Bacterial Populations In Rhizosphere Research Articles

Isolation and biochemical screening of Phosphate Solubilizing Bacteria from Kans grass rhizosphere of Fly Ash Dump Sites near NTPC, Angul

Soil bacteria, capable of converting insoluble phosphorus into soluble, plant-accessible forms, collectively known as phosphate-solubilizing bacteria (PSB), have emerged as an eco-friendly and cost-effective solution for supplying phosphorus to plants. This study presents preliminary insights into the rhizospheric bacterial population associated with the vigorously growing kans grass (Saccharum spontaneum L.) at different fly ash disposal sites of NTPC, Kaniha in Angul district, Odisha. In the quest for efficient plant growth promoting rhizobacteria (PGPR) strains with diverse beneficial activities, a total of sixteen bacterial isolates were collected from the rhizosphere of chosen plant species and identified, with only ten isolates underwent biochemical characterization. Among these, four isolates exhibiting a higher phosphate-solubilizing index were further characterized, serving as a foundation for future exploration of the bio-prospective potential of rhizosphere bacteria in this unique ecological niche. Further assessment of these isolates, showcasing several plant growth-promoting (PGP) traits, is essential to determine their efficacy as potent PGPR agents.

PENGARUH APLIKASI PUPUK KOMPOS DAN BIOCHAR TERHADAP POPULASI BAKTERI DI RIZOSFER DAN PERTUMBUHAN TANAMAN PADI GOGO (Oryza Sativa L.)

This reasearch to describe the effect of the application of compost and biochar on bacterial population in rhizosphere and growth of upland rice (Oryza sativa L.) This research was conducted in November-January 2021. The method used in this study was experimental by conducting experiments in greenhouse of the Faculty of Agriculture, University of Mataram. Meanwhile, the analysis of chemical and biological properties was carried out at the Chemistry and Soil Fertility Laboratory, Faculty of Agriculture, University of Mataram. The results showed that the soil used before planting was relatively less fertile (chemically). The soil used in this study had a pH value of 5.0 and available-P had 0.95 ppm, total N was 0.19%, K-exchanged was 0.22 meq/100g. In addition, the organic matter content as reflected by the C-organic value is only 1.2% which is in the low category. And the value of cation exchange capacity is in the medium category (17.43 meq/100 g of soil). administration of doses of urea and phonska fertilizer combined with the provision of compost and biochar had an effect on the variables of plant height, number of tillers and leaf width where the P1 treatment gave a significant value compared to the P0 and P2 treatments. In the parameters of root weight and stem weight, treatment P1 was more significant than treatment P0 and P2. In the total variable of microorganisms the number of bacterial colonies was significant in the P1 treatment with an average value of 7.14, in the P1 phosphate solubilizing fungus parameter it had a significant value with an average value of 3.17, in the P1 phosphate solubilizing bacteria parameter it had a significant value with an average value of 3.61 while for the respiration parameter of microorganisms p1 has a significant value with an average value of 4.36 mg C-CO2 / g soil.

Compositional shifts in rhizobacterial communities of Brassica napus under salinity stress

Salinity stress severely limits crop production globally. The plant rhizosphere harbors diverse microbial communities that can positively influence plant growth and stress tolerance. Therefore, we examined the rhizosphere bacterial populations of Brassica napus under normal and saline conditions using high-throughput 16S rRNA gene sequencing. The objectives were set to identify key taxa enriched in the rhizosphere and evaluate variations in community structure between control and salt-stressed Brassica napus plants. Proteobacteria, Actinobacteria, Chloroflexi, and Bacteroidetes were the predominant phyla. Key genera enriched in the rhizosphere included Sphingomonas, Streptomyces, Bacillus, and Pseudomonas. Salinity stress increased the abundances of Chloroflexi and Acidobacteria while decreased Actinobacteria. Rhizosphere communities of salt-treated plants showed lower diversity but separate clusters from controls, indicating salinity-induced shifts. Predictive functional analysis revealed that amino acid/carbohydrate metabolism and membrane transport pathways in salt-stressed rhizospheres were elevated. This study provides novel insights into the rhizosphere bacteriome of Brassica napus under salinity, highlighting potential plant-growth-promoting taxa for stress amelioration.

Unveiling the maize-benefit: Synergistic impacts of organic-inorganic fertilizer cooperation on rhizosphere microorganisms and metabolites

Maize, an indispensable staple crop, plays a vital role in ensuring human food security. To shed light on the effects of different fertilizer management modes on maize growth, as well as rhizosphere bacterial populations and metabolites, we employed high-throughput sequencing and non-targeted metabolomics technology. Experimental treatments comprised: CK (no fertilizer), CF (single chemical fertilizer, N-P2O5-K2O), OF30 (30 % organic fertilizer replacement), OF70 (70 % organic fertilizer replacement), and OF100 (100 % organic fertilizer, animal manure and humic acid as raw materials). Compared to the single chemical fertilizer, the dual fertilizer management resulted in a more stable bacterial network and a more complex metabolic system. Notably, under OF70 conditions, the rhizosphere soil exhibited greater prevalence of functional bacteria like Paenibacillus and Pseudoxanthomonas. This stimulation significantly activated biosynthesis processes like unsaturated fatty acids, plant hormone synthesis, and plant secondary metabolite production. Through correlation mining of differential metabolites and differential bacteria, as well as weighted gene co-expression network analysis (WGCNA), we revealed a consistent correlation trend between bacterial population abundance and changes in metabolite content under dual fertilization. The dual fertilizer approach established a more intricate regulatory relationship between plants, bacteria and metabolites, indicative of a more stable rhizosphere environment. Importantly, our findings on the superior growth performance of maize under OF70 conditions, coupled with microecological changes in the rhizosphere (bacteria and metabolites), provide valuable insights for advancing efficient maize cultivation and informing scientifically sound fertilizer management practices. Moreover, these results hold relevance for production considerations in other agricultural crops. However, it is crucial to further explore the generalizability of these findings in field conditions.

Illumina MiSeq sequencing investigation on the contrasting rhizosphere soil bacterial community structures in tea orchard soil under different content of aluminium

The rhizosphere of grown tea (Camellia sinensis (L.) O. Kuntze) becomes acidic, and aluminium (Al) toxicity has been identified as a key constraint on plant development in acidic soils. The current study investigated the composition and functions of rhizosphere bacteria as well as soil enzyme activity under different Al stress conditions. The effect of soil pH, soil enzyme activities, the diversity and structure of the rhizosphere bacterial population under various Al concentrations were studied by the pot experiment. All analyses demonstrated that substantial alterations in the activity of soil enzymes and the composition of the bacterial communities in the rhizosphere could only be seen under conditions of extreme Al stress. Soil enzymes were more concentrated in Al concentrations of 100, 150 and 250 µM, respectively. More than 82,000 valid reads were obtained for each replicate, and the abundance of certain genera in the aluminium treated groups were greater than the control group. Lower Al stress attracted Al-tolerant bacteria such as Burkholderia to increase Al stress resistance. These findings revealed that soil enzyme activities and the structure of the rhizosphere bacterial population in tea orchard soil provided tolerance or resistance capability to tea plants for their development under Al stress.

Viral Community Structure and Potential Functions in the Dried-Out Aral Sea Basin Change along a Desiccation Gradient.

The dried-out Aral Sea basin represents an extreme environment due to a man-made ecological disaster. Studies conducted in this unique environment revealed high levels of pollution and a specifically adapted microbiota; however, viral populations remained entirely unexplored. By employing an in-depth analysis based on the sequencing of metagenomic DNA recovered from rhizosphere samples of Suaeda acuminata (C. A. Mey.) Moq. along a desiccation gradient of 5, 10, and 40 years, we detected a diverse viral community comprising 674 viral populations (viral operational taxonomic units [vOTUs]) dominated by Caudovirales. Targeted analyses highlighted that viral populations in this habitat are subjected to certain dynamics that are driven mainly by the gradient of desiccation, the corresponding salinity, and the rhizosphere bacterial populations. In silico predictions linked the viruses to dominant prokaryotic taxa in the Aral Sea basin, such as Gammaproteobacteria, Actinomycetia, and Bacilli. The lysogenic lifestyle was predicted to be predominant in areas that dried out 5 years ago, representing the early revegetation phase. Metabolic prediction of viral auxiliary metabolic genes (AMGs) suggests that viruses may play a role in the biogeochemical cycles, stress resilience, and competitiveness of their hosts due to the presence of genes that are involved in biofilm formation. Overall, our study provides important insights into viral ecology in an extreme environment and expands our knowledge related to virus occurrence in terrestrial systems. IMPORTANCE Environmental viruses have added a wealth of knowledge to ecological studies with the emergence of metagenomic technology and approaches. They are also becoming recognized as important genetic repositories that underpin the functioning of terrestrial ecosystems but have remain moslty unexplored. Using shotgun metagenome sequencing and bioinformatic tools, we found that the viral community structure was affected during natural revegetation in the dried-up Aral Sea area, a model habitat for investigating natural ecological restoration but still understudied. In this study, we highlight the importance of viruses, elements that are overlooked, for their potential contribution to terrestrial ecosystems, i.e., nutrient cycles, stress resilience, and host competitiveness, during natural revegetation.

Effects of genotype and ecological environment on the community structure and function of symbiotic bacteria in rhizosphere of ginseng

BackgroundGinseng, an important traditional Chinese medicine and a new resource food, has two production modes: farmland ginseng and forestland ginseng. Ginseng faces many problems such as high soil bulk density, easy hardening, low nutrient content, reduced porosity and increased soil acidification because of continuous cropping. Increasing studies indicate that plant rhizosphere symbiotic bacteria have an important effect on plant growth and development. We speculate that differences in microbial community may play an important role in promoting ginseng growth, development and health. To reveal the differences between farmland and forestland ginseng cultivation, and to address problems associated with continuous ginseng cropping, we investigated the effects of differences in plant rhizosphere symbiotic bacterial communities in promoting ginseng growth, development, and health.ResultIn the present study, the microbial communities in the rhizosphere of different genotypes and ecological environments were analyzed using the high-throughput sequencing platform Illumina, phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt), and other technologies. The organic matter, total nitrogen, available nitrogen, and available phosphorus contents in forestland soil were significantly different from those in farmland. The bacterial communities of ginseng in forestland, farmland, and greenhouse environments have specific dominant groups at the phylum and genus levels. There were differences in the gene functions of ginseng root-related bacterial communities between forestland and farmland. There were significant differences in the abundance distribution of rhizosphere bacteria among the different genotypes at the phylum and genus levels.ConclusionsThere is a close relationship between the ecological environment and bacterial population structure, and the ecological environment of forestland is more conducive to the formation of rich rhizosphere bacterial populations; additionally, the genetic diversity is richer than that of farmland. The rhizosphere bacterial community structure of ginseng was influenced by genotype, and there was a correlation between the distance between ginseng genotypes and the stratified clustering of its rhizosphere bacterial community structure.

Differential assembly of root-associated bacterial and fungal communities of a dual transgenic insect-resistant maize line at different host niches and different growth stages.

Transgenic technology has been widely applied to crop development, with genetically modified (GM) maize being the world’s second-largest GM crop. Despite the fact that rhizosphere bacterial and fungal populations are critical regulators of plant performance, few studies have evaluated the influence of GM maize on these communities. Plant materials used in this study included the control maize line B73 and the mcry1Ab and mcry2Ab dual transgenic insect-resistant maize line 2A-7. The plants and soils samples were sampled at three growth stages (jointing, flowering, and maturing stages), and the sampling compartments from the outside to the inside of the root are surrounding soil (SS), rhizospheric soil (RS), and intact root (RT), respectively. In this study, the results of alpha diversity revealed that from the outside to the inside of the root, the community richness and diversity declined while community coverage increased. Morever, the different host niches of maize rhizosphere and maize development stages influenced beta diversity according to statistical analysis. The GM maize line 2A-7 had no significant influence on the composition of microbial communities when compared to B73. Compared to RS and SS, the host niche RT tended to deplete Chloroflexi, Gemmatimonadetes and Mortierellomycota at phylum level. Nitrogen-fixation bacteria Pseudomonas, Herbaspirillum huttiense, Rhizobium leguminosarum, and Sphingomonas azotifigens were found to be enriched in the niche RT in comparison to RS and SS, whilst Bacillus was found to be increased and Stenotrophomonas was found to be decreased at the maturing stage as compared to jointing and flowering stages. The nitrogen fixation protein FixH (clusters of orthologous groups, COG5456), was found to be abundant in RT. Furthermore, the pathogen fungus that causes maize stalk rot, Gaeumannomyces radicicola, was found to be abundant in RT, while the beneficial fungus Mortierella hyalina was found to be depleted in RT. Lastly, the abundance of G. radicicola gradually increased during the development of maize. In conclusion, the host niches throughout the soil-plant continuum rather than the Bt insect-resistant gene or Bt protein secretion were primarily responsible for the differential assembly of root-associated microbial communities in GM maize, which provides the theoretical basis for ecological agriculture.

Pennisetum purpureum Improved Polycyclic Aromatic Hydrocarbons Removal in Weathered-Petroleum Contaminated Soil

Petroleum hydrocarbons are among the major driving forces of advancement in the last Century. Some of the hydrocarbons especially polycyclic aromatics are however of health and environmental significance, due to their recalcitrance and persistence leading to adverse effects on health and ecosystem stability. A number of treatment technologies have been used to cleanup hydrocarbon contaminants and the use of phytoremediation technology have recently been described as promising. In this study, phytoremediation of weathered crude oil contaminated soil was carried out in a microcosm using Pennisetumpurpureum for 60 days. Pristine soil samples were collected and mixed with weathered petroleum contaminated soil to achieve 5%, 25%, 35% and 50% w/w contamination levels. Bacterial species in the rhizosphere were isolated and identified and residual oil was extracted and analyzed using GC-MS. Results showed that there was high bacterial population in rhizosphere (5.0×105 cfu/g to 6.4×105 cfu/g) than non-rhizosphere soil (2.4 ×105 cfu/g to 4.0×105 cfu/g); and Bacillus spp. (64.71%) were observed to be predominant in the rhizosphere followed by Micrococcus spp. (17.65%), Pseudomonas aeruginosa (5.88%), Klebsiella pneumoniae (5.88%) and Flavobacterium sp. (5.88%). Hydrocarbon concentration in the rhizosphere was reduced by 82.5%, 60.5%, 58.0% and 48.8% respectively. Complex polycyclic aromatic hydrocarbon compounds detected in the control using GC-MS were significantly reduced or completely degraded. Polycyclic aromatic hydrocarbons such as anthracene, naphthalene, fluorene, benzo (a) anthracene, pyrene and chrysene were significantly reduced at a rate ranging between 13.33% and 97.54%. Based on the rate of PAHs reduction observed in this study, it was evident that P. purpureumsupports cleanup of persistent hydrocarbon contaminants in soil environment. The use of this plant in large scale petroleum hydrocarbon cleanup under field conditions should be investigated.

Locally Available Organic Waste for Counteracting Strawberry Decline in a Mountain Specialized Cropping Area

Crop decline caused by soil borne fungal pathogens affects specialized cropping systems such as fruit trees and strawberry. A study was carried out to investigate the effectiveness of pre-plant application of waste-derived biomasses in strawberry (Fragaria × ananassa) to reduce that phenomenon. A field experiment was carried out in an alpine strawberry specialized valley in South Tyrol (Italy), in a long term cultivated field selected for yield reduction over recent years. In July 2018, one month before strawberry transplanting, a field experiment with four soil treatments was set up: anaerobic digestate (solid fraction) of liquid manure, compost from anaerobic digestate of organic fraction of municipal solid waste (OFMSW), untreated control and Dazomet as chemical control. Plants were grown for two cycles (2019 and 2020). Dazomet always gave a significant (over 50%) increase in marketable yield per plant in both the years, anaerobic digestates did not improve strawberry production; compost from OFMSW gave phytotoxic effects in the first year, but improved strawberry yield like Dazomet in the second. Changes of rhizosphere bacterial populations and difference in root pathogen abundance, especially that of Dactylonectria torresensis, were correlated to the crop response to treatments. Findings suggest that waste-derived biomasses are a promising eco-friendly option for counteracting strawberry yield decline. Their positive impact was mostly linked to functional improvements induced by microbial variations. However, the use of such organic amendment requires careful evaluation of composition, doses and above all application times to reduce phytotoxic effects that in some cases can occur in the first months after application.

Combining potential oomycete and bacterial biocontrol agents as a tool to fight tomato Rhizoctonia root rot

Biological control of Rhizoctonia root rot and growth-promoting potential on two tomato cultivars was performed using Pythium oligandrum in combination, or not, with three tomato-associated rhizobacterial strains of Bacillus subtilis, B. thuringiensis and Enterobacter cloacae. The three bacterial strains displayed antifungal activity against Rhizoctonia solani, with pathogen growth inhibition up to 60%. P. oligandrum also destroyed R. solani cells by antibiosis and mycoparasitism processes. In a three-month greenhouse assays, for all trials and the two tomato cultivars used, disease suppression potential, as compared to the controls, was up to 80% using the microorganisms mixtures and 74% by using P. oligandrum alone. Increased height in disease-free plants was obtained with the microorganism mixtures (59%) compared to P. oligandrum (49%). Plants grown in R. solani inoculated peat and challenged with microorganism mixtures were higher than controls, whereas those amended with P. oligandrum showed 46 to 87% height increase. All treatments with the microorganisms were more effective in suppressing the disease than chemical fungicide. Increment of aerial parts and root fresh weights on disease-free plants were until 51% for those treated with microorganism mixtures compared to 46% recorded using P. oligandrum. On inoculated plants, these parameters were enhanced using the mixed treatment. No differences in the rhizosphere-bacterial populations were observed by Single Strand Conformational Polymorphism (SSCP) when, either the rhizobacteria, with or without P. oligandrum, or the pathogen, were inoculated. This suggests that the native bacterial communities were not significantly impacted by the various microbial-inoculations. Only differences were obtained for the two tomato cultivars that the native bacterial microflora colonize.

Illumina based high throughput analysis of microbial diversity of maize rhizosphere treated with nanocompounds and Bacillus sp.

Soil microorganisms play a crucial role in the maintenance of the ecosystem. Their diverse enzymatic machinery facilitates the biogeochemical cycling of essential macro/micronutrients. Over the past two decades, significant amount of research has been carried out on the application of nanocompounds in agricultural practices. Some reports support the role of nanocompounds in enhancing crop productivity by providing essential nutrients to plants or by exhibiting antimicrobial activities against different phytopathogens. Meagre information is available on long term impact of agriusable nanocompounds along with plant growth promoting rhizobacteria on microbial population of an agriculture field. In this study, attempts have been made to analyse the impact of nanozeolite and nanochitosan (50 mg L−1) along with a bioinoculant (Bacillus sp.) on the bacterial community of maize rhizosphere under field condition. Total bacterial counts, activities of soil health indicator enzymes and total microbial diversity of the experimental maize rhizosphere were assessed using Illumina based high throughput sequencing after 60 days of the experiment. Obtained results indicated higher bacterial diversity in the treated soil than the control which corresponded to increased number of Operational Taxanomic Units (OTUs). Combined treatment of bioinoculant and nanocompounds showed two fold increase in FDA (Fluorescein diacetate hydrolysis), dehydrogenase and alkaline phosphatase activity than the control. Presence of dominant bacterial genera viz. Actinobacteria, Bacteroidetes, Acidobacteria and Chloroflexi were observed in treated soil sample. Combined treatment of Bacillus sp. and nanocompounds had a strong influence on the composition of rhizospheric microbiota, diversity and richness. We propose that the application of nanocompounds along with a potential bioinoculant is beneficial for the survival of rhizospheric bacterial population and soil health.

Effect of pendimethalin and imazethapyr on the development of microorganisms in vitro and at field conditions

The herbicides may have adverse effects on the soil microorganism. The aim of the study was to investigate the effects of herbicides pendimethalin and imazethapyr and mixture thereof on the growth of Rhizobium leguminosarum M-1, Rhizobium leguminosarum LSMR-1 and Strenotrophomonas maltophilia RB-3 in vitro and on soil microflora (bacteria, fungi and actinomycetes) at field conditions. The tolerance of Rhizobium and Stenotrophomonas to pendimethalin at 180–1980 mg/L and imazethapyr at 26–200 mg/L and mixtures thereof in nutrient media was tested. The tolerance for pendimethalin was higher than for imazethapyr. In field experiments with mungbean, the effects of pendimethalin alone as well as in mixture with imazethaypr at 0.45 and 0.75 kg ha−1 (applied as pre-emergence) and imazethapyr at 50 and 75 g ha−1 (applied at 15 and 25 days after sowing) in the rainy and summer season were tested. Pendimethalin and its mixture with imazethapyr did not influence the population of fungi and actinomycetes in rhizosphere (0–10 cm soil depth) at 35 days after sowing and at harvest. Imazethapyr treatments recorded inhibitory effects on bacterial population in rhizosphere at 35 days after sowing but no adverse effect was observed at harvest. Pendimethalin alone and in mixture with imazethapyr were found safe to investigated microorganism groups.

Vermicompost and cow dung admixture increases rhizosphere bacterial population and promotes rapid physiological maturity in Maize (Zea mays L.)

Incessant application of chemical fertilizers to the agricultural fields may alter the composition and activities of soil microbiota. Thus, the shift of cultivation practices from chemical to organic is considered to be the need of the hour in order to maintain soil health. A study was conducted in the agricultural fields of the University of Burdwan, India to observe the impact of organic manure on rhizosphere bacterial community. The experiments were conducted on maize plants, supplemented with the recommended dose of chemical fertilizer and organic manure (vermicompost and cow dung mixture). Corresponding changes in the plant phenological events and soil health in terms of soil physico-chemical factors and rhizosphere bacterial groups up to the level of CFU g-1× 105 dry soil were noted.The results showed a significant increase in population of nitrifying bacteria, asymbiotic nitrogen-fixing bacteria and protein hydrolysing bacteria in the organically treated plots. Moreover, the organic manure increases the bacterial population of rhizosphere, which in turn has a positive impact on maize growth and yield. The growth of the three groups of bacteria was attributed to the type of organic manure supplied to the agricultural fields.In addition, strong correlation was observed between Zn and protein hydrolysing bacteria. The soil organic carbon and available nitrogen were strongly correlated with nitrifying, fat solubilizing and phosphate solubilizing groups of bacteria.

Impact of application of Trichoderma and biochar on growth, productivity and nutritional quality of tomato under reduced N-P-K fertilization

Extensive use of synthetic fertilizer to maximize the productivity often leads to depletion of essential soil nutrients, environmental degradation and adversely affects soil rhizosphere microbiota. The present study investigates the efficacy of Trichoderma and biochar co-application on tomato productivity, nutritional quality and soil health improvements under reduced N-P-K fertilizer application. The study comprised of five treatments: (i) standard application of N-P-K, (ii) 50% dose of N-P-K (control), (iii) Trichoderma + 50% dose of N-P-K, (iv) biochar+50% dose of N-P-K and (v) biochar+Trichoderma + 50% dose of N-P-K. The growth, yield, and antioxidant properties of tomatoes, as well as their mineral composition, were analysed. The results showed that the combined application of Trichoderma and biochar increased the growth attributes positively and produced 101.45% and 11.33% higher yield compared to half dose and standard dose of N-P-K, respectively. The combined application also elicited an increase in mineral contents, total soluble solids as well as bioactive molecules such as lycopene and ascorbic acid, thereby increased the nutritional and functional quality of the tomato fruits. Collectively, Trichoderma and biochar improved soil fertility, nutrient uptake and promoted the growth of rhizosphere fungal and bacterial populations, which combined resulted in higher tomato yields, antioxidants, and minerals. Therefore, the co-application of Trichoderma and biochar with a 50% dose of N-P-K can be considered an effective technique for the sustainable production of tomato with higher yield and superior quality.

Studies on correlations between soil chemistry and bacterial population in rhizosphere of Bt and non-Bt cotton and characterization of rhizobacteria

The present study was planned to explore the relationship between soil chemistry with bacterial population of Bt and non-Bt cotton and their phenotypic and molecular characteristics. The pre-plant soil and rhizospheres of Bt and non-Bt cotton were collected and analyzed for some soil parameters and bacterial population. The bacterial isolates were analyzed for their morphological, biochemical, and molecular characteristics. Bacterial population showed a significant (p < 0.05) positive correlation with clay content, electrical conductivity, organic matter, total nitrogen, and available phosphorus and potassium negative with correlation with pH. Bt cotton showed a non-significant effect on the soil parameters, significant decrease in bacterial population, change in the morphological and biochemical characteristics of rhizobacteria and replacement of four bacterial species with five new ones suggests the potential effect of Bt cotton on its rhizoflora. The rhizosphere of non-Bt cotton cultivated in the fertile agriculture field was found to be the best for bacterial growth.

Evaluation of Available Soil Nutrients and Nitrogen Fixing Bacterial Population in Rhizosphere of Wild Grasses From agricultural land of Newasa Tahasil of Ahmednagar District (MS) India

Evaluation of Available Soil Nutrients and Nitrogen Fixing Bacterial Population in Rhizosphere of Wild Grasses From agricultural land of Newasa Tahasil of Ahmednagar District (MS) India

Investigation and Assessment for an effective approach to the reclamation of Polycyclic Aromatic Hydrocarbon (PAHs) contaminated site: SIN Bagnoli, Italy

Native plant species were screened for their remediation potential for the removal of Polycyclic Aromatic Hydrocarbons (PAHs) contaminated soil of Bagnoli brownfield site (Southern Italy). Soils at this site contain all of the PAHs congeners at concentration levels well above the contamination threshold limits established by Italian environmental legislation for residential/recreational land use, which represent the remediation target. The concentration of 13 High Molecular Weight Polycyclic Aromatic Hydrocarbons in soil rhizosphere, plants roots and plants leaves was assessed in order to evaluate native plants suitability for a gentle remediation of the study area. Analysis of soil microorganisms are provides important knowledge about bioremediation approach. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria are the main phyla of bacteria observed in polluted soil. Functional metagenomics showed changes in dioxygenases, laccase, protocatechuate, and benzoate-degrading enzyme genes. Indolacetic acid production, siderophores release, exopolysaccharides production and ammonia production are the key for the selection of the rhizosphere bacterial population. Our data demonstrated that the natural plant-bacteria partnership is the best strategy for the remediation of a PAHs-contaminated soil.

Effects of Intercropping Peanut on Soil Nutrient Status and Microbial Activity within Young Camellia oleifera Plantation

ABSTRACTA two-year field trial was conducted to compare the effects of intercropping with peanut and Camellia oleifera monoculture on soil characteristics, nutrients status as well as soil microbial activity in a young C. oleifera plantation on latosolic red soil. Compared with C. oleifera monoculture, the soil porosity in intercropping C. oleifera with peanut was increased by 11.45 and 8.41%, the electrical conductivity by 14.74 and 16.90%, the rhizosphere fungi populations by 21.46 and 15.38%, the rhizosphere bacterial populations by 52.19 and 43.87%, soil organic matter (SOM) by 4.72 and 5.69%, the available nitrogen (N) by 10.71 and 14.51%, available calcium (Ca) by 10.53 and 17.39% and available magnesium (Mg) by 18.18 and 20.00% in 2012 and 2013, respectively. However, intercropping significantly reduced soil bulk density, soil total and exchangeable phosphorus (P), soil total and exchangeable potassium (K) and exchangeable aluminum (Al) in both years. Therefore, the beneficial effect may be attributed to the improvement of bulk density, soil nutrient element and the reduction in pH, as well as the rhizosphere microbial populations in intercropping systems.

Populasi Bakteri Dan Jamur Pada Rizosfer Caisim (Brassica juncea L.) Yang Ditanam Di Tanah Dikontaminasi Insektisida Organoklorin Setelah Aplikasi Konsorsia Mikroba Dan Kompos

Organochlorine insecticide was banned for agriculture but nowadays its residue was still found in some agricultural soil. One of ways to lowering organochlorine residue in soil is by used of degrading-organochlorine microbial consortia accompanied with compost application. However, application of exogenous microbes might affect bacterial and fungal population in soil. The pot experiment has been set up to verify the influence of Pseudomonas mallei and Trichoderma sp. and compost on total bacteria and fungi on rhizosphere of Cai Sim (Brassica juncea L.) grown on Andisols which were contaminated with organochlorine insecticide of heptachlor, endosulfan, dieldrin and DDT. Experimental design was Factorial Randomized Block Design with three replicates. The first factor was microbial consortia of P.mallei and Trichoderma sp., and the second one was kind of compost. The result showed that effect of microbial consortia on total bacteria population was determined by kind of compost. Total bacterial population in rhizosphere of Cai Sim grown with cow manure compost and microbial consortia was more increased. However, microbial consortia as well as any kind of compost did not influence total fungal population in Cai Sim rhizosphere. In this experiment, total bacterial and fungal population in rhizosphere reached 109 cfu g-1 and 104 cfu g-1 respectively, indicating that major microbial population in rhizosphere was in the normal range.