MANURE 



215 



produced annually in the United States is wasted annually. This 

 would mean a loss of soil fertility valued at $750,900,000," 



Influence on Number of Bacteria in Soil— The biological 

 changes which a manure produces in the soil, especially when 

 small applications are made, may be more far-reaching than either 

 the chemical or physical changes which it produces. Every pound 

 of manure carries with it to the soil millions of bacteria. Many 

 of these will find the new conditions unsuited to their growth, 

 but some will continue to function, and in so doing not only will 

 they decompose the manure but also alter other substances of the 

 soil. 



There are added with the manure many new species. The 

 change in the soil from the addition of the manure will greatly 

 modify those already present. The influence of manure on the 

 number of bacteria in the soil is even greater than crop, tem- 

 perature, or cultivation. If we consider the number of bacteria 

 in unmanured land as 100 per cent, the Senior author obtained 

 the following results for manured land: 





Fallow 



Cropped 



No manure 

 5 tons manure 

 15 tons manure 



ICX3 



144 



177 



100 

 123 

 129 



Other workers have obtained even greater increases. The 

 greatest increase is noted in fallow and per ton of manure for 

 small applications. It is quite likely that the greater profit per 

 ton of manure obtained with small over large applications of 

 manure is due to increased bacterial activity. 



Ammonification. — The nitrogen of solid excreta is mainly in 

 the form of complex proteins; that of urine is in the form of 

 urea, hippuric acid, and uric acid. Hence, when manure is 

 added to a soil these compounds are carried into the soil and 

 they furnish food for the millions of bacteria already present. 

 Moreover, the manure contains varieties of organisms which act 



