Data describing intraspecific differences in hybrid bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt Davy] traffic tolerance are linriited. Field research was conducted evaluating the effects of nnowing practices and perennial ryegrass {Lolium perenne L.) overseeding on the traffic tolerance of three hybrid and one improved common bermudagrass. Bermudagrass cultivars (Tifway', 'Patriot', 'Mississippi Choice', and 'Riviera') were subjected to mowing programs (reel mowing at 2.2 cm [RM] or RM plus grooming to a 1.9 cm depth [RMPG]) and perennial ryegrass overseeding (0 kg pure live seed [PLS] ha-1 or 593 kg PLS ha"^). Simulated traffic was applied twice weekly with a Cady traffic simulator. Percent green cover was measured after each simulated traffic event using digital image analysis. On >70% of evaluation dates, Tifway and Riviera yielded higher percent green cover compared to Patriot, while Mississippi Choice ranked intermediate. Reel mowing at 2.2 cm plus grooming to a 1.9 cm depth reduced percent green cover on the majority of rating dates in 2006; however, this response was not observed in 2007. Reel mowing at 2.2 cm plus grooming to a 1.9 cm depth did not reduce thatch accumulation either year. Reductions in bulk density and increases in green cover, thatch accumulation, and saturated hydraulic conductivity were associated with overseeding, suggesting that this practice may protect bermudagrass athletic fields from both components of traffic stress; wear and sou compaction.

Athletic field safety is a top concern of field managers and athletic directors across all sports. Increased field usage on fields with traffic-sensitive cultivars results in reduced turf cover and therefore decreased field safety. Kentucky bluegrass (Poa pratensis L., KBG) is the most widely used cool-season turfgrass on athletic fields due to its dense turf canopy. While most KBG cultivars have strong recuperative potential, significant cultivar differences in ability to withstand athletic field traffic exist. This study was conducted to determine whether leaf epidermal cell sizes predict differences in KBG cultivar traffic tolerance. Upper epidermal cell size, lower epidermal cell size, and intercellular void space (IVS) were measured on three traffic-tolerant and three traffic-sensitive KBG cultivars from the 2011 National Turfgrass Evaluation Program KBG trial, arranged in a randomized complete block design with three replications. Transverse sections of leaf tissue were fixed in an acid/alcohol solution and embedded with paraffin prior to sectioning for imaging by light microscopy. Cell size was determined by counting cells per unit area from light microscopy images. Leaf upper and lower epidermal cell size was not a predictor of traffic tolerance. Differences were measured in IVS at the cultivar level and at the traffic-sensitive vs. traffic-tolerant grouping contrast level. Traffic-tolerant cultivars exhibited larger IVS (2823 μm 2) than traffic-sensitive cultivars (1112 μm 2). Further investigation of these leaf anatomy size theories in relation to athletic traffic tolerance should be conducted on more cultivars, including recently released commercially available genotypes.

Certain sulfonylurea (SU) herbicides are used to remove overseeded cool-season species from bermudagrass. The effects of nitrogen (N) on the efficacy of a new SU herbicide, flazasulfuron, have not been determined. Field and laboratory studies were conducted in 2008 and 2009 evaluating the efficacy of flazasulfuron for control of overseeded perennial ryegrass contaminated with annual bluegrass. Flazasulfuron was applied at rates of 4.4, 8.8, and 17.5 g ha−1alone, and in between sequential applications of N fertilizer at 73 kg N ha−1. N was granularly applied immediately prior to herbicide treatment and 4 wk later. In both years, the level of annual bluegrass control with flazasulfuron and two applications of N at 73 kg N ha−1was significantly greater than following treatment with flazasulfuron alone. This response was observed for all application rates of flazasulfuron on every rating date. The level of annual bluegrass control with flazasulfuron at 4.4 g ha−1and two applications of N at 73 kg ha−1was greater than flazasulfuron at 17.5 g ha−1alone each year. No significant differences in perennial ryegrass control were observed for flazasulfuron with and without N fertility. In laboratory studies with annual bluegrass, treatment with N fertilizer at 73 kg N ha−1increased translocation of14C flazasulfuron (and any potential metabolites) from treated annual bluegrass leaves to other shoot tissues by 18% at 1 h after treatment and 22% at 4 h after treatment compared to plants not treated with N fertilizer. This increase in translocation may explain the increased level of annual bluegrass control observed in the field.

Athletic field playing quality encompasses both aesthetics as well as athlete‐to‐surface interactions that can affect injury incidence. Legislation restricting the use of herbicides on athletic fields may lead to increases in problematic weeds, such as large crabgrass (Digitaria sanguinalis L.) and white clover (Trifolium repens L.), which could reduce athletic field playing quality and potentially increase potential for athletic injuries. Research was conducted at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) during 2012 to 2013 to evaluate the playing quality of large crabgrass and white clover compared with weed‐free hybrid bermudagrass (C. dactylon ⋅ C. transvaalensis Burtt‐Davy, ‘Tifway’). All plots (3 by 3 m) were maintained as monostands and subjected to 18 simulated traffic events with a Cady traffic simulator each autumn over 2 yr. Large crabgrass and white clover lost green cover approximately 12 times faster than hybrid bermudagrass in this study. Consequently, surface hardness values on large crabgrass and white clover plots were ∼48 to 52% higher than those measured on hybrid bermudagrass after 18 simulated traffic events were applied. Changes in both surface hardness and rotational resistance were significantly correlated (P < 0.0001) to changes in green cover following simulated traffic. Our findings indicate that groundcover domination by weeds, such as large crabgrass and white clover, compromises the aesthetics and safety of natural grass athletic fields. Additional research is needed to evaluate athletic field playing quality on polystands of hybrid bermudagrass, large crabgrass, and white clover to determine acceptable thresholds of weed cover for player safety. Information of this nature would be useful for justifying various weed control measures such as herbicide applications.

Data describing effects of plant growth regulator (PGR) applications on bermudagrass (Cynodon spp.) traffic tolerance are limited. A 2-year study was conducted evaluating effects of several PGRs on ‘Riviera’ bermudagrass (Cynodon dactylon L.) traffic tolerance. Treatments included 1) ethephon at 3.8 kg·ha−1; 2) trinexapac-ethyl (TE) at 0.096 kg·ha−1; 3) paclobutrazol at 0.28 kg·ha−1; 4) flurprimidol at 0.0014 kg·ha−1; 5) flurprimidol + TE at 0.0014 kg·ha−1 + 0.096 kg·ha−1, respectively; 6) ethephon + TE at 3.8 kg·ha−1 + 0.096 kg·ha−1, respectively; and 7) untreated control. All treatments were applied three times on a 21-d interval before trafficking. Plots were subjected to three simulated football games per week with the Cady Traffic Simulator. Traffic began 2 weeks after the last sequential application of each PGR. Turfgrass color, quality, and cover were quantified weekly using digital image analysis. Turfgrass cover measurements were used to assess traffic tolerance. Improvements in turfgrass color, quality, and cover were observed with applications of TE, ethephon + TE, and flurprimidol + TE. Turfgrass color, quality, and cover were enhanced for ethephon + TE and flurprimidol +TE compared with applications of ethephon and flurprimidol alone. Considering that no differences in turfgrass color, quality, or cover were detected among TE, ethephon + TE, and flurprimidol + TE at any time in the study, the responses observed suggest that TE may have a greater impact than other PGRs on ‘Riviera’ bermudagrass athletic field turf when applied before traffic stress. Chemical names used: rthephon (2-chloroethyl)phosphonic acid; glurprimidol {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl] 5-pyrimidine-methanol}; paclobutrazol, (+/−)-(R*,R*)-β-[(4-chlorophenyl) methyl]-α-(1–1-dimethyl)-1H-1,2,4,-triazole-1-ethanol; trinexapac-ethyl [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester].

Amino acids have been reported to improve turfgrass growth compared with mineral nutrition; however, amino acid catabolism in plants has not been well studied. A number of turfgrass fertilizers contain amino acids; however, some amino acids may be more effective additives in fertilizers than others. Three amino acids that could be effective nitrogen sources for plant growth are the branched-chain amino acids (BCAAs). The BCAA leucine (L), isoleucine (IL), and valine (V) could be effective additives because they are nonpolar and hydrophobic, which can promote plant uptake of these compounds. Although the effect of exogenously applied BCAA on plant growth is not well known, BCAAs have been reported to increase protein synthesis in humans, and that rate of increase is related to the intake ratio of L to IL and V. The objective of this study was to evaluate the use of L, IL, and V as a nitrogen sources on creeping bentgrass (Agrostis stolonifera) and to investigate the effect of BCAAs on plant growth when all three are applied as a combination. Using specially made rooting tubes, L, IL, and V were applied in a complete factorial and compared with equal urea nitrogen at four rates, as well as an untreated control. Where all three BCAAs were applied in combination, the application ratios of 2:1:1 and 4:1:1 (L:IL:V) were tested. At 63 days after seeding, there were no differences in root length, root weight, or shoot weight; however, BCAA 2:1:1 and 4:1:1 increased creeping bentgrass shoot density by 24% and 32%, respectively, compared with equal urea nitrogen. Where shoot density was increased, nitrogen application rate had no effect. On the basis of these results, BCAAs applied in a complete combination using ratios of 2:1:1 or 4:1:1 (3.03 lb/acre N) will provide a greater creeping bentgrass shoot density compared with equal urea nitrogen.

Use of PRE herbicides for control of annual grassy weeds during commercial sod production has been limited. Research was conducted from 2010 to 2013 evaluating the effects of pendimethalin (3.36 kg ai ha−1), dithiopyr (0.56 kg ai ha−1), prodiamine (0.6 kg ai ha−1), oxadiazon (3.36 kg ai ha−1), prodiamine + sulfentrazone (0.84 + 0.41 kg ai ha−1), dimethenamid-P(1.68 kg ai ha−1), and indaziflam (0.03 and 0.05 kg ai ha−1) applications at sprigging on the establishment rate and tensile strength of ‘Tifway' hybrid bermudagrass sod at harvest (377 d after sprigging). All herbicides increased the days required to reach 50% hybrid bermudagrass cover compared with the nontreated control. Days required to reach 50% hybrid bermudagrass cover were lowest for oxadiazon and prodiamine (39 to 44 d), greatest for both rates of indaziflam (65 to 141 d), with dimethenamid-P, prodiamine plus sulfentrazone, pendimethalin, and dithiopyr ranking intermediate (45 to 63 d). Both rates of indaziflam reduced sod tensile strength at harvest compared with the nontreated control during a single year of the study; no other differences in sod strength due to herbicide treatment were detected at any time.

The Shockwave (Imants) offers the potential to minimally disrupt the playing surface, relieve soil compaction, and potentially lower surface hardness. However, data are lacking on how the Shockwave compares to traditional aerification. The effects of hollow-tine (HT), solid-tine (ST), and Shockwave with a single pass (SW1) and perpendicular passes (SW2) were investigated and compared to an untreated control (C) for surface hardness, surface stability, soil moisture, water infiltration, percent green cover, and bulk density on established cultivar Rush Kentucky bluegrass (Poa pratensis L.) turf growing on native soil. Treatments were applied June-August with SW1 and SW2 receiving an additional treatment in September of each year. A modified Baldree traffic simulator was used to simulate 28 traffic events in the fall of each year. Data were analyzed using an exponential decay model, and the slope indicating cover loss event-1 was used to compare treatments. In both years of the study, the HT (-0.031 in 2017 and-0.085 in 2018) treatment had the least green cover loss per event. The SW2 (-0.051) had the greatest cover loss event-1 in 2017, while the C (-0.102) treatments experienced the largest cover loss event-1 in 2018. In 2017 after 20 simulated traffic events, surface hardness on SW2 treatments were 30% lower than the highest surface hardness. After simulated traffic in 2018, SW1 treatments resulted in 10% lower surface hardness compared to the hardest surface, indicating the Shockwave can reduce surface hardness. This research indicates that the Shockwave could replace ST in maintaining athletic fields.