What is thatch in terms of turf grass?

Thatch is defined as a layer of organic material that consists of living and decomposing turfgrass roots, stems, and other plant material that accumulates between the soil surface and the green grass blades. This layer can vary in depth and is an essential aspect of turf health, as it can affect water and nutrient absorption. When thatch builds up excessively, it can hinder the growth of grass by limiting air penetration and creating an environment that may encourage pests and diseases. Proper management of thatch through practices such as aeration, dethatching, and maintaining healthy turf can help mitigate its negative effects and promote a vibrant lawn.

In contrast, the other options do not accurately represent thatch. A layer of soil is the foundational ground where grass grows but does not involve the organic materials specifically associated with turfgrass. Mulch is an external covering used to suppress weeds and retain moisture, and clay is a type of soil texture that can affect drainage but does not describe the organic buildup relevant to thatch.