Zinc-solubilizing Pseudomonas strains accelerate the release of zinc from tire waste powder and improve maize growth and zinc nutrition

Abstract

Car tires contain considerable amounts of zinc (Zn), hence, tire waste materials can be a potential source of Zn for plants. The present study was conducted to investigate the potential of Zn-solubilizing Pseudomonas strains to release Zn from tire waste powder (TWP) in a liquid medium and soil. A pot experiment was also conducted to investigate the effects of TWP and Pseudomonas strains on growth and Zn nutrition of maize. Fourteen bacterial strains were grown in liquid Pikovskayas (PVK) medium supplemented with TWP, and ten superior Pseudomonas strains with high Zn solubilization activities were selected for the subsequent Zn kinetics study. In the liquid PVK medium supplemented with TWP, the concentration of Zn was higher in all inoculated treatments compared to the non-inoculated control in a time-dependent manner. Likewise, in the TWP-treated soil, the concentrations of DTPA-extractable Zn were significantly higher in inoculated treatments than those in the control treatment in all incubation times. Individual application of Pseudomonas strains or TWP treatments significantly increased the shoot biomass of maize plants. Furthermore, the combined application of Pseudomonas strains and TWP led to higher shoot Zn concentration of plants as compared to the individual applications, reflecting enhanced Zn availability in TWP-treated soil upon bacterial inoculation. These findings indicate that co-application of effective Pseudomonas strains (with high Zn solubilization activity) with TWP in soils can lead to higher Zn bioavailability for plants, i.e. indicating the potential of TWP as a slow-release Zn fertilizer for crops.