Salt tolerant bacterial inoculants as promoters of rice growth and microbial activity in coastal saline soil

Abstract

Salinity stress is one of the major abiotic stresses to rice crop production in coastal saline soils. The aim of the present investigation was to study effect of salt tolerant microbes and organic matter supplementation on rice plant growth and soil chemical and biological properties in coastal saline soils under pot condition. Three microbial inoculants-Pseudomonas multiresinivorans, Microbacterium esteraromaticum, and Bacillus subtilis individually and their consortium with amended farmyard manure (FYM) were compared against untreated control and FYM without the microbial inoculant. The treatments with combined application of B. subtilis with FYM and consortium with FYM were the best performers. Highest root fresh (67.8 g) and dry (13.9 g) weight and root volume (113 ml) were recorded in treatment with Bacillus and FYM. FYM caused 37.6, 63 and 83.4 percent increase in root volume, root fresh weight and dry weight respectively over treatment with Bacillus only. A similar trend was observed for consortium and consortium with FYM. Consortium with FYM caused significantly (p less than 0.01) highest shoot fresh (21.5 g) and dry (8.11 g) weight. This treatment also showed highest phosphatase (105 mu g PNP g sup(-1) soil day sup(-1)) activity, soil microbial biomass carbon (2985 mu g C g sup(-1) soil) and soil microbial biomass carbon as a fraction of soil organic carbon (0.3 percent). Thus, combined application of salt tolerant microorganisms and organic amendment helps rice plants alleviate salt stress and improves plant growth. Furthermore, evaluation of these microorganisms under field conditions needs to be undertaken through systematic experimentation.