High soil acidity is a significant cause of low and stagnant agricultural productivity in Kenya, particularly for maize, which is the country’s main staple crop. Few small-scale farmers test their soils to make soil management decisions. This ALL-IN project is testing practical ways to encourage farmers to test their soils and to apply appropriate soil amendments. It includes an estimate of farmers’ willingness to pay for soil testing. The results provide guidance on promoting effective soil management for sustainable agricultural productivity growth in Kenya and across Sub-Saharan Africa.