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.