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Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

While new agricultural technologies may lead to substantial yield improvements, the take-up rates in developing countries have frequently been low. There are many possible reasons why a farmer might refrain from adopting a new technology, and literature has pointed to several possible reasons in different settings. A key area for research is to understand what policies could encourage higher adoption rates. This thesis studies the research question by using a case study of fertiliser adoption in cocoa farming in Ghana. Chapter I investigates whether returns to fertiliser in cocoa farming are high and whether farmers' adoption decisions can be explained by comparative advantage. Chapter I uses data from Ghana to measure the returns to fertiliser using a correlated random model and static and dynamic panel models of homogeneous returns to fertiliser. The estimated returns in different models are positive, high and strongly significant statistically. The chapter also presents a correlated random effects model of heterogeneous technology, which allows for farmer-specific comparative advantage. The effect of the comparative advantage is found not to be statistically significant. Chapter II explores the fertiliser investment decisions and risk preferences of Ghanaian cocoa farmers in a framed field experiment. The experimental subjects decided whether to invest in fertiliser, and the fertiliser return depended on a stochastic weather realisation. An inexpensive index insurance scheme with a positive level of basis risk was found to have a minor positive effect on the fertiliser take-up, but this effect was statistically insignificant. An expensive index insurance scheme with no basis risk was found to have a substantial positive effect, and this effect was strongly significant. The experimental findings suggest that farmers are willing to pay for an index insurance if it successfully shields them from income variability. Chapter III investigates the effect of trust and of an ambiguous environment on fertiliser investments under index insurance. These two behavioural factors were studied by means of a framed field experiment conducted with Ghanaian cocoa farmers. The subjects had an option to invest in a package of fertiliser bundled with index insurance with a positive level of basis risk. The returns depended both on the subjects ́ investment choices and a stochastic weather realization. The key ingredient of the study was that for different subjects, the nature of the basis risk was framed differently. Substantially fewer subjects adopted fertiliser when possible losses of fertiliser investment were framed as resulting from the insurer ́s failure to meet its contract obligations, compared with an alternative in which the losses were framed as resulting from a mismatch between their own weather realizations and those on which the index insurance was based. A large negative effect on fertiliser investments was also found in treatments with either a small or large ambiguity regarding the exact level of basis risk. Both negative treatment effects were strongly significant. This may suggest that technologies with which farmers are relatively more experienced are more likely to be adopted under index insurance schemes. The overall experimental findings provide evidence that trust and ambiguity may be significant factors other than basis risk, limiting the effectiveness of index insurance in promoting agricultural innovation.

Cette thèse est composée de trois articles qui posent chacun une question sur les discriminations. Le premier article interroge si les habitants de la Seine-Saint-Denis sont statistiquement discriminés sur une violence supposée ; où la pratique d’un sport de combat serait un signal de violence. Le second article regarde si les accents marseillais sont discriminés sur le marché du travail. Le dernier article se demande si les employeurs pourraient utiliser le patronyme et l’adresse des candidats à l’embauche pour faire des corrélations sur leur accent et, s’ils infèrent qu’ils ont l’accent des grands ensembles, de les discriminer sur ce point. La méthode du « testing » est utilisée pour répondre à ces trois questions. Les deux premiers testings amènent à répondre par la négative aux deux premières questions. Concernant la troisième question, même si l’on ne peut pas y répondre, le troisième testing prouve que l’accent des grands ensembles est discriminé. De plus, il démontre que la discrimination sur le patronyme peut mettre dans l’ombre celle sur l’adresse. De façon générale, ce travail permet de mettre en évidence que les employeurs ne prennent pas en compte le sport dans leur pratique d’embauche et que lors de l’élaboration du design d’un testing on doit distinguer les signaux forts des signaux faibles. Il montre aussi que les testings peuvent être utilisés jusqu’au moment où les employeurs contactent les candidats par téléphone et qu’ils engagent des stéréotypes différents selon l’accent qu’ils entendent. Enfin, il propose aux décideurs publics de chercher à d’abord diminuer la discrimination basée sur le patronyme s’ils veulent diminuer la discrimination totale. / This thesis is composed of three articles. Each of them asks one question about discriminations. The first article interrogates if Seine-Saint-Denis inhabitants are statistically discriminated on a supposed violence ; where to do a fighting sport would be a violence signal. The second article investigates if Marseille accents are discriminated in the labor market. The third article asks if employers may use the name and the address as proxies to determine job candidates’ accent and, if they infer he holds a poor area accent, to discriminate on the basis of this accent. I use the correspondence study method to reply to these three questions. The first two correspondence studies lead to conclude to the negative to the first two questions. Concerning the third question, even if we cannot reply to it, the third correspondence study proves that the poor area accent is discriminated. Moreover, it shows that the name discrimination may overcomes the address one.General conclusions are that this thesis indicates employers do not take into account the practiced sport to hire and that to elaborate the design of a correspondence study implies to consider weak and strong signals. It also shows that correspondence studies can be used up to the moment where employers contact job applicants by phone and that they have different stereotypes in mind according to the accent they hear. Finally, it proposes to public policy makers to first decrease the name discrimination if they want to significantly impact the total discrimination.

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Bibliography: leaves 203-212. / xiii, 212 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study investigated the genetic diversity for tolerance of durum wheat (Triticum turgidum L. var durum) to micronutrient deficient soils with an emphasis on manganese. 69 genotypes were studied under field conditions at Marion Bay (Lower Eyre Peninsula) and Coonalpyn. Durum genotypes, notably Stojocri, were identified as having higher tolerance than commerical durum varieties. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1999

Bibliography: leaves 190-212. This thesis reports on the results of 3 glasshouse and 3 field experiments. The glasshouse experiments measure the effects of depth of placement and level of phosphorus (P) on the growth of field peas (Pisum sativum L. cv. Alma). The results of all the experiments suggest that placing P fertiliser 4-5 cm below the seed of field pea crops will be beneficial in terms of nodulation, P uptake, grain yield and grain P concentration.

Bibliography: leaves 203-212. This study investigated the genetic diversity for tolerance of durum wheat (Triticum turgidum L. var durum) to micronutrient deficient soils with an emphasis on manganese. 69 genotypes were studied under field conditions at Marion Bay (Lower Eyre Peninsula) and Coonalpyn. Durum genotypes, notably Stojocri, were identified as having higher tolerance than commerical durum varieties.

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