The project “Sensing for Smart Fertilization”, or SMAFER, explores the potential of remote sensing and in-field sensors for improving the nitrogen (N) fertilization practice of arable crops. Advances in remote sensing using drones or satellites allow real-time monitoring of crop N status, providing actionable insights for site-specific fertilization. In-field soil nitrate sensors provide real-time indication of the current nitrogen availability to plants, with the potential to improve the accuracy of nutrient recommendations. Other sensors can be used to measure the current soil enzymatic activity, which is related to N release dynamics in the soil. In the future, a combination of such technologies with data-driven decision models will enable precision N fertilizer application, reducing environmental impact while ensuring high productivity. The SMAFER project contributes to the development of the necessary knowhow and scientific basis, by making extensive use of Agroscope’s long-term fertilization experiments and lysimeter facilities.