Productivity and management of agroforestry parklands in the Sudan zone of Burkina Faso, west Africa

This study focuses on the bio-economic justification of maintaining trees in parklands of a frontier village of southern Burkina Faso, West Africa. It also attempts to understand how parklands are established and managed by farmers. Methods included comparative vegetation inventories of fields and adjacent uncultivated lands, farmer interviews, sorghum yield trials between karite (Vitellaria paradoxa) trees, and a two-year karite fruit production trial. Parklands result from drastic changes in density and species richness of the original woody vegetation at clearing time. Slightly declining density, increasing dominance of a few species and increasing average tree diameter characterize developing parklands. Practice and duration of fallow, gender of field manager, method of field cultivation, soil mapping unit, original karite density, and farmer perception of the effect of trees on crop production affected parkland tree density. Crop grain and biomass production were higher at the edge of medium-sized karite canopies than either under the canopy or at mid-distance between trees. The zone at the edge of canopies had higher soil fertility (organic matter and potassium) and soil moisture, and lower sunlight intensity than in the middle of the field. Karite trees depressed grain yields under their crowns by an average of 15%. The decreased grain yields under crowns are probably due to competition for light or excessive moisture. Karite trees were found to increase overall sorghum production at densities between 12 and 31 trees/ha. Therefore, farmers do not improve cereal production by reducing tree densities below these levels. Karite trees produced an average of 2 kg of dry kernels. There was a ten-fold difference between average and highest nut-producing trees. Additionally, nut production was four times higher in 1994 than in 1993. Mass selection would thus be valuable for increasing karite nut production. The intercropping of medium-sized and large karite trees in Thiougou was economically superior to a treeless annual cropping system