CHAPTER XIII 



THE RELEASE OF SOIL NITROGEN: THE RETURN TO 



THE AIR 



A very close relationship exists between the soil, the 

 plant, and the animal. Each must perform its work that 

 the other two may do their part. 



Nature has just a simple plan : she stores in the soil 

 and air the elements that plants require : she hands these 

 same elements on to animals through the plant; for in 

 the animal body are found the same chemical elements 

 that are present in the plant. Plants, however, must come 

 first: they gather from soil and air simple compounds 

 from which they manufacture other compounds more 

 complex in nature just such materials as animals need. 

 For all higher animals, you know, get their food either 

 through eating plants or eating other animals that feed 

 on plants. Plence, animal life is dependent either directly 

 or indirectly on plant life for sustenance. Then the ani- 

 mal dies ; maybe the plant dies : out of their decay and 

 decomposition soil is made again or reenforced ; air is 

 given back the compounds it previously had lent the plant 

 during its stage of growth, and of plant building. Thus 

 the plant depends for food on materials stored in the 

 plant, in the soil, and in the air; and the soil and air 

 depend for their normal supply of elemental things on the 

 plant and animal. 



Here is the cycle : out of soil grows the plant, out of 

 the plant grows the animal ; from the plant and animal 

 develops the soil. 



Life and death. Both life and death are concerned in 



