economic return. In the Midwest, the primary
philosophical approach to developing a N fertilizer
recommendation for corn is to consider, as independent
variables, yield goal, economic return, management level,
and some measure of the inherent differences in soil
productivity (Oberle and Keeney, 1990).
Increased use of fertilizer nitrogen (N) in agricultural
production has however raised concerns, because the N
surplus is at risk of leaving the plant-soil system and
thereby causing environmental contamination. This is in
addition to increased costs associated with the
manufacture and distribution of N fertilizer (Alizadeh and
Ghadeai. 2006). Liberal application of nitrogen fertilizer