We examine the productivity of fertilizer used on maize in Central Malawi using field‐level panel data from over 1,200 observations on more than 500 fields over 4 harvest years. There are several novel aspects of this analysis compared to other on‐farm fertilizer efficiency studies, including (a) precise and accurate yield measurement using crop cuts, (b) estimating the impact of timely weeding, (c) the use of data on multiple soil characteristics from a panel of soil samples, and (d) the ability to control for field‐level fixed effects by tracking the same land over time. We find critical ecological and management threshold effects on fertilizer effectiveness at 0.94% soil carbon content, 57–58% sandiness, and weeding within 4 weeks of planting. Overall, we estimate lower yield response to fertilizer than reported in earlier studies: 2.6 maize kg/N kg under ideal circumstances, and statistically nil under many other conditions. We discuss the implications of our findings for farmers, policymakers, and researchers.

中文翻译：

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对马拉维中部玉米对肥料的玉米产量反应的深入研究表明，利润低而杂草过多

我们使用来自4个收获年500多个田地的1200多个观测值的田间面板数据，研究了马拉维中部玉米使用的肥料的生产力。与其他农田肥料效率研究相比，该分析有几个新颖的方面，包括（a）使用割草进行的精确，准确的产量测量，（b）估计及时除草的影响，（c）使用多种肥料的数据一组土壤样品的土壤特性，以及（d）通过随时间推移跟踪同一块土地来控制田间固定效应的能力。我们发现在种植后4周内，土壤碳含量为0.94％，沙质含量为57-58％以及除草时，肥料的有效性受到了严重的生态和管理阈值影响。总体而言，我们估计对肥料的产量响应比早期研究报告的要低：2。在理想情况下为6千克kg / N千克，在许多其他条件下统计为零。我们讨论了我们的发现对农民，政策制定者和研究人员的意义。