86 



CHEMISTRY OF FARM PRACTICE 



Rotation encourages diversified farming, which, when 

 properly carried on r greatly aids in keeping the land in 

 good condition. When the single -crop system is employed, 

 if that crop is a clean-cultured one, as is usually the case, 

 the organic matter of the soil becomes depleted, the soil 

 erodes more easily and, consequently, " gullying " sets in. 

 When land once begins to wash, it is difficult to keep the 

 most valuable part of the soil from being lost. The top- 

 soil is the most active in furnishing plant food and in pro- 



FIG. 31. A cover crop on corn land. (Permission F. G. Tarbox, 

 S. C. Exp. Station.) 



moting plant growth. When this soil is washed away, 

 the land becomes unproductive and it takes many years 

 of careful building to restore it to its former fertility. The 

 rebuilding of soil is time-consuming and expensive, there- 

 fore care should be exercised to prevent erosion. Erosion 

 may be prevented by the incorporation of organic matter, 

 deep plowing, and, in some cases, by terracing. 



66. Proper Sequence of Crops. In arranging rotations, 

 the endeavor should be to avoid having a crop that feeds 



