Land evaluation is a process that estimates the land use potential based on its properties. A large variety of analytic models can be used in this process. In Brazil, the two most widely used land evaluation systems are the "Sistema de Classificação da Capacidade de Uso da Terra" and "Sistema FAO/Brasileiro de Aptidão Agrícola das Terras". Although different in several aspects, both require the crossing of countless environmental variables. ALES (Automated Land Evaluation System) is a computer program that allows the construction of specialist systems for land evaluation. ALES evaluates map units of either general or detailed character. The area of this evaluation comprised the Chapecó and Xanxerê microregions, in the west of the state of Santa Catarina, and covered 54 municipal districts. Soil data and landscape characteristics were obtained from the state soil survey, at a scale of 1:250.000. This study developed the specialist system ATOSC (Land Evaluation in western Santa Catarina), which defines the requirements of different land use types, and the subsequent comparison of these requirements with the attributes of each map unit. The land use types considered were: bean, corn, soy and wheat in sole cultivations without irrigation, under the characteristic management of these crops in the state. The information on natural resources comprises climatic, soil and landscape attributes that affect the crop yields. In ATOSC, the code, name and land use requirements were specified for each land use type. The crop requirements were defined by a specific combination of the selected land characteristics that determine the severity level of each one in relation to the crop. We established 4 severity levels that indicate a limitation increase or a potential decrease for a certain land use: none or slight limitation (favorable); moderate limitation (moderately favorable); strong limitation (not very favorable); and very strong limitation (unfavorable). In the decision tree, a basic component of the specialist system, rules are implemented that allow a classification of the regions in defined suitability classes, based on the requirements of each land use type. The ATOSC made the comparison between the regional characteristics of the microregions Chapecó and Xanxerê and the requirements of the considered land use easier. The evaluation is automatic, reducing the time spent in the process. The Chapecó and Xanxerê microregions were fit, for the most part, in the suitability classes not very favorable (3) and unfavorable (4) for the considered crops. The main limiting factors in these microregions were identified as natural fertility and erosion risk for bean and corn; and mechanization conditions and erosion risk for soy and wheat.
specialist system; land evaluation; ALES
