Seeding Rate Effect on Soybean Grain Yield

Abstract

Increasing costs of soybean seed as well as new varieties, seed treatments, and production practices required a reevaluation of seeding rate recommendations. Previously recommended seeding rates do not account for new varieties, improved cultural practices, improved seed treatments, and precision planting equipment. Also, a recommended seeding rate does not account for changes between regions, soil types, or even across a field; therefore, the need for a fall stand recommendation. Chapter 5, the Soybean Production section of the Ohio Agronomy Guide (Lindsey et al., 2017) suggests Ohio farmers should have a fall stand of 100,000 to 120,000 plants per acre if planted before May 20. The objectives of this research were to test this recommendation and evaluate the effect of row width and seeding rate in small-plot research trials. Stand counts were taken at the V4 and R8 stages to note whether desired planting populations were achieved and compared to plant population at harvest to recorded yields. Ten plant samples were taken from the field to measure plant height, lowest pod height, nodes per plant, branches per plant, number of pods, and seed weight on branches and main stems. Seeding rate influenced yield at 5 out of 6 site-years. Row width and seeding rate had a significant effect on branches per plant, pods per plant, and seeds per main stem and seeds per branch. The results were very close to the Ohio State University recommendations and showed ideal agronomic optimal fall stand (AOFS) was 123,000 plants per acre. Plants compensated for low seeding rate by producing more branches and seeds per plant.