جستجوی مقالات مرتبط با کلیدواژه « کانی شناسی » در نشریات گروه « آب و خاک »

Improving the mechanical properties of soil in order to build civil projects is one of the important concerns of civil engineers. For a long time, various methods have been recommended to improve the soil used in projects, and most of these methods have been the result of using past experiences, among which the use of different additives to the desired soil has been one of the most common methods. Today, by using high-tech laboratory equipment, it is possible to select additives needed to improve soil properties based on the type of minerals that make up that soil. Therefore, in the research, using scanning electron microscope and X-ray diffraction method, the type of constituent minerals and the morphology of the soils used in the channels of Azadegan Plain, which mainly had a chalky texture, were studied. The results of the research show that there are changes in the paste limit for all related samples, the lowest value for the sample with 5% lime is an increase of 7.65% and the highest value for the sample with 7% cement is an increase of 113.74%. The angle of internal friction for all samples shows, the lowest value related to the sample with 5% lime, 5% slag is equal to 22.2% and the highest value related to the sample with 5% cement is equal to 6.4% increase.

Urmia Lake is the largest saltwater in the Middle East, which has been located in the northwest of Iran. Nowadays, various factors have exposed it to dryness and wind erosion, the result of which is the increase in soil salinity, the thinning of solute crystals, and the occurrence of dust storms. Identifying the nature of these dusts specially the mineralogy of them is important in providing solutions to deal with the crisis. Investigating the characteristics and mineralogy of dusts in the region are useful in predicting and controlling ways to reduce their damages, and dust mineralogy is a practical method to determine their origin. In other words, the deposition of dust in different areas can affect the nearby ecosystems by making changes in the texture, composition of elements and even the acidity of the soils of the affected areas. The source of dust is very important in the mineralogy of sedimentary particles and depends on various factors such as geology and soil characteristics as well as climatic conditions. Also, the height of atmosphere which the dusts are there can be useful in studying the affect of mineralogy in this height.

For this purpose, three flat sites without vegetation and prone to fine dust production were selected from the eastern shore of Urmia Lake, and each site was divided into 3 layers based on the height from sea level, but the first layer was omitted from the studying areas because of the high soil moisture due to low distance to lake, which results in decreasing dust production by this layer, and eventually 2 random samples (0-5 cm) were picked up from each layer. This research work carried out based on 12 selected soil samples from 3 sites and their layers. The soil samples from 0 to 5 cm depth as a surface soil of layers were transferred to trays with dimensions of 3 x 40 x 30 cm in the wind tunnel of agriculture faculty of Tabriz University, with 370cm length, 50cm width and 70cm height, and wind erosion was simulated by applying the maximum wind speed of 45 meters per second to it was done for 15 minutes at each height. Then, the dust particles released at 2 heights of the wind tunnel (10 and 30 cm from the floor of the device) and the control soil sample were subjected to XRD analysis and the obtained diffractions were interpreted using High Score software. Finally, statistical analysis was performed using a nested design to find the effect of factors such as the location, layer and height of the wind tunnel on the content of minerals in windblown dust.

The obtained results showed that the dominant minerals in the most dust samples, were quartz, calcite, halite and gypsum with the highest average percent of quartz, because of the widespread occurrences of this mineral in the earth crust. The statistical analysis results revealed the significant effect of layer on quartz at the p<0.01 level, but the effect of site on calcite was significant at the p<0.05 level. But the maximum amount of quartz appeared in layer 2 of site 2, while its minimum amount has observed in layer 2 of site 1. The maximum and minimum amount of calcite was found in site 2 and 3 respectively, but predominance of quartz in the dust samples can be attributed to the wind blow within a short distance. This differences can be related to the nature of the parent materials of sites from which soils were derived. The presence of calcite as the main mineral in samples is due to study area temperature and precipitation increase and decrease respectively, which cause lake dryness, while gypsum and halite are produced in result of chemical equilibrium process and distribute in salty soils. Gypsum also can be produced during the reaction of calcite and sulfates of sea salts. The dryness of the lake also results in rising the gypsum minerals from dried floor of lake. Also, the presence of halite is affected by Urmia Lake salts that remain after water evaporation in dried land as a main mineral in soil and dust samples of affected lands.Key Words: XRD analyze, Wind erosion, Mineralogy, Wind tunnel, Urmia Lake.

The identification of soil fractions minerals types that have different vegetations is a matter of special importance. The aim of this study is investigation of the soil particles’minerals under continues cultivation. Hence, three different regions with similar soil moisture regime (xeric) including Gyan, Doroud and Kangavar plains were selected. Then 13 pedons with different properties and crops’cultivation history were selected and soil profiles were dug and analysed. The selected soils were under cultivation of rice, wheat, canola and sugar beet. Soil samples were collected from different horizons and their physicochemical and mineralogical characteristics were measured in the laboratory. All size fractions were separated and content of minerals in sand, silt and clay fraction was determined. X-ray diffraction, TEM and SEM analysis results from clay fraction in rice cultivation indicated that the most semi quantitative of minerals is sequential: chlorite> vermiculite> smectite> illite. The ponding condition provided a suitable posotion for stability of chlorite and vermiculite minerals. The presence of vermiculite in paddy rice might cause biotite weathering. The most of smectite content was observed in clay fraction in sugar beet cultivation and then in canola cultivation. The neoformation of smectite containing Ca as exchangeable cation was dominant in cultivated soils. The mixed minerals as vermiculite–chlorite, illite- smectite and illite-vermicultie were predominantly observed in silt fraction under rice cultivation and then in sugar beet and canola cultivations. The variability of sand fraction mineral was negligible and it was similar in all cultivation almost.

The knowledge about K forms and its distribution in different soils can help to apply properly K fertilizers. This study was performed to investigate the different K forms in the soil and their relationship with physical-chemical properties and clay mineral diversity of the soil. The results showed that the amount of soluble K had negative correlation with clay content but exchangeable or available K value had positive correlation with clay content. Also, the fixed K value had good correlation with type and among clay content in these soils. Structural K had positive and significant correlation with Fe and clay content but negative correlation with gypsum. Total K had good correlation with clay content and consequently with Fe, Al, and Si that are the main performed elements of the clay particles. The amount of K in the soil was increased with increasing of illite content but it was decreased with increasing the chlorite and palygorskite. The results showed a significant difference between the K values with the presence and absence of OM, CCE, and gypsum in the soils. Generally speaking, the available K content was corresponded to the parent material (clay mineral type), cultivation type and age, heavy irrigation and leaching which causes a reduction in illite clay mineral in these soils.

Human activities such as intensive cultivation and land use changes alter nutrients fluxes (mainly iron) and mineralogy in soil and terrestrial ecosystems. Iron is an essential element for plants and microorganisms and its solubility is controlled by stable hydroxides, oxyhydroxides, and oxides. In general, parent material, climate, and landscape position are the major factors that accelerate the weathering of the minerals and rocks containing Fe in the regional scale. However, long-term cultivation and intensified agriculture may be the dominant attributes of modifications in soil properties like Fe compounds mainly in arid and semiarid regions, where the irrigational and agricultural practice is current over long-term periods. Although substantial data is documented on Vertisols properties, few studies are available to assess the effects of long-term continuous cultivation on the characteristic and distribution of iron oxides and their mineralogy, mainly in calcareous environments.
This study was conducted in the Piranshahr - Pasvah area (36° 46 to 36° 50 N and 45° 09 to 45° 50 E, 1500 m above sea level), West Azarbaijan Province, northwest of Iran. Six soil profiles belonging to three subgroups of Vertisols order (Chromic Calcixererts, Typic Haploxererts, and Typic Calcixererts) were described and sampled from the cultivated soils and similar soils from the nearby uncultivated region as grassland. Soil samples were air-dried and passed through a 2-mm mesh sieve before the analysis. Soil analysis included particle-size distribution, pH and electrical conductivity (EC), soil organic carbon (SOC), calcium carbonate equivalent (CCE), cation exchange capacity (CEC), the determination of iron oxides forms and mineralogical composition. Free or pedogenic Fe oxides (Fed) including crystalline, poorly crystalline, and organically bound Fe were extracted by dithionite–citrate–bicarbonate (DCB) method. Poorly crystalline and organically bound Fe (Feo) were extracted using 0.2 M ammonium oxalate (AO). Organic complex of Fe (Fep) was extracted by 0.1 M Na-pyrophosphate at pH 10. All Fe oxide forms were determined using atomic absorption spectrometry. The difference between DCB-Fe and AO-Fe was considered as an estimation of crystalline Fe oxides form.
The results showed that long-term cropping caused a considerable drop in organic carbon and calcium carbonates along with a noticeable rise in the values of clay and cation exchange capacity as a result of accelerated alteration by farming activities and interactions between the used irrigation water and soils receiving it. Long-term cultivation improved the amount of Fed and Fecry (crystalline Fe) from 1 to 64% and 44 to 90%, respectively, than those of uncultivated soils which can be explained in some pathways: (1) accelerated weathering of Fe-bearing minerals (such as biotite, chlorite, feldspars, amphibole, and pyroxene) in the cultivated soils and (2) the higher temperature condition and the more number of wetting–drying cycles in the cultivated soils compared to the uncultivated soils. Despite the fact that long-term cultivation caused a significant decrease in organic matter, a pronounced increase in organic complex of Fe with the range of 19 to 61% was recorded with farming practices. Such pattern can be contributed to the chemistry of organic matter and the presence of more stable fraction (passive fraction) of soil organic matter in the cultivated soils. The XRD patterns of primary Fe-bearing minerals (such as amphibole, pyroxene, and feldspar) had less intense in the cultivated soils compared to those of the adjacent uncultivated soils, indicating that probably cultivation promoted the instability and weatherability of Fe-bearing minerals as well as the loss of Fe from the minerals. In contrast, the X-ray reflections of secondary Fe-oxide minerals such goethite appeared to be higher, sharper and intense by long-term cropping, suggesting that agricultural practices also promoted the crystallization of the soil Fe oxides. Compared to the uncultivated soils, long-term agricultural practices caused some changes in X-ray reflections of chlorite, illite, and smectite.
The results showed that the weathering of Fe-bearing minerals and layer silicates, as well as the production of Fe oxide forms were promoted under long-term continuous cropping. Under cultivation, a pronounced increase in Fe-oxide forms, particularly Fed and Fecry, was recorded for the most of the examined soils which can be associated with the combined effects of increased soil temperature and moisture content from irrigation and farming practices. As emphasized, the combined effects of increased compounds from agricultural input (such as chemical and organic fertilizers, the compound of irrigation water, and moldboard tillage) as well as increased precipitation from irrigation interacted to create conditions for: (1) more intense the weathering of Fe-bearing minerals and (2) the more production of iron oxides forms in the cultivated soils.

The aim of this study was soil and clay mineral diversity in alluvial soils of Karoon River. For this, 14 profiles were described on transect perpendicular to the direction of eastern Karoon River bank. These profiles has 1 Kilometer distance and have different drainage and land use. The results show that soil salinity increased and OM decreased with increasing distance from Karoon bank. It was refer to drainage class changes. Ochric epipedon was diagnostic in all pedons. The subsurface horizons were restricted to cambic and salic horizons. The cambic horizon was formed due to wetting and drying under irrigation or rain, due to this crack and cleavage was formed in subsoils. Also, salic horizons was formed under high saline water table. Chlorite, illite, kaolinite, vermiculite, smectite, and quartz were identified by XRD. Kaolinite, illite, chlorite, and quartz was inherited from parent material. Vermiculite was formed from illite simple transformation due to cultivation and K depletion in soil surface near River bank. Also, smectite was formed in surface of this pedon. These clay were not seen in subsurface of these soils. Illite and chlorite intensity was decreased in surface that this was refer to transformation to vermiculite and smectite. In spite of first pedon, these clay mineral was identified in subsurface soil. This clay mineral was related to high pH, salinity, and Mg concentration in ground water. More study show that this smectite is trioctahedral.

Quaternary sediments have occupied most of the agricultural and natural resources of urmia region. Recognition of physicochemical and mineralogical properties of these soils is essential to optimum and stable use of these lands. In this study, eight soils profiles excavated on Quaternary sediments of Urmia region were investigated. The results showed that little thickness and evolution of studied soil was possibly due to the sequential soil erosion and sedimentation processes.Consecutive erosion-deposition processes at different periods led to the formation of calcic horizons and sedimentary layers in lower depths indicating climatic fluctuation, along with dissolution and translocation of carbonate in wetter periods as well as its deposition and accumulation in drier periodsClay mineralogical results revealed smectite, kaolinite, illite, chlorite and vermiculite as dominant clay minerals in the study area. Illite, cholorite and kaolinite mainly considered as inheritance fromthe parent materials while pedogenic formation explain the presence of vermiculite. Moreover, smectites was found to have three origins of inheritance, neoformation and transformation and its abundance was increased with depth. The origin of smectite in the buried horizons was attributed to the illite transformation. According to the heavy moisture demand on illite weathering, the occurrence of this process can be associated with more humid condition during the past climate. So the achieved results of present study can be a clue to recognize the climatic changes in the study area.

Potassium (K) is an important cation in saline soils of arid lands، and its content، distribution and availability may be affected by native plants. To study the effect of halophyte species on different K forms in Korsia region located in western Darab (Fars province)، three dominant halophyte species including Juncus gerardi، Halocnemum strobilaceum، and Salsola rigida were selected. Sampling was done from soils in canopy and between plants at the depth of 0-15 (surface) and 15-30 cm (subsurface) in triplicate. Soil physical and chemical properties including soil texture، organic matter، calcium carbonate، pH، cation exchange capacity، saturation percentage and electrical conductivity and different K forms including soluble، exchangeable and non-exchangeable were determined. Results indicated that organic matter، CEC، pH، and EC were affected by plant species. Juncus gerardi increased exchangeable K and decreased soluble K، but it had no effect on non-exchangeable and HNO3-extractable K. Halocnemum strobilaceum significantly increased soluble، exchangeable and HNO3-extractable K in surface and subsurface soils rather than soils between plants. This finding may be due to K uptake by plants from subsoils and also transfer of soluble K from soils between plants to roots. Salsola rigida had no effect on K status. Generally، soils between plants had more soluble and exchangeable K in surface than subsurface horizon. The studied halophyte species showed differences in growth and development pattern، soluble salts and K absorption and secretion، grazing by livestock، returned organic matter to soil، soluble salts and K reserves in their organs، and water uptake and thereby water and K diffusion from soil far from rhizosphere to roots، which may have different effects on K distribution in soils. Juncus gerardi، as regards effects on decreasing salinity and soluble K and increasing exchangeable K، may be recommended as a suitable species for remediation of the studied soils.

Nowadays, changing the rangelands to agriculture and garden is common. To investigate the impact of land use change on the soils type and clay mineralogy, four land uses including rangeland with poor vegetation, agricultural land, new and old apple orchards were selected in Safashahr area, Fars province. In each land use, three soil profiles were excavated and described and one profile was considered as representative. After required physical and chemical analyses, they were classified according to Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB). Selected surface and subsurface samples were also collected for clay mineralogy studies. Results showed that changing land use did not have significant effect on soil type and clay minerals and all soils consist of mica, chlorite, smectite, kaolinite and mixed layer minerals. Results demonstrated that ST is more efficient compared to WRB to classify the studied soils.

The objective of this research was to demonstrate the ability of canola to take up structural potassium from muscovite and biotite. The experiment was carried out in a completely randomized design with factorial combinations and three replicates. Culture medium was a mixture of sandy quartz and K-bearing minerals including muscovite or biotite with two sizes: <4 μm and 4-60μm (as silt) and the plants fed during a period of three-months by two different nutrient solutions (K+ and K–). At the end of the experiment, shoots were separated and their K content was determined with flame photometer. In- K treatment, total K uptake of plant was significantly influenced by the type of culture medium. The maximum K absorption was related to plants grown in culture medium containing biotite. However, the minimum value was observed in the muscovite and quartz bearing medium with K-free nutrient solution. Mineralogical results after treatment showed clay size biotite which was fed with K-free nutrient solution weathered more than silt sized biotite and partially transformed to vermiculite because in smaller size, the confinement layers of potassium are more weathered and will release their K more quickly and release it to the plant. On the contrary, there was no significant difference in the degree of muscovite weathering when fed with K+ and K– free nutrient solutions in both media. Muscovite was resistant in this situation.

Wind is the most important factor of erosion in arid regions. Movement of soil by wind is a complex phenomenon that is under the influence of some factors such as climatic and geomorphological conditions. This research was performed to identify dunes morphology، physical and chemical characteristics، and mineralogical specifications of Abardej''s sand dunes in southeast of Tehran province، Iran. At the first stage، different characteristics of the sand dunes were studied such as dunes morphology، kind of sands granulation، form of sand gravels، and so on. Based on these observations، the morphology of the dunes was transverse، indicating the existence of a dominant wind in one direction. Chemical analysis of Abardej''s dunes showed no important limitation for cultivation of plants. The main minerals of the dunes gravels were quartz، feldspar and calcite. Based on morphoscopic study، gravels of the sand dunes had steep angles. This result showed that the dunes had local sources. The sand gravels were almost shiny and halo، indicating that the dunes came from river - beds. The mean of sand gravels'' diameters was about 200 micron and about 20-25 percent of the gravels had diameters about 250 microns or more. This point، too، showed that the dunes had a local and nearby source.

Identification of dust sources and its potential to disperse is important, particularly in assessing atmospheric pollution by dust. The atmosphere of Isfahan Province is heavily affected by dust. To study the properties of deposited dust in the Isfahan area, 36 locations distributed over the cities of Isfahan (an urban area with heavy traffic), Khomeinishahr and Falavarjan (an urban area with low traffic) and Zarinshahr and Mobarakeh (an urban and industrial area) were randomly chosen. Dust samples were taken from all the locations for a period of 5 months in 4 periods from August to Mid December 2010. Geochemical and mineralogical characteristics of all the dust samples were examined. The mean EC value of the dust samples was 5.6 dS m-1 showing that it was highly affected by the Na concentration. This variable decreased from Isfahan to Zarinshahr. Dust particles had an average silt, sand and clay content of 52%, 17% and 31%, respectively. In all the 3 areas, kaolinite, palygorskite, chlorite, smectite, illite, quartz, feldspar and plagioclase dominated the clay fraction of dust. These minerals are similar to those reported for the soils of eastern Isfahan. In conclusion, climatic data as well as chemical, physical and mineralogical properties of the dust samples show that, beside the local anthropogenic sources, the soils occurring in eastern Isfahan appear to be the major source of dust in the region.

One of the best indicators of the geological and environmental events in the Quaternary is the alternation of loess-paleosol. In this study, for paleoenvironmental identification of buried paleosols in loess sequences, 14 sections located between 36˚ 49′ 6˝ to 36˚ 49′ 20˝ northern latitude and 54˚ 26′ 45˝ to 54˚ 26′ 52˝ eastern longitude in the southern part of Gorgan (Kharazmi town) were studied. The disturbed soil samples for physico-chemical analysis and clay mineralogy and undisturbed samples for prepration of thin sections were collected. The physico-chemical results (calcium carbonate content, particle size distribution, cationexchangable capacity and Feo/Fed) indicated that the soils had experienced several pedogenic periods. The result of mineralogy showed that a high amount of smectite, vermiculite and mixed layer mica-smectite in paleosols compared to loess deposits probably indicates moister regims through interglacial compared to glacial periods. The micromorphological observations revealed many evidences on the occurance of pedogenic processes. One of the most important index of pedogenesis, clay coating and hypocoating around void are presented only in buried paleosols, which is the evidence for moist climate conditions, enough for leaching and translocation of clay. Formation of the studied loess and paleosols, probably took place in glacial and interglacial cycles with different climate condition, respectively.

Land use change from paddy soils to kiwi orchards in north of Iran is one of the most common problems in Mazandaran and Guilan provinces which is mainly caused by agricultural communities to compensate the damages caused by unstable rice marketing. Due to insufficient income of rice cultivation in this area, the conversion of paddy to kiwi orchard is inevitable which causes changes to soil physico-chemical, mineralogical and micromorphological properties. The experimental farm of Rice Research Station (West of Tonekabon, Northern Iran) was selected and 7 pedons were dug, described and sampled and their physicochemical, mineralogical and micromorphological properties were analyzed. Features such as roots rot due to very poor drainage, intense chlorosis and yield decrease of kiwi were the main consequences of incorrect land use change. Available iron and manganese amounts in paddy soils were higher while phosphorus and potassium contents were lower than the soils under kiwi plantation. This could be attributed to the reduced condition and different land management practices. Mineralogical results indicated that smectite was the most dominant mineral in the studied paddy soils while under kiwi fruit land use with moderately drainage condition, smectite content decreased and some vermiculite formed. Micromorphological results also indicated that due to unsaturated condition at the upper layers and high biological activities, pore volume increased and more developed iron features have been revealed after kiwi orchard establishment.

Soil is one of the most important natural resources and perhaps is the most fundamental factor in formation of civilization. In addition to food supply، the soil will also provide other human necessities such as clothing، residence، bury wastes، wild life، recreation and etc. Climate plays a very important influence on enhancing and processes of soil formation، and in addition the climatic factors play a considerable influence on plant growth، production and land use. In each region، topographic factor also influence soil characteristics. Its influence on soil development and plant growth depend on its direction and elevation. In other to study the effects of topography and depth of ground water on soil genesis، Dasht-E-Arjan plain with xeric and mesic soil moisture and temperature regimes، were selected. Based on aerial photographs and also topographic maps، the location map of the study area was drawn. Then on two transversal sections، six profiles were dug. Among them four representative profiles were selected for detailed studies. The results of field studies and also profile description showed that Entisols and Inceptisols orders were developed on alluvial-colluvial fans، while on piedmont plains and lowlands only Inceptisols were formed. The physico-chemical characteristics of studied soils showed that، among the studied profiles، there are remarkable differences in soil texture، organic matter، saturation percentage، pH، EC، and CEC. The most important soil forming processes were accumulation of surface soil organic matter and also formation of Cambic and Calcic horizons. Because of extensive cultivation، the color and thickness requirements do not satisfy for the formation of MollicEpipedon، which show great future hazards for all Mollisols of the country. The XRD results of clay minerals showed more smectite mineral with respect to kaolinite، illite and chlorite minerals. This could be due to its higher content in parent materials and also transformation of illite to smectite due to more wetness of low lying physiographies.

Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity، potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K، clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties، mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids، Typic Endoaquepts، Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.)، it seems soil porosity can also affect Kava. mainly through their effects on extension of roots، water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava، in these soils. presence of HIS. poor soil drainage، reduction of Fe3+ in smectite crystal lattice in Inceptisols، and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.

Golestan Province considered as a major agricultural region, contains a vast area of salt affected soils in the northern parts originated mainly from the near surface water table and/or high evaporation. The present study was performed to investigate the physico-chemical and mineralogical properties of saline-sodic soils and to determine the concentrations of salts, identification of the type of salts and their sources. For this purposes, four profiles were selected and sampled at the north of Gorganrood and south of Atrak river basins based on the available maps and studies at the North and South of Gorganrood. These profiles were located in the different distances (km) from the Caspian Sea. Profiles number 1 and 2 are closer to the sea and the distance increases towards the profiles number 3 and 4. All the routine physico-chemical analyses were carried out on the sampled soil horizons. Profiles 1 and 3 were classified as Aquisalids and profiles 4 and 2 classified as Haplosalids and Cambids based on the Soil Taxonomy. In WRB system all of the profiles except profile number 2 that is classified as Cambisols, are classified as Solonchaks. To identify the types of salts, at first XRD analysis was carried out on the powder sample and then SEM/EDS analyses was done. Gibbs chart was used to determine the source of these salts. The salts identified by XRD analyses included gypsum, halite, hexahydrite, epsomite and mirabilite. Gypsum in the profiles was found at the surface and subsurface horizons in the form of lenticular crystals. Halite was also present in the profiles at the both surface and subsurface horizons. Epsomite in profile 1 was observed at the surface and in profile 3 at the subsurface horizons. Mirabilite was observed only in profile number 1 at the surface horizon. The source of these salts in these zones based on the results of the cation and anion analyses of the available ground and surface water and using the Gibbs modeling was recognized as evaporate minerals.

There are more than 70000 hectares of Mollisols in the southern part of Gorgan River, in the Golestan province, Iran. Taking into account the mollic intergrades, it reaches to 150000 hectares. Parent materials of the studied lands are loess materials. The main objectives of the present study were to examine the mineralogy of Mollisols and Mollisols like soils and also effective factors on the distribution of clay minerals. Clay mineralogical studies showed that the dominant minerals of loess parent materials were illite, smectite, chlorite, and kaolinite. The general order of the dominance of clay minerals in the studied Mollisols, were: Illite > Smectite > Chlorite > Kaolinite. Illite was the dominant clay mineral in most of the studied soils especially toward the eastern parts of the province. Smectite was the dominant mineral in the poorly drained soils in low lands of the western parts. Drainage condition therefore seems to play an important role for the occurrence of smectite besides the inherited origin in the studied area.

Potassium is essential plant macronutrients. According to the conceptual approach soil potassium (K) can be classified into four forms: soil solution K, exchangeable K, fixed K and structural K. In this research, potassium forms were determined in loess and loess like derived soils of Golestan Province and in the silt and clay fractions of them. The objective of this research was to determine the contribution of soil separates in release of potassium and to be fertilizer management in the soils. Mean extracted potassium content in clay particles of all soils was more than that of soil and silt fraction. The quantity of K extracted by HNO3, NH4oAc and HF in soils varied from 632 to 1200, 103 to 476 and 12000 to 17800 mg/Kg, respectively. The mean of exchangeable, nonexchancheable and total potassium contents were 160.6, 1155.1 and 19100 mgKg-1, respectively in clay fraction. The quantity of non exchancheable K extracted from silt fraction was a half of its quantity in clay fraction.

Soil organic matter is an indicator of soil, agriculture and environmental quality, playing important roles in soil strength and sound environmental functions. Size and chemical fractionation of soil organic matter are long-standing approaches in clarifying their key role in soil processes. Twenty seven surface samples (0-20 cm) and 6 pedons from different landform units were sampled and described according to USDA, 2002 and by means of illustrating the surface as well as vertical distribution of different size and varied chemical fractions of organic carbon. Physico-chemical, mineralogical, physical and chemical fractionations were carried out following standard methods. The results revealed that organic carbon content increases by decrease in the fraction size, reaching its maximum at <250 μ. Also it was observed that 2:1 expandable clays show relatively higher capability in organic carbon complication in comparison with the other mineralogical suits. The results for chemical fractionation demonstrated that humic to fulvic acid ratio increases by increase in organic matter input, itself being followed by increase in soil biological activity.