I represented our project at a recent conference on mulching in arid regions, held in Burkina Faso. Despite the amazing results we have gained in our project, most scientists did not seem to grasp the importance of regenerating trees on the farm. There is an old assumption that trees hinder the performance of the principal crop and their number should be reduced. I think this comes from assuming less stressful conditions than we find in the Sahel. Typically under stress conditions, you would indeed expect that more competition from trees will hinder crop production.
The realities of Sahelian conditions are more extreme: very high soil temperature, high winds, high evaporation rates, and very low fertility/organic content. Under these conditions, we have found that more trees are better, at least up to forty and even a hundred or more trees per hectare (16-40/acre)
Most scientists recommended cultivating grass species in one location and transporting the cut grass to the farms for use as mulch. The problem is that very few farmers are willing to give up scarce land to cultivate a grass. Then there is the issue of time required to move the grass to where it is needed (estimates of 180 hours per ha). Regenerating trees takes very little labor and gives added benefits of wind protection, wood sales, cooking fuel, building materials, fodder, human food, and overall increase in biomass production that the a separate field of grass does not provide. The abundant biomass production from trees eliminates the huge labor problem of cutting and carrying grass to the fields.
ECHO Staff 1998. Mulch or trees in the Sahel. ECHO Development Notes no. 62