1900.] rUBLIC DOCUMENT — No. 33. 29 



Comparison of Different Potash Salts. (Field G.) 

 The object in this experiment is to determine the relative 

 manurial value for our various crops of the different promi- 

 nent potash salts. The experiment was begun in 1898, the 

 crop that year being the soy bean. The results were inde- 

 cisive and unsatisfactory, the crop where no potash was 

 used in numerous instances being as great as where potash 

 manures were applied. The potash resources of the soil 

 were clearly too large to allow satisfactory deductions to be 

 made. This had, however, been anticipated. From the 

 nature of the problem it was recognized that the experiment 

 must continue for a series of years. We must study not 

 simply the immediate effect upon the crop, but the effect 

 upon the soil of long-continued use of the different salts, — 

 and as well the effect upon the crop of such continued use. 



In this experiment the plots are one-fortieth of an acre 

 each, duly separated by dividing strips. There are forty 

 plots, each manuring being five times duplicated. Every 

 plot receives yearly materials estimated to furnish nitrogen 

 and phosphoric acid in liberal amounts. All receive the 

 same materials, save plots 6, 14, 22, 30 and 38, on which 

 the potash salt used is the nitrate, so that the amount of ni- 

 trate of soda for these is made only sufficient (.5 pounds) to 

 furnish to these plots the same amount of nitrate nitrogen as 

 to the others. With this exception, the materials applied 

 as sources of nitrogen and phosphoric acid are, per plot : — 



Pounds. 



Nitrate of soda, 7.0 



Tankage, 7.5 



Acid phosphate, 10.0 



In order to make certain that there should be no failure 

 through deficiency of lime, the entire field received an ap- 

 plication at the rate of one ton to the acre of lime freshly 

 slacked, which was wheel-harrowed in early in the spring of 

 1898. 



The various potash salts where used were applied in 

 amounts intended to furnish an equal quantity of actual 

 potash (K2O) to each plot, as follows : — 



