4 BULLETIN 917, U. S. DEPARTMENT OF AGRICULTURE. 
is easily kept in good tilth. The Maricopa sandy loam has a more 
open texture, and water soaks rapidly into the ground. This re- 
quires greater skill in the application of irrigation water. This loam 
is underlain by a compact subsoil, which has a tendency to cause 
seepage in some low spots, but it is a soil that retards the movement 
of water from the irrigation canals and ditches. The Maricopa 
sandy loam and the Fresno fine sandy loam are well adapted to most 
of the crops commonly grown in the Arkansas Valley. 
In the selection of a soil for the growing of crops in an irrigated 
region, it is necessary to have one that has good drainage, especially 
subsoil drainage. A soil for irrigation should not be too compact or 
water will not penetrate it quickly. Such a soil is also likely to crust 
or bake when irrigated or after a hard rain. Most of the soils of this 
semiarid region are high in mineral fertility, and the problem of selec- 
tion is in regard to their water absorbing and holding capacity, as 
water is most often the limiting factor in maximum crop production. 
CLIMATIC CONDITIONS. 
A limited rainfall (Table II) of approximately 13 inches a year, a 
low atmospheric humidity, occasional high winds, and but few cloudy 
days are the characteristic features of the Colorado climate. These 
conditions cause a rather heavy evaporation of moisture from the 
soil. In order to produce crops, irrigation is practiced in regions 
where there is an available supply of water for this purpose. The 
principal irrigated sections are located in the valleys and drainage 
section of the South Platte River in northern Colorado and of the 
Arkansas River in southern Colorado. Rocky Ford was selected as 
typical of the southern section and the Greeley and Fort Morgan 
districts as typical of the northern section. 
Table II. — Average annual rainfall of two sugar-beet districts in northern Colorado 
and one district in southern Colorado. 
[Depth of rainfall expressed in inches.] 
Greeley. 
Fort Morgan. 
Rocky Ford. 
Month. 
188Stol915 
(meam. 
1917 a 
lS92tol917 
(mean). 
1917 
1888 to 1917 
(mean 1 . 
1917 
Januarv 
0.30 
.46 
.86 
1.66 
2.64 
1.45 
1.83 
.93 
.92 
.S9 
.32 
.44 
0.10 
.18 
.40 
"".'62' 
.09 
.28 
0.24 
.44 
. 75 
1.84 
2.36 
1.84 
2.48 
0.45 
.22 
.25 
.40 
7.14 
1.33 
1.02 
0.25 
.35 
.56 
1.68 
1.85 
1.32 
2.60 
1.45 
.87 
.84 
.41 
.49 
0.17 
F ebruarv 
.22 
March 
.35 
April 
.99 
Mar 
1.62 
.25 
July.. 
1.60 
1.63 2.31 
.93 | 1.53 
.92 1 .49 
.29 .30 
.39 .24 
1.18 
2.45 
.12 


Total annual precipitation 
12.70 
4.639 
14.06 
4,338 
15.68 
12.67 
4,177 
8.95 
Altitude— feet 
a Data incomplete for 191' 
