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There is increasing recognition that spatial variability in soils occurs across the landscape within a field and that differential management practices are warranted. Differences in herbicide persistence in the soil can result in variation in crop injury across the landscape. Soil pH, which is also reported to vary across the landscape, influences herbicide persistence. Thus, this study investigates the ability to map and delineate within-field soil pH variability using landscape segmentation analysis and provide a tool for predicting herbicide persistence. The area, comprising a conventional and a no-till field in southern Alberta, was surveyed using a dual frequency global positioning system; a digital elevation model was created and landform segments defined. Four landform segments were effective in delineating soil pH zones that could be related to herbicide persistence. The lower slopes in both fields, with pH < 6.0, showed imidazilinone persistence. Carryover of sulfonylurea and triazine herbicides was evident in the upper slopes of the conventional till field only (pH 7.8(7.9). The results suggest that landscape segmentation modeling could provide a valuable tool in managing field spatial variation in soil. [ABSTRACT FROM AUTHOR]