PrincipaIv Dry-Farming Regions 527 



among these is Sulphur Spring Valley, containing approximately 

 1,000,000 acres. 



The soil is a fertile decomposed limestone, and "caliche"' ap- 

 pears in many places. A large alkali flat lies east of Willcox and 

 Cochise, and alkali spots, in the vicinity of Whitewater and through- 

 out the southern end of the \^alley, make reclamation of a large part 

 of the area by dry-farming impracticable. Considerable agricul- 

 tural development has occurred since 1907. In the valley proper, 

 underground water is usually found at less than fifty feet depth and 

 often in quantities sufficient to make irrigation with pumped water 

 practicable. A small acreage in the vicinity of Whitewater is re- 

 claimed in this way. On the first mesas of the valley the water 

 table is from 75 to 200 feet below the surface but the soil is often 

 considered superior to the lower lands for dry-farming.* 



Farming conditions in San Simon Valley are comparable to 

 those of Sulphur Spring Valley. Flowing artesian wells have been 

 developed near San Simon ; and near Bowie artesian water has 

 risen near enough to the surface to make pumping for irrigation 

 feasible. 



The upper San Pedro Valley contains a large acreage of dry- 

 farming lands similar to Sulphur Spring and San Simon Valleys. 

 Intermittently successful dry-farming has been carried on for about 

 ten years. 



In general the soils of the three valleys are loams and sandy 

 loams. They are quite fertile and well supplied with lime. Water 

 penetrates them readily and is quite efficiently retained. The soil 

 samples of which the mechanical and chemical analyses are re- 

 ported in Tables XVI and XIX are from the Sulphur Spring Valley 

 Dry-farm near Cochise, and are representative of the soils of the 

 three valleys. The bottom land soil reported in Tables XVI and 

 XVII is a loam with a coarse textured stratum at the fifth foot, 

 which hinders the rise of capillary moisture from below. The fine 

 texture of the surface foot retards water penetration, especially that 

 of light summer showers. For these reasons many farmers prefer 

 the sandier mesa soils. The bottom lands contain fair quantities of 

 nitrogen and humus in the first four feet, but the lower four feet 

 are deficient in these materials. Potash, phosphoric acid, and lime 

 are present in ample amounts. The lighter type of soil is repre- 



*For a detailed report on geologic and soil conditions in .'^ulphnr Siiring Val- 

 ley, see Paper No. 320 U. S. Geological Survey, "Water Resources of the Sulphur 

 Spring Valley." 



