REFERENCES 1G1 



atmospheric nitrogen into a form which can later be made 

 available to crops. The nitrogen fixers live for the most 

 part in colonies on the roots of leguminous plants and arc 

 supplied with carbohydrates by the legumes. These carbo- 

 hydrates they use as a source of energy for the fixation 

 of nitrogen. Some of this fixed nitrogen is used by the 

 bacteria themselves and some by the legume plants. 



REFERENCES 



Bulletins of Bureau of Soils, U. S. Dept. of Agriculture. 



Cameron. The Soil Solution. 



Hall. The Soil. 



Halligan. Soil Fertility and Fertilizers. 



Hilgard. Soils. 



Hopkins. Soil Fertility and Permanent Agriculture. 



Lyon and Fippin. Soils. 



Russell. Soil Conditions and Plant Growth. 



Van Slyke. Fertilizers and Crops. 



Whitson and Walster. Soils and Soil Fertility. 



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