Critical Seed Moisture Content for Germination in Crop Species

In this study, critical seed moisture content required for germination was examined and seedling emergence was compared under various soil water potentials. Moisture content of seeds was controlled with soaking period and the seeds with various moisture contents were germinated to determine the least moisture content at which germination occurs. The critical seed moisture content for seed germination was higher in proteinous seed like soybean and lower in starchy seed like rice. The least moisture content of soybean, Chinese cabbage, hot pepper, pea, sesame, radish, barley, corn, wheat, and rice was 49.3%, 44.0%, 42.9%, 41.5%, 39.4%, 35.0%, 34.0%, 32.1%, 32.0%, and 29.5%, respectively. Cereal seeds showed lower seedling emergence rate as the water potential decrease to -3.15 mbar except for barley and wheat. Other cereals showed poor emergence rate at -3.15 mbar. Rice and pea, particularly, showed extremely low emergence rate below 10% at -3.15 mbar. Seedling emergence rate of barley and wheat was 80% and 77%, respectively, at -3.15 mbar, respectively. The decreased rate of emergence of vegetable seeds as soil water potential decrease, however, was lower than that of cereal crop. Most of vegetable crop showed decreased in seedling emergence as the soil water potential was lowered to -1.86 mbar. Emergence rate of radish, sesame, and Chinese cabbage was greater than 90% at -1.86, -0.65, and -0.52 mbar, respectively. There was close relationship between the least seed moisture content required for germination and critical soil water potential required for proper seedling emergence rate (greater than 90%). Rice showed the lowest value (29.5%) of the least seed moisture content and germinated at extremely poor soil moisture condition (-3.60 mbar). Soybean, however, showed the highest value of the least seed moisture content required for germination among crops tested in the experiment and began germination at relatively moist condition (-1.86 mbar). These results suggest that there was positive relationship between the least moisture content of seed and soil required for germination.