Physiological potential of seeds from different positions of the soybean plant at reduced seeding rates

Reducing seeding rates is a technique that has been studied as a strategy to reduce soybean production cost without yield losses. However, this method can directly impact seed production and formation, because it alters plant morphology and modifies intraspecific competition, water use efficiency, and microclimates. This study investigated whether soybean cultivation utilizing reduced seeding rates alters the physiological potential of seeds at different stratum of plants in two cultivars with discrepant branching abilities. The experimental design was completely randomized, with split plots containing five seeding rates (100, 80, 60, 40, and 20% of the amount recommended by the breeder) and three seed positions of the plants (low, medium, and high) within the subplot. The cultivars BRS 1010 IPRO and NS 5959 IPRO were used. Germination, first count upon germination, seedling length, dry mass, electrical conductivity, accelerated aging, and sand emergence were evaluated. The physiological potential of the seeds was higher in the upper stratum of the plant compared to the lower stratum. Reducing the seeding rate to values up to 40% did not cause notable impacts on the physiological potential of the seeds. A drastic reduction of the seeding rate to only 20% resulted in decreased seed vigor. Seed germination of the cultivars NS 5959 IPRO and BRS 1010 IPRO was highest in seeding rates ranging from 40 to 80% of those recommended by breeders.