GIS – based land suitability assessment for vanilla cultivation in Eastern Uganda

Abstract

Globally, vanilla annual consumption has increased, yet its production is almost constant across all areas. In Uganda, it faces significant challenges due to inadequate spatial knowledge of ideal soil conditions and climatic factors. Prior studies have centered on biophysical factors like soil texture, elevation, and land use in identifying suitable areas. In previous research, climate and soil chemical properties have not been included in the biophysical assessment of land. This study incorporates them in evaluating land areas suitable for vanilla growing, particularly in eastern Uganda with low vanilla production. Land suitability assessment (LSA) was made using climatic conditions, topography, and soil chemical and physical properties integrated with multicriteria decision-making (MCDM). Climatic data such as temperature was obtained from the climatic research unit (CRU) for a ten-year average period (2014–2023), and rainfall data for ten years (2014–2023) was obtained from climate hazards infrared precipitation (CHIRPS). Topographical data, such as the digital elevation model, was obtained from the United States Geological Survey (USGS). Soil's physical and chemical properties were obtained from Food and Agriculture Organization (FAO) data. Thematic maps for each parameter were developed using ArcGIS 10.8.2. Each parameter was reclassified; a weighted sum overlay was implemented to investigate the final land suitability assessment map. Ten composite soil samples were taken from randomly sampled areas of the case study and sent to the laboratory for standard soil tests on texture and pH to validate the suitability model. This showed a strong positive correlation between the model data and the observed sampled data. The highly suitable category covered 0.000425%, very suitable—77.487%, suitable—17.6159%, moderately suitable—4.5909%, marginally suitable—0.3161%, and not suitable—0%. Most of the land in the study area is in a very suitable category, which shows that the region can become a significant player in the vanilla industry. However, parts with moderately and marginally suitable categories need intensive land management activities to increase land quality for better vanilla yields. Therefore, LSA is recommended before a land utilization decision has to be made.