Evaluating inland valley agro-ecosystems in Ghana using a multi-scale characterization approach

As part of measures for improving the productive capacities of inland valley systems for rice-based cropping systems, a published multi-scale characterization approach was used in Ghana to assess the constraints and variables which must be understood before agronomic interventions are made. Macro, reconnaissance, semidetailed and detailed levels of characterization at their respective scales were used. Between 1996 and 1999, Geographical Information System (GIS) and transect studies were carried out, after which the extent of variability in the biotic and abiotic characteristics of two agro-ecologies were identified. Ten agro-ecological units were identified for Ghana based on map overlays and cluster analysis. The method allowed for the selection of Mankran and Jolo-Kwaha watersheds representing the equatorial and savanna agro-ecologies, respectively. Socio-economic parameters (markets, population density and suchlike) were recognized as the essential variables, which should be considered alongside lithology, climate, hydrology and others, for the choice of valleys for development interventions for crop production. At the detailed level of characterization, hydrological and soil characteristics underscored the need to properly understand the watershed-level and valleyspecific constraints before meaningful rice-based research and cropping systems are developed. En tant que partie de mesures pour ameliorer les capacites productives de systemes de vallee de l\'interieur pour les systemes de culture bases sur le riz, une approche de caracterisation multiechelle publiee etait employee au Ghana en vue d\'estimer les contraintes et les variables qu\'il faut comprendre avant que les interventions agronomiques soient faites. Les niveaux macro, reconnaissance, semi-detaille et detaille de caracterisation a leurs echelles respectives etaient utilises. Entre 1996 et 1999, l\'etude transversale et du Systeme Informationnel Geographique (SIG) etaient faites a la suite de quelle l\'etendue de variabilite de caracteristiques biotiques et abiotiques de deux agro-ecologies etaient identifiees. Dix unites agro-ecologiques etaient identifiees pour le Ghana base sur l\'analyse de revetements et de rassemblement sur la carte. La methode permettait la selection de lignes de partage des eaux de Mankran et de Jolo-Kwaha representant respectivement les agroecologies equatoriales et savanes. Les parametres socioeconomiques (les marches, la densite de population, etc.) etaient reconnus comme les variables essentielles, qui devraient etre considere a cote de la lithologie, le climat, la hydrologie, etc.; pour le choix de vallees pour les interventions de developpement pour la production des cultures. Au niveau detaille de caracterisation, les caracteristiques de hydrologie et de sol soulignent la necessite de comprendre vraiment les contraintes de niveaux de lignes de partage des eaux et les contraintes specifiques a certaines vallees avant que la recherche et les systemes de culture utiles bases sur le riz soient developpes. Ghana Journal of Agricultural Science Vol. 40 (2) 2008: pp. 141-157