1846. THE CULTIVATOR. 235 
have a greater value for the production of roots and 
foliaceous plants than those of man or of birds, which 
contain only a small quantity of those mineral substan¬ 
ces which they require for their development. 
If we compare, for instance, the composition of guano 
with the excrements of the cow—>solid and fluid excre¬ 
ments in the same state of dryness—it is found, that in 
an equal weight, the latter contain five to seven times 
more of the mineral ingredients of turneps and potatoes, 
than the former. If, in a soil, which is deprived of all 
these mineral substances, we wish to force a crop of 
turneps by means of guano, we require at least five 
times more of guano than dung of cattle. 
The same thing happens, though vice versa, if we 
wish to produce a rich crop of grain by means of animal 
excrements; in this case, one part of guano and five 
parts of animal excrements produce the same effect, as 
13.15 parts of animal excrements. 
To understand the proper meaning of these numeri¬ 
cal proportions, it is sufficient to mention, that 400 
pounds of bones contain as much phosphoric acid as 
1000 pounds of wheat; these 400 pounds of bones can 
furnish sufficient phosphoric acid to 8 acres. 
If we take the importation of bones into Great 
Britain, in the last ten years, to amount to one million 
of tons, enough phosphoric acid has been supplied to 
the fields for 25 millions of tons of wheat; but only a 
small proportion of the phosphoric acid of the bones is 
in a state to be assimilated by the plants and applicable 
to the formation of the grain. The plants, in order to 
apply the other far greater part of that phosphoric acid 
to their formation, must find a certain quantity of alka¬ 
line bases besides the bone earth, which are not given 
to the plants in the bones, because they contain neither 
potash nor soda. 
To have increased the fertility of the fields in the 
right proportion, 800,000 tons of potash ought to have 
been added to the one million of tons of bones, in a 
suitable form. 
The same is the case with guano; 60 to 100 pounds 
of it are sufficient to furnish phosphoric acid to one 
acre of turneps; but the four to eight fold quantity is 
required to furnish the turneps with the necessary al¬ 
kaline bases, and it is still doubtful whether they can 
be at all provided with the latter, by means of the salts 
with alkaline bases, which the guano contains. 
At a time, when the necessity of the mineral sub¬ 
stances for the growth and development of the plants, 
and the direct relation which the effect of manure has 
to its amount of the same substances, had not been 
ascertained, a prominent value was ascribed to the 
organic matters which it contains. For a long time it 
was thought that the produce of a field of those substan¬ 
ces, containing nitrogen, which serve as food for man 
and animals, stood in a direct proportion to the nitro¬ 
gen contained in manure. It was believed that its com¬ 
mercial value, or its value as manure, might be ex¬ 
pressed in per cents by its proportion of nitrogen, but 
later and more convincing observations have induced 
me to contradict this opinion. 
If the nitrogen and carbonic acid formed by the de¬ 
cay and decomposition of the vegetable ingredients of 
manure, were the cause of its fertilizing power, this 
ought also to be seen if the mineral substances are ex¬ 
cluded. Direct experiments have shown, that the ni¬ 
trogen of the excrements can be assimilated by the 
plants, in the form of ammonia; but that ammonia as 
well as carbonic acid, although it is indispensable for 
the development of all plants, can accelerate the growth 
of plants and increase the produce of a field of grain, 
roots, and tubercles only , if at the same time, the mine¬ 
ral ingredients contained in the manure which is applied, 
are in a state in which they are suited for assimilation. 
If the latter are excluded, carbonic acid and ammonia 
have no effect on vegetation. 
On the other hand, experience has shown that on 
many fields the produce which is rich in carbon and 
ammonia, can be increased to an extraordinary amount 
without any supply of such matters as furnish these 
substances. 
On fields which are provided with a certain quantity 
of marl or slacked lime, or with bone earth and gypsum, 
substances which cannot give up to the plants either 
carbon nor nitrogen—rich crops are obtained in many 
places, of grain, tubers, and roots, entirely in contra¬ 
diction with the view which ascribes the effect of the 
manure to its amount of ingredients containing nitrogen 
or carbonic acid. 
To explain this process, which is so opposite to the 
common opinion, the marl, the lime, the gypsum, the 
alkalies, and the bone earth were regarded as stimu¬ 
lants, which acted on the plants like spices on the food 
of man, of which it was believed that they increased 
the power of assimilation, and allowed the individu¬ 
als to consume larger quantities of food. 
This view is contradicted, if we consider that stimu¬ 
lants mean such substantives as do not serve for the 
nourishment of the organism or for the formation of 
organic elements, and can only increase the weight of 
the body, if at the same time a certain increase of food 
is given. In supplying the fields with the above men¬ 
tioned substances, the weight of the plants became in¬ 
creased in all their separate parts, without their having 
been provided with the quantity of food, which accord¬ 
ing to theory, was necessary to this extraordinary in¬ 
crease, viz., with carbonic acid and ammonia. 
Chemical analysis shows that these so called stimu¬ 
lants are either actual ingredients of manure, as gypsum, 
bone earth, and the active substances of the marl, or 
that they are the means by which the mineral element? 
contained in the soil are resolved into a state adapted 
for being assimilated by the plants; this is generally 
effected by the application of slacked lime. They 
consequently exercise on the vital process of the plants 
not a mere stimulus like the spices, but are consumed 
for the development of the leaves, seeds, roots, &e.; 
they become constituent parts of them, as can be shown 
with certainty by chemical analyses. 
The success which has followed the application of 
these substances to the fields has explained, in a most 
striking manner, the origin of the carbon and nitrogen 
in the plants. 
In the marl, in the bone earth, in the gypsum, in the 
nitrate of soda, no carbon is provided to the fields; and 
yet, in many cases, the same produce, in some even a 
higher one was obtained, than by the application of a 
manure containing carbon and nitrogen. As the soil, 
after the crop, does not contain less carbonaceous or 
nitrogenous substances, it is evident that these products 
which had been obtained without any carbonic or 
azotic manures, must have got the carbon and nitrogen 
of their leaves, roots, and stalks, from the atmosphere; 
it follows therefore that the productiveness of the fields 
cannot be in proportion with a supply of carbonaceous 
anu azotic substances, but that the fertility depends only 
on the supply of those ingredients which should be pro¬ 
vided by the soil. 
The soil does not only serve the purpose of fixing 
the plants and their roots; it participates in vegetable 
life through the absorption of certain of its elements. 
If these elements are present in sufficient quantity and 
in appropriate proportions, the soil contains the condi¬ 
tions which render the plant capable of absorbing car¬ 
bonic acid and ammonia from the air, which is an in¬ 
exhaustible storehouse for them, and renders their ele¬ 
ments capable of being assimilated by their organism. 
The agriculturist must, therefore, ponfine himself to 
giving to the field the composition necessary to the de¬ 
velopment of the plants which he intends to grow; it 
must be his principal task to supply and restore all the 
elements required in the soil, and not only one, as is so 
frequently done; the ingredients of the air, carbonic 
acid and ammonia, the plants can, in most cases,' pro¬ 
cure without man’s interference; he must take care to 
give to his field that physical condition which renders 
possible and increases the assimilation of these ingredi¬ 
ents by the plant; he must remove the impediments 
which diminish their effect. 
The favorable influence which bone earth, gypsum, 
nitrate of soda, exercise on the fields has induced many 
farmers to the belief, that in applying them they can 
dispense with manure or with the other elements of the 
