3. Adjust seeding depth according to soil conditions. Plant between 1½ and 2 in. deep to provide for frost protection and adequate root development. Seeding depth should be monitored regularly during the planting operation and adjusted for varying weather and soil conditions. Irregular, especially shallow, planting depths contribute to uneven plant emergence, which can reduce yields. See last week’s newsletter article for more on the importance of avoiding shallow planting depths.

4. Adjust seeding rates on a field-by-field basis. Adjust planting rates by using the yield potential of a site as a major criterion for determining the appropriate plant population. Higher seeding rates are recommended for sites with high-yield potential with high soil fertility levels and water holding capacity. OSU plant population studies conducted from 2006 to the present suggest that on highly productive soils, with long-term average yields of 190 bu./acre or more, final stands of 33,000 plants/acre or more may be required to maximize yields.

Lower seeding rates are usually preferable when droughty soils or late planting (after June 1) limit yield potential. On soils that average 120 bu./acre or less, final stands of 20,000-22,000 plants/acre are adequate for optimal yields. On soils that average about 150 bu./acre, a final stand of 30,000 plants/acre may be needed to optimize yields.

Seeding rate can be cut to lower seed costs but this approach typically costs more than it saves. Most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates (unless lodging becomes more severe at higher population levels) and harvest delays occur. When early planting is likely to create stressful conditions for corn during emergence, e.g. no-till in corn residues in early to mid April, consider seeding rates 10-15% higher than the desired harvest population. Follow seed company recommendations to adjust plant population for specific hybrids.