ROOTS AND THE SOIL. 1 29 



then pass through an animal's body, but it will 

 pass back to the soil eventually. Man interferes 

 with this natural improvement by withdrawing crops 

 and animals for his own support. He is therefore 

 obliged to intercalate fallow with his ordinary farm 

 crops, in order to permit nature to form the soil afresh. 



(B7) 



