How long should rice seeds be soaked?

Soaking at below 20°C requires 48-72 hours; when the soaking temperature is 20-25°C, soaking for 30-48 hours is sufficient; when the soaking temperature is above 25°C, soaking requires only 24-30 hours. For rice seeds sown in early to mid-May, the soaking time can be slightly longer, but do not exceed 60 hours; for plastic-tray seedling throwing after May 20, and for direct-seeded rice in early to mid-June, all varieties should be soaked for 24 hours.

1. Determine the soaking time according to the temperature at the time of soaking.

The purpose of soaking is to make the rice grains evenly absorb enough water needed for germination. The minimum water absorption requirement for rice seeds is to absorb 26% of the seed's own weight to germinate normally. The speed of water absorption by rice grains is related to temperature, and the soaking time needed for rice grains to absorb enough water for germination varies with water temperature. Under normal circumstances, soaking at below 20°C requires 48-72 hours; when the soaking temperature is 20-25°C, soaking for 30-48 hours is sufficient; when the soaking temperature is above 25°C, soaking requires only 24-30 hours. When the soaking temperature is 25°C, the germination rate gradually decreases as the soaking time is prolonged. For indica rice and a few japonica rice varieties whose glumes do not close tightly, water absorption is faster. Therefore, for rice seeds sown in early to mid-May in our area, the soaking time can be slightly longer, but do not exceed 60 hours; for plastic-tray seedling throwing after May 20, and for direct-seeded rice in early to mid-June, all varieties should be soaked for 24 hours. Prolonging the soaking time will cause the germination rate to decline noticeably

2. Choose the soaking and sprouting method; the “soak by day, air by night” method is recommended.

Using the “soak by day, air by night” method to treat rice seeds before sowing results in more seedlings and stronger seedlings, is simple to operate, and is easy to master, with no risk of “seed suffocation” or “bud burning.” Therefore, this method is often used for soaking and sprouting rice seeds in rice production. The method is: first spread the selected seeds in good sunlight for 1-2 days, then prepare the chemical solution according to the ratio for chemical seed soaking and the amount of seed, place the seeds in the solution during the day for soaking, and spread them on the ground at night (about 5cm thick) for airing and ventilation. After a period of time, the seeds will break through the hull and show buds, meeting the requirements for sowing. Never pile the seeds in woven bags, to avoid high-temperature bud burning in the middle part of the bag due to respiration; there is even less need to heat the seeds to promote sprouting