Effects of potassium fulvic acid and potassium humate on microbial biodiversity in bulk soil and rhizosphere soil of Panax ginseng

ABSTRACT The purpose of this study was to investigate the mechanism by which phytoremediation systems promote hydrocarbon degradation in soil. The composition and degradation capacity of the bulk soil microbial community during the phytoremediation of soil contaminated with aged hydrocarbons was assessed. In the bulk soil, the level of catabolic genes involved in hydrocarbon degradation (ndoB, alkB, and xylE) as well as the mineralization of hexadecane and phenanthrene was higher in planted treatment cells than in treatment cells with no plants. There was no detectable shift in the 16S ribosomal DNA (rDNA) composition of the bulk soil community between treatments, but there were plant-specific and -selective effects on specific catabolic gene prevalence. Tall Fescue (Festuca arundinacea) increased the prevalence of ndoB, alkB, and xylE as well as naphthalene mineralization in rhizosphere soil compared to that in bulk soil. In contrast, Rose Clover (Trifolium hirtum) decreased catabolic gene prevalence and naphthalene mineralization in rhizosphere soil. The results demonstrated that phytoremediation systems increase the catabolic potential of rhizosphere soil by altering the functional composition of the microbial community. This change in composition was not detectable by 16S rDNA but was linked to specific functional genotypes with relevance to petroleum hydrocarbon degradation.

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Distribution of recently fixed photosynthate in a switchgrass plant-soil system

Plant Soil and Environment ◽

10.17221/532/2011-pse ◽

2012 ◽

Vol 58 (No. 6) ◽

pp. 249-255 ◽

Cited By ~ 12

Author(s):

D.R. Chaudhary ◽

J. Saxena ◽

N. Lorenz ◽

R.P. Dick

Keyword(s):

Panicum Virgatum ◽

Rhizosphere Soil ◽

Microbial Biomass Carbon ◽

Bulk Soil ◽

Energy Crop ◽

Marginal Lands ◽

Soil System ◽

Plant Soil ◽

Panicum Virgatum L ◽

Maintenance Requirements

The use of switchgrass (Panicum virgatum L.) as an energy crop has gained great importance in past two decades due to its high biomass yields on marginal lands with low agricultural inputs and low maintenance requirements. Information on the allocation of photosynthetically fixed C in the switchgrass-soil system is important to understand the C flow and to quantify the sequestration of C in soils. The allocation of 13C labeled photosynthates in shoot, root, soil, and in microbial biomass carbon (MBC) of rhizosphere and bulk soil of 45 days old, greenhouse grown-switchgrass was examined during 20 days 13C-CO2 pulse labeling period. The total 13C recovered in the plant-soil system varied from 79% after 1 day to 42% after 20 days of labeling. After labeling, 54%, 40%, and 6% excess 13C resided in shoot, root and soil, respectively on day 1; 27%, 61% and 11%, respectively on day 5 and 20%, 63% and 17%, respectively day 20 after labeling. The maximum incorporation of 13C from roots into the MB of rhizosphere soil occurred within the first 24 h of labeling. The excess 13C values of rhizosphere soil and rhizosphere MBC were significantly higher than excess 13C values of bulk soil and the bulk soil MBC, respectively. The proportion of excess 13C in soil as MBC declined from 92 to 15% in rhizosphere soil and from 79 to 18% in bulk soil, for 1 day and 20 days after labeling, respectively. The present study showed the effectiveness of 13C labeling to examine the fate of recently photosynthesized C in soil-plant (switchgrass) system and dynamics of MBC.

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Rhizosphere effects on soil nutrient dynamics and microbial activity in an Australian tropical lowland rainforest

Soil Research ◽

10.1071/sr11202 ◽

2011 ◽

Vol 49 (7) ◽

pp. 652 ◽

Cited By ~ 8

Author(s):

Hannah Toberman ◽

Chengrong Chen ◽

Zhihong Xu

Keyword(s):

Nutrient Cycling ◽

Microbial Activity ◽

Tropical Rainforest ◽

Rhizosphere Soil ◽

Critical Role ◽

Total Carbon ◽

Bulk Soil ◽

Soluble Nitrogen ◽

Global Cycles ◽

Rhizosphere Processes

Via vast exchanges of energy, water, carbon, and nutrients, tropical forests are a major driving force in the regulation of Earth’s biogeochemical, hydrological, and climatic cycles. Given the critical role of rhizosphere processes in nutrient cycling, it is likely that rhizosphere processes in tropical rainforests form a major component of the biome’s interactions with global cycles. Little is known, however, about rhizospheric processes in rainforest soils. In order to investigate the influence of rhizosphere processes upon rainforest nutrient cycling, we compared the nutrient status and microbial activity of rhizospheric soil from Australian lowland tropical rainforest with that of the surrounding bulk soil. We found a marked difference in the biological and chemical nature of the rhizosphere and bulk soils. Total carbon, microbial biomass carbon, total nitrogen, soluble nitrogen, and a suite of trace element concentrations, alongside microbial respiration and the rate and diversity of carbon substrate use, were all significantly higher in the rhizosphere soil than the bulk soil. Rhizosphere soil δ15N was significantly lower than that of the bulk soil. Ratios of carbon, nitrogen, phosphorus, and sulfur differed significantly between the rhizosphere and bulk soil. These clear differences suggest that rhizosphere processes strongly influence nutrient cycling in lowland tropical rainforest, and are likely to play an important role in its interaction with global cycles. This role may be under-represented with composite sampling of rhizosphere and bulk soil. Further research is required regarding the mechanisms of rainforest rhizospheric processes and their relationship with ecosystem productivity, stability, and environmental change.

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EFFECT OF PLANT COVERAGE ON MINERALOGICAL CHANGES OF MICA IN RHIZOSPHERE

IRAQI JOURNAL OF AGRICULTURAL SCIENCES ◽

10.36103/ijas.v51i1.948 ◽

2020 ◽

Vol 51 (1) ◽

Author(s):

Al- Jaff & Essa

Keyword(s):

Rhizosphere Soil ◽

Transformation Process ◽

Bulk Soil ◽

X Ray ◽

Weathering Processes ◽

Plant Coverage ◽

Pine Trees ◽

Pear Trees

Three soil sites were chosen in sulaymaniyah governorate, for three types of trees (pine, oak and pear), in order to study the effect of biochemical activities in rhizosphere on weathering of mica and potassium availability comparing with Bulk soil. Results of X-ray showed that the transformation process of mica to 2:1 expandable minerals in rhizosphere was exceeded than in Bulk soil of all type of trees. While the superiority of mica weathering, and increase of smectite content in all rhizosphere were taken a followed sequence. Pine > oak > pear. Results of SEM for clay samples of Bulk soil showed there was no cracks, splitting, Exfoliation, and no separation of the layers on the surfaces of minerals. While the inspection results confirmed two types of mica edges weathering: first, was a complete edge weathering of mica in Bulk soil of pine trees, and second, was un completed edge weathering in Bulk soil of oak and pear. Also a complete pal colour of mica particle surfaces were found in clay samples of rhizosphere soil under pine trees. While the surfaces and edges of mica were less affected by the weathering processes, was found in clay samples of rhizosphere soil of oke and pear trees.

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Variable survival ability of rhizobacteria in cumin (Cuminum cyminum L.) rhizosphere

Journal of Applied and Natural Science ◽

10.31018/jans.v8i3.1025 ◽

2016 ◽

Vol 8 (3) ◽

pp. 1699-1703

Author(s):

Anurag Yadav ◽

Kusum Yadav

Keyword(s):

Bacillus Subtilis ◽

Pseudomonas Fluorescens ◽

Rhizosphere Soil ◽

Population Decline ◽

Dry Weight ◽

Bulk Soil ◽

Subtilis Strain ◽

Initial Population ◽

Final Population ◽

Better Than

A study was undertaken to compare the survival efficacy of two native, previously characterized bacterial biovars viz. Bacillus subtilis BCU5 and Pseudomonas fluorescens PCU17 with Bacillus subtilis strain MTCC1789 and Pseudomonas fluorescens strain MTCC4828, procured from Institute of Microbial Technology, Chandigarh,India in cumin rhizosphere and bulk soil. All the four bacterial types were made rifampicin resistant and the mutants were applied as inoculants at the dosage of 6 log, 7 log and 8 log colony forming units (cfu) g-1 dry soil weight in pots containing cumin seedlings. The cfu of rhizosphere and bulk soil of pots was observed per week for four weeks. The results show that the initial population decline is a common feature of bioinoculants. In rhizosphere and bulk soil, the native bacterial biovars survived better than their procured counterparts. The population of P. fluorescens strain MTCC4828r in rhizosphere soil declined faster and reached below detection limit whereas the P. fluorescens biovar PCUr rhizosphere final population dropped to 3.1 log, 2.9 log and 2.13 log cfu g-1 soil dry weight with 8 log, 7 log and 6 log cfu g-1 soil dry weight inoculum treatment, respectively. In contrast to P. fluorescens strain MTCC4828r, the population of B. subtilis strain MTCC1789r stabilized after some decline and was comparable with B. subtilis biovar BCU5 population. Study concludes that the inoculant population decline in soil was the result of lower microbial load carrying capacity of soil than the provided inoculum densities. Also, the native bacteria survived better than procured ones in rhizosphere soil.

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Variation in Bacterial Community Structure in Rhizosphere and Bulk Soils of Different Halophytes in the Yellow River Delta

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.816918 ◽

2022 ◽

Vol 9 ◽

Author(s):

Yinghan Zhao ◽

Tian Li ◽

Pengshuai Shao ◽

Jingkuan Sun ◽

Wenjing Xu ◽

...

Keyword(s):

Bacterial Community ◽

Bacterial Community Structure ◽

Rhizosphere Soil ◽

Yellow River ◽

Bacterial Community Composition ◽

Yellow River Delta ◽

Bulk Soil ◽

The Yellow River ◽

The Yellow River Delta ◽

Α Diversity

Soil microorganisms play the important role in driving biogeochemical cycles. However, it is still unclear on soil microbial community characteristics and microbial driving mechanism in rhizosphere and bulk soils of different halophyte species. In this study, we analyzed bacterial communities in the rhizosphere and bulk soils of three typical halophytes in the Yellow River Delta, i.e., Phragmites communis, Suaeda salsa, and Aeluropus sinensis, by high-throughput sequencing. The contents of total carbon, total nitrogen, and available phosphorus in rhizosphere soils of the three halophytes were significantly higher than those in bulk soils, which suggested a nutrient enrichment effect of the rhizosphere. Rhizosphere soil bacterial α-diversity of P. communis was higher than that in bulk soil, whereas bacterial α-diversity in rhizosphere soil of S. salsa and A. sinensis was lower than those in bulk soil. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Chloroflexi, and Bacteroidetes, which accounted for 31, 20.5, 16.3, and 10.3%, respectively. LDA effect size (LEfSe) analysis showed that the bacterial species with significant differences in expression abundance was obviously different in the rhizosphere and bulk soil of three halophytes. The principal component analysis (PCoA) showed that bacterial community composition was greatly different between rhizosphere and bulk soils of P. communis and S. salsa, while no difference in A. sinensis. Changed bacterial community composition was mainly ascribed to salinity in rhizosphere and bulk soils. Additionally, salinity was positively correlated with Bacteroidetes and negatively correlated with Actinobacteria and Acidobacteria. Our study clarified the variation in bacterial community structure between rhizosphere and bulk soils with soil physicochemical properties, which proved a biological reference to indicate the characteristics of saline and alkaline land.

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Regular Biochar and Bacteria-Inoculated Biochar Alter the Composition of the Microbial Community in the Soil of a Chinese Fir Plantation

Forests ◽

10.3390/f11090951 ◽

2020 ◽

Vol 11 (9) ◽

pp. 951

Author(s):

Liguo Song ◽

Lingyu Hou ◽

Yongqiang Zhang ◽

Zhichao Li ◽

Wenzheng Wang ◽

...

Keyword(s):

Microbial Community ◽

Microbial Communities ◽

Rhizosphere Soil ◽

Soil Microbial Communities ◽

Principal Component ◽

Nutrient Content ◽

Chinese Fir ◽

Bulk Soil ◽

Ecological Processes ◽

Chinese Fir Plantation

Biochar is a promising material for the improvement of soil quality. However, studies on biochar have mostly been carried out in laboratory conditions or have focused on agricultural aspects. The impacts of the application of biochar on soil characteristics and related ecological processes of the forest ecosystem have not been fully resolved. In this study, we investigated the effects of regular biochar and bacteria-loaded biochar on the microbial communities in the bulk soil and the rhizosphere soil of an annual Chinese fir plantation. In early spring (April), the two types of biochar were added to the soil at the rates of 2.22 t·ha−1, 4.44 t·ha−1, 6.67 t·ha−1, 8.89 t·ha−1, and 11.11 t·ha−1 by ring furrow application around the seedlings, and soil samples were collected at the end of autumn (November). The results showed that biochar addition increased the soil nutrient content and promoted the growth and diversity of soil microbial communities. The diversity of soil fungi was significantly increased, and the diversity of soil bacteria was significantly decreased. Principal component analysis under the different biochar types and application rates demonstrated that microbial communities differed significantly between the treatments and controls and that the effect of biochar on the microbial community of the bulk soil was more significant than that of the rhizosphere soil. Under the same dosage, the effect of bacteria-loaded biochar on soil was more significant than that of regular biochar.

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Stoichiometric theory shapes enzyme kinetics in paddy bulk soil but not in rhizosphere soil

Land Degradation and Development ◽

10.1002/ldr.4141 ◽

2021 ◽

Author(s):

Yuhuai Liu ◽

Muhammad Shahbaz ◽

Yunying Fang ◽

Baozhen Li ◽

Xiaomeng Wei ◽

...

Keyword(s):

Enzyme Kinetics ◽

Rhizosphere Soil ◽

Bulk Soil

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Investigation by electro-ultrafiltration on N and P distribution in rhizosphere and bulk soil of field-grown corn

Soil Research ◽

10.1071/sr02086 ◽

2004 ◽

Vol 42 (1) ◽

pp. 49 ◽

Cited By ~ 3

Author(s):

Michele Arienzo ◽

Vincenzo Di Meo ◽

Paola Adamo ◽

Pietro Violante

Keyword(s):

Zea Mays ◽

Plant Uptake ◽

Rhizosphere Soil ◽

Bulk Soil ◽

Acidic Environment ◽

Available Nutrients ◽

Nutrient Demand ◽

Labile P ◽

P Distribution

The distribution of available levels of N and P in rhizosphere and bulk soils of field-grown corn (Zea mays cv. Forban 300) in response to N, P, K fertiliser supply was investigated by electro-ultrafiltration (EUF). This technique allowed 3 operationally defined nutrient fractions to be extracted: soluble and immediately available (EUF-I), available (EUF-II), and retained reserve (EUF-III). For nitrogen, the NO3– and NH4+ forms were measured in the EUF extracts. The investigation was carried out providing N, N+P, N+K, and N+K+P. The results indicated that only at 40 days after sowing (DAS), rhizosphere soil was significantly less alkaline than bulk soil and characterised by higher organic carbon levels that increased with crop age. The slightly more acidic environment of the rhizosphere at 40 DAS seemed to be related to the lower levels of EUF-N-NH4+ fractions of rhizosphere soil (0.1–3.2 mg NH4+/kg) relative to bulk soil (0.5–4.9 mg NH4+/kg), with more significant differences observed for the soluble NH4+ pool, EUF-I, and when N was combined with P (N+P) or K (N+K). The extensive nitrification of NH4+ and the initially greater availability of NO3– accounted for the larger extraction of NO3– in the EUF-I-NO3– fraction at 40 DAS. The levels of labile extracted NO3– were ~8 times greater than EUF-II and EUF-III fractions, with significantly higher values of 27.4 (rhizosphere soil) and 18.8 mg NO3–/kg (bulk soil) for the N+P treatment. Due to plant uptake, at 40 DAS the EUF-I-NO3– fraction of rhizosphere soil was also the only pool significantly (P�< 0.05) lower than bulk soil, with differences that for N+P treatment were in excess of 45%. Later, at 60–120 DAS, during maximum corn nutrient demand, the levels of all of the EUF-N-NO3– fractions became higher in bulk soil. The pool of labile P, EUF-I-P, was higher in the rhizosphere soil and related to pH lowering, which occurred especially at 40 DAS and fell below the adequate level indicated by the ratio EUF-II-P/EUF-I-P. The use of the EUF methodology allowed a rough estimate of the amounts of different available nutrients of the studied soil as well as of their relationships with soil properties. Issues of rhizosphere sampling in situ were considered and discussed.

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Protist diversity and community complexity in the rhizosphere of switchgrass are dynamic as plants develop

Microbiome ◽

10.1186/s40168-021-01042-9 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Javier A. Ceja-Navarro ◽

Yuan Wang ◽

Daliang Ning ◽

Abelardo Arellano ◽

Leila Ramanculova ◽

...

Keyword(s):

Community Composition ◽

Community Assembly ◽

Panicum Virgatum ◽

Large Scale ◽

Rhizosphere Soil ◽

Bacterial Community Composition ◽

Temporal Variations ◽

Bulk Soil ◽

Growth Stages ◽

Soil System

Abstract Background Despite their widespread distribution and ecological importance, protists remain one of the least understood components of the soil and rhizosphere microbiome. Knowledge of the roles that protists play in stimulating organic matter decomposition and shaping microbiome dynamics continues to grow, but there remains a need to understand the extent to which biological and environmental factors mediate protist community assembly and dynamics. We hypothesize that protists communities are filtered by the influence of plants on their rhizosphere biological and physicochemical environment, resulting in patterns of protist diversity and composition that mirror previously observed diversity and successional dynamics in rhizosphere bacterial communities. Results We analyzed protist communities associated with the rhizosphere and bulk soil of switchgrass (SG) plants (Panicum virgatum) at different phenological stages, grown in two marginal soils as part of a large-scale field experiment. Our results reveal that the diversity of protists is lower in rhizosphere than bulk soils, and that temporal variations depend on soil properties but are less pronounced in rhizosphere soil. Patterns of significantly prevalent protists groups in the rhizosphere suggest that most protists play varied ecological roles across plant growth stages and that some plant pathogenic protists and protists with omnivorous diets reoccur over time in the rhizosphere. We found that protist co-occurrence network dynamics are more complex in the rhizosphere compared to bulk soil. A phylogenetic bin-based null model analysis showed that protists’ community assembly in our study sites is mainly controlled by homogenous selection and dispersal limitation, with stronger selection in rhizosphere than bulk soil as SG grew and senesced. Conclusions We demonstrate that environmental filtering is a dominant determinant of overall protist community properties and that at the rhizosphere level, plant control on the physical and biological environment is a critical driver of protist community composition and dynamics. Since protists are key contributors to plant nutrient availability and bacterial community composition and abundance, mapping and understanding their patterns in rhizosphere soil is foundational to understanding the ecology of the root-microbe-soil system.

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