ABSTRACT

This work studied the biofertilizer potentials of Rhizobium leguminosarum and Pseudomonas aeruginosa on two common tropical vegetables plant Talinum triangulare (waterleaf) and Telfairia occidentalis (pumpkin). The test microorganisms were isolated from agricultural soils, characterised and identified. Each test organism was inoculated into carrier base material (activated charcoals) at three concentrations of 2.50×108 cells/kg, 5.0×108 cells/kg, and 7.5×108 cells/kg for each test vegetable. Controls of uninoculated sterile activated charcoal were set up for each vegetable as well as N.P.K fertilizer applied at rates of Treatment1 (2.50×108 cells/kg dose of the microbes with the carrier base material), Treatment2 (5.0×108 cells/kg dose of the microbes with the carrier base material), and Treatment3 (7.5×108 cells/kg dose of the microbes with the carrier base material) for each vegetable. Three growth performance indices considered for the evaluation of the biofertilizer potentials were plant biomass, plant height and mean leaf area measured after 28 days of cultivation. Result obtained show that there were significant variations in the impact of the test biofertilizer on the both vegetables. Pseudomonas aeruginosa increased the biomass of the vegetables by 100.54% to 142.87% in waterleaf and by 167.75% to 368.10% in pumpkin while Rhizobium leguminosarum caused increases of 107.77% to 286.78% (waterleaf) and 166.52% to 358.26% (Ugu). These were on the average, higher than the measures obtained with N.P.K fertilizer which ranged from 12.78% to 206.69% (waterleaf) and 52.07% to 376.13% (Ugu). Similarly increases were recorded in the mean leaf areas of the vegetables. In the P.aeruginosa innoculated waterleaf, the increase was from 73.03% to 221.16% and for Ugu, it was 92.34% to 208.06%. The corresponding increases in the Rhizobium innoculated vegetables were 172.17% to207.01% (waterleaf) and 23.29% to 164.27% (Ugu). This also varied from the values recorded from the chemically fertilized vegetables; 8.90% to 222.16% (waterleaf) and 48.27% to 187.57% (Ugu). Conversely, much lower impacts were recorded in the plant height of the biofertilized vegetables with values of 4.04% to 30.58% and Pseudomonas and Rhizobium innoculated waterleaf and Ugu recorded increase with the value of 0% to 20.06% respectively. The values for Rhizobium innoculated plants were 36.35% to55.05% (waterleaf) and 13.77% to 36.42% whereas the chemically fertilized vegetables recorded height increases of 0% to 8.09% in waterleaf and 23.33% to 168.53% in Ugu. It was concluded, on the basis of findings recorded in this work, that the two test bacteria (Pseudomonas aeruginosa and Rhizobium leguminosarum), have great potentials for utilization as fertilizers. Since the success of this research work has been established, there is need for tests on these and possibly other organisms on other vegetable types as well as a determination of optimal environment with respect to field validation of this success recorded at in house trials. This is recommended for future works and for trail field validation of this important research finding.