An in‐depth examination of maize yield response to fertilizer in Central Malawi reveals low profits and too many weeds
利用马拉维中部超过500块田地的面板数据，研究发现施肥增产效果远低于以往报告，仅在特定土壤碳含量、沙度和及时除草条件下才有效，对农民和政策制定者有重要启示。
Abstract 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.