Ram LC. Srivastava NK. Jha SK. Sinha AK. Masto RE. Selvi VA. 2006.

ManagementofminespoilforcropproductivitywithligniteyashandbiologicalamendmentsL.C. Rama,*, N.K. Srivastavaa, R.C. Tripathia, S.K. Jhaa, A.K. Sinhaa, G. Singha, V. ManoharanbaCentral FuelResearchInstitute, PO-FRI,828108Dhanbad, Jharkhand,IndiabCentreforApplied Researchand Development,NeyveliLigniteCorporationLimited, Neyveli607801, Tamil Nadu,IndiaReceived 3October2003;accepted21June2005Availableonline26October2005AbstractLong-term eldtrials usinglignite y ash(LFA) werecarried out in ricecrops during the period 19962000 at Mine I, Neyveli LigniteCorporation, Tamil Nadu. LFA, being alkaline and endowed with an excellent pozzolanic nature, silt loam texture, and plant nutrients, hasthe potential to improve the texture, fertility, and crop productivity of mine spoil. The rice crops were the rst, third, fth, and sixth crops inrotation. The other crops, such as green gram (second) and sun hemp (fourth), were grown as green manure. For experimental trials, LFA wasappliedatvariousdosages(0,5,10,20,50,100,and200 t/ha),withandwithoutpressmud(10 t/ha),beforecultivationoftherstcrop.Repeat applications of LFA were made at the same dosages in treatments of up to 50 t/ha (with and without press mud) before cultivation ofthethirdandfthcrops.Pressmud,alightweightorganicwasteproductfromthesugarindustry,wasusedasanorganicamendmentandsource of plant nutrients. Also, a recommended dosage of chemical fertilizer, along with gypsum, humic acid, andbiofertilizer assupplementing agents, was applied in all the treatments, including control. With one-time and repeat applications of LFA, from 5 to 20 t/ha(withandwithoutpressmud),thecropyield(grainandstraw)increasedsignicantly(p!0.05),intherangefrom3.0to42.0%overthecorresponding control. The maximum yield was obtained with repeat applications of 20 t/ha of LFA with press mud in the third crop. Thepress mud enhanced the yield in the range of 1.510.2% with various dosages of LFA. The optimum dosage of LFA was 20 t/ha for both one-time and repeat applications. Repeat applications of LFA at lower dosages of up to 20 t/ha were more effective in increasing the yield than thecorrespondingone-timeapplicationsofupto20 t/haandrepeatapplicationsat50 t/ha.One-timeandrepeatapplicationsofLFAofupto20 t/ha (with and without press mud), apart from increasing the yield, evinced improvement in the texture and fertility of mine spoil and thenutrient content of crop produce. Furthermore, some increase in the content of trace and heavy metals and the level of g-emitters in the minespoil andcropproducewasobserved, but well withinthepermissiblelimits. Theresidual effect ofLFAonsucceedingcropswasalsoencouraging in terms of eco-friendliness. Beyond 20 t/ha of LFA, the crop yield decreased signicantly (p!0.05), as a result of the formationof hardpan in the mine spoil and possibly the higher concentration of soluble salts in the LFA. However, the adverse effects of soluble saltswere annulled progressively during the cultivation of succeeding crops. A plausible mechanism for the improved fertility of mine spoil andthecarryoveroruptakeoftoxictraceandheavymetalsand g-emittersinminespoilandcropproduceisalsodiscussed.q 2005ElsevierLtd.Allrightsreserved.Keywords:Lignite yash;Minespoil;Management;Crop productivity; Sustainability1.IntroductionThe generation of huge amounts of mine spoil (four timesthe amount of coal), comprising unwanted extraneous shalymatter and other refuse from opencast miningextensivelypracticed in India, currentlydisturbs the natural soil strataand ecological balance. Likewise, production of about100 Mt/yearof y ashfrom82 thermalpowerplantsinthecountry poses problems with handling, storage, and disposal(requiring large areas of land), apart fromapprehensionabout possible contamination of soil, crop produce, andgroundwaterwithtoxic traceandheavymetals(Furretal.,1977; CarlsonandAdriano, 1993; RubeinsteinandSegal,1993) and radionuclides (Ramachandran et al., 1990;Vijayan and Behera, 1999), especially in viewof theminimal use made of it. In particular, the mine spoilgenerated by opencast mining of lignite by Neyveli LigniteJournal ofEnvironmentalManagement79(2006)173187www.elsevier.com/locate/jenvman0301-4797/$-seefrontmatter q 2005 ElsevierLtd.Allrightsreserved.doi:10.1016/j.jenvman.2005.06.008* Corresponding author. Tel.: C91 326 2381001-10 (Extn 357/224);fax: C91326 2381113/2381385/2381560.E-mailaddress: [email protected](L.C.Ram).Corporation(NLC),TamilNadu,is moreproblematic, asaresultofitsfragilenature,poorporosity,decientnutrientlevel, and failure to offer any appreciable biological activity.The lignite y ash (LFA) currently generated by twothermalpowerstations(TPSIandII;capacity2070 MW),tothetuneof w1.0 Mt/year, doesnot ndanymajoruse(hardly 12%, mainly in civil construction, buildingmaterials, andlandll), andthisisdistressing. Theminespoil producedinthe extractionof coal andthe yashproduced in power generation are two major environmentalproblems, suggesting a need for a suitable eco-friendlytechnology, inonestroke, not onlytosolvetheenviron-mental concerns, but alsoincreasethegainful bulkuseofthesematerials.Much research and development (R&D) has beencarried out in the recent past on the use of y ash inagricultureandintherevegetationof dumpingsites andsurface mine soil (Fail and Wochok, 1977; Bhumblaet al., 1991), where the potential of y ash as limingagent,sourceofplantnutrients,andsoilmodierhasbeenexploited. Theuptakeor enrichment of various nutrientsandtoxictraceelements insoil after y-ashamendmenthas beeninvestigated, andcropproduce has beenfoundsafe for consumption (Sen et al., 1997). At the CentralFuel Research Institute (CFRI), Dhanbad, investigations(Singhet al., 1997; Singhet al., 1998; Ramet al., 1999)of theapplicationofyashunder varioussoil typesandagroclimatic conditions have suggested the benecialeffects of y ash in agriculture as liming agent, soilconditioner, sourceofessential plant nutrients, andawayto reclaim waste or degraded lands. Though y ashcontains several essential plant nutrients, it is devoidofhumus andnitrogen(Menonet al., 1990), whichcanbesupplemented by organic amendments (Adriano et al.,1978), together with effective reduction in leaching ofmetalsbychelation(LoganandTraina, 1993).TheLFAoftheNLChasbeenreportedtobealkaline(pHZ1012, Ca, 812%), with a cementitious nature usefulin inhibiting the inltration of water into sandy (loose-textured) soils andprovidingplant nutrients essential forcrop growth (CARD (Centre for Applied Research &Development, 1997)). Like most y ashes, LFAbeingdominated by silt-sized particles (Adriano et al., 1980),could be expected to improve the texture, bulk density (BD),water-holdingcapacity(WHC), andfertilityof the minespoil of NLC. Practically no detailed R&D was available onthemanagement of minespoil throughbulk-scaleuseofLFA, andhence this studywas carriedout. The presentpaper describes the results of long-term eld trialsperformed during 19962000 on mine spoil, involvingamendment with various dosages of LFA, with and withoutpress mud, for cultivation of rice crops. The study includesthe effects onthe fertilityof mine spoil, cropyieldandnutrient status, trace and heavy metals content, and the levelofradioactivityoftheminespoilandcropproduce.2. Materialsandmethods2.1.ExperimentaldetailsTheselectedmine-spoilarea(w6000 m2, lleduptoadepthof10 m)wasproperlyleveledandploughedseveraltimes in order to maintain uniform fertility. Theexperimentalsetupwasarandomizedblockdesignhaving18treatments(T1T18),eachinquadruplicateofa15 m!4 marea, treatedwithvarious dosages (0, 5, 10, 20, 50,100, and200 t/ha) of LFA, withandwithout press mud(Table1), wheretreatment T1(control)waswithout LFAand press mud, and T2was with press mud only. IntreatmentsT3, T5, T7, T9, T11, andT13, LFAalone(5, 10,20, 50, 100, and200 t/ha) wasapplied. IntreatmentsT4,T6, T8, T10, T12, andT14, LFA(5, 10, 20, 50, 100, and200 t/ha)wasappliedincombinationwithpressmud;andinT15T18, LFA(5, 10, 20, and50 t/ha) was appliedincombination with press mud. For all applicationsinvolving press mud, the dosage was 10 t/ha. One-timeapplication of LFA was made in T11T18; repeatapplications of LFAweremadebeforecultivationof thethirdandfthcropsinT3T10at thesamerateasbeforethecultivationof therst crop.2.2.CroprotationandotherdetailsThecroprotationwasasfollows:rice(JanApr1997)green gram(AprMay 1997)rice (AprAug 1998)sunhemp (Dec 1998Jan 1999)rice (JanMay 1999)rice (Dec1999Apr 2000). The recommended dosage of NPKfertilizer was 100:50:50 kg/ha as urea (NH2CONH2): singlesuper phosphate (Ca(H2PO4)2) and muriate of potash (KCl)forcultivationofeachricecrop.Table1Treatments detailSl.No. Treatment Detail1 T1Control2 T2Pressmud (10 t/ha)3 T3Ligniteyash(LFA)(5 t/ha)4 T4LFA(5 t/ha)CPM (10 t/ha)5 T5LFA(10 t/ha)6 T6LFA(10 t/ha)CPM (10 t/ha)7 T7LFA(20 t/ha)8 T8LFA(20 t/ha)C(PM 10 t/ha)9 T9LFA(50 t/ha)10 T10LFA(50 t/ha)CPM (10 t/ha)11 T11LFA(100 t/ha)12 T12LFA(100 t/ha)CPM (10 t/ha)13 T13LFA(200 t/ha)14 T14LFA(200 t/ha)CPM (10 t/ha)15 T15LFA(5 t/ha)CPM (10 t/ha)16 T16LFA(10 t/ha)CPM (10 t/ha)17 T17LFA(20 t/ha)CPM (10 t/ha)18 T18LFA(50 t/ha)CPM (10 t/ha)L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 1742.2.1.OtheramendmentsOtheramendments,suchasgypsum(325 kg/ha),humicacid (20 kg/ha), and biofertilizer (RhizobiumCPhospho-bacterium; 8 kg/haeach), wereapplied, alongwithbasaldosageofchemical fertilizers, inall treatments, includingcontrol. Theseamendments weremadeas supplementingagents, especially in viewof the poor fertility of minespoil andthenormal practiceof usingsuchamendmentsby local farmers. No applications of NPKfertilizer andother amendments as green manure were made forgrowing green gram or sun hemp. Press mud, alightweight waste product from the sugar industry,abundantlyavailableinareas nearbytheNLC, was usedasasourceoforganicmatterandplantnutrients(Table2)to improve the texture and fertility of the mine spoil.Gypsum, of a locally available, commercial-grade com-position, including14%sulfur, wasappliedtoreducethecrustformationintheminespoil. Potassiumsaltofhumicacid(20%humicacidcontent),preparedfromlignitebyachemical method at Centre for Applied Research &Development (CARD), NLC, was applied in the minespoil tostimulatemicrobial growthandtoprovidesomeessential plant elements. Biofertilizer, a composition ofRhizobium and Phosphobacterium developed in theCARDmicrobiologicallaboratory, wasmixedwithlignitetoact asacarrier of microbes.2.3.Collectionandcharacterizationofminespoil,LFA,pressmud,andcropproduceThevarious samples of dryLFAusedfor eldtrials,mine spoil and press mud before the start of the eldexperiment (cultivation ofthe rst ricecrop),crop produce(grain and straw), and mine spoil from control and amendedplots after harvest of each rice crop were collected,processed, and analyzed by the standard procedurediscussedbelow.2.3.1.MethodsofanalysisThe physical properties, such as mechanical compo-sition, BD, porosity, WHC, andhydraulicconductivity, ofLFAand mine spoil were determined by the standardmethods (Piper, 1950; Black, 1965; Jackson, 1967).Chemical properties, namely, pH, electrical conductivity(EC), and total and available major secondary nutrients (N,P, K, S, Ca, and Mg) of LFA and mine spoil weredetermined by the standard methods (Black, 1965; Jackson,1967;Tandon,1995).The samples of mine spoil, LFA, and crop produce weredigested in an analytical microwave system (AMS, ProlaboMicrowave Oven), usingvarious Suprapure acids fromMerck,Germany,asreagentsforanalysisoftotalcontentsof micronutrients (Cu, Zn, Mn, and Fe) and trace and heavymetals (Pb, Ni, Co, Cd, etc.). For determination of availabletraceandheavymetalscontentinLFAandminespoil,theextractionofsampleswithdiethylenetriaminepentaacetate(DTPA) was carried out by the prescribed method (Tandon,1995), bywhichtheavailablecontent wasestimated. TheDTPA-extractablefractionoftotalcontenthasbeenfoundto be relatively bioavailable for root uptake (Adriano et al.,2002).Total trace- and heavy-metals content in variousdigestedmine spoil, LFA, grain, andstrawsamples andavailable content in DTPAextracts of mine spoils andLFA were estimated by liquid ion chromatography(Waters). Thedeterminationof Cu, Zn, Mn, Fe, Pb, Ni,Cd, andCowas madewithaC18column, withsodiumoctanesulphonate, tartaricacid, andacetonitrileaseluent;postcolumn reagent; and ultraviolet light (UV) detector(520 nm). The ICPak-AHRcolumn, borategluconateeluent, and UV detector (365 nm) were used fordetermination of Cr (as CrO4K2). The standard samplefor various trace and heavy elements was ICP multi-element standard solution IV(Cat. No. 1.11355.0100),procuredfromMerck.ThedetectionlimitforCu,Co,Mn,and Zn, was 5 ppb; and for Cd, Cr, Fe, Ni, and Pb,15 ppb.TheAsandHgwereanalyzedwithaUnicomSP-2900atomicabsorptionspectrometerbythehydridecold-vapor generationmethod. Thedetectionlimit for As andHgwas5 ppb.The g-emitting radionuclides were measured with ag-rayspectrometer, comprisinga high-puritygermanium(HPGe)detectorwitharesolutionof1.95 kVat1.33 MeVand a volume of 77 cm3. The detector was kept at 2pgeometry for counting. The g-rays emitted from thesampleweredetectedbytheHPGedetector, withtheleadshieldinglinedby1 mmof aluminum, andwerededucedwith a PC-based multichannel analyzer. The data wereanalyzed, and radionuclides226Ra,228Ac, and40Kwereestimated for various samples of mine spoil, LFA, andcropproduce. Thedetectionlimitsof theseradionuclidesinthemine-spoil andLFAsampleswas5 Bq/kg; andforgrainandstrawsamples, 0.05 Bq/kg. ThedehydrogenaseTable2Physico-chemicalcharacteristicsofpress mudValueParameterspH 7.44Electricalconductivity(dS/m) 1.874WHC(%) 149.4Organiccarbon(%) 13.2Moisture(%) 9.4Ash(%) 39.3Volatile matter(%) 47.7Fixedcarbon(%) 3.6Ultimate analysisCarbon (%) 26.19Hydrogen (%) 2.67Sulfur(%) 1.82Nitrogen(%) 0.82L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 175activity in mine spoil was estimated by the standardmethod(Kleinet al., 1971).2.4.StatisticalanalysisOne-way analysis of variance was performed andcomputedfor the critical difference (CD) value with anMSTAT package (Russel et al., 1991), to assess thesignicance (p!0.05) of the yield data, analysis of thesamples, and various biological parameters. For other cases,wherever applicable, standard error has been shown intablesandgures.3. Resultsanddiscussion3.1.BiometricobservationsBiometricobservationof thegrowthanddevelopmentstagesof ricecropsrevealedthat plant height, numberoftillers, and plant population varied between treatments (datanot shown). One-time and repeat applications of LFAfrom 5to20 t/ha, withandwithout pressmud, signicantly(p!0.05) increasedplant growthperformance, withthemostpromisingresults fromrepeat applications of LFAat thesame dosage in treatment T8(20 t/ha LFAwith press mud) ofTable3Physico-chemicalcharacteristicsofminespoilofexperimentalsiteatmine-I,NLCbeforeconduction of eldexperiments,andofLFA appliedatdifferentstagesof eldtrialsOriginalsoil(mine spoil) Lignitey ashParametersSand(%) Coarse 16.2G1.01 30.7137.47Fine 36.9G2.15Silt(%) Coarse 14.6G0.91 51.2861.6Fine 17.8G0.1Clay(%) 14.5G0.85 8.6610.61Bulkdensity(g/cm3) 1.72G0.12 0.881.051WHC(%) 19.8G1.42 41.5950.4Porosity(%) 29.2G1.85 49.2257.81EC(dS/m) 0.436G0.02 3.774.52Dehydrogenase activity (mg/kg hK1) 0.032G0.001 pH 6.50G0.93 10.2310.54Totalmajor nutrientsOrganicC(%) 0.30G0.02 0.1220.180N(%) 0.021G0.001 P(ppm) 46.0G2.69 72.591.24K(ppm) 77.2G5.17 816.4993.4S(%) 0.22G0.012 0.961.15Ca(%) 0.16G0.009 9.2811.28Mg(%) 0.04G0.002 1.191.53Availablemajor andsecondary nutrientsN(%) 0.006 P(ppm) 2.8G0.13 2.863.89K(ppm) 20.6G0.93 52.5268.25S(ppm) 37.8G1.81 93.96105.22Ca(ppm) 40.2G2.13 16952000Mg(ppm) 22.5G1.23 30.2037.01Traceandheavymetals Total(ppm) Ava(ppm) Total(ppm) Ava(ppm)Cu 70.63G4.20 2.30G0.17 40.5751.47 1.962.30Zn 79.38G6.03 1.52G0.15 148.52162.05 1.902.30Mn 133.74G8.69 6.49G0.49 162.17192.19 15.6020.72Fe 1.63bG0.11 19.61G1.31 3.97b5.44 55.9675.66Pb 18.80G1.35 BDL 12.8817.31 0.060.10Ni 44.23G3.01 2.11G0.16 129.13141.82 4.895.23Cd 1.96G0.14 0.03G0.002 10.0312.20 0.140.30Co 15.54G1.15 BDL 19.5424.10 0.370.54Cr 36.43G2.48 BDL 46.8456.88 0.400.66As BDL BDL 1.191.44 BDLHg BDL BDL Radioactivity(Bq/kg)220Ra 15.7G0.67 74.1984.87228Ac 31.9G1.78 74.5087.5240K 150.3G8.14 352.59413.03aAv,DTPAextractable.bTotalFecontent inpercent.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 176the third crop. The overall growth condition of rice plants wasluxuriant, withless incidenceof pests, plant disease, andweeds; uniformandearlymaturity; intensecolorofgreenleaves; and bigger size of panicles in the plots amended withLFA alone and in combination with press mud. However, atdosages beyond 20 t/ha of LFA, with and without press mud,particularly at 100 (T11 and T12) and 200 t/ha (T13 and T14),biometricvalues droppedabruptly, toevenless thanthecorrespondingcontrol values. However, suchloweringofbiometricvaluesdiminishprogressivelyduringthegrowthof successive crops. Also, no apparent symptoms whatsoeverof toxicity due to trace and heavy metals and radionuclidespresent in LFA could be observed.No biometric observations were made of greengram(second crop) or sunhemp(fourthcrop), as these weregrownasgreenmanure.3.2.CharacteristicsofminespoilandLFA3.2.1.MinespoilFrom Table 3, it can be observed that the textural class oftheminespoilissiltloamtypewithmassivestructureandverypoor aggregates andnoappreciable similarity withnormal arablesoils. Thesandisthepredominant fraction(53.1%) followed by silt content (32.4%), wherein bothcontain a higher content of ne fraction than coarse fraction.The clay content (14.5%) is quite low. The BD is very high(1.72 g/cm3), incomparisontoarablesoil. WHC(19.8%)and porosity (29.2%) were found to be very low, comparedwiththecorrespondingvaluesofnormalfertilesoil(ICAR(IndianCouncilofAgriculturalResearch),1969).The mine spoil is just acidic (pHZ6.5). The EC is quitelow (0.436 dS/m) indicating the prevalence of a poor salinecondition.Organiccarbon(OC)isalsolower(0.30%)thannormal for Indian soil, 0.40.6% (ICAR (Indian Council ofAgriculturalResearch),1969).Similarly,theconcentrationoftotalandavailablemajorandsecondarynutrients(N,P,K, S, Ca, and Mg) and micronutrients (Cu, Zn, Mn, and Fe)in mine spoil indicates its poor fertility. The total content oftrace and heavy metals, such as Pb, Ni, Co, and Cr, is in therange15.544.2 ppm, andCdis1.9 ppm. Othertraceele-ments, such as As and Hg, are below detection limit (BDL).The available content of Ni and Cd is 2.11 and 0.03 ppm,respectively, and that of Pb, Co, Cr, As, and Hg is BDL. Thedehydrogenase activity, ectomycorrhiza, P-solubilizingbacteria, and total bacterial count in mine spoil arepracticallynegligible, comparedwiththenormalsoil. Theradioactivitylevel, particularlywithrespect tog-emitters220Ra,228Ac,40K, is 15.7, 31.9, and 150.3 Bq/kg,respectively. Altogether, the physico-chemical character-istics and fertility of mine spoil compare poorly with normalagriculturalsoil.3.2.2.LigniteyashFrom Table 3, it can be observed that the LFA applied atvariousstagesof eldtrialsincludeslowercontentofsandand clay and higher content of silt than mine spoil. The BDis lower, and WHC and porosity are quite a bit higher, thanin mine spoil. EC and alkalinity (pH 10.2510.54) are muchhigherduetothehighercontentofCa(9.2811.28%)andMg(1.191.53%). The OC(0.120.18%) is muchlowerthan in mine spoil. Furthermore, LFA is completely devoidofnitrogenanddehydrogenaseactivity,andthecontentofmajor and secondary nutrients (P, K, S, Ca, and Mg) is muchhigherthanthenegligiblevaluesfoundintheminespoil.Totalandavailablecontent ofmicronutrients, suchasZn,Mn, and Fe, is higher, and Cu is lower. Similarly, total andavailable content of trace and heavy metals Ni, Cd, Co, Cr,and As is higher, and that of Pb is lower. Besides, the levelof radioactivity in respect to g-emitters220Ra,228Ac,40K ishigher. In sum, the LFA could be used to modify the textureand improve the fertility of mine spoil, provided theapplicationiseco-friendly.3.3.CropyieldIt is evident from Fig. 1 that because of the increase in thedosageofLFA(alone)from5to20 t/ha,thegrain yieldofthe rst crop increased signicantly (p!0.05) andprogressivelyintherangefrom11.59to24.63%overthecontrol (T1). An additional increase in the crop yield of 1.510.2%wasduetothecombinedeffectsofLFAandpressmud. However, at higher dosages, the yield decreasedsharply and to lessthan the control,particularly in T11T14(100 and 200 t/ha LFA, with and without press mud).Nonetheless, however little the growth, nosymptoms oftoxicity were noticed from trace or heavy metals present inLFA. This observation of increase and decrease in the yieldalsoholdsforthegrainsofthethird,fth,andsixthcrops.Signicant increase (p!0.05), in the range from3.0 to42.0%over corresponding control values of individualcrops, with increasing dosage of LFA (520 t/ha), with andwithout pressmud, anddecreaseat dosagesbeyondthesevalues were observed. The maximum increase in yield overthe control appearedwithrepeatapplications in T8 (20 t/haLFAand press mud) of the third crop. Also, a greatereffectiveness was noticedof repeat applications at lowerdosages, up to 20t/ha, of LFA made before cultivation of thethird and fth crops, compared with both one-timeapplication at 100 and 200 t/ha of LFA(T11T18) andrepeat applications at 50 t/ha inT9andT10. Hence, theoptimumdosageofLFA(withandwithout pressmud)is20 t/ha for both one-time and repeat applications. TheadverseeffectoftheapplicationofhigherdosagesofLFA(beyond20 t/ha) was observedtodecrease insuccessiveyears of growing crops, and the yield was either at par withthe yield of the corresponding control of a particular crop orslightlyhigher.Thetrendofincreasedyieldwithupto20 t/haofLFA(withandwithout pressmud), togetherwithadecreaseathigherdosages,alsoappearedinstraw,wheretherangeofincreasewasalmost thesame, althoughthedecreasewasL.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 177less. Such adverse effects on the yield were wellcorroborated in a separate investigation (CARD, 1997),and they are possibly attributable to compaction of thesurface (hardpan formation, observed clearly duringcultivation)resultinginpooraerationandrootpenetration,owing to the highly pozzolanic nature of LFA containing theCaAlSi typeofmineralsandtothehighersolublesaltsand silt content with moisture. However, the gradualdecrease in the adverse effects on crop yield at higherdosages of LFA(beyond20 t/ha, withandwithout pressmud), together with progressive improvement in growthperformance, during the course of growing successive crops(on the basis of the biometric observations discussed above),indicatestheprogressiveameliorationoftheconditionsofmine spoil, favorable for crop growth. Furthermore, it seemsthat both green gram and sun hemp grown as green manurehave contributed to enhancing the yield of the next crop. Asanillustrationof the point, the yieldof grain, 1.92and2.05 t/ha in the treatments T1 (without any amendment) andT2 (with press mud only), respectively, of the third crop wasconsiderably higher than that of the correspondingtreatments of the rst crop (1.38 and 1.58 t/ha), whichclearlyindicatesthepositiveeffectofgreenmanure.Thus,theoverall benecial effect of LFAapplicationsof upto20 t/ha, alone and in combination with press mud, insignicantly (p!0.05) increasing the yield of various cropsoverthecorrespondingcontrols(evenuptothelastcrop),suggestsbettermine-spoilhealthandsustainability.3.4.EffectofLFAapplicationoncharacteristicsofminespoil3.4.1.Physico-chemicalcharacteristicsAtrendwasobservedintheminesoil withincreasingdosage of LFA, up to 200 t/ha (with and without press mud),aftertheharvest oftherst crop: adecreasefromcontrolvaluesforsand,from52.8to47.8%;forclay, from14.5to14.2%; and for BD, from1.71 to 1.64 g/cm3and anincreaseforsilt,from32.7to38.0%;forWHC,from20.1to24.2%; andfor porosity, from30.5to34.8%(Fig. 2).Fig. 1. Effect of one-time and repeat applications of different dosages of LFA with and without press mud on the grain yield of rice crops (CD at 5% for CropI0.031, Crop III0.030, CropV0.034, CropVI0.031).L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 178Thisobservationisimportant inagriculture, especiallyasregards the easypenetrationof theroot andbetter plantgrowth. The morphological structure of y ash is such that ithasasphericalhollowshape,anditispossiblethatsmall-sized particles of LFA, containing a larger proportion of silt(54.058.0%) than mine spoil (33.4%), accumulate in voidscreated by bigger-sized particles of mine spoil. Thiscontributed to the modication of the texture of minespoil (Khan et al., 1996). Furthermore, with increaseddosage of LFA, up to 200 t/ha (with and without press mud),anincreaseoccurredinpH, from6.50(control) to7.69;andinEC, from0.413(control) to0.795 dS/m(Fig. 3).051015202530354045T1 T2 T7 T8 T9 T10 T11 T12 T13 T14Silt (%)0102030405060T1 T2 T7 T8 T9 T10 T11 T12 T13 T14Sand (%)024681012141618T1 T2 T7 T8 T9 T10 T11 T12 T13 T14Clay (%)051015202530T1 T2 T7 T8 T9 T10 T11 T12 T13 T14WHC (%)BD (g/cc)0510152025303540T1 T2 T7 T8 T9 T10 T11 T12 T13 T14Porosity (%)1.581.601.621.641.661.681.701.721.74T1 T2 T7 T8 T9 T10 T11 T12 T13 T14(a)(b)(c)(d)(e)(f)Fig.2.EffectofLFAontexture(sand,silt,andclay),WHC,porosityandBDofminespoilafterharvestof rstcrop.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 179TheincreasesinthepHandECvaluescouldbeascribed,respectively, to the alkaline nature and the higher solubilityof the inorganic constituents of LFA. In fact, the increase inEC could be considered high and likelyto suppress normalgrowth, especially as the EC values in the range 0.51.0 dS/mcanreducegerminationandcauseburningorwiltingofsensitivecrops(CSTPA(CouncilofSoilTestingandPlantAnalysis), 1992). Probably, enhancement of EC, particu-larlyenhancement beyond20 t/haof LFA, is oneof thefactors responsible for poor growthandlowyields. Theincrease in OC, from 0.31 to 0.43%, could be ascribed to theapplication of organic matter, such as press mud,biofertilizer,andhumicacid.The available major and secondary nutrients (N, P, K, S,Ca,andMg)intheminespoilaftertheharvestoftherstcropincreaseddistinctivelywithvariousdosagesof LFAof upto200 t/ha, withandwithout press mud(Fig. 4).Forexample, Caincreasedintherangefrom40.6(T1)to44.3 ppm(T13) and from41.3 (T2) to 45.1 ppm(T14),respectively, with increasing dosage of LFA of up to 200 t/ha, alone andin combinationwith press mud. The increaseofMgforcorrespondingtreatmentswasintherangefrom22.8 (T1) to 25.7 ppm (T13) and from 23.4 (T2) to 26.9 ppm(T14). This increase in the content of Ca and Mg reects thegradual increase in pH of mine spoil with increasing dosageof LFA. The available micronutrients (Cu, Zn, Mn, and Fe)weresimilarlyenhanced(Fig.5).Thisobservationisclosetondings byothers(Simsetal., 1994).Alongwiththis,ahigher increase in nutrient status was noticed in combinationtreatments(LFAwithpressmud)thaninindividual ones,which may possibly be ascribed to the benet for cropgrowth of the complementary nutrient status of theseFig.4.EffectofLFA onavailablecontentofmajorandsecondarynutrients inminespoilafterharvestof rstcrop.0.01.02.03.04.05.06.07.08.09.0T1 T2 T7 T8 T9 T10 T11 T12 T13 T14pH0.00.10.20.30.40.50.60.70.80.9OC (%)/EC (dS/m)pH EC (dS/m) OC (%)Fig.3.EffectofLFAonpH,ECandOCvaluesofminespoilafterharvestof rstcrop.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 180amendments. It is pertinent to mention that thoughthe availability of nutrients increased in the mine spoilwhen LFA was increased beyond 20 t/ha (with and withoutpress mud), the enhancement of ECvalues, along withhardpanformation, probablypredominatedtocausebothpoorgrowthandlowyield.Theresultsonavailabletraceandheavymetalsinminespoil after the harvest of the rst crop reveal that even aftertheadditionofvariousdosagesofLFAofupto200 t/ha,with and without press mud, the concentration of Cr, Pb, Co,Cd, and As remained BDL. Conversely, an appreciableincreasingtrendinNiwasnoticed,intherangefrom2.06(T1) to 2.45 (T13) and 2.10 (T2) to 2.48 ppm (T14), up to thehighest dosage of LFA of 200 t/ha, alone and incombinationwithpressmud(Fig.5),whichiswellwithinthepermissiblelimits (SrivastavaandGupta, 1996). Thephysico-chemical characteristicsof minespoil onamend-mentwithLFA,aloneandincombinationwithpressmud,improved appreciably, depending on the dosage andcharacteristics of the amendments, where the rice cropwasnotaffectedduetobuildupofsalinity,particularlyupto20 t/haofLFA.Othershavemadesimilarstudiesoftheeffectsofcoal ashinimprovingphysico-chemical charac-teristics of mine spoil, with no adverse symptoms of toxicity(HillandLamp,1980;MollinerandStreet,1982).Analogoustotheobservationsmadeofminespoilafterthe harvest of the rst crop, a trend of decreased sand, clay,and BDand increased silt, WHC, and porosity was noticed inthe mine spoil after harvest of the third, fth, and sixth crops,where the range of values shows a gradually improvedtexture. The same trend could be observed for pH, EC, andOC; available major and secondary nutrients (N, P, K, S, Ca,and Mg); and micronutrients and trace and heavy metals (Cu,Zn, Mn, Fe, and Ni) in the mine spoil with these crops withincreasing dosage of LFA, with and without press mudwithonlyslight variation. Thisvariationoccurredinaslightlyhigher range for chemical properties and nutrient content andin a lower range for trace and heavy metals than for the minespoil of theprecedingcrops(datanot shown), dependingontheoverall effectsoftheamendmentsdiscussedabove.However, other trace and heavy metals remained BDL.Theimprovementinthephysico-chemicalpropertiesofamended mine spoil indicates its possibly benecial impacton crop yield, where the role of press mud and other organicmatter,viatheirdecompositionandNdemineralization,iscrucial (Adrianoet al., 1982). Theacidifyingtendencyofprotonsfromorganic-matterdecompositionofpressmud,biofertilizer, humic acid, and even gypsum would offset thealkalizingtendencyoftheCaOandMgOpresentinLFA,whichmaintainednear-neutralpH(6.88)oftheminespoilafter the harvest of the last crop (sixth). As a result, the widegap between the pH values of mine spoil (6.5) and those ofLFA (10.2310.54) and the increase in buffering capacity donot matter much and result in no toxicity due to thecontrolled carryover of toxic trace and heavy metals by cropproduce. Here, thehypothesiscanalsobeconsideredthatmixing y ash with biosolids produces a material with morebalancedproperties (e.g. neutral pHandthepresence ofessential elements) and less potential for environmentalcontamination than in either material applied alone(Stevenson, 1982; Sims et al., 1993; Wong, 1993). Thebenecialeffectshavebeenreportedofsewagesludgeandother amendments, such as lime and gypsum, added to coal-ash material in maintaining pH, changing the water-solubleOCandEC,andreleasingN,P,andKforassimilationbyplants during the revegetation of the soil (Martens andBeham, 1976; Pietz et al., 1989). Similarly, a reducedincidenceofpestsinLFA-amendedplotsmight alsohaveenhanced crop yield (Narayanaswamy and Nambirajan,2000). Thus, after application of various dosages of LFA, upFig.5.EffectofLFA onavailablecontentofmicronutrientsandtracemetalsinminespoilafterharvestof rstcrop.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 181to200 t/ha, aloneandincombinationwithpressmudandother amendments as supplementingagents, thephysico-chemical properties and fertility of the mine spoil improved,but with uptake of trace and heavy metals withinpermissible limits. However, hardpan formed, and thesoluble salt content increased, particularly at dosagesbeyond20 t/haof LFA, whichwere, of course, graduallyannulledinthecourseofsuccessivecrops.3.4.2.RadioactivitylevelThe radioactivity levels in the mine spoil after the harvestof thelast crop(sixth), withrespect tog-emitters220Ra,228Ac, and40K, were observed to have gone above thecontrol value,from14.2to 26.1, 29.7to41.6,and145.2to170.3 Bq/kg, respectively, with the application of themaximumdosage of LFAof 200 t/ha alone (data notshown). But the levels of the radionuclides were well withinpermissiblelimits andinagreement withthendings byothers (Ramachandran et al., 1990; McMurphy andRayburn,1996).3.4.3.BiologicalactivityThe biological activity of the mine spoil, almostnegligible initially, was found to have improved signicantly(p!0.05) as a result of the addition of LFA of up to 20 t/ha,aloneandincombinationwithpressmud.Aftertheharvestof the rst crop, a signicant (p!0.05) increase occurred inmicrobial activities over the control. The ectomycorrhizaincreased from0.0 (T1) to 38.0 spores/g; P-solubilizingbacteria, from0.01 (T1) to1.5 CFU!104; total bacterialcount, from 0.18 (T1) to 4.5 CFU!104g; and dehydrogenaseactivity, from0.035 (T1) to 0.068 mg/kg hK1, up to thedosageof 20 t/haof LFAalone(T7). Asimilar trendwasobserved for treatments of up to 20 t/ha of LFA incombinationwithpressmud(T8), withenhancedrangesofdifference (data not shown). This trend was also observed inthe mine spoil after harvest of succeeding crops, withprogressively increased ranges of difference. With appli-cations of LFA beyond 20 t/ha, the total bacterial populationdecreased (as was also evident from a decrease in the enzymeactivities), probablyas a result of hardpanformationanddevelopment of anaerobic and waterlogging conditions.These enhanced microbial activities in the mine spoilmight have played a crucial role in improving the soilfertilityandyieldof various crops appreciably. Here, theorganic amendment as supplementing agent might havecontributed to the improvement in the condition of the minespoil by increasing cation exchange capacity (CEC) andorganic-matter (humus) content, resultinginbetter fertilityandenhancedmicrobial activity, besides enhancedimmo-bilization of toxic elements and other factors inhibitingmicrobes (Chaney and Giardono, 1977). As well, the role ofthe improved texture of the amended mine spoil in enhancingbiological activitycannot beruledout (Lyonet al., 1952).These observations are in agreement with ndings by others(Pitchel,1990;Laietal.,1999).3.5.EffectsofLFAonthecharacteristicsofcropproduce3.5.1.CharacteristicsofgrainFig. 6 shows that the total major and secondarynutrients, suchas N, P, K, S, Ca, andMg, inthe grainsamples fromtreatment T7(20 t/ha of LFAalone) afterharvest of the rst cropincreasedover the control (T1),from1.28to1.34, 0.059to0.071, 0.66to0.75, 0.068to0.70, 0.035to0.42, and0.019to0.026 ppm, respectively.Concomitantly, anincrease occurredinthe total contentof thesenutrients inthegrainsamplefromtreatment T8(20 t/haof LFAwithpress mud), withnotablyenhancedranges of difference. With applications beyond thisamount, the concentration of these nutrients decreased,similar tothecropyield.Fig.6.EffectofLFA onconcentrationoftotalmajor andsecondarynutrients ingrainsamplesof rstcrop.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 182The concentration of micronutrients and trace and heavymetals also increased over the corresponding control valuesin the LFA treatments (with and without press mud) of up to20 t/ha, for each element (Fig. 7). In a trend quite similar tothat of the results obtained for yield and major andsecondary nutrients, the concentration of micronutrientsdecreased with the increase in LFA dosagebeyond20 t/ha,whichsuggests that suchhighdosages of LFAhave noappreciable impact on the nutrient status of grain. Likewise,the concentration of the trace and heavy metals Cr, Pb, andNi inthegrainsamples fromtreatment T7(20 t/haLFAalone) increased over control T1, from 1.64 to 2.39, 1.22 to1.38, and 5.21 to 6.33 ppm, respectively. This observation isalso pertinent to the grain sample from treatment T8 (20 t/haLFAwith press mud) with a notably higher range ofdifference. However, therewasalsoadecreaseat dosagesbeyond20 t/haofLFA(withandwithoutpressmud). Butthe concentrations of Co, Cd, and As were BDL in all LFAtreatments. The trendobservedfor major andsecondarynutrients, micronutrients, andtraceandheavymetalswasalsoobservedfor thegrains fromsucceedingcrops, withranges of difference being a little on the high side in the caseofmajorsecondarynutrientsandbeingonthelowsideinthecaseofmicronutrientsandtraceandheavymetals.Thesmallincreaseintraceandheavymetalscontentissuggestiveof lowavailabilityof traceandheavymetals,which gradually decreased because of the increase in the pHof the mine spoil withincreasingLFAdosage (Fulekar,1993), thepresenceof metalsinoxideform(Pageet al.,1979), an increase in adsorption of metals by soil withincreasedpH, andtheresultingmarginal uptakebycropproduce(Adrianoetal.,1980).However,thepossibilityofmetalsbecoming moresoluble aftera long duration cannotbe entirely ruled out, as the liming effect of y ashapplication is prone to diminish due to natural oranthropogenic soil acidication processes (Sims et al.,1995). Thecarryover of toxictraceandheavymetals ingraindepends onseveral factors, suchas pH, OC, CEC,micro-organisms, concentration of metals, and their form ofoccurrence, andthemobilityofsuchelementstotheroot,theirtransport fromroot surfacetoroot interior, andtheirtranslocation fromroot to shoot (Chaney and Giardono,1977)playsasignicantrole. ThePbandCrabsorbedbyroots normally remain in the root and are not readilytranslocatedtotheshoot(Alloway,1995),whereasCdcanreadily be translocated from root to shoot, but it is the highervalues of Zn and pH that reduce the uptake of Cd. Probablyfor thisreason, theuptakeof thesetoxictraceandheavymetals in the grain was well within the critical toxicity limits(MacNieol andBeckett, 1985; Alloway, 1995; SrivastavaandGupta, 1996). AsfarasthehigheruptakeofNi, from5.21 to 6.35 ppm, is concerned, it is probably because of itsreadily mobile characteristics in plants, leading to itsextensive accumulation in the seeds (Alloway, 1995),which is also not alarming. Furthermore, the concentrationsof Co, Cd, andAswerebelowdetectionlimits, whichisobviously due to their relatively lower initial content in bothminespoil andLFA. Asaresult, thegrainsamplesfromtreatments at theoptimumdosageof LFAhadimprovednutrient status, whereas the carryover of toxic trace andheavy metals was well within permissible limits. Thedecreaseinconcentrationof nutrientsingrainat dosagesbeyond 20 t/ha of LFA is probably due to hardpan formationin the mine soil, together with an increase in its salt content,resulting in poor growth. This observation is well bolsteredbyotherstudies(Pitcheletal.,1994;Senetal.,1997).3.5.2.CharacteristicsofstrawConcomitantly with the variation in the characteristics ofthe grain samples after the harvest of the various rice cropswithdifferent dosagesof LFA, aloneandincombinationwith press mud, the characteristics of the straw samples alsoFig.7.EffectofLFAonconcentration oftotalmicronutrients andtraceandheavymetalsingrainsamplesof rstcrop.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 183varied(datanot shown). Theobservedtrendofdecreasedconcentrations of major and secondary nutrients, micro-nutrients, and trace and heavy metals in the straw, like in thegrain, beyond20 t/haofLFAispossiblyduetothesamereasonsdiscussedabove.3.5.3.RadioactivitylevelincropproduceFig.8showstheradioactivitylevelof g-emitters226Ra,228Ac, and40Kinthegrainsamplesofvariouscropsfromplots amended with higher dosages of LFA in T11 (100 t/haLFA)andT13(200 t/haLFA),suggestingaslightincrease,particularly in226Ra and228Ac. But in40K, the increase wassubstantial, from40.2(control)to52.6and64.8 Bq/kginT11andT13, respectively, inthegrainsampleof therstcrop.Thisobservationalsoholdstrueinthecaseofstraw,with lower ranges of difference (Fig. 9). Furthermore, in thegrainandstrawsamplesofthesucceedingcrops,asimilartrend of progressive increase from one crop to the next crophasbeenobserved,butwithlevelswellwithinpermissiblelimits(EisenbudandThomas, 1977; Boweh, 1996). Thus,the radioactivity levels of these emitters increased onlymarginally, except in the case of40K, probably as a result oftheapplicationofLFAcontainingahighercontentof40K,170.3 Bq/kg, thanminespoil (145.2 Bq/kg). Althoughtheradioactivity of muriate of potash (KCl) was not measured,it is possible that its application as one of the components ofthe basal dosage of chemical fertilizer (NPK) duringcultivationmight havecontributedtotheenhancedlevelof40Kincropproduce(SrivastavaandGupta, 1996). Inaseparatestudy, Geerardo(2001) expressedconcernaboutthe radioactivity in crop produce resulting from theapplication of chemical fertilizers, including KCl. Theapplicationof phosphaticfertilizers, liming, andmanuresto reduce the uptake of radionuclides in crop plantsFig.9.EffectofLFA ongammaradioactivity ofstrawsamplesfromdifferentcrops.Fig.8.EffectofLFA ongammaradioactivityofgrainsamplesfromdifferent crops.L.C.Rametal. /JournalofEnvironmentalManagement79(2006)173187 184(Skiba, 1987) through reduction in exchangeable fraction ofradionuclides has beeninvestigated(ButnikandIshenko,1990).3.6.PlausiblemechanismforimprovementofsoilhealthThe overall benecial effects of y ash on soil health maybe ascribable to the cumulative effect of the improvement inphysico-chemicalandbiologicalcharacteristicsofthesoil.Because of the presence of CaSi minerals with apozzolanic nature (zeolite formation), along with themoisture of the soil (Fulekar and Dave, 1986), y ashbrings about improvements in various physico-chemicalproperties, suchasBD, porosity, WHC, andtheavailablewaterinthesoil.Inparticular,theyashhasahighersiltcontentthansoil, andtheinltrationrateofsandysoilsormine spoil is drastically checked because of the increase insilt (Furr et al., 1977), whereas in the clay-rich type of soils,thereverseis thecase, withbetter water movement andworkability, apart from decreased plasticity or crackformationafterdrying.Asyashhasmostoftheessentialplant nutrients other than nitrogen and humus (Menon et al.,1990), applying it to the soil naturally improves its fertilityby enriching it with these elements, and this results inincreasedcropyield. Theorganicamendmentsmadewithyashalsohelpinimprovingthe humus andmicrobialactivities of the amended soil or mine spoil, besidesadjustingthepHby wayofdecompositionandNdeminer-alization (Adriano et al., 1982; Stevenson, 1982; Sims et al.,1993; Wong, 1993), controllingtheavailabilityof metalstothe plant bychelation, andreleasingnutrients duringvegetation(LoganandTraina,1993).The formation of a zeolite layer on the surface of y-ashparticles results into two exchangeable sites, one with 6-foldcoordinationandthe other with12-foldcoordination, toaccommodatemicro- andmacronutrients, respectively, sothat each ash particle becomes a repository of nutrients anda potential nutrient pump (Sahu, 1999). Besides, adsorption,desorption,andexchangebeingpHdependent,themineralpump is energized selectively for nutrient transfer toachieve rapid growth of plant in the y-ash-amendedsoils. Furthermore, during the ashwater interaction,oxyhydroxide of iron(goethite) is formedandacts as agreat scavenger of trace metals. The oxyhydroxideocculates,eitherascoatingorasdiscretegrains,andthusimmobilizes the heavy metals, leading to their reducedavailability(Leekieetal.,1980).Consequently,thelossofnitrogen fromthesoilbecauseofvolatilization,leaching,and denitricationis signicantly reduced, and thisimproves the N-utilization efciency of nitrogenousfertilizersandminimizessoilwaterpollution. Theplants,then, takeupnitrogeninphases, asandwhenneeded. Flyashalsohelps inthe retentionof the chemical fertilizerappliedthroughinorganic sources inthe soil systemforlongerperiods(CFRI, 2000), leadingtoresidualeffectsofy-ashapplication. Theuptakeandcarryoveroftraceandheavy metals in grain depend on several factors, such as pH,OC, CEC, micro-organisms, concentrationof metals andtheir formof occurrence, their mobility to the root andtransport fromroot surface to root interior, and theirtranslocationfromroottoshoot.4.ConclusionsLFA acts as an excellent soil modier and conditioner, avery good limingagent, anda source of essential plantnutrients for appreciably improving the texture and fertilityof the mine spoil, with signicant (p!0.05) increase in thecrop yield (about 42%) over the control, together with betterresidualeffects, especiallyupto20 t/haofLFA, withandwithout press mud. In general, the optimum dosage of LFAis 20 t/hafor bothone-timeandrepeat applications, andoverallmaximumyieldwasobtainedonrepeatapplicationofthesamedosageof20 t/haofLFAwithpressmud. Noadverseeffectonthequalityofminespoilorcropproducewas observed up to the optimum dosage of LFAapplications, except for hardpanformationinmine spoiland the enhancement of soluble salt content at dosagesbeyondtheoptimum, which, infact, decreasedprogress-ively during cultivation of succeeding crops. The uptake andcarryoverofcertaintraceandheavymetalsandg-emittersin mine spoil and crop produce were well within permissiblelimits. Therefore, aside fromrestoring the ecology of amine-spoil area and making it agriculturally worthwhile, thejudiciousapplicationofLFA,withandwithoutpressmud,provides a gainful and eco-friendly solution to the problemofthedisposalofLFA.AcknowledgementsThe authors express their sincerest gratitude to StandingScientic Research Committee (SSRC), Department ofCoal, India for providing nancial assistance. 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