抄録
In Japan, fallow paddy fields and abandoned paddy fields have increased through the rice acreage reduction policy for dealing with surplus rice, depopulation, or aging of the population. It is important to manage and maintain those paddy fields in a condition in which they are immediately and easily available for use as rice fields in the future. Control of weeds cannot be neglected in order to use fallow paddy fields as a rice fields soon. We think that much manpower and a cost are not necessary, and that the herbicides that have a bad influence on the surrounding environment, especially the rice field ecosystem should not be used for managing fallow paddy fields. As a way of satisfying these conditions, an examination of the control of water by the deeper ponding method was made. First, we examined the relations of the ponding depth of water and the growth of weeds in an experimental rice field. As a result, the abundance of weeds decreased as the ponding depth increased. Also, grass did not grow at all in water 5cm or more in depth during winter and in water over 15cm depth during summer. We arrived at the standard ponding depth of water for managing fallow paddy fields from this examination. Therefore, we proved that though some kinds of waterweed appeared, a grass did not appear as a result of managing the ponding depth of water at about 15cm in summer in an actual fallow paddy field.
