Development and evaluation of phosphate solubilising microbial inoculants for fodder production in problem soils

Abstract

A total of 70 phosphate solubilising bacterial (PSB) isolates and 90 phosphate solubilising fungal (PSF) isolates were obtained from 145 rhizosphere and nonrhizosphere soil samples collected from different parts of India representing problem soils. They were screened for P solubilisation, plant growth promoting substances (IAA, GA) production and abiotic stress (salt and acid) tolerance and plant growth support with 50% reduction in P fertilizer. Ten phosphate solubilising microorganisms (PSMs) were selected based on their abiotic stress tolerance ability and their plant growth promoting potential in normal and problem soils in vitro. They were further evaluated for their efficiency in enhancing biomass of fodder cowpea (cv. BL 2) in normal soil under field condition. The treatments details were T1 : Control [Uninoculated (UIC) + unfertilized]; T2 : RDF (UIC + 100% RDF); T3 : PSF12(1); T4 : PSF47(1); T5 : PSF48(3); T6 : PSF48(4); T7 : PSF131(1); T8 : PSB9a(2); T9 : PSB26(2); T10: PSB68(3); T11: PSB103(1) and T12: PSB136(1). But treatments T3 to T12 had PSM inoculated seeds with 100% of N and K, and 50% of recommended dose of P. The experiment was conducted in randomized block design with 3 replications. PSB136(1) recorded about 5 t/ha green fodder yield higher than RDF (20.2 t/ha) and maximum dry fodder yield (6.3 t/ha) followed by T5 , T6 and T10 which were at par with RDF in normal soil. However maximum seed yield was recorded by T7 (3.78 q/ha). Treatments were non-significant for the plant height, root length and nodule count. The same experiment was replicated for cowpea (BL-2) production in acid soil (pH 5.4). PSB103(1) recorded maximum GFY and DFY (35.2 and 8.1 t/ha) followed by PSB136(1), PSF12(1), PSB26(2) which were at par with RDF (32.0 and 7.4 t/ha). Higher crude protein yield and CP content were also recorded, which were at par with RDF and but significantly more than control (781 kg/ha and 12.7%, respectively). It was concluded that selected PSMs could be used as suitable phosphate solubilising bioinoculants in fodder crops.