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Extension > Minnesota Crop News > Nitrogen Forecast for 2015: First edition April 9, 2015

Friday, April 10, 2015

Nitrogen Forecast for 2015: First edition April 9, 2015

John Lamb, University of Minnesota Extension Nutrient Management Specialist

Nitrogen (N) is important for corn, small grains, and sugar beet growth. This year has been OK so far. It has started to rain this week but I would not get too concerned about N losses until I see a large amount of drainage water coming out of the tile lines. In most cases the soil is on the dry side and has room to store the spring moisture. With this in mind, the chances for loss of N fertilizer are low on heavy textured soils. For growers who fall applied their N after the soil temperatures were below 50 degrees, there has been no reason to be concerned about N losses.

If you have not applied your N fertilizer, what are your options? First, waiting until spring gives you more options on what fields need to be fertilized. Nitrogen application for corn in Minnesota is based on the Maximum Return to Nitrogen (MRTN) method. This method incorporates field productivity (most corn fields in Minnesota are of High Productivity), economic conditions (Price of N fertilizer per pound to corn crop value per bushel), and your attitude towards risk. This year the economic situation for corn is tight. One area that should not be shorted is N fertilization. This is a case where the use of the MRTN is very important. Table 1 reports the current MRTN guidelines for corn. These guidelines do take economics into consideration. If you have high N fertilizer prices and low corn grain prices, then the economic optimum N application rate will be less. Notice that as the N price to crop value ratio increases the MRTN decreases. This is based on the fact that with low grain prices, the increase in corn yield you get from the last pound of N fertilizer does not pay for the fertilizer. For those that suffered through a micro economic class, this is where marginal cost (MC) is equal to marginal returns (MR).

Table 1. Guidelines for use of nitrogen fertilizer for corn grown on soils considered to be highly productive.
N price/Crop value Corn/corn Corn/soybeans
Ratio MRTN Acceptable range MRTN Acceptable range
------------------------- lb N per acre -------------------------
0.05 155 130 – 180 120 100 – 140
0.10 140 120 – 165 110 90 – 125
0.15 130 110 – 150 100 80 – 115
0.20 120 100 – 140 85 70 – 100

For more information, go to z.umn.edu/nutrientmgmt.

The bulletin with the title, "Fertilizing Corn in Minnesota" by George Rehm, Gyles Randall, John Lamb, and Roger Eliason is available at
http://www.extension.umn.edu/agriculture/nutrient-management/nutrient-lime-guidelines/fertilizing-corn-in-minnesota/.

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