Achieving food security in Sub- Saharan Africa depends on raising the productivity of smallholder farmers, and in Burkina Faso, there is no option for enhancing crop productivity other than intensification. The soils in the Sahel and Savanna of West Africa are old, deep and poor in soil organic matter, with low capacity to retain nutrients, while this region is also the most densely populated in the continent. Yet, as in other countries of Sub-Saharan Africa, the national agricultural research system formulated fertilizer recommendations during the 1970s and 1980s, but these did not, and still do not, take differing agro-ecologies into account. The heterogeneity of agro-ecological and soil conditions has led to a diversity of farming systems and cropping patterns. This heterogeneity, along with incomplete input markets, creates highly variable economic incentives for smallholder farmers.