COMPARATIVE METHODS OF MEASURING THATCH ON A CREEPING BENTGRASS GREEN

Thatch accumulation continues to be a serious problem in densely grown close mowed turfgrass. Several methods are used to measure thatch, ra nging from very rapid to very slow, with opinions differing concerning the reliability of the various methods. The objectives of these studi es were to evaluate speed of use, precision, reliability, and the prac ticalities of two of the most commonly used methods of measuring thatc h, which are slow, with those of a very rapid method. All three method s were evaluated as part of a held study to determine the effectivenes s of mechanical and chemical treatments in controlling thatch on a cre eping bentgrass (Agrostis palustris Huds.) green growing on a U.S. Gol f Association (USGA) rootzone. Thatch control treatments were vertical mowing (4 and 8x/yr), coring (4x/yr), wetting agent (7x/yr), extra K (4x/yr), lime (4x/yr), and various combinations of these; and interact ions of these with topdressing (3 and 6x/yr). Thatch measuring methods used were the ruler, total organic matter (OM) by loss-on-ignition, a nd a rapid surface sod compression instrument termed the Thatchmeter I I. Treatments and measurements were conducted for 6 yr with results re ported 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 tedio usly slow, taking days to complete, and measured only total OM by weig ht with no determination for depth. As a method relating to thatch dep th, the thatchmeter and ruler methods correlated well with each other with the thatchmeter being more sensitive. The OM method did not corre late with either the thatchmeter or ruler. Based on data from this stu dy, the thatchmeter appears to be the most reliable and practical of t he three methods tested.