- Raymond A. Wuana1*, Phoebe A. Mbasugh2, Moses S. Iorungwa
- Analytical and Environmental Chemistry Division, Department of Chemistry, Federal University of Agriculture, Makurdi, 970001, Nigeria
- Department of Chemistry, Benue State University, Makurdi, 970001, Nigeria
The effects of heavy metal contamination and manure amendment in soil on the growth of green Amaranthus hybridus were studied by pot experiments. A mineral soil was stressed with different doses (100 – 500 mg kg-1) of Cu and Pb using a binary mixture of the metal nitrates and/or amended with poultry or swine manure (at 10:1 soil:manure ratio).
A. hybridus was sown and monitored for changes in growth rate, above-ground dry biomass and tissue Cu and Pb concentration for 49 days. A. hybridus was seemingly intolerant to metal stress as the plants exhibited yellowish appearance, stunted growth and decreased biomass at elevated metal doses in soil, though with reduced severity upon manure (especially poultry) amendment.
Growth profiles were sigmoid at lower metal doses (0 – 300 mg kg-1) but plateau-like at higher doses (400 – 500 mg kg-1). Tissue Cu and Pb increased linearly as metal doses in unamended soils and non-linearly in manure-amended soils. Soil-to-plant transfer factors, f (%), indicated that Cu (11.2 ≤ f (%) ≤ 41.1) was more phyto available to A. hybridus than Pb (8.4 ≤ f (%) ≤ 17.0).
Step-wise modeling of tissue Cu and Pb concentrations from soil pH, organic matter, plant available and pseudototal metal content by multiple regression analysis suggested that the models were more reliable with plant available metal as a covariate than pseudototal metal content.
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