One of the chief values of fallowing lies in the liberation of the
plant-food during the fallow year, which reduces the quantity of
water required the next year for the full growth of crops. The Utah
experiments to which reference has already been made show the effect
of the previous soil treatment upon the water requirements of crops.
One half of the three types of soil had been cropped for three
successive years, while the other half had been left bare. During
the fourth year both halves were planted to corn. For the sandy loam
it was found that, on the part that had been cropped previously, 659
pounds of water were required for each pound of dry matter produced,
while on the part that had been bare only 573 pounds were required.
For the clay loam 889 pounds on the cropped part and 550 on the
previously bare part were required for each pound of dry matter. For
the clay 7466 pounds on the cropped part and 1739 pounds on the
previously bare part were required for each pound of dry matter.
These results teach clearly and emphatically that the fertile
condition of the soil induced by fallowing makes it possible to
produce dry matter with a smaller amount of water than can be done
on soils that are cropped continuously.
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