B. P. I.— 275. 



THE USE OF FELDSPATHIC ROCKS AS 

 . FERTILIZERS. 



INTRODUCTION. 



In view of the great demands that are being made upon the agri- 

 cultural resources of the country, it is a matter of vital importance 

 that consideration be given to the available supplies of elements 

 which are necessary to sustain and maintain the quality and quantity 

 of the crops. It is well known that there are three principal fer- 

 tilizing materials: Nitrogen, phosphoric acid, and potash. The dis- 

 covery of electrochemical and bacteriological processes for fixing 

 the nitrogen of the air, thereby changing it into a form in which it 

 can be used as a plant food, seems to remove all doubt as to the 

 abundance of the supply of this important element for all time to 

 come. An enormous geographical area of this continent is underlain 

 with practically inexhaustible supplies of phosphatic rock, which, 

 with the phosphates obtainable in waste bone, slaughterhouse tank- 

 age, fish scrap, and the basic slags from the iron industry, insure a 

 limitless supply of phosphoric acid. 



With regard to potash alone there has been reason to feel anxiety. 

 Up to the present time no deposit or source of this necessary element 

 in any of the forms in which it has been heretofore considered avail- 

 able as a plant food has been discovered or developed in this country.^ 

 The mines of Stassfurt, Germany, furnish almost the entire supply 

 of potash for fertilizer in the United States, exclusive of that which 

 is used over and over by the processes of natural and green manuring. 

 The potash salts, which up to this time have been exclusively used 

 for fertilizing, consist of muriate, sulphate, nitrate, and carbonate, 

 either in a crude or in a previously purified condition. Kainite is 

 a trade name given to a crude product of the German mines, which 

 contains about 13 per cent of actual potash, largely in the forms of 

 sulphate and chlorid (muriate). The quantity and value of potash 

 salt to be used as fertilizers imported in the fiscal years 1903, 1904, 

 and 1905 are shown in the following table. The price of the potash 

 unit has shown a tendency to increase each year. 



7 



104 



