For instance, in a series of experiments
the following results were obtained. On a sandy loam, not
cultivated, 603 pounds of water were transpired to produce one pound
of dry matter of corn; on the same soil, cultivated, only 252 pounds
were required. On a clay loam, not cultivated, 535 pounds of water
were transpired for each pound of dry matter, whereas on the
cultivated soil only 428 pounds were necessary. On a clay soil, not
cultivated, 753 pounds of water were transpired for each pound of
dry matter; on the cultivated soil, only 582 pounds. The farmer who
faithfully cultivates the soil throughout the summer and after every
rain has therefore the satisfaction of knowing that he is
accomplishing two very important things: he is keeping the moisture
in the soil, and he is making it possible for good crops to be grown
with much less water than would otherwise be required. Even in the
case of a peculiar soil on which ordinary cultivation did not reduce
the direct evaporation, the effect upon the transpiration was very
marked. On the soil which was not cultivated, 451 pounds of water
were required to produce one pound of dry matter (corn), while on
the cultivated soils, though the direct evaporation was no smaller,
the number of pounds of water for each pound of dry substance was as
low as 265.
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