|This farmer in Cameroon has benefited from intercropping her maize with|
calliandra trees. Photo: Charlie Pye-Smith, World Agroforestry Centre
Companion planting is an ancient agricultural technique proving very effective at raising maize yield and restoring depleted soils. Maize intercropped with "fertilizer trees" like Calliandra and Gliricidia produce larger harvests without adding synthetic fertilizer. The trees help the soil retain water over the long term, and their trees shed nitrogen-rich leaves that improve the soil for the next crop.
And of course trees are great carbon sequesters. This is a pretty great tool to disseminate.