A recent series of seventy seven field N rate experiments with corn (Zea mays, L.) in North Dakota was conducted. Multiple regression analysis of the characteristics of the data set indicated that segregating the data into those with high clay soils and those with medium textures increased the relationship between N rate and corn yield. However, the nearly linear positive slope relationship in high clay soils and coarser texture soils with lower yield productivity indicated that rate alone is not a good solution for N management in these soils. Split application of N would be necessary to increase N efficiency in N-loss challenged soils. In sixty of these data sets, the GreenSeeker™ and Holland Scientific Crop Circle™ sensors were used at V6 and V12 growth stages using the red-NDVI and red edge-NDVI optional light and detection filters. Manual canopy measurement was also conducted in these experiments at both growth stages. In 2013, an automatic acoustic height sensor was also tested the date of sensing at most sites. Yield and INSEY (in-season-estimate of yield/ instrument reading divided by growing degree days from planting to sensing) at V6 was generally better related using red-NDVI compared to V12. Red edge NDVI based INSEY was more strongly related to yield compared to red-NDVI based INSEY at V12. Crop height tended to increase the relationship with yield at V6 with red and red edge-NDVI based INSEY, but only the red-NDVI INSEY benefited from crop height at V12. Separate active-optical sensor algorithms are planned for use in residual soils west of the Missouri river. In eastern North Dakota, separate algorithms have been developed for fields in no-till more than six years, for conventional till fields on high clay soils with greater than 9.9 Mg ha^-1 and less than 9.9 Mg ha^-1, and for conventional tilled medium textured soils with greater than 9,9 Mg ha^-1 and less than 9.9 Mg ha^-1.