Soil Productivity – Does CSR2 or Bonitas Work Better in Iowa?.

Agronomists, farmers and government ministries each have deep interest in a successful albeit simple metric of soil productivity. Two well-known indices – at least in their respective areas - are Iowa’s corn suitability rating (CSR2) and Ukraine’s BONITAS. Both are linked to their nation’s soil survey databases. Both use a 100-point scale with the majority of points relating to pedological properties and landscape features. Both were created in regions where Mollisols and large-scale cereal production are the norm. The objective of this research is to evaluate how well each predicts corn yield in Iowa. Ten fields were used in this study. They are distributed across Iowa, with most of the major soil associations being represented. Each field has multiple years of corn yield. All yield data is from calibrated yield monitors. Each field is considered well if not optimally managed from an agronomic perspective. CSR2 and BONITAS were determined for each soil map unit in each field using their respective equations. Expected results are BONITAS and CSR2 will each be generally accurate (and correlate very well with one another) but both will lack precision.