SOILS 91 



if a section again becomes swampy, it will be easier 

 to find any tile that has filled up and failed to do 

 its work. 



The Farmer's Bacteria Friends. We have learned 

 of the tiny bacteria plants that live in the soil and 

 help to prepare food for the plants we cultivate. 

 Some kinds of bacteria live in other places, and 

 others are harmful ; but these soil bacteria are very 

 necessary and helpful, and the farmer works hard 

 to make the soil right for them to grow. There are 

 millions of bacteria in a cubic inch of fertile soil. 

 They do not need sunlight as do most plants, but 

 they do require air, moisture, warmth, and food. 



How They Help. Bacteria pounce upon all vege- 

 table matter, such as leaves, wood, grass, and dead 

 animal matter, that falls upon the ground and 

 begins to decay, or rot. The bacteria break up all 

 these substances into simple foods that are ready for 

 the plant to drink. It would be of no use to manure 

 soil if it were not for bacteria. 



Bacteria and Clover. Some kinds of bacteria set 

 uf) housekeeping ui)on the tiny rootlets of certain 

 l)lants such as clover, alfalfa, soy beans, and cow- 

 peas. They take a certain element, that we call 

 nitrogen, from the air and store it up in little 

 bunches or swellings on the roots of these plants, 

 ready for them to feed upon. Plants must have 

 this nitrogen as food, and soil that contains abun- 

 dance of it is rich soil. Every farmer boy knows 

 that the fields are richest where clover, alfalfa, or 



