S. Ashrafi-Saeidlou; A. Samadi; M.H. Rasouli-Sadaghiani; M. Barin; E. Sepehr
Abstract
Introduction: Potassium (K) is abundant in soil, however, only 1 to 2 % of Potassium is available to plants. Depending on soil type, 90 to 98% of soil K is in the structure of various minerals such as feldspar (orthoclase and microcline) and mica (biotite and muscovite). About 1 to 10 % of soil K, in ...
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Introduction: Potassium (K) is abundant in soil, however, only 1 to 2 % of Potassium is available to plants. Depending on soil type, 90 to 98% of soil K is in the structure of various minerals such as feldspar (orthoclase and microcline) and mica (biotite and muscovite). About 1 to 10 % of soil K, in the form of non-exchangeable K, is trapped between the layers of certain types of clay minerals. The concentration of soluble K, which is directly taken up by plants and microbes in the soil and is exposed to leaching, varies from 2 to 5 mg l-1 in agricultural soils. Imbalanced use of chemical fertilizers, a significant increase of crop yield (depletion of soil soluble K), and the removal of K in the soil system result in a large rate of K fixation in the soil. As a result, K deficiency has been reported in most plants. The annual increase in the price of K fertilizers and the destructive effects of them on the environment have made it necessary to find a solution for the use of indigenous K of soil. The use of biofertilizers containing beneficial microorganisms is one of these strategies. Although K solubilizing bacteria can be an alternative and reliable technology for dissolving insoluble forms of K, lack of awareness among farmers, the slow impact of K biofertilizers on yield, less willingness of researchers to develop K biofertilizers technology and deficiencies of technology in respect to carrier suitability and proper formulation, are the major reasons for why potassium solubilizing microorganisms and K biofertilizers draw low attention.
Material and Methods: The purpose of this study was modeling and evaluating the effects of different vermicompost, phlogopite and sulfur ratios on the solubility and release of K by Pseudomonas fluorescens and indicating the optimized levels of these variables for efficient biofertilizer preparation. 20 experiments were carried out using the response surface methodology (RSM) based on the central composite design and the effect of different values of vermicompost, phlogopite and sulfur variables, in the four coded levels (+α, +1, 0, -1 and -α), was evaluated on K dissolution. The applied vermicompost, phlogopite and sulfur in the experiment were ground and filtered through a 140 mesh sieve and their water holding capacity were determined. According to experimental design, different amounts of mentioned materials were combined and samples were sterilized in autoclave. The required amount of water along with 1 ml of bacterial inoculant were added to the samples. The samples were kept in incubator for 2 months. At the end of experiment, amount of soluble K were measured by the flame photometer.
Results: The analysis of variance (ANOVA) depicted the reliable performance of the central composite predictive model of K dissolution (R2= 0.949 and RMSE=0.8). Based on the results, the interaction of vermicompost with sulfur (p < 0.038) and the interaction of phlogopite with sulfur (p < 0.0083) were relatively high and significant. Sensitivity analysis of the central composite design revealed that the vermicompost (X1), phlogopite (X2) and sulfur (X3) had positive and negative impact on potassium dissolution, respectively. Therefore, when sulfur content increased to 91.70%, K dissolution decreased to around 31.61%. According to the prediction under optimized condition, maximum potassium dissolution was obtained at the presence of 41.78, 24.35 and 10.25% of vermicompost, phlogopite and sulfur, respectively.
Conclusion: The results indicated that the applied fertilizer composition (vermicompost + phlogopite + sulfur) had a desirable impact on Pseudomonas fluorescens solubilizing ability on a laboratory scale. Due to the fact that Iran soils are often calcareous, there are high amounts of insoluble and unavailable nutrients. Under these unsuitable conditions, the application of these nutrients chemical fertilizers cannot reduce deficiencies. Therefore, we must use the ability of efficient microorganisms to dissolve and mobilize soil native elements. A combination of 41.78% vermicompost, 24.35% phlogopite and 10.55% sulfur could create a proper potassium biofertilizer by providing favorable conditions for bacterial activity. Along with solubilizing activities of bacteria, the presence of sulfur reduces soil pH and thereby nutrients availability and stability increase in these soils. Because of its acidity, sulfur has a significant effect on nutrients dissolution such as phosphorus, nitrogen and potassium, and micronutrients. On the other hand, the presence of vermicompost in this fertilizer, while meeting the carbon and energy requirements of bacteria and acting as a suitable carrier, improves the physicochemical properties of the soil, increases the biodiversity of the microbial community and, as a result, promotes the soil quality and health. The evaluation of this fertilizer composition efficiency (using optimal amounts of materials) at the greenhouse and field scales is suggested.
M. Moeinfar; M.H. Rasouli Sadaghiani; M. Barin; F. Asadzadeh
Abstract
Introduction: Dust is one of the most important destructive phenomena in the world, that annually causing damage to human health and the environment. This issue ranks after two major challenges of climate change and water scarcity as the third most important challenge facing the world in the ...
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Introduction: Dust is one of the most important destructive phenomena in the world, that annually causing damage to human health and the environment. This issue ranks after two major challenges of climate change and water scarcity as the third most important challenge facing the world in the 21st century that is considered. Microbial-induced calcite precipitation (MICP) is a relatively green and sustainable soil improvement technique. It utilizes biochemical process that exists naturally in soil to improve engineering properties of soils. The calcite precipitation process is uplifted by the mean of injecting higher concentration of urease positive bacteria and reagents into the soil. In this process, the enzyme present in the bacteria hydrolyzes the urea in the environment and through reacting with the calcium ion, leads in the deposition of calcium carbonate. The main objective of this study is isolation native ureolytic bacteria from different soil of around Urmia Lake and then, the evaluation their efficiency in the MICP for stabilization of sandy soils and reduce windy erosion.
Materials and Methods: In order to isolate ureolytic bacteria, 25 soil samples were taken from different land use in West Azarbaijan province, Iran. To increase the number of ureolytic bacteria in soil samples were used from the enrichment solution and then ureolytic bacteria were isolated and purified. These isolates were subjected to various biochemical tests, as well as the growth curve and urease activity were determined. In order to investigate the potential for soil improvement, a factorial experiment was conducted based on a completely randomized design with two factors including microbial treatment in eight levels (including five isolated bacteria (U3, U8, U16, U35 and U40) and Bacillus pasteurii (as control Positive), non-bacterial and non-cementation (as control negative) and non-microbial but with cementation solution treatments) and another factor including different concentrations of calcium chloride solution with urea at three levels (0.1, 0.5 and 1 molar), in three replications. After injection of cementation solution and bacterial solution to soil, penetration resistance and windy erosion rates in sandy soil were assessed
Results and Discussion: In study, overall 45 isolates of the bacteria were isolated and purified. Among of 44 isolates, five bacterial isolates (U3, U8, U16, U35 and U40) had the highest urease activity. The growth curve of bacterial isolates showed that the highest urease activity and microbial population were in the time period of 13 to 16 hours after microbial culture, which it is represents the best time use bacterial solution in the MICP process. According to the results of soil improvement tests, the amount of soil erosion in the MICP treatment at a wind speed of 25 m/s was zero and the rate of penetration resistance was averaged over 13 MPa, which has a very impressive impact on MICP in controlling wind erosion, especially at high speeds of wind. The results showed that U3 and U16 isolates had the highest amount of urea hydrolysis and also U16 and U3 had the lowest and the highest tolerance to salinity, respectively. The results of the wind tunnel showed that the wind erosion threshold in negative control samples (non-bacterial and non-cementation) were 9.4 m/s and for MICP samples (including five isolated bacteria and Bacillus pasteurii ) were much higher than the wind tunnel speed in the wind tunnel machine in Urmia university (25 m/s). The maximum penetration resistance (13.5 MPa) was obtained in the sample treated with U3 isolate and 1 molar calcium chloride, but negative control treatments (non-bacterial and non-cementation) as well non-microbial but with cementation solution treatments were 0 and 97.0 MPa, respectively.
Conclusion: The amount of soil wind erosion was zero in MICP treatment with the wind tunnel speed 25 m/s that indicates very important effects MICP to control wind erosion of sandy soils to compare control treatments (non-bacterial and non-cementation and non-microbial but with cementation solution) in high wind speeds. The application of MICP treatment in the soil, in addition to increasing its wind erosion resistance, also increased penetration resistance in the soil. Increasing the penetration resistance of MICP treatments (including five isolated and Bacillus pasteurii) can be due to the activity of bacterial isolates, chemical interactions, and the formation of calcium carbonate precipitation into soil cavities, which causes to form a hard layer in soil. Also, obtained resistance by using isolated bacteria indicates that there are many unknown microorganisms that can carry out MICP better than Bacillus pasteurii and probably they will be better compatible and establish because they are native.
S. Ashrafi-Saeidlou; A. Samadi; MH. Rasouli-Sadaghiani; M. Barin; E. Sepehr
Abstract
Introduction: Among the elements, potassium (K) is the third important macronutrient for plant nutrition that plays a significant role in plant growth and development. The development of intensively managed agriculture has led to the consumption of increasing amounts of K, low K supply has therefore ...
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Introduction: Among the elements, potassium (K) is the third important macronutrient for plant nutrition that plays a significant role in plant growth and development. The development of intensively managed agriculture has led to the consumption of increasing amounts of K, low K supply has therefore become an important yield-limiting factor in agriculture. However, more than 98% of potassium in the soil exists in the form of silicate minerals such as illite and lattice K in K-feldspars which K cannot be directly absorbed by plants. Potassium and other minerals can be released when these minerals are weathered. Some microorganisms can play a role in releasing K from minerals. They solubilize K-bearing minerals through different mechanisms including chelation, acidolysis, pH reduction, exchange reaction, complexation, biofilm formation and secretion of organic acid and polysaccharides. Since the use of potassium solubilizing microorganisms (KSMs) as K-biofertilizers reduces the agrochemicals application and supports eco-friendly agriculture, so it is imperative to isolate the KSMs and optimize various growth parameters so as to improve their activity.
Materials and Methods: The present study was an attempt to model and evaluate the effects of pH, incubation time and different amounts of carbon source on K release by Pseudomonas fluorescens using Placket-Burman design and response surface methodology with a central composite design. At the first step, 12 experiments based on Placket-Burman design were carried out to screen and identify the effective carbon source in potassium release. According to the results of the first step, response surface methodology with the central composite design was employed to evaluate and model the effects of the coded independent variables including pH (3-10), incubation time (1-18 days) and carbon source (0.6-12 g L-1) on K release from feldspar and phlogopite. After the completion of each period, samples were centrifuged at 3000 rpm for 10 minutes and filtered using Whatman paper (No. 41). Potassium concentration of samples was measured by flame photometer. Used minerals in the experiment including feldspar and phlogopite were grounded and filtered through a 230 mesh sieve. In order to remove exchangeable K, the samples were saturated by calcium chloride solution (with a ratio of 2:1), after washing with HCl, samples were then dried at 105oC for 48 hours.
Results: Results showed that there was no difference between carbon sources, applied at the first step of the experiment, so each can be employed as alternatives to each other in the culture medium. The central composite design showed R2 of 0.944 and 0.918 with RMSE of 0.82 and 1.47 for predicting K release of feldspar and phlogopite, respectively, indicating high efficiency. Sensitivity analysis of the central composite design revealed that the pH is the most important factor in K release. The highest concentration of the K was observed at the highest levels of pH. Incubation time also had an impact on potassium release. In the early stages of the incubation time, the trend of potassium release was increasing, in middle stages, K amount decreased but it was accelerated over long times of incubation. The maximum potassium release in presence of phlogopite and feldspar was 121.16 and 96/82 mg L-1, respectively, which was observed at pH= 10.36, sucrose amount= 6.5 g L-1 during 10 days. Potassium amount in this treatment hence increased by 31.52% as compared to feldspar. According to central composite design, maximum potassium release of feldspar and phlogopite was obtained at pH= 10.36 and 10.34, sucrose concentrations of 2.26 and 6.92 g L1 at 18 and 2 days, respectively.
Conclusion: Our results showed that pH had a significant impact on K release by Pseudomonas fluorescens using response surface methodology. Overall, increasing incubation time along with high pH leads to the high amounts of K release from minerals. Different minerals released different content of potassium. Application of soil K-bearing minerals in combination with efficient potassium solubilizing bacterial strains as biofertilizers is required to replace chemical fertilizers and reduce the crop cultivation cost. Many bacterial strains have been found to solubilize minerals and improve plant growth under laboratory and greenhouse conditions, but their ability under field conditions remains unexplored. The capability of these bacteria, considering the soil and plant type, and environmental factors, should be thus evaluated under field conditions.
R. Ranjbar; Ebrahim Sepehr; Abbas Samadi; MirHasan Rasouli Sadaghiani; Mohsen Barin; behnam Dovlati
Abstract
Introduction: Potassium (K) is one of the major essential macronutrients for plant growth. Soil has rich reserves of K, among which only 1–2% can be directly absorbed by plants. It may be more economically viable to transform the fixed slow-release K into available K that can be absorbed by plants. ...
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Introduction: Potassium (K) is one of the major essential macronutrients for plant growth. Soil has rich reserves of K, among which only 1–2% can be directly absorbed by plants. It may be more economically viable to transform the fixed slow-release K into available K that can be absorbed by plants. The ability of some microorganisms to dissolve soil K-bearing minerals, such as micas is an important feature for increasing the yield of high-K-demand crops such as tobacco. Also, these microorganisms have both economic and environmental advantage. A large number of saprophytic bacteria such as Bacillus mucilaginosus and fungal strains such as Aspergillus spp. are known for their potential in releasing insoluble native K-source in soil into a plant available nutrient pool. Tobacco (Nicotiana spp.) is one of the most important industrial crops. K plays a vital role in increasing the tobacco yield and controlling quality parameters such as leaf combustibility that is one of the key criteria taken into account by the tobacco industry for assessing quality. Thus, high ranges of K fertilizers are applied in tobacco fields based on plant K requirement to build up soil K in tobacco producing countries. Increasing cost of the fertilizers and environmental risks necessitates alternate means to fertilizers such as application of microorganisms. The use of chemical K fertilizers can be reduced by exploiting the potential of bio-inoculants which are inexpensive and eco-friendly. Information related to K-solubilizing microorganisms in tobacco rhizosphere and their suitability in increasing the available K in tobacco-cultivated soils is not well-documented. Hence, the present study was conducted to screen the KSB isolates from tobacco-cultivated soils and evaluate their potential in dissolving K bearing silicate minerals and increasing soil available potassium.
Materials and Methods: Soil samples were randomly collected from the rhizosphere of tobacco from 25 different locations in northwest of Iran. The serial dilutions of the soil samples were made up to 10-4 and 5 µl of diluted soil suspension plated on Aleksandrov medium plates (on the agar-based culture medium). Aleksandrov medium contained 5.0 g Glucose, 0.5 g MgSO4.7H2O, 0.1g CaCO3, 0.006 g FeCl3, 2.0 g Ca3PO4, 2.0 g insoluble mica powder as potassium source and 20.0 g agar in 1 liter of deionized water. The plates were incubated at 28±2°C in incubator for 10 days. Finally, nine isolates of potassium silicate solubilizing bacteria were isolated and purified. Solid and liquid Aleksandrov media were applied for qualitative (Solubility Index = Diameter of zone of clearance/ Diameter of growth) and quantitative (K content) evaluation, respectively, based on the completely randomized design (CRD) with three replication. Liquid Aleksandrov medium containing 2 g L-1 of mica and feldspar mixture, was inoculated with bacterial isolates. Bacterial isolates creating high solubility index and releasing more K from K-bearing minerals into liquid medium, were selected as effective isolates. In order to evaluate the efficiency of the potent bacterial isolates for increasing soil available K, an experiment was conducted with three replication and eight potent bacterial isolates along with a control (non-inoculated soil). Sterilized soil samples were inoculated with bacterial isolates separately and incubated at 25°C, with 75% field capacity moisture levels for 90 days. After incubation, available K in soil samples were extracted with Ammonium Acetate 1M. Variance of solubility index, K concentration into liquid Aleksandrov medium and soil available K were analyzed using SPSS (Statistical Package for the Social Sciences). Student-Newman-Keuls (SNK) test comparisons were also used to compare available soil K using SPSS 16.0.
Results and Discussion: Eight KSBs isolates, including KSB20, KSB30, KSB40, KSB22, KSB42, KSB90, KSB92 and KSB10, were isolated and purified as effective isolates for dissolving mica and feldspar minerals. Most isolates were gram-positive, rod-shaped, and white in appearance. The studied isolates, except KSB22, KSB40 and KSB20, had α-amylase enzyme activity. Bacterial isolates, including KSB20, KSB30, KSB42 and KSB10, were significantly superior in sucrose and glucose hydrolysis. The isolate of KSB10 also had fluorescence properties. The highest solubility index (2.8, 2.7 and 2.5) was obtained from the activity of KSB22, KSB42 and KSB10 isolates in solid Aleksandrov medium, respectively. The highest concentration of potassium into liquid Aleksandrov medium was found for the KSB42 and KSB10 isolates (9.40 mg L-1). The KSB42 and KSB10 isolates increased medium K concentration approximately three times more than non-inoculated medium. In addition, KSB42 and KSB10 isolates were more effective in releasing potassium from soil potassium-bearing minerals. The amount of available potassium in soil incubated with KSB42 and KSB10 isolates increased by 44 and 46 mg kg-1 compared to the control, respectively.
Conclusion: Among bacterial isolates purified from the tobacco rhizosphere, the KSB42 and KSB10 isolates increased more significantly the solubility of potassium minerals and potassium availability in soil compared to other isolates. These bacteria isolates increased potassium concentration into Aleksandrov liquid medium by more than three times and also increased soil available potassium by about 44 to 46 mg kg-1 compared with the control. As a result, these isolates (KSB42 and KSB10) can be used as a bio-fertilizer to reduce potassium fertilizer application and increase the quality of tobacco after field experiments.
Roghayeh Vahedi; Mirhasan Rasouli-Sadaghiani; mohsen barin
Abstract
Introduction: Trees pruning wastes by turning into compost and adding to soil improves the physical, chemical and biological properties of the soil. Soil biological indices are important aspects of soil quality, so soil quality is measured using different biological properties. The organic compounds ...
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Introduction: Trees pruning wastes by turning into compost and adding to soil improves the physical, chemical and biological properties of the soil. Soil biological indices are important aspects of soil quality, so soil quality is measured using different biological properties. The organic compounds are regularly released from plants into the rhizosphere, which increase the activity of the soil microbial community and improve the health of the soil. The organic matter such as compost, stimulates microbial activity like the enzymatic activity and microbial biomass in the soil. Another method to improve soil quality is the use of the microorganisms potential. The arbuscular mycorrhizal fungi (AMF) in soil can stimulate and increase soil microbial activity and also improve the activity of enzymes and microbial biomass in soil. The application of microorganisms and the addition of the organic matter to the rhizosphere can change the microbial communication composition of the rhizosphere. The Limiting roots to investigate the biological and chemical changes and the extent of these properties in the rhizosphere are challenges that have been less addressed. The rhizobox is one of the used tools to study the rhizosphere changes. The main objective of the present study was to investigate the effects of the compost prepared from pruning wastes of apples and grapes trees and also pruning wastes of apples and grapes trees on soil quality, in the presence of arbuscular mycorrhizal fungi, in rhizosphere of the wheat under the rhizobox conditions.
Materials and Methods; The present study was carried out in a completely randomized factorial design with three replications in rhizobox under greenhouse condition. The factors included the organic matter (compost of trees pruning wastes, trees pruning wastes and control) and soil (the rhizosphere and non-rhizosphere soil) in mycorrhizal inoculation conditions. The soil sample with light texture and low available phosphorus was prepared. The pruning wastes of apple and grape trees were collected from urmia orchards. Also, the compost of trees pruning wastes was prepared from the research greenhouse of Urmia University. The compost and pruning wastes were ground and crushed and then passed through a 0.5 mm sieve for the greenhouse experiment. The plants were planted in the rhizobox with the dimensions of 20 × 15 × 20 cm (length × width × height). The compost and pruning wastes were added to the boxes based on 1.5% pure organic carbon (each box contained 5.799 kg of soil). Glomus fasciulatum as mycorrhizal inoculation was used. The control treatments contained sterile soil with mycorrhizal inoculation and without organic matter. The wheat seeds (Triticumae stivum L.) of Pishtaz cultivar were grown in rhizoboxes. At the end of the growth period, organic carbon (OC) by Walkley-Black method, microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP) by fumigation extraction method, metabolic quotient index (qCO2) (microbial respiration per unit of biomass), microbial quotient index (microbial biomass carbon per unit of organic carbon), carbon availability index (CAI) (substrate-induced respiration/microbial biomass ratio), colonization Percentage of arbuscular mycorrhizal fungi, and acid (ACP) and alkaline (ALP) phosphomonoesterase enzymes activities by spectrophotometry method, were determined.
Results and Discussion: The results showed that the application of compost significantly increased organic carbon, microbial biomass carbon, microbial biomass phosphorus and decreased MBC/MBP compared with the control treatment. Furthermore, compost increased the organic carbon, microbial biomass carbon and microbial biomass phosphorus in the rhizosphere soil by 8.08, 45.79 and 37.18 % compared with the non-rhizosphere soil, respectively. The pruning wastes increased 1.45, 1.26 and 1.30 fold metabolic quotient, carbon availability and acid phosphomonoesterase activity in the rhizosphere compared with non-rhizosphere soil, respectively.The highest activity of the alkaline phosphomonoesterase enzyme and the percentage of mycorrhizal root colonization were also related to pruning waste treatments in rhizosphere soils.
Conclusions: Different characteristics of the organic matter and the microbial inoculation led to an increase in the biological indices in the rhizosphere zone compared with non-rhizosphere soils. The application of organic matter in the soil, along with microbial inoculation, will accelerate the biological activity of the soil and thus contributes to a better cycle of nutrients in the soil. Following the application of organic matter, microorganisms rapidly grew and led to an increase in biological activity, such as increase activity of phosphomonoesterase enzymes, carbon and phosphorus of microbial biomass in the rhizosphere. It could be argued that increased activity of phosphomonoesterases and the microbial biomass and decreased metabolic quotient in the soil were influenced by the application of the organic materials and mycorrhizal inoculation. The findings of this study have a number of important implications for future practice. Therefore, the use of the organic materials and biological potential of the microorganisms are one of the most important tools to maintain organic carbon balance of the soil, contributing to the stimulation of soil microbiological activities.
mohsen barin; Ehsan Ehsan-Malahat; Farrokh Asadzadeh
Abstract
Introduction: Soil is a complex and dynamic biological system, and it still is difficult to determine the composition of microbial communities in soil. Most soil microorganisms are dormant, so their rate of respiration is low. However, their respiration can be stimulated by adding an easily decomposable ...
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Introduction: Soil is a complex and dynamic biological system, and it still is difficult to determine the composition of microbial communities in soil. Most soil microorganisms are dormant, so their rate of respiration is low. However, their respiration can be stimulated by adding an easily decomposable substrate. Also, by adding a simple organic matter, respiration may rapidly increase to a maximum and remains at a constant rate for more than 4 h. Glucose is commonly used as a substrate because most soil microorganisms can readily utilize it as a carbon source. The substrate-induced respiration (SIR) method was modified and adapted to measure fungal, bacterial and total microbial contributions to glucose-induced respiration and the potentially active microbial biomass on decaying plant residues of different composition. Decomposing residues from natural and agricultural ecosystems were chopped and sieved to include the >1 mm fraction for routine SIR analyses on a continuous flow-through respiration system. Substrate induced respiration is a main factor for the assessment of the soil microbial activity. This technique is already used widely in soil microbial studies. Different factors such as the source of carbon, temperature and incubation may play a significant role in the amount of SIR. Therefore, optimizing the test conditions is one of the important criteria for SIR determination. For this purpose, statistical methods such as central composite design (CCD) and response surface method can be used as a useful tool for determining optimal conditions. This study was carried out to model and compare the effect of carbon source (glucose), temperature and incubation time on the SIR of forest and agricultural soils.
Materials and Methods: In this research, 40 experiments were conducted for two soil types including agricultural soil (with relatively low organic matter content) and forest soil (with relatively high organic matter content). Soil samples were collected from the topsoil (0-20 cm) layer. In the laboratory, all visible roots were removed and the soil samples were divided into two parts. One part was kept in plastic bottles at 4°C for SIR analysis. And the rest was air dried in the shade at laboratory temperature for chemical and physical analysis. Electrical conductivity (EC) and pH were determined in saturated soil extract and organic carbon persent (%OC) was determined by di-chromate oxidation. Soil texture was determined using a Bouyoucos hydrometer in a soil suspension. Response surface methodology based on the central composite design was applied in modeling procedure. Different ranges of the independent variables including glucose (0.5-10 mg g-1), incubation time (1-10 hr), and temperature (15-30˚C) were used in central composite design experiments. Totally, 40 experiments based on the coded values of the independent variables were conducted for two soils.
Results and Discussion: Experimental results indicated that the SIR in forest soil is two times greater than the agricultural soil, which may be related to the higher organic matter content and more microbial activity in this soil. Results also revealed the efficiency of the central composite design in predicting the SIR of forest (R2= 0.823) and agricultural (R2=0.919) soils. Among the three independent variables, the linear effect of temperature on the SIR were significant for both soils. However, the substrate (glucose) content has more significant effect in forest soil in comparison with agricultural soil which may be associated with the higher decomposable organic matter content of the forest soil. Glucose enhancement didn’t have significant effect on SIR alteration rate which can be attributed to low organic matter content in agricultural soil. Totally, with increasing time and temperature, the amount of SIR was significantly increased, however with increasing glucose, SIR amount was not significantly increased especially in the agricultural soil. In the forest soil, the process of SIR changes is clearly distinct in response to independent variables compared to agricultural soil. Maximum levels of the SIR in forest soil is clearly associated to the highest time and glucose levels. This indicates that increasing glucose and sufficient time in the forest soil, which contains high amounts of digestible organic matter, can stimulate microorganisms to decompose more organic matter and it outcome is increasing SIR.
Conclusion: This study indicated the high efficiency of response surface methodology in SIR modeling for both forest and agricultural soils. However, the quantitative amounts of SIR were very different in two soils. The amounts of SIR in the forest soil were almost twice relative to agricultural soil. In the forest soil, the amounts of glucose and temperature were as the main variables in increasing SIR, while the temperature and time variables were more determinant in agricultural soil on it.
MirHassan Rasouli-Sadaghiani; Roghayeh Vahedi; Mohsen Barin
Abstract
Introduction: Millions of tons of trees pruning waste are produced annually in Iran, which can contribute to supplying soil organic matter. Soils in arid and semi-arid regions, due to lack of sufficient vegetation and the return of low amounts of plant residues to the soil, contain little organic matter. ...
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Introduction: Millions of tons of trees pruning waste are produced annually in Iran, which can contribute to supplying soil organic matter. Soils in arid and semi-arid regions, due to lack of sufficient vegetation and the return of low amounts of plant residues to the soil, contain little organic matter. These soils are often calcareous, and as a result, many plants in these soils are faced with nutritional problems, especially phosphorus deficiency. Phosphorus, as an essential element for plant growth, combines with soil components and changes into less soluble and insoluble compounds in calcareous soils with low amounts of organic matter. Organic matter and biological amendments can affect the solubility and mobility of nutrients in the rhizosphere and improve their bioavailability by creating different chemical and biological conditions. The pruning waste of trees can be used to produce biochar and compost and consequently improves soil physical and chemical properties and plays an important role in the dynamics and living of soil microorganisms. Biochar is a carbon-rich solid material produced during pyrolysis which is the thermal degradation of biomass under oxygen limited conditions. It has recently received much attention as a soil amendment which can be used to increase nutrient availability, improve the soil microbial diversity and biological activities such as enzyme activity in rhizosphere and sequester carbon in agricultural soils. In addition, compost is a chemical derived product from organic waste and contains many beneficial elements that are gradually released into soil and available to plants. Another approach to improve the bioavailability and mobility of phosphorus in the rhizosphere is the use of potential of phosphate-solubilizing microorganisms including arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR). Limiting the roots to examine the biological and chemical changes and the extent to which these properties have expanded in the rhizosphere are challenges that have been less addressed .Rhizobox is one of the systems used to study rhizosphere changes. The aim of this study was to investigate the effect of biochar and compost prepared from pruning waste of apples and grapes trees as well as microbial inoculation on phosphatase activity and phosphorus availability at wheat rhizosphere under rhizobox condition.
Materials and Methods: This study was carried out on a completely randomized design with a factorial arrangement in three replications, under greenhouse condition in rhizobox. The factors were organic matter (pruning waste biochar (PWB), pruning waste compost (PWC) and control (without organic matter)), microbial inoculation (AMF and PGPR) and soil type (rhizosphere and non-rhizosphere soil). For this purpose, a soil sample with light texture and low available phosphorus content was prepared. PWB used in the experiment was produced from mix pruning waste of apple and grape at the final temperature of approximately 350°C for 3 hours. Moreover, pruning waste compost of apple and grape trees was prepared from Department of Soil Science, Urmia University. The biochar and compost were ground and screened through a 0.5 mm sieve for the greenhouse experiment. The seeds of wheat were planted in 20 × 15 × 20 cm rhizobox (length, width and height). At greenhouse experiment, the biochar and compost were added to the boxes in terms of 1.5% pure organic carbon before planting (each box contained 5.8 kg of soil). In control treatments (without organic matter), sterile soil was used with microbial inoculation. Microbial strains used for inoculation included Pseudomonas aeruginosa, Pseudomonas fluorescens and Pseudomonas putida) and mycorrhizal fungus (Glomus fasciculatum). Wheat seeds (Triticum aestivum L. cv. Pishtaz) were grown in rhizobox. At the end of the vegetative growth period, acid phosphatase (ACP) and alkaline phosphatase (ALP) enzymes activities were asseyedassayed by spectrophotometry method. Soil available P was extracted with 0.5 M NaHCO3 (Olsen-P) in the rhizosphere and non-rhizosphere soils and phosphorus concentrations in the root and shoot were determined by the standard method.
Results and Discussion: The results showed that the application of PWC and microbial inoculation significantly increased ACP and ALP enzymes activity and the availability of phosphorus compared to the control. The highest increase in ALP enzyme activity and available phosphorus was observed in PWC treatment inoculated with PGPR. Furthermore, PWC increased the ACP and ALP enzymes activities in the rhizosphere soil by 1.39 and 1.33 times compared to non-rhizosphere soil, respectively. However, phosphorus availability in the non-rhizosphere soil of the PWC treatment was 21.19% higher than that in the rhizosphere soil. The lowest available phosphorus content was observed in rhizosphere soil of AMF treatment. In addition, the highest phosphorus concentrations in plant root and shoot were, respectively, found in the compost and biochar treatments inoculated with AMF. In PWB treatment, the inoculation of AMF increased shoot phosphorus concentration by 1.31 times relative to PGPR inoculation.
Conclusions: In general, applying organic matter and microbial inoculation had a significant positive effect on phosphorus availability and plant growth. Adding organic matter to the soil, such as compost and inoculation with microorganisms particularly PGPR bacteria in the root zone, led to increased soil available phosphorus. The activity of phosphatases in soil was influenced by using organic materials such as compost and microbial inoculation which enhance the bioavailability of inorganic phosphorus. More positive interaction of PWC and PWB with AMF than PGPR in the rhizosphere caused greater increase of phosphorus bioavailability in the root zone and plant phosphorus uptake. In general, according to the results of this study, it seems that the use of organic materials and biological potential of the microorganisms have a significant effect on phosphorus availability and improve plant growth.
sanaz ashrafi saeidlou; Mirhasan Rasouli-Sadaghiani; Abbas Samadi; mohsen barin; ebrahim sepehr
Abstract
Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most ...
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Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most soils. Regarding that low molecular weight acids (LMW) play an important role in improving the bioavailability of soil nutrients such as non-exchangeable K (NEK), and the release rate of NEK plays a significant role in supplying necessary K for plants, the purpose of this study was comparison of potassium release kinetic from K-bearing including feldspar, illite as well as phlogopite minerals and choose the best kinetic equation describing potassium release process, influenced by organic as well as mineral extractants.
Material and Methods: The experiment carried out in a completely randomized design with three replications. Experiment factors were including extractant type (0.01 mol l-1 oxalic acid, 0.01 mol l-1 calcium chloride, control (deionized water)), potassium mineral type (feldspar, illite and phlogopite) and incubation time (1, 2, 4, 8, 12, 16, 24, 32, 48, and 64 hours). Elemental composition of minerals identified by Fluorescence spectroscopy device (S4 Pioneer). Used minerals in the experiment including feldspar, phlogopite and illite were ground and filtered through a 230 mesh sieve. In order to remove exchangeable K, samples were saturated by calcium chloride solution (with a ratio of 2:1), after washing with HCl, samples were dried at 105 °C for 48 hours. 100 mg of washed minerals, was weighed carefully and transferred to centrifuge tubes. Then 20 ml of each of extractants (oxalic acid and calcium chloride 0.01M) was added to the tubes. After 15 minutes shaking, tubes containing a mixture of minerals-extractants was carried out in a controlled incubation chamber for periods of 1, 2, 4, 8, 12, 16, 24, 32, 48 and 64 hours at 25 °C. After each period, samples were centrifuged at 3000 rpm for 10 minutes and filtered using Whatman paper (No. 41). pH and potassium concentration of samples were measured by pH meter and flame photometer, respectively. Data related to potassium release was fitted by zero order, first order, second order, power function, parabolic diffusion and ellovich equations.
Results and Discussion: Results showed that the effect of extractant type was significant on kinetic of potassium release, so that potassium release amount in samples extracted with oxalic acid was 1.48 and 2.35 times higher than samples extracted with calcium chloride and control (deionized water), respectively. Also, different minerals released various amounts of potassium. K release from phlogopite was 1.99 and 2.95 times higher than feldspar and illite, respectively. The maximum potassium concentration (440 mg kg-1) was seen in phlogopite which was extracted with oxalic acid. So that, amount of potassium in this treatment was 3.15 times higher than control one. Furthermore, the effect of extraction time on K release was significant. So that, at the beginning of incubation period the release of potassium by different extractants was more, but its amount decreased over time and finally continued with a constant speed. Kinetic equation fitting showed that zero order, first order, power function, parabolic diffusion and ellovich equations are able to describe potassium release but second order model cannot justify it. Among these five equation, the power function and parabolic diffusion equations with the maximum coefficient of determination (R2) and the least standard error of estimate (SE), could reasonably describe the K release kinetics, so they are introduced as the best models for data fitting. The slope (b) and interception (a) of ellovich equation indicate interlayer and initial K release, respectively. Oxalic acid and phlogopite had the most amount of interception, it means that the impact of oxalic acid on initial and interlayer release rate of K in phlogopite, is more effective than calcium chloride.
Conclusions: It is concluded that different factors like mineral and extractant type influence kinetic of potassium release and organic extractant have more ability in extracting non-exchangeable potassium from minerals structure. Also, the adjustment of the results of this study with first order, parabolic diffusion and power function equations suggest that nonexchangeable potassium release from minerals can be affected by diffusion process from the surface of the study minerals, indicating that NEK release rate is controlled by K diffusion out of the mineral interlayer.
MirHassan Rasouli-Sadaghiani; Habib Khodaverdiloo; Mohsen Barin; Solmaz Kazemalilou
Abstract
Introduction: Heavy metals (HMs) are serious threat for environment due to their dangerous effects. These metals as contaminants that can be accumulated in soil and after absorption by plants, finally will be found in food chains. Cadmium (Cd) is one of the dangerous HMs that threats the health of plants, ...
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Introduction: Heavy metals (HMs) are serious threat for environment due to their dangerous effects. These metals as contaminants that can be accumulated in soil and after absorption by plants, finally will be found in food chains. Cadmium (Cd) is one of the dangerous HMs that threats the health of plants, living organisms and human. Physicochemical remediation methods may cause large changes in different characteristics of soils . Recently environmental-friendly strategies including phytoremediation have been emphasized by researchers. Phytoremediation that refers to the use of plants and their assistance with microorganisms for remediation of contaminated soils is an effective and low cost method for reclamation of heavy metals polluted soils. The most important limitation of phytoremediation is low availability of heavy metals and sensitivity of plants to contamination. There are evidences that soil microbes can help to overcome these limitations through several ways. Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth and survival in heavy metal contaminated soils through different mechanisms including producing promoting metabolites, auxin, siderophore and antibiotics. In this study the role of some strains of PGPR (a mixture of Pseudomonas species including P. putida, P. fluorescens, and P. aeruginosa) and AMF (a mixture of Glomus species including G. intraradices, G. mosseae and G. fasciculatum), on uptake and accumulation of Cd, Fe, Zn and Cu as well as some physiological properties of Onopordon (Onopordon acanthium L) were evaluated.
Materials and Methods:This study was carried out under greenhouse condition as a factorial experiment based on a randomized complete block design with two factors including Cd concentration (four levels) and microbial treatment (three levels) in three replications. Consequently, a soil was selected and spiked uniformly with different concentrations of Cd (0, 10, 30 and 100 mg Cd kg-1 soil) at greenhouse of agricultural college in Urmia University. The contaminated soils were then sterilized and subsequently inoculated with arbuscular mycorrhizal fungi (a mixture of Glomose species including G. intraradices, G. mosseae and G. fasciculatum) and plant growth promoting rhizobacteria (a mixture of Pseudomonas species includeing P. putida, P. fluorescens, and P. aeruginosa). The seeds of Onopordon plants were grown in 2.5 kilogram pots under greenhouse condition. At the end of growing season the shoot dry weight, Cd, Fe, Zn and Cu concentration and element contents and some of physiological parameters of plant as well as microbial properties were analyzed. Furthermore, the effect of soil Pb level on population, activity and efficiency of the inoculated microbes was studied.
Results and Discussion: Significant difference was observed for plants’ dry weights. At different Cd levels, the yield of inoculated plants was higher than that of control plants. Furthermore, at elevated Cd concentration, plant height, biomass, relative yield, chlorophyll a, b, carotenoids, relative water content (RWC) decreased significantly (P < 0.05), however, plants inoculated with plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi showed considerable amount of dry matter, chlorophyll a, b as well as RWC. Mycorrizal and bacterial inoculation and Cd treatment also had significant effect on leaf photosynthetic pigments concentration and plant relative water content. In general, concentrations of photosynthetic pigments and RWC were higher in inoculated plants at every level of soil Cd. The microbial inoculation effectively decreased the inhibitory effects of Cd on plant growth. Shoot yield of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria plants increased by 2.7 and 2.1 times as well as microbial respiration increased by 2.17 and 2.01 times compared to control treatment. The results showed inoculated plant absorbed more Cd than non-inoculated plants. Plant growth promoting rhizobacteria were more effective than arbuscular mycorrhizal fungi inoculation in shoot Cd concentration. Cd contamination reduced soil microbial population and basal respiration. Results showed that with increasing soil Cd concentration shoot Fe, Zn and Cu concentrations significantly decreased. Root colonization rates decreased significantly with 10 mg kg-1 Cd addition for AMF treatments, and drastically with 100 mg kg-1 Cd added. Plant roots in the control and PGPR treatment were not colonized.
Conclusion: It is concluded that plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi inoculation could be sustained and promoted plant growth in phytoremediation processes. Therefore, under Cd contamination it can be use PGPR and AMF as growth promoters and finally enhance phytoremediation efficiency.