1849. 
THE CULTIVATOR. 
203 
pose slowly, the food it contains remains locked up and 
comparatively useless to vegetation. In quickening 
the decay of this inert or slowly decomposing matter, 
it is easy to see, therefore, how lime should render the 
land more fertile, and should do so more sensibly where 
vegetable matter is more abundant. 
The mineral and rocky fragments in the soil are act¬ 
ed upon in a similar manner. 
Among the earthy constituents of soils, there often 
exists fragments of feldspar and other minerals, deri¬ 
ved from the granitic and trap rocks, as well as por¬ 
tions of the slaty and other beds from which the soils 
have been formed, and which, as they crumble down, 
yield more and more of those inorganic substances on 
which plants live. 
The decomposition of these minerals and rocks pro¬ 
ceed more or less rapidly under the conjoined action 
of the oxygen, the carbonic acid and the moisture of 
the atmosphere. But the presence of lime promotes 
this decomposition, and the consequent liberation of the 
inorganic substances which the rocks contain. 
The silicates of potash and soda are among the most 
important compounds which these minerals and rocky 
fragments contain. These silicates, after being heated 
to redness with quick-lime, readily yield a portion of 
their potash or soda to water poured upon the mixture. 
The same result follows, but more slowly, when with¬ 
out being heated, the silicates and the lime are mixed 
together into a paste with water, and left for a length 
of time at the ordinary temperature of the atmosphere. 
It is reasonable, therefore, to suppose that, in the soil 
of our fields, a similar decomposition will slowly take 
place when quick lime is mixed with it. It will take 
place, also, though still more slowly, when lime is ad¬ 
ded to it in the form of carbonate. 
By some, the liberation of potash and soda in this 
way is supposed to be the most, important action exer¬ 
cised by lime in rendering the land more productive. 
With this extreme opinion I do not agree, though it 
must be conceded, I think, that in numerous instances 
a certain amount of benefit must follow from the che¬ 
mical action it is thus fitted to exercise. 
I have spoken of lime as liberating the inorganic 
constituents of the decaying vegetable matter of the 
soil. The stalks of the grasses, and the straw of our 
corn-bearing plants also contain silicates of potash and 
soda, which lime sets free in hastening the decomposi- 
sition of the vegetable matter of which they form a 
part. Besides liberating, it further decomposes these 
silicates, as it does those of the minerals in the soil, 
and sets their potash and soda free to perform those im¬ 
portant functions they are known to exercise in reference 
to the growth of plants. I am inclined to consider this 
part, of the action of lime as of nearly equal importance 
to vegetation in many instances, with that which it 
exercises upon the mineral silicates. 
While the potash or soda is set free in a soluble 
state, the lime unites with a portion of silica, forming 
a silicate of lime of &hieh traces are to be met with 
in nearl} T all soils. This silicate, again, is slowly de¬ 
composed by the agency of the carbonic acid of the at¬ 
mosphere and of the soil, as I have already explained 
when speaking of this compound as one of the causes 
of the known fertility of soils formed from the decay of 
trap rocks. 
Potash aud soda exist sometimes in considerable 
quantity, in our stiff clay soils, in combination with the 
silica and alumina, of which they chiefly consist. From 
their extreme tenacity, the air is in a great measure 
excluded from these soils, and hence chemical decom¬ 
position proceeds in' them very slowly. The addition 
of lime alters their physical character, and, by making 
them more open, admits the air, and thus promotes its 
decomposing action upon them. But it acts chemical¬ 
ly also, in the same way as it does upon the silicates 
already spoken of, and thus compels them to give up 
more freely to the roots of plants those mineral substan¬ 
ces by which their growth is to be made more luxuriant. 
Action of Lime on Salts of Iron, Magnesia and 
Alumina. — Salts of Iron. —Lime, either in the mild or 
in the caustic state, possesses the property of decom¬ 
posing the sulphate and other saline compounds of iron, 
which especially abound in moorish and peaty soils, and 
in many localities so saturate the subsoil, as to make it 
destructive to the roots of plants. Sprengel mentions 
a case in which the first year’s clover always grew 
well, while in the second year it always died away. 
This, upon examination, was found to be owing to the 
ferruginous nature of the subsoil, which caused the death 
of the plants as soon as the roots began to enter into it. 
When land is rendered unproductive by the presence 
of salts of iron, a dressing with lime will bring the land 
into a wholesome state without other aid than those of 
the drain and the subsoil plow. If sulphate of iron be 
the cause of the evil, the lime will combine with the 
acid and form gypsum, (sulphate of lime,) while the 
first oxide of iron which is set free will, by exposure to 
the air, be converted into the second or red oxide, in 
which state this metal is no longer hurtful to vegetation. 
The drain and the subsoil plow are useful auxiliaries 
to the lime in lessening the injurious effects of the com¬ 
pounds of iron, because they allow the rains to descend 
and gradually to wash away the noxious matter which 
has accumulated in the under soil—because they permit 
the descending water to carry with it portions of the 
lime in a state of solution, and thus to spread its good 
effects through the whole soil—and because they admit 
successive supplies of air as deep as the bottom of the 
drains, by which, while the action of the lime is pro¬ 
moted, those other good effects also are produced 
which the oxygen of the atmosphere can alone accom¬ 
plish. In fact, unless an outlet for the surface water 
be thus provided beneath, by which the lime may be 
enabled to descend, and the rains to wash away slowly 
the noxious substances from the subsoil, even the addi¬ 
tion of a copious dose of lime will only produce a tec" 
porary improvement. 
Salts of magnesia and alumina. —Lime decomposes 
also the sulphates of magnesia and alumina, both of 
which, but especially the former, are occasionally found 
in the soil in too large proportions, and, being very so¬ 
luble salts, are liable to be taken up by the roots in such 
quantity as to be hurtful to growing plants. With the 
sulphuric acid of these salts the lime forms gypsum, as 
it does with the acid of sulphate of iron when this salt 
is present in a soil to which it is added: besides remo¬ 
ving the evil effects of these^ very soluble sulphates, 
therefore, it exercises the beneficial action which gypsum 
is known to exhibit upon many of our cultivated crops. 
Alumina has the property of combining readily with 
many vegetable acids, and in the clay soils exer¬ 
cises a constant influence—though more feeble in de¬ 
gree than that of lime—in persuading organic matter 
to those forms of decay in which acid compounds are 
more abundantly produced. Hence, clay soils almost 
ahvays contain a portion of alumina in combination with 
organic matter. These organic compounds are decom¬ 
posed by lime, and, by the more energetic action of 
this substance, their constituents are sooner made avail¬ 
able to the wants of the new races of plants. 
Charcoal and Feat. 
Whatever opinions may have been formed in relation 
to plants supplying themselves sufficiently with carbon 
and nitrogen from the atmosphere, we think careful ob¬ 
servation has shown that the application of carbonace¬ 
ous and ammoniacal substances is beneficial to th© 
growth of plants; and to this conclusion we believe the 
