جستجوی مقالات مرتبط با کلیدواژه "soil development" در نشریات گروه "آب و خاک"

Rheological characteristics of soils (including their deformation and flow behaviors when subjected to external stress) can provide important information on microstructural and microaggregate stability. One of the newest methods of assessing the stability of aggregates is the use of rheometric discussions in this regard. In other words, rheometry can be used to evaluate the elastic behavior of soil versus its plastic behavior in a range of aggregate deformation and thus a more quantitative interpretation of aggregate formation or stability against stress. In the last decade, Amplitude sweep test (AST) has been used to evaluate the stability of soil microstructure and its elastic behaviors. The present study was designed to determine the aggregate stability and viscoelastic behavior of the soil using the rheometric method. In the present study, physical, chemical, clay mineralogical properties and classification of dominant soil orders in Chaharmahal-va-Bakhtiari Province were studied and compared in order to determine the stability of aggregates and viscoelastic behavior of soils using the rheometric method.

Five different soil orders were described and sampled in Shahrekord, Farsan, and Koohrang cities. After air-drying and sieving of soil samples taken from the genetic horizons, the physical and chemical properties were measured using standard methods. Besides, the type of clay minerals was determined by the X-ray diffraction method. AST was used to quantify the initial rheological parameter values, including the storage (G') and loss moduli (G"), deformation limit (γL: when the material begins to irreversibly deform), deformation at flow point (γf: when the material becomes viscous), loss factor (tan δ = G''/ G') and integral z (which summarizes the overall elasticity of the material) in order to study microstructural stability and microaggregates of the five soil orders. Finally, the correlation diagram was plotted among soil properties and rheological parameters using R software. Besides, the soil was classified based on the American Soil Taxonomy (2014) and WRB (2015).

The studied pedons classified based on the American Soil Taxonomy (2014) and WRB (2015) in five different soil orders and four reference soil groups, including Entisol (Cryosol in WRB), Vertisol, Mollisol (Kastanozem in WRB), Alfisol, and Inceptisol (Calcisol in WRB). Semi-quantitative analysis of clay minerals showed that the soils have different clay minerals assemblage including kaolinite, vermiculite, smectite, illite, chlorite, and quartz. The results of the AST indicated that the deformation limit was significantly higher in subsoil horizons than topsoil horizons and was also higher in the clayey soils compared to sandy soils. The soils with “vertic soil properties” showed the high range of linear viscoelastic region (LVE) that attributed to the samples with high elasticity behavior. Soils with higher clay contents and further evolution showed higher rheological parameters, implying that these soils had more rigid microstructures incomparable with other soil orders which in turn, indicated the higher microstructural and microaggregate stability. In contrast, the horizon, which had high sand content and little soil development, had the lowest values for all properties, thus indicating a lack of micro-aggregate stability. Pearson correlation coefficient analyses revealed that integral z was influenced by soil physicochemical properties, and was higher in soils with the clay fraction dominated by expansive clay minerals and higher cation exchange capacity.

Altogether, the rheological parameters indicated that more developed soils had greater microstructural stability than their less-developed counterparts. As a result, rheological measurements may be useful for identifying the major factors that affect soil aggregation. In addition, these parameters can be used as indicators to evaluate the relative amount of soil evolution in future studies.

Variety of soil reactions govern the distribution of metal micronutrients that includes complexation with organic and inorganic ligands, ion exchange, adsorption and desorption processes, precipitation and dissolution of solids and acid-based equilibria. The relative importance of these reactions depends on many factors such as soil physical, chemical, and mineralogical properties and the nature of metal ions. Environmental factors such as climate, physiographic position, and soil development may affect variability of some soil properties and thereby nutrient availability. The present research was conducted to find relationships between Iron, manganese, zinc, and copper availability and some major soil properties, physiographic condition and soil development.
Golpayegan region is located in northwest of Isfahan province in central Iran. The mean elevation of the studied area is 1790 above sea level. Annual precipitation was about 244mm and mean monthly temperature ranges from -6 in January to 34°C in August. The soils were developed on different physiographic conditions including piedmont plains, alluvial-fan, plateaus, and flood plains belonging to Entisols and Aridisols. Soil samples (0–60 cm) were collected from 98 grid points with 2000m distance in the agricultural area of Golpayegan. Particle size distribution, calcium carbonate, organic carbon, available potassium and phosphorus of the soils were measured by SWRI standard methods. Available Zn, Cu, Mn, and Fe were determined by addition of 10 g soil to 20mL 0.005M diethylentriaminepentaceticþ. The solutions were shaken for 2 h at 25°C, centrifuged, filtered, and Fe, Mn, Zn, and Cu concentrations were measured by an atomic absorption spectrophotometer.
Results Studied soils were developed on calcareous material and about 60% of samples have more than 20% of calcium carbonate. Available Fe ranged from 1.4 to 6.5 mg kg-1 (mean 15.8 mg kg-1). Significant relationships were also found between DTPA-extractable Fe, organic matter (OM) and calcium carbonate. The results indicated that organic matter (OM) is the most influential soil characteristics that predict Fe availability. DTPA-extractable Mn in the soils ranged from 1.8 to 19.8 mg kg-1 (mean 7 mg kg-1). There were also no relationship between available Mn and soil properties. It has been reported that Mn availability in soils is mainly influenced by oxidation-reduction rather than other factors. Available Zn in the studied soils ranged from 0 to 2.4 mg kg-1 (mean 0.8 mg kg-1) and had significant correlations with particle size and OM contents. This result showed the importance of soil exchanger phase (clay and OM) in Zn availability in calcareous soils, and was in agreement with the findings of Wu et al. (2006) in soils of North Dakota. DTPA-extractable Cu ranged from 0.2 to 2.4 mg kg-1 (mean 0.9 mg kg-1). According to the report of Lindsay and Norvell (1978), 90% of soils had sufficient Cu. However, there were variations among soils in available Cu as a function of physiographic position. The highest values were found in the soils developed on piedmont plains. Significant relationships between available Cu and some major soils properties such as sand, clay, OM, and calcium carbonate were also found. This result was in agreement with findings of Wu et al. (2010) who concluded that soil properties influencing the spatial distribution of Cu availability.
Nutrient availability is one of the most critical concerns of plant production in calcareous soils of Golpayegan . Different pedogenic processes, variable deposition and transport, and different weathering regimes affect micronutrient content, distribution, and availability. Results indicated that Fe deficiencies followed by Mn and Zn in the studied soils are more critical than Cu deficiencies. In fact, 90% of soils had sufficient Cu. Mainly micronutrient availability in the studied soils was related to soil texture and organic matter, although Mn availability showed no relationships with major soil properties. It was concluded that the availability of Fe, Zn, and Cu may be predicted to some extent using some factors such as soil properties and physiographic condition. Availability of Fe, Zn, and Cu in Torrifluvents developed on piedmont plain was higher than in other soils and this may be due to the high amounts of OM and clay, whereas Haplocalcids developed on plateaus had the lowest content. Generally, it was concluded that the mentioned factors affect metal distribution and cycling in the soils and thereby metal availability for plants. On the other hand, prediction of micronutrient availability using these factors can be taken into consideration for better management.

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.

Soil scientists have developed different mathematical equations and indices to be able to quantify soil development and to organize soil data. The main objective of the present research was the comparison of different soil development indices (including forms and ratios of iron, magnetic susceptibility, color indices, and modified Harden Index) related to different soils located on Kerman-Baft transect. Eight pedons on different geomorphic surfaces were selected during field studies. All genetic horizons of selected pedons were sampled and routine laboratory analysis performed. Moving from Kerman toward Baft in the studied transect, due to increasing trend of elevation, more humidity was observed. That is why, pedogenic processes were also increased and iron forms and ratios showed this development trend regardless of local conditions. Due to effect of parent material lithology on soil minerogenic magnetic susceptibility, no significant relationship between this property and soil development indices was found. Corelatioon of various forms of Iron with three color indices of Harst, Torent and Alexunder showed that Harst Index was better than the other two indices for the study area. Moreover, since the parent materials of different pedons were not the same, the modified Harden Index was not adopted with soil development trend.

Topography is one of the soil formation factors that has direct and indirect effects on physical and chemical properties, as well as soil formation and development. This study was conducted to investigate the effect of slope position on selected soil characteristics in Chelgerd region of Chaharmahal-va-Bakhtiari, Iran. Three transects were selected on west hill slope and 9 profiles were dug on three slope position, including summit, back slope and foot slope. Soil samples were gathered from each profile for physical and chemical analysis. Soil profiles in the summit and back slope were classified as Inceptisols while soil profiles in the foot slope position were classified as Vertisols. Significant differences between clay, sand and organic matter content in different slope positions were observed. The highest amount of clay and organic matter content were observed in foot slope position and maximum amount of sand was related to back slop position. Mineralogy results showed the presence of different minerals such as smectite, illite and kaolinite in all studied profiles; smectite with more than 70% was the dominant mineral. There was no significant difference between different slope positions in term of mineral composition, but smectite showed a slight increase toward down the slope.

This research was conducted to study the effect of different slope position on some physico-chemical properties of hardwood forest soils. The study area was located in Lahijan region of Guilan Province (northern Iran). After field observations، three ridges were selected and، in each of them، three soil profiles (on the summit، shoulder، and footslope position) were used for sampling in the mountain landform with granite parent material. Physico-chemical analysis including soil texture (hydrometer method)، bulk density (clod method)، organic carbon (Walkley and Black method)، total nitrogen (Kejeldahl method)، electrical conductivity of saturated paste extract using conductivity meter، soil pH by potentiometric method with a glass electrode (in 0. 01 M CaCl2) using a soil solution ratio of 1:2، exchangeable sodium and potassium were measured by flame photometer set. Cation exchange capacity (CEC) were determined by Bower method (1N ammonium acetate، pH=7)، available P (Olsen method) and humic-fulvic acid content (freeze drying method). The results showed that summit position had the maximum amount of clay، organic carbon، total N، P، Ca+Mg، CEC، EC، humic and fulvic acid in comparison with shoulder and footslope positions; whereas، soil pH، bulk density، and exchangeable sodium were significantly higher in footslope. Based on the results، soil properties depend on slope position which in turn influence soil development and soil characteristics.

Magnetic susceptibility (χ) measurements are widely used for the evaluation of soil profile development. Fourteen soil profiles were studied in a relatively wide range of climatic conditions in Fars Province. Citrate-bicarbonate-dithionite (CBD) extraction and micro CT-Scan images were used to evaluate the source of magnetic susceptibility. The results showed that soil samples lost 23 to 91 percent of their magnetic susceptibility after CBD extraction (χCBD), reflecting differences in the source (pedogenic or lithogenic) of magnetic susceptibility. Greater values of the decrease were noticed mostly in well developed soil profiles as well as in soil surface. 22 to 89% of the decrease was observed in frequency dependence of magnetic susceptibility (χfd) after CBD extraction. A significant positive correlation (P<0.01) was obtained between χCBD and χfd in the soil studied. Micro CT-Scan images with a spatial resolution of 33 µm showed lithogenic magnetic Fe oxide (magnetite) grains.