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Maturity and dates to consider when planting this spring

By Staff | Apr 8, 2020

-Farm News photo by Kriss Nelson Zach Mutchler, field service technician with Van Wall Equipment in Perry, inspects a planter recently. Mutchler advises giving all of your spring equipment a thorough inspection before heading to the field.



How each growing season is going to go can be anyone’s guess, but how can producers better prepare for a successful growing season when it comes to knowing what varieties to plant and when?

Mark Licht assistant professor and extension cropping systems specialist with Iowa State University Extension and Outreach said he has been working for a number of years on researching planting date and maturity trials across the state of Iowa.

But with the last two springs bringing wetter than normal conditions and planting delays and then having less an ideal conditions come fall, Licht said it was time to take a closer look at the data and re-focus how we think of planting recommendations.

“We looked at, essentially, where we start seeing the large drops in yield potential when we start planting after a certain date. What is a critical planting date? That’s kind of how we looked at it,” he said.

Research showed, Licht said that for both corn and soybeans, as a statewide analysis, the dates were very close: May 18 for corn and May 20 for soybeans.

“Year in and year out, May 20 is kind of that critical date and after that, we can definitely expect to see yield penalties increasing the further after that date we get,” he said. “That was one of the major shifts in this thinking. The other part was, when we think of an ideal planting window – that shifts around from year to year. It can be as early as the middle of April on corn and end of April, beginning of May on soybeans and then it can shift clear back to the end of May for both of them. It all depends on temperature, soil moisture. Those things that interact with that early season growth and development and vigor of both the crops.”

Maturity group selection

When considering a normal planting timeframe, many of the hybrids and varieties, Licht said are well adapted.

“The seed companies have a done a good job at making sure we have high yielding varieties and hybrids when we are planting in that normal timeframe,” he said.

One area, Licht said he has been researching the last couple of years, is what if we shifted to the longer season side of that well adapted range versus the early season side?

Licht said he has found in corn, specifically in the northern and central parts of Iowa, it seems there is better yield potential with the longer season corn hybrids.

“We’re still staying within the well adapted range, but shifting off to the longer season side of it,” he said. “There is a little bit higher yield potential and less risk overall.”

Licht said he found the higher yielding came from the longer seasons hybrids, 83% of the time versus the early maturity varieties.

“By and large, the longer season hybrids tended to be a little bit higher yielding than the earlier stuff,” he said. “That, I think is a good sign.”

The potential downside to shifting acres over to a longer season hybrid is any issues that can occur with a late planting situation.

“If you plant later, it’s going to push maturity back later into the fall,” he said. “So, do you start to think about how much of a risk to a killing frost am I willing to take?”

Licht said those well adapted hybrids, on the early side to long season side, can be planted until about June 1.

“After June 1, that’s when the fall frost risk really does pick up,” he said. “I would say, if we’re on the longer side of the well adapted’s, we can stay there until about June 1.

If we are on the earlier side, we can stay with those until about the 15th of June. But, even at the mid-June timeframe, the question is should we even be planting corn?”

As far as soybeans, Licht said research shows that there wasn’t the yield response from planting the longer season, higher maturity varieties.

“That’s kind of the good news, I think of as far as looking at maturity groups, if you’re within that well adapted planting range you’re fine,” he said.

That, Licht said is due to soybeans being photo-period sensitive which not only triggers flowering, but also triggers maturity.

“If we get them planted in a decent timeframe – kind of in that before mid-June timeframe – we can definitely stay with what we originally intended, that is in that well adapted range, because they will trigger flowering and they will flower and mature, I will say, on target,” he said. “There will be some delays in there, but delays, typically, don’t put us at a higher frost risk in the fall.”

Planting conditions

Licht said he has begun putting more of an emphasis looking for ideal planting conditions versus an exact planting date or planting window.

“It’s not always soil. We do generally talk about wanting warm soil temperatures -50 degree soil temperatures before we go in to start planting corn. Soybeans, generally we thought of 55-60 degree soil temperatures, but, I think we can, especially with some of the seed treatments that if we use an early planted soybean, I think, we can be planting soybeans a little bit cooler,” he said.

The soil may be warm enough to plant, but, what does the forecast look like?

Licht said it’s not just the day of planting; it’s the following days that are also crucial.

“We also want to have a 24 to 72 hour forecast where those soil temperatures would theoretically be increasing,” he said. “We don’t want a cold snap within the first 24 to 72 hours of planting – that will get us into some cold injury with both corn and soybeans that will reduce stands, reduce some of that seedling vigor. If we look at the forecast and we know we have warm temperatures in the soil and it can expect soil temperatures to increase, that would be a good time period to get some planting done.”

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