Current OSU Recommendations for Corn Seeding Rates in Ohio
Corn seeding rates continues to be a topic of interest. Several seed companies are moving growers in the direction to increase seeding rates to 35,000-40,000 seeds per acre. Research from Ohio State University and Dr. Peter Thomison indicates that recommended plant populations at harvest can range from 20,000 to 30,000+ plants/acre for maximizing yield, depending on the hybrid and production environment.
According to the Ohio Agronomy Guide, final stands of 30,000 plants per acre are recommended for soils with high yield potential (>175 bushel/acre) that have high soil fertility levels and exceptional water holding capacity. On soils averaging 150 bushels/acre, final stands of 26,000 to 28,000 plants/acre may be all that is necessary to optimize yield. Finally, on soils that average 120 bushel/acre or less, final stands of 22,000 plants/acre may be adequate for optimal yields.
In a recent OSU study conducted by Dr. Thomison, effects of early (late April) and late plantings (early to mid June planting dates) on corn response to population (24,000, 30,000, 36,000 and 42,000 plants/acre) were investigated at three locations. Results suggested that final stands of 30,000 to 36,000 plants/acre were required for optimal yield for the late April plantings. However, for the early to mid June planting dates, the results indicated little benefit from increasing seeding rate and a significant yield loss was noted at plant populations above 30,000 plants/acre.
If a grower is allowing their corn to dry as much as possible in-field, which can delay harvest, the grower will have to weigh the benefit from using plant populations above 30,000 plants/acre. Although hybrids may exhibit similar yield potential when harvested early (early/mid October), differences in yield become evident with harvest delays, which can be attributed to differences in stalk quality. With harvest delays, yield losses can occur at the higher plant populations, especially 42,000 plants/acre, due to increased stalk lodging.
Final stands are always less than the number of seeds planted per acre. Cool, wet soil conditions may reduce germination and emergence. Generally, you can expect from 10 to 20 percent fewer plants at harvest than seeds planted. As such, you need to plant more seed than the desired population at harvest to achieve the target harvest population. To determine a corn planting rate, use the following formula: Planting Rate = Desired Population per Acre ÷ (Germination x Expected Survival). Germination is shown on the seed tag (convert to decimal form). Expected survival is the percent of seedlings that emerge and reach harvest maturity under normal conditions (convert to decimal form). Ninety percent survival (or 10% plant mortality) is about average. If you are planting early and the soil is cool and expected to remain cool for several days following planting, you may want to reduce expected survival by 5%. Also, many no-till farmers will recommend reducing expected survival rates by 5% when planting corn in to a true no-till field.