Loess Soils of the Transition Region 



II 



before the supernatant liquid is drawn off. Then, as in the Hil- 

 gard method, the Kjeldahl nitrogen determination is run on the 

 extract. In order to obtain a check on the results in both these 

 methods, a nitrogen determination is also run on the soil resi- 

 dues left after the extraction is completed. The two results 

 are then added together, and the total should equal the total 

 nitrogen content as determined in a separate analysis. The 

 Alway-Bishop method gives results slightly higher than those of 

 the Hilgard method. This is, no doubt, due to a more complete 

 extraction by the Alway-Bishop method. The Alway-Bishop 

 method was adopted for this work, because, although it takes eight 

 days for the extraction, it does not require any attention, other 

 than an occasional shaking, after once started. The Hilgard 

 method, however, requires constant attention, and may take sev- 

 eral days, also, before the extraction is complete; so that, on the 

 whole, more actual time is consumed in the Hilgard method than 

 in the Alway-Bishop method. 



In Table I are shown the results of gravimetric humus deter- 

 minations on Lincoln surface soil, using the different methods de- 

 scribed in the preceding pages. 



121 



