“Maize-N” :A Quasi-Mechanistic Model for Formulating Maize N Fertilizer Recommendations.

Corn (Zea mays L.) is an important global grain crop and a significant consumer of nitrogen (N) fertilizer.  Fertilizer N rate algorithms that are used in the US Corn-belt are highly empirical in nature and use varying degrees of stochastic analysis based on statistical analysis of regional N response curves.  As a result, their utility is limited to the region where they are developed and they usually offer little scientific insight as to the biophysical components governing the variation in actual N need.  The “Maize-N” model is designed to incorporate site-specific weather information and management data to drive estimations of both maize yield potential and indigenous N supply. Indigenous N supply is estimated from daily time step simulation of C and N mineralization of crop residues, soil organic matter and manures.  Site specific long-term average yield potential is provided by the Hybrid-Maize simulation model as a sub-routine from which the upper limit of attainable yield is calculated.  The user may also input site yield history in lieu of simulated yield.   These components of the maize growth environment are coupled to estimates of both maize N resource use efficiency and physiological efficiency derived from detailed analysis of a global database of maize N uptake x yield relationship.  Here we will present the structure, performance and utility of the Maize-N approach.