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Oxygen diffusion and aerobic respiration in soil spheres
Author(s) -
Greenwood D. J.,
Goodman D.
Publication year - 1964
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740150812
Subject(s) - oxygen , respiration , diffusion , chemistry , limiting oxygen concentration , partial pressure , soil respiration , respiration rate , spheres , environmental chemistry , thermodynamics , botany , biology , physics , organic chemistry , astronomy
An equation relating the diffusion of oxygen into moulded spherical aggregates with their aerobic respiration rates was tested by measuring the effect of oxygen partial pressure on the rates of oxygen uptake of aggregates of known size and water content. By inserting these measurements in the equation values (αˆ) were obtained for a diffusion parameter which under the conditions of the experiments would be expected to be constant. It was found that αˆ; was independent of the oxygen concentration surrounding the spheres, of their respiration rates and, over a limited range, of their water contents. These findings support the validity of the equation. However, αˆ was decreased by increases in the period for which the soil was moistened before being moulded into aggregates, and was slightly larger the larger the spheres. Evidence was obtained that the differences in αˆ resulted from colloids affecting the diffusion properties of water, and by the presence of minute gas‐filled channels in the aggregates. Nevertheless, it appears that the equation may be used to indicate the extent to which respiration of soil aggregates is restricted by inadequate oxygen diffusion. Evidence was obtained to support the assumption, used in deriving the equation, that lowering the oxygen concentration did not affect the respiration rate of soil until low concentrations were reached. The respiration rates in the presence of excess oxygen of soil and of baker's yeast were halved when the oxygen concentration in the aqueous phase was reduced to between 2 and 6 μM. Tests of the equation depended on assessing the respiration rates of the aggregates when respiration was not inhibited by lack of oxygen. These assessments were difficult to make because mechanical manipulation of the soil caused an increase in respiration rate that could not be attributed to an improved oxygen supply. The most satisfactory methods of making the assessments were to measure the respiration rates of chopped aggregates under air, and of whole aggregates under high oxygen partial pressures.