Should You Swap Corn Maturities When the Weather Puts You Behind Schedule?

LeRoy Toohey

May 06, 2019

There’s a good chance that you may be looking at the calendar, concerned you are too far behind on planting for things to go smoothly from here. While the calendar is an important tool in determining if it’s time to plant, if soils are saturated or too cold for proper germination, it’s best to sit tight and be patient.

Conventional wisdom says that the earlier we can plant, the higher we can expect yields to be—but while this is typically true, if the conditions are not favorable for planting, it’s better to leave the seed in the bag and wait for conditions to improve. We have seen major two late season snow events in the North and flooding rains in the South. Soil temperatures across many areas have only recently reached 50 degree F and average daily high temperatures have not been conducive to major accumulation of heat units.

If you’ve been asking yourself, “Should I start looking for some earlier maturing varieties,” here are a few things to consider:

  • Full season varieties generally have greater yield potential relative to earlier varieties, even when the overall growing season is cut short. An average of  0.3% yield reduction per day for the first 10 days after the prime planting window has passed is a good rule of thumb. This yield reduction percentage increases as you pass the post 10 day planting window.

  • A recent post from Dr. Bob Nielsen from Purdue University stated that planting date only accounts for 12-16 percent of variability in statewide yields from year-to-year in Indiana, meaning 84-88% of your yield variability happens for other reasons.

  • Corn has the ability to speed up when a full season variety is planted late, so that means if full season varieties are planted later than the prime planting window, the plants may require up to seven fewer heat units per day to reach physiological maturity, compared to planting the same variety in the prime planting window. Corn can limit the number of overall leaves produced, which helps to speed up overall development. This means that you can plant full season varieties a month late and still reach a yield potential as good or better than earlier varieties. For example, if you are generally finished planting corn May 5, you may still see more potential yield by keeping with your full season variety up to June 1.

  • Early varieties planted out of zone may not be able to overcome the yield potential of the full season varieties if you change to the earlier variety too soon. Because genetics play a key role on overall expectations, early varieties genetically may not be as well suited on your farm due to lack of research testing or experience.  

Maybe you’re wondering, “Could I just switch to soybeans?”

You may also be considering a change in crop. It is common to switch to soybeans from corn when the calendar passes your ideal planting window. Keep in mind that if you have inputs designed for corn, you may not have the option to go to soybeans; fertilizer costs, prior herbicide applications, grain marketing contracts and crop rotation may not allow for switching crops. Focus on your net revenue or return on investment (ROI) when considering a switch from corn to beans. And make sure you are looking at the impacts on the 2020 growing season as well.

PRO TIP: Once the weather does cooperate: Do your best not to “mud in” seed or do excessive tillage when the soil is wet. Creating compaction in the furrow and clumping soils is not a good recipe for success whether you are planting timely or late.

For the most part, it’s probably not the best plan to swap from a full maturity variety to an earlier maturity at this time.

The varieties you selected are still the best products for at least the next few weeks. The weather is going to improve, and when it does you are going to burn the midnight oil to get the crops planted. We know you’ll be pushing to get it all done, so be safe and watch out for one another during this planting season.


ALWAYS READ AND FOLLOW LABEL DIRECTIONS. It is a violation of federal and state/provincial law to use any pesticide product other than in accordance with its label. The distribution, sale and use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. It is your responsibility to confirm prior to purchase and use that a product is labeled for your specific purposes, including, but not limited to, your target crop or pest and its compatibility with other products in a tank mix.

LeRoy Toohey

May 06, 2019