Extensive Cultivation Management in Wet-fallow Paddy Fields on the Tama Hills

In this study, we investigated the most suitable extensive cultivation management cycle for conserving floral diversity in a fallow paddy field. The following three studies were made for this purpose:(1) review of the examples of paddy restoration (2) vegetation survey of fallow paddy fields and (3) rhizome study of Phragmites australis. The paddy restoration works involve those aboveground and underground i.e. mowing and plowing. The following two types of plants were found to interfere with mowing: tall-stem plants (e.g. Phragmites australis and Miscanthus sacchariflorus) and rhizome and erect-stem plants (e.g. Isachne globosa and Leersia sayanuka). These plants increased greatly during the second year in fallow. In plowing, plants with strong and long rhizome (e.g. P. australis and M. sacchariflorus) were found to interfere. The weight of their rhizome increased greatly during the forth year in fallow. Plowing is four-times laborious compared to mowing in restoration work. Therefore it is suggested that cultivation of once every four years is effective in restoration from the labor point of view.