What are soils made up of decayed plant and animal matter commonly referred to as?

Soils composed of decayed plant and animal matter are most appropriately referred to as organic soils. This type of soil is rich in organic material, which results from the decomposition of living organisms over time. Organic soils play a crucial role in the ecosystem as they are foundational for supporting plant life, enhancing soil fertility, and improving water retention.

The presence of organic matter contributes to the soil's ability to hold nutrients and improve overall soil structure. This is particularly beneficial in agricultural settings, where soil health directly impacts crop yield.

Other types of soil, such as expansion soils, silty soils, and granular soils, are defined by different characteristics and do not emphasize organic content. While these soils have their own unique properties, only organic soils specifically highlight the decomposed biological material that gives them their name and functional importance in the environment.