M. Deilamirad; Mohammad Reza Sarikhani; Sh. Oustan
Abstract
Introduction: Potassium is a major and essential plant macronutrient and the most abundant absorbed cation in higher plants. Potassium (K) plays an important role in the growth, metabolism, and development of plants. There are three forms of potassium found in the soil viz., soil minerals, nonexchangeable ...
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Introduction: Potassium is a major and essential plant macronutrient and the most abundant absorbed cation in higher plants. Potassium (K) plays an important role in the growth, metabolism, and development of plants. There are three forms of potassium found in the soil viz., soil minerals, nonexchangeable and available form. Soil minerals make up more than 90 to 98 percent of soil potassium. It is tightly bound and most of it is unavailable for plant uptake. Plants can uptake potassium only from the soil solution. Many indigenous soil microorganisms have the potential to absorb and mobilize the fixed form of nutrients from trace mineral sources. The use of plant growth promoting rhizobacteria including potassium-solubilizing bacteria as a biofertilizer could work as a sustainable solution to improve plant nutrient uptake and production. In this study the effect of five isolates of Pseudomonas were assessed on the growth and K uptake of tomato in two different soils with less than 200 mg/kg and more than 400 mg/kg available potassium.
Materials and Methods In this study, two different soil, Khalat pushan (K 400 mg/kg) were used. All the isolates including S6-6, S10-3, S14-3, S19-1 and S21-1 used in this study belonged to Pseudomonas genus and their potential were examined as a potassium releasing bacteria (KRB). Bacterial isolates were cultured in NB medium and were used in pot experiments. Experiment was conducted in a completely randomized design with three replications in two different soils by application of five bacterial isolates and the control without inoculum. Tomato seeds were inoculated with bacterial isolates in non-sterile soil and in the presence of indigenous soil microflora and the experiment continued until the beginning of the reproductive phase. The rate of inoculation was 10 ml of bacteria per pot. Growth and nutritional parameters such as dry weight of shoot and root, chlorophyll index, content of K and P in plant tissue were measured. Data analysis was performed by SPSS software, and the means were compared at α꞊5% by Duncan test.
Results and Discussion: The results of statistical analysis in the soil with less than 200 mg/kg available potassium (Khalatpoushan) showed the significant effect of bacterial inoculation on chlorophyll index, shoot and root dry weight and potassium and phosphorus content in shoot and root in bacterial treatments compared to the control. The highest amount of chlorophyll index, shoot dry weight and shoot absorption of potassium and phosphorus was accounted for S21-1. The highest amount of root dry weight and root absorption of potassium and phosphorus was accounted for S14-3.The results of second experiment in soil with more than 400 mg/kg available potassium (soil collected from Kandovan) showed that the measured properties were not affected by bacterial treatments. The highest amount of chlorophyll index was achieved by S14-3. The highest uptake of shoot potassium and phosphorus were recorded in plants which were inoculated by S14-3 and S21-1; however, the differences were not significant. While in this study we did not measure released K by bacteria in in-vitro condition but in the previous studies, their ability in K releasing from mica minerals such as muscovite and biotite had been measured and reported. Production of organic acid is one mechanism which proposed to explain potassium releasing ability of potassium releasing bacteria. It seems that this mechanism has the role in P solubilization, K releasing and solubilizing other nutients by plant growth promoting rhizobacteria (PGPR).
Conclusions: These results suggested that plant growth stimulating efficiency of bacterial inoculants affected by soil nutritional condition. The bacterial inoculation had a much better stimulatory effect on plant growth in soils with low available potassium. In this experiment, two isolates, S21-1 and S14-3 were better than the other isolates. Study in this area should be done especially in isolation and identification of potassium releasing bacteria from different soil samples. In the next step, these isolates should be tested in different soils under different climate conditions of the country, to choose robust and efficient isolate and intorduce them as KSB biofertilizer in counntry. It was the first report in Iran to test Pseudomonas isolates as KSB, while in the previous studies other genera especially bacteria belonged to Bacillus was reported in Iran.
Mohammad Reza Sarikhani; O. madani; Sh. Oustan
Abstract
Introduction: Potassium (K) is one of the major essential macronutrients for biological growth and development. The ability of some bacteria to release potassium from unavailable forms is an important feature for increasing plant yields of high-K-demand crops. Application of soil microorganisms is one ...
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Introduction: Potassium (K) is one of the major essential macronutrients for biological growth and development. The ability of some bacteria to release potassium from unavailable forms is an important feature for increasing plant yields of high-K-demand crops. Application of soil microorganisms is one approach to enhance crop growth. Some bacteria are efficient in releasing K from mineral sources and in recent years in order to produce and make of potassium biofertilizers, attention to the potassium releasing bacteria has been increased. Production of organic acids and acidic polysaccharides by the microorganisms are the main mechanisms by which K is released. Microorganisms play a central role in the natural P and K cycles. Many microorganisms in the soil are able to solubilize ‘unavailable’ forms of K-bearing minerals, such as micas, illite and orthoclases, by excreting organic acids which either directly dissolves rock K or chelate silicon ions to bring the K into solution. Recently, attention to the release of potassium from bacteria has been increased because some of efficient bacteria can be used as potassium biofertilizers to meet plant K needs. Hence, the objectives of this study were to in-vitro assessment of potassium releasing of some isolates belonged to Pseudomonas genus.
Materials and Methods: A laboratory dissolution study was carried out using a completely randomized design with three replicates. The factorial experiment contained two factors; 1-bacteria (including five bacterial treatments and un-inoclated treatment) and 2- mica minerals (including biotite and muscovite). Micas flakes were powdered and passed through a 0.5 mm sieve. Available forms of K were removed by washing with 0.1 M HCl and then distilled water, before adding the minerals to Aleksandrov medium For this reason, a microbial incubation study in the Aleksandrov liquid medium containing mica and tricalcium phosphate was designed for a period of one month and 5 strains of potassium releasing bacteria belonged to the genus Pseudomonas (S6-6, S10-3, S14-3, S19-1 and S21-1) along with the un-inoculated treatment (control) were applied. In this experiment, the release of potassium and phosphorus in liquid Aleksandrov medium were measured at intervals of 5 days in incubation period of 30 days. Nutrient Broth was used to prepare an overnight culture of bacteria to inoculate Aleksandrov medium. It should be mentioned that Aleksandrov medium was used to determine the amount of released P from tricalcium phosphate (TCP) while muscovite was added to the medium as a sole source of potassium. Concentration of P was determined spectrophotometrically by ammonium-vanadate-molybdate method and K was determined by flame photometry.
Results: The results showed that dissolved potassium and phosphorus in the inoculated medium were significantly increased and the amount of potassium released by the isolates was between 2.17 and 3.23 mg g-1 and the highest potassium release was achieved with isolate S14-3 (3.23 mg g-1), which that compared to the non-bacterial control showed an increase of 48.85 %, and significant difference was found with other isolates. Bacterial incubation experiment indicated the ability of isolates to release potassium from K-containing minerals such as biotite and muscovite and the XRD analysis revealed an alter in chemical structure of clay minerals. Especially, presence of 19.5Å peak in muscovite (saturated with magnesium) treated with isolate S14-3 showed the released space of K from the interlayer is filled or associated with a number of bacterial metabolites. It seems that the same mechanisms could be effective in releasing K from micas and P from TCP, in other words there is a co-solubilizing mechanism for mica and TCP.
Discussion and conclusion: It appears tha depletion of potassium from minerals has occurred but further tests will confirm this topic. The enhanced releasing of mineral K might be attributed to the release of organic acids from the bacteria, a mechanism which plays a pivotal role in solubilizing phosphate from inorganic source of phosphate. The mechanism of potassium release from minerals is still not clear. Productions of acids or chelates are main mechanisms to release K from potassium containing minerals. Among the bacterial strains under study, Pseudomonas sp. S14-3 was the most efficient strain in K release from micas and phosphate solubilization from TCP. However, more experiments need to be done especially in pot and field experiments to study the role of these strains in K nutrition of crops.
Mahdiyeh Leylasi Marand; Mohammad Reza Sarikhani
Abstract
Introduction: Potassium is one of essential elements for plants and it is the most abundant nutrient on soil surface which is important factor on plant growth and development. Factors such as potassium fixation, erosion, run-off and leaching cause reduction in available potassium of soil. Microorganisms ...
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Introduction: Potassium is one of essential elements for plants and it is the most abundant nutrient on soil surface which is important factor on plant growth and development. Factors such as potassium fixation, erosion, run-off and leaching cause reduction in available potassium of soil. Microorganisms especially bacteria play important role in changing unavailable potassium to available form. Hence, such bacteria can be used for increasing available potassium in soil and consequently production and quality of crops. The K- releasing bacteria can be employed as a biofertilizer to provide plant nutrients in a sustainable approach.
Materials and Methods: In this study, 10 bacterial isolates including Enterobacter sp. S16-3, Azotobacter chroococcum 14SP2-1, Pseudomonas sp. 34A-2, Pseudomonas Az-48, Psudomonas Az-8, S11-2 and 36A-2L provided from soil biology laboratory, department of soil science, University of Tabriz, Bacillus sp. 44-1 provided from soil biology laboratory of Gorgan University of Agricultural Sciences and Natural Resources, and S19-1+ S14-3 isolated from Potabarvar biofertilizer produced by Green Biotech Company were used as a potassium biofertilizer. For this purpose, bacterial inoculant prepared in bagasse and perlite carrier was used to inoculate the disinfected seeds of corn (single cross 704). In this research, bacterial treatments were compared with chemical fertilizer treatments including K50 and K100, in these treatments based on soil test, 50% and 100% of fertilizer recommendation were used (equal to 0.115 g and 0.23 g potassium sulfate per pot, respectively). The experiment was conducted based on completely randomized design with three replications. Duration of this study was about 2 months. Parameters measured during growth were stem diameter, height, chlorophyll index and stomatal conductance and after harvesting, wet and dry weight of root, shoot wet and dry weight, total wet and dry weight.
Results and Discussion: The results showed that expect root dry weight, total wet weight and stem diameter, all parameters were significantly affected by the treatments. The highest plant height was observed for fertilizer treatment 50% (100.8 cm) with an increase of 3.5% compared to the negative control. As to bacterial isolates, highest height was measured in Bacillus sp. 44-1 (98.6 cm). Plant height and stem diameters are indicators of vegetative growth, these parameters can thus increase when plant can use soil nutrients more than others. Enterobacter sp. S16-3 had the maximum stem diameter and the lowest height. It can be due to decreased potassium nutrition and auxin and gibberellin transferred from root. The chlorophyll index and stomatal conductance were equal to 9.567 and 0.097, respectively, which were related to A. chroococcum 14SP2-1. These are the factors of photosynthesis parameters. Increase of these factors may be attributed to the hormone balance effects such as cytokinin which can expand root growth and absorbance of nutrients. A. chroococcum is one of plant growth promoting rhizobacteria which can provide more phytohormones and cause improved plant growth. Therefore, photosynthesis activities can be better. The highest wet weight (265.6 g) and shoot dry weight (44.4 g) were found at fertilizer treatments 50% and then 100% fertilizer recommendation, but in regards to bacterial isolates, A. chroococcum 14SP2-1 and Pseudomonas Az-8 had higher values as compared with the control. The maximum root dry weight was observed in Pseudomonas Az-48 (187.2 g). However, the lowest root weight was obtained at 50% fertilizer recommendation. Hence, this can be explained by the root developing types. The highest total dry weight was measured in Enterobacter sp. S16-3 (63.68 g) and Pseudomonas Az-8 and after these bacterial isolates, fertilizer treatments had better condition. Consequently, these bacteria had another effects on plants such phytohormones productions and enzymatic activities that chemical fertilizer did not have such influences. The highest average of shoot potassium content was observed at 100% fertilizer recommendation (1077.3 mg/plant).
Conclusions: The results showed that fertilizer treatments K50 and K100 had better conditions and pots with chemical fertilizer grew more than others in most plants. But some bacterial isolates showed comparable results relative to K50 and K100. These bacteria can affect plants with directly and indirectly mechanisms. Bacterial treatments such as A. chroococcum 14SP2-1 and Pseudomonas Az-8 improved growth parameters through solubilizing potassium and producing phytohormones. Hence, these isolates can be considered for further studies particularly under field condition.
Bahman Khoshru; Mohammad Reza Sarikhani
Abstract
Introduction: Application of chemical and organic carrier and its integration with useful microorganisms including phosphate solubilizing bacteria (PSB) has facilitatedproduction of phosphate microbial fertilizers (PMFs), which are used in granular or powder form. One of the major limitation of thesebiofertilizers ...
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Introduction: Application of chemical and organic carrier and its integration with useful microorganisms including phosphate solubilizing bacteria (PSB) has facilitatedproduction of phosphate microbial fertilizers (PMFs), which are used in granular or powder form. One of the major limitation of thesebiofertilizers is decline or loss of PSB viable cell in the granule preparation process. Accordingly, in this study, isolation of temperature resistant phosphate solubilizing bacteria was performed and temperature tolerance and ability to dissolve phosphate from rock phosphate (RP) and tricalcium phosphate (TCP) sources were evaluated.
Materials and Methods: Firstly, each soil samples incubated for 16 hours at 55 °C, then dilution series were prepared and 100 μl of four final dilutions (10-6, 10-7, 10-8, and 10-9) were used to spread on Sperber solid medium. After spreading the microbial suspensions from the dilutions in the Sperber solid culture medium and the appearance of colonies, screening based on the resistance to soil temperature treatment and, subsequently, the ability to grow in a solid Sperber solid medium and dissolution of low solubility phosphate (formation of transparent halo), was done to isolate PSB. In order toprepare PMF, each of screened PSB were cultured in NB, andthen 1 ml of overnight culture wasmixed with 9 ml sterile distilled water and added to the basal formulation of rock phosphate (45 g), bagasse (30 g) and sulfur (15 g) with initial temperature of20°C.Temperature treatments (55 °C for 16 hours) of bacteria were performed in three steps: a) on sampled soils, b) pure-culture of bacteria and c) bacteria added to the carrier. Microbial population in provided microbial fertilizer was countedin two ways a) half of the microbial fertilizer was kept at normal temperature by maintaining the initial conditions, b) another half after the temperature applied (55 ° C for 16 hours). The semi-quantitative and quantitative test of insoluble inorganic phosphate solubility was performed by isolates in solid and liquid Sperber medium. The 16S rRNA molecular method was used to identify the isolated bacteria by general primers 27F and 1492R.
Results and Discussion: Five bacteria (RPS4, RPS6, RPS7, RPS8, RPS9) out of nine isolated bacteria were able to solubilize mineral phosphate (TCP and RP) but only two isolates (RPS7 and RPS9) were resistant to temperature (55 °C for 16 h). In tricalcium phosphate medium, the RPS9 and RPS7 bacteria had a high ability to solubilize insoluble inorganic phosphate with average of 2.60 and 2.27 for a ratio of (HD / CD) after 12 days, respectively. There was no halo in Sperber medium containing rock phosphate. The amount of solution in the quantitative methods was also obtained to be 563.8 and 324.1 mg / l for RPS9 and RPS7 bacteria, respectively. The prepared microbial fertilizer was counted in two ways (a): half of the sample fertilizer was kept at normal temperature by maintaining the initial conditions; (b):after the maintaining temperature at 55 °C for 16 hours, the population of other half was determined. During counting the initial microbial population (zero time) at normal temperature, all bacteria used in microbial carrier had an acceptable population. During examining the populationsof microbial in the initial carrier, RPS4, RPS6, RPS7, RPS8 and RPS9 bacteria were 3.6, 3.5, 3.6, 3.5, 3.6 and 3.5 (×106 CFU/g), respectively. After 4 months the populations were 4.6, 6.3, 9.6, 7.4 and 8.6 (×105) and in the 6th month, the populations were 3.9, 3.8, 12.3, 4. 7 and 9.2 (×104) seeming to be favorable for the tested bacteria. It seems that this survival time for the tested bacteria is desirable. During countingactive population of temperature treated microbial fertilizers, the initial population of the microbial carrier (at zero time) decreased 10 times with respect to the non-treated carrier. Active population ofRPS9 and RPS7 (temperature-resistant treatments) in the zero time was 4.5 and 4.3 (×105), respectively. Although the RPS9 and RPS7 microbial populations were able to survive in non- temperature treatments for 6 months, it was observed that in the treatment, this viability practically reduced to 4 months. Molecular identification of the isolates RPS7 and RPS9 revealed that they belonged to Pantoeaagglomerans.
Conclusions: According to the findings of this research, using phosphate solubilizing bacteria and temperature resistant Pantoeaagglomerans RPS9, recently isolated and identified, can be considered toindustrially produce granular microbial fertilizers. It is worth mentioning thatfurther studies are required to be carried out on the effectiveness of this formulation with these bacteria infield scale.
Mohammad Reza Sarikhani; N. Chalabianlu; S. S. Alavikia
Abstract
Introduction: Phosphorous is one of the essential macronutrients for plant growth and development but its mobility in soil is very low. The utilization of the soil biological potential, in particular phosphate solubilizing bacteria, is an efficient way which can be used for exploiting available sources ...
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Introduction: Phosphorous is one of the essential macronutrients for plant growth and development but its mobility in soil is very low. The utilization of the soil biological potential, in particular phosphate solubilizing bacteria, is an efficient way which can be used for exploiting available sources of phosphorous in the soil. The principal mechanism for mineral phosphate solubilization is the production of organic acid, and acid and alkaline phosphatases play a major role in the mineralization of organic phosphorous in the soil. Presence and distribution of phosphate solubilizing bacteria in the soil and soil phosphatase activities is influenced by soil conditions such as climate, soil type, vegetation and land uses. In order to understand the relationships and considering the importance of the subject, the soil samples were chosen from two different climates; semi-moist (Fandoghlou-Ardabil) and semi-arid (Namin- Ardabil) under culture of legumes, cereals and uncultivated areas, in this experiment.
Materials and Methods: In order to study the effects of different land uses, climate conditions and soil physicochemical properties on phosphate solubilizing microorganism (PSM) distribiution and soil acid and alkaline phosphatase activity, a factorial experiment based on completely randomized design was performed with considering three different land uses (including legumes, cereals and wasteland) and two climate conditions (semi-moist: Fandoghlu- Ardabil and semi-arid: Namin-Ardabil). Four composite soil samples (0-25 cm) were taken from each land uses. Finally, a total number of 24 soil samples were used to enumerate phosphate solubilizng bacteria and evaluate soil phosphatase activities. The enumeration and selection of bacteria in the mineral Sperber medium was done by attention to the clear zone production in the presence of tri-calcium phosphate and in organic sperber (IHP+BCIP) due to blue phenotype of grown colonies. Also, phosphatase activity of soil samples was assessed based on the usual methods for phosphatase assessment. Moreover, after the evaluation of the physicochemical properties of the soil samples and soil enzyme activities and PSB distribution, all data were analyzed by SPSS and MSTAT-C softwares.
Results and Discussion: The Sperber mediums containing mineral and organic phosphates were used in counting the number of PSB. According to the results, the highest total number of bacteria (>6 log cfu/g) was gained in legume land uses in both climate conditions. Furthermore, the highest numbers of organic and mineral phosphate solubilizing bacteria (5.3 log cfu/g) were counted in samples taken from pastures, in other word in soil samples which were collected from uncultured land in semi-moist climate conditions. Enzyme assay showed that acid phosphatase activity (430 µg pNP/g.h) in semi-moist climate conditions were increased three times in comparison to semi-arid climate conditions. Perhaps, this increase can be explained by parameters such as high moisture content and organic matter which can cause an increase in the number of bacteria and soil enzyme content. Our results showed that, alkaline phosphatase activities (APAs) were affectd by interaction effects of land uses and climate, wherein the highest APA (810 µg pNP/g.h) was measured in legume samples in semi-arid climate conditions. The pH of these soil samples and supporting legume rhizospheres from AP producing microorganisms may be the reasons of this increment.
Conclusion: The highest activity of the soil acid phosphatase was observed in soil samples which were taken from uncultivated area under semi-moist climate conditions (namely pastures) (866.59 µgPNP/g.h) while the soil alkaline phosphatase activity had high mean in legume land use soil samples under semi-arid climate conditions (795.15 µPNP/g.h). The total number of bacteria was the highest in semi-arid leguminous land use (14.13×106 cfu/g) but the total numbers of solubilizing bacteria in both mineral and organic media were the highest in semi-moist uncultivated area (respectively 1.9 ×106 and 1.48 × 106cfu/g).
