Potassium-solubilizing Microorganisms Research Articles

Characterization of potassium-solubilizing fungi, Mortierella spp., isolated from a poplar plantation rhizosphere soil.

Potassium-solubilizing microorganisms are capable of secreting acidic chemicals that dissolve and release potassium from soil minerals, thus facilitating potassium uptake by plants. In this study, three potassium-dissolving filamentous fungi were isolated from the rhizosphere soil of a poplar plantation in Jiangsu Province, China. Phylogenetic analyses based on ITS, 18S, and 28S showed that these three isolates were most similar to Mortierella. These strains also possessed spherical or ellipsoidal spores, produced sporangia at the hyphal tip, and formed petal-like colonies on PDA media resembling those of Mortierella species. These findings, along with further phenotypic observations, suggest that these isolates were Mortierella species. In addition, the potassium-dissolution experiment showed that strain 2K4 had a relatively high potassium-solubilizing capacity among these isolated fungi. By investigating the influences of different nutrient conditions (carbon source, nitrogen source, and inorganic salt) and initial pH values on the potassium-dissolving ability, the optimal potassium-solubilization conditions of the isolate were determined. When potassium feldspar powder was used as an insoluble potassium source, isolate 2K4 exhibited a significantly better polysaccharide aggregation ability on the formed mycelium-potassium feldspar complex. The composition and content of organic acids secreted by strain 2K4 were further detected, and the potassium-dissolution mechanism of the Mortierella species and its growth promotion effect were discussed, using maize as an example.

Impact of Potassium-Solubilizing Microorganisms with Potassium Sources on the Growth, Physiology, and Productivity of Wheat Crop under Salt-Affected Soil Conditions

Salinity adversely affects plant growth and productivity worldwide. To overcome salinity and other abiotic stresses, safe, ecofriendly biofertilizers that stimulate productivity have been experiencing rising demand, alongside decreasing use of mineral fertilizers. The purpose of this study was to examine changes in the growth, yield, physiological and biochemical parameters of wheat crop as a response to two potassium-solubilizing microorganisms (KSMs), Trichoderma asperellum and Bacillus circulans, with 50% or 75% of the recommended amount of K fertilizer (potassium sulphate), combined with no or 25% feldspar as well as 1.5% potassium sulphate (K-leaf) as foliar application, and all treatments were compared with a control treatment under salt-affected soil conditions, during two winter seasons in 2019–2020 and 2020–2021. The randomized complete block design (RCBD) was used to set up the experiment. Results showed that the vegetative growth, yield, physiological and biochemical parameters were affected under salt-affected soil conditions. Nevertheless, inoculation with T. asperellum and B. circulans with potassium application mitigated the deleterious effect of salt-affected soil conditions by improving growth parameters, photosynthetic pigment content, antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, catalase and peroxidase) content, total soluble sugars, relative water content, potassium content in leaves, grains yield, and some biochemical constituents in the grains and straw. Meanwhile, these treatments decreased proline content, Na+ content in leaves, and the Na+/K+ ratio as compared to the control treatment. The most pronounced treatment, inoculation by B. circulans with 1.5% K-leaf as foliar application, significantly increased grain yield by 16.41% relative to the control treatment. It could be concluded that inoculating wheat with KSMs T. asperellum and B. circulans with 1.5% K-leaf as foliar application will increase wheat salinity tolerance and wheat productivity and decrease the detrimental effect of salinity on wheat growth and grain yield quantity and quality under salt-affected soils conditions.

Sustainable agricultural practices using potassium-solubilizing microorganisms (KSMs) in coastal regions: a critical review on the challenges and opportunities

Sustainable agricultural practices using potassium-solubilizing microorganisms (KSMs) in coastal regions: a critical review on the challenges and opportunities

Drought tolerance of Aspergillus violaceofuscus and Bacillus licheniformis and their influence on tomato growth and potassium uptake in mica amended tropical soils under water-limiting conditions.

Drought is a significant abiotic stress that alters plant physiology and ultimately affects crop productivity. Among essential plant nutrients, potassium (K) is known to mitigate the deleterious effect of drought on plant growth. If so, K addition or inoculation of potassium solubilizing microorganisms (KSMs) that are tolerant to drought should promote plant growth during water stress. Therefore, in this study, K solubilizing Aspergillus violaceofuscus and Bacillus licheniformis, isolated from saxicolous environments, were tested for their capacity to tolerate drought using different molecular weights (~4000, 6000, and 8000 Da), and concentrations (0, 250, 500, 750, 1000, and 1250 mg/L) of polyethylene glycol (PEG) under in vitro conditions. The results showed that high concentrations (750 and 1000 mg/L) of PEG with different molecular weight considerably improved bacterial cell numbers/fungal biomass and catalase (CAT) and proline activities. Moreover, the ability of KSMs alone or in combination to impart drought tolerance and promote plant growth in the presence and absence of mica (9.3% K2O) supplementation was tested in Alfisol and Vertisol soil types under greenhouse conditions. The results revealed that the tomato plants inoculated with KSMs individually or dually with/without mica improved the physiological and morphological traits of the tomato plants under drought. Generally, tomato plants co-inoculated with KSMs and supplemented with mica were taller (2.62 and 3.38-fold) and had more leaf area (2.03 and 1.98-fold), total root length (3.26 and 8.86-fold), shoot biomass (3.87 and 3.93-fold), root biomass (9.00 and 7.24-fold), shoot K content (3.08 and 3.62-fold), root K content (3.39 and 2.03-fold), relative water content (1.51 and 1.27-fold), CAT activity (2.11 and 2.14-fold), proline content (3.41 and 3.28-fold), and total chlorophyll content (1.81 and 1.90-fold), in unsterilized Alfisol and Vertisol soil types, respectively, than uninoculated ones. Dual inoculation of the KSMs along with mica amendment, also improved the endorrhizal symbiosis of tomato plants more than their individual inoculation or application in both soil types. These findings imply that the A. violaceofuscus and B. licheniformis isolates are promising as novel bioinoculants for improving crop growth in water-stressed and rainfed areas of the tropics in the future.

Effects of Root Zone Aeration on Soil Microbes Species in a Peach Tree Rhizosphere and Root Growth.

The oxygen content in the root zone considerably affects the growth and development of peach trees. However, few studies have been conducted on the effects of the oxygen content in the root zones of peach trees on soil microbes and root growth. Four-year-old Ruiguang 33/Prunus persica (L.) Batsch trees were used to study the effects of root-zone aeration on soil microbes in a peach orchard, as well as on the soil nutrient contents, peach tree root systems, and plant potassium-to-nitrogen ratios. The results showed that the root-zone aeration substantially increased the soil oxygen content in the root zone and changed the soil microbial community structure. Compared with the control, the relative abundances of soil nitrogen-fixing microorganisms (Beta proteobacteria and Bradyrhizobium elkanii) and potassium-solubilizing microorganisms (Bacillus circulans) under the root-zone aeration conditions were greatly enhanced. Root-zone aeration increased the soil’s alkaline nitrogen content, available potassium content, and organic matter content, as well as the number and thickness of new white roots of peach trees, and root activity was increased significantly. At the same time, root-zone aeration changed the relative contents of total potassium and total nitrogen in the plants and considerably increased the potassium–nitrogen ratio in the shoots. The results indicate that aeration in the root zone can change the soil microbial community structure, increase the abundances of nitrogen-fixing and potassium-solubilizing microorganisms, and increase the plant potassium-to-nitrogen ratio, which are conducive to peach fruit quality.

Potassium sources, microorganisms and plant nutrition: Challenges and future research directions

Until recently, potassium (K) has not received considerable attention because of the general belief that soils contain ample amounts of this element. In addition, low rates of K fertilizer application in agriculture have led to rapid depletion of K in the rhizosphere soil in many underdeveloped countries. This results in various negative impacts, including preventing optimum utilization of applied nitrogen and phosphorus fertilizers. To compensate for these losses, massive use of K fertilizers in agriculture has been suggested. Potassium fertilizers are manufactured from rock minerals, particularly sylvite (KCl) and carnallite (KCl·MgCl2·6H2 O). Unfortunately, to date, there is no cost-effective technology available for converting rock minerals into potassic fertilizers. Potassium-solubilizing microorganisms (KSMs) can release K from soil/minerals into plant-available forms, which could be a sustainable option. The possibility of using KSMs as efficient biofertilizers to improve crop production has been increasingly highlighted by researchers. In this review, the existing forms of K in soils and their availability and dynamic equilibrium are discussed. In addition, different K fertilizers and their advantages and disadvantages for crops are described. Furthermore, the microorganisms usually reported as K solubilizers, the research progress on KSMs, and future insights on the use of these KSMs in agriculture are reviewed. Screening and analyses of the published literature show that organic acid production is the common mechanism of K solubilization by bacteria and fungi. This review may serve as a proposal for the future research avenues identified here.

Microorganisms and Carrier Molecules used in Biofertilizer Formulations

Rhizobacteria with plant growth promoting potential are used widely for agricultural use. They have been used as supplements to chemical fertilizers. Cyanobacteria, nitrogen fixing bacteria, phosphate mineralizing bacteria, and potassium solubilizing microorganisms have been used as biofertilizers for different crops. The survival of these rhizobacteria in soil is affected by number of abiotic as well as biotic factors that limits the growth of rhizobacteria. To enhance the survival rate of rhizobacteria in soil and to enhance their viability and efficiency, the bacteria is mixed with carrier material or additive to increase their activity. Carrier molecule enhances the adhesion of bacteria to the plant roots. The processing of bacteria with carrier molecule ensures easy handling and processing or agricultural use. Addition of additive molecule to the bacterial culture provides excellent survival rate and slow cell release at different soil pH. Different additive molecules used as carrier molecules are discussed in this article.

Isolation and Screening of Zinc and Potassium Solubilizing Microorganisms from Different Rhizospheric Soil

Zinc is considered as a crucial trace micronutrient for proper growth, reproduction and driving of many metabolic reactions in all crops. Potassium is classified as a macronutrient associated with movement of water and nutrients as well as enzyme activation. The present study was aimed for isolation and screening of zinc and potassium solubilizing microorganisms from different rhizospheric soil of rice. Eight different isolates- ZSB1, ZSB2, ZSB3, ZSB4, KSB1, KSB2, KSB3 and KSB4 were obtained and were screened for their Zinc and Potassium solubilizing activities on TRIS minimal agar medium and Aleksandrov’s medium, respectively. Upon characterization, ZSB1, ZSB4 and KSB3 were observed as motile Gram-negative organisms, ZSB2, KSB2 and KSB4 as motile Gram-positive organisms while ZSB3 and KSB1 had mycelial growth with some conidial spore. All isolates gave positive results for starch and lipid hydrolysis. In gelatin hydrolysis, only ZSB3, ZSB4, KSB1 and KSB2 gave positive results. The main purpose to obtain these zinc and potassium solubilizing microorganisms was for their use in plant growth promotion as biofertilizers to increase soil fertility and crop yield.

Influence of different pre-sowing treatments on germination potential of Bakul (Mimusops elengi L.)

A laboratory experiment was conducted on shelf-life of jeevamrutha at Zonal Agricultural and Horticultural Research Station (ZAHRS), Brahmavar, Udupi. In this study cow dung and cow urine of three different desi cow breeds viz., malnad gidda, gir and sahiwal were collected aseptically and separately to prepare Jeevamrutha. After preparation of jeevamrutha samples were collected daily from 1st day to 15th days and enumerated the general and beneficial microorganisms viz., bacteria, fungi, actinomycetes, phosphate solubilizing microorganisms (PSM), nitrogen fixers, Pseudomonas, potassium solubilizing microorganisms (KSM), Zinc solubilizing microorganisms (ZnSM) and Trichoderma with their respective media. Among the three desi cow breeds the jeevamrutha prepared from, malnad gidda breed of cow contained the maximum microbial population. In general, the highest microbial population was noticed between 7 to 9 days after preparation (DAP) of jeevamrutha in all the desi breeds. Hence, it’s considered as a best time for the application of jeevamrutha to soil to improve the soil microorganisms.

Isolation and identification of potassium-solubilizing bacteria from Mikania micrantha rhizospheric soil and their effect on M. micrantha plants

Potassium is directly involved in plant cell turgor-driven cell elongation, this is important for promoting the expansion of invasive plants. Soil potassium-solubilizing microorganisms in some invaded ecosystems may promote plant invasion by increasing potassium availability. The aims of this study were to isolate and identify potassium-solubilizing bacteria and to evaluate their contribution to the solubilization of potassium from potassium-feldspar, and to the potassium uptake of Mikania micrantha. Potassium-solubilizing bacteria were isolated using solid Aleksandrov medium in abandoned orchards that have been highly invaded by M. micrantha for more than 10 years. Our results revealed that 18 strains of efficient bacteria were identified using liquid Aleksandrov medium. Among the isolates, the Burkholderia genus had the highest solubilizing ability (1.75 mg L−1). The results of the pot culture experiment showed that the plant biomass and potassium content of M. micrantha with potassium-solubilizing bacteria were higher than in the control without these bacteria. Incubation with potassium-solubilizing bacteria, especially GZ18, significantly increased the plant phosphorus content. More potassium was solubilized in treatments with potassium-solubilizing bacteria than in the control without bacteria. These results strongly suggest that potassium-solubilizing bacteria in the rhizosphere of M. micrantha could improve potassium solubilization and uptake, and contributed to their success as an invasive species.

ИСПОЛЬЗОВАНИЕ ШТАММОВ МИКРООРГАНИЗМОВ ДЛЯ ПОВЫШЕНИЯ УРОЖАЙНОСТИ ЯРОВОЙ МЯГКОЙ ПШЕНИЦЫ (Triticum aestivum L.)

This paper presents the study results on the effect that presowing seed treatment and spraying nitrogen-fixing, phosphate-, and potassium-solubilizing bacteria on the seedlings of the Primorskaya 39 spring soft wheat (Triticum aestivum L.) cultivar have on the structural elements of productivity, yield, and the number of soil microorganisms. It was found that the total number of bacteria increases in the waxy ripeness stage when using both presowing treatment of seeds and spraying the microorganism strains on the seedlings. The maximum number of bacteria in the soil was detected in the variants when using strains of nitrogen-fixing and potassium-solubilizing microorganisms in presowing treatment (1.9 × 107 CFU/g of soil) and phosphate- and potassium-solubilizing microorganisms when spraying the seedlings (2.0 × 107 CFU/g of soil). The variant N1 + K2 + P6 after presowing treatment with nitrogen-fixing, potassium-, and phosphate-solubilizing microorganisms in the waxy ripeness stage showed the highest content of mobile phosphorus (92 mg/kg). High yield (4.3 t/ha) was shown by the variant N1 + P19 after presowing seed treatment with nitrogen-fixing and phosphate-solubilizing strains.

Effect of potassium solubilizing bacteria and waste mica on potassium uptake and dynamics in maize rhizosphere

Potassium (K), being the third most important primary macronutrient, plays a significant role in crop production. Due to scarcity of K-bearing ores in the Indian sub-continent the K-fertilizers are imported which increases the cost of cultivation. Hence, the alternative K sources like waste mica along with microbial intervention is needed to be explored. So, a pot experiment was conducted during kharif season of 2015-16 and 2016-17 with ten treatments consisting of T1: Control,T2: Recommended dose of fertilizer (RDF: N:P2O5:K2O: 100:40:40 kg ha-1), T3: Full N and P + 75% K and rest 25% by waste mica, T4: Full N and P + 50% K and rest 50% by waste mica, T5: T3 + KSB1 ( Fraturia aurantia ), T6: T4 + KSB1, T7: T3 + KSB2 ( Bacillus edaphicus ),T8: T4 + KSB2, T9: T3+KSB1+KSB2 and T10: T4+ KSB1+KSB2 was conducted with maize ( Zea mays L) as the test crop (var: SHM 1). The results revealed that the water soluble, exchangeable and non-exchangeable pools of K over different stages, ranged from 3-5%, 9-10% and 85- 88%, respectively. Correlation studies between biomass yield, K uptake and different pools of K showed a significant relationship. Out of the ten treatments used in the experiment, treatment, T10: Full N and P + 50% K and rest 50% by waste mica + KSB1+KSB2 was found to be most superior. Application of waste mica co-inoculated with potassium solubilizing microorganisms also had significant effect on biomass yield as well as K uptake by maize.

The Role of Soil Fungi in K+ Plant Nutrition

K+ is an essential cation and the most abundant in plant cells. After N, its corresponding element, K, is the nutrient required in the largest amounts by plants. Despite the numerous roles of K in crop production, improvements in the uptake and efficiency of use of K have not been major focuses in conventional or transgenic breeding studies in the past. In research on the mineral nutrition of plants in general, and K in particular, this nutrient has been shown to be essential to soil-dwelling-microorganisms (fungi, bacteria, protozoa, nematodes, etc.) that form mutualistic associations and that can influence the availability of mineral nutrients for plants. Therefore, this article aims to provide an overview of the role of soil microorganisms in supplying K+ to plants, considering both the potassium-solubilizing microorganisms and the potassium-facilitating microorganisms that are in close contact with the roots of plants. These microorganisms can influence the active transporter-mediated transfer of K+. Regarding the latter group of microorganisms, special focus is placed on the role of endophytic fungus. This review also includes a discussion on productivity through sustainable agriculture.

Effects of Mineral Structure and Microenvironment on K Release from Potassium Aluminosilicate Minerals by Cenococcum geophilum fr

K-bearing minerals with enormous reserve in the world, were not easy to provide the available K nutrient element for plant direct uptake because of the slow K release rate. With the potential potassium-solubilizing microorganisms, the slow K release rate from minerals would be improved significantly. In this work, Cenococcum geophilum Fr, one of the most common ectomycorrhizal fungi in boreal to temperate regions, was adopted to dissolve K-bearing minerals for K release. Five kinds of potassium aluminosilicate minerals were tested by bioleaching experiments in pure culture, including feldspar, nepheline, biotite, muscovite and illite. The available and unavailable potassium amounts in minerals before and after bioleaching were measured and compared with each other. The effect of mineral structure on the potassium solubilization efficiency by Cenococcum geophilum Fr. was discussed. Furthermore, the microenvironment formation between fungi and mineral surface to enhance the K release rate was investigated through detecting K, Al, Si concentrations and metabolites amounts (polysaccharide and organic acids) in microenvironment and external environment, respectively. Experimental results demonstrated that Cenococcum geophilum Fr. was a potential candidate of potassium solubilizing microorganisms, and both mineral structure and microenvironment have significant effects on the K release rate.

Global industrial enzymes market overview 2018 - forecast to 2024

Until recently, potassium (K) has not received considerable attention because of the general belief that soils contain ample amounts of this element. In addition, low rates of K fertilizer application in agriculture have led to rapid depletion of K in the rhizosphere soil in many underdeveloped countries. This results in various negative impacts, including preventing optimum utilization of applied nitrogen and phosphorus fertilizers. To compensate for these losses, massive use of K fertilizers in agriculture has been suggested. Potassium fertilizers are manufactured from rock minerals, particularly sylvite (KCl) and carnallite (KCl·MgCl2·6H2 O). Unfortunately, to date, there is no cost-effective technology available for converting rock minerals into potassic fertilizers. Potassium-solubilizing microorganisms (KSMs) can release K from soil/minerals into plant-available forms, which could be a sustainable option. The possibility of using KSMs as efficient biofertilizers to improve crop production has been increasingly highlighted by researchers. In this review, the existing forms of K in soils and their availability and dynamic equilibrium are discussed. In addition, different K fertilizers and their advantages and disadvantages for crops are described. Furthermore, the microorganisms usually reported as K solubilizers, the research progress on KSMs, and future insights on the use of these KSMs in agriculture are reviewed. Screening and analyses of the published literature show that organic acid production is the common mechanism of K solubilization by bacteria and fungi. This review may serve as a proposal for the future research avenues identified here.

The Rootstock Regulates Microbiome Diversity in Root and Rhizosphere Compartments of Vitis vinifera Cultivar Lambrusco.

Plants belonging to Vitis vinifera varieties are usually grafted on different rootstocks to enhance the plant defenses against pathogens and increase productivity under harsh environmental conditions. Particularly, in Emilia-Romagna region (Italy), Vitis vinifera cultivar Lambrusco can be grafted on a hybrid of V. berlandieri × V. riparia (5BB) or V. berlandieri × V. rupestris (1103P). However, the latter shows potassium absorption problems, with a consequent reduction in grapevine production. Since it has recently been demonstrated that the rootstock has the potential to select for different microorganisms at the root-soil interface, here we hypothesized that the potassium deficiency of 1103P could be partially accounted for by the peculiarities of the rootstock microbiome. We thus employed 16S rRNA sequencing to compare root and rhizosphere microbiomes in plants of V. vinifera cultivar Lambrusco grafted on the two aforementioned rootstocks. According to our findings, 1103P shows a reduced diversity in root and rhizosphere microbiomes, including members of potassium-solubilizing microorganisms, possibly explaining the inadequate potassium absorption of this hybrid. Besides confirming the importance of the rootstock as a determinant of the composition of plant microbiomes, our data indicate the relevance of rootstock-selected microbiomes as possible regulators of potassium absorption by V. vinifera.

Effects of Azorhizophilus paspali and Paenibacillus mucilaginosus as Biofertilizer and Determination of Nutritional Efficiency by Sensors

The benefits of nitrogen-fixing and potassium-solubilizing microorganisms in plant growth were investigated by using micro-sized ion-selective sensors developed in our laboratory. Azorhizophilus paspali (ATCC 23367) having nitrogen-fixing capability and Paenibacillus mucilaginosus (DSM 24461) having potassium-solubilizing capability were used in media. The microorganisms grown in aseptic conditions were mixed with soil and compost in order to improve plant nutrition, and samples taken from growth medium were examined for 23 days by ammonium- and potassium-selective PVC membrane sensors exhibiting almost Nernstian response. The highest nitrate release were obtained on the 14th day of inoculation in samples using A. paspali. The highest potassium release was obtained on 18th day of inoculation in samples using P. mucilaginosus. The results showed that bacterial inoculation had a more stimulating effect on assimilation of N and K in compost than in soil. In addition, the effect of microbial strains on shoot and root growth and nutrient uptake of tomato was tested in pot experiments using compost. A. paspali and P. mucilaginosus inoculation increased the shoot and root dry weight of tomato seedlings, respectively, 7–14 and 12–19% when compared with the control. The results showed that addition of the microorganisms into compost would be beneficial in plant nutrition. Application of these microorganisms as biofertilizers in barren areas will protect soil from the harmful effects of chemical fertilizers with an environmentally friendly approach.

Solubilization of Potassium Containing Mineral by Microorganisms From Sugarcane Rhizosphere

Abstract Potassium solubilizing microorganisms (KSM) isolated from sugarcane rhizosphere and their capability on solubilization from some insoluble potassium were examined. Isolation of potassium solubilizer was carried out from three sugarcane plantations area, on Alexandrov's agar medium. From the 41 isolated microorganisms were selected 15 isolates potassium solubilizing microorganisms which exhibiting highest potassium solubilization (solubility index) on solid medium. All the KSM were found to be capable of solubilizing K from insoluble K-bearing minerals source, and the solubilization zone ranging from 0.15 to 4.5 cm. 13.3% isolate has Solubility Index (SI) more than four on solid medium. Quantitative test result of KSM conducted on liquid medium containing potassium mineral trachyte, feldspar, leucite (Pati and Situbondo), released water soluble-K (exchangeable-K) ranging from 0.13 to 12.25 mg.L−1 (Feldspar); 1.24 to 15.57 mg L−1 (Leucite pati); 1.01 to 4.,59 mg L−1 (Leucite Situbondo); and 0.16 to 6,34 mg L−1 (Trachyte). KSM strain Sbr3 caused maximum solubilization on feldspar (12.25 mg L−1), KSM strain Asb3 on leucite Pati (18.17 mg L−1), KSM strain Prj3 on leucite Situbondo (16.14 mg L−1), whereas KSM strain Prj5 caused maximum solubilization on trachyte (6.92 mg L−1). All isolates produced organic acid citric, ferulic and coumaric, some isolates also produced malic and syringic acid. Total organic acid produced by isolated ranging from 130.42 to 434.44 mg.L−1. Ferulic acid was produced by all isolates on all of K sources higher than other organic acid.