SURVEYS BY THE UNITED STATES BUREAU 129 



alkali, the members of this series are admirably adapted to the production of 

 choice fruits, alfalfa, sugar beets, grains, and truck crops. 



Laramie series. Dark -colored soils, with light-colored gravelly subsoils, de- 

 rived from colluvial mountain wash. These soils have not been extensively 

 developed, owing to their elevation, and are used principally for grazing pur- 

 poses. 



Laurel series. Light gray to black soils, underlain by river sands or gravels, 

 occurring in flood plains along streams. Under favorable moisture conditions, 

 these are fertile soils, adapted according to locality to corn, alfalfa, sugar beets, 

 and truck crops, but the areas are often subject to overflow, and in some cases 

 cannot be drained. 



Mesa series. Light gray to brown soils derived from old flood-plain de- 

 posits, now elevated to form mesa lands. Where these soils have been devel- 

 oped and are susceptible of irrigation, they are used mainly for alfalfa and 

 sugar beets. One member of the series has been quite extensively and very 

 successfully used for the production of apples and peaches. 



Morton series. Brown residual soils, derived from sandstones and shales- 

 The soils lie in the semiarid region, and give good yields of wheat, flax, oats, and 

 potatoes, when rainfall is sufficient. 



San Luis series. Reddish brown gravelly soils, formed from lacustrine 

 sediments of volcanic rock materials. On account of the position and the 

 danger from alkali, these soils have not been successfully developed, but have 

 been used mainly for pasturage and forage crops. 



Wade series. Brown to dark brown alluvial soils, formed by reworking of 

 sandstones and shales. Used for oats, flax, millet, and wheat. 



ARID SOUTHWEST 



The soils of the arid Southwest are mainly of colluvial, alluvial, and lacus- 

 trine origin. They occupy mountain foot slopes, alluvial fans, debris aprons, 

 or sloping plains of filled valleys, sloping or nearly level plains, and bottoms of 

 stream valleys or sinks and drainage basins. The principal colluvial soils of 

 this region are also common to the Pacific coast. The climate of the arid 

 Southwest is characterized by semitropical desert conditions, and where the 

 soils are not capable of irrigation, they have little or no present agricultural 

 value. 



Gila series. Light to dark brown soils of flood-plain alluvium, underlain 

 at varying depths by coarse sands and gravels. Under favorable irrigation and 

 drainage conditions, the members of the Gila series are adapted chiefly to the 

 production of alfalfa, potatoes, truck, and root crops. 



Imperial series. Light-colored or reddish soils formed from old marine 

 or lacustrine sediments modified by more recent deposits, and underlain to 

 great depths by heavy material. These soils are particularly adapted to alfalfa, 

 sorghum, and other forage crops. 



India series. Light-colored soils usually underlain by coarser sands and 



