Feb. 14, 1916 
Nitrogen Content of Humus of Arid Soils 
9 i 3 
Table I .—Comparison of methods for the determination of humus nitrogen 
Humus nitrogen. 
Determination. 
Hilgard-Jaffa method. 
Total 
nitrogen. 
New 
method. 
With potas¬ 
sium hy- 
droxid. 
With sodium 
hydroxid. 
A. First... 
Per cent . ' 
0. 162 
Per cent. 
a 150 
.152 
■ *53 
Per cent. 
0. 176 
. 180 
Per cent . 
Second. 
* 159 
Third.. 
. 169 
Average. 
. 160 
. 152 
* -175 
0. 260 
D. First. 
• 023 
. 020 
. 021 
. 02? 
. 018 
Second. 
. 020 
Third. 
. 020 
.023 
Average. 
. 021 
. 020 
. 022 
•031 
F. First. 
. 024 
.025 
. 023 
. 021 
. 026 
. 026 
Second. 
Third. 
. 020 
Average. 
. 025 
. 021 
. 026 
. 022 
I. First. 
. 058 
. 064 
• 045 
. 046 
.049 
. 037 
Second. 
• i 
. 038 
. O4I 
Third. 
Average... 
. 06l 
. OAH 
. 020 
. 104 
L. First... 
• 047 
.047 
•034 
•035 
. O38 
• 030 
•035 
•035 
Second. 
Third. 
Average. 
. OA 7 
* 936 
. 022 
. O7O 
The results are only fairly concordant, but the extraction of nitrogen 
was as complete as by the Hilgard-Jaffa method, and for our study this 
was the most important consideration. 
Using this method, employing a 4 per cent potassium-hydroxid solu¬ 
tion and shaking at intervals for 9 days, we determined the humus 
nitrogen in 16 samples of arid soils from California (Table II). The 
humus was determined by the Hilgard method (1, p. 319). Duplicate 
and, in most cases, triplicate determinations were made of both the total 
nitrogen and the humus nitrogen, and duplicate determinations of the 
humus. 
