High input prices means farmers will want to be especially judicious about the amount of nitrogen fertilizer they apply on their corn crops this spring.

One way that farmers who have regularly used manure as a nitrogen source — applying it for the past 20 years —can determine how many nitrogen “credits” are in the soil, is to test their soil to determine how much more is needed, said Brad Carlson, University of Minnesota Extension educator, water resources.

Carlson and Dan Kaiser, U of M nutrient management specialist, talked about fertilizer management during the virtual “Strategic Farming 2022: Let's talk crop fertility adjustments,” held online Wed., Jan. 5. The one-hour session was the first of a series of Strategic Farming webinars that will continue on Wednesdays at 9 a.m. Central Daylight Time through March 31.

Other webinar topics about corn include corn grain and silage management, corn insect management and tar spot on corn. There also are webinars scheduled on small grains, weed management and cover crops.

Nitrogen can move within the soil profile, so when farmers this spring soil test the ground in which manure was applied, they should test at a depth of 2 feet, Carlson said at the Jan. 5 webinar.

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Farmers who didn’t apply nitrogen fertilizer and plan to seed corn on last year’s corn or wheat ground also may want to test their soil so they will know how much nitrogen already is available, Carlson said. Generally, when soils are dry in the fall, there is a carryover of nitrogen into the spring, he said.

Because the cost of nitrogen is high, University of Minnesota soil experts are recommending that farmers who didn’t already apply the fertilizer or manure to their fields last fall , decrease their nitrogen application rate this spring by 15 pounds per acre, Carlson said.

There is substantial research that shows that the money farmers saved by reducing fertilizer by 15 pounds per acre offsets the yield loss, he said.

Though fertilizer prices are high, Carlson recommends farmers who haven’t yet bought it, do so now.

"Though, there is an adequate supply of the inputs, dealers don't want to have a large inventory ,so don't have the fertilizer on hand," he said. "I would not recommend to farmers to wait and see what happens. They better get the product booked."

Farmers who are considering using biologicals instead of nitrogen should test them first, Kaiser said.

There has been a big advertising campaign by companies who sell biologicals to use them as an alternative to nitrogen, but research so far has not proved their effectiveness, Carlson and Kaiser said.

The biologicals, which often are the same products that are sold in human health food stores, are tested in a controlled greenhouse environment, so the conditions are different than those in the field under a variety of environmental conditions, Kaiser said.

“It’s just hit or miss,” he said. "What I’ve been stressing with a lot of growers, if you want to test it, go ahead and test it.”

There is no charge for the Strategic Farming 2022 webinars, but registration is required at https://extension.umn.edu/courses-and-events/strategic-farming-lets-talk-crops.