Biological Sciences
Soil Microbiology
Soil microbiology is the study of microorganisms in soil and their interactions with the soil environment. It focuses on the diversity, functions, and roles of bacteria, fungi, protozoa, and other microorganisms in soil processes such as nutrient cycling, organic matter decomposition, and plant-microbe interactions. Understanding soil microbiology is essential for sustainable agriculture, environmental management, and ecosystem health.
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9 Key excerpts on "Soil Microbiology"
eBook - PDF- Hassan G.Dar(Author)
- 2020(Publication Date)
- NEW INDIA PUBLISHING AGENCY (NIPA)(Publisher)
Chapter 1 Soil Microbiology — Origin, History and Diversification Definition : Soil Microbiology is the study of microorganisms living in soil which complete whole or some part of their life cycle in soil. They include both beneficial as well as deleterious microorganisms but as a specialized branch main thrust is laid on their metabolic activities and the role they play in energy flow, cycling of nutrients associated with the primary productivity and soil ecosystem development. Besides, it focuses on environmental impact, whether favourable or unfavourable, on soil microorganisms and the various soil biochemical processes mediated by various microbes. A clear understanding of the interactions between soil microbial communities and elemental soil components is imperative to comprehend total ecosystem function. Atlas and Bartha have defined the Soil Microbiology as ‘ the study of organisms that live in soil; their metabolic activity; their roles in energy flow; their roles in nutrient cycling’. As per Tate Soil Microbiology involves ‘the study of soil ecosystem which is the product of intricate interactions between physical and chemical matrix of highly variable composition and living communities of all form’. The Soil Science Society of America has defined Soil Microbiology as ‘ the branch of soil science concerned - 1 -“The role of infinitely small is infinitely large ” (Louis Pasteur) 2 Soil Microbiology and Biochemistry with soil inhabiting microorganisms, their functions, and activities.’ Since Soil Microbiology also involves the study of various biochemical transformations/ reactions occurring in soil, so it has indispensable role in understanding soil biochemistry, rather the two disciplines are inseparable. Diversity : One kg of soil, on an average, weighs 2200 t ha -1 furrow slice and possesses about 2.7 t nitrogen, of which about 35% is in microbial biomass form.
eBook - PDF- Preethi Kartan(Author)
- 2019(Publication Date)
- Delve Publishing(Publisher)
The Soil Microorganism: An Overview 4 CONTENTS 4.1. Introduction ...................................................................................... 68 4.2. Setting Nutrients Free ........................................................................ 71 4.3. Biological Mechanisms ..................................................................... 72 4.4. Soil Microorganisms ......................................................................... 73 4.5. Harnessing The Power of Soil Microbes For More Sustainable Farming ....................................................................... 79 4.6. Soil Is Alive ....................................................................................... 80 4.7. Fertilization Practices And Environmental Sustainability .................... 82 4.8. Importance Of Soil Microorganisms In Ecosystem ............................. 85 References ............................................................................................... 88 Advancement in Soil Microbiology 68 Soil microorganisms are one of the most important factors in maintaining the quality and texture of the soil in the biosphere. The presence of microorganisms in the soil is beneficial in not only retaining the soil nutrient but it also helps in maintaining a cordial relation in between the plants and the soil. This chapter also talks about the several types of the soil microorganisms, which consist of the bacteria, fungi, algae, protozoa, nematodes, and actinomycetes. This chapter provides insights on harnessing the power of soil microbes for more sustainable farming. This chapter also addresses the manner in which soil microbes break down organic matter, soil microbes recycle the nutrients, soil microbes create humus, soil microbes which create soil structure, soil microbes fix nitrogen, and soil organisms promote the plant promote, soil microbes control pests and diseases.
eBook - PDFChemistry and Biology of Water, Air and Soil
Environmental Aspects
- J. Tölgyessy(Author)
- 1993(Publication Date)
- Elsevier Science(Publisher)
8 Soil biology 8.1 Soil microorganisms The establishment of the cardinal roles that microorganisms play in the biologically important cycles of matter on our planet (the cycles of carbon, nitrogen, and sulphur) was largely the pioneering work of S. Winogradsky and M. W. Beijerinck in the late 19th century. Microorganisms show an extraordinarily wide range of physiological diversity in the biosphere in general and in the soil in particular. One of the most striking examples of microbial physiological speciali- zation is provided by the autotrophic bacteria discovered by Winogradsky. Another discovery, to which both Winogradsky and Beijerinck contributed, was the role that microorganisms play in the fixation of atmosphere nitro- gen, which cannot be directly used as a nitrogen source by most organisms. They showed that certain bacteria and cyanobacteria, some free-living, others symbiotic in higher plants, can use molecular nitrogen for the synthe- sis of their cell constituents. A wide variety of the chemical changes taking part in the soil and related to soil fertility are provided by soil bacteria. It was not until several decades later that comparable interest began to be shown in the soil fungi and their activities. The soil protozoa were comparatively neglected and only in recent times has interest in the soil algae increased. Although it is not possible to assess accurately the concentration of soil microorganisms, the data in Table 8.1 give some idea of the numbers of major groups of microorganisms together with an estimate of the biomass of each of the groups in the top 15 cm of agricultural soil. Bacteria are more numerous than any other group but the biomass of the fungi is larger than that of bacteria. The spatial distribution of microorganisms in the soil is complex. Ge- nerally there is a decrease in numbers with depth (Table 8.2) which is a reflexion of decreasing organic matter content in the soil. However, lo- 699
- Lakshman, H C(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
SECTION I MICROBIOLOGY This ebook is exclusively for this university only. Cannot be resold/distributed. Chapter 1 Beneficial Microbial Life in Soil: The Basis for Sustainable Plant Life on Earth H.C.Lakshman Microbiology Laboratory, P.G. Department of Studies in Botany, Karnatak University, Pavate Nagar, Dharwad – 580 003, Karnataka, India E-mail: [email protected] Introduction Soil is the nature gift to mother earth. The soil mainly consists of sand, silt and clay particles with gaseous and mineral elements such as oxygen (O 2 ), silicon (Si), aluminum (Al), potassium (K), calcium (Ca), magnesium (Mg) etc and soil solution contains dissolved materials. Air in the soil contact with air above ground aerates the roots with oxygen and help to remove excess of carbon dioxide (CO 2 ) from respiring roots. Organic matter, the soul of soil is a major consideration in organic farming. Its presence or absence makes the soil living or dead. The India National Programme for Organic Production (NPOP) recognizes that “The fertility of soil is to be maintained and increased with the biological activity of the soil held intact”. From the point of view of farming, soil can be considered having four important parts; solid minerals, water, air and organic matter (Foster, 1988). Soil contains the required mineral elements and nutrients for the growth and multiplication of several lower forms of plants and animals. These biological species could be broadly divided into microflora and microfauna. The number and kinds of micro-organisms present in soil depend on many environmental factors, such as pH, temperature, moisture, aeration and nutrients available. Soil is medium for growth, reproduction, respiration, nutrition and even decomposition after death for most micro-flora and fauna. They complete their life cycles and later provide the bio-mass for decomposition in the soils. Similarly, soil is This ebook is exclusively for this university only. Cannot be resold/distributed.
eBook - PDF- Yadav, Pawan Kumar(Authors)
- 2018(Publication Date)
- Daya Publishing House(Publisher)
Cannot be resold/distributed. biological, rather than chemical methods to explore soil related process and problems. His work in (1891 to 1910), the microbiological laboratory at the Imperial Institute of Experimental Medicine in St. Petersburg, Russia, expanded his chemosynthesis research to a broad investigation of the manifold importance of autotrophic organisms in soil related process. This work and his students atracted the serious interest of agricultural chemists and soil scientists in Russia and abroad, shifting efectively the way they understood and investigated the role of microbes in the soil. Vinogradskii’s activities in the late 19 th century imitate the changes occurring more largely in soil science. Methods for Studying Soil Microbial Populations Soil is considered a stockroom of microbes and their activity. These Living microfauna are estimated to consist of less than 5% of the total space occupied. Therefore, major microbial activity is restricted to “hot spots” such as aggregates with accumulated organic mater, rhizosphere, detritusphere and biosphere (Pinton et al., 2001). Bacterial and fungal diversity associated with soil is often difcult to characterise, mainly because of their immense phenotypic and genotypic diversity, heterogeneity, cryptcity and due to lack of taxonomic knowledge. Bacterial populations in top layers of the soil profle can produce over 109 cells/g soil (Torsvik and Ovreas, 2002). Most of these cells are not culturable in lab conditions. The portions of the cells which make soil microbial biomass and diversity that have been cultured and studied in detail are less than 5% of the total microbial population. But still, soil can be studied for microbiological, biochemical and functional diversity using diferent approaches (Paul, 2007). Methods of studying microbial diversity can be generally divided into two categories: (1) culture-dependent and (2) culture-independent methods.
eBook - PDF- Ronald Amundson(Author)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
In other words, science only knows of them through their DNA. Most of the organisms in soil are at present unculturable in the lab, and scientists never knew they existed until the recent revolution in molecular biology. There is much to discover about what they all do, how fast they do it, and ultimately what their fundamental roles are. Microorganisms make up an important fraction of the total organic C in soils. The mass of the total soil organic matter that is comprised of microbial biomass is commonly determined in the lab by fumigation of a soil sample (to lyse the microbial cells) and an extraction step. 4 A recent compilation of published biomass estimates shows that on average, microbial biomass is about 1.2 percent of the total C, but that greater fractions of N (2.6 percent) and P (8.0 percent) are contained in living microbes, revealing their importance in biogeochemical processing and cycling. 5 While the percentage of total soil C in living microbes may seem small, globally it totals roughly 37 Gt C, equivalent to nearly 4 years of anthropogenic emissions to the atmosphere. It is these organisms, and their genes, that mediate the vast global cycles of elements that pass through soils and into the atmo- sphere and the hydrosphere. 3.3 The Biological Imprint on Earth’s Biogeochemistry It has been stated 6 that the chemistry of abiotic geochemical reactions tends to be dominated by acid/base reactions (the transfer of protons, H + ). For example, the weathering of silicate minerals is mechanistically driven by proton attack and exchange with cations at the mineral surface, and expressions to describe the weathering rates of silicate minerals commonly incorporate proton concentrations (e.g. pH). In contrast, reactions that include biology are dominated by redox reactions, which involve transfers of both protons and 40 The Biology in Soil Biogeochemistry Figure 3.1 The present view of the tree of life represented by sequenced genomes.
eBook - ePub- Allen I. Laskin(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
III. Methods of Studying Microbial Ecology in SoilThe variety of methods that have been used to study the activity, ecology, and population dynamics of microbes in soil reflects the complexity of this microbial habitat. Despite the multitude of methods, few, if any, have completely achieved their purpose, i.e., to study microbes in soil . Most methods either remove microbes from soil and study them in the laboratory or move soil to the laboratory and there study it for some function. No methods currently available begin to approach the level of the microhabitat, and, therefore, they only provide data which are some mathematical function of enumerable individual microhabitats. This is stated not to denigrate soil microbiologists but to emphasize the difficulties inherent in studying an environment as complex as soil and to underscore the ingenuity that soil microbiologists have demonstrated in their attempts to resolve these difficulties.Perhaps the greatest dereliction on the part of many investigators has been the tendency to extrapolate from relatively simple experiments – even though these may be well designed and employ extremely sophisticated instrumentation and techniques – to the in situ situation without verifying that the phenomena observed in vitro do occur, in essentially the same manner in vivo. Because the real purpose of microbial ecology is to determine what is occurring in the environment of interest – in this instance, soil – and not in the test tube, the investigator must shuttle continuously back and forth between model experimental designs and the in situ condition. Consequently, the soil microbial ecologist, perhaps more than any other microbial ecologist, must operate simultaneously on many levels of experimental complexity, ranging from natural field conditions to artificial pure culture systems and, where necessary, to the molecular level. In this multipronged approach, imagination, ingenuity, and the asking of critical questions are the key ingredients, and, although modern instrumentation can be an asset in many experiments, much can yet be learned by applying standard and relatively inexpensive methods to well-designed experiments.
- Rattan Lal, B.A. Stewart, Rattan Lal, B.A. Stewart(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
Soil structure and functioning are directly affected by fungi, for example, which produce the compound glomalin that “glues” soil particles together. Bacteria and algae likewise produce extracellular, adhesive hygroscopic polymers within the soil that contribute to its aggregation and water-retaining properties. Both the stocks and availability of plant nutrients in the soil are affected by uncountable numbers and species of microbes, through well-known processes such as biological nitrogen fixation (BNF); phosphorus (P) solubi-lization; nitrogen (N) and sulfur (S) cycling; and the conservation and concentration of nutrients in soil, referred to as immobilization. This latter process coexists with the complementary processes of nutrient mobilization and mineralization, critical for both micronutrients and macronutrients, which are mediated by microbial activ-ity (Coleman et al. 2004). At a larger scale, soil nutrients are cycled through immensely complex food chains or food webs with myriad organisms operating at multiple trophic levels (Thies and Grossman 2006; Wolfe 2002). Their biodiversity parallels and even sur-passes that observed above-ground (Wardle 2002). Much is being learned about how plants and microbes interact to mutual benefit (Barea et al. 2005; Berg 2009; Badri and Vivanco 2009; Hartmann et al. 2009). Still, the roles that soil organisms play have been mostly considered in terms of how they modify the chemical and physical parameters of soil systems. Less recognized—except where soil organisms have observable negative effects on crop yield as pathogens or parasites—is how biological agents in the soil them-selves contribute to crop production, directly affecting the measures of yield that are used as indicators of soil fertility. What appear to be the effects of soil physics or soil chemistry may, on closer examination, be biological effects. Put another way, they may be the outcome of inextricably meshed effects of all three dimensions of
- Chandra, Ram(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Chapter 3 Microorganisms and Soil Fertility Ramawatar Meena Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, B.H.U., Varanasi Soils on earth differ from a heap of inert rock particles in many ways, but one of the most important thing is that they have a population of microorganisms living in them, which derives its energy by oxidizing organic residues left behind by the plants growing on the soil or by the animals feeding on these plants. In the final analysis, the plants growing on the soil subsist on the products of microbial activity, for the microorganisms are continually oxidizing the dead plant remains and leaving behind, in a form available to the plant, the nitrogenous and mineral compounds needed by the plants for their growth. On this concept, a fertile soil is one, which contains either an adequate supply of plant food in an available form, or a microbial population, which is releasing nutrients fast enough to maintain rapid plant growth; an infertile soil is one in which this does not happen, as for example, if the microorganisms are removing and locking up available plant nutrients from the soil. The soil microorganisms can be classified into major divisions, such as the bacteria, actinomycetes, fungi and algae – the microflora, and the protozoa, worms and arthropods – the microflora and fauna. Microorganisms, like larger organisms, take in food and excrete by products, which are either products of respiration or components in the food supply. Microorganisms usually excrete the nitrogen of originally combined nitrogen, which is surplus to their requirements as ammonium ions under aerobic conditions, and they excrete urea, uric acid acids such as: citric, tartaric, formic, lactic, oxalic, dibasic acids, succinic acids.
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