12 N treatments in 2020 and 11 in 2021 were replicated four times over four locations in a randomized complete block design. The first research tested the efficacy of CYG for Mississippi corn (Zea mays L.) production. The optimum N rates were calculated by fitting four models. Differences between the CYG rate and AONR were compared. AONR varied from 134 to 301 kg N ha–1 at different management levels. When we compared the AONR to the CYG rate, the CYG rate over-recommended N in 12 of the 14 possible comparisons. The second study compared different VIs, methods, and sensors at various corn stages to predict in-season yield potential. Relative VI measurements were superior for grain yield prediction. MicaSense best predicted yield at the VT-R1 stages, Crop Circle and SPAD at VT, and GreenSeeker at V10. When VIs were compared, SCCCI outperformed other VIs.