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 soilviz., 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. …

Potassium (K) is an essential macronutrient that plays an important role in the growth and development of plants. Throughout the present study the possibility of K-release from mica minerals was evaluated through the action of several Bacteria isolated from rhizosphere samples of grasses. The experiment was conducted as a factorial one, based upon a completely randomized design of three replicates comprised of two factors including 8 isolates of Bacteria and two sources of Potassium mineral. Following isolation of Bacteria from the plant roots through NFB medium, eight selected isolates were ultimately used for the final experiment. Potassium release capability of these isolates was assessed using liquid Aleksandrov culture medium. Acid washed pretreated minerals, as a source of Potassium, were added to 30 ml of Aleksandrov medium. Following incubation for one week at 26 ° C and shaking at 120 rpm, released K in supernatant was assessed through flame photometer. The highest K release on the average was obtained by the isolate Az-8 (11. 16 mg/l) and it was revealed that this bacterium was more efficient in Releasing K from biotite than from muscovite, and the lowest rate of K release was obtained by Az-15 (2. 8 mg/l). The results also revealed that K released from biotite exceed muscovite when the two types of mica compared. Among the Bacterial isolates Az-8, Az-12 and Az-19 showed great potential for K release and their molecular (16S rDNA) and biochemical identification revealed that Az-8, Az-12 and Az-19 belonged to Pseudomonas genus. According to the promising results of in-vitro assays, inoculation and application of these efficient isolates will be recommended in greenhouse and field tests with different crops.

Background and objectives: There are large amount of K in soil but main of that are not in the available form for plants hence Potassium deficiency can occur in this condition. Hence, dissolution of soil minerals with microorganisms is notable and it could be very important to use Potassium Releasing Bacteria for supplying Potassium to plants. Accordingly, this experiment was performed in order to determine the effect of different Bacterial isolates on providing Potassium in corn. Materials and methods: This greenhouse experiment was performed using completely randomized block design with three replications and with application of disinfected seeds of corn (KSC 704). Experiment treatments were including 10 treatments with different Bacterial isolates inoculation (including Pseudomonas, Bacillus, Enterobacter and Azotobacter), fertilizer treatments (K50 and K100; using 50% and 100% of K2SO4 based on fertilizer recommendation) and negative control (no Bacterial inoculation and no fertilizer). The experiment prolonged to the beginning of reproductive phase and after harvesting and oven-drying of plant specimen, dry weight of shoot and root were weighed. Eventually, plant samples were digested and concentration of Potassium, phosphorus and nitrogen were measured in extracts. Results: Results showed expect root dry weight, phosphorus transfer factor and shoot phosphorus concentration, all the parameters were significantly affected by treatments. The highest total Potassium content were obtained in Pseudomonas sp. Az-8 and 100% fertilizer recommendation, respectively equal to 1582 and 1570 mg plant-1. Among Bacterial isolates, the highest total content of phosphorus and nitrogen belonged to Az-8 that was equal to 50. 59 and 264. 5 mg plant-1, respectively. But the highest shoot Potassium concentration and content were in 100% fertilizer treatment, 2. 55% and 1077. 289 mg per shoot weight, respectively. But in regard to Bacterial isolates, this parameter was measured in A. chroococcum 14SP2-1 with an increasing of 24% and 16% as compared with control. The highest root Potassium concentration and content (2. 4% and 605. 1 mg per root weight, respectively) were observed in Pseudomonas Az-8. This isolate has the highest efficiency of Potassium nutrition by 104. 5%. The maximum shoot dry weight was observed in 50% and 100% fertilizer treatments (44. 42 and 44. 06 g). Conclusion: In general results of experiment showed, some Bacterial inoculations were better than chemical fertilizers in some parameters and it could be related to biological effects of Bacteria in soil. Overall, it could be suggested to use selected Bacteria such as Pseudomonas Az-8, A. chroococcum 14SP2-1 and Enterobacter S16-3 for ongoing and future experiments.

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. …

Mineral weathering is a major source of most essential nutrients including Potassium. The micaceous minerals, as the major source of Potassium, are abundant in Iranian soils. The aim of this study was to investigate the effect of silicate dissolving Bacteria and rhizosphere zone on using the structural Potassium from glauconite. A pot experiment was carried out in a completely randomized design with factorial arrangment and three replicates under greenhouse condition.The factors of treatment were nutrient solution (complete or K-free nutrient solution) and silicate dissolving Bacteria (with and without Bacteria). The growth media was mixture of quartz sand (as the filling material) and glauconitic shale.During a period of 100 days, Pots were irrigated with distilled water and stegner nutrients solution. At the end of experiment, shoots were harvested and plant samples were prepared with dry ashing method and the concentration of Potassium was determined with flame photometer. In K-free treatment, plant uptake was significantly affected by silicate dissolving Bacteria at 1% level. In such a way the maximum uptake of Potassium was belong to the complete nutrient solution and with silicate dissolving Bacteria. No significant difference was found between complete nutrient solutions and without Bacteria treatment and K-free nutrient solution and with Bacteria treatment. In general, this indicates the effect of silicate dissolving Bacteria on providing Potassium for plant.

More than one century ago, the first commercial product of biofertilizer was produced in the world and its production in Iran was initiated around 15 years ago. According to the importance of biofertilizers in the sustainable and organic agriculture, in this paper we try to review on the biofertilizer researches in Iran, especially to the mechanism of biofertilizers actions. This paper will focus on nitrogen biofertilizers mainly to the Rhizobia, AzotoBacteria, Azospirilla as well as the phosphate solubilizing Bacteria (PSB) and Potassium Releasing Bacteria (KRB). Attention to the Arbuscular Mycorrhiza (AM) is the other aspect of this study. The isolation methods of most important microorganisms with potential to being used as a biofertilizer are taken into consideration at the end of each section of this article. At the end, we considered results of some researches on application and effects of biofertilizers on growth, yield and quality properties of plants in Iran.

Introduction: Potassium (K) is the third major essential macronutrient for plant growth. Without adequate Potassium, the plants will have poorly developed roots, grow slowly, produce small seeds and have lower yields.Due to imbalanced fertilizer application, Potassium deficiency is becoming one of the major constraints in crop production. The concentrations of soluble Potassium in the soil are usually very low and more than 90% of Potassium in the soil exists in the form of insoluble rocks and silicate minerals. Soil microbes have been reported to play a key role in the natural K cycle and therefore, Potassium solubilizing microorganisms present in the soil could provide an alternative technology to make Potassium available for uptake by plants. Thus, identification ofmicrobial strains capable of solubilizing Potassium minerals quickly can conserve our existing resources and avoid environmental pollution hazards caused by heavy application of chemical fertilizers. …

To investigate the effects of water deficit stress and bio and non-bio fertilizers on Thymus Vulgaris, a split plot experiment was conducted based on randomized complete block design with three replications in 2017 in Asgarya agricultural field in Yazd. The treatments included water tension: W1=7 (Control), W2=12 and W3=17 days irrigation intervals as the main factor and bio and non - bio fertilizers at five levels including B1= control (without fertilizer), B2= endo mycorrhiza (Glomus), B3= Azospirillum Bacteria, B4= Pseudomonas Bacteria and B5= chemical fertilizer (NPK) a sub – factors. Results showed that the highest flowering branches yield, a, b, and total chlorophylls and nitrogen and phosphorus elements were observed in 17 days of irrigation (W3). 12 days of irrigation treatment (W2) showed the highest Potassium element rate. The highest a, b and chlorophylls and nitrogen were observed in Azospirillum treatment (B3). The highest total chlorophyll, phosphorus element, carotenoids and flavonoids were observed in Pseudomonas treatment (B4); the highest Potassium element rate were obtained in mycorrhiza treatment (B2); the highest flowering branches yield were observed in NPK treatment (B5) and control (B1) treatment resulted in the highest anthocyanin

The deficiency of macro-nutrients such as phosphorus and Potassium is very important due to vital roles of these elements. Although the total amount of phosphorus and Potassium in the soil is high, the formation of insoluble forms of phosphorus, as well as the stabilization of Potassium in silicates, has led to the shortage of these essential elements. The use of microorganisms, having the ability to dissolve insoluble phosphate forms and Potassium fixed in silicates, can be effective in reducing the deficiency of these elements for the plant. In this research, 7 species of Trichoderma fungis were selected and their effects on the release of phosphorus and Potassium were evaluated in Pikovskaya’ s, Alexandrov’ s and modified Pikovskaya’ s media. The results showed that in Pikovskaya’ s broth medium, phosphorus release rate by different species of fungi was consistent with decreasing pH. Trichoderma koningii, T. harzianum, T. citrinoviride and T. viridescens had the most phosphate solubilizing ability and increased soluble phosphorus by 244, 205, 191 and 190%, respectively. In both Aleksandrov’ s and modified pikovskaya’ s media, which contain both insoluble inorganic phosphate and Potassium as biotite, it was observed that the dissolution rate of tri-calcium phosphate was lower than that of pikovskaya’ s medium which has available Potassium. T. koningii in Aleksandrov’ s medium and T. harzianum in modified Pikovskaya’ s medium had the highest ability to release Potassium from biotite. These species increased Potassium in solution by 123 and 20% compared to control, respectively. In general, the results showed that Trichoderma fungi has the ability to solubilize phosphate from tri-calcium phosphate and release Potassium from biotite under in-vitro conditions.

One of the main reasons for the low yield of biofertilizers in fish ponds is the use of insoluble mineral phosphorus sources (often tri-calcium phosphate) during the process of isolation and evaluation of phosphorus-Releasing microorganisms. A large part of insoluble phosphorus (50 to 90%) in warm water fish ponds is insoluble organic phosphorus. Therefore, it seems phosphorus-Releasing microorganisms isolated solely from mineral phosphorus sources can not be effective as biofertilizers in warm water fish ponds. The aim of this study was to isolate phosphorus-Releasing Bacteria from warm water fish ponds using NBRIP medium containing organic phosphorus source (calcium phytate) and compare their performance with Bacteria derived from insoluble mineral phosphorus source (tri-calcium phosphate) in microcosm conditions (Erlenmeyer contains sediment: conditions similar to a fish pond). The phosphorus release ability of isolates (33 organic isolates and 19 inorganic isolates) was evaluated in NBRIP solid and liquid medium. The range of soluble phosphorus in the liquid medium containing calcium phytate varied between 57. 40-141. 93 and 108. 16-219. 49 mg/l in the medium containing tricalcium phosphate. In the final step, evaluation of isolates in sediment microcosm showed that three isolates from organic phosphorus source (3P, 13P, and 2P) were the best phosphorus release isolates (with 11. 86, 12. 53, and 28. 18 mg / l respectively) and had better performance compared to isolates from mineral phosphorus source. Molecular identification showed these isolates belonged to priestia aryabhattai, Bacillus zanthoxyli, and Acinetobacter johnsonii. Due to the pathogenic potential of A. johnsonii for fish and humans, the Bacillaceae family strains can be considered candidates for use in biofertilizers for further evaluation.