June is, 1925 Effect of Crops on Yields of Succeeding drops in Rotation 1107 
Fig. 2.—Annual yields of tobacco, 1912-1923, inclusive: (1) In a two-year rotation of tobacco, wheat, 
and cowpeas (turned under), tobacco crop fertilized; (2) in continuous culture, with crimson clover 
as a cover crop, tobacco fertilized; (3) in continuous culture, with crimson clover as a coverlcrop, 
tobacco not fertilized. In all cases the general trend in yield is downward, the initialjgainsffrom 
legumes not being maintained. Omission of fertilizer for tobacco, even when legumes are grown, 
soon leads to practical crop failure 
Pig. 3.—Annual yields of tobacco in continuous culture, 1916-1923, 
inclusive, without use of a cover crop and with rye as a cover 
crop. At the beginning and in certain subsequent years, the 
yields after rye were about the same as without cover crop. 
In relatively wet seasons, however, the,yield is markedly de¬ 
pressed by the rye cover crop 
