Decomposition of Nitrogenous Substances 117 



Taiii.k '21. Influence of Age of Plant (Oats) upon the DEroMrosmov oi- Its 

 Constituent Carbohydrates (from Gerretsen and Waksiiiiini 



IVr rent of docoinposilioii aftt-r 1'2.) days. 



The effect of the added nitrogen is largely concerned with the 

 greater decomposition of the cellulose and hemicelluloses. 



Numerous other transformations take place in the process of 

 decomposition of complex plant materials. 



Decomposition of Proteins and Other 

 Nitrogenous Substances 



Proteins make up 1-20 per cent of all plant residues. They are 

 complexes of amino acids. They contain, on an average, 50-55 per 

 cent carbon, 15-19 per cent nitrogen, 6-7 per cent hydrogen, 21-23 

 per cent oxygen, and small amounts of sulfur; some proteins also 

 contain phosphorus. 



Proteins vary considerably in nature and in functions, depending 

 upon their amino acid make-up. On hydrolysis by specific enzymes 

 or by chemical reagents, the proteins are split first into various 

 polypeptides and finally into simple amino acids. The latter are 

 further attacked by a great variety of bacteria and fungi, gi\'ing rise 

 to ammonia, carbon dioxide, and various organic acids and alcohols. 

 Under anaerobic conditions, various amines and mercaptans are also 

 formed; these are responsible for the "putrefactive" odors produced 

 in the decomposition of protein-rich materials. 



The great majority of soil organisms are capable of attacking pro- 

 teins. The amount of nitrogen finally changed to ammonia depends 

 upon the nature of the organism, nature of the protein, presence of 

 available carbohydrates, and soil conditions. Since in the decom- 



