When grown on top of marker ridges, vetiver grass hedgerows can reinforce ridges, stabilize the soil, and reduce the possibility of ridge breakage. Vetiver grass hedgerows also trap soil and enhance depression storage and thus reduce runoff and soil erosion. Vetiver grass hedgerows are particularly suitable for areas with moderate slopes where frequent ridge breakage is a problem. These recommendations can be more effective in controlling soil erosion only if farmers cultivating hillsides understand that erosion is a common problem that requires village-wide intervention. For instance, farmers whose fields have poor conservation practices often cause serious erosion elsewhere.
Soil erosion is an externality problem.
Because runoff from a farmer s field causes soil erosion on another farmer s field, farmers have little incentive to rebuild broken ridges or adopt better conservation practices. Despite individual farmers efforts to conserve soil, unless soil conservation practices are collectively planned and managed by all farmers cultivating adjacent fields on a hillside, there is less chance to see adoption of better conservation practices and reduction of soil erosion in Malawi. A method developed to assess soil erosion occurrence was tested on 30 farmers fields. Considering the number of rainfall events that produced runoff, this is a very high frequency. It means that ridges on farmers fields got broken almost every rainfall event that produced runoff.