78 



Journal of Agricultural Research 



Vol. XV, No. 1 



That is, the plot dressed with potash now contains, despite the fact 

 that it received 50 pounds of potash a year, about 6,000 pounds less 

 potash than the untreated plot. These differences in potash content of 

 the two plots are doubtless due to their geological rather than their agri- 

 cultural history. Their initial differences in potash content unsuit these 

 two soils for any direct statistical comparison. 



We may, however, assume that if plots i and 4 had had the same potash 

 content at the outstart of the experiment and the same treatment since 

 then the percentage proportion of this potash soluble under the condi- 

 tions here studied would have been alike. To estimate the present differ- 

 ences in potash condition so as to exclude the influences of geological 

 history and to represent only the effects of the differences in agricultural 

 treatment, the respective solubility percentages for the potash in the 

 contrasted plots are used as the quality factors and the present total 

 potash in the plot 4 surface soil as the quantity factor. The present 

 potash supply in the latter plot is slightly greater than it would have 

 been if the potash additions had not been made. The residue of these 

 additions is certainly not greater than 1,371 pounds, or approximately 

 2 per cent of the present potash stock. The influence of this amount 

 upon these admittedly crude approximations has been deemed too slight 

 for consideration in this computation. The potash weights thus com- 

 puted to the acre are: 



Treatment of potash. 



Total potash 



Insoluble in hot, strong hydrochloric acid ( i . 1 1 5 sp. gr. ) 



in 10 hours 



Soluble in 10 hours 



Soluble in N/5 hydrochloric acid, 5 hours at 40° C 



Soluble in distilled water 



Soluble in carbonated water 



Soluble in N/j ammonium-chlorid solution 



Untreated 

 soil. 



Pounds. 



66, no 



59> 731 



6,379 



247 



78 



132 



163 



Potash- 

 dressed 

 soil. 



Pounds. 

 66, no 



58, 512 

 7,598 

 562 

 149 

 261 

 349 



Excess in 

 potash- 

 dressed 

 soil. 



Po^inds. 



1,219 



315 



71 



129 



186 



It has already been observed that the natural stock of potash in the 

 untreated soil is high. At the annual rate of removal in harvested crops 

 for 1910-1913, the total supply would last 3,500 years, and that soluble 

 in strong hot acid about 350 years. Even the quantities soluble upon a 

 few hours' exposure of the soil to weak solvents would suffice for a num- 

 ber of years: The water soluble, 4 years; carbonated water soluble, 7 

 years; weak ammonium chlorid, 9 years; weak, warm acid, 13 years. 

 Vigorous crops of normal quantity would, of course, remove more potash, 

 but even for such growths the amounts readily soluble in the more or 

 less carbonated soil moisture should amply suffice, judging from the 

 observed solubility proportions. Experience on these lands has amply 



