Site-specific nitrogen (N) management in precision agriculture is used to improve nitrogen use efficiency (NUE) at field scale. The aim of this study has been to contribute to improvements in decision support for application of N fertilizer. Specifically, image-based methods were applied and improved to better target the application of N fertilizer via variable rate application (VRA) for small fields, as typical in Swiss agriculture. Multi-spectral images acquired with an unmanned aerial vehicle (UAV) platform and soil N data at reference locations were used to explore the in-field variability of crop in a plot-based field experiment that compared uniform standard (ST) rate to variable rate (VR) application. The VR final yield resulted in the same range as the ST but showed an average 10% reduction in fertilizer use.