Less than one hundred years ago there was a shortage of fertile soil in Holland. Because of the dramatic growth of population fertile soil became exhausted. Fertilizing with manure wasn't effective. The introduction of fertilizer solved the problem. More land became available to agriculture and farmers where able to produce more nutriment.
One of the roots of Afrika's poverty is (as it was in the Netherlands a millennium ago) the decreasing fertility of agricultural soil and the density of population which is too high for the soil. Few African farmers can afford expensive fertilizer.
There is an alternative however: Multiple Purpose Legumes, a plant that has the ability to combine nitrogen from the air.
Herman van Keulen (pedologist) en Ken Giller (plant production systems) both attached to the university of Wageningen, are researching the use of MPL in developing countries.
For Dutch Public Broadcast VPRO we travelled with them through their mission through Kenia and Tanzania.