Soybean planting date and seeding rate effect on germinability and vigor of harvested seed

Seed is one of the most crucial inputs for soybean [Glycine max (L.) Merr.] production due to its influence on plant population, uniformity, and yield, as well as its cost as an input. Seeds of good quality have high germinability and vigor, providing an adequate stand with uniformly good growth and development even under adverse conditions. This study aimed to measure the effect of soybean planting date and seeding rate on harvested seed mass, seed germinability, and seed vigor. Seeds were collected from a field experiment during the 2020 and 2021 growing seasons at two locations in Ohio: Western Agricultural Research Station and Northwest Agricultural Research Station. The study was conducted using a split-plot randomized complete block design (planting date-whole plot; seeding rate-subplot) with four replications. Standard germination and accelerated aging tests were conducted in the laboratory using seeds harvested from the field study. All four site-years demonstrated that planting soybean very late (June 16-July 1) produced lower weight seeds than the other planting dates. Across planting date and seeding rate treatments, the harvested seed germinability was >= 94%. However, soybean planted in early June (June 1-June 15) had the lowest seed vigor results (64%-81%) compared to other planting dates (80%-89%). Rainfall at R7-R8 development stages is negatively correlated with the seed vigor. The results will help seed producers optimize seed production and quality and suggest avoiding planting in June to increase harvested seed vigor. Later soybean planting dates were associated with reduced seed weight.Seeding rate did not impact seed germinability and seed vigor of harvested seed.Germinability of harvested seeds was >= 94% in all site-years, regardless of the planting date or seeding rate.Soybean planted in early June produced seeds with the lowest seed vigor.Rainfall at R7-R8 development stages is negatively correlated with seed vigor.