Comparative Methods of Measuring Thatch on a Creeping Bentgrass Green

Abstract

Thatch accumulation continues to be a serious problem in densely grown close mowed turfgrass. Several methods are used to measure thatch, ranging from very rapid to very slow, with opinions differing concerning the reliability of the various methods. The objectives of these studies were to evaluate speed of use, precision, reliability, and the practicalities of two of the most commonly used methods of measuring thatch, which are slow, with those of a very rapid method. All three methods were evaluated as part of a field study to determine the effectiveness of mechanical and chemical treatments in controlling thatch on a creeping bentgrass (Agrostis palustris Huds.) green growing on a U.S. Golf Association (USGA) rootzone. Thatch control treatments were vertical mowing (4 and 8×/yr), coring (4×/yr), wetting agent (7×/yr), extra K (4×/yr), lime (4×/yr), and various combinations of these; and interactions of these with topdressing (3 and 6×/yr). Thatch measuring methods used were the ruler, total organic matter (OM) by loss‐on‐ignition, and 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. The thatchmeter was easy to use, enabling a set of six readings per sub‐plot to be made much faster than one core sample could be cut and measured with a ruler. The OM method was tediously slow, taking days to complete, and measured only total OM by weight with no determination for depth. As a method relating to thatch depth, the thatchmeter and ruler methods correlated well with each other with the thatchmeter being more sensitive. The OM method did not correlate with either the thatchmeter or ruler. Based on data from this study, the thatchmeter appears to be the most reliable and practical of the three methods tested.