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Journal of the Indian Society of Soil Science, Vol. 64, No. 3, pp 302-309 (2016)
DOI: 10.5958/0974-0228.2016.00043.8
Short Communication
Characterizations of Soil at Different Landforms in Hilly
Areas of Meghalaya State
Dipak Dutta*, Siladitya Bandyopadhyay1, Utpal Baruah1 and Dipak Sarkar2
National Bureau of Soil Survey and Land Use Planning (ICAR), Kolkata, West Bengal
Studies undertaken on the soil–landscape relationship
showed that soil properties and landscape position
are significantly related and that geomorphological
and pedological processes interact on hill slopes,
mainly where the movement of soil and water is
considered (Gerrard 1992; Dahlgren et al. 1997). Such
relationships were used in determining uniform
mapping units for soil survey, soil management and
soil productivity determinations (Daniels and Hammer
1992). Soil is the product of the interactions of
complex pedogenic processes (Buol et al. 1997). The
north-eastern region (NER) of India shows varied soil
resources (Nayak et al. 1996; Singh et al. 1999; Sen
et al. 1997) formed under hilly terrain conditions with
different landforms coupled with different climatic
conditions and vegetation. This offers a scope to study
the soils formed in different landforms under varied
environmental conditions. The present investigation
therefore, aimed at characterizing the soils at different
landforms in East and West Khasi Hills district of
The site is located between 25°15 to 25°22N
latitude and 91°53 to 91°58E longitude and ranges
in elevation from 900 to 1500 m above mean sea
level. Geologically, it is composed of sandstone-
gneiss and alluvium materials. As a whole, the climate
of Meghalaya is influenced by elevation and
distribution of physical relief. The present climate in
the study area is warm per humid. The mean
maximum summer air temperatures raises as high as
26 oC and mean winter temperature falls to 9 oC, and
sometimes it goes below freezing point. Mean annual
temperature is 16.6 oC, and mean summer and mean
winter temperatures are 20.9 oC and 10.6 oC,
respectively. Mean annual precipitation ranges from
4000 to 7000 mm. According to the Soil Taxonomy
(Soil Survey Staff 2010), the calculated soil
temperature regime is thermic; and soil moisture
regime is variable from aquic to udic depending on
local topographical conditions. The vegetation of the
area is characterized by the influence of different
elevation and climatic condition. The main vegetation
of the area is dense forest with grasses whereas some
areas, mainly valley, are under cultivation of paddy,
potato etc.
Soils were studied during soil survey work
(1:50,000 scale) in the investigated area. Sites were
located in different topographical position (hill top,
escarpment, upper slopes, side hill slopes and inter
hill valley). At every site, a soil profile was excavated
and described according to Sehgal et al. (1987). Soils
were studied for morphological properties and samples
were collected from each horizon of the profile for
laboratory analyses. Soil samples from the five
representative profiles were air-dried and passed
through a 2-mm sieve. Standard laboratory methods
(Black 1965) were carried out on the fraction <2 mm,
and included: particle size distribution (pipette),
readily oxidizable organic carbon content (Walkley
and Black 1934), pH (1:2.5 soil-water ratio), cation
exchange capacity (CEC) and exchangeable bases by
NH4OAC method at pH 7.0. Extractable Al was
estimated by 1 N KCl method. The morphological
and physicochemical properties of soils are given in
table 1 and 2, respectively.
Soil of Hill Top: The horizon does not qualify
for mollic epipedon although it is under grassland
vegetation. The B horizons are skeletal in nature
containing more than 35 per cent gravels by volume
and it grades to weathered parent materials. The dark
yellowish brown colour of the horizons may be due
to organic matter as well as oxidized form of iron
content as a result of good drainage condition. It
*Corresponding author (Email:
Present address
1National Bureau of Soil Survey and Land Use Planning
(ICAR), Jorhat, Assam
2National Bureau of Soil Survey and Land Use Planning
(ICAR), Nagpur, Maharashtra
Table 1. Morphological data for representative profiles of the major taxonomic units of each landform position
Horizon Depth Colour Texture Structure Mottling Clay Erosion %
(m) cutan Gravel
Humic Dystrudepts (Landform – Hill Top)
A 0-0.15 Dark Grayish brown loam m1sbk a a Severe 40
Bw1 0.15-0..38 Dark yellowish brown clay loam m1sbk a a 45
Bw2 0.38-0.59 Dark yellowish brown clay loam m1sbk a a 60
Cr 0.59+
Lithic Udorthents ( Landform- Escarpment)
A1 0-0.23 Dark yellowish brown sandy clay loam m1sbk a a Severe 20
A2 0.23- 0.45 Dark yellowish Brown sandy clay loam m1sbk a a 25
R 0.45 + Hard rock
Typic Dystrudepts ( Land form – Upper Hill slopes)
A1 0-0.11 Brown loam f 1sbk a a Severe to 15
10YR4/3 moderate
BA 0.11-0.20 Reddish brown Sandy clay m1sbk a a 10
5YR4/4 loam
Bw1 0.20-0.50 Yellowish red Sandy clay m1to m2sbk a a -
5YR6/6 loam
Bw2 0.50 – 0.88 Reddish brown loam m1 to m2sbk a a -
Cr 0.88 +
Typic Haplohumult (Landform- Side Slopes)
A1 0-0.16 Brown silt loam m1sbk a a Moderate <5
A2 0.16-0.31 Dark reddish brown silt loam m1sbk a a <5
5YR 3/4
Bt1 0.31-0.49 Reddish brown silt loam f1sbk a clay cutan --
Bt2 0.49-0.73 Red clay f1sbk a clay cutan
Bt3 0.73- 0.107 Red clay loam f1sbk a clay cutan
2.5 TR 4/6
Typic Humaquepts (Landform – Inter-hill Valley)
Ap 0-0.18 Dark brown silt loam massive a a Slight to
10YR3/3 moderate
BA 0.18-0.39 Vary dark grayish brown silt loam m1sbk a a
Bwg1 0.39-0.75 Very dark gray silt loam m1sbk c1d a
Bwg2 0.75-100 Black silt loam f1sbk c2d a
Cg1 100-125
Structure: fine (f), medium (m), subangular blocky (sbk)., f- fine;1-weak
Mottling: absent (a), common (c), few (f), many (m);.1-fine; 2-medium
Cutan- Absent ( a)
decreases to less than 10 per cent in the relatively
weathered parent materials. These soils vary from
moderately to strongly acid with pH values as low as
4.8 in the lowermost horizon. The base saturation is
highest in the lower horizon may be due to washing
out of bases from the upper horizon and deposition in
the lower layer. The ECEC value is much lower than
the CEC. Soils are classified as loamy skeletal Humic
Soils of Escarpment: Under natural condition the
surface is covered by sparse litter and soils are
excessively drained. The area is excessively drained
Table 2. Physical and Chemical properties of profiles of the major taxonomic units of each landform position
Horizon Sand Silt Clay CEC/ Clay pH Exchangeable bases CEC Extractable Extractable ECEC Base OC
(2.0-0.05 (0.05- (< 0.002 (1:2.5 Ca Mg Na K Total acidity Al 3+ saturation
mm) 0.002 mm) mm) H2O) cmol(p+)kg-1 (%)
Landform – Hill Top
A 52.43 31.77 15.80 0.61 5.1 0.60 0.20 0.29 0.12 1.21 9.6 2.6 2.4 3.51 13 4.08
Bw1 31.95 28.53 39.52 0.21 5.0 0.50 0.20 0.34 0.08 1.12 8.1 2.4 2.3 3.42 14 2.64
Bw2 29.86 36.13 34.01 0.15 4.8 0.50 0.50 0.33 0.05 1.38 5.1 1.5 1.4 2.78 19 1.12
Landform- Escarpment
A1 70.43 8.19 21.38 0.25 5.2 0.80 0.30 0.28 0.19 1.57 5.34 1.7 1.4 2.97 29 2.06
A2 56.20 22.12 21.68 0.22 5.5 0.70 0.20 0.34 0.05 1.29 4.9 0.60 0.5 1.79 26 0.36
Land form – Upper Hill slopes
A1 44.5 29.4 26.1 0.16 5.0 1.3 0.30 0.33 0.32 2.25 4.35 2.10 2.0 4.25 52 1.28
BA 59.6 16.6 23.8 0.19 5.0 0.50 0.20 0.33 0.13 1.16 4.56 3.40 1.15 2.31 25 0.94
Bw1 52.3 26.6 21.1 0.14 5.1 0.60 0.10 0.38 0.22 1.30 3.25 0.40 0.23 1.53 40 0.50
Bw2 37.2 43.6 19.2 0.13 5.0 0.50 0.20 0.28 0.23 1.21 2.61 1.40 1.38 2.59 46 0.24
Landform- Side Slopes
A1 16.9 57.6 25.5 0.47 5.3 4.2 0.48 0.17 0.31 4.68 12.2 0.70 0.90 5.58 38 3.12
A2 20.2 49.4 30.4 0.34 5.0 3.2 0.30 0.18 0.12 3.50 10.5 0.30 2.30 5.80 33 2.02
Bt1 29.6 30.9 39.5 0.24 5.0 2.2 0.29 0.17 0.12 2.49 9.6 0.30 2.30 4.79 26 1.14
Bt2 18.4 33.8 47.8 0.17 5.1 1.7 0.32 0.20 0.12 2.02 8.4 0.10 2.00 4.02 24 0.52
Bt3 26.6 38.0 35.4 0.23 5.2 2.5 0.28 0.19 0.09 2.78 8.4 0.50 0.90 3.68 33 0.24
Landform – Inter Hill Valley
Ap 20.4 56.5 23.1 0.51 5.2 0.89 0.5 0.22 0.10 1.71 11.95 0.6 0.3 2.01 14 2.22
A2 21.5 56.0 22.5 0.56 5.1 0.60 0.5 0.22 0.08 1.40 12.75 0.7 0.4 1.80 11 2.48
Bwg1 22.3 53.5 24.2 0.56 5.1 0.50 0.40 0.18 0.08 1.16 13.68 0.9 0,3 1.46 9 3.50
Bwg2 22.1 53.2 24.7 0.55 5.0 0.50 0.40 0.15 0.07 1.12 13.68 1.0 0.3 1.42 9 1.90
Cg1 23.8 53.2 23.0 0.54 5.0 0.40 0.40 0.10 0.07 0.97 12.6 1.2 0.3 1.27 3 2.14
and exposed to severe erosional problems. The soils
are usually of coarse textured with the A2 horizon
having the maximum content of clay which decreases
in the C horizon. The pH values of the A horizon
vary from 5.2 to 5.5 and again decreases in the
weathered C horizon. The CEC does not vary much
with depth which is indicative of non contribution of
clay to CEC in lower horizons. Soils are classified as
coarse loamy Lithic Udorthents.
Soils of Upper Hill Slopes: The soil colour is
variable throughout the profile. Overall, the profile is
moderately light textured. The yellowish red to
reddish brown colour may result due to oxidation of
iron as a result of good drainage condition.
Extractable acidity is mainly dominated by Al+3
proving the structural breakdown of minerals in these
acid soils. The ECEC is always less than CEC. The
content of clay is lowest in the lowermost B horizons
as compared to the upper horizons. These soils are
moderately acidic with pH values varying very little
with depth. The OC is usually high in the surface
horizon with a gradual decrease downwards. Soils are
classified as coarse loamy Typic Dystrudepts.
Soils of Side Hill Slopes: The soils of the
landforms are deep and well drained having slopes of
15-20 per cent. Surface colour is brown and grades
into dark reddish brown and red in the below horizons.
The low base status of the soils resulting from the
excessive leaching might have caused intense
weathering and thus made the soils to be dominated
by low activity clay. This is supported by the low
CEC value about 10-12 cmol(p+)kg-1 although the soils
is having, on an average, the highest clay contents.
Extractable acidity is mainly dominated by Al3+
proving the structural breakdown of minerals. This is
supported by the comparatively high amount of
extractable aluminum serving as an indicator of
weathering status of soils. The low CEC and ECEC
confirm the presence of Kandic horizon. Soils are
classified as fine Typic Haplohumults.
Soils of Inter-hill Valley: Soils are very deep
with impferect drainage. The surface horizon is dark
brown colour, mainly contributed by organic matter.
The soil colour is variable throughout the profile. The
surface horizon grades into very dark grayish brown
may be due to hydrated iron oxides. The surface (Ap)
shows massive structure due to disturbance. The
textures of the soil in all horizons of the profiles are
silt loam indicative of transported parent materials.
The lowermost B horizon shows black colour which
might have imparted by manganese as poorly drained
soils show accumulation of iron and manganese
concentrations and concretions (Birkland 1984). The
CEC values ranging between 11.95 to 13.68
cmol(p+)kg-1 also does not show much variation with
depth. The content of extractable Al is very low
ranging from 0.3 to 0.4 cmol(p+)kg-1 among all the
soils indicating less rupture of the clay structure may
be due to protection of clay surfaces by humus. The
low pH values ranging from 5.0 to 5.2 may be due to
washed off soluble organic acids received from the
surrounding hills. Soils are classified as fine silty
Typic Humaquepts.
Landscape Positions and Soil Properties
In each landscape position factors like soil
depth, colour, hydrology, drainage, texture, erosion
etc. have acted in different manners giving rise to the
formation of different kinds of soils. Soils on the hill
top and escarpment are having less depth due to
severity of erosion, although slope for hill top is
slightly less. In these landforms hard rock are
intercepted within shallow depth. Water cannot
infiltrate deep into the soil as a result of steep slope
and is lost as run off causing severe erosional
problems. Depth of soils in the upper hill slope is less
as compared to soils in the side hill slope. The less
slope gradient in these two landforms probably causes
relatively more water to infiltrate into the soil and as
a result, the soil depth is more here due to enhanced
weathering indicating good drainage and good
aeration. Lessivage (downward clay movement) are
reflected in more clay in the argillic horizon in side
hill slope pedon having lesser slope (15-20%) which
allows translocation of clay with the moving water.
The aerated and well drained conditions of soils at
this landform may favour the formation of hematite
(Schewertmann and Taylor 1977) which is supposed
to impart more reddish colour (Bigham et al. 1978).
Melanization (darkening of surface horizon) of
landforms in the hill top, side hill slopes and inter hill
valley are indicated by higher concentrations of
organic carbon with very dark grayish brown to brown
and dark brown colour (low chroma) in the surface
horizons which is in agreement by Dhir (1967).
Weathering and clay formation differences downslope
are most likely due to differential soil moisture status
as determined by slope position. Soils in lower slope
positions can receive more moisture than those in the
upslope positions because of lateral movement
(Birkland 1984). It is also observed that sub soils in
the hill top contains clay in the range of 34 to 39 per
cent in spite of its occurrence at high gradient (30-
40%). The anticipated high moisture status of the
profile due to high content of humus may cause
relatively more weathering and clay formation. Colour
differences between ped interiors and surface within
pedons indicate differential weathering at different
locations reflecting variability in hydrology,
microclimate and erosion. Soils on the higher slopes
are excessively well to well drained, whereas, those
in the depressions (inter hill valley) are poorly drained
and rich organic matter and clay, to some extent, with
signs of gleying which is an agreement with that of
Birkland (1984). Similar observations are made by
other researchers (Nair and Chamuah 1993; Sen et al.
1996) working on soils of north-eastern region.
CEC/Clay Ratio, ECEC and Soil Mineralogy: It
is seen that the CEC of these soils is low lying in the
range of 2.61 to 13.68 cmol(p+)kg-1. According to
USDA Soil Taxonomy (Soil Survey Staff 2010), soils
having CEC/Clay ratios in the range of less than 0.2
are kaolinitic; 0.2-0.3 kaolinitic or mixed; 0.3-0.5
mixed or illitic and 0.5-0.7, mixed or smectitic.
Therefore, it is interred that profile lying at
escarpment and upper hill slopes have kaolinitic type
of mineralogy whereas profiles lying at hill top and
side slopes exhibits dual type mineralogy according
to this ratio. The surface horizon of hill top profile
with a CEC/clay ratio value of 0.6 indicates a mixed
mineralogy, not a smectitic as the existing
environment does not permit the formation of
expanding type of minerals. However, the below
horizon of this profile indicates kaolinitic type of
minerals. The CEC/Clay ratio value ranging from 0.34
to 0.47 for the two upper horizons of the side slopes
profile indicates mixed mineralogy. The Bt horizons
of this profile do indicate kaolinitic minerals with the
CEC/Clay value ranging from 0.17 to 0.24 with high
amount of extractable Al. The different moisture level
at different depths of these two profiles might have
caused differential type of mineral synthesis leading
to the formation of both type of mineralogy.
Alexander et al. (1939) found kaolinite to be the
dominant clay mineral in Hapludults, but increased
kaolinite and gibbsite in the 2-5 µm fractions of the
deeper horizons was found in some of the soils
studied. Rich and Obenshain (1955) found that
vermiculite containing hydroxyl-aluminium interlayers
increased upwards in a soil (Hapludults) developed
from mica. They postulated that the mixed layer
mineral was even more resistant to weathering than
kaolinite and reported decreasing pedogenic chlorite
and increasing kaolinite with depth. Bryant and Dixon
(1963) also observed increase of pedogenic chlorite
and decrease of kaolinite to the surface while studying
mineralogy in Ultisols. They also found in piedmont
Hapludults gibbsite to increase with depth and
postulated that kaolinite and gibbsite formed from the
weathering products leached from the upper horizons.
However, the profiles lying at inter hill valley shows
CEC/Clay value ranging from 0.51 to 0.56 indicating
mixed or smectitic mineralogy. According to
McDaniel et al. (1996) smectites can neoform when
soil solutions have relatively high pH and Si activities.
Generally, these conditions are met where drainage is
impeded by geomorphic positions. But they are
unstable under conditions of low pH and rapid
leaching. Therefore, the possibility of the presence of
smectitic type of minerals is ruled out in this situation.
Bloesch (2012) also used the ratio of CEC to clay as
an index of clay mineralogy. The base saturation
values of these soils are very low ranging from 9 to
36 per cent. Low base saturation indicates the
presence of Al3+ and H+ in the exchange complex.
Extractable Al3+ dominate the exchange complex with
values rangeing from 0.3 to 3.10 cmol(p+)kg-1. These
observations are in close agreements with those of
Nair et al. (1989). Nair and Chamuah (1988) working
on soils of Meghalaya also observed that soils are
acidic throughout. The CEC and ECEC as obtained
by summation of bases of all the soils are less than 16
and 12 cmol(p+)kg-1, respectively. Low CEC as
supported by CEC/clay ratio of these soils suggests
that these are low activity clay and the possibility of
the existence of kandic horizon is suggested. But only
the profile located at side slopes landform qualifies to
be a Kanhaplohumults. Other profiles cannot be
described as having a kandic horizon since they lack
required development in terms of horizon formation,
clay translocation etc due to various factors. Sen et
al. (1996) observed that ECEC supposed to give more
realistic CEC of these acid soils and found always
lower ECEC than the respective CEC.
Correlation Study
This study was carried out by pulling more no
of soil profiles data from the state irrespective of
landforms positions (Table 3). This primarily aims at
seeing the relationship between different soil
parameters in this hilly environment. The Pearson’s
correlation analysis (2-tailed) showed that CEC is
positively correlated (r=0.343*) with clay and highly
significantly correlated with silt (r=0.726**) and
positively with base saturation (r=0.365*). pH
maintains a significant positive correlation between
Ca (r=0.481**) and negative correlation between
extractable acidity (r=-0.491**) and extractable Al
Table 3. Pearson’s correlation coefficient for different soil parameters
Parameters Sand Clay Silt pH Ca Mg CEC Extract- Extract- Base OC ECEC
able acidity able Al saturation
Sand 1
Clay -0.555** 1
Silt -0.543** -0.334* 1
pH -0.061 0.097 -0.056 1
Ca -0.144 0.124 0.047 0.481** 1
Mg -0.085 -0.022 0.099 0.446** 0.559** 1
CEC -0.397** 0.343* 0.726** 0.138 0.049 0.156 1
Extractable acidity 0.461** -0.335* -0.246 -0.491** -0.394** -0.276 -0.158 1
ExtractableAl 0.425** -0.110 -0.363* -0.347* -0.145 0.333* -0.233 0.406** 1
Base saturation 0.230 0.056 -0.258 0.522** 0.633** 0.696** 0.365* -0.254 -0.110 1
OC -0.073 0.076 0.140 -0.071 -0.123 -0.140 0.302* -0.018 0.005 -0.204 1
ECEC 0.102 -0.89 -0.192 0.386** 0.855** 0.625** -0.080 -0.192 0.180 0.739** -0.130 1
Correlation significant at the 0.01 level, **Correlation significant at the 0.05 level
(r=-0.357*). Organic carbon shows only positive
correlation (r=0.302*) with CEC while non-significant
relations with other parameters. Base saturation and
ECEC exhibits significant and positive correlation
with pH (r=0.522*) and (r=0.368**), Ca (r=0.634**)
and (r=0.855**), Mg (r=0.696**) and (r=0.625**). In
addition to these, there are some non-significant
negative and positive correlations between different
parameters which are not taken into consideration.
From the above, it is inferred that landscape
position have influenced the soil development which
are reflected in differing soil characteristics. The
surface layer always contains highest organic carbon.
The profile located in the inter hill valley shows
organic carbon 2 per cent throughout the entire
depth which may be due to washing off soluble
organic fractions from the surrounding hill areas. Only
soils in the side slope position shows the presence of
Ultisols: a humults. Prediction of the clay mineralogy
using CEC/Clay ration has shown dual mineralogy in
the soil profiles which are interpreted as due to
variation in soil moisture. The valley soils indicate
the presence of mixed type of minerals with a clay
ratio of > 0.5. Most of the pedogenic processes that
occur within the study area are being favoured by
humid conditions, well to impeded drainage and
strong leaching environments. The differences in the
rate of hydrologic and geomorphic processes in
various landform positions causes differences in the
types and intensity of pedogenic processes leading to
formation of different types of soils.
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titration method. Soil Science 37, 29-38.
Received 31 January 2014; Accepted 15 June 2016
... Haliyal and Hangal soils from the study site are deep to very deep. Surface horizon of Haliyal was having dark brown colour both in moist and dry conditions and can be attributed to presence of organic matter (Dutta et al., 2016) [3] . Sub-surface horizons of Haliyal soils also exhibited 7.5YR (dark brown) hue for the soil matrix whereas that of Hangal pedon down the profile exhibited more reddish hue value ranging from 7.5YR to 5YR and 2.5YR. ...
In Karnataka rice is grown under a variety of soils and wide range of rainfall and temperature. A study was carried out to characterize and classify the rice-growing soils of hilly zones of Karnataka. Two pedons each from Haliyal taluk of Uttara Kannada district and Hangal taluk from Haveri district were selected for the study. Haliyal soils (pedon 1) were deep (>120 cm), moderate, medium, sub-angular blocky in structure, dark brown (7.5YR) in colour, clay loam to silt loam in texture, strongly acidic to slightly acidic in reaction, low CEC (16.60 to 21.50 cmol (p+) kg-1 soil) and medium to high base saturation. Hangal soils (pedon 2) were very deep (>160cm), moderate, medium, sub-angular blocky in structure, dark brown to reddish brown or red (7.5YR-5YR-2.5YR) in colour, clay loam to clay in texture, strongly acidic to slightly acidic in reaction, low CEC (10.20 to 14.60 cmol (p+) kg-1 soil) and medium to high base saturation. Haliyal soils were classified as Aquic Haplustepts and Hangal soils as Oxyaquic Haplustalfs at subgroup level.
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While soils formed in tephra are typically dominated by poorly crystalline clay minerals, the occurrence of smectite in E horizons of podzolized soils (Spodosols) has been well-documented. We have observed a well-crystallized smectite mineral dominating the clay fraction of E horizons in tephra-derived soils of northern Idaho. This study was initiated to examine properties and distribution of this mineral along a developmental sequence of high-elevation, forested Spodosols formed in 6800-yr-old Mazama tephra. Three soils exhibiting strong, moderate, and weak E horizon development were sampled along an elevational and climatic gradient. The smectite mineral was identified as beidellite based on expansion and layer charge characteristics. Heated, Li-saturated samples from the most strongly developed E horizon exhibited relatively complete expansion to 1.8 nm with glycerol solvation and mean layer charge was calculated to be 0.44 mole/formula unit using sorption characteristics of alkylammonium ions. Apparent crystallinity and relative abundance of the beidellite in clay fractions decrease with decreasing E horizon development. The more poorly crystalline beidellite is associated with a non-expansive 1.4-nm mineral with considerable Al-hydroxy interlayering. Beidellite was not detected in underlying glacial drift or in a thin layer of 200-yr-old ash that mantles these soils, suggesting it is not inherited from these materials. Rather, our results indicate that beidellite forms in these soils in an environment characterized by low pH and a large flux of organic metal-complexing agents.
The ratio of cation exchange capacity to clay (CCR) has been used as an index of clay mineralogy in subsoils low in organic matter in place of the standard X-ray diffraction measurement. Laboratory determination of this ratio is time-consuming and expensive and involves two analyses. In this paper, the CCR has been successfully predicted from mid-infrared diffuse reflectance spectra using partial least-squares regression (PLSR) with a square-root transformation of the CCR values (R-2 = 0.860; root mean squared error of prediction = 0.089; relative per cent deviation = 2.660 for an independent validation set). The most important wavelengths used in the PLSR calibration were identified. The prediction of CCR using mid-infrared spectroscopy provides a cheaper and faster alternative to laboratory determination.
Mineralogical and chemical properties of Madison soil derived from quartz mica schist reflected the degree of weathering. The Madison soil had sandy surface horizons and clayey 13 horizons. The clay in surface horizons contained more mica than clay in the subsoils; a maximum of about 40 per cent mica in the coarse clay of surface horizons. Intergradient chlorite-vermiculite was present in appreciable quantities in clays of sur- face horizons. The presence in the whole soil of B2 horizons of about 15 per cent gibbsite and 12 per cent free iron oxides indicated a high degree of weathering. Kaolinite and gibbsite increased with depth and were the major clay minerals in all clay fractions in the lower portion of the profiles. Kaolinite and gibbsite also were important accessory minerals of the coarse and medium silt fractions and increased in percentage with depth. The B3 horizons had much of the morphology of the schist. Results indicated a high weathering intensity in the subsoil and leaching of weathering products.