RATIONALE "Fertexpert" is a set of tools that calculates the right dose of the right fertilizer formula for each coffee plantation. Unlike current methods that require taking a soil sample per surveyed plot to determine the fertilizer formula, our system makes use of the achievements of coffee nutrition research. Therefore, our tool is particularly suitable for companies I NGOs that support small coffee planters and have to provide adapted fertilizer recommendations to a large number of planters (for up to 20,000) at an easily affordable cost. METHODS The model combines fertilizer formulas obtained from thematic maps (based on soil and climate maps) with easily measurable field descriptors using IOT, making it quick and inexpensive. The tool set uses survey forms (built with Open Data Kit) and a GIS (QGis). The geolocalized data are then processed using a spatial query followed by statistical queries to select the available commercial fertilizer formulas and doses that are best adapted to the surveyed coffee plantations. It has been tested in Cote d' Ivoire and Burundi. The results were compared to those given by the soil diagnosis method using a PCA statistical analysis to assess the relevance of the descriptors. RESULTS The tool set was developed on a CIRAD web portal. The online system only uses open source tools with a free license. The fertilizer recommendations per coffee plot are displayed on both a table and a digital map. The comparison of recommendations given by the Fertexpert tool and the traditional recommendations from soil diagnosis showed non significant differences. CONCLUSIONS & PERSPECTIVES Fertexpert allows providing each coffee farmer with a fertilizer formula and dose that corresponds to the real context of their plots (right formula at the right place). A fully usable version of the tool on tablet and smartphone (in offline mode) is also under study.