In the paddy field with gravel and sand subsoil that was low groundwater level, the plane changes in concentrations of oxygen and carbon dioxide were investigated over 2 years. The soil air was sampled from the subsoil in about 50cm depth at 1, 5, 10 and 15m from the levee to the center. Those points situated one line and three lines were investigated in this paddy field.
Following results were obtained. Those oxygen concentrations at each point gradually decreased in irrigation period and the lowest concentration were observed in early September. In non-irrigation period, those concentrations increased, and eventually reached the atomospheric level. On the other hand, the carbon dioxide concentrations in the subsoil increased gradually in irrigation period and the highest concentration were observed in early September. In non-irrigation period, those concentrations decreased. This tendency of changes in carbon dioxide was in inverse relation to that in oxygen. These annual changes in concentrations of two parameters were recognized. As the distance from the levee increased, the oxygen concentration tend to be lower and those carbon dioxide concentrations higher. The total concentrations of oxygen and carbon dioxide became nearly equal to 21% at each sampling point.