Abstract
Tie dye is an age long industry in West Africa and a major economic activity of people in Abeokuta. This industry generates a large volume of dyestuff waste that ends up in natural water courses. In Abeokuta western Nigeria this dye-laden waste water discharged into streams is used as irrigation water for the production of Amaranthus cruentus L. Hitherto, the effects of dyestuff on growth factors of the plant has not been evaluated. This paper investigates the effect of dyestuffs (Indigo, Vat Blue RS-AF, Vat Yellow GCN and Bordeaux RR) on the growth, yield and metal uptake of Amaranthus plants. The experiment was laid in a split-plot design with dyestuff as main plots and concentration as sub-plots. Solutions of the dyestuffs were applied at the rate of 0, 100, 200, 300, 400 and 500 mg/L and replicated three times. The plants were pre-grown with fresh water for one week and later irrigated with 200 ml of treatments three times weekly for another five weeks. Results of chemical analyses of dyestuffs showed that they contain plant nutrients and heavy metals. Among the rates, treatment with 100 mg/L concentration gave the largest shoot dry matter yield (DMY) and this was in the order Vat Yellow > Bordeaux > Vat Blue > Indigo. Dye concentration above 100 mg/L significantly (p < 0.05) decreased number of leaves, plant height, stem girth and DMY. Tissue heavy metal accumulation increased with dye concentration. Shoot accumulation of Manganese, Iron, and Zinc exceeded 0.3 mg/kg allowable limits set by World Health Organization, Food and Agricultural Organization and Federal Environmental Protection Agency in vegetables. Copper and Chromium levels were, however, within allowable limits. The use of dye-laden wastewater for irrigation of crops potentially constitutes environmental hazard in the food chain and poses a danger to human health.
