The Acacia-Soil Quality booster?

In Treehugger:

Dennis Garrity of ICRAF states "Growing the right tree -the Acacia- in the right place on farms in sub-Saharan Africa—and worldwide— has the potential to slow climate change, feed more people, and protect the environment. This tree, as a source of free, organic nitrogen, is an example of that. There are many other examples of solutions to African farming that exist here already."

More here