Abstract

POSADA ALMANZA, RAÚL HERNANDO et al. Inoculum of Arbuscular Mycorrhizal Fungi on Brachiaria decumbens (Poaceae) Pastures in Valley and Hilly Terrain. Acta biol.Colomb. [online]. 2007, vol.12, n.1, pp.113-120. ISSN 0120-548X.

The diversity of factors influencing the distribution of arbuscular mycorrhizal fungi inoculum (spores and hyphae), plant species, pH, soil humidity, conductivity, P availability, nutrients and heavy metals have been reported. Reports are contradictory and mostly supported on data from temperate zones; under tropical conditions it is difficult to determine the edaphycal and environmental factors that stimulate inoculum production, and how it happens. Brachiaria decumbens is the dominant grass species in plain and hilly landscapes on the Amazonian piedmont of Colombia. There are few studies on its mycorrhizal relationships. In this study the spore density and external hyphae were determined in 26 B. decumbens pastures, on plain and hilly landscapes; simultaneously phosphorus availability (ppm), pH, and soil relative humidity (%) were measured. Spearman (ranks) correlations coefficients and nonparametric KruscallWallis one way ANOVA were performed and found that: the inoculum has a different distribution in plain and hilly, the spore densities were higher in hilly terrain than in plain soils, and the external hyphae were more homogeneous in plain than in hilly terrain. Phosphorus availability, pH and soil humidity have no effect on the density of inoculum of HMA.

Keywords : arbuscular mycorrhiza; inoculum; Amazon.

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