Influence of arbuscular mycorrhizal fungi and phosphorus on early growth and nodulation of indigenous albizia species

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This study was conducted to determine the response of four (4) species of arbuscular-mycorrhizal fungi (Glomus clarum, Glomus iritraradices, Glomus etunicatum, Gigaspora rosea) on early growth and nodulation of Albizia species (A. adianthifolia, A. ferruginea, and A. zygia), and to evaluate the interaction of phosphorus-fertilizer in the form of tripple superphosphate (TSP) with arbuscular-mycorrhizal fungus (Glomus clarum). Albizia seedlings were grown in pots under nursery conditions and treatments applied to both sterilised and unsterilised soil conditions. Arbuscular- mycorrhizal fungi differed in their effectiveness in enhancing early growth, dry matter accumulation, nutrient (N, P, K, Ca, and Mg) uptake and root colonization in all the three Albizia species. Glomus intraradices was the most preferred fungus in A. adianthifolia, Glomus clarum in A. ferruginea and Glomus etunicatum in A. zygia. In general, Glomus clarum proved to be the most efficient fungus in almost all the parameters considered. Moreover, A. ferruginea gave the most promising initial growth characteristics as well as nutrient uptake and root colonization. However, sterilised uninoculated soil treatment showed superiority in almost all the three Albizia species in terms of the growth measurements taken which was contrary to earlier reports made by some authors but recorded significantly low root colonization. -Phosphorus addition in the form of TSP markedly stimulated nodulation (nodule number and nodule dry weight), increased plant growth, nutrient uptake and mycorrhizal infection in both uninoculated and inoculated seedlings of A. ferruginea but more pronounced in the inoculated seedlings. Phosphorus fertilizer application at 50kg/ha (l00mgTSP) gave significantly higher plant growth and arbuscular- mycorrhizal fungal infection whilst these parameters declined above l00kg/ha(200mgTSP). The outcome of this study indicates that arbuscular- mycorrhizal fungi differ in their effectiveness on indigenous Albizia species. In P-deficient soils it is possible to reduce the phosphorus fertilizer application with AM fungal inoculation and still maintain high productivity. Therefore in most tropical soils AM fungi strains may help plant growth and establishment on degraded soil or plants that cannot adequately meet their nutrient requirements.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the award of Master of Science degree in Agroforestry