Mziwanda Mangwane

Coal mining involves the removal of natural vegetation, heavy excavation; combustion and ignition accompanied by a release of coal dust to the atmosphere that drastically reduce the ecosystem services. A study was conducted to assess of veld grasses around a coal mine in Emalahleni in Mpumalanga. Six 100 m line transects were established on rehabilitated site and natural veld in Kleinkopje coal mine. Plant identification, leaf and tiller counting, and biomass harvesting were conducted on each of five 1 m² sampling quadrats placed at intervals of 20 m along the transect. Nineteen (19) grass species, some (07) forbs and (03) sedges were recorded. Therefore, Eragrostis curvula (31.5%) was the most frequent on the natural veld, followed by Cynodon dactylon (28.36%) and Panicum maximum (22.25%) on the rehabilitated. On the natural veld, Aristida congesta had higher tiller production (17 tillers per plant) while E. curvula averaged 11 tillers per plant on the rehabilitated site. On the rehabilitated site, U. mosambicensis produced averaged 94 leaves per plant than all other species on both sites. Basal cover, species diversity and richness did not differ (p > 0.05) between rehabilitated site and natural veld. Rehabilitated site had a generally higher biomass production of 4.35 kg DM ha^− 1 than natural veld with 3.24 kg DM ha^− 1. E. curvula and C. dactylon had higher contribution to the total biomass production on both sites. However, their biomass production was insignificantly different (p > 0.05) from that of Urochloa mozambicensis and P. maximum on rehabilitated site and Heteropogon contortus on natural site. Our results indicated that E. curvula and C. dactylon are highly persistent and productive hence they are ideal for mine rehabilitation.

Coal mining is known to have negative impacts on the environment, necessitating land rehabilitation after mining activities. Amongst the problems associated with coal mining is the accumulation of acid mine drainage characterized by large amounts of heavy metals and high acidity. The impact of these environmental problems on the ecosystem around mining areas underscores a need to devise strategies that will ensure sustainable restoration of the ecosystem integrity to ensure environmental protection. Of these, treatment of acid mine drainage using calcium sulfate dihydrate, which is subsequently used for irrigation during phytoremediation, holds great promise for restoration of open-cast mines. However, although grasses are used for rehabilitation of coal mined areas, the impacts of treated mine water on the germination, seedling emergence, and plant growth of grasses are not well known. The aim of the study was to evaluate the germination and early seedling growth responses of different forage grasses to treated mine water. Seven forage grass species were selected, with four species represented by two varieties while others were represented by one variety, totaling 11 forage grasses. For each plant entry, 100 seeds were placed in J.R. Petri’s dishes lined with Whatman No. 2 filter paper and watered with distilled and mine water to assess germination. For the seedling establishment experiment, only five species were studied, in which twenty seeds per species were sown in pots containing mine soil and irrigated using distilled and treated mine water. The final germination percentage (FGP), germination rate index (GRI), corrected germination rate index (CGRI), and T₅₀ were determined for the germination trail and total biomass was assessed for the seedling growth trail. The highest FGP for all grasses was attained under controlled conditions, using distilled water, ranging from 38–94%. All grasses germinated when watered using treated mine water and had a FGP ranging from 20–91%. Relative to distilled water, GRI and CGRI were highest only for L. multiflorum cv AgriBoost when seeds were watered using the treated mine water. All grasses watered with treated mine water produced high biomass for the first two weeks, after which biomass production started to decline. Two grasses, Eragrostis curvula cv Ermelo and Lolium multiflorum cv Archie, showed tolerance to treated mine water irrespective of its high electrical conductivity (557 mS∙m⁻¹). Therefore, these grasses could be used in the rehabilitation of coal-mined areas irrigated with treated mine water.