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Chunhua Liu, James J. Camberato, S. Bruce Martin, and Amy V. Turner

Rough bluegrass (Poa trivialis L.) is being utilized more frequently to overseed bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] putting greens and rapid seed germination is necessary for successful establishment. Cultivar and seed lot differences in germination rate and sensitivity to cold may exist. Germination of 10 rough bluegrass cultivars/seed lots was examined in growth chambers at 12-hour day/12-hour night temperatures of 25/15, 20/10, 15/5, and 10/0 °C, and on a bermudagrass putting green at three overseeding dates. Differences in germination among cultivars and seed lots were minimal at 25/15 or 20/10 °C, but substantial at lower temperatures. When seeded on the bermudagrass putting green, differences in germination among cultivars/seed lots were greater at the last seeding date (average daily max./min. of 16/2.7 °C), than at the first seeding dates (average daily max./min. of 21/6.1 °C). Use of blends of several cultivars or seed lots is suggested to ensure the successful establishment of rough bluegrass when overseeding at low temperatures.

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Fahed A. Al-mana and David J. Beattie

A study of applying growth retardants under overhead and subsurface irrigation systems was conducted on bermudagrass (Cynodon dactylon L. cv. Tifway) grown from rhizomes in 15-cm pots containing sand medium. Paclobutrazol (50%) at 2 mg/pot was used as foliar spray or charged-hydrophilic polymers (Super Sorb C) and either incorporated or put below medium surface. Mefluidide (28%) at 0.01% ml/pot was used only as foliar spray. Before spray treatments, grasses were cut at 2 cm from medium surface, and the second cut was made at the 6th week from treatment. All growth retardant treatments reduced grass height compared to non-treated plants. The lowest grass height was produced by paclobutrazol as foliar spray under overhead irrigation in the 6th and 9th week. By the 9th week, all hormonal treatments under the two irrigation systems had no effect on grass quality, color, and establishment rate. Both paclobutrazol foliar spray and below medium surface charged-polymer treatments under subsurface irrigation had the lowest water loss and dry weight by the 6th and 9th week. The paclobutrazol charged-polymer treatment under subsurface irrigation had also the the lowest root dry weight among all treatments. Although mefluidide foliar spray was less effective on grass height than paclobutrazol, they had similar effect on water loss and shoot dry weight.

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Wheeler G. Foshee, William D. Goff, Michael G. Patterson, and Donald M. Ball

Hairy vetch (Vicia villosa Roth), common vetch (V. sativa L. `Cahaba White'), arrowleaf clover (Trifolium vesiculosum Savi `Yuchi'), crimson clover (T. incarnatum L. `Tibbee'), red clover (T. pratense L. `Redland II'), yellow nutsedge (Cyperus esculentus L.), buckwheat (Fagopyrum sagittatum Gilbert), hairy indigo (Indigofera hirsuta L.), bahiagrass (Paspalum notatum Flugge `Pensacola'), common bermudagrass [Cynodon dactylon (L.) Pers.], and centipedegrass [Eremochloa ophiuroides (Munro) Hack] were grown for 3 years in a 3 × 3-m spacing around young pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. Compared to weed-free plots, all cover crops suppressed tree growth substantially, and there were no differences among cover crops in the degree of suppression. Mean trunk cross-sectional area of weed-free trees increased 26-fold by the end of the third growing season but increased only 13-fold for trees grown with any cover crop. These results suggest that cover crops, if grown in young pecan orchards to promote beneficial insects, should be excluded from the immediate area around the young trees.

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Patricia Sweeney, Robert Golembiewski, and Karl Danneberger

Random amplified polymorphic DNA (RAPD) markers from leaf tissue extractions are effective for discrimination of turfgrass varieties. The usefulness of RAPD markers for turfgrass variety identification can be enhanced by use of seed rather than leaf tissue for DNA extraction. To determine whether DNA extracted from turfgrass seed was suitable for amplification, DNA was extracted from bulk samples and individual seeds of bermudagrass [Cynodon dactylon (L.) Pers.], chewings fescue (Festuca rubra var. commutata Gaud.), Poa annua L., Poa supina Schrad., creeping bentgrass [Agrostis stolonifera L. var. palustrus (Huds.) Farw.], Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.). All samples were successfully amplified using an arbitrary primer. Amplification intensity varied among species. With an almost infinite number of arbitrary primers available, it is likely that suitable primers can be found to amplify DNA from most turfgrass species. Amplification of turfgrass seed DNA, whether bulk or individual seed, is possible and should prove more useful than amplification of leaf tissue DNA for discrimination of turfgrass varieties.

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J.M. Goatley Jr., V.L. Maddox, and K.L. Hensler

Bermudagrass turfs in the southern United States often receive late growing season applications of nitrogen (N) in order to sustain turfgrass color prior to dormancy, even though such applications might increase winterkill potential. Yearly research trials were initiated in the last week of Sept. 1989 to 1991 at Mississippi State Univ. to evaluate fall and spring color responses and rhizome levels of total nonstructural carbohydrates (TNC) of `Tiflawn' and Arizona (AZ) Common bermudagrass [Cynodon dactylon L. (Pers.)] treated with various N sources delivering N at 98 kg·ha-1 in a single application. The fertilizers were ammonium nitrate (AN), sulfur-coated urea (SCU), a natural organic (`Milorganite', NO), isobutylidene diurea (IBDU), ureaformaldehyde (UF), and methylene urea (MU). Color responses from N fertilization were most prominent in the fall except when there was an early frost event in Oct. 1990. The most rapid greening response and highest color ratings were consistently observed for the water-soluble AN. Of the slow-release sources, SCU, MU, and IBDU provided color responses as long as temperatures remained warm enough to promote bermudagrass growth. The NO source provided an unexpected, significant greening response in Oct. 1989 and 1991 on `Tiflawn', but not on AZ Common. The UF consistently provided the lowest color ratings. There were virtually no differences in TNC levels between N treatments for either grass. At no time was there any indication that N fertilization increased bermudagrass winterkill potential; to the contrary, the predominant responses were better fall and spring color than the nontreated control.

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Jayne M. Zajicek, Nowell J. Adams, and Shelley A. McReynolds

Landscape plantings have been designed traditionally using aesthetic criteria with minimal consideration given to water requirements. The primary objective of this research was to develop quantitative information on water use of plant communities conventionally used in urban landscapes. Pots of Photinia × Fraseri (photinia Fraseri), Lagerstroemia indica 'Carolina Beauty' (crape myrtle), or Ligustrum japonicum (wax leaf ligustrum) were transplanted from 3.8 l into 75.7 l pots with either Stenotaphrum secundatum 'Texas Common' (St. Augustinegrass), Cynodon dactylon × C. transvallensis 'Tiffway' (bermudagrass), Trachelospermum asiaticum (Asiatic jasmine), or left with bare soil. Whole community water use was measured gravimetrically. In addition, sap flow rates were recorded for shrub species with stem flow gauges. Sap flow measurements were correlated to whole community water use recorded during the same time intervals. Whole community water use differed due to the groundcover component; bermudagrass, Asiatic jasmine, and bare soil communities used less water than St. Augustinegrass communities. Differences were also noted in stomatal conductance and leaf water potential among the species.

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Haibo Liu

Aluminum toxicity is a major limiting factor for turfgrass establishment and growth when soil pH is <5.0. Limited information on aluminum resistance is available among warm-season turfgrasses and these turfgrasses often grow in the areas with acid soil conditions. The objectives of this study were 1) to evaluate seeded bermudagrass (Cynodon dactylon L.) cultivars for the ability to tolerate a high level of aluminum and 2) to measure the extent of aluminum damage to the root systems. In total, 16 bermudagrass cultivars were evaluated under greenhouse conditions using a solution culture and an acid Tatum soil (Clayey, mixed, thermic, typic, Hapludult). The soil had pH 4.4% and 69% exchangeable aluminum. A concentration of 640 μm aluminum and a pH 4.0 was used for solution culture. The grasses were grown for 28 days in solution culture; 28 days in the acid Tatum soil; and 78 days in the acid Tatum soil before harvesting. Aluminum resistance was determined by measuring the longest root length, the longest shoot length, dry root weight, dry shoot weight, and shoot to root ratio in comparing the control to obtain the relative Al resistance among the cultivars. The results indicate that seeded bermudagrass cultivars differ in their aluminum resistance.

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, and Ted Whitwell

Research was conducted in two studies at the Clemson University Greenhouse Complex, Clemson, S.C., with the objective of evaluating `TifEagle' bermudagrass (Cynodon dactylon × C. transvaalensis) response to paclobutrazol. TifEagle bermudagrass plugs were placed in 40 cm polyvinylchloride containers, with 20.3-cm-diameters and built to U.S. Golf Association specifications with 85 sand: 15 peatmoss (by volume) rootzone mix. Paclobutrazol was applied to separate containers at 0, 0.14, 0.28, and 0.42 kg·ha-1 (a.i.) per 6 weeks. Minor phytotoxicity occurred with 0.14 kg·ha-1 applications, but turf quality was unaffected. Severe bermudagrass phytotoxicity occurred from paclobutrazol at 0.28 and 0.42 kg·ha-1. Total clipping yield from 12 sampling dates was reduced 65%, 84%, and 92% from 0.14, 0.28, and 0.42 kg·ha-1, respectively. Root mass after 12 weeks was reduced 28%, 45%, and 61% for turf treated 0.14, 0.28, and 0.42 kg·ha-1, respectively. Paclobutrazol reduced root length 13%, 19%, and 19% by 0.14, 0.28, and 0.42 kg·ha-1, respectively. Turf discoloration and negative rooting responses advocate caution when using paclobutrazol on `TifEagle' bermudagrass. Chemical names used: (+/-)-(R*,R*)-ß-[(4-chlorophenyl) methyl]-alpha-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).

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J.M. Goatley Jr., V.L. Maddox, D.L. Lang, R.E. Elmore, and B.R. Stewart

The ability of a temporary turf cover and foliar-applied iron (Fe) to sustain or promote bermudagrass (Cynodon dactylon (L.) × transvaalensis Burtt-Davy `Tifway' growth beyond its normal growing periods in central Mississippi was evaluated during the fall, winter, and spring seasons of 1998-2001. The application of a polypropylene turf blanket when night temperatures were predicted to be ≤4 °C extended acceptable bermudagrass turf quality by 5 to 8 weeks in the fall and winter period as compared to the uncovered control plots. Also, complete green-up of the turf occurred 4 to 6 weeks earlier the following spring. There was no enhancement in bermudagrass quality by temporarily covering at predicted night temperatures of ≤15 or ≤9.5 °C. Foliar applied iron (Fe) further enhanced turf quality in the fall and winter months, but resulted in no visible turf response the following spring. Total nonstructural carbohydrate (TNC) concentrations in rhizomes that were sampled during November, January, and April 2000 and 2001 were generally increased by the cover application as compared to the uncovered control. Foliar Fe applications did not influence TNC levels.

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Panayiotis A. Nektarios, Garyfalia Economou, and Christos Avgoulas

Fresh, senesced, and decaying pine needles from Pinus halepensis were evaluated for their allelopathic potential on Festuca arundinacea, Cynodon dactylon and the biosensor plants Avena sativa and Lemna minor through in vivo and in vitro studies. The in vivo study was performed in growth chambers, using 6, 12, and 18 g of pine needle tissue mixed with screened perlite as a substrate. The effects of the different pine needle types were evaluated by determining the total root length, total root surface, root dry weight, total shoot length, total shoot surface, and shoot dry weight. The in vitro study was performed in Petri dishes where seeds from each species were subjected to an increasing concentration of pine needle extract. The extracts were obtained from pine needle ground tissue that was diluted with water and either shacked at room temperature or placed in water bath at 40 °C for 24 h. The evaluation of the allelopathic potential was performed with the determination of radicle length. The allelopathic potential of the pine needle tissues was confirmed with bioassays using oat (A. sativa) and duckweed (L. minor). The results strongly suggested the allelopathic potential of the pine needle tissue, being more pronounced in the fresh, moderate in the senesced, and low in the decaying pine needles. The allelopathic substances were species-specific, and the inhibition resistance of the species tested followed the order F. arundinacea > C. dactylon > A. sativa. The inhibition of the L. minor suggested that the water soluble phytotoxic compounds were inhibitors of Photosystem II.