| Sumario: | This technical report synthesizes agronomic trial evidence and spatially explicit ex-ante modeling to assess the productivity and economic returns to agricultural lime application in maize-based systems of Malawi, Tanzania, and Zambia. The analysis is motivated by increasing policy interest in soil health investments as a pathway to improve fertilizer use efficiency, close yield gaps, and enhance the cost-effectiveness of public and private agricultural investments. While soil acidity is widespread across Southern and Eastern Africa, the evidence shows that the economic case for liming is highly heterogeneous and context specific. Across Malawi and Tanzania, agronomic responses to lime are generally modest and spatially constrained, translating into limited short-term profitability under prevailing price conditions. Only small, localized pockets achieve benefit–cost ratios above unity, underscoring the risks of blanket recommendations or nationwide subsidy programs. In contrast, Zambia exhibits substantially stronger yield responses and more favorable economic returns, with a large share of maize-growing areas showing positive net benefits from lime application. However, even in Zambia, profitability remains sensitive to lime prices, transport costs, and spatial variation in soil acidity and yield potential. Taken together, the findings highlight the need for targeted, data-driven soil health strategies that explicitly account for spatial heterogeneity, market conditions, and risk. Lime investments are most defensible when embedded within broader soil fertility and input intensification strategies, rather than promoted as a stand-alone solution.
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