158 Bacteria in Relation to Country Life 



same manure in a different soil twenty pounds in the 

 first year, five pounds in the second year, and two or 

 three pounds in the third year. Evidently, the trans- 

 formation would be more economical in the first instance; 

 and the differences noted might be attributed to a greater 

 proportionate loss from the soil, or the change of a greater 

 proportion of the manure nitrogen to very inert com- 

 binations. 



The losses responsible for a low rate of availability 

 may be twofold. They may be due to the setting free 

 of gaseous nitrogen in the course of decomposition, or 

 they may be due to the leaching out of the soluble 

 nitrates. In the first instance, there are conditions ex- 

 tremely favorable to rapid decay, that is, a rapid union 

 of the carbon and hydrogen of the humus with atmos- 

 pheric oxygen. The humic nitrogen is not allo.wed to 

 retain its hold on the hydrogen, as it would do when the 

 processes of decay are more gradual; hence, it is forced 

 to return to the atmosphere in the gaseous state. 



Rapid decomposition of this character can only 

 occur in very open soils in which the aerobic bacteria 

 may develop unhindered in the presence of sufficient 

 moisture. The losses from the leaching of nitrates will 

 depend again upon the amount of rainfall and the 

 character of the crop. Excessive precipitation may 

 wash the nitrates into the subsoil beyond the reach of 

 the roots, and thus diminish the proportion of nitrogen 

 available to the crop. Some crops possessing a deeper 

 root system will forage more thoroughly in the soil, 

 and will prevent large losses of nitrate. 



It is thus evident that the economical utilization of 



