The soil along the stream bottoms at a slight elevation above their
beds is usually a heavy, black, clayey loam, and though rich and
fertile is soon clogged by water, and then in drying, cakes on the
surface, killing the young plants. On this account the irrigators
seldom water these bottom lands until after the crop has acquired a
healthy growth, preferring to trust to the early rains to force the
young sprouts above the surface, rather than run the risk of its
crusting and thus preventing them from breaking through.
These bottom lands though really the poorest for irrigating, are nearly
the only lands now cultivated, because of the greater ease and
cheapness of supplying them with water. From two to three tons of hay
and from 35 to 50 bushels of grain per acre are raised even on these
inferior soils.
The best, and by far the more abundant agricultural lands, are the
"bench lands," these are situated high above the stream beds and the
soil is usually a warm open, rich, sandy-loam, several feet in depth
and usually underlain by a deep bed of gravel. Though in irrigating,
this soil at first requires more water, it will, owing to its excellent
natural drainage, last for all time and will neither clog with water
nor cake on the surface.
It is these bench lands which will be rendered irrigable by government
aid and surveys, though to develop them will require large amounts of
capital; still, they are so extensive in area that the work can
generally be conducted on a grand and economical scale.