Natural air Drying and Storage of Soybean Seed and Implications on Germination Rates, Vigor, and Oil Quality

Abstract. Recently-introduced in-bin drying and storage technology comprised of cables used to monitor grain moisture content and temperature throughout the entire grain bin mass during the drying offers means to utilize natural air drying for soybean seed. However, firm understanding of the implications of using these new bin drying systems on seed quality is yet to be determined. The objectives for this study was to simulate conditions typically encountered in on-farm, in-bin drying systems and investigate impact of seed cultivar, moisture content and duration of storage on seed germination rates, vigor (electrical conductivity), and oil quality. This study used Soybean of different cultivars (ES5650, ES5507, and ES5542) that were harvested at different moisture content of 13% and 16% for each of the cultivars. The Soybean seed were placed in a relative humidity chamber for 2 months at typical bin drying temperatures of 20°C, 30°C, and 40°C, and relative humidity that varied between 20-80%. Samples from each of these treatments were collected after 0, 5, 10, 20, 30, 40, and 60 days of storage for germination and vigor (electrical conductivity) and oil quality test were carried out using ISTA standard procedures. Results showed the 5542 cultivar seed germination potential dropped from 98% at day 0 to 27% at day 60 as temperature increase from 20°C to 40°C. Similarly, the electrical conductivity increased by from 280µ/s to 1017µ/s with increase in storage durations (p <0.05). Cultivar 5507 had the least change in germination (98% - 63%) and electrical conductivity (280µ/s –685µ/s) within 60 days of the test at 20°C. In addition, as moisture content increased from 13 % to 16 %, the germination rate reduced by 67%, 20%, and 17 % for ES5507, ES5542, and ES5650 cultivar respectively at 20°C. This study showed that seed viability can be maintained when the moisture content is at 13% and grain temperature must be within 20–30°C.