فهرست مطالب m.h. farpoor٭

Chemical indices are widely used for characterizing the degree of weathering. In this study, we focused on evaluating the capability of chemical weathering indices to distinguish the sequence of aeolian-fluvial sediments in an arid region of Iran. Seven dominant geoforms were selected in Rafsanjan region, southeast of Iran, namely pediment, alluvial fan, margin of pediment and sand sheet, desert pavement, margin of fan and cultivated clay flat, active drainage, and margin of fan and uncultivated clay flat. One representative pedon was selected, described, and sampled for each geoform. The soil physicochemical properties of different horizons of each pedon were determined. We calculated various weathering indices, including weathering index of Parker (WIP), product index (PI), chemical index of alteration (CIA), silica-sesquioxide ratio (Kr), and CIA/WIP ratio (IR), and elucidated their depth distributions. The heterogeneity of the parent material within a given pedon was confirmed with field evidence, depth functions of clay-free sand fractions, and the uniformity value (UV) index. The horizon sequence with lithologic discontinuities (LDs) indicated that the studied pedons were formed by cyclic deposition of aeolian and fluvial sediments. The vertical variations of the weathering indices as well as the vertical trend of the Al2O3/SiO2 ratio (as a grain size index) were entirely consistent with the presence of the LDs. The results suggested that different factors, such as grain size, sedimentation cycling, and their interactive effects, should be considered in order to accurately assess the vertical trend of chemical weathering indices.

Soil classification is useful to better understand and manage soils. The objective of the present research was to compare the capability of Soil Taxonomy (2014) and WRB (2015) systems to describe and classify soils in Lut Desert. Marginal and central parts of Lut with typical aridic/thermic and extreme aridic/hyperthermic soil moisture/temperature regimes were selected. Twelve representative pedons on alluvial fan, plain, rock pediment, Gandom Beryan lava plateau, and playa were described and sampled. Results of the study clearly showed that the WRB system was more capable to reflect soil forming processes. However, it is recommended that anhydritic qualifier to Solonchaks, Solonetz, and Gypsisols; aquatic qualifier to Solonchaks and Solonetz; and abruptic, leptic, and paralithic qualifiers to Solonchaks be added. The ST system has not been successful in expressing soil forming processes because this classification system considers only two great groups for saline soils and gives priority to Salids in comparison to the other suborders of Aridisols. That is why Petrosalids, Gypsisalids, Natrisalids, and Argisalids great groups and Anhydritic Natrisalids, Anhydritic Argisalids, Anhydritic gypsisalids, Anhydritic Petrosalids, Calcic Natrisalids, Calcic Argisalids, Calcic Gypsisalids, Natric Petrosalids, Natric Haplosalids, Natric Gypsisalids, Petrogypsic Petrosalids, and Epipetrosalic Aquisalids subgroups are suggested to be added to Soil Taxonomy system. Meanwhile, definition of anhydritic horizon, considering textural difference in strongly contrasting particle size classes of family level, and aquic conditions in playa were among the strong points of Soil Taxonomy. It is also suggested to remove (or adopt) colour (Hue) requirement of anhydritic horizon in ST system.

Soil carbon (C) sequestration is recognized as a potentially significant option to off-set the elevation of global atmospheric carbon dioxide (CO2) concentrations. Soils are the main sink/source of carbon and also, an important component of the global C cycle. Total soil carbon (C) comprises of the soil organic C (SOC) and the soil inorganic C (SIC) components. The soil inorganic C (SIC) stock mainly consists of carbonates and bicarbonates. Processes governing the dynamics of the soil carbon stock differ among ecoregions and strongly interact with soil properties. Understanding the distribution of organic and inorganic carbon stocks in soil profiles is essential for assessing carbon storage at the regional and global scale. Although global estimates provide a general view of carbon stock levels, accurate local estimates and factors affecting soil carbon dynamics are very important. As a result, there is an essential requirement for accurately estimating the distribution of carbon reserves and their differences with regard to soil properties. The study area is located in the Sardooeyeh region, South of Kerman, under semiarid conditions. A total of 5 soil profiles were excavated. Percentage of coarse fragments (> 2 mm) using a 2 mm sieve, total organic C by the K2Cr2O7-H2SO4 oxidation method of Walkley-Black, soil inorganic carbon using the Gravimetric carbonate meter method were determined. Bulk density was measured by drying core samples in an oven overnight and dividing the weight of dry soil by the volume of the core occupied by the soil after correction for coarse fragments. Organic carbon in the surface horizons of all profiles is maximum due to vegetation and decreases with increasing soil depth. As the altitude increased, the amount of organic carbon increased in the surface horizons. Lower temperature and higher humidity at higher altitudes lead to the lower organic matter decomposition and consequently higher organic carbon content of the soil. Although the upper soil layers had the maximum soil organic C content, the maximum soil inorganic C content was observed in the sub-surface layers. The soil organic carbon storage was between 5.52 to 9.48 kg m-2 and the storage of soil inorganic carbon in profiles was between 14.41 and 91.34 kg m-2. The total soil carbon storage in the profiles varied between 19.92 to 100.83 kg m-2 and the average was 42.66 kg m-2. The average of soil organic carbon storage in 0-25, 25-60, 60-120 cm depths were 2.6, 1.97 and 1.26 kg m-2, respectively. The amount of soil inorganic carbon storage in 0 -25, 25-60 and 60-120 cm depths were equal to 2.7, 10.40 and 8.26 kg m-2, respectively. Therefore, it seems that more than 50% of the total soil inorganic carbon storage is stored at a depth of 25-60 cm from the soil surface. The portion of inorganic carbon storage of total soil carbon was 77.5%, and about 89% of it was stored in sub-surface horizons (below 25 cm). The portion of organic carbon storage of total soil carbon was 22.4%. It seems that an increase in the partial pressure of CO2 in soils leads to some dissolution of the pedogenic carbonate in the top soil. Dissolved pedogenic carbonate transfers to the deep soil and then re-crystallizes under relatively dry conditions and low CO2. The results showed that soil organic carbon storage was mostly higher in surface horizons, and soil inorganic carbon storage was higher in sub-surface horizons. On average, the ratio of soil inorganic carbon storage to soil organic carbon storage was 4.27. The high percentage of soil inorganic carbon storage in total soil carbon, shows that inorganic carbon plays a very important role in semi-arid regions. Almost 89% of the soil inorganic carbon content and about 80% of the total soil carbon were accumulated in the sub-surface horizon of soil (below 25 cm), indicating the importance of sub-surface soil for storing carbon in semi-arid regions.

The availability of the applied phosphorus (P) is controlled by sorption-desorption reactions in soil. Since the sorption-desorption reactions are affected by physical and chemical properties of the soil, the presence of organic matter (OM) and carbonates can also effect on the P sorption capacity in soil. The purpose of this study was to investigate the effects of OM and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province.

Six surface soil composite samples (0-30) were collected from Kerman Province located in southeast of Iran. The soils with a wide range of OM and calcium carbonate were selected for sampling. Samples were air dried and passed through a sieve of 2 mm. Physicochemical properties of the soil samples were determined according to the Soil Survey Laboratory Manual. Thereafter, the soil samples were divided into three parts. One portion was used for treatment with sodium hypochlorite to remove organic matter. The second part was treated with sodium acetate buffer (pH = 5) to remove carbonates. The third was used as a control without any treatment. Batch experiments were carried out to determinthe P-sorption isotherms in soil. The sorption behavior of P was studied by Langmuir and Freundlich isotherm models. All experiments were conducted in three replications.

The results showed that organic matter and equivalent calcium carbonate, removed from the studied soils with an average efficiency of 86.7% and 84.9%, respectively. Although the isotherms data showed that both Langmuir and Freundlich equations fits to data,Langmuir equation with higher mean of correlation coefficient (R2=0.982) and lower standard error (0.022) showed the best fit to P-sorption data for all soil samples (with and without treatment). Removal of organic matter by sodium hypochlorite increased the phosphorus adsorption capacity in the studied soils. After removal of soil organic matter, an increase in phosphorus adsorption capacity in the studied soils. With respect to control, removing the organic matter increased the adsorption capacity parameters (qmax and kf) about 37 to 104 mg.kg-1 and 11 to 23 L.kg-1, respectively. These results indicate that Fe- and Al-oxides and other available adsorption sites on the mineral surfaces are coated by organic matter and are activated after removal of OM. Removal of carbonates from the soil significantly reduced the P-sorption capacity. qmax and kf were decreased by 17% and 32%, respectively, compared to untreated soils. It is, therefore suggested that available P adsorbing surfaces decreases by removing carbonates from the soil.Constants related with bonding energy increased by 17.03% and decreased by 28.78% by removal of OM and calcium carbonate, respectively. The P maximum buffering capacity is an important indicator for assessing phosphorus stabilization capacity in soil. The greater P buffering capacity, the fewer ability of phosphorus replacement to soil solution. After removal of carbonates, this parameter decreased by an average of 42.5%. The results suggested that carbonates is an important factor in availability of phosphorus in soil. The required phosphorus standard increased by 14.43% by removing OM in the studied soils. However, the removal of carbonates reduced the need of soil for phosphorus by 40.5%.

In this study was investigated the effect of removing organic matter and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province. The results of this study showed that P sorption capacity is affected by the amount of carbonates and organic matter. Removal of organic matter from the soil increased the sorption capacity of phosphorus due to Fe- and Al-oxides. Other available adsorption sites on the mineral surface which are coated by the organic matter are active. Carbonates is known as an active site for maintaining phosphorus in the soil and its removal from soils reduces the phosphorus adsorption capacity. Applying/Preserving organic matters to/in soil can increases the efficiency of phosphate fertilizer application and improves plant nutrition. The removal of carbonates from the studied soils reduced their need for phosphorus. Therefore, as well as the addition of organic matter to soil, the removal or reduction of carbonates from agricultural soils is important for improving phosphorus utilization efficiency and plant nutrition management.

Soil and desert varnish are powerful records capable of saving invaluable data regarding environmental factors and processes during their formation stages. The present research was carried out to identify the environmental variations and paleoclimate reconstruction in the central deserts of Iran using soil and varnish micromorphological characteristics. Mantled pediment, alluvial fan, and alluvial plain landforms were selected. A minimum of one representative pedon was described and sampled on each geomorphic surface, amounting to a total of eight pedons. Varnished rocks were further collected from all geomorphic surfaces and studied by petrography microscope. Clay (coatings and micro layers), calcite (nodules, coatings, quasicoatings, and infillings), anhydrite (nodules), halite (coatings) pedofeatures, clay coating-calcite infilling, and anhydrite nodule-clay coating compound pedofeatures were investigated in the thin sections of the soil. Lenticular, vermiform, and platy gypsum crystals were identified as nodules and interlocked plates. Desert varnishes (100-600 µm) were different from host rocks as far as color, texture, and formative components are concerned. According to micromorphological evidence, the area probably experienced two different climates. Coatings and infillings of clay in soils and rock crevices were developed in an environment with more available humidity. Evaporite minerals were formed in soils and clay coatings on rock surfaces in the following period with less available moisture. The study results showed that micromorphology could be a necessary and useful tool in pedology and paleopedology investigations.

Soil spectroscopy in the visible and near infrared (Vis-NIR) range has widely been used as a rapid, cost-effective, and non-destructive technique to predict soil properties. Since little data is available about soil properties determined by using this technique, the present research was carried out to evaluate the efficiency of Vis-NIR spectroscopy to estimate several soil properties in Bardsir area, Kerman Province. About 150 complex surface soil samples were collected from four different land uses from depth of 0-20 cm. Soil organic carbon, equivalent calcium carbonate, pH, and the amount of silt, clay and sand particles were measured by routine laboratory methods. Reflectance spectra were obtained from air-dried samples under controlled laboratory conditions using an ASD FieldSpec Pro spectroradiometer in 350-2500 nm wavelength range. Partial least squares regression was used for calibration of spectral and laboratory data using cross validation. Coefficient of variation for organic carbon, equivalent calcium carbonate, sand, silt, clay, and pH values were 0.68, 0.62, 0.64, 0.66, 0.3, and 0.01, respectively. Based on RPD values (Ratio of Prediction to Deviation), the precision of the prediction model for sand and silt contents was quite suitable, and for organic carbon and equivalent calcium carbonate it was suitable. [H1] However, the predictions of the model for clay content and pH were poor.Furthermore, standard normal variate (SNV) was the best pre-processing method to predict organic carbon, whereas, first derivative with SG smoothing (FD-SG) showed better estimation for carbonate, sand, and silt. Consequently, Vis-NIR spectroscopy is capable of predicting several soil properties at the same time. As the model accuracy is acceptable, it has the potential to substitute conventional laboratory analyses of selected soil properties.

Biocalcite infilling and bridging in a sandy soil was studied in the present research. Effects of 2 bacterial species (Sporosarcina pasteurii and Sporosarcina ureae)، 3 reactant concentrations (0. 5، 1. 0، and 1. 5 M of urea and CaCl2 mixture)، and 6 reaction times (12، 24، 48، 96، 192، and 288 hr) on saturated hydraulic conductivity and mechanical strength of a sandy soil were studied as a factorial experiment. Soil samples were selected from sand dunes of Joopar area، Kerman Province. Bacterial inoculums and reactant solutions were daily added to soil columns. Results of the study showed that S. pasteuriihad had a higher effect on decreasing hydraulic conductivity of the treated samples (11. 57 cm/h) compared to the blank (41. 61 cm/h) than S. ureae. Increasing reaction times (from 12 to 288 hrs) and reactant concentrations (from 0. 5 to 1. 5 M) decreased hydraulic conductivity by 49 and 16 %، respectively. S. pasteurii increased strength of treated samples up to 2. 6 Mpa pressure compared to S. ureae. Reactant concentrations and reaction times increased soil strength significantly (2. 13 and 4. 1 Mpa، respectively). Micromorphological observation showed calcite crystals bridging soil particles and filling pore spaces.

Paleosols provide invaluable data on paleoclimatic conditions of the area. These soils widely exist in central Iran. Micromorphology and clay mineralogy are among valuable techniques which are useful for interpretation and identification of these soils. The present research was performed to compare the micromorphology and clay mineralogy of paleosols and modern soils of Jiroft area. After field studies, 4 pedons (located on different geomorphic surfaces including stable mantled pediment, stable and unstable transitional surfaces of pediment and alluvial plain, and stable surface of alluvial plain) were sampled for physicochemical, micromorphological, and clay mineralogical analyses. Clay coatings in argillic horizons of paleosols were found during micromorphology observations. On the other hand, clay coatings in present soils were only found in natric horizons, which were attributed to high amounts of Na in these soils. Moreover, smectite, palygorskite, illite, chlorite, and kaolinite clay minerals were recognized in paleosols, but chlorite was not detected in modern soils. The presence of palygorskite in the soils under study was related to the stability of geomorphic surface. Results of the present research showed that a more humid climate was present at the time of paleosols formation.

Geomorphology and soil genesis and its development are closely related. Besides, soil-landscape studies provide a better understanding of soil forming processes. The objectives of the present research include soil genesis studies, micromorphology and clay mineralogy of soils related to geomorphic surfaces in Jiroft area. Soil temperature and moisture regimes of the area are hyperthermic and aridic respectively. Alluvial fan, mantled pediment, intermediate surfaces, alluvial plain, and lowland landforms were identified. Each landform was divided into different surfaces due to geomorphic stability. One representative pedon was studied and sampled on each geomorphic surface. Routine physicochemical, clay mineralogy, and micromorphology analysis were performed on soil samples. The results showed that electrical conductivity, pH, and SAR contents increased from mantled pediments toward lowland positions. Besides, fine soil textures were found in downward positions. Chlorite, illite, palygorskite, smectite, and kaolinite clay minerals were found. Moving down toward alluvial plain, palygorskite stability decreased due to high water table, that is why smectite is the dominant clay mineral in alluvial plain. Source of palygorskite in mantled pediment, intermediate surfaces, and alluvial plain is inherited, pedogenic, and detrital respectively. Clay coating and infillings in Btn and Btk horizons of stable and unstable surfaces were investigated during thin section observations. Besides, calcite coating and infilling were found in Btk horizon at stable geomorphic surfaces. Results of the present research show that difference in soil characteristics is highly affected by geomorphology.