OXYGEN-SUPPLYING POWER OF THE SOIL AS INDI¬ 
CATED BY COLOR CHANGES IN ALKALINE PYRO- 
GALLOL SOLUTION 1 
By LEE M. Hutchins, Pathologist, Fruit Disease Investigations, Bureau of Plant 
Industry, United States Department of Agriculture, and Burton E. Livingston, 
Professor of Plant Physiology, Johns Hopkins University 
INTRODUCTION 
It is generally agreed among students of plant physiology and agricul¬ 
ture that the roots of many plant forms require free oxygen, obtained 
from the surrounding soil, for their healthy activity. The careful experi¬ 
mental work of Free, Cannon, and others, as well as the general experi¬ 
ence of agriculturists and horticulturists, indicates that many kinds of 
plants suffer markedly and even die when access of free oxygen to their 
roots is cut off. One of the reasons given for cultivating the soil in 
agricultural work is that tillage tends to facilitate the entrance of atmos¬ 
pheric oxygen into the soil in which the roots are found. It is often ob¬ 
served that low areas of a field of grain, for example, collect water, which 
stands on the surface of the ground for some time after a rain, and the 
poor plant growth frequently noticed in such areas—even after the sur¬ 
face water has disappeared—is often explained by supposing that the 
flooding of the soil hindered or prevented the downward movement of 
oxygen from the air. 
From considerations of this kind it is at once suggested that, if health 
is to be maintained, the roots of any individual plant must receive ele¬ 
mentary oxygen from the surrounding soil at' a rate sufficiently rapid to 
keep their physiological processes adequately supplied. As is indicated 
by the experiments of Livingston and Free 2 it is to be expected that this 
necessary rate of oxygen supply will be found to be different for different 
kinds of plants and probably for different plants of the same kind grown 
under sufficiently different conditions. It would then follow that a plant 
in an otherwise suitable environment would remain healthy only so long 
as the conditions in the soil about its roots were such as to allow the 
necessary rate of oxygen absorption through the root surfaces. The 
health of the plant would be impaired if the ability of the surrounding 
soil to supply oxygen to the roots were sufficiently diminished so that the 
rate of arrival of oxygen at the root periphery fell below the rate of ab¬ 
sorption necessary for healthy activity. It seems clear that a given root 
surface can not absorb oxygen any more rapidly than this substance comes 
to it from the surroundings. 
The ability of soil to supply oxygen to an oxygen-absorbing surface, 
such as that of a root, might be expected to be greater with relatively dry 
and loose soils, and especially near the soil surface, while it would be less 
for the more compact or wetter soils and for greater depths. This 
oxygen-supplying power of the soil may sometimes be related, in a general 
way, to the oxygen content of the soil in the vicinity of the absorbing 
1 Accepted for publication May 2, 1923. 
2 Livingston, B. E. , and Free, E. E. the effect of deficient son, oxygen on the roots of higher 
plants. In Johns Hopkins Univ. Circ. 293, p. 182-185. 1917. 
(* 33 ) 
Journal of Agricultural Research. 
Washington, D. C. 
afo 
Vol. XXV, No. 3 
July 21, 1923 
Key No. G-319 
