110 The Sweet Potato 



ficient water was given to supply all needs of the 

 plants." ^ In many sections of the South, the growth 

 of leguminous crops in the sweet potato rotation would 

 be a most desirable means of supplying both nitrogen 

 and humus, which are much needed on many of these 

 soils. If the crops in rotation are corn, cotton, oats or 

 wheat, leguminous crops should be sown with these, or 

 after they are harvested, in which case they might also 

 be used as a winter cover-crop. Velvet beans, peas or 

 clover may be planted with the corn, or clover may fol- 

 low oats or wheat. Very good results are secured by 

 turning under a heavy crop of crimson clover early in 

 the spring. Green-manuring, however, consists of more 

 than growing a leguminous crop which is removed from 

 the soil. It means the growing of a crop on the land 

 which is plowed under. Many fields of so called " worn- 

 out " land could be made to produce bountiful yields of 

 high quality sweets by the use of one or two crops of 

 legume turned under as manures. 



Other materials as fertilizers. 



Stable-manure, though supplying organic matter in 

 its most desirable form and also adding nitrogen and 

 smaller quantities of other food elements to the soil, 

 should never be applied directly to a crop of sweet 

 potatoes. When so applied it has a tendency to cause 

 too rapid growth, resulting in large rough tubers of 

 poor quality. When applied excessively, vine growth is 

 over-stimulated at the eixpense of the tubers. Stable- 

 manure is best applied to the crop immediately preced- 

 ing the sweets and even then it should be well rotted. 

 Well-rotted stable manure may be used at the rate of 



I Bull. 147, R. I. Exp. Sta. 



