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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Percepção de pequenos e médios produtores rurais sobre a tecnologia Integração Lavoura-Pecuária-Floresta (iLPF) no município de Ipameri - GO / Perception of small and medium-sized farmers on the integration technology Crop-Livestock-Forestry (iLPF) in the city of Ipameri - GO

Sueli Aparecida de Oliveira 06 May 2016 (has links)
As práticas agrícolas, muito além de processos estritamente ecológicos, constituem processos sociais. Simplificações na dinâmica ecológica, impostas pela artificialização dos sistemas agrícolas, tem causado desequilíbrios entre produção e diversidade de espécies. A utilização de modernas tecnologias de manejo agrícola, desenvolvidas com o intuito de restabelecer o funcionamento de agrossistemas complexos e facilitar mecanismos de autoregulação do ambiente, estão amplamente conectadas a questões socioeconômicas. Concebidas com o propósito de conservar e ampliar a biodiversidade, facilitar a ciclagem de nutrientes, assim como diminuir impactos ao solo (tais como erodibilidade e compactação) além de, entre outros efeitos, preservar a umidade dos solos e propiciar microclima mais estável e ameno, as tecnologias de integração agropecuária e florestal tem sido implementadas em diferentes regiões do mundo. Pesquisas tem sido conduzidas quanto às práticas de implementação adequadas a cada ecossistema e às especificidades locais, com a expectativa de obtenção de resultados satisfatórios a partir das perspectivas ecológica, agronômica, econômica e social. Identificar e avaliar o grau de identificação dos pequenos e médios produtores rurais do município de Ipameri, sudeste de Goiás, com formas de produção agrícola diversificadas e integradas, bem como a viabilidade de utilização destas tecnologias em seu cotidiano, são os propósitos desta pesquisa. Buscou-se compreender, a partir da perspectiva destes atores sociais, as implicações dos efeitos decorrentes de variáveis econômicas, sociais, ambientais e simbólicas inerentes às práticas agronômicas eleitas por estes produtores, para condução de suas atividades e expressão de seus valores, preceitos, tradições e estilos de organização social. Concluiu-se que os sistemas integrados constituem alternativas para recuperação de áreas de pastagens degradas e da paisagem, representam oportunidades de geração de empregos, diversificação de renda para micro, pequenos e médios produtores locais. A despeito das dificuldades elencadas pelos interagentes da pesquisa para sua implementação, constitui-se em uma estratégia compreendida como viável e de interesse para os potenciais usuários / Agricultural practices, beyond strictly ecological processes, are social processes. Simplifications in the ecological dynamics imposed by the artificiality of agricultural systems, has caused imbalances between production and species diversity. The use of modern farm management technologies developed in order to restore the functioning of complex agrosystems and facilitate environmental autoregulation mechanisms are widely connected to socio-economic issues. Designed in order to build and expand biodiversity, facilitate nutrient cycling, as well as to reduce impacts to the soil (such as erodibility and compression) besides other effects, to preserve the moisture of the soil and provide more stable and mild microclimate, the agricultural and forestry integration technologies have been implemented in different regions of the world. Researches have been conducted on appropriate implementation practices for every ecosystem and to local conditions, with the expectation of obtaining satisfactory results from the ecological, agronomic, economic and social perspectives. Identify and assess the degree of identification of small and medium farmers in the municipality of Ipameri, southeast of Goiás, with forms of diversified and integrated farming as well as the feasibility of using these technologies in their daily lives, are the purposes of this research. We seek to understand, from the perspective of these social actors, the implications of the effects of economic, social, environmental and symbolic variables inherent to agronomic practices elected by these producers to conduct their activities and to express their values, principles, traditions and styles of social organization. It was concluded that integrated systems constitute alternatives for recovery of degraded areas of pastures and landscape, representing opportunities for job creation, diversification of incomes for micro, small and medium local producers. Despite the difficulties listed by interactors, its implementation is a strategy understood as feasible and of interest to potential users
62

Capital sol et arrangements institutionnels dans les agrosystèmes du Nord-Cameroun / Soil Capital and institutional arrangements in North Cameroon

Balarabe, Oumarou 07 December 2012 (has links)
Dans un contexte de dégradation des ressources naturelles agricoles, notre étude se propose d'élaborer un concept de capital sol permettant de réexaminer l'analyse économique des sols, en intégrant l'ensemble des services fournis par cet écosystème. Un retour sur les différents cadres d'analyse en agronomie et en sciences environnementales a permis de redéfinir les différentes perspectives associées à l'usage des sols. Une revue de la littérature sur les modèles de l'érosion et de la conservation des sols a été effectuée, et a permis de jeter les bases d'un modèle bio-économique en contrôle optimal du capital sol, basé sur la matière organique du sol et les engrais minéraux. L'étude des états stationnaires associés aux différents régimes a mis en évidence l'importance de la dynamique des stocks de matière organique, ainsi que les apports d'engrais minéraux. Ainsi, en fonction de la vitesse de minéralisation de la matière organique, les régimes miniers atténués (par la restitution de la matière organique) ou bien minier compensé (par des apports d'engrais minéraux) sont stationnaires. Les résultats obtenus par l'estimation économétrique du capital sol par une fonction de production de type translog, à partir des données expérimentales en panel obtenues au Nord-Cameroun, a permis de confirmer le poids de la matière organique et des engrais minéraux. L'estimation des élasticités des facteurs « quantité de mulch » et « quantité d'engrais apporté » a également révélé qu'elles sont négatives à leur valeur minimale, et positive au delà. De même, ces deux facteurs sont substituables à leur valeur minimale, et complémentaires au delà de cette valeur, pour maintenir un stock de capital sol identique. L'analyse des droits de propriété liés au capital sol dans le contexte du Nord-Cameroun a révélé que l'une des contraintes les plus importantes concerne la dissociation entre les droits d'exclusion et les droits de gestion, réduisant de fait l'incitation à investir pour le capital sol. L'étude suggère la prise en compte de l'innovation institutionnelle complémentaire, et propose une nouvelle typologie des innovations basée sur la proportion des deux types d'innovations (technologique et institutionnelle) nécessaires pour maintenir le capital sol. Enfin, l'étude a permis de discuter les principaux instruments de politiques publiques à mesure d'assurer la convergence entre l'optimum privé et l'optimum social. Ces mesures concernent une meilleure définition des droits de propriété, les incitations économiques pour suppléer à la défaillance des marchés, l'action collective pour la définition des arrangements institutionnels endogènes et le paiement et les marchés des services écosystémiques liés au capital sol. / Within a global context of agricultural natural resources degradation, our study aims at elaborating a soil capital concept, which will help renewing soil economic analysis by considering overall ecosystem services provided. A feedback analysis on agronomic and environmental issues related to soil made it possible to clarify different perspectives associated to soil use. Additional litterature review on soil erosion and conservation models helped to lay the foundation of an optimal control model of soil capital, based on organic matter return to soil, and mineral fertilizer application rate. Steady state conditions associated to different soil capital regimes revealed the importance of organic matter stocks, as well as mineral fertilizer in soil capital dynamics. According to organic mineralization rate, attenuated (by organic matter restitution) mining regime, and compensated (by fertiliser application) mining regime of soil capital appeared to be steady state regimes. Results from econometric modelling through translog production function based on 7 years experimental panel data in Northern Cameroon helped confirming organic matter and fertiliser importance in soil capital asset. Production elasticity of factors « mulch quantity » and « fertilizer quantity » revealed that elasticities are negative around minimal values, and positive at medium and maximum values of soil capital. Also, it appeared that these factors are substitutes at minimum value and complementary at medium and maximum value of soil capital. Property rights analysis on soil capital in Northern Cameroon revealed that dissociation between holders or exclusion rights and management rights is among most important constraints in soil capital investment incentive. The study also suggested to take into account complementary institutional innovations, and proposed a specific innovation's typology, according to relative dimensions of technical and institutional innovations on soil capital. Finally, the study discussed the main tools of public policy enabling to reconciliate private and social optimum in soil capital. These include suitable property rights definition, economic incentives to supplement market failures, collective action and paiement and markets for ecosystem services.
63

Approche pragmatiste de l'accompagnement d'une transition agroécologique : une recherche action avec une association d'éleveurs et conseillers dans le rayon de Roquefort / A pragmatist approach to support agroecological transition : action research with a farmers and advisers association in the Roquefort area

Lacombe, Camille 29 November 2018 (has links)
Ce travail de thèse explore les aspects organisationnels de l’accompagnement local de la transition agroécologique. Cet accompagnement nécessite d’articuler différents processus individuels et collectifs de transformation des activités de la production et du développement agricole. En construisant un dispositif de recherche-action au sein d’un projet de transition agroécologique porté par une association d’éleveurs et conseillers dans le rayon de Roquefort, nous mettons en oeuvre avec eux une forme d’expérimentation sociale qui nous permet de comprendre le problème de l’accompagnement de la transition à la fois sur le plan théorique et pratique. Dans notre cas, l’articulation des transformations individuelles et collectives a été permise par un travail de co-conception entre éleveurs et conseillers des outils de l’accompagnement des changements dans les fermes. Ce processus a permis de débattre de la diversité des modèles agricoles et des représentations des acteurs de la transition agroécologique au sein du groupe, ainsi que d’engager conjointement éleveurs et conseillers dans la transformation de leurs pratiques. Ces transformations ont été d'autant plus facilitées que la coconception a été envisagée comme un processus dialogique entre conception et expérimentation dans différentes situations réelles d’usage dans les fermes. A l’issue de ce travail, nous proposons une approche pragmatiste pour accompagner localement la transition agroécologique / We explore in this research the organizational dimensions of agroecological transition and the ways to support it locally. The support of agroecological transition requires connecting differentprocesses of individual and collective transformations of agricultural development and production activities. We design a device for action reseach within an agroecological transition project, carriedby a farmers and advisers association in the Roquefort area. We implement with them a social experiment to explore this problem both from theoretical and practical point of view. In our casethe connection between individual and collective transformation of participant activities required farmers and advisers to design together tools to accompany the agroecological transition on farms. This process allowed the debate about the diversity of agricultural models and representations that actors have regarding agroecological transition. It as well allows engaging advisers and farmers jointly in the agroecological transition. These transformations have been enhanced by the fact that the co-design process was organized as a dialogical process between design and experimentation of the tools in diverse real situations of use on farms. At the end of this journey, we propose to develop a pragmatist approach to accompany locally the agroecological transition
64

VALUE-ADDED STRATEGIES IN THE SPECIALTY CROP INDUSTRY: EXPLORING FARMERS' DRIVERS AND STRATEGIES AT THE FARM LEVEL

Orlando Francisco Rodriguez Izaba (10711716) 06 May 2021 (has links)
Value-added (VA) technologies can help farmers in the specialty crop industry generate new products, increase off-season income sources, expand market access, and improve overall profitability. These technologies can support the development of rural economies through the generation of new businesses and job creation. The USDA defines VA products as those 1) changed physical, 2) produced in a manner that enhances their value, and 3) physically segregated in a manner that results in enhancement of their value. Drawing from this definition, this study investigated VA technologies such as drying, cutting into customer-ready portions, washing and labeling specialty crops. The objectives of this study are threefold. First, we analyze how market access and diversification drive specialty crop farmers to adopt VA technologies. Second, we address the potential endogeneity between the adoption of VA technologies (vertical diversification) and the number of crops (horizontal diversification). Lastly, we investigate how market access drives farmers to utilize food labels for VA products. Data for this study came from a 2019 web-based survey of specialty crop farmers. A total of 766 farmers completed the survey, with a response rate of 21.5%. The questionnaire included questions related to farmer’s demographics (i.e., educational attainment, gender, farming experience), farm characteristics (i.e., crops, markets, and growing technologies), and farmers’ beliefs regarding their farm system. Results suggest that market access is a significant driver of VA technology adoption. Also, the size of the farm, networks, farmer’s perceptions, and employment growth influence adopting VA technologies. The results also show us that farmers adopting VA technologies tend to experience economic growth.
65

Genetic mapping and evaluation of cassava (manihot esculenta crantz) for drought tolerance and early bulking in marginal Savannah ecology of Nigeria

Ewa, Favour January 2021 (has links)
Thesis (Ph.D. (Plant Production)) -- University of Limpopo, 2021 / Cassava (Manihot esculenta Crantz) is a widely cultivated crop in many tropical countries in Africa, Latin America, and Asia. Cassava is a staple food security crop for over one billion people worldwide. It is a multi‑purpose and well adapted to different agricultural production systems. Although cassava is adaptable to marginal soils with low fertility, and to irregular rainfall conditions, as it allows a relatively stable productivity and flexibility for harvesting process, the challenges posed by global climate change (both temperature and drought severity increasing) have caused negative impacts on this crop‘s productivity. Given the increasing demand for higher productivity to improve food security and alleviate poverty in the dry prone regions of Africa, there is a concurrent increasing demand to expand production into marginal ecologies and improve its adaptation in such ecologies. Breeding efforts have resulted in the development of high-yielding varieties, but due to late bulking and long time taken before crop is ready for harvest, the improved varieties were not easily adopted by farmers. The complex nature of yield and other productivity traits, coupled with the biology of cassava, make it more challenging to improve the crop. However, biotechnology has revolutionised breeding with the development of advanced molecular tools that have facilitated breeding-by-design approaches leading to effective manipulation of genes for complex traits. The potential and impact of the new tools are now providing a stronger basis to adopt molecular breeding to genetically improve the crop for key traits. The main objectives of the research were to: (i) Develop a mapping population and identify traits driving the physiological basis of drought tolerance in F1 cassava genotypes; (ii) Identify traits linked with early bulking in the F1 population; (iii) Identify quantitative trait loci (QTLs) for drought tolerance and early bulking in F1 cassava genotypes; and (iv) Estimate the genetic improvement for drought tolerance in the F1 population. Two genotypes (TMS98/0505 and TMS98/0581) with contrasting desirable traits such as high yield in marginal environment, good disease resistance, vigour, and flowering potentials were used in the development of the mapping population used in this study. Results indicate that there was a positive correlation between yield, yield-related traits .and morphological/physiological traits. Principal component analysis identified the scar level, height of stem with leaf, fresh root yield, dry root yield, root number and dry-matter content as traits driving drought tolerance in marginal environment. This study also identified early-bulking cassava varieties in the F1 population and traits associated with early bulking. Fresh root yield was significantly associated with morphological and productivity traits while principal component analysis identified important traits such as root weight, root number, plant biomass, fresh root yield, plant height, , and stem diameter. Composite interval mapping identified 27QTLs and 30 QTLs in the first and second year, respectively, associated with the traits phenotyped in dry savannah ecology of Nigeria, while 16 and 12 QTLs associated with early bulking at 7 MAP were identified in the first and second year. Identification of these loci will aid breeding for drought tolerance and early root bulking in cassava. There was a better performance among traits such as biomass, root number, dry-matter content, number of scars, number of leaves, and length of stem with leaf in the second population (population C) than in the first population (population B). Twenty superior genotypes were selected from population C, which will be incorporated in the breeding programmes for further evaluation and germplasm enhancement. KEY WORDS: Composite interval mapping, Fresh root yield, Manihot esculenta, morphological traits, Population C, physiological traits. / National Root Crops Research Institute (NRCRI) Umudike
66

Stimuler la conception distribuée de systèmes agroécologiques par l’étude de pratiques innovantes d’agriculteurs / Fostering the distributed design of agroecological systems by studying farmer’s innovative practices

Salembier, Chloé 13 May 2019 (has links)
Aujourd’hui, dans un nombre croissant d’initiatives de la R&D agricole, on cherche à apprendre de pratiques ‘innovantes’ d’agriculteurs, pour soutenir l’évolution des systèmes agricoles, souvent dans le projet de l’agroécologie. Ces initiatives émergent dans un contexte où, en agronomie, on explore de nouveaux itinéraires de production de connaissance pour faire face aux enjeux contemporains qui induisent des questions inédites comme : Comment prendre en compte, dans la conception de systèmes agroécologiques, des équilibres naturels peu prédictibles et en partie inconnus ? Quelles représentations des processus agronomiques permettent d’imaginer des systèmes affranchis des intrants de synthèse? Ou encore, quelles connaissances produire pour concevoir des solutions techniques propres aux situations et attentes de chaque agriculteur ?… Dans cette thèse, nous faisons l’hypothèse que l’étude de pratiques innovantes d’agriculteurs serait une voie, empruntée par certains acteurs, pour explorer de nouvelles manières de produire dans le contexte actuel. En particulier, nous explorons comment et à quelles conditions l’étude de pratiques jugées innovantes d’agriculteurs peut stimuler la conception de systèmes agricoles aujourd’hui.Un détour par l’histoire de l’agronomie nous permet de mettre en perspective cette dynamique contemporaine avec les façons dont des agronomes ont, par le passé, étudié des pratiques d’agriculteurs pour générer des prescriptions visant à faire évoluer les pratiques en ferme. Dès les fondements de l’agronomie, au 18ème siècle, certains s’inspiraient de pratiques d’agriculteurs ; puis, en lien avec l’évolution de la discipline, ce lien aux pratiques est devenu marginal dans de nombreux travaux. Nous montrons que le rapport aux pratiques d’agriculteurs se renouvelle face aux enjeux contemporains de l’agriculture et c’est ce renouvellement que nous approfondissons ensuite avec un focus sur l’étude de pratiques innovantes d’agriculteurs. Par l’étude d’un panorama d’initiatives contemporaines, nous montrons qu’il existe différentes manières d’étudier des pratiques innovantes d’agriculteurs et nous proposons une manière d’organiser cette diversité. D’abord, nous montrons ce qu’apporte l’étude de ‘pratiques innovantes’ à ceux qui la réalise (fédérer une communauté de concepteurs, renouveler les représentations agronomiques, acquérir des connaissances sur des systèmes techniques inconnus…). Nous identifions des traits communs dans les raisonnements sous-jacents à l’étude de pratiques innovantes (ex. s’orienter vers des pratiques innovantes en formulant un inconnu désirable), et des variantes dans leurs réalisations (ex. différents types d’analyses systémiques) qui, parfois, influent sur ce qu’en apprennent leurs initiateurs. Enfin, nous montons que ce travail permet d’enrichir de différentes façons des dynamiques collectives de conception de systèmes agricoles innovants : à la fois en stimulant, par l’étude de pratiques, l’émergence de nouveaux systèmes techniques en ferme ; et en contribuant à la génération de prescriptions agronomiques originales venant soutenir la conception par les agriculteurs (témoignages contextualisés, logiques d’action génériques ...).Ces initiatives illustrent l’émergence, en agronomie, de formes originales de contributions à des dynamiques de conception distribuée dans les territoires agricoles. Cette thèse éclaire des ressorts et des modalités de réalisation de l’étude de pratiques innovantes d’agriculteurs et ses relations à des activités de conception, et elle contribue à la formulation de repères pour penser leur articulation dans l’action. / Today, in an increasing number of initiatives in the R&D agricultural sector, we want to learn from farmer’s innovative practices to foster change in agriculture toward agroecology. These initiatives, still poorly known, emerge in a context where agronomists explore new ways to produce knowledge to face current issues and answer new questions such as : while designing agroecological farming systems, how to deal with natural regulations, partly unknown and poorly predictable? What kind of models of agroecosystems allow to imagine chemical-free cropping systems? Or, what knowledge should we produce to design technical options adapted to every farmer’s expectations? … In this thesis, we assume that studying farmer’s innovative practices would be one way, taken by certain actors, to explore innovative farming systems today. More precisely, we explore how and in which conditions the study of farmer’s innovative practices could foster the design of agricultural systems.First, by exploring the history of agronomy, we show that since the foundation of the discipline, in the 18th century, agronomists draw inspiration from farmer’s practices; then, with the evolution of the discipline, the study of farmer’s practices marginalised. Today, new ways to study farmer’s practices emerge, in relation with contemporaneous challenges and we then propose to focus on ways to study ‘farmer’s innovative practices’. Through the analysis of a panorama of 14 initiatives from the agricultural R&D sector we show that it exists various ways to study farmer’s innovative practices, and we propose to organize this diversity. First, we shed light on what people get from the study of innovative practices depending on their own situation (to federate a designer’s community, to renew agronomic models, to get knowledge on unknown technical systems…). We then shed light on common traits in agronomist’s reasoning underlying the study of farmer’s innovative practices (ex. They all spot innovative practices formulating desirable unknown), and we show variants in ways to analyse them (ex. various systemic analysis). We finally show that studying innovative practices allows to enrich collective design dynamics: by fostering the emergence of new technical systems on farm, and by contributing to the emergence of original prescriptions aiming to support the design on farm of innovative systems (contextualised testimonies, generic action logics…)These initiatives illustrate the emergence of original forms of contributions, in agronomy, in a distributed design organisation, spread in territories. This thesis contribute to the understanding of what’s studying farmer’s innovative practices in relation to a design activity, and it gets to the formulation of reflexive keys to study farmer’s practices while designing in agronomy.
67

Integrating Pest and Pollinator Management: Assessing the Impact of Commercial Watermelon Production on Pests and Pollinators

John Jay Ternest (6635369) 14 May 2019 (has links)
Fruit set in cucurbit crops such as watermelon is entirely dependent upon pollinators, which makes them an important aspect of grower management. This reliance on pollinators means that growers must consider them when making pest management decisions, especially when using pesticides, which can have a negative impact on pollinators. Thus, pest management in watermelon production faces a potential trade-off between pests and pollinators. The ways in which growers manage this trade-off could have a large impact on the communities of both groups and the yield of the crop. <br>
68

Multitrophic plant insect interactions in dependence of belowground processes / Multitrophische Pflanze-Insekt Interaktionen in Abhängigkeit von unterirdischen Prozessen

Poveda Morciniec, Katja Andrea 19 May 2005 (has links)
No description available.
69

Skirtingo našumo dirvožemių pokyčiai ekologinėje ir tausojamojoje žemdirbystės sistemose / Changes in soil productivity parameters in organic and sustainable cropping systems

Masilionytė, Laura 07 December 2011 (has links)
1. Ištirti skirtingo humusingumo glėjiškame rudžemyje alternatyviose intensyviajai žemdirbystės sistemose su daugiamečių žolių atolu ir tarpinių pasėlių biomase į dirvožemį įterptų biogeninių elementų kiekį ir jų poveikį sėjomainos augalų produktyvumui. 2. Įvertinti su trąšomis įterptų ir su derliumi prarastų biogeninių elementų NPK balansą ekologinės bei tausojamosios žemdirbystės sistemose ir nustatyti judriųjų fosforo ir kalio pokyčius dirvožemyje. 3. Nustatyti tausojamosios ir ekologinės žemdirbystės sistemose tarpiniuose pasėliuose augintų augalų biomasėje sukaupto azoto poveikį Nmin. dinamikai dirvožemyje. 4. Ištirti naudotų trąšų ir tarpinių pasėlių poveikį humuso ir jo sudėties pokyčiams ekologinės bei tausojamosios žemdirbystės sistemose. 5. Įvertinti ekologinės ir tausojamosios žemdirbystės sistemose naudotų agropriemonių poveikį pagrindinių dirvožemio fizikinių rodiklių stabilumui, agrofitocenozių dominantėms ir augaluose sukauptai bendrajai energijai. / 1. In the cropping systems alternative to the intensive cropping system, set up on a gleyic Cambisol with a different humus status, perennial grasses and biomass of catch crops are a significant reserve of biogenic elements for the productivity of crop rotation plants. 2. In the organic and sustainable cropping systems, farmyard manure and biogenic elements incorporated with it have a greater positive effect on the NPK balance and changes in available phosphorus and potassium in the soil compared with green manure. 3. Catch crops are important from the environmental viewpoint, since by accumulating nitrogen in their biomass they reduce Nmin. concentration in the soil and become a reserve of nutrients for succeeding plants. 4. In the soil with a different humus status, alternative cropping systems have a diverse effect on humus stability and changes in its quality. 5. In the sustainable and organic cropping systems, catch crops and their biomass play an important role for soil physical parameters, agrophytocenoses dominants and total energy.
70

A Complex Co-Evolutionary Systems Approach to the Management of Sustainable Grasslands: A Case Study in Mexico

Martinez-Garcia, Alejandro N. Unknown Date (has links)
The complex co-evolutionary systems approach (CCeSA) provides a well-suited framework for analysing agricultural systems, serving as a bridge between biophysical and socioeconomic sciences, allowing for the explanation of phenomena, and for the use of metaphors for thinking and action. By studying agricultural systems as self-generated, hierarchical, complex co-evolutionary farming systems (CCeFSs), one can investigate the interconnections between the elements that constitute CCeFSs, along with the relationships between CCeFSs and other systems, as a fundamental step to understanding sustainability as an emergent property of the system. CCeFSs are defined as human activity systems emerging from the purposes, gestalt, mental models, history and weltanschauung of the farm manager, and from his dynamic co-evolution with the environment while managing the resources at his hand to achieve his own multiple, conflicting, dynamic, semi-structured and constrained purposes. A sustainable CCeFS is described as one that exhibits both enough fitness to achieve its multiple, dynamic, constrained, semi-structured, and often incommensurable and conflicting purposes while performing above threshold values for failure, and enough flexibility to dynamically co-evolve with its changing biophysical and socioeconomic environment for a given future period. Fitness and flexibility are essential features of sustainable CCeFSs because they describe the systems' dynamic capacity to explore and exploit its dynamic phase space while co-evolving with it. This implies that a sustainable CCeFS is conceived as a set of dynamic, co-evolutionary processes, contrasting with the standard view of sustainability as an equilibrium or steady state. Achieving sustainable CCeFSs is a semi-structured, constrained, multi-objective, and dynamic optimisation management problem with an intractable search phase space, that can be solved within the CCeSA with the help of a multi-objective co-evolutionary optimisation tool. Carnico-ICSPEA2, a Co-Evolutionary Navigator (CoEvoNav) used as a CCeSA's tool for harnessing the complexity of the CCeFS of interest and its environment towards sustainability, is introduced. The software was designed by its end-user - the farm manager and author of this thesis - as an aid for the analysis and optimisation of the "San Francisco" ranch, a beef cattle enterprise running on temperate pastures and fodder crops in the central plateau of Mexico. By combining a non-linear simulator and a multi-objective evolutionary algorithm with a deterministic and stochastic framework, the CoEvoNav imitates the co-evolutionary pattern of the CCeFS of interest. As such, the software was used by the farm manager to "navigate" through his CCeFS's co-evolutionary phase space towards achieving sustainability at farm level. The ultimate goal was to enhance the farm manager's decision-making process and co-evolutionary skills, through an increased understanding of his system, the co-evolutionary process between his mental models, the CCeFS, and the CoEvoNav, and the continuous discovery of new, improved sets of heuristics. An overview of the methodological, theoretical and philosophical framework of the thesis is introduced. Also, a survey of the Mexican economy, its agricultural sector, and a statistical review of the Mexican beef industry are presented. Concepts such as modern agriculture, the reductionist approach to agricultural research, models, the system's environment, sustainability, conventional and sustainable agriculture, complexity, evolution, simulators, and multi-objective optimization tools are extensively reviewed. Issues concerning the impossibility of predicting the long-term, detailed future behaviour of CCeFSs, along with the use of simulators as decision support tools in the quest for sustainable CCeFSs, are discussed. The rationale behind the simulator used for this study, along with that of the multi-objective evolutionary tools used as the makeup of Carnico-ICSPEA2, are explained. A description of the "San Francisco" ranch, its key on-farm sustainability indicators in the form of objective functions, constraints, and decision variables, and the semi-structured, multi-objective, dynamic, constrained management problem posed by the farm manager's planned introduction of a herd of bulls for fattening as a way to increase the fitness of his CCeFS via a better management of the system's feed surpluses and the acquisition of a new pick-up truck are described as a case study. The tested scenario and the experimental design for the simulations are presented as well. Results from using the CoEvoNav as the farm manager's extended phenotype to solve his multi-objective optimisation problem are described, along with the implications for the management and sustainability of the CCeFS. Finally, the approach and tools developed are evaluated, and the progress made in relation to methodological, theoretical, philosophical and conceptual notions is reviewed along with some future topics for research.

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