Abstract

CORDOVA-BAUTISTA, Y et al. Detection of beneficial bacteria in soils with banana (Musa AAA Simmonds) cultivar 'Gran enano' and its potential to prepare a biofertilizer. Universidad y ciencia [online]. 2009, vol.25, n.3, pp.253-265. ISSN 0186-2979.

The densities of free living total N-fixing bacteria in soil down to a depth of 110 cm and in rhizospheric soils of banana plants established in a eutric Fluvisol, were evaluated. Soil samples were collected from the six horizons of the profile and from 30 rhizospheric sampling points (0-10 cm depth) randomly distributed throughout 10 000 m ². Populations of Azospirillum and Azotobacter were isolated at depths of 59 and 110 cm, respectively. The largest isolates were 42x10⁴ and 11x10⁵ CFU g^-1 of dry soil for Azotobacter and Azospirillum, respectively. Three isolates of Azospirillum and Azotobacter each were used in the formulation of sustained microbial inoculants in organic media (chicken manure, chicken manure + soil, rachis of banana raceme, rachis of banana raceme + soil) and in control soil. Two integrated bioassays with 10 treatments each were established for 60 days of incubation. Densities were counted on days 1, 30 and 60, and total nitrogen was quantified on day 60. Azospirillum grew best on rachis of banana raceme + consortium with 15x10⁵ CFU per gram of biofertilizer, whereas Azotobacter grew best on 63x10⁴ CFU per gram of the biofertilizer formulated with rachis of banana raceme + soil + consortium. The greatest total nitrogen content was 5.25% released into the soil with chicken manure and bioaugmented with the Azospirillum + Azotobacter consortium. However, the Azospirillum and Azotobacter populations decreased to 68x10⁴ and 20x10⁴ CFU g^-1 of biofertilizer, respectively.

Keywords : Azospirillum; Azotobacter; biofertilizer; total nitrogen.

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