Cumulative Effect of Three-Year Application of Municipal Solid Waste Compost and Compost Accompanied with Chemical Fertilizers on the Concentrations of Some Heavy Metals in Various Organs of Rice Plant

In order to investigate the cumulative effect of three-year application of municipal solid waste compost (C) and the compost accompanied with chemical fertilizer (CF) on the concentrations of some heavy metals in various organs of rice plant، a field experiment with completely randomized design in three replications was performed in 2009. Treatments were as follows: Control (without C and CF)، CF (100 kg urea، 100 kg super phosphate and 100 kg potassium sulphate per ha)، 15، 30 and 45 tons of C without CF، 15، 30 and 45 tons of C with 25%، 50% and 75% CF. Results showed that application of compost in three years would increase the amounts of Ni، Pb، Cd and Cr in different organs of rice plant. Also، application of C accompanied with CF increased the amount of Ni، Pb، Cd and Cr in various organs of rice compared to C. The highest concentration of nickel and lead (9. 1 and 7. 8 mg. kg-1 respectively) were obtained in grains in 45 ton C + 50% CF per ha treatment. Meanwhile، the maximum content of cadmium in grain (1. 6 mg. kg-1) in 30 ton C + 75% CF ha-1treatment، and the highest amount of chromium in grain (1. 8 mg. kg-1) resulted from 30 ton + 25% CF ha-1treatment.