CHAPTER 

 FERTILITY AND SOIL LIFE: BACTERIA 



Soil Fertility Dependent on Bacteria. The fertility of 

 soil depends upon certain things which you have already 

 learned. But it also depends upon another thing which we 

 have not mentioned. That thing is the hidden life within 

 the soil. This " hidden life " to which we refer is not the life 

 of the roots of plants whose stems and leaves grow up into 

 the air and sunshine. Nor is it the life of animals which, 

 like earthworms, burrow in the soil, though they, too, affect 

 soil fertility. It is life which is hidden not only because 

 it is hi the soil, but because, even when we do uncover it, 

 we cannot see it. The individuals which compose it are 

 too small to be seen by the naked eye. They are micro- 

 organisms (mikros, small); organisms so small that they 

 can be seen only with the aid of a microscope. 



These micro-organisms are mostly plants, but they are 

 not green plants, and their life habits are very different 

 from those of green plants. They are not capable, as green 

 plants in sunlight are, of making their own food; that is, 

 they cannot take inorganic materials from soil and air and 

 transform them into organic materials. None the less, 

 their way of life appears to be very successful, for they 

 occur in teeming millions. Rich soil is as full of invisible 

 life as is stagnant water. Forest soil, especially, supports 

 within itself a population more dense than the population 

 of our most crowded cities, and the plants which grow up 



