(a) Soil in central Iowa with dark, organic-matter-rich topsoil. Iowa's average topsoil depth decreased from 35-45 cm to 15-20 cm during the 20th century due to farming. (b) Severe gully erosion ...

a product that often gives carbon-rich soils their characteristic dark color (Fig. 2). These various forms of SOC differ in their recalcitrance, or resistance to decomposition. Humus is highly ...

A worm burrows its way through the dark earth, ingesting particles of soil and expelling nutrient-rich casts in a constant forage for food. Charles Darwin described earthworms as one of the most ...

Thousands of years of prairie grass growth, death and decomposition have left a thick layer of dark, organic matter ... and silt to form a nutrient-rich type of soil called loam.

On Saturday, Jan. 18, the “Rich Soil” exhibit opened at the Lewis Ginter Botanical Garden, featuring 29 life-size sculptures presented in seven groupings located in areas throughout the garden.