Abstract

BROWN, George G.; KRETZSCHMAR, André  and  PATRON, José C.. Modification of root density in pot experiments with two tropical earthworm species. Acta Zool. Mex [online]. 2010, vol.26, n.spe2, pp.241-259. ISSN 2448-8445.

Three greenhouse experiments were performed to assess the role of two common tropical geophagous endogeic earthworm species, Pontoscolex corethrurus and Polypheretima elongata, on root density of several plant species in two soil types, a clayey Andosol and a sandy Alfisol, from Veracruz, Mexico. The equivalent of about 12 kg dry soil were placed into 20 l plastic pots and 3-14 individuals were inoculated to pots planted with common beans (Phaseolus vulgaris), Brachiaria decumbens pasture grass under four P fertilization regimes (0, 1.6, 8.4 and 10 kg P ha^-1) and maize (Zea mays) with or without surface residues. Pots received only one species of earthworms (either P. corethrurus or P. elon-gata). At harvest, the pots were cut in half and a transparent plastic sheet (overheads) used to draw root and earthworm structures (burrows, casts) in vertical and horizontal (every 5 cm) planes. The drawings were scanned, binarized and submitted to image analysis techniques to determine the density of roots, casts and burrows. Root density was generally higher and there was a trend for more even distribution of roots in the soil, both horizontally and vertically, in the presence of earthworms. Nevertheless, few relationships were observed between root density and shoot biomass or the density of earthworm casts and burrows. A more diffuse (less aggregated) root distribution due to earthworms may aid plants in resistance to stress, although the induced changes in the root system may not necessarily lead to greater yields

Keywords : Rhizosphere; earthworm-plant interactions; plant growth; root distribution.

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