Understanding the potential of kenaf in heavy metals contaminated soils

The increasing demand for biomass for the production of bioenergy is generating land-use conflicts which might be avoided through the establishment of dedicated energy crops on marginal land, e.g. heavy-metal contaminated land. Yet, heavy metals contaminated soils might induce the reduction of crop yields and the quality of agricultural products, desertification, and the loss of ecosystem services. Therefore, assessment of bioenergy from marginal land should take into account constraining factors, such as productivity and biomass quality. Hence, the aim of this work was to study the effects of soils contaminated with heavy metals (Chromium, Copper, Lead and Zinc) on growth and productivity of kenaf. The study was performed in a pot essay and the plants were tested in sandy soils and clay soils. The soils were artificially contaminated, and the concentrations chosen were based on the limits established by the Decree Law 276 of 2009 (Portuguese regulation that establishes the regime for the use of sewage sludge in agricultural soils)-Zn: 450 mg/kg; Cr: 300 mg/kg; Pb: 450 mg/kg and Cu: 200 mg/kg. Results indicate that all the contaminated soils affected the growth and yields of kenaf. Highest yield reduction was observed in sandy contaminated soils than in clay contaminated soils, although this trend was not statistically significant. Copper was the metal that affected most yields and growth of kenaf in clay soils. In sandy soils, it was chromium that affected most, yields and growth of kenaf. Overall, yield reduction due to heavy metals contamination was above 50%, which may hinder its economical exploitation. Biomass is being characterized to evaluate the phytoremediation ability of this cultivar to the heavy metals studied.