JOURNAL OF MCOLTOAL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. VII Washington, D. C., October 9, 1916 No. 2 
COMPARISON OF THE NITRIFYING POWERS OF SOME 
HUMID AND SOME ARID SOILS 1 
By C. B. Ljpman, Soil Chemist , California Agricultural Experiment Station , P. S. 
Burgess, Chemist , Hawaiian Sugar Planters* Experiment Station t and M. A. Klein, 
Assistant Soil Chemist , California Agricultural Experiment Station 
INTRODUCTION 
It will be remembered by those who are interested in the subject 
under consideration that Stewart (ii) 2 took occasion in 1912 to question 
the correctness of the view then prevalent, due principally to the high au¬ 
thority of Hilgard (3, p. 68), that nitrification proceeds with great intensity 
in arid soils. It will also be remembered that in the statement above 
cited and in subsequent papers (12,13) Stewart controverted the theory 
of Headden (1, 2) with respect to the cause of unusually large nitrate ac¬ 
cumulations in certain Colorado soils on similar grounds. The evidence 
presented for the latter controversion consisted of numerous analyses 
of irrigated and unirrigated soils at the Utah Agricultural Experiment 
Station and of soil and soil-forming material of the Book Cliff areas in 
Utah and Colorado. The analyses represented the quantity of nitrogen 
in the form of nitrates or the quantities of other “alkali” salts, or both, 
in the various soils and soil-forming materials at the time the sampling 
was done. As a result of his studies of these data, Stewart con¬ 
cluded that the intense power of nitrification attributed to arid soils, 
because of the large amounts of nitrates present in the field, is 
nonexistent, that it may actually be feeble as compared with that 
of humid soils, and that the large quantities of nitrates found as noted 
can be more readily and plausibly explained on the basis of accumulation 
by water movement from adjacent soil or soil-forming materials rich 
in salts (including nitrates). The latter contention is supported by 
numerous analyses of the large variety of soils, sandstones, and shales 
1 The samples of soil from the different States were sent us by the chemists or agronomists of the several 
Stations, and acknowledgment in addition to that already made is here publicly expressed. We owe and 
express our sincere thanks also to Prof. C. F. Shaw, in charge of the soil-survey work of the California 
Agricultural Experiment Station, for allowing us a portion of every soil sample collected iu the soil-survey 
areas which have already been mapped in this State. 
2 Reference is made by number to “ Literature cited,” p. 82, 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
fs 
(47) 
Vol. VII, No. a 
Oct. 9, 1916 
Cal.—6 
