Thatch is a layer of partially decomposed organic matter between green shoot tissue and the soil surface, and mat is thatch partially intermixed with topsoil. Excessive thatch-mat layering (.2.54 cm) is generally detrimental to turfgrass management, and numerous techniques including various mechanical and topdressing regimes, have been attempted to reduce its severity. This factorial experiment investigated the effectiveness of combining mechanical-biological and topdressing treatments for controlling thatch-mat levels in an established USGA-specified golf green planted with 'A-1' creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)]. Two levels of topdressing were used, and the mechanical-biological treatments included vertical mowing at two different depths and timings, core cultivation, grooming, a biological granular supplement (Thatch-X), and combinations of core cultivation with grooming and/or vertical mowing. Differences among the mechanical-biological treatments were detected following 2 consecutive yearly applications. Thatch-mat depth (mm) was 12 to 15% greater for Thatch-X and topdressing alone compared with other treatments. Organic matter content (g kg 21 ) increased 32% for the untreated and decreased 19% for core cultivation combined with vertical mowing and grooming, whereas all other treatments maintained pre-study levels. Compared with the untreated, surface hardness was reduced |9% for all treatments using core cultivation, while water infiltration rates increased 127 to 168%. Vertical mowing treatments improved water infiltration rates by 40 to 65%. Turfgrass quality was not greatly impacted by the mechanicalbiological treatments as ratings ranged from 8.4 to 10.0. However, mower scalping and dry spots contributed to unacceptable or only marginally acceptable turfgrass quality (6.4-7.2) for the untreated by the end of the study. Compared with topdressing alone, ball roll distance was decreased 6% by vertical mowing 7 days after treatment (DAT) and 5 to 8% by core cultivation up to 14 DAT. Sand topdressing alone was insufficient for managing thatch-mat levels in an established creeping bentgrass golf green.

gressive horizontal growth quickly develops undesirable excessive thatch-mat layering. Excessive (Ͼ1.3 cm) thatch and mat layering of turfgrass is consid-Thatch, a tightly intermingled layer of living and dead ered undesirable because it reduces hydraulic conductivity, water infiltration, increases localized dry spots and pest problems, and reduces stems, leaves, and roots of grass, develops between the pesticide effectiveness and turf tolerance to temperature extremes. green turfgrass vegetation and soil surface. It is formedThe objective of this 2-yr study was to determine the efficacy of primarily from periodically sloughed roots, intact fitopdressing alone and in combination with several mechanical and brous roots, horizontal stems (stolons and rhizomes), biological methods to control thatch-mat accumulation in a newly nodes, crown tissue, and vascular strands of stems and established 'L-93' creeping bentgrass [Agrostis stolonifera L. var palleaf sheaths (Engel, 1954;Roberts and Bredakis, 1960; ustris (Huds.) Farw.] sand-based golf green. Mechanical and biological Hurto et al., 1980). Thatch accumulation occurs when methods included vertical mowing at various depths and timings, core the production rate of organic matter exceeds the decultivation, grooming, a biological thatch control agent (Thatch-X), composition rate (Beard, 1973). Any climatic, edaphic, and combinations of core cultivation with grooming, core cultivation or biotic factor that stimulates excessive plant growth with vertical mowing, and core cultivation combined with grooming and vertical mowing. No treatment prevented thatch-mat accumula-Center; J.J. Camberato,