DECOMPOSITION OF NON-NITROGENOUS ORGANIC MATTER 



451 



decomposition in the soil. This points conclusively to the fact that 

 the stimulating influence of cow and horse manure is due to its nitro- 

 gen content. Tables 38 and 39 and figures 24 and 25 show the in- 

 fluence of manure, soil reaction and nitrogen source on cellulose 

 decomposition in various soils, as determined by Charpentier. 



The content of available nitrogen in the soil is thus found to be the 

 most important factor controlling cellulose decomposition. The ratio 

 between the cellulose decomposed and nitrogen required by the or- 

 ganisms is about 30-35 to l. 74 This ratio will depend of course upon 

 the amount of available nitrogen. When the latter is in excess and is, 



TABLE 38 

 Composition of soils used for study of cellulose decomposition 



SOIL TYPE 



Clay soil I . 

 Clay soil II 

 Sandy soil. . 

 Peat soil . . 



DRY MATTER 

 PER CENT 



82.0 

 82.0 

 92.0 

 40.0 



ASH 

 PER CENT OF 

 DRY MATTER 



94.8 

 93.5 

 97.8 

 19.9 



CELLULOSE 

 PER CENT OF 

 DRY MATTER 



0.06 

 0.01 

 0.04 

 0.03 



pH 



6.12 

 7.08 

 6.56 

 5.44 



TABLE 39 

 Influence of cellulose (1 per cent) upon soil reaction (using clay soil I) 



therefore, not the limiting factor, the above ratio will hold true. When 

 the amount of available nitrogen is low, it will be utilized by the or- 

 ganisms over and over again, i.e., a part of the synthesized protoplasm 

 of the microorganisms will be decomposed, liberating some of the 

 nitrogen which is immediately again assimilated thus enabling the 

 organisms to decompose more cellulose. The process will be con- 

 tinuous, tending to give a higher ratio between the cellulose decom- 

 position and apparent nitrogen assimilation. 



74 Waksman and Heukelekian, 1924 (p. 443). Anderson, J. A. The influ- 

 ence of available nitrogen on the fermentation of cellulose in the soil. Soil 

 Sci., 21: 115-126. 1926. 



