360 
ARE ROTATIONS OF CROFS NECESSARY ? 
ARE ROTATIONS OF CROPS NECESSARY? 
They are, in many instances, a convenient and 
economical system of farming, but in none are 
they absolutely essential to successful cultivation. 
Chemical analysis in regard to plants, has ad¬ 
vanced thus far in its investigation, that it has 
placed within our knowledge, beyond the possi¬ 
bility of doubt or contradiction, all the dements 
that are necessary to their perfect development. 
We can now, by the aid of this subtle science, 
take to pieces the several portions of a plant, as the 
mechanic or builder can separate the different 
parts of his machine or building, and assort and 
measure them, and estimate the exact proportions 
which are essential to its perfection; while even 
a superficial acquaintance with botany and prac¬ 
tical farming, enables us to determine what are 
' the necessary requisites to their reformation under 
the controlling influence of nature. Whatever 
substances have not been formed under the laws 
of vitality, may not only be separated, but recom¬ 
bined by the man of science ; but wherever the 
mysterious principle of life has once impressed 
its seal, no art of man can imitate the operation. 
The Deity has chosen to limit the successful ef¬ 
forts of human investigation on the very threshold 
of his own peculiar sphere. “ Thus far—and no 
farther,” is the incontrovertible fiat, to which the 
highest intelligence, when under the control of 
reason, will find its duty equally with its interests 
to consist. The study of Nature’s laws, not the 
imitation of her vital operations, is the legitimate 
object of finite intelligence. Happily, we have, 
within the well-defined limits of human research, 
depths enough to fathom and explore, to busy the 
profoUndest intellect while hemmed in by this 
mould of clay; and it is a pleasing and should be a 
satisfactory consideration, that those pursuits, 
which contribute to the melioration of our present 
condition, and most effectually minister to the wants 
of humanity, are among the most useful and at¬ 
tractive, as they are among the most recondite 
studies that can occupy the mind of genius. But 
we are wandering. If we ascertain the exact 
quantity of each constituent of the soil extracted 
by any given crop, which is always susceptible of 
estimate, we know precisely what is essential to 
be added to enable it again to yield a similar one. 
It was customary among many of the ancients, 
and especially the Greeks and Romans, to raise 
the same crops on the same ground for successive 
generations, a practice which has descended to the 
best agriculturists, even to within a few years. 
But this management required the adoption of the 
wasteful fallow system, by which, generally, 
every alternate year was required for the soil so 
far to recover itself as to be enabled to renew its 
accustomed yield. The present generation of en¬ 
lightened farmers adopt the wiser and more 
economical method of rotation, which, without 
any waste of time oi season, insures the same re¬ 
sult. 
The rationale of the fallow system is, that any 
given crop takes from the soil certain of its fixed 
or mineral constituents, as potash, soda, lime, the 
silicates, phosphates, &c.; and that these exist 
only to a limited extent, even in the most fertile 
soils, in a condition to be taken up by the grow¬ 
ing plant; that is, that although there may be 
one hundred, or one thousand times as much of 
each as is required for immediate use, yet they 
may be so combined with each other* as not to be 
available for the same species of crop, except at 
intervals of one, two, or more years. By allowing 
the land a rest, as in fallow, the chemical action 
of the atmosphere, and dews and rains upon the 
materials of the soil, liberates an additional quan¬ 
tity of them, sufficient for the supply of another 
crop, after a sufficient time, even without the aid 
of manure. 
The substitution of a system of rotation for fal¬ 
low, combines the same object with superior 
economy; for by alternating roots, the legum- 
inoste, clover, and the grasses with the white or 
grain crops, they appropriate from the soil the 
same materials in part, but in such different pro¬ 
portions as to be fully supplied with what is es¬ 
sential to them, while the former crop, if on the 
ground, might have been starved for the want of 
a single ingredient in sufficient quantity to give 
the plant full maturity. Some soils are found 
to sustain a much shorter rotation for grain than 
others, owing to the greater abundance of lime 
and silicate of potash, &c., contained in them. 
Thus, all volcanic soils, such as are found in the 
island of Sicily and the neighborhood of Vesuvius, 
afford, after a very short respite, sufficient pabu¬ 
lum, without the aid of manure, to furnish another 
crop ; and from this cause, the former, from a pe¬ 
riod anterior to Roman history, has been called 
the granary of the Mediterranean. Such soils also, 
as are annually overflown by streams, bearing in 
their turbid waters, not only the organic manures, 
but are charged, in addition, with the inorganic, or 
salts in solution, which are plentifully deposited 
on the expanded surface, are thus rendered capable 
for ever of yielding abundant crops of grain. Such 
are the Nile and Ganges, whose banks, since the 
subsidence of Noah’s flood, have borne large annual 
burthens of the same exhausting crops; and such, 
too, will prove the bottom-lands of American 
streams, which are submerged by annual freshets, 
highly chargedwith the same materials. A similar 
effect is measurably produced by irrigation, when 
the water is strongly impregnated with benefi¬ 
cial salts. 
But in nearly all cases, however rich the soil 
when first subjected to tillage, an annual supply 
of the salts or inorganic matter equivalent to what 
is abstracted from the soil by crops, or drainage, 
(which last is frequently a large item, though 
little perceptible, except in its effects,) is neces¬ 
sary to be added, to maintain a high state of pro¬ 
ductiveness. A slow disintegration and solution 
of the earthy salts is constantly going on in soils 
subject to cultivation, which yield the crops a 
supply as fast as prepared. But some soils do not 
furnish all the constituents in sufficient quantities 
for the demand of the plants, some being deficient 
in lime, some in potash, some in soda, some in the 
phosphates, &c. It would be well, and doubtless 
the most economical mode wherever attainable, 
to subjec soils to analyses, and by learning its de¬ 
ficiencies the right materials could be added with- 
