The Farmer Logo

Carryover N could be up to 30% higher for some Minnesota farmers this year.

June 14, 2022

3 Min Read
sprayer in field
CHECK SOIL FERTILITY: Variable — that’s the only way to describe carryover nitrogen in Minnesota fields following last year’s drought and this spring’s cool, wet weather.Paul McDivitt, U-M Extension

University of Minnesota soil fertility researchers around the state measured carryover nitrogen (N) levels last fall and noticed unusually high amounts of N left in the soil. This was because the dry conditions during the 2021 growing season limited the corn crop’s growth, resulting in a lower-than-usual need for N as well as lower yields.

After a grinding Minnesota winter and a rainy spring, how much of that carryover N from the fall is still left in farmers’ fields?

The answer, according to Fábian Fernández, U-M Extension nitrogen management specialist, depends on which part of the state you farm.

In south-central, southwest and west-central Minnesota, soil samples taken in late April and early May of this year indicated that carryover N levels were 25% to 30% higher than normal. This means that farmers who planted corn again this year, and haven’t already applied their full N rate, could apply a lower rate in-season than they were planning on.

“If weather conditions are favorable this season, it may be possible to reduce your N fertilizer rate by about a quarter,” Fernandez says.

Carryover N likely in almost all parts of state

Southeast Minnesota, in contrast, had what would be considered a typical carryover N level this spring. The research site in central Minnesota is on irrigated, sandy soil, which is prone to nitrate leaching, so it had very low carryover N levels this spring.

yield and N carryover table

Fernandez recommends that corn growers use the university’s regional N rate calculator, which uses data from around Minnesota, and customizable corn and N fertilizer prices to calculate an economically optimal nitrogen rate (EONR).

“We encourage farmers to use this information in the context of their individual weather, current and last season’s crop conditions, and soil and location information to decide how much of a N credit they should take,” Fernandez adds.

While there was significant rainfall in May, Fernandez points out that it was also cool, which limits N loss to the atmosphere. In addition, it takes a lot of water to move N below the root zone or leach into tile drains. He estimates that only 5 to 20 pounds of N per acre leached out this spring at the U-M drainage research plot in southwest Minnesota.

And while some N has moved further down into the soil profile, it should still be available to this year’s corn crop — once it finally warms up.

The research is part of a long-term nitrogen study funded by Minnesota’s fertilizer tonnage fee through the Agricultural Fertilizer Research and Education Council. Data from the study, along with data from other nitrogen management research in Minnesota, shapes U-M's corn fertilizer guidelines.

To learn more, visit z.umn.edu/7sq6.

McDivitt is a University of Minnesota Extension communications specialist.

Source: University of Minnesota Extension, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all of its subsidiaries are not responsible for any of the content contained in this information asset.

 

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like