Feb. 14, 1916 
Nitrogen Content of Humus of Arid Soils 
9i5 
which F and G were secured. H was from virgin soil, while I was from 
land which had been formerly cultivated, but allowed to revert to 
grass about 10 years before. Samples J and K were taken from two 
fallowed fields of red land about 2 miles east of Clovis. The remaining 
samples were from near Delano—L from a field under cultivation for 
15 years and M and N from fallows on red land north of the White 
River. 
Of the 16 samples only 5 show as high as 10 per cent of nitrogen in 
the humus. For the 6 samples of virgin soil the average is 8.5 per cent, 
with a maximum of 12.0 and a minimum of 4.0 per cent. For the 
10 of cultivated soils the corresponding data are 8.1, 11,8, and 5.6 per 
cent, respectively. The maximum possible percentages of nitrogen in 
the humus-H:he relation of the total nitrogen to the humus—ranged 
from 5.5 to 19.6 per cent, with an average of 13.1. Hilgard (9, p. 424), 
in a comparison of the average composition of 313 arid and 466 humid 
soils, reports the former to show 0.75 per cent humus and 15.87 per 
cent of nitrogen and the latter 2.70 per cent of humus, with only 5.45 
per cent of nitrogen. 
There is no reason to doubt the reliability of the humus determina¬ 
tions upon which Hilgard’s generalizations are based. A careful study 
(1) has shown that his method, as carried out by himself, gives results 
strictly comparable with those of the Moores-Hampton method. We 
have examined the original data on the humus determinations by 
Hilgard and his assistants and in only a very few cases do we find a 
humus-ash content sufficiently high to make the determination appear 
inaccurate. These percentages of humus ash, while not reported in 
the tables in Hilgard’s articles discussing the relation of the nitrogen 
content of humus to climate, may be found in the original reports re¬ 
ferred to above. 
In that we found 5 out of 16 arid soils to have over 10 per cent of 
nitrogen in the humus after having failed to find any humid or semiarid 
soil with such a high percentage, our study tends to confirm the work of 
Hilgard that high percentages are to be found in the arid but not in the 
humid soils. This high nitrogen content of the humus, however, does 
not appear so general in the arid soils as to serve as an at all reliable 
means of identification. 
LITERATURE CITED 
(1) Airway, F. J., Files, E. K., and Pinckney, R. M. 
1910. The determination of humus. In Jour. Indus. Engin. Chem., v. 2, no. 7, 
p. 317-322. 
(2) -and Pinckney, R. M. 
1912. The photometric and colorimetric determination of humus. In Nebr. 
Agr. Exp. Sta. 25th Ann. Rpt. [1911], p. 2-16. 
(3) -and Trumbull, R. S. 
1908. Studies on the soils of the northern portion of the Great Plains region: 
Nitrogen and humus. In Amer. Chem. Jour., v. 40, no. 2, p. 147-149. 
