Dry-Farming | Page 7

good supply of rainfall. The
foothills of the mountains are almost invariably excellent dry-farm
lands. Newell estimates that 195,000,000 acres of land in the arid to

sub-humid sections are covered with a more or less dense growth of
timber. This timbered area roughly represents the mountainous and
therefore the nonarable portions of land. The same authority estimates
that the desert-like lands cover an area of 70,000,000 acres. Making the
most liberal estimates for mountainous and desert-like lands, at least
one half of the whole area, or about 600,000,000 acres, is arable land
which by proper methods may be reclaimed for agricultural purposes.
Irrigation when fully developed may reclaim not to exceed 5 per cent of
this area. From any point of view, therefore, the possibilities involved
in dry-farming in the United States are immense.
Dry-farm area of the world
Dry-farming is a world problem. Aridity is a condition met and to be
overcome upon every continent. McColl estimates that in Australia,
which is somewhat larger than the continental United States of America,
only one third of the whole surface receives above 20 inches of rainfall
annually; one third receives from 10 to 20 inches, and one third
receives less than lO inches. That is, about 1,267,000,000 acres in
Australia are subject to reclamation by dry-farming methods. This
condition is not far from that which prevails in the United States, and is
representative of every continent of the world. The following table
gives the proportions of the earth's land surface under various degrees
of annual precipitations:--
Annual Precipitation Proportion of Earth's Land Surface Under 10
inches 25.0 per cent From 10 to 20 inches 30.0 per cent From 20 to 40
inches 20.0 per cent From 40 to 60 inches 11.0 per cent From 60 to 80
inches 9.0 per cent From 100 to 120 inches 4.0 per cent From 120 to
160 inches 0.5 per cent Above 160 inches 0.5 per cent Total 100 per
cent
Fifty-five per cent, or more than one half of the total land surface of the
earth, receives an annual precipitation of less than 20 inches, and must
be reclaimed, if at all, by dry-farming. At least 10 per cent more
receives from 20 to 30 inches under conditions that make dry-farming
methods necessary. A total of about 65 per cent of the earth's land
surface is, therefore, directly interested in dry-farming. With the future
perfected development of irrigation systems and practices, not more
than 10 per cent will be reclaimed by irrigation. Dry-farming is truly a
problem to challenge the attention of the race.

CHAPTER IV
DRY-FARM AREAS.--GENERAL CLIMATIC FEATURES

The dry-farm territory of the United States stretches from the Pacific
seaboard to the 96th parallel of longitude, and from the Canadian to the
Mexican boundary, making a total area of nearly 1,800,000 square
miles. This immense territory is far from being a vast level plain. On
the extreme east is the Great Plains region of the Mississippi Valley
which is a comparatively uniform country of rolling hills, but no
mountains. At a point about one third of the whole distance westward
the whole land is lifted skyward by the Rocky Mountains, which cross
the country from south to northwest. Here are innumerable peaks,
canons, high table-lands, roaring torrents, and quiet mountain valleys.
West of the Rockies is the great depression known as the Great Basin,
which has no outlet to the ocean. It is essentially a gigantic level lake
floor traversed in many directions by mountain ranges that are
offshoots from the backbone of the Rockies. South of the Great Basin
are the high plateaus, into which many great chasms are cut, the best
known and largest of which is the great Canon of the Colorado. North
and east of the Great Basin is the Columbia River Basin characterized
by basaltic rolling plains and broken mountain country. To the west,
the floor of the Great Basin is lifted up into the region of eternal snow
by the Sierra Nevada Mountains, which north of Nevada are known as
the Cascades. On the west, the Sierra Nevadas slope gently, through
intervening valleys and minor mountain ranges, into the Pacific Ocean.
It would be difficult to imagine a more diversified topography than is
possessed by the dry-farm territory of the United States.
Uniform climatic conditions are not to be expected over such a broken
country. The chief determining factors of climate--latitude, relative
distribution of land and water, elevation, prevailing winds--swing
between such large extremes that of necessity the climatic conditions of
different sections are widely divergent. Dry-farming is so intimately
related to climate that the typical climatic variations must be pointed

out.
The total annual precipitation is directly influenced by the land
topography, especially by the great mountain ranges. On the east of the
Rocky Mountains is the