Snow in April? We think the groundhog certainly got it wrong this year! Odds of “early” or normal planting this year don’t look promising. We know research has shown in normal years earlier planting typically equates to higher yields. But, what is a normal year? Our average planting date throughout most of Cornelius Country has moved nearly a week sooner than in the early 1970’s. So, when do you consider changing maturities? Today’s seed, because of genetics and seed treatments can be planted in lower soil temperatures than in past years, but it MUST be planted into a good seedbed.

We need to do everything we can to avoid replant. The first thing to remember is to plant in ideal soil conditions – no matter the date. “Plant in mud, it’ll turn to crud!” Soil conditions are extremely important and should allow for good seed to soil contact, avoid air pockets and sidewall compaction. Soil temperatures for corn planting should be near 50°F and expected to rise. Soybean planting soil temperatures should be near 56°F. Give serious consideration to using soybean fungicide seed treatments. The rule of thumb for corn seed depth is 2” and soybean seed depth is 1.5”. Aim for equidistant plant spacing. Keep seeding rates and populations the same, even with later planting dates.

Research shows that corn planting delayed beyond May 1st decreases the number of growing degree days (GDD) from planting to silking by about 1.6 GDD’s per day of delayed planting. The necessary GDD’s from planting to black layer decreases by about 6.8 GDD’s per day of delayed planting. For example, a 110-day hybrid planted May 25th will mature similarly to a 108-day hybrid planted May 1st. The later maturity hybrid will also have more yield potential than switching to an earlier maturity hybrid. The 110-day hybrid will need less GDD’s to reach flowering and black layer than if it was planted before May 1st. Why? Because seed will germinate and emerge more quickly due to the warmer soil temps.

In summary, stay with your current corn hybrid until at least May 25. You and your Cornelius Seed Rep chose each hybrid and field placement for specific reasons and goals. Stay with your plan and it will pay off in the long run.

What about soybeans? Soybeans respond to delayed planting much differently than corn. They are much more adaptive to later planting. Soybean flowering corresponds to photoperiod (length of daylight and dark).
Late planted soybeans will be fast to emerge and quick to respond to the longer daylights. Flowering will correlate after the days begin to shorten in late June. Normally, switching soybean varieties is not considered until after June 10.

Work with your Cornelius Seed Rep or District Sales Manager to make the best decision possible for your farm. Don’t be quick to change up varieties just because of calendar dates. Consider why you chose the varieties you did and what the weather is doing and what your soil conditions are.

Be Patient. Plant Once.

Article Sources:
Elmore, Roger W. "Best Corn Planting Dates for Iowa" (2012). Integrated Crop Management News. 168. Iowa State University Extension
Nielsen, R.L and Thompson, Peter. “Delayed Planting & Hybrid Maturity Decisions” (2003). Agronomy Guide – Purdue University Cooperative Extension.
Lauer, Joe. “The Risk in Early Planting Dates” (2010). Field Crops 28.421-77 Agronomy Advice – University of Wisconsin Agronomy Department.