Phytostabilisation of copper-contaminated soil in Katanga: an experiment with three native grasses and two amendments

This study evaluates the feasibility of using the grass species Rendlia altera, Monocymbium ceresiiforme, Cynodon dactylon, and amendments (compost and lime) for the phytostabilisation of soils contaminated by Cu in the province of Katanga (Democratic Republic of Congo). Species were grown on control and Cu-contaminated plots (artificially contaminated with 2,500 mg kg(-1) Cu) unamended (NA), amended with 4.5 kg compost m(-2) or 0.2 kg lime m(-2). R. altera was also grown on contaminated plots amended with 22.5 kg compost m(-2) or 1 kg lime m(-2). Plant survival, growth, and reproduction were monitored for two years. Cu-concentration in leaves of R. altera and M. ceresiiforme were analysed. pH and extractable Cu (0.01 M CaCl2) in soil were analysed in April 2007 and 2008. Results showed that R. altera seems to be the best candidate because of its highest survival on NA, followed by M. ceresiiforme, while liming was necessary to ensure survival of C. dactylon. Lime increased plant reproduction and reduced Cu accumulation in leaves compared to compost. However, higher survival and number of spikes of R. altera obtained in experiment 2 with 22.5 kg compost m(-2) suggest that lime x compost interactions should be investigated in further studies.