naser boroumand; saleh sanjari
Abstract
Introduction: Soil and geomorphology are closely related to each other. That is why considering geomorphic concepts in soil genesis and classification studies may cause a better understanding of soil genesis processes. Paleosols with argillic horizons were investigated on stable pediment surfaces in ...
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Introduction: Soil and geomorphology are closely related to each other. That is why considering geomorphic concepts in soil genesis and classification studies may cause a better understanding of soil genesis processes. Paleosols with argillic horizons were investigated on stable pediment surfaces in Jiroft area, central Iran, by Sanjari et al. (2011). They found that secondary gypsum and calcium carbonate were accumulated in mantled pediments, but moving down the slope toward lowlands, salts more soluble than gypsum have been accumulated.
Clay mineralogy in soil researches helps to better studying soil genesis and development. A quantitative and qualitative study of clay minerals together with their structural composition provides valuable data on the absorption, fixation, and desorption of different cations in soils. Smectite, chlorite, illite, vermiculite, kaolinite, palygorskite, and sepiolite were reported as dominant clay minerals found in arid and semi-arid areas. The objectives of the present study are to evaluate the clay mineralogy of Jabalbarez-Jiroft soils on different geomorphic surfaces.
Materials and Methods: The study area was located in Jabalbarez, 200 Km south Kerman, Central Iran. Fig. 1 showed the exact location of study area. Soil temperature and moisture regimes of the area were thermic and aridic, respectively. Hill, rock pediment, mantled pediment and piedmont alluvial plain landforms were identified, using aerial photo interpretation, topography and geological map observation, in addition to detailed field works. Air-dried soil samples were crushed and passed through a 2-mm sieve. Routine physicochemical analyses wereperformed on the samples. Undisturbed soil samples from the Bt horizon of pedons 4, 5 and 6 were chosen for micromorphology investigations. Beside, eight samples including A and C2 horizons of pedon 1, A and Bt horizon of pedon 3, Bt and Bw horizons of pedon 4, and Bt and C horizon of pedon 5 were selected for clay mineralogy.
Results and Discussion: Argillic horizon found in mantled pediment and piedmont alluvial plain surfaces and stable hill, respectively. In thin horizons coating of clay were observed. Pedofeatures formed in this geomorphic surface, seemed to have been buried in the soil, due to the favorable conditions in terms of the time factor and the presence of moisture in the past. Fig. 2 showed clay coatings in the Bt horizon of pedons 4,5 and 6. The presence of argillic horizons in the arid climate of the research area is attributed to a more humid paleoclimate, which was also reported by Farpoor et al. (2002), Khademi and Mermut (2003), and Sanjari et al. (2011) in Rafsanjan, Isfahan and Jiroft, central Iran, respectively. Clay minerals illite, smectite, chlorite and kaolinite were identified by using X-ray diffractometer. Similar results were also obtained by Sanjari et al. (2011) in the Jiroft area. Kaolinite and illite in soils of arid and semi-arid environments of Iran have been reported with an inherited origin (Khormali and Abtahi, 2003; Sanjari et al., 2011). As the environmental conditions are not favorable for the pedogenic formation of such minerals in soils of this study area , it is proposed that they might be inherited from their parent material. Just as previously stated by other researchers that the origin of the kaolinite minerals in the dry climate regionsis due to itsinheritance from parent materials (Farpoor et al., 2002; Khormali and Abtahi, 2003). The dominant of smectite minerals in soils on stable geomorphic surfaces ofhills and mantled pediment can be cause of stable level and more moisture content in the past and the present, which may be resulted to smectite formation from illite and chlorite transformation. Also, chlorite minerals on stable surface of mantled pediment were not observed. High amount of leaching, low pH level (
Parisa Farzamnia; Shahram Manafi; Hamidreza Momtaz
Abstract
Introduction: Minerals are one of the main components of soils which play different roles in the soils. Minerals make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases ...
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Introduction: Minerals are one of the main components of soils which play different roles in the soils. Minerals make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases plant nutrients which are retained by other minerals through adsorption, cation exchange, and precipitation. Minerals are indicators of the amount of weathering that has taken place, and the presence or absence of particular minerals gives clues to how soils have been formed. The physical and chemical characteristics of soil minerals are important consideration in planning, constructing, and maintaining of buildings, roads, and airports. Clay minerals can be used for understanding of soil formation, optimum management of dry and wet lands and interpretation of paleo environments. Moreover, clay minerals can provide some valuable information such as the origin of sediments, transportation and precipitation of sediments and also some information about intercontinental weathering regimes. Quaternary sediments have occupied most of the agricultural and natural resources of Urima plain and recognition of mineralogical of these soils is essential to optimum and stabile use of these soils. Additionally, caly mineralogical investigation can provide some information about the intensity of weathering processes and climate change in this area. Thus, in this study clay minerals of quaternary sediments in northeast of Urmia and the mechanisms of their formation and also tracing probable climate change in this area were investigated.
Materials and Methods: This study was performed in theUrmia plain in west Azerbaijan Province. The study area is located on quaternary sediments and physiographically, this area is a part of a river alluvial plain with the gentle slope toward Urmia Lake. The mean annual precipitation and temperature of this area are 345.37 mm and 10.83 °C respectively and the soil moisture and temperature regimes are dry xeric and mesic respectively. In this study, eight soil profiles in quaternary sediments were dug and sampled and the morphological, physical, chemical and mineralogical properties were determined using standard methods.
Results and Discussion: According to the results, Illite, smectite, Kaolinite, chlorite, vermiculite and hydroxy interlayer vermiculite (HIV) were the dominant clay minerals in these soils. The origin of illite, chlorite and kaolinite were related to inheritance from parent material. Regarding to the present of some smectite in the parent material of these soils, some of smectites have been inherited from parent material. Nevertheless it seems that, the most of smectites in these soils have pedogenic origin. Based on mineralogical results and trends variation of smectite and illite along studied profiles, we concluded that some of smectites in these soils have been formed from illite transformation. In profiles 4 and 6, regarding to low depth water table and consequently poor drainage, high pH and high values of calcium and magnesium cations, provide suitable conditions for the neoformation of smectit and so, some of smectites have been formed via neoformation from soil solution. In these soils, vermiculites were pedogenic and have been formed during transformation of illite to smectite. Small amounts of hydroxy interlayer vermiculites were present in buried horizons and regarding that they were not present in parent material, it might be because these minerals are pedogenic and have been formed in a past wetter climate. The transformation of illite to smectite in lower horizons needs high moisture and regarding to recent semiarid climate of study area, the suitable amount of moisture for this transformation, especially in lower depths and also in buried horizons, is not present. Thus, it seems the transformation of illite to smectite in lower depths and buried horizons has been taken place in a wetter past climate. So we concluded that smectite and hydroxy interlayer vermiculite are evidences of a wetter past climate in this area.
Conclusion: In this study the origin of smectite in buried horizons was related to transformation of illite. According to high moisture condition which is necessary for the weathering of illite, the occurrence of this process related to more humid climate of the past. Additionally, the presence of hydroxy interlayer vermiculites was related to previously wetter climate as well. So results of this study can be used for recognition of climatic change in the study area.
P. Alamdari; V. Kamrani; M. H. Mohammadi
Abstract
Introduction: Potassium is an essential element for plant growth and its importance in agriculture is well known. Total soil potassium reserves are generally large; although the distribution of K forms differs from soil to soil as a function of the dominant soil clay minerals present. The objectives ...
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Introduction: Potassium is an essential element for plant growth and its importance in agriculture is well known. Total soil potassium reserves are generally large; although the distribution of K forms differs from soil to soil as a function of the dominant soil clay minerals present. The objectives of the present study were: (i) the content, forms, and distribution of K as a function of clay mineralogy in different physiographic units; (ii) to investigate the relationship between K fractions and their physiographic units.
Materials and Methods: The study area is located in south of eastern Azarbaijan province, north of Iran. The region stands between 37° 45' and 38° 00' N latitudes and 46° 00' and 46° 15' E longitudes. The present climate of the region has dry and hot summers, cold and wet winters; with an average rainfall of 334 mm. soil moisture and temperature regimes of study area are xeric and mesic, respectively. Site selection for studied pedons was based on a reconnaissance survey from different physiographic units, namely, pedons 1, 2 and 3 located on Piedmont Plain (PP), pedons 4, 5 and 6 on Rivera Alluvial Plain (RAP) and pedons 7, 8 and 9 on Low Lands (LL). Soils were described and classified based on soil survey manual and keys to soil taxonomy. Samples were air dried, crushed and passed through a 2mm sieve. Particle size distribution, organic matter, Calcium Carbonate Equivalent (CCE), pH, Electrical Conductivity (EC) and Cation Exchange Capacity (CEC) and different forms of K (total, soluble, exchangeable and nonexchangeable) were determined. X-ray diffractograms were obtained through a Shimadzu XRD 6000 defractometer employing a Ni-filtered CuKa radiation source from oriented clay (40 kV, 30 mA). The content of clay minerals was estimated according to Biscaye method.
Results and Discussion: All soil samples were calcareous, calcium carbonate content was between 10 and 17%, with relatively high clay content, ranging from 18 to 36%. Soil organic carbon contents were between 0.3 to 1.9%. Land use affected the amount of organic matter so the pedons located on piedmont plain showed more organic matter than other units. Variation in soil characteristics were considerable, which was most affected by physiography. The variation was also especially noticeable in clay minerals and K pools. Soluble K, ranging from 6 to 14 mg/kg, had higher content in piedmont plain than other units. Nonexchangeable k was between 345 to 545 mg/kg and piedmont plain had higher amount because of existing more illite. Exchangeable K, ranging between 278-416 mg/kg had highest content in piedmont plain and lowest content in river alluvial plain. The release rate of non-exchangeable K is the result of the type and particle size of K bearing minerals and soil conditions. The XRD data for the less than 2 μm fractions of the studied soils indicated that the soils were similar in their clay mineralogy, mainly consisted of illite, smectite, kaolinite and chlorite, but were different in content. Illite and smectite were higher in Piedmont Plain (PP) and Low Lands (LL) had higher content of smectite in comparison with River Alluvial Plain (RAP) due to low drainage condition. Several factors such as differences in geomorphological conditions and clay mineralogy between physiographic units caused the differences in K forms. The statistically significant relationship between clay content and most forms of k was because of high specific surface of clays. A highly significant positive relationship between non exchangeable K and illite content (r2 = 0.81, P
