236 
FERTILIZERS. 
frequently spoken of as calcareous manures; but there are others, as the chloride of lime, ni¬ 
trate of lime, phosphate of lime and silicate of lime, which are never spoken of under this de¬ 
signation. In each of these compounds lime is the base ; and in each it is probably quite es¬ 
sential to the effects which are produced. 
The most common form in which lime is employed as a fertilizer is that of a subcarbonate, 
or partially slaked lime ; in this state it still retains a slight caustic state, but is not burning 
and pungent. Lime, when first taken from the kiln, is caustic, and in this condition it is too 
active to be employed in agriculture ; it should be exposed to the air and allowed to absorb 
carbonic acid and water. During this exposure it swells and falls to a fine powder, and loses 
its sharp causticity. If used in the condition in which it is first taken from the kiln, it destroys 
the vegetable tissues, from its strong affinity for water ; it is too drying, it should, therefore, 
be partially saturated with water and carbonic acid : it increases in bulk, during this absorp¬ 
tion, to the amount, that one bushel will measure, after absorption, at least five pecks. 
Much has been said of the modus operandi of lime, and many opinions have been advanced 
as to its value. When we know that lime is one of the essential constituents ot plants, we 
can have no doubt that one of the most important functions of lime in the soil, is to supply 
this element to the plants directly; and I think we may be satisfied that it is a nutriment, and 
enters the tissues, as an essential part of the internal skeleton. No plant is destitute of lime; 
but in the bark or outside it exists in its maximum quantity. But besides this, some trees, as 
well as plants, contain, as a whole, a much larger proportion than others : compare the analysis 
of hickory with the white and red elm, and it will seem that lime is much more abundant in 
the former than the latter. It is scarcely possible to manufacture common soft soap from the 
ashes of the hickory, in consequence of the want of potash and the predominance of lime. In 
what form lime is received into the roots of plants is not yet made clear, by well conducted 
experiments. It is, however, probable that the carbonate or subcarbonate is decomposed in 
the soil by an organic acid, as the crenic and apocrenic acids, which are generated in the soil 
from vegetable matters, or from the decomposition of leaves and roots, and organic matters in 
general. These matters absorb or combine with oxygen ; or in other words, they undergo a 
slow combustion : and here I may remark, though the subject has been under consideration, 
that in order that these vegetable matters may oxidise, dryness of the soil is required. When, 
for example, they are saturated with water, they become peat; if the soil is drained of water, 
the capacity of the soil for air is increased ; it replaces the water, and hence the amount of 
oxygen in the soil is increased, and combustion or oxidation is more perfectly performed. 
But to return to the consideration of lime. Lime, when added to the soil in the condition I 
have stated, carries with it carbonic acid. This will be set free, provided the organic acids 
are present in the soil. When free it acts with considerable energy on compounds which 
contain phosphoric acids; and it may, therefore, be regarded as an active agent in the decom¬ 
position of many bodies in the soil, or in forming new combinations; or it may be dissolved in 
the water of the soil, and be absorbed by the roots of plants. But another effect of lime, es¬ 
pecially where clay predominates, is to decompose the silicates of potash and soda, which 
