Productivity is not in question
Central Illinois soils are among the best in the world for corn and soybeans, and the market prices them accordingly. Productivity indexes are the standard valuation measure, and a parcel's index correlates directly with what it will command.
What varies is drainage quality, field configuration, and whether the ground has been maintained. Ask about tile age and condition, because replacing a failed system is expensive and its absence shows up in yields long before it shows up in a listing.
The tax burden changes the arithmetic
Illinois property taxes are high by any national comparison. Farmland benefits from use-value assessment, which is a genuine mitigation, but the rates applied on top of that assessment are still meaningful.
For an investor buying for cash rent, the relevant number is net after property tax rather than gross rent. That calculation can make a lower-priced parcel in a neighbouring state more attractive than a superior Illinois parcel, and it is worth running before assuming productivity settles the question.
Drainage districts
Districts maintain the tile and open drainage that makes flat Illinois ground farmable, funded by assessments on benefited land. Confirm district membership, current assessments and any pending reconstruction before buying.
Leases and tenants
Most Illinois cropland is tenanted. Illinois law sets notice requirements for lease termination, and a buyer may take subject to an existing lease for the coming crop year. Establish the arrangement, the rent, and the notice status before closing.
What to verify
Productivity index and comparable sales. Property tax history — actual bills, not estimates. Drainage district status. Lease terms and termination notice. The risk scorecard covers the rest.