The Formation of Vegetable Mould Through the Action of Worms: With Observations on Their HabitsDarwin, Charles
Science
The Formation of Vegetable Mould Through the Action of Worms: With Observations on Their Habits
Darwin, Charles
Earthworms; Humification; Soils
Dry and indurated castings, after their disintegration into small
fragments or pellets, are sometimes, probably often, blown by a strong
wind to leeward. This was observed on four occasions, but I did not
sufficiently attend to this point. One old casting on a gently sloping
bank was blown quite away by a strong south-west wind. Dr. King believes
that the wind removes the greater part of the old crumbling castings near
Nice. Several old castings on my lawn were marked with pins and
protected from any disturbance. They were examined after an interval of
10 weeks, during which time the weather had been alternately dry and
rainy. Some, which were of a yellowish colour had been washed almost
completely away, as could be seen by the colour of the surrounding
ground. Others had completely disappeared, and these no doubt had been
blown away. Lastly, others still remained and would long remain, as
blades of grass had grown through them. On poor pasture-land, which has
never been rolled and has not been much trampled on by animals, the whole
surface is sometimes dotted with little pimples, through and on which
grass grows; and these pimples consist of old worm-castings.
In all the many observed cases of soft castings blown to leeward, this
had been effected by strong winds accompanied by rain. As such winds in
England generally blow from the south and south-west, earth must on the
whole tend to travel over our fields in a north and north-east direction.
This fact is interesting, because it might be thought that none could be
removed from a level, grass-covered surface by any means. In thick and
level woods, protected from the wind, castings will never be removed as
long as the wood lasts; and mould will here tend to accumulate to the
depth at which worms can work. I tried to procure evidence as to how
much mould is blown, whilst in the state of castings, by our wet southern
gales to the north-east, over open and flat land, by looking to the level
of the surface on opposite sides of old trees and hedge-rows; but I
failed owing to the unequal growth of the roots of trees and to most
pasture-land having been formerly ploughed.
Public-domain text, read in full here on John Shaqi.
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