This study was conducted on four adjacent 16-ha (40-ac) fields within the Clarion-Nicollet-Webster soil association to (1) determine if crop yield interpretations derived from 1:15840 soil survey maps could be used for developing field-scale management plans: and (2) to determine if soils in adjacent fields were derived using a computer-based Soil Information System (SIS) and compared with measured yields. Soil map units in all four fields were taxonomically variable, but this did not affect expected crop yields. Average expected and measured corn and soybean yields agreed within 9 and 12% for conentional management at the field-scale. We conclude that yield interpretations from county soil surveys can be used to develop field-scale management palns for central Iowa farms, and that taxonomic soil differences would not confound comparisons of conventional and alternative farming practices in these fields.