By law, seed sold in Ohio must include the percentage of germination on the seed tag along with the date tested (Figure 1). In most years, soybean seed germination is at least 90%.
However, given the challenging weather conditions at harvest last year, we are anticipating some seed sources to have a lower-than-normal germination percentage.
Before planting, make sure you check your seed tags for germination percentage. To calculate your seeding rate, divide your desired plant population per acre by the germination percentage (converted to decimal form). For example, if your desired plant population is 120,000 plants per acre and the germination percentage on the seed tag is 85%, divide 120,000 by 0.85. To achieve a plant population of 120,000 plants per acre, you would need to seed at least 141,000 seeds per acre. (Keep in mind, not all ‘live’ seeds will survive and produce a plant due to abiotic and biotic stressors at planting, so further seeding rate adjustments may be needed depending on your specific field conditions and environment.) Table 1 gives soybean seeding rates to achieve the desired soybean plant population based on the germination percentage.
Table 1. Soybean seeding rate needed to achieve desired plant population for several germination percentages.
|
Desired Soybean Plant Population (plants/acre) |
|||||
|
% Germination |
100,000 |
120,000 |
140,000 |
160,000 |
180,000 |
|
Seeding Rate (seeds/acre) |
|||||
|
70 |
143,000 |
171,000 |
200,000 |
229,000 |
257,000 |
|
75 |
133,000 |
160,000 |
187,000 |
213,000 |
240,000 |
|
80 |
125,000 |
150,000 |
175,000 |
200,000 |
225,000 |
|
85 |
118,000 |
141,000 |
165,000 |
188,000 |
212,000 |
|
90 |
111,000 |
133,000 |
155,000 |
178,000 |
200,000 |
|
95 |
105,000 |
126,000 |
147,000 |
168,000 |
189,000 |
In addition to adjusting your seeding rates, consider the use of fungicide seed treatments to prevent pathogen infection from seeds to seedlings. Implement crop rotation with non-host plants to reduce soil-borne pathogen levels and lower future outbreak risks. Use integrated pest management (IPM) strategies to control pests like bean leaf beetles and aphids, which can introduce viruses and facilitate fungal infections. These measures, collectively, will strengthen soybean crop health and unpredictability.
In Ohio, at least 100,000 plants per acre is recommended for April and May planting dates. However, lower plant populations may achieve near 100% yield potential, especially for earlier planting dates. Soybean plants are incredibly flexible at adjusting to a wide range of plant populations. Soybean plants in low populations will produce more branches, more pods, and more seeds per plant. For more information on soybean plant population density, see this Science For Success FactSheet: https://bugwoodcloud.org/resource/files/30379.pdf