Most books covering the use of computer models in agricultural management systems target only one or two types of models. There are few texts available that cover the subject of systems modeling comprehensively and that deal with various approaches, applications, evaluations, and uses for technology transfer. Agricultural System Models in Field Res

The symposium In the next decades, agriculture will have to cope with an ever-increasing demand for food and raw basic materials on the one hand, and with the necessity to use resources without further degrading or exhausting the environment on the other hand, and all this within a dynamic framework of social and economic conditions. Intensification, sustainability, optimizing scarce resources, and climate change are among the key issues. Organized thinking about future farming requires forecasting of consequences of alternative ways to farm and to develop agriculture. The complexity of the problems calls for a systematic approach in which many disciplines are integrated. Systems thinking and systems simulation are therefore indispensable tools for such endeavours. About 150 scientists and senior research leaders participated in the symposium 'Systems Approaches for Agricultural Development' (SAAD) at the Asian Institute of Technology (AIT), Bangkok, Thailand, in December 1991. The symposium had the following objectives: - to review the status of systems research and modeling in agriculture, with special reference to evaluating their efficacy and efficiency in achieving research goals, and to their application in developing countries; - to promote international cooperation in modeling, and increase awareness of systems research and simulation. The symposium consisted of plenary sessions with reviews of major areas in systems approaches in agriculture, plus presentations in two concurrent sessions on technical topics of systems research. Subjects of studies were from tropical and temperate countries.

In December 1993, ISNAR, in collaboration with International Consortium for Application of Systems Approaches, organized a three-day workshop on systems approaches and modelling for agricultural development. Sponsored by the Dutch Ministry for Development Cooperation, the workshop was attended by participants from 12 national agricultural research systems (NARS), nine international agricul tural research centers (lARCs), and five advanced research organizations (AROs). Although application of systems approaches in agricultural research and resource management is a rather new field, there is already increasing demand for implemen tation of these approaches. This will require a critical mass of specialists in the NARS and IARCs. Before this critical mass can be obtained, however, the experience that has been gained in this area needs to be evaluated, further possibilities need to be explored, and new objectives and targets need to be set. This book, which contains the papers presented at the workshop, assesses the state of the art of systems approaches in agricultural research, resource management, and rural planning. It also gives an impression of the evolution of this interdisciplinary field and its use in national and international research centers. Another, less tangible, outcome of the workshop was its contribution toward strengthening the network of NARS, lARCs, and AROs. It gave participants and organizers a chance to develop contacts, and provided an opportunity to make the first proposals for collaborative programs. Special thanks are due to Peter Goldsworthy and Luc Boerboom for their crucial role in making the workshop a success in this regard.