The Soil A Reservoir
The rains of the summer rarely are adequate to
the needs of growing plants. Some water runs off the surface, some
passes down through crevices beyond the effect of capillary attraction,
and much quickly evaporates. The part that becomes available is only a
supplement to the store of water made by the rains of the fall, winter,
and early spring.
If the soil were viewed as a medium for the holding of water to meet
the daily needs of plants, and were given rational treatment on this
basis, a long step toward higher productiveness would have been taken.
As has been stated, rotted organic matter gives a soil more capacity
for holding water. It is an absorbent in itself, and it puts clays and
sands into better physical condition for the storage of moisture. An
unproductive soil may need organic matter for this one reason alone
more than it may need actual plant-food.
Fall-plowing for a spring crop enables land to withstand summer's
drouth if it gains in physical condition by full exposure to the
winter's frost. It is in condition to take up more water from spring
rains than would be the case if it lay compact, and it does not lose
water by the 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.
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