6o 
Journal of Agricultural Research 
Vol. XI, No. 2 
Below are given the relative averages of carbon dioxid evolved in the two 
experiments just cited: 
Oxygen, per cent. o i. 6 6 n 16 21 
Carbon dioxid evolved, mgm. per 
kgm. of soil in 24 hours. 9. 03 10. 4 16. 25 16. 05 15. 85 17. 5 
It is evident, therefore, that for either the process of carbon dioxid 
formation (partially aerobic) or nitric acid formation (obligate aerobic) 
the oxygen content of the soil atmosphere can be reduced to one-half 
normal atmospheric oxygen content or below without any appreciable 
effect upon the processes. Also, the total air content of the soil can be 
reduced very low without any detrimental effect upon the bacterial 
activities in question, a fact entirely in accord with the data submitted 
in this paper. With this information available accurate analysis of soil 
atmosphere, both as to quantity present and composition, should give 
us valuable information as to the probability of sufficient quantities of 
oxygen being available under that particular condition. Fortunately 
there are a number of recent carefully executed investigations upon soil 
gases, particularly those of Lau (7), Russell and Appleyard (11), Djarenko 
(3), Jodidi and Wells (4), and Leather ( 8 ). 
Lau (7), working with three very different types of soil (sand, loam, 
and peat) at Rostock, Germany, found, upon analyzing the soil atmos¬ 
phere monthly for a period of one year, that the carbon-dioxid content 
varied from 0.11 to 0.143 per cent at a depth of 6 inches; 0.157 to 0.65 
per cent at 12 inches; and 0.29 to 2.09 per cent at 24 inches. The oxygen 
varied from 20.35 to 20.77 P er cent at a depth of 6 inches; 19.99 to 20.63 
per cent at 12 inches; and 18.42 to 20.19 P er cen t at 24 inches. Manur¬ 
ing a sandy soil and cropping to potatoes increased the carbon-dioxid 
from 0.11 to 0.57 per cent and decreased the oxygen content from 20.79 
to 20.22 per cent. 
Russell and Appleyard (11) analyzed the soil gases under the following 
conditions at the Rothamstead Station; Broadbalk wilderness (unculti¬ 
vated) ; Boradbalk wheat field, both manured and unmanured; and Hoos 
field, both under wheat and fallow. Analyses were made on an average 
of three times a month for periods in most cases extending over approxi¬ 
mately two years. Below are given the extreme and average results of 
their analysis when air was drawn from a depth of 6 inches: 
Constituent. 
Minimum... 
Maximum. 
Average. 
Carbon dioxid. 
Per cent. 
O. 02 to O. 28 
17. 6l to 20. 44 
78.49 to 79. 01 
Per cent. 
O. 38 to 2. 27 
20. 8l tO 21. 30 
79. 38 to 80. 48 
Per cent. 
0. 30 to 0. 52 
20. 19 tO 20. 46 
79. 25 to 79. 30 
Oxveen. 
Nitrogen. 
