A comparison of alley cropping and block planting systems in sub-humid Bénin

Alley cropping would be acceptable to farmers in West Africa, if the amount of tree-crop competition could be reduced and crop yields increased and stabilized. The importance of overall tree-crop competition in alley cropping was therefore quantified at three locations in the Republic of Bénin, by comparing the performance of a maize-cassava intercrop and mixed hedges of Gliricidia sepium and Flemingia macrophylla in an alley cropping system, where the tree-crop interaction was high, and in a cut and carry system with block plantings, where the interface was restricted to one face. The establishment and productivity of trees in both agroforestry systems depended strongly on the natural soil fertility of the site, K and Ca being critical for both species. Alley hedges produced progressively more cut dry matter with higher leaf proportions than tree blocks and hence yielded significantly higher nutrient masses. Overall, the cut dry matter from five cuttings per cropping season ranged among locations from 855 to 1651 kg ha^–1 yr^–1 for alley hedges and from 777 to 869 kg ha^–1 yr^–1 for tree blocks. Differences in yields of maize and cassava between both systems were insignificant in all three environments and all cropping years under observation. The results of this study suggest that the overall effect of tree-crop competition was unimportant, but that tree-tree competition was the decisive factor in determining the total system productivity.