lO 



Morris J. Blish 



however, were made by the Kjeldahl method, which is too well 

 known to need any description. 



THE DETERMINATION OF HUMUS NITROGEN 



A considerable number of determinations of nitrogen in humus, 

 or " humus nitrogen " were made, however, and but two methods 

 were tried. These two are the Hilgard method and the Alway- 

 Bishop method. The extraction in the Hilgard method is carried 

 out in the same manner as the extraction in the determination of 

 humus by the Hilgard method, except that 4 per cent potassium 

 hydroxid instead of ammonium hydroxide is used; a determina- 



18" ZO" 22' 2A" 26" 28" 30" 32" 



Map of Nebraska, showing outline of the Loess Area (unshaded), the 

 location of the prairie fields sampled, and the normal 

 annual precipitation 



tion of nitrogen in this extract is then carried out by the Kjeldahl 

 method. In the Alway-Bishop* method, however, the extraction 

 is made in a different manner. The extraction is started in the 

 same way as in the Official method for the determination of 

 humus, with the exception that 4 per cent potassium hydroxide in 

 place of 4 per cent ammonium hydroxide is used, and the contain- 

 ers are allowed to remain eight days, with an occasional shaking 



*E. S. Bishop. Thesis for Master's degree, Univ. of Nebr.. 1911. 



120 



