Abstract

MORATTO, Claudia; MARTINEZ, Luis Joel; VALENCIA, Hernando  and  SANCHEZ, Jimena. The effect of land use on phosphate solubilising fungi and diazotrophic bacteria on the bleak uplands of páramo of Guerrero, Cundinamarca department. Agron. colomb. [online]. 2005, vol.23, n.2, pp.299-309. ISSN 0120-9965.

The effect of land use on phosphate-solubilising fungi (PSF) and nitrogen-fixing bacteria (NFB) populations was investigated. The soils selected were that from two potato crop varieties ['Parda Pastusa' (p) and 'Pastusa Suprema' (s)], agricultural soil at present lying fallow (d) and soil from beneath forested areas (b). Active fungi (14 genera) and sterile chlamydospore -and basidiomycete-like mycelia were isolated by washing the soil. Mucorales presented low incidence in cultivated soil, except for Mucor racemosus. Circinella, Mucor and Zygorrhynchus genera were predominant in forest (b) soil. The most efficient calcium phosphate solubilisation assessed in liquid medium was registered for Trichocladium canadiense, Mucor sp1 and Penicillium sp2 isolated from (d) and (b), (>15% P- solubilisation). No correlation was found between fungal biomass and P solubilising efficiency; however, there was negative correlation with pH. Qualitative differences were found between land use and PSF, while significant differences were registered between NFB and bacterial populations. Azospirillum, Beijerinckia, Pseudomonas and Derxia dizotrophic bacterial species were isolated. The study revealed the functional groups' sensitive response to the microorganisms being evaluated, according to land use.

Keywords : soil microorganisms; active mycelium; soil quality bioindicators.

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