Farmers have spent the past two weeks working on planters and thinking about planting strategies and potentially cold soil. Soil temperatures have been bouncing around 45 to 50 degrees F at the 4-inch depth this past week. Farmers are ready to plant corn as soon as the soil temperature warms to the 50 degree range at planting depth.
Iowa State University Extension field agronomist Clarke McGrath has had a few farmers asking him, "Can we plant a little shallower than we usually do, to try to get corn up and out of the ground faster since the soil may be cold?" Farmers who normally plant corn 2 to 3 inches deep are thinking about planting 1.5 inches or less. "In my very humble opinion, but based on years of digging up corn planted from 1 inch to 5 inches deep, targeting 1.5 inch for a planting depth is not my preference," says McGrath.
So how deep should you plant corn?
Some agronomists say "2 to 3 inches", and some say "1.5 to 2 inches." How about McGrath? He advises "target your corn planting depth at 2 inches."
So, as you get off the planter to check seed spacing and depth, take a good read on where the seed is at and make sure it is at least 1.75 inches deep, says McGrath. "And remember that rain may (and probably will) settle the soil around the seed zone and shallow up the planting a little. So plan your depth accordingly. This is especially relevant if you happen to run your trash whippers more aggressively. Disc openers tend to work better around the 2 inch target in my experience, too."
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Target 2.5 inches for your planting depth if the soils get dry again, advises McGrath. Planting "too deep" (say 2.5 to 3 inches deep) isn't typically nearly as problematic as too shallow, he adds, "but I have seen some loss of stand, less vigor and uneven emergence from 3-inch depths when corn is planted in cool, wet soils. You see that occasionally. I see many more season-long issues with shallow planted corn than I do with deep planted corn, however."
Plant corn too shallow and you'll run into problems
"Yes, you can run into big problems, if you plant too shallow," notes McGrath. "Such as rootless corn, sidewall compaction, poor root development, increased seed and root system mass in the herbicide zone. Also, poor seed zone closing, and the shallow seed zone can dry out. No doubt I am forgetting some other maladies, but you see where I am going with this. Err on the side of "too deep" rather than planting too shallow."
McGrath and ISU agronomist Mark Licht worked with Wallaces Farmer last year, which shares a little more detail if needed
On April 9 at least one cornfield was planted in eastern Iowa
On April 9 there was some corn planted south of Maquoketa in eastern Iowa. That's the first corn planting Wallaces Farmer has heard of this year in Iowa. In northwest Iowa, Bruce Rohwer, past president of the Iowa Corn Growers Association, is ready to start planting on his farm near Paullina, perhaps next week, weather allowing.
"We are about a week away from opening of corn planting here," he said on April 9. "Soils are still on the cool side. As soon as sun comes out and we quit having these little misty showers, planters will be in the fields."
Related: How Deep Should You Plant Corn?
More corn or more soybeans this year? "We really follow a corn-soybean rotation," says Rohwer. "Here in northwest Iowa there's not really a lot of switching of acres. There are other parts of the state where that can happen. But here in O'Brien County and the surrounding area I look for farmers to follow pretty closely their corn-bean rotation."
Most of Iowa has good reserve of subsoil moisture for 2015 crops
Going into planting season, the way things look now, we should have a very good corn crop this year in Iowa, says Rohwer. Of course, there's a lot of weather that has to occur yet before harvest. But Iowa is going into planting season with good reserves of subsoil moisture.
How is O'Brien County doing on rainfall? "We're short," says Rohwer. "We haven't had the normal amount of spring precipitation. Winter was short of snow. Iowa is getting some rain this week, more in the southern half of the state than the northern half. Here in Iowa's northwest corner, we're drier than a lot of the state. It would be good to get an inch of rain. We do have a good reserve of subsoil moisture. It's not like the tank is empty, but it is getting lower and we'll need some timely rains this spring and summer."