Nitrogen fertilizer recommendations for corn production in Iowa have been based on yield expectations and adjustments for estimated amounts of N supplied by animal manures or previous legume crops. These recommendations include adjustments for three groups of soil associations, which generally reflect different parts of the state. However, the recommendations have no provisions for adjusting rates of N fertilizer application for weather conditions, management practices, or different soil types within the three groups of soil associations. This situation exists because there has been a lack of suitable methods for making N fertilizer recommendations that are site specific (i.e. adjusted for a specific soil type within a field within a year).