434 INVESTIGATION BY CULTURE EXPERIMENTS 



values at 75 cents per TOO pounds of ear corn, 32 cents a bushel 

 for oats, $1.33 per 100 pounds of wheat, $2.50 a ton for corn stover 

 and straw, and $10 a ton for hay. 



TABLE SIP. PENNSYLVANIA FIELD EXPERIMENTS 



The last two lines in the table are lo-year averages computed 

 by the author, all other figures being copied from Pennsylvania 

 Bulletin 90. 



In his discussion of these experiments, Doctor Hunt makes the 

 following comments (Bulletin 90, page 14) : 



"The most striking fact brought out by this table is that the application of 48 

 pounds of phosphoric acid and 100 pounds of potash in alternate years to a 

 rotation consisting of corn, oats, wheat, and mixed hay (timothy and clover), 

 namely, to the corn and wheat, has, during twenty-five years, maintained the 

 crop-producing power of the soil. There is no evidence thus far to show but 

 what the supply of nitrogen can be indefinitely maintained on this limestone 

 soil by means of a rotation containing clover, provided the mineral fertilizers are 

 abundantly supplied." 



