114 



BACTERIA AND SOIL FERTILITY 



Material Ammonified. — ^Although all nitrogenous substances 

 which reach the soil are broken down by bacteria and usually with 

 the formation of ammonia, the speed with which this change 

 occurs varies with the substance. Concentrated tankage, ground 

 iishj and liquid cow manure are rapidly broken up with the liber- 

 ation of ammonia, while the process with solid cow manure and 

 cottonseed meal is slow. This is illustrated by the following 

 results obtained by Lipman and his associates. The numbers rep- 

 resent the percentages of the total nitrogen of the various sub- 

 stances which were transformed into ammonia in six days. 



Concentrated tankage 56.66 per cent 



Ground fish 47.16 per cent 



Cow manure, solid and liquid excreta ^2.60 per cent 



Dried blood 16.74 per cent 



Bonemeal 16.65 per cent 



Cow manure, solid excreta 5.39 per cent 



Cottonseed meal 4,95 per cent 



The loss of the liquid portion of cow manure makes of it a 

 slowly decomposing manure. This difference in ammonification 

 in different manures accounts for the generally understood fact 

 among gardeners that horse manure is a rapid decomposer and 

 forces plants, whereas cow manure is much slower. The addi- 

 tion of manure to a soil greatly increases the ammonia produced 

 in a soil. This is illustrated by the following results obtained by 

 the senior author. In the first column is given the per cent of 

 ammonia found. The untreated soil is taken as 100 per cent. 

 The various quantities of manure were applied to the soil in pots 

 and after four months the ammonifying powers determined. In 

 the second and third column are given the results from actual 

 field soils receiving each year the designated quantity of manure. 



Treatment 



Pot 

 Experiment 



Field 



Experiment 



Fallow 



Cropped 



No manure 



100 



100 





100 



5 tons manure 



122 



H7 





120 



10 tons manure 



140 









15 tons manure 



152 



188 





183 



20 tons manure 



160 









a 5 tons manure 



180 









