Nitrogen response functions targeted to technology extrapolation domains in Ethiopia using CERES‐maize

Abstract The profitability of fertilizer‐N use can be optimized using N response functions specific to climate‐based technology extrapolation domains (TED). Crop growth simulation can complement field research for targeting of response functions. The objective of this study was to target maize ( Zea mays L.) N response functions to seven TED in Ethiopia through CERES‐Maize simulation of continuous maize over 30 yr. The complete factorial set of treatments included seven levels of N in 25 kg ha −1 increments under no‐till (NT) and conventional tillage (CT) systems. The CERES‐Maize simulated experiments were done for two or three sites per TED. Nitrogen response functions were generated for each TED with tillage‐specific functions for three TED with tillage × N interactions. The N rate responses for all TED fit curvilinear to plateau functions but with differing magnitudes and shapes of response. The mean yield with NT was 6% less than with CT, but the difference declined with increased N rate. The economically optimum N rate (EONR) ranged from 65 to 179 and 103 to 243 kg ha −1 for high and low‐cost fertilizer‐N, respectively. The EONR was 6% less and the profit cost ratio was 11% higher with CT compared to NT, indicating greater fertilizer‐N need with NT than with CT. The application of N for maize was highly profitable for all TED. The EONR from CERES‐Maize were higher than past field research results. This suggests that the CERES‐Maize N response functions were most appropriate for well‐managed crop production situations in Ethiopia.