Farm operational knowledge including dynamic processes as well as heuristics for expert planning and management for machinery, labor and other resources has been represented and manipulated utilizing knowledge engineering concepts of artificial intelligence (AI) in logic programming (PROLOG) . The new approach permitted integration of simulation, expert systems and databases under one single environment, thus leading to a seamless decision support system. It also enabled imparting some of the "intelligent" functions of simulation processes, generally performed by human experts, to computers, thus facilitating their usage by non-experts. A decision support system (FARMSYS) with four components, namely, object-oriented simulation, logic-based expert system. knowledge-based yield estimation system and intelligent information system, has been designed, constructed and evaluated. A team of experts evaluated professional qualifications of FARMSYS and found its structure excellent with a comprehensive framework for a variety of applications. All its components functioned correctly, intelligently, and in harmony with one another, using knowledge from an operational farm in north Florida. The Operations Simulator successfully simulated field operations for complete cropping season and responded correctly to scheduled work hours and to the withdrawal of machinery and laborer. The Expert Analysis component successfully imitated the behavior of machinery management expert (s) . Its recommendations and other support were effective, and demonstrated the possibility of reducing the machinery and labor force from the test farm without significantly affecting the timeliness of the majority of farm operations. The Yield Estimation system responded to different work hours during critical operations showing their effects on crop yields and profits. The Information Management System expedited the development and updating process of the farm knowledge-bases to carry out different tests with FARMSYS, thus demonstrating its successful functioning as an integrated decision support system. PROLOG facilitated simulating field operations in an object-oriented manner, a new AI method of programming. Its inferencing capabilities have been utilized to incorporate several expert systems within and outside the simulation and other components of FARMSYS. The object-oriented approach allowed for the modeling of aspects of the system that are typically ignored or difficult to model when using conventional approaches.