Bioavailability of zinc and lead from a contaminated soil amended with pine bark-goat manure compost

ABSTRACT

The distribution in soil and plant uptake of zinc (Zn) and lead (Pb) as influenced by pine bark-goat manure (PBG) compost additions were investigated from the soils artificially contaminated with Zn or Pb ions using maize (Zea mays L.) as a test crop. Soils were amended with four rates of pine bark-goat manure compost (0, 50, 100, and 200 tons ha⁻¹) and four rates (0, 300, 600 and 1200 mg kg⁻¹) of Zn or Pb. Maize was planted and grown for 42 days. At harvest, plants samples were analyzed for Zn and Pb concentration. Soils samples were analyzed for pH, extractable and diethylene triamine pentaacetic acid (DTPA) extractable Zn and Pb. Extractable Zn and Pb was lower in PBG compost amended soils than in unamended soils and steadily declined with increasing amount of compost applied. The extractable fraction for Zn dropped by 62.2, 65.0 and 44.6% for 300, 600 and 1200 mg Zn kg⁻¹, respectively when 200 t ha⁻¹ of PBG compost was applied. Metal uptake by maize plants were directly related to the rate of applied heavy metal ions with greater concentrations of metals ions found where metal ions were added to non-amended soils.

KEYWORDS:

• Bioavailability
• pine bark-goat manure compost
• heavy metals

Acknowledgements

We acknowledge with gratitude The Director, Kenya Agricultural Research Institute for granting study leave to the first author. Special appreciation is extended to Mr. Mupondi, L.T for the preparation and characterization of the compost used in this study.

Funding

The authors are grateful to the University of Fort Hare and the National Research Foundation of South Africa for granting a postdoctoral fellowship to the first author.