The West African savanna’s short rainy season constrained staple crop agriculture.

Evidence

The dominant geographical feature of French West Africa was the savanna, a broad expanse (6oo miles wide) of undulating grassland, studded with trees and bounded by the Sahara to the north and the rain forest to the south. Its soil was fertile, although its main crops, millet and sorghum, had to be grown during a short summer rainy season. — Alice L. Conklin, A Mission to Civilize_ The Republican…, 94