In 2006 nitrogen (N) recommendations for corn in Wisconsin began to follow the maximum return to N (MRTN) approach, which uses a database of accumulated N responses from field experiments. The MRTN approach identifies an economically optimum N rate (the MRTN) based on corn and N fertilizer prices and also provides a range of N rates that produces profitability within one dollar per acre of the MRTN. Wisconsin made a further refinement to the MRTN by providing N recommendations based on soil yield potential (SYP). Soil yield potential has been a part of N recommendations since 1991 and is defined for each soil series and is based on soil characteristics such as water holding capacity, drainage, depth of root zone, and length of growing season. For the purposes of N recommendations there are four categories: very high/high SYP, medium/low SYP, irrigated sands/loamy sands, and non-irrigated sands/loamy sands. Nitrogen response functions have been found to vary by SYP. For example corn grown on irrigated sands is very responsive to N and has a large N fertilizer recommendation. While corn grown on a medium SYP soil is not as responsive to N and thus, has a lower N fertilizer recommendation. Categorization of a soil series into a SYP group is not perfect science in that SYP is based on soil series descriptions and is not experimentally determined. However, refinement of the MRTN using additional site information to categorize sites within the database has the potential to improve N rate recommendations in other states as well.