Influence of ultra-drying with desiccants on the viability of some crop seeds stored in sealed container.

Among the kinds of desiccant tested, calcium oxide had the highest moisture absorbing capacity, followed by hydrogel and silica gel, whereas in time to attain moisture absorbing capacity, silica gel was fastest, and hydrogel slowest under the same RH within the range of 0 to 45 percent at 26 deg C. Under RH of 0, 5, 10 and 15 percent at 26 deg C, the corresponding EMC were 1.84, 3.23, 4.74, 5.98 percent for corn; 1.87, 3.31, 4.90, 5.98 percent for mungbean; 1.08, 2.61, 3.86, 4.37 percent for kenaf; and 0.91, 2.10, 3.02, 3.32 percent for chinese cabbage. Corn and mungbean seeds showed very small difference in EMC and chinese cabbage seeds had the lowest. After 4 months, corn seeds with initial moisture content [MC] of 9.14 percent had MC of 4.12, 5.00, 6.15, at 5, 10, 15 percent RH, respectively when stored with silica gel and with calcium oxide the MC's were down to 4.29, 5.29, 6.54 percent, respectively. In mungbean, MC decreased from 8.79 percent to 3.71, 4.78, 5.71 when stored with silica gel and 3.68, 4.72, 5.81 percent with calcium oxide. In kenaf, the decrease was from 8.19 percent to 2.83, 3.76, 4.51 percent with silica gel and 3.08, 3.94, 4.74 percent with calcium oxide. In chinese cabbage, the increase was 4.46 percent 2.24, 2.85, 3.30 percent with silica gel and 2.48, 2.90, 3.57 percent with calcium oxide. EMC was reached after at least 2-4 months depending on initial moisture content and kind of seed. Ultra-drying of seeds by packing them with silica gel or calcium oxide as desiccant did not induce any significant change in seed germination and vigor during 4 months storage. However, mungbean seeds showed deep cracks across cotyledons, slow growth rate, and greater electrical conductivity. Corn seeds also showed slightly higher electrical conductivity. These were attributed to insufficient humidification prior to the test resulting in inhibition injury from rapid uptake of water by the still very dry seeds and not to ultra-drying injury. Hardseededness was observed in mungbean (2-7 percent) and kenaf (6-11 percent) as a result of ultra drying.