Late Planting Population Options

Those big storms that rolled across the center section of the Midwest this week doled out hail and wind damage that brings up the topic of replanting. Farmers in some northern regions are also still trying to get the first crop in the ground.

Should you increase the corn population 10% or 20% to compensate for shorter corn plants, fewer leaves and smaller ears?

Most farmers know late-planted soybeans benefit from narrowing the row spacing to increase light interception and increasing plant population to get more nodes and pods per acre. Late planting means less time for development, resulting in smaller plants with fewer nodes.

However, corn is not as responsive. Adding more plants just translates into smaller ears and potentially less yield due to competition. My rule of thumb has always been to select the optimal population for the environment, soil and management level and stay with it regardless of planting early or late.

Emerson Nafziger, University of Illinois crop scientist, has done extensive studies on plant populations and planting dates in corn. "The optimum plant population does not change with planting date," he told DTN. "Maximum yields come at around 35,000 plants, regardless of planting date or 30,000 or 25,000 plants per acre depending on where (what region) you are at."

Late-planted corn can occasionally produce better stands because of better soil conditions, better seed-to-soil contact, warmer soil temperatures and less seed loss.

"Late planting can produce better stands with a higher percentage of the seed germinating compared to early planting because of better soil conditions," Nafziger said. "This was especially true 15 or 20 years ago. But with today's seed treatments protecting most of the seed, failure to germinate isn't much of an issue anymore." Today's planters also have better down pressure control, more precise metering mechanisms and better row cleaner technology. Farmers pay more attention to planting in the right conditions and that is adding to better emergence.

However, Nafziger added in some situations where the late-planted corn will come under early stress, such as from heat or drought or saturated soils, lower populations might actually help the crop perform better and help yield later. Nafziger explained that he hasn't seen that situation often enough to recommend a lower planting population will be beneficial if planted late and a stress period follows.

My general rule of thumb is to not change population regardless of planting date. This rule is based on what I was taught and not on what I have personally tested.

However, producers may have different experiences increasing plant population when planting very late and selecting shorter-season hybrids. If you have tried this, what were your experiences? Did you increase population 5% or 10%? Were you able to increase yield by doing so? Or was it just a wasted investment? Let us know at askdrdan@dtn.com.

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