characteristics and genesis t2 terrace soil of kelantan ... papers/pert vol. 4 (2) dec. 1981... ·...
TRANSCRIPT
Pertanika 4(2), 160-169(1981)
Characteristics and Genesis T2 Terrace Soilof Kelantan, Peninsular Malaysia
J. SHAMSUDDIN, and E. TESSENSSoil Science Department, Faculty of Agriculture, Universiti Pertanian Malaysia,
Serdang, Selangor, Malaysia
Key words: Inherent fertility; mineralogy; classification; Kelantan.
RINGKASAN
Tanah-tanah teres T2 Kelantan berasal daripada bahan-bahan zaman Holosen. Enam jenis siri tanahiaitu Nangka (varian pasir), Nangka, Kg. Pusu, Lunas, Bt. Tuku dan Kerayong telah dikaji bagi mencirikantanah-tanah tersebut. Secara kimia, tanah-tanah tersebut adalah berkurangan di dalam bahan-bahan kes,nitrogen dan fosfor, tetapi tinggi di dalam aluminium. Pecahan tanah liatnya pula adalah didominasi olehkaolinit, gibsit dan geothit.
Secara kimia-fizikal, tanah-tanah ini adalah di dalam peringkat luluhawa pertengahan dan adalahdijangka akan bertindakbalas baik kepada pengapuran dan pembajaan yang harus termasuk pencampuranbahan-bahan organik.
SUMMARY
T2 terrace soils of Kelantan are derived from alluvial materials of Holocene age. Six soil series,namely Nangka (sandy variant), Nangka, Kg Pusu, Lunas, Bt Tuku and Kerayong Series were studied tocharacterize the soils. Chemically, the soils are deficient in bases, nitrogen and phosphorus, but high inaluminium. The clay fraction is dominated by kaolinite, gibbsite and goethite. Physico-chemically, the soilsare in the intermediate stage of weathering and can be expected to respond well to liming and fertilization,which should include additions of organic matter.
INTRODUCTION
A large fraction of the Kelantan plains stretch-ing from the vicinity of Pasir Mas right into theThailand border (Fig. 1) has been known for yearsas an area of low productivity. Arnott (1957)described the area as a "deficiency area". It is alsoknown that animals grazing in the area suffer frombone disease. Ismail (1976) attributed theoccurrence of such disease to the lack of Co, Caand P.
The soils in the area are mainly those ofCherang Hangus, Nangka, Gong Chenak, Awang,Sogomona, Holyrood, Bt Tuku, Lubok Kiat,Kg Pusu and Tebok Series of the Malaysian soilclassification system (Paramananthan, 1980); thesesoils fall under general term of T2 terrace soils.
This paper reports the fertility characteristicsof the soils with respect to the availability ofnutrients and relates them to their agriculturalsuitability, and to the genesis of the soils on T2terrace in Kelantan.
MATERIALS AND METHODS
Six soil series representing soils on T2 terracein Kelantan were selected for the study. The soils
South China
Sea
T2 Terrace
Figure 1. Part of Kelantan showing GeographicalPosition of T2 Terrace Soils.
160
J. SHAMSUDDIN AND E. TESSENS
belong to the Nangka (s), Kg. Pusu, Bt. Tuku,Kerayong, Lunas and Nangka Series. The soilseries were identified in the field and confirmedby laboratory data following the definitions ofthe Department of Agriculture Malaysia(Paramananthan, 1980) (Table 1). As can be seenin Table 1, Nangka series has a fine loamy texture;the Nangka (s) belongs to the sandy family (SoilTaxonomy, 1975) and can be considered as avariant of the Nangka series s.s.
Physico-chemical data were obtained from thefine earth fraction (<2mm). Particle-size analysiswas carried out by successive sedimentation. Veryfine sand (VFS) of size 50-1 00^ was sieved out ofthe sand fraction. The VFS was separated into theheavy and light fraction by bromoform and studiedunder the microscope. pH (1:1) was determinedboth in water and 1 N KC1. CEC was determinedboth in 1 N NH4OAc buffered at pH 7 and I NNH401 and also by sum of cations. Bases weredetermined from NH4OAc solution. ExchangeableAl was estimated by the procedure of Yuan(1959). hxtractable acidity was estimated by TEA-KCl solution at pH 8.2. Free iron oxide wasdetermined by the method of Mehra and Jackson(1960). Organic carbon was estimated by theWalkley-Black method (Allison, 1965), while
nitrogen was estimated by the method of Bremner(1965). Total K, total P were determined byconventional methods (HCIO4 extraction) andavailable P was determined by the Olsen method.Clay and silt mineralogy were studied by X-raydiffraction and thermal analysis on untreatedsamples; and moisture retention was determinedby pressure plate apparatus.
RESULTS AND DISCUSSION
Geographical SettingSoils on T2 terrace in Kelantan are situated
in the plain in the vicinity of Pasir Mas (Fig. 1 ).This area is popularly known as the "deficiencyarea". This "deficiency area" is bounded bylatitude 5° and 6°N and longitude 102° and103°E. The annual rainfall in the area taken overa period of five years (1965-1970) is about3000 mm. The highest rainfall is in the month ofDecember (630.9 mm) and the lowest is themonth of March (64 mm).
Field characteristicsThe field characteristics are recorded in the
profile descriptions in Table 2. The Bukit Tukuseries soil meets the requirements for Plinthudult, asthere are more than 50% red mottles which harden
TABLE 1Soil series according to Paiamananthan (1980) and Biot (pers. comm.) on the T2 terrace
Drainageclass
Tex-t meclass
verypoorly
drained(0)
somewhatvery poorly
drained
(1)
somewhat somewhatpoorly poorly imperfectly imperfectly
drained drained drained drained(2) (3) (4) (5)
moderately wellwell drained drained
very fineclayey JELUTONG(>6(r; clay)
tineclayey(35-602 cl)
fineloamy(18-35% d)
coarseloamy(< 18% cl)
sandy(sand orloamy sand)
SOGOMANA
CH. HANGUSKG. PUSU
MANIK
LUNAS (fine sand)
SEGARI (coarse sand)
SUBANG
S1TIAWAN
GONGCHENAKLUBOK KIAT
BUKIT TUKU (fines.)
AWANG (coaise s.)
KERAYONG TEBOK
RASAU (fine s.)
HOLYROOD (coarse s.)
NANGKA (fine s.)
L1NTANG (coarse s.)
161
TABLE 2Field Characteristics of Soils on T2 terrace in Kelantan
Soil Horizon Dcptli Colour Texture Structure Consistency Remarks
Nangka (sandy var.) Ap
Oxic Dystropept (B)2i
Well drained (B)22
0-25 Black (7.5YR 2/0) sand w.m. sub. friable
25-69 Light yellowish brown lo. na w.m. sub. friable(10YR6/4)
69-120+ Yellowish brown sa. lo. w-m. m. sub. friable(10YR5/4)
j3 Lunas
^ Aerie Tropaquult
Somewhat poorlydrained
Ap 0-21 Dark grey (2.5Y 4/0) cL lo.
B 2 U 21-46 Light grey (2.5Y 7/3) cL lo.
B2 2 t 46-90+ . Light grey (2.5Y 7/1) cl. lo.
m. m + f. ca friable
m. m + f. sub. firm
m. co. sub. firm
thin, patchy cutans
7.5YR6/8 mottles in B2i
>70
o£2non
aowAW
Bukit Tuku
Plinthudult
Somewhat imp. dr.
Mprayong
AquicTropudult
•' Mod. well dr.
Kg. Pusu
Typic Tropaquult
Poorly drained
Nangka
Oxic Dystropepi
Mod. well dr.
Ap
B21t ;-•
B22t
Ap
B21t
B22t
Ap
B21t
R "**"" 2 2 1 ' -
A2
(B)21 "II (B)22
II BC
0-16
16-58
58-125 +
0-28
28-64
64-120+
0-20
20-54
54-80+
0-16
16-37
37-5757-82
82-110+
Light brownish grey(2.5Y 6/3)
Light yellowish brown
White (5Y 8/1)
Very pale brown(10YR7/4)
Brownish yellow(10YR6/6) :
Brownish yellow(10YR6/6)
Light grey (5Y 7/1)
Light grey (N7)
Light grey (N7)
Daxk greyish brown(10YR4/2)
Grey (2.57 6/1)
Light brownish greyWhite (2.5Y 8/2)
White (2.5Y 8/2)
loam
cL lo.
cl. lo.
clay
clay
sil. cl.
clay
sil. cl.
sil cl. .
lo. sa.
sa. lo.
sa. lo.sa. lo.
sa. cl. lo.
m-w. m. sub.
m. co + m. sub.
m. co + m. sub.
m. m. sub.
m. m. sub.
m. m. sub.
w. m. ang.
m. co. ang.
m. - w.m. ang.
w. co - f. sub.
w. co - m. sub.
w. co. sub.w. co. - m. sub.
w. co. - m. sub.
friable
firm ^
firm
firm ;
firm
firm
stickynon-plastic
stickysi. plastic
stickysi. plastic
friable
friable
friablefriable
friable
grey (2.5Y 6/1) mottles ,_/ \;
thin, patchy cutans; strong a rbrown (7.5YR 14/6) mottles.?; -
thin, patchy cutans; red ;;• .*.,.(2.5YR 4/6) mottles.
thin, continuous cutans - ;:
thin, continuous cutans •; :
light grey (2.5Y 7/1)and strong brown (7.5YR 5/6)mottles.
yellowish brown (10YR 5/6)mottles.
thin, patchy cutans; reddishyellow (7.5YR 6/8)
Brownish yellow (10YR 6/6)mottles.Pctroplinthite below 1.25 m.
SIS
T2
mTO
>ntr{/)oFcF K
EL
AN
TA
N,
en
Zonr?o
>
>
J. SHAMSUDDIN AND E. TESSENS
lipon exposure. This is not the case for theKg. Pusu or Lunas soils. These three soils, togetherwith the Kerayong series have clay cutans in theirB2 horizons, visible in the field. It can be notedthat cutans become more evident as the drainageimproves.
Physio-chemical characteristics
Particle-size distributionThe particle size distribution of the soils
under study is given in Table 3. Except for theNangka (s) series, all soils are dominated in theirsand fraction by very fine and fine sand; thispoints to a similar origin of all these soils. Thesilt: clay ratios in all soils are high, confirmingthat the soils are still in an early stage of physicalprofile development (Van Wambeke, 1962).
Moisture availabilityMoisture retention at 0.001, 0.01, 0.1, 0.33
and 15 bar is given in Table 4. Out of these data,available water (0.33 - 15 bar) was obtained. Itis seen in general that water retained at any given
suction depends on the texture of the soil : soilsof the clayey family such as Lunas and KerayongSeries retain more water than those of the loamyfamily. There is no clear relation between moistureretained at any given suction with depth. However,available water in most soils shows a tendency todecrease with depth. Higher water availability inthe upper horizons is probably related to thehigher porosity in those horizons; higher porosityis also reflected by the lower bulk density inthose horizons. The relationship between % clayand 15-bar moisture is shown in Figure 2. Thecurves represented are:
(a) linear: y = 3.50 + 0.49XF1;18 = 166.40
(b) exponential : y = 1.59XFI.,R = 207.45
>2 _
( ° - 7 2 )
= 0.90**
R2 =0.92**
It will be clear that a factor of 2 is involved torelate both variables instead of the more commonlyused 2.5 factor (Soil Taxonomy 1975).
No relation could be found between availablewater content and clay and silt percentages.
uor.
U1
n
DCa:3m
3 0
-
/
a • SIrvi n
T2 C L R Y
-f-
XSILI s
Figure 2. Relationship between % clay and 15-bar moisture.
163
CHARACTERISTICS AND GENESIS T2 TERRACE SOIL OF KELANTAN, PENINSULAR MALAYSIA
TABLE 3Particle-size distribution of T2-tenace soils of Kelantan
SERIES HORIZON DEPTH CLAY SILT VI S FS MS CS VCSS11 ICLAY
Nangka(sandy)
Lunas
Bt. Tuku
Kerayong
Kg. Pusu
Nangka
ApB21B22
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApA2B21IIB22IIBC
0-2525-6969-120+
0-2121-4646-90+
0-1616-5858-125 +
0-2828-6464-120+
0-2020-5454-80+
0-1616-3737-5757-8282-110+
8.509.20
12.1
35.437.929.4
17.928.731.5
53.559.854.4
64.153.143.2
9.907.70
13.015.922.6
8.5012.810.5
25.321.620.4
41.939.136.3
38.132.143.9
34.344.247.3
10.613.110.29.80
12.8
4.734.604.78
10.811.414.2
17.015.314.8
2.914.081.16
1.022.237.03
16.316.219.316.414.8
28.3 27.5 13.9 8.3223.6 27.8 15.7 6.2023.6 27.1 15.2 6.44
19.318.824.2
19.914.715.2
49.748.947.545.940.7
5.70 2.89 0.596.54 2.93 0.747.40 3.14 1.38
2.60 0.61 0.091.86 0.23 0.051.63 0.44 0.18
4.04 0.57 0.37 0.503.82 0.16 0.04 00.39 0.09 0.04 0
0.31 0.12 0.04 0.050.32 0.09 0.05 00.86 0.20 0.16 0.82
9.409.909.307.898.40
3.46 0.653.45 0.623.82 0.723.22 0.722.30 0.71
11.390.86
0.710.570.69
2.341.361.15
0.710.530.79
0.530.831.09
1.071.700.790.620.5 7
TABLE 4Moisture ehaiacteristies of T2"terrace soils of Kelantan
MOISTURE CONTENT (w/w)%
SERIES
Nangka(sandy
Lunas
Bt. Tuku
Kerayong
Kg. Pusu
Nangka
HORIZON
ApB21B22
ApB21tB22t
ApB21tB22
ApB21tB22t
ApB21tB22t
A P
A2B21IIB22IIBC
B.D.
1.381.381.53
1.011.591.65
1.501.541.51
0.901.211.24
1.061.12l.^O
1.271.471.361.371.41
0.001
30.129.635.4
68.931.526.7
28.736.434.0
76.242.337.4
50.855.549.9
31.326.529.832.133.3
0.01
23.325.526.9
5 3.428.823.2
24.425.221.8
50.638.233.5
46.849.345.3
29.923.022.722.625.6
0.1
16.018.820.1
42.425.019.6
22.019.618.8
45.234.833.0
44.845.641.4
21.918.616.517.621.2
0.33
13.019.113.0
37.022.518.3
17.918.318.2
43.433.831.8
40.743.340.1
17.814.613.615.318.5
15 bar
7.7010.49.50
28.719.615.6
11.314.415.5
33.228.529.0
32.735.127.2
8.307.409.60
11.313.4
0.33-15 bar
5.304.703.50
8.302.902.70
6.603.902.70
10.25.302.80
8.008.20
12.9
9.507.204.004.005.10
164
J. SHAMSUDD1N AND E. TESSENS
Cation Exchange Capacity and ExchangeableBases
The CEC of the fine earth fraction wasdetermined by extraction with 1N NH4 OAc(pH 7), IN NH4CI (unbuffered) and by the sumof cations. It is now generally recognised that thedetermination of the exchange capacity at pH 7is agronomically useless (Gillman and Bell, 1976).A realistic estimate of the exchange capacityof tropical soils is obtained with CEC (NH4CI).The sum of the cations usually underestimatesthe exchange capacity. It can be seen in Table 5,that for the loamy family soils CEC (NH4C1)and CEC (sum) agree fairly well; the agreementbecomes less where soils are more clayey. A t-teston paired observations for all horizons studied(n = 20) gives t-stat = 3.34, which is not significantat the 0.01 level and both CEC (NH4C1) and CEC(sum) can be considered to measure the sameexchange capacity. When the apparent exchangecapacity (CEC-NH4Cl/100g clay) is compared, allsoils tend to fall within the range 16-24 meq, asfar as their subsoils are concerned. This indicatesthat physico-chemically they are in the inter-mediate stage of weathering, and that their clayfraction contains some 2:1 minerals, besides theomnipresent kaolinite. As for the bases, all soils are
deficient in exchangeable K, for which the absoluteminimum is 0.10 meq/lOOg soil (Boyer, 1972).Exchangeable Ca and Mg are also inadequatewithout liming. The cation balance appearssatisfactory.
Organic matter, nitrogen and phosphorusOrganic matter in soil is determined by
multiplying organic carbon by a factor 2. It isseen that organic matter in the topsoils variesfrom about 1% to 3% (Table 6). According toSanchez (1976), organic matter in tropical soilsaverages around 3.5%, which is somewhat higherthan those of the soils under study. It must beconcluded therefore that the organic mattercontent is inadequate.
As far as N is concerned, the value is low.Normal fertile soils should contain about 0.2% N(Sanchez, 1976). Heavy nitrogen fertilization isnecessary in order to bring the soils to acceptablelevels for plant growth. Low nitrogen contentof the soil is reflected by poor crop growth andlow productivity. The C/N ratio, in general, iserratic but low indicating that humification andmineralization go on at normal rate.
The fertility of a soil is also reflected by itsphosphorus content. In the soils under study, the
TABLE 5CEC and bases of T2 terrace and soils of Kelantan
SERIES
Nangka(s)
Lunas
Bt. Tuku
Kerayong
Kg. Pusu
Nangka
HORIZON
ApB21B22
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApA2B21IIB221IBC
CEC
NH4OAc
5.603.602.90
18.111.512.2
14.310.911.2
16.210.111.2
17.915.213.4
4.63.42.74.708.00
(me/lOOg)
NH4C1
2.901.801.60
6.604.805.40
2.704.806.20
9.6010.111.0
14.413.212.0
2.903.002.202.404.00
SUM
3.151.783.75
4.573.473.25
3.093.384.41
3.735.045.88
6.719.269.92
2.992.362.192.322.91
EXCH. BASE
Na
0.08t
0.04
0.04t
0.04
0.040.04
t
0.12tt
0.040.040.04
0.04ttt
0.04
K
0.060.020.02
0.120.020.02
0.080.020.02
0.170.210.05
0.080.050.07
0.050.020.020.020.04
(meq/lOOg)
Mg
0.170.110.08
0.320.090.09
0.220.080.10
0.060.190.28
0.244.446.02
0.130.070.070.070.07
Ca
2.361.412.71
0.570.400.38
0.430.360.37
2.980.400.35
0.510.730.91
0.370.350.340.390.04
B.S. (%)
NH4OAC
484398
644
554
3986
53553
13131610
2
(NH4CI)
lOOg cl
32.619.613.2
18.612.618.4
15.116.719.7
17.916.920.2
22.524.927.7
29.339.016.915.117.7
165
CHARACTERISTICS AND GENESIS T2 TERRACE SOIL OF KELANTAN, PENINSULAR MALAYSIA
TABLE 6Free iron, organic carbon, nitrogen and phosphorus content of T2 terrace soils of Kelantan
SERIES
Nangka(s)
Lunas
Bt. Tuku
Kerayong
Kg. Pusu
Nangka
HORIZON
ApB21B22
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApA2B21IIB22IIBC
re2o3%
0.210.290.29
0.860.970.21
0.361.141.04
1.772.292.29
1.254.724.72
trtrtr
0.290.07
O.C%
1.270.240.12
5.310.180.03
0.810.090.06
1.740.240.09
0.510.180.09
0.960.390.300.060.06
N%
0.090.050.02
0.160.050.05
0.090.050.05
0.050.040.04
0.060.020.04
0.050.040.010.020.01
C/N
14.14.806.00
33.23.600.60
9.001.801.20
34.86.002.25
8.509.002.25
19.29.75
30.03.006.00
Av. P(Ppm)
0.500.801.74
6.201.451.16
3.581.601.60
8.161.161.16
2.612.323.80
2.900.801.601.200.80
Tot. P%
4.570.832.08
6.239.552.08
4.151.661.66
16.64.595.81
6.647.068.30
2.910.831.661.250.83
Av/Tot.
98.596.483.7
99.515.255.8
86.396.496.4
49.225.320.0
39.332.945.8
99.796.496.496.096.4
amount of available P varies from low tomoderately low according to the rating ofKanapathy (1976). Available P is found to behigher in the Ap than in lower horizons in mostcases; this is related to the higher amounts oforganic matter in the Ap and to the lower amountof free iron oxides.
Acidity CharacteristicsTable 7 gives the acidity characteristics of the
soils. From pH(H2O), it can be ascertained that allsoils are acidic in nature. Consistent with theintermediate weathering stage of the soil, pH (KC1)is always lower than water. It can be seen furtherin Table 7 that the Nangka (s) and Kerayong soilhave been limed.
In general, however, the acidic nature of thesesoils is due to the presence of Al : a classicalrelationship exists between pHKCl and exchange-able Al (Fig. 3).:
pH(KCl) = 4.65 - 0 . 3 7 VFi;i8 =46.36
R2 =0 .72**
Acid conditions in soils are accompanied byAl and Mn toxicities and Mo deficiencies; correctionthrough liming is the obvious management practicefor these soils. The last column in Table 7 gives therequired amounts in ton/ha, based on therecommendations of Kamprath (1970).
Mineralogy
(a) Sand fraction
The very fine sand fraction (50-100ji) wasstudied for its mineralogical composition. Theheavy and light sand fractions were separated bybromoform. The light fraction is dominantlyquartz with or without muscovite. Some feldsparsmay be present but it is difficult to locate thembecause of the quartz. In the heavy fraction,zircon, opaque minerals and tourmaline dominate.The opaque minerals are mainly magnetite andilmenite. Rutile is also present in small amounts.Heavy minerals are less than 1% of the very finesand fraction.
(b) Silt fraction
The silt fraction was analysed by X-raydiffraction. This fraction was composed mainlyof quartz, kaolinite and gibbsite. Soils of Lunas,Kerayong, Kg. Pusu and Nangka series containmica and feldspars.
(c) Clay fraction
Figure 4 gives the X-ray diffractograms of theclay fraction of the soils under study. From thediagrams it is clear that the clay fraction isdominated by kaolinite (7.3A, 3.57A) and gibbsite(4.86A). Reflections at 4.18A and 10A point to
166
1•ya!
H .
H .
H .
H .
H .
H .
3 .
3 .
3 .
3 .
5
H
3
I
0
B
V
-
\ + 4-
\
J.
4- ,
—
SHAMSUDDIN AND E. TESSENS
4-
4- 4- 4-4- 4 - ^ ^ ^ - ^ ^ ^
4- 4-
•
R n
K C L - E ; X C H R N G E R B L E R
4-
4-
X
L
4-
I—
3.33
Figure 3. Relationship between KCl-exchangeable Al and pH-KCl.
7.3
"221
IIBC
Figure 4. X-ray diffractograms of the clay fraction.
166a
CHARACTERISTICS AND GENESIS T2 TERRACE SOIL OF KELANTAN, PENINSULAR MALAYSIA
TABLE 7Acidity characteristics of T2-terrace soils of Kelantan
pH (1:1) EXCH - Ac EXCH - Al EXCH - HSERIES HORIZON
H2O 1NKC1 me/lOOgAl C A T(O
bAl(/
148
24
758582
748488
28386
843827
7777767591
LIME.REQ.
ton/ha
0.710.231.49
5.304.704.11
3.534.295.94
0.180.186.95
7.475.304.41
3.352.592.412.483.00
Nangka (s)
Lunas
Bt. Tuku
Kerayong
Kg. Pusu
Nangka
ApB21B22
ApB21B22t
ApB21tB22t
ApB21tB22t
ApB21tB22t
ApA2B21IIB221IBC
5.76.05.3
4.95.05.1
4.85.05.0
5.95.05.2
4.75.15.3
4.64.54.84.84.8
4.44.24.2
4.03.83.8
3.73.83.7
4.43.93.8
3.73.73.9
3.84.04.14.03.8
0.480.240.90
3.522.962.72
2.322.883.92
0.404.245.20
5.844.002.88
2.401.921.761.842.72
0.430.140.90
3.212.852.49
2.142.603.60
0.113.854.21
4.533.212.67
2.031.571.461.501.82
0.050.10
t
0.310.110.23
0.180.280.32
0.290.390.99
0.310.790.21
0.370.350.300.340.90
the respective presence of goethite and mica (illite).Soils of the Nangka (s) series contain high amountsof quartz (4.26A, 3.33A). Some soils gave areflection at around 14-16A. The clay did notexpand on glycol treatment. On K-treatmenf andheated to 500°C, the peak greater than 14Acollapsed. This behaviour points to the presence ofa chlorite-vermiculite mixed layer. The peak at6.26A present in the Clay of the Kg. Pusu Seriesis probably due to the presence of lepidocrocite.Lepidocrocite is common in hydromorphic soils,generated by oxygen deficiency (Schwertmannand Taylor, 1977; Ross et al, 1979).
At first appearance, the presence of gibbsitemay seem at odds with the intermediate stage ofphysico-chemical weathering. It was found,however, that gibbsite readily forms upon weather-ing of primary minerals, particularly under condi-tions of intensive leaching (Hsu, 1977). This is inagreement with theoretical considerations,involvingthermodynamic stability constants (Helgesonet al, 1969), whereby upon weathering, gibbsiteis the first secondary mineral to be formed. Onlywhen other ions are present in sufficient amountswill other minerals precipitate. It is therefore not
surprising to find that sandy soils are conspicuouslyhigh in gibbsite (in their clay fraction), as theyare very permeable, with low reserves of ions otherthan Al1981).
3+and H4Si04 (Tessens and Shamshuddin,
ClassificationThe soils are classified according to Soil
Taxonomy (USDA, 1975). The subgroup andfamily name are given in Table 8. Soils of Nangka(s) and Nangka Series are Inceptisols, while thoseof Kg. Pusu, Bt. Tuku, Kerayong and Lunas Seriesare Ultisols. Kg. Pusu and Lunas Series are typicalpadi soils (Tropaquult), but their suitability islimited by their fertility. Soils of Bt. Tuku Seriessatisfy the requirements of a Plinthudult.
Soil formationThe district of Pasir Mas (Figure 1), where
T2-terrace soils in Kelantan are most widespread,is situated in the middle of the Kelantan plain.To the south of the area, lie the sedimentary rocksof Triassic and Permian age (Dawson et alt 1967).Schists and granite, in that order, occur to thesouth of the formation. To the southeast of theplain lies a large mass of granite outcrops ofMesozoic age.
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J. SHAMSUDDIN AND E. TESSENS
TABLE 8Taxonomic classification of T2-terrace soils of Kelantan
SERIES SUBGROUP
Nangka (s) Oxic Dystropept
Lunas Aerie Tropaquult
Bt. Tuku (Typic) Plinthudult
Kerayong Aquic Tropudult
Kg. Pusu Typic Tropaquult
Nangka Oxic Dystiopept
FAMILY
Sandy, siliceous,isohyperthermic
Fine clayey,kaolinitic,isohyperthermic
Fine loamy, mixedisohyperthermic
Fine clayey,kaolinitic,isohyperthermic
Fine clayey,kaolinitic,isohyperthermic
Coarse loamy,siliceous,isohyperthermic
The soils in the plains are characterized by thenature of the rocks lying to the south and south-east of the area. It is seen that granite andsedimentary rock formations form topographichigher areas in the place where they are found.Over the years, the weathered materials from thehighlands were washed down and deposited inthe valley forming soils of various mineralogicalcomposition and stages of formation.
The mouth of Sg. Kelantan itself has movednorthwards; the displacement was estimated to beabout 35 km (Tjia, 1970). Fluctuation of the sealevel in the Quaternary (Screvinor, 1949; Nossin,1961), and the movement of rivers have played animportant role in the characterization of the soilsin the plain. The formation of a fluvial terraceitself is due to the lowering of the sea-level, follow-ing which the rivers were rejuvenated causingsevere erosion of the valleys.
It was reported that the highest sea level inthe Quaternary was 100 m above and the lowestwas 30 m below the present sea-level (Tjia, 1973).It was during the successive lowering of sea-levelthat the respective T3, T2 and Ti terraces wereformed. The characteristics and classification oftHse terraces have been described in detail byGopinathan (1968); the T2 terrace (intermediateterrace) was considered to be of subrecent age.The age and mineralogical nature of the depositsare reflected by the nature of the soils.
The coastal plains of Kelantan experienceabout 3000 mm rainfall per annum. Maximumrainfall occurs in November and December atthe beginning of Northeast Monsoon. These areasthus experience either udic or aquic moistureregime, depending on the topography. Thetemperature regime of the soil is isohyperthermic.Heavy rainfall results in the leaching of bases andhigh Al saturation (Table 7). Silica is also leachedbut to a lesser extent. This condition favours theformation of kaolinite and sesquioxides (Figure 4).The plain may be flooded during the height of theMonsoon, during which replenishment of nutrientstakes place.
The weathering process in these environmentsfollows the following general pattern (Tessens,1975):
Primary minerals
1st process: (superficial decationisation)
silicates withaccidental charges
Phyllosilicates withpermanent charges
(feldspar products) - kaolinite-illite-sec. chlorite
i i2nd process:
(desilification)
k(strong decationisation
and desilification)
oxides with accidental charges
goethite hematite gibbsite
From the data presented earlier, the soilsstudied have already undergone the first processof superficial decationisation. Further decationisa-tion is continuing but the process of desilificationhas not yet reached its maximum intensity. Assuch kaolinite is accompanied by some 2:1minerals, and this is expressed in a relativelyhigh exchange capacity of the clay. The silt/clayratios also confirm the presence of reserve silicaand bases, and a relatively low intensity of physicalweathering. All these soils are therefore still in anintermediate stage of weathering, which is inconformity with their geomorphological position.
CONCLUSION
Soils of the T2 terrace in Kelantan are still inthe intermediate stage of physico-chemicalweathering, dominated in their clay fractions by
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CHARACTERISTICS AND GENESIS T2 TERRACE SOIL OF KELANTAN, PENINSULAR MALAYSIA
kaolinite and gibbsite, but with still someappreciable amounts of 2:1 minerals. They are,under natural conditions, deficient in nutrientsas N, P, K, and high in Al. However, it can beexpected that they will respond favorably toliming and fertilization. Their organic mattercontent is inadequate, and this should also becorrected.
ACKNOWLEDGEMENT
The authors wish to record their gratitude toJohan Vercruysse for his help in the field workand Malaysian Agricultural Research and Develop-ment Institute for the use of their X-ray facilities.
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(Received 22 April 1981)
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