They formed in Kansan or Nebraskan glacial till. Mean annual temperature is approximately 51 degrees F, and mean annual precipitation is about 29 to 33 inches. The Shelby series occurs in association with and topographically below the Marshall , Sharpsburg , Grundy , Seymour , Arispe , and Otley soils which formed in loess. They are also associated with the Adair , Burchard , Clarinda , Lamoni , Lineville , Pawnee , and Steinauer soils which formed in till and with Caleb soils which formed in side valley alluvium on high benches or dissected remnants of benches. Adair and Lineville soils have redder hues or reddish mottles in the upper part of the B horizon.
Caleb soils have more stratification in their lower sola.
Clarinda and Lamoni soils have a gray, finer textured B horizon. Pawnee soils have a finer textured B horizon. Steinauer soils are calcareous throughout. Moderately well drained or well drained. Permeability is moderately slow.