Nickel and chromium status in soil and rice under vermicompost treatment

In order to investigate the influence of vermicompost (VC) on the concentration of nickel (Ni) and chromium (Cr) in soil and rice this research was conducted as a split plot based on randomized complete block design with three replications in 2008. Main factor (fertilizer) was added to soil in 6 levels, 20 and 40 ton ha-1 VC, 20 and 40 ton ha-1 VC enriched with 50% chemical fertilizer (CF), CF (based on soil testing comprise 100 kg. ha-1 urea, 150 kg. ha-1 triple super phosphate and 100 kg. ha-1 potassium sulphate) and control. Sub plot, were considered application periods that comprise 1, 2 and 3 years application. Results showed that the maximum available Ni (2.20 mg kg-1) belonged to 3 years application of 40 ton enriched VC. In 3 continuous years application of enriched 20 and 40 ton ha-1 measured the highest available Cr (0.109 mg kg-1). The highest concentration of Ni in root belong to 3 continuous years application of 40 ton VC +50% chemical fertilizer that was about 63% more than control treatment. With application of 40 ton VC per hectare during 2 and 3 years, measured the maximum Ni concentration in grain with about 2 times of control treatment. Also, the most content of Cr in root (8.43 mg kg-1) and grain (4.25 mg kg-1) belonged to 3 years application of enriched 40 and 20 ton ha-1, respectively.