In conserving the supply of water in the soil the mulch
plays an important work. The dry air is constantly taking up the water
from the surface of land, and when the surface is drier than the soil
below, the moisture moves upward if there is no break in the structure
of the surface soil. The mulch is a covering of material that does not
readily permit the escape of water.
The only available material for a mulch in most instances is the soil
itself. Experience has taught that when the top layer of soil, to a
depth of two or three inches, is made fine and loose, the water beneath
it cannot escape readily. It is partly for this reason that the
smoothing-harrow should follow the roller after land has been plowed.
The plow is used to break up the soil into crumbs that will permit air
to enter. The loosening is excessive when the planting must follow
soon, permitting rapid escape of water. The roller or plank-drag is
employed to compress the soil, and to crush crumbs of soil that are too
large for good soil conditions. The harrow follows to make a mulch of
fine, loose soil at the surface to assist in prevention of evaporation.
A sandy soil will retain its mulch in effective condition for a longer
time than a fine clay, if no rain falls. When the air is laden with
moisture, clay particles absorb enough water to pack together and form
an avenue for the rise of water to the surface, where the dry air has
access to it.
Next: Mulches Of Foreign Material
Previous: The Plank-drag