Comparing the growth and yield of kenaf (Hibiscus cannabinus L.) produced in two different climatic types in soils contaminated by zinc, copper, chromium and lead

Soil is an important natural resource for agriculture and deserves special attention to possible problems that may arise. Heavy metal contamination of the soil can cause serious problems for the ecosystem in general, with consequent impact on water resources, soil quality, crop yield and human health due to the potential for heavy metal bioaccumulation in the different trophic levels of the food chain. Remediation of heavy metal contamination in soils can be done by using crops that have potential of growth and biomass production in marginal soils. The main objective of this work was to compare the growth and biomass production of Kenaf (cultivar H328, developed by IBFC in China) in soils contaminated by zinc (Zn), copper (Cu), chromium (Cr) and lead (Pb) in two different climate types (Tropical climate and Mediterranean climate). The study was performed in a pot essay and the plants were tested in 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 the growth in Mediterranean climate contaminated soils was more affected than in tropical climate. On average, the yields in Mozambique were 4900 g/m2, and in Portugal, merely 107 g/m2. Characterization of biomass indicate that kenaf can phytoextract zinc, copper, chromium, and not so much lead.