Soil Chemistry and Pollution
Alireza Abdollahpour; Mojtaba Barani Motlagh; Amir Bostani; Farshad Kiani; Farhad Khormali; REZA GHORBANINASRABADI
Abstract
Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, ...
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Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, microbial and animal masses in various stages of decomposition and is a mixture of heterogeneous organic materials that are closely related with mineral components. Soil organic matter has beneficial effects on the chemical (buffering and changes in pH) and biological (precursor and supply of nutrients for microbes) properties of the soil and thus affects the fertility capacity of the soil. The quality and quantity of soil organic matter is the most important criterion for sustainable soil management. Total organic carbon (TOC) consists of labile and non-labile forms of SOC and have different degrees of sensitivity to different types of land use changes and management operations. The purpose of this research is to investigate the effect of changing land use on the chemical components of soil organic carbon and carbon recalcitrant index in Toshan Watershed, Golestan provinceMaterials and Methods For this research, four major and dominant types of land use were considered in the study area, including forest, cropping land, garden and abandoned lands in the Toshan watershed in the northwest of Gorgan city of Golestan province. The soil organic carbon and total C of soils were measured. Furthermore, the soil carbon fractionation was performed by Young's method (using hydrolysis methods with HCl and Labile fraction). In this research, Acid hydrolysis method was used to separate the recalcitrant SOM pool. For this purpose, one gram of SOM sample was treated with 25 ml of 6 M hydrochloric acid solution at 105°C for 18 hours in a Pyrex tube in a hydrolysis package. After cooling, the remaining non-hydrolyzed materials were separated by centrifugation. Then, they were dried in an oven at a temperature of 60 degrees Celsius and considered as a part of resistant organic matter. The resistant part of the soil organic carbon was determined with the CHNS Analyzer device. The Labile fraction consists of water soluble carbon, microbial biomass carbon and mineralizable carbon are measured using the following methods and the labile part of carbon is calculated from their sum. Water-soluble organic carbon is extracted by adding 20 ml of distilled water to 10 grams of wet soil. The mixture will be shaken and centrifuged, filtered. Then they will be quickly analyzed by TOC Analyzer. Microbial biomass carbon will be determined by the chloroform fumigation-extraction method. Mineralizable carbon determined as follow. The amount of CO2 will be measured by titration of NaOH solutions with 0.1 M HCl in the presence of BaCl2. Cumulative amount of CO2-C emitted in 30 days of incubation is called Mineralizable carbon. The data were analyzed based on the factorial test in the form of a completely randomized design (CRD) with two levels of soil depth and four land uses with five replications. Correlation between traits was also estimated. Statistical analyzes were performed using SAS software. Therefore, it can be concluded that depending on the climatic conditions and the condition of the soil, the forest, in terms of natural cover, the correct management of agricultural lands (using modern methods of no-tillage or low-tillage) can be a potential practice. It is to store carbon in the soil as well as various soil components and increase soil formation, which will subsequently reduce the concentration of carbon dioxide in the atmosphere.Results and Discussion The results showed that the first depth of forest use has the highest amount of total carbon and soil organic carbon (6.12% and 3.5% respectively). Also, the highest amount of resistant organic carbon (HCl hydrolysis), water-soluble organic carbon, microbial biomass carbon, and microbial mineralizable carbon were observed in forest land use. The second depth (10-20 cm) of forest land use had the highest and the second depth (10-20 cm) of garden land use had the lowest organic carbon resistance index (82.1% and 50.17%, respectively). In all land uses, except for the forest, the soil organic carbon resistance index decreased with increasing sampling depth. Due to the fact that the carbon management index can be easily calculated, it can be a suitable index for quick assessment of soil quality.Conclusion The results showed that with the change of land use and cultivation, the soil organisms received more oxygen and the speed and intensity of respiration in the soil increased in the short term, which caused more decomposition of organic matter and with the decrease of organic matter in the long term, the quality of soil decreases after a while.
maryam sebti; F. Khormali; afshin soltani; kamran Eftekhari; abdolazim ghanghermeh; esmaeil dordipour
Abstract
Introduction Increasing concerns about global warming and climate change have led to special attention to soil and its capability in carbon sequestration in recent years. About 540,000 hectares of soils in Golestan province are under agronomic activities and so far no studies have been conducted on soil ...
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Introduction Increasing concerns about global warming and climate change have led to special attention to soil and its capability in carbon sequestration in recent years. About 540,000 hectares of soils in Golestan province are under agronomic activities and so far no studies have been conducted on soil organic carbon changes and its interactions with climate change. The total organic carbon in soils is approximately twice the amount of carbon atmosphere, so changes in soil carbon have significant effects on climate change. On the other hand, factors such as climate change or changes in land use and management affect soil organic carbon changes. As soil temperature increases, the rate of organic carbon decomposition will increase, which potentially increases the average release of soil carbon dioxide emission into the atmosphere. Therefore, finding low-cost and rapid methods for estimating soil organic carbon in large ranges and predicting its changes in the future has became a necessity.Modeling is a tool that can be used to evaluate the feasibility of various land management techniques, and with the help of the results, the best methods can be selected and researched. In the field of soil organic carbon studies, the RothC model is one of the most widely used models, which is of great interest to researchers due to its simplicity and availability of inputs. Climatic changes are also investigated using the output of general circulation models (GCMs) under greenhouse gas emissions scenarios. These data are used after exponential microscale, in which Lars-WG statistical method has been used in this research.Materials and methods The purpose of this study is to investigate the status of soil organic carbon storage in agricultural lands of Golestan province and the effect of climate change on soil organic carbon storage in the coming decades. Therefore, in order to conduct this research along the northeast_southwest of the province were selected 3 points in 3 arid climates, semi-arid and Moist climate. In selected points, soil samples were collected by digging 3 profiles and several augers and soil organic carbon, soil texture and soil apparent specific weight were measured (year 2018). The Roth C model has been used to investigate changes in soil organic carbon storage in the future. Roth C model has been used to investigate future changes in soil organic carbon storage. In order to validate the Roth C model, the results of previous studies (1997 and 2004) were used. Also, the climatic data used in this project were extracted from the statistics of 1371 to 1398 weather stations of Chat, Kalaleh and Ramyan and using the output of general circulation models (GCMs), scaled by Lars WG6 model and precipitation and temperature data were predicted of future decades.Results and Discussion The study of temperature changes showed that by 2040, based on scenario 4.5, the temperature will increase between 0.6 and 0.8 and based on scenario 8.5 between 0.6 and 1.3 °C. Also, by 2080, based on scenario 4.5, the temperature increase was predicted between 1.5 and 2.3 and based on scenario 8.5 between 2.2 and 3.2 °C. Climate change in different regions can reduce, increase or no change in precipitation. According to the forecast of the third report of the InterGovernmental Panel on Climate Change, precipitation will increase in winter and decrease in the summer. Based on the findings of this study, the amount of precipitation in the studied stations will increase in the future (in 2040 and 2080) based on two scenarios of 4.5 and 8.5. The results of prediction of soil organic carbon storage show that in 2040 based on scenario 4.5 the amount of soil organic carbon storage in agricultural land use will decrease between 0.5 and 5.3 tons per hectare. Also, based on scenario 8.5, the reduction of soil organic carbon storage in these lands was predicted between 0.8 and 6 tons per hectare. Based on these results, the greatest reduction in soil organic carbon storage was predicted in the humid and rainy areas of the province in 2040. According to this research, in the three investigated stations, in 2080, based on scenario 4.5, the amount of soil organic carbon storage in agricultural land use will decrease between 1.5 and 13.1 tons per hectare. However, in this year, based on MIROC5 and MPI-ESM-MR climate models in Sufian station, we will see an increasement in soil organic carbon storage between 0.6 and 3.9 tons per hectare. Also, according the scenario 8.5, in 2080, the reduction of soil organic carbon in these lands is predicted between 0.5 and 10.5. According to these results, the greatest reduction in soil organic carbon storage in 2080 was calculated in wet and rainy areas (Ramian station).Conclusion According to the obtained results, the Rothamsted model has been able to simulate the dynamics of soil organic carbon storage in the study area with appropriate accuracy. The output of the four climate models showed that future temperature changes will increase in 2040 and 2080 based on scenarios 4.5 and 8.5. these findings are consistent with the results of most climate studies that have predicted temperature enhancement in the future decades. According to the findings of the current research, the amount of precipitation in the studied stations will increase in the future (in 2040 and 2080) based on two scenarios of 4.5 and 8.5. The results of Roth C model simulations for predicting soil organic carbon storage showed that soil organic carbon storage will decrease in 2040 and 2080 in both climatic scenarios. According to these results, with increasing of temperature, the rate of decomposition of soil organic carbon increases. Increasing the rate of decomposition in agricultural land use due to the lack of surface vegetation in periods of the year causes the waste of soil organic carbon in the form of CO2 in the upper layers of the soil. Some studies have shown that low vegetation cover (agricultural compared to rangeland) areas will be severely affected by climate change and will lead to soil organic carbon waste in these areas.
Alireza Abdollahpour; Mojtaba Baranimotlagh; Amir Bostani; Farshad Kiani; Farhad Khormali; REZA GHORBANINASRABADI
Abstract
Introduction Globally, deforestation is the dominant land use change process and has severe effects on soil biogeochemical properties. Large areas of the north facing slopes of the Alborz mountain range in northern Iran are covered by extensive loess deposits. Loess often contain little clay results ...
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Introduction Globally, deforestation is the dominant land use change process and has severe effects on soil biogeochemical properties. Large areas of the north facing slopes of the Alborz mountain range in northern Iran are covered by extensive loess deposits. Loess often contain little clay results in a loss of SOC under cultivation. Deforestation and cultivation on the loess hillslopes in northern Iran have resulted in a deterioration of soil quality, particularly significant reduction in SOC. Loess lands of Golestan province in northern Iran is densely being cultivated following deforestation. Labile fractions of soil organic matter (SOM), rather than total SOM, have been used as sensitive indicators of soils' quality and response to agricultural management changes. Several physical, chemical, and biological methods have been used to distinguish between labile (or biologically active) and recalcitrant pools of SOM. So, this research aims to investigate the effect of land use change from pristine and undisturbed forest as a reference to other land uses on soil organic carbon components and fractions as an important indicator in the sustainable soil management system and maintaining fertility and controlling soil erosion. Also, the effect of these land use changes on total carbon, soil organic carbon, and finally on the physical and chemical components of soil organic carbon.Materials and Methods The study area is the Toshan watershed, which is located in the northwest of the city of Gorgan (Golestan province) in the north of Iran. Four major and dominant types of land use were considered in the study area, including a) garden (olive), b) agricultural (cotton), c) virgin or untouched forest, d) abandoned (raspberry). Soil carbon fractionation was done by two physical methods (soil aggregate fractionation method) and chemical method (hydrolysis of organic matter with hot water). The selection of soils in different land uses was such that they have similar initial conditions and therefore the change in soil carbon in each use is related to the change in land use. The obtained data were analyzed based on the factorial design in the form of completely randomized design and using SAS software.Results and Discussion The results showed that the highest amount of total carbon and soil organic carbon was observed in the forest treatment and in the first depth (6.02% and 3.5%, respectively), which had a significant difference compared to other land use treatments studied. The results showed that despite the absence of a significant difference between the two depths, the amount of stable organic carbon increased with increasing soil depth in agricultural and abandoned uses. The forest land use had the highest amount of stable organic carbon at the depth of 0-10 cm at the rate of 2.51%, followed by garden treatment at the same depth. The lowest amount of stable organic carbon was recorded in the abandoned land use treatment. The highest amount of organic carbon dissolved in water at both investigated depths was obtained in the forest management treatments and then in the abandoned management. While no significant difference was observed between the two investigated depths in the abandoned land use. A significant decrease in organic carbon fractions that can be extracted with hot water was observed in abandoned and agricultural uses, as well as their increase in forest land uses. After the forest land use, the olive garden land use had the highest amount of total and organic carbon, however, there was no significant difference between the agricultural and abandoned treatments. In forest and garden treatments, the amount of stable carbon at a depth of 0-10 cm is significantly higher than the amount of stable organic carbon at a depth of 10-20 cm. In the garden use treatment, the amount of organic carbon in the soil at a depth of 10-20 cm showed a significant increase of 35% compared to the first depth.Conclusion A significant decrease in organic carbon fractions that can be extracted with hot water was observed in abandoned and agricultural uses, as well as their increase in forest uses. In total, the results showed that the carbon of labile fraction was more responsive to the type of land use than other fractions, and among the different methods of carbon fractionation, physical methods showed a clearer response to land use change.
M. Soleimanzadeh; F. Khormali; M. Sohrabi; R. Ghorbani Nasrabadi; M. Kehl
Abstract
Introduction Biological soil crusts are a widespread community of cyanobacteria, green alga, lichens, mosses, and other organisms. These crusts play important roles in arid and semi-arid ecosystems, such as carbon and nitrogen fixation, soil protection against water and wind erosion, and water retention. ...
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Introduction Biological soil crusts are a widespread community of cyanobacteria, green alga, lichens, mosses, and other organisms. These crusts play important roles in arid and semi-arid ecosystems, such as carbon and nitrogen fixation, soil protection against water and wind erosion, and water retention. In arid and semi-arid regions, the biological soil crusts also possess a key role in the global carbon cycle due to the carbon fixation (photosynthesis) and its release (respiration) into the atmosphere. These organisms increase the organic carbon content of the soil in arid and semi-arid regions by performing photosynthesis. Soil organic carbon is a mixture of various components and one of the important characteristics for soil quality evaluation. Biological attributes of soil quality include many soil components and processes related to the organic material cycle, such as total organic carbon and nitrogen, microbial biomass, carbon and nitrogen mineralization, labile fractions of elements, the activity of enzymes, and animals and plants in soil. These biological attributes respond rapidly to natural and human-derived changes, and therefore they are used as indices for quality of soils. Biological soil crusts are the main cover of the loess soil surface in the northern parts of Golestan Province. The region that was selected to be studied in the province was Maraveh Tappeh. This region has arid and semi-arid climate and is attributed to low vegetation, especially on the slopes to the south. In these slopes, biological and physical crusts are dominant. Therefore, a study was conducted to investigate the effect of lichen biological soil crusts on organic carbon and different fractions of labile carbon. Materials and Methods After extensive field studies, two species of lichen biological soil crusts were collected and transferred to the laboratory for identification. The results elucidated that the studied species were Diploschistes Diacapsis (Ach.) Lumbsch, and Fulgensia Fulgens (Sw.) Elenk, based on taxonomical identification. Soil sampling was done from 0-2 and 2-5cm depths under lichen biological and physical crusts. Soil samples were transferred to the laboratory, and then the organic carbon, carbohydrate, permanganate oxidizable carbon, microbial biomass carbon, cold-water extractable organic carbon, and hot-water extractable organic carbon were measured by standard methods. Results and Discussion Results show that lichen biological soil crusts led to the increase in soil organic carbon and different fractions of labile organic carbon related to the physical crust. As a result, the highest values for these traits were observed in soils affected by lichen biological soil crusts. Soil covered by the Diploschistes Diacapsis species had the highest amount of soil organic carbon and different fractions of labile organic carbon in comparison to the Fulgensia Fulgens species in 0-2cm depth, which had a significant difference at 5% probability level. the physical crusts had the least amount of soil organic carbon and different fractions of labile organic carbon related to the lichen biological soil crusts, which was caused by the loss of topsoil and the lack of biological coverage. There was a positive correlation between the measured traits. There was a high correlation between hot water-extractable carbon and carbohydrate. There were high correlation coefficients between organic carbon with microbial biomass carbon, hot water-extractable carbon, and carbohydrate. In general, there was a high correlation coefficient between hot water-extractable carbon with organic carbon and other labile fractions of organic carbon except for cold water-extractable carbon, whereas there was low correlation coefficient between hot water-extractable carbon with organic carbon and other labile fractions of organic carbon. Conclusion According to the results attained from the following study, the presence of biological soil crusts on loessial soils led to the increase in organic carbon, carbohydrate, permanganate oxidizable carbon, microbial biomass carbon, cold-water extractable organic carbon, and hot-water extractable organic carbon. Diploschistes Diacapsis Species have the highest impact on organic carbon and different fractions of labile organic carbon. The High correlations show that the best attributes to evaluate the quality of soil organic carbon in the studied area are microbial biomass carbon, carbohydrate, and hot water-extractable carbon and these may be used as a good indicator to evaluate soil quality. The studied area falls within the arid and semi-arid climate, and given the erosion-prone nature of loess deposits, improper management may lead to severe problems, such as erosion and dust production. Hence, protecting lichen biological loess crusts against human activity and livestock grazing may result in lower water and wind erosion, and increase soil quality in this region.
Micromorphology and Clay mineralogy
Masoumeh Pourmasoumi Parashkouh; Farhad Khormali; Shams Ollah Ayoubi; Farshad Kiani; Martin Kehl; Eva Lehndorff
Abstract
Introduction The loess-paleosol sequences in Northern Iran are important archives that represent several cycles of Quaternary climate change and can be used to complete the information gap on loess between Europe and central Asia. Last interglacial soils derived from loess in northern Iran is represented ...
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Introduction The loess-paleosol sequences in Northern Iran are important archives that represent several cycles of Quaternary climate change and can be used to complete the information gap on loess between Europe and central Asia. Last interglacial soils derived from loess in northern Iran is represented by strongly developed Bt horizons of forest soils. In Golestan and Mazandaran area, soils under the forest are mainly classified as Alfisols or Luvisols. Interestingly, E horizons are generally not found in these soils. In the Caspian Lowlands, a pronounced precipitation gradient is reflected in mean annual precipitation rates decreasing from about 1850 mm at Bandar Anzali in the west to about 435 mm at Gonbad- e Kavoos in the east. The results of the loess climosequence in Northern Iran showed that with increasing precipitation, soil pH and calcium carbonate contents decrease, whereas soil organic carbon, clay content, and cation exchange capacity increase. For years, many efforts to quantify the soil properties led to the provision of indices of soil development. Among these indices are forms and ratios of iron, morphological, and micromorphological indices. Many studies have been carried out on the loess-paleosol sequences and modern loess soils in Northern Iran with focus on micromorphology, mineralogy, and dating but more investigation is needed with an emphasis on the forest soils with well-pronounced clay illuviation as a proxy for paleo-moisture. For this purpose, we used micromorphology and soil color indices to report the effects of precipitation gradient on the variability in the formation of soils under forest vegetation. Materials and Methods The study area is located at the northern slopes of Alborz Mountain Ranges, covered with Caspian or Hyrcanian deciduous forests. Field sampling started in summer 2015. More than ten soil pedons with loess parent material were investigated based on former studies. Finally, six representative modern pedons were selected and dug in an east-west direction on loess deposits. The climate data shows that precipitation varies from 500 mm in Qapan (Pedon 1) to up to 800 mm in Neka. Physiochemical properties of soils were studied using standard methods. Thin section prepared for soil micromorphological studies were studied and interpreted based on Bullock et al. and Stoops guideline using a polarizing microscope. The micromorphological index of soil development (MISECA), suggested by Khormali et al (2003), was calculated. Also, color indices were calculated based on Hurst (1977), Torrent (1983), and Alexander (1985) by using the Munsell color chart. In all color indices, Munsell color hue converts to a single number. Results and Discussion The results showed that the downward decalcification and the subsequent clay illuviation were the main criteria influencing the assessment of soil development in this study. So, all of the soils host argillic and calcic horizons and are classified as Alfisols and Mollisols. Micromorphological studies confirmed the morphology studies in the field and the results of physico-chemical analyses. MISECA index showed pedological changes in different pedons in the studied areas. A significant positive relationship between climate gradient (increasing rainfall) and MISECA index was found. The area and thickness of clay coatings show an increasing trend with rainfall. Occurrence and preservation of clay coatings are more pronounced in more humid regions with illite and vermiculite as the dominant clay minerals. These minerals reduce the shrink/swell potential and increase the number of clay coatings present. In Argillic horizons of all pedons, except Toshan, dominant b-fabric is speckled due to carbonate leaching, while in Toshan, it is striated b-fabric. In calcite horizon, b-fabric is crystallitic. The correlation of various forms of iron with three color indices of Hurst, Torrent, and Alexander showed that Torrent and Alexander indices were better than the other one for the study area. Moreover, there was a good correlation between MISECA and Torrent color index. Conclusion The results showed that the soil evolution in the studied areas is strongly influenced by soil formation factors, especially in a climate which shows a change in the micromorphological characteristics of soils. With increasing the rainfall from the east to the west in this gradient, the amount and thickness of clay coating, as well as secondary calcium carbonate accumulation, change significantly. In addition, the micromorphological and color indices of soil evolution can be used as two indicators for assessing the effects of rainfall gradient on soil formation in northern Iran. On the other hand, knowledge of the development of modern loess-derived soils could help to better understand the paleoenvironment.
Soil Chemistry and Pollution
Narges sousaraeS; Mojtaba Baranimotlagh; Farhad Khormali; Esmaeil Dordipour
Abstract
Introduction Biochar is a charcoal, pyrolyzed from a wide range of carbon-rich biomass materials, such as crop and wood residues, animal manures and a range of industrial wastes and once added into soil, it can store the soil carbon for a long period, improve the soil structure and increase the crop ...
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Introduction Biochar is a charcoal, pyrolyzed from a wide range of carbon-rich biomass materials, such as crop and wood residues, animal manures and a range of industrial wastes and once added into soil, it can store the soil carbon for a long period, improve the soil structure and increase the crop yield. However, the physical and chemical characteristics of biochars are influenced by the properties of the feedstock and pyrolysis conditions, such as highest temperature treatment and furnace residence time. Considering the large variation in biochar properties, it is not surprising that crop yields vary with different biochars. We investigated the effects of biochars on corn growth in the greenhouse. The specific objectives were (a) to assess whether feedstock properties or pyrolysis temperature are important in preparing of biochar and (b) to quantify the effects of varying biochar characteristics on corn growth and chlorophyll index in a calcareous soil under greenhouse condition. Materials and Methods Biochar was produced from crop residues including rice, cotton and canola. Feedstock was oven-dried before pyrolysis. The pyrolysis process was conducted for 1 h at 10°C min‒1 heating rate to produce biochars at different temperatures of 350 and 700 oC under oxygen-limited conditions. All biochars were ground and passed through a 2-mm sieve before experimentation. Ash content and char yield was calculated and biochar pH and electrical conductivity (EC) were measured using 1:20 solid: solution ratio. The soil used in this experiment was taken from the Research Farm of Gorgan University of Agricultural Sciences and Natural Resources. The soil was air-dried and ground to pass through a 2-mm sieve then analyzed for various soil physico-chemical properties using standard methods. A greenhouse experiment was set up using pots with 5 kg prepared soil. Various treatments comprising of 3 biochars type produced at different pyrolysis temperatures (350 and 700°C) from three crop residues (rice, cotton and canola) at three application rates (0, 2 and 5% w/w). A completely randomized design was used in factorial arrangement and treatments were replicated four times. After the soil had been prepared and biochar added, six seeds of maize were planted approximately 20 mm deep in the center of the pots and thinning to seedlings of four plants pot‒1 was done at plant establishment. Distilled water was used to maintain moisture contents of the soil in all the pots during the experimental period. Plant stem and leaves were harvested 96 days after planting. Washed with distilled water then dried with tissue paper. The leaf and stem samples were air-dried and then oven dried at 65˚C to a constant weight in a forced air driven oven. The studied traits included leaf and stem fresh and dry weight, plant height, number of leaves, time to first flowering, chlorophyll index (SPAD), concentration of chlorophyll a, chlorophyll b and total chlorophyll. The analysis of variance (ANOVA) with the factors biochar type, application rate and pyrolysis temperature were performed using a completely randomized design. Significantly different treatment means were separated using least significant difference (LSD) test at PResults and Discussion The results showed that pyrolysis temperature significantly influenced the measured chemical properties of biochars. EC values were tended to increase with pyrolysis temperature. The pH of the biochars was also influenced by temperature. Biochars pH ranged from 6.8 to 9.6. The pH of the biochars was increased with increasing temperature and highest pH (9.6) was observed at 700°C of rice residues. These increases in pH values are mainly due to separating of alkali salts from organic materials by increased pyrolysis temperature. The results showed that the yield of biochars was reduced by increasing pyrolysis temperature and ranged from 19.4% to 40.1%. This decline in yield content is mainly due to the destruction of some compounds such as cellulose and hemicellulose as well as combustion of organic materials with increased pyrolysis temperature. By contrast to biochar yield, the biochar ash content increased with increasing pyrolysis temperature. The lowest values of leaf and stem fresh and dry weight was observed at 700°C of canola residues. These results suggest that biochar produced at high pyrolysis temperature (especially at 700°C), when applied to the soil, may increase soil salinity and subsequently provide undesirable impacts on the plant growth. It has been reported that the negative impacts of high salinity on the plant growth could be due to the following reasons: (1) the low osmotic potential of the soil solution, resulting in water stress, (2) specific ion effects, resulting in salt stress, and (3) nutrient imbalances. Addition of each three types of biochars caused a significant increase in chlorophyll concentration compared to control. Conclusion The type of feedstock material is an important factor that determines the final application of the biochar and its effect on plant growth papameters. Therefore, there is further need for research focusing on the effects of biochar addition on soil properties and plant growth in order to assess biochar as a valuable resource for agriculture.
Soil Genesis and Classification
Mehdi Taheri
Abstract
Introduction During the last decade, considerable progress has been made in the study of known loess deposits and their paleoclimatic implications in Northern Iran, whereas little information is available about the red soils which are beneath the these loess. So, in this study, major and trace element ...
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Introduction During the last decade, considerable progress has been made in the study of known loess deposits and their paleoclimatic implications in Northern Iran, whereas little information is available about the red soils which are beneath the these loess. So, in this study, major and trace element concentrations were analyzed on the samples from a red sequence of Iranian Loess Plateau at Golestan province. The main objectives of this research are a) to address the origin of the red soils with compare to the other geochemical results such as upper Pleistocene loess-paleosol, upper continental crust and Jiaxian Red Clays in China, b)to examine the geochemical behaviors of certain elements and their ratios such as Al2O3/Na2O, Na2O/K2O, MgO/TiO2, Rb/Sr and Chemical Index of Alteration (CIA) during pedogenesis and finally, to reconstruct the early Pleistocene climate. Materials and Methods This study was carried out on a 19-m-thick sequence of deposits exposed in a limestone quarry located near the Agh Band village of Golestan province in the east of the Iranian Loess Plateau (latitude 37.688889 N and longitude 55.158333 E). The so-called Agh Band red sequence underlies an upper Pleistocene loess-paleosol sequence and covers yellow limestone of the Akchagyl formation belonging to the Upper Pliocene of Kopet Dagh sedimentary basin. It is the first sequence one of red soils described for the loess plateau of Iran. Based on the paleomagnetically dating, this section is formed during ~2.4-1.8 Ma. The present-day climate of the study area is semi-arid, with mean annual precipitation and temperature of ca. 300 mm and 17◦ C, respectively. The soil moisture regime is Xeric-Aridic and the temperature regime is Thermic. In a field campaign in autumn 2014 the morphological characteristics of the section were recorded. Based on field observations, the sequence has been subdivided into 24 units, designated consecutively as U1-U24 from the top of limestone to the bottom of the Upper Pleistocene Loess. From each unit, representative samples were taken for color measurements, grain-size and geochemical analysis. Each air-dried sample was gently crushed, taking care not affect the grain size, and then measured using a Konica-Minolta CM-700 color meter. Grain size was measured using a Malvern Mastersizer 2000 laser grain-size analyzer following the pre-treatment procedures described in the text and the concentrations of major and trace elements were determined using a PANalytical PW2403/00 X-ray fluorescence spectrometer. All of the measurements were made in the Key Laboratory of Western China’s Environmental systems, Lanzhou University. Results and Discussion The grain-size distribution of the red section is dominated by fine-grained silts with the average of 86.6 percent, in addition, the amount of clay and sand are 10.9 and 2.6 percent, respectively. Angular or sub-angular blocky structures are dominated in the red sequence. The section is mainly characterized by alternations of reddish yellow )10 YR 6/6) and brownish-red (7.5 YR 3/6) to reddish (5YR) layers. In general, the color of the soil horizons in the red deposits is much redder than that in the overlying loess (7.5YR vs.10YR, respectively), and this is one of the principal differences between the red soils and the overlying loess. Another different is the amount of carbonate nodules and the size of them (up to~20 cm diameter). These soils have been subjected to relatively intensive pedogenesis, as demonstrated by the presence of clay skins and Fe-Mn coatings. The high correlation of major and trace element compositions between Agh Band red soils section, upper loess and paleosol and the Jiaxian red clay in China supports the proposal that the Agh Band red soils was wind-blown in origin. The value of CIA index (69.6 for red soils versus 59.8 for the upper loess deposits), Al2O3/Na2O, K2O/Na2O and Rb/Sr ratios are higher in the red deposits than in the upper Pleistocene loess, also, the lower amount of MgO/TiO2 ratio in reddish soils, suggesting stronger chemical weathering and thus a wetter climate during the formation of red soils in early Pleistocene. Conclusion Finally, our main findings are as follows: 1) The geochemical composition of the red-colored sedimentsis similar to the overlying upper Pleistocene loess suggesting a similar origin; 2) wind-blown origin of the red deposits and continuous atmospheric dust deposition in the Iranian Loess Plateau during the Early Pleistocene; 3) red soil sequence formed under wetter and more humid climate compared with the Upper Pleistocene loess.
Micromorphology and Clay mineralogy
masoomeh najafinia; Fashad Kiani; mojtaba Baranimotlagh
Abstract
Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past ...
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Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that these sediments have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Extensive sedimentological and chronological studies have been carried out on the middle to upper Pleistocene loess during the past decades, but it is necessary to do a comparative research on the older loess deposits. So, this study aimed to conduct a mineralogical and physicochemical investigation on the early Pleistocene loess and to compare it with modern loess soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan. Materials and Methods The study area is located in a hot and dry climate in loess Plateau east Golestan. According to the previous studies, a total of six profiles were excavated and studied. Then, physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Clay separation was carried out with a specific method to separate the clay as well as identification of clay minerals. After preliminary field observations and determining the horizons for each profile in the region, soil classification was done based on soil taxonomy and WRB. Then, soil samples were prepared from each horizon for physicochemical and mineralogical studies in sufficient quantities. Results and Discussion Comparing the results of physicochemical properties (such as color, lime percentage, the cation exchange capacity and the ratio of iron, etc.) in paleosol and modern loess soils indicates that in paleosol soils, soil forming processes have passed several stages. Clay mineralogy is a good indicator for past climate change studies in loess.The existence of the arglic horizons and the evolved calcic in paleosols and their absence, in comparison with the modern soils in which they are present, indicate the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region, this color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Decrease in the amount of annual precipitation in the region, compared to the past, has led to decreased smectit and increased chlorite. Therefore, presence of smectit cannot be attributed to the present situation of the region. The presence of these clay minerals in paleosols can be due to wet weather conditions as well as weathering of clay mineral deposits. On the other hand, the dominance of less weathered clay minerals such as illite and chlorite in the late Pleistocene modern loess soils is correlated with the present dry climatic conditions. Conclusion The simultaneous presence of modern and old loess soils in the studied areas demonstrates the general evolution of geographical and climatic conditions during the Pleistocene period which has altered the properties of these layers and ultimately left out the effects of high clay conditions, which is a combination of climatic evidence and intermittent pedogenic soil formation processes. The presence of early Pleistocene loess soils between late Pleistocene loess sediments in Golestan province and the conditions of the study provided pedological and mineralogical comparisons of modern and paleosols in these areas and the results clarified a part of the climate change in northern Iran. The past climate study allows for prediction of the current and future climate change process. Therefore, a more accurate study of clay minerals as the key to all soil behaviors and past climate change in different parts of the eastern Golestan plateau can be very useful in completing studies of evidence of past climate change in paleosol soils
Soil Chemistry and Pollution
Somayeh Sefidgar shahkolaie; Mojtaba Baranimotlagh; Farhad Khormali; Esmael Dordipour
Abstract
Introduction At present, contamination of water and soil resources is an important environmental challenge. Therefore, decontamination of such is a prerequirement for using these resources. Cadmium (Cd) and lead (Pb) often coexist in contaminated soils and there is currently no effective means for their ...
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Introduction At present, contamination of water and soil resources is an important environmental challenge. Therefore, decontamination of such is a prerequirement for using these resources. Cadmium (Cd) and lead (Pb) often coexist in contaminated soils and there is currently no effective means for their concurrent removal. Concerns about their mobility and bioavailability have increased because of food safety, potential health risks and its detrimental effects on the ecosystems. The stabilization/solidification is a cost effective remediation method that prevents spreading of heavy metals in soil and water resources. In this process, contaminated soil reacts with amendments such as organic and liming materials to form low soluble or non-soluble stable materials. The objective of this study was to evaluate the effect of several low cost amendments on Cd and Pb stabilization by a sequential extraction method. Materials and Methods In this research, 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 and Cd stabilization in a contaminated soil, an incubation experiment was carried out. One kilogram of each amended soil and the control soil were packed into respective pots. Soils were amended in the laboratory using biochar 640 (BI1), biochar 420 (BI2) bentonite (BE), pumice (P), leca (LE), and zeolite (Z). A control treatment (C) without adding amendment was also prepared. The amendment materials were applied at 1 and 5 percent wt. Each treatment was performed in three replicates and the samples were incubated in the dark at 14°C for 6 months. At the end of the incubation time, the potential bioavailability of Cd in non-amended and amended soils was evaluated by extraction with DTPA and ethylenediamine tetraacetic acid (EDTA). Total Cd (CdT) and Pb (PbT) was extracted by aqua regia (HNO3 + HCl) extraction. The chemical fractions of Cd and Pb were determined by a sequential extraction method which is a five-step chemical fractionation based on the work of Tessier et al. (1979). 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 additions of amendments to soils reduced the concentration of DTPA and EDTA-extracted Pb and Cd. The smallest concentration of Pb-extracted DTPA and EDTA was observed in organic amendments treated soil (biochar 640°C, and biochar 420°C) and treated with 5% biochar 640°C, respectively. The high sorbent capacity of the BI used in this study could be due to its high pH, high content of organic carbon and cation exchange capacity (CEC). The highest decreasing rate of DTPA and EDTA-extractable of Cd was observed in treated with 5% pumice and zeolite, respectively. Application of the amendments (except for 1% LE) decreased exchangeable fraction (F1) of Pb compared to the non-amended soil. Also, the amendments (except for 1% P, Z and BE) decreased exchangeable fraction (F1) of Cd compared to the non-amended soil. Although the biochar 640 (5%) showed the highest decreasing rate of exchangeable fraction (F1) of Pb and Cd, they increased the oxide (F3) and organic (F4) fractions, which might be due to its rich O-containing functional groups and high alkalinity leading to an increase in the binding of Cd and Pb to organic compounds and mineral oxides. Conclusion Results indicated that application of amendments was successful in lowering the potential bioavailability of Pb and Cd soils. The 5% biochar 640 treatment had the greatest decrease in extractable Pb. Also, the 5% zeolite and pumice treatment had the greatest decrease in extractable Cd. Application of BI resulted in a significant decrease in both Pb and Cd exchangeable fraction (F1). This reduction in the exchangeable fraction (F1) of Cd and Pb in the soil was due to an increase in the fraction of heavy metals bound to the soil organic matter (F4) oxides (F3) after BI addition. Enhanced precipitation or co-precipitation and complexation of metals with amendments led to the reduction of the solubility of the metals. The P, LE, BE, and Z altered the exchangeable fraction (F1) of Cd and Pb to the oxide fraction (F3) and the carbonate fraction (F3), respectively. Application of BI amendment causes the highest decreasing rate of solubility Cd and Pb, suggesting this as the suitable amendment for the remediation of Cd and Pb in contaminated soils.
Soil Genesis and Classification
Maryam Mohammadzadeh Mohammadabad; F. Khormali; Farshad Kiani; mohammad ajami
Abstract
Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties ...
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Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties and biological capabilities of soil. The investigating of undisturbed and natural soil structure using microscopic and ultramicroscopic techniques provides invaluable information about the physicochemical, mineralogical, morphological properties and soil genesis and calcification. Image analysis is an advanced method for quantifying soil properties and increasing the precision of morphological and micromorphological studies. Materials and Methods In this study, in order to investigate the impact of different land uses on porous and microstructure of surface soil horizons, 9 profiles in different land uses, including natural forests, artificial forest, abandoned land, orchard and cropland were extracted and described. Then one sample was taken from each horizon for physical and chemical analysis as well as a few undisturbed samples for micromorphological studies. Physical and chemical parameters such as texture, bulk density (BD), calcium carbonate equivalent (CCE), organic carbon (OC) and mean weight diameter (MWD) were measured. After preparation of thin sections of soil, micromorphological studies were conducted by polarizing microscope. Then from each thin section, 20 photos were taken randomly in plane polarized light (PPL) and cross polarized light (XPL) and transferred to image tool software. The percentage of total porosity of soil, feret diameter and area pores parameters were studied quantitatively. Three classes of feret diameter in micrometer and five classes of area in square micrometers were considered for pores in the soil thin sections. After importing photos to the software and performing calibration, grayscale and subtracting two images, the range of pores was identified by the software. Then in the classification section of software, the highest level of classes in each part was determined and the percentage of pores in each class was calculated and data obtained were analyzed by SPSS 16.0 software. Results and Discussion Micromorphological observations showed that in natural and artificial forests, a significant amount of organic matter in the soil has resulted in the formation of granular and subangular blocky dominant microstructure. While in cropland land use the type of microstructure is mainly massive and angular blocky, due to deforestation and agricultural practices, which resulted in the degradation of soil microstructure. Appropriate environmental conditions and dense vegetation in natural and artificial forests land use lead to significant biological features in comparison to other land uses that were subjected to deforestation. In natural and artificial forests land uses, the percentage of channel and large vughs pores is more than other land uses mentioned above. Tillage results in degradation of soil structure in cropland land use, the majority of pores observed in thin section are vugh and plane. Also, the results of image analysis showed that in natural forests and orchard land uses, pores with diameters ranging from 2 to greater than 10 micrometer and areas ranging from 500 to greater than 1000 square micrometers had the highest frequency in terms of percentage of soil pores. Hence, these soils are considered as quite porous class, while in cropland land use, tillage results in the degradation of large pores showed that pores with diameters less than 2 to 10 micrometers and areas smaller than 5 to 50 square micrometers comprised and the highest percentage of soil pores. Conclusion Asignificant amount of organic matter and low bulk density, and the highest percentage of total porosity are found in natural forest and orchard land uses, while deforestation and cultivation in cropland land use has led to compression and destruction of soil structure. This fact reflects itself in the increased bulk density and decreased total porosity. Agricultural practice has a significant effect on destruction of surface soil structure. Microstructure and voids of cropland land use are mainly massive and angular blocky and plane and vughs, respectively. With changes of land use from forest to cropland, and consequently incorrect land management causes decrease in organic matter. Shortage of organic matter causes decreasing biological activity in surface soils. The best way to prevent degradation of the soil in this area is to preserve natural forests and change cropland land use to orchard and artificial forest land uses.
Micromorphology and Clay mineralogy
masoomeh najafinia; Farhad Khormali; Farshad Kiani; mojtaba Baranimotlagh
Abstract
Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past ...
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Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that Early Pliestocene loess (Reddish loess) have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Micromorphology is an important technique to identify and interpret the loess- paleosol for paleoclimate studies. Microscopy is a method of studying undisturbed soil samples with the help of microscopic techniques (and sometimes with ultramicroscopic ones), in order to identify their constituents, determine their mutual relations in space and time and interpret their formation conditions. Micromorphology uses these characteristics to make interpretations, generally on the soil formation processes. This study aimed to conduct a micromorphological investigation on the early Pleistocene loess and to compare it with the modern loess derived soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan. Materials and Methods The study area is located in semiarid climate in loess Plateau east Golestan. Six profiles were selected and studied. Physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Then, soil samples were prepared from each horizon for micromorphology studies. For micromorphological studies, thin sections were prepared from undisturbed, oriented and dry clods by standard methods and described under a polarizing optical microscope. Results and Discussion Comparing the results of physicochemical properties (such as color, carbonate percentage, the cation exchange capacity, etc.) in paleosol and modern loess soils indicates that the in paleosols, soil forming processes have passed several stages. The existence of the argillic horizons and the evolved calcic in paleosols and their absence in the modern soils in which they are present, indicates the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region. This color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Reducing annual precipitation decrease soil pedogenesis. Conclusion Comparison of the results obtained from paleosols of early Pleistocene with modern soils indicates that the time and climate change caused alterations in the soil micromorphology features (such as the type and amount of pores, soil structure and b-fabric and pedofeatures etc.). One of the most important pedofeatures was clay coating around void, presented only in buried paleosols, which is the evidence for moist climate conditions and subsequently enough leaching for clay translocation. Further, the presence of planar void caused by shrink and swell of clay is evidence for evolution in the paleosols. In argillic horizons of paleosols, dominant b-fabric is speckled due to carbonate leaching while in calcite horizon, it is crystallitic b-fabric. The micromorphological index of soil development calculated, showed that these red-colored deposits are formed under an annual precipitation of about 450- 650mm which represents more humid conditions at the time of their formation than the modern loess soils. In modern soils derived from recent loess, lack of clay coating can be a reason for weakly developed soil formation.
Soil Biology, Biochemistry and Biotechnology
S. A. Hosseini; mhsen olamaee; S. A. Movahedi Naeini; F. Khormali; R. Ghorbani Nasrabadi
Abstract
Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many ...
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Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many fields. Cultivation and lack of the application of potassium fertilizers in agricultural soils of Iran have caused the depletion of potassium and the amount of available potassium in most soils has reached below the critical level. The compensation of depleted potassium in the soil through indigenous resources and use of potassium bio-fertilizers is therefore very important. Weathering of silicate minerals by bacteria is considered as one of the essential K source for plant growth and development. The objective of this study was to isolate and identify potassium solubilizing bacteria from the shale containing glauconite mineral in Golestan Province and determine some traits related to plant growth promotion and selecting a superior strain in order to incubate in wheat lands. Materials and Methods Accordingly, a total of 5 samples 1 kg of rhizosphere of wheat from a depth of 0 to 30 cm and 5 samples 1 kg from shale stone (containing glauconite) were collected from Aitamir formation in Golestan Province in May 2015 and were transferred to the laboratory of Gorgan University of Agricultural Science and Natural Resources. Isolates were transferred to Aleksandrov media containing glauconite and muscovite and incubated for 10 days and the isolated strains were stored in the refrigerator at 4 oC. The amount of potassium release in solutions after 10 days was measured. Some biochemical and morphological properties of isolates were determined based on standard methods. PGPR tests were done in the isolates which were morphologically different and had high potential in releasing K. Finally, a strain whith high ability in releasing potassium and growth promoting properties was identified using nucleotide sequence of 16S rRNA gene. Results and Discussion Results showed that 40 strains from the first stage, 20 strains from rhizospherial soil and 20 strains from the soil resulting from glauconite mineral powders were isolated. Biochemical and potassium release tests showed that the highest released potassium was related to isolate No. 39 with an amount of 34.2 mg l-1 in muscovite, and 31.8 mg. l-1 in glauconite. The amount of siderophore produced in the superior strains showed that the lowest and the highest ratios of the diameter of the colony, were 1.12 and 3.1 related to isolate No. 19 and No. 39, respectively. The highest and the lowest auxins produced were also related to the isolate No. 39 and No. 27 with the amount of 52.25 and 5.15 mg per liter, respectively, measured at 72 and 96 hours. The results showed that the soluble phosphorus between different isolates was significantly different (P <0.05), its greatest concentration at 72 hours was related to isolates No. 39 with an amount of 295 mg per liter and the lowest at 24 hours was related to isolate No. 31 with an amount of 80 mg per liter. Also, the production of hydrogen cyanide test showed that none of the isolates was capable of producing siderophore. The obtained results from nucleotide sequence of 16S rRNA gene showed that the selected strain belonged to Arthrobacter phenanthrenivoran species. Conclusion It can be concluded that silicate bacteria contribute to the dynamics and mineralizing of elements in the soil and eventually K release from glauconite containing shale minerals mainly by reducing rhizosphere pH, the secretion of organic anions and complex formation with the surface cations of mineral and secreted extracellular Polysaccharides and soluble compounds and decomposition of soil organic matter. Among 40 isolated strains and the various tests and the results of released potassium in both minerals, the results showed that the potential of potassium releasing was different between the tested strains. Moreover, this study showed that in addition to the effect of these strains on potassium releasing, siderophore production, auxin and inorganic phosphate solubility, they can be effective in plant growth and in land inoculation. This study revealed the potential of indigenous bacteria species in the release of K from shale containing glauconite. It is anticipated that shale containing glauconite can provide a part of the need of the crops for potassium.
H. Tazikeh; F. Khormali; A. Amini; M. Barani Motlagh
