The Yuma Mesa 



235 



of the soil. Associated with the calcareous incrustation occurs a 

 considerable part of the phosphorus and potassium found in the 

 soil, which would account for the ready availability of the mineral 

 plant foods present. 



CHEMICAL COMPOvSITIOX OF THE YUMA SAND 



In Bulletin No. 6 of the Arizona Agricultural Experiment Sta- 

 tion, Collingwood reports the analysis of a sample of this soil 

 taken from Blaisdell Heights and compares it with an analysis of 

 a sample from the Fruitdale Tract, Fresno, California, made by 

 Dr. Hilgard. The analyses are comparable, having been made 

 from the same portion of the soil by the same methods of analysis. 

 In each case the "fine earth" passing 0.5 m. m. sieve w^as used, 

 and solution was effected by the same strength (1.115-sp. gr.) 

 hydrochloric acid. Analyses are given in Table III. 



TABLE HI — ANALYSIS OF FRESNO AND YUMA HEIGHTS SOIL 



Fruitvale 



Tract 



Fresno, Cal. 



Blaisdell 



Heights 



Yuma, Ariz. 



Insoluble matter 



Potash 



Soda 



Lime 



Magnesia 



Oxide of iron 



Alumina 



Pliosphoric acid 



Sulpluiric acid 



Carbonic acid 



Water and organic matter 



The Fruitdale soil showed more acid soluble constituents, one, 

 however, to large amounts of iron and alumina ; whereas the Yuma 

 Mesa soil showed very much more calcium carbonate. In the 

 Yuma soil the sum of the lime and carbonic acid corresponds almost 

 exactly to the theoretical amount of calcium carbonate correspond- 

 ing to the carbonic acid. This indicates that practically all the 

 lime found in the acid soluble portion of the soil existed as calcium 

 carbonate. The acid soluble phosphoric acid content of the two 

 soils was identical, and the potash content corresponded quite 

 closely. The inference would be that the Yuma soil was the equal 

 if not the superior of the Fresno soil due to the association of its 

 plant food elements wath well distributed calcium carbonate rather 

 than with iron and alumina. 



