THE COMPOSITION AND PROPERTIES OF FARM-YARD AND LIQUID MANURES.
In the preceding chapter, a general manure has been defined as one
containing all the constituents of the crop to which it is to be
applied, in a state fitted for assimilation. This condition is fulfilled
only by substances derived from the vegetable and animal kingdoms, and
most effectually by a mixture of both. On this account, and also because
its properties are such as enable it to act powerfully on the soil,
farm-yard manure must always be of the highest importance. It is, in
fact, the typical manure, and in proportion as other substances approach
it in properties and composition, is their value for general purposes on
the farm.
Farm-yard manure is a mixture of the dung and urine of domestic animals,
with the straw used as litter; and its value and composition must
necessarily depend upon that of these substances, as well as on the
proportion in which they are mixed. The dung of animals consists of that
part of their food which passes through the intestinal canal without
undergoing assimilation; the urine containing the portion which has been
assimilated and is again excreted, in consequence of the changes which
are proceeding in the tissues of the animal. Their composition is
naturally very different, and must be separately considered.
_Urine._--Urine consists of a variety of earthy and alkaline salts, and
of certain organic substances, generally rich in nitrogen, dissolved in
a large quantity of water. That of the different domestic animals has
been frequently examined, but the analyses of Fromberg give the most
complete view of their manurial value:--
Horse. Swine. Ox. Goat. Sheep.
Extractive matter } 2.132 0.142 2.248 0.100 0.340
soluble in water }
Extractive matter } 2.550 0.387 1.421 0.454 3.330
soluble in spirit}
Salts soluble in } 2.340 0.909 2.442 0.850 1.957
water }
Salts insoluble in} 1.880 0.088 0.155 0.080 0.052
water }
Urea 1.244 0.273 1.976 0.378 1.262
Hippuric acid 1.260 ... 0.550 0.125 ...
Mucus 0.005 0.005 0.007 0.006 0.025
Water 88.589 98.196 91.201 98.007 92.897
------ ------- ------- ------- -------
100.000 100.000 100.000 100.000 99.863
_Composition of the Ash of these Urines._
Horse. Swine. Ox. Goat. Sheep.
Carbonate of lime 12.50 ... 1.07 trace 0.82
Carbonate of magnesia 9.46 ... 6.93 7.3 0.46
Carbonate of potash 46.09 12.10 77.28 trace ...
Carbonate of soda 10.33 ... ... 53.0 42.25
Sulphate of potash ... ... 13.30 ... 2.98
Sulphate of soda 13.04 7.00 ... 25.0 7.72
Phosphate of soda ... 19.00 ... ... ...
Phosphate of lime }
Phosphate of magnesia } ... 8.80 ... ... 0.70
Chloride of sodium 6.94 53.10 0.30 14.7 32.01
Chloride of potassium ... trace ... ... 12.00
Silica 0.55 ... 0.35 ... 1.06
Oxide of iron and loss 1.09 ... 0.77 ... ...
------ ------ ------ ------ ------
100.00 100.00 100.00 100.00 100.00
Human urine has been accurately examined by Berzelius, although his
estimate of the proportion of urea is generally admitted to be above the
average. His analysis gives the following numbers:--
Natural. Dry Residue.
Urea 3.010 44.70
Lactic acid, lactate of ammonia,} 1.714 25.58
and extractive matter }
Uric acid 0.100 1.49
Mucus 0.032 0.48
Sulphate of potash 0.371 5.54
Sulphate of soda 0.316 4.72
Phosphate of soda 0.294 4.39
Biphosphate of ammonia 0.165 2.46
Chloride of sodium 0.445 6.64
Muriate of ammonia 0.150 2.46
Phosphates of magnesia and lime 0.100 1.49
Silica 0.003 0.05
Water 93.300
------- ------
100.000 100.00
Among the special organic constituents of the urine are three
substances, urea, uric acid, and hippuric acid, which are of much
importance in a manurial point of view. The first of these is found in
considerable quantity in the urine of all animals, but is especially
abundant in the carnivora. Uric acid is found only in these animals, and
is the most remarkable constituent of the excrement of birds, serpents,
and many of the lower animals. Hippuric acid is most abundant in the
herbivora. These substances are all highly nitrogenous. They contain--
Urea. Uric Acid. Hippuric Acid.
Carbon 20.00 36.0 60.7
Hydrogen 6.60 2.4 5.0
Nitrogen 46.70 33.4 8.0
Oxygen 26.70 28.2 26.3
------ ----- -----
100.00 100.0 100.0
They are extremely prone to change, and in presence of animal matters
readily ferment, and are converted into salts of ammonia. Thus human
urine, which, at the time of emission is free from smell of ammonia, and
has a slightly acid reaction, becomes highly ammoniacal if it be kept
for a few days. This is due to the conversion of urea into carbonate of
ammonia; and the same change takes place, though more slowly, with uric
and hippuric acids.
It is obvious, from the foregoing analyses, that great differences must
exist in the manurial value of the urine of different animals. Not only
do they vary greatly in the proportion of solid matters which they
contain, but also in the kind and quantity of their nitrogenous
constituents. They differ also in regard to their saline ingredients;
and while salts of potash and soda form the principal part of the ash of
the urine of the ox, sheep, goat, and horse, and phosphoric acid and
phosphates are entirely absent, that of the pig contains a considerable
quantity of the latter substances, and in this respect more nearly
resembles the urine of man. Human urine is also much richer in urea and
nitrogenous constituents generally, and has a higher value than any of
the others.
It is especially worthy of notice that the urine of the purely
herbivorous animals (with the exception of the sheep, which contains a
small quantity), are devoid of phosphates and urea; and consequently,
when employed alone, they are not general manures--a matter of some
importance in relation to the subject of liquid manuring, which will be
afterwards discussed.
_Dung._--The solid excrement of animals is equally variable in
composition. That of the domestic animals which had the ordinary winter
food was found to have the following composition:--
Horse. Cow. Sheep. Swine.
Per-centage of water in the } 77.25 82.45 56.47 77.13
fresh excrement }
Ash in the dry excrement 13.36 15.23 13.49 37.17
100 parts of ash contained--
Horse. Cow. Sheep. Swine.
Silica 62.40 62.54 50.11 13.19
Potash 11.30 2.91 8.32 3.60
Soda 1.98 0.98 3.28 3.44
Chloride of sodium 0.03 0.23 0.14 0.89
Phosphate of iron 2.73 8.93 3.98 10.55
Lime 4.63 5.71 18.15 2.63
Magnesia 3.84 11.47 5.45 2.24
Phosphoric Acid 8.93 4.75 7.52 0.41
Sulphuric acid 1.83 1.77 2.69 0.90
Carbonic acid ... trace trace 0.60
Oxide of manganese 2.13 ... ... ...
Sand ... ... ... 61.37
---- ---- ---- ----
99.80 99.29 99.64 99.82
Human faeces contain about 75 per cent of water; and their dry residue
was found by Way to have the following composition:--
Organic matter 88.52
Insoluble siliceous matters 1.48
Oxide of iron 0.54
Lime 1.72
Magnesia 1.55
Phosphoric acid 4.27
Sulphuric acid 0.24
Potash 1.19
Soda 0.31
Chloride of sodium 0.18
------
100.00
In a sample analyzed by myself there were found--
Organic matter 86.75
Phosphates 8.19
Alkaline salts, containing 1.18 of phosphoric } 2.53
acid }
Insoluble matters 2.53
------
100.00
Nitrogen 4.59
Equal to ammonia 5.57
It is to be observed that the urine and dung of animals differ
conspicuously in the composition of their ash, the former being
characterized by the abundance of alkaline salts, while the latter
contains these substances in small proportion, but is rich in earthy
matters, and especially in phosphoric acid. Salts of potash, for
example, form nine-tenths of the inorganic part of the urine of the ox,
while less than three per cent of that alkali is found in its dung.
Phosphoric acid, on the other hand, is not met with in the urine, but
forms about ten per cent of the dung. Silica is the most abundant
constituent of the dung, but a large proportion of that found on
analysis has been swallowed in the shape of grains of sand and particles
of soil mechanically mixed with the food, although part is also derived
from the straw and grains, which contain that substance in great
abundance. The difference in the quantity of nitrogen they contain is
also very marked, and is distinctly shown by the following analyses by
Boussingault, which give the quantity of carbon, hydrogen, nitrogen,
oxygen, and ash in the dung and urine of the horse and the cow in their
natural state, and after drying at 212 deg..
+---------+--------------------------+--------------------------+
| | HORSE. | COW. |
| +-------------+------------+-------------+------------+
| | Natural. | Dry. | Natural. | Dry. |
| +-------------+------------+-------------+------------+
| |Urine.| Dung.|Urine.|Dung.|Urine.| Dung.|Urine.|Dung.|
| +------+------+------+-----+------+------+------+-----+
|Carbon | 4.46| 9.56| 36.0| 38.7| 3.18| 4.02| 27.2| 42.8|
|Hydrogen | 0.47| 1.26| 3.8| 5.1| 0.30| 0.49| 2.6| 5.2|
|Nitrogen | 1.55| 0.54| 12.5| 2.2| 0.44| 0.22| 3.8| 2.3|
|Oxygen | 1.40| 9.31| 11.3| 37.7| 3.09| 3.54| 26.4| 37.7|
|Ash | 4.51| 4.02| 36.4| 16.3| 4.68| 1.13| 40.0| 12.0|
|Water | 87.61| 75.31| 0.0| 0.0| 88.31| 90.60| 0.0| 0.0|
| +------+------+------+-----+------+------+------+-----+
| |100.00|100.00| 100.0|100.0|100.00|100.00| 100.0|100.0|
+---------+------+------+------+-----+------+------+------+-----+
Hence, weight for weight, the urine of the horse, in its natural state,
contains three times as much nitrogen as its dung; that of the cow twice
as much; and the difference, especially in the horse, is still more
conspicuous when they are dry.
It is obvious that the quality of farm-yard manure must depend--1. On
the kind of animal from which it is produced; 2. On the quantity of
straw which has been used as litter; 3. On the nature of the food with
which the animals have been supplied; 4. On the extent to which its
valuable constituents have been rendered available by the treatment to
which it has been subjected; and 5. On the care which has been taken to
prevent the escape of the urine, or of the ammonia produced by its
decomposition.
The composition of farm-yard manure has engaged the attention of several
chemists; but there are still many points on which our information
regarding it is less complete than might be desired. Its investigation
is surrounded with peculiar difficulties, not merely on account of its
complexity, but because its properties render it exceedingly difficult
to obtain a sample which fairly represents its average composition. In
the case of long dung, these difficulties are so great that it is
scarcely possible to overcome them; and hence, discrepancies are
occasionally to be met with in the analyses of the most careful
experimenters. The most minute and careful analyses yet made are those
of Voelcker, who has compared the composition of fresh and rotten dung,
and studied the changes which the former undergoes when preserved in
different ways. He employed in his experiments both fresh and rotten
dung, and subjected them to different methods of treatment. His analyses
are given in the accompanying table, in which column 1 gives the
composition of fresh long dung, composed of cow and pig dung. 2. Is dung
of the same kind, after having lain in a heap against a wall, but
otherwise unprotected from the weather for three months and eleven days
in winter, during which time little rain fell. 3. The same manure, kept
for the same time under a shed. 4. Well rotten dung, which had been kept
in the manure heap upwards of six months. 5. The same, after having lain
against a wall for two months and nine days longer.
+-------------------------------+-------------+-------------+--------------+
| | 1 | 2 | 3 |
+-------------------------------+-------------+-------------+--------------+
| Water | 66.17 | 69.86 | 67.32 |
| Soluble organic matters | 2.48 | 3.86 | 2.63 |
| Soluble inorganic matters. | | | |
| Silica | 0.237 | 0.279 | 0.239 |
| Phosphate of lime | 0.299 | 0.300 | 0.331 |
| Lime | 0.066 | 0.048 | 0.056 |
| Magnesia | 0.011 | 0.019 | 0.004 |
| Potash | 0.573 | 1.096 | 0.676 |
| Soda | 0.051 | 0.187 | 0.192 |
| Chloride of sodium | 0.030 | 0.106 | 0.058 |
| Sulphuric acid | 0.055 | 0.160 | 0.119 |
| Carbonic acid and loss | 0.218 | 0.775 | 0.445 |
| | ----- 1.54 | ... 2.97 | ----- 2.12 |
| | | | |
| Insoluble organic matters | 25.76 | 18.44 | 20.46 |
| Insoluble inorganic matters-- | | | |
| Soluble silica | 0.967 | 0.712 | 1.893 |
| Insoluble silica | 0.561 | 0.857 | 1.075 |
| Oxide of iron, alumina, and | | | |
| phosphates | 0.596 | 0.810 | 1.135 |
+-------------------------------+-------------+-------------+--------------+
+-------------------------------+-------------+-------------+
| | 4 | 5 |
+-------------------------------+-------------+-------------+
| Water | 75.42 | 73.90 |
| Soluble organic matters | 3.71 | 2.70 |
| Soluble inorganic matters | | |
| Silica | 0.254 | 0.147 |
| Phosphate of lime | 0.382 | 0.129 |
| Lime | 0.117 | 0.018 |
| Magnesia | 0.047 | 0.018 |
| Potash | 0.446 | 0.960 |
| Soda | 0.023 | 0.082 |
| Chloride of sodium | 0.037 | 0.052 |
| Sulphuric acid | 0.058 | 0.072 |
| Carbonic acid and loss | 0.106 | 0.584 |
| | ----- 1.47 | ----- 2.06 |
| | | |
| Insoluble organic matters | 12.82 | 14.39 |
| Insoluble inorganic matters-- | | |
| Soluble silica | 1.424 | 1.10 |
| Insoluble silica | 1.010 | 1.54 |
| Oxide of iron, alumina, and | | |
| phosphates | 0.947 | 0.37 |
+-------------------------------+-------------+-------------+
+-------------------------------+-------------+-------------+--------------+
| | 1 | 2 | 3 |
+-------------------------------+-------------+-------------+--------------+
| Containing phosphoric acid |(0.178) |(0.177) |(0.298) |
| Equal to bone earth |(0.386) |(0.277) |(0.646) |
| Lime | 1.120 | 1.291 | 1.868 |
| Magnesia | 0.143 | 1.029 | 0.078 |
| Potash | 0.099 | 0.127 | 0.208 |
| Soda | 0.019 | 0.046 | 0.038 |
| Sulphuric acid | 0.061 | 0.099 | 0.098 |
| Carbonic acid and loss | 0.484 | 0.929 | 1.077 |
| | ----- 4.05 | ----- 4.90 | ----- 7.47 |
| | ----- | ----- | ------ |
| | 100.00 | 100.00 | 100.00 |
| | | | |
| Containing nitrogen | 0.149 | 0.270 | 0.170 |
| Equal to ammonia | 0.181 | 0.320 | 0.206 |
| Containing nitrogen | 0.494 | 0.470 | 0.580 |
| Equal to ammonia | 0.599 | 0.570 | 0.700 |
| Total nitrogen | 0.643 | 0.740 | 0.750 |
| Equal to ammonia | 0.780 | 0.890 | 0.906 |
+-------------------------------+-------------+-------------+--------------+
+-------------------------------+-------------+-------------+
| | 4 | 5 |
+-------------------------------+-------------+-------------+
| Containing phosphoric acid |(0.274) |(0.06) |
| Equal to bone earth |(0.573) |(0.10) |
| Lime | 1.667 | 2.25 |
| Magnesia | 0.091 | 0.02 |
| Potash | 0.045 | 0.12 |
| Soda | 0.038 | 0.01 |
| Sulphuric acid | 0.063 | 0.10 |
| Carbonic acid and loss | 1.295 | 1.44 |
| |----- 6.58 | ---- 6.95 |
| | ----- | ------ |
| | 100.00 | 100.00 |
| | | |
| Containing nitrogen | 0.297 | 0.149 |
| Equal to ammonia | 0.360 | 0.180 |
| Containing nitrogen | 0.309 | 0.613 |
| Equal to ammonia | 0.375 | 0.744 |
| Total nitrogen | 0.606 | 0.762 |
| Equal to ammonia | 0.735 | 0.924 |
+-------------------------------+-------------+-------------+
On examining and comparing these analyses, it appears that the
differences are by no means great, although, on the whole, they tend to
show that, weight for weight, well-rotten dung is superior to fresh,
provided it has been properly treated. Not only is the quantity of
valuable matters existing in the soluble state materially increased,
whereby the dung is enabled to act with greater rapidity, but, owing to
evaporation and the escape of carbonic acid, produced by the
decomposition of the organic substances, the proportion of those
constituents which are most important to the plant is increased. This is
particularly to be noticed, in regard to the nitrogen, which has
distinctly increased in all cases in which the dung has been kept for
some time; and the practical importance of this observation is very
great, because it has been commonly supposed that, during the process of
fermentation, ammonia is liable to escape into the air. It would appear,
however, that there is but little risk of loss in this way, so long as
the dung-heap is left undisturbed; and it is only when it is turned that
any appreciable quantity of ammonia volatilizes. It is different,
however, with the action of rain, which soon removes, by solution, a
considerable quantity of the nitrogen contained in farm-yard manure; and
the deterioration must necessarily be most conspicuous in rotten dung,
which sometimes contains nearly half of its nitrogen in a soluble
condition. The effect produced in this way is conspicuously seen, by the
results of weighings and analyses of small experimental dung-heaps, made
by Dr. Voelcker at different periods. The subjoined table shows the
composition of the heap, lying against a wall, and exposed to the
weather at different periods:--
+--------------------------+-------------------------------------------+
| | WHEN PUT UP. |
| +---------+------------+---------+----------+
| | Nov 3d | April 30th | Aug 23d | Nov 15th |
| | 1854. | 1855. | 1855. | 1855. |
| +---------+------------+---------+----------+
| Weight of manure in lbs. | 2838 | 2026 | 1994 | 1974 |
| +---------+------------+---------+----------+
| Water | 1877.9 | 1336.1 | 1505.3 | 1466.5 |
| Dry Matter | 960.1 | 689.9 | 488.7 | 507.5 |
| +---------+------------+---------+----------|
| Consisting of-- | | | | |
| Soluble organic matter | 70.38 | 86.51 | 58.83 | 54.04 |
| " mineral matter | 43.71 | 57.88 | 39.16 | 36.89 |
| Insoluble organic matter | 731.07 | 389.74 | 243.22 | 214.92 |
| " mineral matter | 114.94 | 155.77 | 147.49 | 201.07 |
| +---------+------------+---------+----------+
| Total nitrogen | 18.23 | 18.14 | 13.14 | 13.03 |
| Equal to ammonia | 22.14 | 22.02 | 15.96 | 15.75 |
+--------------------------+---------+------------+---------+----------+
In this case, during the winter six months, which were very dry, the
manure lost 541.8 lbs. of water and 270.2 lbs. of dry matter, but the
nitrogen remained completely unchanged. But during the succeeding
semi-annual period, when rain fell abundantly, the quantity of nitrogen
is diminished by nearly a third, while the water has increased, and the
loss of dry matter by fermentation, notwithstanding the high temperature
of the summer months, was only 182.4 lbs. The soluble mineral matters
also, which increased during the first period, are again reduced during
the second, until they also fall to about two-thirds of their maximum
quantity. That this effect is to be attributed to the solvent action of
rain is sufficiently obvious, from a comparison of the results afforded
by the other heaps, which had been kept under cover during the same
period, as shown below.
+--------------------------+----------------------------------------------|
| | WHEN PUT UP. |
| +----------+------------+----------+-----------+
| | Nov. 3d, | April 30th | Aug. 23d | Nov. 15th |
| | 1854. | 1855. | 1855. | 1855. |
| +----------+------------+----------+-----------+
| Weight of manure in lbs. | 3258 | 1613 | 1297 | 1235 |
| +----------+------------+----------+-----------|
| Water | 2156.0 | 917.6 | 563.2 | 514.5 |
| Dry Matter | 1102.0 | 695.4 | 733.8 | 720.5 |
| +----------+------------+----------+-----------|
| Consisting of-- | | | | |
| Soluble organic matter | 80.77 | 74.68 | 53.56 | 66.28 |
| " mineral matter | 50.14 | 54.51 | 39.55 | 54.68 |
| Insoluble organic matter | 839.17 | 410.24 | 337.32 | 341.97 |
| " mineral matter | 131.92 | 155.97 | 303.37 | 257.57 |
| +----------+------------+----------+-----------+
| Total nitrogen | 20.93 | 19.26 | 16.54 | 1.79 |
| Equal to ammonia | 25.40 | 23.33 | 20.08 | 2.81 |
+--------------------------+----------+------------+----------+-----------+
The loss of nitrogen is here comparatively trifling, and during the
whole year, but little exceeds two pounds, of which the greater part
escapes during the first six months, and the soluble inorganic matters
are almost unchanged. The total weight of the manure, however, undergoes
a very great reduction, due chiefly to evaporation of water, but in part
also to the loss of organic matters evolved in the form of carbonic acid
during fermentation.
When the manure is spread out, as it is usually found under cattle in
open yards, the deterioration is very great, a quantity thus treated
having lost, in the course of a year, nearly two-thirds of its nitrogen,
and four-fifths of its soluble inorganic matters.
The general conclusion deducible from these analyses is that, provided
it be carefully prepared, farm-yard manure does not differ very largely
in value, although the balance is in favour of the well-rotten dung.
This result is in accordance with that obtained by other experimenters,
who have generally found from 0.5 to 0.6 per cent of nitrogen, and 1 or
2 per cent of phosphates. But when carelessly managed, it may fall
greatly short of this standard, as is particularly seen in a sample
examined by Cameron, which had been so effectually washed out by the
rain, as to retain only 0.15 per cent of ammonia. These cases, however,
are exceptional, and well made and well preserved farm-yard manure will
generally be found to differ comparatively little in value; and when
bought at the ordinary price, the purchaser, as we shall afterwards more
particularly see, is pretty sure to get full value for his money, and
the specialities of its management are of comparatively little moment to
him. But the case is very different when the person who uses the manure
has also to manufacture it. The experiments already quoted have shown
that, though the manure made in the ordinary manner may, weight for
weight, be as valuable as at first, the loss during the period of its
preservation is usually very large, and it becomes extremely important
to determine the mode in which it may be reduced to the minimum.
In the production of farm-yard manure of the highest quality, the object
to be held in view is to retain, as effectually as possible, all the
valuable constituents of the dung and urine. But in considering the
question here, it will be sufficient to refer exclusively to its
nitrogen, both because it is the most important, and also because the
circumstances which favour its preservation are most advantageous to the
other constituents. In the management of the dung-heap, there are three
things to be kept in view:--First, To obtain a manure containing the
largest possible amount of nitrogen; secondly, To convert that nitrogen
more or less completely into ammonia; and thirdly, To retain it
effectually.
As far as the first of these points is concerned, it must be obvious
that much will depend on the nature and quantity of the food with which
the animals yielding the dung are supplied, and the period of the
fattening process at which it is collected. When lean beasts are put up
to feed, they at first exhaust the food much more completely than they
do when they are nearly fattened, and the manure produced is very
inferior at first, and goes on gradually improving in quality as the
animal becomes fat.
When the food is rich in nitrogenous compounds, the value of the manure
is considerably increased. It has been ascertained, for instance, that
when oil-cake has been used, not less than seven-eighths of the valuable
matters contained in it reappear in the excrements; and as that
substance is highly nitrogenous, the dung ought, weight for weight, to
contain a larger amount of that element. That it actually does so, I
satisfied myself by experiments, made some years since, when the dung
and urine of animals fed on turnips, with and without oil-cake, were
examined; but unfortunately, no determination of the total quantity of
the excretions could be made, so that it was impossible to estimate the
increased value. It has been commonly supposed that when cattle are fed
with oil-cake, the increased value of the manure is equal to from
one-half to two-thirds the price of the oil-cake; but this is a rather
exaggerated estimate as regards linseed-cake, although it falls short of
the truth in the case of rape, as we shall afterwards more particularly
see.
Although it may be possible, in this way, to increase the quantity of
nitrogen as a manure, there is a limit to its accumulation, due to the
fact, that it is contained most abundantly in the urine, which can only
be retained by the use of a sufficient supply of litter. Where that is
deficient, the dung-heap becomes too moist, and the fluid and most
valuable part drains off, either to be lost, or to be collected in the
liquid manure-tank. In the well managed manure-heap, the quantity of
litter should be sufficient to retain the greater part of the liquid
manure, and to admit of only a small quantity draining from it, which
should be pumped up at intervals, so as to keep the whole in a proper
state of moisture. Attention to this point is of great moment, and
materially affects the fermentation. When it is too moist or too dry,
that process is equally checked; in the former case by the exclusion of
air, which is essential to it; and in the latter, by the want of water,
without which the air cannot act. The exact mode in which the manure is
to be managed must greatly depend on whether the supply of litter is
large or small. In the latter case the urine escapes, and is collected
in the liquid manure-tank, and must be used by irrigation, and in some
cases this mode of application has advantages, but in general, it is
preferable to avoid it, and have recourse to substances which increase
the bulk of the heap sufficiently to make it retain the whole of the
liquid. For this purpose, clay, or still better, the vegetable refuse of
the farm, such as weeds, ditch cleanings, leaves, and, in short, any
porous matters, may be used. But by far the best substance, when it can
be obtained, is dry peat, which not only absorbs the fluid, but fixes
the ammonia, by converting it more or less completely into humate.
Reference has been already made to the absorbent power of peat in the
section on soils, but it may be mentioned here that accurate experiment
has shown that a good peat will absorb about 2 per cent[L] of ammonia,
and when dry will still retain from 1 to 1.5 per cent, or nearly twice
as much as would be yielded by the whole nitrogen of an equal weight of
farm-yard manure. Peat charcoal has been recommended for the same
purpose, but careful experiment has shown that it _does not absorb
ammonia_, although it removes putrid odour; and though it may be
usefully employed when it is wished to deodorize the manure heap, it
must not be trusted to for fixing the ammonia.
Much stress has frequently been laid on the advantage to be derived from
the use of substances capable of combining chemically with the ammonia
produced during the fermentation of dung and gypsum, sulphate of iron,
chloride of manganese, sulphate of magnesia, and sulphuric acid, have
been proposed for this purpose, and have been used occasionally, though
not extensively. They all answer the purpose of _fixing_ the ammonia,
that is, of preventing its escaping into the air; but the risk of loss
in this way appears to have been much exaggerated, for a delicate
test-paper, held over a manure-heap, is not affected; and during
fermentation, humic acid is produced in such abundance, as to combine
with the greater part of the ammonia. The real source of deterioration
is the escape of the soluble matters in the drainings from the
manure-heap, which is not prevented by any of these substances; and
where no means are taken to preserve or retain this portion, the loss is
extremely large, and amounts, under ordinary circumstances, to from a
third to a half of the whole value of the manure. Manure, therefore,
cannot be exposed to the weather without losing a proportion of its
valuable matters, depending upon the quantity of rain which falls upon
it. Hence it is obvious that great advantage must be derived, especially
in rainy districts, from covered manure-pits. This plan has been
introduced on some farms with good effect; but the expense and doubts
as to the benefits derived from it, have hitherto prevented the practice
becoming general. The principal difficulty experienced in the use of the
covered dung-pit is, that, where the litter is abundant, the urine does
not supply a sufficiency of moisture to promote the active fermentation
of the dung, and it becomes necessary to pump water over it at
intervals; but when this is properly done, the quality of the manure is
excellent, and its valuable matters are most thoroughly economized.
Although covered dung-pits have been but little used, their benefits
have been indirectly obtained by the method of box-feeding, one of the
great advantages of which is held to be the production of a manure of
superior quality to that obtained in the old way. In box-feeding none of
the dung or urine is removed from under the animals, but is trampled
down by their feet, and new quantities of litter being constantly added,
the whole is consolidated into a compact mass, by which the urine is
entirely retained. Whatever objection may be taken to this system, so
far as the health of the animals is concerned, there is no doubt as to
the complete economy of the manure, provided the quantity of litter used
be sufficient to retain the whole of the liquid. But its advantage is
entirely dependent on the possibility of fulfilling this condition.
Whether box manure is really superior to that which can be prepared by
the ordinary method is very questionable, but it undoubtedly surpasses a
large proportion of that actually produced. It is more than probable,
however, that the careful management of the manure-heap would yield an
equally good product. It is manifest that the same number of cattle, fed
in the same way, on the same food, and supplied with the same quantity
of litter, must always excrete the same quantities of valuable matters;
and the only question to be solved is, whether they are more effectually
preserved in the one way than the other? It will be readily seen that
this cannot be done by analysis alone, but that it is necessary to
conjoin with it a determination of the total weight of manure produced;
for though, weight for weight, box manure may be better than ordinary
farm-yard manure, the total quantity obtained by the latter method, from
a given number of cattle, may be so much greater, that the deficiency in
quality may be compensated for. At the present time our knowledge is too
limited to admit of a definite opinion on this subject, but it is highly
deserving of the combined investigation of the farmer and the chemist.
Supposing the conditions which produce the manure containing the largest
quantity of nitrogen to have been fulfilled, we have now to consider
those which affect its evolution in the form of ammonia. This change is
effected by _fermentation_. When a quantity of manure is left to itself
it becomes hot, and gradually diminishes in bulk, and if it be turned
over after some time, the smell of ammonia may be more or less
distinctly observed. This ammonia is produced, in the first instance,
from the urine, the nitrogenous constituents of which are rapidly
decomposed, and the fermentation thus set up in the mass of manure
extends first to the solid dung, and then to the straw of the litter,
and gradually proceeds until a large quantity of ammonia is produced.
When fresh manure is deposited in the soil, the same changes occur, but
they then proceed more slowly, and experience has shown that a much
smaller effect is produced on the crop to which it has been applied than
when it has been well fermented in the heap. This effect is consistent
with theory, which would further indicate that well-fermented dung must
be especially advantageous when applied to quick-growing crops, and less
necessary to those which come slowly to maturity. As a rule, well
fermented manure is to be preferred, provided it has been well managed
and carefully prepared; but when this has not been done, and the manure
has been exposed to the weather, or made in open courts or hammels, the
economic advantages are all on the side of the fresh dung. It may be
questioned also whether, now that there are so many other available
sources of ammonia, it may not in many instances be advantageous to use
the dung fresh, conjoined with a sufficient quantity of some salt of
ammonia, or other substance fitted to supply the quantity of that
element necessary for the requirements of the crop.
After the farm-yard manure has been prepared at the homestead, it is
often necessary to cart it out to the field some time before it is to be
applied, and it is a question of some importance to determine how it may
be best preserved there. The general practice is to store it in heaps in
the corners of the fields, but some difference of opinion exists as to
whether it should be lightly thrown up so as to leave it in a porous
state, and so promote its further fermentation, or whether it should be
consolidated as much as possible by driving the carts on to the top of
the heap during its construction. Considering the risks to which the
manure is exposed on the field, the latter plan would appear to be the
best. It is advisable also to interstratify the dung with dry soil, so
as to absorb any liquid which may tend to escape from it, and it should
also be covered with a well-beaten layer of earth, in order to exclude
the rain. Although these precautions must not be omitted if the manure
is to be stored in heaps, it will probably be often found quite as
advantageous to spread it at once, and leave it lying on the surface
until it is convenient to plough it. The loss of ammonia by
volatilization will, under such circumstances, especially in the cold
season of the year, be very trifling, and the rain which falls will only
serve to incorporate the soluble matters with the soil, where they will
be retained by its absorptive power.
In the actual application of the manure to the crop, several points
require consideration. It is especially important to determine whether
it ought to be uniformly distributed through the soil, or be kept near
the roots of the plants. Both systems have their advocates, and each has
advantages in particular cases. The choice between the two must greatly
depend upon the nature of the crop and the soil. When the former is of a
kind which spreads its roots wide and deep through the soil, the more
uniformly the manure can be distributed the better; but when it is used
with plants whose roots do not travel far, it is more advantageous to
accumulate it near the seeds. Obvious advantages also attend this
practice in soils which are either too heavy or too light. When, for
example, it is necessary to cultivate turnips in a heavy clay, the
manure put into the drills produces a kind of artificial soil in the
neighbourhood of the plants, in which the bulbs expand more readily than
in the clay itself. On the other hand, when a large quantity of dung, in
a state of active fermentation, comes into immediate contact with the
roots, its effect is not unfrequently injurious. These and many other
points, which will readily suggest themselves to any one who studies the
composition and properties of farm-yard manure, belong more strictly to
the subject of practical agriculture, and need not be enlarged on here.
In the present state of agriculture, a proper estimate of the money
value of farm-yard manure is of much importance in an economic point of
view, and many matters connected with the profitable management of a
farm must hinge upon it. If an estimate be made upon the principle which
will be explained when we come to treat of artificial manures, it
appears that fresh farm-yard manure of good quality is worth from 12s.
to 15s. per ton, and well-rotted dung rather more. It is questionable,
however, whether the system of valuation which is accurate in the case
of a guano or other rapidly acting substance, is applicable to farm-yard
manure, the effects of which extend over some years. A deduction must be
made for the years during which the manure remains unproductive, and
also for the additional expense incurred in carting and distributing a
substance so much more bulky than the so-called portable manures, and it
would not be safe to estimate its value at more than 7s. or 8s. per ton.
_Liquid Manure._--This term is applied to the urine of the animals fed
on the farm, and to the drainings from the manure-heap, which, in place
of being returned to it, are allowed to flow away, and collected in
tanks, from which they are distributed by a watering-cart, or according
to the method recently introduced in Ayrshire, and since adopted in
other places, by pipes laid under-ground in the fields, and through
which the manure is either pumped by steam-power, or, where the
necessary inclination can be obtained, is distributed by gravitation.
That liquid manure must necessarily be valuable, is an inference which
maybe at once drawn from the analyses of the urine of different animals
already given, and of which it chiefly consists. In addition to the
urine, however, it contains also the soluble organic and mineral matters
of the dung, as well as a quantity of solid matters in suspension, among
which phosphates are found, and thus it possesses a supply of an
element which would be almost entirely deficient if it were composed of
urine alone. In the following analyses by Professor Johnston, No. 1 is
the drainings of the manure-heap when exposed to rain; and No. 2 the
same, when moistened with cows' urine pumped over it, the results being
expressed in grains per gallon:--
No. 1. No. 2.
Ammonia 9.6 21.5
Organic matter 200.8 77.6
Ash 268.8 518.4
----- -----
Total solids in a gallon 479.2 617.5
The ash contained--
Alkaline salts 207.8 420.4
Phosphates 25.1 44.5
Carbonate of lime 18.2 31.1
Carbonate of magnesia, and loss 4.3 3.4
Silica and alumina 13.4 19.0
----- -----
268.8 518.4
More elaborate analyses of the same fluid have since been made by Dr.
Voelcker, with the subjoined results per gallon:--
1. 2. 3.
Organic matters and ammoniacal } 263.80 250.63 70.121
salts }
Silica 2.49 9.98 1.154
Oxide of iron 0.70 0.68 ...
Lime 5.34 25.18 13.011
Magnesia 2.96 15.33 1.660
Potash 103.23 112.26 13.411
Chloride of potassium 72.00 77.38 7.712
Chloride of sodium 17.18 46.03 17.258
Phosphoric acid 2.70 9.51 2.304
Sulphuric acid 22.31 37.60 3.408
Carbonic acid, and loss 33.90 27.95 14.025
------ ------ -------
Total solids 526.61 612.53 144.064
Ammonia 114.16 22.31 26.647
The differences are here very remarkable, especially in the quantity of
ammonia, which is exceedingly large in the first sample. All of them are
particularly rich in potash, and contain but a small proportion of
phosphoric acid. The general inference to be deduced from them is, that
liquid manure is a most important source of the alkalis and ammonia, and
must be peculiarly valuable on soils in which these substances are
deficient.
The system of liquid manuring, originally introduced by Mr. Kennedy of
Myremill, Ayrshire, and which has since been adopted in some other
places, differs from liquid manuring in its _strict_ sense, for not only
are the drainings of the manure-heap employed, but the whole solid
excrements are mixed with water in a tank, and rape-dust and other
substances occasionally added, and distributed through the pipes.
It has been abandoned on Mr. Kennedy's farm, but is in use at Tiptree
Hall, and on the farm of Mr. Ralston, Lagg, where the fluid is
distributed by gravitation.
The arrangements employed by Mr. Mechi are identical with those formerly
in use at Myremill. The greater part of the stock is kept on boards, and
the liquid and solid excrements are collected together in the tank, and
largely diluted before distribution. The liquid from the tanks has been
recently examined by Dr. Voelcker, who found it to contain per gallon--
Organic matter and ammoniacal salts 53.03
Soluble silica 6.47
Insoluble siliceous matter (clay) 15.17
Oxide of iron and alumina 2.36
Lime 6.60
Magnesia 1.73
-----
Potash 0.35
Chloride of potassium 1.95
Chloride of sodium 4.81
Phosphoric acid 3.72
Sulphuric acid 1.94
Carbonic acid, and loss 0.47
-----
Total solids 96.60
Ammonia 8.10
The quantity of this liquid distributed per acre is about 50,000
gallons, at a cost of 2d. per gallon. As this quantity contains about 39
lbs. of ammonia, it must be nearly equivalent to 2 cwt. of Peruvian
guano, which costs, with the expense of spreading, from 28s. to 30s. per
acre, while the cost of distributing the liquid exceeds L1: 17s. per
acre. On the other hand, the rapidity with which liquid manure produces
its effect must be taken into account. It is on this that its chief
value depends, and especially when applied to grass land in early
spring, it produces an abundant crop just when turnips and other winter
food are exhausted. Mr. Telfer, Cunning Park, who has used this system
for a good many years, has come to the conclusion that it is only in
this way that it can be made profitable; and though pipes are laid all
over his farm, he has latterly restricted the use of the liquid manure
entirely to Italian ryegrass. Its effect on the cereals is much less
marked, and it can scarcely be considered as capable of advantageous
application to the general operations of the farm. Neither can liquid
manure be applied to all soils. It fails entirely on heavy clays, but is
peculiarly adapted to light sandy soils; and even barren sand may by its
repeated application, be made to yield luxuriant crops. It is not likely
that the system of liquid manuring will extend, except in localities
where it is possible to distribute it by gravitation; and even then, it
will probably be found most economical to restrict its use to one
portion of the farm; and for that purpose, the poorest and most sandy
soil ought to be selected.
_Sewage Manure._--The use of the sewage of towns as a manure is closely
connected with that of the liquid manure produced on the farm. Its
application must take place in a similar manner, and be governed by the
same principles. Although numerous attempts have been made to convert it
into a solid form, or to precipitate its valuable matter, none of them
have succeeded; nor can it be expected that any plan can be devised for
the purpose, because the most important manurial constituents are
chiefly soluble, and cannot be converted into an insoluble state, or
precipitated from their solution. In its liquid form, however, sewage
manure has been employed with the best possible effect in the
cultivation of meadows. The most important instance of its application
is in the neighbourhood of Edinburgh, where 325 acres receive the sewage
of nearly half the town, and have been converted from barren sand into
land which yields from L20 to L30 per acre. The contents of the sewer,
taken just before it flows into the first irrigated meadow, near
Lochend, were found to contain per gallon--
Soluble organic matter 21.90
Insoluble organic matter 21.70
Peroxide of iron and alumina 2.01
Lime 10.50
Magnesia 2.00
Sulphuric acid 6.09
Phosphoric acid 6.14
-----
Chlorine 12.20
Potash 2.89
Soda 13.27
Silica 6.50
------
105.20
Ammonia 14.90
It is interesting to notice that this sewage is superior in every
respect to the liquid manure used at Tiptree Hall; and the good effects
obtained from its application, in the large quantities in which it is
used in the Craigentinny meadows, may be well imagined. It operates, not
merely by the substances which it holds in solution, but also by
depositing a large quantity of matters carried along in suspension, and
is in reality warping with a substance greatly superior to river-mud. A
deposit collected in a tank, where the sewage passes through a farm, is
used as a manure, and contains--
Peroxide of iron and alumina 4.45
Lime 1.74
Magnesia 0.39
Potash 0.10
Soda 0.06
Phosphoric acid 1.08
Sulphuric acid 0.16
Organic matter 17.95
Sand 20.51
Water 53.56
------
100.00
Ammonia 0.93
And even, though containing more than half its weight of water and 20
per cent of sand, this substance has considerable value as a manure.
The growing evils of the existing system of sewage, and the enormous
waste of a manurial matter, which the experience of the Craigentinny
meadows has shewn to be productive of the most important effects, has
recently directed much attention to the conversion of the contents of
our sewers into a useful manure. Numerous plans for its precipitation
and conversion into a solid manure have been proposed, but most of these
have shewn an entire ignorance of the fundamental principles of
chemistry, and the best only succeed in precipitating a very small
proportion of its valuable matters, and leave almost the whole of the
ammonia, as well as the greater part of the fixed alkalies, in solution.
Nor is it to be expected that any process will be discovered by which
these substances can be precipitated, because solubility is the special
characteristic of their compounds, and no means is known by which it is
possible to convert them into an insoluble form. If sewage is to be used
at all, there seems little doubt that it must be by applying it entire,
and in the liquid state. But here again, the expense of conveying it on
to the land becomes an obstacle which it must frequently be impossible
to overcome. When it can be conveyed by gravitation, as is the case in
the neighbourhood of Edinburgh, it may undoubtedly be used with the
utmost advantage, and with the very best economic results. But when it
requires to be carried to a great distance through pipes, and raised to
a high level by pumping, all these advantages disappear. If the cost of
application amounts to 2d. a gallon, as in Mr. Mechi's case, or even to
half that sum, it may be fairly concluded that it cannot be used with
any great prospect of large economic results, and that, unless under
very exceptional cases, it must be unprofitable.
The chances of success must also greatly depend upon the kind of soil on
which it is used. Experience has shewn that its effects are most
beneficial on light and deep sandy soils, but that on heavy retentive
clays it is without effect, or even absolutely injurious. In clay soils
it is important to use every means of getting rid of moisture, and any
plan which adds 200 or 300 tons of water to them, only aggravates their
natural defects to an extent which more than counterbalances the
benefits derived from the manurial matter it contains. Whatever the
ultimate result of the use of town sewage in the liquid form may be, it
is unlikely that it will be employed in general agricultural practice.
It is more probable that it will be found necessary to set apart a
certain breadth of land to be treated by it exclusively. Many plans have
been proposed for conveying it through considerable districts, and
selling to the surrounding farmers the quantities which they require,
but wherever large sewage-works are established, it will be impossible
to depend on a precarious demand, and the promoters of such schemes will
be compelled, as part of their speculation, to supply not only the
manure, but the land on which it is to be used. Indeed, the difficulties
attending the whole question are so formidable, that even those who are
most anxious to see a stop put to the waste of manurial matter must
admit that the prospect of a successful economic result is not
encouraging. Nor is it likely that anything will be done until the whole
system of managing town refuse is changed, and in place of deluging it
with water, some plan can be contrived which, while fulfilling sanatory
requirements, shall preserve it in a concentrated form, or convert it
into a dry and inodorous substance.
FOOTNOTES:
[Footnote L: Report on the economic uses of peat. Highland Society's
Transactions, N.S., vol. iv. p. 549.]