Laboratory Studies on the Release of Cations and Anions in Acid Sulf ate Soils from Pulau Lumut, Selangor.

Transcription

1 PERTANIKA 14(3), (1991) Labratry Studies n the Release f Catins and Anins in Acid Sulf ate Sils frm Pulau Lumut, Selangr. J. SHAMSHUDDIN 1 and EDGARDO A. AUXTERO 2 ; DepL f Sil Science, Faculty f Agriculture, Universiti Pertanian Malaysia Serdang, Selangr Darul Ehsan, Malaysia 2 Cllege f Agriculture, Central Mindana University, Musuan, Bukidnn, 8710, The Philippines Key wrds: Acid Sulfate Sils, ph, Aluminium, Oxidatin. ABSTRAK Tanah asid sulfat di Semenanjung Malaysia dicirikan leh phyang rendah dan Alyang tinggi. Pengurangan in-in tksik leh saliran terkawal adalah disyrkan. Walaubagaimana pun, keasidan ptensi masih wujud di dalam tanah leh sebab lambatnya keluar in-in tksik ketika mineral meluluhawa. Satu kajian telah dibuat untuk menentukan pelepasan Al dan in-in lain leh ekstraksi berulang tanah daripada ladang dan leh pengeraman aerbik cnth di makmal Keputusan menunjukkan Al terlepas berterusan daripada tanah walau pun selepas ekstraksi keenam. abila tanah dibiarkan mengalami pengudaraan bebas di dalam keadaan aerbik Al y Mn, Fe, Ca, Mg, K, Na, dan S terkeluar ke dalam tanah leh pemecahan mineral lempung. Aktiviti in-in ini bertambah dengan bererti, mengakibatkan pertambahan pengaliran elektrik larutan tanah. Tambahan lagi, ph larutan tanah turun. Sifat tanah asid sulfat yang biasa dilihat ini mempunyai implikasi yang besar terhadap pengurusan praktiknya. ABSTRACT Acid sulf ate sils in Peninsular Malaysia are characterized by lw ph and high amunts fal Alleviatin f txic ins in the sils by cntrlled drainage is recmmended. Hwever, ptential acidity remains in the sils due t slw release f txic ins during mineral weathering. A study was cnducted t determine the release f AI and ther ins by repetitive extractin f samples frm the field and by aerbic incubatin f samples in the labratry. The results shwed that Al was released cntinuusly frm the sils even after the sixth extractin. When the sils were allwed t underg free xidatin under aerbic cnditins Al, Mn, Fe, Ca, Mg, K, Na and S were released int the sil slutins due t breakdwn f clay minerals. Activities f these ins increased significantly, resulting in an increase f electrical cnductivity f the sil slutin. Additinally, ph f the sil slutin drpped. These cmmnly bserved prperties f acid sulfate sils have great implicatins n their management practices. INTRODUCTION It is estimated that acid sulfate sils cver an area f apprximately 110,000 ha in Peninsular Malaysia (Kanapathy 1973). The sulfiric hrizn in these sils is develped frm xidatin f pyrite (FeS 2 ) n expsure t atmsphere by drainage. The sils are characterised by very lw ph values (< 3.5) and the presence f yellwish jarsite (KFe 3 (SO 4 ) 2 (OH) 6 ) mttles. Cnditins cnducive frjarsite frmatin are lw ph and strngly xidising envirnments (Van Breemen 1982). Althugh jarsite is very insluble with K = 10~ 986 (Vlek etal 1974), it can hydrlyse slwly and change t gethite (Van Breemen 1982). Other minerals fund in the clay fractin f acid sulfate sils in Malaysia are kalinite, mica, smectite and mica-mixed layers (Shamshuddin^ al. 1986: Auxter et al. 1991) and Al-hydrxy-sulfates such as alunite, basaluminite and jurbanite (Shamshuddin and Auxter 1991). Acid sulfate sils in Peninsular Malaysia are almst exclusively fund in the castal plains f the west cast. Under natural cnditins, the sils are waterlgged and are ften inundated with sea water. When the sils are drained fr agricultural

2 J. SHAMSHUDDIN AND EDGARDO A. AUXTERO prductin, as in the case f many parts f the west cast f Peninsular Malaysia, the sils becme very acidic. Very ften sil ph ges belw 3.5, prmting further breakdwn f clay minerals in the sils. Si, Al, Fe, Ca, Mg, Na, K and anins are released int sil slutin, and later frm secndary minerals and/r are lst by leaching. The release f these catins and anins is a functin f intensity and length f time f drainage, mineralgy, climate, depth and size f drain and climatic cnditins. Auxter and Shamshuddin (1991) shwed that the grwth f il palm seedlings was affected by water regime and Al. Sme acid sulfate sils in Malaysia are utilised fr cultivatin f il palm (Pn 1977; Pn and Blmfield 1977), ccaandccnut (Chewetal. 1984) with prper water management practices (Th and Pn 1982). Reclamatin prcedures have included applicatins f inrganic amendments, such as lime (Chew et al 1984) and bunch ash (Yew etal 1977). Changes in physicchemical prperties f the sils resulting frm these reclamatin prcedures and their effects n the release f catins and anins have nt been studied in detail in the past. Astudywas, therefre, cnducted with these specific bjectives: 1. T assess the release f Al in acid sulfate sils by repetitive extractin using 1MKC1 2. T determine changes in the activities f Al 3+, Fe^, Mn 2+, Ca 2+, Mg 2+, K +, Na +, and SO/" in the sil slutin as a cnsequence f aerbic incubatin. MATERIALS AND METHODS Lcatin and Sil Type Acid sulfate sils fr the study were sampled frm Pulau Lumut, which is an island cvering an area f apprximately 6000 ha, situated ff Prt Kelang, Selangr, Malaysia. Detailed descriptins f the area, chemical and mrphlgical prperties f the sils have already been given by Auxter et al (1991). The drained part f the island can be divided int cultivated areas (reclaimed > 25 yr) and newly drained areas (drained in 1982). Sil types fund n the island, classified accrding t Sil Taxnmy (Sil Survery Staff 1987) are given in Table 1, while Table 2 gives the relevant physicchemical prperties f the sil prfiles. Chemical Analyses Sils were sampled accrding t genetic hrizns. The samples were air-dried, grund and sieved thrugh a 2 mm sieve. ph (1:2.5) was measured n TABLE 1 Acid Sulfate Sils in Fulau Lumut Classified Accrding t Sil Taxnmy (Sil Survery Staff, 1987). Lcatin Cultivated areas Newly drained areas Series Parit Btak Jawa Tngkang (siltya) (silty b) Subgrup Typic Sulfaquept Typic Sulfaquept SulficTrpaquept Sulfic Trpaquept Typic Sulfaquept Typic Sulfaquept the fresh and air-dried samples n suspensin f sil in water after 1 h f intermittent shaking and vernight standing. Electrical cnductivity (EC) f the air-dried samples was measured in a suspensin f sil in water at 1:5 rati after 1 h f intermittent shaking and vernight standing. CEC was determined by the NH 4 OAc methd buffered at ph 7 (Chapman 1965). Basic catins were determined frm the NH 4 OAc extracts; Ca and Mg were determined by atmic absrptin spectrphtmetry, while Na and K were determined by flame phtmetry. Al was extracted by 1 M KC1 and determined clrimetrically (Barnhisel and Bertsch 1982). Free irn was determined by the methd f Mehra andjacksn (1960). Particle size distributin was determined by the pipette methd f Gee and Bauder (1982)! Water-sluble sulfate was extracted by shaking 10 g sil in 50 ml H g O fr 30 min fllwed by centrifugatin at 2000 RPM. Ttal sulfur was extracted by the nitric-perchlric acid methd (Tabatabai 1982). Sulfur in bth extracts was determined by the methd f Freeney (1986). Ttal Analysis Selected samples were taken fr ttal elemental analysis. Fr this analysis, sil samples were taken mstly frm and hrizns. Sme elements (Si, Al, Fe, Ca and Mg) were determined in terms f their xides %by scanning electrn micrscpyenergy dispersive X-ray analysis (SEM-EDAX). Repetitive Extractin A logsample in 50 ml 1MKC1 slutin frm each hrizn f all prfiles was shaken fr 1 h. The sample was then centrifuged and the supernatant cllected. The sample was later subjected t 5 mre extractins. Al in each extract was determined. 258 PERTANIKAVOL. 14NO.3, 1991

3 TABLE 2 Chemical prperties f acid sulfate sils frm Pulau Lumut, Selangr, Malaysia. I < p b SERIES Parit Btak Jawa Tngkang (silty a) (silty b) HAD >fc HOR* Bj Bj Bw Bw Bj Bg Bw *j dentesjarsite mttles ph(h 2 O,1:2.5) Fresh Air-dried E.C (1:5) ds/m Na K Catin; Mg Ca cml(+)/kg Al : \ j 2.03 ] 1.59 ': 8! 27.10! I Fe Clay (%) Sulfur Water-sl Ttal TORY i C! H M s w 0 > > "Z 0 en2 in ULFAI w SC O

4 J. SHAMSHUDD1N AND EDGARDO A. AUXTERO Accelerated Oxidatin Samples frm jarsitic layers f and Jawa series sils were expsed fr a perid f 12 mnths. The sils were kept mist by sprinkling water regularly t prmte xidatin. Sub-samples were taken every 3 mnths fr the extractin f sil slutins. Etractin f Sil Slutin and Chemical Speciatin Air-dried sil samples frm the accelerated xidatin experiment were rewetted with distilled water t a matrix suctin f 10 kpa (field capacity). Sil slutins were extracted after 1 day f equilibratin, fllwing the recmmendatin f Menziesand Bell (1988), by centrifuge fr 2 h at 2000 RPM. The slutins were then filtered thrugh 0.22 urn Millipres. ph and EC were immediately determined n a 2 ml sub-sample. The rest f the sil slutins were kept fr the determinatin f Na, K, Ca, Mg,Fe,Mn,Cl,S,P and Al by inductively cupled plasma atmic emissin spectrscpy (ICPAES). The GEOCHEM cmputer prgram f Spsit and Mattigd (1980), which was mdified by Chaney (1987), was used t speciate metals and ligands in the sil slutin. Input cnsisted f an estimate f inic strength f the sil slutin based n EC (Griffin and Jurinak 1973), metal cncentratins (Na, K, Mg, Ca, Mn, Fe, Al), ligand cncentratins (P, S, Cl) and ph f sil slutin. RESULTS AND DIGCUSSION Sil Prperties Chemical, mineralgical and mrphlgical prperties f the sils at Pulau Lumut, Selangr have been described elsewhere (AuxtcretaL 1991; Shamshuddin and Auxter 1991). The sils are mrphlgically variable in nature, with grey clurs reflecting the pr drainage cnditins. The clay fractin is dminated by kalinite, mica and smectite, with minr amunts f hallysite,gibbsite and mica-mixed layers (Auxteretal. 1991). Jarsite was bserved in vids and/ r rt channels where xid-reductin nrmally takes place. Table 3 gives the ttal elemental cmpsitin f and hrizns f sils in the cultivated areas. Nte that nly SiO 2, A1 2 O 3, Fe 2 O 3> CaO and MgO are given here; it is seen that SiO 2 is the majr element in the cmpsitin f the sils, fllwed by A1 2 O 3. Under very acid cnditins, Si is stable, and thus des nt g int slutin. On the ther hand, Al and Fe disslve readily at lw ph. Once in slutin Al and Fe hydrlyse, resulting in the prductin f prtns. Series TABLE3 Ttal chemical cmpstin f sils in the cultivated areas. Parit Btak Jawa Tngkang Hr SiO Cmpsitin ( %) A1 2 O Fe 2 O CaO Mg < < 0.1 Extractability fal Aluminium in the sub-sils extracted by 1 M KCl was very high. The hrizns f, Jawa, Tngkang and silty type series cntained 26.80, 16.50, 9.20 and cml (+)/kg sil, respectively (Table 2). The abundance f Al in the sils is assciated with the xidatin f pyrite and the subsequent lwering f the sil ph, which then breaks dwn clay minerals and releases Al. In all hrizns, Al saturatin in the sils is very high, a cnditn unfavurable fr grwth f mst crps. Aluminium is reprted t adversely affect the grwth perfrmance f il palm grwn in acid sulfate sils (Pn 1977; Pn and Blmfield 1977). The quantity f Al extracted six times by 1 M KCl is shwn in Fig. L It was bserved that the quantity f Al remved after the sixth extractin was lw; the amunt being lwer in the (Fig. 1A) than the jarsitic layer (Fig-. IB). Nevertheless, Al was still being extracted at the sixth extractin, indicating the high buffering capacity f the sils, especially in the jarsitic layer. Under field cnditins, Al is expected t be cntinuusly released int the sil slutin when Al in the sil slutin is lst by leaching. Hwever, a lng span f time wuld be required befre Al is remved cmpletely frm the sils by this mechanism. Cumulative Al in the sils remved by 1 M KCl after six extractins was pltted against extractin number. A hyperblic relatinship was btained between cumulative Al and extractin number. An example f such a curve is given in Fig. 2fr series sil. A similar trend was fund fr all the sils 260 PERTANIKAVOL 14NO.3, 1991

5 LABORATORY STUDIES ON THE RELEASE OF CATIONS AND ANIONS IN ACID SULFATE SOILS & pbk A Sdu Jwa Tfcf Sdu ( ) Sdu(b ) Hrizn Series Y : , X E 0 20 * \ \ A \\ # pbk Sdu Jwa Tfcg Sdu(a ) Sdu(b) 15 i l0 I Extract in Jrsitlc Layer Number Fig: 7: Amunts f Al extracted by 1M KCl against extractin number in sils frm andjarsitic layer. under study. After the furth extractin, the increment in Al remved was linearly related t extractin number, indicating a cnstant remval rate f Al. A similar bservatin was reprted by Oates and Kamprath (1983). They suggested that a cnstant rate f remval f Al with repeated extractin represented nn-exchangeable Al. Sivasubramaniam and Talibudeen (1972) prpsed that exchangeable Al can be estimated by extraplating the last pints n the cumulative curve t zer extractin. Aluminium value btained by this prcedure cnfrmed very well with the sum f Al remved after 2 extractins (Fig. 2). Sil Oxidatin in Artificially Aerated Samples ph and Electrical Cnductivity. Changes in sil slutin chemical prperties f Jawa series underging accelerated xidatin are shwn \nfig. 3. A similar Extractin Number Fig. 2: Cumulative Al extracted by 1M KClfrm and hrizns f series. trend was als bserved in Series sil. After six mnths f xidatin, the ph f the sil slutin f Jawa series decreased frm 3.3 t3.1 (Fig.3A). The ph decreased further t after anther six mnths f xidatin. The decrease in ph with time was due mainly t the release f acidity by the cntinued xidatin f pyritic materials and partly frm the hydrlysis f acidic catins such as Al and Fe. There culd als be sme acidity frm the hydrlysis fjarsite, al thugh jarsite itself is knwn t be quite insluble (Vlek et al 1974). EC increased steadily frm 1.33 ds/m t 3.78 ds/m in Jawa series in 12 mnths as shwn in Fig, 3A. In series, EC increased frm 0.85 ds/mt4.86ds/m (data nt shwn). A significant increase in EC within a cmparatively shrt span f time suggests thatjarsitic layers f acid sulfate sils shuld nt be drained cmpletely and that the drainage canals shuld be kept shallw. A drp in ph and an increase in EC are expected t take place in the dry mnths fjune tjuly. An increase in the inic strength arising frm an increase in EC results in an increase in Al 3+ activity (Bruce etal 1989). Irn and Manganese. Fig. 3A shws changes in the activities f Fe and Mn in the sil slutin fjawa series underging xidatin. The calculated activities f Fe increased sixteenfld in 12 mnths, while thse f Mn increased sixfld. In the fresh sample fjawa series, Mn activity was nly 3.3 p,m. At 12 mnths, the activity had gne up t 20.3 im. These increases in activities f Mn and Fe culd be detrimental t il palm grwth. Similar increases in the activity f Fe and Mn in the sil slutin f the series were nted (data nt shwn). Basic Catins. Magnesium and Kin the sil slutin were very high in Jawa series, cnsisting f abut 95% f basic catins in the sil slutin. This PERTANIKAVOL. 14NO.3,

6 J. SHAMSHUDDIN AND EDGARDO A. AUXTERO gd plant grwth, prvided that txic catins, such as Al and Mn, are alleviated. There was a slight increase in Ca and Na activities. I a O, A A a / K* N* C'* ^ - B /-' - * / - 1 Fig. 3:pH, EC and activities f catins and anins in sil slutin fjawa series. bservatin was als true fr the sil slutin f series. The activities f these catins increased significantly as a result f xidatin fr a perid f 12 mnths. In thejawa series, Mg activity increased furfld, while K activity increased threefld (Fig. 3B). Sme f the Kand Mg in the sil slutin were derived frm the weathering f mica-mixed layers and Mg-bearing minerals like smectites. This was prmted by an increase in sil acidity and the subsequent lwering f ph. Clay minerals break dwn faster under lw ph than under high ph. The presence f high K and Mg activities in the sil slutin may help prmte Aluminium and sulfate. Al 3+ activity in Jawa series was veryhigh (Fig.3Q. TherewasaslightincreaseinAl activity in respnse t a decrease in sil slutin ph (Fig. 3A). The increase in Al 3+ activity was partly due t an increase in the inic strength f the sil slutin (Bruce etal. 1989). SO 4 2 ~activity increased twfld in 12 mnths. Lindsay (1979) reprted that Al 3+ and S 4 2 " in slutin will react instantly t frm Al (SO ) +. In this study, a threefld increase in A1(SO 4 ) + activity was nted within the study perid. After 12 mnths f xidatin, activity f Al (SO 4 ) + in Jawa series was 2770 fim. Mnrneric Al species, such as Al 3+ and Al (SO 4 ) +, are the majr Al species in the sil slutin. Management Implicatins. Acid sulfate sils at Pulau Lumut shuld be managed taking int accunt the chemical prperties f the sils and factrs influencing the grwth perfrmance f crps such as il palm. Remval f water using a system f drainage (ThandPn 1982), which keeps the water table level abve the pyritic layer may be gd fr Sulfic Trpaquepts (Jawa and Tngkang series) j but may nt be suitable fr Sulfaquepts ( series). Fr Sulfaquepts, nce flding is intrduced Al, Mn and ther txic ins are released and brught t the surface, causing injury t plants. The presence f high amunts f catins and anins in the sil slutin f the surface sils increases EC t a high level, which may als affect crp grwth. The deleterius effect f EC n il palm seedlings grwn n acid sulfate sils f Pulau Lumut in pt experiments has been shwn in an earlier paper (AuxterandShamshuddin 1991). A suitable system f drainage is required t allw the remval f excess water, especially during the rainy mnths. Since the cncentratins f Al and sulfate are high in the water frm drainage canals and sil pits (Shamshuddin and Auxter, 1991), regularflushingfthis water int the main drain is advcated. During the dry mnths the level f the water table in the sils recedes. This cnditin prmtes the drying up f the sils in the island, resulting in a further xidatin f pyritic materials and subsequent release f sulfate and acidic catins (Auxter etal. 1991). A drastic drp in ph f the sil results in an increase in the activities f Al and 262 PERTANIKA VOL. 14 NO.3, 1991

7 LABORATORY STUDIES ON THE RELEASE OF CATIONS AND ANIONS IN ACID SULFATE SOUS Mn. This may happen in the case f Sulfaquepts ( series and silty). Remval f the excess ins by leaching is nt advcated because f the slw prcess f mineral weathering and subsequent release f ins. CONCLUSION One f the majr elements in the cmpsitin f acid sulfate sils in Pulau Lumut is Al. This Al is released by the breakdwn f clay minerals during drainage, being prmted by lw ph. As the release is slw, remval f this txic in by leaching is nt practical. If these acid sulfate sils are allwed t freely xidize, ther ins are released, whereby activities f A1 3 \ Mn 2+, Fe 3+, Ca 2+, Mg 2+, K +, Na + and SO 4 2 "in the sils slutin increase. ph f the sil slutin drps and EC increases, causing injury t crps such as il palm. The sils shuld be managed such that the excess water is remved and Al kept lw, while keeping the pyritic layer under reduced cnditins. ACKNOWLEDGEMENTS The authrs wish t recrd their appreciatin t Universiti Pertanian Malaysia and the Natinal Cuncil fr Research and Science Develpment fr technical and financial supprt during the cnduct f the research. REFERENCES AUXTERO, E.A., J. SHAMSHUDDIN and S. PARAMANANTHAN. 199L Mineralgy, Mrphlgy and Classificatin f Acid Sulfate Sils in Pulau Lumut, Selangr. Pertanika 14(1): AUXTERO, EA. and J. SHAMSHUDDIN Grwth f Oil Palm (Elaeis guineensis) Seedlings n Acid Sulfate as Affected by Water Regime and Al. Plant and Sil 137: BARNHISEL, R. and P.M. BERTSCH Aluminium. In Methds f Sil Analysis, ed. A.L Page et al. Part 2. 2nd ed., p Agrnmy Mng. 9. ASA and SSSA, Madisn, WI. BRUCE, R.C., L.C. BELL, D.G. EDWARDS and L.A. WARRELL, Chemical Attributes f sme Queensland Acid Sils. 11: Relatinship between Sil and Slutin Phase Cmpsitins. Aust. J. Sils Res. 27: CHANEY,R.F GEOCHEM-PC USDA-ARS, Sil-Micrbial Labratry. Bldg, 318, BARC, Beltsville, MD., 20705, USA. CHAPMAN, H.D Determinatin f Catin Exchange Capacity. In Methds f Sil Analysis, ed. C.A. Black Part 2. lsted. p Agrnmy Mng. 9. ASA and SSSA, Madisn, WI. CHEW, P.S., K.KKEE and L.H. Oi Management f Ccnut and Cca n Acid Sulfate Sils. Planter 60: FREENEYJ.R Analytical Methds fr Determining Sulfur in Sils and Plant. In Prc. Internatinal Sympsium n Sulfur in Agricultural Sils, ed. Sam PrtchandGhulamHussain. p Bangladesh Agricultural Research Cuncil and Sulfur Institute. GEE, G.W. andj.w. BAUDER Particle-size Analysis. In Methds f Sil Analysis, ed. A.L. Page et al Part 1. 2nd edn. p Agrnmy Mng. 9. ASA and SSSA, Madisn, W.I. GRIFFIN, R.A. and J J. JURINAK Estimatin f Activity Cefficient frm Electrical Cnductivity f Natural Aquatic System and Extracts. Sil Sd. 115: KANAPATHY, K Reclamatin and Imprvement f Acid Sulfate Sils in West Malaysia. In Prc. Syspsium n Add Sulfate Sils, ed H. Dst, p ILRI 18, Vl. 2, Wageningen. LINDSAY, W.L Chemical Equilibries n Sils. New Yrk: Jhn Wiley and Sns. MEHRA, O.P. and M.L.JACKSON Irn Oxide Remval frm Sils and Clays by Dithinite-citrate System with Bicarbnate Buffer. Clays and Clay Minerals 7: MENZIES, N.W. and L.C. BELL Evalutin f the Influence f Sample Preparatin and Extractin Technique n Sils Slutin Cmpsitin. Aust. J. Sil Res. 26: OATES, K.M. and EJ. KAMPRATH Acidity and Liming: 1. Effects f Extracting Slutin Catin and ph n the remval f Aluminium frm Acid Sils. SilSci. Sc. Am.J. 47: POON, Y.C The Management f Acid Sulfate Sils and its Effect n the Grwth f Oil Palm. Malays. Agric.J. 51: PON,Y.C.andC.BLOOMFiELD The Ameliratin f Acid Sulfare Sils with Respect t Oil Palm. Trp. Agric (Trinidad) 54: SHAMSHUDDIN, J., S. PARAMANANTHAN and W. NIK MOKHTAR Mineralgy and Surface Charge Prperties f Tw Acid Sulfate Sils frm Peninsular Malaysia. Pertanika9: SHAMSHUDDIN, J. and A. AUXTERO Sil Slutin Cmpsitin and Mineralgy f sme Active Acid Sulfate Sils in Malaysia as Affected by Labratry PERTANIKA VOL. 14 NO.3,

8 J. SHAMSHUDDIN AND EDGARDO A. AUXTERO Incubatin with Lime. Sil Sa. 152: SIVASUBRAMANIAM, S. and O. TALIBUDEEN Ptassium-Aluminium Exchange in Acid Sils: 1. Kinetic./ SilSci. 23: SOIL SURVEY STAFF Keys t Sil Taxnmy. SMSS Technical Mng. 6. Crnell Univ., USA. SPOSITO, G. and S.V. MATTIGOD GEOCHEM: A Cmputer Prgram fr Calculatin f Chemical Equilibrium in Sils Slutin and Other Natural Water Systems. Kearney Fundatin f Sil Science, University f Califrnia, Riverside. TABATABAI, M.A Sulfur. In Methds f Sil Analysis,ed. A.L. Page^a Part2.2ndedn. p Agrnmy Mng. 9. ASA and SSSA, Madisn, WI. TOH, P.Y. and YC. POON Effect f Water Management n Field Perfrmance f Oil Palm in Peninsular Malaysia. In Prc f Bangkk Sympsium n Acid Sulfate Sils, ed. H. Dst and N. Van Breemen p ILRI Publicatin 31, Wageningen. VAN BREEMEN, N Genesis, Mrphlgy and Classificatin f Acid Sulphate Sils in Castal Plains. In Acid Sulfate Weathering ed.j.a. Kittriek et al p SSSA Special Publicatins N 10 Madisn: Wl VLEK, P.L.G., J.M. BLOM, J. BEEK and W.L LINDSAY Determinatin f Slubility Prduct f Varius Irn Hydrxides andjarsite by Chelatin Methd. Prc. Sil Sci. Sc. Am. 38: YEOW, KM., Y.C. POON and P.Y TOH Effects f Bunch Ash n Oil Palm Perfrmance and Sil Prperties f Acid Sulfate Sils. In Prc. Cnference n Classificatin and Management f Trpical Sils. ed. ICT.Jseph,p Malays. Sc. SilSci., Kuala Lumpur. (Received 20 September 1990) 264 PERTANIKA VOL. 14 NO.3, 1991