52O AGRICULTURAL ANALYSIS 



In 1889 the Maine State College Experiment Station success- 

 fully grew oats in plats using ground feldspar in connection with 

 nitrate of soda and superphosphate. 13 In 1890 Headden in Colo- 

 rado carried on a similar set of experiments on oats. 14 The conclu- 

 sion was reached that the oat plant can use finely divided feldspar 

 as a source of potash. 



At about the same time Hensel in Germany was advocating the 

 use of stone meal as a fertilizing agent. Conflicting reports have 

 been made as to the results of these experiments, and in any case 

 it would appear that the material used had not been ground fine 

 enough to render it quickly available. 



The investigations of Cushman have reopened the question and 

 systematic experiments are under way which should settle this 

 important question once and for all. E^en should it appear that 

 such material is directly useful as a fertilizer, the question as to 

 its wide spread use will necessarily depend upon the cost in- 

 volved in grinding and transporting it. 



440. Cushman's Later Investigations. Investigation of the 

 availability of potash in feldspathic rocks has been continued by 

 Cushman in connection with the experiments in the actual grow- 

 ing of crops. 15 He finds that a cubic foot of granite weighs 

 about 170 pounds and contains about 8.5 pounds of potash, and 

 that loo feet square and 100 feet in depth will contain about 

 8,500,000 pounds of potash. It is evident, therefore, that feld- 

 spathic rock which is accessible in the United States would af- 

 ford an almost inexhaustible supply of potash if it could be util- 

 ized. Very large deposits of this feldspathic rock are found in 

 various parts of the country, and these have been developed for 

 building and other purposes in Maine, Connecticut, Pennsylvania 

 and Maryland. The feldspathic rocks obtained from these mines 

 have been ground to fine powders, chiefly for use in potteries. 



Orthophyric feldspathic rock contains 16.8% of potash, but 

 the feldspar from the sources above mentioned contains only 

 from 8% to 10%. 



Cushman says : 



13 Annual Report of the Maine State College Agricultural Experiment 

 Station, 1889 : 143. 



14 Colorado Agricultural Experiment Station, Bulletin 65, 1901 : 28. 



15 Bureau of Plant Industry, Bulletin 104, 1907. 



