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. 1 



Month. 



Greeley. 



1888 to 1915 

 (mean). 



Fort Morgan. 



1892 to 1917 

 (mean). 



Rocky Ford. 



1888 to 1917 

 (mean). 



January 



February 



March 



April 



May 



June 



July 



August 



September _' 



October 



November 



December 



Total annual precipitation 

 Altitude— feet 



0.30 



.46 



.86 



1.66 



2.64 



1.45 



1.83 



.93 



.92 



.89 



.32 



0.10 

 .18 

 .40 



.62 

 .09 

 .28 



0.24 



.44 



.75 



1.84 



2.36 



1.84 



2.48 



1.63 



.93 



.92 



.29 



.39 



0.45 



.22 



.25 



.40 



7.14 



1.33 



1.02 



2.31 



1.53 



.49 



.30 



.24 



12.70 

 4,639 



14.06 

 4,338 



15.68 



0.25 



.35 



.56 



1.68 



1.85 



1.32 



2.60 



1.45 



.87 



.84 



.41 



.49 



12.67 



4,177 



0.17 

 .22 

 .35 

 .99 



1.62 

 .25 



1.60 



1.18 



2.45 

 .12 











.95 



« Data incomplete for 1917. 



