Bringing together emerging lessons from biophysical and social sciences as well as newly available data, we take stock of what can be learned about the relationship among perceived soil fertility, measured soil fertility, and farmer management practices in east Africa. We identify the correlates of Kenyan and Tanzanian maize farmers’ reported perceptions of soil fertility and assess the extent to which these subjective assessments reflect measured soil chemistry. Our results offer evidence that farmers base their perceptions of soil quality and soil type on crop yields. We also find that, in Kenya, farmers’ reported soil type is a reasonable predictor of several objective soil fertility indicators while farmer-reported soil quality is not. In addition, in exploring the extent to which publicly available soil data are adequate to capture local soil chemistry realities, we find that there is still immense value to the time-consuming collection of soil samples where highly accurate soil measures are important to research objectives. However, in the estimation of agricultural production or profit functions, where the focus is on averages and where there is low variability in the soil properties, there may be limited value to including any soil information in the analysis.