Positive Study on the Presence of Rice Cultivation before the Beginning of Rice Cultivation in Paddy Fields

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To detect plant opals contained in pottery sherds is one of effective methods to prove the existence of plants which supplied the detected plant opals before the period when the potteries were made. In this study, it is examined about the period the cultivation of rice (Oryza sativa L.) and other Gramineae crops began in Japan. The result is summarized as follows.1. The situation in the early stage of Jyomon periodAs a result of the investigation in Uenohara site (Kagoshima prefecture), Barnyard grass (Echinochloa crus-galli Beauv.) plant opals are detected from the soil layer just under the tephra layer which was accumulated around 9000 B.C.. Barnyard grass and Japanese millet are edible and closely related. So, these results suggest the possibility that the primitive cultivation of Japanese millet had begun in the early stage of Jyomon period.2.The situation in the early Jyomon periodA lot of Barnyard grass plant opals were detected in pottery sherds which derived from Sannaimaruyama site (Aomori prefecture). Considering the scale and the character of this site, there may be possibility that the cultivation of Japanese millet was done.3 .The situation in the last part of Jyomon periodRice plant opals were detected from pottery excavated from Okayama University premise site (Okayama prefecture) and Minamimizote site (Okayama prefecture). These potteries are estimated to have been made around 3500 B.P.. This result shows that rice cultivation already had begun in the western part of Japan in this period.And as a result of the investigation in Hietabaru site (Nagasaki prefecture), rice plant opals were detected from the soil layer just under the volcanic ash layer which was accumulated by Mutsuki pyroclastic flow glad around 3600 B.P..Considering the location of this site and the existence of other plant's remains, rice growing here possibly had been done at upland fields.