THE ORGANIC MATTER OF THE SOIL 



149 



100. Influence of the original material on the resultant 

 humus. — It is evident that the source from which any 

 humus material is derived will exert a profound influence 

 on its composition, especially its nitrogen content. 

 Snyder * has investigated this by mixing certain materials 

 with a soil poor in humus and allowing the process of 

 decay to proceed for a year under favorable conditions. 

 At the end of the period the humus was extracted by the 

 Grandeau method. The results are given below : — 



The Composition of Humus produced from Various Or- 

 ganic Materials 



Although the humification may not have reached 

 completion in this case, the great variation in nitrogen 

 is striking. Existing, as it probably does, mostly as 

 acid amides and monamino acids, it will change readily 

 to ammonia and exert a marked effect on plant growth. 

 Possibly the variation of the nitrogen in soil humus is 

 the most potent factor in the nutritive functionings of 

 this material. The variability of the carbon,* hydrogen, 

 and oxygen of the soil humus is not such an important 

 factor, as these elements can easily be supplied to the 



1 Snyder, Harry. Production of Humus from Manures. 

 Minnesota Agr. Exp. Sta., Bui. 53, p. 25. 1897. 



