'Plan B' for N

Corn Producers' Fertilizer Application Plans Changing With Weather

Russ Quinn
By  Russ Quinn , DTN Staff Reporter
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Wet conditions in some parts of the Corn Belt delayed or prevented fall nitrogen applications in 2018 and 2019. That has left some farmers reconsidering if fall applications are still a viable solution. (DTN file photo by Pamela Smith)

OMAHA (DTN) -- Corn producers could be forced into "Plan B" or even "Plan C" when it comes to applying nitrogen fertilizers with wet weather keeping them from implementing their first plan. The timing of the applications, the rate and even the form of nitrogen fertilizer all might have to change with extremely wet field conditions.

Wet conditions in some parts of the Corn Belt delayed or prevented fall applications in 2018 and 2019. That has left some farmers wondering if fall applications are still a viable solution, which was discussed during a recent webinar about nitrogen management by the University of Minnesota Extension.


Jeff Vetsch, a soil science researcher with the University of Minnesota Extension located at the Southern Research and Outreach Center in Waseca, said the state of Minnesota is receiving more precipitation than in the past. His research has shown that, from the 1920s to today, the state is seeing about 0.15 inch more precipitation annually, which is significant, he said.

Next year at this time is when researchers will calculate a new 30-year normal for Waseca. Currently, they sit at 36.25 inches annually, and this normal will likely increase by 2 inches next year.

"This is a huge change," Vetsch said.

For 2019, the annual precipitation was at 48 inches and the previous year they were in the upper 30s or lower 40s, he said. During the last five years, the area has been getting about 60% of this precipitation within the growing season.

Vetsch said the only recent year with near-normal precipitation was 2017. The other four years of the last five had annual rainfall anywhere from 30% to 50% greater than normal, he said.

This all means corn producers have to manage how they apply nitrogen fertilizer completely differently than they managed it back in the 1980s or certainly even in the 1990s, Vetsch said.


Dan Kaiser, University of Minnesota Extension nutrient management specialist, said he believes now is the time to start having some discussions on what the best course of action is when it comes to applying nitrogen. From talking to people, he has heard some concern about fertilizer retailers eliminating ammonia anhydrous and shifting toward applying more urea because of the wet falls they have had in the state in recent years.

He believes University of Minnesota Extension is going to have to start looking at Best Management Practices (BMC) for fall nitrogen applications and make some modifications. These changes might not be well received by farmers and fertilizer retailers, but risky application practices in the fall could lead to regulations along with lost nitrogen, he said.

Another effect of the wet weather is the nitrogen rate is slowly increasing as farmers put more nitrogen on to make up for what is lost.

Vetsch said he has tried to emphasize to start with pre-plant application of nitrogen somewhere around their recommended rates and then have a "Plan B." If it gets wet, assume you are going to have to put on supplemental nitrogen, and this can be in whatever form of nitrogen you can obtain, he said.

Farmers almost have to have a couple different backup plans for applying nitrogen because the weather has been so uncooperative the last few years, he said.

Brad Carlson, a University of Minnesota Extension educator at the Mankato Regional Office, said those who apply nitrogen still need to follow good practices, even with wet weather. An example of a bad practice would be applying 200 pounds of urea in the fall following soybeans when it is still too warm.

Despite the wet weather, Carlson is not ready to give up completely on fall nitrogen fertilizer application. As a region, southeastern Minnesota does not apply nitrogen in the fall, but fall application in other parts of the state can still occur, he said.


One practice that could help application in wet conditions could be split application of nitrogen. Multiple trips across the field allow for another chance for application and put the nutrients in the soil closer to when plants need the fertilizer.

While the practice does have certain advantages, Kaiser is not a proponent of split application for the entire state. There are some areas that probably should start looking into it, he said.

Vetsch said if you look at research in south-central and southeastern Minnesota going back 10 to 15 years, there is only about 25% of the time you would see an advantage to utilizing a split application of nitrogen. But if you look at just the five years with extremely wet field conditions, the number is closer to 50% or greater where you are going to get a response to split application, he said.

Carlson said one cropping situation that has the largest response to split application would be corn-on-corn.

"We've always found that split applying is a fine practice to do, but not necessarily always found a yield advantage to that," Carlson said.

Vetsch said farmers who plant corn-on-corn really need to consider putting at least 50% of nitrogen on pre-plant and then putting the remaining amount on via a sidedressing trip. Or maybe it could be split two-thirds and then one-third, he said.

Another practice corn producers should consider in wet field conditions is utilizing products such as nitrogen inhibitors.

"We know that urease inhibitors work well in terms of what they're supposed to do," Kaiser said. "It's really the nitrification inhibitors that have been more of the issue, that have been more of the question mark."

To listen to the University of Minnesota Extension nitrogen management webinar or read a transcript please visit https://blog-crop-news.extension.umn.edu/….

Russ Quinn can be reached at russ.quinn@dtn.com

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Russ Quinn