Technical Abstract: The popularity of the precision agriculture movement is driven by economic incentives and the intuitive potential for increased environmental stewardship. Global positioning (GPS) technologies adapted from a military play a major role in rapidly providing the precise latitude of positions in fields. By merging information about the precise location within a field and site-specific information about soil properties or crop growth, a map can be generated that may help make management decisions. Aerial photographs frequently complement maps generated by intensive ground sampling. A study with irrigated corn production showed that patterns of soil color matches those of crop canopy color during the growing season. A map of corn grain yield showed general areas with relatively low production coincided with areas having a low relative fertility. Crop nitrogen sensors mounted on a high- clearance sprayer generated a map that was highly correlated with patterns seen in an aerial photograph taken at the same stage of growth. Techniques that provide an indication of spatial variability in vegetative cover during the growing season help evaluate the effectiveness of early season fertilizer practices and provide an early indication of potential yield variability.