Crop yields across sub-Saharan Africa are much lower than what is attainable given the environmental conditions and available technologies. Closing this ‘ecological yield gap’ is considered an important food security and rural welfare goal. It is not clear, however, whether it is economically sensible for farmers to substantially increase crop yields. Here we estimate the local yield response of maize to fertilizer across sub-Saharan Africa with an empirical machine-learning model based on 12,081 trial observations and with a mechanistic model. We show that the average ‘economic yield gap’—the difference between current yield and profit-maximizing yield—is about one-quarter of the ecological yield gap. Furthermore, although maize yields could be profitably doubled, the economic incentives to do so may be weak. Our findings suggest that agricultural intensification in sub-Saharan Africa could be supported by complementary agronomic approaches to improve soil fertility, lowering the fertilizer cost, and by spatial targeting of fertilizer recommendations.

鉴于环境条件和现有技术，撒哈拉以南非洲的作物产量远低于可达到的水平。缩小这种“生态产量差距”被认为是重要的粮食安全和农村福利目标。然而，尚不清楚农民大幅度提高作物产量在经济上是否明智。在这里，我们使用基于 12,081 次试验观察的经验机器学习模型和机械模型来估计撒哈拉以南非洲地区玉米对肥料的局部产量反应。我们表明，平均“经济产量差距”——当前产量与利润最大化产量之间的差异——约为生态产量差距的四分之一。此外，尽管玉米产量可以翻倍，但这样做的经济激励可能很弱。