Mycorrhiazal association in relation to soil properties and plant species density in Sidama of Southern Ethiopia

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs) (villages within districts where 300 to 500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity of AMF based on selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total colonization was recorded for shade trees Millettia ferruginea (84%) and Erythrina brucei (80%) followed by intercropped perennial crops Ensete ventricosum (86%), Catha edulis (85%) and Coffea arabica (80%) and the lowest percentage colonization was recorded for Rhamnus prinoides (53%) and Colocasia esculenta (52%). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066±19.33) and Catha edulis (1054±53.12) and the lowest spore density was recorded for Dioscorea alata (100.00±2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P<0.05 level.