Using the Population Ratings

This month’s blog is focused on seed population and the importance of ensuring you're using the population ratings listed on our hybrid tech sheets, to get the best yield.

What Effect Does Population Have on Hybrids?

Corn hybrids vary in their response to population for two key reasons: genetics of the plant, and yield level.

How Do Hybrids Respond to Population Via Yield Level?

Yield should be the first factor you consider when determining the optimal seeding rates for your fields. Higher yield conditions respond better to higher seeding rates, whereas fields with less optimum growing conditions will likely be less responsive to higher seeding rates.

How Do Hybrids Respond to Population Via Genetics?

The genetics of a hybrid can also play a role in responsiveness to seeding rates. Some hybrids are very well adapted to higher seeding rates, while others perform better at more moderate seeding rates.

However – Hybrid differences are not large enough to overcome the effect of yield environment.

Understanding and Interpreting Yield Rating Symbols

You will gain the best economic return by matching your seeding rating to the yield environment of the field, as well as the specific response characteristics of the hybrid being planted.

Rob-See-Co rates our corn hybrids based on their response to seeding rate. We determine these ideal rates based on a combination of how the hybrid performs compared to itself over a range of seeding rates in population density trials, as well as how the hybrid performs compared to other hybrids in yield trials.

Our rating symbols make it easy to tell at a glance how well a hybrid will respond to being planted at various populations.

These symbols are then applied to five seeding rate categories: Well Below Normal, Below Normal, Normal Population for Growing Environment, Above Normal and Well Above Normal. Where “Normal Population for Growing Environment” is given in the table below and each step represents approximately +/- 3,000 seeds/acre.

How Do I Know if a Hybrid Can “Flex”

If a hybrid has the capacity to compensate for a lower population, the normal population for a growing environment, it will have a light green or dark green rating found in the Below Normal and/or Well Below Normal population categories. This may be in lower than normal, or above normal population guidelines.

Example: This hybrid flexes well from “Well Below Normal” to “below normal” populations, but only shows average performance in “Well Above Normal” populations.