OF SOUTH CAROLINA. : 243 
. 
Lime alone, applied to the land, will be certain to impoverish it; and hence it is a dangerous instru- 
ment in the hands of an injudicious planter. Lime adds so little, itself, and helps the crops so 
bountifully to what is already in the soil, that if the supply be not kept up by the addition of 
organic matter, the consequence is obvious. 
It was, probably, this effect of lime that gave rise to the term “stimulants,” applied to mineral 
manures. It does not, however, convey a correct idea of their action, for they are really as much 
a part of the substantial food of lenis as any other of their elements. 
Rorarion or Crops. 
Besides the agency of manures, other means of improving the soil have been introduced, and 
none with greater success than the rotation of crops. ‘T'o those countries whose staple crops and 
whose climate enable them to practice it to its full extent, scarcely any improvement in agriculture 
has been fraught with greater blessings. 
Before the functions of plants, and their relations to soils, were clearly understood, many attempts 
were made to explain the fact that when land has become exhausted, by the cultivation of successive 
crops of the same plant, it may again be restored, after the intervention of two or more crops of 
different plants, so as to be capable of producing a crop of the first plant. Without stopping to 
notice these explanations, [ will point out what I believe to be the true one. 
Every one knows that when land has been exhausted, by repeated cropping, it may be restored, 
by resting for a certain length of time. If the soil has been a “naturally fertile” one, that is to 
say, if the subjacent rock, or the sub-soil, be such as produces a good-soil, the time necessary for 
such restoration will be much shortened. The effect will be produced in a still shorter time by the 
thorough breaking up of the soil, and by the exposure of fresh surfaces to the agencies of the 
atmosphere. Now this is effected simply by the decomposition of the mineral ingredients of the 
soil, and by the rotting of the roots or other vegetable matter that may have remained in it from 
previous crops. In a word, by this process there is, to a certain extent, a new soil produced, which 
may again be cultivated. So that by simple resting, a soil may acquire a certain degree of fertility. 
The objection to this mode of: renovation is, that it is connected with a considerable loss, by 
requiring the land to remain idle—a loss which is felt in proportion to population, or the scarcity of 
arable land. 
Now if, while the process described above is going on, we could cultivate a crop of another plant, 
it would lessen, very materially, the loss complained of. A plant, to succeed another in this way, 
must not exhaust the soil of the same ingredient, to the same extent, as the plant that preceded it; 
and if a third plant be found that differs from both of these, in what it requires from the soil, it 
may follow in the rotation, and by this time the soil may have recovered from the exhausting 
effects of the first plant. 
The chemical composition of cultivated plants solves the problem of the selection of the proper 
plants for a rotation, always, of course, taking into the account their adaptation to the climate, com- 
mercial or other value, &c., which are considerations that belong to the practical agriculturist. For 
example, besides the elements common to all cultivated plants, the grasses and grain plants require 
a great quantity of silica ; others, such as beets, turnips, and Trish potatoes, take from the soil a large 
