Foundational concepts for characterization of nitrogen (N) nutrition in field crops are necessary to define true N gains in crops under different genotype-environment-management (GxExM) scenarios. A study (Ciampitti and Lemaire, 2022) emphasized the requirement to redefine N use (herein termed as effective use of N term) and provided new insights into crop yield improvement based on improving crop N status over time. Future breeding progress is needed to combine two strategies by linking progress in both biomass (in terms of harvestable organs) and yield with progress in intrinsic N uptake capacity, i.e. the capacity of the crop to capture soil N resources. This chapter outlines a prior N framework for targeting optimal N supply and proposes the utilization of a new approach to shift our current paradigm to more directly target necessary N gains in crop improvement.