Mechanical resistance to penetration encountered by growing plant roots is one of the fundamental soil physical factors affecting crop growth and yield. This thesis presents two inter-related studies examining measurement and application of soil penetration resistance and its effects on crop performance on a southern Ontario landfill cover. Study 1 examines the enhancement of a pedotransfer function for penetration resistance and its application for use in the field. Improvements in the function's predictive capability for laboratory samples were achieved (R2 increased from 0.731 to 0.813). However, its usefulness under field conditions was characteristically low. Using the function established in Study 1, Study 2 examined the relationship between crop yield and the proportion of days the soil water content was outside the least limiting water range. Correlation between these variables was low, however, water-related plant stress was minimal as the study took place under near optimal weather conditions.