Le travail de cette thèse s'inscrit dans le cadre du projet MAISEO qui associe, entre autres partenaires, la CACG, gestionnaire de l'eau sur des bassins hydrographiques du Sud-Ouest, Météo-France et le CESBIO. Un des objectifs est de proposer des méthodes innovantes et opérationnelles pour l'estimation des besoins en eau des cultures à l'échelle d'un territoire. Il s'agit de fournir au gestionnaire des outils qui lui permettront de mieux gérer la demande en eau d'irrigation liée à la culture dominante présente dans le Sud-Ouest de la France: le maïs. L'objectif de la thèse consistait à estimer les rendements et les besoins en eau du maïs sur de grandes surfaces. Pour cela, nous avons utilisé un modèle agro-météorologique couplé à l'imagerie satellitaire optique. De nombreuses images à haute résolution spatiale et temporelle provenant de différents capteurs ont été utilisées, préfigurant l'arrivée des données Sentinel-2 lancé en 2015. Il s'agissait dans un premier temps de coupler les données satellitaires avec le modèle SAFY (Simple Algorithm For Yield estimates, Duchemin et al., 2008a), qui simule le développement des plantes en se basant sur la théorie des efficiences (Monteith, 1972), afin d'estimer la biomasse et le rendement du maïs. De nombreuses données terrain ont permis de valider les sorties du modèle. A l'échelle régionale, les résultats ont été agrégés et comparés aux statistiques départementales Agreste. Les résultats ont conduit à proposer une nouvelle version du modèle SAFY permettant de prendre en compte la variation temporelle de l'efficience de conversion de la lumière effective (ELUE) et de la surface spécifique foliaire (SLA). Cette modification permet une meilleure prise en compte de la dynamique de croissance de la végétation et une amélioration de l'estimation du rendement tant à l'échelle locale que régionale. La méthode de calibration a également été améliorée afin de limiter le recours aux données in situ difficilement accessibles sur de grandes surfaces. Nous avons pu mettre en évidence l'apport de la double logistique, utilisée pour interpoler les profils temporels de NDVI. Cette interpolation a permis d'affiner la délimitation du cycle cultural et de contraindre plus précisément certains paramètres du modèle comme la date de levée. Une fois contraint par les données satellitaires, le modèle SAFY est capable de reproduire les rendements sur les deux départements avec une bonne précision et ce sans prendre en compte l'évolution du stock d'eau dans le sol (Battude et al., 2016) / This Ph.D. thesis is part of the MAISEO project associating partners among them: the CACG, managing the water supply of several watersheds located in the south west of France, the Meteo-France center and the CESBIO. One of the goals is to develop innovative and operational tools to estimate crops' water needs at the territory scale. The aim is to provide managers tools to better manage the water supplies linked to the predominant crop encountered in south west of France: maize. The objective of the thesis was to estimate the yield and water requirements of maize crop over large areas. For this purpose, we used an agro-meteorological model coupled to optical satellite imagery. Numerous high spatial and temporal resolution images from different sensors have been used, prefiguring the arrival of the Sentinel-2 data launched in 2015. The first part was to combine remote sensing data with the SAFY (Simple Algorithm For Yield estimates) crop model (Duchemin et al., 2008a) that simulates plant development based on Monteith theory (Monteith, 1972) in order to accurately estimate maize biomass and yield. Numerous field data have been used for the validation at local scale. At regional scale, the results have been aggregated and compared to Agreste yield statistics provided by the French government. Results led us to propose a new formulation of the SAFY model taking into account the temporal variation of the effective light use efficiency (ELUE) and of the specific leaf area (SLA). This modification allows a better simulation of the crop growth dynamics and an improvement of yield estimates at the local and regional scale. Furthermore, we changed the calibration method in order to limit the use of in situ data that are difficult to access over large areas. We also highlighted the contribution of the double logistic function, used to interpolate the NDVI time series. This interpolation enables an accurate determination of the crop growing season and it allows constraining some model parameters such as the emergence date. The SAFY model constrained by remote sensing data is able to well reproduce the yield for the two departments without taking into account the evolution of the soil water storage (Battude et al., 2016)

Thesis (Ph.D. (Agricultural Economics)) -- University of Limpopo, 2015 / Various types of management practices/institutional arrangements of the irrigation schemes exist in the world. According to the principles delineated in literatures, these irrigation schemes are categorized in terms of their management practices. The study was designed to compare the level of technical efficiency of farmers at different management practices of the irrigation schemes (i.e. integrated, specialised and multipurpose water management practices of the irrigation schemes) in Limpopo Province. Data were collected using a structured questionnaire which was administered on 200 farmers at different irrigation schemes. Stochastic frontier production function of Cobb-Douglas type was employed to analyse the data and thereby ascertain the level of technical efficiency and its determinants. The results indicated the mean technical efficiency of 0.74, 0.72 and 0.76 for the integrated, specialised and multipurpose water management practices of the irrigation schemes respectively which implied that, there is a greater scope to increase maize, tomato, onion and spinach production with the current technology and resources available at the irrigation schemes. The most important contributors in maize, tomato, onion and spinach production efficiencies were seed, fertilizer, capital and land. Thus an appropriate amount of seed, fertilizer, capital and land could increase the productivity of maize, tomato, onion and spinach. The results further revealed that education level of farmers, age of the farmers and land size were negatively significant toward the technical inefficiency of farmers at different irrigation schemes, which imply that an increase in any of the three variables will reduce the inefficiency and enhance the efficiency. While the family size of the farmer was positively significant, which implies that the bigger the family size, the higher the inefficiency farmers would become for the production of maize, tomato, onion and spinach. Gender and income level of the farmers at different irrigation schemes were revealed to be insignificant toward the inefficiency. The institutional arrangements or the management practice of the irrigation schemes showed slight differences in affecting the efficiency of farmers at different irrigation schemes. Policies designed to educate famers at different irrigation schemes through proper agricultural extension services could have a great impact in increasing the level of efficiency and hence maize, tomato, onion and spinach productivities. The Department of Agriculture should allocate more funds to strengthening the extension directorate and expanding the delivery of extension services to farmers at different irrigation schemes. Irrigation schemes were established in order to insure food security, alleviate poverty, job creation, among others. Therefore, it is of paramount importance for the government of South Africa in collaboration with the private sector to revitalise the irrigation schemes in Limpopo Province irrespective of the institutional arrangements. It is of vital concern for the policy makers to focus on the benefits of economies of scale in agricultural farming system. Therefore, land size should be increased for the farmers in integrated water management practice of the irrigation schemes to an optimum level in order for them to improve the level of technical efficiency.

A case study was conducted at the Kaudulla irrigation system in the city zone of Sri Lanka. The principal objective of the study was to perform a comprehensive evaluation of the system in operation with primary focus on identifying major constraints to effective irrigation management through a multi-disciplinary research approach. Inadequate control facilities and neglected maintenance of the channel system were the major problems affecting irrigation management. Other constraints identified were the lack of motivation among management personnel and insufficient funds available for maintenance, which were dependent on constraints external to the system, namely the national economic and political environment. The delicate economic status of a majority of the farmers, grassroot level political environment and the economic vicissitudes of the entire country have resulted in the formation of vicious economic cycles that have contributed to a breakdown in the institutions essential for an engineering system to function effectively. Irrigation management alter:aat:ives were developed on the basis of generating motivational incentives to the management personnel and financial resources to sustain the technical capability of the engineering system to effectively distribute the irrigation water. Techniques for integrating these aspects into new community organizations in addition to existing organizational framework were outlined. These procedures should assist in eliminating the major constraints to effective utilization and management of irrigation water. / Ph. D.

Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The use of capacitance water sensors for the scheduling of irrigation for hydroponic tomato and cucumber crops grown in coir was investigated in a series of laboratory and glasshouse experiments in the Free State province of South Africa. Laboratory experiments in a climate controlled chamber were conducted to accurately calibrate ECH2O capacitance sensors, models EC-10 and EC-20, in coir with an improved calibration procedure. Water content predictions by the coir-specific calibration and manufacturer’s calibration equations were compared to actual water content measured from mass loss of the coir sample. The manufacturer’s calibration equation indicated a poor accuracy of prediction, which mostly underestimated the volumetric water content, compared to the near perfect prediction of the coir-specific calibration of individual sensors. A rapid calibration procedure for EC-10 and EC-20 sensors was proposed to reduce the calibration time of the sensors and promote their commercial use for irrigation management in coir. The accuracy of prediction by the rapid calibration procedure for the plant available water content range was high for both EC-10 and EC-20 sensors and allowed for the compensation for variation between sensors. Glasshouse studies aimed to characterise the water retention and ability of coir to supply water to greenhouse tomato and cucumber crops through the continuous monitoring of medium water content in small and large growing bags with the EC-10 and EC-20 capacitance sensors during a drying cycle, compared to well-watered plants. Stages of crop water stress were identified and, based only on the plant’s response to the drying cycle, it was suggested that water depletion can be allowed to the point of mild water stress for both greenhouse tomato and cucumber crops, which can be detected by soil water sensors. In a second series of glasshouse experiments, the identified stages of crop water stress were used to determine and apply depletion levels in coir and compare this irrigation strategy to a well-watered treatment for greenhouse cucumber and tomato plants, with regard to the water balance components, yield and water use efficiency for different bag sizes. Results indicated that irrigation was successfully managed to the pre-determined water depletion levels for cucumber and tomato plants in coir, through the use of in situ calibrated capacitance sensors. For both crops the depletion of water varied between bag sizes, indicating that various bag sizes require different irrigation management strategies. Scheduling to the highest pre-determined by 124 L m-2 in the small and 240 L m-2 in the large bags for cucumbers and 427 L m-2 in the small and 487 L m-2 in the large bags for tomato plants, compared to the well-watered treatments. Yields achieved by the greenhouse tomato plants in the large growing bags and cucumber plants in the small and large bags were maintained or improved when scheduled to the highest depletion level (approximately 60% available water content) compared to the well-watered treatment. The combination of reduced irrigation and improved or maintained yields resulted in improved water use efficiencies (based on irrigation and transpiration) for the highest depletion level compared to the well-watered treatments. In all glasshouse experiments the well-watered treatment resulted in luxury water use by the plants. Finally, a study was conducted in order to compare crop water stress of greenhouse cucumber and tomato plants under luxury water supply and cyclic water deficit conditions. The comparison was based on the transpiration ratio and yield, while the use of capacitance sensors was evaluated for irrigation scheduling in coir for both crops. Transpiration data indicated that cucumber and tomato plants subjected to luxury water supply experience water stress earlier than plants subjected to cyclic water deficit conditions, irrespective of bag size. Results also indicated that irrigation scheduling according to water depletion levels in small bags is not yet recommended for greenhouse tomato and cucumber plants grown in coir, until further research is conducted. Scheduling to water depletion levels in large bags is, however, justified by the improved or maintained yields of the greenhouse cucumber and tomato plants. The estimated depletion levels for large bags beyond which yield are reduced was at 85% for tomatoes and 70% for cucumbers. In conclusion, the results clearly indicated that the use of capacitance sensors in large growing bags improves irrigation management of hydroponic cucumbers and tomatoes in coir by eliminating over-irrigation and improving water use efficiency. More research is needed before a conclusion can be made regarding irrigation scheduling with capacitance sensors in small growing bags. / AFRIKAANSE OPSOMMING: Die gebruik van kapasitansie water sensors vir besproeiingskedulering van tamatie en komkommer plante wat hidroponies in kokosveen gegroei is, is ondersoek in ‘n reeks laboratorium en glashuis eksperimente in die Vrystaat provinsie van Suid Afrika. Laboratorium eksperimente is uitgevoer in ‘n klimaat beheerde kas om ECH2O kapasitansie sensors, modelle EC-10 en EC-20, akkuraat te kalibreer vir kokosveen deur ’n verbeterde kalibrasie prosedure. Waterinhoud voorspellings deur die kokosveen spesifieke kalibrasie en die vervaardiger se kalibrasie vergelykings is vergelyk met die werklike waterinhoud wat gemeet is deur die kokosveen monster se massaverlies te monitor. Akkuraatheid van voorspelling deur die vervaardiger se kalibrasie vergelykings was swak en het meestal die volumetriese waterinhoud onderskat in vergelyking met die byna perfekte voorspelling deur die kokosveen spesifieke kalibrasie van individuele sensors. ’n Vinnige kalibrasie prosedure vir die EC-10 en EC-20 sensors is voorgestel om die kalibrasie tyd te verkort en die kommersiële gebruik van die sensors vir besproeiingsbestuur in kokosveen aan te moedig. Die akkuraatheid van voorspelling deur die vinnige kalibrasie prosedure, binne die grense van plant beskikbare waterinhoud, was hoog vir beide EC-10 en EC-20 sensors, terwyl die prosedure ook voorsiening maak vir variasie tussen sensors. Glashuis studies is uitgevoer om die water retensie en vermoë van kokosveen om water te voorsien aan tamatie en komkommer gewasse in kweekhuise, te karakteriseer. Dit is bereik deur die mediumwaterinhoud van klein en groot plantsakke deurlopend te monitor met behulp van die EC-10 en EC-20 kapasitansie sensors gedurende ’n uitdroging siklus, en dit te vergelyk met ’n waterryke behandeling vir elke gewas waarvolgens die plante agt keer per dag besproei is. Fases van gewas waterstremming is geïdentifiseer en, volgens die reaksie van die plant tot die drogingsiklus, is dit voorgestel dat wateronttrekking toegelaat kan word tot die punt van matige waterstremming wat aangewys kan word deur kapasitansie water sensors vir beide kweekhuis tamatie en komkommer gewasse. In ’n tweede reeks glashuis eksperimente is die geïdentifiseerde fases van gewas waterstremming gebruik om onttrekkingsvlakke vir kokosveen te bepaal en toe te pas as besproeiingskeduleringstrategie vir kweekhuis komkommer en tamatie plante. Toegepaste vlakke is vir elke gewas vergelyk met ’n waterryke behandeling ten opsigte van die waterbalans komponente, opbrengs en watergebruiksdoeltreffendheid in verskillede sakgroottes. Resultate het aangedui dat besproeiing suksesvol bestuur is tot die voorafbepaalde wateronttrekkingsvlakke vir komkommer entamatie plante in kokosveen, deur gebruik te maak van in situ gekalibreerde kapasitansie sensors. Die onttrekking van water deur beide gewasse het verskil tussen klein en groot sakke, wat aangedui het dat verskillende sakgroottes verskillende besproeiingsbestuur strategieë vereis. Skedulering tot die hoogste voorafbepaalde onttrekkingsvlak het, in vergelyking met die waterryke behandelings, besproeiing verminder met 124 L m-2 in die klein en 240 L m-2 in die groot sakke vir komkommers, en 427 L m-2 in die klein en 487 L m-2 in die groot sakke vir tamatie plante. Opbrengste van kweekhuis tamatie plante in die groot plantsakke en komkommer plante in die klein en groot sakke is gehandhaaf of verbeter deur skedulering tot die hoogste onttrekkingsvlak (ongeveer 60% van beskikbare water inhoud), in vergelyking met die waterryke behandeling. Die kombinasie van verminderde besproeiing en verbeterde of gehandhaafde opbrengste het gelei tot verbeterde watergebruiksdoeltreffendheid (besproeiing en transpirasie) vir die hoogste onttrekkingsvlak, in vergelyking met die waterryke behandelings. In al die glashuis eksperimente het die waterryke behandeling gelei tot oorvloedige watergebruik deur plante. ’n Finale studie is uitgevoer om gewas waterstremming van kweekhuis komkommer en tamatie plante wat onderwerp is aan oorvloedige watervoorsiening deur agt keer per dag te besproei en sikliese watertekorttoestande, te vergelyk. Die vergelyking is gebaseer op die transpirasie verhouding en opbrengs, terwyl die gebruik van kapasitansie sensors vir besproeiingskedulering in kokosveen vir beide gewasse geëvalueer is. Transpirasie data het aangedui dat komkommer en tamatie plante wat onderwerp is aan oorvloedige watervoorsiening vroeër waterstremming ervaar as plante wat onderwerp is aan sikliese watertekorttoestande, ongeag van die sakgrootte. Resultate het aangedui dat besproeiingskedulering volgens wateronttrekkingsvlakke vir klein sakke nog nie aanbeveel kan word vir kweekhuis tamatie en komkommer plante alvorens verdere navorsing gedoen is nie. Skedulering tot wateronttrekkingsvlakke vir groot sakke word egter geregverdig deur die verbeterde of gehandhaafde opbrengste van kweekhuis komkommers en tamaties. Die beraamde laagste onttrekkingsvlakke vir groot sakke wat nie opbrengs betekenisvol sal beïnvloed nie is 85% vir tamaties en 70% vir komkommers. Ten slotte dui die resultate duidelik daarop dat die gebruik van kapasitansie sensors in groot plantsakke besproeiingsbestuur van hidroponiese komkommers en tamaties in kokosveen verbeter deur oorbesproeiing uit te skakel en die watergebruiksdoeltreffendheid te verbeter. Meer navorsing is nodig alvorens ’n gevolgtrekking gemaak kan word ten opsigte van besproeiingskedulering met kapasitansie sensors in klein plantsakke.

À la suite de l'effondrement de l'Union soviétique, les états nouvellement formés de l'Asie centrale ont entrepris, à différents niveaux, des réformes de leurs secteurs agraires. Du point de vue de l'utilisation de l'eau d'irrigation, les réformes consistent notamment en des changements aux régimes fonciers et dans la décentralisation de la gestion du système de drainage et d'irrigation. La plupart des institutions qui, durant l'époque soviétique, géraient le système d'irrigation et de drainage ont été abolies. Cela a créé un vide institutionnel et permis le développement d’institutions au niveau local qui puissent être participatives et appartenir aux utilisateurs. Pourtant, le contexte historique et contemporain de la région pose des défis particuliers pouvant nuire à un tel développement. Les associations d'utilisateurs d'eau ou le gouvernement local gèrent l'irrigation et les systèmes de drainage au niveau local. Ces associations représentent souvent des initiatives conduites par les donateurs internationaux. Parallèlement, les institutions informelles et les modes traditionnels de coopération qui ont survécu à l'ère soviétique deviennent importants et quelques institutions créées durant cette ère demeurent toujours pertinentes. Cette recherche consiste à évaluer le rôle d’action collective dans un système de gestion d’irrigation et de drainage dans le bassin versant de la rivière Syr-Darya dans un contexte changeant concernant les droits d’usage de l'eau et de la terre. L'étude cherche à (1) saisir l'importance de l'eau d’irrigation dans les moyens de subsistance des utilisateurs dans la région de recherche; (2) explorer certaines caractéristiques des institutions formelles et informelles à travers lesquelles les fermiers dirigent des systèmes de drainage et d’irrigation; et (3) identifier les institutions qui appuient l'action collective et celles qui entravant son développement. La méthodologie de recherche repose une revue bibliographique et sur un travail de terrain dans la vallée de Ferghana, au Kirghizistan, entre le 30 avril et le 31 juillet 2008. Les résultats de la recherche sont présentés comme une étude de cas. / Following the collapse of the Soviet Union, the newly independent countries of Central Asia undertook reforms of their agrarian sectors with varying degrees of speed and depth. In general, the reforms consisted of changes in the nature of land tenure and in the decentralization of irrigation and drainage management. Through these reforms, former state management institutions were abolished leaving an institutional vacuum that presented an opportunity for the development of local-level management institutions. However, the historical context of the region poses particular challenges that may impede users to capitalize on such opportunities.     Water User’s Associations or the local administration manage irrigation and drainage systems at the local level. Water User Associations represent international donor-driven initiatives to introduce equitable, democratic and participative institutions for irrigation and drainage management. There are indications that those informal institutions and traditional modes of cooperation that survived the Soviet era are gaining importance. This study maps out the various institutions, defined as "rules in use", that farmers employ to manage the irrigation and drainage system in the Ferghana Valley within the context of changing land and water rights. The key objectives of the study are (1) to understand the importance of irrigated water for local livelihoods in the research area; (2) to explore certain characteristics of the formal and informal institutions through which farmers manage irrigation and drainage systems; and (3) to depict ways in which “collective action” in irrigation water management can be strengthened. The methodology consists of a synthesis of existing literature and fieldwork in the Ferghana Valley in Kyrgyzstan, from April 30 until 31 July, 2008. The results of the research are presented as a case study.

Conhecimentos sobre fisiologia da produção de mudas cítricas sob condições de deficiência hídrica são necessários para fomentar as práticas de irrigação em viveiros telados. O objetivo deste trabalho foi avaliar o efeito de deficiência hídrica induzido por polietileno glicol (PEG) e por interrupção da irrigação sobre o desenvolvimento e variáveis fisiológicas de mudas de laranja Valência (Citrus sinensis L. Osbeck) enxertada sobre limão Cravo (Citrus limonia Osbeck) e citrumelo Swingle (Poncirus trifoliata (L.) Raf x Citrus paradisi Macf). As mudas foram produzidas em sacolas plásticas de 4,5L contendo substrato a base de casca de pinus e submetidas à deficiência hídrica durante três fases fenológicas, e em duas estações do ano (outono-inverno e primavera-verão). O trabalho foi dividido em dois experimentos. No primeiro, avaliaram-se plantas mantidas em capacidade de container e submetidas à interrupção intermitente da irrigação, até o potencial hídrico do substrato atingir -15kPa, e a duas concentrações de PEG, correspondentes ao potencial hídrico no substrato de respectivamente -15 e -25kPa. No segundo experimento, avaliaram-se plantas mantidas em capacidade de container e submetidas a interrupção intermitente da irrigação até o potencial hídrico do substrato atingir respectivamente -15 e -25kPa. Dados coletados incluíram variáveis biométricas, concentrações foliares de nutrientes, de prolina e de clorofila, concentração de carboidratos em raízes, caule e folhas, aproveitamento comercial de mudas, taxa de assimilação de CO2, condutância estomática, transpiração e eficiência do uso da água. O delineamento adotado foi o de blocos ao acaso, seguindo o esquema fatorial 2 x 3 x 4 (porta-enxerto x fase de crescimento x deficiência hídrica), perfazendo 24 tratamentos e cinco repetições para o primeiro experimento, e esquema fatorial 2 x 3 x 3, com 18 tratamentos e seis repetições no segundo experimento. A parcela experimental foi constituída de seis plantas. Mudas de laranja Valência enxertadas sobre limão Cravo e citrumelo Swingle apresentam crescimento e características fisiológicas distintas, sendo que maior vigor é induzido por aquele porta-enxerto. O emprego de PEG como osmólito em estudos para indução de deficiência hídrica in vivo não é indicado para citros em vasos, já que este material acarreta efeitos fisiológicos distintos daqueles apresentados por plantas submetidas à interrupção da irrigação. Mudas sobre ambos porta-enxertos são afetadas pela interrupção da irrigação entre a retirada do fitilho e a maturação do segundo fluxo de crescimento do enxerto, sendo os prejuízos proporcionais à duração da deficiência hídrica. Os efeitos da seca temporária são mais intensos quando aplicados isoladamente a partir da maturação do primeiro fluxo de crescimento, devido ao maior tamanho das plantas. A interrupção da irrigação até que o potencial hídrico do substrato seja de -15kPa permite produção satisfatória de mudas de laranja Valência sobre limão Cravo e citrumelo Swingle, independentemente do período em que ocorra a deficiência hídrica. A interrupção da irrigação até que o potencial hídrico do substrato atinja -25kPa afeta significativamente a produção das mudas cítricas. O limão Cravo induziu maior aclimatação à copa, apresentando grande capacidade de recuperação do crescimento e do desempenho fisiológico após sucessivos ciclos de suspensão / restauração da irrigação. / Physiological aspects of citrus nursery tree production submitted to water deficit are necessary to support irrigation management in screen houses. This work evaluated water stress induced either by polyethylene glycol (PEG) or irrigation suspending on growth and physiological traits of Valencia sweet orange (Citrus sinensis L. Osbeck) budded on Rangpur lime (Citrus limonia Osbeck) and Swingle citrumelo (Poncirus trifoliata (L.) Raf x Citrus paradisi Macf). Nursery trees were produced in 4.5L containers filled with composted pine bark, and submitted to water stress in three phenological phases in two seasons (autumn-winter and spring-summer). Experimental works were divided in two trials. In the first one, evaluation was carried on plants submitted to container capacity, irrigation suspending when substrate water potential dropped to -15kPa, and two PEG concentrations in water equivalents to substrate water potential of -15 and -25kPa. In the second trial, evaluation was carried on plants submitted to container capacity and irrigation suspending when substrate water potential dropped to -15 and -25kPa. Data collected included biometric variables, leaf concentrations of nutrients, proline and chlorophyll, carbohydrates concentrations in roots, stems and leaves, commercial feasibility of nursery trees, CO2 assimilation rate, stomatal conductance, leaf transpiration and temperature, and water use efficiency. Experimental design was randomized blocks with a 2 x 3 x 4 factorial (rootstock x phenological phase x water stress), performing 24 treatments and five replicates for the first experiment, and a 2 x 3 x 3 factorial with 18 treatments and six replicates for the second experiment. Experimental unit consisted of six nursery plants aligned on concrete benches. Valencia sweet orange budded on Rangpur lime and Swingle citrumelo had different growth and physiological behavior, with the first rootstock inducing higher vigor. PEG should not be used for in vivo water stress studies in containerized citrus, as a result of toxicity and physiological effects distinct from those observed in plants submitted to suspended irrigation. Nursery trees on both materials are affected by suspended irrigation from unwrapping to the maturation of scion second growth flush. Damages to plant development due to water deficit are proportional to stress duration. However, temporary drought is more harmful when partially induced after the scion first growth flush, probably because of higher plant size and container restriction. Substrate water potential of -15kPa can be used as adequate irrigation threshold for Valencia sweet orange nursery production on Rangpur lime and Swingle citrumelo rootstocks regardless of phenological phase. On the other hand, substrate water potential of -25kPa significantly reduces horticultural value of citrus nursery trees. Rangpur lime induces higher morphological and physiological acclimation to the scion due to irrigation suspending, and it also has great plasticity and recovery of growth and physiological performance after successive suspending / restoring irrigation cycles.

Atualmente a água é o recurso mais limitante para o desenvolvimento urbano, industrial e principalmente agrícola devido à constante contaminação em função da falta de planejamento e uso inadequado dos recursos hídricos pela humanidade. Assim o presente trabalho teve o objetivo de estudar o impacto ambiental da irrigação nos recursos hídricos da microbacia hidrográfica do ribeirão dos Marins e testar a capacidade do modelo hidrológico MIKE SHE em pequenas áreas irrigadas da microbacia e conseqüentemente detectar problemas relacionados à irrigação e a falta de manejo da água nessas áreas. Avaliou-se a qualidade da água de irrigação utilizada na produção de hortaliças; a qualidade da irrigação praticada pelos produtores, a quantidade de água na microbacia hidrográfica e simulou-se a área irrigada da microbacia. Os parâmetros de qualidade de água analisados foram: sedimentos em suspensão, pH, condutividade elétrica, alcalinidade, turbidez, potássio, cálcio, magnésio, cobre, ferro, manganês, zinco, sódio, fósforo, sulfato, cloreto, nitrogênio amoniacal e nitrato, durante 10 meses. A qualidade da irrigação foi avaliada através do manejo da irrigação via tensiômetros, instalados em duas propriedades agrícolas e em duas profundidades, e avaliação do coeficiente de uniformidade de Christiansen (CUC) foi feito em quatro propriedades agrícolas. A avaliação do impacto ambiental foi feito por meio dos indicadores de qualidade da água e do CUC. Os dados coletados e avaliados permitiram concluir que a agricultura irrigada provoca pouco impacto na microbacia hidrográfica. De acordo com as classificações de Ayers e Westcot e USDA a água pode ser considerada boa para ser utilizada na agricultura. Observou-se que a umidade do solo no período amostrado ficou próxima da saturação. O uso do modelo para a simulação da área irrigada permitiu economia de água quando o manejo da irrigação foi utilizado. / Nowadays the water is the most limiting resource to the urban, industrial and agricultural development due to constant contamination and inadequate water use by the mankind. Then this work aimed to study the environmental impact of irrigation at the Marins stream watershed and to check the ability of the model MIKE SHE in small irrigated area, consequently, to detect problems related with irrigation operations at the small watershed. It were evaluated the water quality used in the horticultural production, the irrigation quality practiced by the farmers, water quantity in the watershed and simulation was done for the irrigated area. The parameters analyzed were physicals and chemicals: suspense sediments, pH, electric conductivity, alkalinity, turbidity, potassium, calcium, magnesium, cupper, iron, manganese, zinc, sodium, phosphorus, sulfate, chlorine, ammonia nitrogen, and nitrate, during 10 months. The irrigation quality was evaluated through the irrigation management by tensiometers installed in two properties and two depths and by the Christiansen uniformity coefficient (CUC) measured in four properties. The environmental impact of irrigation was made by the water quality indicators and the CUC. The results permitted to conclude that irrigated agricultural causes few impact at the Marins stream watershed. The water showed a acceptable quality when compared with the classification proposed by Ayers & Westcot and USDA to irrigation. It was observed that the soil wet was near the saturation. The model allowed to save water when water management was used.

Magister Philosophiae - MPhil (LAS) (Land and Agrarian Studies) / Government's decision to devolve irrigation management to farmers was partly influenced by international policy imperatives, which were propounded mainly by institutions associated with the Consultative Group for International Agricultural Research (CGIAR) and the inability by the government to continue funding operation and maintenance costs. The central question of the study is to understand the effects of Irrigation Management Transfer (IMT) on productivity, operation and maintenance in the Mamina Irrigation Scheme. Interviews with various primary and secondary stakeholders that included the irrigators, local political leadership and locally-based agriculture extension officers were carried out. The interviews were aimed at getting an insight on land tenure, participation and representation of women, water and electricity supply system and pricing, effects of irrigation management arrangements on equity and productivity, understanding the irrigators' food security status, operation and maintenance arrangement after Irrigation Management Transfer (IMT). Findings of this study suggest that the existing governance arrangements have partly led to low crop productivity, increased water and electricity bill arrears, poor water distribution, change to uneconomic plot sizes, unsustainable increase in the number of irrigators, failure to organise for operation and maintenance. The key factors influencing the poor performance include poor collaboration, pumping system that utilised more electricity, inability of the irrigators to replace leaky pipes, failure of the irrigators to contribute towards electricity and water bills, failure of the irrigators to contribute towards operation and maintenance. The study identified nine challenges that affected the success of IMT. The challenges that lay at the heart of Mamina irrigation scheme were mainly caused by the poor irrigation technology design, pricing structure of electricity, water permit system, inequalities in water distribution, low gender participation and representation, non-availability of formal markets for certain crops, food insecurity, plot alloction and land disputes. Poverty analysis has shown that the irrigators' ability to escape from poverty or food insecurity is critically dependent upon their access to assets. Different assets are required to achieve different livelihood outcomes. The cycle of accumulation of utility bill arrears continued even after devolution because the same defective irrigation infrastructure was transferred to the irrigators. In the case of Mamina irrigation scheme, modernisation of the scheme was required to achieve different livelihood outcomes, but because this did not happen the recurrent utility bill arrears, low productivity and food insecurity continued to be a very serious challenge even after IMT.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2016-08-09T17:08:28Z No. of bitstreams: 2 Tese - Walter da Costa Mendes - 2016.pdf: 18186028 bytes, checksum: 929f8cf89490e9b207c2c363003c05fa (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2016-08-09T20:40:12Z (GMT) No. of bitstreams: 2 Tese - Walter da Costa Mendes - 2016.pdf: 18186028 bytes, checksum: 929f8cf89490e9b207c2c363003c05fa (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-09T20:40:12Z (GMT). No. of bitstreams: 2 Tese - Walter da Costa Mendes - 2016.pdf: 18186028 bytes, checksum: 929f8cf89490e9b207c2c363003c05fa (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-02-25 / The growing global demand for food and a decrease in opening up new areas for expansion due to pressure by environmental preservation, has intensified the process of verticalization of agricultural production, resulting in the shift of extensive to intensive standard. In the Brazilian Cerrado, traditionally with low soil fertility and well defined hydrological cycle, it is observed that this of intensification process has characterized itself by applying large amounts of fertilizer and irrigation. However, mismanagement of irrigation and the doses and times of application of nutrients, especially these with high mobility in soil, can cause losses per leaching, resulting in economic and environmental damage. The objective of this thesis was to quantify the losses of nitrate (NO3-) and potassium (K+), under different managements of irrigation, in sandy and clay soils in greenhouse, and at field, the effects in bean crop irrigated by sprinkling in clay soil. The first experiment was conducted in 2014, Urutaí, Goiás, Brazil. Indeformed soil columns were arranged in a randomized complete blocks design with three replications. As nitrogen source was used calcium nitrate with 15.5% of Total Nitrogen (N) and as source of K+ was used potassium chloride with 58% of K2O. In fertilized columns were used four blades of water, equivalent to 50, 100, 150 and 200% of the water layer obtained by the mass difference of the columns of the treatments 100%. The irrigations were applied every three days for a period of 81 days. The losses of NO3- and K+ in the columns were quantified. Joint analysis of data was performed according to the time factor. The second experiment was conducted in 2014 in Oxisol Red Dystrophic clayey, in Urutaí, Goiás, Brazil. Four irrigation levels were applied, the equivalent to 50, 100, 150 and 200% of crop evapotranspiration (ETc), estimated by the method of Class A tank. The plots were arranged in a randomized complete block design with four replications, and seven evaluations of soil solution throughout the experiment. As K+ source was used the potassium chloride with 58% K2O and as N source was used calcium nitrate with 15.5% of N. To collect soil solution, extractors of solution were installed at depths of 0.20, 0.40, 0.60, 0.80 and 1.00 m, and certain of the extracted solution, the concentrations of NO3- and K+. In crop harvest were evaluated the production components and productivity of beans. With the first experiment it is concluded that the movements of N-NO3- and K+ varied depending on the soil and irrigation levels, being that, the higher the applied water blade, the greater the amount of leached ions NO3- and K+. With the second experiment it is concluded that the movements of NO3- and K+ in the soil profile varied between the treatments, showing increased losses, below the roots, due to the application of greater irrigation blade, and that the correct irrigation management in the bean (100% the ETc), combined with appropriate doses and periods of nitrogen and potassium applications provide the best yield of grains / A crescente demanda mundial por alimentos e a diminuição na abertura de novas áreas para expansão, devido à pressão pela preservação ambiental, vem intensificando o processo de verticalização da produção agrícola, resultando na mudança do padrão extensivo para o padrão intensivo. Na região do Cerrado, tradicionalmente com solos de baixa fertilidade e ciclo hidrológico bem definido, observa-se que este processo de intensificação, tem se caracterizado por aplicação de grandes quantidades de fertilizantes e irrigação. Entretanto, o manejo incorreto da irrigação e das doses e épocas de aplicação de nutrientes, principalmente os de alta mobilidade no solo, podem causar perdas por lixiviação, resultando em prejuízos tanto econômicos quanto ambientais. Assim, o objetivo desta tese foi quantificar as perdas de nitrato (NO3-) e potássio (K+), sob diferentes manejos de irrigação, em solos arenoso e argiloso em ambiente protegido, e a campo, os efeitos na cultura do feijoeiro irrigado por aspersão em solo argiloso. O primeiro experimento foi conduzido em 2014, em Urutaí, Goiás. As colunas de solo indeformado foram arranjadas em blocos completos casualizados com três repetições. Como fonte de nitrogênio utilizou-se o nitrato de cálcio com 15,5% de Nitrogênio Total (N) e como fonte de K+ utilizou-se o cloreto de potássio com 58% de K2O. Nas colunas adubadas foram aplicadas quatro lâminas de água, equivalentes a 50, 100, 150 e 200% da lâmina de água obtida pela diferença de massa das colunas dos tratamentos 100%. As irrigações foram realizadas a cada três dias, por um período de 81 dias. As perdas de NO3- e K+ nas colunas foram quantificadas. Foi realizada análise conjunta dos dados de acordo com o fator tempo. O segundo experimento foi conduzido em 2014, num Latossolo Vermelho Distrófico de textura argilosa, em Urutaí, Goiás. Foram aplicadas quatro lâminas de irrigação, equivalentes a 50, 100, 150 e 200% da evapotranspiração da cultura (ETc), estimadas pelo método do tanque Classe A. As parcelas foram arranjadas em blocos completos casualizados com quatro repetições, sendo sete avaliações da solução do solo ao longo do experimento. Como fonte de K+ utilizou-se o cloreto de potássio com 58% de K2O e como fonte de N utilizou-se o nitrato de cálcio com 15,5% de N. Para coleta da solução do solo foram instalados extratores de solução nas profundidades de: 0,20, 0,40, 0,60, 0,80 e 1,00 m, sendo determinadas da solução extraída, as concentrações de NO3- e K+. Na colheita da cultura avaliaram-se os componentes de produção e a produtividade dos grãos de feijão. Do primeiro experimento concluiu-se que as movimentações de N-NO3- e K+ variaram em função do solo e das lâminas de irrigação, sendo que, quanto maior a lâmina de água aplicada, maiores as quantidades lixiviadas dos íons NO3- e K+. Do segundo experimento concluiu-se que as movimentações de NO3- e K+ no perfil do solo variaram entre os tratamentos, evidenciando perdas cada vez maiores, abaixo das raízes, em função da aplicação de maiores lâminas de irrigação, e que o manejo correto da irrigação no feijoeiro (100% da ETc), combinado com doses e épocas adequadas de aplicações de nitrogênio e potássio, proporcionam o melhor rendimento de grãos da cultura.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O abacaxizeiro ornamental à uma espÃcie rÃstica e exÃtica que produz âfloresâ de grande beleza, apreciadas por consumidores do mundo inteiro. Atualmente, em decorrÃncia da alta demanda do mercado consumidor, a cultura està sendo produzida em escala comercial por meio da micropropagaÃÃo, uma tÃcnica da cultura de tecidos que apresenta cinco etapas igualmente importantes. Uma delas, a aclimatizaÃÃo, à uma fase muito crÃtica, pois costuma responder pelos altos Ãndices de mortalidade e baixas taxas de crescimento das plantas. Essa situaÃÃo ocorre porque as poucas informaÃÃes sobre o manejo da cultura nessa fase sÃo, na maioria das vezes, baseadas no empirismo. Assim, as plantas aclimatizadas acabam nÃo sendo atendidas em todas as suas necessidades, o que leva a perdas considerÃveis e/ou a obtenÃÃo de mudas de qualidade variÃvel. Para minimizar esse problema e preencher a lacuna existente com informaÃÃes tÃcnicas e cientÃficas sobre o adequado manejo da cultura, o presente trabalho teve como objetivo avaliar os efeitos de distintas lÃminas e freqÃÃncias de irrigaÃÃo e de diferentes tipos e volumes de substrato na aclimatizaÃÃo de mudas micropropagadas de abacaxizeiro ornamental (Ananas comosus var. erectifolius). A pesquisa, que constou de quatro experimentos, foi conduzida em um viveiro pertencente a Embrapa AgroindÃstria Tropical, situada no municÃpio de Fortaleza-CE (3Â44â S e 38Â33â W). No primeiro experimento foram analisadas quatro lÃminas de irrigaÃÃo: 1, 2, 3 e 4 mm de Ãgua. As plantas contidas em tubetes de 180 cm3 e cultivadas no substrato pÃ-de-coco verde com hÃmus de minhoca (3:1) receberam as diferentes lÃminas dâÃgua em duas irrigaÃÃes diÃrias. No segundo experimento foram estudadas quatro freqÃÃncias de rega: 1, 2, 3 e 4 irrigaÃÃes ao dia. As plantas cultivadas em tubetes de 180 cm3, contendo o substrato pÃ-de-coco verde com hÃmus de minhoca (3:1), foram irrigadas com uma lÃmina de 3 mm de Ãgua. No terceiro experimento foram testadas quatro distintas combinaÃÃes de substratos na proporÃÃo 3:1: pÃ-de-coco seco com VitasoloÂ; pÃ-de-coco seco com hÃmus de minhoca; pÃ-de-coco verde com Vitasolo e pÃ-de-coco verde com hÃmus de minhoca. As plantas contidas em tubetes de 180 cm3 e cultivadas nos diferentes substratos foram irrigadas com uma lÃmina dâÃgua de 3 mm, aplicada duas vezes ao dia. No quarto experimento foram avaliados quatro tipos de recipiente: tubete de 300 cm3; tubete de 180 cm3; bandeja de 40 cm3âcÃlula−1 e bandeja de 30 cm3âcÃlula−1. As mudas contidas nos recipientes foram cultivadas no substrato pÃ-de-coco verde com hÃmus de minhoca (3:1) e irrigadas com uma lÃmina dâÃgua de 3 mm, aplicada duas vezes ao dia. As variÃveis agronÃmicas, avaliadas aos 52 e aos 83 DAT, foram o nÃmero de folhas, a maior largura da 3 folha e o maior diÃmetro da roseta. Entre os 93 e 97 DAT, analisaram-se os pesos fresco e seco das partes aÃrea e radicular. O delineamento experimental foi de blocos ao acaso, com 4 tratamentos e 5 repetiÃÃes para as variÃveis relacionadas com o desenvolvimento foliar, e 4 tratamentos e 4 repetiÃÃes para as variÃveis relacionadas com o peso da planta. Os resultados dos experimentos evidenciaram o melhor desenvolvimento das mudas micropropagadas de abacaxizeiro ornamental quando: irrigadas com as lÃminas de 1 mm atà os 52 DAT e de 2 mm atà os 83 DAT; submetidas à freqÃÃncia de duas aplicaÃÃes diÃrias da lÃmina dâÃgua durante todo o experimento; o substrato utilizado foi formado pela combinaÃÃo pÃ-de-coco seco com hÃmus de minhoca e cultivadas em tubetes de 180 cm3. / The ornamental pineapple is a rustic and exotic spe cies that it produces "flowers" of great beauty, appreciated by consumers of the whole world . In the present time, due to the high demand of the consumer market, the culture is being produced in commercial scale through the micropropagation, a tissue culture technique th at presents five important stages. One of them, the acclimatization, is a very critic phase b ecause it answers for the high death rates and low growth rates of the plants. This happens becaus e the little information about the culture management in this phase is based on the empiricism most of the time. Therefore, the needs of acclimatized plants are not meet, what takes to considerable losses and/or acquisition of seedlings of variable quality. To minimize this pro blem and to fill out the existent gap with technical and scientific information about the appr opriate culture management, the objective of this work was to evaluate the effects of differe nt irrigation levels and frequencies and different types and volumes of substrate in the acc limatization of micropropagated seedlings of ornamental pineapple (Ananas comosusvar.erectifolius ). The research was carried out in a greenhouse of the Embrapa Tropical Agroindustry, located at Fortaleza-CE (3Â44' S and 38Â33' W) and it consisted of four experiments. Four irrigation levels were analyzed in the first experiment: 1, 2, 3 and 4 mm. The plants, cultivated in the green coir dust substrate with wormcompost (3:1) in 180 cm 3 plastic containers, were irrigated twice a day. Four watering frequencies were studied in the second experiment: 1, 2, 3 and 4 irrigations by the day. The plants were cultivated in 180 cm 3 plastic containers that contained green coir dust substrate with wormcompost (3:1) and they were irrigated with a 3 mm water level. Four different combinations of substrate were tested in the third experiment 3:1: dry coir dust with Vitasolo Â; dry coir dust with wormcompost; green coir dust substrate with Vitasolo and green coir dust substrate with wormcompost. The plants, cultivated in the different substrates in 180 cm3 plastic containers, were irrigated with a 3 mm water level twice a day. Four plastic container types were evaluated in the fourth experi ment: 300 cm 3 plastic container; 180 cm 3 plastic container; tray of 40 cm 3Âcell −1 and tray of 30 cm 3 Âcell −1 . The seedlings were cultivated in the green coir dust substrate with wormcompost (3:1) and they were irrigated with a 3 mm water level twice a day. At 52 and 83 days after the transplant, number of leaves, largest width of the 3rd leaf and largest diameter of the r osette were evaluated. Between 93 and 97 days, root and shoot fresh/dry weight were analyzed . The experimental design was a randomized block with 4 treatments and 5 repetition s for the variables related to foliar development, and with 4 treatments and 4 repetition s for the variables related to plant weight. Results evidenced the best development of the micro propagated ornamental pineapple seedlings when: were irrigated with a 1 mm water level at 52 DAT and with a 2 mm at 83 DAT; were irrigated twice a day during whole experiment; were cultivated in 180 cm 3 plastic containers and when the substrate used was composed by dry coir dust and wormcompost.