GIS-based Analysis of Indigenous and Technical Knowledge of Soil Suitability Evaluation of Cocoa, Citrus and Oil Palm in Ejisu-Juabeng District, Ashanti Region, Ghana

摘要

A study was carried out to assess local knowledge about soil suitability in four villages in the Ejisu- Juabeng District in the Ashanti region of Ghana. This study described two approaches in soil mapping using geopedologic approach promoted by Zinck (1988) and the farmer approach using their spatial knowledge and experience. Both maps were assessed for their suitability for cocoa, oil palm and citrus. First, farmers created their soil map and then assessed the soil suitability for a selected number of tree crops which are important for them economically. Secondly, on the other side which is the side of the expert, the approach for soil suitability classification was performed using the Automated Land Evaluation System (ALES) which uses the Food and Agriculture?Organization (FAO) framework for land evaluation that defines suitability by employing matching (comparison) between land quality/land characteristics and land use requirement. The expert and farmer suitability maps were then compared using spatial analysis within the Geographic Information Systems (GIS) environment to determine levels of spatial correlation and the level of agreement among the maps. Farmers’ suitability maps for cocoa accounted for 81% of the study area, citrus and oil palm accounted for 71% and 26% respectively. In the expert suitability map 66% of the study area was suitable for cocoa, citrus and oil palm accounted for 41%and 39% respectively. The overall accuracy from the map comparison was 67% for cocoa, 43% for citrus and 14% for oil palm. The results of spatial correlation between expert and local soil suitability map units reflect differences and similarities in the ways both systems classify soils. Critical is the evaluation of topsoil characteristics, as the understanding and monitoring of topsoil dynamics are fundamental for land use decision-making by farmers. Merging technical and local thinking is indispensable to formulate sustainable land management schemes for agricultural production.