WEED MANAGEMENT AND TALL FESCUE QUALITY AS INFLUENCED BY MOWING, NITROGEN, AND HERBICIDES

A 3-yr field study was conducted to determine the influence of N level (98 and 196 kg ha-1 yr-1), mowing height (3.2, 5.5, and 8.8 cm), and three herbicides on weed encroachment and overall quality of tall fesc ue Festuca arundinacea Schreb. cv. Rebel 11. The major objective of th is study was to identify cultural methods of excluding weed developmen t in tall fescue. Dithiopyr [3,5-pyridinedicarbothioic acid, thylpropy l)-6-(trifluoromethyl)-S,S-dimethylester] and pendimethalin [N-(1-ethy lpropyl)-3, 4-dimethyl-2,6-dinitrobenzenamine] were applied preemergen ce for smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Mu hlenb.] control, and fenoxaprop [(+/-)-2-[4-[(6-chloro-2-benzoxazolyl) oxy]- phenoxy]propanoic acid] was applied postemergence for crabgrass control. Rates of dithiopyr and pendimethalin were reduced or eliminat ed on selected plots in the last 2 yr of the study to determine if red uced herbicide inputs would continue to provide effective crabgrass co ntrol. Tall fescue mowed at 8.8 cm resisted smooth crabgrass invasion, exhibited best visual summer turf quality in 1990 and 1991, had poore st winter turf quality, and had highest white clover (Trifolium repens L.) populations. Other environmental factors and lower mowing height (3.2 or 5.5 cm) reduced summer turf quality in 1990 and 1991. High N i mproved fall and winter turf quality, but not summer quality. Nonherbi cide-treated plots receiving high N had less smooth crabgrass than low N plots, but high N provided no additional crabgrass reduction in her bicide-treated plots. High mowing (8.8 cm) was the best cultural manag ement strategy for reducing smooth crabgrass encroachment and maintain ing tall fescue cover. Results indicated that smooth crabgrass control with label use rates of herbicides was warranted when mowing tall fes cue at 3.2 or 5.5 cm.