Role Of Soil Microbes Research Articles

Soil carbon sequestration potential in semi-arid grasslands in the Conservation Reserve Program

The Conservation Reserve Program (CRP) in the USA plays a major role in carbon (C) sequestration to help mitigate rising CO2 levels and climate change. The Southern High Plains (SHP) region contains >900.000ha enrolled in CRP, but a regionally specific C sequestration rate has not been studied, and identification of the C pools and processes important in controlling C sequestration rates remain unresolved. We aimed to address these gaps by utilizing a CRP chronosequence with historical rangeland as a reference ecosystem. Soil samples (0–10 and 10–30cm) were collected in 2012 and 2014 from a total of 26 fields across seven counties within the SHP and included seven croplands (0 y in CRP), 16 CRP fields that ranged from 6 to 26y (as of 2012), plus three rangelands. Multiple regression analysis was conducted to gauge the rate of C sequestration under CRP within C pools: soil organic C (SOC), particulate organic matter C (POM-C), and microbial biomass C (MBC), with two additional predictors (soil clay+silt content and precipitation). Despite attempts to control for soil texture by targeting a dominant soil series (Amarillo fine sandy loam), the percent of clay+silt (15.2–48.7%) significantly influenced C accrual. The C sources (C3 from previous cropping systems or C4 from CRP grasses) in SOC and POM-C were assessed using stable C isotope signatures. Additionally, the role of soil microbes in C sequestration was evaluated by investigating the relationship between MBC and CO2 flux and C sequestration. SOC increased at a rate of 69.82 and 132.87kgCha−1y−1 and would take approximately 74 and 77 y to reach the rangeland C stocks at 0–10 and 0–30cm, respectively. The C4‐C primarily from the introduced grasses was the main source of C sequestration. SOC gains were essentially due to increases in POM-C and MBC, accounting for 50.04 and 15.64% of SOC sequestration at 0–30cm, respectively. The highest semi-partial correlation coefficients between the increasing years under CRP restoration and MBC indicated CRP had the strongest effect on MBC compared to other C pools. In addition, increasing soil CO2 flux and MBC:SOC ratio with years of CRP restoration indicated MBC played a critical role in the C sequestration process. Conservation of CRP lands and efforts to sustain perennial systems in this highly erodible landscape should be a high priority of conservation programs. In doing so, significant offsets to increasing atmospheric CO2 levels may be achieved in addition to erosion control and improved wildlife habitat.

The Role of Soil Microbes in Promoting Plant Growth

More and more food is needed all over the world in order to meet rapidly growing population demands, while the modern agriculture on increasing output has already reached its limit. It is badly in need to cultivate new crop varieties for increase the yield and resistant to environmental stress and insects. However, crops are still need to provide the necessary fertilizer nutrients which is insufficient in soil. Recently, many evidences showed that soil microbes provide an opportunity for reducing agricultural demand in inorganic fertilizer. Microorganisms, due to their huge gene pool, are also used for a potential resource in biochemical reactions, which recycle nutrients for plant growth. Therefore, we need to modify and better use of soil microbiota to promote plant growth. In this review, we mainly summarized the role of soil microbiota by explaining the ecological balance, nitrogen fixation, nutrient elements, interactions and communication medium.

Biological response of using municipal solid waste compost in agriculture as fertilizer supplement.

Waste management and declining soil fertility are the two main issues experienced by all developing nations, like India. Nowadays, agricultural utilization of Municipal Solid Waste (MSW) is one of the most promising and cost effective options for managing solid waste. It is helpful in solving two current burning issues viz. soil fertility and MSW management. However, there is always a potential threat because MSW may contain pathogens and toxic pollutants. Therefore, much emphasis has been paid to composting of MSW in recent years. Application of compost from MSW in agricultural land helps in ameliorating the soil’s physico-chemical properties. Apart from that it also assists in improving biological response of cultivated land. Keeping the present situation in mind, this review critially discusses the current scenario, agricultural utilization of MSW compost, role of soil microbes and soil microbial response on municipal solid waste compost application.

Characteristics of Soil Microbial Community Structure in the Rhizospheric Soil of Ammopiptanthus mongolicus by Phospholipid Fatty Acid (PLFA)

To measure and manage plant growth in arid and semi-arid sandlands, improved understanding of the spatial patterns of desert soil resources and the role of soil microbes is required. The rhizosphere soils of Ammopiptanthus mongolicus in Wuhai, Dengkou, and Alxa, Inner Mongolia, China were collected in July 2015. Soil microbial community structure in the rhizosphere of A.mongolicus was analyzed by phospholipid fatty acid (PLFA) combined with Sherlock microbial identification system. The results showed that the soil microbial PLFA had a higher diversity and 41, 31 and 48 kinds of phospholipid fatty acids were respectively detected in the rhizosphere of A.mongolicus in three different sites. 16:0, 16:0 10-methy1, 18:1ω9c and 16:1ω7c were the dominant PLFA, and the PLFA of 16:0 (indicating bacteria) had a maximum value. However, the differences in contents of 16:0 10-methy, 18:1ω9c and 16:1ω7c were found in the three sites. Soil microbial community in the rhizosphere of A.mongolicus had obvious spatial heterogeneity:the gram positive bacteria were the dominant microorganisms in all soil samples. AM fungi, gram positive bacteria, gram negative bacteria and fungi were all characterized by Alxa > Wuhai > Dengkou, and total PLFA content of actinomycetes followed the order of Wuhai > Alxa > Dengkou. AM fungi occupied the biggest proportion in the soil fungal biomass, especially in Dengkou and Alxa, which accounted for 91% and 92%, respectively. We concluded that AM fungi were an important component of soil microorganisms in the desert ecosystem. AM fungi, gram positive bacteria, gram negative bacteria, fungi and actinomycetes were positively correlated with soil acid and alkaline phosphatase, total glomalin, ammonia nitrogen and pH. G+/G- were extremely negatively correlated with soil urease, organic carbon and easily extractable glomalin. However, the fungi/bacteria were extremely positively correlated to soil urease, organic carbon and easily extractable glomalin. The results of this study support the conclusion that soil acid and alkaline phosphatase, total glomalin, ammonia nitrogen and pH were the main factors influencing soil microbial biomass and activities in desert zone.Moreover, the changing pattern of soil microbial community might be useful to monitor desertification and soil degradation.

Soil microbes alleviate allelopathy of invasive plants

Soil microbes are one of the most important determinants of allelopathic effects in the field. However, most studies testing the role of allelopathy in biological invasions did not consider the roles of soil microbes. Here we tested the hypothesis that soil microbes which can degrade allelochemicals may accumulate in soils over time by adaptation and therefore increase the degradation of allelochemicals and alleviate the allelopathic effects in biological invasions. As expected, soil microbes significantly decreased the allelopathic effects of leaf leachates of eight in the nine invasive plant species studied. In addition, Ageratina adenophora showed lower allelopathic effects in soil with long or intermediately invasion history than those in soil with short invasion history. The two main allelochemicals of the invader were degraded more rapidly with increasing invasion history in the soil. Correspondingly, biomass and activity of the soil microbes were higher in the soils with long invasion history than in that with short invasion history. Our results indicate that soil microbes may gradually adapt to the allelochemicals of Ageratina and alleviate its allelopathic effects and thus support the above hypothesis. It is necessary to consider the effects of soil microbes when testing the roles of allelopathy or the novel weapons hypothesis in biological invasions.

土壤微生物在植物获得养分中的作用

土壤微生物在植物获得养分中的作用

System of Rice Intensification for Increased Productivity and Ecological Security: A Report

The present technology of paddy production leaves behind ecological foot prints caused by overuse of fossil fuels and synthetic fertilizers that pollute almost a quarter to one third of world’s annual fresh water supply. Overuse of water contributes to emission of greenhouse gases causing more global warming. Besides, input costs are high and the additional inputs, particularly synthetic fertilizers to increase production are leading to diminishing or constant returns over the years. The method is ill suited for rain-fed areas. Despite this, India has relied on such input management practices attempting to improve yield for its food security. Such highly intensive agriculture dependent on fossil fuels, damaging to soil and fresh water, and crop diversity is becoming questionable today. The real challenge therefore is to develop/adopt strategies based on sound ecological principles and integrate traditional organic farming practices and biodiversity with scientific knowledge. System of Rice Intensification (SRI) is a promising resource conserving method of growing rice both under irrigated and rain fed conditions as the method is based on alternate wetting and drying interval. Application of controlled irrigation reduces nitrogen export to the environment in comparison with flooding irrigation management and reverses climate change. Around 40 countries of the world today are reaping the benefits of SRI. Rice is grown on 42.5 m ha in India, which is the largest area among rice growing counties and provides 29% of the calorie requirement in India with a production of 85.59 million tons and average yield of 2.2 t per ha. Area under rice is expected to be reduced to about 40 million ha in the country in the next 15 to 20 years due to water shortage and rapid industrialization and urbanization. The Problems confronted in rice production particularly by resource deficient small and marginal farmers and rain-fed areas are well known. G. B. Pant Social Science Institute, University of Allahabad, Allahabad organized a two-day National Consultation session on the subject on 6th and 7th, April, 2015. The Consultation explored the alternatives ways of resource efficient SRI method for paddy cultivation in comparison to the existing resource intensive post Green Revolution conventional method. It focused on examination of the SRI method, considering particularly the contributions of soil organic matter, indigenous rice varieties, responses and roles of soil microbes, resourceuse efficiency, and labor use efficiency and productivity. It considered SRI and its relationships to biodiversity and ecological security, linking agricultural practices to the larger natural environment in which we live and produce. The Consultation also envisioned on a more desirable future, looking at SRI expansion across the country, at the roles and empowerment of farmers, and at the institutions, policies and knowledge-deepening that will make this all possible.

Vertebrate decomposition is accelerated by soil microbes.

Carrion decomposition is an ecologically important natural phenomenon influenced by a complex set of factors, including temperature, moisture, and the activity of microorganisms, invertebrates, and scavengers. The role of soil microbes as decomposers in this process is essential but not well understood and represents a knowledge gap in carrion ecology. To better define the role and sources of microbes in carrion decomposition, lab-reared mice were decomposed on either (i) soil with an intact microbial community or (ii) soil that was sterilized. We characterized the microbial community (16S rRNA gene for bacteria and archaea, and the 18S rRNA gene for fungi and microbial eukaryotes) for three body sites along with the underlying soil (i.e., gravesoils) at time intervals coinciding with visible changes in carrion morphology. Our results indicate that mice placed on soil with intact microbial communities reach advanced stages of decomposition 2 to 3 times faster than those placed on sterile soil. Microbial communities associated with skin and gravesoils of carrion in stages of active and advanced decay were significantly different between soil types (sterile versus untreated), suggesting that substrates on which carrion decompose may partially determine the microbial decomposer community. However, the source of the decomposer community (soil- versus carcass-associated microbes) was not clear in our data set, suggesting that greater sequencing depth needs to be employed to identify the origin of the decomposer communities in carrion decomposition. Overall, our data show that soil microbial communities have a significant impact on the rate at which carrion decomposes and have important implications for understanding carrion ecology.

The role of microorganisms at different stages of ecosystem development for soil formation

Abstract. Soil formation is the result of a complex network of biological as well as chemical and physical processes. The role of soil microbes is of high interest, since they are responsible for most biological transformations and drive the development of stable and labile pools of carbon (C), nitrogen (N) and other nutrients, which facilitate the subsequent establishment of plant communities. Forefields of receding glaciers provide unique chronosequences of different soil development stages and are ideal ecosystems to study the interaction of bacteria, fungi and archaea with their abiotic environment. In this review we give insights into the role of microbes for soil development. The results presented are based on studies performed within the Collaborative Research Program DFG SFB/TRR 38 (http://www.tu-cottbus.de/ecosystem ) and are supplemented by data from other studies. The review focusses on the microbiology of major steps of soil formation. Special attention is given to the development of nutrient cycles on the formation of biological soil crusts (BSCs) and on the establishment of plant–microbe interactions.

Soil fungi of three native tree species inhibit biomass production and shift biomass allocation of invasive Mikania micrantha Kunth

Soil microbes contribute to native plant species successful resistance against invasive plant. Three native tree species, Heteropanax fragrans (HF), Cinnamomum burmanii (CB), and Macaranga tanarius (MT) were effective in controlling the notorious invasive vine Mikania micrantha (MM). Biomass production and allocation patterns (shoot/root biomass ratio (shoot/root)) are important indicators of MM climbing coverage and competitive light-capturing capacity. An investigation was conducted to test the role of soil microbes associated with the three native tree species to inhibit MM biomass production and shift MM shoot/root. Rhizosphere soils originating from preculture HF, CB, MT, and MM plots were collected separately for use as inocula. The inocula were mixed with sterilized river sand at a 1:9 (w/w) ratio to grow MM. The fungicide carbendazim (methyl benzimidazol-2-ylcarbamate) was applied to half the treatments to kill pathogenic soil fungi. Two nutrient levels were established based on the natural soil nutrient concentration from a field stand invaded by MM. MM were grown from seeds in a glasshouse, harvested 15 weeks after sowing, and separated into shoot and root portions. Results showed that under interaction of soil origin and nutrient levels, MM biomass production was unchanged, but biomass allocation patterns were significantly different. MM biomass production grown in the three native tree soils under two nutrient levels was similar or higher than MM biomass production in MM conspecific soil, indicating the absence of species-specific pathogens that inhibited MM biomass production in native tree soils. However, in both conspecific and tree soils, MM biomass production was significantly reduced in the presence of pathogenic soil fungi, i.e. MM experienced significant fungal inhibition, demonstrating the pathogenic soil fungi promoted native tree resistence to MM. MM exhibited decreased shoot biomass allocation when cultivated in native tree soil relative to MM conspecific soil under field stand nutrient level conditions. Reduced resource allocation to shoot biomass could result in diminished capacity to climb, cover, and subsequent smother to native trees, and reduced surface area exposed to available light. Following fungicide application, significant biomass allocation differences disappeared, suggesting the native tree soil fungi were responsible for decreasing MM shoot biomass. The overall results indicated tree soil fungi serve an integral role in controlling invasive MM through fungal inhibition on MM biomass production, and shifts in MM biomass allocation patterns.

Ethylene: potential key for biochar amendment impacts

Significant increases in root density, crop growth and productivity have been observed following soil additions of biochar, which is a solid product from the pyrolysis of biomass. In addition, alterations in the soil microbial dynamics have been observed following biochar amendments, with decreased carbon dioxide (CO2) respiration, suppression of methane (CH4) oxidation and reduction of nitrous oxide (N2O) production. However, there has not been a full elucidation of the mechanisms behind these effects. Here we show data on ethylene production that was observed from biochar and biochar-amended soil. Ethylene is an important plant hormone as well as an inhibitor for soil microbial processes. Our current hypothesis is that the ethylene is biochar derived, with a majority of biochars exhibiting ethylene production even without soil or microbial inoculums. There was increased ethylene production from non-sterile compared to sterile soil (215%), indicating a role of soil microbes in the observed ethylene production. Production varied with different biomass sources and production conditions. These observations provide a tantalizing insight into a potential mechanism behind the biochar effects observed, particularly in light of the important role ethylene plays in plant and microbial processes.

The Roles of Soil Microbes in the Global Environment

The Roles of Soil Microbes in the Global Environment

The role of soil microbes in plant sulphur nutrition.

Chemical and spectroscopic studies have shown that in agricultural soils most of the soil sulphur (>95%) is present as sulphate esters or as carbon-bonded sulphur (sulphonates or amino acid sulphur), rather than inorganic sulphate. Plant sulphur nutrition depends primarily on the uptake of inorganic sulphate. However, recent research has demonstrated that the sulphate ester and sulphonate-pools of soil sulphur are also plant-bioavailable, probably due to interconversion of carbon-bonded sulphur and sulphate ester-sulphur to inorganic sulphate by soil microbes. In addition to this mineralization of bound forms of sulphur, soil microbes are also responsible for the rapid immobilization of sulphate, first to sulphate esters and subsequently to carbon-bound sulphur. The rate of sulphur cycling depends on the microbial community present, and on its metabolic activity, though it is not yet known if specific microbial species or genera control this process. The genes involved in the mobilization of sulphonate- and sulphate ester-sulphur by one common rhizosphere bacterium, Pseudomonas putida, have been investigated. Mutants of this species that are unable to transform sulphate esters show reduced survival in the soil, indicating that sulphate esters are important for bacterial S-nutrition in this environment. P. putida S-313 mutants that cannot metabolize sulphonate-sulphur do not promote the growth of tomato plants as the wild-type strain does, suggesting that the ability to mobilize bound sulphur for plant nutrition is an important role of this species.

Ethylene and carbon dioxide concentrations of soils as influenced by rhizosphere of crops under field and pot conditions

A method for collecting low volumes of soil gas from a small region, and a technique for determining small concentrations of ethylene using an enrichment process are described. Using these methods, it was found that ethylene and carbon dioxide (CO2) concentrations of soils varied considerably depending on the presence or absence of a rhizosphere. Ethylene was much higher (31–375 nL L−1; mean: 207) in non-cropped areas (i.e., soils without rhizosphere) than in the rhizosphere region (8–136 nL L−1; mean: 38) of a field in which maize or soybean were grown. On the other hand, CO2 concentrations were higher in rhizosphere than in non-rhizosphere soil, especially in pot experiments. The rate of ethylene decomposition was, however, much greater in rhizosphere soil (55 nL g−1 day−1) than in non-rhizosphere soil (34 nL g−1 day−1). Higher microbial activity was presumed to result in the decrease of ethylene concentration and the increase in CO2 in rhizosphere regions. The implications of these results in relation to the influence of ethylene in rhizosphere on plant growth, and the role of soil microbes on decomposition of ethylene is discussed.