Corn Planting Depth Crucial to High Yields

As crucial a chore as setting seeding depth is, Bob Nielsen laments that farmers still largely ignore the task. “Human nature, being what it is, tends to make us simply leave the planter’s depth-control setting at the same position as in previous years,” the Purdue University agronomist explains. “Indeed, many agronomists agree that a seeding depth of 1½ to 2 inches is a fairly all-purpose range that works well in most situations.

But it you don’t pay attention to it, seeding depth can quickly become a yield robbing issue, Nielsen warns.

Even placement into moisture

Shallow or deep, the key is a combination of even placement is placing seed in an adequate supply of moisture for uniform germination. In fact, Nielsen says, most corn could come up from 6 inches deep with uniform emergence, if that’s where the moisture was even and if the planter could drop it there.

Newly planted corn seed starts imbibing moisture, if available, in the first 24 to 48 hours after planting. “It’s important to tailor your seeding depth to the conditions, that day, in that field.

“Sometimes, conditions are different in every field. If you wait on rain to give you uniform moisture, you’re in trouble,” Nielsen continues. “Rain may come a week late. Some seed may have enough moisture to germinate almost immediately. Other seeds down the row simply wait for the rain. When they finally germinate, there’s delayed emergence, uneven field stands, and all the potential for yield loss.”

Getting a uniform stand of corn today is easier than ever before in terms of equipment and seed. It’s a nonissue if you’re an alert equipment operator who’s determined to put the seed into moisture.

Be aware of your surroundings, Nielsen urges. Just recognize that you do need to pay a little more attention when conditions are less than perfect. Expect that something isn’t working the way it’s supposed to.

“Take time to get out on the ground and check the seed depth and placement, and the moisture,” he emphasizes. “You want to spend all your time planting, but a few minutes out of the day can certainly pay dividends if it leads to more uniform germination and emergence.”

If rainfall remains a scarce commodity over the weeks before planting, assess soil moisture at seeding depth in every field you plant. There will be situations where a 2-inch seeding depth does not provide uniformly adequate soil moisture. There will be situations where you should place seed deeper to minimize the risks of uneven germination.

You may hesitate, seeding deeper on soils that are prone to crust following intense rainfall. “The surface-crusting issue is more about timing than depth of seeding,” Nielsen explains. “A dense surface crust can impede penetration of the seedling coleoptile whether the seed was planted 1½ inches deep or 3 inches deep, if the crust develops shortly after planting.”

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Reduced-till tips

Neilsen offers several tips for planting this season.

“Dark-color soils will typically warm more quickly than light-color soils. If soils dry out differently across the field, the drier areas will typically warm faster than the wet areas,” he explains. “Uneven residue cover (surface trash) in reduced-tillage systems causes significantly lower soil temperatures under the heavier cover than under barer spots. Uneven seeding depth exposes deeper-planted seeds to slightly cooler seed zones than seeds placed shallower.”

In this situation, consider employing row-cleaning attachments on the planter. They will move aside the surface trash during planting and expose the seedbed to sunlight and its warming effects.

Also, consider strip-tillage practices in the future to better manage surface trash in a reduced-tillage system, Nielsen says.

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