Oct. 14, 1918 Fertilizer Potash Residues in Hagerstown Silty Loam 77 



The excess removal by crops from plot 4 thus calculated is probably 

 too great. The crop yields of plot i have been decreasing, but those 

 also of plot 4 have been falling off at a similar rate. The potash stock 

 of plot I has been drawn upon without replacement; that of plot 4 has 

 been increasing. For, even at the rates apparent in 1910-1913, the 

 average annual removals of potash in crops from the respective plots 

 were: From plot i, at the rate of 18.7 pounds to the acre; from plot 4, 

 30.7 pounds; whereas the average annual potash addition to plot 4 was 

 50 pounds to the acre. It is very possible, therefore, that the excess 

 percentage of potash in a unit weight of harvested crop removed from 

 plot 4 over that from plot i is now greater than in the earlier years of 

 the experiment. 



At the utmost, therefore, only 430 pounds of the 1,800 pounds of 

 fertilizer potash applied to plot 4 has been removed in the crops har- 

 vested if, for this computation, we assume that the withdrawal from the 

 original soil stocks were the same on each plot for each unit weight of a 

 given crop harvested and that the excess removal on plot 4 is to be 

 charged to the fertilizer potash. This leaves a balance of 1,370 pounds 

 of fertilizer potash to be accounted for. 



Upon the same basis of computation the crops of plot 4 used of the 

 fertilizer applied only 12 pounds out of 50, or less than one-fourth. The 

 smallness of this utilization is to be ascribed to the large natural supply 

 of potash in this soil and the little crop increase the potash fertilizer here 

 induces. 



The actual weights of potash existing in the soils in different states 

 of solubility remain to be considered. From data presented in an 

 earlier section of this paper, the following facts appear as to the respective 

 fine soil weights for the surface acre 7-inch layers and the total potash 

 percentages : 



Plot I. Plot 4. 



Weightsof fine soil of acre 7 inches, .pounds. . i, 890, 644 i, 865, 947 



Total potash per cent . . 3- 82 1 3. 543 



Total potash pounds.. 72,241 66,110 



