Concentrations of soil gases differ from those of atmosphere, because soil microorganisms and soil animals respire and gases diffuse through soil pores in proportion to the gradation of their concentrations. The objective of this paper is to make clear the correlation between the distribution of microorganisms and CO₂, O₂ gas concentrations in a field under rotating use.
Sail air, sampled by using gas sampling pipes, was analyzed by gas chromatography. The number of microorganisms was counted by dilute plating method. Although the profiles of the number of microorganisms changed little, CO₂ and O₂ gas concentrations in the soil air changed remarkably. The simulation of CO₂ gas concentrations by using Fick's law revealed that the respiration of microorganisms contributes to the construction of soil gas distribution. Relatively high CO₂ gas concentration in October was attributed to relatively high activity of microorganisms in this season due to the high soil moisture contents and relatively high temperature.