Especially in districts of very low rainfall is this practice to be
recommended. In the Great Plains area, where the summer rains tempt
the farmer to give less attention to the soil-moisture problem than
in the dry districts with winter precipitation farther West, it is
important that a fallow season be occasionally given the land to
prevent the store of soil moisture from becoming dangerously low.
To what extent is the rainfall stored in soils?
What proportion of the actual amount of water falling upon the soil
can be stored in the soil and carried over from season to season?
This question naturally arises in view of the conclusion that water
penetrates the soil to considerable depths. There is comparatively
little available information with which to answer this question,
because the great majority of students of soil moisture have
concerned themselves wholly with the upper two, three, or four feet
of soil. The results of such investigations are practically useless
in answering this question. In humid regions it may be very
satisfactory to confine soil-moisture investigations to the upper
few feet; but in arid regions, where dry-farming is a living
question, such a method leads to erroneous or incomplete
conclusions.
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