Effects of Storage Temperature and Relative Humidity on Viability and Vigor of Treated Soybean Seeds

ABSTRACT Seed treatments are applied to soybean [Glycine max (L.) Merr.] seeds to control early season diseases and insects. Unsold, treated soybean seed must be disposed in a different manner than untreated seed. To minimize treated seed disposal costs, it is necessary to improve seed storage. The objective was to determine the best storage environments that would minimize deterioration of treated soybean seed. Twenty‐four soybean varieties, different in lipid and protein contents and from four maturity groups, were treated either with fungicide or a mixture of fungicide plus insecticide or were untreated and were stored in three storage environments differing in temperature and relative humidity: a cold storage (CS) (10°C), a warm storage (WS) (25°C), and a warehouse (WH). Seed viability and vigor were evaluated each 4 mo for 20 mo using standard germination and accelerated aging tests. Seed viability remained high throughout the study for seeds stored in CS (>92%) and moderate in the WS (>78%) but decreased to almost 0% after 20 mo in the WH. The seed viability of treated seed was significantly higher than that of untreated seed after 16 mo in the WH while in the CS and WS the positive effects lasted for 20 mo. Seed vigor was affected by only seed lipid content for seeds stored for 12 mo, regardless of storage environment. Treated soybean seeds could be carried over for two seasons if the storage temperature is maintained at 10°C and the relative humidity is below 40%.