306 THE SMALL GRAINS 



be noted that soil erosion is less frequent where there is 

 good drainage. 



331. Soil efficiency. Over a large part of the East- 

 ern area, particularly the timbered portions, the soils 

 are well known to be lacking in one or more essential 

 cereal plant-foods or inefficient in other respects, or both 

 may be true. This condition may simply show the soil 

 to be originally deficient, or may be the result of long 



FIG. 87. Terrace or contour farming at Tennessee Agricultural Experi- 

 ment Station, Knoxville. 



periods of cropping without proper soil replenishment. 

 Whichever the cause, it is true that the productive power 

 of the soil decreases after years of cropping, if not prop- 

 erly treated. In previous chapters, the efficiency of the 

 cereal plant and its improvement have been considered. 

 It is equally important that the soil be efficient. 



332. Soil amendments are means employed to over- 

 come certain soil deficiencies. The defects that may 

 exist in the soil are several. (1) It may lack one or more 



