Determining corn seeding rates
By David G. Hallauer
Meadowlark Extension Agent, Crops & Soils/Horticulture
The optimal corn population for any situation will depend on the anticipated environment and how the hybrid responds to that environment. Producers can look back to their corn crop from the previous growing season or wait until the current growing season is nearly complete and evaluate whether the population they used was adequate.
Individual hybrids can respond differently, but the following guidelines may help in deciding if current seeding rates need to be adjusted. If more than about 5 percent of the plants are barren or if most ears have fewer than 350 kernels per ear, the population may be too high. If there are consistently more than 500 kernels per ear or if most plants have a second ear contributing significantly to grain yield, the population may be too low. Of course the growing conditions will influence ear number and ear size as well, so it is important to factor in the growing conditions for that season when interpreting these plant responses.
Don't be too concerned if a half-inch or so of the ear tip has no kernels. If kernels have formed to the tip of the ear, there may have been room in that field for more plants contributing to grain yield. Again, "tipping back" will vary with individual hybrids and with growing conditions. Potential ear size is set before silking and the actual final number of kernels is not determined until after pollination and early grain fill.
Kansas State University's recommended planting rates attempt to factor in various production factors and methods for the typical corn growing environments found in Kansas. In our NEK dryland environments, 100- to 150-bushels-per-acre yield potential fields should be planted at 26,000 to 29,500 to get a final plant stand of 22,000 to 25,000 plants per acre. If your yield potential is above 150 bushels per acre, plant 28,000 to 33,000 to attain a final stand of 24,000 to 28,000 plants per acre. Adjust within the recommended ranges depending on the specific conditions you expect to face and depending the hybrid you plan to use. This assumes high germination and that 85 percent of seeds produce plants. Seeding rates can be reduced if field germination is expected to be more than 85 percent.
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