36 THE POTATO 



producing conditions which aid the development of 

 scab. 



Barn Manure. — Applying barn manures is com- 

 monly pradliced for potatoes with profitable results. 

 Lawes and Gilbert ' showed that only a small portion 

 of the nitrogen of farm manures is taken up by the crop; 

 thus, with an annual manuring of 15.5 tons per acre, 

 containing 200 pounds of nitrogen, continued for twelve 



Courtesy R. I. Exp. Sta. See Bui. 40. 



FIG. lO — INFLUENCE OF LIME UPON POTATOES 

 Shpwing the influence of lime upon the yield, and that it increases the per- 

 centage of scabbed potatoes. Kight, unlinicd. Lf/t, limed. Other fertil- 

 izers the same in both cases. 



years, but 8.3 per cent, of the nitrogen was recovered 

 in the crop. ' ' These results seem to indicate that this 

 crop is able to avail itself of a less proportion of the 

 nitrogen of the manure than any other farm crop. 

 Yet, in ordinary pradlice, farm-yard manure is not only 

 largely relied upon for potatoes, but is often applied in 

 larger quantities for them than for any other crop." 

 Taft," of Michigan, found that twenty-four loads of 

 manure per acre gave the largest yield, while at the 



» Rothamsted Memoirs, Vol. VI. ' Mich. Bui. 131, p. 10. 



