Excessive thatch accumulation is a serious problem in maintenance of turfgrasses. Several turfgrass management practices have been shown to influence thatch accumulation. The present study was undertaken to determine the effectiveness of various management practices alone and in combinations in preventing thatch accumulation in common Kentucky bluegrass (Poa pratensis L.), and the relationship between thatch accumulation, turf quality, and leaf spot damage. Treatment effects on thatch accumulation were assessed by measuring total amount of organic matter in the thatch layer. Ratings for turf quality and leaf spot damage caused by Helminthosporium spp. were based on color and stand density. Three sets of treatments were arranged in a split‐split plot design: (A) Mower clippings removed vs. not removed; (B) lime applied as needed to maintain a soil pH 7, lime applied at 4.8 to 7.3 kg/are biannually, and no lime (soil pH 5.4); and (C) sub‐sub‐plots that were: (a) aerified (coring), (b) handraked, (c) verticut, (d) had applications of a wetting agent, (e) had additions of organic matter (Milorganite®3), and (f) untreated. Thatch accumulation was not significant during the first 5 years of the study. Clipping residue left on plots significantly contributed to thatch accumulation when all treatments were averaged, and after thatch had built up to approximately 1.25 cm in depth. Residue from clippings did not increase thatch on aerified turf or turf receiving the wetting agent. Maintenance of soil pH of 6.8 and biannual lime applications effectively reduced thatch accumulation over that of untreated soil. Biannual lime applications did not increase decomposition beyond that of liming as needed to maintain a favorable soil pH. Aerification resulted in the least amount of thatch followed by the verticut and handraked treatments. The wetting agent did not effectively reduce thatch, and the addition of Milorganite® significantly increased thatch production. The highest quality turf was produced by permitting clippings to remain on the turf, maintaining a favorable soil pH and aerification. Clippings increased turf quality during temperature and moisture stress periods. Leaf spot damage was reduced by aerification, applying the wetting agent, and removing clippings. There was no significant difference in thatch level among the check, aerified, handraked, verticut, and wetting agent 14 months after their discontinuance.

Effects of glyphosate [N-(phosphonomethyl)glycine] and paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) on turfgrass seed germination were evaluated in the greenhouse. Glyphosate caused little effect on germination of Kentucky bluegrass (Poa pratensis L.), red fescue (Festuca rubra L.), and tall fescue (F. arundinacea Schreb.) when applied to the soil immediately before seeding or when applied directly over the seed on the soil surface. Paraquat sprayed directly over the seed on the soil surface prevented germination of most of the seeds of the three grass species. Covering seeds on the soil surface with clippings from grass turf sprayed with paraquat greatly reduced germination. About half of those that germinated either died later or were severely chlorotic. Covering seeds on the surface of the soil with clippings from turf that had been sprayed with glyphosate did not significantly reduce the number of seedlings established.

Annual applications of three nitrogen (N) rates, two broadleaf herbicides, and six annual-grass herbicides in Kentucky bluegrass (Poa pratensisL.) turf were made from 1974 to 1981. With each increment increase in N (2, 4, and 6 kg N/200 m2), the percentage cover of crabgrass (Digitariaspp.) and number of common dandelion (Taraxacum officinaleWeber # TAROF) plants were reduced when compared with the next lower rate. There was an interaction between crabgrass control by the annual-grass herbicides and fertilizer rates. When highly effective herbicides were used, there were no differences in crabgrass control related to N rate. When less effective herbicides or no annual-grass herbicides were used, there were great changes directly related to N rate. Each increment of increased N rate increased the turf quality rating. The broadleaf herbicides resulted in differential quality ratings, although differences were relatively small. Highest quality ratings were for plots treated with the three most effective annual-grass herbicides. Residues in the ppb range of some herbicides were detected in soils sampled about a year after the eighth annual herbicide treatments, but residues were below the phytotoxic level and therefore would have had no effect on control of weeds.

Preemergence applications of herbicides were evaluated for their effect on establishment of zoysiagrass (Zoysia japonicaSteud.) with competition from either smooth crabgrass [Digitaria ischaemum(Schreb.) Muhl. # DIGIS] or goosegrass [Eleusine indica(L.) Gaertn. # ELEIN]. When ‘Meyer’ and ‘Belair’ zoysiagrass plugs were grown in sand and treated in the greenhouse, none of the herbicides reduced root weight or length. When plugs were grown in a Sassafrass sandy loam, bensulide {O,O-bis(1-methylethyl)-S-[2-[(phenylsulfonyl)amino] ethyl] phosphorodithioate} and simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine) reduced root weight, and simazine reduced root length of Belair, but not Meyer. In smooth crabgrass-infested field plots, more stolons were produced from Meyer plugs treated with simazine, oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one}, and siduron [N-(2-methylcyclohexyl)-N′-phenylurea] than plugs treated with bensulide, metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], or the untreated control. At the end of two growing seasons, metribuzin-treated plots had significantly less zoysiagrass than other plots. Oxadiazon, DCPA (dimethyl tetrachloroterephthalate), and siduron enhanced the field establishment rate where Meyer zoysiagrass was competing with high populations of smooth crabgrass.

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