PLANT FOOD IN THE SOIL 69 



small that it would take several hundred of them 

 to reach across the edge of this sheet of paper. We 

 cannot see them with the naked eye but only with 

 the most powerful microscopes. Some of these 

 minute plants are great friends to the farmer, for 

 it is largely through their work that food is made 

 available for the higher plants. Some of them 

 break down the organic matter and help prepare 

 the nitrogen for the larger plants. Others help the 

 leguminous plants to feed on the nitrogen of the 

 air. To do their work they need warmth, moisture, 

 air, and some mineral food; these conditions we 

 bring about by improving the texture of the soil 

 by means of thorough tillage and the use of organic 

 matter. 



