Sampling bias, ignoring drainage class (40-60 bu/acre difference), missing wetland boundaries, unchecked flood zones, county averages vs parcel-specific scores, overlooking groundwater trends.
Each failure quantified: drainage misclassification alone can mean $500-$1,500/acre overpayment.
SSURGO + NWI + FEMA + USGS + CropScape + NASS: six federal sources eliminating blind spots in a single integrated analysis.