[en] One of the four neighboring fields tended to show slightly higher contamination of radioactive cesium in rice grain soon after Fukushima Daiichi Nuclear Power Plant accident. In order to understand the reason, the oxidative/reductive atmosphere in the paddy field was investigated using ⁵⁷Fe Mӧssbauer spectroscopy. The iron concentration variation was also investigated based on soil size distribution. It was suggested that the oxidative/reductive condition of iron state may reflect the features of the soils and then affect the solubility of potassium and radioactive cesium in the field. Oxidative atmosphere and in particular more abundant iron in larger size soil may affect the transfer of radioactive cesium from soil to rice grain.