Cultural and Chemical Controls of Thatch and Their Influence on Rootzone Nutrients in a Bentgrass Green

Thatch accumulation is a serious problem in densely grown turfgrass maintained under low mowing heights. Opinions differ concerning effectiveness of cultural and chemical controls of thatch. The objectives of these studies were to determine the effectiveness of mechanical and chemical treatments in controlling thatch and their influence on soil nutrient retention and pH in a creeping bentgrass (Agrostis palustris Huds.) green growing on a U.S. Golf Association (USGA) rootzone. Thatch control treatments were vertical mowing (VM 4 and 8×/yr), coring (core 4×/yr), wetting agent (Wet Ag 7×/ yr), extra K (4×/yr), lime (L 4×/yr) and various combinations, and interactions of these with topdressing (Tpd 3 and 6×/yr). Rootzone nutrients determined were Ca, K, and P and rootzone pH levels were determined. Thatch measurements were determined with a rapid surface sod compression instrument termed the Thatchmeter II. Treatments and measurements were conducted for 6 yr with results reported for the last 3 yr. Lowest non‐significant levels of thatch resulted following VM 4× or 8×/yr and VM + coring. Tpd 3× or 6×/yr also effectively prevented thatch buildup. When combining mechanical and chemical methods with Tpd, lowest non‐significant levels of thatch resulted following VM 4× or 8×/yr, VM + coring, and VM + L, all combined with Tpd 6×/yr. Extra K (VM + K + L, K + L, K) and Wet Ag resulted in increased thatch. Lime did not influence thatch depth. Loss of rootzone K was 94% and increased with mechanical and chemical treatments. Loss of rootzone P was 86% but extra K and L treatments reduced P loss, especially under pH 7.3 following L treatments. Loss of rootzone Ca was 56% but L and extra K treatments under pH 7.3 reduced this loss.