Open Journal of Soil Science, 2012, 2, 20-27
http://dx.doi.org/10.4236/ojss.2012.21004 Published Online March 2012 (http://www.SciRP.org/journal/ojss)
Morphological and Physico-Chemical Characteristics and
Classification of Vertisol Developed on Deltaic Plain
Orhan Dengiz*, Mustafa Sağlam, F. Esra Sarioğlu, Fikret Saygin, Çağla Atasoy
Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Ondokuz Mayıs University, Samsun, Turkey.
Received January 27th, 2012; revised February 24th, 2012; accepted March 8th, 2012
ABSTRACT
The name of Vertisol is derived from Latin “vertere” meaning to invert. This case restricts development of soil horizons
in profile. These soils have the cap acity to swell and sh rink, inducing cracks in the upp er parts of the soil and distinctiv e
soil structure througho u t the soil. Th e fo rmation of these speci fic features are caused by a heavy texture, a dominance of
swelling clay in the fine fraction and marked changes in moisture content. The swell-shrink behavior is attributed to the
wetting and drying of the soil mass. In this study, morphology, physico-chemical characteristics and classification of
vertisols that were formed on alluvial delta plains, were investigated. Those soils formed on the Bafra Plain found in the
Kızılırmak Delta and located in the central Black Sea region of Turkey. All studied Vertisols are characterised by a dark
colour in surface soil, a heavy clayey texture, hardpan formation under top soil (high bulk density a high compaction)
and very high COLE values. In addition, they have deep wide-opened desiccation cracks at the surface, slickensides at
the middle part of the profiles and a poor differentiation of their horizons. Physico-chemically, the studied soils are
slightly basic to very basic, non-saline and poor in organic matter, which is slightly higher in the surface horizon. In
addition, cation exchange capacity, sum of exchangeable bases and base saturation of soils are very high. On the basis
of morphological and physicochemical analysis, soil profiles were classified as Sodic Haplustert, Typic Calciaquert,
Sodic Calciustert according to Soil Taxonomy (Soil Survey Staff, 1975 and 1999) and as Sodic Vertisol and Calcic
Vertisol according to FAO/ISRIC (2006) classification systems.
Keywords: Vertisol; Soil Morphology; Soil Classification; Bafra Delta Plain
1. Introduction
The materials that form vertisols can be either alloch-
tonous or autochtonous in origin [1]. The former are geo-
graphically more extensive and generally occur in the lo-
wer parts of the landscape. Vertisols are known to de-
velop on a wide variety of parent materials such as ba-
salts in Australia [2], calcareous rocks in the West Indies
[1], gneisses and sandstones in India [3], deltaic deposits
in the United States of America [4], lacustrine deposits in
Trinidad [5], glacio-lacustrine in Saskatchewan [6], ma-
rine deposits in Guyana [7], and marls [8]. It is reported
that in all cases (except fo r the vertisols developed on la-
custrine deposits), the materials were recently deposited
and that soil formation was still at its early stages [9]. In
the case of vertisols developed from lacustrine deposits
in Trinidad, it is believed that extensive weathering and
clay-mineral synthesis had occurred prior to deposition
[10].
The name of vertisol is derived from Latin “vertere”
meaning to invert. This case restricts development of so il
horizons in profile [9]. These soils have the capacity to
swell and shrink, inducing cracks in the upper parts of
the soil and distinctive soil structure throughout the soil
[11]. The formation of these specific features are caused
by a heavy texture, a dominance of swelling clay in the
fine fraction and marked changes in moisture content [12].
The swell-shrink behaviour is attributed to the wetting
and drying of the soil mass. Vertisols exhibit cracks a
depth of 50 cm down that are at least 1 cm wide and ex-
tend upward to the surface or the base of the plough layer
or surface crust. These soils exhibit minimal horizon dif-
ferentiation as a result of pedoturbation. They are also
very plastic and sticky when wet [13]. Vertisols are de-
scribed by Glossary of Soil Science Terms [14] as “min-
eral soils that have 30% or more clay, deep wide cracks
when dry and either gilgai microrelief, intersecting slicken-
side or wedge-shaped structural aggregates tiled at an an-
gle from the horizon. It was added as an order in US sys-
tem of soil taxonomy.
Depressions and level to undulating areas, mainly in
*Corresponding a uthor.

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain 21
tropical, semi arid to sub humid and Mediterranean cli-
mates with and alternation of district wet and dry season s.
An estimated 150 million hectares is potential crop land
[15]. According to a map called the Turkey Soil Zones
Map at the scale of 1:2,000,000 prepared from the results
of the Turkey Development Soil Maps Survey at a scale
of 1:100,000, vertisols comprise 598 ,693 hectar es or 0.86
percent of the land area of Turkey [16,17].
Vertisols are important agricultural soils in left side of
Bafra Delta Plain. Soils are mostly used for rice cultiva-
tion. The main ai ms of this research were to determine th e
morphological and some physico-chemical characteristics
of these soils and to classify the soils according to the
USDA Soil Taxonomy and FAO/ISRIC soil classifica-
tion systems.
2. Material and Methods
2.1. Description of the Study Area
This study was carried out in the left side of Bafra Plains
found in the Kızılırmak delta located in the central Black
Sea region of Turkey (Figure 1). The Bafra Delta Plain is
far 30 km from north of the Samsun province. The cur-
rent climate in the region is semi-humid. The summers
are warmer than winters (the average temperature in July
is 22.2 and in January is 6.9˚C). The mean annual tem-
perature, rainfall and evaporation are 13.6˚C, 764.3 mm
and 726.7 mm respectively. According to [18], soil tem-
perature regime is mesic and moisture regime is ustic in
the study area. The mean annual temperature, rainfall and
evaporation are 13.6˚C, 764.3 mm and 726.7 mm respec-
tively in Bafra plain that area is mainly flat and slightly
Figure 1. Location map of the study area.

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain
22
sloped (0% - 2.0%). The study area has been under in-
tensive agricultur al activities. Rice, wheat, maize, pepper,
watermelon, cucumber and tomato with sprinkler and
furrow irrigations in the summer, and cabbage and leek
in the winter have been produced in the study area.
2.2. Physical and Chemical Analysis
Four vertisol profiles formed on deltaic deposits were
selected for this study in left side of Bafra delta plains.
Morphological p roperties of these four soil pro files in the
field were identified and sampled by genetic horizons.
Nineteen soil samples were taken to investigate for their
physical and chemical properties at the laboratory. Dis-
turbed soil samples were dried under atmospheric condi-
tion and passed through a 2 mm sieve to prepare for la-
boratory analysis. In soil samples, particle size distribu-
tion was determined by the hydrometer method [1 9]. Dry
bulk density was determined by the core method [20].
Soil reaction (pH), electrical conductivity (EC) and CaCO3
content were determined by standard procedure [21]. Ex-
changeable cation s an d cation ex chang e cap acities (CEC)
were measured using a 1 N NH4OAc (pH 7) extraction
method [22]. Organic matter content was determined us-
ing the Walkley-Black wet digestion method [23]. Coef-
ficient of linear extensib ility (COLE) was determined ac-
cording to [18]. In addition, these four soil profiles were
classified according to [18-24].
3. Results and Discussions
3.1. Soil Morphology and Classification
Two main types of vertisols can be distinguished: Litho-
morphic vertisols and topomorph ic vertisols [24,25]. L itho -
morphic vertisols are formed on various parent rocks
whose weathering generates base-rich environments fa-
vourable for smectite synthesis, while topomorphic ver-
tisols are formed mainly in favour of low land scape posi-
tions which favour the accumulation of bases. In this study,
morphological characteristics of selected four soil profiles
formed on alluvial delta plains are presented in Table 1.
Table 1. Selected morphological characteristics of pedons.
Colors
Horizon Depth
(cm) Boundary Dry Moist
Structure Consistence Special features
Pedon I (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 18 as 10YR3/2 10YR3/3 3mgr sh fi st pt cracks
Bss1 18 - 45 cw 10YR4/3 10YR4/3 3mab k h fi st pt cracks, slickenside
Bss2 45 - 70 dw 2.5YR6/2 2.5YR5/2 3mpr h fi st pt cracks, slickenside
Bss3 70 - 116 dw 2.5YR5 /3 2.5YR5/3 3cpr h fi st pt cracks, slickenside
C 116+ - 10YR5/3 10YR5/4 m h fi st pt -
Pedon II (Typic Calciaquert/Calcic Vertisol)
Ap 0 - 25 aw 2.5YR4/3 2.5YR4/4 3mgr h fi st pt cracks
Bss1 25 - 70 cw 5Y5/3 5Y5/2 3mpr h fi st pt cracks
Bss2 70 - 116 cs 5Y6/1 5Y6/2 3mpr h fi st pt slickenside
Ck 116+ - 2.5YR7/3 2.5YR6/3 sg so fr ss ps carbonate mycelium and nodules,
water table
Pedon III (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 15 as 2.5YR4/3 2.5YR4/3 3mgr sh fi st pt cracks
Ad 15 - 44 gw 2.5YR5/3 2.5YR4/4 3msbk h fi st pt densitic layer
Bssg1 44 - 73 gw 10GY6/1 10GY5/1 3mpr h fi st pt slickenside, redoximorphic feature
Bssg2 73 - 108 dw 10GY6/1 10GY5/1 2mpr h fi st pt slickenside, redoximorphic feature
Cg 108+ - 2.5YR6/3 2.5YR6/3 m sh fi ss pt redoximorphic feature
Pedon IV (Sodic Calciustert/Sodic Vertisol)
Ap 0 - 18 as 10YR4/2 10YR3/2 3cgr sh fi st pt cracks
Ad 18 - 50 aw 10YR 4/3 10YR 3/4 3msbk sh fi st pt densitic layer
Bss 50 - 82 cw 2.5YR6/3 2.5YR6/3 3mpr sh fi st pt slickenside
Bssk 82 - 125 cw 2.5YR7/3 2.5YR6/3 3mpr si fi st pt slickenside, carbonate mycelium
and nodules
C 125+ - 2.5YR7/3 2.5YR6/3 sg so fr ss ps -
Abbreviations: Boundary: a = abrupt; c = clear; g = gradual; d = diffuse; s = smooth; w = wavy; i = irregular Structure: 1 = weak; 2 = moderate; 3= strong; sg
= single grain; m = massive; vf = very fine; f = fine; m =medium; c = coarse; gr = granular; pr = prismatic; abk = angular blocky; sbk = subangular blocky.
Consistance: (Dry) lo = loose; so = soft; sh = slightly hard; h = hard; (Moist) lo = loose; vfr = very friable; fr = friable; fi = firm; (Wet) so = nonsticky; ss =
slightly sticky; st = sticky; po = nonplastic; ps = slightly plastic; pt = plastic.

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain 23
[11,26,27] stated that many vertisols have deep and dark
topsoil. In addition, [28] reported the dark colour (low
chroma) could be related to the strong impregnation of
profile by organic matter during pedogenesis or to pro-
long waterlogging . In this research, colour of the all pro-
files in hue changed 10YR and 2.5Y, value was 3 - 4 (dry
and moisture conditions) in surface soils. Thus, the find-
ing was showed coherent with these researchers. On the
other hand, colo ur changed due to redoximorphic featur e
(10GY 6/1) in subsurface horizon in Profile III and car-
bonate accumulation (high value-2.5YR7/3) in Ck and
Bssk horizons of PII and PIV. Besides, carbonate nod-
ules and mycelium were also recognised in these pedons
within 120 cm depth due to calcification process.
Extensive swelling and shrinking upon wetting and
drying is the major characteristics of these soils. This re-
sults to pedoturbation or mixing of the soils and minimal
horizonation [9]. Shrinkage causes the formation of wide
deep cracks and washing of surface materials into these
cracks. Vertisols may exhibit open cracks, which are up
to 50 cm deep and at least 1 cm wide and extend upward
to the surface or the base of the plow layer or surface
crust [13]. Moreover, cracks are a unique feature in soils
with strong shrink–swell potential and are used as one of
the criteria in defining vertisols and vertic intergrades in
soil taxonomy [18]. Cracking takes place as a result of
seasonal fluctuation. The moisture regime influences the
duration and intensity of cracking. The degree and fre-
quency of changes in moisture content of the soil are per-
haps the most important parameters th at control cracking
intensity [6]. Cyclic cracking and swelling contribute to
the formation of slickensides. Most of the subsurface ho-
rizons (except for C horizons) of profiles were character-
ised by numerous smooth and shiny surfaces called
slickensides that separated different blocks and prismatic;
their diameters varied between 5 and 15 cm. While Ap
horizons of profiles have strong, medium and coarse granu-
lar structures, due to high clay content blocky and pris-
matic structures were determined in 100 cm of profiles.
Consistencies of all B horizon of profiles wer e very hard
when dry and plastic when wet conditions.
Due to the fact that main soil formation process and
other features such as slickenside, cracking, carbonate
accumulation and redoximorphic symptoms, four soil
profiles were classified as Sodic Haplustert, Typic Cal-
ciaquert, Sodic Calciustert by taking into consideration
of Soil Taxonomy [18]. In addition, these soils were
classified as Sodic Vertisol and Calcic Vertisol according
to FAO/ISRIC [24].
3.2. Physico-Chemical Characteristics
3.2.1. Chemical Properties
Vertisols are generally found on sedimentary plains as
the result of thousands of years eroding the clay content
out of the surrounding hills. They can also be found on
level land and in d epressions. [29] also reported that v er-
tisols are typically developed on alluvial material in flat
inland areas. The pedons selected for the present study, it
was found significantly vation in pH values among all
the soil layers. The pH values varied from 7.84 to 9.39.
The increase in pH with depth of pedons is a characteris-
tic feature of all pedons and could imply the proximity of
the horizons to the alluvial parent material that is rich in
alkaline earth cations (Ca and Mg) and water table fluc-
tuation due to sea effect that includes high sodium ion
concentration. In parallel, increasing of sodium concen-
tration with depth caused increasing of ESP values in all
pedons. [30] reported that high ESP values in vertisols
cause dispersion of fine particles, leading to blockade of
pore spaces. This ultimately rend ers the soils non-porou s
as reflected by low permeability. Poor drainage conditions
lower the rate of organic matter decomposition. The or-
ganic matter values varied from 3.2% to 4.8% in surface
horizons whereas, these ratios decreased with depth and
varied from 0.5% to 2.5%. The higher organic matter at
the surface could be linked to the continuous addition of
crop residues on the surface of cropped fields in the area.
The cation exchange capacity for all the studied soils
ranged between 32.6 and 80.7 cmol·kg–1 of soils (Table
2). It increased regularly with pro file depth. Calcium and
magnesium were the dominant exchangeable cations,
with contents ranging between 25.6 and 73.5 cmol·kg–1 of
soils. It was followed by sodium (3.0 to 12.2 cmol·kg–1),
while potassium showed more modest values (0.6 to 1.0
cmol·kg–1). The CaCO3 content of the soils increased with
depth and values varied from 1.4% to 34.7%. The highest
values were observed at the subsurface horizons in Pro-
file II and Profile IV due to calcium carbonate leaching
and accumulation process. [31] reported that pedogenic
carbonates accumulation in the Texas Gulf Coast Prairie
Vertisols form by leaching of detrital carbonate in the
fine earth fraction of the sediments to just below the ef-
fective meteoric infiltration.
3.2.2. Physical Properties
The soils selected for the present study belong to verti-
sols and their intergrades. Logically, the sand, silt and
clay content should be within the range to qualify them
as Vertisols [18]. The contents of sand, silt and clay vary
as shown in Table 3. The clay content of all studied pe-
dons varies from 52.2% to 85.7% except for C horizons
of pedons while, sand content changes between 5.3% -
17.6% in pedogenetic horizons. While the clay contents
were the highest in Pedon IV and ranged between 80.1%
and 85.7% within 80 cm depth, the highest sand content
(20.0%) was observed in Pedon II. The representation of
various grain size fractions on [32] Jamagne’s textural
diagram showed that the all soils layers of pedons had a
heavy clayey texture (Figure 2).

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain
24
Table 2. Some chemical properties of pedons.
Exchangeable cations (cmol·kg–1)
Horizon Depth (cm) pH EC (dS m–1) CaCO3 (%)O.M (%)CEC (cmol·kg–1) ESP (%) Na+ K
+ Ca++ + Mg++
Pedon I—Coordinate: North: 4,6 1 6,083 m - East: 73 7,858 m (UTM) (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 18 7.89 0.88 9.1 3.9 64.2 4.7 3.0 0.9 62.1
Bss1 18 - 45 8.39 0.51 13.4 2.3 60.6 5.9 3.6 0.8 57.6
Bss2 45 - 70 8.60 0.73 12.5 1.8 56.3 8.2 4.6 0.8 52.5
Bss3 70 - 1 16 9.04 0.45 9.1 1.6 59.8 14.2 8.5 0.9 52.7
C 116+ 9.15 0.70 12.4 1.1 53.5 17.4 9.3 0.9 46.0
Pedon II—Coordinate: North: 4,616,541 m - East: 737,542 m (UTM) (Typic Calciaquert/Calcic Vertisol)
Ap 0 - 25 8.30 0.73 1.4 3.2 65.4 5.0 3.3 0.9 62.9
Bss1 25 - 70 8.52 1.99 6.3 2.5 6 1.7 12.8 7.9 0.8 55.3
Bss2 70 - 1 16 8.86 0.91 6.6 1.2 53.7 17.7 9.5 0.8 46.0
Ck 116+ 9.39 0.48 34.7 0.5 33.9 13.6 4.6 0.6 30.6
Pedon III—Coordinate: North: 4,617,456 m - East: 736,809 m (UTM) (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 15 7.84 1.36 11.6 4.6 80.7 7.2 5.8 1.0 72.8
Ad 15 - 44 8.49 1.25 13.7 2.4 73.9 12.3 9.1 0.8 70.4
Bss1 44 - 73 8.97 1.24 14.1 2.0 54.2 17.9 9.7 0.8 50.8
Bss2 73 - 108 9.07 0.68 11.0 1.7 58.0 15.0 8.7 0.7 53.2
C 108+ 8.94 0.82 21.6 1.3 56.0 16.8 9.4 0.7 50.1
Pedon IV—Coordi nate: North: 4,618,055 m - East: 736,735 m (UTM) (Sodic Calciustert/Sodic Vertisol)
Ap 0 - 18 7.92 1.15 11.7 4.8 78.7 9.0 7.1 1.0 73.5
Ad 18 - 50 8.78 0.36 15.0 2.3 71.0 13.0 9.2 0.8 67.8
Bss 5 0 - 82 8.89 0.71 10.9 1.9 63.6 18.2 11.6 0.9 58.3
Bssk 82 - 125 9.22 0.54 28.3 1.9 62.8 19.4 12.2 0.8 56.4
C 125+ 8.26 2.92 6.7 0.9 32.6 30.1 9.8 0.6 25.6
EC: Electrical conductivity; CEC: Cation exchange capacity; O.M: Organic matter; ESP: Exchangeable sodium percentage.
Table 3. Some physical properties of pedons.
Particle size distribution (%)
Horizon Depth (cm) COLE Clay Silt Sand Class
BD
(gr·cm–3)
Pedon I (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 18 0.221 68.1 24. 2 7. 8 C 1.15
Bss1 18 - 45 0.274 66.0 23.4 10.6 C 1.21
Bss2 45 - 70 0.264 65.1 21.8 13.0 C 1.23
Bss3 70 - 116 0.285 79.4 13.2 7.4 C 1.29
C 116+ 0.225 72.9 13.7 13.5 C 1.34
Pedon II (Typic Calciaquert/Calcic Vertisol)
Ap 0 - 25 0.211 68.1 17.4 14.5 C 1.24
Bss1 25 - 70 0.281 72.1 15.7 12.2 C 1.22
Bss2 70 - 116 0.191 61.5 17.5 21.0 C 1.27
Ck 116+ 0.025 28.9 35.3 35.8 L 1.35
Pedon III (Sodic Haplustert/Sodic Vertisol)
Ap 0 - 15 0.280 79.7 13.3 7.0 C 1.23
Ad 15 - 44 0198 80.4 9.1 10.5 C 1.48
Bss1 44 - 73 0.190 55.1 29.4 15.4 C 1.27
Bss2 73 - 108 0.191 52.2 34.9 13.0 C 1.30
C 108+ 0.111 40.5 10.7 48.8 C 1.50
Pedon IV (Sodic Calciustert/Sodic Vertisol)
Ap 0 - 18 0.269 80.5 11.0 8.5 C 1.20
Ad 18 - 50 0.219 85.7 9.0 5.3 C 1.57
Bss 50 - 82 0.231 80.1 2.3 17.6 C 1.31
Bssk 82 - 125 0.174 62.5 25.9 11.6 C 1.35
C 125+ 0.021 23.5 53.6 22.9 SiL 1.55
COLE: Coefficient of linear extensibility; BD: Dry bulk density; C: Clay, SiL: Silty loam; L: Loam

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain 25
Figure 2. Soil textural classes with reference to Jamagne’s triangle (1967).
Bulk density (BD) indicates the weight of all the or-
ganic and inorganic materials of a given volume of soil.
Higher organic matter lowers BD. High clay content and
introduction of farm machinery causes compaction of sub-
surface layer, which increases the BD. Bulk density also
varies with the content of coarser fragments in soils. There
is a growing acceptance of the view that BD changes due
to change in land use pattern [33]. A study was conducted
with soil profil es from arable area used for field crop (rice)
and vegetables for 30 - 40 years. The highest BDs were
determined in parent materials of all pedons including
high sand content. On the other hand, BD of pedogenetic
horizons ranges between 1.15 and 1.35 g·cm–3 except for
Ad horizons of Pedon III and IV that soils have particu-
larly used for rice cultivation. Due to heavy tillage sys-
tem and field traffic on these soils leading to hard pan
formation, BD increased 1.57 g·cm–3. Similar results were
reported by [34] that over the years, continuous tillage
practices resulted bulk density increased from 1.22 g·cm–3
to 1.38 g·cm–3 in a tropical forest ecosystem of Bangla-
desh. In additio n, due to compression caused by ov erbur-
den weight, the BD values usually increase with soil depth
in all pedons. It has been reported that vertisols may have
BD values as high as 2.1 g·cm–3 [35]. It has been also
shown that at the swelling limit, the gravimetric water con -
tent decreases and BD values increase with depth [36].
Coefficient of linear ex tensibility (COLE) helps to p re-
dict the potential of a so il to shrink and swell. The LE of
a soil layer is the product of the thickness in cen timetres,
multiplied by the COLE of the layer in question. The
COLE of a soil is the sum of these products for all soil
horizons [18]. According to soil taxonomy, a soil should
be qualified for vertic subgroups if the COLE value is
more or equal to 6 between the mineral soil surface and
either a depth of 100 cm or a lithic contact, whichever is
shallower. In case of vertisols slickensides, cracks and
higher COLE values are mutually inclusive. Since higher
COLE values indicate the presence of more shrink-swell
minerals, namely smectite, a positive correlation between
COLE and smectite content can exist [37]. According to
COLE classification given in Table 4, it was also found
that high COLE values should have a positive relation
with vertic characteristic properties of shrink-swell soils
and cracking and vary from 0.174 to 0.281 in pedoge-
netic horizons of all pedons in Table 3.
Vertisols are important agricultural soils in left side of
Bafra Delta Plain. However, vertisols are difficult to work,
they are of very hard consistence when dry and very plas-
tic and sticky when wet. Therefore, th e workability of th e
soil is often limited to very short period s of medium (op-
timal) water status. Vertisols are imperfectly to poorly
drained, leaching of soluble weathering products is lim-
ited, the contents of available sodium, calcium and mag-
nesium are high and the pH is usually above 7.5. Once
they have reached their field capacity, practically no wa-
ter movement occurs, this is due to the very low hydrau-
lic conductivity of a vertisol. In addition, flooding lead-
ing to crop damage can be a major problem in areas with
higher rainfall.

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain
26
Table 4. Coefficient of linear extensibility (COLE) classifi-
cation.
Class COLE
Low <0.03
Moderate 0.03 - 0.06
High 0.06 - 0.09
Very high >0.09
4. Conclusion
In this study, it was aimed at investigating the morpo-
logical and analytical characteristics of vertisols formed
on fluvial land in Bafra Deltaic Plain, in order to high-
light their particularities as well as to envisage their prac-
tical uses and management. From the morphological and
physical point of view, the vertisols of the Bafra Deltaic
Plain region are characterised by a dark colour, a heavy
clayey texture, hardpan formation under top soil (high bulk
density a high compaction) and very high COLE value,
deep wide-opened desiccation cracks at the surface,
slickensides at the middle part of the profiles and a poor
differentiation of their horizons. Physico-chemically, the
studied soils are slightly basic to very basic, non-saline
and poor in organic matter, which is slightly higher in the
surface horizon. Cation exchange capacity, sum of ex-
changeable bases and base saturation are very high. Ove-
rall, considering their characteristics in majority similar
to those of a majority of world deltaic vertisols, those
soils are still unused or are used only for extensive graz-
ing, wood chopping, charcoal burning and the like [24].
In agriculture, optimum yields could be attained if ap-
propriate management techniques are set up for a more
efficient exploitation, protection and conservation of these
soils. The comparatively good ch emical fertility and their
occurrence on extensive level plains where reclamation
and mechanical cultivation can be envisaged are assets of
vertisols. Their physical soil characteristics and, notably,
their difficult water management cause problems. The
physical properties and the soil moisture regime of verti-
sols represent serious management constraints. The heavy
soil texture and domination of expanding clay minerals
result in a narrow soil moisture range between moisture
stress and water excess. Tillage is hindered by stickiness
when the soil is wet and hardness when it is d ry. The su s-
ceptibility of vertisols to waterlogging may be the single
most important factor that reduces the actual growing
period. Especially due to those properties, these vertisol
soils have been generally used for rice cultivation in the
study area. On the other hand, this case is not suitable
other plants. Particularly, due to their very high of COLE
values, namely, very high shrink-swell potential plant
roots can be damaged from this soil activity. Zero till is
commonly advocated as a preferred cropping system to
conventional, multicultivation practices. Zero till is par-
ticularly attractive on clay soils to minimize compaction
and induce natural structure formation [17]. In particular,
the soil stru cture of vertisols h as strong potential to attain
optimal conditions for plant growth through activation of
their inbuilt resiliency via shrink-swell cycles [38,39]. It
is accepted that the major purposes of tillage are to re-
duce bulk density and soil strength and to control pests
and diseases [40,41]. However, soil cultivation affects
soil quality in various ways. With high clay content, cul-
tivation may lead to the formation of a hard pan below
the plough layer that restricts root penetration and down-
ward movement of water [42]. Therefore, many resear-
chers strongly recommend that close attention should be
taken into account for the soil cultivation, irrigation sys-
tem and time depending on the these soil types.
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