Turfgrass Quality Research Articles

Osmotic Adjustment Associated with Variation in Bentgrass Tolerance to Drought Stress

Osmotic adjustment (OA) is a major physiological mechanism associated with maintenance of cell turgor in response to dehydration stress. The objectives of this study were to examine changes in capacity for OA in relation to plant tolerance to drought stress for two cool-season turfgrass species, creeping bentgrass (Agrostis stolonifera L.) and velvet bentgrass (A. canina L.), and to determine major solutes contributing to OA in these grass species. Plants of `L-93' creeping bentgrass and `Greenwich' velvet bentgrass were grown in a growth chamber in polyvinyl chloride (PVC) tubes (5 cm diameter, 40 cm high) filled with a 1:3 (v/v) sterilized mixture of sand and sandy loam soil. The experiment consisted of two soil moisture treatments: 1) well-watered control, irrigated three times per week to maintain soil moisture near pot capacity; and 2) drought stress, irrigation completely withheld. Velvet bentgrass exhibited higher drought tolerance compared to creeping bentgrass, as manifested by higher visual turfgrass quality (TQ) and leaf relative water content (RWC) under drought stress. Both creeping bentgrass and velvet bentgrass exhibited OA in response to drought stress; however, velvet bentgrass exhibited 50% to 60% higher magnitude of OA, which could be related to the maintenance of higher leaf RWC and TQ for greater drought duration compared to creeping bentgrass. OA for both creeping bentgrass and velvet bentgrass was associated with accumulation of water soluble carbohydrates during the early period of drought and increases in proline content following prolonged period of drought; however, inorganic ion content (Ca2+ and K+) did not considerably change under drought stress and did not seem to contribute to OA in these species.

Response of Six Bermudagrass Cultivars to Different Irrigation Intervals

A 2-year greenhouse study was conducted at Clemson University, Clemson, S.C., in 2003 and 2004 to determine drought responses of six bermudagrass (Cynodon spp.) cultivars at four irrigation intervals. Cultivars selected from the 2002 National Turfgrass Evaluation Program Bermudagrass Trial were `SWI-1012', `Arizona Common', `Tift No.3', `Tifsport', `Aussie Green', and `Celebration'. Treatments included 5-, 10-, and 15-day irrigation intervals plus a control (irrigated daily). Volumetric soil water content (VSWC) and evapotranspiration (ET) rates were recorded every 3 days. Turfgrass quality (TQ) was observed weekly and root weight was measured at the end of a 6-week study. `Aussie Green' and `Celebration' produced the highest TQ rating (>7) at week 4 when watered daily. After 4 weeks of the 5-day irrigation interval, all cultivars showed unacceptable quality ratings (<7). However, `Aussie Green' and `Celebration' were able to maintain an acceptable TQ rating (7), compared to `Arizona Common' (5.1) and `Tift No.3' (5.8) at week 2 (5-day treatment). `Celebration' produced 114% and 97% greater root weight than `Tifsport' and `Aussie Green', respectively, when pooled across all irrigation treatments. At the 15-day irrigation interval treatment, six bermudagrass cultivars pooled together produced 78%, 22%, and 11% greater root weight vs. control, 5-day, and 10-day treatments, respectively. When pooled for all treatments, `Aussie Green' and `Celebration' VSWC was 5% and 7% lower than `Tift No.3', and ET rates were 26% and 30% greater than `Arizona Common'. Based on these results, irrigating bermudagrass in 5-day intervals should be carefully monitored.

Effects of Compost Topdressing on Turf Quality and Growth of Kentucky Bluegrass

Long-term over-application of manure to agricultural fields has increased nitrate and phosphorus contamination of groundwater and surface water along the South Platte River basin. Concerns about water quality issues have contributed to the increasing interest in composting manure and topdressing it on turfgrass. The objectives of this research were to evaluate the effects that topdressing manure compost has on: (i) turfgrass quality, (ii) turfgrass growth rates, and (iii) root mass and distribution. Compost treatments at rates ranging from 0 to 99 m³/ha were topdressed onto two cultivars (‘Nuglade’ and ‘Livingston’) of Kentucky bluegrass (Poa pratensis L.) in May and September 2003 and May 2004. A synthetic fertilizer (Urea 46-0-0) was applied to balance inorganic nitrogen rates among treatments. Topdressing compost at 66 and 99 m³/ha increased the overall quality by 10% of both cultivars during the growing season, and allowed the turfgrass to retain color in the fall and early winter and green up faster in the spring. During July and August, the 66- and 99-m³/ha compost treated plots had 48 and 56% higher clipping yield than the control, respectively. No differences in rooting mass among treatments were detected in the 0- to 50-cm depth. These results suggest that compost can improve turf quality and shoot growth via its action as a slow-release fertilizer.

Effects of Core Cultivation Tine Entry Angle on Golf Putting Greens

Hollow tine cultivation is a routine practice on golf course putting greens, where the tine entry angle normally is 90°. Effects of various tine entry angles impacting putting green surfaces have not been investigated. The hypothesis was that different tine entry angles during cultivation would impact a greater area of the soil profile by enhancing water infiltration rates, reducing localized dry spots, and enhancing turf quality. Therefore, a 2-year field study in 2003 and 2004 was conducted to determine the impact of core cultivation tine entry angle on `Crenshaw' creeping bentgrass (Agrostis stoloniferous var. palustris). Treatments included three angles of hollow tine entry at 50°, 70°, and 90° and an untreated plot without cultivation. Manual cultivators consisted of four 1/4-inch- and 1/2-inch-diameter hollow tines 3 inches in length, spaced 2 inches apart. Treatment applications were in April, May, September, and October. Measurements included visual turfgrass quality (TQ), molarity ethanol droplet test (MED), and water infiltration. No treatment (control, 50°, 70°, 90°) effects in years I and II for TQ were noted. MED scores in May were 23% higher than in August and September. Tines of 1/2-inch diameter reduced soil hydrophobicity (MED) 6% compared to tines of 1/4-inch-diameter tines. Tines of 50°, 70°, and 90° had 129%, 163%, and 211% greater water infiltration than the untreated, respectively.

Pemanfaatan Cendawan Mikoriza Arbuskula dan Bakteri Azospirillum sp. untuk Meningkatkan Efisiensi Pemupukan pada Turfgrass

Introduction turfgrass varieties require fertilization with high dosage, but it can contaminate environment. The increasing efficiency of fertilizer absorbtion was expected to reduce fertilizer requirement. The experiment was conducted to study the effect of arbuscular mycorrhizae and Azospirillum sp. on nutrient uptake, fertilization efficiency, growth and visual quality of turfgrass. The experiment consisted of two factors, i.e. the dosages of fertilizer and inoculant types. The dosages of fertilizer were the relatif dosage from recommended dosage (RD) i.e 100%RD, 75%RD, 50%RD, and 25%RD. The recommended dosage was 0.5 kg N + 1.5 kg P 2 O 5 + 0.5 kg K 2 O per 100 m 2 /month by compound fertilizer (15-15-15). The treatment of 100%RD without inoculant was used as control. The inoculant types were no inoculant, arbuscular mycorrhizal fungi (AMF), Azospirillum sp., and AMF+ Azospirillum sp. Factorial experiment was arranged in Randomized Block Design with three replications. The results showed that interaction between inoculant type and dosage of fertilizer affected nutrient uptake, fertilizer efficiency, growth, and visual quality. AMF inoculation and 25%RD increased shoot N uptake and N fertilizer efficiency, compared with control. Azospirillum sp. inoculation at 75% RD increased shoot N concentration, but did not affect on shoot N uptake and N fertilizer efficiency compared with control. Inoculant did not affect shoot P concentration, shoot P uptake, and P fertilizer efficiency. Azospirillum and AMF+ Azospirillum inoculation increased shoot K concentration. AMF+ Azospirillum inoculation and 100%RD increased shoot N concentration and shoot N uptake, compared with control. Key words : Arbuscular mycorrhizal fungi, Azospirillum , fertilizer efficiency, nutrient uptake, turfgrass.

The Role of Leaf Pigment and Antioxidant Levels in UV-B Resistance of Dark- and Light-green Kentucky Bluegrass Cultivars

Ultraviolet-B [UV-B (280-320 nm)] radiation is one of the major factors causing quality decline of transplanted sod. Pigments and antioxidants are associated with plant stress resistance, but their roles in turfgrass tolerance to UV-B damage are not well understood. The objectives of this study were to determine if kentucky bluegrass (Poa pratensis L.) cultivars with darker green genetic leaf color possessed greater pigment and antioxidant defense capacities and if such characteristics were associated with greater resistance to UV-B. Two cultivars, `Moonlight' (dark green) and `Limerick' (light green), were selected and subjected to continuous, artificial UV-B radiation (70 μmol·m-2·s-1). UV-B irradiation reduced turf quality by 58% (`Moonlight') and 77% (`Limerick') relative to day 1 when measured 10 days after initiation of UV-B exposure. Higher canopy photochemical efficiency (PEc) was found in `Moonlight' relative to `Limerick' under UV-B stress and during recovery. `Moonlight' contained greater levels of chlorophyll (1.5 to1.6-fold), carotenoids (1.3-fold), superoxide dismutase [SOD (1.0-fold)] and catalase [CAT (1.5-fold)] than `Limerick' when measured at 10 days after UV-B initiation. Turfgrass quality and PEc were positively correlated with pigments (chlorophyll and carotenoids) and antioxidant enzymes (SOD and CAT), and negatively correlated with lipid peroxidation. The results suggest that selecting dark-green cultivars with greater pigment content and antioxidant activity may be an effective approach for turfgrass breeders and sod producers to improve tolerance of newly transplanted sod to environments with higher UV-B radiation.

Biostimulant Influences on Turfgrass Microbial Communities and Creeping Bentgrass Putting Green Quality

Immature sand matrix golf putting greens are considered to be inhospitable environments for microorganisms as compared to native soils. Subsequently, turfgrass quality may suffer in the absence of beneficial microbe–plant interactions. The turfgrass industry has responded by marketing a wide array of biostimulant products that claim to improve putting green quality through influences on soil microbial activity. A field study was conducted to determine what influences five commercial biostimulants have on the root-zone microbial community and creeping bentgrass (Agrostis stolonifera L.) quality. A three year old U.S. Golf Association (USGA) specification sand-based putting green (e.g., 80% sand: 20% peat humus by volume) was the test site. Commercially available biostimulants and fertilizer were applied biweekly from May until August 2000. The soil microbial community was characterized using soil enzymes and substrate utilization profiles. Turfgrass quality was determined visually by evaluating color, percentage of localized dry spot (LDS), and overall uniformity. Nutrient uptake levels were monitored to ascertain if increases in quality related to plant health. Visual quality of the putting green was significantly improved (p < 0.05) by the commercial biostimulants. The positive response to biostimulants was not of a nutritional origin. The biostimulants did not effectively alter the putting green microbial community in terms of enzyme activity or substrate utilization. However, a seasonal decline was detected in cellulase activity, which prevailed over any treatment effect, suggesting the root-zone microbial community responded to summer decline of bentgrass roots and concomitant decreases in quantities of root exudates. Visual improvements in putting green quality during the period of summer stress were primarily associated with the incidence of LDS. Visual LDS ratings were significantly reduced (less LDS) by applications of the biostimulants on each observation date (p < 0.05) and over the entire course of the experiment (p < 0.10). Surfactant properties of the biostimulants therefore appeared to play a major role in the improvements in putting green quality. This does not negate the fact that the seaweed extracts and humic acids in the biostimulants may have improved the heat and moisture stress tolerance of the bentgrass once the LDS formed.

Growth Response of Three Turfgrass Species to Nitrogen and Trinexapac-ethyl in Shade

Previous research on the potential of the gibberellin inhibiting growth regulator trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] to improve quality and density of shaded turfgrass has been conducted under neutral-density shade. However, some phytochrome-mediated growth responses of turfgrass, such as tillering, are different under deciduous shade versus neutral-density shade. The objectives of this study were to investigate 1) whether TE would result in improved stand density and quality of turfgrass grown under deciduous shade as has been observed under neutral-density shade and 2) the shade tolerance of sheep fescue (Festuca ovina L. `Quatro') compared to tall fescue (Festuca arundinacea Schreb. `Plantation'), and rough bluegrass (Poa trivialis L.). Trinexapac-ethyl at either 0 or 29 kg·ha–1 a.i. and nitrogen at 12 or 36 kg·ha–1 were applied on 23 May, 3 July, and 15 Aug. 2003 and 21 May 2004 to each species in a randomized complete block design under deciduous shade (about 9% of full sun). Clipping yield, color, and density data were collected for 6 weeks after the May applications in each year. Visual quality was assessed for 6 weeks after application in 2004 only. In 2003, TE significantly reduced clipping yields by 35% to 50% on sheep fescue, 58% to 76% on tall fescue and 55% to 80% on rough bluegrass. However, in 2004, yield reduction was 0% to 50% for all three species and there was no interaction between week, TE, and species. `Plantation' tall fescue had the highest overall visual quality and density. Sheep fescue also provided an acceptable quality turf stand. TE application did not significantly impact the quality of these species. Rough bluegrass performance was unacceptable, and high rate applications of TE to this species in shade resulted in significant (P < 0.05) losses in density. Trinexapac-ethyl application, based on the results of this study, may not enhance turf quality of cool season grasses grown under dense tree shade.

Seeded Zoysiagrass Establishment in a Perennial Ryegrass Sward

Many golf course superintendents in the transition zone of the USA are interested in converting their perennial ryegrass (Lolium perenne L.) fairways to warm‐season grasses to reduce irrigation and fungicide expenses. This research was conducted to identify strategies for converting perennial ryegrass swards maintained under golf course fairway conditions to seeded ‘Zenith’ zoysiagrass (Zoysia japonica Steudel). An experiment was initiated in 1999 (Study I) at the Rocky Ford Turfgrass Research Center at Manhattan, KS, to evaluate the influence of traffic, plant growth regulator (PGR), or glyphosate [N‐(phosphonomethyl) glycine] application to perennial ryegrass and perennial ryegrass scalping on zoysiagrass emergence and coverage. In 2000, a second experiment (Study II) was initiated to evaluate zoysiagrass coverage response after perennial ryegrass was treated with glyphosate or scalping, as in Study I, and a zoysiagrass strip‐seeding technique was also evaluated. Each study was evaluated for three consecutive years. Before seeding zoysiagrass at 42 kg pure live seed (PLS) ha−1 in mid June, plots in all treatments were aerified and verticut. Trafficking turf with a smooth power roller in Study I reduced turfgrass quality during the first year of establishment and reduced zoysiagrass seedling emergence 6 wk after seeding and coverage in each of three evaluation years. Plant growth regulators applied to perennial ryegrass before seeding in Study I did not enhance zoysiagrass seedling emergence or coverage. Perennial ryegrass treated with glyphosate or scalped during the first 6 wk after seeding exhibited greater zoysiagrass seedling emergence than PGR‐treated or untreated turf in Study I. Zoysiagrass coverage in glyphosate‐treated perennial ryegrass was 75 and 84% by October of the first year in Studies I and II, respectively. Scalping perennial ryegrass resulted in 75% (Study I) and 40% (Study II) zoysiagrass coverage by the end of the third season of establishment. Strip seeding zoysiagrass at 84 kg PLS ha−1 into 7.6‐cm wide glyphosate‐treated strips, spaced 33 cm apart, resulted in 73% coverage by the end of the third season of establishment in Study II. In general, the treatments that resulted in greatest perennial ryegrass suppression resulted in the largest percentage of zoysiagrass coverage 3 yr after seeding.

Overseeding Buffalograss Turf with Fine‐Leaved Fescues

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] use as a turf in the northern USA is limited to a certain extent by its extended winter dormancy. A mixture of buffalograss with cool‐season turfgrasses might extend the turf's green appearance and enhance quality. Research was conducted to determine the effects of overseeding fine‐leaved fescue (Festuca spp.) in buffalograss turf on turfgrass color and quality and the effects of species, seeding rate and date, and core cultivation on fine‐leaved fescue establishment in buffalograss turf. Hard fescue (F. longifolia Thuill.), blue fescue (F. ovina L. var. glauca Lam.), and Chewings fescue (F. rubra L. ssp. commutata Gaud.); seeding rates (10, 20, and 30 g m−2); seeding dates (fall, spring, or split fall–spring); and core cultivation (single or double pass) were evaluated for species composition, turfgrass quality, color, and green cover at the John Seaton Anderson Turfgrass Research Facility located near Mead, NE. Buffalograss turf overseeded with blue fescue in fall had the highest turfgrass quality, color, and green cover ratings. Fall overseeding resulted in the highest shoot density values. Spring overseedings were below acceptable levels. Botanical composition of the mixtures overseeded in fall reached 75 to 80% fescue and 20 to 25% buffalograss after 2 yr. Seeding rate effect was linear with each increment between 10 g m−2 and 30 g m−2 increasing fine‐leaved fescue shoot density, turfgrass quality, color, and green cover. Blue fescue–buffalograss mixtures overseeded in the fall exhibited 80% green cover when buffalograss was dormant. Turfgrass green cover in the mixture was extended by 2 months when compared to buffalograss monostands growing in areas adjacent to the study. The results of this study support the use of fine‐leaved fescue and buffalograss mixtures to extend turfgrass green appearance and enhance quality.

Kentucky Bluegrass Response to Use of Aquatic Plants as a Soil Amendment

Rapid aquatic plant growth in Michigan's smaller lakes has reduced their navigability and recreational use. Harvested aquatic weeds have posed a new waste disposal issue for municipalities. Application of lake weeds as a soil amendment on area farms was viewed as a possible waste management option that might benefit local sod producers. The objectives of this study were to 1) estimate the amount of plant-available N (PAN) released from lake weed material, 2) determine the chemical composition of aquatic plant tissues and their effect on plant-available moisture, and 3) study turfgrass response to lake weed applications using the criteria of turfgrass quality, growth, and N uptake. Rates of lake weed refuse applied to field plots were 96, 161, and 206 Mg·ha-1. Two 47-day laboratory incubations were conducted with the same rates of refuse. Relative to biosolids, the metal content of the lake weeds was low and the nutrient content high. One megagram of lake weeds contained 0.37 kg of P and 2.5 kg of K. The decay constant for the C fraction in lake weeds was 8 to 10 days and 16 days for the N fraction. Estimates of the N supplied by lake weeds (570, 960, and 1200 kg PAN/ha) were based on data from C and N incubations. Application of lake weeds significantly increased plant-available soil moisture and significantly enhanced sod establishment and turf density, resulting in decreased weed pressure. However, excess N was present at higher application rates. Management concerns during the application of lake weeds should focus on nutrient loading and the timing of plant-available N release. Depending on methods of weed harvesting, we observed that large amounts of unwanted trash present in the plant biomass could discourage use by growers. Land application of lake weed refuse could ease waste disposal problems, reduce fertilizer inputs for sod growers, and improve the moisture status of sands. Further, this information can be of value to environmental regulatory agencies in determining safe and proper use of such waste materials.

Bur Seeding Rate Effects on Turf-type Buffalograss Establishment

Little or no research information exists in the literature regarding recommended seeding rates of improved turf-type buffalograss (Buchloë dactyloides) cultivars, like `Bowie'. This research was conducted to determine the effect of bur seeding rate on turfgrass establishment of `Bowie' buffalograss. Two experiments were initiated on 21 July 2002 on diverse sites at the John Seaton Anderson Turfgrass Research Facility located near Mead, Nebr. Bur seeding rate effects on turfgrass quality, shoot density and cover, and seedling density were evaluated during the 2002 and 2003 growing seasons. Burs were seeded at 2.5, 5, 10, 20, and 40 g·m–2 (0.51, 1.0, 2.0, 4.1, and 8.2 lb/1000 ft2) of pure live seed (PLS). Turfgrass quality ratings increased linearly with bur seeding rate during the first growing season. However, by early in the second growing season, the response was quadratic with little or no difference in quality between 10 and 40 g·m–2. Turfgrass cover ratings responded in a similar manner to the quality ratings. Buffalograss is reported to establish slowly, taking more than one growing season to establish an acceptable level. In this study, `Bowie', a turf-type cultivar, had acceptable turfgrass quality (≥5.0) and cover (≥75%) ratings by 3 months at bur seeding rates of 5 to 40 g·m–2 of PLS, and acceptable quality and cover ratings were obtained at slightly over 1 month at rates of 20 to 40 g·m–2. These results indicate that bur seeding rates of 20 to 40 g·m–2 are advisable where rapid establishment of turf-type buffalograss is desired, and rates as low as 5 g·m–2 can be used when establishment within two growing seasons is deemed reasonable.

Turfgrass Reflectance Measurements, Chlorophyll, and Soil Nitrate Desorbed from Anion Exchange Membranes

There is not extensive research on the potential of anion exchange membranes (AEMs) for determining available N in soils of turfgrass systems, nor on the use of reflectance meters for quantifying turfgrass color. The two objectives of this study were to determine relationships between (i) turfgrass color measurements and soil nitrate (NO 3 -N) desorbed from AEMs and (ii) reflectance meter measurements and turfgrass chlorophyll concentration. A field experiment was conducted on a 90% Kentucky bluegrass (Poa pratensis L.) stand across 2 yr. Anion exchange membranes were inserted into the soil and exchanged weekly. Desorbed NO 3 -N from the AEMs was quantified. Turfgrass color and chlorophyll measurements were taken monthly. Reflectance meter measurements were significantly related to chlorophyll concentration. Linear response plateau models suggested critical levels of AEM soil NO 3 -N, above which turfgrass color did not improve, from 0.31 to 0.43 μg cm -2 d -1 . These models suggest that critical levels of soil NO 3 -N could be determined that maximize turfgrass quality without excessive N application. These findings suggest both AEMs and hand-held reflectance meters could be useful tools for N management in turfgrass.

Predicting Runoff and Associated Nitrogen Losses from Turfgrass using the Root Zone Water Quality Model (RZWQM)

Nitrogen fertilizers are used to maintain optimum turfgrass quality, but off-site movement of this primary nutrient can affect water quality. We conducted a 4-yr study (1998-2001) designed to measure nitrate N runoff from turfgrass, gathering data to be used in the model. The process-based Root Zone Water Quality Model (RZWQM) was used to predict nitrate associated with runoff from turfgrass. The measurements were made on 12 sloped (5%), 25-m2 plots of 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers.], managed as golf course fair-ways and exposed to natural and simulated rainfall. Surface runoff volume and nitrate N loads were monitored after applying simulated rainfall at an average intensity of 27.4 mm h(-1). The irrigation occurred (25 or 50 mm) 4 through 168 h after treatment with various rates of N fertilizers for 1998-2001. RZWQM adequately simulated water runoff volumes (<19%; nonsignificant, paired t test) in the first three (normal or wet) years, but overpredicted (70%) in the fourth, dry year. RZWQM overpredicted nitrate N loads by a factor of 1.3 for the first three years (nonsignificant), and by a factor of almost 6 for the fourth year (highly significant). These overpredictions occurred when the runoff volumes and N loads were very small. The research has shown that refinements to RZWQM are needed for turfgrass management applications.

Late Fall and Winter Nitrogen Fertilization of Turfgrass in Two Pacific Northwest Climates

Late fall N fertilization of cool-season turfgrass in northern climates is a common practice. Previous research has been focused in climates where freezing temperatures prevail. Research in more moderate northern climates where turf may not go through winter dormancy is scarce. Four fertilizer N sources and an untreated control were applied in four different months (November, December, January, or February) to perennial ryegrass (Lolium perenne L.) in Puyallup, Wash., and to kentucky bluegrass (Poa pratensis L.) In Pullman, Wash., to compare their effects in moderate (Puyallup) and freezing (Pullman) winter climates. In Pullman, only November applications of ammonium sulfate (AmS) or polymer coated sulfur coated urea (PCSCU) enhanced winter turfgrass quality. In Puyallup, November or December application of AmS, PCSCU, or polymer coated urea (PCU) resulted in enhanced winter quality. Polymer coated urea yielded a delayed initial response and a longer residual effect in the spring. Isobutylidenediurea (IBDU) did not improve winter turf quality in either Pullman or Puyallup. Although there was no quality response following January fertilizer application, there was suppression of red thread [Laetisaria fuciformis (McAlpine) Burds.] symptoms in Puyallup, indicating N uptake. Late fall fertilizer N in eastern Washington should be confined to November, using soluble or more quickly available slow-release nitrogen fertilizers. The application window can be extended to December in western Washington, and more slowly available coated ureas can be effectively used.

PRINCIPLES OF FLOW AND TRANSPORT IN TURFGRASS PROFILES, AND CONSEQUENCES FOR MANAGEMENT

Sport turfs require specific soil and water management strategies to achieve optimal sport turf performance and grass quality. In this study the know-how of flow and transport mechanisms in turfgrass porous media is highlighted under drought conditions when water repellency cause preferential flow. An illustration is given of the principles that cause soil water repellency and dry spots for the Ouddorp site in the Netherlands, and ways to prevent or alleviate dry spots. The concept of the critical soil water content is discussed and illustrated with field observations and with computer simulation results. Furthermore, an integrated monitoring and management system is proposed aiming at optimizing soil and water management strategies for sport turfgrass systems. The system is based on the integrated knowledge of soil profile characteristics, the actual soil water content status, and short-term weather expectations.

Nitrogen Rate and Mowing Height Effects on Turf‐Type Buffalograss

Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is a turfgrass species with reduced irrigation and fertilization requirements, relative to traditional turfgrasses. Interest in reducing the amount of chemicals and water applied to turfgrass has resulted in increased efforts to improve buffalograss as a turfgrass. As interest in using the new turf‐type buffalograss cultivars has increased, the need for nitrogen rate and mowing height recommendations supported by research have become necessary. ‘Cody’, ‘Texoka’, ‘378’, and ‘NE 91‐118’ buffalograss cultivars were planted at sites located in Nebraska, Kansas, and Utah to determine nitrogen rate and mowing height effects on buffalograss quality, color, density, and clipping yield. There were significant cultivar × nitrogen rate interactions at all sites for quality, color, and density. Regardless of cultivar, nitrogen rate × year interactions at all sites revealed that the 98 kg N ha−1 rate sustained quality, color, and density over the 3‐yr evaluation period, while lower nitrogen rates had decreased quality, color, and density. The 195 kg N ha−1 rate improved quality over the 3‐yr period but also had the highest clipping yields. Regardless of the cultivar selected, the data support the general mowing height recommendation for turf‐type buffalograss of 5.0 to 7.5 cm. For golf course fairways maintained at a mowing height of 2.5 cm, the vegetatively established cultivars (NE 91‐118 and 378) are the best choice to achieve high turfgrass quality.

Root physiological factors involved in cool-season grass response to high soil temperature

High soil temperature is a critical factor limiting growth of cool-season grasses. This study was designed to examine changes in water, nutritional, and hormonal status in response to high soil temperature for creeping bentgrass ( Agrostis stoloniferavar. palustris) and to compare the sensitivity of those parameters to high soil temperatures. Plants of ‘Penncross’ were exposed to 35 °C soil temperature (heat stress) or 20 °C (control) in water baths while air temperature was maintained at 20 °C in growth chambers. Turfgrass quality, shoot growth rate, and root biomass decreased below the control levels at 15, 15, and 10 days of heat stress, respectively, while root mortality increased above the control level at 5 days of heat stress. Relative water content (RWC) of leaves decreased below the control level at 15 days of heat treatment. Root N content increased while P and K content did not change over time at 35 °C. Shoot N, P, and K content decreased below the control level at 15, 15, and 10 days of heat stress, respectively. Root abscisic acid (ABA) content decreased below the control level at 10 days while shoot ABA content increased above the control level at 5 days. The content of cytokinins (zeatin (Z) and zeatin riboside (ZR), dihydrogen zeatin riboside (DHZR), and isopentenyl adenosine (iPA)) decreased below their respective control levels as early as 5 days of heat stress for roots and 10 days for shoots. The decline in cytokinin content was also more dramatic than changes in other parameters. Our results suggested that cytokinin was most sensitive to high soil temperature among parameters examined, suggesting that changes in cytokinins could serve as an early stress indicator for plant responses to high soil temperature; however, decreased water, nutrient (N, P, and K), and cytokinin content, and increased ABA could all contribute to the decline in shoot and root growth for creeping bentgrass exposed to high soil temperatures.

Morphological Characterization of Turf-type Tall Fescue Genotypes

Recently, turfgrass breeders have developed many improved turf-type tall fescue (Festuca arundinacea Schreb.) cultivars. Due to the large number of cultivars currently available to turfgrass managers and researchers, we have classified turf-type tall fescue cultivars into six groups based primarily on several morphological measurements. This type of classification is important for turfgrass breeders because many breeding decisions are made based on observations in a spaced-plant nursery. The major objective of this study was to classify tall fescue cultivars and selections based on spaced-plant measurements and to then compare those results with turf performance. A spaced-plant nursery consisting of 36 cultivars and selections was established in September 1998 at Adelphia, N.J. Plant height, panicle length, flag leaf width and length, subtending leaf width and length, and subtending internode length were measured 10 days after anthesis in 1999 and 2000. Additionally, a turf trial was established at North Brunswick, N.J., that included the same 36 cultivars and selections. The turf plots were evaluated for several traits including overall turfgrass quality, density, and susceptibility to brown patch disease. Based on principal component analysis of morphological measurements, along with turf trial data, all cultivars and selections were assigned to one of six groups: forage, early-standard, standard, early semi-dwarf, semi-dwarf, and dwarf. In turf plots, the semi-dwarf, early-semi dwarf, and dwarf groups were the top-performing types in terms of overall turfgrass quality, and the forage and early-standard cultivars had the lowest overall quality ratings. The dwarf types did not perform well under summer stress, especially in terms of brown patch disease incidence. The results of this study suggest that when developing cultivars for higher maintenance situations, turf-type tall fescue breeders should focus on the development of semi-dwarf cultivars.

Influence of Fall-applied Treatments on Spring Transition of an Overseeded Bermudagrass Green

Bermudagrass [Cynodon dactylon (L.) Pers × C. transvaalensis Burtt-Davy] greens across the southern United States are normally overseeded in the fall to provide a uniform green playing surface and tolerance to wear during winter bermudagrass dormancy. The spring transition from overseed grass back to bermudagrass is a major problem associated with overseeding because there can be a decline in putting green quality and playability. There have been recommendations, but relatively few published reports, on the effect of treatments associated with seedbed preparation and overseeding on bermudagrass spring transition. The objective of this 2-year study was to determine if spring transition of an overseeded `Tifgreen' bermudagrass green was influenced by fall-applied scalping level, chemical, and seed rate treatments. Treatment factors and levels were designed to reflect the range of practices used by golf course superintendents in the region at the time of the study. The green was located in the Palm Springs, Calif. area, which has relatively mild winters and a low desert, southern Calif. climate. The first year of the study was from September 1996 to July 1997 and the second year was from September1997 to July 1998. Scalping level treatments included a moderate and severe verticut and scalp; chemical treatments included a check, trinexapac-ethyl at two rates, and diquat; and seed rate treatments included a high and low rate of a mixture of `Seville' perennial ryegrass (Lolium perenne L.) and `Sabre' rough bluegrass (Poa trivialis L.). The plot was maintained under golf course conditions and a traffic simulator was used to simulate golfer traffic. Visual ratings of percent green bermudagrass coverage were taken every 3 weeks from 20 Feb. 1997 to 29 July 1997 and from 11 Nov. 1997 to 22 July 1998. Visual turfgrass quality ratings were taken during the second year of the study. Results showed that spring transition was not influenced by fall-applied treatments during both years. Also, visual turfgrass quality was not influenced during the second year. Chemical names used [4(cyclopropyl-_hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl); 9,10-dihydro-8a-, 10a-diazoniaphenanthrene (diquat).