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Orientador: Claudia Regina Baptista Haddad / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-15T15:33:32Z (GMT). No. of bitstreams: 1 Noleto_LeonardoGoncalves_D.pdf: 8581995 bytes, checksum: 12b214dbb64d8243d691234477807b02 (MD5) Previous issue date: 2010 / Resumo: Árvores e lianas possuem diferentes estratégias de alocação de recursos durante o ciclo fenológico. As lianas são componentes florísticos importantes e parte significativa das espécies de florestas tropicais, mas ainda pouco estudadas no Bioma Cerrado. A duração do ciclo de vida foliar de diferentes espécies reflete sua adaptação ao habitat, bem como as concentrações de certos compostos orgânicos nitrogenados, que influenciados por fatores ambientais estão relacionados com o crescimento vegetativo. Entre os elementos minerais o nitrogênio é um dos mais limitantes em plantas e sua conservação é dependente da sua disponibilidade no ambiente. O reaproveitamento do nitrogênio é mensurado pela eficiência de reaproveitamento do nitrogênio, pela eficiência no uso do nitrogênio e pela proficiência de reaproveitamento de nitrogênio. A baixa disponibilidade do nitrogênio no solo é determinante para sua conservação, mas muitas espécies vegetais conservam esse nutriente apresentando folhas com alta longevidade. Embora as lianas e árvores do presente trabalho ocorram no mesmo ambiente, presume-se que os índices relativos à conservação do nitrogênio sejam menores nas lianas, quando comparados aos das espécies arbóreas, já que alguns autores verificaram que lianas possuem um sistema vascular e radicular mais eficiente que os das árvores, o que pode possibilitar uma aquisição mais eficiente de nutrientes minerais. Além disso, as lianas ocorrem com freqüência em áreas florestais perturbadas, onde árvores são derrubadas, onde há abundância da quantidade de luz e serrapilheira (fonte de N disponível no solo). Compostos fenólicos normalmente são encontrados em maiores concentrações em espécies com folhas longevas. Esses compostos exercem papel de defesa contra herbívoros e patógenos. A concentração desses compostos é influenciada pelo balanço carbono/nutriente nos tecidos vegetais, bem como por fatores climáticos. A hipótese que norteia a presente pesquisa é a existência de diferentes estratégias fisiológicas apresentadas por árvores e lianas no que diz respeito aos índices de conservação do nitrogênio, investimento em estruturas vegetativas (longevidade foliar, massa foliar por área, e diâmetro basal do fuste) e concentrações de compostos fenólicos e nitrogenados. Os objetivos deste trabalho foram: 1- Relacionar os índices de conservação do nitrogênio a aferições biométricas (longevidade foliar, massa foliar por área e diâmetro do fuste à altura de 30 cm) e concentração foliar de compostos fenólicos e nitrogenados nas espécies de árvores e lianas; 2- Verificar se há diferenças entre as árvores e lianas quanto aos aspectos acima mencionados e 3- Investigar o efeito da estacionalidade sobre as concentrações de compostos fenólicos e nitrogenados em folhas desses dois grupos de plantas. O trabalho foi conduzido em duas épocas distintas (seca e chuvosa) em um fragmento de cerrado denso, conhecido como Valério, na Estação Experimental de Itirapina, no estado de São Paulo. O diâmetro basal dos caules das espécies estudadas correlacionou-se negativamente com a massa foliar por área. Comparando-se os diâmetros basais de lianas e árvores verificou-se que as primeiras apresentaram caules mais finos, o que poderia indicar um maior investimento de compostos orgânicos na parte aérea dessas plantas. Apresentaram também uma menor massa foliar por área, provavelmente indicando a existência de sistemas radiculares e de transporte mais eficientes do que nas árvores, ou estratégias diferentes de distribuição de matéria orgânica nos dois grupos funcionais, ou, ainda, maior síntese de compostos estruturais de carbono nas espécies arbóreas, o que explicaria a maior concentração de compostos nitrogenados nas folhas de lianas. As lianas apresentaram o menor desempenho na conservação do nitrogênio. Esse desempenho das lianas pode estar relacionado à maior concentração desse elemento nas folhas maduras dessas plantas. Quando se compara as duas épocas analisadas, verifica-se que os compostos nitrogenados aumentaram na época chuvosa, paralelamente ao aumento de fenóis totais. Como a época chuvosa é também a época mais quente na região estudada, a combinação de maior disponibilidade de água e temperaturas mais altas pode ter propiciado um aumento no sistema de absorção e transporte de nitrato na planta, que se refletiu na maior concentração de aminoácidos. É possível que tenha havido aumento suficiente na concentração de aminoácidos precursores para sustentar os aumentos nas sínteses de proteínas e fenóis nesse período. O aumento da concentração de taninos condensados na época seca pode estar relacionado com efeitos da amplitude térmica diária sobre o metabolismo desses compostos ou com aumento de herbivoria no período seco, resultando na maior produção de taninos pelas plantas / Abstract: Trees and lianas present different strategies for allocating resources during the phonological cycle. Whereas Lianas are important floristic components and account for a significant number of rainforest species, few studies have been conducted in the Cerrado (a savanna like vegetation) biome. The duration of the leaf life span in different species reflects both its adaptation to the habitat, and the concentrations of certain organic nitrogen-containing compounds, which are influenced by environmental factors and are related to vegetative growth. Nitrogen is one of the most limiting mineral elements in plants, and its conservation depends on its availability in the environment. Nitrogen resorption is measured by nitrogen resorption efficiency, nitrogen use efficiency, and by nitrogen resorption proficiency. The low availability of nitrogen in the soil is a determining factor for its conservation, but many plant species preserve this nutrient with leaves that present a long life span. Although the lianas and trees from this research work share the same environment, it is assumed that the parameters related to nitrogen conservation are lower in the lianas when compared to those of the woody species, as some authors have verified that lianas present a more efficient vascular and root system than that of trees, which might provide them with a more efficient absorption of mineral nutrients. Moreover, lianas frequently occur in disturbed forest areas where trees are torn down, and there is an abundance of light and litterfall (a N source available on the soil). Larger concentrations of phenolic compounds are normally found in species whose leaves present a long life span. Such compounds protect these species against herbivores and pathogens. The concentration of these compounds is influenced by the carbon-nitrogen balance in plant tissues, as well as by climatic factors. The hypothesis that guides this research work is the existence of different physiological strategies presented by both trees and lianas regarding nitrogen conservation mechanisms, investment in vegetative structure (leaf life span, leaf life ratio, and basal diameter of the stem), and concentrations of phenolic and nitrogencontaining compounds. This research work aimed at: 1- Relating nitrogen conservation mechanisms to biometric measurements (leaf life span, leaf life ratio, and basal diameter of the stem at 30 cm high), and to the leaf concentration of phenolic and organic nitrogen-containing compounds in tree and liana species; 2- Establish differences between trees and lianas regarding the aforementioned aspects, and; 3- Investigate the effect of seasonal changes on the concentrations of phenolic and organic nitrogen-containing compounds in the leaves of both kinds of plants. This research work was conducted in two different seasons (dry and rainy) in a fraction of a dense cerrado area known as Valério, at the Itirapina Experimental Station, in the state of São Paulo, Brazil. The researched species presented a negative correlation between the basal diameter of the stems and the leaf mass area. Comparison of the basal diameters of both lianas and trees showed that lianas have thinner stems and a lower leaf mass area, indicating a more efficient vascular and root system than that of trees, or different strategies for distribution of organic compounds in both kinds of plants, or a higher synthesis of structural carbon compounds in the tree species, which could explain the greater concentration of nitrogen-containing compounds in liana leaves. Lianas presented lower performance in nitrogen conservation. Such a performance may be related to the greater concentration of nitrogen in mature liana leaves. Comparison of the two analyzed seasons shows that in the rainy season there was an increase in the concentration of nitrogenous compounds, as well as an increase in the contents of phenolic compounds. Since the rainy season is also the hottest in the research area, the combination of larger availability of water and higher temperatures may have caused an increase in the absorption and transportation system of nitrate in the plants, which reflected in a greater concentration of amino acids. There may have been a sufficient increase in the concentration of precursor amino acids to sustain the increase in protein and phenol synthesis during this period. The increase in the concentration of condensed tannins in the dry season may be related to the effects of the daily temperature range on the metabolism of these compounds, or to the increase in herbivory during the dry season / Doutorado / Doutor em Biologia Vegetal

Excess nitrogen (N) excretion from animal agriculture results in reduced air and water quality, and poses a risk to human health. Although the dairy industry utilizes milk urea N (MUN) to monitor protein feeding and N excretion, phenotypic diversity among cows may influence MUN and thus bias feed management. An initial study using data from 2 previously published research trials and a field trial, observed that cow had a significant effect on MUN variation. Regression models, utilized to predict MUN, corrected for dietary nutrients and some animal effects, and thus the observed effect of cow on MUN variation may reflect genetic selection decisions of animals with either poor or efficient urea transport. A second trial observed that MUN and PUN concentrations were positively correlated with gut urea clearance, providing evidence for differences in urea transport activity among cows. The presence of urea transport variation suggests that current protein recommendations may not estimate true requirements. A third trial observed that animals fed sub-NRC levels of RDP and RUP had reduced N intake and excretion of fecal N, urinary urea-N, and MUN. Animals maximized N efficiency and had no loss in milk production, suggesting a possible overestimation of RDP and RUP in the current NRC prediction model. The present project provides evidence for phenotypic variation among cows, which may be partially explained by differences in urea transport activity. Future work confirming genetic variation among urea transporters may provide an opportunity to improve feeding management if cow urea efficiency is known. / Master of Science

The global phenomenon of burgeoning coastal population growth has led to coastal watershed landscape transformation and ecosystem degradation, prompting policy-makers to set limits on freshwater withdrawals and labile nutrient loads. Important components of Florida’s economies lie in the state’s expansive coastal zone; the organisms driving the billion-dollar recreational fishing industry are rooted in coastal habitats, while the agriculture and real-estate industries sprawl throughout numerous coastal watersheds. This study aimed to identify the connections between anthropogenic land use and essential juvenile fish nursery habitats within the coastal zone, which is the first critical step for sustaining the ecology and related economies of the region. The need for this study arises from the fact that these economies are interconnected through nitrogen, and therefore nitrogen management can influence their prosperity or collapse. Juvenile fish nursery habitats are located in waters that receive nitrogen from adjacent landscapes. Runoff delivers nitrogen derived from human nitrogen use and processing within the watersheds to the juvenile fish nursery habitats. Ecosystem managers must understand that although copious amounts of nitrogen applied to land may ultimately support nursery habitat foodwebs, overwhelming nitrogen loads may also create algal blooms that decay and cause lethal hypoxic events leading to ecosystem degradation. This study aims to pinpoint the specific nitrogen sources that support primary production and ultimately fish production in watersheds dominated by agricultural landscapes and residential neighborhoods. Stable isotopes are versatile tools used to identify these connections. The nitrogen and carbon compounds that make up the moieties of an ecosystem inherently carry information on major nitrogen sources, trophic structure as well as the crucial information concerning dominant nitrogen removal and transformative processes that occur within sediments. Specifically in this study, the stable isotopes of carbon and nitrogen of dissolved inorganic nitrogen, primary producers, and fish were used to identify 1) the connections between urban and agricultural landscapes and the nutrients that percolate through the foodweb, 2) the primary producers that support fish biomass, 3) the origins of sedimentary organic matter that can provide new nitrogen via recycling, and 4) the heterogeneous function of fish nursery habitats in polluted systems. This study was conducted during the region’s wet and dry seasons and in over thirty watersheds that differ from each other in terms of size and anthropogenic influence. In agricultural watersheds, nitrogen derived from row crops and tree crops ultimately supported fish production during the wet season. Convective afternoon thunderstorms coupled with runoff delivered nitrogen from the landscape to receiving waters. These nutrients supported phytoplankton which deposited into the sediments and supported benthic foodwebs. During the dry season, nitrogen derived from row crops and nitrogen transformation in the sediments ultimately supported fish production. In this case, irrigation water used for agriculture delivered nitrogen from lands covered with row crops to the nursery habitats in receiving waters. The dry season was characterized by the nitrogen transformation process known as dissimilatory nitrogen reduction to ammonium (DNRA), where biologically available nitrate is converted to biologically available ammonium. Phytoplankton deposits, most likely delivered during the wet season, were recycled through the slow burning DNRA processes, which provided nitrogen for the benthic microalgae that dominated in the dry season. These organisms in turn supported benthic communities which ultimately supported dry season fish production.  In small urban watersheds, nitrogen derived from septic tanks, lawn irrigation, leaky sewage pipes, and atmospheric deposition ultimately supported fish production via phytoplankton, but unlike the nitrogen sources in agricultural watersheds, these sources (with the exception of atmospheric deposition) were seasonally consistent because a mechanisms to deliver nitrogen derived from septic tanks, lawn fertilizer, and leaky sewage pipes were, at least to some extent, available during both seasons. In polluted, tidal, fish-nursery habitats, the specific mechanism that allowed nursery habitats to decrease the ratio of mortality over growth rates of juvenile fish was not consistent among systems. These mechanisms were likely dependent on physical-chemical parameters and stream geomorphology. If the geomorphology or physical-chemical characteristics of nursery habitats are not adequate to set up an efficient nitrogen transfer process to fish, these habitats become more of a haven from predators rather than a source of food for fish.  This study has several implications for management. Managers must first recognize that microalgae are dominant supporters of tidal nursery foodwebs. Managers must define the relationship between nitrogen loads and fish abundance. If this relationship is unknown, the results of increasing nitrogen loads on fish production will remain uncertain; foodwebs in nursery habitats may collapse due to eutrophication, or fish abundance may increase due to increases in food supply. Connectivity factors derived from stable isotope mechanistic mass-balance models can be used as measurable targets for groups of watersheds. The use of wetlands as nitrogen remediation tools may not be effective at removing nitrogen; nitrogen transformation processes such as DNRA likely outweigh removal processes in wetland soils.

For the time different challenges are facing the world to stop the environment impacts  and availability of vital resources. Electrical and electronical Equipment (EEE) are contained harmful compounds which considered to be a major threat for living organisms and might cause long term impacts on environment (Md. Abdur Rakib, 2014). Furthermore, evolution of technology leads to production of a huge amount of electronic waste globally, which need to be treated by innovative technologies in order to minimize their environmental impact and simultaneously maximize their recovery rates. Pyrolysis is a promising method for treating these fractions of waste because it can potentially convert these waste into energy and metals.  Waste of Electrical and electronical Equipment (WEEE) contains both valuable and harmful materials, industrial waste are various physically and chemically from household waste. To avoid the opposite influence on environment and human health, presuppose particular recycling and treatment technique depending on the waste type (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Two types of WEEE have been processed using typical pyrolysis (Nitrogen) and pyrolysis (steam) at 600 °C, Fixed bed reactor was used in addition to a separate boiler for producing steam. Two samples were investigated Printed circuit board- main body and -sockets. The main focus of this work was to investigate the influence of steam presence on pyrolysis for recovering energy and metals from recycling WEEE. The comparison between pyrolysis at inert atmosphere and steam pyrolysis results of two various fractions of E-Waste were prepared, in addition to literature investigation related to recycling of E- waste and traditional routes which are followed in recovering materials nowadays was done. The results of this study  provides the incentive to continue experiments around pyrolysis process by using other methods.

Le zooplancton est un important fournisseur de composés bioréactifs pour les bactéries par l’excrétion. Cependant, l'interaction entre le zooplancton et la boucle microbienne est mal comprise. Sur la base d'une approche expérimentale, nous déterminons le rôle du zooplancton dans le recyclage de N et du P dans la région d'upwelling du chili et dans le pacifique sud tropical occidental (WTSP). Le DON est le principal produit d’excrétion dans des conditions automne/hiver, et l'ammonium et la DOP au printemps/été dans le centre-sud du chili. En automne/hiver, l'ammonium a été rapidement consomme par la communauté microbienne coïncida avec une augmentation des copies de transcription d'archaeal et bactéries ammonium oxydatrices, alors qu'une communauté microbienne différente, probablement hétérotrophique, a réagi a l’entrée d'azote par excrétion par des copépodes nourris avec une fraction de taille réduite. Au cours du printemps/ete, un changement dans la composition de la communaute bacterienne active a été associe a la réponse du phylum bactérien opportuniste Proteobacteria et Bacteroidetes. Dans le WTSP, les copépodes contribués d'ammonium, de DON et de DOP. L'excrétion de copépodes peut améliorer le processus de reminéralisation et moduler la composition de la communauté bactérienne active, caractérisée par des changements dans Alteromonadales et SAR11. Nous concluons que l'azote et le phosphore excrétés par copépodes peuvent être utilises directement par des communautés microbiennes, y compris des nitrifiants, fournissant de N reminéralisé pour soutenir la production nouvelle et régénérée dans l'océan supérieur des différents écosystèmes marins. / Zooplankton are important suppliers of bioreactive compounds for marine bacteria through fecal pellet production, sloppy feeding and excretion of dissolved compounds. However, the interaction between zooplankton metabolism and microbial loop is poorly understand. Based on experimental approach we determine the role of zooplankton in the recycling of N and P in the central/southern Chile and in western tropical south pacific (WTSP). DON was the main excretion product under autumn/winter conditions, and ammonium and DOP in spring/summer in central/southern Chile. in the autumn/winter ammonium was rapidly consumed by microbial community and this consumption coincided with increased archaea and bacteria ammonia-oxidizing amoA transcript copies in copepods fed with the larger-sized fraction, whereas a different microbial community, probably heterotrophic, reacted to the input by copepods fed with the smaller-sized fraction. During spring/summer a shift in the composition of active bacterial community was associated with the response of common-opportunistic seawater surface phyla, Proteobacteria and Bacteroidetes. In the WTSP, copepods contributed elevated levels of ammonium, DON and DOP. Copepod excretion can enhance the remineralization process and reshape the composition of the active bacterial community, characterized by shifts in Alteromonadales and SAR11. We concluded that N and P excreted by copepods can be used directly by microbial community, including nitrifying ones, providing significant remineralized N for sustaining new and regenerated production in the upper ocean of different marine ecosystems.

Made available in DSpace on 2014-06-11T19:33:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-13Bitstream added on 2014-06-13T19:04:51Z : No. of bitstreams: 1 rocha_rjs_dr_jabo.pdf: 825439 bytes, checksum: 2af7dcdaa1a7cdb8311729451dfa2d74 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O nitrogênio é nutriente absorvido em maiores quantidades na cultura do milho e o que proporciona maiores produtividades de grãos, sendo seu uso no sistema solo-planta alterado pelo sistema de cultivo utilizado. Com o objetivo de avaliar o efeito de sistemas de cultivo e doses de nitrogênio na produção de matéria seca, nitrogênio na planta, nitrogênio foliar, produtividade de grãos e eficiência do nitrogênio no milho, foi implantado experimento de campo nos anos de 2008 e 2009, em um Argissolo Vermelho-Amarelo, distrófico, sob irrigação. Utilizou-se o delineamento experimental em parcelas subdivididas, com oito repetições. As parcelas foram constituídas pela semeadura direta (SD) e plantio convencional (PC). Nas subparcelas, foram aplicadas seis doses de N (0; 40; 80; 120; 160 e 200 kg ha-1) na forma de uréia. Em 2009 a fim de avaliar a velocidade de decomposição e liberação do nitrogênio do feijão utilizado como cobertura morta, esses resíduos foram acondicionados em sacolas de náilon, as quais foram dispostas sobre o solo nas parcelas correspondente a SD e o seu conteúdo analisado em intervalos de 25 dias, até 100 dias após sua instalação. A adubação nitrogenada aumentou significativamente as variáveis relacionadas com a produtividade, sendo que a SD proporcionou a maior produção de matéria seca da parte aérea, matéria seca do grão, nitrogênio na parte aérea, nitrogênio do grão, produtividade de grãos, eficiência de absorção e uso do nitrogênio. A faixa de suficiência de nitrogênio na folha variou de 25,7 a 28,4 g kg-1. As doses máximas econômicas em 2008 e 2009 foram respectivamente de 125 e 160 kg ha-1 N / Nitrogen is the nutrient absorbed in largest quantities in maize which provides more grain yields, and its use in soil-plant system is modified by the tillage system utilized. Aiming to evaluate the effect of cropping systems and nitrogen rates on dry matter production, nitrogen in the plant, leaf nitrogen, grain yield and nitrogen efficiency in maize, field experiment was established in 2008 and 2009 in a dystrophic red-yellow Argisoil under irrigation. The split-plot experimental design were used with eight replications. The plots were established by no-tillage (NT) and conventional tillage (CT). Subplots were set in six levels of N(0, 40, 80, 120, 160 and 200 kg ha-1) as urea. In 2009, in order to assess the speed of decomposition and nitrogen release from the bean plant used as cover crop, plant residues were packaged in nylon bags, which were arranged on the ground in the plots corresponding to NT and its contents examined at intervals of 25 days until 100 days after its installation. The nitrogen fertilization increased significantly the variables related to productivity, being that no-tillage provided the highest dry matter yield on shoot, dry matter of grain, nitrogen on shoot, grain nitrogen, grain yield, nitrogen uptake efficiency and nitrogen use efficiency. The sufficiency range of leaf nitrogen ranged from 25.7 to 28.4 g kg-1. The maximum economic rates in 2008 and 2009 season were respectively 125 and 160 kg ha-1N

Resumo: O nitrogênio é nutriente absorvido em maiores quantidades na cultura do milho e o que proporciona maiores produtividades de grãos, sendo seu uso no sistema solo-planta alterado pelo sistema de cultivo utilizado. Com o objetivo de avaliar o efeito de sistemas de cultivo e doses de nitrogênio na produção de matéria seca, nitrogênio na planta, nitrogênio foliar, produtividade de grãos e eficiência do nitrogênio no milho, foi implantado experimento de campo nos anos de 2008 e 2009, em um Argissolo Vermelho-Amarelo, distrófico, sob irrigação. Utilizou-se o delineamento experimental em parcelas subdivididas, com oito repetições. As parcelas foram constituídas pela semeadura direta (SD) e plantio convencional (PC). Nas subparcelas, foram aplicadas seis doses de N (0; 40; 80; 120; 160 e 200 kg ha-1) na forma de uréia. Em 2009 a fim de avaliar a velocidade de decomposição e liberação do nitrogênio do feijão utilizado como cobertura morta, esses resíduos foram acondicionados em sacolas de náilon, as quais foram dispostas sobre o solo nas parcelas correspondente a SD e o seu conteúdo analisado em intervalos de 25 dias, até 100 dias após sua instalação. A adubação nitrogenada aumentou significativamente as variáveis relacionadas com a produtividade, sendo que a SD proporcionou a maior produção de matéria seca da parte aérea, matéria seca do grão, nitrogênio na parte aérea, nitrogênio do grão, produtividade de grãos, eficiência de absorção e uso do nitrogênio. A faixa de suficiência de nitrogênio na folha variou de 25,7 a 28,4 g kg-1. As doses máximas econômicas em 2008 e 2009 foram respectivamente de 125 e 160 kg ha-1 N / Abstract: Nitrogen is the nutrient absorbed in largest quantities in maize which provides more grain yields, and its use in soil-plant system is modified by the tillage system utilized. Aiming to evaluate the effect of cropping systems and nitrogen rates on dry matter production, nitrogen in the plant, leaf nitrogen, grain yield and nitrogen efficiency in maize, field experiment was established in 2008 and 2009 in a dystrophic red-yellow Argisoil under irrigation. The split-plot experimental design were used with eight replications. The plots were established by no-tillage (NT) and conventional tillage (CT). Subplots were set in six levels of N(0, 40, 80, 120, 160 and 200 kg ha-1) as urea. In 2009, in order to assess the speed of decomposition and nitrogen release from the bean plant used as cover crop, plant residues were packaged in nylon bags, which were arranged on the ground in the plots corresponding to NT and its contents examined at intervals of 25 days until 100 days after its installation. The nitrogen fertilization increased significantly the variables related to productivity, being that no-tillage provided the highest dry matter yield on shoot, dry matter of grain, nitrogen on shoot, grain nitrogen, grain yield, nitrogen uptake efficiency and nitrogen use efficiency. The sufficiency range of leaf nitrogen ranged from 25.7 to 28.4 g kg-1. The maximum economic rates in 2008 and 2009 season were respectively 125 and 160 kg ha-1N / Orientador: Edson Luiz Mendes Coutinho / Coorientador: Adeodato Ari Cavalcante Salviano / Banca: Luiz Evaldo de Moura Pádua / Banca: Takashi Muraoka / Banca: José Carlos Barbosa / Banca: José Eduardo Corá / Doutor

Les exploitations mixtes d'agriculture-élevage sont le pilier des systèmes agricoles des pays en développement. Dans les hauts plateaux de Madagascar, les exploitations familiales d'agriculture-élevage sont basées sur l'association riz et élevage bovin. Les bovins ont un rôle central dans l'économie et la reconnaissance sociale de ces exploitations malgaches. Cependant ces exploitations sont souvent confrontées à des problèmes de faibles productivités liés à la dégradation de la fertilité des sols et à un accès limité aux intrants. Dans ce contexte, les exploitants doivent gérer les ressources végétales pour trouver un compromis entre alimentation humaine, alimentation animale et retours aux sols. Certaines pratiques de gestion des biomasses peuvent aggraver les phénomènes de dégradation de la fertilité des sols et remettre alors en cause la durabilité des exploitations. L'objectif de cette thèse est de montrer que la diversité des pratiques de gestion des biomasses au sein des exploitations familiales d'agriculture-élevage des hauts plateaux de Madagascar conditionne la durabilité des systèmes en termes de fertilité des sols, de recyclage des éléments nutritifs, de revenus et de sécurité alimentaire. Pour cela, il a été nécessaire de : i) caractériser au préalable la diversité des exploitations familiales d'agriculture-élevage du Vakinankaratra et de comprendre le fonctionnement de ces exploitations mixtes ; ii) étudier les effets des pratiques de gestion des parcelles sur la variabilité de la fertilité des sols des exploitations ; iii) évaluer la durabilité des exploitations d'agriculture-élevage et tester l'impact d'améliorations des pratiques d'alimentation animale, de gestion des effluents et de fertilisation sur la durabilité des exploitation. Quatre exploitations d'agriculture-élevage du Vakinankaratra, sélectionnées à dires d'experts, ont été enquêtées par immersion. Une étude typologique des exploitations d'agriculture-élevage du Vakinankaratra a été effectuée. Des prélèvements de sol ont été effectués pour l'ensemble des parcelles des quatre exploitations d'agriculture-élevage étudiées. Un outil de calcul des flux d'azote au sein des exploitations a été élaboré, puis a été associé aux matrices du Network Analysis afin de générer des indicateurs environnementaux, sociaux et économiques. Cet outil a été utilisé pour simuler les options d'améliorations des pratiques d'alimentation animale, de gestion des effluents et de fertilisation.L'étude typologique a identifié six types d'exploitations d'agriculture-élevage au Vakinankaratra. L'étude du fonctionnement des exploitations sélectionnées a mis en évidence d'une grande diversité des pratiques d'alimentation des animaux, de gestion des effluents d'élevage et de fertilisation. Une hétérogénéité de la fertilité des sols induite par les pratiques de gestion des parcelles a été révélée. Pour les quatre exploitations étudiées, l'amélioration des pratiques d'alimentation du troupeau bovin laitier associée à l'amélioration des pratiques de gestion des effluents d'élevage a permis d'améliorer la durabilité environnementale (efficience azotée globale, recyclage de l'azote, bilan azoté du sol), économique (marge brute agricole) et sociale (autosuffisance alimentaire).Ce travail a permis de caractériser la diversité des exploitations d'agriculture-élevage du Vakinankaratra, la diversité des pratiques et leurs effets sur la fertilité du/des sol. Cette étude s'est avérée être une approche intéressante pour évaluer des options d'amélioration de la durabilité des exploitations d'agriculture-élevage dans un contexte peu documenté. / Mixed crop-livestock systems constitute the backbone of agriculture in developing countries. In highlands of Madagascar, crop–livestock systems are based on rice and cattle. Cattle play a major role in the economy and the social recognition of these smallholder farms. Smallholder farms used to face with low crop productivity related to soil fertility degradation and to low access to inputs. In this context, smallholders have to manage plant resources in order to find a trade-off between food, feed and soil returns. Some biomass management may increase soil fertility degradation and then compromise farms sustainability.The objective of this thesis is to show that the diversity of biomass management on smallholder crop–livestock systems of highlands of Madagascar determines the sustainability of farming systems in terms of soil fertility, nutrients recycling, incomes and food security. For this, it was necessary to: i) characterize the diversity of crop-livestock systems in the region of Vakinankaratra and understand how smallholder farms are managed; ii) study the effects of soil management on the soil variability; iii) assess the farms sustainability and explore improvements of feeding, manure management and fertilization.Four crop-livestock farms of the Vakinankaratra (selected with local experts) were surveyed using participant observation methodology. A typology of crop-livestock farms was performed. Topsoil samples were collected in all plots of the four cases studies. A nitrogen flows calculating tool was developed and has been associated with Network Analysis matrices to generate environmental, social and economic indicators. This tool was used to simulate improvements in feeding, manure management and fertilization.The typology identified six farm types of crop-livestock systems in the Vakinankaratra. The farms study revealed a great diversity of animal feeding practices, manure management and fertilization. Heterogeneity of soil fertility induced by farmer management was shown. For the four case studies, improved feeding practices on dairy combined with improved manure management have increased environmental (farm nitrogen efficiency, nitrogen recycling, soil nitrogen balance), economic (agricultural gross margin) and social (food self-sufficiency) sustainability.This study characterized the diversity of crop-livestock farms of the Vakinankaratra, the diversity of practices and their effects on soil fertility. It proved to be an interesting approach to explore options for improving sustainability of crop-livestock farms in context of data scarcity.

A series of experiments were conducted to investigate how dietary and ruminal factors regulate urea-N recycling in ruminants. In Experiments 1, 2, and 3, urea-N kinetics were measured using 4-d intra-jugular infusions of [15N15N]-urea. In Experiment 1, the objective was to determine how interactions between dietary ruminally-degradable protein (RDP) level and ruminally-fermentable carbohydrate (RFC) may alter urea-N transfer to the gastrointestinal tract (GIT) and the utilization of this recycled urea-N in rapidly-growing lambs fed high N diets. The dietary factors were: 1) dry-rolled barley (DRB) vs. pelleted barley (PB) as the principal source of RFC; and 2) dietary levels of RDP of 60 vs. 70% (% of CP). Nitrogen intake, fecal and urinary N excretion increased as dietary RDP level increased; however, method of barley processing had no effect on N use. Dietary treatment had no effect on urea-N kinetics; however, endogenous production of urea-N (UER) exceeded N intake. For all diets, 0.669 to 0.742 of UER was recycled to the GIT; however, 0.636 to 0.756 of the GER was returned to the ornithine cycle. In Experiment 2, the objective was to delineate the effects of partial defaunation of the rumen on urea-N kinetics in lambs fed low or high N diets. Treatments were: 1) partial defaunation (PDFAUN) vs. faunation (FAUN); and 2) low (10%, LOW) vs. high (15%, HIGH) dietary CP. Linoleic acid-rich sunflower oil was fed as a partially-defaunating agent. Partial defaunation decreased ruminal NH3-N concentrations. The UER and urinary urea-N excretion (UUE) were lower, and the GER tended to be lower in PDFAUN as compared to FAUN lambs; however, as a proportion of UER, GER was higher and the proportion of recycled urea-N that was utilized for anabolism (i.e., UUA) tended to be higher in PDFAUN lambs. The UER, GER and UUE were higher in lambs fed diet HIGH; however, as a proportion of UER, GER and its anabolic use were higher in lambs fed diet LOW. In Experiment 3, the objective was to delineate how, at similar N intakes, interactions between ruminal partial defaunation and altering dietary RFC may alter urea-N kinetics and N metabolism in lambs. Treatments were: 1) PDFAUN vs. FAUN; and 2) DRB vs. PB. Urinary N excretion was lower and retained N was higher in PDFAUN compared to FAUN lambs. The UER was similar across treatments; however, the GER, expressed as absolute amounts or as a proportion of UER, UUA, and microbial N supply were higher in PDFAUN compared to FAUN lambs. As a proportion of UER, GER was higher, whereas UUE was lower in lambs fed PB compared to those fed DRB. In Experiment 4, the objective was to determine the effects of feeding oscillating dietary CP compared to static dietary CP concentration on N retention and in vitro urea flux across ruminal epithelia. Dietary treatments consisted of a medium CP diet (MEDIUM; 12.8% CP) or diets with oscillating CP content (OSC) fed in two different sequences i.e., 2 d of low CP (9.7% CP) followed by 2 d of high CP (16.1% CP; OSC-HIGH) or vice-versa (OSC-LOW). Ruminal epithelial tissues were collected and mounted in Ussing chambers under short-circuit conditions and the serosal-to-mucosal urea flux (Jsm-urea) was measured using 14C-urea. Although N intake was similar, retained N and microbial N supply were greater in lambs fed the OSC diets compared to those fed the MEDIUM diet. The total Jsm-urea was higher in lambs fed the OSC-LOW compared to those fed the OSC-HIGH diet. Across diets, the addition of phloretin (a known specific inhibitor of facilitative urea transporter-B; UT-B) reduced Jsm-urea; however, phloretin-insensitive Jsm-urea was the predominant route for transepithelial urea transfer. In summary, data presented in this thesis provide new insights that the improved N retention typically observed in defaunated ruminants and in ruminants fed oscillating dietary CP concentrations is partly mediated via increased urea-N recycling to the GIT and utilization of recycled urea-N for anabolic purposes.