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Corn yields mostly impressive despite limited rainfall

Jeff Coulter, University of Minnesota Extension Corn Agronomist

Jeff Coulter, University of Minnesota Extension corn agronomist. Photo by David L. Hansen.

Despite a lack of rainfall, Minnesota produced an exceptional corn crop in 2021.

Numbers from the November Minnesota Ag Stats show an average yield of 186 bushels per acre – up an astounding 8 bushels from the October estimate of 178 bushels per acre.

While the 2021 yields couldn’t match 2020’s average of 191 bushels per acre, Minnesota farmers produced more corn in 2021. Minnesota’s 2021 production was 1.45 billion bushels (BB) compared to 1.43 BB in 2020.

The 2021 corn is excellent quality, which shows that the Land of 10,000 Lakes produces good corn with less-than-normal rainfall.

“We were very impressed with the corn yields given the limited rainfall this year,” said Jeff Coulter, University of Minnesota professor and Extension agronomist.

Areas of the state that were dry the first half of the growing season but received plentiful rain in August and September (without wind) generally did well.

“Those areas that were very dry throughout all of the growing season, the yields were lower than we would have liked,” he added.

What is more surprising is how well the corn pollinated and developed kernels during July 2021’s dryness.

The month finished second-driest on record on a statewide basis, and driest on record in many northern Minnesota counties, according to the Minnesota Department of Natural Resources Climate Journal (, with most areas receiving less than half of the normal precipitation.

The drought receded beginning in August across corn production areas.

Northwest Minnesota, as well as a band of counties in east central Minnesota, remained abnormally dry to moderate drought in mid-December 2021.

Coulter made some observations during the 2021 growing season that could help farmers moving forward.

Preplant tillage management important

What he noticed was that some farmers ended up doing preplant tillage several days before planting. In some cases, the practice resulted in dry conditions.

“It may have been to incorporate fertilizer, but it also gave extra time for the soil to dry out,” he said.

Some fields that were tilled around April 18 and planted around April 25 lost substantial topsoil moisture, resulting in unevenness in emergence. If we experience dry springs in the future, completing preplant tillage closer to planting may be a good choice.

“If it was a little wet at the time of preplant tillage, that created clods and caused some problems with uniformity of emergence. All of those decisions about tillage are really important,” he said. “Looking back to 2020, there were some big soybean yields that left lots of soybean residue in the field. In some of these fields, farmers did not do fall tillage, but instead made a second preplant tillage pass in the spring to manage the extra residue. That second pass of tillage caused more soil moisture to be lost.”

Early, but timely, planting required

Early corn roots took advantage of dry conditions to burrow down for moisture. This creates strong plants that can withstand a variety of growing season conditions and stressors.

If the soil temperature is going to drop about 40 degrees or below within 1-2 days of planting, Coulter suggests waiting to plant until it warms up due to the risk of imbibition chilling.

“We did have that in 2021, when the soil temperature dropped into the lower 40s,” he said. “Most farmers waited to plant, and I think that was a good decision.”

Planting depth

While a 2-inch planting depth is appropriate in many years, in 2021, a 2.25- to 2.5-inch depth may have been better if the topsoil was dry at planting. The law of averages suggests that while most of the seed is planted at the set depth, some corn will be planted a little shallower.

“You didn’t want to be planting too shallow in a year like 2021,” he said. “It can take a day or two longer for the deeper-planted corn to emerge, but the uniformity and emergence can be so much better. Having all those plants coming up at the same time, that’s the most important thing.”

Pre-emerge herbicide made a difference in 2021

Rain is needed to activate a pre-emerge herbicide, but even under dry conditions, the pre-emerge chemical was beneficial in 2021, Coulter said.

“It’s risky to not use a pre-emerge herbicide, even in a dry year,” he said. “We were impressed how well they worked given how dry it was.”

Timely post-emerge herbicide treatments are needed in a dry year to prevent weeds from competing for limited soil moisture.

Conventional tillage vs. conservation tillage

While each farmer knows what is best for their fields, Coulter observed that corn grown within conventional tillage produced slightly better than that with conservation tillage.

Because of the very cold and dry conditions in May, fields with a lot of residue cover didn’t necessarily do as well as the conventional tillage fields.

Coulter theorized that corn grown under high levels of residue would start out slow but would catch up and out-produce conventional tillage due to more retention of soil moisture. Instead, he notices that corn in high-residue fields started behind early on and didn’t catch up. It seemed that the roots didn’t go as deep early in the season, so the roots were unable to access deep soil moisture when the drought set in.

Work begins on 2022 planting

This winter, Coulter encourages farmers to go through their planters carefully to make certain they are ready for planting.

The input costs for producing corn will be high in 2022, so there will be little room for planting mishaps. He asks farmers to come up with a realistic plan for regular planting checks.

If a farmer is older, or has an injury, and can’t get out of the tractor easily, or repeatedly, it’s time to think about how seed depth can be checked regularly.

“If you have someone who can check the planting depth and make sure you are getting down at the right depth, that is really important,” he said. “Sometimes the row units on the planter wings are not able to get the seed placed deep enough – especially if it’s dry and cloddy on the top.

“If you don’t check planting depth early on and regularly, you could have many acres of corn planted before you realize you have a problem,” he added.

Checking seeding depth in each field, and under different residue conditions is important. Making certain the row cleaners are working properly is another important management item.

Inputs, management practices put to the test in 2022

Every growing season is unique, but what we do know is that most 2022 inputs will be expensive. The threat of corn rootworm is severe in some areas and the potential exists for a lack of some farming chemicals.

The most valuable assets a farmer can count on is their own knowledge, their ability to prepare and plan for the growing season, and their farming team.

Coulter encourages producers to consider taking an extra day or two to complete corn planting if needed to get the job done as right as possible when conditions are the best.

“Many farmers can get all their corn planted in 5-7 days,” he said. “It’s okay to take a little longer to get it done correctly.”

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