Agroeconomic assessment of mineral fertilizers in cocoa agroforestry systems

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In Cameroon, cocoa agroforestry systems dominate production but underperform due to suboptimal fertilizer use, as commercial-product recommendations are ill-adapted to local edapho-climatic conditions (e.g., soil properties, rainfall patterns, hybrid cultivars). A customized fertilizer (Cameroon Fertilizer [CMR]) for the forest–savanna transitional zone (Ntui) and rainforest (Ebolowa) zones, was evaluated alongside commercial fertilizers (SOLEVO, YARA, OCP) at three rates (i.e., 100 g, 200 g, 300 g·plant⁻¹·year⁻¹). The 300 g·plant⁻¹ ·year⁻¹ were used either in a single application or in two split applications of 150 g each. Results showed CMR and SOLEVO outperformed others, with spatial specificity: SOLEVO excelled in Ebolowa, while CMR did in Ntui. Productivity was high with the rate of 100 g·plant⁻¹ ·year⁻¹ , followed by the split application of 150 g·plant⁻¹ ·year⁻¹ twice a year. Economically, CMR and SOLEVO demonstrated significantly higher value cost ratios (VCRs > 4) compared to YARA and OCP (VCRs < 2). The findings showed the critical need to adapt fertilizer formulations, and develop fertilizer recommendations tailored to edapho-climate conditions, which often vary by locations, shifting from “one-size-fits-all”. The poor performance of high fertilizer rates including the official rate (300 g·plant⁻¹·year⁻¹), applied in single application per year, requires further investigation including environmental fate and impact. The situation call for a paradigm shift toward context-specific fertilization to close yield gaps and enhance nutrient agronomic use efficiency in cocoa agroforestry systems.