Dissertations / Theses on the topic 'Microbial amendments'
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Kruger, Matthew Wayne. "Can Soil Microbial Activity Be Improved With the Use of Amendments?" Thesis, North Dakota State University, 2020. https://hdl.handle.net/10365/31824.
Full textAdhikari, Deepak. "Microbial response to different carbon source amendments in agricultural soils as monitored by culture-independent techniques." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 127 p, 2008. http://proquest.umi.com/pqdweb?did=1605142671&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full textLekkas, Panagiotis. "The Microbial Ecology Of Listeria Monocytogenes As Impacted By Three Environments: A Cheese Microbial Community; A Farm Environment; And A Soil Microbial Community." ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/463.
Full textSummerville, Kevin M. "Effectiveness of Amendments and Microbial Treatments on Plant Growth in Urban Garden Soils." Youngstown State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1495712379969062.
Full textBuckley, Elan. "Change in the Structure of Soil Microbial Communities in Response to Waste Amendments." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/101499.
Full textM.S.
Soil is complicated, both in terms of its physical makeup and the organisms that live inside of it. Predicting changes in soil based on the addition of foreign material such as chemicals or biological waste is not an easy process, and whether or not it is even possible to reliably predict those changes is a matter of some dispute. This study is designed to illustrate that such changes can in fact be reliably and consistently predicted even with regard to the addition of complicated materials to the soil. In this study, specifically, the material in question is chicken litter. A mix of the bedding and waste produced by chickens, litter is commonly handled by composting and is added to soil in farms as a fertilizer rich in organic matter. It is possible to point at specific elements of the soil such as the chemistry and bacteria and see how it is changed with the addition of chicken litter, which allows us to determine the nature and extent of the change that chicken litter has on soil. This study is conducted on a larger scale than similar experiments conducted in the past, making it apparent that these relationships exist on a repeated basis. It is the object of this study to pave the way and make it easier for scientists in the future to determine these relationships in other unique contexts.
Van, Schoor Louise. "Effect of biological amendments on soil microbial properties and performance of pome fruit trees." Thesis, Stellenbosch : Stellenbosch University, 2009. http://hdl.handle.net/10019.1/4602.
Full textENGLISH ABSTRACT: The global movement in agriculture is towards more environmentally friendly, sustainable production practices, since the role of soil microbial functions in ensuring crop production and soil fertility has become more evident in agricultural systems. Furthermore, with the impeding phase-out of methyl bromide, apple replant disease (ARD) is becoming an increasingly important problem and biological management practises are needed. Since microbial activity is generally carbon-limited in agricultural soil, it is widely accepted that management practices providing a range of organic compounds on a regular basis will tend to maintain an active and diverse microbial population. It was hypothesised that the application of various biological amendments can affect soil microbial numbers and function, thereby having a positive effect on fruit tree growth and yield. The effect of continued applications of organic material, various microbial inoculants and biostimulants on tree performance were evaluated in conventional management systems. Field trials were established in a conventional pear orchard, potential apple replant disease sites, as well as an optimally managed, high density apple orchard under controlled fertigation. The use of compost, compost extracts, a Bacillus inoculant and humates were investigated intensively. Furthermore, to improve our understanding of soil biological systems a combination of simple, practical methods were used to evaluate the effect of biological amendments on soil microbial properties and effects were related to tree performance. Regular application of compost extract in combination with compost showed the most significant effect in improving tree performance in commercial pome fruit orchards under various conditions. In the pear orchard, cumulative yield over the first two seasons was improved by more than 50% compared to controls, while in the fertigated orchard yield was improved by 22%. Biological amendments also showed improved growth in orchards suffering from stunted growth symptoms typical of ARD. However, in severe ARD cases methyl bromide fumigation showed the most consistent effects. Other biological amendments which showed positive effects on yield were application of Bacillus inoculants (Biostart®) in combination with a labile C source and a low dosage humate product, as well as a combination of compost and humates. It was clear that a combination of labile organic matter and a diverse group of microorganisms showed most promise. Although for some specific treatments increased microbial numbers and activity may have resulted in improved tree performance, in general, changes in culture-based plate counts, soil enzyme activity and carbon utilisation profiles could not be used as an indicator of yield. It was suggested that improved synchronisation of nutrient release and plant uptake, as well as microbial phytohormone production, may play an important role in improving tree performance with application of biological amendments. More research is needed on the exact mechanisms through which compost extracts improve yield and studies on root growth proliferation, as well as effects in the rhizosphere are recommended.
AFRIKAANSE OPSOMMING: Binne lanbouverband is daar tans wêreldwyd die neiging om die uitwerking van produksie-praktykte op die omgewing in ag te neem en sodoende meer verantwoordelik op te tree. Omdat die belangrike rol wat grondmikro-organisme funksionering in volhoubare verbouingspraktyke speel nou deeglik besef word, word meer volhoubare bestuurspraktyke bepleit. Hiermee saam, noodsaak aspekte soos die uitfasering van metielbromied vir die beheer van appelhervestigingsiekte, dat biologiese bestuurspraktyke meer aandag geniet. Daar word geredelik aanvaar dat gereelde toediening en aanvulling van organiese materiaal ‘n aktiewe, diverse mikrobe populasie in die grond tot gevolg sal hê. Die hipotese is gestel dat die toediening van ‘n verskeidenheid biologiese produkte grondmikrobe getalle en werking gunstig kan beïnvloed. Dit kan moontlik weer aanleiding gee tot positiewe reaskies wat die groei en drag van vrugtebome betref. In hierdie studie is die uitwerking van voortgesette toedienings van organiese materiaal, mikrobiese inokulante, asook biostimulante, op die prestasievermoë van vrugtebome ondersoek. Veldproewe is uitgelê in ‘n konvensionele peerboord, verskeie boorde met moontlike appelhervestigingsiekte probleme, asook ‘n hoëdigtheidsaanplanting appelboord onder optimale bestuur. ‘n Deeglike ondersoek is gedoen met betrekking tot die gebruik van kompos, komposekstrak, Bacillus-inokulante en humate. Eenvoudige, praktiese metodes is aangewend om vas te stel hoe biologiese toevoegings grondmikrobe eienskappe beïnvloed en of dit verband hou met veranderinge in boomprestasie. Die studie het aangetoon dat die gereelde toediening van komposekstrak saammet kompos, betekenisvolle verbetering in boomprestasie van kernvrugboorde teweeg bring onder verskeie omstandighede. Die kumulatiewe opbrengs van ‘n peerboord is oor twee seisoene met meer as 50% verhoog teenoor die kontrole. In ‘n optimaal bestuurde appelboord onder sproeibemesting, is opbrengs met 22% verhoog in vergelyking met die kontrole. Biologiese toevoegings het ook groei verbeter in boorde waar appelhervestigingsiekte bome se groei vertraag het. In die geval van ernstige appelhervestigingsimptome het metielbromied egter steeds die mees konstante positiewe uitwerking gehad. Ander biologiese toevoegings wat ‘n gunstige uitwerking op opbrengs getoon het, was ‘n kombinasie van Bacillus inokulante, ‘n lae dosis humaat en ‘n aktiewe koolstofbron, asook kompos in kombinasie met humate. Dit is duidelik dat ‘n kombinasie van ‘n maklik afbreekbare koolstofbron (soos kompos) tesame met ‘n diverse groep mikroorganismes mees belowend is vir gebruik in biologiese verbouingssisteme. Resultate toon dat veranderings in aantal organismes gemeet deur plaattellings, die aktiwiteit van grondensieme, en verbruikspotensiaal van verskillende koolstofbronne, nie as ‘n aanduiding van boomprestasie gebruik kan word nie. Daar is voorgestel dat verbeterde sinkronisasie van voedingselementvrystelling en plantopname, sowel as produksie van plantgroeihormone deur mikrobe, moontlik ‘n rol speel by boomreaksies op biologiese toevoegings. Meer navorsing wat verband hou met die meganisme waardeur komposekstrak opbrengs verbeter, is nodig. Verder word studies op fynwortelontwikkeling sowel as aspekte van die wortelrisosfeer aanbeveel.
Lucas, Shawn T. "MANAGING SOIL MICROBIAL COMMUNITIES WITH ORGANIC AMENDMENTS TO PROMOTE SOIL AGGREGATE FORMATION AND PLANT HEALTH." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/24.
Full textLanza, G. R., and Phillip R. Scheuerman. "Effect of Soil Amendments on In Situ Biodegradation in Creosote Contaminated Soils." Digital Commons @ East Tennessee State University, 1996. https://dc.etsu.edu/etsu-works/2910.
Full textGebhardt, Martha Mary. "Soil Amendment Effects on Degraded Soils and Consequences for Plant Growth and Soil Microbial Communities." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/556614.
Full textPark, Kee Choon. "Enzymatic activity, microbial diversity, and weed seed banks in soils receiving different organic amendments and the biological fertilizer EM(tm) /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3164535.
Full text(tm) after EM in title is for Trademark symbol. Typescript. Vita. Includes bibliographical references (leaves 120-142). Also available on the Internet.
Abis, Letizia. "Study of the effect of organic waste products amendments (OWPs) and microbial diversity on volatile organic compounds (VOCs) emissions by soil." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS443.
Full textVOCs emissions play a pivotal role on the atmospheric pollution. Biogenic sources of VOCs are between 10 and 11 times higher than VOC emissions from anthropogenic sources. Recently, the importance of the characterization of the VOC fluxes by soils and microorganisms has been highlighted. Instead, VOCs emissions from soil and microorganisms are possible precursors of the particulate matter and the O3 formation. This work is focused on the characterization of the VOCs emissions by soils amended with OWPs over the long and short terms application. The influence of the microbial diversity in soil on VOCs emissions was also analysed. VOC emissions were detected using the PTR-QiTOF-MS technique and all the experiments were performed under controlled laboratory condition using dynamic chambers for the detection of the VOCs emissions from samples. The results showed that different OWPs released different quantity of VOCs emissions and also the chemical and physical properties of the soil were linked to the emissions. Analyses on the influence of microbial biodiversity on VOCs emissions have shown that while the microbial diversity was higher VOC emissions by soils were lower. Furthermore, the diversity of the VOCs decreases when the VOCs emissions by soil are higher. Finally, the study of the dynamics of VOC emissions from microcosms amended with fresh OWPs, showed that the VOC emission flux increased in the first 49 hours after the OWP amendment, due to a disturbance of the microbial community in the soil
Laudick, Julia Ann. "Microbial Biostimulants in Organic Farming Systems: Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271.
Full textElfstrand, Sara. "Impact of green manure on soil organisms : with emphasis on microbial community composition and function /." Uppsala : Department of Soil Sciences, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200723.pdf.
Full textIlstedt, Ulrik. "Soil degradation and rehabilitation in humid tropical forests (Sabah, Malaysia) /." Umeå : Swedish University of Agricultural Sciences, 2002. http://diss-epsilon.slu.se/archive/00000233/.
Full textAbstract inserted. Appendix reprints four papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.
Torres, Bocero Irene Florentina. "Dynamics of carbon in degraded semiarid soils : effects of organic amendments and associated soil microbial communities= Dinámica del carbono en suelos degradados de zonas semiáridas: implicación de enmiendas orgánicas y comunidades microbianas asociadas." Doctoral thesis, Universidad de Murcia, 2015. http://hdl.handle.net/10803/313226.
Full textSoil plays a highly important role in sustaining life on earth but soil desertification, in arid and semiarid areas, negatively impacts on a significant loss of organic matter, and therefore of organic carbon, which negatively affects the quality and sustainability of the soil. In such degraded soils, it is of vital importance to restore levels of soil organic carbon to sufficient thresholds to maintain its basic functions. For this reason, the aim of this Doctoral Dissertation is to understand the carbon cycling of semiarid soils and the development of strategies for soil restoration. To reach this goal we have focused on the following topics in particular: the ability of this type of soil to respond to exogenous sources of carbon derived from plants; the role of the microbial community in the degradation of these carbon sources; and the link between these carbon sources and the biogeochemical cycling of the important elements (C, N and P), with a particular focus on carbon. The general working Hypothesis of this Doctoral Thesis is that the microbial communities in arid and semiarid soils have a limited capacity for processing carbonaceous substrates as a result of the low content of organic matter usually found in these soils. In order to obtain complete information concerning the dynamics of organic carbon and plant-derived organic amendments with respect to the microbial populations associated with processing of this organic matter, we conducted experiments in both controlled laboratory and field conditions. The first part of the thesis (Chapters 1, 2 and 3) was carried out in controlled laboratory conditions using three molecules of varying complexity: glucose, cellulose and lignin. These molecules are an essential part of the natural plant inputs to soil. We used glucose, cellulose and lignin molecules enriched with 13C (a stable isotope of carbon) in order to track the dynamics of these organic materials and the microbial populations involved in their processing in high resolution. In these experiments we applied, among other techniques, those based on the analysis of the isotopic composition of CO2, water-soluble fractions of C and of humic substances and the isotopic composition of fatty acids (PLFA-SIP). These techniques made it possible to thoroughly track the C cycle, evaluating the persistence and mineralisation of C in addition to the microbial populations associated with the dynamics of the added molecules. The second part of the thesis (Chapters 4 and 5) was carried out in the field, which represents a real setting for the study of soil restoration. In Chapter 4, we evaluated the long-term effects of plant-derived organic amendments (fresh and composted pruning waste) and of the applied dose (150 and 300 t ha-1) on the chemical, biochemical and microbiological properties of a semiarid soil. Different techniques were used to measure the changes in microbial activity after the addition of organic matter. Furthermore, phospholipid fatty acid analysis and the microbial community-level physiological profile were used to study changes in the biomass and the structure of the microbial community Finally, in the Chapter 5, we studied the long-term effect of organic amendments on the enzymes involved in the carbon cycle in semiarid conditions. In this chapter, we also evaluated the influence of organic amendments on microbial biomass and community structure. Furthermore, we aimed to complete our knowledge of the carbon cycle in semiarid soils by studying the diversity of isoenzymes exhibiting cellulase and β-glucosidase activity by zymography. Changes caused by the amendments in the biomass and the structure of the microbial community were studied by phospholipid fatty acid analysis . Taking a global picture of this Doctoral Thesis, we have reached the conclusion that semiarid soils, despite their advanced state of degradation and the fact they have not received much organic C input, nevertheless have a high level of biotic availability for handling plant-derived organic matter of different levels of complexity and stability. We observed that only a small fraction of the microbial community is able to degrade the more complex forms of carbon, but this microbial fraction is crucial for starting the carbon cycle in semiarid soils and therefore for the sustainability of semiarid areas. Moreover, adding organic matter to the soil improves the quality of semiarid soils in the long term. Indeed, organic amendments increase the content of organic carbon in such soils at long-term, favour the growth of the microbial biomass and change the functional structure of the microbial community as an ecological adaptation to the presence of new soil metabolites derived from the organic matter added. Furthermore, the addition of molecules composed solely of carbon not only has an effect on the carbon cycle but also influences other biogeochemical cycles such as the nitrogen and phosphorus cycles, which we were able to observe through changes in the enzyme activity related to these elements. This implies that these cycles cannot be considered as independent from one another but that they in fact act together to determine the quality and sustainability of a soil.
Malosso, Elaine. "Effects of plant amendment on microbial community structure and fungal biomass in Antarctic soils." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289240.
Full textBailey, Kathryn Lafaye. "Assessing the Microbial Consequences of Remediation: Surrogate Microbial Screening and Native Metabolic Signatures in Tc(VII) Contaminated Sediments." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3965.
Full textWilson, John A. L. "Microbial community structure and dynamics in the Colne Estuary, in situ and in response to nutrient amendment." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555229.
Full textShort, Nicolyn. "Implications of green manure amendments on soil seed bank dynamics." University of Western Australia. School of Earth and Geographical Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0022.
Full textPankow, Christine Ann. "Effect of Soil Type, Composting, and Antibiotic Use on Fate of Antibiotic Resistance Genes and Microbial Community Composition in Dairy and Beef Manure Applied Soils." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/86672.
Full textMaster of Science
Bamminger, Chris [Verfasser], and Ellen [Akademischer Betreuer] Kandeler. "Biochar amendment for C sequestration in a temperate agroecosystem : implications for microbial C- and N-cycling / Chris Bamminger ; Betreuer: Ellen Kandeler." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2018. http://d-nb.info/1155824075/34.
Full textMangse, George. "Investigating the effects of biochar and activated carbon amendment on the microbial community response in a volatile petroleum hydrocarbon-contaminated gravelly sand." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3147.
Full textOlofsson, Madelen. "On the investigation of chemical parameters reflecting microbial activity linked to nutrient availability in forest soil." Doctoral thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-25994.
Full textFORE
Das, Mitali. "Microbial Community Structure and Interactions in Leaf Litter in a Stream." Kent State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=kent1144953748.
Full textChaineau, Claude-Henri. "Devenir et effets des hydocarbures dans le cas de l'épandage extensif de déblais de forage en agrosystème." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL150N.
Full textHinkle, Matthew. "Effects of Microbial Litter Amendments on Broiler Performance, Litter Quality and Ammonia Production." 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8983.
Full textGardner, Wendy, Klaas Broersma, Anne Naeth, and Al Jobson. "Influence of biosolids and fertilizer amendments on selected soil : physical, chemical and microbial parameters in tailings revegetation." 2003. http://hdl.handle.net/2429/9097.
Full text"The use of microbial and organic amendments in the revegetation of smelter-affected soils near Flin Flon, MB." Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-05-1047.
Full textPinto, Renata Machado dos Santos. "Recuperação de um solo florestal queimado por aplicação de residuos orgânicos. Respiração induzida por substrato dos microrganismos do solo." Master's thesis, 2009. http://hdl.handle.net/10400.5/2077.
Full textOrganic amendments were made to a naturally burned soil (BS), unburned soil (fresh soil) and soils treated at 65, 105 and 250 oC simulating fire effects. Digested pig slurry (PS), composted municipal solid waste (MSW) and a mixture of both residues were applied to soil samples and incubated for 2 months. To determine the effects of fire and organic amendments on soil microorganisms and if changes occurred in their functional diversity, microbial community level physiological profiles were assessed using different carbon substrates. Substrate induced respiration and basal respiration were determined by the MicroRespTM method. BS showed greater respiration values than other treatments, suggesting that the ability of soil microorganisms to use carbon substrates was not reduced in BS, probably due to low fire intensity. PS seemed to be more effective improving microbial activity in BS, while in 65 and 105 oC soils MSW was more successful. Fresh soil often showed lower respiration than 65 and 105 oC soils suggesting a change in microbial communities after treatment, eventually with destruction of less tolerant microorganisms and consequent increase of available organic matter. Microorganisms introduced by organic residues seemed to play an important role in microbial respiration recovery.---------------------------------Foram aplicados resíduos orgânicos a um solo queimado (SQ) em fogo florestal, solo não queimado (solo fresco) e solos tratados a 65, 105 e 250 oC em estufa. Chorume de porco digerido (CP), resíduo solo urbano compostado (RSU) e uma mistura destes dois resíduos foram adicionados aos solos e incubados durante dois meses. Para avaliar os efeitos do fogo e da aplicação de resíduos aplicados nos microrganismos do solo e se as mudanças ocorreram ao nível da sua diversidade funcional, determinaram-se os perfis fisiológicos da comunidade microbiana através da utilização de diferentes substratos carbonados, pelo método MicroRespTM. O SQ apresentou maior respiração, sugerindo que a capacidade dos microrganismos utilizarem os substratos não ficou reduzida pelo fogo, que provavelmente foi de baixa intensidade. O CP terá sido mais eficiente a melhorar a actividade microbiana no SQ, e nos solos a 65 e 105 oC o RSU. O solo fresco obteve frequentemente menores valores de respiração que os solos tratados a 65 e 105 oC, sugerindo uma mudança nas comunidades microbianas após tratamento, com eventual destruição de microrganismos menos tolerantes e aumento de matéria orgânica disponível. Os microrganismos introduzidos pelos resíduos parecem desempenhar um papel importante na recuperação da respiração microbiana.
Gaulin, Eric Richard. "Development of microbial community structure in turfgrass rootzone mixtures varying by amendment, age, presence of plants, and environment." 2009. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051015.
Full textXu, Yilu. "A study on microbial carbon use efficiency in soil." Thesis, 2018. http://hdl.handle.net/1959.13/1387394.
Full textSoil organic carbon (SOC) plays a critical role in soil health and also in maintaining its ecological service. The stabilization of SOC involves physical, chemical, and biological processes in soil. Soil microorganisms serve as a carbon (C) biological sink as well as biochemical agents in C transformation in soil. The plant litter inputs and root exudates provide microorganisms with both labile and recalcitrant C sources. The C availability and soil habitat environment alter microbiota, consequently impacting the organic C decomposition processes in soil. Anthropogenic disturbances such as organic amendments, contaminants, tillage and grazing practices impact soil ‘biophysicochemical’ properties. The addition of organic C sources such as manure composts and biochar can lead to processes such as priming effect and microbial population shifts. In metal contaminated soils, organic-metal bonding can be beneficial to the immobilization of heavy metals, thereby reducing their bioavailability and biotoxicity. Microorganisms also develop strategies for the purpose to adapt to soil environment stress conditions. These stress tolerance processes include alteration of microbial community composition, and the redistribution of energy between catabolism (respired CO₂) and anabolism (biomass C). Although a number of studies have examined soil C biogeochemical dynamics, very few comprehensive studies have been reported on the role of soil microorganisms in relation to the mobilization and immobilization ((im)mobilization) processes of organic C dynamics. In this research, soil microbial function and community composition in relation to C dynamics as affected by environmental factors were investigated. The definition of ‘microbial carbon use efficiency’ (CUE) was introduced for the purpose of assessing the fraction of microbially decomposed organic C that is subsequently assimilated into microbial biomass. The specific objectives of this research include: (i) to determine microbial CUE involving different approaches in relation with various sources of C and nitrogen (N) inputs; (ii) to investigate the influence of land use practices on soil microbial functions in relation to CUE; (iii) to evaluate metal stress on microbial function in relation to CUE; and (iv) to examine the influence of biochar on metal toxicity in relation to microbial CUE. The first experiment was aimed to compare four approaches to measure microbial CUE using isotopic labelled glucose as an organic C source. The first approach (Cs) for microbial CUE measurement was based on monitoring C depletion, while the second (Cm) and third (Cp) approaches were based on detecting of microbial biomass accumulation, the forth approach (Cr) was aimed at calculating the ratio of the increased microbial biomass to the decreased C content. The microbial CUE values varied amongst the four approaches, and the Cm values were generally higher than other measurements. Because the main aims of the subsequent experiments were to understand the microbial mediation of soil C and the accumulation of C in microbial community, the microbial CUE measurement based on the accumulation of microbial biomass C (Cm) was used in the remaining chapters. In the first experiment, the 13C labelled glucose was evenly applied to soils to trace the C flow as measured by the release of CO₂, C incorporation into microbial biomass, and C remaining as undecomposed C input. Microbial phospholipid fatty acids (PLFAs) were extracted and analysed as biomarkers in order to identify the microbial community composition. Results revealed that organic amendment coupled with mineral N [(NH₄)₂SO₄] stimulated both microbial activity and biomass, leading to a positive priming effect (PE). However, as different C:N ratios were introduced in this experiment, the PE intensity stimulated by different exogenous C and mineral N sources showed variation amongst C sources, similar to microbial CUE values as determined by above approaches. The labile C source (glucose) with low N contributed to relatively higher microbial PE. Microbial community varied with C input sources, the readily available C source (glucose) favoured bacteria community growth over fungi, while fungi population increased with mineral N application. In conclusion, microbial CUE measurements are related to the methods and parameters used, and the C use preference and community composition are highly dependent on the exogenous C and mineral sources. Based on the microbial CUE measurement results of the first experiment, the second experiment used soils from three land use systems: cropping, pasture and natural forest soil. Three types of organic amendments were introduced: glucose as a labile C source, and wheat straw and macadamia nutshell biochar as a relatively recalcitrant C material. Microbial biomass C, and basal and substrate-induced respiration were measured to determine microbial CUE. Microbial community composition was determined based on the measurement of PLFAs. Land use history generally affects soil physiochemical and microbial properties. The natural forest soil had the highest organic C content while having relatively low soil nutrient contents. Because of constant disturbance and management, cropping soil had relatively lower values in microbial activity and biomass. Although there were no significant differences of microbial CUE values in soils from different land systems, the organic amendments lead to distinct microbial CUE values. Therefore, the exogenous C source applied to cropping land during cultivation played a more important role in terms of microbial C use preference. Glucose input significantly (p > 0.05) increased microbial respiration with less biomass formation, thereby resulting in a decrease in microbial CUE, while wheat straw and biochar inputs increased microbial CUE compared to glucose. However, microbial community composition differed among land use systems. Fungi was dominant in natural forest soil while bacteria population was larger in cropping and pasture soils. The type of organic amendment inputs also altered microbial community composition. The addition of an easily degradable C source such as glucose stimulated a growth in Gram-positive bacteria, while biochar input favoured fungi population growth. The biotoxicity of heavy metal(loid)s was evaluated by monitoring microbial CUE and community composition in soil samples spiked with Cd(II) and Pb(II), both individually and in combination. The bioavailable metal concentrations, soil properties, and microbial parameters including microbial respiration, biomass and microbial PLFAs were determined at two sampling periods during the 49 days incubation experiments. Microbial CUE was determined as the ratio of accumulated biomass to decomposed C amount. Metal contamination had no significant effect on (p > 0.05) on soil properties such as pH and EC, while significantly (p < 0.05) inhibiting microbial activity and biomass formation. Notably, the microbial CUE decreased due to metal contamination, and the higher heavy metal concentration lead to lower microbial CUE values. Both total PLFAs and PLFA diversity decreased under metal stress. The microbial community composition and PLFA patterns also differed among treatments. Heavy metal pollution had greater negative influences on fungi population compared to bacteria. This might result in a vulnerable soil ecosystem with less resilience ability. Based on the third experiment, biochar was introduced as an effective method for the remediation of metal contaminated soils. In this fourth experiment, Cd and Pb spiked soils treated with macadamia nutshell biochar (5% w/w) were monitored during a 49 days incubation period. Soil properties, metal bioavailability, microbial respiration, and microbial biomass C were measured after the incubation period. Microbial CUE was calculated from the ratio of C incorporated into microbial biomass to the C mineralised. Microbial community composition was determined by measuring microbial PLFAs. Results showed that total PLFA concentration decreased to a greater extent in metal contaminated soils than uncontaminated soils. Microbial CUE also decreased due to metal toxicity. However, biochar addition alleviated the metal toxicity, and increased total PLFA concentration. Both microbial respiration and biomass C increased due to biochar application, and CUE was significantly (p < 0.01) higher in biochar treated soils than untreated soils. Heavy metals reduced the microbial C sequestration in contaminated soils by negatively influencing the CUE. The improvement of CUE through biochar addition in the contaminated soils could be attributed to the decrease in metal bioavailability, thereby mitigating the biotoxicity to soil microorganisms. In conclusion, microbial properties are essential indicators in the determination of soil health. The microbial CUE values vary depending on the measurement adopted. As such, there is a need for a comprehensive conceptual understanding and unified method of determination of microbial CUE. For the purpose of this research, the microbial CUE measured based on the accumulation of microbial biomass was more appropriate to examine microbial function in terms of microbial C utilization. Land use histories, organic amendments and environmental factor all alter the direction and dimension of microbial CUE, as well altering the microbial community composition. Especially certain microbial species such as bacteria and fungi could reveal soil functional status because of the difference in C use and allocation preference among these communities. Biochar could be beneficial to microbiota under metal stress, not only because of its high C content, but also because of its remediation ability as metal sorbents.