Application of the method of rice seedling emergence in flatly arranged nursery boxes to the normal-season culture of rice in Gunma Prefecture - the relationship between covering materials and emergence of seedlings.

摘要

In Gunma Prefecture, rice seedlings are usually grown in nursery boxes kept stacked up by pool-raising method. In this method, however, the boxes need to be moved several times, which is a laborious task. In a new method developed in Tochigi Prefecture, seeds are sown in boxes arranged flatly and seedlings are grown without the moving of boxes. However, this technology was developed for use in a greenhouse but not for pool-raising. Hence, we applied this method to outdoor pool-raising in the normal-season culture of rice in Gunma Prefecture. Covering the soil with several kinds of materials delayed seedling emergence only about 0-3 days. Non-covering delayed seedling emergence due to the low temperature and drying of covered soil, indicating that a covering material was necessary for good emergence. Passlight, Kenbyo-sheet and Daiorussell-1600-Black were excellent as covering materials. Covering with these materials decreased the even growth, high temperature and drying of covered soil, and eliminated the greening process. In some cases, the seedling length increased and leaf age advanced with covering, but the final growth of seedlings equalled that in rice grown by the standard method. Therefore, the method using the covering materials used could be useful for seedlings emergence in nursery boxes arranged flatly in Gunma Prefecture.