Evaluation of chemical and biological consequences of soil sterilization methods

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1 Cspin J. Env. Si. 27, Vol. 5 No.2 pp. 87~91 Copyright y The University of Guiln, Printe in I.R. Irn [Reserh] CJES Cspin Journl of Environmentl Sienes Evlution of hemil n iologil onsequenes of soil steriliztion methos S. Rzvi rr, A. Lkzin* Soil Siene Deprtment, Agriulturl Collge, Ferowsi University of Mshh, Mshh, Mshh, Irn *Corresponing uthor s E-mil: lkzin@yhoo.om ABSTRACT Sterilize soils re ommonly use for the stuy of xenoioti sorption n s n ioti ontrol in ioegrtion experiments. They re lso use for the hemil stuy of nitrogen n ron yle proesses n the elimintion of the iologil ftors. In this reserh the effets of ifferent soil steriliztion methos suh s utolving, fumigting n exposure to ultrviolet n mirowve irrition on soil hemil n iologil properties (soil iity, eletril onutivity, tion exhnge pity, optil ensity, extrtle ron n nitrogen n olony forming unit) were exmine uner lortory onitions. All the steriliztion methos signifintly (t P<.5) erese ph n inrese eletril onutivity (EC), optil ensity (OD), extrtle ron n nitrogen s ompre to nonsterilize soil smples. The results showe tht utolving metho ws the most effetive metho in eliminting soil miroorgnisms n ultr violet irrition ws the less effetive one. These inue hnges were likely ue to relese of solule orgni is from humi mterils n e miroorgnisms. Keywors: Autolving, Colony forming unit, Fumigtion, Mirowve irrition, Soil steriliztion, Ultrviolet irrition. INTRODUCTION Soil steriliztion inlues erition or ontrol of ny mjor lss of soil orne pests suh s wees, wee sees, nemtoes, fungi, teri n plnt iseses (Nutter, 1957). There re ifferent methos of soil steriliztion in orer to inhiit miroil tivity in soils (Trevors, 1996; Shw, 1998). Most ommonly, these inlue utolving, gmm irrition, hloroform fumigtion, ethylene or propylene oxie, ultrviolet n mirowve irrition. Sine these methos re gretly ifferent in terms of properties n usefulness, the hoie of the est steriliztion metho my signifintly vry from one sitution to nother. It hs een reporte tht soil steriliztion methos ommonly lter soil physil n hemil properties. For exmple, ethylene n propylene oxie sterilnts ret with ii hyrogen of orgni mtter to inue n inrese in soil ph n orgni ron ontent (Do et l., 1982; Wolf et l., 1989; Negre et l., 1995). These inue hnges lter the sorptive ehvior of ompouns with funtionl groups whose retivity to orgni mtter is sensitive to ph hnge (Do et l., 1982) or orgni ron ontent. Gmm irrition uses epolymeriztion of rohyrtes suh s ellulose n retes free hyrogen n hyroxyl rils tht re retive s reuing n oxiing gents to leve C-C ons (Puri n Brrlough, 1993). Jenkinson n Powlson (1985) reporte tht hloroform fumigtion of soil use n immeite inrese in mmonium n orgni ron extrtle with 1N K 2SO 4. Some hemils suh s methyl romie n hemil gses re toxi in their nturl forms (Venkinson n Powlson, 1985). A numer of ifferent riteri suh s toxiity, ptility, ost, resiul perio n hzrness of the metho re lso importnt ftors in Online version is ville on or

2 88 seleting speifing soil steriliztion metho. Beuse of the ost, equipment involve n time n lor require, some sterilnts re more ptle thn others. For exmple, teril spores re more resistnt to ry het steriliztion thn utolving, therefore, it my e neessry to inute the wet soil smples for 1-2 ys to llow spores to germinte prior to ry het steriliztion. Cost of hemils, lor, equipment n the nger of humn toxiity must ll e onsiere in hoosing steriliztion opertion. Although the soil steriliztion is n importnt proess in some sientifi experiments, however, there is no report on hemil n iologil onsequenes of soil steriliztion in lrious soils of Irn. Therefore, the im of this reserh ws to investigte the effets of four ifferent soil steriliztion methos (utolving, hloroform fumigting n exposure to ultrviolet n mirowve irrition) on some soil hemil properties. MATERIALS AND METHODS Soil smpling Soil smples were ollete from to 25 m epth of Hplmi soil, ir rie, sieve (2 mm) n ple in plsti gs n store t 4 o C until nlysis were performe. Experimentl esign n nlytil proeures Five susmples were me from eh soil smple (with 3 replites for eh susmple). One set of susmples were left with no tretment s ontrol smples (C). The seon set of susmples were utolve (AU) for 15 min (121 o C, 15 psi). The other set of susmples were expose to mirowve irrition (MW) t full power (11 w) (Wng et l., 21). The fourth set of susmples were ple in vuum esitor ontining hloroform (CHCl 3) vpor for 24 hour (FU). The lst series of susmples were expose to ultrviolet irrition (UV) for 45 minutes in lminr flow inet. Immeitely, the moisture ontents of ll the trete smples were etermine n they were overe with sterile luminum foil. A 2 grm susmple of eh tretment ws mixe with 5 ml istille wter n were shken for out 15 minutes n st Evlution of soil striliztion sie for 3 hours n the soil iity (ph) n eletril onutivity (EC) of soil smples were etermine in 1:2.5 soil suspension y using EC n ph meter. Extrtle ron ws etermine y potssium ihromte oxition metho pte from Vne et l., (1987) n Dll (1979). Potssium ihromte (1 ml, 1 N) n 7 ml onentrte H 2SO 4 were e to 5 ml extrts n hete, n resiul potssium ihromte ws etermine y titrtion ginst ferrous mmonium sulphte (.5 N) using o-phenn throlin ferrous omplex s the initor. Extrtle nitrogen ws etermine y Miro-Kjelhl igestion (Pe et l., 1982; Dvison et l., 1989). Ction exhnge pity (CEC) ws mesure y using Chopmn (1956) metho. Optil ensity of.5 M K 2SO 4 extrts of ifferent tretments ws etermine t 42 nm. In orer to investigte ifferent tretment effets on the teril popultion, eh tretment ws serilly ilute n ulture on Nutrient gr. The numer of olony forming units (CFU) of ll the tretments ws lulte perioilly. Sttistil nlysis Sttistil signifine of ifferene etween tretment mens were ssesse y one wy ANOVA. Tretment mens were ompre using Dnkon n the lest signifint ifferene test t p.5. RESULTE AND DISCUSSION Effet of ifferent tretments on soil hemil n iologil properties Optil ensity hnge epening on the soil steriliztion metho. Optil ensity of extrte soil solution vrie from.57 to.343 for ontrol n utolve tretments, respetively. However, ll the tretments exept ultrviolet irrition use signifint inrese (p.5) in optil ensity in omprison to ontrol (fig. 1). The yellowish rown sustnes were likely humifie ompouns (Puri n Brrlough, 1993), n the inrese in optil ensity in ll the tretments my e ue to epolymeriztion of rohyrtes n leve of C _ C ons. It seems tht high temperture n stem pressure involve in utolving tretment resulte in highest vlues of optil ensity. An ppreile

3 Rzvi rr & Lkzin 89 portion of extrtle ron relese y tretments my hve originte from the non- iomss frtions of soil orgni mtter whih is onsistent with the finings of Puri n Brrlough (1993) n Islm n Weil (1998). Optil ensity ( 42 nm) Fig 1. Influene of ifferent soil steriliztion methos on optil ensity. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion n UV=ultr violet irrition. Relese of extrtle ron followe pttern similr to tht of optil ensity. Extrtle ron of ifferent tretments vrie from 494 to 1155 mg Kg -1 for ontrol n utolve tretments, respetively, n were sttistilly signifint (p.5) for ll the tretments in omprison to ontrol smples (fig.2). As stte efore, this inrese my e ue to the relese of solule orgni is presumly from humi mtter n e miroorgnisms. Slonius et l., (1967) n Do et l., (1982) lso foun tht utolve n other tretments relese solule orgni ron from soil smples. High temperture n stem pressure from utolving h signifint effet on C flushes, ut relese of high ontent of extrtle ron in fumigtion tretment my e ue to the long time exposure to hloroform vpor (24 h) tht kille miroorgnisms n relese their ron. The ifferene etween the vlues of extrtle ron of mirowve n ultrviolet irrition ws not signifint (p>.5). In this respet, it seems tht low length of time for these tretments my e resulte in low extrtle ron vlues s ompre with utolve n fumigtion tretments. Similrly, in lmost ll the tretments there ws inrese in the extrtle nitrogen Tretments in omprison to ontrol tretment (fig. 3). Autolve n fumigtion tretments were not signifintly ifferent (P<.5). Clevge of nitrogen ons in iomss n non - iomss omponents of soil nee higher energy ompre to C-C ons. The high temperture n long time in utolving n fumigtion tretments presumly resulte in relese of high ontent of extrtle nitrogen in omprison to ontrol, ultrviolet n mirowve irrition tretments. Extrtle ron (mg kg -1 ) Fig 2. Influene of ifferent soil steriliztion methos on.5 M K2SO4 extrtle ron. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition. Extrtle nitrogen (mg kg -1 ) Fig 3. Influene of ifferent soil steriliztion methos K2SO4- extrtle nitrogen. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition. Almost ll the tretments use signifint inrese in eletril onutivity (P<.5) in omprison to ontrol (fig. 4). The eletril onutivity of soil smples in utolve, fumigtion n mirowve tretments were not signifintly ifferent (P<.5). Cleve of ifferent ons in humi mteril n resiul kille iomss inue y these tretments relese ifferent ions in Tretments Tretments

4 9 extrte soil solution n resulte in inrese in eletri onutivity. Slonius et l., (1967) lso foun tht sterile soils hve higher eletril onutivity in omprison to non- sterilize soil smples. EC (s m -1 ) Fig 4. Influene of ifferent soil steriliztion methos on eletri onutivity (EC). Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition Soil ph signifintly erese y utolving, fumigting n mirowve irrition tretments (p.5) ompre to the ontrol. Autolving h the highest influene on ph; however, the ifferenes etween fumigtion n mirowve irrition tretments were not signifint (P<.5) (fig. 5). This erese in ph in ifferent tretments my hve resulte from soluiliztion of orgni is, however, the mgnitue of the erese epene on ii uffering pity of the soils. In ition, the effet of hnge in ph on the surfe hrge n hyrophoiity of soil orgni mtter shoul e onsiere. Slonius et l., (1967) foun tht utolving reue the ph vlue of lyey soil, wheres Wolf et l., (1989) reporte no hnge in ph for utolve soils. ph Fig 5. Influene of ifferent soil steriliztion methos on ph. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition. Tretments Tretments Evlution of soil striliztion Influene of ifferent steriliztion methos on tion exhnge pity (CEC) i not follow n ovious pttern (fig. 6). All the tretments use signifint inrese (P<.5) in tion exhnge pity in omprison to ontrol, ut the ifferenes etween fumigtion n ultrviolet irrition were not signifint (p.5), while these tretments h the highest tion exhnge pity. It is possile tht through other effets inue y fumigtion n ultrviolet tretments ph epenent hrge of the soils inrese n this my hve resulte in inrese of tion exhnge pity of these tretments. CEC (mol kg -1 ) Fig 6. Influene of ifferent soil steriliztion methos on tion exhnge pity. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition. The results of olony forming unit (CFU) of ifferent soil steriliztion tretments showe tht the ifferenes mong the tretments n non sterilize soil smples were signifint (p<.5). The olony forming units vrie from to in one g of soil smple for utolve n ontrol tretments respetively, however, mirowve n fumigtion h the sme effet (fig. 7). CFU.1 8 gr -1 soil Fig 7. Influene of ifferent soil steriliztion methos on olony forming unit. Mens followe y the sme letter re not signifintly iffernet t P<.5. C=ontrol, AU=utolving, MW=mirowve irrition, FU=hloroform fumigtion, n UV=ultr violet irrition. Tretments Tretments

5 Rzvi rr & Lkzin 91 It oul e onsiere tht ll the tretments were effetive in reuing miroil iomss n in this respet, utolve ws the strongest metho. Despite the limittion of these methos, they n still form goo sis for etter unerstning of hemil n iologil hnges inue in steriliztion methos espeilly with lk of relile reserh informtion. It seems tht further reserh is neee to evlute physil onsequenes of soil steriliztion methos. ACKNOWLEDGMENTS The uthors re grteful to stff of Soil Siene Deprtment of Ferowsi University of Mshh for their ssistne in fiel n lortory. REFERENCES Dll, R.C. (1979) Simple proessure for the etermintion of totl ron n its riotivity in soils n plnt mterils, Anlyst. 14, Do, T.H., Mrx, D.B., Lvy, T.H. n Drgun, J. (1982) Effet, n sttistil evlution, of soil steriliztion on nline n iuron sorption isotherms. Soil Si. So. Am. J. 46, Dvison, E.A., Ekert, R.W., Hrt, S.C. n Firestone, M.K. (1989) Diret extrttion of miroil iomss nitrogen from forest n grssln soils of Cliforni. Soil Bio. Biohem. 21, Islm, K.R. n Weil, R.R. (1998) Mirowve irrition of soil for routine mesurement of miroil iomss ron. Biol. Fertile. Soils. 27, Negre, M., Gennri, M., Crehio, C. n Ruggiero, P. (1995) Effet of ethylene oxie steriliztion of soil orgni mtter spetrosopi nlysis n sorption of ifuorfen. Soil Siene. 159, Nutter, G.M. (1957) Soil steriliztion prties in turf. USGA Journl n Turf mngement. pp Pe, G.M., Mkown, C.T., n Volk, R.J. (1982) Minimizing nitrte reution uring kjelhl igestion of plnt tissue extrts n stem exutes. Plnt Physiology. 69, Powlson, D.S. n Jenkinson, D.S. (1985) Chloroform fumigtion n the relese of soil nitrogen: the effet of fumigtion time n temperture. Soil Bio. Biohem. 17, Puri, G. n Brrlough,D. (1993) Comprison of 245 MHz mirowve rition n hloroform fumigtion-extrtion to estimte soil miroil iomss nitrogen using N-leling. Soil Bio. Biohem. 25, Slonius, P.O., Johnson, J.B. n Chse, F.E. (1967) A omprison of utolve n gmm-irrite soils s mei for miroil oloriztion experiments. Pl. Soil 27, Shw, L.J. (1999) Re-inoultion of utolve soil s non-sterile tretment for xenoioti sorption n ioegrtion stuies. Soil Eo. J. 11, Trevors, J.T. (1996) Steriliztion n inhiition of miroil tivity in soils. Journl of Mioiol. Methos. 26, Vne, E., Brookes, P.C. n Jenkinson, D.S. (1987) Miroil iomss mesurements in forest soils, the use of the hloroform fumigtion inution metho in strongly i soils. Soil Biol. Biohem. 19, Wng, W.J., Dll, R.C. n Mooy, P.W. (21) Evlution of the mirowve irrition metho for mesuring soil miroil iomss. Soil Sie. So. Am. J. 65, Wolf, D.C., Do, T.H., Sott, H.D. n Lvy, T.L. (1989) Influene of steriliztion methos on selete miroiologil, physil n hemil properties. Environment. Qul. J. 18,