herts, where since 1866, successive crops of corn have
been grown, and entirely with the use of artificial manures.
The real difficulty with farm-yard manure is to get enough of it, and,
if it were available in sufficiency, it would be safe to say that
farmers generally would not require to go farther in regard to the
manuring of any of the crops of the farm. Moreover, experiments at
Rothamsted and Woburn have shown of how "lasting" a character
farm-yard manure is, its influence having told for some 15 to 20 years
after its application had ceased.
Light land is benefited by farm-yard manure through its supplying to
the soil organic matter, and imparting to it "substance" whereby it
becomes more consolidated and is better able to retain the manurial
ingredients given to it. By improving the soil's moisture-holding
capacity, moreover, "burning" of the land is prevented.
With heavy clay soils the advantages are that these are kept more open
in texture, drainage is improved, and the soil rendered easier of
working. On light land, well-rotted manure is best to apply; and in
spring, whereas on heavy land freshly-made, "long," manure is best,
and should be put on in autumn or winter.
Farm-yard manure, where the supply is limited, is mostly saved for the
root-crop, which, however, generally needs a little superphosphate to
start it, as farm-yard manure is not sufficiently rich in this
constituent. It serves a great purpose in retaining the needed
moisture in the soil for the root crop.
For potato-growing, for vegetables, and in market-gardening, farm-yard
manure is almost indispensable. On grass-land and on clover-ley it is
also very useful, and in the neighbourhood of large towns is employed
greatly for the production of hay.
For corn crops also, and especially for wheat on heavy land, farm-yard
manure is much used, and, in a dry season in particular, shows
excellent results, though experiments at Rothamsted and Woburn have
shown that, on heavy and light land alike, heavier crops of wheat and
barley can be produced in average seasons by artificial manures.
_Seaweed._--Along the sea-coast seaweed is collected, put in heaps and
allowed to rot, being subsequently used on the land, just as farm-yard
manure is. According to the nature of the weed and its water-contents,
it may have from .3 to 1% of nitrogen, or more, with potash in some
quantity.
_Green-manuring._--Though properly belonging to cultivation rather
than to manuring, and acting chiefly as a means of improving the
condition of the soil, the practice of green-manuring carries with it
manurial benefits also, in that it supplies humus and nitrogen to the
soil, and provides a substitute for farm-yard manure. The ploughing-in
of a leguminous green-crop which has collected nitrogen from the
atmosphere should result in a greater accumulation of nitrogen for a
succeeding corn-crop, and thus supply the cheapest form of manuring.
Green-manuring is most beneficial on light land, poor in vegetable
matter.
_Manure Cakes, Malt Dust, Spent Hops, &c._--Many waste materials of
this kind are used because of their supplying, in the form of
nitrogenous organic matter, nitrogen for crop uses. The nitrogen in
these is of somewhat slow-acting, but lasting, nature. In addition to
nitrogen, some of these materials, e.g. rape cake, cotton cake and
castor cake, contain appreciable amounts of phosphoric acid and
potash. Rape cake, or "land cake," as it is called in Norfolk, is used
considerably for wheat. It is also believed to be a preventive of
wireworm, and so is often employed for potatoes and root-crops.
Rape-seed from which the oil has been extracted by chemical means, and
which is called "rape refuse," is made use of in hop-gardens as a
slowly acting supplier of nitrogen. It will contain 4 to 5% of
nitrogen with 3 to 4% of phosphates. Damaged cotton and other
feeding-cakes, no longer fit for feeding, are ground into meal and put
on the land. Castor cake is directly imported for manurial purposes,
and will have up to 5% of nitrogen with 4 to 5% of phosphates. Spent
hops, malt dust and other waste materials are similarly used. The
principal use of these materials is on light land, and to give bulk to
the soil while supplying nitrogen in suitable form.
_Wool-dust, Shoddy, &c._--The clippings from wool, the refuse from
cloth factories, silk, fur and hair waste, carpet clippings and
similar waste materials are comprised in this category. They are
valuable purely for their nitrogen, and should be purchased according
to their nitrogen-contents. They are favourite materials with
hop-growers and fruit-farmers, whose experience leads them to prefer a
manure which supplies its nitrogen in organic form, and which acts
continuously, if not too readily. It is the custom in hop-lands to
manure the soil annually with large quantities of these waste
materials till it has much fertility stored up in it for succeeding
crops. According to its nature, wool-dust or shoddy may contain
anything from 3% of nitrogen up to 14%.
Leather is another waste material of the same class, but the process
of tanning it has undergone makes its nitrogen but very slowly
available and it is avoided, in consequence, as a manure. There have
been several processes started with the object of rendering leather
more useful as a manure.
_Hoofs and Horns._--The clippings and shavings from horn factories are
largely used by some hop-growers, and, though very slow in their
action, they will contain 14 to 15% of nitrogen. They are sometimes
very finely ground and sold as "keronikon," chiefly for use in
compound artificial manures.
_Dried Blood_ is another purely nitrogenous material, which however
seldom finds its way to the farmer, being used up eagerly by the
artificial manure maker. It will contain from 12 to 14% of nitrogen.
It is obtained by simply evaporating down the blood obtained from
slaughter-houses. It is the most rapidly acting of the organic
nitrogenous materials enumerated, and, when obtainable, is a favourite
manure with fruit-growers, being also used for root and vegetable
growing.
_Soot_ is an article of very variable nature. It owes its manurial
value mainly to the ammonia salts it contains, and a good sample will
have about 4% of ammonia. It is frequently adulterated, being mixed
with ashes, earth, &c. Flue sweepings of factory chimneys are
sometimes sold as soot, but possess little value. Besides the ammonia
that soot contains, there would undoubtedly seem to be a value
attaching to the carbonaceous matter. Soot is a favourite top-dressing
for wheat on heavy land, and is efficacious in keeping off slugs, &c.
Speaking generally, the lighter a sample of soot is the more likely is
it to be genuine.
_Sewage Manure._--Where methods of dealing with the solid matters of
sewage are in operation, it frequently happens that these matters are
dried, generally with the aid of lime, and sold locally. Occasionally
they are prepared with the addition of other fertilizing materials and
made up as special manures. It may be taken for granted that sewage
refuse by itself is not worth transporting to any distance. When made
up with lime, the "sludge," as it is generally termed, is often useful
because of the lime it contains. But, on the whole, the value of such
preparations has been greatly exaggerated. Where land is in need of
organic matter, or where it is desirable to consolidate light land by
the addition of material of this class, sludge may, however, have
decided value on mechanical and physical grounds, but such land
requires to be near at hand.
b. _Imported or Manufactured Nitrogenous Manures._
These are nitrate of soda; sulphate of ammonia; calcium cyanamide;
calcium nitrate.
_Nitrate of Soda._--This is the best known and most generally used of
purely nitrogenous manures. It comes from the rainless districts of
Chile and Peru, from which it was first shipped about the year 1830.
By 1899 the export had reached to 1,344,550 tons. It is uncertain what
its origin is, but it is generally believed to be the deposit from an
ancient sea which was raised by volcanic eruption and its waters
evaporated. Another theory puts it as the deposit from the saline
residues of fresh-water streams. The crude deposit is termed
_caliche_, and from this (which contains common salt and sulphates of
soda, potash and lime) the nitrate is crystallized out and obtained as
a salt containing 95 to 96% pure nitrate of soda. It is sold on a
basis of 95% pure, and is but little subject to adulteration.
As a quickly acting nitrogenous manure nitrate of soda has no equal,
and it is in great demand as a top-dressing for corn crops, also for
roots. On grass-land, if used alone, it tends to produce grass but to
exterminate leguminous herbage. Its tendency with corn crops is to
produce, if used in quantity, inferiority of quality in grain. It can
be employed in conjunction with superphosphate and other artificial
manures, though it should not be mixed with them long before the
mixture is to be put on. It is a very soluble salt, and the nitrogen
being in the form of nitrates, it can be readily taken up by plants.
On the other hand, it is readily removed from the soil by drainage,
and its effects last only for a single season. Owing to its
solubility, it requires to be used in much larger amount than the crop
actually will take up. On a heavy soil it has a bad influence if used
repeatedly and in quantity, causing the land to "run," and making the
tilth bad. Though, doubtless, exhaustive to the soil, when used alone,
there is no evidence yet of nitrate of soda causing land to "run out,"
as has been shown to be the case with sulphate of ammonia. One cwt. to
the acre is a common dressing for corn crops, but for mangels it has
been used to advantage up to 4 cwt. per acre. As a top-dressing for
corn crops it differs little in its crop-results from its rival
sulphate of ammonia, but in a dry season it answers better, owing to
its more ready solubility and quicker action, whereas in a wet season
sulphate of ammonia does better.
_Sulphate of Ammonia._--This is the great competitor with nitrate of
soda, and, like the latter, is useful purely as a nitrogenous manure.
It is obtained in the manufacture of gas and as a by-product in the
distillation of shale, &c., as also from coke ovens. By adding
sulphuric acid to the ammoniacal liquor distilled over from the coal,
&c., the salt is crystallized out. It is seldom adulterated, and, as
sold in commerce, generally contains 24 to 25% of ammonia. It is not
quite so readily soluble as nitrate of soda; it does not act quite so
quickly on crops, but is less easily removed from the soil by
drainage, leaving also a slight amount of residue for a second crop.
It is nearly as efficacious as a top-dressing for corn crops as is
nitrate of soda, and for some crops, e.g. potatoes, it is considered
superior. It may also be used like nitrate of soda for root crops. On
grass-land its effect in increasing gramineous but reducing leguminous
herbage is similar to that of nitrate of soda, but with corn crops it
has not the same deteriorating influence on the quality of grain. It
can be mixed quite well with superphosphate and other artificial
manures, and is therefore a common form in which nitrogen is supplied
in compound manures. It does not produce the bad effect on the tilth
of certain soils that nitrate of soda does, but it is open to the
objection that, if used continually on soil poor in lime, it will
gradually exhaust the soil and leave it in an acid condition, so that
the soil is unable to bear crops again until fertility is restored by
the addition of lime. A usual dressing of sulphate of ammonia is 1
cwt. per acre.
_Calcium Cyanamide._--This is a new product which represents the
earliest result of the utilization, in a commercial form, of
atmospheric nitrogen as a manurial substance. It is obtained by
passing nitrogen gas over the heated calcium carbide obtained in the
electric furnace, the nitrogen then uniting with the carbide to form
calcium cyanamide. The product contains from 19 to 20% of nitrogen,
and, though still under trial as a nitrogenous manure, it bids fair to
form a valuable source of supply, especially should the natural
deposits of nitrate of soda become exhausted. The cost of production
limits its manufacture to places where electrical power can be cheaply
generated. In its action it would seem to resemble most closely
sulphate of ammonia.
_Calcium Nitrate._--This is another product of the utilization of
atmospheric nitrogen as a manurial agent. Nitrogen and oxygen are made
to combine within the electric arc and the nitric acid produced is
then combined with lime, forming nitrate of lime. Nitrate of lime
contains, as put on the market, about 13% of nitrogen. In its action
it should be very similar to nitrate of soda, with, possibly, some
added benefit to certain soils by reason of the lime it contains. Like
cyanamide, it is still in the experimental stage as regards its
agricultural use, and can only be produced where electric power is
cheaply obtainable.
Neither material is altogether free from objection, the cyanamide
heating when mixed with other manures and even with soil, and being
liable to give off acetylene gas owing to the presence of calcium
carbide, whereas the calcium nitrate is a salt which on exposure to a
moist atmosphere readily deliquesces.