Establishment and bioavailability of lead and cadmium in soils and Vernonia amygdalina at market gardening sites in Southern Benin

Abstract

Vegetables from market gardening sites are contaminated with lead and cadmium. Agricultural inputs such as fertilizer and contaminate from the environment are suspected of making these toxic metals bioavailable. The research aims to establish the parameter that makes lead and cadmium bioavailable in soils for Vernonia amygdalina at market gardening sites in Southern Benin. Different agricultureral inputs were used on market gardening sites in southern Benin on Vernonia amygdalina crops in a controlled environment. The impact of the inputs on plant growth by measuring stem length and leaf biomass was evaluated. The levels of lead and cadmium in leaves was determined using Atomic Absorption Spectrophometry. Fisher’s analysis of variance, Dunnett’s test showed that only the mixing of inputs had a positive impact on plant growth (significance p=0.05). Using plants that received no inputs as a reference, all other parameters contributed to an increase in both toxic metals. For Cd (chicken droppings ˂ urea ˂pesticides ˂contaminated water ˂mixture), and Pb (pesticides ˂urea ˂chicken droppings ˂ contaminated water ˂mixture). It would be very difficult to raise awareness against the use of agricultural inputs because of their positive impact on agricultural yield. The research concludes that lead and cadmium are bioavailable in soils for Vernonia amygdalina at market gardening sites.