Corn Suitability Rating 2 (CSR2)
Definition
Corn Suitability Rating 2 (CSR2) is an index of a soil's inherent productivity for row crops, mainly corn, developed by Iowa State University for Iowa soils. It runs from 100 for the most productive soils down to 5 for the least. Each soil map unit's rating is computed from soil survey data with the equation CSR2 = S - M - W - F - D ± EJ, where S reflects the soil's taxonomic subgroup, M its particle-size family, W its available water-holding capacity, F field conditions such as slope and erosion, D soil depth and tolerable erosion, and EJ an expert-judgment adjustment used mainly for very dense, clayey or sandy parent materials. Iowa State publishes two versions: CSR2-ISU, which treats a map unit as its named soil series, and CSR2-NRCS, which area-weights the dominant soil and its inclusions; they usually agree within a point or two. A farm's CSR2 is normally reported as the area-weighted average across its tillable acres, and Iowa land sales are often compared per CSR2 point.
Why it matters
In Iowa farmland, CSR2 is the shorthand for soil quality that appears in listings, appraisals and auction results, and price per CSR2 point is a common way to say whether a sale was high or low. For investors in Iowa farms through fractional platforms, the farm's CSR2 is the first check on whether the price fits local comparables. It is also easy to misuse: quoted across total rather than tillable acres, compared with indexes from other states, or treated as a yield. A CSR2 figure is most useful when it comes with the map-unit breakdown, the version used, the tillable acres it covers and the farm's yield history.
Common misconceptions
- •CSR2 is not a national index. It applies to Iowa soils.
- •CSR2 is not a yield. It rates inherent productivity.
- •A farm's CSR2 should not include non-farmed acres. Weight it over tillable acres.
- •The two versions are not always identical. CSR2-ISU and CSR2-NRCS can differ for map units with many inclusions.
- •Price per point does not capture drainage, buildings or location.
Technical details
The equation
CSR2 = S - M - W - F - D ± EJ.
S: taxonomic subgroup of the soil.
M: family particle-size class; W: available water-holding capacity.
F: field conditions such as slope and erosion; D: soil depth and tolerable erosion.
EJ: expert-judgment correction, mainly for very high bulk density or unusually clayey or sandy parent materials.
Worked farm calculation
Tillable map units: 80 acres at CSR2 88; 50 acres at 76; 20 acres at 60 (150 tillable acres).
Weighted CSR2 = (7,040 + 3,800 + 1,200) / 150 = 80.3.
If the farm also has 10 acres of timber and farmstead rated at 30 and they were wrongly included, the figure would fall to 77.1 ((12,040 + 300) / 160), understating the farmed land.
At $12,000 per tillable acre, the price is about $149 per CSR2 point.
Using CSR2 in diligence
Ask for the soil map, map units, acres and CSR2 values, and which version (ISU or NRCS) was used.
Confirm the weighting covers tillable acres only.
Compare price per point with recent nearby sales on similar drainage.
Check tile maps and yield history alongside the rating.
How investors apply the term
Investors usually apply this term by tying the definition back to the controlling documents and then asking which cash flows, rights, restrictions, or valuation assumptions it changes. A useful review looks at the term alongside fees, leverage, liquidity, reporting frequency, and manager discretion rather than treating it as a standalone concept.
The practical diligence test is simple: identify who benefits if the assumption is wrong, who has control when conditions change, and what evidence the investor receives after closing. Terms that cannot be reconciled to documents, cash movements, and monitoring data should be treated as marketing shorthand until proven otherwise.
Frequently asked questions
- What is CSR2 and how does it affect farmland value?
- CSR2 rates the inherent productivity of Iowa soils from 5 to 100. Higher-rated soils generally yield more and rent for more, so Iowa land prices tend to rise with a farm's average CSR2, and buyers compare sales in dollars per CSR2 point. It is one input to value alongside drainage, location, buildings, field layout and the local market.
- How is a farm's CSR2 calculated?
- Each soil map unit on the farm has a CSR2 value. The farm figure is usually the area-weighted average across the tillable acres: multiply each map unit's acres by its rating, add them up, and divide by total tillable acres. Including non-farmed acres, such as farmstead, timber or waterways, would distort it.
- Can CSR2 be used outside Iowa?
- No. It was built for Iowa soils and survey data. Other states use their own indexes, such as Illinois' productivity index and Minnesota's crop productivity index, on different scales. AcreTrader's offerings cite CSR2 for Iowa-type Midwest farms and a productivity index for its Illinois farms.
- Does a higher CSR2 guarantee higher yields?
- No. It rates inherent soil potential. Actual yields also depend on drainage, fertility, management, weather and pests. A farm's multi-year yield history is the better evidence of what it produces.