Paul Stapleton introduces “evergreen agriculture.” In Africa, intercropping with trees of the genera Sesbania, Gliricidia, Tephrosia, and others improves yields and provides other benefits; dropped leaves from the trees provide natural fertilizer.
The indigenous African acacia (Faidherbia albida) is perhaps the most remarkable of these fertiliser trees. Faidherbia sheds its nitrogen-rich leaves during the early rainy season and remains dormant throughout the crop-growing period. The leaves grow again when the dry season begins. This makes it highly compatible with food crops, because it does not compete with them for light, nutrients or water during the growing season: only its bare branches spread overhead while the food crops grow to maturity.