SECTION XLIII. GERMS IN THE SOIL 



THE farmer could not grow profitable crops without the 

 help of several kinds of germs that live in the soil. Some 

 of these live in the tubercles on the roots of leguminous 

 plants and change the nitrogen of the air into fertilizer 

 nitrogen. These might be called the nitrogen-trapping 

 germs because they catch or trap the nitrogen gas. 



Nitrate-forming germs. Other kinds of bacteria that 

 work faithfully for the farmer may be called the nitrate- 

 forming germs. These finally change certain compounds 

 in vegetable matter in the soil into nitrates, the only form 

 in which most plants can use nitrogen. The heaviest 

 growth of cowpeas or clover might be plowed under as fer- 

 tilizer, and the plants growing on that field the next season 

 could not use a pound of its nitrogen if there were no 

 nitrate-forming germs. These germs are too small to see, 

 so small indeed that many millions have been found in a 

 thimbleful of soil. The farmer should care for these tiny 

 useful plants that are helping him to grow larger crops. 



Helping our friends in the soil. Men who have spent 

 their lives in studying these tiny plants under powerful 

 microscopes have found that what the nitrate-forming 

 germs need in order to increase rapidly and to help the 

 soil and the crop are the following : 



