Application of sheep manure and potassium fertilizer to contaminated soil and its effect on zinc, cadmium and lead accumulation by alfalfa plants

In Jebel Ressas mining area (Southern of Tunisia), the dispersion of particles that contain Pb, Zn and Cd results in the contamination of the surrounding agricultural soils. These soils have high concentrations of Pb (970 mg kg−1), Zn (9641 mg kg−1) and Cd (53 mg kg−1). This glasshouse study examined the effect of application of fertilizers, i.e., organic fertilizer as local sheep manure and inorganic fertilizer as potassium chloride (KCl), on the growth, uptake and translocation of Cd, Pb, and Zn of alfalfa (Medicago sativa L.) grown on a contaminated soil. Obtained results showed that alfalfa could tolerate high Cd, Pb, and Zn concentrations in soil and had very good growth performance. Regarding to biomass generation it was observed, in every case, that plant growth is not affected in the treated soil compared with blanks sown in an untreated control soil; improvement ranged from 80% for the KCl to 97% for sheep manure. Application of sheep manure increased electrical conductivity and reduced DTPA-extractable metal concentrations in the soils. But KCl fertilizer favored their accumulation in plants. So, KCl could be a useful amendment for phytoextraction of metals by accumulator species, while sheep manure can be very useful for phytostabilisation.