What term describes an organic layer made up of decomposing plant materials just above the soil surface?

The term that describes an organic layer made up of decomposing plant materials just above the soil surface is thatch. Thatch is a buildup of organic matter consisting of grass clippings, leaves, and other plant debris that can accumulate in a lawn or turf area. This layer plays a critical role in protecting the soil, retaining moisture, and providing a habitat for beneficial microorganisms.

While compost is a controlled mixture of decomposed organic materials used primarily to enrich soil, and mulch serves as a protective covering to retain soil moisture and suppress weeds, neither of these terms specifically refers to the layer of decomposing materials that is directly associated with turf management and growth. Dew, on the other hand, refers to moisture that condenses from the atmosphere onto surfaces, which is unrelated to the organic layer in question. Therefore, thatch is the most accurate term to describe this specific layer of material in a turf environment.