ABSTRACT.- Context: The greenness index of the ear-leaf in maize (Zea mays L.) has been used to assess crop nitrogen (N) status, but it may not accurately predict yield responses to late N fertilization. Objective: This study aimed to i) analyze differences in the greenness index and N sufficiency index (NSI) across maize canopy leaf positions and their relationship with soil N availability, N nutrition index (NNI), and grain yield, and ii) evaluate the accuracy of NSI determined in different leaf positions in predicting the grain yield response to N fertilization at silking. Methods: The greenness index was measured across the maize canopy profile under varying N rates and application timings in five field experiments. Bell-shaped models described the greenness index distribution, and relationships among NSI, NNI, and relative grain yield (rGY) were analyzed. © 2025 Elsevier B.V.