Effect of iron slag and municipal sewage sludge compost addition to soil on decreasing cadmium availability in pot marigold

Interaction effect of heavy metal and some metals such as Fe can affect soil heavy metal availability. Thus, this research was conducted to investigate the effect of Arak municipal sewage sludge compost with iron slag on decreasing cadmium uptake by pot marigold. : Treatments were consist of applying enriched Arak municipal sewage sludge compost (0, 15 and 30 t ha-1) with 0 and 5% pure Fe from iron slag of Mobarakeh Steel Complex in a polluted soil (0, 5, 10 and 15 mg Cd kg-1 soil). After 60 days, soil physic-chemical properties and root and shoot Cd concentration of pot marigold was measured and the least significant difference (LSD) statistical analysis was used to determine the differences between the means (p=0.05). Increasing the loading rate of Arak municipal sewage sludge compost from 0 to 15 and 30 t ha-1 in a Cd polluted soil (10 mg Cd soil-1) caused a decreasing in Cd availability by 15 and 35 percent, respectively, while the Fe availability increased by 5.6 and 8.4 times, respectively. Similar to this result, root and shoot Cd concentration was decreased by 24 and 18%, respectively. The result of this study showed that applying sewage sludge compost enriched with 5% Fe pure can probably affect soil physico-chemical properties that increasing soil and plant Fe availability and thereby, decreasing Cd availability.