Potency of nitrogen fixing bacteria isolated from POME disposal pond and their effect on the growth of Caesalpinia pulcherrima (L) Sw

Nitrogen fixing bacteria (NFB) play an important role to promote plant growth through nitrogen fixation and IAA hormone production. The objective of this research was to obtain the functional bacteria (nitrogen fixing bacteria) isolated from POME disposal pond that show the ability in nitrogen fixation and the potential as plant growth promoting rhizobacteria (PGPR), as well as to investigate the potential of these bacteria through in vitro and in vivo growth of Caesalpinia pulcherrima (L) Sw, and its effect on bacterial populations in media contaminated by POME. In vitro plant growth promoting activity characterization included N-fixing activity, Indole Acetic Acid production, and C. pulcherrima germination (inoculant + POME). In vivo plant growth promoting activity used sterile sand inoculated with NFB and watered with POME, whereas the control was not inoculated and watered with aquadest. Five strains were found as potential PGPR, namely Azotobacter sp., Azospirillum sp1-3., and Rhizobium sp. In addition, Azospirillum sp.1 is the best PGPR that produced highest seed vigour index (SVI), seed germination in vitro, and seed germination in vivo respectively. Azospirillum sp. 1 and Rhizobium sp. have the ability to promote growth of C. pulcherrima in vitro and in vivo with bacterial populations as much as 10⁷cfu mL⁻¹ in POME contaminated media. The bacteria and C. pulcherrima are potential for reclaiming infertile soil.