Balancing environmental sustainability and agricultural productivity is a major global challenge. In particular, increasing crop productivity while reducing fertilizer inputs is central to achieving sustainable intensification among smallholder farmers in Sub-Saharan Africa. This study evaluates the impact of P-dipping—an innovative technique for lowland rice production that enables farmers to achieve high yield with a small amount of fertilizer by placing a triple superphosphate (TSP) fertilizer near the root system at transplanting— on yield, income, and profit. Despite the technological advantages of P-dipping, its diffusion would require improvements in the fertilizer supply chain, as TSP fertilizer remains largely unavailable in rural markets. We conducted a randomized controlled trial (RCT) to answer two primary questions: the effectiveness of P-dipping training for farmers on productivity, and whether providing training to both farmers and local fertilizer retailers would enhance the development of the TSP market. We compared three groups: a control group without training, farmers trained only, and farmers trained together with fertilizer retailers. We find that the adoption of P-dipping increased fertilizer use efficiency by 10.6 to 14.0 kilograms of paddy per kilogram of fertilizer applied. Furthermore, the adoption increased rice yield by 6.9 to 14.1 kilograms per are compared to non-P-dipping plots, resulting in higher income and profit even under an international fertilizer price surge that occurred in 2022 during the experimental period from 2021 to 2024. Our intention-to-treatment effects show that providing P-dipping training to both farmers and fertilizer retailers results in more sustained adoption than training farmers only. Retailers, however, stopped stocking TSP when project logistical support ended, resulting in a decline in adoption rates. These findings suggest that while P-dipping can significantly improve fertilizer use efficiency and productivity, its long-term success depends on viable supply chains.
