Ex-situ evaluation of cactus pear (Opuntia ficus-indica): establishment on amended mine tailings

Abstract

In Chile, mining operations produce a lot of solid waste that is piled up (tailings); there are currently about 870 deposits, of which 746 are abandoned. In the semiarid Mediterranean climate of north-central Chile, the fine particles of dried tailings are exposed to physical agents such as wind and short, heavy rains, which can disperse them to the environment, contaminating waterways and surrounding soils. Cactus pear [Opuntia ficus-indica (L.) Mill.] cultivation could be an option for the phyto-stabilization of post-operative tailings in arid and semiarid zones, as its biomass can be used for clean energy production (among other productive uses). The present study evaluated the establishment of cactus pear on tailings amended with goat manure and mine leaching gravel at different rates. The experiment was conducted for 20 weeks under controlled laboratory conditions. Physical and chemical characteristics of the substrates and chemical characteristics of soil solution were determined. Additionally, both aerial and root biomass production and metal (Cu, Zn and Fe) concentration in roots and shoots were measured. The results indicated that application of both goat manure and mine leaching gravel increased the rooting capability of cactus pear on mine tailings. Even though differences in aerial biomass production were found between controls and the treatments, it is not possible to state that the application of these amendments results in increased production over a short period. Goat manure and mine leaching gravel applications decreased the bioavailability of mineral elements, reducing their translocation to aerial structures; however, they were not very effective at decreasing absorption of Cu by roots. It was not possible to ignore the possible external contamination of root tissues by metals. Salinization problems were detected in treatments in which goat manure was added, which affected root growth.