632 



EXPERIMENT STATION RECORD. 



Production of humus from manures, H. Snyder {Minnesota Sta. 

 Bui. 53, pp. 12-35, fig. 1). — This is a continuation of previous work. 1 

 In order to study the variation in composition of humus and humates 

 of different origin these products were prepared from known materials 

 in the following- way: 2H0 gm. of sugar was mixed with 3,000 gm. of 

 soil containing a small known amount of organic matter, placed in a 

 tight box, and allowed to undergo decomposition out of doors for one 

 year. Humus was produced in the same way from cow manure, green 

 clover, meat scraps, wheat flour, sawdust, oat straw, and asparagin. 

 The humus produced was extracted from the soil, after treatment with 

 dilute hydrochloric acid and distilled water, with a 3 per cent solution 

 of potassium hydroxid. The precipitates obtained by neutralizing with 

 hydrochloric acid were washed, dried, and analyzed. The results are 

 given in the following table: 



Composition of humus produced by different organic substances. 



This table shows wide variations in the composition of humus pro- 

 duced by the decomposition of different materials. None of the mate- 

 rials analyzed agreed in composition with the formulas in Mulder's 

 classification, and " it is evident that any formulas applied to the com- 

 pounds as a whole would, to say the least, fail to express the composi- 

 tion of humus." 



"It would seem best, in the present state of our knowledge of the humus coin- 

 pounds, to make the division on the basis of the uitrogeu content ; that is, divide 

 the humus compounds into classes, as follows: 



" (1) Non-nitrogenotis group, as sugar humus. (2) Humus containing 1 to 2 per 

 cent nitrogen, as sawdust humus. (3) Humus containing 2 to 4 per cent nitrogen, as 

 oat-straw humus. (4) Humus containing 1 to 8 per cent nitrogen, as rlour and cow 

 manure humus. (5) Humus containing over 8 or 9 per cent nitrogen. 



-" Such a division would give an approximate idea as to the nature of the material 

 from which the humus has been produced, as well as an approximate idea of its 

 agricultural value. . . . 



"The huiuate compounds do not form well-defined crystallized bodies, and it is 

 almost impossible to obtain any one of these compounds in a pure state, to study the 

 structural composition." 



In order to decide whether the mineral constituents found in humus 

 are furnished entirely by the mineral matter in the humus-forming 

 material or are partly derived from the soil by the chemical action of 

 the humus, the phosphoric acid and potash in the soil and humus- 

 forming materials at the beginning of the experiment and in the humus 



1 Minnesota Sta. Buls. 30 and 41 (E. S. R., 5, p. 857; 7, p. 476). 



