PROMISING GREEN-MANURE CROPS. 29 
to enable them to stand much trampling or other hard usage without 
injury. 
The time and manner of seeding this crop are much the same as 
with common vetch. As the seed is a little smaller, however, a 
smaller quantity may be used inseeding. From 50 to 60 pounds per 
acre is advised. 
BLACK BITTER VETCH. 
Black bitter vetch (Vicia ervilia), another very promising green- 
manure crop for California, is different from most other vetches in 
that it is upright inits habit of growth, rather than vinelike. Like 
Fic. 8.—A field of black bitter vetch at Chico, Cal. 
the black-purple vetch, it possesses the desirable quality of making a 
good growth during the cool weather of early winter and is much 
superior to common vetch in this respect. (See fig. 8.) In this 
connection it should be noted that different strains of this vetch 
have given different yields, so that some will doubtless be found 
superior to others. 
Its upright habit of growth makes this crop very easy to turn under 
with an ordinary moldboard plow. The viny growth of common 
vetch makes it objectionable to some orchardists. The root system, 
while quite well covered with nodules, is perhaps not so extensive as 
that of some of the other vetches. The plant has a more definite 
190 
