Web Soil Survey (free, authoritative, clunky interface). CropScape (satellite crop maps, no yields). NASS Quick Stats (county-level ag economics).
Climate FieldView, Granular: designed for active farming operations, not pre-acquisition analysis.
SoilOptix, EarthOptics: high accuracy but require field access and cost $5-$15/acre.
Productivity assessment, crop suitability scoring, lease rate estimation, conservation eligibility, and conversion analysis — all from a single parcel lookup.