Effects of Different Amendments on Fractions and Uptake by Winter Wheat in Slightly Alkaline Soil Contaminated by Cadmium and Nickel

Abstract

The effects of a single application of three amendments (biochar, lignite, and chicken manure) on the fraction transformations of soil Cd and Ni and uptake by winter wheat are reported to provide reference for passivation and the remediation of heavy metals in soil. Field experiments were conducted to investigate the effects of different passivators on the forms of Cd and Ni in soils at different growth stages of winter wheat, and to analyze the contents of Cd and Ni in different organs of wheat. The results showed that biochar increased soil pH and that lignite reduced soil pH, but not significantly. Chicken manure significantly reduced soil pH at booting and mature stages, and decreased by 0.23 and 0.20 pH units, respectively. The single application of biochar, chicken manure, or lignite did not reduce the exchangeable Ni content significantly, whereas the effect on the exchangeable Cd was significant. Lignite 2% treatment had the greatest decrease in exchangeable Cd at different growth stages of wheat, which were 30.50%, 43.34%, and 31.20%, respectively. The contents of Cd and Ni in the shoots and underground parts of wheat decreased to some extent, and the extent of these decreases increased with the increase of passivator dosage. The decrease of Cd content in wheat roots was the largest under the treatment of lignite 2% at different growth stages, reaching 38.35%, 58.00%, and 50.20% respectively. The greatest decline of Ni content in wheat roots occurred in the lignite 2% treatment at the booting (41.33% decline) and mature stages (51.35%). All the three amendments reduced the availability of Cd and Ni in slightly alkaline soil, and the passivation effect on Cd was better than that of Ni. All three amendments also effectively reduced the content of Cd and Ni in different organs of wheat plants in different growth period. The order of decreasing effect of Cd in wheat organs was lignite > biochar > chicken manure at the same dose of these three passivators.