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 ma intained under lo mowing heights. Opinions differ concerning effective ness of cultural and chemical controls of thatch. The objectives of th ese studies were to determine the effectiveness of mechanical and chem ical treatments in controlling thatch and their influence on soil nutr ient retention and pH in a creeping bentgrass (Agrostis palustris Huds ,) green growing on a U.S. Golf Association (USGA) rootzone, Thatch co ntrol treatments were vertical mowing (VRI 4 and 8x/yr), coring (core 4x/yr), wetting agent (Wet Ag 7x/yr), extra K (4x/yr), lime (L 4x/yr) and various combinations, and interactions of these with topdressing ( Tpd 3 and 6x/yr). Rootzone nutrients determined were Ca, Ii, and P and rootzone pH levels were determined. Thatch measurements were determin ed with a rapid surface sod compression instrument termed the Thatchme ter II, Treatments and measurements were conducted for 6 yr with resul ts reported for the last 3 yr. Lowest non-significant levels of thatch resulted following VM 4x or 8x/yr and VRI + coring. Tpd 3x or 6x/yr a lso effectively prevented thatch buildup. When combining mechanical an d chemical methods with Tpd, lowest non-significant levels of thatch r esulted following Vm 4x or 8x/yr, VM + coring, and VM + L, all combine d with Tpd 6x/yr. Extra Ii (VRI + K + L, Ii + L, K) and Wet Ag resulte d in increased thatch. Lime did not influence thatch depth. Loss of ro otzone K was 94% and increased with mechanical and chemical treatments . Loss of rootzone P was 86% but extra K and L treatments reduced P lo ss, especially under pn 7.3 following L treatments. Loss of rootzone C a was 56% but L and extra K treatments under pH 7.3 reduced this loss.