Abstract
Under the condition of pool raising in Gunma Prefecture, we reduced the amount of soil in the nursery box to reduce the whole weight of the nursery box and to reduce the cost for raising paddy rice seedlings. The depth of covering soil was maintained at 7 mm in all plots, and the depth of basing soil was adjusted to 17, 13, 11, 7, and 0 mm. They were compared with the standard depth of 17 mm. We found that the 7 mm depth of basing soil and even no basing soil with 7 mm covering soil were able to raise seedlings having little effect on the accuracy of transplanting. However, in the bed without basing, it raised many seeds over covering soil and also the method of preventing seed-scattering out of nursery box was necessary for seeding. Moreover, for transplanting we must handle the thin mat much more carefully because the mat was too thin. Thus, we judged that the use of zero or 7 mm depth basing soil was unpractical. Considering the handling of mat and the accuracy of transplanting, we judged that the practical depth of the soil in a nursery box was 18 mm which was composed of 11 mm-depth basing soil and 7 mm covering soil. By this method, the weight of nursery box was reduced to about 20%, and the cost of the soil to about 25% compared with the conventional method.
