Soil science
Zeinab Barati; Hamidreza Owliaie; ebrahim adhami; Mahdi Najafi Ghiri
Abstract
Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) ...
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Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) is the main tree species forming these forests. Potassium (K) is considered to be the most important nutrient cation in terms of its quantity in plant tissue and its physiological and biochemical functions. Soil tests measure the quantity of a nutrient element that is extracted from soil by a particular extracting solution. Over the years, many different soil testing methods and extracting solutions were evaluated to identify a technique that provides the most reliable prediction of crop yield response to nutrient application. It was determined that some soil testing procedures are best suited for particular soil types and climatic regions. There has been no research on the general status of K in the soil of Zagros forests, related to oak trees. It is important to introduce appropriate K extractants for extracting available K in these soils. Therefore, this research was carried out to achieve the mentioned goals in some forest areas of this Province.
Materials and Methods
Ten forest areas with dominant coverage of oak trees were selected in different parts of Kohgiluyeh and Boyerahmad Province. The physiochemical properties of the soil samples were determined based on standard methods. Soil pH, texture, electrical conductivity, calcium carbonate equivalent (CCE), organic carbon, and cation exchange capacity (CEC) were identified. The content of K present in different forms was determined by standard methods. Solution K was measured in the saturated extract. Exchangeable K was determined by extraction of 5 g soil sample with 20 mL 1 M NH4OAc (pH 7) for 5 min. Nitric acid-extractable K was measured by extraction of 2.5 g soil sample with 30 mL of boiling 1.0 M HNO3 for 1 h. Non-exchangeable K was calculated as the difference between HNO3-extractable K and NH4OAc-extracteable K. Total K was determined following digestion of 0.5 g soil sample with 10 mL of 48% HF and 1 mL of aqua regia. The 12 extracting solutions were 1M NaCl, 2M NaCl, 0.01M CaCl2, Morgan, AB-DTPA, 1M NH4OAC, 0.25M NH4OAC, 1M MgOAC, 1M NaOAC, 2M HCl, 0.1M HNO3, and 0.025M H2SO4. The K content of leaf samples was determined in 1g of each sample. The samples were dried and then ashed in 450°C for 4 h. 2M HCl was used to digest the samples. Potassium was measured on all filtrated extracts using a Corning 405 flame photometer.
Results and Discussion
The soils are all calcareous (average of 42.9 and 44.7% CCE in surface and subsurface, respectively), with pH in range of 7.0-7.8. The textural classes were sandy clay loam, clay loam, and clay. The range of soluble potassium is between 4.8 to 32.7 with an average of 15.4 mgkg-1, exchangeable potassium from 65.1 to 364 (with an average of 247 mgkg-1, non-exchangeable potassium from 106 to 876 with an average of 515 mgkg-1, structural potassium was from 761 to 7322 with an average of 4026 mgkg-1and total potassium was from 1051 to 8110 with an average of 4493 mgkg-1. Soluble, exchangeable, non-exchangeable, and structural potassium were 0.49, 9.6, 12.1, and 77.8%, of the total K, respectively. Among the 12 tested methods, 1.0 mol/L NH4OAC extracted the highest amount of K (mean 229.3 mgkg-1, ranging 64.9-384.2 mgkg-1) and 1.0 mol/L MgOAC removed the lowest amount of K (mean 53.0 mgkg-1, ranged 19.1-88.0 mgkg-1). Correlation coefficients between K extracted by 12 extractants were positive and significant. Maximum correlation between K leaf and extracted soil K was noticed in AB-DTPA, 0.25M NH4OAC, 1M NaCl, and Morgan-Wolfe (r=0.60, 0.59, 0.56, and 0.55, respectively) and the minimum correlation was noticed in 2M HCl and 0.025 M H2SO4 (r= 0.41 and 0.44, respectively). The amount of potassium in oak leaves (in the range of 0.65% to 1.18%) showed a significant correlation with exchangeable potassium in the soil. The amount of potassium in 50% of the oak leaf samples was less than the critical limit (1%). As a general result, 1M NaCl and 0.25M NH4OAC extractants are recommended for extracting potassium, due to greater correlation, simplicity of the method, and economic considerations.
Conclusion
The results of this research showed that the range of the values of different forms of potassium in different parts of the province had a relatively large difference (6 and 8 times difference in exchangeable and non-exchangeable potassium values). The amounts of available forms of potassium in the western regions of the province with less rainfall were in most cases higher than the more humid eastern regions. The average amount of exchangeable potassium in 60% of the studied areas was less than the critical limit of 250 mgkg-1 soil. Also, the average amount of leaf K in 50 percent of the samples was less than the critical level. Considering the great importance of potassium in the nutrition of oak trees and dealing with environmental stress, especially the shortage of soil moisture, it is recommended to pay more attention to the conditions of this element in the soil of the forest areas of the province. Also, fertilizing and foliar spraying of trees in some forest areas should be considered.
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.
Moghbeli Z.; S. Sanjari; E. Adhami
Abstract
Introduction: In sustainable agriculture, it is essential to know soil various characteristics for increasing the soil productivity. The relationship between soil and geomorphology in arid and semi-arid regions has been considered by many researchers. Faryab plain is located in arid region of Kerman ...
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Introduction: In sustainable agriculture, it is essential to know soil various characteristics for increasing the soil productivity. The relationship between soil and geomorphology in arid and semi-arid regions has been considered by many researchers. Faryab plain is located in arid region of Kerman Province and has diversity in geomorphic positions and parent materials. No previous study has been conducted in this region. Therefore, the objectives of the present research were 1) to study the genesis and development of soils related to different geomorphic surfaces in Faryab region, 2) to study the physicochemical properties, clay mineralogy and micromorphology of soils, and 3) to classify the soils according to Soil Taxonomy (ST) (2014) and World Reference Base (WRB) (2015) systems and compare them.
Materials and Methods: Faryab region with a mean elevation of 630 m above sea level is located in Kerman province, south-eastern of Iran. Mean annual rainfall and temperature of the area are 160 mm and 23.8 oC, respectively. Soil temperature and moisture regimes of the area are thermic and aridic, respectively. From geological point of view, the studied area is a part of west and south west zones and Flysch zone of east of Iran. Ten representative pedons on different geomorphic units including hill, alluvil-colluvial fan, alluvial plain, and lowland were selected, sampled, and described. Routine physicochemical analyses, clay mineralogy, and micromorphological observations performed on soil samples. Soil pH, texture, electrical conductivity, calcium carbonate, Na, Ca, Mg, cation exchangeable capacity and gypsum were identified. Eight samples were selected for clay mineralogy investigations. Four slides including Mg saturated, Mg saturated treated with ethylene glycol, K saturated, and K saturated heated up to 550 oC were analyzed. A Brucker X-Ray diffractometer at 40 kV and 30 mA was used for XRD analyses. Undisturbed soil samples from some representative pedons were selected for micromorphological observations. A vestapol resin with stearic acid and cobalt as hardener was used for soil impregnation. A Lite petrographic microscope was used for micromorphology investigations.
Results and Discussion: The results of the present study indicated that the soils with more evolution were located on the geomorphic surfaces of the lowland and alluvial plain and the soils with lower development on the hill and alluvil-colluvial fan. The most important pedogenic processes of the soils were the eluviation of salt, gypsum, calcium carbonate as well as clay, and the formation of calcic, gypsic, petrogypsic and natric horizons. The soils of the region were classified using ST as Aridisols with three suborders of Argids, Calcids and Gypsids and classified according to the WRB as three soil reference groups of Solonetz, Gypsisols and Calcisolos. A new subgroup of Calcic Natrigypsids is suggested for inclusion to ST for the soils with aridic soil moisture regime and three horizons of gypsic, calcic and natric. The WRB system, due to its flexibility in the use of principle and supplementary qualifiers, prepare a better qualification than ST for the soils of the region. According to mineralogical results, the observed minerals consisted of illite, palygorskite, chlorite, smectite, kaolinite, vermiculite and quartz. The highest amount of palygorskite was observed in the gypsic horizons of hill and alluvil-colluvial fan. By moving to the central part of the plain (lowland), the amount of palygorskite was greatly reduced and the amount of smectite was increased. Two origins of inheritance and transformation (illite and palygorskite) are suggested for the occurrence of smectite in the soils. Due to the lack of the conditions for the formation of kaolinite, illite and chlorite, these minerals are inherited from parent materials. SEM observations suggested a pedogenic pathway for the occurrence of large amounts of palygorskite in the soils of the region. Calcareous and gypsiferous media seems to prepare a favorite environment for the pedogenic formation and stabilizing of this mineral in the studied soils. Coating and infilling of gypsum and calcite crystals in voids and channels, clay coating along chanels as well as Fe and Mn oxide nodules were among the common pedofeatures observed in the thin sections of the studied soils. Occurrence of variable habits of gypsum crystals in different geomorphic surfaces suggested a dynamic soil environment. Larger lenticular gypsum crystals were found in the soils with lighter texture located on more stable geomorphic surfaces.
Conclusion: Different geomorphic situations in the region affected the development and evolution, physicochemical properties, clay mineralogy, micromorphology and soil classification and caused the differences in these characteristics in the Faryab region.
Banafsheh Afrasiabi; ebrahim adhami; Hamidreza Owliaie
Abstract
Introduction: Cadmium is one of the toxic heavy metals which is highly problematic in today's industrial world. It is essential to study the techniques for removing or reducing its availability, toxicity and consequently its hazardous effects in environment. Biochar is an amendment reported to be efficient ...
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Introduction: Cadmium is one of the toxic heavy metals which is highly problematic in today's industrial world. It is essential to study the techniques for removing or reducing its availability, toxicity and consequently its hazardous effects in environment. Biochar is an amendment reported to be efficient in fixing heavy metals. Pyrolysis temperature is among the most important factors affecting biochar's characteristics, such as pH, CEC and specific surface area and generally it's potential to sorb heavy metals. On the other hand, soil moisture regime could affect pH and EC and consequently the Cd availability. Iran is the second producer of pistachio in the world and consequently a large volume of pistachio waste byproducts would be created annually. Converting this byproduct to biochar may be an efficient tool to prevent its accumulation. On the other hand, the produced biochar could be used as a soil amendment. The present study was conducted to evaluate biochar produced from pistachio nutshell under different temperatures for reducing Cd availability under different moisture regimes.
Materials and Methods: The soil texture in the present study was sandy-loam. Raw pistachio nutshell (RPN) was used to produce biochar under different temperatures. RPN was rapped in aluminum foils and heated for 2 h in a muffle furnace under 200, 400 and 600 °C. The pH, EC and concentrations of P, K, Fe, Mn, Zn and Cu of RPN and produced biochars were determined. A completely randomized experimental design with factorial arrangement including nine biochar treatments (control (no amendment), RPN and biochars produced under 200, 400 and 600 °C at 2% and 4% rates), and two moisture regims (20% w/w and waterlogging) was carried out with two replications. The samples were spiked with 25 and 50 mg Cd kg-1 and incubated for 90 days under laboratory temperature. Available Cd extracted by DTPA-TEA on 15, 30, 60 and 90 days after incubation. Cadmium concentration determined by Atomic Absorption Spectrometry (Mark and Model: HITACHI- ZCAST 2300). Analysis of variance and compare of means used to evaluate the effects of various treatments on DTPA-Cd.
Results and Discussion: The nutrient concentrations of biochar were increased with increasing the production temperature. The RPN and biochar of 200 ºC had the least nutrient concentrations while the biochar of 600 ºC showed the highest nutrient concentrations. The increases of pH and EC occurred with increasing the biochar production temperature. The pH ranged from 6.36 to 9.36 and EC range was 13.5-31.9 dS m-1. The analysis of variance showed that biochar, moisture regime and their interaction significantly affected DTPA-Cd on all of the studied times (P< 0.01) in both Cd levels. The cadmium availability was reduced by incubation times in all of the treatments and 600°C biochar caused the highest decrease of DTPA-Cd. In 25 mg Cd kg-1 level, the application of 600°C biochar caused significant decrease of DTPA-Cd by 54.2, 73, 53.5 and 60.5 % in comparison with control on 15, 30, 60 and 90 d, respectively. In 50 mg Cd kg-1 level, 600°C biochar in 4% w/w and 20% w/w moisture contents reduced DTPA Cd by 38.6, 43.4, 39.8 and 45.7 mg kg-1 on 15, 30, 60 and 90 d, respectively. The DTPA-Cd was reduced by increasing the biochar application rate to 4% w/w, but only for biochar of 600°C, this reduction had a significant difference with 2% application rate. Four percent biochar application rate on waterlogging condition reduced DTPA-Cd by 60.1%, 34.1 % and 53.6 % compared with 2% application rate on 30, 60 and 90 d, respectively. These changes on 50 mg Cd kg-1 in 20 % moisture level were 36.8, 43.8, 37.7 and 35.2 % on 15, 30, 60 and 90d, respectively. In 20% moisture level, the application of 600 °C biochar reduced DTPA-Cd compared with waterlogging while raw pistachio nuts and 200 and 400 °C biochars showed a reverse trend and increased DTPA-Cd in 20% moisture level compared with waterlogging.
Conclusion: Generally, regarding the decrease of DTPA-Cd by biochars, especially biochar of 600 °C, it can be concluded that biochar of pistachio nut shell particularly under 600 °C might be considered as an inexpensive and green environmental sorbent for Cd, however its potential to reduce Cd uptake by plants and Cd movement in environment requires further studies. Furthermore, the knowledge of the mechanisms that are responsible for Cd retention on biochar and desorption kinetic of sorbed Cd need further investigation.
Mehri Ahrarai; Hamidreza Owliaie; ebrahim adhami; Mehdi najafi Ghiri
Abstract
Introduction: Evaluation of the nutrient status in soil is important from the nutritional, environmental, and economical aspects. Potassium is an essential element for plant growth and is a dynamic ion in the soil system. Soil testing is a useful tool that can help to ensure the efficient use of applied ...
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Introduction: Evaluation of the nutrient status in soil is important from the nutritional, environmental, and economical aspects. Potassium is an essential element for plant growth and is a dynamic ion in the soil system. Soil testing is a useful tool that can help to ensure the efficient use of applied plant nutrients. Soil tests measure the quantity of a nutrient element that is extracted from a soil by a particular chemical extracting solution. The measured quantity of extractable nutrient in soil is then used to predict the crop yield response to application of the nutrient as fertilizer, manure, or other amendments. Over the years, many different soil testing procedures and extracting solutions were evaluated in an effort to identify a method that provides the most reliable prediction of crop yield response to nutrient application. It was determined that some soil testing procedures are best suited for particular soil types and climatic regions, whereas other soil testing procedures are better suited for different soil types and climates. Olive is a strategic and economic product in Iran. Fars province is the second largest olive producer in Iran. There is no general information about K status in the soils and olive trees of the Fars province as well as no introduced appropriate K extractants for theses soils. Therefore, the objectives of this study were: i) evaluating potassium status of some soils of olive orchards of Fars province and ii) introducing appropriate k extractants for extracting available K in these soils.
Materials and Methods: Fars province, with an area of 122000 km2 is located in southern Iran. The elevation varies from 500 m to 4400 m above mean sea level. Based on the information regarding olive orchards of Fars province, 13 typical olive orchards were selected. 26 surface (0-30 cm) and subsurface (30-60 cm) soil samples were taken. Physiochemical properties of the soil samples were determined based on standard methods. Soil reaction, texture, electrical conductivity, calcium carbonate, organic carbon, and cation exchange capacity were identified. The 12 K extracting solutions were 1M NaCl, 2M NaCl, 0.01M CaCl2, Morgan, AB-DTPA, 1M NH4OAC, 0.25M NH4OAC, 1M NaOAC, 2M HCl, 0.1M HNO3, 1M HNO3, and 0.025M H2SO4. The K contents of leaf samples were determined in 1g of each sample. The samples were dried and then ashed in 450°C for 4 h. 2M HCl was used to digest the samples. Potassium in all the filtrated extracts were then analyzed using flame photometer.
Results and Discussion: The all soils were calcareous (average of 48.7 and 50.2% calcium carbonate equivalent in surface and subsurface, respectively) with pH in range of 7.05-7.8. The textural classes were loam, clay loam, and sandy loam. The results showed that the concentrations of K extracted varied widely with the used method, because each extractant remove different portions of K. Among the 12 tested methods, boiling 1 mol/L HNO3 extracted highest amount of K (mean 696.1 mg/kg and range of 203.3-1893 mg/kg) which extracted soluble, exchangeable, and non-exchangeable potassium forms due to its high concentration of H+ and 2mol/L HCl removed the lowest amount of K (mean 32.7 mg/kg and range of 2.6-148.5 mg/kg). Correlation coefficients between K extracted by 12 extractants were determined. The correlation between potassium extracted by all the chemical methods was positive and significant except for boiling 1M HNO3. Between all tested extractants, 0.25M NH4OAC and 1M NH4OAC had the highest correlation (p≤0.01, r= 0.999). The relationship between soil potassium and potassium concentration in olive leaves were evaluated. Maximum correlation between leaf K and extracted soil K were noticed in 2M NaCl, 0.25M NH4OAC, 1M NaOAC, and AB-DTPA (r=0.721, 0.718, 0.717, and 0.714, respectively) and the minimum correlation was noticed in 1M HNO3 (r= 0.661).
Conclusion: The concentrations of K extracted varied widely with applied method, because of desorbing different portions of K by each method, different concentrations of each extracting solution, and the different times of equilibration. On average, the quantity of extracted K by 12 methods were in the following order: boiling 1M HNO3> 1M NH4OAC> 0.25M NH4OAC> AB-DTPA> morgan> 0.1 HNO3> 0.025M H2SO4> 0.01M CaCl2> 1M NaCl> 1M NaOAC> 2M NaCl> 2M HCl. This study showed that 2M NaCl, 0.25M NH4OAC and 1M NaOAC would be suitable as soil testing methods for determining available K for olive in the soils of Fars province. These extractants were the best because of high correlation with plants potassium. In addition, advantages of these extractants are low cost and simplicity. As a recommendation, using of K fertilizers in most olive orchards of the province will improve quantity and quality of the yield.
Fatemeh Mehmandoost; Hamidreza Owliaie; Ebrahim Adhami; Reza Naghiha
Abstract
Introduction: Land use changes such as conversion of forest to cultivated lands, significantly affect soil properties and modify soil forming processes. Land use changes can drastically affect the soil environment, which in turn markedly affect soils and soil processes. Human activities that are not ...
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Introduction: Land use changes such as conversion of forest to cultivated lands, significantly affect soil properties and modify soil forming processes. Land use changes can drastically affect the soil environment, which in turn markedly affect soils and soil processes. Human activities that are not associated with proper planning have undesirable effects on natural resources such as soil, including land use change. The results of the investigations in different parts of the world show that changing the use of natural ecosystems to managed ecosystems has destructive effects on soil properties. Cutting off the forest trees and converting pastures into agricultural lands will destroy or disrupt natural ecosystems and reduce the current or future production capacity of the soil. One of the important issues in the world is the destructive effects of agriculture on soil quality. These destructive effects can include a wide range of soil changes including physical properties such as soil compaction, soil water depletion, soil structure destruction and soil texture change, chemical properties such as accumulation of some elements such as N, P, K, and soil salinity, and soil biological properties such as soil microbial population and soil fauna activity changes, soil organic matter reduction and also effect on useful soil enzymes. Land use change from forest to agriculture does not necessarily lead to soil degradation. Land use changes and forest destruction in Yasouj region has increased in last decades. In this study, we investigated the effects of land use change on some soil characteristics in Servak plain, Yasouj region.
Materials and Methods: Servak region is located in 4 km south of Yasouj city. Three main land uses of dense forest, degraded forest, and dry farming were chosen to study the role of land use change on some soil properties.. The elevation of the region varies from 1833 to 1869 m above sea level. Five soil samples (0-20 cm) were taken from each land use. Samples from each land use were taken from almost similar elevation and slope to minimize the effect of topography. Soil samples were transferred to the laboratory, air dried and passed through a 2mm sieve. The chemical and biological analyses were carried out. The determination of soil organic carbon was carried out based on the Walkley-Black chromic acid wet oxidation method. Available K was extracted with 1N ammonium acetate at pH=7 and was determined by flame photometry. The Olsen method was used for the determination of available phosphorus. Total nitrogen was measured using the Kjeldahl method. Soil bacterial communities were counted using culture medium (Nutrient agar. The basal respiration rate was estimated by back-titration of the unreacted NaOH to determine CO2 evolved over 10 h. The substrate-induced respiration was measured by adding 2 ml of 1% glucose to soil samples over 6 h. Soil suspensions were prepared by 10-fold serial dilutions with 1g soil. Counting the soil fungal community was done using a culture medium (Potato dextrose agar) and was prepared by 10-fold serial dilutions. The activity of alkaline and acid phosphate enzymes was measured based on a colorimetric method using p-nitrophenol.
Results and Discussion: The land use change from a dense forest to dry farming has modified many chemical and biological soil properties. The results of analysis of variance and comparison of the means of data obtained from this study showed that as a result of land use change from dense forest to dry farming, Organic matter, total nitrogen, exchangeable potassium, basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents were decreased. Also, soil bacterial communities were increased at 1% level in dry farming land use. The amounts of phosphorus did not show any significant difference. In general, it can be concluded that following the degradation of the forest and land use change, the soil organic matter and relevant properties, especially biological indices, are more affected compared to the other properties. Soil organic matter plays a key role in ensuring agroecosystem productivity and the long-term conservation of soil resources.
Conclusions: Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Servak region, has greatly affected the physicochemical and biological properties of the soils. Generally, the conversion of the natural ecosystem to agroecosystems decreased organic carbon content and relevant indices such as basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents in the top-soils at depth of 0 to 20 cm. The decrease of organic carbon in cropped farms could be attributed to the enhanced oxidation of soil organic C caused by cultivation. The results of this study showed that any management and type of land use that decreases soil capabilities can reduce soil quality and increase the susceptibility to degradation. So, in order to maintain soil quality, appropriate management practices should be done.
Mahmoud Enjavinejad; Hamidreza Owliaie; Ebrahim Adhami
Abstract
Introduction: Magnetic susceptibility measurements can serve a variety of applications including the determination of changes in soil-forming processes, the study of parent material effects, understanding sedimentation processes, soil drainage conditions, and even the separation and identification of ...
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Introduction: Magnetic susceptibility measurements can serve a variety of applications including the determination of changes in soil-forming processes, the study of parent material effects, understanding sedimentation processes, soil drainage conditions, and even the separation and identification of soil delineations. The technique is especially attractive since it is relatively rapid, non-destructive, and can be applied to both intact and disturbed samples of soils. Magnetic susceptibility is defined as the ratio of the total magnetization induced in a sample relative to the intensity of the magnetic field that produces the magnetization. Iron oxides are the most abundant of the metallic oxides in most soils; they are present in all climatic regions, in several mineral forms, and at variable concentrations. Typically, selective dissolution techniques are used to quantify the relative proportion of Fe oxides. Due to the large contribution of iron-bearing minerals to magnetic susceptibility, their presence in most soils, and the effects of the biophysical environment on them, pedologists have been paying growing attention to magnetic susceptibility as a means to understand soil and landscape processes. The effects of topography on χ were studied for example by many workers. They found that soil susceptibility changes with the position of a soil profile on a slope. Texture and drainage class assumed to be the main reasons. The soils of the Beshar Plain formed on the relatively same parent materials and are mainly affected by topography and land use. The objective of this study was to examine the role of topography and land use on pedogenic processes and their relation to soil χ, as well as, profile distribution of secondary Fe oxides, and the χ profiles.
Materials and Methods: This study was conducted on the Beshar Plain, Kohgilouye Province, in southwest of Iran. Physiographically this plain comprises hill, piedmont plain, river traces, and plateau. Eleven representative pedons were dug along a transect crossing the main physiographical units. Five pedons demonstrated aquic soil moisture regime. The mean annual temperature and precipitation at the site was 14.7°C and 800 mm, respectively. Soil moisture and temperature regimes of the study area were xeric and thermic, respectively. The soils were classified according to soil taxonomy and WRB. The soil pH was measured in a saturation paste and electrical conductivity (EC) in a saturation extract. Cation exchange capacity (CEC) was determined using sodium acetate (NaOAc) at a pH of 8.2. Soil texture was determined using the pipette method. Calcium carbonate equivalent (CCE) was measured by acid neutralization. Organic carbon was determined by wet oxidation method. Pedogenic Fe (Feo) and pseudo-total Fe (Fen) were extracted with the CBD method and HNO3, respectively.The magnetic susceptibility of bulk samples was determined using a Bartington MS2 meter equipped with the MS2B Dual Frequency sensor, capable of taking measurements at both low (χlf at 0.46 kHz) and high (χhf at 4.6 kHz) frequencies.
Results and Discussion: The soils were classified as taxonomic orders of Entisols, Mollisols, Inceptisols and Alfisols, according to the world reference base for soil resources (WRB) as reference soil groups of Kastanozems, Regosols, Gleysols, Luvisols, Fluvisols and cambisols. The dominant pedogenic processes in the soils were the accumulation of organic matter, the leaching of carbonates, and formation of calcic horizons, the mobilization of clay and development of argillic horizons. The results indicated that the soils are affected mainly by topography, drainage class and land use. Most pedons exhibited maximum of χ at the soil surface, suggesting preferential loss of diamagnetic components, as well as more pedogenic formation of antiferromagnetic minerals. Magnetic measurements showed that the χ values of aquic soils were much lower than those of non-aquic soils (43%). The highest value of χ was noted in pedons which are located on stable physiographic units and the lowest belong to those which are located on river lower terraces. Fed and fen was also positively correlated with χ in the soils studied. Aquic condition also decreased Fed and Fed/Fen, 44 and 65 percent, respectively with no clear effect on Fen. Low to medium amounts of χfd in the studied soils indicated that superparamagnetic gains are not too dominant in the soils. Higher values of χfd were typically observed in the A horizons than at depth, suggesting a greater proportion of ultrafine grains at soil surface. A positive correlation existed between χfd and χ in the soils.
Mohamad Rahmanian; AliReza Hosseinpour; Ebrahim Adhami; Hamidreza Motaghian
Abstract
Introduction: Rhizosphere is commonly defined as the zone where root activity significantly influences the biological and chemical properties of the soil. Biological, physical and chemical characteristics of rhizosphere, especially metal availability and metal chemical forms are different than the bulk ...
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Introduction: Rhizosphere is commonly defined as the zone where root activity significantly influences the biological and chemical properties of the soil. Biological, physical and chemical characteristics of rhizosphere, especially metal availability and metal chemical forms are different than the bulk soil. Plant roots continuously release compounds such as sugars, amino acids, and carboxylic acids. Plant roots have the ability to transform metal fractions for easier uptake through root exudation in the rhizosphere. This study was conducted to investigate change in availability and fractions of Copper in the rhizosphere of sunflower (Helianthus annuus L.) in a sandy contaminated soil treated with chelators (EDTA, citric acid and poultry manure extract (PME)) in greenhouse condition.
Materials and Methods: In this study, EDTA and citric acid were used at concentrations of 0, 0.5 and 1 mmol kg-1 soil and PME was used at concentrations of0, 0.5 and 1 g kg-1 soil. Three seeds of sunflower were planted in the rhizobox. After 10 weeks, plants were harvested and rhizosphere and bulk soils were separated. Dissolved organic carbon (DOC), microbial biomass carbon (MBC), available Cu (by using 7 chemical procedures including DTPA-TEA,AB-DTPA, Mehlich1, Mehlich3, CaCl2 0.01 M, rhizosphere-based method and distilled water) and Cu-fractions were determined in the rhizosphere and bulk soils.
Results and Discussion: Rhizosphere soils properties were different with bulk soils. The results showed that the mean of DOC and MBC in the rhizosphere soils were higher than the bulk soils, but this difference was significant in some treatments. The mean value of pH in the rhizosphere soils was significantly (p
Niloofar Sadri; Hamidreza Owliaie; Ebrahim Adhami; Mahdi Najafi
Abstract
Introduction: Potassium is an essential element for plant growth and exists as four forms in soils: soluble, exchangeable, non-exchangeable, and mineral. Soluble and exchangeable K are considered as readily available and non-exchangeable K as slowly available. Organic matters and acids play an important ...
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Introduction: Potassium is an essential element for plant growth and exists as four forms in soils: soluble, exchangeable, non-exchangeable, and mineral. Soluble and exchangeable K are considered as readily available and non-exchangeable K as slowly available. Organic matters and acids play an important role in increasing the bioavailability of nutrients especially potassium in the soils. Organic acids are low-molecular weight CHO containing compounds which are found in all organisms and which are characterized by the possession of one or more carboxyl groups. Depending on the dissociation properties and number of these carboxylic groups, organic acids can carry varying negative charge, thereby allowing the complexation of metal cations in solution and the displacement of anions from the soil matrix.The ability of an organic acid to release K from soils depends on some factors such as: diffusion rate of the organic acid in soil, the diffusion capability of organic acid-element complexes, the contact time of the organic acid on a mineral surface, the ionization of the organic acid, the functional group of the organic acid and its position, and the chemical affinity between the organic acid and the mineral elements. This study was conducted in order to evaluate the effect of organic acids and vermicompost on transformation of K in some selected soils of Fars Province, southern Iran.
Materials and Methods: In this study, nine soils with enough diversity were selected from different parts of Fars Province. The experiment was done as a completely randomized design with three replications, consisting of three incubation times (5, 15 and 60 days) and four organic compounds (including 2% vermicompost, three acids of citric, malic and oxalic acid eachat a concentration of 250 mmolkg-1and one control). The samples were incubated at 50% of saturation moisture at 22°C. Routine physicochemical analyses and clay mineralogy were performed on soil samples. Soil reaction, texture, electrical conductivity, calcium carbonate, and gypsum were identified. Soluble, exchangeable, non-exchangeable and mineral potassium were measured. The amounts of K forms in each sample were determined. Total K was determined following digestion of soil (110°C) with 48 % HF and 6 M HCl. Water soluble K was measured in the saturated extract. Exchangeable K was extracted with 20 ml 1.0 M NH4OAc (pH 7.0) for 5 min. Nitric acid-extractable K was measured by extraction of a soil sample with boiling 1.0 M HNO3 for 1 h. Potassium was measured on all filtrated extracts by flame photometer. The content of clay minerals was determined semi-quantitatively, using peak areas on the diffractograms of ethylene glycol solvated specimens. Statistical analysis was accomplished using the SPSS 16.0 software and the comparison of mean values was done using the Duncan test at the 5% level of significance.
Results and Discussion: The amount of different forms of K including water soluble, exchangeable, HNO3-extractable, and mineral K are relatively high in the studied soils. Mineralogical analysis indicated that smectite, illite, palygorskite and chlorite were the major minerals in the clay fractions. The results also showed that exchangeable, non-exchangeable and total potassium were in the range of 166 to 378, 282 to 1694, and 2312 to 8437 mg/kg-1, respectively.Organic acids and vermicompostwere led toa significant increase in soluble K at all times compared to control and vermicompost treatment exhibited greater effect. These treatments also significantly increased exchangeable potassium compared to control. Significant differences between exchangeable potassium of organic acids and vermicompost treatments were not observed at 5 and 15 days, but significant differences were observed between treatments of mallic and oxalic acids at 60 days. Compared to the control, the non exchancheable K showed significant increase in all three organic acid treatments and vermicompost at 15 and 60 days.
Conclusion: Based on the results, while exchangeable and non-exchangeable (NEK) potassium showed a clear trend in treatments, solution potassium was first increased and then showed a decreasing trend due to the rapid changes in liquid phase compared to the solid phase. All treatments significantly increased soluble potassium in each 3 times. The greatest potassium increase associated with vermicompost. In general, oxalic acid> malic acid>vermicompost> citric acid, were increased exchangeable potassium, while the trend for NEK was in the order of oxalic acid> malic acid> citric acid>vermicompost, respectively. All treatments at all times (except for treatment 5 days of NEK), showed a significant increase in the exchange and NEK potassium compared to the control. The results also reflect the effect of the dominant soil clay mineral on transformation of exchangeable and NEK, so that the highest and lowest rate of increase was related to the soils with dominant palygorskite and illite, respectively. In general, it seems that the use of organic acids and organic matter leads to a rapid increase of potassium, which must be properly managed in the soils with high leaching. Due to the complexity of soil environment in terms of soil physical, chemical and biological aspects and the role of these factors on potassium transformation, repeating of this experiment in other soils is recommended.
N. Sadri; H.R. Owliaie; E. Adhami; M. Najafi Ghiri
Abstract
Introduction: The optimum and sustainable use of soil is only possible with a correct and complete understanding of its properties. Potassium (K+) is an essential element for plant growth and is a dynamic ion in the soil system and its importance in agriculture is well recognized. According to increasing ...
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Introduction: The optimum and sustainable use of soil is only possible with a correct and complete understanding of its properties. Potassium (K+) is an essential element for plant growth and is a dynamic ion in the soil system and its importance in agriculture is well recognized. According to increasing order of plant availability, soil K exists in four forms: mineral (5000-25000 ppm), nonexchangeable (50-750 ppm), exchangeable (40-600 ppm), and solution (1-10 ppm). K cycling or transformations among the K forms in soils are dynamic. The objectives of the present research were to study the relationship between different forms of potassium and clay mineralogy as well as soil evolution of 14 surface soil samples from some selected locations of Fars Province.
Materials and methods: Fars provinces, with an area of 122000 km2 located in southern Iran. The elevation varies from 500 m to 4400 m above mean sea level. Mean annual precipitation ranges from about 350 mm to 850 mm. Mean annual temperature ranges from 10°C to 24°C. According to Soil Moisture and Temperature Regime Map of Iran, the soils comprise xeric, and ustic moisture regimes along with mesic, thermic and hyperthemic temperature regimes. Based on the previous soil survey maps of Fars province, 14 surface soil samples were collected. Routine physicochemical analyses and clay mineralogy were performed on soil samples. Soil reaction, texture, electrical conductivity, calcium carbonate, and gypsum were identified. Soluble potassium, exchangeable potassium, non exchangeable potassium, and mineral potassium were measured. The amounts of K forms in each sample were determined. Total K was determined following digestion (110°C) of soil with 48 % HF and 6 M HCl. Water soluble K was measured in the saturated extract. Exchangeable K was extracted with 20 ml 1.0 M NH4OAc (pH 7.0) for 5 min. Nitric acid-extractable K was measured by extraction of a soil sample with boiling 1.0 M HNO3 for 1 h. Potassium was measured on all filtrated extracts by flame photometer. The content of clay minerals was determined semi-quantitatively, using peak areas on the diffractograms of ethylene glycol solvated specimens.
Results and discussion: The soils are all calcareous (average of 43% calcium carbonate equivalent) with relatively high clay contents (average of 34 %). The different forms of K including water soluble, exchangeable, HNO3-extractable, and mineral K are also relatively high in the studied soils. Mineralogical analysis indicated that smectite, illite, palygorskite and chlorite, were the major minerals in the clay fractions. The results also showed that exchangeable, non-exchangeable and total potassium were in the range of 230 to 436, 282 to 1235, and 2312 to 9201 mg/kg-1, respectively. The soils categorized into three groups based on the soil evolution, clay mineralogy, and total potassium. Well developed soils (Alfisols), slightly developed soils (Aridsols and Inceptisols), and non developed soils (Entisols), were categorized in groups of1, 2, and3. Except for soluble K, maximum of the other potassium forms were observed in group 1. Moreover, there was a high correlation between allpotassium forms andillite content, except for soluble potassium. Mineralogical results revealed that smectite and illite were the major clay minerals in Alfisols resulting high amount of available potassium. The differences among the soil groups in terms of clay percentages may be the results of differences in parent material. K concentration is greater in soils with higher content of calcium carbonate and this is resulted in the greater leaching of K in these soils. This is in consistent with the finding of the other authors, who concluded that calcite and gypsum have a positive effect on the concentration of K in soil solution and leaching of this element from soil.
Conclusion: The results of the present study indicated that the arid and semiarid soils of southern Iran have a relatively high content of K pools. Exchangeable and HNO3-extractable K exist in equilibrium with each other, but the exchangeability of HNO3-extractable K is greater in soils dominated with illite and montmorrilonite than other soils dominated with chlorite and palygorskite. It found that calcium carbonate content had a negative effect on different soil K pools except for water soluble K. The relationship obtained in this study will be allowed determination of soil K pools from clay mineralogy and chemical and physical properties such as exchangeable K, clay content and calcium carbonate content.