In fall 2005 the Department of Soil Science unveiled a nitrogen (N) rate guideline tool to aid producers in determining a N fertilizer rate for corn that is appropriate for their economic situation. This tool is called the maximum return to nitrogen (MRTN) approach. MRTN will be described briefly; for more details please see Laboski et al. (2006) and Laboski (2006).

The new N rate guidelines for Wisconsin are provided in Table 1. In order to determine the N application rate using this table, one must first know:

• Soil yield potential. All soils in Wisconsin have been classified into yield potential categories based on the soil’s rooting depth, water holding capacity, drainage, and length of growing season. Soil yield potentials can be found in UWEX publication A2809 “Nutrient application guidelines for field, vegetable, and fruit crops in Wisconsin.”
• Previous crop.
• N:corn price ratio. This is the price of N per pound divided by the price of corn per bushel