.DECOMPOSITION OF ORGANIC MATTER IN THE SOIL 323 



common soil bacteria) proved itself particularly eflacient in the breaking 

 down of nitrogenous materials and the production of ammonia. 1 



Since the publication of these experiments a large number of investi- 

 gators, both in Europe and America, have studied ammonia production 

 in culture solutions as well as in the soil itself. It has been shown that 

 under favorable conditions the breaking down of protein compounds and 

 the formation of ammonia may be very rapid; for instance, in some ex- 

 periments carried out by Lipman and his associates the following pro- 

 portions of nitrogen were transformed into ammonia in the course of 

 six days: 



Dried blood 16 • 74 per cent 



Concentrated tankage 56.66 per cent 



Ground fish 47 • 16 per cent 



Cotton-seed meal 4-95 per cent 



Bone meal 16 . 65 per cent 



Cow manure, solid and liquid excreta 32.60 per cent 



Cow manure, solid excreta S -39 per cent 



The experiments were carried out in equal quantities of soil and with 

 equivalent quantities of nitrogen in the different substances. It will 

 be observed that more than 56 per cent of the nitrogen ih the con- 

 centrated tankage was transformed into ammonia, whereas under the 

 same conditions cotton-seed meal yielded less than 5 per cent. 



Mechanism of Ammonia Production. — The relatively large protein 

 molecules are readily broken into larger or smaller fragments. This 

 may be accomplished by purely chemical means, as, for instance, by 

 boiling with acids or alkalies, or by biological activities. Among the 

 first cleavage products albumoses and peptones are quite prominent. 

 These in turn undergo further cleavage and the various amino-acids 

 and their derivatives, as well as anamonia, make their appearance. In 

 so far as the different species of bacteria are concerned, ammonia pro- 

 duction seems to depend, to a marked extent, on the ability to secrete 

 proteolytic enzymes. With the aid of such enzymes the proteins are 

 more readily hydrolyzed and further changed into amino- and hydroxy 

 acids, ammonia and carbon dioxide. 



Infiuence of Soil and Climatic Conditions. — Ammonia production in 

 the soil is affected by (a) its mechanicial and chemical composition; by 

 (b) the amount and distribution of rainfall; by (c) the prevailing tem- 

 peratures; by (d) fertilizer treatment; and by (e) methods of tillage and 



