Evaluating the Adapt‐N model for dynamic nitrogen recommendation in Brazilian maize ( Zea mays L.) systems

Several nitrogen rate recommendation methods have been developed to help farmers fertilize close to the economic optimum N rate (EONR). The objectives of this study were to (i) evaluate a dynamic method (Adapt‐N) for N rate recommendations for maize ( Zea mays L.) in Brazil relative to EONRs determined specifically for each trial and (ii) compare the estimated maize yield, N balance, and profit using the N rate recommendation methods. Seventy‐five N response trials were performed at 14 sites with maize cultivation from different regions in Brazil, most without tillage following soybean ( Glycine max (L) Merrill). On average, the N rate recommendation was higher for Adapt‐N compared with EONR and Official (137, 121, and 115 kg ha −1 , respectively). Average maize yields were similar for EONR (8816 kg ha −1 ), Adapt‐N (8789 kg ha −1 ), and Official methods (8668 kg ha −1 ). The mean profit was around $1400 ha −1 for the methods with no difference. The N average balance (N applied − N removed) was higher in Adapt‐N than for other methods, resulting in positive values in most sites (84%), avoiding soil fertility depletion, whereas EONR and Official methods showed a negative balance in 50%. Overall, Adapt‐N was nearly as good as the EONR calculated for each trial using the actual achieved yield, but with slightly more N applied. Further studies should investigate Adapt‐N when legumes are cultivated as no‐till cover crops in tropical conditions.