Perlite as a carrier for bacterial inoculants

Growth and survival of Rhizobium leguminosarum bv. phaseoli, R. tropici, Bradyrhizobium japonicum and Bacillus megaterium in peat and perlite-based inoculants were evaluated. In general, survival was similar for all strains in both carriers. Better survival was observed when inoculants were maintained at 4°C compared to 28°C. Studies with two different stickers suggested the existence of interactions between carriers and adhesives and showed that combination of a sucrose adhesive with the perlite carrier gave better survival of bacteria on seeds. Bean and soybean field experiments indicated that perlite-based inoculants produced similar number of nodules, nodule dry weight, crop yield and nitrogen content, as peat-based inoculants.