A FERTILE SOIL 



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have the power of taking nitrogen from the air 

 which finds its way into the soil. After using the 

 nitrogen the germ gives it to the plant which then 

 uses it to build stem, leaves and roots. In this wav 

 the legumes are able to make use of the nitrogen of 

 the soil air, and these germs which help them to do it 

 by catching the nitrogen are called nitrogen-fixing 

 germs. 



The work of these germs makes it possible for 

 the farmer to grow nitrogen, so to speak, on the 

 farm. 



By growing crops of legumes and turning them 

 under to decay in the soil, or leaving the roots and 

 stubble to decay after the crop is harvested, he can 

 furnish the following crop with a supply of nitrogen 

 in a very cheap manner and lessen the necessity of 

 buying fertilizer. 



NITRIFYING GERMS 



Almost all the nitrogen of the soil is locked up 

 in the humus and cannot in that condition be used 

 by the roots of plants. The nitrogen caught by the 

 nitrogen-fixing germs and built into the structure 

 of leguminous plants which are grown and turned 

 under to feed other plants cannot be used until the 

 humus, which is produced by their partial decay, is 

 broken down and the nitrogen built into other sub- 

 stances upon which the root can feed. The break- 

 ing down of the humus and building of the nitrogen 

 into other substances is the work of another set of 

 bacteria or germs called nitrifying germs. 



