Accumulation of millions of worn automotive tires poses a considerable environmental problem. The annual production of scrap tires throughout the world is estimated at 1000 million, representing a significant treatment and disposal problem. As an important part of the solid waste stream in today’s society, worn tires have traditionally been discarded in landfills or stored in stockpiles. Over the past several decades, however, innovative alternatives to disposal have been developed, partly as a result of high tipping fees charged by landfill operators. In general, automobile tires consist of rubbers (50%), carbon black (26%), metal codes (10%), and compounding additives like zinc oxide and stearic acid (6%), and bead wires (5%). It seems that waste tire is appropriate for using as a soil amendment in sport fields. This residue contains high amount of Zn that causes the possibility of its using as a Zn source for crops in agricultural lands. The aim of this study was to investigate the effect of using crumb waste tire as a soil amendment on some soil quality indices. A fine loamy, mixed, thermic, Typic Haplargid soil was selected in Lavark research farm, Isfahan University of Technology. A factorial experiment with a randomized complete block design with two sizes of waste tire chips (1-2 and 3-5 mm) at three application rates (5, 10, and 20 Mg ha-1) in triplicates was used. An additional untreated control soil was used. Waste tire chips were added to the soil layer on May 2007 and thoroughly mixed with the surface (0-30 cm) layer. Eight months after application of waste tires, soil samples were taken from each plot and analyzed for pH, EC, total N, organic carbon, C: N ratio, DTPA-extractable Cd, Pb, Fe, Cu, and Zn. Selected physical (soil bulk density, resistance to root penetration, and MWD) and biological (soil respiration) properties were also determined. The results showed that addition of crumbed used tire, regardless of size and rate of application, had no significant effect on measured soil physical properties. Also, waste tire application had no significant effect on the soil pH, EC, total N, Cd, Fe, and Cu concentration. A significant improvement in the soil hydraulic conductivity was found in the plots that had revived waste tire chips in comparison with the plots that had not received waste tires. The DTPA-extractable Zn and C: N ratio significantly increased as a result of using waste tires in the soil. A significant interaction was found between the size and amount of waste tire applied on the DTPA-Zn. Used tire chips in both three sizes significantly increased soil organic carbon content. The results indicated that waste tire application in different sizes and application rates could not greatly affect measured soil physical properties in short time while it can be used as a good source of Zn for crops with low impurity of Cd. Further investigation is needed to find out other
