This dataset primarily contains mental model data and respondent characteristics from 485 households across five communes in the Irodo watershed (Anketrakabe, Ambolobozobe, Antsoha, Sadjoavato, and Anivorano). Using a stratified proportional sampling design, one adult per household rated how various factors influence fertilizer use decisions using the M-Tool (–3 to +3 scale). The dataset also includes detailed information on respondents and household characteristics (e.g., gender, education, land ownership) as well as household livelihoods, including primary and secondary activities.