Many factors contribute to achieving high corn yields

STREATOR, Ill. — Farmers have the least control over weather, but it has the largest impact on producing high corn yields.

“Weather dictates when you can plant and the weather after you plant dictates the success of your planting date,” said Fred Below, professor of crop physiology at the University of Illinois.

“Sometimes you can plant too early so if you have to plant something, plant soybeans first,” said Below during a presentation at a Nutrient Stewardship Field Day.

“In August when the grain fills, every night the temperature stays above 73 degrees, you can kiss a bushel goodbye,” he said.

The university professor discussed the top factors that contribute to high corn yields. However, he said, there are several things that must be in place for farmers to reach 300-bushel corn yields.

The prerequisites include soil structure and drainage.

“The tile guy is my best friend and don’t compact the soil,” Below said. “You can’t have weeds, pests or diseases because they take yield away.”

Below conducts research at three Illinois locations — Yorkville, Champaign and Nashville.

“Protection for foliar disease seems to be a little more important in the south than the north,” the professor said.

“Last year it was dry and we didn’t have any disease,” he said. “But we saw a seven-bushel increase in yield from fungicides even when we didn’t have visual leaf diseases.”

Proper pH and adequate base levels of soil nutrients are also prerequisites for high corn yields.

Fertility is a factor that farmers can impact.

“When nitrogen moves in the soil, it moves down — that’s why you can see nitrogen deficiency right to the row,” Below said.

“If we’re going to grow high corn yields, we’re going to have to do a better job of fertilizing,” the professor said.

“When you grow 300-bushel corn, you’re taking a lot of nutrients off your field and sending them somewhere else,” he said. “You’ve got to replace that and it all comes down to better source, rate, time and place.”

Not all mineral nutrients are absorbed at the same rate and used in the same way.

“Nitrogen comes from fertilizer or the soil in roughly equal proportions — half from soil mineralization and half from the fertilizer,” Below said.

“During initial growth of the corn plant, you are setting the yield potential with the number of potential kernels,” the professor said.

“The peak uptake time for nitrogen is from V10 to a little after flowering when you are growing the leaves or the photosynthesis part of the plant,” he said. “There is an enormous demand for nitrogen at seven pounds of nitrogen per day.”

Placement of fertilizer for the corn plant is key.

“The root system only extends six to eight inches,” Below said. “Roots do not cross the row.”

Therefore, the professor said, strip-till is the future for planting corn.

“When we band fertilizer under the row, we see a screaming improvement in early growth,” he said.

During the growing season, using Y-drops puts the fertilizer right along the row to take advantage of the funneling nature of the corn plant.

“Corn plants funnel water down their stem,” Below said.

Not all corn hybrids are created equal.

“Top hybrids tend to have a fuller maturity and they tend to be the newer hybrids,” said Sam Leskanich, graduate research assistant at the U of I crop physiology lab. “But the new hybrids tend to be more expensive.”

Hybrids also differ in root size.

“The small rooted hybrids are the racehorse hybrids and the large rooted hybrids are the workhorse hybrids,” Leskanich said.

“The racehorse hybrids have a high yield potential, but they will crash under stress,” he said. “The workhorse hybrids handle stress, but they might have a capped top end yield.”

Plant population is another factor in high corn yields.

“Plant population has increase 400 plants per acre per year,” Leskanich said.

“As we increase plant population, we tend to see smaller roots,” he said. “There’s a 2.5% decrease in root mass per every 1.000 increase in plant population.”

One way to elevate population stress is to move from 30-inch rows to 20-inch rows.

“With 30-inch rows there is a 4.8-inch plant to plant spacing and with 20-inch rows there is a 7.1-inch plant to plant spacing,” Leskanich said.

“Going from 30 to 20-inch rows, you add 6,000 plants that have about the same root mass,” he said.

Biologicals are another factor that farmers can use to increase corn yields.

“If you don’t have your seed, fertility and pest management set right, we don’t want to have a conversation about biologicals,” said Connor Sible, postdoctoral research associate of the U of I crop physiology lab. “Biologicals are the next step but they won’t replace good agronomic management.”

There are three categories of biologicals — plant growth regulators, beneficial microbes and biostimulants.

Nitrogen-fixing bacteria take the atmospheric nitrogen and put it into a usable form for plants and microbes.

“We’re really excited about the potential of a third source of nitrogen,” Sible said.

Since not all phosphorus in the soil is plant available, phosphorus-solubilizing bacteria can put this nutrient into a form the plant can use.

“We’ve had really good success with in-furrow application with the starter,” Sible said. “It needs contact with a growing root so placement is important.”

Enzymes and phosphatases can increase the availability of organic phosphorus.

“They are not all the same so depending on what type of organic matter you’re working with will determine which enzyme to use,” Sible said.

Marine extracts and sugars can be applied in season to help mitigate drought.

“For sugars, we see the biggest success with soil application in furrow to stimulate the microbes,” Sible said.

“Biologicals can be an effective tool at improving grain yields, but it depends on the product you’re using,” he said. “If you really want it to work, know the product first and find the right way to integrate it for you.”