Parent material has been recognized as an important factor in soil formation since the earliest scientific consideration of soils (Jenny, 1980). According to Joffe (1949) the formation of soil in a region can occur within a certain period of time depending on the parent material, climate, topography and vegetation of the region (Buol et al., 1980; Dinc et al., 1987). Different parent materials affect the morphology and chemistry of soils under the same conditions, such as topography and vegetation, especially in arid and semiarid regions. Differences in physical, chemical and mineralogical properties of soils are related primarily to parent material (Washer and Collins, 1988). A soil landscape pattern generally reflects the original parent material; however, saprolite was highly weathered prior to soil formation (Wysocki et al., 1988). The original separation of soils was based on the type of parent rock and on morphological properties.
Harran, as a local area of Sanlýurfa, is inside of The Southeastern
Anatolia Region. Turkey, which has 81 administrative provinces, is divided into
seven geographical regions and one of them is Southeastern Anatolia region which
is generally called the Southeastern Anatolia Project (SAP, Turkish initials
GAP) Region. The Southeastern Anatolia Project (SAP) is Turkey’s largest
and most multifaceted development project and also, one of the largest development
projects of its kind in the world (Kaygusuz, 1999; Bulut, 2003). The project
area covers nine provinces (Adıyaman, Batman, Diyarbakır, Gaziantep,
Kilis, Mardin, Siirt, Sanlıurfa and Sırnak) of the Southeastern Anatolia
Region, which is a relatively underdeveloped region in Turkey. The project covers
such sectors as irrigation, hydroelectric power production, agriculture, urban,
rural and agricultural infrastructure, transportation, industry, forestry, tourism,
education and health.
General location of Harran region
Its water resources program envisages the construction of 22 dams and 19 power
plants and irrigation schemes on an area extending over 1.7 million ha (GAP,
2003). Parallel to this development, an intensive investment activity is expected
to be undertaken in the region.
The objective of this study was to examine the effects of parent material on
the physical, chemical, mineralogical and morphological properties of soils
in the arid and semiarid regions of the Southeast Anatolia Region of Turkey
MATERIALS AND METHODS
Description of the area: The study area was characterised by arid climate and lies between 37°46' and 36°43' N latitudes and 37 and 39°46' E longitudes in the Southeast Anatolia Region of Turkey. The average amount of annual rainfall is 320 mm in south of region and 400 mm in the north of region and total evaporation is 2047.75 mm. The mean annual air temperature was 17.8°C. The mean annual soil temperature at 50 cm depth was 19.9°C. The vegetations of study area were grasses, cereal and leguminous crops.
Method: The soil profiles were described in the field according to Soil
Survey Staff (1993). Disturbed soil samples for laboratory analysis were collected
from each horizon and air dried to pass a 2 mm sieve. The particle size distribution
of each sample was determined by the pipette method (Mc Keague, 1978) after
removal of organic matter and carbonates. The pH and salt content (electrical
conductivity, EC) were measured on saturation extracts (Radiometer PHM 82 standard
pH meter and Radiometer CDM 83 conductivity meter). Percent salt content was
calculated from EC values. Organic C was measured by using a modified Walkley-Black
procedure (Nelson and Sommers, 1982). Carbonate content was determined by the
Sheibler calciometer method (Black, 1965). Exchangeable cations were determined
after replacement with Ba (Mc Keague, 1978) and cation-exchange capacity by
Mg saturation followed by NH4 substitution. The clay fraction from
each soil was analyzed by x-ray diffraction to determine the clay mineralogy.
Treatments of the samples included Mg saturation and glycerol solvation and
K saturation and heating to 105, 300 and 550°C (Jackson, 1974). Extractable
Fe, Si and Al oxides by the citrate dithionite-bicarbonate method and total
chemical analysis were carried out by the HF fussion method (Jackson, 1979).
The results of total element analysis were used to determine the β leaching
factor. β leaching factor was determined according to Jenny (1941) following
β: The ba value of leaching horizon (A1)
The ba value of parent material (C1, C2 or C3 horizon)
The ba value was determined following formulation:
ba value: Na2O + K2O/Al2O3
The soils were classified according to Soil Taxonomy (Soil Survey Staff, 2006) and the World References Base For Soil Resources (FAO ISRIC, 1998).
RESULTS AND DISCUSSION
Soil formation and morphological properties: The major morphological
properties of the soils were presented in Table 1. Profiles
PL1 and PL2 have developed on the limestone as a result of decomposition and
fragmentation of the calcareous parent material. Secondary carbonate nodules
which apparently were evidence for carbonate leaching and accumulation were
identified in the profiles PL 1 and PL2. Calcic horizon has developed in the
Ck1 horizon of Profile PL 1 and Ck horizon of Profile PL 2 as a result of carbonate
accumulation. A Cambic B definition horizon has developed in the profiles PL
1 and PL2 as a result of structure formation and reddish brown colour. Some
researchers have claimed that a cambic horizon has developed along with a calcic
horizon in soils of arid and semiarid regions (Buringh, 1979; Buol et al.,
1980; Dinc et al., 1987). β leaching factor is 0.48 in the Profile
PL1 and is 1.29 in the Profiles PL2 (Table 1). The low eaching
factor (< 1) in the Profile PL1 may be attributed to extensive weathering
of parent material. The high leaching factor (> 1) in the Profile PL2 may
be associated with the low weathering of parent material.
Profiles PL3 and PL4 have developed on the marine parent material. A Cambic
B horizon has developed as a result of structure formation. The morphology of
profile PL4 was similar to the profile PL3.
Selected some morphological characteristics and leaching
factor of soils
†: CL: Clay loam, C: Dlay, SC: Sandy clay . ‡:
1: Weak, 2: Moderate, 3: Strong; m: Medium; gr: Granular, abk: angular
blocky, sbk: subangular blocky, ma: Massive
However, surface horizon of the profile PL4 has abraded by erosion due to
the sloppy topography. β leaching factor is 0.79 in the Profile PL3 and
is 0.14 in the Profiles PL4. The low leaching factor (< 1) in the Profile
PL3 may be attributed to weathering. The low leaching factor (< 1) in the
Profile PL4 may be associated with error of analysis.
Profile PL5 has developed on the alluvium materials, deposited during the Holocene. A Cambic B horizon developed in these soils due to the prizmatic structure formation. Prizmatic structure formation was related with the shrink-swell potential of the parent material. Slickensides have developed in the B horizons of profile PL5 as a result of shrink-swelling. β leaching factor is 0.33 in the Profile PL5.
Profiles PL6 and PL 7 have developed on the basalt rocks of the Pleistocene
age. Parent material has affected the morphological characteristics of these
soils. Profile PL6 has the finest texture and the reddest coloured soils in
the study area (Table 1 and 2). The red
colour of profiles PL6 and PL 7 may be associated with the high Fe oxide content
of the parent material. A Cambic B horizon developed in these soils due to the
prizmatic structure formation. Prizmatic structure formation was related with
the shrink-swell potential of the parent material. Slickensides have developed
in the B horizons of profiles PL6 and PL7 as a result of shrink-swelling. β
leaching factor is 0.82 in the Profile PL6 and is 0.74 in the Profiles PL7.
The low leaching factor (< 1) may be attributed to extensive weathering of
The physical and chemical properties: The major physical and chemical
properties of the soils were presented in Table 2. The clay
content in the A horizon is slightly greater than 35 % in profiles of PL3, PL6
and PL7. The clay contents of all profiles were generally increasing with depth,
especially in the B horizons (Table 2). Clay content in the
surface of the all soils is lower than subsoil. The low clay content of surface
soil may be associated with leaching from surface to subsoil. The clay content
of the soils, developed on the basalt parent material was considerably higher
than the other soils. The differences in the particle-size distribution of the
soils may reflect differences in chemical composition of the parent rocks The
clay content of Profile PL 6, developed on the basalt, was considerably high
and change between 50.67% (in the Ap horizon) and 62.11% (in the Ck1
horizon). Fine texture of Profile PL 6 can be attributed to extensive decomposition
and chemical characteristic of the basalt material. Calcium carbonate content
of the soils were high and an increase was found in the carbonate accumulation
horizons (Table 2). The high CaCO3 content of profiles
PL1, PL2, PL3 and PL4 were associated with calcareous parent material. The CaCO3
content of profiles PL6 and PL7 on the basalt rocks were high and changed between
14.4 and 18.4%. The CaCO3 contents of these soils (profiles PL6 and
PL7) may be attributed to eolian additions from the calcareous soils.
Because, eolian additions play an important role in pedogenesis in many arid
regions (Stolt et al., 1991). The lime content of basaltic soil (R horizon)
taken from Profil 7 was very high (14.4%) as shown Table 2.
Basaltic rocks do not consist of CaCO3 naturally. Therefore, it was
supposed that basalt contents of soil was formatted due to the inactive Volcano
of Karaca Mountain and some lime layers was lain under 10 m of basaltic layer.
The pH of the soils was moderately alkaline and increases with depth as a result
of accumulation of CaCO3 with depth. The cation exchange capacity
(CEC) values of the soils change between 14.81 and 56.66 cmol kg-1.
The high CEC values may be associated with high clay content. Some researchers
reported that high clay content have increased cation exchange capacity of soils
in arid regions (Yılmaz, 1990; Irmak et al., 1991).
The CEC of the soils, on the basalts, were higher than other soils. The cation
exchange capacity values in the profiles PL6 and PL7 developed on the basalt
material, change between 46 and 56 cmol kg-1. High CEC value of the
soils was due to high clay content. CEC values were especially increase as depending
on high clay content (Table 2). Exchangeable Ca++
and Mg++ contents of the all soils were considerably high. Exchangeable
Ca++ and Mg++ account for > 95% of the exchangeable
complex as a result of dissolution of carbonates and possible weathering of
feldspar and ferromagnesian minerals present in the soils. The high contents
of Ca++ and Mg++ may be associated with the chemical composition
of the parent material. Exchangeable Na+ and K+ levels
were rather low and K+ level decreases gradually with depth (Table
2). The organic C content of the soils was very low and decreases gradually
with depth and measured between 0.69 and 2.97 g kg-1. The low content
of organic C can be attributed to long arid periods and poor vegetation.
The total elemental composition of soils: The major total element analysis
of the soils was presented in Table 3. Extractable Fe contents
of the soils, developed on the basalts, were relatively higher than the other
soils and change between 0.56 and 2.05%. The extractable Fe content of profile
PL4, developed on the marine, was very low and changes between 0.26 and 0.37%.
Extractable Al2O3 content, parallels clay content in the
profiles PL5, PL6 and PL7, with a maximum in the Bwss1 horizon of PL6. The extractable
Fe contents in the A horizons of profiles PL2, PL5, PL6 and PL7 may be attributed
to weathering of the parent material.
Extractable SiO2 contents of the soils were very low and change between 0.035 and 0.087%. The low SiO2 content may be attributed to weathering of quartz. Some researchers reviewed eleven reports on the trends of extractable Fe content in B horizons with soil age. He noted that, for two of the reports, the values for the extractable Fe increased with soil age to a maximum, then decreased with further time (Jacob et al., 1990). Other researchers have shown that increasing rubification over time was a function of Fe oxide accumulation (Birkeland, 1974). Several researchers report that the amount of Al that substitutes for Fe in goethite may be a useful criterion to estimate the extent of soil formation (Fitzpatrick and Schwertmann, 1982).
Total Fe2O3 of the soils, on the basalts, was higher than the other soils and changes between 4.36 and 6.70%. The total Fe2O3 content of profiles PL l and PL 2 on the CaCO3 rocks changed between 2.06 and 5.46%. The total Fe2O3 content of profiles PL3 and PL4 on the marine changed 1.01 and 3.52%. The total Fe2O3 content of PL5 on the alluvium material was similar to PL3 and PL4 and changed between 1.08 and 3.35%.
The total Al2O3 content of profiles PL6 and PL7 on the
basalts obtained relatively higher than the other soils and change between 4.92
and 8.72%. The total Al2O3 content of PL3 and PL4 soils
on the marine was lower than the other soils and change between 0.12 and 4.11%.
The high total Fe and Al oxide contents of the soils on the basalts might be
associated with the chemical composition of basalt rocks. Analysis of the unweathered
basalt rock samples of profile PL7 on the basalts also was showed similar mineralogical
Total MgO contents of the soils on the CaCO3 rocks changed between 0.211 and 0.263%. Total MgO contents of the soils, on the marine, changed between 0.219 and 0.250%.
Total MgO contents of the soils, on the basalts, changed between 0.187 and
0.257%. Total CaO contents of the soils on the CaCO3 rocks were higher
than the other soils and change between 2.047 and 14.994%. The high CaO contents
were related with chemical composition of CaCO3 rocks. Total CaO
content of the soils on the marine changed between 1.380 and 2.156%. Total CaO
contents of the soils on the basalts changed between 2.338 and 9.030%. Total
K2O contents of the soils on the CaCO3 rocks changed between
0.269 and 0.855%. Total K2O contents of the soils on the marine changed
between 0.235 and 0.487%. Total K2O contents of the soil on the basalt
changed between 0.371 and 0.837% (Table 3 ).
Clay mineralogy: The clay fraction from each soil was analyzed by x-ray
diffraction to determine the clay mineralogy in the four soil profiles on the
four different parent materials. The results of X-Ray Diffraction analysis were
presented in Table 4. X-Ray Diffraction analysis data show
that smectite was the dominant clay mineral in all the soils. The presence of
smectite was in agreement with the CEC and swelling properties of the soils.
The level to very gently undulating landscape and semiarid conditions, high
pH and saturation of the soils with water for a period of time may have ensured
the accumulation of bases and therefore the formation of smectite and other
2:1 clay mineral (Buol et al., 1980; Dinc et al., 1987; Yesilsoy,
Some researchers have claimed that excess Ca++ content in the soil
of arid regions would increase the formation of smectite but decrease the formation
of kaolinite (Kapur, 1975; Yesilsoy, 1994). Many researchers have reported that
smectite was the most abundant clay mineral in most of the soils formed on parent
material with CaCO3 (Singer, 1989; Yılmaz, 1990).
Palygorskite was the second most abundant mineral after smectite (Table
4). Presence of smectite and palygorskite minerals has led to the thesis
that a genetical relationship of these two minerals comes from the similar origin
of parent materials (Kapur, 1975; Singer, 1989; Dixon and Weed, 1989; Irmak
et al., 1991). Palygorskite and smectite commonly coexist in soils suggesting
that palygorskite might be transformed to smectite by weathering (Bigham et
al., 1980). Some researchers claimed that palygorskite has formed in the
porous CaCO3 grains and discharged into the soil by dissolution (Kapur,
1975; Yılmaz, 1990; Stolt et al., 1991; Sumner, 2000). Palygorskite
minerals exhibit weak crystal peaks that can be associated with the presence
of iron oxide coatings on clay minerals and amorphous subtances in the environment.
The soils also contain, in low amounts, kaolinite and illite minerals. For
kaolinite formation, the ratio of Si/Al must be under 2.0, the basic cation
content must be less, pH<7.0 (Buol et al., 1980; Dinc et al.,
1987; Dixon and Weed, 1989; Sumner, 2000). According to this theorem, the rainfall
must be in a sufficient amount to translocate silicou and basic cations to a
certain limit in the profile.
The presence of kaolinite mineral in the basic cations-rich in study area
with low amounts of rainfall can be associated with rainy climatic changes in
Pliocene. Furthermore, a low amount of kaolinite mineral might have formed gradually
over a very long period of time, even under current climatic conditions. Kaolinite
minerals exhibit weak crystal peaks that may be associated with the weathering.
Contents of illite mineral of profile PL1, developed on the limestone and profile
PL3 developed on the marine was low. The low content of illite mineral may be
associated with the mica content of limestone and marine. Profile PL5 developed
on the alluvium material and profile PL7 developed on the basalts did not contained
illite mineral. It may be associated with mineral composition of basalt and
alluvium material. Some researchers have claimed that potassium-rich mica decomposition
should be metamorphosed into illite mineral (Yılmaz, 1990). The others
showed that the content of illite mineral was very high in the soils of arid
regions (Singer, 1989).
Classification of soils: The soils were classified according to Soil
Taxonomy (Soil Survey Staff, 2006) as Aridisol, Entisol, Vertisol and Inceptisol
Profile PL1 was classified as Xeric Haplocalcid because of it has xeric soil
moist regime, contained Calcic horizon that has its upper boundary within 100
cm of the soil surface.
Profile PL2 was classified as Lithic Xeric Haplocalcid because of they have
aridic soil moisture regime, contained Calcic horizon and had a lithic contact
within 50 cm of the soil surface.
Clay mineralogy of the soils
* Dominance, ** Crystallization, xxxxx: Very much, xxxx:
Much, xxx: Fair xx: ++++: Very good, +++: Good, ++ :Fair, Few +: Poor
Soil Classification according to Key to Soil Taxonomy (2006)
and FAO (1998)
Profile PL3 was classified as Vertic Haplocambid because of xeric moist regime,
in Cambic horizon and have 1-5 cm width cracks at 50 cm depth.
Profile PL4 was classified as Xeric Torriorthent because of it didn’t
contain definition horizon but Ochric epipedon and it has aridic moist regime.
Profiles PL5 and PL7 was classified as Typic Calcitorrert because of they
have aridic moist regime, a Calcic and Cambic horizon and cracks 1-5 cm in width
extending to 1.0 m below the surface.
Profile PL6 was classified as Typic Haplotorrert because of it has aridic
moist regime, a Cambic horizon and cracks 1-5 cm in width extending to 1.0 m
below the surface.
Profile PL1 and Profile PL2 were classified as Haplic Calcisol because of
an aridic soil moist regime and contain Calcic definition horizons in the subsurface
of soil (FAO, 1998).
Profile PL3 was classified as a Vertic Cambisol because of xeric moist regime,
in Cambic horizon and have 1-5 cm width cracks at 50 cm depth.
Profile PL4 was classified as Calcaric Regosol because of an Ochric A epipedon
but no other definition horizon and the soil matrix 20-50 cm below the surface
contains calcium carbonate.
Profiles PL5 and PL7 were classified as Calcic Vertisols because of they have
cracks in arid periods and a Calcic horizon.
Profile PL6 was classified as Haplic Vertisol because of it has cracks 1-5
cm in width extending to 1.0 m below the surface.
It was observed that parent materials of soil layer in the Harran region considerably affected the morphology and chemical contents of the soils. Especially clay layer will be affected on moisture content of soil and irrigation systems of different plant cultivations. Some chemical characteristics of the soils were affected by composition of parent rocks. The differences in the chemical properties of the soils were reflected differences in chemical composition of the parent rocks.
If suitable soil types and methods of soil preparation are used efficiently,
it is certain that this region will be a potential source for plant cultivating
in Southern Anatolia. However negative affects of regional erosion on soil formation,
depending on irregular raining, powerful wind and meteorological conditions,
being minimum levels should be prevented by using different methods. The Harran
Region as an arid plain had been used for agricultural activities throughout
historical ages periodically and Euphrates is an important river in Southern
Anatolia; flows into the Persian Gulf; was important in the development of several
great civilizations in ancient Mesopotamia. Nowadays, The Southeastern Anatolia
Project (SAP) has been continuing to earn maximum profit on commercial applications.
The soils generally were found in fine texture. The soils have been classified according to Soil Taxonomy as Xeric Haplocalcid, Lithic Xeric Haplocalcid, Vertic Haplocambid, Xeric Torriorthent, Typic Calcitorrert and Typic Haplotorrert. These soils have been classified according to FAO/Unesco as Haplic Calcisol, Vertic Cambisol, Calcaric Regosol, Calcic Vertisols and Haplic Vertisols.
The cultivatings of main industrial plants such as corn, cotton, soybean, sunflower, wheat and others have been increased gradually. Especially the production of cotton for textile sector of Turkey has been reached high levels recently. For this aim, the encouragements of authorities on developing of organic agriculture will be improved to raise the quality of soil layers. Because measured organic contents of Harran Region’s Soils were obtained insufficient level for agricultural activities.