68 



HATCH EXPERIMENT STATION. 



[Jan. 



It will be seen from the above analyses that there is a 

 great difference in the percentage of the fertilizing constitu- 

 ents present in the different samples. There remains, how- 

 ever, no doubt that these materials when properly studied 

 furnish a valuable source of plant food, when they can be 

 conveniently obtained, and supplemented by such ingredients 

 as potash and phosphoric acid compounds, to render them 

 more suitable for manurial purposes in case of different crops. 



4. Notes on Phosphatic Slag as a Source of Phos- 

 phoric Acid for Manurial Purposes. 



The phosphatic slag, sometimes called Thomas basic phos- 

 phatic slag, or odorless phosphate, in advertisements of 

 dealers of commercial fertilizers, is obtained as a by-product 

 in the conversion of phosphorus containing iron ores into 

 phosphorus free metallic iron. Investigations regarding its 

 fitness as an economical source of phosphoric acid for manu- 

 rial purposes have received, from the date of its first pro- 

 duction, the special attention of agricultural chemists and 

 agriculturists of Germany and other European countries. 

 Field observations in the United States date back, as far as 

 the writer is informed, to the year 1888. Summing up the re- 

 sults of the past, it will be admitted that a genuine phosphatic 

 slag, judiciously applied, has proved a valuable addition to our 

 phosphoric-acid-containing manurial resources, and that its 

 use is only limited by its supply at a reasonable cost. 



The subsequent tabular statement may convey some more 

 definite idea regarding the general character of the phos- 

 phatic slag tested at Amherst, Mass. : — 



Analyses of Phosphatic Slag (Per Gent.). 



[I., German phosphatic slag (sent on), 1887 ; II., English phosphatic slag (sent on)> 

 1887 ; III., German phosphcatic slag (imported for station use), 1888 ; IV., phos- 

 phatic slag received from England, 1888.] 



