334 Journal of Agricultural Research voI.x.no. 7 



and 0.108 per cent of sulphuric acid. Regarding the conception of the 

 derivation from preexisting geological deposits, Dorsey (4, p. 10) says: 



In some cases it may be regarded as fairly evident that the salts do come from more 

 or less deep-seated deposits resulting from the desiccation at more or less remote 

 periods of time of bodies of sea water. In many cases, however, there is a total lack 

 of confirmatory geologic evidence, and this explanation must be regarded as very 

 imsatisfactory. 



It may thus be seen that there are a number of theories proposed 

 regarding the origin of "alkali" of the arid regions. The following are 

 some of the most important: (i) Derivation from gypsum by action of 

 sodium carbonate, as proposed by Antisell; (2) accumulation of the 

 unused portion of the soil or refuse, as proposed by Medlicott; (3) Hil- 

 gard's conception of the formation of soluble salts in the soil by ordinary 

 process of weathering and their concentration in the lower depths by the 

 action of the limited rainfall; (4) Whitney and Means's conception of 

 their formation by oxidation of the sulphids of the shales; (5) Buffum's 

 view of the presence of isolated deposits or lakes of the alkali salts in the 

 country rock; (6) Cameron's theory regarding the formation of hydro- 

 chloric and sulphuric acid from the chlorin and sulphur content of the 

 country rock and the subsequent leaching action of these acids on the 

 insoluble silicates of the soil or rock; and (7) the deposition by wind 



spray from sea water. 



THE PROBLEM 



Our attention was directed forcibly toward the alkali problem in con- 

 nection vnth our investigation regarding the origin of the "niter spots," 

 a special phase of the more general alkali problem. 



The results of these investigations, which have been presented else- 

 where (9), led us to a very definite conception regarding the origin of 

 alkali in at least a large portion of Utah, Colorado, Wyoming, Montana, 

 Alberta, Canada, and undoubtedly in many other areas of the arid region. 

 The preponderance of evidence submitted by us clearly demonstrates 

 that the "niter spots" are the direct result of the leaching action of 

 water upon the nitrates preexisting in the country rock and their con- 

 centration at the points of greatest evaporation. The nitrate accumula- 

 tions are always accompanied by the other water-soluble so-called 

 alkali salts. The facts led us to formulate a definite hypothesis regard- 

 ing the origin not only of the nitrates themselves but also of the other 

 salts as well. 



The hypothesis upon wnich the following work was based is: The 

 "alkali" is derived from the soluble salts preexisting in the country 

 rock of the observed area. This coimtry rock rich in alkali not only 

 contributes to the soil formation but is adjacent to and underneath the 

 agricultural soils of the affected areas. The original soil may not have 

 sufficient salts present to prevent crop production, but upon the appli- 

 cation of the irrigation water the alkali salts existing in the country 



