Effect of mycorrhiza and pruning regimes on seasonality of hedgerow tree mulch contribution to alley-cropped cassava in Ibadan, Nigeria

Abstract

Field experiments were carried out on an alley-cropping farm in Ajibode village, near Ibadan where cassava alley-cropped with three hedgerow trees (Leucaenaleucocephala, Gliricidia sepium and Senna (Syn Cassia) siamea), and sole planted cassava (all in three replicates) were arranged with arbuscular mycorrhizal fungi (AMF) inoculation (with Glomus deserticolum) in a completely randomized block design. Each plot was split after the first year into two and hedgerows within subjected to 2 and 3-month pruning regimes. Wet and dry season mulch contribution by pruning to alley-cropped cassava, as well as cassava yield characteristics in both alley-cropped and sole plots as affected by AMF inoculation and pruning regimes were monitored over two consecutive planting periods. During the first pruning year, AMF inoculation promoted dry season pruning production which was masked in Leucaena at 3 months by biomass diversion into flowering and in Gliricidia with both flowering and mite infestation. No definite patterns were observed in the second pruning year due to development of indigenous AMF symbiosis in all plots. Total yield of cassava increased with inoculation in all plots but dry season leaf area values and tuber yield indices were relatively higher in cassava alley-cropped with Senna and sole cassava than in others. The low total yield of sole cassava makes cassava alley cropped with Senna (inoculated or uninoculated) the best option for maintaining steady tuber yield with time in a continuing alley-cropping system. Key words: Biomass diversion, cassava tuber yield index, mycorrhizal contribution.