How to Read a Soil Productivity Index Report Before You Buy Illinois Farmland
What the Listing Says vs. What the Soils Actually Show
A 160-acre parcel in central Illinois lists with this description: "Highly productive farmland, average Soil Productivity Index of 118, long-term tenant in place, PI verified by seller." The asking price is $11,200 per acre — $1.792 million total. You are trying to figure out whether 118 PI justifies that price in the current market, and what 118 PI actually means for this specific piece of ground.
The number alone tells you almost nothing useful without context. A PI of 118 on deep, well-drained Flanagan silty clay loam in McLean County is a very different asset from a PI of 118 on Drummer silty clay loam with drainage problems in a low-lying Sangamon County field, or from a PI of 118 that is averaged across a mixed parcel with some 135 PI ground and some 98 PI ground that brings the average down. The score is a starting point for due diligence, not a conclusion.
Here is how to go from the number in the listing to an informed understanding of what you are actually buying.
Step One — Pull the NRCS Web Soil Survey for the Parcel
The Natural Resources Conservation Service maintains the Web Soil Survey at websoilsurvey.nrcs.usda.gov — a publicly available, free tool that maps soil types by parcel across the United States. You do not need a subscription or a login. You need the parcel's legal description or township/range/section coordinates to locate it on the map.
Once you locate the parcel, use the area of interest tool to outline the field boundaries and run the Soil Data Explorer report. The report will show you every soil map unit present on that parcel, the acreage of each map unit, and the dominant soil series within each unit. Cross-reference those soil series against the Illinois NRCS Soil Productivity Index ratings for each series in that county.
What you are looking for: how many different soil types are present, how concentrated the dominant soil type is, and whether the soil types present match the PI claim in the listing. A parcel where 85 percent of the acreage is Drummer silty clay loam rated at 130 PI is a very different parcel from one where the acreage is split across five different soil series with varying PI ratings that average to the claimed number.
Step Two — Understand the Difference Between PI and CSR2
Illinois uses two related but distinct productivity scoring systems, and listings sometimes use them interchangeably without clarifying which one they mean. The Soil Productivity Index is a county-specific rating system used primarily in northern and central Illinois counties. The Corn Suitability Rating 2 — CSR2 — is the statewide system developed by the University of Illinois, and it is the basis for the Illinois property tax assessment framework.
A parcel described as "118 PI" may be using the county-specific PI rating, or it may be using CSR2. In many counties, the numbers are similar but not identical — a field rated 118 PI might have a CSR2 of 110 to 122 depending on the specific soil series and county. When you are comparing one parcel's stated productivity number to another parcel's stated number, confirm that both are using the same rating system before drawing conclusions.
The farmdoc land value research out of the University of Illinois uses CSR2 as its primary productivity variable for correlating land values to soil quality. If you are trying to use farmdoc price-per-point benchmarks to evaluate a listing, you need the parcel's CSR2 specifically — not just the PI, and not just the county average.
Step Three — Pull the FSA Farm Records
The Farm Service Agency maintains production records for farms enrolled in federal commodity programs, and those records are transferable with the parcel at sale. The FSA farm record for a given field shows the farm number, the base acres eligible for commodity program payments, and — critically — the yield history the farm has established under past program elections.
This yield history is a real-world validation of the soil quality claim. A field with a claimed average PI of 118 should have a yield history consistent with what 118 PI ground produces in that county under normal management. If the FSA records show an Approved Yield for corn of 165 bushels per acre on ground being marketed as capable of 200-bushel corn, that discrepancy requires an explanation. Conversely, a field with a 195-bushel Approved Yield history on 118 PI ground tells you something positive about the management history and drainage condition of that specific parcel.
Request the FSA farm records as part of your due diligence before you finalize an offer. Most sellers with productive, well-documented ground will provide them without friction. Reluctance to provide FSA records is itself information.
Step Four — Evaluate the Drainage
Central Illinois soil productivity is inseparable from drainage. The highest-PI soils in the state — Drummer, Flanagan, Sable, Ipava — are productive precisely because generations of tile drainage have converted what were once seasonally saturated prairie wetlands into some of the most productive agricultural soil on earth. Remove the drainage infrastructure and the soil productivity collapses. The PI score was earned with the tile in place, and maintaining the tile is what maintains the score in practice.
On any farmland due diligence, ask for the tile map. Not every farm has a complete tile map — especially for older systems installed before GPS field mapping was standard — but the seller and the current tenant should be able to describe the tile system, the outlet condition, and any known drainage problems. Walk the field in person during wet conditions if the timing allows. Standing water, wet spots, or evidence of surface drainage problems are red flags that the listed PI score does not reflect the ground's actual performance in wet years.
Central Illinois has experienced significant rainfall variability in recent years. A farm with drainage problems is a different asset in a wet year than its PI score suggests, and wet years have been recurring with enough frequency to make drainage condition a material due diligence item rather than a secondary consideration.
What to Do With Everything You Have Found
After running the Web Soil Survey, cross-referencing CSR2, reviewing FSA records, and evaluating drainage, you have a picture of what you are actually buying. Compare that picture to the farmdoc county-level price-per-CSR2-point benchmarks for recent sales in that county. Is the asking price consistent with what that productivity level is trading for in the current market?
If the due diligence has confirmed the PI claim, the yield history is consistent, and the drainage is solid, you have a clean picture of a well-documented productive parcel. If due diligence has raised questions — mixed soils, inconsistent yield history, drainage concerns — those questions belong in the negotiation before you close, not in the problem list after you own it.
Farmland at central Illinois pricing is not a transaction where post-close surprises are inexpensive. On a 160-acre parcel at $11,000 per acre, you have committed $1.76 million. Do the soil work before you write the check — it takes a few hours and it is the difference between informed and hopeful.
Jared Williams is the Managing Broker and owner of Archer Realty & Auction LLC. He serves on the Menard County Board of Review and specializes in agricultural land sales, farmland auction, and land evaluation across central Illinois. Start the conversation at archerrealty.net.
