Soil Chemistry and Pollution
Mina Hashemi Tazangi; Soheila Ebrahimi; Reza Ghorbani Nasrabadi; Seyed Alireza Movaheddi Naeeni
Abstract
Background and objectives: Hydrocarbons derived from petroleum and gas have gained increased attention as the most important fossil resources of energy as well as crude material for petrochemical industries. However, environmental issues such as pollution due to extraction, exploitation and transportation ...
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Background and objectives: Hydrocarbons derived from petroleum and gas have gained increased attention as the most important fossil resources of energy as well as crude material for petrochemical industries. However, environmental issues such as pollution due to extraction, exploitation and transportation of these materials has raised concerns as an environmental warning. In recent years, utilization of biochar (via biomass burning) has been regarded as a soil refiner to reduce or eliminate pollution, especially in in situ studies. Biochar is a product rich in carbon, which is produced during the pyrolysis of various types of woods, fertilizers, leaves, straws as well as agricultural wastes under abiotic conditions. It seems that biochar can be suggested as a suitable compound to manage biomass wastes as well as to enhance soil fertility. Thus, kinetic behavior of biochar in reduction of gasoil pollution of soil, its changes of this pollutant over time and changes in the microbial activity in this time period were investigated.Materials and methods: The soil polluted with gasoil was collected from the vicinity of the gasoil tanker located in Shiraz refinery. The soil had been polluted for years due to the leakage of gasoil. Then, after the measurement of the initial total petroleum hydrocarbon content and physical and chemical properties (soil texture via hydrometry, electrical conductivity in the saturated paste, available phosphorous using the Olsen method, total nitrogen using the Kjehdahl method, pH of soil in the saturated paste, soil carbon using the Walkey and Black method) of the polluted soil, 700 gram soil samples containing wheat straw biochar at one and two mm sizes and 20, 40, 60, 80 and 100 g kg-1 weight doses were prepared as split-split-plot experiment based on a completely randomized design with three replicates. The samples were then rested in a 50% constant humidity for four weeks at 28 ± 2 °C, and were aerated two times a week. Finally, the results of the changes in the total petroleum hydrocarbon and microbial activity over time were recorded. A three- parameter sigmoidal function was fitted to the data related to the total petroleum hydrocarbon and microbial activity over time. Analysis of variance was carried out using the SAS software v. 9.0. The leas significant difference method (LSD) was used to compare the means. The changes in the total petroleum hydrocarbons and microbial activity were analyzed using the SigmaPlot software v. 12.5. Microsoft Excel v. 2013 and SigmaPlot v. 12.5 were used to draw the figures. Results: According to the results of the present study, the application of biochar had a significant effect on the reduction of gasoil pollution of the soil. The results related to determination of the kinetic model for the reduction of pollution during the biochar application process showed that the kinetic of reduction in total petroleum hydrocarbon was of first order equation; so that in the first 28 days of the experiment, the rate of total petroleum hydrocarbon degradation was increasing, whereas it decreased 35 days after the beginning of the experiment. Biodegradation constant (k) was higher for the soil treated with the refiner and these soils had a lower half-life compared with the polluted control. The rate of reduction in half-life and Biodegradation constant rate increased with increasing refiner weight. On the contrary, half-life increased and Biodegradation constant decreased with increasing refiner size. The results indicated a significant difference in the traits as a result of applying various sizes and weights of refiner. Weekly monitoring of the pollution degradation and bioremediation performance in all refiner sizes and weights showed that the lowest time to 50% pollutant removal was obtained in 100g kg-1 and 1 mm size treatment. Investigation of the respiration under the mentioned conditions showed that the lower sizes and higher weights of biochar led to improved hydrocarbon degradation. Also, according to the results, biological efficiency (E%) of biochar was calculated 40.05 at the end of the 60 day period.Conclusion: According to the present study, biochar refiner has a great potential for utilization as a cheap and relatively new strategy to eradicate or reduce soil hydrocarbon pollution. This method is compatible with the in situ bioremediation in the soils polluted with petroleum and other petroleum derivate compounds, due to being less costly and posing less hydrocarbon threat to the environment. It is also a suitable tool to devise bioremediation strategies.
Parisa Khajeh; Mina Taghizadeh
Abstract
Introduction Sansevieria trifasciata is a perennial plant from the liliaceae family, which originates from tropical and semi-tropical regions of the world. Sansevieria trifasciata variateis are one of the most popular ornamental indoor plants due to having types with striped leaves. Today, conventional ...
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Introduction Sansevieria trifasciata is a perennial plant from the liliaceae family, which originates from tropical and semi-tropical regions of the world. Sansevieria trifasciata variateis are one of the most popular ornamental indoor plants due to having types with striped leaves. Today, conventional propagation methods are not adequate to meet the marketable requests of Sansevieria trifasciata due to the slow growth of cutting. So, it is conceivable to use rooting and growth stimulator agents. This study aimed to investigate the effects of arbuscular mycorrhiza and biochar application on some morphophysiological parameters in Sansevieria trifasciata var. cuttings.Materials and Methods This research was conducted in the greenhouse of the faculty of agriculture and environmental science of Arak University with controlled conditions of 25 ◦C, 70% humidity and 10,000 lux of light. The effect of biochar application (5 and 10%) and arbuscular mycorrhizal fungi (Glomus etunicatum, Glomus intraradices, Glomus mossea) (6 and 12%) was investigated on propagation and growth of Sansevieria trifaciata var. Laurentii and Sansevieria trifaciata var. Moonshine cutting. The experiment was conducted as factorial an in a completely randomized design at three replicates. The leaf cutting with V-shape end were keep on the lab condition for two days to callus initiation of wound surface. Subsequiently, healed cutting were cultured in pots that were containing cocopeat-perlite and different treatments of arbuscular mycorrhiza and biochar. Morphological and physiological traits were measuremed after 8 months of cultivation, which were included rooting and bud stimulation time, roots number and length, length of the longest root, buds number, length, anddiameter, the amount of cutting rot, the number of leaves, the size of callus based on the rating of 1 to 3, fresh weight (FW) of roots and leaves, the dry weight (DW) of roots and leaves, relative water content (RWC), electrolyte leakage, chlorophyll pigment. Arbuscular mycorrhizal root colonization was determinded by grid-line intersect method. Results and Discussion The results showed that the application of 10% biochar in culture bed had an increasing effect on leaf number, root biomass percentage, root colonization percentage and leaf dry weight in both cultivars but also caused to increase the decay rate of the cuttings of these two cultivars. Application of 6% arbuscular mycorrhizal fingi increased the number of buds, root colonization and bud motivation time, and led to decrease leaf biomass and cuttings rot percentage. The root colonization decreased at lower application level of arbuscular mycorrhizal fungi and biochar. The maximum root colonization (80%) was observed in the culture medium with 10% biochar and 12% arbuscular mycorrhiza. The application of the arbuscular mycorrhizal fungi in the medium of Sansevieria trifaciata cuttings directed to an increase in the biomass compared to the control. The amount of leaf electrolyte leakage of leaf was higher (28.37%) by application of 10% biochar in the culture bed compared with the cuttings treated with 5% biochar and control. Plants from the cuttings grown in the bed containing 10% biochar and 6% mycorrhizal inoculum had the highest number of leaves (2.83). It was approximately two folds compared to the control. The leaf electrolyte leakage was higher (28.37%) than the plants obtained from the cuttings treated with 5% biochar and control by application of 10% biochar. The total chlorophyll content of the leaf in both cultivars increased significantly with the application of different concentrations of biochar compared to the control. Biochar application influenced on microbial biomass through altering the soil porosity, soil moisture and temperature. Also, biochar stimulated plant growth through the positive effects on microbial population. These results suggested that the applications of biochar at an appropriate proportion could change plant growth and microbial community.Conclusion Biochar and arbuscular mycorrhizal fungi by establishing a symbiotic relationship between fungus and root, stimulated rooting growth. These treatments were able to root in different cultivars of Sansevieria trifaciata propagation. Root colonization of arbuscular mycorrhizal fungi was depended on the variety of plant. The applied treatments showed more impact on morphological and physiological traits in Sansevieria trifaciata var. Moonshine than that in Sansevieria trifaciata var. Laurentii cultivar. The rotting of Sansevieria trifaciata var. Laurentii cuttings was more than that of the Sansevieria trifaciata var. Moonshine. The best treatment for Sansevieria trifaciata variateis cuttings was application of 5% biochar and 6% arbuscular mycorrhiza and cultured in cocopeat-perlite bed.
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.
Plant Nutrition, Soil Fertility and Fertilizers
Yaser Azimzadeh; Nosratollah Najafi; Adel Reyhanitabar; Shahin Oustan; Alireza Khataee
Abstract
Introduction Phosphorus (P) is an essential element for living organisms. Discharging P from various sources, such as industrial wastewater and agricultural waters, into surface water causes eutrophication and undermines the balance of aquatic ecosystems and imposes many costs due to water quality degradation. ...
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Introduction Phosphorus (P) is an essential element for living organisms. Discharging P from various sources, such as industrial wastewater and agricultural waters, into surface water causes eutrophication and undermines the balance of aquatic ecosystems and imposes many costs due to water quality degradation. In addition, mineral resources of P-fertilizers in the world are unrecoverable and are coming to an end. Therefore, it is very important to develop adsorbents to remove P from contaminated water and then be used as P-fertilizer for surmounting the eutrophication and P-fertilizer exhausting challenges. In the last few years, biochar and hydrochar have been considered as low-cost porous eco-friendly adsorbents with a high surface area and easy to produce and use. Biochar and hydrochar are carbonaceous solids that are produced from the carbonization of biomasses and could be used as adsorbents and soil amendments. However, because of their high negative charge and very low ability to absorb anions, especially phosphate, they cannot be used as phosphate adsorbents. In recent years, several methods have been introduced to change the surface of biochar and hydrochar to increase their anion adsorption capacity. In this respect, the successful results of the production and the use of engineered biochars, such as layered double hydroxides (LDHs) functionalized biochar (LDH-biochar) and LDH-hydrochar composites have been provided. Layered double hydroxides (LDHs) are brucite-like compounds with a large specific surface area, high positive charge, and exchangeable interlayer anions. LDHs functionalized biochar and hydrochar composites are environmentally friendly adsorbents for the removal of phosphate from aqueous solutions. Also, P-loaded LDH-biochar and LDH-hydrochar composites have the potential application as a P-fertilizer. These composites may increase soil available-P through the slow release of P and can improve soil properties and fertility due to the presence of the biochar and hydrochar in their structure. So, the P-loaded LDH-biochar and LDH-hydrochar may affect the availability of soil nutrients and plant growth. Nitrogen (N), P, and potassium (K) are the macronutrients that have a direct and great influence on plants growth. Therefore, the aims of this study were: (I) producing LDH-biochar and LDH- hydrochar composites and loading them with phosphate. (II) Investigating the effects of the biochar, hydrochar, LDH, LDH-biochar, LDH-hydrochar, the P-loaded LDH-biochar (LDH-biochar-P), and LDH-hydrochar (LDH-hydrochar-P) on dry matter and concentrations of P, N, and K in corn shoot and root. Materials and Methods Biochar was produced from applewood feedstock through slow pyrolysis at 600 ºC for 1 h under Argon flow conditions. Hydrochar was produced through hydrothermal carbonization of the applewood feedstock at 180 ºC and 11 bars pressure for 12 h. Then by precipitation of LDH particles on the biochar and hydrochar surfaces, LDH-biochar and LDH-hydrochar composites were prepared. The LDH particles were synthesized via a combined fast co-precipitation and hydrothermal treatment route. Each gram of LDH-biochar and LDH-hydrochar composites was loaded with 51 and 47 mg P, respectively. Then using a factorial experiment on the basis of completely randomized design with three replications, the effects of biochar, hydrochar, LDH, LDH-biochar, LDH-hydrochar, LDH-biochar-P, and LDH-hydrochar-P were studied in presence and absence of monocalcium phosphate fertilizer on corn dry matter and concentrations of N, P, and K in corn shoot and concentrations of P and K in corn root. Results and Discussion The results showed that the biochar had a higher yield and ash percentage, pH and electrical conductivity (EC) as compared with the hydrochar. The concentrations of all studied nutrients in the biochar, except for N, were greater than those of hydrochar and biomass. The P, K, Na, Fe, Mn, and Zn concentrations in biochar and hydrochar were significantly greater than the initial biomass. The application of P-fertilizer increased root and shoot dry matters in all treatments, except for LDH-biochar-P and LDH-hydrochar-P treatments. Biochar and hydrochar had no significant effects on root and shoot dry matter in non-P-fertilized treatments and had no significant effects on P and K concentrations of corn root and shoot. However, biochar and hydrochar increased shoot dry matter in P-fertilized treatments. The highest root and shoot dry matters, P concentrations of root and shoot, and N concentration of shoot were obtained in the presence of the LDH-biochar-P and LDH-hydrochar-P, and the lowest root and shoot dry matters of corn were observed in the presence of the LDH. Application of P-fertilizer increased P concentrations of corn root and shoot in the presence of the LDH-biochar and LDH-hydrochar but decreased the K concentration of root in biochar, LDH-biochar and no amendment treatments and had no significant effects on N and K concentrations in the shoot. The application of P-fertilizer decreased P translocation factor in presence of the LDH-biochar and LDH-hydrochar and had no significant effect on P translocation factor in all other treatments. Using P-fertilizer had no significant effect on K translocation factor in all treatments. Biochar, hydrochar, LDH, LDH-biochar, and LDH-hydrochar had no significant effects on P and K translocation factors. The translocation factor of P was greater than 1 in all treatments, except for the LDH-biochar-P and LDH-hydrochar-P treatments. Also, the translocation factor of K was greater than that of P in all treatments. Conclusion Due to the structural similarities between biochar and hydrochar, LDH-biochar and LDH-hydrochar, and LDH-biochar-P and LDH-hydrochar-P, the root and shoot dry matter and concentrations of the studied elements in corn root and shoot were not significantly different between the biochar and hydrochar, LDH-biochar and LDH-hydrochar, and LDH-biochar-P and LDH-hydrochar-P treatments, respectively. P-fertilizer had synergistic relationships with biochar, hydrochar, LDH-biochar, and LDH-hydrochar but antagonistic relationships with LDH, LDH-biochar-P, and LDH-hydrochar-P composites in terms of dry matter and P concentrations in corn root and shoot. So, applications of the biochar, hydrochar, LDH-biochar, and LDH-hydrochar accompanied by P-fertilizer and the use of LDH-biochar-P and LDH-hydrochar-P without the application of P-fertilizer can be proposed for corn cultivation under similar conditions.
Soil Biology, Biochemistry and Biotechnology
Maryam Talebi Atouei; mohsen olamaee; REZA GHORBANI NASRABADI; seyed alireza movahedi Naeini
Abstract
Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction ...
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Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction of reactive oxygen species (ROS). Antioxidant capacities and osmolytes play a vital role in protecting plants from salinity that causes oxidative damages. Applying biological methods such as using of halotolerant plant growth promoting rhizobacteria (PGPR) is very important to reducing the harmful effects of salinity on plants. Also exopolysaccharide production by plant growth-promoting strains helps in binding cations, including Na+, and thus decreases the content of Na+ available for plant uptake. This is especially useful for alleviating saline stress in plants. Biochar can also alleviate the negative impacts of salt stress in crops. Biochar can enhance plant growth either by its direct or indirect mechanisms of actions. The direct growth promotion relates to supplying mineral nutrients, such as Ca, Mg, P, K and S etc., to the plant, whereas, indirect mechanisms involve improving soil physical, chemical and biological characteristics. Materials and Methods In this research, the effect of halotolerant plant growth promoting bacteria, biochar and gypsum was investigated on enzymatic and non-enzymatic defense mechanisms of barley such as Catalase, Superoxide Dismutase, Proline and Membrane stability under salinity stress. The experiments were carried out as a factoria with a completely randomize design in greenhouse conditions for 2016-2017. The factors included: bacteria (without inoculation (T0), bacterial isolate T5 (megaterium Bacillus), bacterial isolate T17 (licheniformis Bacillus ), biochar (0 and 5percent w/w), gypsum ( 0and 50 percent gypsum requirement ) and soil leaching (without and leaching with) with three replications. The activity of catalase (CAT) was determined by changes in absorbance at 240 nm (IUg−1FW) (Aeby, 1984). Superoxide dismutase (SOD) activity was determined by nitroblue tetrazolium (NBT) reduction, according to Minami and Yoshikawa (1979) and the enzyme activity was expressed as (IUg−1FW). Proline content was estimated according to Bates et al., (1973) and expressed as µ mol g−1 fresh weight (FW). Membrane stability was estimated according to Sairam and. Saxena (2001). All statistical analyses were performed using SAS software. The means of different treatments were compared using LSD (P ≤0.05) test. Results and Discussion The results showed that using halotolerant bacteria and biochar reduced the activity of antioxidant enzymes in barley plants. This reduction was higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and with leaching. Also, inoculated plants with both bacteria had the highest concentration of proline, which was significantly higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and gypsum. Also, application of halotolerant bacteria, biochar and gypsum improved the membrane stability of plant. This increase has been remarkable in inoculated treatments with T17 bacteria (Bacillus licheniformi) in saline soil with leaching associated with 50 percent gypsum requirement Conclusion Generally, results showed that halotolerant bacteria, biochar and gypsum can be used as a tool for reducing adverse effects of salt stress. Inoculation of soil with these bacteria has helped in alleviating saline stress by changing several physiological, enzymatic, and biochemical agents in plant. Bio-remediation of salt affected soils is one of the cheap and eco-friendly approaches for remediation of salt affected lands as the traditional physical and chemical techniques are becoming costly. The plant growth promoting halotolerant bacteria helps in Bio-remediation of salt affected soils and thereby improving the agricultural crop yields. Incorporation of biochar into salt-affected soil could diminish salinity stress by decreasing soil bulk density, increasing in soil cation exchange capacity, potassium and calcium concentrations, water holding capacity and nutrient and water availability in soil. Also, bichar due to high organic matter content can play a dramatic role in salt affected soil with organic compound defficiency. According to these amended features of biochar in soil, we suggest, more experiments conducted by biochar with different material and ratios under saline - sodic soils.
Soil Physics, Erosion and Conservation
shamsollah ayoubi; zanyar feizi; Mohammad reza Mosaddeghi; Ali asghaar besaltpour
Abstract
Investigating the application of biochar, bentonite clay and polyvinyl acetate polymer on some mechanical properties of sand deposits Introduction Wind erosion seriously threatens bare soils and is recognized as a global environmental problem; however, little is known about this process in comparison ...
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Investigating the application of biochar, bentonite clay and polyvinyl acetate polymer on some mechanical properties of sand deposits Introduction Wind erosion seriously threatens bare soils and is recognized as a global environmental problem; however, little is known about this process in comparison to rainfall or tillage erosion. Due to the heavy costs of controlling wind erosion and the difficulty of detecting which control measure is the most effective, the correct selection of technical methods is indispensable for a suitable land management. Since the last decades, the methods of sand stabilization studied are diverse, but basically based on wind speed reduction by including chemical, mechanical and biological methods. One of the most important methods of stabilizing sandy soils is the use of mulches. In recent years, due to the disproportionate development of residential in peri-urban areas, humans use polymeric and oil mulches to stabilize sandy soils. Therefore, in this research, the effects of bentonite clay, polyvinyl acetate and palm biochar on reducing soil erosion by wind in peri-urban areas were investigated. Methods and Materials Three selected treatments were compared with a control plot without any treatment: palm biochar, polyvinyl acetate and bentonite clay. In order to prepare the palm biochar, palm remnants including the trunk, foliage and palm leaves were poured into the mill and turned into small pieces. The fragments were passed through a 2 mm sieve. The remnants transmitted from the sieve were poured into the trays of the discharger unit and placed inside a discharger at 350°C for 4 hours, and the biochemicals were prepared to the extent necessary for this research. Polyvinyl acetate treatment was provided by Isfahan Resin Co. and the bentonite clay by the Derin Kashan enterprise (both of them from Isfahan, Iran). To apply the treatments, each of them was mixed with a certain proportion of water per m2: i) 20 g l-1of palm biochar treatments; ii) 7 g l-1 of polyvinyl acetate treatment; and, iii) 20 g l-1 of bentonite clay.In order to apply the treatments, 36 galvanized trays with a same size (5×35×105 cm) were prepared and filled up from the air to the top edge with sand. After 1, 2, 4, 10 and 20 weeks some mechanical and physical properties were measured in laboratory. Results and Discussion A significant difference was observed among different treatments in terms of the impact on aggregates formations and stabilities at different moments. The application of bentonite clay treatment significantly increased the stability of formed aggregates compared to control treatment. The rest of treatments showed lower aggregability. The mean weigh diameter (MDW) for the control plot was 0.28 mm. The lowest MWD was obtained by the palm biochar treatment, which increased by 20.1, 14.9, 9, 2.5 and 1.6% after the first, second, fourth, tenth and twentieth weeks of application, respectively. Polyvinyl acetate treatment increased MDW by 65.1, 61.6, 58.8, 41.9 and 31.5% after the first, second, fourth, tenth and twentieth weeks, respectively. The highest MWD was obtained by bentonite clay treatment, which generated an increase by 77.8, 71, 65.1, 59.9 and 49.7% in the first, second, fourth, tenth and twentieth weeks, respectively). The images from thin sections of bentonite clay and polyvinyl acetate treatments showed that soil particles were joined to form larger aggregates in all of cases. No significant differences was observed for hydraulic conductivity at different times were observed. There was a significant difference among different treatments at different monitoring periods. The application of bentonite clay significantly reduced the fractal dimension. On the contrary, the lowest effect was registered for the palm biochar treatment. The effect of bentonite clay treatment on soils was higher than other selected treatments showing a reduction by 10.6, 9.7, 8.7 6.7 and 6.3% in the first, second, fourth, tenth and twentieth weeks, respectively. The impact of different treatments on shear resistance showed that the application of the selected treatments significantly increased the shear strength in all the cases. Among the selected treatments, the effect of bentonite clay treatment on shear resistance was higher than other treatments. The lowest and the highest shear resistance were registered for the palm biochar and bentointe clay, respectively. Palm biochar increased shear resistance by 9.3, 9.3, 8, 5.3 and 3.3% compared to the control plot in the first, second, fourth, tenth and twentieth weeks after its application. On the other, bentonite clay registered the highest improvement in shear resistance by 44.7, 44.7, 42.7, 37.3 and 31.3% in the first, second, fourth, tenth and twentieth weeks, respectively. Keywords: Mulches, Bentonite, Clay, Biochar, Palm, Mechanical properties
