To date, there has been little research into the role of microbial community structure in the functioning of the soil ecosystem and on the links between microbial biomass size, microbial activity and key soil processes that drive nutrient availability. The maintenance of structural and functional diversity of the soil microbial community is essential to ensure the sustainability of agricultural production systems. Soils of the same type with similar fertility that had been under long-term organic and conventional crop management in Canterbury, New Zealand, were selected to investigate relationships between microbial community composition, function and potential environmental impacts. The effects of different fertilisation strategies on soil biology and nitrogen (N) dynamics were investigated under field (farm site comparison), semi-controlled (lysimeter study) and controlled (incubation experiments) conditions by determining soil microbial biomass carbon (C) and N, enzyme activities (dehydrogenase, arginine deaminase, fluorescein diacetate hydrolysis), microbial community structure (denaturing gradient gel electrophoresis following PCR amplification of 16S and 18S rDNA fragments using selected primer sets) and N dynamics (mineralisation and leaching). The farm site comparison revealed distinct differences between the soils in microbial community structure, microbial biomass C (conventional>organic) and arginine deaminase activity (organic>conventional). In the lysimeter study, the soils were subjected to the same crop rotation (barley (Hordeum vulgare L.), maize (Zea mais L.), rape (Brassica napus L. ssp. oleifera (Moench)) plus a lupin green manure (Lupinus angustifolius L.) and two fertiliser regimes (following common organic and conventional practice). Soil biological properties, microbial community structure and mineral N leaching losses were determined over 2½ years. Differences in mineral leaching losses were not significant between treatments (total organic management: 24.2 kg N ha⁻¹; conventional management: 28.6 kg N ha⁻¹). Crop rotation and plant type had a larger influence on the microbial biomass, activity and community structure than fertilisation. Initial differences between soils decreased over time for most biological soil properties, while they persisted for the enzyme activities (e.g. dehydrogenase activity: 4.0 and 2.9 µg g⁻¹ h⁻¹ for organic and conventional management history, respectively). A lack of consistent positive links between enzyme activities and microbial biomass size indicated that similarly sized and structured microbial communities can express varying rates of activity. In two successive incubation experiments, the soils were amended with different rates of a lupin green manure (4 or 8t dry matter ha⁻¹), and different forms of N at 100 kg ha⁻¹ (urea and lupin) and incubated for 3 months. Samples were taken periodically, and in addition to soil biological properties and community structure, gross N mineralisation was determined. The form of N had a strong effect on microbial soil properties. Organic amendment resulted in a 2 to 5-fold increase in microbial biomass and enzyme activities, while microbial community structure was influenced by the addition or lack of C or N substrate. Correlation analyses suggested treatment-related differences in nutrient availability, microbial structural diversity (species richness or evenness) and physiological properties of the microbial community. The findings of this thesis showed that using green manures and crop rotations improved soil biology in both production systems, that no relationships existed between microbial structure, enzyme activities and N mineralisation, and that enzyme activities and microbial community structure are more closely associated with inherent soil and environmental factors, which makes them less useful as early indicators of changes in soil quality.

Made available in DSpace on 2014-07-29T15:16:36Z (GMT). No. of bitstreams: 1 Joyce Rover.pdf: 514538 bytes, checksum: aaa943196dccf7fe52627b0d975e29e2 (MD5) Previous issue date: 2009-05-30 / The soil quality indicators analyses during and after the transition period of conventional to organic production system are very important to evaluated the sustainability of agricultural systems. Soil microbiological and biochemical indicators shall quickly indicate changes occurred on both, soil management and production systems. The objective of this work was to evaluated shifts on microbiological and biochemical soil indicators of a conventional common bean production system in transition to an organic system, under conventional and non-tillage soil management systems after cover crops. Total enzymatic activity (AET), betaglucosidase activity (betaglucosidase), acid fosfatase activity (fosfatase), carbon (CBM) and nitrogen (NBM) of the microbial biomass, the basal soil respiration (RBS) and the metabolic quotient (qCO2) were evaluated on soil samples collected at tillage common bean cycle. The experiment was carried out at Embrapa Rice and Beans, in Santo Antônio de Goiás GO, and it was also collected soil samples in a secondary forest area close to the experiment to be used as a reference. The content of carbon and nitrogen of the soil microbial biomass, as well as, microbial and enzymatic activities in conventional and non-tillage systems were independent of the cover crop specie used. Under the experimental conditions, the soil management systems did not show effect in the enzymatic and microbial soil activities. The total and acid fosfatase enzymatic activities of the cropped soils were lower than in the forest soil. The betaglucosidase enzymatic activity was higher in cropped soil than under forest soil in the raining season and lower in the dry season. The soil tillage performed before common bean sowing promoted shifts on the CO2 efflux from soil to the atmosphere, which was verified by an increase on both, basal soil respiration and metabolic quotient. / A análise da qualidade do solo durante e após o período de transição de um sistema produtivo convencional para um sistema orgânico é importante como indicador de sustentabilidade. Indicadores microbiológicos e bioquímicos da qualidade do solo devem responder rapidamente a mudanças no manejo e alterações nos sistemas de produção. Assim, este experimento teve como objetivo avaliar as alterações nos indicadores microbiológicos e bioquímicos do solo em um sistema de produção em transição para cultivo orgânico do feijoeiro comum (Phaseolus vulgaris L.), sob sistema de preparo convencional (SPC) e direto (SPD) do solo, após o manejo de diferentes plantas de cobertura de solo. Avaliaram-se a atividade enzimática total (AET), a atividade de betaglicosidase (β-glicosidase) e de fosfatase ácida (Fosfatase), o carbono (CBM) e o nitrogênio (NBM) da biomassa microbiana, a respiração basal do solo (RBS) e o quociente metabólico (qCO2) em amostras de solo coletadas durante o ciclo de cultivo do feijoeiro comum. O experimento foi conduzido na Embrapa Arroz e Feijão, em Santo Antônio de Goiás GO e área de mata nativa próxima ao ensaio foi utilizada como referência. O teor de carbono e nitrogênio da biomassa microbiana no solo, assim como de atividades microbianas e enzimáticas avaliadas, tanto sob SPD quanto sob SPC, foi independente da espécie de planta de cobertura de solo utilizada. Nas condições testadas, o sistema de preparo de solo não teve influência na atividade das enzimas do solo e nem na atividade microbiana do solo. No solo agricultável testado, a atividade enzimática total e de fosfatase ácida foi menor do que em solo não agricultável. No período chuvoso, a atividade de betaglicosidase foi maior em solo agricultável do que em solo não agricultável e menor no período seco. O preparo do solo para a semeadura do feijoeiro comum provocou aumento da perda de gás carbônico, verificado em decorrência de aumento na respiração basal do solo e no quociente metabólico.

Les nématodes à galles demeurent l'un des problèmes les plus graves des ‎agriculteurs de serres du Liban et du Moyen-Orient. Dans le passé, la fumigation du sol au ‎bromure de méthyle a été considérée comme la meilleure mesure de contrôle contre ces ‎nématodes. Toutefois, à la lumière de l'élimination globale du bromure de méthyle, l'accès ‎aux alternatives efficaces et durables est devenu une nécessité essentielle.‎L'objectif de cette étude est d'évaluer l'efficacité des deux engrais verts, le radis ‎huileux (Raphanus sativus oleifera) et à la roquette (Eruca vesicaria sativa) appliquées ‎avec ou sans bâche en plastique, séparément et en combinaison avec Oxamyl, dans la ‎gestion des nématodes à galles en cultures de concombres de serre. En outre, cette étude ‎vise à évaluer la faisabilité financière de la technique de biofumigation avec les deux ‎cultures utilisées et de la rentabilité finale de ces engrais verts en termes de taux coût-profit ‎par rapport au bromure de méthyle.‎A cette fin, trois expériences sur le terrain ont été menées dans des serres ‎commerciales, situées sur la zone côtière du Liban.‎Dans les deux expériences A et B, des résultats cohérents ont été enregistrés en ‎termes de production de rendements significativement plus élevés et de la réduction des ‎populations de nématodes avec les engrais verts‎ utilisés avec ou sans bâche en plastique, ‎par rapport au témoin non traité.‎Quant aux résultats obtenus par les engrais verts‎ par rapport ‎ au bromure de ‎méthyle, dans l'expérience A, le rendement produit par le bromure de méthyle était ‎significativement plus élevé que celui du radis huileux avec bâche en plastique. ‎Cependant, la différence n'était pas significative entre la réduction de la population de ‎nématodes résultant du bromure de méthyle et celle du radis huileux avec bâche en ‎plastique. Les différences du rendement ainsi que la réduction des nématodes étaient ‎significatives entre le bromure de méthyle et le radis huileux sans bâche en plastique.‎Dans l'expérience B, aucune différence significative n'a été observée dans le ‎rendement ni la réduction de la population de nématodes entre aucun des deux engrais ‎verts‎ utilisés avec bâche en plastique et le bromure de méthyle. Ces différences étaient ‎significativement en faveur du bromure de méthyle uniquement lorsque le radis huileux a ‎été utilisé sans bâche en plastique.‎Dans l'expérience C, où Vydate (Oxamyl) a été appliqué à la dose de 1 litre par 1,000 ‎m2 à tous les traitements, il n'y avait pas de différence significative dans le rendement ni la ‎réduction de la population de nématodes entre chacun des deux engrais verts utilisés avec ‎ou sans bâche en plastique et le bromure de méthyle.‎L'analyse coût-profit menée sur tous les traitements appliqués dans les 3 ‎expériences a montré que dans tous les cas, tous les traitements appliqués, qu'ils soient ‎chimiques, non-chimique (avec ou sans bâche en plastique) ou en association ont produit ‎des bénéfices nets supérieurs au bromure de méthyle, même lorsque le rendement produit ‎par le bromure de méthyle était significativement plus élevée.‎L'utilisation du plastique pour couvrir les radis huileux a généralement produit de ‎meilleurs résultats en termes de production de rendements plus élevés, une meilleure ‎réduction des populations de nématodes à galles dans le sol, ainsi conduisant à des ‎augmentations raisonnables des profits nets.‎A la base de ces résultats et à la lumière de l'élimination globale du bromure de ‎méthyle, on peut conclure que l'utilisation du radis huileux et la roquette comme engrais ‎verts avec bâche en plastique peut être considéré comme un outil alternatif pour la gestion ‎des nématodes à galles dans la production de concombres de serre dans les conditions ‎libanaises.‎ / Root-knot nematodes remain one of the most serious problems faced ‎by ‎greenhouse farmers of Lebanon and the Middle East region. In the past, soil fumigation ‎with methyl bromide has been considered as ‎the best control measure against root-knot ‎nematodes. However, in the light of the global phase out of methyl bromide, finding ‎efficient and viable alternatives is an essential necessity.‎The objective of this study is to evaluate the efficacy of the two biofumigation ‎crops ‎Oil Radish (Raphanus sativus oleifera) and Arugula (Eruca vesicaria sativa) applied ‎with ‎and without plastic tarp, separately and in combination with Oxamyl in the ‎management of ‎the root-knot nematodes in greenhouse cucumber crops. Additionally, this ‎study aimed at ‎assessing the financial feasibility of the biofumigation technique with the ‎two cops used ‎and the final profitability of these green manure crops in terms of cost to ‎benefit ratio as ‎compared to methyl bromide.‎For this purpose, three field experiments were carried out in ‎commercial ‎greenhouses situated on the coastal zone of Lebanon.‎In both experiments A & B consistent results were recorded in terms of production ‎of ‎significantly higher yields and reduction of nematode population with the ‎biofumigation ‎crops used whether with or without plastic cover, as compared to untreated ‎fallow.‎As to the results achieved by the biofumigation crops with respect to methyl ‎bromide, ‎in experiment A yield produced by methyl bromide was significantly higher than ‎oil radish ‎with plastic cover. However, no significant difference was found between ‎reduction of ‎nematode population resulting from methyl bromide and oil radish with plastic ‎cover. ‎Difference was significant between methyl bromide and oil radish without plastic ‎cover in ‎both yield and reduction of nematodes.‎In experiment B no significant difference was observed in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with ‎plastic ‎cover and methyl bromide. These differences were significantly in favor of methyl ‎bromide ‎only when oil radish was used without plastic cover.‎In experiment C where Vydate (Oxamyl) was incorporated at the rate of 1 liter ‎per ‎‎1,000 m2 to all treatments, there was no significant difference in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with or ‎without ‎plastic cover.‎Cost-benefit analysis made on all treatments applied in the 3 experiments ‎showed ‎that in all cases, all treatments applied, whether chemical, non-chemical (with or ‎without ‎plastic cover) or in combination have produced higher net profits than methyl ‎bromide, ‎even when yield produced by methyl bromide was significantly higher.‎Use of plastic for covering oil radish has generally produced ‎better results in terms ‎of ‎production of higher yields, better reduction of soil ‎populations of root-knot nematodes‏‎ ‎and ‎‏leading to ‎‏reasonable increases of net profits.‎Based on these findings and in the light of global phase out of methyl bromide, ‎it ‎can be concluded that the use of oil radish and arugula as biofumigation crops with ‎plastic ‎cover can be considered as ‎an alternative management tool for the root-knot ‎nematode in ‎greenhouse cucumber ‎production under Lebanese conditions.‎