208 THE CULTURE OF FARM CROPS. 



of the soil which is favorably affected by the chemical ac- 

 tion of the decaying vegetable matter. The total amount 

 of this accumulation is not accurately known, but is cer- 

 tainly very large. And \vhen the grass or hay from the 

 land is all consumed upon the farm, and the manure is re- 

 turned to the land, the soil of a permanent or old meadow 

 becomes exceedingly rich in plant food, from the annual 

 top dressings which it receives naturally from the decay of 

 the leaves and stems and of the matured and used up roots. 



