Phosphate Solubilizing Microorganisms Research Articles

Isolation, Mutagenesis, and Organic Acid Secretion of a Highly Efficient Phosphate-Solubilizing Fungus.

The highly effective phosphate-solubilizing microorganisms are significant for making full use of the potential phosphorus resources in the soil and alleviating the shortage of phosphorus resources. In this study, a phosphate-solubilizing fungus was isolated from wheat and cotton rhizosphere soils in the lower reaches of the Yellow River in China and was identified as Penicillium oxalicum by morphological and ITS sequencing analysis. In order to obtain a fungus with more efficient phosphorus solubilization ability, we tested three positive mutant strains (P1, P2, and P3) and three negative mutant strains (N1, N2, and N3) through low-energy nitrogen ion implantation mutagenesis. Compared with the parental strain, the phosphate-solubilizing capacity of P1, P2, and P3 was enhanced by 56.88%, 42.26%, and 32.15%, respectively, and that of N1, N2, and N3 was weakened by 47.53%, 35.27%, and 30.86%, respectively. Compared with the parental strain, the total amount of organic acids secreted significantly increased in the three positive mutant strains and decreased in the negative mutant strains; the pH of culture medium was significantly lower in the positive mutant strains and higher in the negative mutant strains. The capacity of phosphate-solubilizing fungus to secrete organic acids and reduce the growth-medium pH was closely related to its phosphate-solubilizing ability. The changes in the amount of organic acids secreted by mutants can alter their acidification and phosphate-solubilizing capacity. In conclusion, this study offers a theoretical basis and strain materials for the exploration and application of phosphate-solubilizing fungi.

Isolation of phosphate solubilizing bacteria from root rhizosphere to supplement biofertilizer

In soil, a large amount of supplemented phosphorus (P) are immediately transferred into insoluble forms and only 0.1 % of them is available for plant uptake. Therefore, exploring naturally occurring phosphate-solubilizing microorganisms is an essential activity to exploit them in reducing mineral phosphorus added to agricultural soils. In this study, we screened and isolated 7 bacteria that solubilized phosphate at different phosphate solubilization indexes, ranging from 4.2 to 226.1. Of them, the most efficient isolate is PSB31, which solubilized tri calcium phosphate (Ca3(PO4)2 at a rate of 962 mg l-1 and molecularly identified as Bacillus sp. (in: Bacteria) strain IMAU61039. This bacterial strain generated the low supernatant pH and the phosphatase, which are involved in the phosphorus solubilization mechanism. Furthermore, greenhouse experiments showed that tomato seedlings grown in PSB31-inoculated soil contained higher P amount and had much higher biomass than those plants grown in soil without PSB31 addition. These results suggest that the PSB31 strain has potential use as a biofertilizer.

A Review on Potential of Plant Growth Promoting Microorganisms in Silviculture of Neolamarckia cadamba to Industrial Timber Production Areas (ITPAs) in Malaysia

Abstract Sarawak had around 62% forest area coverage in 2018, contributed 40% of forest area in Malaysia. Two million hectares of licensed forest area was designated as Industrial Timber Production Areas (ITPAs) to sustain industrial timber production. Neolamarckia cadamba was one of the tropical indigenous timber species selected for the development of ITPAs. The selection is based on its local environment adaptation, pest and disease resistance, fast growing properties, soil maintenance contributions, its wood quality suitable for plywood industry. Tropical soils are infamous for poor plant available nutrients profile, contributed by high precipitation rate in tropical climate and acidic soil orders. Plant growth promoting microorganisms in wild environment would be a feasible solution for N. cadamba planting activities. Such studies on N. cadamba were limited whilst drafting this review paper. Nonetheless, potential strains, i.e Nitrogen fixing microorganisms, phosphate solubilising microorganisms and potassium solubilising microorganisms, were discussed. They could potentially provide three major plant available nutrients. For industrial production, their processing with solid, liquid or solid-liquid integrated carrier materials would provide long shelf-life, better survivability in the field and easy handling in different application strategies. Keywords: Biofertilisers, Neolamarckia cadamba, plant growth promoting microorganisms, Malaysia, tropical soils

Phosphate Solubilizing Microorganism Bacillus sp. MVY-004 and Its Significance for Biomineral Fertilizers' Development in Agrobiotechnology.

Simple SummaryAgriculture is one of the most significant and important sectors globally. Soil fertility and agricultural production are highly dependent on which plant protection and growth promotion substance is used. Although applying mineral fertilizers can promote rapid crop growth, extensive mineral fertilizer use has reduced soil quality worldwide. Such environmental aspects have led to the search for more sustainable methods to provide plants with nutrients, especially phosphorus. Phosphorus is one of the macronutrients that is indispensable for plant development and growth. Phosphate solubilizing microorganisms are widely applied in agronomic practices to increase the productivity of crops while maintaining the health of soils. Nowadays, special attention is focused globally on ecological farming. One of the new technologies in agriculture is the mixing of agricultural bio-stimulants with mineral fertilizers. Agricultural bio-stimulants are bioproducts that contain substances of natural origin along with beneficial microorganisms. They can be used to activate seeds, plants, and soil. Bio-stimulants are used in plants to improve nutritional efficiency, cause changes in vital and structural processes to affect plant growth, enhance abiotic and biotic stress tolerance and increase the yield and quality of products.In this study, a phosphate solubilizing microorganism was isolated from the soil of an agricultural field in Lithuania. Based on 16S rRNA gene sequence analysis, the strain was identified as Bacillus sp. and submitted to the NCBI database, Sector of Applied Bio-catalysis, University Institute of Biotechnology, Vilnius, Lithuania and allocated the accession number KY882273. The Bacillus sp. was assigned with the number MVY-004. The culture nutrient medium and growth conditions were optimized: molasses was used as a carbon source; yeast extract powder was used as an organic source; NH4H2PO4 was used as a nitrogen source; the culture growth temperature was 30 ± 0.5 °C; the initial value of pH was 7.0 ± 0.5; the partial pressure of oxygen (pO2) was 60 ± 2.0; the mixer revolutions per minute (RPM) were 25–850, and the incubation and the fermentation time was 48–50 h. Analysis using Liquid Chromatography Time-of-Flight Mass Spectrometry (LC-TOF/MS) results showed that Bacillus sp. MVY-004 produced organic acids such as citric, succinic, 2-ketogluconic, gluconic, malic, lactic, and oxalic acids. Furthermore, the experiment showed that Bacillus sp. MVY-004 can also produce the following phytohormones: indole-3-acetic (IAA), jasmonic (JA), and gibberellic (GA3) acids. In the climate chamber, the experiment was performed using mineral fertilizer (NPS-12:40:10 80 Kg ha−1) and mineral fertilizers in combination with Bacillus sp. MVY-004 cells (NPS-12:40:10 80 Kg ha−1 + Bacillus sp. MVY-004) in loamy soil. Analysis was performed in three climate conditions: normal (T = 20 °C; relative humidity 60%); hot and dry (T = 30 °C; relative humidity 30%); hot and humid (T = 30 °C; relative humidity 80%).

Responses of Phosphate-Solubilizing Microorganisms Mediated Phosphorus Cycling to Drought-Flood Abrupt Alternation in Summer Maize Field Soil.

Soil microbial communities are essential to phosphorus (P) cycling, especially in the process of insoluble phosphorus solubilization for plant P uptake. Phosphate-solubilizing microorganisms (PSM) are the dominant driving forces. The PSM mediated soil P cycling is easily affected by water condition changes due to extreme hydrological events. Previous studies basically focused on the effects of droughts, floods, or drying-rewetting on P cycling, while few focused on drought-flood abrupt alternation (DFAA), especially through microbial activities. This study explored the DFAA effects on P cycling mediated by PSM and P metabolism-related genes in summer maize field soil. Field control experiments were conducted to simulate two levels of DFAA (light drought-moderate flood, moderate drought-moderate flood) during two summer maize growing periods (seeding-jointing stage, tasseling-grain filling stage). Results showed that the relative abundance of phosphate-solubilizing bacteria (PSB) and phosphate-solubilizing fungi (PSF) increased after DFAA compared to the control system (CS), and PSF has lower resistance but higher resilience to DFAA than PSB. Significant differences can be found on the genera Pseudomonas, Arthrobacter, and Penicillium, and the P metabolism-related gene K21195 under DFAA. The DFAA also led to unstable and dispersed structure of the farmland ecosystem network related to P cycling, with persistent influences until the mature stage of summer maize. This study provides references for understanding the micro process on P cycling under DFAA in topsoil, which could further guide the DFAA regulations.

Phosphate-solubilising microorganisms mainly increase plant phosphate uptake by effects of pH on root physiology

Phosphate-solubilising microorganisms mainly increase plant phosphate uptake by effects of pH on root physiology

Population Distribution of Phosphate-solubilizing Microorganisms in Agricultural Soil

Phosphorus (P) is an essential macronutrient for plant growth and is mainly present in agricultural soil in unavailable forms. Phosphate-solubilizing microorganisms (PSMs) increase soil P availability. The objective of the present study was to assess the population and type of PSMs and their relationships with soil characteristics in the agricultural soil of Manokwari. Twenty-one composite soil samples (0–20‍ ‍cm) were collected at the rhizospheres of plants in the Prafi and Masni Districts. A dilution technique and plate count method on Pikovskayas agar medium were used to examine the PSM population, phosphate-solubilizing index (PSI), and various soil properties. The results obtained showed that the total population of phosphate-solubilizing bacteria ranged between 25×103 and 550×103 CFU g–1 of soil, while that of phosphate-solubilizing fungi was between 2.0×103 and 5.0×103 CFU g–1 of soil at all locations. The PSI of the isolates ranged between 1.1 to 3.6‍ ‍mm, with the most efficient and highest PSI being obtained for Bacillus sp. (strain 8) and the lowest for Pseudomonas sp. (strain 15). Six isolates found at all locations were identified at the genus level: Chromobacterium sp., Pseudomonas sp., Bacillus sp., Micrococcus sp., Caulobacter sp., and Aspergillus sp. A correlation was observed between the number of PSMs and the level of soil P availability and moisture content, indicating an increase in soil P availability with a greater abundance of PSMs in soil.

Phosphate Availability Modulates Root Exudate Composition and Rhizosphere Microbial Community in a Teosinte and a Modern Maize Cultivar

Domestication and breeding have affected interactions between plants and their microbiomes in ways that are only beginning to be understood but may have important implications for recruitment of rhizosphere microorganisms, particularly under stress conditions. We investigated the responses of a modern maize (Zea mays subsp. mays) cultivar and its wild relative, teosinte (Z. mays subsp. parviglumis), to different phosphate availabilities. We appraised responses of the plant-microbial holobiont to phosphate stresses by profiling root exudate metabolomes, and microbial communities in the root endosphere and rhizosphere. We also performed plate assays to quantify phosphate-solubilizing microorganisms from the rhizosphere. Although root exudate metabolite profiles were distinct between the teosinte and modern maize under high phosphate, both plants shifted exudate compositions in response to phosphate stress toward a common metabolite profile. Root and rhizosphere microbial communities also responded significantly to both plant type and the phosphate availability. A subset of bacterial and fungal taxa were differentially abundant under the different phosphate conditions, with each of the three conditions favoring different taxa. Both teosinte and maize rhizospheres harbored phosphate-solubilizing microorganisms under all growth conditions. These results suggest that the root exudation response to phosphate stress was conserved through the domestication of maize from teosinte, shifting exudation levels of specific metabolites. Although microbial communities also shifted, plate-based assays did not detect selective recruitment of phosphate solubilizers in response to phosphate availability.

Phosphate-Solubilizing Microorganisms Regulate the Release and Transformation of Phosphorus in Biochar-Based Slow-Release Fertilizer

Phosphate-Solubilizing Microorganisms Regulate the Release and Transformation of Phosphorus in Biochar-Based Slow-Release Fertilizer

Addition of Phosphatases and Phytases to Mature Compost to Increase Available Phosphorus: A Short Study

Agriculture depends on fertilizers to provide nutrients for plants. Phosphorus (P) is one of these nutrients and is the second-most necessary for plant growth. Global production of P fertilizer is concentrated in Morocco, China and the United States. A large amounts of P resources are found in organic wastes that can be transformed through phosphate-solubilizing microorganisms during the composting process. In this study, we first determined the enzymatic activity of phosphatases and phytase from Pseudomonas aeruginosa ATC 15442. Second, we evaluated the mineralization of P in mature compost when inoculated with P. aeruginosa ATC 15442, phytases, a cocktail of phosphate-solubilizing enzymes and their combinations. Finally, we evaluated different concentrations of the cocktail trying to release more P in the compost. The results indicated that P. aeruginosa exuded alkaline phosphatases, acid phosphatase, neutral phosphatase and phytase. The enzymatic cocktail increased inorganic P (Pi) when added to the mature compost: this was able to release up to 95% more Pi in the compost compared to the amount of Pi released in the control compost. The current study demonstrated the importance of adding the cocktail to enhance Pi in mature compost; however, further studies are required to confirm the results and practical applications.

Influence of fertilization and pre-seeding inoculation systems on phosphate-mobilizing bacteria of sugar beets rhizosphere

This article presents the results of research the influence of fertilizer systems and seeds inoculation on phosphate-mobilizing bacteria in sugar beet rhizosphere. For seeds bacterization was applied the Polymyxobacterin (contains spores and cells of Paenibacillus polymyxa, which can transform insoluble inorganic phosphates and organophosphates and to produce the phytohormonal substances) and mixture of the Polymyxobacterin with Trichoderma (Trichoderma). Microbiological analysis of rhizosphere soil of non-inoculated sugar beet plants was shown that the distribution of phosphate solubilizing microorganisms depends on the agricultural conditions. The using of both mineral and organo-mineral fertilizers stimulates the development of studied microorganisms. For increasing in rhizosphere of non-inoculated sugar beet plants a quantity of microorganisms that soluble mineral phosphates the use of mineral fertilizers (N160P120K160) with the addition of 32 t/ha manure is optimal. The application only mineral fertilizers to increase the number of microorganisms which capable to transform organic phosphorus compounds. In all trials including control without fertilizers, seed treatment by Polymyxobacterin increases the number of bacteria that soluble mineral phosphates. The most optimal conditions for the development of microorganisms that solubilize mineral and organic phosphorus compounds are the treatment of sugar beet seeds by mixture of Polymyxobacterin and Trichoderma and application of mineral fertilizers. Therefore, the obtained results indicate about significant impact of fertilizer types and seed treatment by microorganisms on the amount and composition of phosphate-mobilizing bacteria in the rhizosphere of sugar beet plants.

Differential effects of indigenous arbuscular mycorrhizal fungi and phosphate solubilizing bacteria on maize growth in phosphate-fertilized and unfertilized acid soil

Biofertilizers may be developed using indigenous arbuscular mycorrhizal (AM) fungi and phosphatesolubilizing microorganisms (PSM) isolated from rhizosphere of maize grown on acid laterite soil in eastern India. Microbial colonies thus screened yielded a pigmented, gram negative eubacterial strain which solubilized P bound as ferric phosphate. Fungal inocula for AM were prepared from dried rootlets. Potcultivated maize seedlings were inoculated with PSM and AM fungal propagules under application of two levels of inorganic P (0 and 100 mg/kg soil). Analysis of shoot samples and rhizosphere soil harvested at 20 and 40 days after sowing (DAS) indicated that AM fungi efficiently acquired P for the seedlings in highly depleted soil, gaining over 186% shoot biomass over non-inoculated seedlings in P-0 condition. Inoculation with PSMs gave high concentrations of mobilized P in rhizosphere under P100 condition. Joint treatment with AM, PSM and P100 gave more than 32% increase in shoot dry weight at 40 DAS over solo P100 application – significantly higher than the next best level of shoot biomass obtained (12.4% over solo P100 application) at AM treatment under P0 condition. These results indicated opposite nutrient utilization strategies by AM fungi and PSM in maize rhizosphere, emphasizing holistic application of native biofertilizer components.

Phosphate-solubilising Microorganisms as Potential Biofertilizer: A Review

After the nitrogen phosphorus is the second most important plant nutrient to necessary for plant development and growth. The use of excess phosphate fertilizers potentially causes surface and ground water pollutions and soil fertility depletation and accumulation of phosphate in soil which is unavailable for plant. Biofertilizers play a very significant role in improving soil fertility by fixing atmospheric nitrogen, both, in association with plant roots and without it, solubilized insoluble soil phosphates and produces plant growth substances in the soil. There have been a number of reports on plant growth promotion by microorganisms that have the ability to solubilize inorganic and organic P from soil. There is a dynamic and complex relationship among the different forms of P involving soil, plant and microorganisms. Microorganisms can enhance the capacity of plants to acquire P from soil through various mechanisms. They are able to solubilize unavailable form of unsolubilized phosphate in available form. Purpose of this review is to focuses on the understanding of the mechanism of phosphate solubilisation their role of PSMs(phosphate solubilizing microorganisms) in crop production as biofertilizers.

CHARACTERIZATION OF PHOSPHATE SOLUBILISING BACTERIA ISOLATED FROM THE TEA RHIZOSPHERIC SOIL FROM DARJEELING HILLS

Most soils contain insoluble inorganic phosphates but they are of no use to crops unless it is solubilised. Hence phosphate solubilising microorganisms play a key role in solubilising the tricalcium phosphate (TCP) and make it available to the plants. The present study was aimed to isolate and characterize the selected phosphate solubilizing bacteria from rhizospheric soil of tea from Singla Tea Estate, Darjeeling. Bacteria which showed clear zones in Pikovskaya’s agar were selected and screened for further characterization. The two isolates were found to solubilise TCP in Pikovskaya agar and were designated as GCS1 and GCS2. In vitro phosphate solubilisation ability of these isolates was determined and it was observed that phosphate solubilisation was associated with the reduction in the pH of the medium. These isolates were also found to produce growth promoting substance IAA. These isolates were found to survive well at different pH levels of 5, 7 and 9 and at two different temperatures (room temperature and 370C). Germination of fenugreek seeds were augmented by these isolates. The isolates were identified as Kurthia sp. (GCS1) and Bacillus cereus (GCS2) at IMTECH, Chandigarh, India. This study revealed the presence of potent phosphate solubilising bacteria from rhizosphere tea plants which may be used as bioinoculants after detailed on-farm as well as off-farm investigations.

Utilization of soil residual phosphorus and internal reuse of phosphorus by crops.

Phosphorus (P) participates in various assimilatory and metabolic processes in plants. Agricultural systems are facing P deficiency in many areas worldwide, while global P demand is increasing. Pioneering efforts have made us better understand the more complete use of residual P in soils and the link connecting plant P resorption to soil P deficiency, which will help to address the challenging issue of P deficiency. We summarized the state of soil “residual P” and the mechanisms of utilizing this P pool, the possible effects of planting and tillage patterns, various fertilization management practices and phosphate-solubilizing microorganisms on the release of soil residual P and the link connecting leaf P resorption to soil P deficiency and the regulatory mechanisms of leaf P resorption. The utilization of soil residual P represents a great challenge and a good chance to manage P well in agricultural systems. In production practices, the combination of “optimal fertilization and agronomic measures” can be adopted to utilize residual P in soils. Some agricultural practices, such as reduced or no tillage, crop rotation, stubble retention and utilization of biofertilizers-phosphate-solubilizing microorganisms should greatly improve the conversion of various P forms in the soil due to changes in the balance of individual nutrients in the soil or due to improvements in the phosphatase profile and activity in the soil. Leaf P resorption makes the plant less dependent on soil P availability, which can promote the use efficiency of plant P and enhance the adaptability to P-deficient environments. This idea provides new options for helping to ameliorate the global P dilemma.

Experimental and numerical study of the impinging aerosols method for the micro-encapsulation of phosphate solubilising microorganisms (PSMs)

This study demonstrates the application of the impinging aerosols method in encapsulating phosphate solubilising microorganisms (PSMs), replacing the microbial inoculant method. The method encapsulates PSMs in microbeads by impinging the bacteria-alginate droplets and CaCl2 sprays. Efficient coalescences between the bacteria-alginate and CaCl2 droplets warrant the birth of microbead-encapsulating microorganisms. The proposed method is modelled using a Eulerian–Lagrangian approach. The primary and secondary breakups and wall impingement are modelled using the Huh atomisation, Reitz–Diwakar models, and Bai–Gosman model, respectively. The resulting model is validated against the sizes and spray angles of experimental droplets with different flow rates. The simulation demonstrates that the flow rate, spray angle, droplet size, spray pattern, and alginate and CaCl2 concentrations must be considered to produce robust alginate microbeads and minimise the material loss caused by the formation of a fluid film on the wall. A lower alginate flow rate and concentration of CaCl2 should be used to promote the formation of the alginate microbeads.

Periphytic biofilm and rice rhizosphere phosphate-solubilizing bacteria and fungi: A possible use for activating occluded P in periphytic biofilms in paddy fields

Periphytic biofilm is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. They have been shown to assimilate and store bio-available phosphorus (P) in paddy fields. However, it is necessary to make the occluded P available to the rice plant in the final stage of the plant growth. It has been reported that phosphate-solubilizing bacteria and fungi have a role in activating the occluded P in the periphytic biofilms. However, the ability of the bacteria and fungi isolated from the periphytic biofilms to solubilize sparingly soluble phosphates has not been reported. The aim of this study was to investigate the ability of bacterial and fungal isolates isolated from periphytic biofilms and rice rhizosphere soil, as an origin of bacteria and fungi present in periphytic biofilms, to dissolve different sparingly soluble phosphate sources as single and in combination. In addition, effective phosphate-solubilizing bacterial and fungal isolates and the organic acids produced by these microbes were also identified. The isolated bacterial and fungal isolates had different ability to solubilize various P sources. The order of P dissolution from different P sources by bacterial and fungal isolates was as follows: Ca3PO4 ˃ Ca5(PO4)3(OH) ˃ mixed medium (a combination of 7 different P sources) ˃ Ca5(PO4)3Cl ̴ C6H17NaO24P6 ˃ Ca5(PO4)3F ˃ AlPO4 ˃ FePO4. The type and amount of the organic acids produced by these isolates depended on the type of microbe (bacterial isolate or fungal isolate), used P source, microbial inoculation (single or consortium), and type of the microbe used in consortium (bacterium-bacterium, bacterium-fungus, and fungus-fungus). Based on this assay, it was found that the bacterial and fungal consortiums, due to diversity in the production of different organic acids, showed a better ability to dissolve different forms of P. Based on the sequence of 16S rRNA gene and ITS region, the effective rhizosphere isolates of 8BR15, 8BR17, 2FR3, and 2FR18 and the effective periphytic biofilm isolates of 6BP11, 13BP25, 8FP12, and 6FP9 showed the most similar to Burkholderia vietnamiensis, Arthrobacter luteolus, Talaromyces minioluteus and Talaromyces pinophilus, and Acinetobacter calcoaceticus, Bacillus cereus, Talaromyces stipitatus and Talaromyces minioluteus, respectively. According to these results, periphytic biofilms and rice rhizosphere soil can be as a potential repository for isolating bacteria and fungi effective in solubilizing various P source. In general, the results suggest that the effective phosphate-solubilizing microorganisms have the potential to be used as microbial inoculants to release the bio-available P assimilated and stored in periphytic biofilms for sustainable rice cultivation in paddy lands.

Assessment of soil micro flora in rice-wheat cropping system through continuous and rotational herbicide applications

A long term experiment was conducted at CCS Haryana Agricultural University, Regional Research Station, Uchani (Karnal), India. Assessment of fix and rotational herbicides with and without green manure on the microbial population were studied in wheat crop during 2017-18. The treatments included fix/continuous herbicide (Clodinafop) and rotational herbicide (Sulfosulfuron) to control weeds along with weed free and weedy checks. Rhizosphere samples of wheat were collected from different plots of fixed and rotational herbicides treated soil to assess the total bacterial count, phosphate solubilizing microorganisms, actinobacteria, fungi and free-living diazotrophs. Weed free and weedy check served as check (control) for total microbial populations in the soil. Initially, herbicidal application showed negative effect on the soil microbes but retain the number later on as compared to weedy check under both conditions. But the effects of the herbicides on the micro flora in soil could be nullified through green manure.

Study of tolerance ability in phosphate solubilising microorganisms isolated from tea plantations soil of lower Darjeeling hills

BackgroundTea is an important plantation crop in India and world. Introduction of fertilisers and pesticides for better production polluted tea garden soils. Phosphates in agricultural soils are converted into soluble forms by phosphate solubilising microorganisms (PSMs). Consortium of PSM having high tolerance level is an attractive option for bioremediation of degraded tea plantation soils. This research initiative was to isolate PSM from tea plantation soil and detect their tolerance against pesticide, antibiotic and antifungal.ResultsIsolated consortia from organic and inorganic tea plantation soils of Darjeeling showing halo was considered for tolerance study. Phorate was most and Deltamethrin was the least tolerant pesticide for the isolated PSM consortia. So, Phorate may be considered as most used or most accumulated pesticide. Erythromycin was most and Ofloxacin was the least tolerant antibiotic while Fluconazole was most and Itraconazole was the least tolerant antifungal agent for the isolated PSM consortia. It was noted that there was no or partial inhibition of PSM growth by some pesticide, antibiotic and antifungal agents. In all the three tolerance studies it was observed that there is no relation between collection sites but in all the assays average inhibition zones were more in organic plantations than inorganic plantations.ConclusionsThus, it may be said that inorganic practice induces tolerance to microbes. So, other than cultural practice use of chemicals, micro-ecosystem and antibiosis exhibited by microbes do play a role in conferring tolerance.

Bioformulation of Azotobacter spp. and Streptomyces badius on the productivity, economics and energetics of wheat (Triticum aestivum L.)

Wheat production is directly linked to energy inputs of high yielding varieties, chemical fertilizer and mechanization. In spite of their benefits, fertilizers are associated with high energy consumption. Thus there is need to develop energy-efficient agricultural systems with low input energy compared with the output of food. The only alternate to increase and/or sustain the productivity by developing a system in which nutrients are added through combined use of organic sources biofertilizers and PGPR's. Biofertilizers comprised of efficient strains of nitrogen fixing or phosphate solubilizing microorganism can play pivotal role in this regard. Thereupon the present investigation was planned with combination of chemical fertilizer and biofertilizer to find out the best combination and to get maximum profit with energy saving. The field experiment was carried out at two locations with nine different chemical and biofertilizer combination in randomized complete block design. Maximum grain yield was observed in 87.5% N and 87.5% P + Azotobacter spp and Streptomyces badius (seed treatment) at both the locations. Results indicated that Azotobacter spp and Streptomyces badius may be used synergistically as a potential source with reduction of chemical fertilizer to 12.5–25% without compromising yields.