Which term refers to a unique soil taxonomic unit characterized by distinguishing soil features?

The term that refers to a unique soil taxonomic unit characterized by distinguishing soil features is indeed a soil map unit. A soil map unit represents a specific area on a soil map that is uniform in soil characteristics and properties, which are important for understanding how different soils behave in terms of drainage, aeration, nutrient retention, and other factors relevant to septic system design and installation.

Soil map units are determined based on soil surveys and are integral in guiding decisions related to land use, agriculture, and environmental management. They help in identifying the suitability of soil types for various applications, including how well they can absorb effluent from a septic system.

In contrast, soil evaluation generally refers to the broader process of assessing soil for its various properties and uses. The soil absorption rate measures how quickly soil can absorb water, which is a critical factor but does not describe the concept of a unique soil unit. Soil incorporation refers to the mixing of soil with organic matter or fertilizers, which is not relevant to the taxonomic classification of soils.