INJURY OF LAND BY DRAINAGE.
Most Land cannot be Over-drained.--Nature a Deep
drainer.--Over-draining of Peaty Soils.--Lincolnshire Fens; Visit
to them in 1857.--56 Bushels of Wheat to the Acre.--Wet Meadows
subside by Drainage.--Conclusions.
Is there no danger of draining land too much? May not land be
over-drained? These are questions often and very naturally asked, and
which deserve careful consideration. The general answer would be that
there is no danger to be apprehended from over-draining; that no water
will run out of land that would be of advantage to our cultivated crops
by being retained. In other words, soils _generally_ hold, by capillary
attraction, all the moisture that is of any advantage to the crops
cultivated on them; and the water of drainage would, if retained for
want of outlets, be stagnant, and produce more evil than good.
We say this is generally true; but there are said to be exceptional
cases, which it is proposed to consider. If we bear in mind the
condition of most soils in Summer, we shall see that this apprehension
of over-draining is groundless. The fear is, that crops will suffer in
time of drought, if thoroughly drained. Now, we know that, in almost all
New England, the water-table is many feet below the surface. Our wells
indicate pretty accurately where the water-table is, and drains, unless
cut as low as the surface of the water in the wells, would not run a
drop of water in Summer.
Our farmers dig their wells twenty, and even fifty, feet deep, and
expect that, every Summer, the water will sink to nearly that depth; but
they have no apprehension that their crops will become dry, because the
water is not kept up to within three feet of the surface.
The fact is, that Nature drains thoroughly the greater portion of all
our lands; so that artificial drainage, though it may remove surplus
water from them more speedily in Spring, cannot make them more dry in
Summer. And what thus happens naturally, on most of the land, without
injury, cannot be a dangerous result to effect by drainage on lands of
similar character. By thorough-drainage, we endeavor to make lands which
have an impervious or very retentive subsoil near the surface,
sufficiently open to allow the surplus water to pass off, as it does
naturally on our most productive upland.
OVER-DRAINING OF PEATY SOILS.
No instance has yet been made public in America, of the injury of peat
lands by over-drainage; but there is a general impression among English
writers, that peat soils are often injured in this way. The Lincolnshire
Fens are cited by them, as illustrations of the fact, that these lands
do not require deep drainage.
Mr. Pusey says, "Every one who is practically acquainted with moory
land, knows that such land may be easily over-drained, so that the soil
becomes dusty or _husky_, as it is called--that is, like a dry
sponge--the white crops flag, and the turnip leaves turn yellow in a
long drought."
These Fens contain an immense extent of land. The Great Level of the
Fens, it is said, contains 600,000 acres. Much of this was formerly
covered by the tides, and all of it, as the name indicates, was of a
marshy character. The water being excluded by embankments against the
sea and rivers, and pumped out by steam engines, and the land
under-drained generally with tiles, so that the height of the water is
under the control of the proprietors, grave disputes have arisen as to
the proper amount of drainage.
An impression has heretofore prevailed, that these lands would be too
dry if the water were pumped out, so as to reduce the water-table more
than a foot or two below the surface, but this idea is now controverted.
In July 1857, in company with three of the best farmers in Lincolnshire,
the writer visited the Fens, and carefully examined the crops and
drainage. We passed a day with one of the proprietors, who gave us some
information upon the point in question. He stated, that in general, the
occupants of this land entertain the opinion, that the crops would be
ruined by draining to the depth of four feet. So strongly was he
impressed with the belief that a deeper drainage was desirable, that he
had enclosed his own estate with separate embankments, and put up a
steam-engine, and pumped out the water to the depth of four feet, while
from the land all around him, it is pumped out only a foot and a half
below the surface, though in Summer it may sometimes fall somewhat
lower.
The crops on this land were astonishing. Our friends estimated that the
wheat then growing and nearly ripe, would yield fifty-six bushels to the
acre. Although this was considered a very dry season, the crops on the
land of our host were fully equal to the best upon the Fens.
The soil upon that part of the Fens is now a fine black loam of twelve
or eighteen inches depth, resting upon clay. Upon other portions, the
soil is of various depth and character, resting sometimes upon gravel.
Attention is called to these facts here, to show that the common
impression that these lands will not bear deep drainage, is controverted
among the occupants themselves, and may prove to be one of those errors
which becomes traditional, we hardly know how.
Most peat meadows, in New England, when first relieved of stagnant
water, are very light and spongy. The soil is filled with acids which
require to be neutralized by an application of lime, or what is cheaper
and equally effectual, by exposure to the atmosphere. These soils, when
the water is suddenly drawn out of them, retain their bulk for a time,
and are too porous and unsubstantial for cultivation. A season or two
will cure this evil, in many cases. The soil will become more compact,
and will often settle down many inches. It is necessary to bear this in
mind in adjusting the drains, because a four-foot drain, when laid, may,
by the mere subsidence of the land, become a three-foot drain.
A hasty judgment, in any case, that the land is over-drained, should be
suspended until the soil has acquired compactness by its own weight, and
by the ameliorating effect of culture and the elements.
Mr. Denton, alluding to the opinion of "many intelligent men, that low
meadow-land should be treated differently to upland pasture, and upland
pasture differently to arable land," says, "My own observations bring me
to the conclusion, that it is not possible to lay pasture-land too dry;
for I have invariably remarked, during the recent dry Summer and Autumn
particularly, that both in lowland meadows, and upland pastures, those
lands which have been most thoroughly drained by deep and frequent
drains, are those that have preserved the freshest and most profitable
herbage."
While, therefore, we have much doubt whether any land, high or low, can
be over-drained for general cultivation, it is probable that a less
expensive mode of drainage may be sometimes expedient for grass alone.
While we believe that, in general, even peat soils may be safely drained
to the same depth with other soil, there seems to be a well-founded
opinion that they may frequently be rendered productive by a less
thorough system.
The only safety for us, is in careful experiment with our own lands,
which vary so much in character and location, that no precise rules can
be prescribed for their treatment.