VASSILEVA, MARÍA, NIKOLAY VASSILEV,JOSÉ-MIGUEL BAREA & ROSARIO AZCÓN.
Departamento deMicrobiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Prof. Albareda 1,18008 Granada
A series of micro cosmos experiments were carried out aimed at evaluating the effectiveness of a bacterial inoculant based on viable cells of a phosphate-solubilizing Enterobacter sp., encapsulated in agar and calcium alginate. This inoculant was introduced into a soil deficient insoluble P in which either mycorrhizal or non-mycorrhizal plants were grown. In a first experiment, crushed agar beads, containing bacterial cells, and free cells, were inoculated in the rhizosphere of non-mycorrhizal onion plants. Both treatments improved similarly plant growth and P uptake. In a second experiment, the effect of calcium alginate, skim-milk amended cell-gel beads was assessed on both non-mycorrhizal and mycorrhizal lettuce plants grown in soil amended with rock phosphate. In general, both free and encapsulated Enterobacter sp., improved the growth and P uptake by non-mycorrhizal plants but encapsulated-cell formulation caused better plant response. Enterobacter sp. cells increased plant P uptake in all cases but mycorrhizal inoculation enhanced such beneficial effect, particularly when the bacterial inoculum was formulated as encapsulated cells. In fact, the combined inoculation of encapsulated bacterial cells and G. deserticola provided the best microbial inoculum since it increased plant growth by 96 %, as compared to the non-inoculated control.