some t2 terrace soils of peninsular malaysia: ii ... papers/pert vol. 8 (2) aug. 1985...kaolinit...

Pertanika 8(2), 159- 168 (1985)

Some T 2 Terrace Soils of Peninsular Malaysia: II.Mineralogy and Physico-chemical Characteristics*

J. SHAMSHUDDIN and E. TESSENS +

Department of Soil Science,Faculty of Agriculture,

Universiti Pertanian Malaysia,Serdang, Selangor, Malaysia.

Key words: Mineralogy; gibbsite; water dispersible clay; water retention

ABSTRAK

fumlah gibsit di dalam bahagian lempung tanah teres T2 didapati bertambah dengan per-tambahan kandungan pasir dan pembaikan keadaan saliran. Kaolinit ialah mineral utama di dalambahagian lempung tanah yang dikaji. Tanah kurang salir bolehyuga mengandungi sedikit mika,klorit, lapisan bercampur dan feldspar. Anatas berkumpul di dalam bahagian kelodak tanah yangbaik salir. Kehadiran lempung 1:1 dan/atau seskuioksida digambarkan oleh sifat-sifat fiziko-kimia-nya. KPK lempung berkurangan dengan pengurangan nisbah kelodak/lempung. % LSA/lempungdidapati berkurangan dengan bertambahnya AI dan/atau bahan organik, Nisbah itu juga ber-kurangan apabila pH menghampiripH .

ABSTRACT

The amount of gibbsite in the clay fraction of T2 terrace soils appears to increase with theincrease of sand content and with the improvement of drainage conditions. Kaolinite is the mainmineral in the clay fraction of soils. The imperfectly and poorly drained ones may also contain somemica, chlorite, mixed layers and feldspar. Anatase accumulates in the silt fraction of the well drainedsoils. The dominance of 1:1 clay minerals and/or sesquioxides is reflected in their physico-chemicalproperties. Apparent CEC decreases with a decrease in silt/clay ration. WDC/clay % appears todecrease with an increase in Aland/or organic matter. The ratio also decreases as the pH approaches

INTRODUCTION

Under the influence of high temperatureand high rainfall, tropical soils in the well drain-ed areas undergo physico-chemical weatheringreadily. The mineralogy of these soils is usuallydominated by kaolinite and/or gibbsite. Underimpeded drainage conditions, a somewhat diffe-rent kind of mineralogy is expected. Smectite,vermiculite and mixed layers or even primary

minerals can be present. The choice of crops tobe grown on these soils should be based on theirphysico-chemical and mineralogical propertiesbecause availability of nutrients and fertilizerrequirements of such soils are related to thoseproperties.

This study reports the mineralogy of someT2 terrace soils in Peninsular Malaysia, andrelates it to the physico-chemical properties of

*Part I was published in PERTANIKA 6(3): 61-89.+ Present address: Rietgrochtstraat 14, 9030 Wondelgem, Belgium.

J. SHAMSHUDDIN AND E. TESSENS

the soils. The data available from this study canbe used for classification purposes as well as foragricultural planning.

MATERIALS AND METHODS

The soils for the study are alluvial soilsformed on T 2 terraces (Paramananthan, 1981).The micromorphology and classification of thesesoils have already been studied (Shamshuddinand Tessens, 1983). The soils selected are thoseof Nangka (1, 9), Kampung Pusu (2), BukitTuku (3), Kerayong (4, 12), Cherang Hangus(5), Lintang (6), Sungai Buloh (7, 8, 13),Subang (10), Sogomana (11), Rasau (14), Napai(15), Chuping (16), Awang (17) and HolyroodSeries (18). Data on routine analyses are avail-able from the earlier paper (Shamshuddin andTessens, 1983).

20 g of soil was put in an end-over-endshaker for 16 hours. The amount of clay dispers-ed, henceforth referred to as water dispersibleclay (WDC), was measured. This is expressed as% of the total clay (WDC/clay %). Moistureretention measurements and bulk density werecarried out from core samples. Moisture reten-tion was taken at the suction of 0.001, 0.01, 0.1,0.33 and 15 bar.

Chloride free samples (clay and silt) fromboth Ap and B horizons were X-rayed (untreatedsamples). Whenever necessary, the clay fractionswere X-rayed after treatment with Mg, glycol, Kand K heated at 550°C. These are repectivelyreferred to as Mg, glycolated, K and heatedsamples. Interpretation of the diffractogramswas done according to DeConink (1978). Select-ed samples were taken for the study of anatase.These samples were deferrified and X-rayedboth before and after heating at 550°C.

Untreated clay samples were also analysedby differential thermal analysis (DTA), differen-tial scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA), using the Du Pont

990 Thermal Analyser. Transmission ElectronMicroscopy (TEM) was also employed to identifyclay minerals. The VFS fraction, taken from 50cm depth, was separated using bromoform, intoheavy and light minerals. Mounting and count-ing of the heavy minerals were done according toStoops (1974).

RESULTS AND DISCUSSION

Mineralogy

General Considerations

The minerals in the clay and the silt frac-tion were first identified on the diffractograms ofthe untreated samples. They were subsequentlyconfirmed by DTA. The amount of gibbsite andgoethite was estimated by DSC, while theamount of kaolinite was estimated by TGA.Note that the % of mica/chlorite can be estimat-ed by combining TGA and charge studies(Shamshuddin and Tessens, 1985).

Kaolinite and Halloysite

Kaolinite is the most common mineral inthe clay fraction. It was identified by XRD peakat 7.2A and 3.57A, and DTA peak at 5 5 0 -550°C. In most cases, kaolinite occupies 40 —60% of the clay fraction (Table 1), in agreementwith the earlier postulated recent and inter-mediate weathering stage. The presence of signi-ficant amounts of kaolinite cannot be regardedas an expression of an advanced stage ofweathering as primary minerals, such as micaand feldspar, are also present.

From XRD, DTA, TGA and DSC studies, itis not possible to identify the presence of halloy-site. However, looking at TEM micrographs(Plate la and b), one can see some tubularminerals present among the kaolinite crystals.These are the halloysite tubes, whose shape aredistinctly different from kaolinite, which arehexagonal.

160 PERTANIKA VOL. 8 NO. 2, 1985

T TERRACE SOILS OF PEN. MALAYSIA: MINERALOGY AND PHYSICO CHEMICAL CHARACTERISTICS

TABLE 1The % of kaolinite, gibbsite and geothite in the clay fraction

SERIES

Nangka (1)

Kampung Pusu (2)

Bukit Tuku (3)

Kerayong (4)

Cherang Hangus (5)

Lintang (6)

Sungai Buloh (7)

Sungai Buloh (8)

Subang (10)

Rasau (14)

Napai (15)

Chuping (16)

Awang (17)

Holyrood (18)

HOR

ApB

2 2

ApB

2 2

ApB

2 2

ApB

2 2

ApB «ApB

2 2

ApC

ApA C 3

ApA C

2

\B

2 4

A n23tcn

A ,

22tcn

ApB3/BC

ApB » ,

Kaolinite

48.852.0

52.067.0

44.659.6

48.448.4

59.648.4

55.855.8

14.97.4

59.655.8

63.244.6

55.859.6

57.655.8

16.718.6

67.059.5

59.663.2

MINERAL (% clay)

Gibbsite

5.88.6

2.21.1

1.60.4

2.51.9

1.54.3

8.68.6

63.350.5

8.610.1

2.90.3

2.92.9

0.71.4

1.4

Goethite

0.2

1.0

1.5

1.2

—

—

:

—

i . i1.2

0.5

Plate 1: TEM micrographs of the clay fraction from B horizon (mag. X35,000): a. Kaolinite (hexagonal) andhalloysite (tubular) in the B22 horizon ofChgHangus Series (5). b. Kaolinite and halloysite in the B23thorizon of Holyrood Series (18).

PERTANIKA VOL. 8 NO. 2, 1985 161


Gibbsite

Gibbsite is very common in these soils. Itwas identified by the XRD peak at 4.86A andDTA peak at 250-270°C. The temperature ofdehydroxylation is rather low. According to Hsu(1977), this may be due to large size gibbsite, assmall crystals normally give a peak at 300 -330°C.

The amount of gibbsite in the soils appear-ed to depend on the texture as well as drainageconditions. Light textured soils contain moregibbsite than the heavier textured ones (Table2), and better drained soils contain more gibb-site than the others.

The formation of gibbsite in soils is found tobe controlled by pH and the concentration of Aland Si in the solution (Hsu, 1977). Under slowleaching, Si may gradually accumulate andconsequently combine with Al to form kaoli-nite. Transformation of primary minerals togibbsite implies intense leaching. Such con-ditions prevail in the soils of Sungai Buloh Series(7, 8).

Iron Minerals

The most common form of iron oxide insoils is goethite. This mineral is identified by theXRD peak at 4.18A and DTA peak at about

350°C. Hematite is the second most commoniron oxide in soils. Under hydromorphic con-ditions, hematite is converted to goethite(Schwertmann and Taylor, 1977).

Some of the T g terrace soils contain goe-thite. On many occasions, the goethite peak at4.18A is not clear as it goes together with quartzpeak at 4.26A. The amount of goethite, when-ever present, was estimated by DSC. Theamount of goethite in the soils does not exceed2%. The highest % is found in the soils ofKerayong Series (4), where the value is 1.5%.

Lepidocrocite is rather rare in tropical soils.It is reported to be found exclusively in hydro-morphic soils, generated by oxygen deficiency(Schwertmann and Taylor, 1977; Ross et al.y1979). The colour of lepidocrocite is morereddish than goethite (10YR) and less reddishthan hematite (2.5YR) (Schwertmann andFitzpartric'k, 1977). In the T 2 terrace soils,Cherang Hangus Series (5) is the only soil con-taining lepidocrocite, shown by the XRD peak at6.26A and by the reddish yellow mottles.

Anatase

Anatase (TiO2) occurs as an alterationproduct of titanium-bearing minerals such assphene and ilmenite, believed to accumulate inweathered tropical soils rich in kaolinite (Brownet ai, 1978). To identify anatase in the studied

TABLE 2The effect of texture and drainage conditions on the formation of gibbsite in T terrace soils

Texture

Sandy

Coarse

Loamy

Fine

Loamy

Clayey

Series

Sg. Buloh (7)Sg. Buloh (8)Subang (10)

Nangka (1)

Lintang (6)

Bt. Tuku (3)

Rasau (14)

Kg. Pusu (2)Kerayong (4)

Hor

Ap

B 2 *

Ap

B24

ApAp

Drainage

excessiveexcessivepoor

well

well

imperfect

well

poormoderate

Gibbsite (clay)

63.310.14.3

8.6

8.6

1.6

2.9

2.22.5


T TERRACE SOILS OF PEN. MALAYSIA: MINERALOGY AND PHYSICO-CHEMICAL CHARACTERISTICS

soils, silt and clay fractions were selected forXRD. Selection of samples was based on theexistence of XRD peak at around 3.5 —3.6A.These samples were treated with DCB (Mehraand Jackson, 1960) to remove iron oxide andamorphous materials. The Fe-free samples wereX-rayed before and after heating at 550°C.

Figure 1 gives the X-ray diffractograms ofsoils of Lintang (6), Nangka (9) and SungaiBuloh Series (13), both before and after heatingat 550°C. One can see that before heating, thereare XRD peaks at 3.5A and 3.57A, but afterheating only the 3.5A peak remains. This pointsto the presence of anatase in the samples. Mostof the studied soils show this property.

In order to obtain a better understanding ofthe distribution of anatase, the diffractograms ofclay and silt from soils under different moistureregimes were examined (Figure 2). An exami-nation of these suggests:

a. Anatase is more in the sandy than in theclayey soils.

b. Anatase is more in the silt than in the clay.

c. Anatase is more in the well and excessivelydrained soils (Nangka (9) and Sungai Buloh(8) respectively) than the poorly drainedsoils (Subang (10) and Sogomana (11)series).

Fig. 1. X-ray diffractograms of Fe free sil^and claybefore (above) and after heating (below).

Fig. 2. X-ray diffractograms of the silt and clay(heated) from soils under well (8, 9) and poorlydrained conditions (10, 11).



Mica, Chlorite and Mixed Layers

Most of the T 2 terrace soils (Table 3)contain mica and some soils contain chlorite.These minerals are associated with soils in therecent or intermediate stage of weathering,especially under poorly drained conditions. Micaappears as plate-like bodies (Plate lc), with a sizeslightly bigger than kaolinite. This mica ismainly muscovite, as evidenced by the study ofthin sections.

During weathering, mica is completely orpartially converted to secondary minerals. The

Plate lc: Mica plate in the B22 horizon atRt. Tuku Series (3).

latter are referred to as mica mixed layers, ofwhich the most commonly reported in soils aremica-vermiculite and mica-smectite (Table 3).In these soils, mica-vermiculite is identified bythe presence of XRD peak at 12A in Mg treatedand glycolated samples. On the other handmica-smectite expands to 14.5A on glycolation.

Weathering of chlorite wholly or partiallyleads to the formation of secondary minerals.The former will result in the formation of vermi-culite and/or smectite, while the latter results inthe formation of chlorite mixed layers. Thechlorite mixed layers found in soils are chlorite-vermiculite and chlorite-smectite. The presenceof chlorite-vermiculite in these soils was confirm-ed by the presence of XRD peak of 12A in Ksaturated and heated samples, while thepresence of chlorite-smectite was shown by thepresence of 12A peak in K saturated and heatedsamples, and 16A in the glycolated samples.

In T 2 terrace soils of Peninsular Malaysia,the soils containing chlorite and/or chloritemixed layers are mostly poorly or imperfectlydrained soils. The only well drained soil thatcontains chlorite mixed layers is the Napai Series(15) (Table 3).

Series

TABLE 3Mica, chlorite and their mixed layers in T g terrace soils of Peninsular Malaysia.

(M = mica, Vc = vermiculite, Sm = smectite, Chi • chlorite)

Minerals (clay)

Nangka (1)

Kg. Pusu (2)

Bt. Tuku (3)

Kerayong (4)

Chg Hangus (5)

Subang (10)

Sogomana (11)

Kerayong (12)

Napai (15)

Chuping(16)

Awang (17)

Holyrood (18)

M, Vc

M, M-Vc, M-Sm, Chl-Sm

M, M-Vc, Chi, Chl-Vc

M, M-Vc, M-Sm, Chl-Sm

M, M-Vc, M-Sm, Chi

M, M-Sm, Chi, Chl-Sm

M, M-Vc, Vc

M

M, M-Sm, Chl-Vc

M, M-Vc, M-Sm, Chl-Sm, Sm

M, M-Vc, M-Sm

M, M-Vc, Chi, Chl-Vc


T2 TERRACE SOILS OF PEN. MALAYSIA: MINERALOGY AND PHYSICO-CHEMICAL CHARACTERISTICS

Silica

The most common silica mineral in soils isquartz, shown by the XRD reflections at 4.26Aand 3.34A. Quartz makes up an importantportion of the silt fraction of the studied soils. Inthe study of anatase, XRD peak at 4A (Figs. 1and 2) appears many times in the silt fractionand occasionally in the clay fraction. The inten-sity of XRD peak does not change with heatingat550°C.

The 4A reflection could either be due to thepresence of crystobalite (Wilding et ai, 1977) orsilica of biological origin (Brown et ai, 1978).An examination of the thin sections of the samesoils indicates the presence of phytoliths.Phytoliths are opaline silica derived from plants(Stoops, 1978). Thus 4A reflection is believed tobe due to the presence of phytoliths.

Heavy Minerals

Checking through the mineralogy of heavyminerals in the VFS fraction of various regions,

the following points have been noted (Table 4):

a. Soils of Kelantan. The most importantheavy mineral in Nangka (1) and BukitTuku Series (3) is zircon, while KampungPusu (2) and Kerayong Series (4) aredominated by opaque minerals. Similarityin heavy mineralogy in the Nangka andBukit Tuku Series suggests that these soilsare derived from parent materials of similarorigin. The parent material of these soilscould have originated from granite.

b. Soils of Trengganu. Soils of Lintang Series(6) contain mostly tourmaline.

c. Soils of Selangor-Johore. Sungai BulohSeries (7) of Selangor contains an importantamount of tourmaline. On the other hand,Sungai Buloh (8) and Nangka (9) of Johorecontains dominantly zircon in the VFS frac-tion. The two Johore soils are situated neareach other, thus their parent materialscould be of similar origin (probablygranite).

TABLE 4Heavy minerals in the VFS fraction of T g terrace soils

SERIES HORHEAVY MINERALS VFS (%)

Tourmaline

22.5

31.5

22.3

33.1

51.9

48.8

3.4

8.2

28.1

48.2

5.0

96.0

88.7

Zircon

39.4

34.8

43.3

16.3

10.7

36.4

59.3

64.4

43.8

25.9

6.9

0.3

2.5

Opaque

38.1

34.0

34.4

50.6

37.4

15.8

37.3

27.4

28.1

25.9

88.1

3.7

8.8

Nangka (1)

Kg. Pusu (2)

Bt. Tuku (3)

Kerayong (4)

Lintang (6)

Sg. Buloh (7)

Sg. Buloh (8)

Nangka (9)

Subang (10)

Kerayong (12)

Napai (15)

Awang (17)

Holyrood (18)

"21

AC,

AC,

B

B

B

21

21

21tcn

22t



d. Soils of Perak. Zircon is the most importantmineral in Subang Series (10), while tour-maline is the most important mineral in theKerayong (12) and Sungai Buloh Series (13).

e. Soils of Kedah- Perlis. There is a cleardominance of tourmaline in the soils ofAwang (17) and Holyrood Series (18). Bothof these soils are believed to have beenderived from parent materials of graniticorigin containing an important amount oftourmaline.

Physico-chemical Properties

General Considerations

arePhysico-chemical properties of soilsrelated to their mineralogical composition.Exchange properties, water retention, dispersi-bility and textural composition are now discuss-ed in relation to the mineralogy of the soils.

Cation Exchange Capacity

The CEC of a soil is related to the amountand type of clay minerals and organic matter.The clay fraction of the soil contributes most ofthe CEC. 2:1 clay minerals, such as smectite andvermiculite, have isomorphic substitution,resulting in the production of a high amount ofnegative charges. On the other hand, 1:1 clayminerals and sesquioxides do not show theseproperties and therefore their CEC is low. CEC,is thus, a good indicator of the stage of soilformation (Sys, 1978).

The CEC of the studied soils is given in theappendix of the earlier paper (Shamshuddin andTessens, 1983). As these soils are either in therecent or intermediate stage of weathering andcontain kaolinite and sesquioxides, with some2:1 clay minerals and/or mixed layers, the CECvalues of the top soils are high; in the subsoilsthey are high to medium. The values averagearound 16 meq/100 g soil in the top soil. TheA1 /Ap horizons report higher values than thesubhorizons due to the presence of more organicmatter in the upper horizons. It was also foundthat the apparent CEC is correlated to the silt/

clay ratio, with an R value of 0.819**. The plotof the apparent CEC against silt/clay ratio isgiven in Figure 3.

5 0

40

30

APP. CEC = 10.92+21.02(SILT/CLAY)

r = 0.819**

n = 13

0 0.5 1.0 1.5 2.0

SILT/CLAY RATIO

Fig. 3. The relationship between apparent CECand silt /clay ratio for soil at 50 cm depth.

Water Retention

The amount of water retained in the soil isinfluenced by the amount and nature of the clayminerals and organic matter present in the soil.Water retained at 15-bar (mm/m) is related tothe clay content. To test the validity of theserelationships, 15-bar water was plotted againstclay content and a regression equation wasdetermined. For A horizons of loamy and clayeysoils, the relationship is given by the equation: —

Water 15-bar = 6.08 + 0.47 (clay %)r = 0.96**, n = 12

For B horizons, the following regressionequation was obtained: —

Water 15-bar = 5.84 + 0.54(clay%)r = 0.97**, n = 22

One can observe that the conversion factorbetween 15-bar water and % clay is 2, ratherthan 2.5 as proposed in Soil Taxonomy.


T TERRACE SOILS OF PEN. MALAYSIA: MINERALOGY AND PHYSICO CHEMICAL CHARACTERISTICS

Water Dispersible Clay

Data on WDC for the studied soils are givenin Table 5. It is seen that WDC/clay % is higherin the Ap than in the Bg2 horizons. This is wellillustrated by the soils of Bukit Tuku (3),Kerayong (4) and Lintang Series (6). The changeof WDC with depth is related to the Al and/ororganic matter.

To test the validity of this assumption, thecorrelation between WDC/clay % and Al (foisubhorizons) and between WDC/clay % andorganic carbon (for A horizons) were determin-ed. The former is given by the regressionequation: —

WDC/clay % = 45.36 - 14.54 Alr = 0.67**, n = 18

The latter is given by the regression equation:

WDC/clay % = 36.02 - 7.13 O.C.r = -0.62*, n = 16

It is found that the WDC/clay % decreases withthe increase of Al and/or organic matter.

Dispersion and deposition phenomena arerelated to the point of zero charge (pH ) of thesoil in some way. It was found that all these soils

are net negatively charged in the pH range of 3to 6 (Shamshuddin and Tessens, 1985). Thepoint of zero charge of the variable chargecolloid (pHQ) is therefore used to characterisethe dispersion and deposition phenomena inthese soils.

WDC/clay % and pHQ values for some ofthe soils are given in Table 5. It is seen that asdifference between pH (water) and pH Q in-creases, the WDC/clay % increases. The regres-sion equation for the relationship betweenWDC/clay % and pH (HgO) - pHQis given bythe equation: —

WDC/clay % = -11.75 + 34.89 (pH - pHQ)r = 0.58**, n = 12

This is well illustrated by the soils of Kera-yong (4), Awang (17) and Holyrood Series (18).In these soils, WDC/clay % decreases from Apto B horizon and so is pH — pH

It is considered that WDC approaches aminimum value close to pH because at pHcolloids flocculate (Eswaran and Sys, 1979).When the pH of the soil is equal to its p H ,surface potential and charge is zero (Uehara andGillman, 1980). The absence of potential andnet charge pH results in the flocculation ofcolloids.

TABLE 5Flocculation and dispersion phenomena in relation to pH

Series Hor p H ( H O ) WDC/Clay%

Bt. Tuku (3)

Kerayong (4)

Lintang (6)

Napai (15)

Awang (17)

Holyrood (18)

ApB

2 2

ApB

2 2

ApB «A nApB3/BC

4.85.0

5.95.2

5.14.7

4.9

5.24.9

4.5

4.084.20

4.144.24

4.184.28

4.00

3.883.70

4.15

0.720.80

1.760.96

0.920.42

0.90

1.321.20

0.35

14.03.3

31.00

46.01.3

0.7

82.917.7

0

PERTANIKA VOL. 8 NO. 2. 1985 167


CONCLUSION

Gibbsite dominates the clay fraction ofexcessively drained, sandy soils. The loamy andclayey well drained soils contain dominantlykaolinite. Mica, chlorite, mixed layers andfeldspar are present in imperfectly and/or poorlydrained soils. Anatase accumulates in the siltfraction of well drained soils. Apparent CECdecreases with a decrease of silt/clay ratio. Idealconditions for dispersion are low Al and/ororganic matter and a pH far from pH .

ACKNOWLEDGEMENT

Thank are due to Universiti PertanianMalaysia and the government of Belgium forfinancial support.

REFERENCES

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DE CONINCK, F. (1978): Physico-chemical aspects ofpedogenesis. ITC, Rug., Belgium.

ESWARAN, H. and SYS, C. (1979): Agrillic horizon inLAC soils: formation and significance to classifi-cation. Pedologie. 29(2): 175 - 190.

HSU. P.H. (1977): Aluminium hydroxides and oxyhy-droxides. In: Minerals in Soil Environments.Dixon, J.B. and Weed, S.B. (Edi.). Soil Sci. Soc.Am., Madison, pp. 99-143.

ROSS, G.J. and KODOMA, H. (1979): Occurrence anddetermination of lepidocrocite in Canadian soils.Con./ SoiL Sci. 59:155-162.

SCHWERTMANN, U. and FlTZPATRICK, R.M. (1977):Occurrence of lepidocrocite and its associationwith goethite in Natal soils. Soil Sci. Soc. Am. J.41: 1013-1018.

SCHWERTMANN, U. and TAYLOR. R.M. (1977): Ironoxides. In: Minerals in Soil Environments. Dixon,J.B. and Weed, S.B. (Edi.) Soil Sci Soc. Am.,Madison, pp. 145-180.

SHAMSHUDDIN, J. and TESSENS, E. (1983): Some T 2

terrace soils of Peninsular Malaysia: 1. Micromor-phology, genesis and classification. Pertanika.6(3): 61 -89 .

SHAMSHUDDIN, J. and TESSENS, E. (1985): Some T 2

terrace soils of Peninsular Malaysia: III. Surfacecharge properties. (In press).

STOOPS, G. (1974): Short provisional notes on soilmineralogy and microepedology: 11. Methods issoil mineralogy. ITC, Rug., Belgium.

STOOPS, G. (1978): Provisional notes on micrope-dology. ITC, Rug., Belgium.

SYS, C. (1978): Evaluation of land in the humidtropics. Pedologie. 28: 307 - 335.

UEHARA, G. and GILLMAN, G.P. (1980). Chargecharacteristics of soils with variable and perma-nent charge minerals: 1. Theory. Soil Sci. Soc.Am.J. 44: 250 -252.

WILDING, L.P., SMECK. L.E. and DRESS. L.R. (1977):Silica in soils: quartz, crystobalite, trydymite andopal. In: Minerals in Soil Environments. Dixon,J.B. and Weed, S.B. (Edi.). Soil Sci. Soc. Am.,Madison, pp: 471 -552.

(Received 25 February, 1983)


some t2 terrace soils of peninsular malaysia: ii ... papers/pert vol. 8 (2) aug. 1985...kaolinit...

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