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The development of restoration strategies for prime agricultural soils following mineral sands mining in the Coastal Plain of the eastern USA
... Therefore, a particular focus of our work on this project since 1990 has been to evaluate topsoil substitutes versus conventional topsoil return strategies. In precursor studies to the work reported here (Daniels et al., 1991(Daniels et al., , 1996, we evaluated soils reconstructed from tailings:slimes mixtures in 1.2 m reconstructed profiles in barrels in the greenhouse and found that the simulated mine soils could serve as suitable plant growth media if significant levels of P were added to offset fixation potentials along with appropriate pH adjustment via liming. In a follow-up study (Daniels et al., 1999) on pilot mining pits between 1995 and 1998, we compared the effects of thick (25 cm) topsoil return vs. topsoil substitution via the addition of 112 Mg/ha yardwaste compost to mixed tailings and slimes following heavy P-fertilization, liming, and ripping of the reclamation surface. ...
... in deep barrels (Daniels et al., 1991(Daniels et al., , 1996, the development of adequate subsoil structure and associated macro-porosity over time appears to be a critical requirement for the return of these soils to high levels of row-crop productivity. Also, mine soil amendments or strategies that increase soil organic matter should be utilized where economic and feasible. ...
... It is notable, however that the surface soil levels of extractable P were still quite low (1 to 25 mg/kg) in relationship to fertilizer rates applied of 300 to 500 kg P 2 O 5 per ha. In most instances, this is attributed primarily to very strong P-sorption which we documented earlier in these materials (Daniels et al., 1991). In pit 9806, the low P levels were again due to the lack of fertilization before sampling, but similar very low levels (1.0 mg/kg P) in pit 9801, which was supposedly heavily P-fertilized, were unexpected. ...
Significant areas of prime farmland in the upper Coastal Plain of Virginia and North Carolina will be disturbed by heavy mineral sands (Ti/Zr- bearing ilmenite, rutile, zircon) mining over the next 20 years. The physical and chemical properties of mine soils that result from the mining and reclamation process were studied in a replicated small plot experimental setting between 1994 and 1997 and in detailed transects over a succession of eight mining pits reclaimed between 1997 and 2002. Separation of sandy tailings from silt+clay slimes in dewatering pits leads to significant differences in soil texture, seasonal wetness and bearing capacity across the reclamation surfaces. Plant growth in sandy tailings areas is directly limited by low water holding capacity while that in finer textured zones is limited by the massive and laminated nature of the slimes. Compaction of the surface and subsurface also limits rooting in non-sandy reclaimed areas. Freshly deposited materials tend to be very low in pH (< 5.2) and in plant-available nutrients due to the highly weathered nature of the original deposit and the mineral separation processes employed. Native topsoil on-site is very high in heavy mineral content, and is therefore subject to being processed rather than saved for reclamation. An array of reclamation protocols have been implemented at the site including heavy liming and P application, deep ripping, and the utilization of biosolids to improve post-mining productivity. Revegetation of eight mining pits produced between 1997 and 2002 was positively affected by the utilization of topsoil, and extremes in surface texture limited revegetation where topsoils were not employed. Issues associated with differential settlement as the fills dewater over time, and the possibility of P leaching in areas of pure sandy tailings warrant further study.
... Virginia Tech worked closely with all stakeholders to develop appropriate restoration protocols and to coordinate their implementation. Early (1990Early ( -1995 baseline research efforts included detailed soil and crop productivity mapping, wetland soil and geohydrologic studies and characterisation of simulated tailings and reconstructed soils (Daniels et al, 1991(Daniels et al, , 1996Daniels, Orndorff and Schroeder, 2003). These early studies revealed that: ...
... • quartz tailings generated by the proposed mine would be dominantly fine to medium sands • the silt+clay slimes were primarily iron coated kaolinites • the slimes content would range from ~30->50 per cent of the bulk ore depending on extent of subaerial weathering • the combined tailings+slimes stream would be very low in pH (4.5-5.0) and plant available phosphorus (P) (Daniels et al, 1991). In a parallel study, re-blended tailings and slimes mixtures were evaluated in the greenhouse and it was found that the simulated mine soils (without topsoil) could serve as suitable plant growth media if significant levels of fertiliser P (>300 kg P/ha) were added to offset fixation potentials along with appropriate pH adjustment via liming. ...
... Treatment effects were observed for three full growing seasons in this study. In a precursor study to the work reported here, Daniels et al. ( 1991Daniels et al. ( , 1996 evaluated reblended tailings:slimes mixtures in the greenhouse and found that the simulated mine soils could serve as suitable plant growth media if significant levels of P were added to offset fixation potentials along with appropriate pH adjustment via liming. ...
... Our earlier laboratory and greenhouse results (Daniels et al. 1991 ;1996) clearly indicated that recombined tailings and slimes can serve as productive soil materials if they are limed, fertilized, and placed properly following mining. In the greenhouse, however, we unifonnly reblended tailings with slimes to prescribed ratios and then wet-slurried them into pots or barrels without mechanical compaction. ...
The Old Hickory mineral sands orebody in Virginia is >2,000 ha (>5,000 acres) in size and currently supports a productive row-crop agriculture. Reclamation experiments were implemented on pilot-scale mining pits from 1995 to 1998. Half of each mining pit was, topsoiled with 25 cm (10 in.) of soil. The remaining half was left as either mixed tails/slimes or as regraded subsoil over tails/slimes treated with 112 t/ha (50 st/acre) yard waste compost. Postmining productivity was estimated to be reduced by 23, 3, 27 and 20 percent for each crop (wheat/soybeans/corn/cotton) in sequence when compared to undisturbed soils. The variability in surface texture and compaction limit the restoration of soil productivity.
... Two important components of the Old Hickory mining lease negotiation process were (1) assurances by RGC of their intent to return the lands to intensive agricultural production following mining, and (2) RGC's willingness to employ our university (Virginia Tech) to develop a dedicated pre-mining reclamation research program (Daniels et al., 1991(Daniels et al., , 1996. ...
Mineral sands mining for ilmenite, rutile, and zircon will disturb over 2,500 ha of prime agricultural farmland in Virginia and North Caro-lina (USA) over the next 20 years. Mining of the Virginia deposit was initiated in 1997 and approximately 750 ha have been disturbed to date with approximately 150 ha reclaimed to support a mix of agricultural post-mining land uses. While considerable university research and corporate effort were devoted to developing environmental management systems and reclamation protocols for these lands, specific indicators of sustainability and restoration success were lacking. By 2003, it became apparent to the mining operator (Iluka Resources), local landowners/farmers, local government, and the regulatory authority that testable indicators of reclamation success were essential for long-term sustainability. Virginia Tech worked cooperatively with all stakeholders to review the pre-existing research base and to propose reasonable expectations of post-mining soil productivity levels. The state regulatory authority reinforced its position on a number of associated issues including necessity of topsoil return and specific comparative crop yield targets. Virginia Tech, Iluka Resources, and a local leaseholder (Car-raway-Winn family) agreed to jointly manage a 45-ha research demonstration farm where the effects of alternative soil reconstruction practices are being rigorously monitored for both row crops (corn and wheat) and forage production. All mined land crop yields are also compared to an adjacent undisturbed exceptional quality prime farmland soil. Corn and wheat yields in 2005 and 2006 were significantly above county average yields (regulatory target level) and approximately 75% of undisturbed adjacent prime farmlands. This cooperative effort allows all clientele groups to objectively assess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry.
... Two important components of the Old Hickory mining lease negotiation process were (1) assurances by RGC of their intent to return the lands to intensive agricultural production following mining, and (2) RGC's willingness to employ our university (Virginia Tech) to develop a dedicated pre-mining reclamation research program (Daniels et al., 1991(Daniels et al., , 1996. ...
Mineral sands mining for ilmenite, rutile, and zircon will disturb over 2,500 ha of prime agri-cultural farmland in Virginia and North Caro-lina (USA) over the next 20 years. Mining of the Virginia deposit was initiated in 1997 and approximately 750 ha have been disturbed to date with approximately 150 ha reclaimed to support a mix of agricultural post-mining land uses. While considerable university research and corporate effort were devoted to developing environmental management systems and recla-mation protocols for these lands, specific indica-tors of sustainability and restoration success were lacking. By 2003, it became apparent to the mining operator (Iluka Resources), local landowners/farmers, local government, and the regulatory authority that testable indicators of reclamation success were essential for long-term sustainability. Virginia Tech worked coopera-tively with all stakeholders to review the pre-existing research base and to propose reasonable expectations of post-mining soil productivity levels. The state regulatory authority reinforced its position on a number of associated issues in-cluding necessity of topsoil return and specific comparative crop yield targets. Virginia Tech, Iluka Resources, and a local leaseholder (Car-raway-Winn family) agreed to jointly manage a 45-ha research demonstration farm where the effects of alternative soil reconstruction prac-tices are being rigorously monitored for both row crops (corn and wheat) and forage produc-tion. All mined land crop yields are also com-pared to an adjacent undisturbed exceptional quality prime farmland soil. Corn and wheat yields in 2005 and 2006 were significantly above county average yields (regulatory target level) and approximately 75% of undisturbed adjacent prime farmlands. This cooperative ef-fort allows all clientele groups to objectively as-sess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry.
... Virginia Tech worked closely with all stakeholders to develop appropriate restoration protocols and to coordinate their implementation. Early (1990-1995) baseline research efforts included detailed soil and crop productivity mapping, wetland soil and geohydrologic studies, and characterization of simulated tailings and reconstructed soils (7,8). In a precursor study, we evaluated reblended tailings:slimes mixtures in the greenhouse and found that the simulated mine soils (without topsoil) could serve as suitable plant growth media if significant levels of P were added to offset fixation potentials along with appropriate pH adjustment via liming. ...
Significant deposits (> 4,000 ha) of heavy mineral sands were discovered in the USA Coastal Plain of Virginia and North Carolina in 1989. The majority of these lands support highly productive row crop agriculture, and the development of restoration protocols that would return these lands to agricultural use was deemed to be critical to the long term sustainability of mining operations. Virginia Tech worked closely with all stakeholders to develop appropriate restoration protocols and to coordinate their implementation. Full-scale mining operations at the Old Hickory Project in Virginia were initiated in 1997 by Iluka Resources Inc., and restoration protocols have continued to evolve in response to a variety of economic, technical, and social issues. Approximately 750 ha of land are in various phases of backfilling and final reclamation. Return of these lands to agricultural row-crop production has been complicated by lateral variability in mine soil physical conditions, excessive compaction, and limited topsoil return. However, within the past two years, a series of tailings deposition and soil reconstruction practices have been developed and implemented that significantly improve post-mining soil productivity. Deep ripping and appropriate use of organic soil amendments have been particularly effective at restoring post- mining soil productivity.
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