Shortcommunication Effectofpotassiumsaltsanddistilleryeffluenton carbonmineralizationinsoil SureshChandra,H.C.Joshi * ,H.Pathak,M.C.Jain,N.Kalra Division of Environmental Sciences, Nuclear Research Laboratory Building, Indian Agricultural Research Institute, New Delhi 110 012, India Received3September2001;receivedinrevisedform4November2001;accepted26November2001 Abstract Distilleryeffluent,arichsourceofpotassium,isusedforirrigationatmanyplacesintheworld.Alaboratoryexperimentwas conductedtostudytheinfluenceofpotassiumsaltspresentinpost-methanationdistilleryeffluent(PME)alongwithtwoothersalts, KClandK 2 SO 4 ,onmineralizationofcarboninsoil.PMEoxidizedwithH 2 O 2 ,rawPME,KClandK 2 SO 4 solutionscontainingK equivalentto10%,20%,40%and100%ofKpresentinPMEwereaddedtothesoilseparately,maintainingfourreplicationsfor eachtreatmentandcontrol.AdditionofsaltsuptoacertainconcentrationstimulatedCmineralizationbutadeclinewasnoticedat higherconcentrations.AllthelevelsofsaltscausedhigherCO 2 evolutionthanthecontrolsuggestingthatthepresenceofKsalts enhancedthemicrobialactivityresultinginincreasedCO 2 evolution.TheinfluenceofK 2 SO 4 wassignificantlyhigherthanKClin stimulatingCmineralizationinsoil.Oxidizedeffluenthadahigherstimulatingeffectthaninorganicsalts,showingtheinfluenceof othersaltsaccompanyingKinthePME.RawPME,whichcontainedexcessorganicC,increasedCO 2 evolutionevenatthehighest saltlevel(100%PME)signifyingtheeffectofaddedConalleviatingthesaltstressonmicrobialactivity. Ó 2002ElsevierScience Ltd.Allrightsreserved. Keywords: Carbonmineralization;Microbialactivity;Post-methanationdistilleryeffluent;Potassiumsalts 1. Introduction Distilleriesareconsideredtobeamongthemostpol- luting industries as their effluents, if discharged into waterbodies,defilethenaturalecosystems.However,the effluentisarichsourceofpotassiumandcanbesuitably appliedtoagriculturalfields(Pathaketal.,1999).Several studieshavebeenconductedonmanurialvalueofPME (Joshietal.,1996)buttheeffectofitsexcesssaltcontent on carbon mineralization in soil has not been studied. Salts,whichmayoccurorbeappliedtosoilsinvarious operations have significant influence on microbial ac- tivity.Theliteraturesuggeststhattheeffectsofsaltson microbialactivitiesarehighlyvariableandaredependent onsoiltype(Laura,1974,1976,1977;PathakandRao, 1998). Although, at lower salt contents, increase in ac- tivity was noted in most of the studies where organic carbonwaslessthan1%.Anattemptwasmadetostudy the effect of inorganic salts on C mineralization and comparewiththesaltsfromdistilleryeffluentwithand withoutitsorganicCcomponent.Sincedistilleryeffluent isrichinpotassium,KClandK 2 SO 4 ,whicharealsoused as K fertilizers, were chosen for the present study to compare their impact with effluent application on C mineralizationinsoil.Theresultsmayeventuallyhelpin evaluating the suitability of PME as a substitute for conventionalpotassiumfertilizers. 2. Methods 2.1. Soil SoilsampleswerecollectedfromtheIndianAgricul- tural Research Institute Farm, New Delhi, India from the0to15cmsoillayer.Theentirevolumeofsoilwas thoroughlymixedandallowedtoairdry.Thesoilswere sieved through a 2 mm screen and a representative samplewasdrawnforanalysesusingstandardmethods (Pageetal.,1982).Thesoilwassandyloamintexture and contained 0.34% organic carbon, 0.06% total N, water-soluble K60mgkg 1 , ammonium acetate ex- tractable K151mgkg 1 , electrical conductivity (EC, 1:2soil:water)0:40dSm 1 ,pH(1:2soil:water)8.6,and waterholdingcapacity38.8%. BioresourceTechnology83(2002)255–257 * Correspondingauthor.Tel.:+91-11-5781490;fax:+91-11-5811112. E-mail address: him_ensc@iari.ernet.in(H.C.Joshi). 0960-8524/02/$-seefrontmatter Ó 2002ElsevierScienceLtd.Allrightsreserved. PII:S0960-8524(01)00230-9