THE AMMONIA CONTENT OF SOIL, AND ITS RELATION TO 
TOTAL NITROGEN, NITRATES, AND SOIL REACTION 1 
By Horace J. Harper 
Assistant Chief in Soil Chemistry , Iowa Agricultural Experiment Station 
INTRODUCTION 
Although the ammonia content of soil has been studied by several 
investigators, in most cases only a few soils have been examined. 
Russell (12) 2 found that the ammonia content of unmanured soil 
varied from 0.5 to 1.6 parts per million; that in manured soils it 
varied from 4 to 7 parts per million; and that three other field soils 
contained from a trace to 2.2 parts per million. Matthews (10) 
reported the ammonia content of nine soils in his work on methods. 
The maximum amount of ammonia found was 8 parts per million, 
and the minimum 1.4 parts per million. Potter and Snyder (11) 
found from 7 to 25 parts of ammonia per million in seven soils. Ellis 
and Morison (2) found more ammonia in acid peats than in neutral 
peats, varying from 79 parts per million in the neutral peats to 296 
parts per million in the acid peats. This difference was attributed to 
unfavorable conditions for nitrification. About 50 to 80 per cent of 
the ammonia in the peats could be extracted with distilled water. 
Jodidi (6) : (7), (<§), in his investigation of the chemical nature of the 
organic nitrogen in the soil, reported on the ammonia content of a 
few peats and on a plot of soil receiving different kinds and amounts 
of organic matter. The amount of ammonia varied from 50 to 440 
parts per million in case of peats, and from 1.68 to 15.08 parts per 
million in one series of soil experiments, and from 27 to 33 parts per 
million in another. Kelley (9) foqnd that the ammonia content of 
uncultivated soils varied from 2 to 42 parts per million, and that in 
cultivated soils the variation was from 4.2 to 33.6 parts per million. 
EXPERIMENTAL DATA 
This investigation was planned to determine whether there is any 
relation between the ammonia content of soil, soil reaction, total 
nitrogen, or the amount of nitrates present. In the first experiment 
24 soils were used. Five samples were obtained from Professor 
Truog, of Wisconsin; five from Professor Duley, of Missouri; and 
the others from various parts of Iowa. All samples were placed in 
pyrex beakers and left in a covered box in the greenhouse from March 
20 until July 5. They were made up to an optimum moisture content 
occasionally. At three different times during the incubation period 
they were allowed to become quite dry, with the object of approxi¬ 
mating the conditions in fallow plots. All of the soils were moist 
when the ammonia and nitrate contents were determined. Samples 
were dried and ground for the total nitrogen determinations. 
i Received for publication Nov. 3,1924; issued October, 1925. 
* Reference is made by number (italic) to “Literature cited/’ p. 553. 
Journal of Agricultural Research, 
Washington, D. C. 
( 549 ) 
Vol. XXXI, No. 6 
Sept. 15, 1925 
Key No. Iowa-9 
