Objective <p>Agricultural productivity is influenced by climate, soil, management, and technology, yet the role of field geometry, including field size, shape, and edge effects, remains poorly understood. This study investigates how geometric field properties relate to crop yield and within-field yield variability in corn, soybean, and wheat, and evaluates the potential effects of edge management through simulated buffering.</p> Methods <p>More than twenty years of combine harvester yield monitor data from the US Midwest were analysed. Starting from 18,529 raw yield maps, rigorous geometric cleaning and georeferencing corrections produced a high-quality dataset of 7,207 fields. Mean yield and within-field yield variability were related to field area, perimeter, perimeter-to-area ratio, and compactness, both individually and in combination. In addition, inward buffering of 10 m and 30 m was simulated to quantify the effects of edge removal on field productivity and yield variability.</p> Results <p>Field geometry was not a dominant driver of agricultural productivity, although consistent patterns emerged across the dataset. Larger and more compact fields tended to exhibit slightly higher yields and lower within-field variability, whereas smaller and more irregular fields performed less favourably. Simulated buffering consistently increased whole-field mean yields, particularly in small fields with high perimeter-to-area ratios, while also producing modest reductions in within-field yield variability.</p> Conclusion <p>Although the influence of field geometry on crop productivity is generally modest, edge effects represent a measurable source of yield reduction and spatial variability. The findings suggest that geometry-aware management, including the introduction of ecological buffer zones, could improve both agricultural productivity and environmental sustainability with limited loss of productive land.</p>