A bioassay of mine-affected soils and ameliorants in semi-arid rehabilitation

Abstract

Global restoration is a priority given the onset of the United Nations’ decade for restoration. It is challenging to restore arid lands from mining impacts, especially where topsoil deficits exist. Successful rehabilitation is essential for alternative land use after mining. This bioassay aimed to establish whether and why some combinations of iron ore mine-affected soils and ameliorants are more effective in promoting plant growth than others. We examined the responses of one thousand radishes (Raphanus sativus) to five mine-affected soils and four soil ameliorations (soil improvement using fertiliser and organic matter) over two different seasons (early and late rainy seasons). We found that soil characteristics affected plant production regardless of amelioration and that some soil/amelioration combinations were significantly better than others. Topsoil ameliorated by moderate fertiliser application produced the best results. Waste rock could support germination and plant production when ameliorated with certain organic compost and fertiliser combinations. Untreated mine-affected soils had low to no plant production. Plant responses to the different soil/amelioration combinations were affected by season. Our findings suggest that area-specific bioassay investigations and their results could improve management decisions to achieve rehabilitation targets for mine-affected soils.

Keywords:

• mining rehabilitation
• radish trials
• slow-release fertilisers
• topsoil
• waste rock

Acknowledgements

The authors thank Sishen Iron Ore Mine, specifically Werner Voigt and his environmental team, for soil samples, laboratory analyses and support. Field assistance and administrative support were generously provided by Jan-Hendrik Neethling, Marinda de Wet, Ryn Tanga and Jane van Rooi. Thank you also to Dr Dries Bloem for his initial input. We appreciate the constructive and insightful input of the reviewers.