INFLUENCE OF FOUR BACILLUS STRAINS, ISOLATED FROM CALCAREOUS SOILS, ON PHOSPHATE SOLUBILIZATION
SVETLANA GEORGIEVA BRATKOVA*, ANTONIYA MITEVA KAISHEVA, VIKTORIYA TAVIT MANUKYAN
Department of Engineering Geoecology, Faculty of Geoexploration,
University of Mining and Geology “St. Ivan Rilski”, Sofia, Bulgaria
*Corresponding author: s_bratkova@yahoo.com
Keywords: Bacillus, calcareous soils, phosphate solubilization, IAA, cress
Abstract: The phosphate solubilization by four strains belonging to the species В. subtilis and B. amiloliquefaciens were studied. The strains were isolated from rhizosphere of Cichorium intybus (Common chicory), inhabiting calcareous soils. The phosphate solubilizing activity was determined by using Pikovskaya’s medium. The concentration of dissolved phosphate increased by 28 to 56 mg/l for different strains. Also, all four strains produce Indole-3-acetic acid. The effect of strains on growth of Lepidium sativum L. (Cress) in vivo was evaluated in pot vegetative experiments. Two type of substrates were used: perlite and perlite mixed with 0,1% Fe3(PO4)2. In the first case the plants are fed with a nutrient solution which contains all required nutrients. The nutrient solution for plants, growing in perlite mixed with Fe3(PO4)2 didn’t contain any source of phosphorous. The fresh and dry shoot weight of treated plants in both experiments were above those of controls by 8 to 50%.