The use of Geographic Information Systems (GIS) in estimating a potential fadama land area for inland farming: The buffering technique

The buffering technique in the Geographic Information Systems (GIS) was used to estimate the land area of a fadama for inland farming. The investigation was carried out in Akure (7°15´N, 5°15´E) in May 2008. The Ikonos satellite image of the five hundred hectare land area at 4 m resolution was georeferenced using ArcView 3.3 GIS software to make locations on the image align to positions on the earth’s surface. A submap of the image that contained a perennial stream was generated and the stream buffered at a distance of 100 m away from the stream on all sides. The buffered zone depicting the fadama land was polygonized and the total area computed as 34.19 hectares and locations for soil studies in the buffered zone identified on the map. The field work entailed locating on the ground with the use of the Global Positioning System (GPS) receiver the points for soil studies already identified on the digital map. Soil samples were taken from the surface (0-30 cm) and subsoil (30-100 cm) for laboratory analysis of soil physical and chemical properties. ArcView statistical analysis was used to obtain the minimum, maximum and average values of soil properties. The soils were sandy loam on the surface (0-30 cm) and sandy clay loam in the subsoil (30-100 cm) with low gravel content both at the surface and subsoil. The pH indicated a slightly acidic to neutral soil with moderate organic matter, nitrogen and total exchangeable bases. The farming system adoptable in the fadama was the cultivation of swamp rice during the rainy period of June to September while leaf and fruit vegetables could be cultivated during the dry season of October to March. Buffering as a geospatial technology had been used to estimate the accurate size in hectares and also in a precision soil fertility investigation of the potential fadama farmland.