As populations continue to rise and land becomes scarcer in Africa’s rural areas, there is increasing urgency for farmers to adopt land management practices that sustainably raise land and labor productivity. Considerable effort has focused on promoting inorganic fertilizers, but it is increasingly recognized that smallholder farmers’ demand for fertilizer can be depressed by soil conditions that reduce crop response to and the profitability of fertilizer use. This article quantifies the impacts of soil characteristics on maize response to fertilizer in Zambia using a nationally representative sample of 1,453 fields. In addition to economic and farm management surveys, composite soil samples were collected and analyzed for several characteristics at the Zambia Agricultural Research Institute.