Accounting for uncertainty in fertilizer recommendation strategies: Example of smallholder maize production in Ghana

Context: Fertilizer management in smallholder maize production systems in sub-Saharan Africa faces major challenges due to high environmental variability, uncertain input-output prices, and diverse farmer risk preferences. Conventional fertilizer recommendations often fail to account for these factors, resulting in poor adoption rates and inefficient fertilizer use. Objective: This study aimed to develop a fertilizer recommendation framework that integrates yield uncertainty and farmer risk profiles to improve fertilizer application decision-making. Specifically, it examined how uncertainty and farmer risk preferences affect optimal nutrient application rates. Methods: Using 4496 maize field experimental observations, a Quantile Regression Forest model was trained to predict maize yield responses to nitrogen, phosphorus, and potassium and assessed their profitability in 14 representative sites across three agro-ecological zones in Ghana. A utility-based economic model was then applied to simulate farmer decisions under varying levels of risk aversion. Results: Nitrogen emerged as the key yield-limiting nutrient, with yield responses increasing steeply up to approximately 90 kg N ha⁻¹. Phosphorus and potassium showed minimal agronomic and economic benefits under prevailing farmer conditions. Profit-maximizing nitrogen rates generally ranged from 60 to 90 kg ha⁻¹ but declined to 10–80 kg N ha⁻¹ under risk-sensitive scenarios, particularly for strongly risk-averse farmers. Importantly, our approach revealed site-level heterogeneity in optimal strategies, even within the same agroecological zone. Conclusions: Incorporating uncertainty and farmer behaviour into fertilizer decision-making produces more realistic and relevant nutrient recommendations. Implications: By accounting for uncertainty and farmer behaviour, this study offers a framework to improve the relevance and efficiency of fertilizer recommendations. The findings provide new insights into adaptive agronomy within the context of sustainable intensification and support a shift toward yield-enhanced, site-specific, and risk-informed nutrient management strategies that better reflect the realities of smallholder decision-making under increasingly uncertain conditions.