What is the primary function of thatch in turfgrass, and at approximately what depth does water infiltration and gas exchange begin to be restricted?

• A. Thatch protects soil and moderates temperature; when thatch depth exceeds about 0.5 inch (12–13 mm), infiltration and gas exchange can be restricted.
• B. Thatch primarily stores nutrients for the turf and improves drainage when deeper than 1 inch.
• C. Thatch is mainly a disease barrier; restricted infiltration occurs only after 2 inches of thatch.
• D. Thatch has no significant function; restriction occurs at any depth.

Answer: (A)

Thatch acts as a protective blanket for the soil, helping to moderate surface temperature and conserve moisture. This insulation is beneficial up to a point, but when thatch becomes about a half inch deep (roughly 12–13 mm) the mat fills in pore space enough to slow water moving into the soil and restrict diffusion of gases between the soil and the atmosphere. That’s why water infiltration and gas exchange begin to be limited at roughly 0.5 inch of thatch. The other ideas aren’t as accurate: thatch isn’t primarily a nutrient reservoir or a disease barrier, and significant infiltration restriction can start well before two inches of thatch.