The Potential for Energy and Climate Change Benefits From the Adoption of Faidherbia albida Agroforestry

Faidherbia albida is an important tree species native to Africa and the Middle East with unusual phenology such that it leafs up during the dry season and sheds its leaves at the start of the rainy season. The tree is frequently integrated into cropping systems where it provides substantial benefits, primarily through the addition of plant nutrients and organic matter, added to the soil during leaf drop. As the species is usually dormant during the cropping season it does not compete with the crop for light, water or nutrients. Among its many benefits the species contributes substantial quantities of nitrogen to the soil under its canopy, enhancing crop productivity in its area of influence. This nitrogen benefit can be analyzed in relation to its equivalent in manufactured urea nitrogen fertilizer. This fertilizer equivalent can be expressed in terms of the energy that would be required to manufacture and transport an equivalent quantity of urea fertilizer to the cropping area. This energy contribution is in effect, a substitution of the solar energy that the Faidherbia albida tree uses to obtain nitrogen from the atmosphere, for the fossil fuels used in the manufacture and transport of the urea fertilizer. This energy contribution to the Ethiopian farming system is estimated, in the current study, as 30.57 GJ ha^-1 year^-1 , based on an fertilizer equivalent contribution by the trees of 1.15 ton urea ha^-1 year^-1. In other agricultural systems, large additions of energy to the system have been associated with increases in productivity and such increases might also be realized through the addition of energy provided by the adoption of Faidherbia agroforestry. As the agroforestry system substitutes solar energy for fossil fuel energy, the greenhouse gas emissions, avoided by this substitution, can be counted as a climate mitigation benefit in the amount of 0.643 tons CO2 ha^-1 year^-1. The potential extent of adoption of Faidherbia ablida agroforestry is quite substantial and the potential benefits for agricultural rural development and climate change mitigation are great