The advent of newer soybean varieties with different genomic configurations over the past decades has necessitated the need to update information on the allowable storage time used by producers and processors. Therefore, the objective of the study was to evaluate the effect of typical storage temperatures (-15 °C, 4 °C and 22.5 °C) and soybean moisture contents (11%, 13%, 15%, and 17% wet basis) on the allowable storage time of three soybean varieties (EL30-33, XF31-32N and P23A40E) with relative maturity (RM) groups (0.3, 1.3 and 2.3) for 9 months. Quality parameters used to determine the allowable storage time were germination, fungal (mold and yeast count) development, and oil quality (peroxide, free fatty acid (FFA), and P-anisidine value). The allowable storage time (AST) of 11% moisture content seeds was 270 days except for variety P23A40E at 240 days. The 13% moisture content seeds of P23A40E showed quicker deterioration at 22.5 °C with an AST of 60 days compared to the other varieties with about 150 and 180 days. At lower storage temperatures of -15 °C and 4 °C, for all varieties, AST was 270 days. Seeds at 11% moisture content had stable mold counts for all varieties till the end of the storage period. Mold counts for 13% moisture content seeds of P23A40E were below the defined AST limit at the end of week 36, but the mold counts for seed variety EL30-33 increased between weeks 16 and 24, and maximum counts were recorded for XF31-32N by the end of week 36. The mold count increased significantly for the 15% and 17% moisture seeds under the same temperature by the end of week 2 and 4 respectively. Free fatty acid content increased significantly by weeks 8, 12, and 16 exceeding acceptable limits of 0.75% for high moisture (15% and 17%) seeds at 22.5 °C. There was little difference in the FFA, peroxide, and P-Anisidine value of seeds stored at lower moisture contents (11% and 13%) at all storage temperatures. These results suggest that seed variety and maturity group affect storability, especially at warm temperatures. This information will be used to update existing allowable storage timetables for soybean to enable producers to make informed management decisions.

Updated soybean allowable storage time information is necessary for producers, processors, and industry stakeholders to make important management decisions. Based on the different varieties and relative maturity groups of the soybeans used in this storage study, the following conclusions are drawn: 1. Based on germination percentage, there is a varietal difference. This was very evident in the seeds stored at room temperature (22.5 °C). The allowable storage time based on germinability varied for all moisture contents at this temperature. At lower moisture contents of 11% and 13% and storage temperatures of -15 °C and 4 °C, the germination percentage was above 90%. However, secondary infections, poor vigor, and stunted seedlings were observed in some of the 13% M.C. seeds after week 12. This suggests that factors like variety, relative maturity group, and initial seed composition may affect seed storability. 2. The estimation of soybean AST based on fungal development showed more information on seed quality changes at lower temperatures (4 °C) of storage than germinability. At 11% moisture content, there was no increase in mold count at any temperature on all varieties. At 13% moisture content, there was an increase in mold count after 16 weeks at room temperature. At 15% moisture content, mold count was immediately increased at room temperature and 16 weeks at the cold room temperature. For the 17% soybeans, the mold count increased immediately, and in the cold room, there was a variety difference with one increasing in mold count after 12 weeks and one after 16 weeks. More variation in AST days was also observed in seeds stored at 22.5 °C. 3. Free fatty acids content in the oil exceeding the recommended limits of 0.75% was observed as early as 60 days for 17% moisture seeds stored at 22.5 °C. There was variation based on the allowable storage time for free fatty acid development for the three varieties. This suggests that variety and relative maturity affect the soybean AST. 4. There are differences between the current recommendations with the NDSU guidelines matching the USB research more closely. However, some adjustments are needed in the existing tables based on the results of the research. Also, there is some variation between varieties, so the estimated allowable storage times should only be considered an ESTIMATE.