Th is paper presents electronic tool to support farmers in fertilization planning. It is developed as a spreadsheet model, utilizing optimization potential of mathematical programming techniques. Described problem of fertilization planning is rather simple from technological-expert viewpoint, but methodological application of multi-criteria paradigm makes it more complicated. In the paper focus is put on economic effi ciency of fertilization. Hypothetical case illustrates its application as well as strengths and weaknesses of methodology applied.