386 THE SMALL GRAINS 



In these trials the character of the cultivation, including 

 depth of plowing, was the same on the several plats as 

 at Modesto, but the results were less striking, probably 

 because the soil on the State Farm is normally richer in 

 humus, and naturally more retentive of moisture (Shaw, 

 1911, pp. 261-271). 



Any residual or permanent effect upon the soil by the 

 green-manuring is not considered in these comparisons, 



FIG. 123. Plowing under rye for green-manure, in preparation for 

 wheat, at Modesto, California. 



and yet is important, especially as summer tillage on the 

 other hand is an exhaustive method. The course of 

 operations with green-manure crops is about as follows : 

 The stubble ground is double-disked as soon as possible 

 after the wheat or barley is removed. The rye and vetch, 

 or rye and field peas, are sown as soon as it is possible to 

 plow the land 4 to 5 inches in the fall. There is usually 

 sufficient moisture for seeding green-manure crops by 

 December 1. The crop is turned under about 8 inches 

 deep early in March of the following year, before the soil 

 is too dry for deep plowing (Fig. 123). The ground is 



