This study develops a basis for a land information system for the 40 ha subtropical highland catchment of Wang Jia, Yunnan Province, China. Information, including meteorology, geology, geomorphology, biology, pedology and crop productivity, was integrated using a geomorphopedological approach and expressed as maps using GIS. The developed protocol is proposed as a generic system, applicable to agricultural land evaluation in subtropical highland catchments. The results demonstrate that Wang Jia Catchment is relatively representative of the region, in terms of geomorphological features and land cover. Catchment soils, developed from residual, colluvial and alluvial materials of sandstone, shale and dolomite on different landscapes, were still young and strongly influenced by their geological parent material. Soils were normally slightly acidic to neutral. Soil fertility varied from poor to very fertile. Maize yield was significantly correlated with soil pH, total N, available N, P and K and thus the Soil Fertility Index. In 2002, maize yield was significantly correlated with manure and urea applications. There was considerable potential to increase maize yield with modified and innovative cropping practices in the catchment. Adopted primarily as a soil conservation practice, contour cultivation did not increase maize yield compared to downslope cultivation. Polythene mulch tended to increase maize yield in most years. These results largely accord with the results from controlled research plots in the same catchment. Analysis of intra-plot variations showed that soil samples from planting pits had higher total soil organic matter, total N, available N, available P and available K than inter-row samples, but with higher standard deviations. Most soil fertility parameters for inter-row samples were more similar to traditional random composite samples. These results suggest if composite samples were taken only from inter-rows, the results would have been similar, but the risk of sampling error would have been reduced. The land information system established in this study is suitable for designing, evaluating and monitoring sustainable agricultural practices central to soil conservation and crop yield improvement and thus contributing to decision-making for sustainable agricultural land management in this region.

La gestion des villes d’Afrique de l’Ouest pose problème à la période contemporaine : extension urbaine non maitrisée, services de base insuffisants, insécurité foncière. À travers l’aide internationale, d’importantes réformes visant à améliorer son efficacité ont pourtant été mises en place, mais elles semblent avoir été inefficaces. Dépassant ce constat d’échec, la thèse vise à comprendre comment se déroule l’acte de gérer la ville dans les circonstances particulières des villes d’Afrique de l’Ouest. La mise en œuvre du Registre foncier urbain (RFU), système d’information foncière municipal multi-fonctions introduit au Bénin à travers des programmes de développement au début des années 1990, constitue le prisme à travers lequel la gestion urbaine est analysée. Celle-ci est ainsi approchée par les actes plutôt que par les discours. S’appuyant sur une démarche socio-anthropologique, la mise en œuvre de l’instrument est analysée depuis le point de vue des acteurs locaux et selon une double grille de lecture : d’une part, il s’agit de saisir les logiques de l’appropriation locale dont le RFU a fait l’objet au sein des administrations; d’autre part, il s’agit de comprendre son interaction avec le territoire, notamment avec les dynamiques complexes d’accès au sol et de sécurisation foncière. Une étude de cas multiple a été menée dans trois communes : Cotonou, Porto-Novo et Bohicon. Deux ensembles de conclusions en découlent. Tout d’abord, le RFU s’est imposé comme l’instrument pivot de la fiscalité locale, mais est mis en œuvre de manière minimale. Ce fonctionnement particulier est une adaptation optimale à un contexte fait de rivalités professionnelles au sein d’administrations cloisonnées, d’enjeux politico-financiers liés aux différentes sources de revenus communaux et de tensions politico-institutionnelles liées à une décentralisation tardive. Les impacts du RFU en termes de développement des compétences professionnelles nationales sont insuffisants pour réformer la gestion urbaine depuis l’intérieur de l’administration municipale. Ensuite, alors qu’il vise à centraliser l’information sur les propriétaires présumés de la terre, le RFU se heurte à la marchandisation de cette information et à la territorialisation de la régulation foncière. La mise en œuvre du RFU s’en trouve affectée de deux manières : d’une part, elle s’insère dans ces circuits marchands de l’information foncière, avec cependant peu de succès ; d’autre part, elle a un impact différencié selon les territoires de la régulation foncière. En définitive, l’acte de gérer la ville au Bénin n’est pas devenu automatique avec l’introduction d’instruments comme le RFU. La municipalité se repose plutôt sur les piliers classiques de l’action publique, l’administration et le politique, pour gérer la ville plurielle de manière différenciée. À l’endroit des concepteurs d’action publique, cette thèse plaide pour une prise en compte des modes de régulation existant dans les sociétés africaines, fussent-ils pluriels, reconnaissant les voies originales que prend la construction des institutions en Afrique. / The management of West African cities is problematic nowadays: uncontrolled urban sprawl, insufficient basic services, and land insecurity. Yet, major reforms had been put in place with the assistance of international aid to enhance the effectiveness of urban management; which seems to have failed. Going beyond this policy failure statement, the present dissertation aims at understanding how “managing the city” takes place in the particular context of West Africa. The implementation of the Urban Land Registry (RFU), a municipal and multi-purpose land information system that has been put in place in Benin through development programmes in the early 1990s, is the lens through which urban management is examined. Urban management is then studied through the actions taken rather than through the discourses. With a socio-anthropological approach, the implementation of the instrument is analysed from the stakeholders’ perspectives and according to a double analysis grid. On the one hand, the analysis aims at understanding the local appropriation of the RFU inside public administrations; and on the other hand, its aims at comprehending the interaction of the RFU with the territory, in particular with the complex dynamics of access to the land and land security. A multiple case study was conducted in three municipalities: Cotonou, Porto-Novo, and Bohicon. This study led to two main conclusions. First, the RFU is recognized as the key instrument of local taxation, but it is minimally implemented. This particular functioning is an optimal adaptation to a context made of: 1) professional rivalries in a compartmentalized administration, 2) political and financial stakes related to different sources of local revenues, and 3) political and institutional tensions provoked by the late decentralisation. Then, the RFU’s impacts in terms of national professional capacities are insufficient to reform urban management from inside municipal administration. Second, a key function of the RFU that is centralizing information on presumed landowners is impeded by the commodification of land information and by the territorialisation of land regulatory modes. This affects the implementation of the RFU as it takes part in this land information market, but with little success; and its impact is differentiated according to the ‘land regulation territory’ it applies. Finally, ‘managing the city’ in Benin is not an automatic task, even with the introduction of management instruments such as the RFU. Administration and politics continue to shape municipal policies, and the pluralistic city is managed in a differentiated manner. To the designers of public action (policies), this dissertation encourages to take into account existing regulation modes in African societies, even if they are multiple and complex, and it recognises the singular process of institution building in Africa.