Nitrogen
Managing Nitrogen for Profit and Conservation
Achieving profitable yields requires an adequate Nitrogen supply. However, over-applying nitrogen harms soil health, wastes money on fertilizers, and can contaminate the groundwater that supplies our drinking water.
UW-Extension has developed the Wisconsin Maximum Return to Nitrogen (MRTN) based on experiments conducted on Wisconsin soil. These quick and easy nitrogen rate recommendations are based on optimizing economic return and were not developed as an environmental standard. This allows the producer to select an N rate that is appropriate for their economic situation. In addition, implementing the MRTN can have positive soil health impacts, such as increased organic matter, calcium levels, and pH.
The 4Rs are helpful to keep in mind when managing N to minimize losses:
Right Rate – Nitrogen rates have the potential to make the largest impact on both crop production and the environment. Account for your nitrogen credits by using the UW-Extension MRTN guidelines, then adjust with soil or plant tissue testing.
Right Source – Keep in mind that N is mobile and there are differences in how N fertilizers interact with the environment, which can affect both availability and loss. For example, some forms like Urea can volatilize when surface-applied, and other forms are more prone to leaching. A nitrification inhibitor could make financial sense in some situations.
Right Time – The nutrient supply should be synchronized with crop demand and uptake as much as possible. Weather conditions play an important role too. Apply urea before rain, only fall apply on loamy soils after the soil has cooled <50 degrees, side-dress or split apply N on sandy or poorly drained soils, and wait for better soil conditions if too wet or too dry.
Right Place – Nutrients should be placed where the crop can use them. With urea, incorporate or apply as a liquid, inject anhydrous, and incorporate manure if possible. Special considerations need to be made regarding sensitive soils or near wells; these areas can be seen on your Nutrient Management Plan maps.
Check out these great resources:
Find out your economic return for Nitrogen using the Corn Nitrogen Rate Calculator.
Home:: Nitrogen Rate Calculator (cornnratecalc.org)
Finding out your Corn N rate in the palm of your hand. Click the link below to learn more about the N rate App put out by University of Madison.
N Rate App – Integrated Pest and Crop Management – UW–Madison (wisc.edu)
Why is Nitrogen Important? The University of Madison has resources to learn more about what you are putting into your soil.
Nitrogen – Soil Science Extension (wisc.edu)
Check out the Nitrogen Cycle provided by the University of Wisconsin Extension.
UWNPM_NitrogenCycle.pdf (wisc.edu)
Want to accurately adjust your Nitrogen Rate? Explore Preplant Nitrate Test and Pre-Sidedress Nitrate Test below.
UWSoilNitrateTests_final.pdf (wisc.edu)
University of Wisconsin Nitrogen Guidelines for Corn
NitrogenGuidelinesCornWisconsinMRTN.pdf
The Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin has updated N rate guidelines for corn and wheat using an MRTN approach.