CONTRIBUTION OF ARBUSCULAR MYCORRHIZAL (AM) FUNGI AND HEDGEROW TREES TO THE YIELD AND NUTRIENT-UPTAKE OF CASSAVA IN AN ALLEY-CROPPING SYSTEM

A field trial on alley-cropping was conducted at the University of Iba dan research farm in the 1990/91 cropping season to assess the contrib utions of arbuscular mycorrhizal (AM) fungi and hedgerow woody legumes to the yield and nutrient uptake of cassava (Manihot esculenta Crantz ) as an intercrop in an infertile soil. The trial also investigated th e influence of AM fungi on the interplanting of a nonnodulating woody legume Senna siamea (syn. Cassia siamea) with a nodulating woody legum e (Leucaena leucocephala). AM contributions to cassava were greater th an the hedgerow contributions, which demonstrated that AM associations are an essential component in the nutrition of cassava. In contrast t o cassava, AM inoculation only influenced the leaf dry weight and upta ke of nutrients of non-interplanted woody legumes but not the above-gr ound biomass and P uptake of interplanted woody legumes. However, non- inoculated interplanted Leucaena benefited more from indigenous AM fun gi than the competing Senna. The negative contributions to the nutrien t uptake (K, Ca and ME) of cassava by hedgerows and the lack of respon se to AM inoculation in interplanted hedgerow woody legumes could be a ttributed to root competition among the different plant species growin g in close proximity to each other. The present results show that cass ava benefits more from AM association than Leucaena which in turn bene fits more than Senna in an alley-cropping system.