The United States as a Farming Country 31
Fic. 18. Above the northern line marked 52° agriculture is not possible. A few crops may be
srown, to a limited extent, in sheltered valleys opening toward the south; but in general people
who live north of that line must depend on hunting, fishing, or mining for their living.
Methods of farming used to offset unfavorable rainfall. In some
parts of the dry regions large crops are grown by irrigation; that is,
water is taken from the rivers by means of canals and is then led into
little ditches in the dry but rich soil. The regions irrigated under
the control of the United States government are shown in Figure 19.
In other dry sections winler farming is practiced. Advantage is
taken of the rains that come regularly in the winter, and a hardy
winter crop is raised.
In still other regions, especially those just east of the Rocky Moun-
tains, the farmers make the most of the light rainfall by means of
what is called dry farming. Before the rainy season begins, they
plow the ground to let the rain soak in as much as possible. After
the soil is wet they keep the surface finely pulverized with a harrow
so that the moisture will not evaporate. Then, too, they are careful
in selecting crops that can thrive on light rainfall, such as wheat,
Kafir corn, and alfalfa.
In these various ways the effect of unfavorable rainfall is partly
overcome even in the dry West. Nevertheless, this section contains
large deserts which cannot be used even for grazing, irrigation, win-
ter farming, or dry farming. The driest and most barren of these
deserts are in Nevada, southeastern California, Arizona, and Utah
‘Fig. 22).