e airing in the spring that plowing gives.

Early spring-plowing leaves land less subject to drouth than does later
plowing. As the air becomes heated, the open spaces left by the plowing
serve to hasten the escape of moisture. If a cover crop is plowed down
late in the spring, the material in the bottom of the furrow makes the
land less resistant to drouth because the union of the top soil with
the subsoil is less perfect, and capillary attraction is retarded. It
is usually good practice to sacrifice some of the growth of a cover
crop, even when organic matter is badly needed, and to plow fairly
early in the spring in order that the moisture supply may be conserved.

The Land-roller.--The breaking-plow is a robber of soil water when used
in warm weather. The air carries the water away rapidly. The air-spaces
are large. The corrective of this condition is the land-roller. It
presses the soil together, driving out the excess of air. Large crumbs
are pressed down into the mass, and are kept from drying into hard
clods. The roller never should be used on land when fresh-plowed in a
moist condition, and it is not needed after fall-plowing, or early
spring-plowing in most instances, but land broken when the season is
advanced should be rolled before much water evaporates.

[Illustration: Making an earth mulch in a New York orchard.]

The Plank-drag.--An excellent implement on a farm is the plank-drag. It
is usually made of over-lapping heavy planks, and when floated over the
surface, it both pulverizes and packs the soil. The effectiveness is
controlled by the weight placed upon it, and oftentimes the drag is to
be preferred to the roller.

The Mulch.--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 pe