The Illinois State Soil, known as the Drummer soil series, is one of the most fertile and extensive in the state. Covering over 600,000 hectares (1.5 million acres), this dark-colored soil developed under prairie vegetation in northern and central Illinois. The Drummer soil is a deep, poorly drained, silty clay loam. It has a high organic content from decaying prairie grass roots. This organic matter holds nutrients and contributes to the fertility of the soil.
Drummer Series Prairie Soil Zones
A. 0–48 centimeters (0 to 19 in.) deep. Black to dark gray silty clay loam with blocky structure. Many medium and small roots. Slightly acidic.
B. 48–119 centimeters (19 to 47 in.) deep. Dark gray to gray silty clay loam with prism-shaped to blocky structure. Many fine roots and worm holes in upper part, but these decrease with depth. Contains yellowish masses of iron accumulation. Neutral (not acidic or alkaline).
C. 119–152 centimeters (47 to 60 in.) deep. Dark gray layered loam and sandy loam. Massive (uniform with no plate-like or blocky layers) structure. Contains olive brown masses of iron accumulation. Slightly alkaline.
"
Black, fertile prairie soils developed from the decay of the dense root
systems of prairie grasses. These roots decay into organic matter that
holds nutrients and clay in the soil. This rich prairie soil makes Illinois
one of the most productive agricultural regions in the world."
This image is courtesy of the US Dept. of Agriculture, Urbana Extension Service, UIUC.