2l6 



BACTERIA AND SOIL FERTILITY 



on each of these compounds. Hence, the addition of manure to 

 a soil from a bacteriological viewpoint accomplishes two things. 

 First ^ it furnishes food for the native bacterial flora, and second, 

 it brings to the soil a richer and mightier flora. At times when 

 only small quantities of manure are applied this second function 

 may be even more important than the first. Some recent work 

 indicates that small applications of manure for inoculating soil 

 are even more eflScient than the use of the pure cultures. This 

 is especially true with regard to the use of manure on alkali soil 

 that has just been leached of its salts. It also plays a very im- 

 portant role when added to a soil into which is being plowed green 

 manures. It cannot, however, be depended upon as an inoculat- 

 ing medium for legumes, as it is quite evident that the manure 

 can contain only those organisms which are in the alimentary 

 tract of the animal and was on the food. Hence, if legumes are 

 fed which had grown on inoculated soil the manure would con- 

 tain a goodly seeding of the legume organisms. That the manure 

 does greatly increase the rate with which the nitrogen of the soil 

 is ammonified is seen from the following: 





Per Ceni of Ammonia 





Pots Fallow 



Field Fallow 



Field Cropped 



No manure 

 5 tons manure 

 1 5 tons manure 



100 

 122 



152 



100 



HI 

 188 



100 

 129 

 183 



The unmanured soil was considered as producing 100 per cent 

 ammonia. Here the increase is nearly proportional to the quan- 

 tity of manure used, but it is usually found to be the case that 

 small applications are considerably more effective, ton for ton, 

 than are large applications. Moreover, the increase in the fallow 

 soil due to the greater aeration is greater than in the cropped soil. 



Nitrification. — ^Although fresh farmyard manure does not 

 nitrify in the pile, yet when applied to a soil the increase in am- 



