Illinois Soils Explanation
We use Agri Data Inc which has a productivity index column from the University of Illinois’ Bulletin 811. The number boxed in blue in the attached photo is what we use as the corn yield rating and the numbers boxed in green are what we use to calculate our soils. These numbers are based on the property as a whole and not just tillable acreage.
Our classifications for soils are as followed (based from the productivity index column):
A Soil: 133-147
B Soil: 117-132
C Soil: 100-116
D Soil: 99 – Below
The only time a farm would have single soil rating is if the farm was 80% of a certain soil. For example 82% of the productivity is labeled B soil and 18% C soil; that farm would be rated as a B soil farm. Otherwise we use double soil ratings such AB or DC to try and total at least 80% of the land. The highest percentage of a certain soil for that farm will be the soil labeled first. For example 57% productivity is A soil and 43% is C soil; that farm would be rated AC.
A-C classification comes from the soil classes from Bulletin 811 and soil class D is a label given by Land Sales Bulletin. It is for non-prime land such as woods or pasture.