An accurate estimate of nitrogen (N) mineralized during the growing season is needed for agronomically and environmentally sound N fertilizer recommendations. The objective of this study was to evaluate mineralization potential (No) of the predominate soil series in the Saginaw Valley and Thumb region of Michigan with the goal of utilizing this information to formulate N fertilizer recommendations. Air‐dried samples representing 17 sites were incubated and NO3and NH4produced were measured periodically. These data were used to determine N‐mineralization potential (No) utilizing exponential and hyperbolic models. The initial hypothesis for this study was the existence of a unique Novalue for each soil series. If this were the case, then this measurement could be used to formulate soil series specific N recommendations. Results show there is as much variability in Novalues within soil series as between soil series. Consequently, utilizing a single Novalue for a soil series in formulating N recommendations is not practical.