A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1187 



point of diminishing returns was reached. The yields increased sufficiently, 

 up to the highest value of manure and fertilizer used, to warrant the cost. 

 Evidently it would be safe to recommend the use of larger amounts on 

 potatoes in this region. The positive coefficient of correlation shown in 

 figure 138 is 0.258 0.036, a value significant and consistent with the 

 coefficients for the other regions. 



a 3 



Yield per acre, in bushels 



O *O O *O O to O 



$ 1-$ 5 



8 8 $ 6-$10 



* $11-$15 



g fe $16-$20 



S J $21-$25 



B g $26-$30 



o3 $31-$35 



| $36-$40 



S" $41-$45 



1 



38 



40111 



44 



121 



76 



43 



10 



5 











1 



300 



70 50 61 34 24 

 r = 0.258 =b 0.036 



FlG. 138. CORRELATION OP VALUE OP MANURE AND FERTILIZER, AND YIELD, ON 300 MONROE 



COUNTY FARMS IN 1913 



Value of manure and fertilizer in Franklin and Clinton Counties 



A constant increase in yield for each increase in value of manure and 

 fertilizer used, is shown in table 27 for the Franklin and Clinton County 



TABLE 27. RELATION OF VALUE OF MANURE AND FERTILIZER TO YIELD ON 290 FRANKLIN 

 AND CLINTON COUNTY FARMS IN 1913 



