A fast-growing interest in the concepts and application of systems research has spawned a wide and general literature over the past decade. Most disciplinary areas have been touched, but commerce, engineering and military studies have, perhaps, been best served with outstanding texts. No provision has so far been made for a general book at introductory level of direct relevance to agricultural science, technology and management. General reviews are, of course, valuable to the agricultural-systems researcher but agricultural systems, with important biological components interacting with equally vital social and economic elements, embody particular characteristics which influence the approach to their study. This book is written in the belief that the concepts as well as the technology of the systems approach have a basic role in the rational advancement of the agricultural discipline and in the improvement of efficiency in agricultural research and practice. A basic and introductory text is an essential pre­ requisite to this role being realised. A reiteration of basic concepts is expressed in the introductory chapter while in the final chapter particular attention is given to the general problems of integrating systems concepts in research, extension and practice. The dialogue of these chapters is necessarily brief and in some respects speculative but it is supported by appropriate bibliography. The main body of the text is concerned with the methodology of systems research; the conception, construction, implementation, validation and exploitation of computer-based simulation models of agricultural systems.

1. Principles of Model-building.- Why the Computer?.- A Definition of System.- System Simulation.- A General Statement of Procedure in Systems Simulation.- Concluding Remarks.- 2. Model-construction.- Getting Started.- The Process of Modelling.- Summary.- Workshop.- 3. Computer Considerations.- Choosing a Language.- Design Criteria for Computer Modelling.- Summary.- Workshop.- 4. Stochastic Specification.- The Case For and Against Stochasticity in Modelling.- Autocorrelation.- Generating Random Variates.- Some Final Words.- Workshop.- 5. Model-evaluation.- Testing Models Against Design Criteria (Verification).- Validation of Simulation Models.- Validation Procedures.- A Long-term View of Model-evaluation.- 6. Design of Simulation Experiments.- Factors, Treatments and Replicates.- Computer-based Experimentation.- Optimum-seeking Designs.- Concluding Comments.- 7. Model-application.- Systems Involvement in the Research Process.- Systems Involvement in Farmer Decision Making and Business Control.- Design Pointers for Successful Agricultural-information System Designs.- Future Developments in Agricultural-information Systems.- Skeleton Models in Applied Research Direction.- Final Synthesis.