Soil Biology, Biochemistry and Biotechnology
Elham Sadeghi; REZA GHORBANINASRABADI; Seyed Ali Reza Movahedi Naini; Mojtaba Barani Motlagh; Mostafa Khoshhal Sarmast; Mohammad Reza Pahlevan Rad
Abstract
Introduction Plant growth and crop productivity may be adversely affected under unfavorable environmental conditions, such as a lack of organic matter in the soil. To counteract the negative impacts of these challenges, a unique strategy is required. The paucity of organic inputs, which is common in ...
Read More
Introduction Plant growth and crop productivity may be adversely affected under unfavorable environmental conditions, such as a lack of organic matter in the soil. To counteract the negative impacts of these challenges, a unique strategy is required. The paucity of organic inputs, which is common in conventional agricultural production, can lead to soil degradation, erosion, and loss of soil organic matter, which are unfortunate consequences. Soil organic amendments have been shown to have beneficial effects on crop production and a wide range of soil properties in agricultural systems. However, the limited availability of phosphorus (P) in soil can significantly restrict crop growth and productivity, particularly in maize crops. Adequate P supply has been found to enhance early maturity, crop quality, and yield. However, the prolonged use of chemical fertilizers such as NPK has been found to have adverse effects on soil fertility and crop quality. As a result, the combined application of organic and chemical fertilizers has been proposed as an effective approach compared to the single application of organic or chemical fertilizer alone. Therefore, this study aimed to assess the potential benefits of using compost and Triple Super Phosphate fertilizer (TSP) application on the chemical and biological properties of soil, as well as the properties of forage maize (cv. SC704), in loess soil.Materials and Methods A factorial experiment was conducted using a completely randomized design with three replications. A total of 36 samples were performed in two separate cultivated and incubated experiments. A pot experiment was conducted to invwstigate the effects of simple and enriched compost, containing urea and Streptomyces, and varying amounts of TSP fertilizer (0, 10, 40, and 100 mg/kg), on soil properties and maize plant growth. In addition, an incubation experiment was conducted to measure the effects of the same treatments on soil microbial biomass and activity. The effect of treatments were analyzed as factorial under a completely randomized design. The biomass of maize plants was measured at the time of harvesting (the time from planting to harvesting of forage maize was 80 days). Some parameters such as available phosphorus, substrate-induced respiration, microbial biomass carbon, and some enzyme activity (acid phosphatase, alkaline phosphatase, catalase and urease) were measured in soil.Results and Discussion The findings of this study indicated that the application of compost and TSP fertilizer had significant effects on plant biomass. Specifically, compost application led to an increase in microbial biomass carbon and enzymes activity (acid phosphatase, alkaline phosphatase, catalase and urease) in the soil, ultimately promoting plant growth. Moreover, the combined application of compost and TSP fertilizer increased the availability of phosphorus, substrate-induced respiration, and microbial biomass carbon in the soil. Based on the findings, the combined application of TSP and compost resulted in further increases in substrate-induced respiration (63-168%), microbial biomass carbon (72-167%), available phosphorus (29-103%), and enzyme activity (acid phosphatase (4-21), alkaline phosphatase (14-34%), catalase (13-32%), and urease(54-159%)) compared to the application of each amendment alone. This suggests that the addition of both TSP and compost promotes the availability of easily accessible nutrients for microbial growth and soil enzymes (acid phosphatase, alkaline phosphatase, catalase and urease) activity. The highest amount of available phosphorus, microbial biomass carbon, substrate-induced respiration, catalase activity and urease activity in cultivated soil (23%, 270%, 93%, 68%, 1.8%, respectively) and incubated soil (18%, 243%, 90%, 53%, 1.2%, respectively) were observed in C2P3 treatment. The results also indicated that the enriched compost+TSP treatment led to the highest substrate-induced respiration and microbial biomass carbon, followed by simple compost+TSP, enriched compost only, simple compost only, TSP fertilizer only, and the control. The increase in enzyme activity (P<0.01, r=0.90), and available phosphorus (P<0.01, r=0.60) in the soil positively influenced plant growth. Specifically, the simultaneous application of compost and TSP had a greater effect on maize plant biomass. The highest root biomass (2.80 g), stem biomass (10.4 g), and leaf biomass (2.27 g) were observed in the enriched compost and 100 mg kg-1 TSP treatment, which differed significantly from the other treatments.Conclusion The results of this study demonstrated that the addition of compost and TSP to loess soils can promote microbial biomass carbon, substrate-induced respiration, enzyme activity (acid phosphatase, alkaline phosphatase, catalase, and urease), available phosphorus, and maize plant growth. Moreover, the use of compost can protect soil microbial and enzymatic activities in loess soils. Thus, the simultaneous application of enriched compost with TSP can reduce the use of chemical fertilizers and their negative environmental impacts.
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 ...
Read More
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.
Soil Chemistry and Pollution
Hadi Habiby; Alireza Movahedi; Mojtaba Khoshravesh; Alireza Saberi
Abstract
Introduction Increasing the yield and, consequently, increasing the concentration of macro and micro nutrients in the plant is one of the important aspects of agriculture. The improvement of the quality and quantity of some elements, such as potassium, zinc, and iron in the soil can cause an increase ...
Read More
Introduction Increasing the yield and, consequently, increasing the concentration of macro and micro nutrients in the plant is one of the important aspects of agriculture. The improvement of the quality and quantity of some elements, such as potassium, zinc, and iron in the soil can cause an increase in the yield of the crop and the concentration of these elements in plant tissues. The increase in the concentration of these elements in plants can be effective in the health of livestock and consequently the health of humans. One of the new approaches that can be used in this field is the use of magnetic water. Magnetic water is obtained by passing water from a magnetic field. An externally applied magnetic field causes changes in the atomic, molecular, and electronic structure of the treated water, such as changes to its solidifying and boiling points, viscosity and the dielectric constant, the formation of clustering structures from linear and ring hydrogen-bound chains of molecules, the magnetic interaction between these clustering structures, and increasing the polarization effects of water molecules. The biological effects of magnetic field or electromagnetic field treatments depend on the strength and exposure period of water conditioning, in particular, the ion content, quality, and the volume of water. Materials and Methods For this purpose, a field experiment was conducted in a factorial arrangement with two main treatments, adding and without adding potassium and zinc fertilizers, and five sub-treatments (magnetic field strengths, including a 0.4 Electromagnetic Coil (EC), 0.3 magnet, 0.3 EC, 0.1 EC, and the control treatment) in four replications at Research Station of Goran University of Agricultural and Natural Resources. The size of each experimental plot was 2 m × 2.5 m. Corn was planted in each plot with the distances of 15 cm from each other and rows with distances of 70 cm from each other. An electromagnetic coil and a permanent magnet were used to create a magnetic field. Water was passed from the middle of this magnetic field through a hose and the plots were irrigated with this magnetic water. The irrigation was conducted based on soil moisture content and continued until the harvest and drying of the plants. Soil and plant samples were taken at two flowering and harvesting stages and were transferred to the laboratory for analyzation. Concentrations of Zn and Fe in the soil and plant tissues were measured. Statistical analysis was performed using the SAS software. Results and Discussion The results of this study showed that all the plots that were irrigated by magnetic water had corn plants with greater height and more yield was obtained than the control treatments. This could be due to the ease of absorbing water from the soil. Magnetic water has lower surface tension than untreated water, so the plant needs less force to absorb water from soil particles. Also, the plants that were irrigated by magnetic water had higher concentrations (P <0.01) of elements such as zinc and iron in their cobs. Magnetic water can increase the availability of the elements in the soil. So, more concentration of elements can be absorbed by the roots and transferred to the aerial parts of the plants. Among the magnetic water treatments, 0.4 Tesla strength treatment had the highest effect on the yield and corn height, as well as zinc and iron concentration in cobs (P <0.01). Higher strengths of the magnetic field (0.4 T) had more effect on the availability of elements in the soil and their absorption by the plants. The yield of corn in 0.4 EC, 0.3 M, 0.3 EC, and 0.1 EC treatments that potassium and zinc fertilizers were added to them increased as compared to the control. So, increasing the strength of the magnetic field had more effects on some soil properties. The treatments that K and Zn fertilizers were added to them had more yield than other treatments that these fertilizers were not added to them. This could be attributed to the fact that magnetic water has increased the solubility of K and Zn fertilizers. In fact, magnetic water has been able to increase the uptake of Zn from the soil. Conclusion These results indicate that the magnetization of water can be used as an appropriate approach to increase the quantity and quality of product yield and the concentration of the elements in the crops.
Soil Physics, Erosion and Conservation
Sahar Akhavan; Soheila Ebrahimi; Maryam Navabian; Mahmoud Shabanpour; Alireza Movahedi; Ali Mojtahedi
Abstract
Introduction Soil macropores are the prominent factor in the transfer of wastewater, fertilizers, and microorganisms, including fecal bacteria to deeper soils and even underground waters. On the other hand, a vast majority of land in Iran is located in arid and semi-arid regions. Therefore, the use of ...
Read More
Introduction Soil macropores are the prominent factor in the transfer of wastewater, fertilizers, and microorganisms, including fecal bacteria to deeper soils and even underground waters. On the other hand, a vast majority of land in Iran is located in arid and semi-arid regions. Therefore, the use of salty and unconventional waters has recently gained considerable importance. The aim of this study is to investigate the preferential transportation and storage of Escherichia coli (as an important bacterium in commonly used fertilizers) under the condition of saline water application. Materials and methods The laboratory studies were conducted in a preferential flow system with artificial macropores with different diameters (1 and 2 cm) and varying salinity treatments (1, 2 and 4 dsm-1) under a saturated flow condition. The leaching test was performed at 20°C within several phases. Microbial transfer tests were carried out in two phases with boundary conditions and flow velocities similar to the zero-phase condition. In order to evaluate the bacteria in the soil profile, after the end of the bacterial transfer test, the soil column was divided and cut into 3 layers. Two samples were collected from 3 depths and at macropore and matrix zones. The experiment was conducted in a factorial format and completely randomized design with three replications. The results showed that the mutual effect of salinity and macropore diameter was significant (at 5%) on mean output concentration (Cav), soil filtration coefficient (fλ), relative absorption index (SR), and maximal predicted depth of bacteria transfer (Zmax). Results The results indicated that the bacteria were affected by the treatments during the transfer, so that with increasing the salinity and reducing the diameter of macropores, the average bacterial concentration output decreased. The presence of macropores and the integrity of pores in a column with a diameter of 2 cm accelerated the bacterial movement and increased the pollutant outflow index due to high porosity; therefore, more bacteria passed (compared to the control column without macropores). The salinity treatment, however, served as an inhibitor and hindered further transmission of bacteria. Moreover, The macropore-free column with a salinity of 4 dsm-1 exhibited a higher refining coefficient (0.85 cfuml-1) compared to other treatments. A salinity treatment involving a 1 dsm-1 salinity and a pore diameter of 2 cm showed the least filtration coefficient (0.82 cfuml-1), so by doubling the ionic strength, 30% reduction can be seen in the bacterial filtration coefficient. Increasing the salinity up to 2 dsm-1 and decreasing the macropores diameter increased the relative absorption index. The macropore-free treatment with a 2 dsm-1 salinity showed the highest relative sorption index (0.92). Although the bacterial growth and mortality are unknown during the bacterial transfer process, according to the results, it is expected that the bacterial mortality rate increases by the salinity enhancement from 2 to 4 dsm-1 and the relative adsorption index reduction which may result in lower surface sorption. The significant treatment for the maximum predicted depth of bacterial transfer was the mutual effect of salinity and diameter at a probability level of 5%, which confirmed the significant impact of salinity on the bacterial filtration and transfer. The maximum depth of predicted bacterial transfer was obtained in the macropore-free treatment with the salinity of 1 dsm-1 (16.81 cm). The role of the underlying layers in the bacterial refinery seems to be more profound compared to the surface layer. Conclusion Overall, the results showed that the main source of transmission of bacteria is the preferential flow due to the macropore continuity. However, the salinity reduced the amount of bacterial refining by increasing the ionic strength of the soil solution. The salinity had a significant effect on the average output bacterial concentration, bacterial refining coefficient, relative sorption index, and maximum predicted bacterial transmission depth. The results of this study revealed that increased ionic strength of soil solution can enhance the bacterial refining and the further elimination of bacteria which can be effective in controlling the pollution of underground water by saline irrigation management. Regarding the quantitatively and qualitatively critical water status in the country, conditions can be provided for the use of unconventional water sources, without threatening the environment and contaminating the underground water.
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 ...
Read More
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.
Plant Nutrition, Soil Fertility and Fertilizers
Elham Mirparizi; Mojtaba Barani motlagh; Alireza Movahedi; REZA GHORBANINASRABADI; Somayeh Bakhtiary
Abstract
Introduction: Among the micronutrients required by plants, iron deficiency has the maximum limitation for agricultural crops. Iron plays an important role in synthesis of chlorophyll, energy transfer in plants, formation and synthesis of special enzymes, and fixation of nitrogen. Deficiency of iron in ...
Read More
Introduction: Among the micronutrients required by plants, iron deficiency has the maximum limitation for agricultural crops. Iron plays an important role in synthesis of chlorophyll, energy transfer in plants, formation and synthesis of special enzymes, and fixation of nitrogen. Deficiency of iron in plants causes chlorosis or yellowing of young leaves. Iron deficiency is developed due to imbalance of metal ions including copper and manganese, large phosphorus in soil, poor aeration, low temperatures, soil iron deficiency, low organic content, and high concentration of bicarbonate in the root environment. To solve the problem of iron deficiency in plants, very expensive methods are used. Usage of solid wastes of copper melting factories such as slag as soil modifying materials can be useful in iron nutrition. The possibility of using reverb furnace slag of Sarcheshmeh Copper complex as an iron fertilizer was examined in a calcareous soil. Since copper slag contain considerable amount of iron (53.8% iron oxides), therefore, its proper management can solve the problem of iron deficiency in calcareous soils. Materials and Methods: To investigate the effect of copper slag and organic compounds on iron availability and growth of Sorghum plant, (Speed Feed cultivar), a soil sample was harvested with low soil absorbable iron and organic compound. After air-drying, the soil samples were passed through a 2-mm sieve. Some physiochemical properties of the soil sample used, organic compounds, and the slag were characterized by typical experimental methods. The experimental design was performed as a factorial experiment (copper slag and organic compounds) in a completely randomized design with three replicates. The experimental treatments included five levels of organic compound (pistachio shell and cow manure at two levels of 2% , 4% and the control sample) and 10 levels of iron (copper slag, copper slag with sulfur, copper slag with sulfur and thiobacillus, acidic slag (each at two levels), Fe-EDDHA, and control sample). The experimental treatments were incubated for 3 months. Treatments were then applied to 3 kg samples of soils and the treated samples were incubated in plastic containers at field capacity (FC) moisture content for up to 90 days. At the end of incubation period, 10 sorghum seeds were cultivated in each pot. Foliar application of Fe-EDTA with a concentration of 5 ppm in addition to the mentioned treatments. Harvesting sorghum shoot was performed 90 days after the cultivation. The plant samples were dried for 48 h at 70°C. After digestion of the plant samples by wet oxidation method, concentration of iron, zinc, nickel and cobalt were measured by atomic absorption spectrophotometer. Soil samples were also taken from the pots. After being air-dried, the soil samples were passed through a 2-mm sieve. Amount of electrical conductivity, soluble sodium, concentration of calcium and magnesium as well as iron, zinc, nickel, and cobalt were measured. All statistical analyses were performed using SAS software. Means of different treatments were compared using LSD (P ≤0.05) test. Results and Discussion: Application of acidic slag increased the soluble sodium and sodium absorption ratio and decreased the soil absorbable iron content. Application of 4 times critical level as slag (S4) increased iron and zinc absorbable by soil, as well as increased concentration of the plant iron. The copper slag with sulfur and thiobacillus developed the maximum absorbable zinc in soil. Comparison of the organic compounds indicated that cow manure has a greater influence on the amount of absorbable iron in soil, iron concentration and uptake by the plant than pistachio shell. On the other hand, with reduction of the concentration of heavy metals, its application is recommended in comparison with pistachio shell. The content of zinc, nickel, and cobalt in the studied plant did not exceed the toxicity level. Heavy metals have low mobility in the soil and are often stabilized by soil colloids or precipitate as different compounds. For this reason, their mobility and transference to shoot diminish. Conclusion: The slag from copper melting has micro nutrient including iron and zinc. Therefore, it can be concluded that the copper slag has the potential of a source supplying elements for plants. These results confirm the lack of use of acidic treatments. In addition of iron and zinc availability for plants, measurement of other heavy metals in the plant showed that the concentration of measured heavy metals was below their toxicity level. Therefore, suitability of this compound for agriculture will be confirmed. Since addition of heavy metals to soil has various environmental effects, thus repetitive use of slag and its use in large amounts are not recommended. As in absorption of nutrients, immobility in soil, stabilization of metal in the root, and preventing its transference to shoot organs are among the mechanisms of plant when exposed to high concentration of heavy metals, it is suggested that the amount of heavy metals be studied in the root.
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 ...
Read More
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.
A Ardeshiri Lajimi; R Ghorbani Nasrabadi; M Barani Motlagh; S A Movahedi
