Effect of Azadirachta indica A. Juss (Neem) on the Growth, Physiology and Yields of Associated Crops in Agroecosystems in the Sudano-Sahelian Zone of Burkina Faso, West Africa

Neem is an exotic species used for reforestation, but its competitive effects on surrounding crops have not been thoroughly explored in Burkina Faso. This research aimed to assess the effect of neem on cowpea, millet, and sorghum within agroecosystems in Burkina Faso. The experimental design involved systematically allocating treatments based on the gradient of the tree's effects, with three replicates of each crop, totalling nine neem trees. The treatments concerned three plots located based on their distance from the isolated neem trunk: one plot was situated directly under the crown, another was 11 m away from the trunk, and the third was 22 m away. Key parameters, such as stem length, crop leaf area index, photosynthetically active radiation, linear electron flux, grain and straw yields, were measured. Results indicated that fall crops, stem length, photosynthetically active radiation, linear electron flux, and crop leaf area index were significantly lower under the neem crown compared to areas outside the crown (P<0.05). For instance, the photosynthetically active radiation was significantly lower in plots situated directly under the crown compared to plots outside the crown at 22 m from the trunk, across all crops (P<0.05). Additionally, grain and straw yields were significantly reduced under the neem crown compared to the border and areas outside the crown for all crops studied (P<0.05). These findings suggest that neem has detrimental effects on intercropping within agroecosystems.