AGRICULTURAL CHEMISTRY. — NO. 16. 
351 
AGRICULTURAL CHEMISTRY,— Wo. 16. 
There is no division of the subject, of which I 
have been treating, of more practical importance to 
the agriculturist than that which relates to the 
composition, management, and application of ma- 
nures. All substances of whatever nature, which 
aid in fertilizing a soil are called manures. They 
are classified by writers under the heads of animal, 
vegetable, and mineral substances. The first two 
classes are called organic manures, because they 
are formed from organized matter, and abound in 
organic elements, namely, carbon, oxygen, hydrogen, 
and nitrogen. All mineral manures, including 
salts, are called inorganic. But without confining 
myself to any particular mode of classification, I 
6hail proceed to treat of some of the substances 
most commonly used and are most valuable for fer- 
tilizing properties. 
Among the great class of fertilizing agents, farm- 
yard manure deserves to rank foremost in import- 
ance. But, in order to know how to manage and 
apply most advantageously the mass of matter, 
which yearly accumulates in his yard, it is neces- 
sary that the farmer should first understand its 
composition ; and before this knowledge can be 
available, he must be familiar with the several in- 
gredients of which it is composed, and their com- 
binations. To tell an uneducated man that barn- 
yard manure is composed of silicates, carbonates, 
phosphates, &c, and that one of its most valuable 
constituents is ammonia, which is of a volatile na- 
ture and liable to escape unless fixed by sulphate 
of lime, would be like talking to him in an un- 
known tongue. Farmers, whose knowledge is 
thus limited, are liable to fall into many errors, both 
in theory and practice. 
The following are some of the incorrect opinions 
which prevail among the body of farmers in regard 
to the management and application of their farm- 
yard deposites. First, it is supposed that no ad- 
vantage is gained by sheltering the manure ; second, 
that there is no loss, or only a trifling one, by fer- 
mentation and evaporation ; third, that liquid ma- 
nure is of little or no value; fourth, that manure 
does most good when applied in the full of the 
moon ; fifth, that it is always more advantageous 
to apply it on the surface, than to plow it under. 
After briefly examining its composition, we shall 
see how these opinions accord with the more en- 
lightened teachings of science. 
The proportions of the several constituents of 
farmyard manure, will, of course, vary with the 
food of the animals, their litter, and the various 
materials allowed to accumulate in the yard. It 
should be borne in mind, however,, that when ani- 
mals are well fed, the value of. the manure is pro- 
portionally increased. Those elementary bodies 
previously described by me,, as entering into the 
composition of plants, also form the ultimate con- 
stituents of farmyard manure ; for, no new elemen- 
tary substance is ever produced by the change 
which matter undergoes, either in its passage 
through the vegetable or animal system. The 
hodies of animals must therefore be composed of 
the same matter that has previously existed in 
those vegetables which they have consumed ; and, 
this matter, as I have already shown, may be re- 
duced to sixteen elements. These constituents, or 
elementary bodies, move, as it were, in a circle. 
Plants draw them from the earth and air, and 
thither they are again returned, after having per- 
formed their office, first in the vegetable, and after- 
wards in the animal constitution. You see, then, 
that the ultimate constituents of farmyard manure 
are those identical, elements with which you are 
already familiar. Most of them are found, on 
analysis, in the form of salts, such as the sulphates, 
carbonates and phosphates of lime, magnesia, and 
soda, most of which are soluble in water. The 
knowledge of this fact leads to an important conclu- 
sion, as I will endeavor to show. If you place a 
mixture of common salt and charcoal upon the 
ground, and pour water upon it, the salt will be 
dissolved and sink into the earth, while the char- 
coal, not being soluble, will remain. The case is 
precisely the same with manure. If it is exposed 
to drenching rains, the soluble salts, which it con- 
tains, and which are valuable fertilizers, will he 
dissolved, and either sink deep into the earth, where 
they are not needed, or they will be washed aw r ay. 
The analysis of the liquid thus produced shows it 
to be rich in these soluble salts, which are thus 
nearly, if not entirely wasted. Here, then, is a con- 
clusive argument to show the advantage of shelter- 
ing manure where it can be done without too great 
an expense. 
But some of the ingredients of farmyard manure, 
namely, carbon, oxygen, hydrogen, and nitrogen, are 
of a volatile nature, and commence making their 
escape as soon as fermentation begins. The most 
valuable of these ingredients is nitrogen, which 
escapes in the form of ammonia. The escape of 
this gas is attended by a very perceptible smell, 
like that of hartshorn. I have previously spoken 
of the importance of nitrogen or ammonia to vege- 
tation, and it is unnecessary to add anything fur- 
ther on that topic. This loss may be prevented by 
mingling with, or spreading over, the heap of ma- 
nure a plentiful supply either of charcoal, or sul- 
phate of lime (piaster). The former has the 
power of absorbing and retaining ammonia in its 
pores ; the latter arrests its escape in the following 
manner. The ammonia, which escapes from fer- 
menting manure, is in the form of a carbonate. 
When this gas, (carbonate of ammonia,) comes in 
contact with sulphate of lime, a mutual decomposi- 
tion takes place. The carbonic acid of the former 
unites with the lime of the latter, forming carbon- 
ate of lime ; while the ammonia combines with the 
sulphuric acid of the plaster, forming sulphate of 
ammonia, which is not, like the carbonate, a vola- 
tile substance. The sulphate of ammonia, there- 
fore, remains fixed until it is dissolved by water 
and conveyed into the earth to administer to the 
wants of plants. 
The loss, which manure sustains by fermentation 
and evaporation, is much greater than is commonly 
supposed. Johnston, in treating on this topic, says' 
" Recent manure loses weight by lying in the 
farmyard. The moisture evaporates and volatile 
matters escape by fermentation. By the time the 
straw is half rotten, the loss amounts to one fourth 
of the whole weight, while the bulk is diminished 
one half. If allowed to lie still longer, the loss in- 
creases till, at length, it may approach to one half 
of the whole, leaving a weight of dung little 
