Annals of Arid Zone 36(4): 311-326, 1997

Recent Developments in the Reclamation of Surfa~e Mined Lands

1 2 1 1 s' S 1KD. Sharma, L.P. Gough, Suresh Kumar B.K Sharma and .K axenaICenh'al Arid Zone Research Institute, Jodhpur 342 003, India2u.s. Geological Survey, MS 973, Federal Centre, Denver, CO 80225, U.S.A.

Abstract: A broad review of mine land reclamation problems and challenges inarid lands is presented with special emphasis on work recently completed in India.

The economics of mining in the Indian Desert is second only to agriculture inimportance. Lands disturbed by mining, however, have only recently been tile focusof reclamation attempts. Studies were made and results compiled of problems associatedwith gennplasm selection, soil, plant and overburden characterization and manipulation,plant establisIunent methods utilized, soil amendment needs, use and conservationof available water and the evaluation of ecosystem sustainability. Emphasis is madeof tile need for multi-disciplinary approaches to mine land reclamation researchand for the long-tenn monitoring of reclamation success.

Key words: Land reclamation, mined lands, overburden, revegetation, gypsum, lime-stone, lignite, wastelands, dryland silvicultme ..

Successful wasteland reclamation canbe evaluated using two main criteria-sta-bilization of surface materials through ap-propriate geomorphic landscape recon-struction and the establishment of long-term sustainable vegetation communities.These criteria present unique challenges inarid environments not only because of lowprecipitation, high winds, and high eva-potranspiration rates, but because lands be-ing reclaimed in the Thar Desert regionofIndia also must be returned to agriculturaluse. The latter usually means being subjectedto intense grazing pressures. Therefore, notonly must appropriate soils be found fromavailable overburden, but soil amendmentsmust be evaluated, rainwater harvestingtechniques must be utilized, and plantgermplasm must be screened and testedfor their vigor, utility, and sustainability.

Reclamation studie.s in the Indian desertbegan with sand dune stabilization effortsand saline soil rehabilitation (Anon., 1986).It has only been within the last decadethat attention has been given to the im-portance of reclaiming land disturbed bymining. For example, it is estimated that12,525 ha of productive land has been aban-doned following mining over the last 40years in western Rajashtan alone (BalakRam, Personal Communication). Theselands, if left unattended, would remain un-usable for centuries. Research in the U.S.A.and other countries began about 50 yearsago and has focused on the selection, place-ment, and general management of coal over-burden (Gough and Severson, 1995). Studies'that examined the unique aspects of thereclamation of acidic, metal laden minetailings have only recently received atten-

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312 SHARMA et al.

tion. It should be emphasized that hundredsof hectares of land presently used for ag-riculture will be "turned upside down"in Rajasthan within the ne:\-1:few yearsby new lignite surface mining efforts. Ifthese lands are to be reclaimed in the future,pre-mining plans that involve topsoil evalu-ation and overburden characterization andselective placement must begin soon.

We report the results of four years ofwork in western Rajasthan at a gypsumand a limestone mine. These studies em-phasize the importance of conducting post-mining soil and spoil inventories that bothanticipate potential reclamation problemsand help define possible long-ternl eco-system stability. Particular emphasis isplaced on understanding the characteristicsof successful germ plasm selection, in char-acterizing the physical and chemical prop-erties of soil and overburden, in conservingand utilizing available moisture throughrain\vater harvesting, and in evaluating plantcommunity sustainability.

Cover Soil and Overburden Concerns

Special considerations in arid environments

The successful reclamation of disturbedlands (including mined areas) in arid regionsinvolves the application of principles fromdisciplines such as: range management, wa-tershed management, the identification ofconstraints found in the harsh, arid climateof the tracts (i.e., infertile, shallow soilsthat directly affect the productivity of es-tablished vegetation), and the selection ofsuitable plant germplasm. Indian arid soilscan be deep but are generally shallow withminimal profile development. Soil salinity

is ever present and may range from onlyslight to severe.

Overburden excavation, characterizationand placement

A limited resource for reclamation ofmined lands is topsoil. Often the averagesoil depth is less than 'j cm on the uplandareas. In the valley bottoms, the alluviumis relatively deep but only the surface fewcentimeters is biologically active. Topsoilmay not be sufficient or readily availablein a timely period for the capping of over-burden to the necessary depth (McKell,1978). Stockpiling topsoil is used, but thispractice could have undesirable effects onsoil biological activities. In addition, costs

.of stockpiling and massive topsoiling arealso important considerations that must becarefully examined. Any cost-reducingmethods in the use oftopsoil will be valuablein overall cost projections. The researchin progress involves mixing mine over-burden materials to achieve a mixture ofsand, silt and clay that resembles the de-sirable soil. The soil that results from thisspoil mixture (cover soil) is being usedfor the re-establishment of trees, shrubsand various grass mixtures (Sharma et al.,1996).

Pre-mining overburden characterizationis required by all states in the arid andsemi-arid western U.S.A. The objectivesfor overburden evaluations are to determinethe chemical and physical characteristicsof the materials, to estimate the verticaland lateral extent of unsuitable materials,and to develop appropriate mining and rec-lamation plans which will insure reclanlationsuccess of the post-mining root zone andaquifers. Critical to post-mining reclamation

RECLAMATION OF SURFACE MINED LANDS 313

sustainability are the impacts on the qualityof surface and groundwater resources andthe quality of materials within. the post-mining root zone (Boon et 01., 1987). Inaddition, trace elements can affect recla-mation success. The elements of particularenvironmental concern in arid regions beingmined include B, Mo, S, and Se (Goughand Severson, 1995).

Although the characteristics of soil andoverburden are site specific, varying frommine to mine or within a mine, most over-burden and spoils in the region of the coalmines in the Northern Great Plains (westernU.S.A.) have certain' common .charac-teristics. For example, they are typicallyneutral or alkaline, contain appreciableCaC03, and contain variable quantities ofsoluble salts (Power et 01., 1978). Theyare almost universally deficient in plantavailable P and biologically active formsof organic N, but may contain appreciableamounts of inorganic N (Poweretal., 1974).Texture varies widely from location to 10-'cation, ranging from clays to sands. Gen-erally, bulk density of spoils is 10-30%lower than that of the original overburden.However, the pyritic sandstone, associatedwith uranium roll-front deposits, and re-duced carbonaceous materials associatedwith coal deposits (such as is found inthe Gas Hills region of Wyoming, U.S.A.),have the potential for producing toxic metaland/or acid conditions. These materials canpotentially contribute water soluble toxicelements to the reclaimed ecosystem.

In reclamation planning at rock phos-phate mines near Dehradun, India, Soniand Vasistha (1987) found overburden withthe following characteristics: pH (7.0-7.3),P (P20S: 0.5-3.8%) acid-base balance (14.2-

76.0%) and heavy metals like Fe (Fe203:1.6-2.8%) and Al (Ah03: 2.5-3.8%). Theoverburden consisted of shale, limestone,chert and a fraction of topsoil (8-10%).The limestone mine spoil/debris in the Mus-soorie Hills, India, was found to be a sandy!oam, rich in Ca, alkaline in reaction, highin bulk density and low in water holdingcapacity and organic matter (Dadhwal et01., 1989). The infiltration rates of minespoils were found to be 1.5- to 2.1-timesgreater as compared to normal soil in' anadjoining area.

Many of the problems encountered inreclamation can be solved by covering un-desirable spoils with good soil material.Sandoval et 01. (1973) found that a coverof as little as 5 cm of topsoil over spoilsincreases the infiltration rate several fold,absorbs raindrop impact, reduces surfacesealing and runoff, decreases sediment pro-duction, increases the availability of bene-ficial micro-organisms and improves pl~tsurvival and growth. However, a minimumnon-compacted thickness of 1 01 is desirableto ensure long-term mine soil productivityfor a variety of post-mining land uses(Sharnla et 01., 1996). Shrub establishmentincreased substantially from the older gradedspoils with no topsoil to the newer directhaul topsoiled areas (Pfannenstiel andWendt, 1985). Natural shrub establishmentis maximized when the topsoil resourG.esare either direct hauled or stockpiled forless than one year, replaced by lifts, andhauled during moist soil conditions. Man-agement practices such as minimized seed-bed preparation and vegetation shreddingprior to topsoil removal also promote higher.shrub densities. Topsoiling also induces tree

314 SHARMA et al.

succession in reclaimed bauxite mine lands(Hussain, 1988). In recognition of the bene-fits of covering mine spoils with suitablesoil material, legislation has been enactedin major mining countries requiring thatsuitable soil materials be saved and respreadover graded spoils (Boon et al., 1987).

Placement of topsoil in a narrow trenchat the site of planting constitutes an effectivebut limited use of topsoil (McKell, 1978).As a necessary growing medium to receivethe plants, the topsoil would provide aninoculum of soil micro-organisms, a partialsource of native plant seeds and a bufferagainst high salt concentrations that mightdevelop from below. The percolation ofrainwater through the topsoil in the trenchwould keep the salinity levels around theroot zone within the tolerance of the trans-planted species.

Amendment llse and engineering practices

Various types of mulching materials areused on replaced mine soils to help controlerosion until plant growth is established.Many woody residues are the source ofwater soluble organic materials that per-colate into the planting media and are readilyutilized by soil micro-organisms.· Cosz etal. (1978) mixed naturally occurring humusin mine spoils and thus increased the mois-ture-holding capacity and decreased the al-kalinity so as to enhance the success ofrevegetation in New Mexico (U.S.A.) ura-nium mines. Sopper (1992) used municipalsludge for the reclamation of coal minespoils which are acidic, droughty, and de-void of organic matter. Sludge has beenshown to improve soil structure, water hold-ing capacity, and bulk density in additionto adding N, P, K and other plant nutrients.

The use of sludge as a spoil amendmenteliminated the initial lag period that char-acterizes conventionally reclaimed sites,during which plant gro\\1h and microbialactivity were at a low level. Sludge anlend-ments quickly increased the numbers andactivity of micro-organisms, whose activi-ties enhanced the development of a soilenvironment conducive to continued plantgrowth. As in the U.S.A., fly ash, whenused as a topsoil substitute, may providea desirable alternative to conventional meth-ods in the reclamation of abandonedmine land and coal refuse in India. Rec-lamation of minelands that contain acidspoil materials could be achieved by ap-plying dry flue gas desulfurization (FGD)by-products from thermal power plants asan alkaline amendments (Stehouwer et aI.,1995). These by-products were effectivein raising the pH of the spoil materials.Leachate pH, electrical conductivity, dis-solved organic C, Ca, Mg and S tendedto increase with increased FGD amendment ,while AI, Fe, Mn and Zn decreased. Overall,with FGD amendments of 120 g kg-lorless, leachate concentrations of most ele-ments of environmental concern were lessthan drinking water standards. Moore etal. (1991) used gypsum and wood residueamendments to facilitate maximum plantgro\\1h through anlelioration of non-top-soiled bentonite mine spoil sodicity. Thiswas particularly effective for the growthof dominant seeded perennial grasses.

Mine Tailings and Drainage

Characterization

Mine tailings, defined here as any ma-terial being dumped that has been processedin some way by the mining operation, are

RECLAMATION OF SURF ACE MINED LANDS 315

almost universally deficient in N and Pand are commonly deficient in K. In ad-dition, secondary or micronutrient elementsare sometimes deficient. Successful plantestablishment is difficult to achieve becausetailings are usually fine tex1ured and easilyeroded. In the western U.S.A., mine tailingsare commonly pyritic and extremely acidic(pH 3.0). Without the mechanical regradingof steep tailings slopes, erosion progressesrapidly and results in the movement ofacidic materials over nearby native, pro-ductive soils ..

Mine drainage

Waters containing the highest metal con-centrations have been collected from thebase of tailings piles of Alaskan (U.S.A.)sulphide deposits (Gray and Sanzo lone,1996). These waters contain as much as3600 ppb Cu, 3300 ppb Zn, 21000 ppbFe, 220 ppb Pb, 10 ppb Cd, and 311 ppmsulphate and have pH values as low as2.6. Mine drainage from a gold mine inJuneau (U.S.A.) that is well buffered bycalcareous host rocks has a pH of 8 andconcentrations of <0.05 ppb Ag, 0.6-2.7ppb As, <0.2 ppb Cd, <2 ppb Cu, <100ppbFe, <0.2 ppb Pb, ppb Hg, 39 to52 ppb Zn, and 230 to 340 ppm sulphate.Except for sulphate and Zn, these data aresimilar to those of background waters col-lected from unmineralized areas. In the NukaBay District (U.S.A.), a maximum con-centration of 130 ppb As was measuredin water immediately downstream from atailings pile. The Alaska State drinking waterquality standard for As is 50 ppb. Minedrainage from certain ore deposit types (e.g.,chromite deposits in Alaska), however, cancontain heavy metal concentrations wellbelow drinking water standards.

Germplasm Selection-Principles for theArid Regions

Germplasm selection is guided by thepost-mining environmental setting. In gen-eral, arid. soils have poorly structured pro-files. Wetter regions in arid areas, and desertfringes, show some profile development.However, mining entails removal of thissoil and quite often these soils are notstockpiled. Consequently, overburden ma-terial is often used as soil material. Lossof the true soil results in extreme impov-erishment of microflora, alteration in bulkdensity, moisture holding capacity, infil-tration rate, capillary fringe, as well aschanges in pH, EC and micro-, macro-nutrient status. There is also a loss of thesoil seed bank, both persistent and per-manent plant types, thus making naturalregeneration difficult to start and slow toprogress. Further, this newly created sub-

rstratum can bec<1mecolonized by aggressiveweeds whose propagules from adjoiningareas can invade quickly. Since a largeproportion ofland in arid areas is perpetuallydegraded, overstocked and over utilized,these support communities are often domi-nated by hardy, aggressive annual and per-ennial weeds. Post mining areas face adual risk of being both floristically de-pauperate as well as having normal suc-cession severly impacted. The followingare factors that affect revegetation success -imposed by mining-induced alteration ofthe surface:

• Irregular configuration of the soil sur- -face.

• Soil depth limitation-either too'ioose ortoo shallow.

316 SHARMA et al.

• Soil te:-..1urallimitations-loose gravellywith less loam and/or clay.

• Soil bulk density affecting aeration, com-pactness or looseness .

• Soil moisture holding capacity-often toolow.

• Soil microflora-almost absent.

• Soil nutrients-both micro- and macro-nutrients are either limiting or in non-

o available forms.

• Soil seed bank-practically absent.

• Risk of unwanted invader species.I

• Biotic disturbance in post rehabilitationregime is more often a rule than exceptionbecause of both domestic and wild animalgrazmg.

In view of the above limitations, thegerm plasm for reclamation of mine spoilsshould be such as"to either adjust and adaptor overcome these conditions and limita-tions. Further, these species should alsobe able to adapt to the following naturalclimatic vagaries of arid areas:

• Erratic, irregular, and inadequate rainfall.

• Extremes of temperatures-up to 45-50°Cin summer and O°C in winter.

• High rates of moisture loss and con-sequently high evapotranspiration rates.

• High wind velocity.

• Droughts of varying intensity and pe-riods.

• Frosts of varying intensity and periods.

According to McKell (1978), the idealcharacteristics of germ plasm for successfulmine spoil reclamation should:

• Have a desired rooting habit (configu-ration).

• Serve as feed for livestock and/or wild-life.

• Be tolerant to utilization.

• Propagate easily.

• Establish successfully.

• Be compatible with other speCIes.

• Should be able to provide quick vege-tative cover using pioneer species.

• Should be able to promote the revivaland growth of other desirable species(nurse species).

• Should be a succession facilitator spe-CIes.

• Should possess strategic adaptations inits phenological cycle and morphologyso as to be able to evade/adapt to criticalperiods of extremes of temperatures,drought and salinity.

• Should have a competitive edge overinvaders.

• Should be reasonably resistant to pestand microbial infections.

• Should have minimum or no require-ments for e:-..1emally added fertilizers.

• Should have rapid seedling growth andseedling drought/frost tolerance .

• Should have an overall wide ecologicalamplitude in its lifecycle strategy.

In the light of the above limitations,and the requirement of plants for successfulreclamation, plant germ plasm should in-clude both the indigenous and exotic species.The indigenous species that have evolvedover millennia in these conditions are ex-

RECLAMATION OF SURF ACE MINED LANDS 317

pected to have many, if not all, of thedesired characteristics listed above. How-ever, the Vavilovian principle (which statesthat sometimes species perform better intheir secondary centre of diversity followingintroduction from a primary center of di-versity) may mean that exotic species fromsimilar edapho-climatic regions ofthe worldcould also be suitable reclamation material.These may include species introduced intoan area long ago and which have becomenaturalized over the years. The other groupof species may be newly introduced.

Establishment requirement

Plant establishment involves the follow-ing six phases:

Species selection: A judicious mix ofnative and exotic species is recommendedfor use in mine land rehabilitation. Exoticspecies have their problems, however, andmay in time adversely affect communitysustainability. Important criteria for selec-tion of species should include their readyavailability, water-use efficiency, utility asfeed/fodder, and sustainability over time.

Procurement of seedslpropagules: It isdesirable to collect the seeds of speciesto' be used for rehabilitation from envi-ronments which are similar to that of therehabilitation site. This facilitates better sur-vival and gro\\th and provides a competitiveadvantage over those seeds which comefrom an alien environment.

Raising 0.(saplings/seedlings in the nurs-ery: The direct sowing of seeds on therehabilitation sites in dry areas should beavoided so as to minimise the mortalityof seedlings. The germination phase is themost sensitive period in the entire reha-bilitation scheme. In view of this, it is

appropriate to raise saplings in the nurseryand then transplant them at the site duringthe rainy season, Seed germination in thenursery requires knowledge of specific ger-mination requirements. For example, manyleguminous species require seed coat scari-fication involving boiling in water or treat-ment with sulfuric acid for varying du-rations. Stem cuttings also greatly benefitfrom treatments with rooting hormones.

Transportation to the site of planting:Though seemingly trivial, proper transpor-tation of planting materials is importantso as to reduce sapling mortality. Suffi-ciently mature saplings are required whichcan better withstand the shock of transport.Further, saplings need to be acclimatizedin the new environment. Hence, the majorpre-requisites for transportation are:

• Sufficiently mature saplings.

• Minimum transport time.

• Suitable period of time for on':site hard-enmg.

• Upright arrangement of polypacks (plas-tic sapling sleeves within which theyare grown).

• Immediate watering of saplings uponarrival at the site.

• Relatively dry soil in the polypacks atthe time of transport.

Planting ofsaplings/'ieedlings: Our stud-ies utilize the application of water at thetime of planting. The planting scheduleis adjusted to coincide with the monsoonrains; however, it is sometimes necessaryto continue the application of water forcertain drought-sensitive species, particu-larly if the monsoon rains are late or b~ef.

318 SHARMA et al.

Chemical fertilizers are not used. Farmyard manure is commonly mixed with othersoil amendments and it greatly enhancesthe seedling establishment success rate.

Post plantation operations: After plan-tation the saplings should be watered, atintervals, for a length of time necessaiyfor the establishment. We have found thathoeing of the soil in the planting pits isalso necessary in the first three months.

Measures of Success and Long-term Sus-tainability

Socio-economic

Efforts to revegetate disturbed areas anddisposal sites in arid regions have generallymet with failure because of the harsh en-vironmental conditions and the lack of suit-able technology. Nevertheless, present so-cietal attitudes and legislation require thatlands disturbed in the process of devel-opment be. rehabilitateq. In arid regions,harsh sites with limited precipitation presenta challenge to revegetation. The philosophyexpressed in the US National EnvironmentalPolicy Act (1969) declares a national com-mitment to the quality of the environmentto be an objective concurrent with the regularmission of all federal agencies. The affectedlands must be returned to usable and pro-ductive condition, which is compatible withexisting adjacent undisturbed natural areasand which support biota of the same kindand in the same numbers as those existingat the time the baseline data were obtained.The National Academy of Science StudyCommittee (1975) on the rehabilitation po-tential of US western coal lands states:

"... any decision to surface mine forcoal in a particular area must include

a strong commitment to rehabilitatethe land concurrently ..."

Legislation should be enacted that willprovide more flexibility in managing surfacemined lands and other disturbed ecosystems(Cairns, 1983). This flexibility can onlybe justified if more systematip managementoptions for coping with the ecological prob-lems caused by mining activities are de-veloped and supported by a broad scientificbase. The four basic management optionsfor surface mined land are: (a) restorationto original condition, (b) rehabilitation ofsome desirable characteristics, (c) devel-opment of alternative ecosystems that maybe quite unlike the original but may bedesirable for a variety of reasons, and (d)neglect (or natural, unaided reclamation)when evidence suggests that unaided naturalprocesses will produce better results thanhuman interventions. Creative use of re-search opportunities provided by the man-

;,agement options are of considerable aca-demic benefit and ultimately of social andeconomic benefits.

Nutrient/energy flow

Surface mine spoils exhibit considerablevariation due to a wide range of factorsincluding geological formations, previousland use, reclamation procedures and plantspecies used to reclaim these areas. Soniet al. (1989) showed that in slightly acidicspoil material, vegetation helped increasesoil pH and electrical conductivity. Thisin turn favours the release of nutrients andenhances microbial occurrence and abun-dance. K concentrations were found to de-crease from 15%, in unreclaimed sites, to12% in reclaimed sites in a period of fiveyears.'However, no significant change was

RECLAMA nON OF SURF ACE MINED LANDS 319

observed in the Ca and Na ions. Alexander(1992) studied the effect of twenty yearsof Eucalyptus camaldulensis growth on tin-mine spoils in Nigeria. If was observedthat as a result of additional input of organicmatter from leaf fall, etc., the reclaimedtopsoil had a significantly higher contentof organic C, N and cation exchange ca-pacity. Of most interest and concern wasthe decrease in base saturation from 39to 22%. Similarly by planting Faidherbiaalbida, significant increases in organic C,N, Ca, Mg and base saturation were ob-served.

Community heterogeneity

In a rock phosphate mined reclamationsite the floristic composition (plant diver-sity) increased significantly from the initialbaseline level over a period of five years(Soni et aI., 1989). The number of plantspecies increased from 20 to 31, whichis nearly equal to the adjoining undisturbedforest. During the same period the amountof litter also increased from 433 to 1025kg ha-I resulting in an increase of 21 %in soil nitrogen levels.

Soil development

In recent years, as reasons for observedreclamation successes or failures have beeninvestigated, a greater number of studieshave addressed the question of minesoildevelopment, particularly management ofthe early developmental processes. Typi-cally, soil development is a gradual processtaking hundreds of years. While this istrue for mature soils, relatively rapid chemi-cal changes may be expected for un-weathered overburden with little or no re-placed topsoil or subsoil. In the arid westernU.S.A. expected chemical changes can range

from sodium' accumulation in the rootingzone, to rapid development of acidity fromoxidation of sulphide minerals (Gough andSeverson, 1995). Although mine spoils caneventually recover 'soil' characteristicsthrough intensive reclamation and manage-ment techniques, annual fertilizer additionsare usually required for several years. Chich-ester and Hauser (1991) examined changesin the chemical properties of lignite mi-nespoils developed under forage grass inTexas and found these changes to be stronglyinfluenced by weathering processes. Incor-poration offertilized crop residues increasedtotal C, Nand P in the near-surface layers.Both pH and residual C increased in mi-nespoils. Electrical conductivity increasedwith depth as salts leach from the surfacesoil. A detailed examination of both re-claimed and unreclaimed mine lands byAlexander (1992) demonstrated that suc-cessful agricultural activities could be es-tablished on tin mine spoil using inputsof both standard chemical fertilizers anda range oflocally available organic manuresincluding urban refuse. Thus, 'waste' tinmine land and 'waste' urban refuse havebeen brought together with animal 'waste'to produce agriculturally fertile soils.'

Rehabilitation of Mined Wasteland inthe Indian Desert - A Case Study

Surface mining is second only to ag-riculture in economic, importance in India

.and is spread over about 700,000 ha (Soniand Vasistha, 1986). The direct effects ofsurface mining on the site include removalof vegetation, disturbance of the soil profile,and compaction. These effects may causeincreased surface erosion and sedimentation,changes in surface water and groundwaterchemistry, development of unusable waste-

320 SHARMA et al.

lands, and reduced aesthetics at the site(Sidle and Brown, 1992). Additionally, masswasting (landslide) hazards may exist onsteeper slopes.

Suiface mining of gypsum and limestoneplays an important role in. the economyof the Indian desert. Out of the estimatedreserve of 1.08x109 t of gypsum in India,970x106 t occurs in the desert; the annualproduction are 18.78lx 1if t. Gypsum isused in the manufacture of cement, fertiliser,plaster of Paris, pottery, sulphuric acid,building plaster, and in the reclamation ofalkaline soils The estimated limestone re-serves in the 'country are 76.446x109 t andthe annual production is 120.5x106 t. Lime-stone is used as a flux in iron-ore smelting,cement manufacturing, mortar and lime pro-duction, aiid for paving roads. However,the broad-scale open-cast mining of gypsumand limestone and the absence of envi-ronmental protection practices, have causedthe destruction of land resources. Reha-bilitation of such degraded sites is a chal-lenging task in the arid regions due tothe harsh environmental conditions and thelack of suitable technology.

The objective of this study is to producean ecologically stable rehabilitated site. Sta-bilitv is defined in terms of a diverse vege-tati~e cover an'a an enhanced or favourablesoil environment but without continued in-puts of resources (such as water and fer-tilizer) and without the requirement ofcomplete protection from animal use. Thishas been achieved through an optimumcombination of rainwater harvesting, soilprofile modification and the application ofappropriate plant species. A silvipastoralsystem 'has been designed for rehabilitation

of these mined wastelands. This systemcomplements the needs of the local popu-lation which, prior to mining, was usedlargely as grazing land.

The gypsum mine is located at Kavas(25.5°N, 71.4°E) in northwest, arid India.The average annual rainfall is 265 mm;about 90% of which occurs as summermonsoon rainfall between June and Sep-tember. The site has a mean daily maximumtemperature of 35°C (the highest being48.6°C) and a minimum temperature of18°e. The gypsum is a sedimentary depositwhich occurs in the area as a seam orbands intercalated with sand and silty ma-terials and is of recent to sub-recent origin.The gypsum bed, overlain by thin sandcover, is generally flat and occurs at arelatively lower elevation compared to thesurrounding area The limestone mine islocated at Bilara (26.2°N, 73.5°E), alsoin the northwest, arid India. The averageannual rainfall is 424 mm, generally oc-curring as summer monsoon rainfall. Thestudy area has a Jmean daily maximumtemperature of 33dC and a minimum tem-perature of 20°e. The limestone outcropsare of sedimentary origin and of Cambrianage.

A mine area rehabilitation plan makeslogical and effective use of natural resourcesavailable in each area such as locally adaptedplant species, precipitation, topsoil and to-pography. In addition, the revegetation sys-tem should be as cost-effective as possible(McKell, 1978; Sharma et al., 1996). Fol-lowing compaction (employed to stabilizethe mine spoil and to reduce its permeability)the surface of the gypsum and limestonespoil material was shaped into terraces and

RECLAMATION OF SURF ACE MINED LANDS

Table i. Plallt species used .ill the rehabilitatioll of milled wastelallds, illdia

321

,\

Indigenous NaturalizedLeguminous Non-legluninous leguminous

Kavas (Gypsum)Tamarix aphylla Pithecelobillm dlliceSalvadora oleoides Acacia tortilisSalvadora persica Acacia famesiallaAzadirachta illdica Acacia sellegalTecomella IlIIdlllata Parkillsollia aculiataHoloptelia illtegrifoliaZiziplllls lIImmllllariaCapparis decidlls

Life foml

Tree

Slmlb

Grass

Tree

Slmlb

Grass

Prosopis cilleraria

Alimosa hamata

Acacia catechuAcacia plallifrolls

Prosopis julifloraDichrostachys mlltallCeasalpillllia cora ria

CellelllltS cilimis

CymbopogolljwarallclIsa

Bilara (Limestone)Azadirachta illdica Ballhillia racemosaSalvadol'G oleoides Pithecellobillm dlliceHoloptelia illtegrifolia Acacia sellegal

Acacia tortilisAlbizia amam

A1aytelllls emargillata A1aytelllls emargillataCommiphora wightiiZiziplllls lIImmllllariaGrewia tellaxCellelllltS ciliG/isCymbopogolljwarallclIsa

Exoticleguminous

Acacia IIl1bicaCercidillm floridllmCassia st11ltiiColopllOspel71l1/mmopalle

Cercidillm jIoridllmDichrostael~vs iII/tali

slopes providing a catchment for harvestingprecipitation and a terrace for receivingtransplanted seedlings. The rainwater har-vesting techniques were designated as mi-cro-catchment, ridge and furrow, half-moonterraces and inward sloping bench terraces.These were replicated four times in a ran-domised block design.

In addition to water, another limitingresource of these mined wastelands is top-

soil. The· soil survey of tracts indicatesthat the average soil depth is less than15 em. Because of cost and low successi~ recoverability, topsoil st~ckpiling wasnot used. Transplanting of container-grownnative plants directly into favorable spoilmaterial was done in auger holes that were15 em in diameter and I m in depth (Table1). The container-grown plants gave betterresults than either direct seeding or bare-root

322 SHARMA et al.

seedling transplants. Necessary soil amend-ments were added to the auger holes andconsisted of a:mixture of .fine sand, topsoil,farm-yard manure and bentonitic clay. Itwas expected that the percolation of har-vested rainwater from the catchment slopesinto the auger holes would keep the rootzone moisture to an optimum level forgrowth of the tran~planted native species.Monthly supplemental irrigation was ap-plied as an added safeguard during extendeddrought periods in the early two years ofthe study. The study was initiated during1992 in 16 ha area of gypsum mined waste-land and in 10 ha area of limestone minedwasteland. The study area was fenced witha live Prosopis juliflora hedge.

During the study period (1992-1995),the annual rainfall at Kavas varied between300 ,and 481 mm in 12 to 46 rainy daysas compared to 283 to 583 mm in 25to 39 rainy days at Bilara; 81 to 98%of precipitation was received as summermonsoon rainfall during June-September.Typical of the desert climate, the rainfalloccurred with relatively high intensity andextreme variability both from year to yearand within each rainy season.

Striking differences were found at Kavasbetween topsoil and gypsum mine spoil:pH varied only from 7.8 to 7.9; however,electrical conductivity of mine spoil was1.79-2.21 dS m -1 as compared to 0.20 dSm -1 of tops oil. Higher water holding capacity(28.0-32.5%), moisture equivalent (6.1-9.8%) and silt plus clay content (12.1%)was found for mine spoil as compared totopsoil (25.0-28.0%, 3.1-4.0% and 6.6%,

respectively). The mine spoils were ex-tremely low in organic carbon (0.09-0.14%).

The chemical analysis of mine spoiland topsoil at both the sites indicated anadequate total concentration, of a numberof elements such as Na, K, Ca, Mg, Fe,Mn and B (Table 2). Calcium is dominantover Mg in all the samples. Limestonemine spoil and topsoil of gypsum minescontained the highest amount of total Ca.Gypsum mine spoil and topsoil oflimestonemines showed the greatest Mn levels. Ingeneral, the gypsum and limestone minespoils are deficient in P (0.01-0.06%), Mo«2.00 ppm) and Se (0.10-0.17 ppm). Thesesites are not deficient in Cu, Zn and Co.The topsoil and mine spoils show excep-tionally high B content, and a potentialfor phytotoxicity in the growing mediumexists.

Soil moisture storage was recorded everymonth, using a neutron moisture probe,at both the study areas, up to 1 m indepth at 20 cm increments. In the gypsummined area, among various rainwater har-vesting treatments, on an average the mi-cro-catchment recorded the highest soilmoisture storage (4.6%) followed by thehalf-moon terraces (4.4 %), ridge and furrow(4.2%) and planted control (4.2%). Thisis in contrast to 2.9% moisture recordedin the unmined area. However, throughoutthe year, the highest soil moisture storageoccurred in the unplanted control sites(6.5%) as there were no plants to utilizethis moisture. Among the rainwater har-vesting treatments, no significant differencewas observed in the soil moisture values.In the unsaturated phase the moisture move-

RECLAMATION OF SURF ACE MINED LANDS 323

Table 2. A comparisoll of mille spoil alld topsoil chemical parameters

Element Gypsum mine Limestone mineMine spoil Topsoil Mine spoil Topsoil

Na (%) 1.40 ·0.58 0.21 0.69K (%) 1.16 0;59 0.38 1.19Ca (%) 6.5 16.2 23.0 7.8Mg (%) 0.86 1.73 5.00 0.79P (%) 0.05 0.04 0.01 0.03Al (%) 4.57 2.32 1.50 4.30Fe (%) 1.72 0.96 0.74 1.90Mn (ppm) 437 350 130 433Zn (ppm) 22.4 18.0 10.0 30.0Cu (ppm) 7.33 7.75 4.00 13.0Mo (ppm) <2.00 <2.00 <2.00 <2.00Co (ppm) 7.11 5.75 5.00 8.70B (ppm) 53 51 20 53Li (ppm) 15.7 30.8 10.0 18.7Cd (ppm) <2.00 <2.00 <2.00 <2.00Cr (ppm) 39 26 21 62Se (ppm) <0.10 <0.10 0.10 0.17

ment in mine spoils was slow (0.02% daiI)due to an extremely dense and impededsoil profile.

Throughout the year in the limestonemined area, the middle of the mine spoilmound recorded significantly higher soilmoisture storage (8.1 %) than the top (4.9%)and base (4.2 %) of the mound. On anaverage the 'tear-drop' rainwater harvesting

configuration recorded 4.4% moisture. Thehigher soil moisture at the middle of moundresulted in significantly better plant growthat that site as compared to any other location(Table 3). However, limestone outcropsshowed a high~r soil moisture storage(6.4%).

Over a period of three year's time, aslight increase in the electrical conductivity

Table 3. Growth of Acacia sellegal ill relatioll to soil moishlre storage (1995)

Mean soil moisture storage (% volume)Plant character (mean)

Cover (m2)

Height (m)

Branch length (m)Collar girth (cm)

Top of spoil mound4.9

8.92.4

22.85.3

Middle of spoil mOllild8.1

10.02.7

23.47.5

lj

324 SHARMA el al.

of mine spoil was observed (a range of2.1-2.5dS m-I from 0.8-1.87 dS m-\ How-ever, no significant difference in pH wasfound-values fluctuated around 7.8. OrganicC showed a steady increase from 0.02-0.05%to 0.06-0.18%due to decompositionoffarm-

. yard manure. This increase was greaterunder the micro-catchment and half-moonterraces (0.15-0.18%) than under the ridgeand furrow system (0.06-0.08%). Similarly,the available P in mine spoils' increasedfrom 5-8 kg ha-I to 7-11 kg ha-I, overa period of three years.

Based on the gro\\th performance re-corded in terms of plant cover, plant height,number of branches, branch length and collargirth, the four best performing plant specieswere identified at each site. In the gypsummined area Cercidium floridum, Tamarixaphylla, Salvadora persica. and Pithecel-lobium dulce were superior in terms ofmean annual incremental height, branchspread, relative nunlber of branches, andcollar girth. Mi~ro-catchment and half-moonrainwater harvesting techniques performedequally well, in terms of plant gro\\th,as compared to the control.

In the limestone mined area, Acaciaplan~frons, Acacia senegal, Cercidium flo-ridum, and Dichrostachys nutans performedbetter in terms of the growth parameters.Acacia senegal gained a maximum heightof 1.51 m in a period of three years. Cer-cidium floridum exhibited the highest rela-tive growth (24.3%) followed by the Acaciasenegal (18.3%).

Rehabilitation of mined wastelands indry areas is a difficult and time consumingexerci~e. It involves the development oftec~n610gy, field testing of methods, and

a reliance on good pilot studies. Since thegrowth of plant species is slow in aridzones due to adverse climatic and edaphicfactors and competition for water and nu-trients it takes five to six years to developa reasonable plant canopy. Therefore, atthis time, no significant difference couldbe observed in plant growth among variousrainwater harvesting techniques. This studyhas not only developed methods of minedwasteland rehabilitation but also has helpedin the understanding of the processes thataffect that rehabilitation. The resultsachieved so far are promising for the suc-cessful rehabilitation of degraded lands andthe establishment of sustainable plant com-munities.

Future Challenges and ResearchDirections

Detailed elemental analysis of reclaimedvegetation may be appropriate in the future.This is because vegetation, utilized by hu-mans and grazing animals, may reflect theelevated element levels commonly foundin active and abandoned uranium, coal, andhard-rock mines. The phenomenon of mi-nespoil weathering results in the releaseof available forms of trace elements; grassesand forbs can act as accumulator speciesfor these elements. Because of work bysuch authors as Smith and Boon (1985),who found that plant analyses reflect spoilchemistry (correlations were strong betweenSe, Mo, B, etc. and specific geologicalmaterials), this type of study may be im-portant in our work. In addition, work needsto be done for a broader range of revegetationspecies in developing standard plant wash-ing techniques, in estimating appropriatesampling times, and in assessing appropriateplant parts to be sampled.

RECLAMATION OF SURF ACE MINED LANDS 325

There are major uncertainties with ourknowledge of mined land reclamation, es-pecially in arid zones. An interdisciplinaryeffort is needed to further define the chem-istry of overburden, the methodologies nec-essary for identifying and mapping unsuit-able overburden, and the amount of mixingthat should be accomplished during normalmining operations. Further, as Boon et al.(1987) emphasize, regraded spoil samplingintensities need further study, as well asmethodologies for predicting spoil waterquality, the most appropriate placement ofunsuitable materials in relation to the post-mining groundwater quality.

Ghosh and Ghosh (1990) proposed toutilize the abandoned coal quarries for stor-ing municipal and industrial refuse, whichis expected to increase greatly in the nearfuture. However, the risk of contaminatinggroundwater resources by the liquid· ef-fluents needs to be examined in greaterdetails.

Ellsworth (1991) has successfully ap-plied computer video-imaging for pre-dis-turbance planning and post-disturbance re-habilitation evaluation of mineland recla-mation. The technology has great poteniialfor broad-scale application in disturbed landrehabilitation.

Acknowledgement

This study is funded by a USDA Grant:IN-AES-681 (FG-IN-721 ).

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