Soil microorganisms are important for the stabilization and preservation of a good soil structure. Management practices can affect the diversity and population of microorganisms, which could beneficially change soil properties and promote a more sustainable dryland system. This study was established near Pontotoc, MS on Atwood silt loam to evaluate the impacts of cover crops and fertilizer sources on selected biologically related soil properties in a no-tillage, dryland soybean system. Soil analyses included total carbon and nitrogen, permanganate oxidizable carbon (POXC), easily extractable glomalin-related soil protein (EE-GRSP), water stable aggregate (WSA) and soil pH. Cover crop biomass and percent groundcover, soybean leaf area index (LAI), plant height, and yield were also determined. Results indicated that fertilizer source did have an impact on total nitrogen, EE-GRSP and soybean yield. A positive impact on soil properties is expected with the use of cover crops if studied for a longer period of time.

Entomopathogenic nematodes (EPNs) in the families Heterorhabditidae and Steinernematidae, and their bacterial symbionts, have been studied intensively because of their role as natural mortality factor for soil-dwelling arthropods, and their potential as biological control agents for belowground insect pests. Moreover, EPN are recognized as key players in regulating soil food webs and triggering trophic cascades. However, most studies of interactions with EPN have been conducted under laboratory setting and simplified conditions, without consider the dynamic of the EPN and their interactions with other soil components in a wider context. In this respect, knowledge of the effect that other soil organisms or human induced factor may have on EPN dynamic and life cycle in the soil may contribute to improve tactics for their implementation and success as natural regulators of herbivores. The present investigation focused on the interactions of EPN with a selection of insecticides, and biotic (saprobic fungus and plant parasitic nematodes) elements that may be present in the soil, and may potentially interact with EPN. Specifically, I investigated how these factors may affect the life cycle (host search behavior, virulence and reproduction) of EPN. Appendix A shows the effect that a group of selected synthetic and biological insecticides have on EPN virulence and reproduction. The results obtained from this study revealed that most combinations of EPN and insecticides under study increased the mortality of the insect host. However, it was also found that some of these combinations reduced the nematode progeny production and emergence of IJs from the insect cadaver. In contrast in Appendix B, when examining the effect of the saprobic fungus Fusarium oxysporum in the life cycle of the EPN Heterorhabditis sonorensis, it was found that this fungus negatively affected the virulence and reproduction of the EPN in the insect host. In the third study of this dissertation (Appendix C) the interactions studied considered the effect of two EPN on an organism of a different trophic guild, the plant parasitic nematode Tylenchulus semipenetrans. This plant parasitic nematode causes serious diseases in citrus plants by infecting their roots and defoliating their branches. Previous studies have shown that some EPN species may negatively affect the life cycle of plant parasitic nematodes by reducing the damage produced by this plant parasite. Results from this study confirm the antagonistic effect between the selected EPN and the citrus nematode. Specifically, it was found that the presence in the soil of both EPN reduced the survival of infective juveniles of the citrus nematode and their penetration to the root. Moreover, the presence of EPN had an antagonistic effect in the production of eggs of T. semipenetrans females.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A degradaÃÃo ambiental e as restriÃÃes hÃdricas de regiÃes semiÃridas comprometem a produÃÃo agrÃcola e reforÃam a necessidade de manejo da Ãgua para manutenÃÃo da produtividade das culturas. Pesquisas sugerem o uso de Ãgua produzida, obtida no processo de extraÃÃo do petrÃleo, como alternativa de irrigaÃÃo, especialmente em Ãreas prÃximas aos campos petrolÃferos com escassez de Ãgua. No entanto, tÃm-se limitaÃÃes da aplicaÃÃo dessa Ãgua devido à presenÃa comum de sais, compostos tÃxicos e metais que podem impactar negativamente o solo. Este estudo teve por objetivo avaliar atributos microbiolÃgicos do solo cultivado com oleÃferas irrigadas com diferentes Ãguas (subsolo e Ãgua produzida) e comparÃ-los com solos controles nÃo cultivados e sob vegetaÃÃo nativa. Experimentos com espÃcies de girassol e mamona irrigadas com Ãgua captada do subsolo (AC), Ãgua produzida tratada com filtragem simples (APF), Ãgua produzida tratada por osmose reversa (APO) e solo nÃo cultivado (NCNI) foram conduzidos na fazenda BelÃm, Aracati, CearÃ. O solo rizosfÃrico da camada superficial (0-10 cm) foi coletado nos perÃodos prÃ-plantio e durante as fases de crescimento e florescimento das culturas, e avaliado atravÃs das variÃveis densidade populacional de fungos filamentosos e bactÃrias cultivÃveis, carbono orgÃnico (COT), carbono da biomassa microbiana (CBM), respiraÃÃo basal (RB), quociente metabÃlico (qCO2) e atividade enzimÃtica. A partir dos resultados pÃde-se concluir que tratamentos com APF e APO afetam de forma distinta os atributos do solo, com o primeiro alterando positivamente o nÃmero de micro-organismos e a atividade enzimÃtica, enquanto o segundo reduz a desidrogenase e as populaÃÃes de fungos e bactÃrias do solo. A irrigaÃÃo com AC e APF teve efeitos semelhantes sobre os indicadores estudados. NÃo foram detectadas diferenÃas entre tratamentos de manejo do solo quando analisados os parÃmetros COT, CBM, RB e qCO2 no primeiro ciclo das culturas. Os valores da maioria dos indicadores microbiolÃgicos avaliados foram similares na mata nativa e nas Ãreas cultivadas com oleÃferas irrigadas. / Environmental degradation and water restrictions in semiarid regions undertake agricultural production and reinforce the need for water management to maintain crop productivity. Researchers suggest the use of produced water, obtained in the process of oil extraction, as alternative of irrigation, especially in areas close to oil fields with water scarcity. However, there have been limitations on application this water due to the common presence of salts, metals and toxic compounds that may to impact negatively the soil. This study aimed to evaluate soil microbiological attributes in areas under cultivation of bioenergy plants irrigated with different waters (underground and produced water) and compare them with controls uncultivated and native vegetation soils. Experiments with species of sunflower and castor beans irrigated with water collected from underground (AC), produced water treated with simple filtering (APF), produced water treated by reverse osmosis (APO) and uncultivated soil (NCNI) were conducted on BelÃm farm, Aracati, Cearà state, Brazil. The surface layer of soil (0-10 cm) was collected in the ranks of pre-planting and planting during the growing and flowering plants, and evaluated by the population density of filamentous fungi and cultivable bacterias, organic carbon (COT), microbial biomass carbon (CBM), basal respiration (RB), metabolic quotient (qCO2) and enzyme activity. The results of this study revealed that treatment with APF and APO affect differently soil attributes, with the first positively changing the number of microorganisms and enzyme activity, while the second reduces dehydrogenase and populations of fungi and bacterias of soil. However, treatments with AC and APF had similar effects on indicators studied. Differences were not found between treatments when analyzed soil parameters of management COT, CBM, RB and qCO2 in first crop cycle. The values of most microbiological indicators evaluated were similar in native forest and areas cultivated with bionergy plants irrigated.

Soil microorganisms play important roles in maintaining soil quality and ecosystem health. Development of effective methods for studying the composition, diversity, and behavior of microorganisms in soil habitats is essential for a broader understanding of soil quality. Forest management strategies and practices are of vital significance for sustainable forest production. How the different forest management measures will influence soil microbial communities is a widespread concern of forest industry and scientific communities. Only a small proportion (~0.1%) of the bacteria from natural habitats can be cultured on laboratory growth media. Direct extraction of whole-community DNA from soil, followed by polymerase chain reaction (PCR) and other analysis circumvents the problems of the culture-dependent methods and may shed light on a broader range of microbial communities in the soil. DNA-based molecular methods rely on high quality soil microbial DNA as template, and thus extraction of good quality DNA from soil samples has been a challenge because of the complex and heterogeneous nature of the soil matrix. The objectives of this research were to establish a set of DNA-based molecular methods and to apply them to investigate forest soil microbial composition and diversity. Soil samples were collected from different forest ecosystems, i.e., the natural forest (YNF) and the first rotation (~ 50 years) (Y1R) and the second rotation (~ 1 year) (Y2R) of hoop pine plantations at Yarraman, and from different forest residue management practices (the experiments had established 6.4 years before the samples were collected) at Gympie, two long-term experimental sites of the Queensland Department of Primary Industry-Forestry in subtropical Queensland, Australia. Some DNA-based molecular techniques, including DNA extraction and purification, PCR amplification, DNA screening, cloning, sequencing and phylogenetic analyses, were explored using Yarraman soil samples, which were high in organic matter, clay and iron oxide contents. A set of methods was assembled based on the recommendations of the method development experiments and applied to the investigations of the microbial composition and diversity of the Yarraman and Gympie soil samples. Four soil DNA extraction methods, including the Zhou method (Zhou et al., 1996), the Holben method (Holben, 1994), the UltraClean (Mo Bio) and FastDNA (Bio 101) soil DNA extraction kits, were explored. It was necessary to modify these methods for Yarraman soil. I designed and introduced a pre-lysis buffer washing step, to partially remove soil humic substances and promote soil dispersion. This modification greatly improved the quality of the extracted DNA, decreasing co-extracted humic substances by 31% and increasing DNA yield by 24%. The improved Holben method was recommended for fungal community studies, and the improved Zhou method for bacterial community studies. The extracted DNA was good in quality, with a consistent size of ~20 kb and a yield of 48-87 g g-1 soil, and could be successfully used for 16S (Zhou method) and 18S (Holben method) rDNA amplifications. For less difficult environmental samples, UltraClean kits could be a good option, because they are simple and fast and the extracted DNA are also of good quality. Screening of the DNA PCR products using TGGE, Heteroduplex-TGGE and SSCP was also explored. These methods were not so effective for the screening of the soil DNA PCR products, owing to the difficulty in interpretation of the results. Cloning was a necessary step to obtain a single sequence at species level in soil microbial community studies. The screening of the clone library by TGGE, Heteroduplex-TGGE and SSCP could only separate the clones into several major bands, although SSCP gave better separation. Sequencing of selected clones directly from the clone library obtained ultimate results of microbial taxonomic composition and diversity through well-established sequence analysis software packages and the databases. It was recommended that, in this project with the target of microbial community composition and diversity, soil DNA PCR products were directly cloned to construct clone libraries and a sample of clones were sequenced to achieve an estimate of the taxonomic composition of the soil. Fungal communities of the Yarraman soil samples under the natural forest (YNF) and the hoop pine plantations (YHP) were investigated using 18S rDNA based cloning and sequencing approaches. Twenty-eight clone sequences were obtained and analysed. Three fungal orders, i.e., Zygomycota, Ascomycota and Basidiomycota were detected from the YNF and YHP samples. By contrast, culture-based analyses of fungi in the literature were mostly Ascomycetes. YNF appeared to have more Ascomycota but less Zygomycota than YHP, and within the Zygomycota order, YHP had more unidentified species than YNF. Bacterial communities of Yarraman soil samples of YNF, Y1R and Y2R were investigated using 16S rDNA-based cloning and sequencing approaches. 305 16S rDNA clone sequences were analysed and showed an overall bacterial community composition of Unclassified bacteria (34.4%), Proteobacteria (22.0%), Verrucomicrobia (15.7%), Acidobacteria (10.2%), Chloroflexi (6.9%), Gemmatimonadetes (5.6%), and Actinobacteria (5.2%). There was a significant difference among YNF, Y1R and Y2R in the taxonomic group composition. YNF had a greater proportion of Acidobacteria (18.0%), Verrucomicrobia (23.0%) and Chloroflexi (9.0%) than Y1R and Y2R (corresponding to 6.3%, 12.1% and 5.9%, respectively), while Y1R and Y2R had a higher percentage of the Unclassified group (38.5% for Y1R and 46.5% for Y2R) than YNF (18.0%). For the Proteobacteria group, YNF had more Alpha-subdivision but Y1R and Y2R had more Delta-subdivision. From YNF to Y1R to Y2R, the clone sequence variable site ratios, 5% and 10% OTU numbers and Shannon's diversity index H' values tended to decrease, indicating the soil bacterial diversity decreased from the natural forest to the first and the second rotation hoop pine plantations. The large amount of unclassified clone sequences could imply a novel group of bacteria in the soil, particularly in the hoop pine soil samples. Alternatively they may result from artefacts during the PCR process. Bacterial communities of the Gympie soil under different residue management practices, i.e., residue (litter plus logging residue) removed (G0R), residue retained (G1R), and residue doubled (G2R), were also investigated using the 16S rDNA-based cloning and sequencing approaches. Acidobacteria (37.6%) and Proteobacteria (35.6%, including Alpha-subdivision of 29.9% and Gamma-subdivision of 5.7%) were dominant components of the communities, followed by Actinobacteria (14.7%), Verrucomicrobia (7.3%) and Unclassified bacteria. There was no significant difference among G0R, G1R and G2R in the bacterial community compositions and diversity. These findings provided an in-depth vision of the soil microbial communities under different forest management practices. Their combination with other soil analysis results, such as physical and chemical properties, and forest production data, could provide an improved understanding of sustainable forest management strategies.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 3 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Made available in DSpace on 2016-08-12T19:18:36Z (GMT). No. of bitstreams: 1 PaulaGMLN_TESE.pdf: 802985 bytes, checksum: ea2cf5b10e3c0b5eb8042341897c1301 (MD5) Previous issue date: 2015-06-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aimed to quantify the microbial community of soil cultivated with muskmelon and evaluate the incidence of root rot in muskmelon at the no-tillage (NT) and conventional tillage (CT) systems associated with soil coverages.Two experiments (two muskmelon crop cycles) were conducted in a naturally infested area with soilborne pathogens. The incidence of root rot was evaluated in both crop cycles, while the microbial community was quantified only in the first crop cycle.The experiments were conducted at the AgrícolaFamosa s farm, located between the cities of Tibau-RN and Icapuí-CE, in the Northeast region of Brazil.The randomized block design was used with split-plot.At the main plots evaluated two planting systems with and without soil revolving (NT and CT) and the subplots consisted of seven soil cover crops (Sunn hemp; Pearl millet; Sunn hemp + Pearl millet; Corn + Brachiaria; Spontaneous vegetation, Spontaneous vegetation + Black polyethylene film and Soil without vegetation).At the conventional tillage system, the plant materials were dried and incorporated into the soil, while in the no-tillage system were maintained on the ground.It was realized six soil samplings (Fallowed area; Green manure implementation; Muskmelon transplantation and at 20, 40 and 60 days after transplantation-DAT) in each subplot for quantification of total bacteria, fungi, Bacillus spp. and Pseudomonas fluorescens. For isolation and cultivation of microorganisms, serial dilutions were prepared and transferred to plates containing the desired solid medium for each analyzed group.After fruits harvest, all melon plants were collected from subplots, washed and analyzed for the incidence of root rot.The soil microbial communities (total bacteria, fungi, Bacillus spp. e Pseudomonas fluorescens) varied according to the tillage systems (no-tillage and conventional tillage) at the different epochs of sample collection during the muskmelon cycle. The sunn hemp cultivation associated with no-tillage in muskmelon provided greater amount of colony forming units (CFU) of total bacteria compared to the conventional tillage.The planting systems and soil coverages did not affect the amount of total fungi and Pseudomonas fluorescens. The microbial community of soil cultivated with muskmelon is influenced by the planting and soil coverage systems.The incidence of root rot in muskmelon was lower in the no-tillage system pre-cultivated with Sunn hemp, Pearl millet and Spontaneous vegetation. Fusarium solani, Macrophomina phaseolina, Monosporascus cannonballus e Rhizoctonia solani were the pathogens that occurred in muskmelon, being the first fungus the most frequent in both planting systems. The incidence of root rot in muskmelon depends on the cropping and planting systems / O presente trabalho teve como objetivo quantificar a comunidade microbiana do solo cultivado com meloeiro e avaliar a incidência de podridão radicular no meloeiro, nos sistemas de plantio direto (PD) e convencional (PC) associado à coberturas do solo. Dois experimentos (dois ciclos do meloeiro) foram conduzidos em área naturalmente infestada com patógenos habitantes do solo. A incidência de podridão radicular foi avaliada nos dois ciclos, enquanto a quantificação da comunidade microbiana do solo apenas no primeiro ciclo. O experimento foi conduzido na fazenda Agrícola Famosa entre os municípios de Tibau-RN e Icapuí-CE, no Nordeste do Brasil. O delineamento experimental foi o de blocos casualisados, no esquema de parcelas subdivididas. Nas parcelas foram avaliados dois sistemas de plantio com e sem revolvimento do solo (PC e PD) e nas sub-parcelas, sete coberturas de solo (Crotalária; Milheto; Consórcio crotalária + milheto; Consórcio milho + braquiária; Vegetação espontânea; Vegetação espontânea + filme de polietileno; Solo sem vegetação). Os materiais foram dessecados e, incorporados ao solo, no plantio convencional enquanto no plantio direto, foram mantidos sobre o solo. Foram realizadas seis coletas do solo (Área em pousio; Implantação dos adubos verdes; Transplantio do meloeiro e, aos 20, 40 e 60 dias após o transplantio-DAT), em cada subparcela, para quantificação de Bacillus spp. , Pseudomonas fluorescens, bactérias totais e fungos totais. Para a quantificação de microrganismos, utilizou-se o método de diluição seriada e plaqueamento em meio de cultura específico para cada grupo analisado. Após a colheita dos frutos todas as plantas de meloeiro das subparcelas foram coletadas, lavadas e analisadas quanto à presença de podridão radicular. A comunidade microbiana do solo (Bacillus spp. ,Pseudomonas fluorescens bactérias totais e fungos totais) variou em função dos sistemas de plantio (direto ou convencional) nas diferentes épocas de coleta de amostras no ciclo do meloeiro. O cultivo da crotalária associada ao plantio direto do meloeiro causou maior quantidade de UFCs de bactérias totais em relação ao plantio convencional. Os sistemas de plantio e as coberturas do solo não alteraram a quantidade de fungos totais e Pseudomonas fluorescens. A comunidade microbiana do solo cultivado com meloeiro é influenciada pelo sistema de plantio e de cobertura do solo. A incidência da podridão radicular no meloeiro foi menor no sistema de plantio direto pré-cultivado com crotalária, milheto, ou vegetação espontânea. Fusarium solani, Macrophomina phaseolina, Monosporascus cannonballus e Rhizoctonia solani foram os patógenos que ocorreram no meloeiro, sendo o primeiro fungo, o de maior ocorrência em ambos os sistemas de plantio. A incidência de podridão radicular do meloeiro é dependente do sistema de cultivo e de plantio

LOPES, Eva Dayana Oliveira Rios. Efeito da água produzida nos atributos microbiológicos do solo sob cultivo de plantas no semiárido. 2013. 55 f. Dissertação (Mestrado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2013. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-19T20:20:06Z No. of bitstreams: 1 2013_dis_edorlopes.pdf: 951633 bytes, checksum: eb905fc184592cb0c4bc4f03338b7291 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-27T20:14:02Z (GMT) No. of bitstreams: 1 2013_dis_edorlopes.pdf: 951633 bytes, checksum: eb905fc184592cb0c4bc4f03338b7291 (MD5) / Made available in DSpace on 2016-05-27T20:14:02Z (GMT). No. of bitstreams: 1 2013_dis_edorlopes.pdf: 951633 bytes, checksum: eb905fc184592cb0c4bc4f03338b7291 (MD5) Previous issue date: 2013 / Environmental degradation and water restrictions in semiarid regions undertake agricultural production and reinforce the need for water management to maintain crop productivity. Researchers suggest the use of produced water, obtained in the process of oil extraction, as alternative of irrigation, especially in areas close to oil fields with water scarcity. However, there have been limitations on application this water due to the common presence of salts, metals and toxic compounds that may to impact negatively the soil. This study aimed to evaluate soil microbiological attributes in areas under cultivation of bioenergy plants irrigated with different waters (underground and produced water) and compare them with controls uncultivated and native vegetation soils. Experiments with species of sunflower and castor beans irrigated with water collected from underground (AC), produced water treated with simple filtering (APF), produced water treated by reverse osmosis (APO) and uncultivated soil (NCNI) were conducted on Belém farm, Aracati, Ceará state, Brazil. The surface layer of soil (0-10 cm) was collected in the ranks of pre-planting and planting during the growing and flowering plants, and evaluated by the population density of filamentous fungi and cultivable bacterias, organic carbon (COT), microbial biomass carbon (CBM), basal respiration (RB), metabolic quotient (qCO2) and enzyme activity. The results of this study revealed that treatment with APF and APO affect differently soil attributes, with the first positively changing the number of microorganisms and enzyme activity, while the second reduces dehydrogenase and populations of fungi and bacterias of soil. However, treatments with AC and APF had similar effects on indicators studied. Differences were not found between treatments when analyzed soil parameters of management COT, CBM, RB and qCO2 in first crop cycle. The values of most microbiological indicators evaluated were similar in native forest and areas cultivated with bionergy plants irrigated. / A degradação ambiental e as restrições hídricas de regiões semiáridas comprometem a produção agrícola e reforçam a necessidade de manejo da água para manutenção da produtividade das culturas. Pesquisas sugerem o uso de água produzida, obtida no processo de extração do petróleo, como alternativa de irrigação, especialmente em áreas próximas aos campos petrolíferos com escassez de água. No entanto, têm-se limitações da aplicação dessa água devido à presença comum de sais, compostos tóxicos e metais que podem impactar negativamente o solo. Este estudo teve por objetivo avaliar atributos microbiológicos do solo cultivado com oleíferas irrigadas com diferentes águas (subsolo e água produzida) e compará-los com solos controles não cultivados e sob vegetação nativa. Experimentos com espécies de girassol e mamona irrigadas com água captada do subsolo (AC), água produzida tratada com filtragem simples (APF), água produzida tratada por osmose reversa (APO) e solo não cultivado (NCNI) foram conduzidos na fazenda Belém, Aracati, Ceará. O solo rizosférico da camada superficial (0-10 cm) foi coletado nos períodos pré-plantio e durante as fases de crescimento e florescimento das culturas, e avaliado através das variáveis densidade populacional de fungos filamentosos e bactérias cultiváveis, carbono orgânico (COT), carbono da biomassa microbiana (CBM), respiração basal (RB), quociente metabólico (qCO2) e atividade enzimática. A partir dos resultados pôde-se concluir que tratamentos com APF e APO afetam de forma distinta os atributos do solo, com o primeiro alterando positivamente o número de micro-organismos e a atividade enzimática, enquanto o segundo reduz a desidrogenase e as populações de fungos e bactérias do solo. A irrigação com AC e APF teve efeitos semelhantes sobre os indicadores estudados. Não foram detectadas diferenças entre tratamentos de manejo do solo quando analisados os parâmetros COT, CBM, RB e qCO2 no primeiro ciclo das culturas. Os valores da maioria dos indicadores microbiológicos avaliados foram similares na mata nativa e nas áreas cultivadas com oleíferas irrigadas.

Made available in DSpace on 2014-06-11T19:31:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-05Bitstream added on 2014-06-13T21:02:53Z : No. of bitstreams: 1 rocha_mm_dr_botfca.pdf: 1150326 bytes, checksum: 893acd7e01d7f269b3eaa875876c771e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O manejo agrícola altera, em muito, as características físicas, químicas e biológicas dos solos. A cultura e as condições climáticas, assim como o tipo de solo propriamente dito, afetam a decomposição da matéria orgânica do solo e, consequentemente, a biogeociclagem dos nutrientes. A matéria orgânica é uma característica importante em relação à fertilidade do solo, de modo que o impacto do uso do solo precisa ser avaliado principalmente em agroecossistemas. O conhecimento dos efeitos do uso da terra e das práticas agrícolas sobre a comunidade microbiana é de fundamental importância, em vista das importantes funções que os microorganismos desempenham no solo e que irão se refletir na produtividade agrícola. Neste sentido, uma avaliação da biomassa microbiana e de microorganismos do solo pode evidenciar diversas alterações no ecossistema do solo que estão associadas ao teor de argila e/ou sistemas de plantio. No presente estudo, caracterizou-se a camada superficial do perfil de solos sob plantio direto e plantio convencional em quatro fazendas no Brasil em relação a alguns de seus componentes microbiológicos. Para tanto, analisou-se, mensalmente, a respiração do solo, a biomassa microbiana e grupos de microorganismos. A avaliação da biomassa microbiana foi feita através da técnica da fumigação-incubação (FI), utilizando-se a Equação: [(C-CO2 liberado pelo solo fumigado, no período de 0-10 dias de incubação) - (C-CO2 liberado pelo solo não-fumigado, ao longo de 10-20 dias de incubação)]/0,45. Os cálculos indicaram um conteúdo de carbono da biomassa microbiana significativamente maior nos solos sob sistema de plantio direto em relação àqueles sob plantio convencional, na camada amostrada (0-10 cm de profundidade). Quantidades significativamente maiores... / The crop management changes greatly the physical, chemical and biological soil properties. Furthermore, the crop and soil types, and the climatic conditions would affect on soil organic matter decomposition and on nutrients biogeociclying. Soil organic matter is a important characteristic in relationship soil fertility. The knowledge about effects on soil using and agriculture practices on soil microbial communities is very important, due to the function that microorganisms have in soil and it was going to in soil fertility. In this sense, evaluation of the soil microbial biomass and micro-organisms greatly aids predictions several changes in the soil ecosystems are associated with reduced tillage as compared with conventional tillage. Surface soils from long-term no-till and conventional tillage plots at four Brazil farms were characterised for microbial components. Soil respiration, microbial biomass carbon and counts of microorganisms were measured at intervals monthly. The evaluation of microbial biomass carbon was done by fumigation-incubation technique (FI). For calculating the soil microbial biomass carbon, the equation used was: Equation = [(CO2-C evolved by fumigated soil, 0-10 days) - (CO2-C evolved by unfumigated soil, 10-20 days)]/0,45. Significantly greater amounts of CO2-C were released from no-till than from conventional tilled soils. qCO2 values were not significantly different between tillage systems. This observation confirms that the tillage affected biological activity in those soils, further that qCO2 values didn't have significantily different which two tillage systems, in studied soils. Number both fungi and bacteria were assayed by Most Probable Number (MPN) by the agar drop counting technique and the microorganisms groups were calculated using by traditional Most Probable Number (MPN) method...(Complete abstract, click electronic access below)