In this research study, we tested the possibility of using some biological treatments to hasten the degradation of waste tire rubber in soil and thus the release of zinc and sulfur. A zinc-deficient calcareous soil was collected for the experiment from Rudasht research field in Isfahan province, central Iran, and three rates of ground tire rubber (0, 150, and 300 mg/kg) were incorporated into the soils. The ground rubber was applied as 0.6 mm diameter particles. The Zn addition from the 150 and 300 mg kg -1 rubber was estimated 3.0 and 6.0 mg Zn/kg soil. Ground rubber contains very low levels ( 0.64 µg g -1 ) of Cd. Before adding to the soil, ground rubber was exposed to four microbial treatments including no inoculation, inoculation with R. erythropolis , inoculation with R. erythropolis + E. coli , and inoculation with R. erythropolis + E. coli + A. calcoaceticus. The inoculums used on the zero rubber treatment were the same amount (5 × 10 6 cells/ml) as added to the rubber before it was mixed with the soil in the rubber treatments. The soils were incubated at 25 0 C and their moisture was kept at 70% field capacity using deionized water. Sub-samples of soil were collected from each treatment at 1, 3, 6, and 10 weeks after inoculation and soil pH and DTPA-extractable concentrations of Zn, Pb, Cu, Fe, and Cd were measured. Results showed that application of ground tire rubber and microbial inoculation treatments caused reduction of soil pH and the magnitude of this reduction was increased over time. Addition of ground rubber in combination with microbial inoculation caused an increase in DTPA-extractable soil Zn and Fe. The increase in the DTPA-extractable Zn and Fe of rubber-amended soils was increased over time so that the highest concentration of available Zn and Fe was found at week 10. The microbial inoculation of soils by itself decreased pH and increased DTPA-Zn and Fe. The highest decrease in soil pH and increase in soil available Zn and Fe was achieved by application of 300 mg/kg ground tire rubber inoculated with R+E+A. After 10 weeks, the extractable-Cd and Pb concentrations in all un-amended and rubber-amended soils were below the detection limit of AAS. The result of the present study showed that the inoculation of ground rubber with the rubber-biodegrading bacteria species was effective to hasten the increase in DTPA-extractable Zn and Fe in the studied calcareous soil. The best microbial and rubber treatment of the first experiment was selected for the second experiment (pot experiment). Corn and sunflower were cultivated in 2 kg pots and 60 days after seeding, they were harvested. Shoot and root dry weight and the concentration of iron, copper, lead and cadmium was measured. Results showed that microbial inoculation of rubber powder increased zinc and iron concentration in plant shoots. Adding of rubber powder alone, increased the shoot concentration of zinc while it had no effect on shoots iron concentration. Key words: Ground tire rubber, Calcareous soil, Zn fertilizer, R. erythropolis , E. coli , A. calcoaceticus