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Frank G. Bethea Jr., Dara Park, Andrew Mount, Nick Menchyk, and Haibo Liu

concentration, and leaf micronutrient concentrations were reported from creeping bentgrass ( Agrostis stonlonifera L.) fertilized frequently using liquid solutions ( Schlossberg and Schmidt, 2007 ). However, the combination of liquid and granular fertilizers

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Qi Zhang and Kevin Rue

Saline and alkaline conditions often coexist in nature. Unlike salinity that causes osmotic and ionic stresses, alkalinity reflects the impact of high pH on plant growth and development. In this research, seven turfgrass species, tall fescue (Festuca arundinacea Schreb.), kentucky bluegrass (Poa pratensis L.), creeping bentgrass (Agrostis stolonifera L.), perennial ryegrass (Lolium perenne L.), zoysiagrass (Zoysia japonica Steud.), bermudagrass [Cynodon dactylon var. dactylon (L.) Pers.], and alkaligrass [Puccinellia distans (Jacq.) Parl.], were germinated under 10 saline–alkaline conditions [two salinity concentrations (25 and 50 mm) × five alkalinity levels (pH = 7.2, 8.4, 9.1, 10.0, 10.8)] in a controlled environment. Seed germination was evaluated based on final germination percentage and daily germination rate. Alkaligrass and kentucky bluegrass showed the highest and lowest germination under saline conditions, respectively. Limited variations in germination were observed in other species, except bermudagrass, which showed a low germination rate at 50 mm salinity. Alkalinity did not cause a significant effect on seed germination of tested turfgrass species.

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Qingzhang Xu and Bingru Huang

Roots play important roles in plant responses to environmental changes. The objective of this study was to investigate seasonal changes and cultivar variation in root growth, respiratory activity, nitrogen uptake, and carbon allocation in relation to turf performance for two cultivars of creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.)] under field conditions. Two cultivars, `Penncross' and `L-93', were managed under USGA-specification putting green conditions, with daily irrigation and mowing at a 3-mm height from May to November in 1999 and 2000. Turf quality of both cultivars declined from the highest rating of 7 to 9 in May to 4 to 5 in August and September, and recovered to above 7 in October and November in both years. This corresponded to seasonal changes in root dry weight, dehydrogenase activity, nitrate reductase (NR) activity, carbon allocation to roots, and 15N uptake. Compared to Penncross, L-93 generally maintained better turf quality, as well as higher root dry weight, 15N uptake, NR activity, and carbon allocation during summer months. Previous studies often emphasize the important of a large, extensive root system. The results in the present study demonstrated that root metabolic activities followed the same seasonal pattern and cultivars variation as turf performance, and suggested that decline in root metabolic activities could be contributed to summer decline in turf quality for creeping bentgrass.

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Gerald M. Henry, Stephen E. Hart, and James A. Murphy

Field trials were conducted in 2000 and 2001 to determine the potential of converting pure stands of annual bluegrass [Poa annua L. spp. reptans (Hauskins) Timm.], maintained at a 3.2-mm height, to bentgrass (Agrostis spp.). Parameters evaluated included three overseeding dates and four cultivars from two bentgrass species. Overseeding dates were 1 July, 18 Aug., and 18 Sept. 2000 and 27 June, 17 Aug., and 17 Sept. 2001. Three creeping bentgrass (A. stolonifera L.) cultivars (`Penncross', `L-93', and `Penn A-4') and one velvet bentgrass (A. canina L.) cultivar (`SR7200') were evaluated. Initial bentgrass establishment was evident across all seeding dates and cultivars in October of the year of overseeding. However, the 1 July 2000 and 27 June 2001 overseeding dates had the highest levels of bentgrass coverage 12 months after overseeding across all cultivars except `Penncross'. Coverage of `Penn A-4' and `L-93' increased to 72% in the 1 July 2000 overseeding date, 24 months after the initial overseeding. When overseeded in early summer, velvet bentgrass `SR7200' showed the greatest potential for establishment with annual bluegrass. `SR7200' and creeping bentgrass cultivars `Penn A-4' and `L-93' exhibited the greatest potential for long-term competitiveness with annual bluegrass, while `Penncross' exhibited the lowest potential.

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Chunhua Liu, R.J. Cooper, and D.C. Bowman

Humic acids (HA) reportedly enhance the growth of numerous crops; however, little information is available as to their effects on turfgrasses. Experiments were conducted to evaluate the effect of a commercial preparation of HA on the photosynthesis, chlorophyll concentration, rooting, and nutrient content of `Crenshaw' creeping bentgrass (Agrostis stolonifera L.). Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0, 100, 200, or 400 mg·L-1 with measurements made weekly for 1 month. The photosynthetic rates of plants growing in 100 or 200 mg·L-1 rarely differed from that of the control, but 400 mg·L-1 significantly enhanced net photosynthesis on all four observation dates. Chlorophyll content was unaffected by HA rate on all observation dates. Root dehydrogenase (DH) activity and root mass regrowth were significantly increased by HA at 400 mg·L-1 on all dates. The 100 and 200 mg·L-1 rates increased root DH activity on two of four observation dates, but root regrowth was unaffected. At one or more of the rates used, HA increased tissue concentrations of Mg, Mn, and S and decreased those of Ca, Cu, and N, but had no influence on the concentrations of P, K, Fe, Mo, and Zn.

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W.J. Hill, J.R. Heckman, B.B. Clarke, and J.A. Murphy

Take-all patch, caused by Gaeumannomyces graminis (Sacc.) Arx. & D. Olivier var. avenae (E.M. Turner) Dennis (Gga), is a disease of creeping bentgrass (Agrostis stolonifera Huds.), which most often is associated with golf courses. Synthesis of ligneous and phenolic compounds by plants requires adequate Mn+2 and Cu+2 nutrition and may be a factor in disease resistance. An experiment was conducted on a creeping bentgrass fairway naturally infested with Gga to determine if foliar applications of Mn+2 (1.02 and 2.04 kg·ha–1 per application) and Cu+2 (0.68 kg·ha–1 per application) would reduce take-all severity. Prior to initiating treatments, soil pH was 6.4 and Mehlich-3 extractable Mn+2 and Cu+2 were 5 mg·kg–1 and 1.7 mg·kg–1, respectively. Manganese and copper sulfate treatments were initiated in July 1995 and foliarly applied every 4 weeks through 1997 with the exception of December, January, and February. Disease incidence was decreased from 20% on untreated turf to 5% with the high rate of MnSO4. For both years, turf treated with the high rate of Mn+2 had less disease than turf receiving the low rate of Mn+2. The application of CuSO4, however, did not influence disease development.

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Keith J. Karnok and Kevin A. Tucker

Localized dry spot (LDS) caused by water repellent soil is a common problem on golf course putting greens having a predominately sand root zone. Fairy ring often causes LDS by developing hydrophobic soil. Although the fungicide flutolanil is labeled for the control of fairy ring, golf course superintendents often apply flutolanil to all LDS caused by hydrophobic soil and other conditions. The objective of this study was to determine the effect of flutolanil on an existing hydrophobic soil. The study was conducted on a creeping bentgrass [Agrostis palustris (synonym A. stolonifera)] experimental golf green in which the top 4 inches (10.2 cm) of the root zone was a moderately hydrophobic sand. Six treatments were used: uncored, cored, flutolanil (two applications.), flutolanil + Primer wetting agent (two applications.), Primer (two applications.) and Primer (three applications.). Plots receiving the fungicide and wetting agent treatments were cored before application. Each treatment containing the wetting agent significantly reduced soil water repellency. Flutolanil without wetting agent had no effect on soil hydrophobicity.

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D.S. Gardner, E.K. Nelson, M.A. Waldecker, and W.R. Tarter

Plant establishment and lateral growth of glyphosate-resistant creeping bentgrass [Agrostis stolonifera (synonym A. palustris)] were assessed to determine if the insertion of the construct conferring herbicide tolerance affected establishment rate or aggressiveness characteristics in unmowed situations. Field studies were carried out in Michigan, Illinois, Ohio, and Oregon in 2000 and 2001 to examine the relative lateral growth of several transformed lines of creeping bentgrass, non-transformed controls, and cultivar standards. Vegetative plugs of creeping bentgrass were transplanted into replicated bare-soil plots and irrigated as needed to prevent moisture stress for an initial 6-week period. Measurements of maximum and minimum stolon spread, percent cover, and stand density for each entry were made in the field at all locations during 2000 and 2001. Few statistical differences (P = 0.05) in establishment and lateral growth were observed between individual lines of transgenic creeping bentgrass, non-transformed control lines, and standard cultivars and over a 15- to 18-month period. Overall, lateral growth and establishment rate of transgenic lines were similar to their non-transformed parent and the standard cultivars tested. Transgenic creeping bentgrass lines should have no greater potential for lateral growth than conventional creeping bentgrass cultivars currently in use.

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M.A. Fidanza, P.F. Colbaugh, M.C. Engelke, S.D. Davis, and K.E. Kenworthy

Fairy ring is a common and troublesome disease of turfgrasses maintained on golf course putting greens. Type-I fairy ring is especially destructive due to the development of hydrophobic conditions in the thatch and root zone, thus contributing to turfgrass injury and loss. The objective of this 2-year field study was to evaluate the application and novel delivery method of two fungicides and a soil surfactant for curative control of type-I fairy ring in a 20-year-old creeping bentgrass [Agrostis palustris (synonym A. stolonifera)] putting green. In both years, all treatments were applied twice on a 28-day interval. In 1998, flutolanil and azoxystrobin fungicides were applied alone and in combination with Primer soil surfactant by a conventional topical spray method, and fungicides without Primer applied via high-pressure injection (HPI). Acceptable type-I fairy ring control was observed in plots treated with flutolanil plus Primer, HPI flutolanil, azoxystrobin alone, azoxystrobin plus Primer, or HPI azoxystrobin. In 1999, treatments were HPI flutolanil, HPI flutolanil plus Primer, HPI azoxystrobin, HPI water only, and aeration only. Acceptable type-I fairy ring control was observed in plots treated with HPI flutolanil plus Primer or HPI azoxystrobin. HPI of fungicides alone or in combination with a soil surfactant may be a viable option for alleviating type-I fairy ring symptoms on golf course putting greens.

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Qi Zhang, Liqi Yang, and Kevin Rue

Drought is the most important abiotic stress in crop production including turfgrass management. Using drought tolerant plants can help minimize stress damage. In this study, 23 commercially available cultivars of creeping bentgrass (Agrostis stolonifera) were evaluated for their responses to drought stress that was induced by polyethylene glycol (PEG) 6000 in a hydroponic system during the seed germination and seedling growth stage. In such a system, water potential was adjusted to 0.0 (the control), −0.3, and −0.6 MPa to mimic the drought condition. The absolute water content (AWC), shoot dry weight (SDW), root dry weight (RDW), longest root length (LRL), specific root length (SRL), and root-to-shoot dry weight ratio (RSR) in the plants grown for 4 weeks in the treatment were determined. Results showed that SDW and LRL were unaffected by drought; however, RDW and RSR increased, whereas SRL and AWC were reduced under drought. Among the 23 creeping bentgrass cultivars evaluated, Independence and Crystal Bluelinks had a higher turfgrass performance index (TPI), which represented the number of times a cultivar ranked in the top statistical group across all parameters. The results suggest that ‘Independence’ and ‘Crystal Bluelinks’ may be more adapted to drought than the other cultivars at the seedling stage.