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Unformatted text preview: Busey and Johnston: Cultural factors and turf weeds • 961 Weed Science, 54:961–967. 2006 Impact of cultural factors on weed populations in St. Augustinegrass turf Philip Busey Corresponding author. University of Florida, 3205 College Avenue, Fort Lauderdale, FL 33314-7719; [email protected] Diane L. Johnston University of Florida, 3205 College Avenue, Fort Lauderdale, FL 33314-7719. Managing weeds in lawns using cultural practices such as mowing, irrigation, and fertilization may be important in integrated management. A field experiment eval- uated the impact of cultural factors on weed populations in St. Augustinegrass turf. Irrigation treatments were daily to replace evapotranspiration (‘‘Daily’’), weekly to saturate the root zone only when wilted (‘‘Conditional Weekly’’), and as needed to saturate the root zone after severe wilt (‘‘Severely Wilted’’). Averaged over 3 yr, the Daily, Conditional Weekly, and Severely Wilted irrigation treatments resulted in 30, 6, and 2% dollarweed cover, respectively. Except for dollarweed and mat lippia, the largest cover of other weeds was under Severely Wilted irrigation. Fertilization rates were 0, 14, or 28 g N m 2 2 yr 2 1 ; in 2002, the highest fertilization rate had the smallest cover of weeds other than dollarweed. Mowing heights were 64, 89, or 114 mm; in 2003, the shortest mowing height had the smallest cover and dry weight of weeds other than dollarweed. After 3 yr of cultural management, most plots were excessively weedy, and turfgrass quality for all cultural management-treatment com- binations, in the absence of herbicides, was unacceptable. Nomenclature: Dollarweed or water pennywort, Hydrocotyle umbellata L. HY- DUM; mat lippia, Phyla nodiflora (L.) Greene LIPNO; St. Augustinegrass, Stenota- phrum secundatum (Walt.) Kuntze STPSE. Key words: IPM, lawn. There are few reports regarding the impact on weed pop- ulations in turf from cultural factors such as mowing, fer- tilization, irrigation, cultivation, planting, and turfgrass se- lection (Busey 2003). Irrigation amount decreases, increases, or has no effect on weed populations, depending on the species of weed and the situation (Busey 2003). For exam- ple, irrigation daily with 7.6 mm water vs. three times per week with an amount to replace 80% of evapotranspiration (a 67% reduction) has no effect on smooth crabgrass [ Dig- itaria ischaemum (Schreber) Schreber ex Muhlenb.] or dan- delion ( Taraxacum officinale Weber in Wiggers) populations in perennial ryegrass ( Lolium perenne L.) (Jiang et al. 1988). In contrast, more regular or larger amounts of irrigation are sometimes associated with denser infestation by annual blue- grass ( Poa annua L.) (Gaussoin and Branham 1989; Qian and Engelke 1999; Youngner et al. 1981). Greater rates of N fertilization (100 to 300 kg N ha 2 1 yr 2 1 ) and taller heights of mowing (40 to 80 mm, depending on turf spe- cies) are associated with smaller weed populations, particu- larly of crabgrass species (...
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