Soil erosion - - FAO 'Fertisuelos" project: FAO/BOL/018/BOL. The FAO "Fertisuelos" project works with 36 communities in the region, which involves approximately 1800 families. The altitude in this area is between 3200 m. and 3500 m. The rainfall varies between 500 mm and 600 mm. per annum. Many villages in the area