Does farmer knowledge of soil quality influence input allocation decisions and productivity outcomes?: Implications on sustainability

Land degradation, characterized by declining soil fertility and erosion, is a major constraint to maize productivity in Malawi, where more than half of the arable land is degraded. Although knowledge of soil fertility is critical for efficient input allocation, most smallholder farmers rely on subjective assessments of soil quality, potentially leading to imprecise decisions. This study examines how farmers’ perceptions of soil fertility and erosion influence input allocation and maize productivity among smallholder farmers in Malawi. Using plot level data from the Malawi Integrated Household Survey, we apply a Conditional Mixed Process estimator and Stochastic Frontier Analysis to assess input use behaviour and technical efficiency. Results indicate that farmers allocate more labour and inorganic fertilizer to plots perceived as fertile, and adoption of improved maize varieties is lower on plots perceived as poor. In contrast, organic manure is more frequently applied on degraded plots. Mean technical efficiency is estimated at 0.62, indicating substantial inefficiency relative to the production frontier. Technical efficiency declines monotonically with worsening soil conditions, falling from 0.76 on good plots to 0.52 on poor plots and 0.47 on highly eroded plots. These findings highlight sustainability risks and underline the need for improved soil diagnostics and targeted extension services.