Effects of Planting Population on Yield in Full Season Soybeans
Sustainable Production
Field management Nutrient managementSoil healthTillageYield trials
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Kelly Nichols, University of Maryland
Co-Principal Investigators:
Matt Morris, University of Maryland
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

The current soybean planting population recommendation for full season soybeans in Maryland is is based on research conducted in the early 2000s on initial Roundup Ready varieties in minimum-tillage systems. Today, farmers have switched to no-till soybean production and have access to the second generation of Roundup Ready soybeans, as well as many newer varieties. While the recommended seeding rate provides adequate yield from these newer varieties, this research determine if lower planting rates are practical for reducing input costs while maintaining optimum yield. The project also evaluate two methods of counting plant populations.

Key Benefactors:
farmers, agronomists, Extension agents

Information And Results
Final Project Results

Shortly before harvest, stem diameter measurements were taken in order to determine if lower populations resulted thicker stems. Soybean plants with thicker stems are thought to be a more favorable environment for Dectes stem borer larvae, who bore into the stem. Soybeans were harvested on October 3 and October 24 at the Tuscarora and Thurmont farms, respectively. Price per bushel and seed cost were taken into consideration when calculating the net amount per acre.

View uploaded report Word file

Yield ranged from 67 to 70 bu/A at the Thurmont farm, and 61 to 63 bu/A at the Tuscarora farm. When analyzed statistically, there were no significant differences in yield between any of the planting populations on either farm, indicating that on these two farms in 2019, lower populations did not adversely affect yield.

Soybeans were $9.51/bu at the time of harvest. At the Thurmont farm, the seed cost was $71.00 per unit of 140,000 seeds. At the Tuscarora farm, the seed cost was $59.00 per unit of 140,000 seeds. (Note that these costs do not include any discounts or seed treatments.) At the Thurmont farm, the 100,000 planting population had the highest net per acre at $598.19, while the 140,000 and 160,000 populations had the lowest net, around $581/A. At the Tuscarora farm, the 120,000 planting population had the highest net per acre at $560.13, while the 160,000 population had the lowest net at $515.76/A.

The average stem diameter measurements showed a trend that as population increases, stem diameter decreases. This indicates that higher populations with thinner stems may be less favorable for Dectes stem borer larvae.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.