Mark Glady

Mark Glady, WinField United Regional Agronomist, stands in front of a corn plant that received no additional nitrogen in 2019. Although the plant was producing an ear, nitrogen deficiency is apparent from the inverted V-shape on the center corn leaf. 

MINNEOTA, Minn. – Corn production is made up of two elements – number of kernels per ear and weight of each kernel.

You get those things by creating a good environment for each corn plant to grow, timely planting, keeping weeds, disease and insects at bay, and fertilizing.

Getting that wily nitrogen into the corn roots at the correct time can be tricky, said Mark Glady, WinField United regional agronomist, but it can make a huge difference in yield.

“That corn plant is going to take up 75 percent of the total nitrogen it needs from knee-high to tasseling,” said Glady speaking at an Answer Plot event near Minneota, Minn. “Whatever you do, you cannot short your plant on nitrogen from June 1-July 20.”

He has three management items to have ready to go and on the calendar for June 1, 2020. Completing these tasks means careful planning this winter to make sure they get done, especially for farms that include large acreages.

The goal of these tasks is to minimize financial or environmental costs from over-applications.

Rainfall per month

Ahead of time, write down your average rainfall per month over the last 30 years. As of June 1, write down rainfall amounts for the month of April and May 2020.

Glady noted that in the northern region of southwest Minnesota (Lyon, Lincoln and Yellow Medicine counties) average rainfall is 5 inches for April, 5 inches for May, and 5 inches for June.

“If you’ve had more than 10 inches of rain by June 1, it’s not the end of the world, but it’s a red flag,” he said. “There’s a chance that you’ve leached out more of your nitrogen if you’ve got it on.”

Soil nitrate tests

Take pre-side-dress 12-inch soil nitrate tests. That will take a bit of planning this winter to get it done in the spring, but getting it lined up will help.

“In June, we’re all busier than a one-arm paper hangar, but raising high yielding corn isn’t easy either,” he said. “I strongly suggest taking a nitrate test right prior to that rapid uptake phase from knee-high through pollination.”

Tissue samples

Get tissue samples done to determine how much nitrogen is in the plant. With good root development, that nitrogen can move into the plant and the test helps identify where your nitrogen is, he said.

If you have average or below-average rain, high soil N rates, and high tissue samples, there’s a high percentage chance that the plant is not short of nitrogen. It should reach optimum yields because it isn’t limited by N.

If there’s above-average rain, low soil tests or low tissue samples, some nitrogen deficiency is likely occurring.

“That can be a lot of confidence to recommend adding more nitrogen to correct it,” Glady said. “I always encourage growers to use stabilizers, especially the farther in front of June 1 you get. The farther away from when our corn plant needs nitrogen that we apply it, the more important nitrogen stabilizers become.”

He concluded by saying that at 80 degrees Fahrenheit air temperature at side-dress time, using anhydrous ammonia, it takes about 10 days to two weeks to get anhydrous ammonia converted to the nitrate form.

When the air temp is closer to 55 degrees and soils are cold too, it takes a long time for bacteria to convert anhydrous ammonia to nitrate. Glady said “anhydrous” means “without water,” so that form of ammonia kills the bacteria. The bacteria have to grow back and chew on the ammonia to convert it to nitrate.

He encourages growers to look for nitrogen deficiency that shows up as a yellow inverted V-shape on the corn leaves. Also, corn hybrids have “Response to Nitrogen” (RTN) ratings, and Glady suggests selecting hybrids with high RTN scores if growers are planning to apply additional or late season nitrogen. Hybrids with low to moderate RTN scores may work best when nitrogen will be limited.

“We know what hybrids have a very high response to nitrogen and should be the first to get side-dressed if they are short,” he said. “We know others are very tolerant and scavengers and can tolerate low nitrogen levels.”

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