Growth
promotion of rice by phosphate solubilizing bioinoculants in a Himalayan
location
Three bacterial species, viz. Bacillus megaterium, B. subtilis and Peudomonas corrugata, originally isolated from temperate locations in the Indian Himalayan region, were examined for their growth promotion ability using both pot and field based assays. A local landrace of rice was used as test crop. The three bacterial species exhibited in vitro phosphate solubilizing activity in following order: P. corrugata > B. megaterium > B. subtilis. The bacterial treatments (broth based in pot and charcoal based in field experiments) resulted in improved plant performance. Out of the three treatments, B. subtilis gave best performance resulting in 1.66 and 1.55 fold increase in grain yield of rice in pot and field trials, respectively. Inoculations also stimulated the rhizosphere associated bacterial and actinomycetes populations and suppressed the fungal flora. Colonization of roots by mycorrhizal fungi improved in all the treatments. Out of the three bacterial inoculants, B. subtilis was the best in affecting these changes. Bacterial treatments also resulted in higher values for phosphorus in shoots and grains in inoculated rice plants. The study indicates that the stimulation of native bacterial flora, including mycorrhizae, in and around roots is one of the important parameters playing indirect role in improving the overall plant growth. The study suggests that charcoal based B. subtilis cultures can be developed as an efficient bioinoculant for rice fields in the mountains.