132 MASS. EXPERIMENT STATION BULLETIN 212. 



Table 2. — The Check Plots. 



The Effect of Potash. — The most marked and most striking result of 

 the test, especially as indicated by the corn crop, was the great response 

 to potash. The following table shows the average yields of corn for the 

 two periods under discussion for those treatments which include this 

 plant food : — 



Table 3. — The Treatments containing Potash. 



Potash alone was effective, although the difference between the first 

 period and the second period is very large. This treatment outyielded 

 the potash and nitrogen treatment in the first period, but results were 

 reversed in the second. 



The use of a mineral plant-food ration consisting of phosphoric acid 

 and potash gave marked results. Here again, however, the decrease in 

 jaeld between the two periods was fully as great as, in fact somewhat 

 larger than, the decrease on either the potash or potash and nitrogen 

 plots. On the complete fertilizer, however, the decrease was even greater; 

 for whereas this treatment was definitely superior in yield during the first 

 period, it was very little better than the phosphoric acid and potash 

 treatment in the second. 



There are two explanations for this apparent decrease in yielding power 

 in the two periods under discussion. The weather conditions may not 



