DECOMPOSITION OF PROTEINS 



501 



the nitrogenous and the accompanying non-nitrogenous organic substances, 

 will lead to the development of different microorganisms capable of decom- 

 posing the nitrogenous materials; the carbon-nitrogen metabolism of these micro- 

 organisms is different; this leads, therefore, to differences in the amounts of 

 ammonia liberated in a free state. 



These various reactions lead to a transformation of a larger or smaller 

 part of the nitrogen of the organic complexes into ammonia, which, 

 either as such or after it has been oxidized to nitrates, is available as 

 a source of nitrogen for the growth of cultivated plants. In view of 

 the fact that the liberation of this ammonia is of such great economic 

 importance, numerous contributions have been made to the subject, 

 known as "ammonification.'' These studies were chiefly limited to 

 adding about 1 gram of the nitrogenous organic material to 100 <:,rams 

 of soil, mixing, placing in tumblers, then bringing the moisture content 

 of the soil to optimum (CO per cent saturation), incubating for 4 to 14 

 (usually 7) days, then measuring the amount of ammonia present in 

 the soil by distilling with MgO. 



These studies resulted in a most extensive literature. It was found, 79 

 for example, that organic nitrogenous materials of different origin 

 liberated ammonia with a different degree of rapidity as follows: 



The difference in rapidity of decomposition of the organic nitrogen 

 compounds with the liberation of ammonia is due to the nature of 

 the nitrogen complex, 80 accompanying non-nitrogenous substances 

 (see p. 505) and environmental conditions, which favor the develop- 

 ment of specific organisms and, therefore, specific processes. 



Influence of nitrogenous decomposition products on the growth of plants 



79 Lipman, J. G., Blair, A. W., Owen, I. L., and McLean, H. C. The avail- 

 ability of nitrogenous materials as measured by ammonification. N. J. Agr 

 Exp. Sta. Bui. 246. 1912. 



80 Jodidi, S. L. Amino acids and acid amides as sources of ammonia in soils. 

 Iowa Agr. Exp. Sta. Res. Bui. 9. 1912; Lathrop, E. C. Protein decomposition 

 in soils. Soil Sci., 1: 509-532. 1916. 



