A Comparison of Iowa's Original Corn Suitability Rating to the New Corn Suitability Rating 2.

In 1971 Dr. Thomas Fenton and several colleagues at Iowa State University (ISU) developed the Corn Suitability Rating (CSR) providing producers and assessors a soil productivity index for Iowa. The CSR for a soil is based on its inherent soil properties to a depth of 152- to 203-cm, mean weather data for a 30-yr period, and its potential for row crop production.  In 1984 CSR data was combined with existing Soil Conservation Service (SCS) form SOILS-5 data, Map Unit Use File (MUUF), and Iowa CONS-9 data to create a single computer file of compiled soils data called the Iowa Soil Properties and Interpretations Database (ISPAID).  ISPAID improved the availability and distribution of soil properties and interpretation data for Iowa soils, and is widely used today by researchers, teachers, extension education programs, land evaluators, and producers as a reference for determining land values and productivity.  Since the establishment of the CSR, changes in the way soils are classified have been made while advances in technology have enhanced and expanded our knowledge of soil properties. In turn, this changed the way CSR is calculated making it a more robust, yet, an expert driven index. In 2013, ISU introduced a more transparent and consistent method for calculating CSR, called CSR2, so interested individuals could clearly understand the factors underlying the index. The factors used for calculating CSR2 are inherent soil properties, specific field conditions for a soil map unit, soil depth and erosion resilience, and expert judgment; while weather was removed as a factor from the calculation. Soil CSR2 values are generally comparable to CSR. An exception to this is greater CSR2 values in areas where the weather factor was limiting with CSR.