Made available in DSpace on 2015-03-12T11:55:52Z (GMT). No. of bitstreams: 1 AfranioCA_TESE.pdf: 5802290 bytes, checksum: fd6a3b6955fd8eca343b02a54254a104 (MD5) Previous issue date: 2014-02-24 / The exceeded use of the natural resources required by the modern agriculture has been caused soil impoverishment, soil salinization and soil compaction. The unreasonable use of chemical fertilizers and pesticides causes chemical imbalances in the plant tissues, nutritional losses, taste chances and human health problems. The monocrops are more vulnerable to the pest and disease attacks. The aim of this work were to indicate the better relative planting time of the cowpea bean for the sesame/cowpea bean intercropping based on the evaluation of agronomic, economic, ecological and physiological parameters and to evaluate the viability of the cow urine and cassava wastewater use as alternative fertilizers on the sesame cultivation. In a field essay, when the sesame/cowpea bean was evaluate, the mainly treatments were the single planting of the two cultures and the multiple cropping, with the cowpea bean being planted on the same time, 7, 14 and 21 days after the sesame. The mainly treatments of the second essay were the combined doses of the cow urine (0 and 50 ml) and cassava wastewater (0, 500 and 1000 mL). In the intercrop evaluation significant differences were found between the treatments for the most of the parameters. It was verified that as the sowing of the cowpea bean was retarded in relation to the sesame sowing, the sesame performance increased when the cowpea bean performance decreased. The treatment 7 days balanced the competition relations that occurred between the two crops in the intercrop. The sesame presented little pronounced responses to the different doses of cassava wastewater. The cow urine affected the sesame growth and the growth rates increased with the increasing of the application of the product. The responses of the sesame growth to the cow urine application must be related both the nutritional richness of the product and the presence of growth stimulating substances. The obtained results indicated that in the sesame/cowpea bean intercropping, when the sesame is planted 7 days after the sesame, there is a higher possibility of the net gains to the farmer. Cow urine and cassava wastewater may be used as additional organic fertilizers / A explora??o exacerbada dos recursos demandados pela Agricultura Moderna vem provocando empobrecimento, saliniza??o e compacta??o dos solos. O uso irracional de fertilizantes qu?micos e agrot?xicos tem causado desequil?brio qu?mico nos tecidos vegetais, perdas nutricionais, altera??es no sabor e problemas na sa?de humana. As monoculturas est?o mais sujeitas ao ataque de pragas e doen?as, sendo altamente dependentes de agrot?xicos. Objetivou-se, com este trabalho: (1) indicar a(s) ?poca(s) relativa(s) mais apropriada(s) de plantio do feij?o caupi no cons?rcio com o gergelim a partir da avalia??o de aspectos agron?micos, econ?micos, ecol?gicos e fisiol?gicos e (2) avaliar a viabilidade da utiliza??o de urina de vaca e manipueira como fertilizantes alternativos no cultivo do gergelim. No ensaio de campo, quando o cons?rcio gergelim/feij?o caupi foi avaliado, os tratamentos principais foram os monocultivos das duas culturas e os cultivos consorciados, sendo a Fabacea plantada no mesmo tempo, 7, 14 e 21 dias ap?s a Pedaliaceae. No experimento em vasos, os tratamentos principais constaram de doses combinadas de urina de vaca (0 e 50 mL) e manipueira (0, 500 e 1000 mL). Na avalia??o do cons?rcio, foram verificadas diferen?as significativas entre os tratamentos para a maior parte das vari?veis. Percebeu-se que na medida em que se atrasava a semeadura do feij?o caupi em rela??o ao plantio do gergelim, obtinham-se respostas proporcionalmente mais positivas para a Pedaliaceae, o contr?rio ocorrendo para o feij?o. Destacou-se o tratamento 7 dias como o ponto de equil?brio considerando as rela??es competitivas estabelecidas entre as duas culturas no cons?rcio. O gergelim apresentou respostas pouco pronunciadas ?s diferentes doses isoladas de manipueira. A urina de vaca exerceu efeito sobre o crescimento vegetativo do gergelim, o que se refletiu no aumento das taxas de crescimento em resposta ? aplica??o do produto. As respostas do crescimento do gergelim ? aplica??o da urina de vaca devem estar relacionadas tanto ? riqueza nutricional do produto quanto ? presen?a de subst?ncias estimuladoras do crescimento. Os resultados encontrados sugerem que, no cons?rcio gergelim/feij?o caupi, quando a Fabacea ? plantada 7 dias ap?s o gergelim, h? maior possibilidade de ganhos l?quidos para o produtor e que urina de vaca e manipueira podem ser utilizados como complementos na aduba??o do gergelim

This thesis consists of a study on the Pedagogy of Alternation as a pedagogical method incorporated to the principles of Field Education, and its contribution to the spreading of ecological agriculture practices, through what was experienced at Escola Família Agrícola de Ladeirinhas (EFAL), located in the town of Japoatã, state of Sergipe, Brazil. EFAL is engaged in the education of young children of rural workers, in different times and places: in social-occupational aspects (family, community, and work) and in educational aspects (students go to boarding schools and have technical education for professional development in farming). By means of a qualitative approach, elements of ethnography grounded in hermeneutical phenomenology were used as a way to interpret the day-to-day experiences observed. This research was categorized as a case study. Data were collected by means of various instruments, such as the observation of classes and practical activities, document analysis, field journal entries, photographic record, and semi-structured interviews with students, school monitors, and the families involved. EFAL is part of regional and national networks which articulate the different Family Centers of Education by Alternation and aim at providing and enhancing the mastering of the required knowledge through alternation, and makes up an educational alternative in rural areas. While analyzing the use of the Pedagogy of Alternation in the dissemination of sustainable principles and practices, it became understood that such method, adapted to the various realities of rural areas, enables individuals to have an integral education. Immersed in territories of inequity intensified by the agribusiness, and affected by policies which encourage the use of unsustainable technology resulting from green revolution packages, EFAs make use of principles and instruments that attempt to reinforce the dialogue between the school world and the life world, between theory and practice. The articulation of the data collected and their analysis made way for critical reflections on the times of school, family, the working of the land, and daily routines, and showed that despite the difficulties in the preparation of monitors and administrators for this differentiated pedagogical method, as well as the necessity of self-financing, there is great potential for it to become a method of integral education, based on the restoring of traditional rural worker knowledge. The articulation between such knowledge and that acquired at EFAL makes it possible for rural citizens to think and act towards sustainable rural development. / Essa dissertação consiste no estudo da Pedagogia da Alternância enquanto método pedagógico incorporado nos princípios da Educação do Campo e sua contribuição na difusão de práticas agrícolas de base ecológica, por meio da experiência da Escola Família Agrícola de Ladeirinhas - EFAL, localizada no município de Japoatã, estado de Sergipe. A EFAL atua na formação de jovens, filhos de camponeses, em diferentes tempos e espaços: meio socioprofissional (família, comunidade e trabalho) e meio escolar em regime de internato, na modalidade de educação profissional técnica de nível médio em agropecuária. Por meio de uma abordagem qualitativa, utilizamos elementos da etnografia ancorados na fenomenologia hermenêutica como uma forma de interpretar as experiências cotidianas observadas. Trata-se de uma pesquisa do tipo estudo de caso. Os dados foram coletados por meio de diversos instrumentos, como observações das aulas e experiências práticas, análise documental, anotações em diário de campo, entrevistas semiestruturadas com os estudantes, monitores e famílias envolvidas e registro fotográfico. A EFAL faz parte de redes regionais e nacionais que articulam os diferentes Centros Familiares de Formação por Alternância e que buscam, através da alternância, proporcionar e valorizar o domínio de saberes e se constitui como uma alternativa educacional para o campo. Ao analisar o uso da Pedagogia da Alternância na difusão de princípios e práticas sustentáveis, compreendemos que o método, adaptado as diferentes realidades no campo, possibilita a formação integral do sujeito. Imersos em territórios marcados pela desigualdade, intensificada pelo agronegócio e atingidos pelas políticas de incentivo ao uso das tecnologias insustentáveis advindas de pacotes da revolução verde, as EFAs munem-se de princípios e instrumentos que buscam reforçar o diálogo entre o mundo da escola e o mundo da vida, entre a teoria e prática. A articulação dos dados coletados e suas análises nos permitiram levantar reflexões críticas sobre os tempos escolares, familiares, de trabalhos com a terra e cotidianos, e nos mostraram que apesar das dificuldades na formação de monitores e gestores para esse método pedagógico diferenciado e do financiamento autônomo, existe uma grande capacidade de se tornar um método educativo de formação integral, respaldado no resgate dos conhecimentos tradicionais camponeses. A articulação desses conhecimentos com os aprendidos na EFAL possibilitam proporcionar aos sujeitos do campo a capacidade de refletir e agir para o desenvolvimento rural sustentável.

The availability of small areas for cultivation together with the technical and economic deficiencies often aggravated by socio-cultural aspects, creating the small farms, a scenario likely to farming practices with a high degree of unsustainability. From this contest was held this field study, between September 2008 and October 2009 an agrarian reform settlement aimed at examining different forms of soil management, its potential for improving soil quality and its implications for socioeconomic in small farms. The experimental design was randomized blocks with split plots with four replications. The treatments consisted of plots of crop systems: maize + cowpea (M + FC), maize + Pigeon pea dwarf (M + GA); corn + velvet bean (M + MP) and maize monocrop (MS). The sub-plots by the forms of fertilizer: organic source - turkey litter (AO); Without the addition of nutrients (SA) and mineral source - NPK (AM). We assessed aspects related to grain yield of corn, physical and chemical properties of soil in two layers (0-5 and 5-10 cm depth) and socioeconomic aspects of managements. Water stress led to a negative effect of M + FC on grain yield of maize, which in turn was not affected by M + MP, and were higher in treatments with AM (P <0.05). Cultures GA and MP had the highest intakes of nitrogen (N) via aboveground. The cropping systems showed positive results for bulk density and soil porosity. There was a tendency to decrease in aggregate stability for all systems studied, including the fallow treatment. There was no increase (P <0.05) of soil organic carbon (COT) of the systems studied, only attenuated the decrease of this natural element. Showed an increase (P> 0.05) compared to the initial content of N in the soil, and the consortium M + MP which showed the highest levels in both studied layers. The study also found decreased (P <0.05) in the attributes SMP pH, base saturation, exchangeable potassium content, reflecting the increase (P <0.05) in aluminum saturation. Another aspect observed was the increase (P <0.05) CTCpH7.em both layers. The systems studied showed net negative reflections of the high cost of some inputs and low yields obtained. The demand for labor by the managements of the systems has been affected by sowing cover crops for soil, and the management of these, either by restricting the growth of vegetation or the harvest of the seeds. Although it was short time for consistent evaluations, the results obtained by cropping systems indicate that there are gains in productive aspects, contribution of COT and N, especially in soil physical properties. This condition reflects the possibility of replacing the "conventional" system of cultivation of maize by the systems studied, with gains in sustainability, in many ways. / A disponibilidade de pequenas áreas para cultivo aliada as deficiências técnicas e econômicas, agravadas muitas vezes por aspectos sócio-culturais, cria nas pequenas propriedades, um cenário propenso a práticas agropecuárias com elevado grau de insustentabilidade. A partir deste contesto, foi realizado este estudo de campo, no período de setembro de 2008 e outubro de 2009, num assentamento de reforma agrária objetivando investigar diferentes formas de manejo de solo, seu potencial de melhoria na qualidade do solo e suas implicações sócio-econômicas em pequenas propriedades rurais. O delineamento experimental utilizado foi blocos ao acaso com parcelas subdivididas, com quatro repetições. Os tratamentos foram compostos nas parcelas pelos sistemas de cultivo: Milho + Feijão caupi (M + FC); Milho + Guandu anão (M + GA); Milho + Mucuna preta (M + MP) e Milho em cultivo solteiro (MS). Nas sub-parcelas pelas formas de adubação: Fonte orgânica cama de peru (AO); Sem adição de nutrientes (SA) e Fonte mineral NPK (AM). Foram avaliados aspectos relacionados ao rendimento de grãos da cultura do milho, atributos físicos e químicos do solo, em duas camadas (0-5 e 5-10 cm de profundidade) e aspectos socioeconômicos dos manejos. O estresse hídrico conduziu a um efeito negativo do M+ FC no rendimento de grãos de milho, que por sua vez não foi afetado por M + MP, e foram superiores nos tratamentos com AM (P<0,05). As culturas GA e MP apresentaram os maiores aportes de nitrogênio (N) via fitomassa aérea. Os sistemas de cultivos apresentaram resultados positivos em relação à densidade volumétrica do solo e porosidade. Observou-se a tendência a diminuição da estabilidade dos agregados para todos os sistemas estudados, inclusive no tratamento em pousio. Não houve incremento (P<0,05) de Carbono orgânico no solo (COT) dos sistemas estudados, apenas atenuaram a diminuição natural deste elemento. Observou-se incremento (P>0,05) em relação aos teores iniciais de N no solo, sendo o consórcio M + MP o que apresentou os maiores teores em ambas camadas estudadas. Também foi constatado diminuição (P<0,05) nos atributos pH SMP, saturação por bases, teor de potássio trocável, com reflexos no acréscimo (P<0,05) da saturação por alumínio. Outro aspecto observado foi o aumento (P<0,05) da CTCpH7.em ambas camadas. Os sistemas estudados apresentaram receita líquida negativa, reflexos do alto custo de alguns insumos e baixas produtividades obtidas. A demanda de mão de obra por parte dos manejos dos sistemas foi impactada pela semeadura das plantas de cobertura de solo, e pelo manejo dessas, seja pela contenção do crescimento vegetativo ou pela colheita das sementes. Embora tenha sido curto espaço de tempo para avaliações consistentes, os resultados obtidos pelos sistemas de cultivo indicam haver ganhos, em aspectos produtivos, aporte de COT e N, sobretudo, em atributos físicos do solo. Esta condição reflete na possibilidade de substituir o sistema convencional de cultivo do milho pelos sistemas estudados, com ganhos em sustentabilidade, sob vários aspectos.

Promouvoir le service de contrôle biologique des bio-agresseurs des cultures nécessite de comprendre le fonctionnement des populations d’ennemis naturels dans des mosaïques agricoles qui sont hétérogènes et dynamiques. Cette thèse porte sur l’étude des déterminants de l’abondance des carabes impliqués dans la régulation des adventices via la consommation de leurs graines. L’analyse des variations d’abondance des espèces à une échelle nationale nous a permis d’évaluer le rôle relatif des facteurs locaux et paysagers et de mettre en évidence le rôle important de la proportion de colza et de prairie dans le paysage sur l’abondance de carabes consommateurs de graines dans les parcelles cultivées. Le suivi expérimental de la composition des communautés de carabes ainsi que du statut nutritionnel et des mouvements de plusieurs espèces dans des dispositifs colza/blé et colza/bordure pérenne sur l’ensemble de la période d’activité des carabes nous a permis de mettre en évidence que (i) les carabes répondent l’hétérogénéité de cette mosaïque agricole (type de culture, qualité de l’habitat au sein d’un même type de culture), avec des réponses souvent spécifiques (ii) que le colza d’hiver joue un rôle important dans le fonctionnement des populations de carabes consommateurs de graines du fait de sa haute qualité d’habitat pour ces espèces, (iii) que la variation de la qualité d’habitat peut jouer sur le mouvement des carabes vers l’habitat adjacent et (iv) que la présence d’une bordure pérenne au voisinage d’une culture favorise le maintien et le fonctionnement de plusieurs espèces consommatrices de graines d’adventices dans la mosaïque agricole. / Promoting biological pest control in crops requires to understand the functioning of natural enemies in heterogeneous and dynamic agricultural mosaics. This thesis focuses on the study of the determinants that influence the abundance of ground beetles involved in the regulation of weeds via the consumption of their seeds. In an analysis of the variations of species abundance at a national scale we identified the respective role of local and landscape factors and showed that oilseed rape and grassland proportions in the landscape were key determinants of the abundance of carabid species in cultivated fields. We then studied carabid communities through combined measured of their abundance, nutritional status and between-habitat movements, during an entire cropping season, in pairs of habitats consisting in winter oilseed rape fields with either a crop (winter cereal fields) or a semi-natural habitat (grassy field margins) as adjacent habitat. We demonstrated that (i) ground beetles respond to the heterogeneity of arable mosaic (crop type, habitat quality within the same crop type), often with specific responses, (ii) winter oilseed rape plays an important role in the functioning of weed seed-eating carabid species due to its high habitat quality, (iii) variations in habitat quality can influence the movement of beetles to the adjacent habitat and (iv) the presence of a grassy field margin in the vicinity of a crop promotes the maintenance and functioning of several species in arable mosaics.

L’agroécologie offre de nouvelles perspectives à l’agriculture et ainsi une voie vers une gestion alternative des adventices à travers différents mécanismes écosystémiques de régulation. La prédation des graines est l’un d’entre eux et son étude fait depuis peu l’objet de recherches visant à approfondir les connaissances relatives à ce processus. Ce travail de thèse cherche (i) à caractériser la prédation des graines d’adventices, les principaux prédateurs Carabidæ et la ressource en graines disponible à l’échelle locale dans une culture courante (blé d’hiver); (ii) à étudier précisément les profils de prédation des principaux prédateurs et les interactions entre les composantes biologiques impliquées; (iii) à introduire des éléments de réponse relatifs au potentiel de régulation des communautés d’adventices via la prédation des graines par les Carabidæ. Des approches complémentaires ont été utilisées afin de répondre à ces problématiques : un suivi à long terme de terrain, des tests de préférences en laboratoire, une simulation des taux de prédation à long terme à partir des données ponctuelles ainsi qu’une étude à grande échelle des prédateurs et du stock de graines.L’étude des variations spatio-temporelles de la prédation via un dispositif de terrain durant la période d’activité des prédateurs a mis en évidence trois pics de prédation dont un seul correspond au pic de prédateurs (avant la moisson). La ressource en graines disponible au sol est quant à elle présente majoritairement lors du premier et du dernier pic de prédation, et aucune augmentation de ressource n’a été observée après moisson. Ces dynamiques semblent stables, restant valables indépendamment de l’échelle spatiale (intra ou interchamp) et des espèces carabiques et adventices étudiées.Toutes les espèces adventices ne font pas l’objet de la même intensité de prédation, et de manière générale, les graines de petites tailles ont été préférentiellement prédatées, au champ comme en test de cafétéria au laboratoire. Cependant, les espèces carabiques semblent avoir des profils de prédation différents entre guildes trophiques, ainsi qu’au sein d’une même guilde. De ce fait, la prise en compte des préférences de consommation dans l’étude des relations prédation-prédateurs tout comme la combinaison des données prédateurs et graines disponibles permet parfois d’améliorer les corrélations, notamment pour les espèces les plus prédatées.Une simulation de la prédation annuelle suggère des pertes en graines dues à la prédation non négligeables, pouvant atteindre pour l’espèce la plus prédatée, ici Viola arvensis, jusqu’à près de 80% des graines disponibles. En parallèle, une étude à grande échelle de l’évolution du stock de graines montre une corrélation négative entre prédateurs et évolution de la banque de graines, suggérant une régulation de la banque de graines via les prédateurs carabiques.L’ensemble de ces résultats suggère que prendre en compte la diversité fonctionnelle des communautés de prédateurs et d’adventices est un point important dans la compréhension de la prédation compte tenu des préférences de consommation des prédateurs et des dynamiques temporelles des différents acteurs. / Agroecology gives evidence of new perspectives in agriculture, and open doors for alternative weed management approaches through different regulation mechanisms. Seed predation is one of them, and the interest is growing to deepen knowledge, relative to this process. This Phd work aims (i) to describe weed seed predation, the dominant carabid predators and the available resource at a local scale in a common crop (winter wheat); (ii) to study predation profiles of main predators, and the pair-wise correlations between the biological components of the system; (iii) to bring new insights regarding potential regulation of weed communities, through seed predation by carabid beetles. Complementary approaches have been used to tackle these aspects: a long-term field study, some cafeteria tests, a simulation of annual predation rates from point-to-point estimates, as well as a large-scale field study of predators and seed resource. Study of spatio-temporal variations of predation, via field experiment during the main activity period of carabids, has shown a three-peak pattern, one of them corresponding to predators’ peak, just before harvest. Weed resource available on soil surface is high in the first and last peaks of predation, and no increase of resource has been observed after harvest. These dynamics are independent of the spatial scale (intra or inter-field) and carabid species. The different weed species do not show the same levels of predation, and, as a whole, small-seeded species are more eaten, in both lab and field conditions. However, carabids have different preferences among trophic guilds, but also within a same guild. Therefore, in order to study predation, it is essential to combine predators and seed data, as well as considering preferences of predators. A simulation of annual seed predation shows important rates of seed loss, reaching up to 80% for the most predated species, V.arvensis. A large scale study of seed bank shows a negative correlation between predators’ activity density and seed bank change, assuming that there is a seed bank regulation by carabid predators. All together, these results show that functional diversity of predators’ and weeds’ communities is a key factor in understanding predation.

Les carabes et les araignées sont des auxiliaires généralistes susceptibles d'exercer un contrôle efficace des ravageurs des cultures. La structure et composition de leurs communautés, ainsi que l'efficacité du contrôle biologique, dépendent de l'hétérogénéité des paysages, et en particulier de la présence d'habitats semi-naturels. Mais le rôle de la mosaïque agricole, susceptible de présenter une forte hétérogénéité dans l'espace et dans le temps, reste aujourd'hui peu connu. L'objectif de ce travail a été d'évaluer les effets de l'hétérogénéité spatiale et temporelle des paysages agricoles sur des auxiliaires généralistes et sur le potentiel de contrôle biologique. Nous avons échantillonné les communautés de carabes et d'araignées dans des parcelles de céréales, et estimé le potentiel de prédation par des pucerons sentinelles collés sur des cartes de prédation. Nous avons caractérisé l'hétérogénéité spatiale des paysages autour des parcelles de céréales par le pourcentage d'éléments boisés et la longueur du réseau de haies, la taille moyenne des parcelles agricoles, et la diversité des cultures. Nous avons également mis au point quatre nouvelles métriques qui synthétisent différents aspects de l'hétérogénéité temporelle interannuelle des surfaces cultivées. Nos résultats montrent qu'au printemps les araignées sont plus abondantes dans les parcelles de céréales situées dans des paysages composés de petites parcelles. Au début de l'été, ces paysages favorisent également les taux de prédation de pucerons mesurés par les cartes de prédation, et l'abondance des carabes qui se reproduisent au printemps et qui hivernent en tant qu'adultes dans des habitats semi-naturels. Les carabes qui hivernent dans le sol des parcelles au stade larvaire et se reproduisent à l'automne sont quant à eux favorisés par la diversité des cultures dans le paysage. Nos résultats montrent enfin que l'hétérogénéité temporelle de la mosaïque agricole - caractérisée par les changements de la diversité de cultures au cours des cinq dernières années - favorise elle aussi certaines espèces de carabes communément rencontrées dans les parcelles agricoles (Poecilus cupreus ou Pterostichus melanarius) et susceptibles de jouer un rôle important en tant qu'auxiliaires. Ces résultats mettent en avant le rôle complémentaire des bordures de champs non cultivées et de la mosaïque des cultures pour différents groupes d'auxiliaires, et soulignent l'importance de prendre en compte l'hétérogénéité spatiale et temporelle des surfaces cultivées dans l'étude de la biodiversité des paysages agricoles. Dans le contexte de réduction des produits phytosanitaires, nos résultats suggèrent que des paysages présentant une diversité de cultures importante variable dans le temps, et des petites parcelles qui favorisent l'intrication entre les habitats semi-naturels et les cultures, sont susceptibles de favoriser les auxiliaires généralistes ainsi que le potentiel de contrôle biologique des ravageurs. / In the context of reducing pesticide use, the potential role of some arthropod groups as pest natural enemies provides them an ecological and economic interest. In particular, ground beetles and spiders are generalist predators likely to be effective biocontrol agents. Previous studies have shown that the structure and composition of their communities, as well as the effectiveness of biological control, are influenced by landscape heterogeneity, and in particular by the presence of semi-natural habitats. However, the role of the crop mosaic, which can be highly heterogeneous in space and time, have been little considered. The main objective of our study was to determine the influences of spatial and temporal heterogeneity of agricultural landscapes on generalist natural enemies and the potential for biological pest control. We sampled carabid and spider communities in winter cereal fields, and estimated biological control potential using sentinel aphids glued on predation cards. We characterized the spatial heterogeneity of the landscapes around each cereal field by 1) the amount of wooded habitats and the length of the hedgerow network, 2) the average size of the agricultural fields, and 3) crop diversity. We also proposed four new metrics that synthesize different aspects of the multi-year temporal heterogeneity of cropped areas. Our results show that in spring, landscapes characterized by small fields, and therefore by a high density of non-cropped field margins, promote spiders abundance in cereal fields. In early summer, landscapes with small fields also promote aphid predation rates and the abundance of carabid spring breeders, which overwinter as adults in semi-natural habitats. Crop diversity promotes the abundance of carabids overwintering in soils of arable fields and breeding in autumn. Our results also show that the temporal heterogeneity of the crop mosaic - characterized among other things by the changes in crop diversity over a five year period - benefits some carabid species commonly found in agricultural landscapes (such as Poecilus cupreus and Pterostichus melanarius) which are likely to play an important role as pest natural enemies. These results highlight the complementary role of the crop mosaic and the non-cropped field borders for generalist natural enemies, and show the importance of taking into account the spatial and temporal heterogeneity of the cultivated area in further ecological studies on biodiversity in agricultural landscapes. In the context of reducing pesticide use, our results suggest that landscapes with 1) a high crop diversity that change over time, and 2) small fields that promote the interspersion between crops and semi-natural habitats, are likely to promote generalist natural enemies and biological pest control.

Malgré de nombreux travaux menés, les mécanismes d’assemblage des espèces adventices en communautés restent à identifier. Or cette compréhension est cruciale pour concevoir des stratégies de gestion permettant de préserver la biodiversité des plantes adventices tout en maintenant la production agricole. Ce travail de thèse avait pour objectif de comprendre les mécanismes à la base de la structure fonctionnelle des plantes adventices dans les agroécosystèmes. Trois axes de recherche ont été menés. Le premier axe a permis de proposer un cadre d’analyse général des mécanismes d’assemblage à l’origine de la diversité fonctionnelle dans le cadre de l’approche dites modèle nul. Le second axe, basé sur des analyses empiriques, a mis en évidence (1) le rôle prépondérant des processus stochastiques dans l’assemblage des espèces adventices entre types de culture dans les parcelles agricoles et (2) le maintien d’une flore fonctionnellement plus diversifiée due à la coexistence de stratégies de tolérance et d’évitement de l’ombrage en interface, compartiment adjacent au champ. Enfin, dans le troisième axe, nous avons montré expérimentalement que la compétition entre la plante cultivée et la communauté adventice promeut une unique stratégie d’évitement de l’ombrage se traduisant, à l’échelle individuelle, par un mimétisme fonctionnel des traits de la plante cultivée par les plantes adventices les plus performantes. Ainsi, processus stochastiques et déterministes influencent l’assemblage des communautés adventices, et ce à différentes échelles spatiotemporelles. / Despite numerous studies, weed community assembly mechanisms still remain unidentified. However, a better understanding of these mechanisms is crucial to design management strategies promoting weed biodiversity while maintaining agricultural production. The aim of this PhD was to understand the mechanisms underlying the functional structure of weeds in agroecosystems.Three research axes were conducted. The first axis enabled to propose a general analytical framework of community assembly in the context of a statistical approach called null model. The second axis, based on empirical analyses, revealed (1) the predominant role of stochastic processes in weed community assembly between crop types and (2) the coexistence of two, shade-tolerance and shade-avoidance, ecological strategies, thus explaining the higher functional diversity observed in crop edge, a field element adjacent to the field. Finally, on the third axis, based on experimentation, we have shown that the competition between the crop and the weed community promotes a unique shade-avoidance strategy resulting on a functional mimicry of the crop by the most successful weed plants. Thus, both stochastic and deterministic processes influence weed community assembly, besides at different spatial and temporal scales.

L’intégration culture – élevage à l’échelle territoire représente une voie pour améliorer le fonctionnement métabolique et les services écosystémiques fournis par les systèmes agricoles, malgré les contraintes de spécialisation des exploitations. Cette thèse propose une méthodologie de conception de systèmes culture – élevage au niveau du territoire, dans une démarche participative structurée en trois grandes étapes : diagnostic des enjeux, conception d’options techniques et organisationnelles, évaluation multicritère. Chaque étape est outillée par un cadre conceptuel et une grille d’évaluation multicritère adaptée aux dispositifs de terrain menés sur le bassin versant de l’Aveyron. Les scénarios construits présentent deux modèles de l’intégration culture – élevage : une « filière territorialisée » pour la production de luzerne dans les systèmes de culture de l’aval du bassin à destination des élevages de l’amont, un « collectif d’agriculteurs bio » échangeant directement de la luzerne, des méteils et du fumier dans des groupes locaux. Chaque scénario présente des performances de durabilité améliorées et pourraient être complémentaires pour le changement de pratiques sur le territoire. La méthodologie développée permet la conception multi-niveaux et multi-domaines de scénarios d’intégration, et pourrait être renforcée par une évaluation quantitative des bénéfices attendus et des coûts de coordination entre acteurs. / Crop-livestock integration at territory level may be a pathway to impove metabolic functions and delivery of ecosystem services in agricultural systems, overcoming the constraints of farm specialization. This thesis builds on a methodology of participatory design of integrated crop-livestock systems at territory level in three steps: diagnosis of issues, design of technical and organizational options for change, multicriteria assessment. Each step is supported with a conceptual framework and a multicriteria grid adapted to the case study in Aveyron river basin. The designed scenarios show two approaches of crop –livestock integration: the introduction of alfalfa in downstream cropping systems sold to upstream livestock systems through a local supply chain and the direct exchanges of alfalfa, cereal-legume mixtures and animal manure in local groups of organic farmers. Both scenario present improved sustainability performances and could be complementary to initiate more sustainable practices in local farming systems. The methodology allows designing multi-level and multi-domain scenarios of crop-livestock integration. It could be improved with models for quantitative assessment of benefits and coordination costs among stakeholders.

La recherche d’une agriculture durable et respectueuse de l’environnement passe par une réduction de l’usage d’intrants de synthèse. L’agroécologie cherche à utiliser les interactions entre les organismes de l’agroécosystème pour optimiser son fonctionnement, comme la régulation naturelle des bioagresseurs. C’est dans cette optique que s’inscrit ce travail de thèse qui étudie l’effet de la fertilisation des cultures sur les épidémies de pathogènes foliaires fongiques des cultures. De plus, nous étudions l’évolution des pathogènes face à des scénarios de fertilisation. Cela questionne la durabilité des pratiques culturales qui participent à la régulation les épidémies. Pour répondre à ces questions, nous avons adopté une démarche de modélisation qui permet de simuler l’effet de différents scénarios de fertilisation. Le point de départ et l’originalité de notre démarche a été de considérer le système hôte-pathogène comme un système ressource-consommateur et d’y appliquer des concepts de l'écologie évolutive pour répondre à ces questions agronomiques. Dans les deux modèles construits durant cette thèse, la fertilisation influence directement la quantité de ressources disponible pour le pathogène. Nous nous y concentrons sur un trait d'histoire de vie du pathogène, la période de latence (durée séparant l'infection du début de la sporulation), qui correspond à la durée minimale d'un cycle infectieux et qui, conditionne la stratégie d'allocation des ressources du pathogène. La latence détermine en effet la quantité de ressource qui sera allouée à la croissance du mycélium (donc sa taille à maturité) et celle qui sera ensuite allouée à la sporulation (en relation avec sa taille). Les modèles développés permettent d'étudier les réponses épidémiologique et évolutive des pathogènes foliaires fongiques à la fertilisation des cultures, avec comme référence le système Blé d'hiver/Rouille brune. Nous avons considéré différentes échelles dans ce travail : depuis la lésion où le pathogène se nourrit directement sur son hôte, jusqu’à la parcelle où se développent les épidémies et au paysage où les flux de spores entre les parcelles sont source d’extension des épidémies dans l’agroécosystème. Un premier modèle, à l'intersection des modèles épidémiologiques "SEIR" et des modèles de populations structurées, couvre les échelles de la lésion à celles de l’épidémie et de la parcelle. Le second modèle, à l'intersection des modèles SEIR et des modèles spatiaux d'épidémiologie du paysage, couvre les échelles de la parcelle au paysage agricole. Nous étudions les dynamiques épidémiologiques et évolutives, en comparant des concepts de fitness empiriques et d’invasion. Nous montrons que la fertilisation des cultures, en déterminant la dynamique des ressources disponibles pour les pathogènes, impacte fortement les épidémies. Nos modèles prédisent que la latence des pathogènes évolue en réponse à des compromis écologiques variés, d’une part pour optimiser l’allocation des ressources au niveau des feuilles, mais également pour gagner la course face à la croissance du couvert. La fertilisation, en changeant les concentrations de métabolites foliaires et les dynamiques de croissance du couvert, impacte donc épidémies et réponses évolutives de la latence des pathogènes. A l’échelle du paysage, l’introduction de pratiques variées de fertilisation dans un paysage préalablement homogène pourrait permettre de réduire les épidémies. Cependant, notre modèle prédit une durée limitée de cet effet du fait de l’évolution et de la diversification des pathogènes dans un paysage hétérogène. Ce travail ouvre la voie à des travaux sur l’effet et la durabilité des pratiques pour réguler les épidémies dans l’agroécosystème. Enfin, nous montrons par un travail de méta-analyse qu’il existe une relation forte entre type trophique et latence du pathogène, suggérant que les différents types de pathogènes répondront différemment à des scénarios de réduction de fertilisation / The quest for a sustainable agriculture requires a reduction in the use of synthetic inputs. In this perspective, agroecology seeks to use interactions between organisms in the agroecosystem to replace inputs by ecosystem services, such as the natural regulation of pests and diseases. In this context, this thesis studies the effect of crop fertilization on epidemics of crop fungal foliar pathogens. We also take into account the evolution of these pathogens in response to fertilization scenarios. This allows us to study the sustainability of agricultural practices that contribute to the regulation of epidemics. To answer these questions, we adopted a modelling approach that simulates the effect of different fertilization scenarios. The starting point and originality of our approach was to consider the pathosystem as a consumer-resource system and to use concepts of evolutionary ecology to answer the abovementioned agronomic questions. In the two models developed in this thesis, fertilization directly determines the quantity of resources available for the pathogen. We focus on one of the pathogen's life history traits, the latent period (time period between infection and the onset of sporulating lesions), which corresponds to the minimum duration of an infectious cycle and constrains the pathogen's resource allocation strategy. The latent period determines the amount of resource that will be allocated to either growth of mycelium (and therefore to pathogen size at maturity) or to sporulation (proportional to the pathogen’s size). The models we developed make it possible to study the epidemiological and evolutionary responses of fungal foliar pathogens to crop fertilization. We parameterized our models according to our biological knowledge of the wheat-rust pathosystem. Our modelling work encompasses different spatial and temporal scales: from the lesion where the pathogen feeds directly on its host, to the field and the landscape where the spores that flow between fields are the source of epidemics in the agroecosystem. The first model, at the intersection of the "SEIR" epidemiological models and structured population models, covers the scales of a lesion, the crop canopy and the field. The second model, at the intersection of SEIR and spatial landscape epidemiology models, covers the scales of the field and the agricultural landscape. We study epidemiological and evolutionary dynamics of pathogen populations by comparing empirical and invasion fitness concepts. We show that crop fertilization, by determining the dynamics of available resources for pathogens, has a strong impact on foliar fungal epidemics. Our models predict that pathogen latent period evolves in response to various ecological trade-offs; on the one hand to optimize resources allocation at the leaf scale, on the other hand to win the race against canopy growth. By changing the leaf metabolite content and the rate of canopy growth, fertilization therefore impacts both epidemics and evolutionary responses of pathogen latent period. At the landscape scale, the introduction of various fertilization practices in a previously homogeneous landscape could help to partially regulate epidemics. However, our model predicts that the beneficial effects of heterogeneity will vanish due to the evolution and diversification of pathogens in heterogeneous landscapes. This work sets the stage for further work on the effect and sustainability of agricultural practices on the regulation of crop epidemics in agroecosystems. Finally, by performing a meta-analysis, we bring out a strong relation between pathogen trophic type and latent period, suggesting that different trophic types of pathogens will respond differently to decreasing fertilization scenarios

Lo scopo della tesi di dottorato è comprendere gli effetti dell'adozione degli approcci agroecologici sul Sustainable Livelihood Framework dei piccoli agricoltori. Sono state adottate tre metodologie di ricerca, revisione della letteratura, meta-analisi e caso di studio, al fine di valutare i benefici derivanti dall'attuazione degli approcci agroecologici sul capitale umano, sociale, naturale, finanziario e fisico. I risultati della tesi hanno mostrato come l’adozione dei sistemi agroecologici possono migliorare i mezzi di sussistenza dei piccoli agricoltori, senza che si verifichino trade-off su una serie di indicatori socio-economici e ambientali selezionati. La tesi evidenzia come i metodi agroecologici possano essere considerati uno strumento praticabile ed efficace per promuovere l’Obiettivo di Sviluppo Sostenibile 1 "Porre fine ad ogni forma di povertà nel mondo" e l’Obiettivo di Sviluppo Sostenibile 2 "Porre fine alla fame, raggiungere la sicurezza alimentare, migliorare la nutrizione e promuovere un’agricoltura sostenibile", in particolare per i piccoli agricoltori con scarse risorse nei paesi in via di sviluppo. / The purpose of the PhD thesis is to understand the effects of the adoption of agroecological approaches, both systems and practices, on the Sustainable Livelihood Framework of smallholder farmers. Three research methodologies, literature review, meta-analysis and case study, have been adopted in order to assess the benefits derived from implementing agroecological approaches on human, social, natural, financial and physical capitals. The results of the thesis have contributed to building evidence which demonstrates that agroecological approaches can improve the livelihood of smallholders farmers, without any trade-offs occurring in a wide range of socio-economic and environmental indicators. The thesis highlights that agroecological methods can be considered as a viable and effective tool to promote SDG1 “End poverty in all its forms everywhere” and SDG2 “End hunger, achieve food security and improved nutrition and promote sustainable agriculture”, especially for poor-resource farmers in developing countries.