Bermudagrass is the predominant turfgrass used for athletic fields in the southern United States. Numerous bermudagrass cultivars are utilized for sports field use. Two frequent variations in management among facilities include mowing and nitrogen fertility regimes. Research is needed to determine the influence of bermudagrass cultivar, mowing regime, and nitrogen fertility on traffic tolerance. Research conducted at Texas A&M Univeristy studied the traffic tolerance of Tifsport, GN-1, Princess, and NuMex Sahara bermudagrasses. These grasses were mowed once weekly at 3.80 cm and three times weekly at 1.90 cm and fertilized with 146, 292, 585, or 1171 kg ha-1 yr-1. Digital images were taken before and after simulated traffic to provide a quantitative value for percent coverage. Images were analyzed for percent green canopy coverage using Sigma Scan Pro. The number of green pixels was divided by the total image pixels a yielding a percent coverage value. Shoot density, visual quality, tissue water content, and tissue dry mass values were taken monthly. Percent tissue nitrogen was taken for three months. Analysis of digital images revealed variability in traffic injury tolerance between varieties. Tifsport, GN-1, and Princess maintained higher percent coverage than NuMex Sahara. GN-1, Princess, and Tifsport were able to tolerate traffic but did not maintain acceptable quality. Lower and more frequent mowing increased shoot density and visual quality for all grasses. Increased nitrogen fertility levelsincreased tissue succulence and tissue dry mass but did not affect the traffic tolerance of any variety. Increasing nitrogen fertility above 585 kg ha-1 yr-1 showed no benefit other than increasing visual color. This research provides a guide for managers to make informed decisions on cultivar selection and management practices under traffic conditions.

Field experiments were conducted in 1995, 1996, and 1997 at six locations to evaluate strategies for the use of sethoxydim-tolerant hybrids in Virginia corn production. The specific objectives of this research were to evaluate the effect of graminicides including clethodim, fluazifop-P, quizalofop-P, and sethoxydim, and method of application, on crop tolerance and bermudagrass (Cynodon dactylon L.) control; to evaluate the effect of sethoxydim in combination with broadleaf herbicides on crop tolerance and bermudagrass control; to evaluate sethoxydim-based herbicide programs for annual grass and broadleaf weed control; and to determine the response of sethoxydim-tolerant corn hybrids to these graminicides in the absence of the competitive effects of weeds. All experiments were conducted using a randomized complete block design with four replications. Individual plots consisted of 4 corn rows 7.6 meters in length in which the two inner rows received treatment and the two outer rows served as borders. All applications were made with a CO2-pressurized backpack sprayer delivering 210 L/ha of water at 220 kPa using flat fan spray tips. The dependent variables evaluated included crop response to herbicide treatments, weed control by species, and corn yield. All data were subjected to analysis of variance and appropriate mean separation techniques at the 0.05 significance level. Excellent bermudagrass control was obtained from postemergence broadcast or postemergence directed applications of sethoxydim, fluazifop-P, quizalofop-P, clethodim, and fluazifop-P plus fenoxaprop. Broadcast applications of fluazifop-P and both broadcast and directed applications of clethodim caused significant crop injury, however. Combinations of sethoxydim with bentazon, bentazon plus atrazine, flumiclorac, and halosulfuron resulted in reduced bermudagrass control relative to that control afforded by sethoxydim alone. In experiments to evaluate control of annual species including smooth pigweed (Amaranthus hybridus L.), common lambsquarters (Chenopodium album L.), giant foxtail (Setaria faberi Herrm.), ivyleaf morningglory (Ipomoea hederaceae L. Jacq.), jimsonweed (Datura stramonium L.), large crabgrass (Digitaria sanguinalis L. Scop.), and a perennial, yellow nutsedge (Cyperus esculentus L.), excellent broad spectrum control was achieved with sethoxydim in combination with bentazon, bentazon plus atrazine, nicosulfuron, or primisulfuron. Crop tolerance to these treatments was excellent. In experiments to evaluate sethoxydim-tolerant hybrids and susceptibility to graminicides, no rate of sethoxydim caused significant injury to any hybrid tested. Tolerance of these hybrids to a 1X rate of quizalofop-P was also demonstrated, although 4X and 8X rates of fluazifop-P and quizalofop-P caused significant injury. Clethodim at all rates of application caused significant crop injury. Differential responses to graminicides among hybrids were noted. / Master of Science

Bermudagrass (Cynodon dactylon (L) Pers.), one of the predominant forages in the southeastern US, varies in nutritive value in response to management and environmental factors. Beef cattle supplementation decisions are complicated by this variability. Therefore, our objective was to determine the effect of four protein supplementation levels (0, 82, 119 and 155 mg N/kg BW) on the utilization of three bermudagrass hays (5.6, 6.3, and 8.1 percent CP).Thirteen ruminally fistulated Angus x Hereford steers (BW = 330 plus/minus 19 kg) were used in a 13 x 4 incomplete Latin square design with 13 treatments. Treatments were arranged as a 3 x 4 factorial plus a control bermudagrass hay (10.8 percent CP). Hay was provided ad libitum and protein supplements were offered as range cubes once daily. Periods were 15 d with intake determinations made on d 10 through d 13 to correspond with fecal grab samples collected from d 11 through d 14. Acid detergent insoluble ash was used as an internal marker for determination of fecal output. Hay OM intake of unsupplemented steers increased linearly (P < 0.01) as hay nutritive value increased from 75 to 77, 96 and 94 g/kg BW^0.75 for 5.6, 6.3, 8.1 and 10.8 percent CP hays, respectively. A cubic increase (P = 0.03) in OM digestibility for unsupplemented hays was observed with values ranging from 46 to 65 percent. This resulted in a linear increase (P < 0.01) in total digestible OM intake in response to hay nutritive value from 35 to 45, 51, and 60 g/kg BW^0.75 for 5.6, 6.3, 8.1, and 10.8 percent CP hays, respectively. No significant effects on total digestible OM intake were observed when hays were supplemented with protein. There was a tendency for forage OM intake of the 6.3 percent CP hay to increase linearly with supplemental protein (P = 0.08). Total OM intake increased linearly (P < 0.01) when CP was supplemented to the 6.3 percent CP hay from 77 to 88, 92, and 98 g/kg BW^0.75 for 0, 82, 119, and 155 mg N/kg BW, respectively. We conclude that forage CP content was the primary driver in determining total digestible OM intake, and the effects of protein supplementation on utilization of bermudagrass hay were varied.

Field studies were conducted during the 2003 and 2004 growing seasons to: 1) evaluate the control of silverleaf nightshade and western ragweed, and (2) assess the forage tolerance of Coastal and Tifton 85 bermudagrass hybrids using tank mix combinations of diflufenzopyr. Herbicides that were evaluated in each study included picloram, multiple rates of picloram with diflufenzopyr, triclopyr, triclopyr with diflufenzopyr, dicamba + diflufenzopyr, and diflufenzopyr alone. Visual ratings were taken on the weed control experiments approximately 30, 60 and 90 days after treatment. Phytotoxicity ratings were taken prior to each harvest of the Coastal and Tifton 85 varieties to determine influence of each herbicide treatment. Each bermudagrass variety was harvested twice during each growing season to determine dry matter yield and quality. Forage quality, including crude protein, acid detergent fiber, and neutral detergent fiber, was assessed using near infrared reflectance spectroscopy. Adding diflufenzopyr to triclopyr did not consistently increase control of silverleaf nightshade or western ragweed. In general, picloram + diflufenzopyr and picloram applied alone provided the greatest control of both species at the highest rate of picloram. Increased efficacy was more evident from the addition of diflufenzopyr to picloram in 2004 on western ragweed. By the final ratings in both experimental years, dicamba + diflufenzopyr provided no more than 76% control of either species. Both forage varieties showed significant variability in phytotoxicity between years. Although observed levels of growth reduction were relatively high at the first harvest in 2003, no treatment exceeded a 10% growth reduction by the second harvest for either forage variety. In addition, the only significant reduction in dry matter yield occurred at the first harvest of Coastal in 2003 from picloram + diflufenzopyr applied at the highest rate.

Bermudagrass (Cynodon dactylon (L). Pers.) is considered to be one of the most difficult to control grass weeds in turf throughout the U.S. Recent breeding efforts have produced much more desirable bermudagrass cultivars, and therefore its use has increased. Ironically, as bermudagrass use becomes more popular it poses even greater difficulties to the turf manager. The need to control these warm season turfgrass species, without causing injury to other desirable turfgrass species, is one of the most intractable problems a turf specialist encounters. Herbicides previously used to selectively control bermudagrass such as siduron and oxadiazon have proven to be of only minimal efficacy or to induce significant injury to other desirable turfgrasses. Tests conducted in 1993, 1994 and 1995 have indicated that fenoxaprop plus fluazifop (Horizon 2000R) controlled bermudagrass effectively. Six bermudagrass (Cynodon dactylon) cultivars and tall fescue (Festuca arundinacea) were used in the susceptibility studies. Visual control and cover ratings were taken at two-week intervals until ten weeks after the final treatment. Sequential applications of labeled rates of fenoxaprop or fluazifop alone only temporarily controlled bermudagrass shoots. Horizon 2000 applied at 0.40 kg ai/ha in three sequential applications proved effective in controlling bermudagrass rhizomes and stolons. From results of previous studies and research conducted here it has been hypothesized that synergistic effects of fenoxaprop on fluazifop allow both differential control of various bermudagrass cultivars and increased tall fescue tolerance to these herbicides. / Master of Science

Nitrate contamination of ground and surface waters is of serious concern in the United States. Since nitrate is considered one of the most widespread groundwater contaminants, research continues in many disciplines to identify and mediate possible sources (Petrovic, 1990). An opportunity to evaluate a possible source of nitrate contamination exists during bermudagrass sprig establishment. Since most "improved" bermudagrass varieties are established vegetatively, due to lack of viable seed, turf managers apply large quantities of soluble urea weekly to push growth. During this grow-in, turf managers typically apply 48.8 soluble kg N ha-1 wk-1 for an eight to ten week period. We hypothesize that the quantity of nitrogen applied is in excess and that similar 8 to 10 week grow-in can be achieved with less nitrogen especially during the first 4 weeks when there are few plants per unit area. Three interrelated studies were conducted. A "field trial", consists of 1.8 m2 plots in 4 replications of 27 different nitrogen rates ranging from 4.9 kg N ha-1 wk-1 to 48.8 kg N ha-1 wk-1. A lysimeter study quantified leaching nitrate loss using the same weekly nitrogen rates, however, only six treatments existed. All plots were rated at weeks 4, 8 and 10 for cover, color, and density. A greenhouse study was implemented to evaluate potential nitrogen use for a single bermudagrass sprig, during the early post-sprigging stage. In 1998 and 1999, it appears that typical weekly nitrogen rates of 48.8 kg N ha-1 are in excess. Similar results were found using 48.8 kg N ha-1 to 97.6 kg N ha-1 over the first four week period and 195.2 kg N ha-1 to 244.0 kg N ha-1 during the entire grow-in. A 25 to 50 percent reduction in nitrogen application when compared to the typical 390.4 kg N ha-1. Lysimeter results revealed large quantities of nitrate lost via leaching. The 390.4 kg N ha-1 lost 34.7 and 44.6 percent of applied nitrogen in 1998 and 1999, respectively. Furthermore, similar turfgrass cover, color, and density were achieved using 80 percent less nitrogen during the grow-in period on sand-based media. The greenhouse study suggests that during the early post-sprigging period individual sprigs do not require large quantities of soluble nitrogen even on sand-based media. Results indicated that individual sprigs did not utilize 48.8 kg N ha-1 wk-1 during early post-sprigging. Similar results with respect to shoot weight, shoot length, and root weight were found using 40 percent less applied nitrogen. However, greater nitrogen rates may be necessary as plant density and root development increase later in the establishment period. / Master of Science

Fraze mowing offers a new tool used in both overseeding establishment and removal of perennial ryegrass (Lolium perenne L.). Research objectives were to determine the most effective timing of fraze mowing in overseeding establishment and removal, as well as to compare fraze mowing to other establishment and removal methods. Fall overseeding studies suggest that fraze mowing and scalping in mid-October provides the fastest establishment of ryegrass. However, by mid-March all treatments led to visually similar results. When evaluating removal timings, fraze mowing performed in early- and late-May led to faster visual bermudagrass recovery than March and April timings. Early-season application of glyphosate for ryegrass removal was fairly ineffective; whereas, late-season application was damaging to bermudagrass. Rimsulfuron removed ryegrass more quickly late in the season. Repeated scalping gradually removed ryegrass providing a slower, but complete, bermudagrass recovery. Overall, late-May fraze mowing resulted in the best bermudagrass cover 5 weeks after treatment.

Perennial ryegrass (Lolium perenne L.) is widely used as a fairway turf on golf courses throughout the transition zone. The transition zone represents the geographical areas between the temperate and subtropical climates, where neither warm season nor cool season grasses are well adapted. The late-spring establishment of seeded bermudagrass could potentially enhance summer quality of a perennial ryegrass fairway during periods of extreme summer stress. Studies were conducted over two years on both perennial ryegrass and Chewings fescue (Festuca rubra L. ssp. commutata Gaud.) areas to assess the competitive effects of each species on bermudagrass seed establishment. The use of fungicides, herbicides and a plant growth regulator, as well as cultivation treatment prior to seeding, were evaluated for their effects on bermudagrass establishment, turfgrass quality, disease incidence and summer annual grass control. Turfgrass treated with preventative fungicide applications of propiconazole and chlorothalonil maintained high density and turf quality which inhibited successful establishment of bermudagrass during either year. Bermudagrass establishment in 1996 was moderately successful in plots not treated with fungicides; however, due to disease severity, turfgrass quality was unacceptable. MSMA applications did not influence turfgrass quality or bermudagrass establishment. Crabgrass populations were too low to ascertain the efficacy of either MSMA (1996) or oxadiazon (1997) on summer annual grass control. Oxadiazon followed by activated charcoal prior to bermudagrass seeding did not adversely affect bermudagrass establishment. In 1996, trinexapac-ethyl slightly enhanced bermudagrass seed establishment, but the competitiveness of perennial ryegrass prohibited establishment success. During 1997, glyphosate was evaluated as a means of eliminating competition and increasing bermudagrass establishment. Glyphosate applied in small strips across existing stands of perennial ryegrass and Chewings fescue significantly increased bermudagrass establishment. Preplant aerification and vertical mowing increased bermudagrass establishment, but slightly reduced turfgrass quality. Overall, bermudagrass establishment into existing stands of turfgrass was successful only where glyphosate was strip-treated over plots to eliminate competition or under circumstances where disease pressure reduced competition from the existing turfgrass. / Master of Science

A nitrogen fertility study with Vaughn’s hybrid bermudagrass conducted on a Crider silt loam soil (fine, silty, mixed, active, mesic Typic Paleudalfs) over three (3) years (2008-2011) at the Highland Rim Research and Education Center near Springfield, Tennessee is evaluated in this manuscript. Nitrogen applications are evaluated in both irrigated and non-irrigated plots at five (5) different application rates: 0, 56, 112, 168, and 224 kg N ha-1. These rates are applied beginning in late April, and three (3) additional times upon harvests occurring in June, July, and August. Irrigation plots receive enough water to bring total weekly water up to 2.24 cm/plot whenever rainfall is less than that amount. Normalized difference vegetative index (NDVI) measurements are collected mid harvest and on harvest dates to investigate new nitrogen status indicators between Vaughn’s hybrid bermudagrass yields. Plant tissue samples are collected at harvest. Soil samples are collected mid harvest to investigate soil nitrate nitrogen and its relationship with bermudagrass yields. The results of the study show irrigation has no effect on yields during the period of this study. There is a significant effect resulting from the interaction between month and nitrogen application on yield. Investigation of this interaction reveals two (2) distinct periods of production potential during the growing season. A low to medium yielding period produces an average harvest yield maximum of 3.14 Mg ha-1. A medium to high yield period produces an average harvest yield maximum of 5.4 Mg ha-1. Based on an analysis of variance and mean separation, a nitrogen rate of 56 kg N ha-1 rate is recommended for harvests occurring during the low to medium yielding period, and a nitrogen rate of 113 kg N ha-1 is recommended for those occurring during the high to medium yielding period. NDVI is highly correlated with yield on date of harvest. The results also show NDVI is correlated with mid-harvest yields also, which suggests a possible development of using NDVI as a mid harvest nitrogen status indicator. The results show soil nitrate is not correlated with yield, but did indicate accumulation in the soil as the growing season progressed.

We compared water deficit responses of 'Tifsport', 'Tifway 419', 'Tifgreen 328', and 'MidIron' bermudagrass (Cynodon dactylon x Cynodon transvaalensis), and 'SeaSpray', 'SeaDwarf', and 'Sea Isle 1' seashore paspalum (Paspalum vaginatum Swartz) under a linear gradient irrigation system in the desert Southwest. Target irrigation levels were 100, 80, 60, and 40% (2009) and 100, 80, 70, 60, and 40% (2010) of standard reference evapotranspiration (ETo). Actual water applied (including rainfall) was 100%, 83%, 66%, and 49% of ETo (2009) and 100%, 83%, 75%, 66%, and 49% (2010). Canopy temperatures increased, and quality and dry matter production declined with reduced irrigation. For optimum turfgrass quality, 75 to 83% ETo replacement was required; for acceptable quality turfgrass, 66 to 75% ETo replacement was needed for bermudagrass, and 75 to 80% ETo for seashore paspalum. Spring green-up was delayed by drought. Bermudagrasses, particularly 'MidIron', performed better than seashore paspalums under water stress conditions.