Abstract
Poor germination problems occurred in early-season rice culture in Mie prefecture in 2007 and 2008 when seed soaking was conducted during the cold season (late February – middle March). In this study, the effects of low water temperature given at different periods during seed soaking on the germination percentage were examined to find a method of soaking effective to raise the germination rate. Germination was inhibited by soaking in low-temperature (5°C) water on the first day followed by optimum-temperature water (12.5°C) thereafter. On the contrary, germination percentage was not lowered by soaking in low-temperature water after soaking in optimum-temperature water for one day. An optimum-temperature during the initial 2-8 hours is enough to keep the germination percentage as high as soaking in optimum-temperature water throughout the germination period. It is recommended to keep the water temperature optimum during the initial period of seed soaking to keep a high germination rate for raising the seedlings in the cold season. Germination was inhibited by soaking in low-temperature water in all rice varieties and seed storage periods examined.
