THE CULTIVATOR. 
August. 
234 
are found again in the ashes of plants, are their true 
food; that they are the conditions of vegetable life. 
It is evident, that from a field in which different 
plants are cultivated, we remove with the crop a certain 
quantity of these elements; in the seeds those mineral 
parts which the soil had to provide for their develop¬ 
ment, and in the roots, tubercles, stalks, and leaves, 
those elements which are necessary for their production. 
However rich the field may be in these elements, there 
can be no doubt that, by several cultures, it becomes 
more and more impoverished; that for every plant a 
time must arrive when the soil will cease to furnish, in 
sufficient quantity, those elements which are necessary 
for a perfect growth. Even if such a field, during many 
subsequent years, produced twenty-five or thirty fold 
the amount of the seed; for instance, of wheat, experi¬ 
ence shows that the crop gradually decreases, until at 
last the amount will be so small that it approaches the 
plant in its wild state, and would not repay the cost of 
cultivation. 
According to the unequal quantity in which the mine¬ 
ral elements of grain, tubercles, roots, seeds, leaves are 
contained in a soil, or according to the proportions in 
which they may have removed in the crop, the land 
may have ceased to be fertile for roots and tubercles, 
but it may yet produce good crops of wheat. Another 
may not produce wheat, but potatoes and turneps may 
thrive well in it. The mineral substances contained in 
a fertile soil, and serving as food to the plants, are taken 
up by them with the water, in which they are soluble. 
In a fertile field they are contained in a state which al¬ 
lows of their being absorbed by the plant and taken up 
by the roots. There are fields which are rich in these 
elements, without being fertile in an equal proportion; 
in the latter case they are united with other elements 
into chemical compounds, which counteract the dis¬ 
solving power of water. By the contemporaneous ac¬ 
tion of water and air,—of the oxygen and carbonic acid 
of the atmosphere,—these compounds are decomposed, 
and those of their constituent elements, which are solu¬ 
ble in water, but which had been insoluble by the 
chemical affinity of the other mineral substances, re¬ 
obtain the property of being absorbed by the roots of 
the plants. 
The duration of the fertility of a field depends on the 
amount of the mineral aliments of plants contained in 
it, and its productive power for a given time is in a di¬ 
rect proportion to that part of its composition which 
possesses the capacity of being taken up by the plant. 
A number of the most important agricultural operations, 
especially the mechanical, exercise an influence on the 
fertility of the fields only thus far, that they remove the 
impediments which are opposed to the assimilation of 
the mineral food into the vegetable organism. By 
plowing e. g., the surface of the fields is renewed and 
made accessible to air and moisture. The nutritious 
elements contained in the soil in a latent state, acquire 
by these operations, the properties necessary for their 
transmission into the plants. It is easy to conceive the 
useful influence which, in this respect, is exercised on 
the produce of the fields by the care and industry of the 
farmer. But all these labours and efforts do not increase 
the amount of mineral elements in the field; in render¬ 
ing soluble in a given time, a larger quantity of the 
insoluble substances, and obtaining by these means a 
richer crop—the time is merely hastened, in which the 
soil becomes exhausted. 
The experience of centuries has shown that, with the 
help of manure, of the excrements of animals and 
man, with which we supply those fields which have 
ceased to produce crops of grain, &c., serving as food 
for man and animals, in a sufficient quantity, the origi¬ 
nal fertility can again be restored; an exhausted field 
which scarcely yielded back the seed, is made to pro¬ 
duce a twenty and more fold crop, according to the pro¬ 
portion of the manure provided. 
Regarding the mode of action of the manure, it has 
been observed, that all excrements do not exercise an 
equal influence on plants. The excrements of sheep 
and cattle, for instance, increase in most fields the crop 
of roots and herbaceous plants to a far greater degree 
than those of man and birds, (guano.) The latter act 
far more favorably on the production of the cerelia, 
especially if they are added to the animal excrements, 
and are given to the fields at the same ime. 
A field, for example, which has lost its fertility for 
potatoes and turneps, but on which peas and beans still 
thrive, becomes far more fertile, by a supply of the ex¬ 
crements of horses and cows, for a new crop of potatoes 
and turneps, than by manuring it with the excrements 
of man or with guano. 
The most accurate experiments and analyses have 
pointed out that the excrements of man and animals 
contain those substances, to the presence of which the 
fertility of the soil is due. The fertilizing power of 
manure can be determined by weight, as its effect is in 
a direct ratio to its amount in the mineral elements of 
the food of plants. The truth of the result of these 
chemical analyses must be evident to every one who 
inquiries into the origin of excrements. 
All the excrements of man and animals are derived 
from the plants of our fields; in the oats and hay, 
which serve as food to the horses, in the roots which 
are consumed by a cow, there are a certain quantity of 
mineral ingredients. A horse, in consuming 15 lbs. of 
hay and 4-§ lbs. of oats per day, consumes 21 ounces of 
those substances which the hay and the oats took from 
the fields; he consumes annually 480 lbs. of these con¬ 
stituent elements of the soil, but only a very small por¬ 
tion of them remains in his body. If a horse during 
one year, increases 100 lbs. in weight, this increase 
contains only 7 lbs. of those mineral substances which 
were contained in the food. But what has become of 
the 473 lbs. which we cannot detect in his body? 
The analysis of the fluid and solid excrements which 
the horse gives out daily, shows that the ingredients of 
the soil which do not remain in the body of the animal 
are contained in its excrements; it shows that in an 
adult animal, which from day to day does neither in¬ 
crease nor decrease in weight, the amount of the mine¬ 
ral ingredients of the excrements is equal in weight to 
the mineral ingredients of the food. 
As with the horse, so it is with all animals. In all 
adult animals the excrements contain the ingredients 
of the soil according to the quantities and relative pro - 
portions in which they are contained in their food. 
The mineral substances of the food which have re¬ 
mained in the body of the animals, and served to in¬ 
crease their weight, are found again in the bones and 
excrements of man who consumes the flesh of these 
animals. 
The excrements of man contain the elements of the 
soil, of bread or of grain, of vegetables and meat. 
These discoveries explain, in a most simple and satis¬ 
factory manner, the fertilizing effect which manure 
produces on our fields. 
It is now obvious why manure renders again fertile 
the exhausted fields; why, by its means, their produc¬ 
tiveness can be augmented; why the latter is in a direct 
ratio to the quantity of manure administered. 
The exhaustion of the soil by subsequent crops,—its 
decrease in fertility,—is produced by the gradual remo¬ 
val of the mineral elements, in a soluble state, which are 
necessary for the development of our cultivated plants. 
By a supply of manure they are again restored to that 
state suited to serve as nourishment to a new vegeta¬ 
tion. If the supply of the removed elements of the soil, 
by means of manure, be sufficient; if the quantity taken 
away be restored, the original fertility re-appears^ if 
the supply be greater, the produce increases; a defect¬ 
ive supply gives a smaller produce. 
It is now explained why the different kinds of ma¬ 
nure exercise an unequal effect upon the fields. 
The excrements of man, and the guano containing 
especially the mineral ingredients <5 grain and meat, 
exercise far greater influence on the amount of produce 
in grain in a field in which these ingredients are want¬ 
ing, even if those of the leaves and stalks are present in 
sufficient quantity, than the excrements of an animal 
i which feeds on roots or green fodder. The excre¬ 
ments of the latter contain the mineral elements of the 
1 leaves, stalks, and roots, in prevailing quantity, and 
