DECOMPOSITION OF THE PLANT AS A WHOLE 91 



slower. The decomposition of such compounds, hke the trans- 

 formation of other non-nitrogenous substances, necessitates the 

 presence of considerable nitrogen available from other sources. 



The changes which take place in the plant constituents may be 

 shown in the graphic representation of the decomposition of corn- 

 stover (Fig. 47) . It is apparent that there is a rather rapid decom- 

 position of the water-soluble constituents, hemi celluloses and cel- 

 lulose, and a slow destruction of the lignin. The crude protein, on 



Total Cold -Water- Hemi- Cellulose Lignin Crude 



Material Soluble Celluloses Protein 



A, Original Material; B, Left after 27 Days of Decomposition; 



C, Left after 68 Days of Decomposition; D, Left after 205 Days 



of Decomposition E, Left after 405 Days of Decomposition 



Fig. 47. — -Course of decomposition of various chemical constituents of corn- 

 stover under aerobic conditions (after Tenney and Waksman). 



the other hand, shows a pronounced increase resulting from the 

 synthesis of an abundance of microbial cells at the expense of the 

 water-soluble nitrogen. This does not indicate, however, that 

 the protein constituents are resistant to decomposition. Under the 

 aerobic conditions, the material as a whole had decomposed to one- 

 third of the original amount in the period of 68 days. 



Decomposition of the Plant as a Whole. — The rate at 

 which plants or organic fertilizers decompose is regulated to a large 

 extent by the relative abundance of the various constituents which 

 compose the organic matter and the state of aggregation of these 



