36 THE POTATO 



producing conditions which aid the development of 

 scab. 



Barn Manure. Applying barn manures is com- 

 monly practiced for potatoes with profitable results. 

 L,awes 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 



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



FIG. 10 INFLUENCE OF LIME UPON POTATOES 



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

 centage of scabbed potatoes. Right, unlimed. Left, 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 practice, 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, 2 of Michigan, found that twenty-four loads of 

 manure per acre gave the largest yield, while at the 



1 Rothamsted Memoirs, Vol. VI. " Mich. Bui. 131, p. 10. 



