Establishing Cynodon dactylon on mining tailings and mining-impacted soil of a copper–cobalt mine in the Democratic Republic of the Congo

Abstract

Mining for copper and cobalt generates extensive mounds of removed topsoil and subsoil, and tailings with toxic levels of copper and cobalt. The threat of soil erosion in a high rainfall regime can be countered with rapid establishment of a sod-forming grass, such as Cynodon dactylon, that covers and binds the soil. An experiment was initiated in early 2013 to investigate whether planting vegetative material (plugs) was more effective than sowing of seed, and whether soil amelioration (fertilisation) was necessary on a substrate-specific basis. The experiment was assessed at the end of May 2013. Aerial vegetative cover was correlated with above-ground dry mass. Planting of plugs in combination with fertilisation was overall the most effective. On tailings, seed without fertilisation was a complete failure and fertilisation was essential for growth of plugs. Fertilised plugs resulted in a high density of stolons but fertilised seeds did not, although the response was delayed on tailings. Once phyto-stabilisation has been achieved, C. dactylon might serve as a nursery bed for establishing locally adapted cuprophytes of conservation significance.