Analysis and Interpretation of the Maize Component of Maize and Cassava System with Nitrogen in a Multilocation Experiment

In Nigeria fertilizer recommendation for cassava and maize intercropping is based upon maize data, since cassava is less likely to demand a higher fertilizer level than maize. Recommended levels are the same across the major ecologies in which this crop association is important. Using a wide range of nitrogen levels and three maize varieties (one early and two late maturing), the response of a cassava and maize intercrop was studied at three locations within the three major ecozones in which this crop combination is important. Nitrogen levels for optimum maize grain yield varied with maize variety, ecozone and year (season). Analysis of variance based upon a linear model gave similar results to that based on Additive Main Effects and Multiplicative Interaction (AMMI). However with the AMMI biplot and its spatial configuration of treatment responses, visual clustering was facilitated and therefore locations and maize varieties which responded similarly were determined. Differences in maize yield were attributed to time to maturity in a given ecozone and to nitrogen rate.