The first week of June, I was driving through south Alabama and spotted a field of tasseled corn. It was quite a sight to see considering that some areas of the Midwest are still trying to get corn planted!
While the delays of the 2019 planting season make flowering seem light years away, management decisions between now and the beginning of the reproductive stages are critical for salvaging your remaining yield potential. The period between tasseling (VT) and silking (R1) is one of the most critical in a corn plant’s life cycle, and are dependent on a number of factors, particularly moisture and temperature, to optimize yield potential.
Water usage is at its highest during the reproductive stages. Management decisions that impact available moisture at this stage are critical to yield potential. If a corn plant is under moisture stress during pollination, its first defense is to shut down the reproductive system. That’s why in drought-prone areas, we tend to see corn with leaf rolling, making it look more like a pineapple than a corn plant.
Tassels and silks do not fully emerge, or tassels will start to shed pollen, while silks have not fully emerged. Both of these defense mechanisms can cause a significant reduction in the number of fertilized kernels. In fact, moisture stress during pollination can reduce yield up to 8% in a single day.
While we don’t always have the ability to turn on (or off) rainfall, there are a few management decisions that can help alleviate some of the impact of moisture stress. For areas that do have the ability to irrigate, water requirements at flowering are more than .33 inches of water per day, which is nearly impossible to keep up with. Many areas that have the ability to irrigate are under watering restrictions, so it is critical to prioritize water usage during pollination when planning your irrigation scheduling.
Be sure to select hybrids that have good drought stress tolerance. If you are in an area that is traditionally drought prone, ask your agronomist and do some research around hybrid data under moisture stress. Something to keep in mind when selecting newer corn hybrids: The last few years of breeding selections have had more favorable growing seasons, and drought conditions have been less prevalent, making it harder to screen for drought tolerance. It may be worth considering more mature hybrids that have proven drought stress tolerance over time.
A reduction in the number of plants competing for moisture is another good strategy for stress mitigation. Reduced populations go hand in hand with hybrid selection. You’ll want to consider a hybrid with a leaf orientation that will fully canopy the row, reducing soil surface evaporation and shading out weeds. Consider lowering your planting population next year if this year proves to be too stressful.
In some areas, the limiting factor isn’t moisture but instead is high temperatures, especially during pollination. Temperatures above 95 degrees F can dessicate exposed silks and kill pollen. However, the majority of pollen shed occurs early to mid-morning, before temps are at their highest. High nighttime temperatures are especially detrimental to flowering, because the corn plant is under constant stress and does not have the ability to recover.
Hybrid selection can be a useful tool in areas of the country where extremes in high temperatures during the growing season are the norm. When you go to select a hybrid, be sure to ask about and research how well it can handle heat stress tolerance versus other hybrids you could consider.
Some maturity decisions can help mitigate temperature impact on pollination. By planting a shorter maturity hybrid earlier, it allows the plant to reach flowering before the highest temperatures are reached. Planting a longer maturing hybrid can stretch out the growing season past some of the highest temperatures of the season.
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