Abstract
On the land of dry field or forest in Japan there prevail commonly brown forest soil and its relative. Besides brown forest soil wet forest soil (nasse Waldboden) is also considered to exist on some part of the above land where drainage is impeded. Recently a certain kind of wet forest soil was found by the author on Uenodai Field of Oou-experimental Farm, Imperial Agricultural Experiment Station. On the field, where wet forest soil was observed to be transformed to brown forest soil in a short distance, it was convenient to ascertain the difference of productivity between the dry field of wet forest soil and that of brown forest soil. From the result of sweet potato cultivation dry field of wet forest soil was concluded to incline to be inferior to that of brown forest soil in the productivity.
