Is This Heaven?

Iowa Farm Scene

No. It's Iowa, where it snowed heavily May 2 and 3. What will happen to corn planted right before the big snow?

Published on: May 6, 2013

Not so pretty. That's how you describe 6 inches of snow on the ground in Iowa on May 2 and 3, 2013. Snow is pretty when it clings to trees in winter. But when it's clinging to everything the first couple days of May -- not pretty. It's not winter. And you know you need to be planting corn. Not shoveling snow.

It was strange. First time for school cancellations in May due to snow. I called a farmer in northern Iowa at Forest City where they had a foot of snow on the ground and he told me it was the worst driving conditions they had all winter. "But on May 2 it's no longer winter," he noted.

Instant ice. In Des Moines the snow was sopping wet, a slushy mess with a daytime high temperature of only 35 degrees F May 3. Car tires running over 6 inches of slush on freezing streets create ice, quickly. A friend told me his mother celebrated her 90th birthday May 3, 2013. First time in 90 years that it snowed on her birthday.

CORN PLANTED, THEN IT SNOWED: "We got our 12 acres of Iowa State Mushroom Popcorn planted April 30, 2013," says Chip Mathis of Elkhart in central Iowa. There is potential to see some "chilling injury" to corn seed planted in late April this year. Farmers and agronomists will need to check germination and emergence of fields planted in late April.
CORN PLANTED, THEN IT SNOWED: "We got our 12 acres of Iowa State Mushroom Popcorn planted April 30, 2013," says Chip Mathis of Elkhart in central Iowa. There is potential to see some "chilling injury" to corn seed planted in late April this year. Farmers and agronomists will need to check germination and emergence of fields planted in late April.

So what's going to happen to corn that was already in the ground (and was covered with snow)?
On Tuesday, April 30, a couple days before the weather turned cold, snowy and wet, Chip Mathis of Elkhart, a longtime friend of ours at Wallaces Farmer, sent me an email with a photo attached. The photo showed a tractor pulling a planter in Chip's field. Chip's message said: "Mushroom Popcorn is in the ground and not in the bag! Got our 12 acres of Iowa State Mushroom Popcorn planted April 30, 2013."

What Chip was referring to was the recommendation by many agronomists that "your seed will be better off in the bag" than in the ground if it gets as cold and wet as the forecast says it will for the next four or five days. The agronomists were looking toward the weather forecast for the week of April 29-May 5.

They gave that cautious answer to a question many farmers were asking the last few days of April; "Should I go ahead and plant corn? I know the ground is still a little wet and soil temperature is just barely 50 degrees, but it's almost May 1 and there are many of us who don't have any corn planted yet. Should I go ahead and plant today even if a snowstorm and cold weather are coming in a day or two and are forecast to last for several days, maybe longer?"

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Agronomists advised: "You'll be better off if you leave the seed corn in the bag"
On April 26 the extended weather forecast was for cold, wet weather beginning May 1 or May 2. On April 29 and 30, the ground was dry enough in some fields and soil warmed up to 50 degrees or more. Farmers had to decide -- should I go ahead and plant on April 29 and 30 even though the temperature is expected to drop like a rock, and snow and rain are forecast for the next five to seven days?

The answer from the agronomists: You will be better off if your seed corn stays in the bag. Wait till next week to plant after the weather warms up and soil conditions improve.

So what does cold, wet weather do to corn seed sitting in soil, covered with snow?
Does snow insulate the ground and hold the temperature at a little higher level than it would be if the ground didn't have a snow cover? "Of course, cold, wet weather isn't an ideal situation for early May," notes John Holmes, Iowa State University Extension field agronomist in north-central Iowa. He explains what takes place underground with seed germination for corn in the early stages of development.

When you plant, the corn seed will imbibe water, says Holmes. If that cold water gets into the seed, it's a shock to the new seedling. The cold water stresses the seed. That sometimes stops the seed development process or slows it down, weakening the seedling considerably.

If everything goes according to plan, how long will it take for the seedling to emerge? It can be up to three weeks if the soil and weather stay cold, says Holmes. But usually it takes about a week and a half after planting for corn to emerge.

Here's how he figures this: It takes 125 to 150 growing degree days from corn planting to emergence. "We don't get many 'heat units' or growing degree days accumulating this time of year," he says. "If we get 10 per day, we're fortunate." That figures out to about 15 calendar days from planting to emergence.

What if cold weather or hard freeze hits emerged corn plants?
Holmes reminds corn growers that seed corn today is well- protected with fungicide seed treatments. That's a plus, having fungicide seed treatment to help protect seed when seed is sitting in soil waiting for a warm-up to 50 degrees F or higher.

Luckily, not much corn was planted and only a few fields had emerged in Iowa as of May 2 and 3. If we have more cold weather or a hard freeze, what can happen to the emerged corn plants?

The growing point inside the corn plant is still belowground at this growth stage. So the corn seedling will freeze off down to the soil surface. But the plant will shoot new leaves, regrow and keep coming up. The real concern with frost is if you have leaves fairly well developed, they can become "tied up" at the top of the seedling affected by the frost. The new growth of the recovering corn plant can't emerge through that wad of tied-up leaves. You need to keep an eye on such fields and check germination and emergence. You may need to replant.

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QUESTION: TO PLANT OR NOT TO PLANT? For farmers who are waiting to plant, waiting for the opportunity to get into the field as soon as soil conditions are favorable and weather warms, those farmers are looking at the calendar. Is it still more important, at least at this time in early May that you plant into ideal soil conditions as opposed to what date it is?

"Yes," says Holmes. Long-term ISU research trials show the ideal time is April 15 to May 2 for planting corn in central and northwest Iowa. It's April 11 to May 13 in southern Iowa, and April 12 to May 2 in northeast Iowa. That's to reach 100% of yield potential. But May 13 is 99% here in central Iowa, "so I tell farmers to wait. They're better off planting when weather and soil conditions are more favorable."

Although corn kernels absorb soil moisture when soil temperatures are less than 50 degrees F, they won't begin germination until soil temperatures reach almost 50 degrees F or higher. ISU Extension corn agronomist Roger Elmore offers this guideline to help you make a decision: "If the sun is shining and calendar date for your part of Iowa is on the early side of the range listed above, and if soil temperatures are in the high 40s or higher and climbing, you should look at the five- to seven-day weather forecast. Plant corn if the forecast calls for more of the same. If, on the other hand, the five to seven day forecast calls for a good chance of cold, wet weather settling back in for a while, keep the seed in the bag."