Agronomy and Horticulture, Department of


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Liben FM, Wortmann CS, Yang H, et al. Nitrogen response functions targeted to technology extrapolation domains in Ethiopia using CERES-maize. Agronomy Journal. 2021;113:436–450. doi:10.1002/agj2.20439


Copyright © 2020 F. M. Liben, C. S. Wortmann, H. Yang, T. Tadesse, Z. P. Stewart, D. Wegary, and W. Mupangwa. Agronomy Journal © 2020 American Society of Agronomy. Published by John Wiley & Sons Inc. Used by permission.


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.