Nature-Study Agriculture 



Caver 

 crops 



Making 



weeds 



useful 



Why stock 



FIG. 23. Plowing under a cover crop to enrich the soil. 



It is frequently advisable to raise a quick-growing crop 

 for the purpose of plowing it under while it is still green 

 (Figs. 23, 24, 25, and 26). This is called a "cover crop " or 

 a "green manure crop." It is best not to plow too deep 

 when turning the cover crop under, because the vegetable 

 matter will not decay without air from the surface ; about 

 four or five inches is usually the right depth. Weeds 

 may be treated in this way, as they are often rich in plant 

 food. The best time for plowing them under is when 

 they are in bloom, before they go to seed. 



If, instead of selling all of his crops, the farmer 



would feed to livestock a P art > at least > of what he 

 raises, he could return to the soil, in stable manure, 



much of the plant-food material that is removed by 

 crops. 



