The beneficial effects of
fallowing are therefore clearly twofold: to store the moisture of
two seasons for the use of one crop; and to set free fertility to
enable the plant to grow with the least amount of water. It is not
yet fully understood what changes occur in fallowing to give the
soil the fertility which reduces the water needs of the plant. The
researches of Atkinson in Montana, Stewart and Graves in Utah, and
Jensen in South Dakota make it seem probable that the formation of
nitrates plays an important part in the whole process. If a soil is
of such a nature that neither careful, deep plowing at the right
time nor constant crust cultivation are sufficient to set free an
abundance of plant-food, it may be necessary to apply manures or
commercial fertilizers to the soil. While the question of restoring
soil fertility has not yet come to be a leading one in dry-farming,
yet in view of what has been said in this chapter it is not
impossible that the time will come when the farmers must give
primary attention to soil fertility in addition to the storing and
conservation of soil-moisture.
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