Jafar Sharifi Garmdareh; farhad khormali; Christian Rolf; Martin kehl; Ali shahriari; Manfred Frechen
Abstract
Introduction: The study of the northern Iranian loess is important since they are located in the middle of the Asian and European loess belt. In addition, presence of a climatic gradient i.e. increases in rainfall from north to south and from west to east, and the constant temperature, provide a unique ...
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Introduction: The study of the northern Iranian loess is important since they are located in the middle of the Asian and European loess belt. In addition, presence of a climatic gradient i.e. increases in rainfall from north to south and from west to east, and the constant temperature, provide a unique area to study climate change and environmental conditions. There are many recent studies on loess-palaeosol sequences in this region, that show the grain size variation and clay mineralogy changed with increasing precipitation. The purpose of this study was to investigate the trend of grain size variations and clay mineralogy in this climatic gradient to infer origin of the surface loess in this region.
Methods and Materials: Grain size and XRD analyses were carried out on six soil profiles extending from low precipitation in DashliBorun (200mm) to high precipitation in SeyyedMiran (670mm) regions. The grain size analysis was carried out with Beckman-Coulter LS 13320 PIDS. The device uses the principle of the forward scattering of monochromatic light and its diffraction under a certain angle. The angle of diffraction is inversely proportional to particle size. That means coarser particles cause a smaller angle of diffraction compared to finer particles. This method is quick, its results offer a good reproducibility and the data are digital and direct. Necessity for only small amounts of sample material, and covering a wide range from 0.4 to 2000 mm in diameter are other advantages of this method. Nevertheless, the amount of clay percentage may be subjected to certain underestimations because particles smaller than 0.4 μm diffract light in all directions that can cause problems with detecting the signal correctly. Hence the sum of particles with less than 5.5 mm in diameter were chosen as an estimate of clay percentage. Clay fractions were separated based on the methodology outlined by Kittrick and Hope (1963) and Jackson (1975). The carbonates were initially removed using 1 N sodium acetate buffered at pH 5. The organic matter was then oxidized by treating the carbonate-free soils with 30% H2O2, and digestion in a water bath. Free iron oxides were removed from samples by the citrate dithionate method of Mehra and Jackson (1960). The clay separates were removed by centrifuge and studied by a Bruker D8 Advance X-ray diffractometer. Clay minerals were estimated semi-quantitatively from the relative x-ray peak areas of glycol-treated samples.
Result and Discussion: The grain size analysis by laser diffraction method showed that the amount of clay (12.09 %) and fine silt (7.03%) in the soil located in Dashlibron (200 mm/yr) profile had the lowest amount and the U-ratio (6.35) and the medium grain-sized particle (48.28 µm) had the highest amount during this climatic gradient. Increasing precipitation had clear impact on theses parameters, so that the maximum amount of clay (36.56 %) and fine silt (28.02%) and the minimum amount of U-ratio (1.00) and the average medium grain size (8.78 µm) were observed in SayedMiran profile with the highest precipitation (670 mm/yr). Clay mineralogical study of soil parent material showed mica, chlorite, kaolinite and smectite as dominant minerals in the soils. As the amount of precipitation increases along the climate gradient, the amount of pedogenic vermiculite and smectite increase. Silt minerals included quartz, plagioclase, potassium feldspar, mica, chlorite and calcite. The amount of quartz, plagioclase or potassium feldspar minerals did not change in parent materials. The average medium grain size and U-ratio are function of the maximum wind speed and distance from the source. In addition, weathering can affect the size of the particles and cause changes in the mineralogy and amount of minerals in the size of the silt and clay fractions. On the other hand, understanding the changes of clay minerals can provide origin-dependent changes, transport processes, and climatic variations as they are recorded in these minerals.
Conclusion: In general, it can be concluded that the medium grain size and U-ratio decreased from low rainfall regions to higher rainfall and clay and fine silt contents showed a reverse trend. Clay minerals included mica, chlorite, and kaolinite and dominant silt minerals were quartz and plagioclase in all studied soil profiles along the climatic gradients. The results showed that changes in grain size reflect the distance from the loess material sources and also indicate intensity of pedogenic processes. Mineralogical analysis showed the similar mineral types in all loess parent materials of different regions, probably indicating the similar sources for the loess. The change in minerals abundances in the upper horizons indicate the pedogenic processes affected by climatic conditions along the climate gradient.
Sona Azarneshan; farhad khormali; fereydoon sarmadian; farshad kiani; kamran Eftekhari
Abstract
Introduction: Assessing the soil quality of agricultural land is essential for the economic success and sustainability of the environment in developing countries. Recently, there are many types of methods for assessing soil quality, each of them uses different criteria. Considering that Qazvin plain ...
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Introduction: Assessing the soil quality of agricultural land is essential for the economic success and sustainability of the environment in developing countries. Recently, there are many types of methods for assessing soil quality, each of them uses different criteria. Considering that Qazvin plain is one of the most important regions of agricultural products in Iran as well as Middle East, so the assessment of the soil status using quantitative models of soil quality can be used as an indicator of the status of soils in relation to sustainable agriculture, optimal utilization of resources Natural and better land management. Among the quantitative models of soil quality index, cumulative model integrated quality index (IQI) and Nomero (NQI) index can be mentioned. Therefore, this study intends to evaluate the best quantitative and quality index model by examining and comparing two methods of selecting the appropriate criteria, Total data set (TDS) and Minimum (MDS) and the second order soil quality index, integrated quality index(IQI) and Nomero (NQI) index in Qazvin plain lands.
Material and Methods: The study area with 25220 hectares is located in east of Qazvin Province. The average annual precipitation is 275 mm and the soil moisture and temperature regimes are Thermic, Dry xeric and Weak Aridic, respectively. A total of 76 samples from the depth of 0-20 cm of the soil surface were studied and based on uniformity, soil type and land use. In this study, four types of criteria that affect the quality of soil in terms of their performance, including: upper limit, lower limit, optimal limit and descriptive function were selected. To qualify (normalize), the upper limit, lower limit and peak limit were selected. In the following, the Total Data Set (TDS) and the Minimum Data Set (MDS) set of data were used. In the TDS method, all of the measured characteristics (a total of 19 physicals, chemical and biological properties of the soil) were considered. Then, the degree of soil quality indices was determined based on the combination of TDS and MDS criteria and the final NQI and IQI quality indices.
Result and Dissection: Comparison of soil types in the region showed that the Aridisols had good, moderate and poor quality (19.35% of soil with good quality, 67.76% with moderate quality and 12.94% with poor quality), Entisols have good and medium quality (53.21% of the soil with good quality and 46.79% with moderate quality) and Inceptisols have very good, good, moderate and poor quality (96.9% Soils with very good quality, 66.73% with good quality, 15.85% with moderate quality and 13.44% with poor quality).
According to the TDS standard and the NQI model, the soils with qualities I, II and III were 30.67%, 66.86%, 47.2% of the total soils of the area (lands with poor quality soil quality were not observed in TDSNQI method). Therefore, according to this method, Aridisols has a very good, good and medium quality (13.26% of the soil with a very good quality rating, 73.88% with a good quality and 12.84% with a moderate quality grade), Entisols with The good quality (100% of the soil with good quality degree) and Inceptisols have a very good and good quality (28.11% of the soil with a very good quality grade, 71.88% with a good quality grade). The results of quantitative soil quality by using the MDS standard method and IQI model were showed, soils with very good, good, moderate and poor degree are 2.45, 16.45, 48.93 and 46.3 percent of total land area respectively.
The results of the combination of the MDS and the NQI model also showed that the soils with a very good, good and average grade are 30.67%, 66.86% and 47.2% of the total land, respectively. Also, the results of the combination of the MDS and NQI model showed that the soils with very good, good and average quality are 30.67%, 66.86% and 47.2% of the total land area respectively. The results of the evaluation based on 4 indicators showed that good quality (II) was prevalent in the studied soils and accounted for about 47% of the total area studied in Qazvin plain lands. The map of distribution of soil quality degrees, the distribution of soil degrees is relatively similar to all of four combination methods, the choice of criteria and model. By examining the linear relationship between the indices obtained from TDS and MDS criteria and the IQI and NQI indexes, it is observed that the correlation coefficient is more and more reliable than the NQI model when used in the IQI model (R2 = 0.77). So the highest correlation coefficient we observed two methods for selecting the TDS and MDS criteria when using the IQI model. In general, the results of this study indicate a better performance of the MDS criteria than TDS.
Conclusions: Therefore, the main results of this study suggest using the IQI model with the MDS selection method as the starting point in the global standard path for future studies. Special attention should be paid to the criteria chosen by the MDS. In addition, conducting a series of research into the future in order to modify the MDSIQI model can make it more relevant to international standards.
Somayeh Sefidgar; Mojtaba Barani Motlagh; farhad khormali; Esmael Dordipour
Abstract
Introduction: Soil pollution with heavy metals have become a global concern because of its damaging effects on the environment, including human health, toxicity in plants and long-term effects on soil fertility. Heavy metals stress in plants is characterized by decrease in photosynthesis, nutrient uptake, ...
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Introduction: Soil pollution with heavy metals have become a global concern because of its damaging effects on the environment, including human health, toxicity in plants and long-term effects on soil fertility. Heavy metals stress in plants is characterized by decrease in photosynthesis, nutrient uptake, damaging of roots and finally plant death. Lead (Pb) is found to be the most dangerous heavy metal, responsible for reduced soil fertility and elevated environmental pollution. Lead toxicity causes the inhibition of seed germination and exerts adverse effects on growth and metabolic processes of plants, which retards plant and crop production. The overproduction of reactive oxygen species (ROS) is the best indicator for secondary stress, which results in a number of toxic effects on biochemical processes in many plant cells. The overproduction of ROS due to Pb stress brings about changes in cellular membrane permeability, which in turn damages organelles such as nuclei, mitochondria, and chloroplasts in plant cells which decreased plant growth and yield. Chemical stabilization is an in situ remediation method that uses inexpensive amendments to reduce contaminant availability in polluted soil. The aim of this study was to investigate the immobilization of lead in a calcareous contaminated soil using two types of biochar as organic and Pumice, Leca, Zeolite and Bentonite as inorganic amendments.
Materials and Methods: In order to investigate the effect of organic amendments (biochar 640°C, and biochar 420°C) and inorganic amendments (Pumice, Leca, Zeolite and Bentonite) on Pb stabilization in a contaminated soil (1500 mg/kg), a greenhouse experiment using maize plant was carried out. This experiment was conducted in a completely randomized design consisting of 6 types of amendments (Pumice, Leca, Zeolite, Bentonite, Biochar 420°C, and Biochar 640°C) and at 1% and 5% levels of each amendment (12 amendments plus 1 control). The experimental treatments were incubated for 3 months. At the end of incubation time, the potential bioavailability of Pb in non-amended and amended soils was assessed by chemical extractions, as: extraction with DTPA, with ammonium acetate and with ethylenediaminetetraacetic acid (EDTA). After the end of incubation time, the pots were transferred to a greenhouse and in each pot five maize seeds were planted and then reduced to three seedlings in each pot after germination. After 3 months, all the plants were harvested. The Pb concentration in each plant, its biomass, its chlorophyll and its antioxidant enzyme activities levels were analyzed. All statistical analyses were performed using SAS software. Means of different treatments were compared using LSD (P ≤0.05) test.
Results and Discussion: The results indicated that the addition of amendments to soils reduced the concentration of Pb extracted with DTPA and EDTA. The 5% biochar 640 had the greatest reduction effect on DTPA-extractable Pb. The smallest concentration of Pb in the leaves and root of maize plant was observed in treated soil with organic amendments (biochar 640°C, and biochar 420°C) and treated with 5% zeolite, respectively. The highest increase in plant growth parameters like SPAD value, leaf area, plant height, number of leaves per plant, dry biomass yield and dry matter of roots were observed in organic amendments compared to the control. The application of 5% amendments in soil caused a significant increase in plant height and number of leaves as compared to control. The increase in growth and biomass of zea mays L. under various amendments might be due to decreased bioavailable Pb concentrations in soil amended which may be attributed to reduced Pb toxicity through improvement of soil fertility. Also, the application of amendments resulted in a significant increase in antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), peroxidase (PX), and ascorbate peroxidase (ASP) in maize plants compared to the control. The increase of leaves enzyme activities with addition amendments may be due to a lower Pb accumulation in leaves because excess Pb generates free radicals and reactive oxygen species (ROS) those causes oxidative stress in plants.
Conclusions: The results indicated that the application of amendments were successful in lowering the potential bioavailability of Pb in the soils. The 5% biochar 640 treatment had the greatest reduction effect on extractable Pb. The application of amendments decreased the uptake and accumulation of Pb in maize plants, via the reduction of DTPA- extractable Pb. The amendments also significantly increased leaves antioxidant enzyme activities and photosynthetic pigments compared to the control.
A. Shahriari; F. Khormali; Martin kehl; Ali reza Karimi; M. Mousavidastenaei; E. Lehndorff
Abstract
Introduction: Knowledge about palaeoenviroment and palaeovegetation provides information about how vegetation reacts on climate fluctuations in the past, what will help understanding current and future developments caused by e.g. climate change. Northern Iranian Loess-Plateau forms a strongly dissected ...
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Introduction: Knowledge about palaeoenviroment and palaeovegetation provides information about how vegetation reacts on climate fluctuations in the past, what will help understanding current and future developments caused by e.g. climate change. Northern Iranian Loess-Plateau forms a strongly dissected landscape with steeply sloping loess hills. This loess record reflects numerous cycles of climate change and landscape evolution for the Middle to Late Quaternary period. therefore, this study was done for reconstruction of palaeoenvironment (climate and vegetation) in loess-palaeosol sequences in northern Iran. Therefore, this study aims at a preliminary reconstruction of palaeovegetation and palaeoenvironment, in loess-palaeosol sequences along a cliomosequnce in Northern Iran.
Materials and Methods: Two loess-palaeosol sequences (Agh Band and Nowdeh sections) were chosen in Golestan province, in northern Iran and step-wise profiles were prepared. Agh Band section is located in the western most part of the Northern Iranian loess plateau and has about 50 m thickness of loess deposits. Nowdeh loess-palaeosol sequence is located about 20 km southeast of Gonbad-e Kavus, in the vicinity of the Nowdeh River. Soil sampling was done in several field campaigns in spring 2012. More than 30cm of the surface deposits were removed in order to reach for undisturbed loess and palaeosols and one mixed sample was taken from each horizonA comparison of palaeosols with modern soils formed under known Holocene climatic conditions, which are derived from substrates with similar granulometric and mineralogical composition are suited for reconstructing past climate and environment. Hence, six modern soil profiles were prepared along the climosequnce and the vegetation cover changed from grassland in the dry area to dense shrub land and forest in the moist part of the ecological gradient. For reconstruction of palaeoenvironment (climate and vegetation) some basic physico-chemical properties, clay mineralogy and n-alkane biomarkers were used.
Results and Discussion: Results of soil texture analysis showed silt particles were dominant (more than 50 %) in the modern soil profiles and loess-paleosol sequences which confirmed aeolian source of loess deposit. Clay content increased while silt content decrease in more strongly developed palaeosol horizons which it may reflected weathering processes of clay and/or its translocation. The modern soil profiles were classified as Entisols, Inceptisols, Mollisols and Alfisols which shows impact of climate as an important soil formation factor in the studied area. Clay mineralogy results in two loess-palaeosol sequences showed that illite, chlorite, kaolinite and smectite are dominant in these deposits. Mineralogical changes in the soil horizons are consistent with morphology and soil evaluation, so smectite, illite-smectite (mixed layer) and vermiculite minerals were dominant minerals in more strongly developed palaeosol horizons indicating to high precipitation and good vegetation cover (e.g., forest). The n-alkane biomarker results in the modern soil profiles showed, the average chain length (ACL) and (nC31+nC33)/(nC27+nC29) ratio are very efficient parameters for reconstruction of vegetation, therefore these parameters were used to unravel the palaeovegation in loess-palaeosol sequences. In both sections n-alkane biomarkers studies showed vegetation changes in different periods. These changes were most intense in Nowdeh loess-palaeosol sequence, so grassland and shrub in profil1 (Bk horizon) and profile 2 (ABk horizon) palaeosols (with illite dominance) changes to forest in profile 2 (AB horizon with smectite dominance) and profile 3 (Btky horizon with smectite dominance and vermiculite presence) palaeosols. Agh Band section had one palaeosol including two horizons (Bw and Bk) which based on n-alkane specifications the Bw-horizon indicates grass/shrub vegetation (alsosmectite presence). It could indicate favorable environmental conditions promoting the growth of more dense vegetation.
Conclusions: Results showed that clay mineralogy changes are in line with n-alkane biomarkers results and both analyses reflect climate and environment conditions in soil formation periods and they are more effective for the accurate reconstruction of palaeoenviroment. According to chronological data for Nowdeh and Agh Band loess-palaeosol sequences, Nowdeh section had more suitable environment (more precipitation, more dense vegetation and suitable conditions for formation and development of soil, pedologically) compared with Agh Band section at the same times. Clay mineralogy and n-alkane biomarker resulted in the modern soil profiles and loess-palaeosol sequences showed that the modern ecological gradient (especially for precipitation) existed during the time and climate was an important soil formation factor in the studied region.
Hanifeh khormai1; farshad kiani; Farhad khormali
Abstract
Introduction: Globally, Soil erosion is a principal degradation process resulting in negative impacts on different soil functions (food and other biomass production, water storing, filtering and transformation, habitat and gene pool, physical and cultural environment for mankind, and source of raw materials) ...
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Introduction: Globally, Soil erosion is a principal degradation process resulting in negative impacts on different soil functions (food and other biomass production, water storing, filtering and transformation, habitat and gene pool, physical and cultural environment for mankind, and source of raw materials) which ultimately causes irreversible effect on the poorly renewable soil resource. Determination of the soil erodibility factor (K-factor) is a cumbersome and expensive undertaking in the effort to predict the soil loss rates. Soil erodibility (K-value) is a key parameter in erosion prediction and is important for conservation planning in the face of a rising need for protecting the limited land resources. The technique proposed by Wischmeier& Smith for estimating the soil erodibility factor is among the most important methods in this regard.
Materials and Methods: Given the high amounts of silt and lime content in loess soils of eastern parts of Golestan province, the purpose of this study was to evaluate the ability of Wischmeier& Smith index to estimate the soil erodibility of this region. In this study, soil erodibility was obtained by Wischmeier’s nomograph and then was compared with the actual values obtained by selecting three plots and then performing physical and chemical tests on these samples. The Universal Soil Loss Equation (USLE) developed by Wischmeier and Smith (1978) is the most frequently used empirical soil erosion model worldwide. Soil erodibility is one of six factors affecting soil erosion in the USLE that reflects the ease with which soil is detached by splash during rainfall, surface flow or both. To check soil erosion,three plots of 15 meters long and three meters wide with a slope of 16 percentwere selected in the next sites of the station. The plots were separated by metal fences to a height of 30 cm,.To measure the soil profile parameters, the sampling was performedin one stage from depth of0-30 cm in the middle of July 2010 and the samples were transported to the laboratory. The erosion Wischmeier& Smith Index (A), as well as those obtained by SWAT model and two obvious erosion indices of (R) and Fournier was Carefully evaluate based on the half-hour rainfall intensity.
Results and Discussion: The analysis of soil profile parameters showed that the soilsweremostly silty loamwith 20.29%sand, 66.54% silt and 13.66% clay, with 2% organic matter and 16.6% CaCO3. The soil aggregate stability expressed as MWDwas about 0.8 mm. Overal, 74 rainfallsoccurredin 2010-2011. The minimum and maximum intensities of deposit-producing rainfalls were 2.98 and 73.589 mm h-1, respectively. Using the nomograph, Wischmeier index was calculated to 0.05-0.092 Mg h MJ−1 mm−1. The results showed that Wischmeier index was 182 times the actual value of erosion obtained from plots and half-hour rainfall intensity and 4.11 times that value while considering Fournier index (R); this parameter was also 6 times the value obtained by SWAT model and half-hour rainfall intensity and 0.35 times that value while considering Fournier index. According to the results,there was a negative correlation between clay and soil erodibility factor in USLE, so the rates of erosion in loess soils increases with the decrease in the clay content. Aggregate stability was affected by organic matter content and there was a negative correlation between aggregate stability and the K-factor. The results showed that the soil mostly contained silt and had a medium texture. This is due to the presence of loess parent materials in the soils of the study area. Based on the laboratory results, the actual soil erodibility was0.35 to 182 times smaller than the value estimated by USLE nomograph. The results showed that the parameters used in determining soil erodibility index have shortcomings for use in the soils of the study area. Therefore, corrections must be done according to soil characteristics or other indicators should be used. The particle size and the amount of lime in the soil are two factors that affect the index.
Conclusions: The obtained results showed that the erodibility estimated by Wischmeier& Smith index was higher than the actual measured value. Also,Wischmeier &Smith’snomographhas been proposed by assessing the erodibility of almost non- calcareous soils with limited amount of silt. While in arid and semiarid loess soils of Golestan province, limestone and siltstone have key roles in erodibilityand aggregate stability. On the other hand, the nomograph is based on rainfalls of semi-humid areas of Central America that are different from rain characteristics (intensity and duration) of the study area. Poor performance of this index in loess soils indicates the need for further research in this field.
S. Tajari; mojtaba barani; F. Khormali; F. Kiani
Abstract
Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to ...
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Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to a large degree, determine the fate and transport of P in soils. Fractionation schemes using different chemical sequential extractions have been used in order to describe the many different forms in which P can be found in the soil. The reason for fractionating and studying P forms in the soil is usually to allow a more precise description of the potentials for P release from the soil. The forms and dynamics of soil P can be greatly affected by agricultural management practices. Since inorganic P is the preferred source for plant uptake, knowledge of the inorganic form within soils is fundamental to understanding bioavailability of P and sustainability of agricultural practice. The aim of this study was to investigate the effect of land use change on the form and distribution of inorganic P using a sequential extraction procedure.
Materials and Methods: In order to study the impact of land-use change from forestland to cultivated land, composite samples in four replicates from the upper 10 cm of the different land use systems (natural forest, pasture, bower olive, farmland) were collected. We collected five subsamples from each land use in a radial sampling scheme. The five subsamples were then bulked into one sample. The spacing between the subsamples on the radii ranged from 5 to 10 m. The soil samples were transferred to polyethylene bags and transported to the laboratory where they were slightly crushed, passed through a 2 mm sieve prior to fractionation and chemical analysis. Soil texture, cation exchange capacity, organic carbon (OC), electrical conductivity, pH and calcium carbonate equivalent (CCE) were measured with standard methods. Total P and total inorganic P (Pi) contents were measured by the ignition method, for which P in the ignited (550 °C) and unignited soil samples were extracted by 0.5 M H2SO4. A modified version of the sequential extraction of Olsen and Sommers (1982) was used to fractionate inorganic P. Phosphorus was measured in the extracted supernatants by the molybdate–ascorbic acid method.
Results and Discussion: The results showed that clear-cutting of the indigenous forests and their conversion into agricultural fields significantly decreased total P and total organic P levels. Land-use changes from natural forest to farmland decreased the total P by 23% (from 644 to 495 mg per kg). Clearing and subsequent cultivation of the native woodland resulted in a marked depletion of total organic P. In addition, the land-use conversion from the natural forestland to an agroecosystem (cultivated land) led to increases in total inorganic P and inorganic P forms levels (labile P, P non-occluded, occluded in oxides of iron and aluminum, soluble calcium phosphate and sparingly soluble calcium phosphate). Labile inorganic P (NaHCO-Pi) showed the greatest changes, such as labile inorganic P in the amount of change from 1.75 in the forest land to 13.01 mg per kg of cultivated land, which represent an increase of approximately 8-fold compared to control (natural forest). The results also revealed that the refractory inorganic P fractions (HCl-Pi) were the major inorganic P pool, comprising 50-70% of the total inorganic P pool, indicating CaCO3 control over phosphorus availability in the studied soils. This study indicated that forestland degradation and cultivation caused chemical changes of P dynamics.
Conclusion: Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Toshan region, has greatly impacted the forms and content of P in the soils. Generally, the conversion of natural ecosystem to agroecosystems, decreased the proportion of organic P (Po) in the top-soils at depth of 0 to 10 cm. The depletion in organic P from the cropped fields could be attributed to the enhanced mineralization of soil organic P caused by cultivation and removal of P in the crops. However, the conversion of natural forest to farmland led to increases in inorganic P (Pi). About 50% to 70% of the TP was bound to CaCO3, and thus this solid phase is critical to P fate in the soils and ecosystem of the Toshan Region, Golestan province
M. Valaee; Sh. Ayoubi; H. Khademi; F. Khormali
Abstract
Introduction: Soil moisture regime refers to the presence or absence either of ground water or of water held at a tension of less than 1500 kPa in the soil or in specific horizons during periods of the year. It is the most important factor in soil formation, soil evolution and fertility affecting on ...
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Introduction: Soil moisture regime refers to the presence or absence either of ground water or of water held at a tension of less than 1500 kPa in the soil or in specific horizons during periods of the year. It is the most important factor in soil formation, soil evolution and fertility affecting on crop production and management. Also, it widely is practical in soil classification and soil mapping. The soil moisture regime depends on the soil properties, climatic and weather conditions, characteristics of natural plant formations and, in cultivated soils, is affected by the characteristics of crops grown, as well as the cultivation practices. Determination of soil moisture regime within a landscape scale requires high information and data about moisture balance of soil profile during some years according to Soil Survey Manual (2010). This approach is very expensive, labor, time and cost consuming. Therefore, achievement to an alternative approach is seems essential to overcome these problems. The main hypothesis of this study was to use capability of magnetic susceptibility as a cheap and rapid technique could determine the soil moisture regimes. Magnetic properties of soils reflect the impacts of soil mineral composition, particularly the quantity of ferrimagnetic minerals such as maghemite and magnetite. Magnetic susceptibility measurements can serve a variety of applications including the changes in soil forming processes and ecological services, understanding of lithological effects, insight of sedimentation processes and soil drainage.
Materials and Methods: This study was conducted in an area located between 36°46َ 10˝ and 37° 2’ 28˝ N latitudes, and 54° 29’ 31˝ and 55° 12’ 47˝ E longitudes in Golestan province, northern Iran. In the study region mean annual temperature varies from 12.4 to 19.4 °C. The average annual rainfall and evapotranspiration varies from 230 mm and 2335 mm in Inchebrun district (Aridic regime), to 732 mm and 846 mm in Touskstan uplands (Udic regime), respectively. this study was conducted in four soil moisture regimes (Aridic, Xeric, Udic and Aquic), for exploring the relationships between soil properties and magnetic measures. In each regimes, 25 soil profiles were drug, described and soil samples were collected from each of soil horizons. Soil samples were air-dried and sieved using a 2 mm sieve. The dithionite-citrate bicarbonate (DCB) method was used to measure Fed and acid ammonium oxalate for Feo. In this study, a set of environmental magnetic parameters including magnetic susceptibility at low frequency (χlf), saturation isothermal remnant magnetization (SIRM), isothermal remnant magnetization (IRM100 mT) were measured. Magnetic susceptibility (χ) was measured at low frequency (0.47 kHz; χlf) and high frequency (4.7 kHz; χhf) using a Bartington MS2 dual frequency sensor using approximately 20 g of soil held in a four-dram clear plastic vial (2.3 cm diameter). Frequency dependent susceptibility (χfd) was determined by the difference between the high and low frequency measurements as a percentage of χ at low frequency. IRM was measured at the field of 100 mT generated in a Molspin pulse magnetizer (IRM100mT) and at the back field of 100mT (IRM−100mT). The IRM acquired in the maximum field of 1000 mT was measured and defined as the saturation isothermal remnant magnetization (SIRM) of the soil sample.
Results and Discussion: The results showed that moisture regime induced significant differences for soil physical and chemical properties. Diversities in genetic soil horizons and soil development degree have been increased from Aridic to Udic soil moisture regime. The results also indicated that selected properties including magnetic measures and physical and chemical properties were significantly different in four soil moisture regimes. With increasing rainfall and reducing temperature from aridic to udic soil moisture regime, soil organic matter was increased. Otherwise, in arid environment Gypsic, Calcic and Salic horizons were observed in the near of soil surface. Fed and Fed-Feo were the highest in udic and the lowest in udic soil moisture regime, respectively. Moreover, higher soil development because of climate effect leaded to higher amount of pedogenic ferromagnetic minerals, as well as the highest were observed in the Udic regime. Otherwise, in Aquic moisture regime, the lowest value of magnetic susceptibility was obtained because of dissolution of ferromagnetic minerals (magnetite and maghemite) under supersaturating condition. In overall, close relationships were observed between soil physical and chemical properties and magnetic measures in various soil moisture regimes.
Ali reza Karimi
Abstract
Loess deposits of Kopeh Dagh area usually occur patchy, with low thickness and should be identified and differentiated from other deposits for environmental planning and landscape evolution studies. The objective of this study was to identify distribution and determine the characteristics of loess deposits ...
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Loess deposits of Kopeh Dagh area usually occur patchy, with low thickness and should be identified and differentiated from other deposits for environmental planning and landscape evolution studies. The objective of this study was to identify distribution and determine the characteristics of loess deposits and investigate their formation in the Sarakhs area. Thirty surface samples were collected from the study area and analyzed for particle size distribution. Coarse silt and very fine sand are the dominant fraction of the sediments and overally exceed 70%. Dominance of coarse silt and very fine sand, lack of coarse fragments and abrupt boundary of these sediments with underlying materials are evidences of eolian origin. With decreasing very fine sand and increasing coarse silt, sand dunes in the east and center of the area gradually change to loess deposits from Sarakhs city towards Dousti dam (along Hariroud River) and Kopeh Dag heights in the south and west. The maximum thickness of loess sediment occurred around the Dousti dam. Dominance of coarse silt and very fine sand in the sediments and gradual boundary between sand dunes and loess deposits shows the local source of the particles. Kopeh Dagh heights in southern and western parts of the area, like a barrier have trapped eolian sediments and caused their formation.
