Selection and agricultural use of potential phosphate-solubilizing bacteria isolated from poultry slaughterhouse sludge in maize

In the farming, increasing demands for higher yields has put pressure on land resources which eventually increased demand for phosphate fertilizers (non-renewable resource), given that low availability of phosphorus in many soils is often compensated by the application high doses phosphate fertilizers. Complementary, studies have been made with a view to select phosphate-solubilizing bacteria. The purpose of his study was to: (i) isolate and characterization potential phosphate-solubilizing bacteria from sludge from the wastewater treatment plant of a poultry slaughterhouse; (ii) evaluate the ability of bacteria to solubilize phosphate rock and promoting plant growth. The bacteria were isolated in culture medium containing calcium phosphate. Morphological characterization consisted in cell shape, Gram staining and the characteristics of the colonies. To assess natural phosphate (NPh) solubilization, maize seeds were inoculated together with Araxá phosphate. The experiment consisted of 10 treatments: eight bacterial isolates + NPh, NPh and a control. The experiment was carried out in a greenhouse for 45 days, in a randomized block design, with six replications. The variables measured were the growth characteristics of the maize. Eight strains were isolated, all stained gram-positive, and 90% were rod-shaped and 10% coccoid-shaped. Inoculation with isolate LSOF-7 (Sphinghomonas sp.) combined with NPh induced increased maize dry matter by 20% compared to the treatment containing only NPh and by 67% compared to the control. It was concluded that sludge from wastewater treatment plants of poultry slaughterhouses contains bacterial strains with potential to phosphate-solubilizing and them also probably present promoting plant growth and promote maize plant growth.