Soil science
H.R. Owliaie; E. Adhami; M. Najafi Ghiri
Abstract
IntroductionGlobal observations have confirmed that in recent decades, forests have been converted into agricultural land at a swift pace; this is a major global concern. Forests around the world have also experienced severe disturbances due to other anthropogenic activities. The conversion of forests ...
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IntroductionGlobal observations have confirmed that in recent decades, forests have been converted into agricultural land at a swift pace; this is a major global concern. Forests around the world have also experienced severe disturbances due to other anthropogenic activities. The conversion of forests to cropland often results in soil degradation. Slope gradient and land use change are known to influence soil quality; therefore, the assessment of soil quality is important in determining sustainable land-use and soil-management practices. Magnetic susceptibility (χlf) measurements are widely used to study soil-forming processes. Many efforts have been made to correlate soil magnetic susceptibility with different soil properties, such as topography, parent material, Fe oxide forms, etc. The Yasouj area of Kohgilouye Province is one of the most densely forested areas in Zagros mountainous region. Parts of the area have been cultivated to feed the growing population, which has led to forest degradation. The objectives of this study were to assess some soil properties focusing on soil χlf and Fe- oxides forms in different land uses and slope positions.Materials and Methods Forty soil samples were taken from dense forest, sparse forest, eroded lands and dryland farming from different slops (0-15 and 15-30 percent) in Mokhtar Plain, west of Yasouj city. Soil samples were taken from the depth of 0–15 cm in a completely randomized design with five replications. Soil moisture and temperature regimes in the study area are xeric and thermic, respectively. Particle size distribution was determined by the hydrometer method and soil organic matter, CaCO3 equivalent and bulk density were determined using standard procedures. Fe (Feo) were extracted by acid ammonium oxalate, using a single 4-h extraction at pH 3 in the dark. Total free iron (Fed) was extracted with the CBD method. The total Fe contents (Fet) in the soil samples were determined after extraction with 5 mol L-1 HNO3. Magnetic susceptibility of the soils was measured at low (0.46 kHz; χlf) and high (4.6 kHz; χhf) frequencies, respectively; using a Bartington MS2 dual-frequency sensor, with approximately 10 g of air-dry soil in polyethylene vials. The percentage of frequency-dependent magnetic susceptibility (χfd%) was calculated to study the size of magnetic crystals in soils and the abundance of pedogenic ferrimagnetic in SP-SSD (~0.03 μm) boundary.Results and DiscussionThe results of this study showed that the land use and slope positions were among the important factors affecting the change of soil properties in this area. Land use change along with the reduction of organic matter reduced the stability of aggregates and increased land erosion. This process caused the loss of clay particles and magnetic minerals and affected many soil properties. Organic matter as an important indicator of soil quality, showed a decrease of about 3 times as a result of land use change from dense forest to eroded lands following by an increase in bulk density and a decrease in soil permeability and other soil quality indicators. Long-term afforestation and agricultural activities on sloping lands changed the soil texture from a class of silty loam in the forest to a lighter class of silty loam in agricultural use. Soil magnetic susceptibility, which is a function of soil magnetic particles was greatly affected by land use change and to a lesser extent by slope position. Due to the fact that magnetic susceptibility is influenced by factors such as soil texture, drainage class, erosion conditions, magnetic mineral contents, soil evolution conditions, land use changes from forest to other uses had significant effects (about 2 times) on χlf. Significant decrease in the amount of calcium carbonate in low slope positions was another reason for the increase in magnetic susceptibility in these positions. According to the measured values of χfd (ranged from 1.9 to 7.2%), the magnetic particles of the soils had low to moderate amounts of superparamagnetic (SP) particles, which indicates the combined effect of pedogenic superparamagnetic ultrafine particles and lithogenic (inherited) magnetic particles in χlf of the soils. The effect of slope on Fe forms (Feo, Fed and Fet) has been significant (p < 0.01) in almost all land uses. Due to the relatively high correlation of χlf with some soil properties such as Fe forms, soil clay, the amount of diamagnetic compounds including calcium carbonate in the studied soils, it is possible to estimate the value of these soil properties using χlf, which is a quick and cost-effective approach. Overall, it seems that magnetic susceptibility could be applied successfully to estimate some soil properties in hilly regions of Zagros Mountains of southwestern Iran, especially for monitoring the consequences of land use changes. It should also be noted that any change in the use of the area should be defined in accordance with the potential of the land in the long term to prevent a reduction in soil quality.
Yones Abdoli; siroos jafari; abas Beshkar
Abstract
Introduction: The Fe forms diversity is related to parent materials, climate, soil process, biocycles, water table fluctuation, redox, organic matter and etc. in soil. The main Fe forms are Fed (extracted by dithionite citrate bicarbonate), Feo (extracted by oxalate ammonium) and Fe crystals. Feo/ Fed ...
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Introduction: The Fe forms diversity is related to parent materials, climate, soil process, biocycles, water table fluctuation, redox, organic matter and etc. in soil. The main Fe forms are Fed (extracted by dithionite citrate bicarbonate), Feo (extracted by oxalate ammonium) and Fe crystals. Feo/ Fed ratio also shows active Fe forms. Magnetic susceptibility (MS) increases when ferri-magnetite is formed due to soil processes. This characteristic (MS) changes with parent material, climate, relief, and organism. Therefore, this study was undertaken to evaluate different Fe forms and MS with soil forming factors in some gypsic soils of Khuzestan province.
Material and Methods: The study area was located in Ramhormoz and Haft-Kel regions in Khuzestan province. Soil moisture and temperature regimes were ustic and hypertermic, respectively. Soil parent material consisted of the eluvial deposit of Gachsaran and Aghajari geological formations. The soil profiles location was selected according to topography map, ETM+ Landsat satellite images, and then 14 soil pedons were dug and described according to the standard methods. All horizons or layers were sampled and 5 pedons were selected for the analysis of different Fe forms. Fed and Feowere, respectively, extracted by citrate-bicarbonate-dithionite (CBD) and oxalate ammonium, and Fe cocentration was then determined by atomic absorption spectrometry. Furthermore, MS was determined by MS2 meter Barlington Dual frequency in low (0.46 kHz) and high (4.6 kHz) frequencies. All MS were calculated for carbonates, gypsum, and OM free. These calculations were also done for Fe forms in these samples. The statistical analysis was carried out with SPSS and Pierson methods between Fe forms and MS. The Duncan’s test was used to compare the mean values.
Results and Discussion: Pedons were classified as Entisols, Inceptisols, and Aridisols soil orders. The range of clay content, pHe, ECe, CEC, OM, CCE and gypsum was 15-59%, 7.1-8.5, 0.6-58.1 dS/m, 4.2-22.4 cmol(c)/kg, 0.3-2.4%, 21.2-39.7%, and 0-78.7%, respectively. All epipedons were classified to be ochric and developed soils had cambic diagnostic horizon (Bw) in subsurface. Feo content was maximum in young soil under poor drainage, and minimum Feo content was observed for developed pedons with good drainage class. The sepedons have not been cultivated yet. Feo was maximum at surface soils in all pedons, and decreased with increasing depth. A decreasing trend was observed from surface to subsurface for Fe content in cultivated soils. This negative trend was not, however, detected in poor drainage class or pedons with lithologic discontinuity. This trend can be ascribedto more organic matter content in surface soil in comparison with subsurface soil. Organic matters increase soil acidity and therefore, Feo can not be converted to other Fe forms under this circumstance. Maximum Feo was determined under poor drainage class in low lands. In addition, Fed displayed no trend from the surface to depth at most pedons. Maximum Fed was foundin old plain and the hill slope summit. This Fed was positively strongly correlated with soil development trend. Fed had a positive association with clay content (r=0.463), and negative correlation with sand content (r= -0.411), salinity (r= -0.533), and total carbonate, gypsum and OM (r= - 0.389). Feom (Feo menerogic) was maximum in Byz (4.04 gr/kg soil) and minimum content for Feomwas found in Byb (0.29 gr/kg soil). Maximum andminimum Fedmwas measured in Cy (9.21 g/kg) and Bg2 (1.54 g/kg), respectively. The Feo/ Fed ratio was largerin young soil and decreased with time. These values decreased from the surface to depth with the range from 0.07 to 0.8. The greatest and lowest Feo/ Fedwere, respectively, observed inthe hills and the low lands. There was no significant difference in Feo/ Fed between hill and plain.
MS changed from 5 to 25.5. Maximum and minimum MS was detected in the hills and the low lands. MS decreased with depth in almost all horizons. The highest and lowestMS were, respectively, found in pedon 3 (Byb horizon) and pedon 12 in the Bw3 horizon. The MS minerogenicwas statistically significantly associated to sand content (r=0.56**) and significantly negatively correlated with total carbonates, gypsum, OM (r=-0.667**), silt content (r= -0.506) and clay content (r= -0.456). The positive relationship between sand content and MS can be explained by the effect of magnetic materials inherited from the parent materials.
Conclusion: Fed and Feo- Fed showed a close correlation with soil development. Feo/Fed ratio increased with decreasing soil age. Feo content had a positive correlation with total carbonate, OM, salinity. MS was more in older soils such as hill physiographic unit but it was low in younger soils or soils with weak drainage. MS was greatly affected by sand material size which seems to be linked to parent materials. MS showed no trend with soil development but land use, drainage and parent material largely impacted MS and different Fe forms in these gypsiferous soils.
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.
M.R. Rahimi Ashjerdi; shamsollah Ayoubi
Abstract
Conversion of forest and pasture lands into agricultural lands, which is triggered by the rapid population growth, causes serious soil degradation, especially in the hilly regions with undulating topography. The objective of this study was to explore the slope position and land use change effects on ...
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Conversion of forest and pasture lands into agricultural lands, which is triggered by the rapid population growth, causes serious soil degradation, especially in the hilly regions with undulating topography. The objective of this study was to explore the slope position and land use change effects on some soil properties in hilly region of west of Isfahan province, Feryduhahr district. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backs lope and foot slope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm). The results showed that soil organic matter (SOM) in pasture land (2.1%) was approximately 40% higher than cu1tivated land (1.2%). Overall, SOM, total nitrogen, available potassium, clay and sand content significantly in pasture land were higher than cu1tivated land. In consequence of land use change from pasture to cultivated land, some soil properties in surface soils including calcium carbonate, bulk density and soil acidity showed increasing tendency as compared to pasture soils. The pasture soil with lower soil erosion and higher fine materials (clay), indicated higher magnetic susceptibility as compared to cultivated land. Variability of most of measured soil properties showed significant differences in different slope positions. Improper management practices and consequently water soil erosion was identified as the most possible process which has affected soil properties in different slope positions. In overall, it is conc1uded that slope positions and land use significantly influenced soil physical, chemical and magnetic properties in steep slopes of the study area.
sh. jorkesh; Mohammad hasan Salehi; I. Esfandiarpour
Abstract
One of the most important soil contaminants are heavy metals. Chemical analysis of the samples can be used to evaluate the contamination but these methods are expensive and time consuming. Thus, for rapid evaluation, other techniques such as magnetic susceptibility are considered. The aim of this study ...
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One of the most important soil contaminants are heavy metals. Chemical analysis of the samples can be used to evaluate the contamination but these methods are expensive and time consuming. Thus, for rapid evaluation, other techniques such as magnetic susceptibility are considered. The aim of this study was to compare the spatial distribution of magnetic susceptibilityand cadmium, lead, nickel and copper in soil series of Isfahan, Khomeinishahr and Zayanderood in Lenjan at region, Isfahan province. Estimation of heavy metals via pedotransfer functions using magnetic susceptibility was also investigated. Total concentration of Cd, Pb, Ni and Cu in soil samples was determines and the magnetic susceptibility of the samples was also measured. Results showed magnetic susceptibility does not have high accuracy for estimation of heavy metals contents in the soils of this region. On the other hand, similar trends of continuous maps for heavy metals and magnetic susceptibility suggest that magnetic susceptibility can be a good indicator for trend of soil contamination in this area.
