Corn Planting Running Late? Don’t Rush to Plant Shallow

Though corn planting is in the homestretch and conditions — at least in the Corn Belt — look to be improving for getting the rest of the crop in the ground soon, there are areas where there’s a lot of crop yet to make it into the ground, and the optimal planting window has come and gone. It’s got some farmers in a rush to get things wrapped up, sometimes in conditions that are less than ideal.

Normally, that means planting in damp soils, something that can have long-lasting implications for yield potential down the road. That’s been well-documented this spring as the clock winds down on planting time. But even if your soils are dry and you can run, you still may be compelled to do other things to get your seed in the ground and on its way to emergence as quickly as possible. However, if planting shallower than you normally would is part of your plan, think twice before adjusting your planter to make that happen, specialists say.

“With recent rains elongating the planting season this year, some producers may be tempted to plant shallower to avoid placing the seeds in wet soils or to get the crop to emerge quicker. Unfortunately, corn roots may not develop properly when planting too shallow, and the stands may not grow uniformly,” says University of Nebraska Extension ag engineer Paul Jasa. “Corn should be planted 2 to 3 inches deep to develop a good root system; most corn planters are designed for at least a 2-inch planting depth. The openers cut through residue and soil better when running at least 2 inches deep, and they form a better seed-vee. Soybeans should also be planted about 2 inches deep when using a planter.”

What if you run too shallow? You run the risk of leaving the seed-vee open; without closing properly, the seed is exposed to the elements. The problem is compounded if you are planting shallow in damp soils, namely in how much more difficult it will be for seeds to germinate and get roots established.

“When planting shallower than 2 inches, the angled closing wheels on many planters pack the soil below the seed and don’t properly close the seed-vee. This problem is worse in wet conditions because wet soils are easily compacted, reducing the penetration ability of the corn roots. When the soil dries, it shrinks some and, depending on the clay content, the seed-vee may open up, drying the soil around the seed even faster,” Jasa adds. “If the seed-vee was smeared somewhat at planting time, the smeared sidewalls may bake hard, making root penetration even more difficult. Even if the seed was planted at least 2 inches deep, soil smearing and seed-vee opening may still be a problem if the crop was ‘mudded in,’ which is why it’s important to wait for the proper soil conditions.”

If your field conditions are closer to the other end of the spectrum and things could dry out quickly (if they’re not already), you can have similar problems with early emergence, especially if temperatures are expected to be cooler than normal in your area.

“The seed zone is also more likely to dry out when planting too shallow. While it may have been fairly wet when planted, the top layer of soil dries fairly quickly. If there is an extended warm, dry period after planting, there may not be enough soil moisture in the seed zone to get all the seeds germinated uniformly,” Jasa says. “Some plants may get started early while other seeds are waiting for the next rain for enough moisture to germinate. Worse yet are the seeds that germinate then die because they didn’t have enough soil moisture to get a plant established. Planting deeper provides a more buffered soil moisture for a more uniform emergence and more moisture to get the plants established. The soil temperature is also more buffered, resulting in more uniform growth.”

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