26 a EXPERIMENT STATION. [Jan. 



Field G, Comparison of Potash Salts. 

 This is the twentieth year of the experiment which has had 

 for its object the comparison of seven different materials that 

 may be used as sources of potash. There are 40 plots in all, 

 including 5 check or no-potash plots and 5 plots on which 

 each of the different potash materials are used. The rate of 

 application of actual potash has been in previous years 135 

 pounds of potassium oxide per acre; this year the application 

 was reduced to 75 pounds. The different materials furnishing 

 potash are: kainit, high-grade sulfate of potash, low-grade sul- 

 fate of potash, muriate of potash, nitrate of potash, carbonate 

 of potash and treater dust. All plots receive annually the fol- 

 lowing mixture supplying nitrogen and phosphoric acid: — 



Pounds 

 per Acre. 



Nitrate of soda,^ 250 



Tankage, 270 



Acid phosphate, 360 



In 1915 all plots received the usual application of nitrogen 

 and phosphoric acid, but no potash. This year all plots re- 

 ceived the usual application of nitrogen and phosphoric acid, 

 and all except the fourth series (plots 25-32) received the 

 application of potash. On this set of plots the potash was 

 omitted. 



The crop this ,year was Early Canada Flint corn, which, ow- 

 ing to the late season, was not planted until June 22. The 

 yield per acre of the different plots is shown in the following 

 table : — 



' Plots 6, 14, 22, 30 and 38, which receive nitrate of potash, receive only enough nitrate of 

 soda to make up the deficiency in nitrate, — this year, 108 pounds per acre. 



