GUANO.
_Importance in Agriculture._
In the consideration of _artificial_ manures, guano deserves the first
place. This it does mainly on historical grounds, as it is now largely a
manure of the past. Not merely has it been used in agriculture to an
extent to which no other artificial manure has as yet ever approximated,
but its influence on agricultural practice has been enormous. Introduced
into this country about the middle of the present century, it was the
first of artificial manures to be used in large quantities.[183] It may
be thus described as having introduced the modern system of _intensive_
cultivation, and given rise to the now almost universal practice of
artificial manuring.
_Influence on British Farming._
It is, indeed, difficult to over-estimate the important influence which
the introduction of this most valuable fertiliser has exercised on
British as well as, to a large extent, on European husbandry. Before its
introduction the farmer was almost completely dependent on his farmyard
manure. He was tied down to a great extent, by the exigencies of the
then prevailing agricultural customs, to certain rotations of crops. He
could do little in the way of enriching barren soils or of ensuring a
heavy yield of crop. By the use of this very potent fertiliser, he
quickly discovered that the most wonderful results ensued--results which
must have seemed to him at first little short of miraculous. He found
that by the application of a few hundredweights per acre, poor soils
could be made to yield large returns, and that barren patches in a field
could be brought up to the average of the surrounding portions by
sprinkling merely a few handfuls of it; that by its means a good start
could be ensured to every crop, and one slow of coming away could be
hastened on. In short, in this wonderful brown powder, with such a
characteristic odour, the astonished farmer discovered a manure which,
for the speed of its action, and for the increase of crop it gave,
completely threw into the shade both farmyard manure and bones. What
wonder, then, that its fame as a manure should have become so quickly
known and its use so extensive! It thus gave a most powerful impetus to
intelligent farming by bringing home to the minds of those who used it
the important position nitrogen and phosphates occupied as constituents
of the soil, and the influence they exercised on plant-growth. It
furnished, in fact, on an enormously large scale, a practical
demonstration of the principles of manuring. The educational value which
the use of guano thus exercised may be said to have been very great. It
also led the way to the use of the various artificial manures so much
used during the last fifty years. Impressed by the value of guano,
farmers were favourably disposed towards the use of other fertilisers;
and, largely owing to its widespread popularity, the new practice
speedily gained ground.
_Influence not wholly for Good._
But its influence, it must be admitted, was not wholly for good. In its
very popularity lay the danger of its abuse. Had its value and the
method of its action been more widely understood, and had the principles
upon which the practice of artificial manuring depends been better
realised, agriculturists would have been spared much of the needless
pecuniary losses they sustained by being imposed upon by unscrupulous
manure-dealers. Among the farming community the word guano soon became a
name to conjure with, and under this title many spurious and worthless
manures were attempted to be palmed off on the unwary farmer. Even the
genuine article, there can be little doubt, was at one time largely
adulterated; and as the farmer was almost invariably content to purchase
the article not on any guaranteed chemical analysis, but simply on the
ground of its appearance, colour, and more especially smell, every
facility was given for the successful perpetration of such fraudulent
imposition. Guano, it was very soon found, varied in its composition,
but this variation in quality the farmer did not recognise. In the early
days of its use all guano was in his eyes of the same value. Too often,
as we have just pointed out, provided it had a good colour and a strong
odour, it was all right. Under such conditions, it can scarcely be
wondered at that its introduction should have proved not an unmixed
blessing to agriculture.
_Its Value as a Manure._
Guano derives its value as a manure from the nitrogen, phosphates, and
the small amount of potash it contains. This at any rate is true of the
great bulk of guano which has been used in the past. There are, as we
shall immediately see, certain kinds of guano, known as phosphatic
guanos, which only contain phosphates. The amount of such purely
phosphatic guano directly used as a manure in this country is, however,
inconsiderable, and guano may truly be described as owing its value
chiefly to its nitrogen. Not a little of its value and popularity as a
manure may be said to be due to the fact that it contains all of the
three important manurial constituents, and that in this respect it may
be regarded in a sense as a _general_ manure, thus resembling most
nearly, of all artificial manures, farmyard manure. Although its sources
are now, to a very large extent, exhausted, and its total annual imports
into this country are at present considerably less than what they were
thirty or forty years ago,[184] it may be well, on account of its
historical importance, to give a somewhat detailed account of its
origin, occurrence, and value as a manure.
_Origin and Occurrence._
Guano (which means _dung_)--or huano, as it is spelt in the Spanish
language--was first used in Peru. It seems to have been used there long
before that country was discovered by the Spaniards--probably as early
as the twelfth century. Regarding its origin there can be little doubt.
It is almost entirely derived from the excrements of sea-birds, such as
pelicans, penguins, and gulls, as well as from the remains of the birds
themselves, and of seals, walruses, and various other animals.[185]
Under the influence of a tropical sun, and in a region in which rain
scarcely ever falls, these excrements are soon dried, and remain little
changed in their composition through centuries. Many of the Peruvian
deposits must be extremely old, as they are covered up with sand and
other _debris_, and are of considerable depth. Especially is this the
case with deposits occurring on the mainland, such as those at Pabellon
de Pica, where the layer of sand or conglomerate covering up the deposit
varies in depth from a few feet to over a hundred. The effect of this
superficial covering has been to protect the guano, to a certain extent,
from loss of nitrogen.
Although guano of the best class has been derived from the neighbourhood
of Peru, deposits have also been found in many other parts of the
world--viz., in North America, West Indies, Australia, Asia, Africa, and
among the islands of the Pacific.[186]
_Variation in the Composition of different Guanos._
The guano found in these different deposits varies very considerably in
composition. This is due to the difference in the nature of the
prevailing climate of the places where these deposits occur. Where the
climate is dry and warm, as is the case in Chili and Peru, the
excrements dry quickly and remain very little changed, as one very
important condition of fermentation--viz., moisture--is absent.[187] In
a damp climate, on the other hand, speedy fermentation ensues, resulting
in the loss of nearly all the organic matter, including nitrogen, in
such volatile forms as carbonate of ammonia, carbonic acid gas, water,
&c. The soluble alkalies, the most important of which is potash, as well
as the soluble phosphates, are also, under such conditions, lost to the
guano by being washed out by the rain. We have thus a wide difference in
the quality of the different deposits, depending on the extent to which
decomposition has taken place. Guano thus ranges from the rich
nitrogenous Peruvian kind, which has undergone little or no change from
the time of its deposit, to the purely phosphatic kind (such as those of
Malden and Baker islands), in which everything of manurial value has
been lost except the insoluble phosphate of lime. Even among the
nitrogenous guanos we find a considerable difference in quality, some
deposits being partially impoverished by the action of the atmospheric
moisture, dew, spray or sea-water, but still containing a considerable
proportion of their nitrogen. Other deposits, again, are largely admixed
with sand, which has been blown in upon them to such an extent as to
make them unsaleable. We can divide guano, therefore, into two great
classes--viz., _nitrogenous_ and _phosphatic_.
I.--NITROGENOUS GUANOS.
(_a_) PERUVIAN.
By far the most valuable and abundant deposits as yet discovered have
been those on the Peruvian and Chilian coasts. As already pointed out,
guano seems to have been used in this country from a very early period;
and so impressed were the Incas with its importance as a manure, that
the penalty of death was imposed on any one guilty of killing the
sea-fowl during the breeding season in the vicinity of the deposits.
The occurrence of guano in Peru seems first to have been made known in
Europe in the beginning of the eighteenth century. It was not, however,
till the beginning of the present century--viz., 1804--that A. Humboldt,
the great German traveller, brought some of the wonderful fertiliser
home with him, and that its composition was able to be investigated by
chemical analysis. Shortly afterwards, its practical value was
demonstrated by experiments carried out on potatoes by General Beatson
in St Helena. To Lord Derby is due the credit of having first introduced
it into this country, the earliest importation into Liverpool being in
1840. Experiments were shortly afterwards instituted in different parts
of the country, prominent among which were those by Sir John Lawes and
Sir James Caird; and so striking were the results obtained, that the
manure rapidly found favour with the farming community--so much so, that
ten years later the importations into this country amounted to no less
than 200,000 tons, while in 1855 the total exports from the west coast
of South America reached the enormous amount of 400,000 tons. In all, it
has been estimated that since the year 1840 over 5,000,000 tons of
Peruvian guano have been imported into this country.
_Different Deposits._
Peruvian guano has been derived from various deposits occurring in
different parts of the coast, and from a number of small adjacent
islands. The richest of these was that found on Angamos, a rocky
promontory on the coast of Bolivia. Samples of this guano contained as
high as 20 per cent of nitrogen (equal to 24 per cent ammonia).[188]
Unfortunately, however, the quantity of this deposit was extremely
limited, and became rapidly exhausted. Next to this deposit in quality
was the guano found on the Chincha islands, three little islands off the
coast of Peru. These deposits were the largest which have ever been
discovered, and for a period of nearly thirty years were almost the sole
source of the Peruvian guano sold in commerce, over 10,000,000 tons
having been exported from them alone. Some of this guano contained 14
per cent of nitrogen (equal to 17 per cent ammonia); and although part
of the guano shipped from these islands was not quite so rich, yet it
was all of a high-class order. The deposits on these islands were in
many cases 100 to 200 feet in depth, and rested on rocks of granite. The
lower layers were consequently found to be poorer in quality, and mixed
with pieces of granite. The Chincha island deposits have been long
exhausted,[189] and the chief deposits of Peruvian guano since worked
have been those on Guanape and Macabi islands--a considerably inferior
guano, containing only 9 to 11 per cent of nitrogen (equal to 11 to 13
per cent of ammonia)--which in their turn have become exhausted; from
Ballestas, almost as rich as the Chincha island guano, also now
exhausted; and from Pabellon de Pica, Punta de Lobos, Huanillos,
Independence Bay, and Lobos de Afuera. Quite recently a deposit of very
high-class guano was discovered in Corcovado, and a good many cargoes
have already been shipped to this country. It is found to contain
nitrogen equal to from 10 to 13 per cent ammonia, 30 to 35 per cent
phosphates, and some potash, being thus a most valuable guano.
_Appearance, Colour, and Nature._
In colour it varies from a very light to a very dark brown, the richer
samples being generally lighter. Samples taken from even the same
deposit have been found to differ very considerably in appearance, those
taken from the lower and older layers being usually darker than those
taken from the more recent upper layers. It was soon found also to vary
very much in composition. After a deposit had been worked for some time,
the quality of guano it yielded was found to be inferior and coarser,
and in many cases mixed with pebbles or pieces of granite, porphyry, &c.
This led to the custom of screening it on arrival in this country,
before it was used as a manure. In the richer qualities--_e.g._, in the
Chincha guano--little round concretionary nodules, varying in colour
from pure white to dark brown, were occasionally found. Analysis showed
these nodules[190] to be composed chiefly of potash salts. Sometimes,
also, little crystals of almost pure ammonia salts were found. It soon
became customary, therefore, to prepare guano for the market by
separating the stones and reducing the whole to a fine uniform powder.
One of its most characteristic properties, and the one which seems to
have impressed the public most, was its pungent odour. Undue importance
was attached to this property, in the belief that it was caused by the
ammonia it contained. It may be doubted, however, whether the
characteristic smell of guano is due so much to its ammonia as to
certain fatty acids.
_Composition._
In composition it is of a most complex nature. It contains its nitrogen
in a great variety of forms, the chief of these being urate, oxalate,
ulmate, humate, sulphate, phosphate, carbonate, and muriate of ammonia;
and also in a rare form of organic nitrogen peculiar to guano, called
guanine. According to Boussingault, some guanos contain small quantities
of nitrates. Its phosphoric acid is present both in the soluble
state--viz., as phosphates of the alkalies (ammonia and potash)--and in
the insoluble state as phosphate of lime; and lastly, its potash is
present as sulphate and phosphate. The proportion in which these
different forms of nitrogen and phosphoric acid are present varies
considerably in different samples. The richer a sample, as a rule, the
more nitrogen in the form of uric acid it contains. The most of the
nitrogen is present as uric acid and ammonia. Damp guanos contain more
of their nitrogen as ammonia than dry ones, this being due to the
fermentation which goes on in the former. On an average, about a third
of its total nitrogen is soluble in water. Of its phosphates, on the
other hand, only about a fourth are soluble in water.
The following analyses of a sample of Chincha island guano by
Karmrodt[191] will illustrate this. (Sample dried at 212 deg. Fahr.):--
1. _Constituents easily soluble in Water._
Urate of ammonium 12.74
Oxalate of ammonium 13.60
Nitrogenous and sulphurous organic substances 3.61
Ammonium-magnesium phosphate 4.00
Ammonium phosphate .90
Ammonium sulphate 1.82
Ammonium chloride 1.55
Potassium sulphate 3.30
Sodium chloride 2.44
-----
43.96
-----
2. _Difficultly soluble in Water, soluble in Acids,
Alcohol, and Ether._
Uric acid 21.14
Resin 1.11
Fatty acids 1.60
Nitrogenous and sulphurous organic substances 2.29
Calcium phosphate 18.22
Phosphate of iron 1.04
Silica .64
-----
46.04
-----
In the above analysis it will be noticed that none of the ammonia is
present as carbonate. In most samples, however, of Peruvian guano, the
ammonia in this form amounted to from 1 to 2 per cent. In the inferior
qualities, chiefly those which had been subjected to the action of
water, and consequently of fermentation, to a certain extent, this form
of ammonia was found to be most abundant. Such guanos were most liable
to loss of nitrogen by volatilisation.
The older Peruvian guano contained as high as 14 per cent of nitrogen
(equal to 17 per cent of ammonia), and of phosphoric acid 12 to 14 per
cent (equal to 26 to 28 per cent of phosphate of lime). It, however,
gradually deteriorated in quality as the deposits became worked out, the
percentage of nitrogen becoming year by year less, until latterly
Peruvian guano, as imported, contains only from 3 to 4 per cent of
nitrogen (equal to 4 to 5 per cent of ammonia). This guano is, however,
richer in phosphates, containing often 50 to 60 per cent of phosphate of
lime, and 3 to 4 per cent of potash.[192]
(_b_) OTHER NITROGENOUS GUANOS.
The guanos, other than those which come from Peru, are chiefly purely
phosphatic guanos, so that the term Peruvian has not unfrequently in the
past been used as a generic term synonymous with the term nitrogenous,
and consequently applied to all nitrogenous guanos independent of their
source. There are, however, a few deposits other than the Peruvian
which have yielded considerable quantities of valuable nitrogenous
guano. Of those, the richest in quality--in fact, the richest of any
deposits hitherto discovered--was the Angamos guano, which came from a
rocky promontory on the coast of Bolivia. The few samples of this which
have been analysed showed over 20 per cent of nitrogen. Unfortunately,
the deposit proved to be comparatively insignificant in amount, and has
long been exhausted.
Poorer in quality, but more abundant in quantity, were the deposits
found on the Ichaboe and other islands off the south-west coast of
Africa. These deposits were discovered shortly after the introduction of
Peruvian guano, and for a few years supplied considerable quantities of
valuable manure. The deposits first discovered were soon exhausted, so
that for a number of years Ichaboe guano ceased to be procurable. Fresh
deposits, however, were subsequently found, and considerable quantities
have of late years been used in agriculture.[193] Ichaboe guano is
inferior in value to Peruvian. It exemplifies the influence of small
quantities of rain on guano deposits in impoverishing them in their
nitrogen. In much of the Ichaboe guano imported into this country a
large amount of feathers is found. It also contains an abnormally large
quantity of insoluble matter.
Among the other nitrogenous guanos may be mentioned the Patagonian,
Falkland, and Saldanha Bay. They are, like the Ichaboa, of comparatively
recent origin, and are collected in small quantities after the breeding
season every year.
II.--PHOSPHATIC GUANOS.
Phosphatic guanos, as already pointed out, are similar in origin to
nitrogenous guanos. In their case, however, the nitrogen, alkalies, and
soluble phosphates which they originally contained have been almost
entirely lost by the decomposition of their organic matter and the
action of water.[194] Most of them still contain very small quantities
of nitrogen, amounting to a fraction of a per cent. Of these deposits
there are very many occurring on islands in different parts of the
world. In appearance the guano obtained from them is very different from
nitrogenous guano, being much lighter in colour, and of a fine powdery
nature. It forms a very rich phosphatic guano, containing in many cases
between 70 and 80 per cent of insoluble phosphate of lime. Such guanos
are largely used in the manufacture of high-class superphosphates, by
treating them with sulphuric acid. Being of an insoluble nature, they
are not very suitable for direct application to the soil. Of these
phosphatic guanos the following are the chief--those marked in italics
being still unexhausted:--
1. _Baker_, Jarvis, Howland, Starbuck, Flint, _Enderbury_, _Malden_,
Lacepede, _Browse_, _Huon_, _Chesterfield_, _Sydney_, _Phoenix_,
_Arbrohlos_, _Shark's Bay_, and _Timor_--all found on islands in the
Pacific Ocean.
2. _Mejillones_, on the coast of Bolivia.
3. Aves, _Tortola_, _Mona_, and other deposits in the West Indies.
4. _Kuria Muria_ islands, in the Arabian Gulf.
For further particulars as to the composition of these different guanos,
the reader is referred to the Appendix, Note V., p. 329.
_Inequality in Composition._
That guano was a substance of by no means uniform composition was a fact
early recognised in the history of the trade. Not only did guano from
different deposits show on analysis different percentages of the
manurial ingredients, but different samples of guano from the same
deposit were often found to differ very considerably from one another.
It soon became the custom, therefore, to sell it on chemical analysis,
each separate cargo being carefully analysed. But this custom did not
wholly obviate the difficulty, as the guano in even one cargo might
differ. In the case of the older and richer guanos, there was certainly
more uniformity in quality, but they were liable to differ in their
percentage of nitrogen.[195] As, however, the deposits became gradually
worked out, their lower layers were found more or less largely admixed
with stony and earthy matter, and their composition was naturally
rendered very variable. This state of matters was unsatisfactory to
buyers and sellers, and led to much friction between the two, as it was
found wellnigh impossible on the part of the seller to guarantee the
composition of his manure. The custom of preparing the material by
reducing it to a fine powder before sending it into the market, and the
custom, subsequently introduced, of treating it with sulphuric acid,
have done away with this difficulty to a large extent.
_"Dissolved" Guano._
The treatment of guano with sulphuric acid was first had recourse to in
the case of cargoes damaged with water. In such guano, as has been
already pointed out, fermentation has been permitted to take place, with
the result of the formation of volatile carbonate of ammonia in greater
or less quantity. By the addition of sulphuric acid the ammonia was
fixed, and the guano was prevented from losing its most valuable
constituent. It was soon found, however, that guano so treated possessed
greater activity as a manure. The result of the sulphuric acid was to
increase very materially the amount of its soluble phosphates, and also
its soluble nitrogen compounds.[196] It had, moreover, the effect of
producing a guano of uniform composition. The custom, first introduced
in 1864 by Messrs Ohlendorff & Co., was soon largely practised. The
guano is treated with 25 to 30 per cent sulphuric acid (sp. gr. 1.73).
After a short time the resulting hard mass is, by means of
disintegrators, reduced to a uniform powder.
_"Equalised" or "Rectified" Guano._
As guano decreased in its quality the demand for a high-class article
became more and more difficult to meet. This led to the custom of
"fortifying" or "rectifying"--as it is variously called--the natural
material with sulphate of ammonia. A manure closely resembling in the
percentage of its manurial constituents the older rich guanos is thus
obtained. Of these so-called "equalised" guanos, two qualities are at
present sold, the first being guaranteed to contain nitrogen equal to 8
to 9 per cent ammonia, 30 to 35 per cent phosphates, and 2 to 3 per cent
of potash; the second quality containing only about half as much
nitrogen, but more phosphates.
However valuable this fortified guano may be--and it is, undoubtedly, a
most valuable manure--its action cannot be supposed to be exactly
similar to the old Peruvian guano, which it resembles in the percentage
of its nitrogen, phosphates, and potash. Much of the distinctive value
of guano as a manure, as will be pointed out immediately, lies in the
fact that it contains its manurial ingredients in a variety of
differently soluble compounds, which are gradually rendered available in
the soil for the plant's needs. This undoubtedly is one of the reasons
why the action of guano among manures is quite unique; and there are
other reasons which we probably do not clearly understand. However
skilfully the composition of the guano may be artificially simulated, it
still remains an undoubted fact that the "equalised" guano is not
exactly similar in its action to the genuine article. Nevertheless, that
it is superior in its results to the poorer classes of guano at present
available, and to ordinary compound manures, there can be little doubt.
A great merit of the equalised guano is, however, that it is sold at a
lower price than guano as imported; and as the guano is sold on a
guaranteed analysis, the practice has done much to advance the true
interests of agriculture.
_Its Action as a Manure._
Next to farmyard manure, guano may be regarded as the most "general" of
all the commonly used manures; for in addition to nitrogen, phosphoric
acid, and potash, it contains nearly all the other plant ingredients,
such as lime, magnesia, &c. Its special value as a manure, however, does
not merely consist in the amount of valuable plant-food it contains.
Like farmyard manure, it owes much of its characteristic action to the
state of the intimate mixture of its manurial constituents, and also, as
has already been pointed out, to the fact that it contains those
constituents in a great variety of chemical forms, each of which differs
in its solubility, and consequently availability for the plant's needs.
Take, for example, the great number of different forms of nitrogen it
contains. Some are in the condition in which plants can immediately
absorb them, while the rest are in a series of less and less available
forms, which, however, are gradually converted into available forms as
the plant requires them. Like farmyard manure, again, it may be applied
with almost equally good results to all kinds of crops and on all kinds
of soils. We have in guano, in short, an admirable example of the value
of applying our manurial ingredients in different forms. That this is no
mere theory is abundantly proved by the large number of different
experiments which have in the past been carried out with guano, more
especially the well-known experiments made by Grouven, the German
chemist. In those well-known experiments, guano was tested against a
large variety of different fertilisers, and the tests were so arranged
that in most cases the amounts of nitrogen, phosphoric acid, and potash
were the same in the other manures used. In short, these experiments
prove in a very striking manner that a manure artificially made up out
of most valuable fertilisers, such as nitrate of soda, sulphate of
ammonia, superphosphate, &c., so as to closely resemble in its
composition guano, is by no means similar in its effects to the genuine
article. As in farmyard manure, so in guano: we must look to the
complexity of the composition of both these fertilisers in order to
fully estimate their worth. There is in the action of both manures much
that we cannot explain, or even, as yet, understand. The action of guano
is merely one of many problems in the science of manuring which
illustrate how unsatisfactory, despite the great amount of research
already carried out, is our knowledge of this most important department
of agriculture.[197]
_Proportion of fertilising Constituents in Guano._
Guano must be regarded as a nitrogenous and phosphatic manure, as the
quantity of potash it generally contains is small. In many soils, more
especially in such a country as Scotland, this deficiency in potash is
not of so much importance, as the value of potash as an artificial
manure is less than is the case with the other two ingredients. In
soils, however, lacking potash, guano ought to be supplemented with some
potash manure. With regard to the nitrogen and phosphoric acid, we may
ask if these two constituents are in the best proportions. This question
does not admit of a direct answer. In the first place, the proportion
in which these two ingredients are present is variable. In the old rich
Peruvian guanos, as we have above shown, the nitrogen was more abundant
than is the case at present. Such guanos, it was found, were best
supplemented with phosphatic manure when applied to the field. In the
"equalised" and "dissolved" guanos, which are now so largely sold,
manufacturers attempt to adjust the percentage of nitrogen and
phosphoric acid to what is considered the best proportion in most cases.
As, however, we have again and again to point out, regard must be had
both to the soil and the crop in determining what is the best proportion
of the manurial ingredients in a manure. For cereals it may be well
supplemented by nitrogenous manures, while for roots it may be well
supplemented by phosphatic manures.
_Mode of Application._
Like all manures, it is desirable to apply it in as fine a condition as
possible, so as to ensure as thorough a mixture with the soil-particles
as practicable. In order, furthermore, to prevent any risk of loss
through volatilisation of the ammonia, as well as to ensure even
distribution, it is best applied mixed with dry earth, ashes, sand, or
some other substance,--not lime, however. The custom of applying along
with the guano common salt, has been proved by numerous experiments to
be highly beneficial to the action of the guano as a manure. The exact
nature of the action of salt as an adjunct to manures is a point which
has elicited much discussion. Its action is probably to be ascribed to a
number of causes. For one thing, it probably acts as an antiseptic in
retarding the fermentative action which has a tendency to go on so
rapidly in such manures as guano. It further increases the power of the
manure to attract moisture from the air--a most important property in
the case of drought. Some experiments by Dr Voelcker illustrate this in
a striking manner. Two lots of guano--one pure and one mixed with
salt--were exposed to the action of the air for a month, and were then
tested as to the amount of water they contained, when it was found that
the lot containing the salt had absorbed 2 per cent more water than the
other.
Much stress has been laid on the importance of having the guano buried a
certain depth in the soil; and many experiments have been carried out to
prove how much better it acts when so applied. This is probably due to
the prevention of any loss of volatile ammonia, and the mixture of the
manure with the soil-particles before it comes in contact with the
plant-roots. This last precaution is an important one, for it has been
found that the raw material is apt to have a bad effect on the seed or
the plant's roots. This has been found to be especially the case in
regard to potatoes, the quality of which has been found to suffer when
the guano is brought into direct contact with the tubers. As guano is a
manure which is speedily available, it is desirable to apply it as
shortly before it is required by the plant as possible. It is therefore
generally best applied in spring, shortly before seed-time, or indeed at
the same time. Where farmyard manure is used, the guano has been
recommended to be used as a top-dressing in small quantities. In the
majority of cases it will be advisable, however, not to apply it as a
top-dressing, for the various reasons above-mentioned.
_Quantity to be used._
As to the quantity to be used, this of course will depend on the soil,
the crop, and the amount and nature of the other manures employed: 1 to
4 cwt. per acre have been the usual limits, but even heavier dressings
have been commonly resorted to, especially in Scotland, where 6 to 8 or
even 9 cwt. for turnips are often used. Sir J. B. Lawes and Sir James
Caird long ago, shortly after the introduction of guano, estimated, from
the experiments they carried out, that the application of 2 cwt. per
acre to the wheat crop gave an increase of 8 to 9 bushels in grain, and
added a fourth to the quantity of straw. The former authority recommends
2 to 3 cwt. per acre for wheat, to be sown broadcast and harrowed into
the land before sowing the seed. We have already stated that it may be
used in all soils and for all kinds of crops. While this is so, it has
been found to have specially favourable results when applied to the
turnip crop, when it may be used in larger quantities than in the case
of cereals. When applied to the turnip crop, it is well to use the more
phosphatic guanos or to supplement it with superphosphates. By applying
it in two lots, the larger portion before seed-time and the rest between
the drills after the turnips are up, excellent results have been
obtained. It has also proved an admirable manure for mangels. On the
whole, it gives best results on heavy soils and in a dampish climate.
_Adulteration of Guano._
Probably no artificial manure has been subjected to greater adulteration
in the past than guano. This has been due to the fact that the practice
of selling guano on analysis--especially among retail buyers--did not
largely obtain in the early years of the trade. A good deal of this
adulteration was probably caused by ignorant prejudice on the part of
the farmer, to whom the pungency of its smell and its colour were too
apt to be ranked as its most important properties. The variation in the
quality of different kinds of guano was too often not sufficiently
realised by the buyer, who not unfrequently was made to pay as high a
price for guano of an inferior quality as he ought to have paid for that
of the best quality. Indeed no manure illustrates the importance of
chemical analysis more than guano. Among the different forms of
adulteration practised may be mentioned the addition of such substances
as sawdust, rice-meal, chalk, sulphates of lime and magnesia, common
salt, sand, earth, peat, ashes of various kinds, and water. There can be
no doubt, however, that such adulteration has now long ceased to be
practised to any extent. Nevertheless, it may be of use to draw
attention to one or two of the tests by means of which some of the
commoner forms of adulteration may be detected. One or two are extremely
easily detected--as, for example, adulteration with sand or other
mineral substances. In such a case, the percentage of ash left on
burning a small portion of the guano will be found to be excessive. The
percentage of ash in a sample of genuine Peruvian guano should not
exceed from 50 to 60 per cent. The colour of the ash is another
important point, and may serve as a further indication of adulteration.
In the case of genuine guano, this should be whitish or greyish.
Red-coloured ash generally points to the adulteration of the guano with
some mineral substance containing iron--such, _e.g._, as Redonda
phosphate, a mineral phosphate of iron and alumina. Where the ash is
white, but excessive in quantity, adulteration with common salt,
sulphate of magnesia, gypsum, or chalk, may be suspected. The last-named
substance is easily detected by treating it with any of the common
acids, when brisk effervescence, due to the liberation of the carbonic
acid, will ensue.[198] A further point of importance with regard to the
ash is its solubility in water and in acids. A large insoluble residue
may be taken as indicating adulteration with sand. Adulteration with
water is also easily detected by heating a sample to the boiling
temperature and determining the loss it sustains. Of course the amount
of water varies in different samples. The appearance of the guano will
serve fairly well to detect whether it is abnormally moist. It may be
added, in conclusion, that Peruvian guano is extremely light; and while
this by itself is not a sufficient test of genuineness, it may serve to
confirm other tests.
III.--SO-CALLED GUANOS.
Before concluding this chapter, reference may be made to certain manures
which are commonly known under the name of guanos--such as "fish-guano,"
"flesh-guano," "meat-meal-guano," and "bat-guano,"--as well as to
manures which may more conveniently be described here--viz., "fowl and
pigeon dung."
_Fish-Guano._
The application of fish, not suited for other purposes, to the fields
as a manure is a practice which has obtained in certain parts of the
country for a number of years. In many districts on the sea-coast, where
fishing is the chief industry, the only way in the past of disposing of
a superabundant catch of herrings, for example, has been to utilise them
as a manure. From such a practice has sprung up what is now an important
and ever-increasing trade--viz., the manufacture of fish-guano.
This manufacture was first started, and is still most largely practised,
in Norway. The guano obtained varies very considerably in quality
according to the nature of the process employed, and as to whether the
guano is made from whole fish or merely from fish-offal. The latter
source is the common one. The manufacture is carried on at the
fish-curing stations, and the quality of the guano made from this source
is somewhat different from that made from whole fish, as a large
proportion of the fish-offal is made up of bones and heads. Large
quantities of Norwegian fish-guano are exported to various parts of
Europe.
The best quality of this guano may contain as much as 10 per cent of
nitrogen, but as a rule it is nearer 8 per cent. A very considerable
variation in the amount of phosphoric acid occurs for the reason above
stated, the guano made from fish-scrap being naturally much richer in
this ingredient than whole-fish guano. The phosphoric acid may be said
to range from 4 to 15 per cent, and there is also a small quantity of
potash present.
Guano is also manufactured in Norway from the carcasses of whales. Such
guano contains from 7-1/2 to 8-1/2 per cent of nitrogen, and about
13-1/2 per cent of phosphoric acid.
In America fish-guano is manufactured to a considerable extent--one
important source being the menhaddo, a coarse sort of herring. This fish
is caught for the sake of its oil, which is extracted by boiling, the
residue being manufactured, after pressing and drying, into guano.
In this country the manufacture of fish-guano is carried out to a
considerable and increasing extent. Formerly it was imported from Norway
to a larger extent than is now the case, the present annual imports
amounting only to 1000 or 2000 tons. The total annual production in the
United Kingdom is probably 7000 or 8000 tons.
_Value of "Fish-Guano."_
That fish-guano is a valuable manure there can be no doubt. What,
however, impairs its value is the fact that, as a rule, it contains a
certain amount of oil. The effect of this oil is to retard fermentation
and decomposition when the guano is applied to the soil, and thus render
its action slower than would otherwise be the case.
When applied to the soil, therefore, every opportunity ought to be
given to promote its fermentation. It is best applied some time before
it is likely to be used. It ought to be well mixed with the
soil-particles, and not allowed to lie on the top of the soil. Its best
effect will be on light well-cultivated soils, which permit of the
access both of sufficient moisture and of sufficient air for rapid
fermentation. Its value as a manure for hops, vines, grass, and
strawberries has been found to be considerable. It has been recommended
to be applied along with farmyard manure; and such a mode of application
is no doubt well suited to promote its decomposition. It has also been
used for mixing with superphosphate of lime. Professor Storer has
advocated a more general use of fish as a manure than is at present the
case. He suggests that even fish not suitable for edible purposes might
be caught for the purpose of conversion into manure. The difficulty of
preserving fish, however, is considerable; and he suggests the use of
potash salts, such as muriate of potash, or lime for this purpose. The
benefit of using potash would be twofold. In addition to acting as a
preservative, it would considerably enhance the value of the resulting
guano as a manure. There is much truth in Professor Storer's views; and
no doubt, as our sources of artificial nitrogenous manures grow more
limited, the manufacture of fish-guano will be carried on in the future
on a larger and more systematic scale than hitherto.
_Meat-meal Guano._
What is called "meat-meal guano" is generally that made from the refuse
of the carcasses of cattle after they have been treated for their
meat-extract according to Liebig's process. The meat-meal is used both
for feeding and manurial purposes. Considerable quantities[199] of this
guano are imported annually into this country from South America,
Queensland, and New Zealand,--that coming from Frey Bentos, in Uruguay,
being best known. It is a valuable manure, especially so for its
nitrogen, which varies from 4 to 8 per cent, while it contains of
phosphoric acid from 13 to 20 per cent. Some meat-meal guanos contain as
much nitrogen as 11 per cent.
In some parts of the world, more especially in Germany, the carcasses of
horses, as well as cattle, dogs, pigs, &c., which have died of disease,
are converted into a guano. They are subjected to treatment by steam in
digestors, by which means the fat and gelatine are separated and
utilised, while the remaining portion of the animal is converted into
guano. Other processes are also employed. The resulting manure contains
from 6 to 10 per cent of nitrogen, and from 6 to 14 per cent of
phosphoric acid.
_Value of Meat-meal Guano._
Meat-meal guano is a valuable nitrogenous manure. The same remarks
apply to it as to fish-guano, although it ferments probably very much
more quickly than the latter, and is undoubtedly a more valuable manure.
_Bat Guano._
In conclusion, we may consider bat guano. Bat guano, which is really a
very rare curiosity, has been found accumulated in hot climates in
caves.
The samples which have been analysed have differed very much in quality,
some containing as much as 9 per cent of nitrogen and 25 per cent of
phosphoric acid. Provided it could be obtained in any quantity, and of a
quality even approximating to the above analysis, it need scarcely be
pointed out that bat guano would be a most valuable manure.
A singular point about its composition is, that it has been found to
contain a considerable proportion of its nitrogen (as much as 3 per
cent) in the form of nitrates.
_Pigeon and Fowl Dung._
Pigeon dung is a manure which historically is of great importance. The
dung of pigeons was used as a manure by the ancient Romans; and even in
modern times, more especially in France, it was considered a most
important fertiliser. Despite these facts, pigeon dung is by no means a
rich manure, and its composition compares most unfavourably with that of
the guanos we have just been considering. According to Storer,[200] it
only contains from 1-1/4 to 2-1/2 per cent of nitrogen, and from 1-1/2
to 2 per cent of phosphoric acid, and a little over 1 per cent of
potash.
The dung of poultry is just about as poor, fowl dung containing from .8
to 2 per cent of nitrogen, 1-1/2 to 2 per cent of phosphoric acid, and a
little under 1 per cent of potash; while that of ducks and geese is even
poorer.[201]
From these statements it will be seen that the excrements of pigeons,
hens, and ducks do not form a rich manure. One thing about pigeon dung
which is to be noticed, is the fact that it ferments very quickly.
None of the pseudo-guanos, however rich they may be in manurial
ingredients, can be regarded as equal in their action to the genuine
article, for reasons which we have gone into already when considering
the action of guano.
FOOTNOTES:
[183] Bones, it is true, were in use long before guano; but popular as
they deservedly were, they had not been used, at the time of the
importation of guano, to any very considerable extent.
[184] The total annual imports at present may be taken at under 30,000
tons, whereas in 1855 they amounted to over 200,000 tons. For statistics
on this point the reader is referred to the Appendix, Note I., p. 327.
[185] With regard to the origin of certain guano deposits, which are of
very recent date--_e.g._, _Angamos_ and _Ichaboe_--there can be no doubt
whatever, because we can witness the process of formation still taking
place. It is not so, however, with regard to older deposits, for which
some have been inclined to claim mineral origin. The best proof that
such deposits owe their origin mainly to bird excrements is the
comparatively large quantity of _uric acid_ they contain. On the other
hand, the evidence in support of the belief that they are also formed
from the remains of the birds themselves and other animals, is to be
found in the large proportion of phosphates they contain, and the
presence in the deposits of feathers and the fossilised skeletons of the
animals above mentioned.
[186] A complete list of the various deposits will be found in the
Appendix, Note II., p. 327. It may be noticed that nearly all the
deposits lie within 10 deg. to 20 deg. north and south of the Equator.
[187] See Chapter on Farmyard Manure, p. 257.
[188] According to Nesbit, some of the cargoes of this guano contained
hard saline lumps of very little manurial value--over 50 per cent being
common salt.
[189] The salt exports were made in 1868.
[190] For analyses of these nodules and crystals, see Appendix, Note
III., p. 328.
[191] See Heiden, vol. ii. p. 356.
[192] See Appendix, Note IV., p. 329.
[193] The Ichaboe guano at present exported is a fresh deposit, and is
annually collected for shipment.
[194] Further chemical changes have occurred in certain cases between
the guano and the limestone rock beneath, resulting in the formation of
what is called a "crust" guano. Such guanos form a soft phosphatic rock,
and are extremely rich in phosphates. As examples of these "crust"
guanos may be mentioned Sombrero, Curacao, Aruba, Mexico, and Navassa
phosphates.
[195] The presence in the old Peruvian guano of concretionary nodules
has already been referred to.
[196] According to Vogel the nitrogen as urates is converted by the
sulphuric acid into ammonia salts.
[197] See Appendix, Note VI. p. 330.
[198] It must be remembered, however, that even genuine guano contains a
certain quantity of carbonate of lime, and will give a slight amount of
effervescence when so treated.
[199] The annual imports may be stated at from 3000 to 4000 tons.
[200] Agricultural Chemistry, vol. i. p. 367.
[201] See Appendix, Note VII., p. 331.
APPENDIX TO CHAPTER VIII.
NOTE I. (p. 297).
PERUVIAN GUANO IMPORTED INTO THE UNITED KINGDOM, 1865-1893.
Year. Tons. | Year. Tons.
1865 213,024 | 1881 33,393
1870 247,028 | 1882 27,382
1871 144,735 | 1883 36,713
1872 74,964 | 1884 15,802
1873 135,895 | 1885 -
1874 94,346 | 1886 28,733
1875 86,042 | 1887 5,784
1876 158,674 | 1888 16,446
1877 111,835 | 1889 17,000
1878 127,813 | 1890 19,000
1879 45,475 | 1891 11,000
1880 58,631 | 1892 14,000
NOTE II. (p. 298).
GUANO DEPOSITS OF THE WORLD.
SOUTH AMERICA--
_Peru._--In various islands off the coast--viz., Chincha, Guanape,
Ballestas, Macabi, Lobos, and Patillos; and on different parts of the
coast--viz., Pabellon de Pica, Chipana, Huanillos, Punta de Patillos,
Independence Bay, and Lobos de Afuera.
_Columbia._--In different parts of the States of Venezuela, New Granada,
and Ecuador. Guano coming from these parts is often known as Columbian
guano, or according to the name of the State in which it is found.
Maracaibo and Monks guanos come from the coast of Venezuela. Deposits
are also found on the Galapagos Islands, to the west of Ecuador.
_Bolivia._--Mejillones, Patagonia, Leon's.
NORTH AMERICA--Deposits have been found on the coasts of Mexico and
California; on the Raza and Patos Islands; and on the coasts of
Labrador. They have also been found on the Islands of Curacao, Aruba,
and Navassa in the Gulf of Mexico.
AFRICA--On the west coast deposits have been found at Algoa
Bay, Saldanha Bay, and on the Island of Ichaboe.
AUSTRALIA--Shark's Bay and Swan Island.
WEST INDIES--Sombrero, Aves, and Cuba.
PACIFIC OCEAN--On the Islands of Baker, Jarvis, Howland,
Malden, Starbuck, Fanning, Enderbury, Lacepede, Browse, Huon, and
Surprise.
ASIA--Deposits at Kuria Muria on the Arabian coast, and on the
Sandwich Islands. (See Heiden's 'Duengerlehre,' vol. ii. p. 349.)
NOTE III. (p. 303).
COMPOSITION OF CONCRETIONARY NODULES.
(_Analyses by Karmrodt._)
No. 1.
Potassium sulphate 7.49
" phosphate 9.52
Sodium " 9.08
Ammonium " 7.57
Calcium sulphate 3.40
Ammonium urate 4.09
" oxalate 41.28
Nitrogenous organic matter 10.17
Water 7.40
-----
100.00
------
Nitrogen 14.84
No. 2.
Potassium sulphate 45.64
Sodium " 13.22
Ammonium " 10.23
" oxalate 9.14
Basic ammonium phosphate 12.09
Precipitated ammonium phosphate 4.78
Organic matter .94
Insoluble 1.90
Water 2.06
------
100.00
------
NOTE IV. (p. 306).
The following analyses, being the average of a large number of different
samples analysed from time to time in the chemical laboratory of the
Pommritz Agricultural Experimental Station, show the gradual
deterioration of Peruvian guano, as regards its percentage of nitrogen,
during the years 1867-81:--
Nitrogen. Nitrogen.
1867 13.16 | 1873 9.16
1868 11.98 | 1874 9.83
1869 13.66 | 1878 7.10
1870 12.37 | 1879 6.95
1871 10.04 | 1880 7.07
1872 10.72 | 1881 6.93
NOTE V. (p. 309).
COMPOSITION OF DIFFERENT GUANOS.
The following is a list of the more common nitrogenous and phosphatic
guanos which have been used in the past or are at present in use. Those
printed in italics are still being worked. As their value depends on
their nitrogen and phosphoric acid, these alone have been given. The
percentages must be taken as mere approximations, as the quality of
different cargoes from the same deposits varies very much. The table may
be found useful for reference.
_Nitrogenous Guanos._
Phosphoric } { Tricalcic
Nitrogen = Ammonia. acid } = { phosphate.
per cent. per cent. per cent. per cent.
Angamos 20 24 5 11
Chincha 14 17 13 28
Ballestas 12 15 12 26
Egyptian 11 13 19 41
Guanape 11 13 - -
Macabi 11 13 12 26
Corcovado 11 13 15 33
_Saldanha Bay_ 9 11 9 20
_Ichaboe_ 8 10 9 20
Independence Bay 7 9 12 26
_Pabellon de Pica_ 7 9 14 31
_Punta de Lobos_ 4 5 15 33
_Huanillos_ 6 7 18 28
Penguin 5 6 11 24
Patagonian 4 5 18 39
Falkland Islands 4 5 14 31
_Phosphatic Guanos._
Phosphoric } { Tricalcic
acid } = { phosphate.
per cent. per cent.
Maracaibo, or Monks 42 92
Raza Island 40 87
Curacao 40 87
_Baker Island_ 39 85
Starbuck 38 83
_Enderbury_ 37 81
Californian 35 76
_Aves_ 34 74
Fanning Island 34 74
Howland 34 74
_Sidney Island_ 34 74
Mejillones 33 72
Lacepede Island 33 72
_Malden Island_ 32 70
Sombrero 32 70
_Browse Island_ 31 68
_Huon Island_ 28 61
Patos Island 24 52
Jarvis Island 20 44
Cape Vert 11 24
NOTE VI. (p. 314).
It may be of interest to refer to a theory put forward by Liebig as to
the action of oxalic acid in guano. This, he considered, had the effect
of gradually rendering the insoluble calcium phosphate soluble, and
giving rise to the formation of ammonium phosphate and calcium oxalate.
Such an action would probably take place were the guano allowed to
ferment by itself. We know, however, that when it is brought in contact
with the soil-particles, all its soluble phosphate is converted into
precipitated phosphate.
NOTE VII. (p. 326).
ANALYSES OF DUNG OF FOWLS, PIGEONS, DUCKS, AND GEESE. (Storer's
'Agricultural Chemistry,' vol. i. p. 367.)
Fowls. Pigeons. Ducks. Geese.
Water 56.00 52.00 56.60 77.10
Organic matter 25.50 31.00 26.20 13.40
Nitrogen 1.60 1.75 1.00 .55
Phosphoric acid 1.5-2.00 1.5-2.00 1.40 .54
Potash .80-.90 1.0-1.25 .62 .95
Lime 2.00-2.50 1.5-2.00 1.70 .84
Magnesia .75 .50 .35 .20
According to a computation by a Belgian farmer, a pigeon yields about 6
lb. of dung in a year, a hen about 12 lb., a turkey or goose about 25
lb., and a duck 18 lb.