Land suitability is generally established based on a combination of land qualities required by rice. In this study, the evaluation is accomplished with objective of examining a quantitative aggregation of land qualities with the multicriteria decision analysis (MCDA) model using GIS. The study area is the Chi basin, Northeast Thailand with an area of about 4,947,700 ha. The procedure of fusing the land qualities entailed the excluded area, the MCDA model applied for fusing the land qualities in the rest while the multiplicative model used with limiting conditions. The land qualities used in the MCDA encompass water availability, nutrient availability index, nutrient retention, water retention, salt hazard. Each was treated as a thematic layer in the GIS database. The rooting condition is limiting condition used for spatial overlay with the MCDA layer by the multiplicative model. The results obtained are checked against the harvesting plots and Land Development Department (LDD) map, yielding high accuracy. It is evident from the study that land suitability for rice covers about 26% of the area for highly and moderately suitable land. The GIS technology offers the tool to effectively model the land suitability with its capability in variable fusion.
