SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 19 



Areas of different soils. 



PINAL. GRAVELLY SANDY LOAM. 



The Pinal gravelly sandy loam is a grayish-red to light reddish 

 broAvn calcareous sandy loam, carrying a large quantity of rounded 

 and subangular gravel, as well as bowlders and stones. The stony 

 surface material usually extends to a depth of 6 to 10 inches, where 

 a gray, calcareous hardpan or " caliche " is encountered. The soil is 

 of rather loose, friable structure, owing to the large content of coarse 

 material. It is high in lime but low in organic matter. The hard- 

 pan is a firmly cemented, gravelly layer or series of layers, varying 

 in thickness from 12 to 36 inches or more. The subsoil consists of a 

 grayish or grayish-brown, calcareous, compacted mass of gravel and 

 bowlders in a matrix of material finer than that in the surface soil. 

 It extends in many places to a depth of 6 feet or more, but locally is 

 underlain at varying depths by compact, heavy and more silty mate- 

 rial, free from gravel. A deep, gravelly substratum underlies the 

 type. This also is calcareous. 



The Pinal gravelly sandy loam occurs in areas of varying size, the 

 largest lying west of Florence along the Blackwater and Florence 

 Road. For several miles this area, occupying a more or less eroded 

 terrace, forms the southern boundary of the Gila Valley. Areas of 

 similar characteristics skirt the valley north of the river, but only a 

 small part is included in this survey. Three small areas are mapped 

 east of Casa Blanca and one southeast of Casa Grande. The latter 

 is of particularly stony character. 



The surface of the type is somewhat undulating and eroded and 

 not well adapted to irrigation. The gravelly, stony nature of the 

 soil and the nearness of the " caliche " to the surface render the type 

 difficult to handle. The surface run-off is rapid and the soil is not 

 retentive of moisture. 



The Pinal gravelly sand}' loam is at present used solely for pasture. 

 It supports only a sparse growth of grasses or creosote bush, and its 

 pasturage value is low. 



