Conservation agriculture (CA) is often promoted as a key to intensifying agricultural production in sub-Saharan Africa. Despite significant efforts to promote CA, however, adoption remains limited in this region. This article contends that CA requires a fourth principle of appropriate fertilizer use to complement the already accepted principles of minimal tillage, maintaining a soil cover, and crop diversification. In regions where CA was widely adopted, fertilizer application was an essential part of agricultural systems, and a key to the success of CA. Appropriate fertilizer application is necessary for CA to be a successful alternative to conventional production in sub-Saharan Africa.