Soils in the west Africa savanna are characterized by low organic matter content and low nutrient holding capacity. Poor crop response to inorganique fertilizers and low nutrient use efficiency, particularly at long-term, are often recorded. Added benefits, in terms of maize yield, from the combination of organic resources and fertilizers have been observed particularly under water stress. A number of studies are focussing on the development of appropriate cropping systems for increasing organic inputs in soil while trying to understand mechanisms responsible of the benefits associated with the presence of an organic resource. Increase in water availability and reduction of nutrient losses are some of the mechanisms of interest.