21 



4. Oxidation results with liberation of carbon dioxide and 

 ammonia and the formation of a fatty acid containing one less car- 

 bon atom. A type reaction may be represented as follows : 



R-CHr-CH(NH 2 )-COOH + O a - ->R-CH 2 -COOH + CO 2 +NH 3 



That oxidation is a factor in the organic matter of the soil 

 is self-evident from the fact that carbon dioxide is constantly pres- 

 ent in the soil atmosphere in excess of the amount present in the 

 air, thus representing degradation of the organic matter to carbon 

 dioxide and water, arid also from the fact that ammonia is trans- 

 formed into nitrates, a process known in soil chemistry as nitrifica- 

 tion, a reaction which is carried out in the laboratory by the most 

 violent chemical oxidation, e. g., chromic acid. A further step in 

 this oxidation carries the nitrates through denitrification which re- 

 sults in the liberation of free nitrogen. 



In carrying to completion these processes on protein material 

 one can easily postulate an almost unlimited number of organic 

 compounds, which are theoretically (and in all probability) pos- 

 sible. Very recently Robbins (1916) has produced some evidence 

 that the existence of certain of the organic compounds in the soil is 

 limited somewhat narrowly by specific bacteria, which either utilize 

 the nitrogen or the carbon of the compound as a source of energy. 

 Thus pyridine is destroyed by a specific bacterium which is able to 

 utilize the nitrogen, and the carbon of cumarin and vanillin is like- 

 wise a source of carbon for other specific bacteria. 



G. Nitrogen Distribution in the Soil 



The chemistry of soil nitrogen may to a large extent be con- 

 sidered as being the chemistry of protein undergoing hydrolysis. 

 The isolation of a number of amino acids indicates that proteins are 

 decomposed in the soil in much the same way as in acid hydrolysis 

 or animal digestion. Just how far the cleavages have already gone 

 in the soil previous to acid hydrolysis remains a matter of much 

 work before definite conclusions can be drawn. 



Walters (1915) has reported the presence of certain decompo- 

 sition products in the soil, presumably proteoses and peptones, 

 resulting from either a partial hydrolysis of proteins or by the syn- 

 thetic action of microorganisms. It has been recorded by Hoppe- 

 Seyler (1909, p. 413) that intermediate protein decomposition prod- 

 ucts may result from the action of water at high temperature, by 

 mineral acids, alkalies, oxidizing agents, enzymes and microorgan- 

 isms. There is little reason to suppose that the action of micro- 

 organisms is other than that of the enzymes which they produce. 

 Effront (1914) states that under the influence of the various tryp- 

 sins secreted by putrefactive bacteria, the protein molecule is split 

 into proteoses, peptones and amino acids. The proteoses and pep- 

 tones represent stages of decomposition between that of true pro- 

 teins and amino acids. Walters concludes 



that proteins undergo hydrolytic decomposition in the soil in much the same 

 way as in dig-estion by enzymes, acids, or alkalies, in the laboratory. 



