Residual bioavailability of nickel in nickel spiked sandy loam soil: Impact on swede rape (Brassica napus L.) growth and uptake of micronutrients

Abstract

In screenhouse experiment, a sandy loam soil (Typic Ustipsamment) was spiked with six levels of nickel (Ni) viz. 0, 5, 10, 25, 50, 100 mg kg−1 soil to investigate residual bioavailability of Ni and its impact on Swede rape grown after rice. The residual effect of Ni was investigated on growth of swede rape and uptake of micronutrients by it. Swede rape [Brassica napus (L.) Czern.] was grown for 60 days for dry matter accumulation, content of nickel and micronutrients. A linear and significant decrease in dry matter yield (DMY) was observed with the residual effect emanating from each successive level of Ni contamination except for that observed under 5 mg kg−1 Ni spiking. Maximum reduction in DMY (50%) was observed at 100 mg Ni kg−1 soil contamination level as compared to control. Nickel uptake by Swede rape increased substantially from 15.3 pg pot−1 in control to 397.8 pg pot−1 at 100 mg Ni kg−1 soil. Nickel spiking reduced the concentration of micronutrients in Swede rape, but significant reduction occurred only for iron at levels higher than 10 mg kg−1 soil. However, the uptake of iron, manganese, and zinc registered a significant decline at 5 mg Ni kg−1 soil and successive higher rates. Even after the harvest of Swede rape, 14.2 mg Ni kg−1 soil remained in the soil spiked with 100 mg Ni kg−1. This suggests that several cropping cycles would be required to make a contaminated soil safe for cultivation.