Effect of Organic Fertilizer on Cadmium Uptake by Rice Growing in Contaminated Soil

The effects of organic fertilizer on the cadmium uptake by rice growing in contaminated soil were studied in a nursery experiment. The types of soil used were uncontaminated and fertilizer free, contaminated and fertilizer free, contaminated and organically fertilized at 3.25 ton/ha, contaminated and organically fertilized at 6.25 ton/ha and contaminated and organically fertilized at 12.5 ton/ha. Four varieties of Thai rice, Khao Dawk Mali 105 (KDML105), RD6, Phitsanulok3 and Niaw San-Pa-Tong, were planted in each container. Samples of the soil and plants, consisting of the above-soil growth, below-soil growth, husk and grain, were taken every 30, 60, 90 and 120 days to determine the amount of cadmium uptake in each part. After 120 days, the results showed that the Niaw San-Pa-Tong variety grown in the contaminated soil with organic fertilizer at 12.5 ton/ha displayed the lowest accumulated cadmium uptake in the above-soil parts, at 4.1 mg/kg, whereas Phitsanulok3 grown in the contaminated soil and fertilized at 6.25 ton/ha showed the lowest cadmium uptake in below-soil parts, at 9.19 mg/kg. The lowest level of cadmium deposited in the grain, at 0.06 mg/kg, was found in the Phitsanulok3 cultivar growing in the contaminated soil fertilized at 12.5 ton/ha. With regard to the accumulative cadmium uptake, we propose that a concentration of organic fertilizer ranging between 6.25-12.5 ton/ha produces the best results.