The objectives of the study were: 1. To determine the magnitude and extent of soil compaction and structural degradation on the flat, clay soils of Southwestern Ontario. 2. To assess the relative impact of soil compaction and structural degradation on phosphorus delivery and crop yield. 3. To evaluate the utility of existing knowledge of soil structure and subsoil compaction predictive models in assessing the nature and extent of the problem. 4. To evaluate prospective ameliorative techniques. 5. To recommend potential avenues for further research. The study was initiated in November 1987 and involved three major types of data collection: field investigations of soils supported by laboratory analysis, farmer interviews, and a review of the literature. This report describes the methods used in collecting and statistically analyzing the data, presents the results and makes comparisons to findings reported in the literature, summarizes the study findings and gives recommendations for further work to help clarify data gaps and to help minimize compaction problems. A series of appendices provide abbreviations and definitions of classes used, summaries of data collected, and selected statistical analyses.