Natural compounds enhancing growth and survival of rhizobial inoculants in vermicompost-based formulations

The present study demonstrates the usefulness of natural microbial growth-promoting compounds for improving the stability and life of vermicompost-based (both granular and its aqueous extract) bioformulations. Granular vermicompost maintained the number of cells of Rhizobium meliloti Rmd 201 up to 5.9 x 10(8) after 180 days at 28A degrees C compared with 2.1 x 10(8) in charcoal (powdered), while aqueous extract of the vermicompost supported the 5.6 x 10(7) rhizobia numbers even after 270 days. The addition of 25 mu L/mL cow urine and 0.01 mM calliterpinone, a natural plant growth promoter, increased the rhizobia number significantly in granular vermicompost and its aqueous extract, respectively.