AN EVALUATION OF SOIL SURVEY CROP YIELD INTERPRETATIONS FOR 2 CENTRALIOWA FARMS

This study was conducted on four adjacent 16-ha (40-ac)fields within t he Clarion-Nicollet-Webster soil association to (1) determine if crop yield interpretations derived from 1:15840 soil survey maps could be u sed for developing field-scale management plans; and (2) to determine if soils in adjacent fields were sufficiently similar to not confound farming system comparisons. Expected crop yields were derived using a computer-based Soil information System (SIS) and compared with measure d yields. Soil map units in all four fields were taxonomically variabl e, but this did not affect expected crop yields. Average expected and measured corn and soybean yield agreed within 9 and 12% for convention al management at the field-scale. We conclude that yield interpretatio ns from county soil surveys ran be used to develop field-scale plans f or central Iowa farms, and that taxonomic soil differences would not c onfound comparisons of conventional and alternative farming practices in these fields.