Dormancy, germination, and emergence of red rice (Oryza sativa L.)

Abstract

Germination of blackhull and strawhull red rice (Oryza sativa L.) compared to 5 rice (Oryza sativa L.) cultivars--"Dawn", "Early Colusa", "Labelle", "Nato", and "Starbonnet"--within 30 days after anthesis indicated that both red rice types were more dormant initially than Dawn, Labelle, and Starbonnet. Strawhull red rice was slightly more dormant than blackhull red rice. Viable seeds of Labelle, blackhull red rice, Nato, Starbonnet, strawhull red rice, Dawn, and Early Colusa were obtained 9, 12, 12, 12, 15, 15, and 18 days after anthesis, respectively. As the time after anthesis increased, the storage time at 30 C necessary to break dormancy of blackhull red rice decreased. Blackhull red rice harvested at 12, 18, 21, and 24 days after anthesis reached 80% germination after 6, 4, 4, and 2 weeks at 30 C, respectively, while strawhull red rice harvested 18, 21, and 30 days after anthesis reached 80% germination after 4, 2, and 2 weeks at 30 C, respectively. However, strawhull red rice harvested 24 and 27 days after anthesis failed to reach 80% germination even after 10 weeks at 30 C. Percent emergence and meanplant heights of non-dormant seed of blackhull and strawhull red rice planted at 0 to 16 cm in soil was significantly higher than for all other varieties at 3 days after emergence. However, 17 days after emergence, plant heights for all varieties at all planting depths were not significantly different. Molinate (S-ethyl hexahydro-1H-azepine-1-carbothioate) granules incorporated into the top 2 cm of soil provided good suppression of red rice emerging from 1 to 8 cm in Beaumont clay if the soil was kept saturated with water. On lighter soil (Crowley fine sandy loam), or if Beaumont clay and Crowley fine sandy loam were not saturated, red rice emergence was obtained from 8 and 12 cm in soil treated with molinate.