Updated corn nitrogen rates: What are we currently seeing for N fertilizer requirements in Minnesota?

By: Dan Kaiser, Extension nutrient management specialist & Fabian Fernandez, Extension nitrogen management specialist

A recent update has been made to University of Minnesota Extension’s suggested nitrogen (N) fertilizer rates for non-irrigated corn. The update adds data from the 2022, 2023, and 2024 growing seasons to our long-term dataset. The tables below summarize the current values which are included in the updated Fertilizing Corn in Minnesota web page and publication, as well as the Corn Nitrogen Rate Calculator.

The inclusion of the newer data resulted in an increase in suggested N application rates for both corn following corn and corn following soybean, with an increase in suggested N rates of around ten pounds per acre in both situations. 

For those using the Corn Nitrogen Rate Calculator, results may vary from the below tables within 1-2 lbs. for similar price ratios due to rounding of the values used in the tables.

The acceptable range is included to account for uncertainty within the dataset and reflects only a small ($1.00) profit increase/decrease from the MRTN.

Regional differences

This update reflects only non-irrigated corn grown in Minnesota for the bulk of the acres south of I-94. For those growing corn in the Red River Valley, we would still suggest following North Dakota State University guidelines for similar soils to what you have in your fields.

We have been looking at data from our irrigated corn locations for the past few years but have not seen a substantial, if any, increase in the amount of N needed for corn grown on irrigated sandy soils. We will be looking at the irrigated corn guidelines more closely soon but we do not anticipate major changes to those guidelines. (Suggested nitrogen rates for irrigated corn following corn can be found in Table 2 of the Fertilizing Corn in Minnesota web page and publication.)

We are also looking at whether silt loam soils in southeast Minnesota have lower corn nitrogen requirements. A nitrogen application rate at the lower end of the acceptable range may be better suited for these soils.

Maximum Return to Nitrogen Rate (MRTN) approach

University of Minnesota Extension’s nitrogen fertilizer guidelines use a data-driven approach based on annual plot studies at sites around Minnesota. MRTN stands for Maximum Return to Nitrogen Rate, which is the nitrogen rate our research suggests will maximize profit. Applying a profitable nitrogen rate can be a win-win for farmers and the environment by limiting unnecessary overapplication of nitrogen fertilizer. Targeting maximum yield instead of maximum profit can lead to slightly higher corn yields, however, the additional cost of nitrogen fertilizer outweighs the economic benefit of the higher yields, while also leading to significant nitrogen loss to the environment (see Figure 1 below).

Figure 1. Maximum Return to Nitrogen Rate (MRTN)

Table 1: Suggested nitrogen rates for non-irrigated corn following corn

Prior Crop	N price/crop value ratio	MRTN	Acceptable range
Corn	0.075	200 lbs. N/acre	180-220 lbs. N/acre
Corn	0.100	185	170-200
Corn	0.125	175	160-190
Corn	0.150	165	150-175

Table 2: Suggested nitrogen rates for non-irrigated corn following soybean

Prior Crop	N price/crop value ratio	MRTN	Acceptable range
Soybean	0.075	155 lbs. N/acre	145-170 lbs. N/acre
Soybean	0.100	150	135-160
Soybean	0.125	140	130-155
Soybean	0.150	135	125-145

Why are corn nitrogen requirements increasing?

Corn nitrogen requirements have been climbing steadily across the Midwest for decades, and Minnesota is no different. Recent research shows that the economic optimum nitrogen rate (similar to the MRTN) for corn grown in the United States has increased at the same rate as the increase in grain yields, 1.2% per year from 1991 to 2021. In addition, precipitation changes may be impacting corn N requirements. In wet years, soggy soils often lead to denitrification (loss of nitrogen to the atmosphere). Increasing the suggested rates of N does not mean more N is being lost to ground and surface waters.

Additional resources

• Making sense of Minnesota’s corn fertilizer guidelines: Frequently asked questions and answers (2023 blog post)
• Nitrogen Smart online courses
• Advancing Nitrogen Smart podcast
• Four things I’ve learned about nitrogen management for corn based on a decade of research in Minnesota (2025 blog post)
• What to know about the Maximum Return to Nitrogen (MRTN) approach to corn N rate guidelines (2022 podcast episode)
• How Extension is addressing nitrate water quality issues in southeast Minnesota
• Southeast Minnesota nitrogen meeting presentations available online
• On-farm research helps to complement, challenge Minnesota's corn nitrogen guidelines (2021 blog post)

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