Soil fertility management can be improved by use of precision agriculture technologies. Global positioning systems (GPS), yield monitors, various forms of remote sensing, geographical information system (GIS) software, and variable-rate technology (VRT) are available for use by producers. Dense soil sampling, crop scouting, and other practices complete the new technological package. Soil testing is a diagnostic tool especially adapted for site-specific management. At the same time, GPS and GIS can greatly improve soil testing when these technologies are used to better describe nutrient levels across a field. The spatial variation of plant nutrients over a field makes soil sampling the most important and common source of error in soil testing. Therefore, Georeferenced soil sampling, soil test mapping, and fertilizer application with VRT can improve the efficacy of fertilization compared with the conventional practice of collecting a composite soil sample from large areas and applying a single fertilizer rate over a field.