Elham Afzali Moghadam; naser boroumand; vahidreza jalali; saleh sanjari
Abstract
Introduction: The hydraulic parameters are very important for perception of water flow in unsaturated soil and using pollutants and nutrient flow modeling in the soil. The effect of soil management and land uses on soil parameters can directly alter soil hydraulic parameters. Because of interactive and ...
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Introduction: The hydraulic parameters are very important for perception of water flow in unsaturated soil and using pollutants and nutrient flow modeling in the soil. The effect of soil management and land uses on soil parameters can directly alter soil hydraulic parameters. Because of interactive and tight relationship between soil and plant covering, studying the soil parameters and its changing during different land uses is vital. The main object of this study was evaluating the effects of different land uses on soil saturated hydraulic conductivity.
Materials and Methods: This study was performed in about 100 hectare fields of Khezrabad region in the 25 km south of the Jiroft county located in south eastern of Kerman province. The region gridded into 1000×1000 meter grids with use of Google earth and Arc GIS software, sampling places has been selected in the center of each grid. Measurement of soil saturated hydraulic conductivity done with the Guelph permeameter in the center of each grid. For the measurement of physical parameters such as bulk density, percent of sand, silt, clay in the laboratory, sampling done from 30cm depth so samples transferred to the laboratory. In this study in order to ensure the normal distribution of variables, the Kolmogorov-Smirnov test has been used with SPSS14 software. The Kriging method was used for interpolation and providing spatial maps.
Results and Discussion: Agriculture, garden and sterile lands were selected for the object of the present study. The study area includes garden, agriculture and sterile lands at the same time. The study area contains 3 classes of soil texture as: sandy, sandy-loamy and loamy-sand. The results showed that soil saturated hydraulic conductivity (ks) with strong spatial correlation had a high spatial variability. The fluctuation ranges of its values changes from 0.02 to 2325.71 cm per hour. The lowest value of ks was observed in garden land (by having the lowest value of soil bulk density) while the highest value was observed in sterile land (by having the highest value of soil bulk density). The results also showed that semi-variogram of garden, agriculture and sterile land were not the same, and it may gain from different types of agricultural operations, type of land use and various textures so that from garden land to sterile land, the soil texture becomes lighter and level of saturated hydraulic conductivity changes completely different. Several reasons maybe considered including soil different structures due to different type of agricultural operations and type of cultivation for every single land use. The change process of saturated hydraulic conductivity for garden and agricultural land was identical and for both the Gaussian model were fitted. According to the nugget effect ratio to the sill (C0/C0+C), variability of saturated hydraulic conductivity in agricultural land has a stronger spatial correlation (0.0006) and also has a higher radius of effect range (11740m) compared to garden land in which the ratio of the nugget effect ratio to sill is 0.28 and its radius of effect range is 8030 meters. the radius of effect range in sterile land had the lowest value among studied land uses, though having strong correlation, the effect range of this correlation is low and, compared to other lands, the changes process was more randomly obtained. To mention the reasons of this finding it is possible to refer to area of the sterile land, dispersion of the sampling points and long distance between pair points. The lowest spatial correlation belonged to garden land with middle spatial correlation class and the reason can be explained as due to increase of sand, decrease of clay and silt, bulk density of soil increases as well and leads to increase of coarse pores and consequently increasing saturated hydraulic conductivity of soil.
Results showed that soil saturated hydraulic conductivity (ks) with strong spatial correlation has high spatial variability and these variability consist lowest quantity in the garden lands and highest quantity in the sterile lands. The distribution pattern of Ks was seen similar to the sand and the soils bulk density, this pattern was opposite to the clay distribution pattern, this indicates the effect of soil physical parameters on saturated hydraulic conductivity.
Conclusion: According to the evaluation parameters CRM, MAE and MBA, Gaussian model is the best fitted model to soil saturated hydraulic conductivity data and soil parameters such as saturated hydraulic conductivity consist spatial variability related to sampling scale. The factors of land type and consequently type of land cultivation, lands management system, type of agricultural operations, soil particles size and bulk density of soil have the most impact on variability of Ks.
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 (
Mojtaba Moqbeli; Mohsen Farahbakhsh; Naser Boroumand
Abstract
Introduction: Boron (B) is an essential plant micronutrient whose soil availability is influenced by many soil factors.Understanding the processes controling activity of boron (B) in the soil solution is important for soil fertility management. The reaction of adsorption and desorption of boron in soil ...
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Introduction: Boron (B) is an essential plant micronutrient whose soil availability is influenced by many soil factors.Understanding the processes controling activity of boron (B) in the soil solution is important for soil fertility management. The reaction of adsorption and desorption of boron in soil determines the amount of boron that is available to plants. Adsorption–desorption processes play a major role on boron equilibrium concentration and therefore on its bio-availability. Ionic strength, pH and ionic composition in exchangeable phase are among themajor factors affecting B adsorption reactions.Reducedadsorption of boron at high pH is because of a surface potential decrease onminerals with pH-dependent charge. Ionic strength has also a considerable effect on B adsorption.Several studies have been performed inthe adsorption of boron and the effect of factors such as ionicstrength and cations has been understudied, however, the effect of sodium adsorption ratio and itsinteraction with the ionic strength on boron adsorption behavior has not been reported. In thisstudy, the adsorption isotherms of boron in the soils affected by the combined effects of ionic strengthand sodium adsorption ratio were investigated.
Materials and Methods: In order to assess the effects of ionic strength (IS) and Sodium Adsorption Ratio (SAR) on availability of B, the adsorption of B was investigated in a calcareous soil that hadlow levels of electrical conductivity, sodium adsorption ratio and available P. For this purpose, 5 g soil wasequilibrated with 20 mL of B solution (0, 2, 5, 8, 10, 15, 20 mg L-1) in 0.02, 0.06 and 0.12 M background solutions (prepared by NaC1,CaC12.2H2O, MgCl2.6H2O), at two SAR levels (20 and 100).The reaction temperature was 25◦C. The suspension was centrifuged, filtered, and a sample was removed and B was determined by Azomethine-H spectrophotometric method (at a wavelength of 420 nm). B adsorption in Soil was obtained by subtracting B in solution after filtration, from added boron.
Results and Discussion: The Langmuir isotherm waswell fitted to the adsorbtiondata based on the R2 and SEE.At different IS and SAR levels, the soil exhibited different adsorption behaviors. The effect of SAR on the boron adsorption was greater at high concentrations.The results showed the increase in sodium adsorption ratio,increased soil pH and Boron adsorption.An increase in sodium adsorption ratio up to 100 resulted in a small increase in Boron adsorption compared to SAR=20. With sodium adsorption ratio of 100, soil pHincreased from 8.3 to 8.7. At about PH=9.5, maximum adsorption occurs because boron dissociation is greater when pka = pH. Increasing ionic strength increased the boron adsorption; the absorption rate wasmuch higher at higher ionic strength.Model-predicted and experimental parameters obtained using the Langmuir equation pointed to the large effect of salt concentration on the boron adsorption which wasan increase of around 10% and 75% in q max as a result of an increase in salt concentration from 0.02 to 0.06 and 0.12 M respectively. We can ignore the effect ofsalt at very low equilibrium concentration; however, it increases gradually with increasing the equilibrium concentration of boron.
Conclusions: The results of the present study showed that sodium adsorption ratio was low, in low equilibrium concentration related to low boron concentration, but the equilibrium concentration of boron increased with increasing the sodium adsorption ratio.In sodium adsorptionratio of 100, increasing pH increased the adsorption of boron. Boron adsorption was increased with increasing ionic strength; the adsorption rate was muchhigher than the rate of increase in ionic strength.Increasing the ionic strength suppresses the DDL on planar surface and therefore more negative borate ions are able to move close enough to interact with the adsorption sites located on the edge surfaces. Assuming that this phenomenon affects the adsorption of boron, the effect of ionic strength on boron adsorption can be partly dependent on it. Due to the high variability of soil minerals and the differences in their chemical properties, interpretation of the effect of ionic strength on adsorption of boron is not easy, but we can say that it is the sum of the effects of the above-mentioned factors. The positive effect of ionic strength on boron adsorption may suggest that the formation of inner sphere complex is the dominant mechanism for boron adsorption.
saleh sanjari; Saeid Barkhori
Abstract
Geomorphologies have an important role in soil genesis and micromorphology. So for survey of pedogenic processes at different levels of geomorphic awareness of soil micromorphology a characteristic is essential. In this study micromorphological properties of soils in the south Roudbar region, part of ...
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Geomorphologies have an important role in soil genesis and micromorphology. So for survey of pedogenic processes at different levels of geomorphic awareness of soil micromorphology a characteristic is essential. In this study micromorphological properties of soils in the south Roudbar region, part of Jazmoryan area study and affected geomorphology on this properties were investigated. In this study, seven soil profiles in playa and alluvial fans landforms that each of them was divided into several different surface geomorphic dug and samples were taken for preparation of thin sections. Geomorphic surfaces of thin sections in median geomorphic and base of alluvial fans represented clay coating, lenticular and interlocked plates of gypsum crystal and gypsum infilling in by and 2Bt1 horizons. While in the levels of different geomorphic surfaces landform playa were shown gypsum infilling and sporadic clay coating and composed pedofeatures included clay coating and calcite. Toward geomorphic surface playa saline puffy ground was added to lenicular crystals and gypsum microcrystals. The view of clay coating in paleosol according to current climate there is evidence of sufficient rainfall and humid paleoclimate for leaching and transport of clay. Also the presence of composed pedofeatures is indicated polygenetic of these soils. Observation of sporadic clay coating is showed natric horizon in effected of sodium ions diffusion were moved and accumulated. Overall, we conclude that presence of micromorphologic observations is showed paleoclimate and wet and dry periods in the last.