COMMERCIAL FERTILIZER MATERIALS 465 



Ashes are beneficial to acid soils through the action of both 

 the potassium and calcium salts. 



Insoluble forms of potassium, existing in many rocks 

 usually in the form of a silicate, are not regarded as having 

 any manurial value. Experiments with finely ground feld- 

 spar have been conducted by a number of investigators, but 

 have, in the main, offered little encouragement for the suc- 

 cessful use of this material. Leucite and alunite have given 

 but little better results. An insoluble form of potassium is 

 not recognized as of value when a fertilizer is rated on the 

 basis of chemical analysis. 



During the World War, since the German importation of 

 potash salts ceased, potassium was sought commercially from 

 a number of sources in this country. Alunite, a hydrous sul- 

 fate of aluminum and potassium, has been experimented with 

 to some extent as have also the green-sand marls which carry 

 glauconite. In a number of cases the recovery of potash 

 from flue dust has proven commercially profitable. It is esti- 

 mated that 87,000 tons of potash are lost yearly from cement 

 kilns alone in the United States and Canada. During the war 

 considerable progress was made in harvesting and drying the 

 kelp which grows off the coast of southern California. The 

 kelp was later extracted for its potash. This source' of potas- 

 sium is rather expensive, however, when brought into com- 

 petition with European products. 



Perhaps the most reliable sources of domestic potash are 

 the brines of certain alkali lakes of western United States and 

 from the deposits in old lake beds in the same region. 1 The 

 exploitation of such sources will, of course, depend upon the 

 price at which German potash can be laid down in this 

 country. 



1 Such salts unless properly prepared are likely to contain borax 

 which is usually toxic when applied at a greater rate than five pounds 

 to the acre, the influence being more intense at low soil moisture. 



Neller, J. K., and Morse, W. J., Effects upon the Growth of Potatoes, 

 Com and Beans, Resulting from the Addition of Borax to the Fertilizer 

 used; Soil Sci., Vol. XII, No. 2, pp. 79-105, 1921. 



