FIELD SCIENCE

Choosing the best time forseeding mixtures of Kentucky bluegrass

and perennial ryegrassBy Dr. John Stier

II~ombinations of Kentucky bluegrass and perennial rye-grass are commonly used for sports fields in the northernsection of the U.S. because they mix well together froman appearance standpoint.

Each species also brings valuable contributions to thepairing. Kentucky bluegrass has an appealing texture (leaf width) and per-haps the best general appearance of any cool-season grass. It produces under-ground creeping stems (rhizomes) that produce new plants when a gapoccurs in the surface turf cover, providing an evenly smooth turf. Kentuckybluegrasses tend to have tremendous genetic uniformity, meaning each grassplant looks and acts like all the others if a single cultivar is planted.

However, its slow rate of establishment is unacceptable in many situa-tions: seed germination can take anywhere from 1-4 weeks depending ontemperature. It can take longer to fill in an area as shoot production is slow-er than some other grasses and many weed species. Furthermore, pure standsof Kentucky bluegrass are subject to the dramatic die-back symptomscaused by necrotic ring spot disease.

Perennial ryegrass can germinate in 5-7 days: its ability to provide aquick turf is the main reason it's usually mixed with Kentucky bluegrass.Seed distributors also like to use perennial ryegrass in mixtures because it ischeaper than Kentucky bluegrass. Pure stands of perennial ryegrass are oftennot desirable because the species is subject to diseases such as gray leaf spotand crown rust or environmental stresses such as winterkill or drought.

A common goal is to achieve a turf stand that is about 50% eachKentucky bluegrass and perennial ryegrass. Recommendations for the prop-er amount of perennial ryegrass to use in mixtures with Kentucky bluegrassvaries but is generally less than 50% by seed weight. Too much perennialryegrass in a seed mixture results in a virtually pure stand of perennial rye-grass turf because its fast germination and establishment crowds out andprevents Kentucky bluegrass from getting established.

Most recommendations suggest the amount of perennial ryegrass belimited to between 5-30% of the seed mix weight. A previous study at theUniversity of Wisconsin-Madison showed that common types of Kentuckybluegrass are less competitive with perennial ryegrass than improvedKentucky bluegrass cultivars. Common types include low-cost cultivars suchas Park, Kenblue, Alene, Ronde, and South Dakota. Improved types makeup the majority of the cultivars sold commercially but often cost more thancommon types.

Information from our previous study has been increasingly used in contractspecifications for sports field construction but is really limited to situationswhere seeding is done in late summer and the field is given nearly a year orlonger to establish. Many sports fields are constructed under tight timelines,though, and such an extended establishment period is often not available.

Dormant seedingIn some cases sports fields are seeded in the spring and need to be played

on later that year. However, spring is also a prime time for many weeds togerminate and the heat of summer often reduces cool season grass growth.Sometimes contracts require grass to be seeded the year before play is tobegin, but construction delays result in the grass being seeded too late in thefall for germination to occur. This is called dormant seeding: the grass seedsare expected to survive the winter and germinate the following spring.Dormant seeding is often an accepted practice for roadsides, golf courseroughs, and some lawns but not much is known about its success rate inareas prone to winters with below freezing temperatures.

One of the goals of the University of Wisconsin-Madison turf programis to provide research-based information that can be used by the sports turfindustry. Because of the uncertainty involved with seeding cool-season sportsturf mixtures at different times of the year, and the potential difficultiessports field managers may face if a particular mixture is seeded at the wrongtime of year, we compared the relative success of seeding various Kentuckybluegrass:perennial ryegrass mixtures in late summer, as a dormant seeding inlate autumn, and as an early seeding in spring. Our idea was to use the threeseeding times to determine the best time for various seed mixtures to beseeded before football game season that begins in mid to late August.

We seeded plots to mixtures containing 95, 80, 70, or 0% Kentucky blue-grass with the remainder being perennial ryegrass. The varieties used wereall high quality, commercially available cultivars. Kentucky bluegrass culti-vars were equal proportions of Touchdown, Odyssey, and Fairfax. Perennialryegrass cultivars were equal proportions of Manhattan 4, SR 4500, andFiesta 3. The soil type we used was a Batavia silt loam with a pH of 7.4.

Plots were seeded in late summer (about September 1), as a dormantseeding in late November, and in late April about three weeks after winter

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FIELD SCIENCEsnow melted. We fertilized with a starter fertilizer (13-26-12) at the time ofseeding to provide 0.5 lb P per 1,000 square feet. Additional fertilizer wasapplied in early October (summer-seeded plots only), late May, earlySeptember, and early October using 25-2-4 to supply 1 lb N per 1,000square feet with each application.

Irrigation was applied following summer and spring seedings to encour-age germination; dormant seedings were irrigated at the same time as springseedings. Afterwards, irrigation was applied once each week during thegrowing season to replace 100% of the estimated evapotranspiration, whichwas determined with a Toro SitePro irrigation program using data from aCampbell Scientific weather station.

We rated each plot for turf quality every month, weed cover in mid-Junebefore we applied herbicide to control broadleaf weeds, and counted theamount of Kentucky bluegrass and perennial ryegrass plants in a represen-tative area of each plot several times over the year. Beginning in mid-August, we simulated four games of football each week through mid-November using a Brinkman Traffic Simulator. We conducted the firststudy in 200412005 and repeated the study in 200512006.

We found that turf quality varied depending on the year and month. Ingeneral, turf seeded to 100% perennial ryegrass tended to provide the bestquality during May and June, but in one of the 2 years crown rust diseaseseverely reduced turf quality during August and September compared to themixtures with Kentucky bluegrass. All three mixtures with Kentucky blue-grass gave good turf quality by July of the first study, but had unacceptablylow turf quality until September of the second study due to lower springtemperatures, which suppressed growth.

Dormant seedings produced the worst turf quality, though plots seeded

KBG:PRGin seedmixture

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Figure 1. Time of seeding Kentucky bluegrass.perennial ryegrass mixtures affectsthe amount of weeds in the turf differently depending on the mixture used.

to 100% perennial ryegrass were less affected by seeding time than plotsseeded to mixtures of Kentucky bluegrass and perennial ryegrass. Dormantseeded plots had high levels of weeds that required herbicide application(Fig. 1). Turf seeded in late summer, as usually recommended by universityextension programs, had few weeds and wouldn't have required herbicideapplications.

We also found that seeding time had a profound effect on the amountof Kentucky bluegrass that became established in a turf. Both late summerand dormant seedings produced turf that had 60-75% Kentucky bluegrasswhen seed mixtures contained at least 70% Kentucky bluegrass seed byweight (Fig. 2). However, turf seeded in the spring needed 95% Kentuckybluegrass in the seed mix to provide more than 50% Kentucky bluegrass inthe turf stand.

We also found that perennial ryegrass in lower-lying areas tended to dieout during winter but the impact was relatively minor partly because of theshort time frame, just over 1 year, for each of the studies. While perennialryegrass can continue to dominate mixtures with Kentucky bluegrass foryears in states such as Missouri and Kentucky, we wouldn't expect the sameresults in areas prone to severe winters because it lacks the cold temperaturetolerance of Kentucky bluegrass.

In a large perennial ryegrass cultivar trial, subsidized by the NationalTurfgrass Evaluation Program, we've lost an average of about 80% of theperennial ryegrass since the trial was planted in September 2004. Most ofthese losses have occurred following the winters of 2005106 and 2007108 .•

Dr. John Stier isprofessor and chair,Department of Horticulture, Universityof Wisconsin-Madison.

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Time of seeding

Figure 2. Time of seeding various Kentucky bluegrass:perennial ryegrass mixturesresults in different amounts of Kentucky bluegrass in the turf stand.

Study results you can useOur results suggest that if an area must be seeded in the spring, only pure

perennial ryegrass seed or perhaps mixtures containing mostly perennial rye-

grass can be relied upon to give acceptable quality turf by the beginning of

football season.However, in northern climates where perennial ryegrass is sub-

jected to winterkill, or if crown rust disease is undesirable because of the orange

appearance of the turf and resulting orange powder on clothes/shoes, then

seed mixtures containing 70% or more Kentucky bluegrass should be used.

Such seed mixtures should be planted the summer or fall the year before the

fields are to be used. Dormant seedings should not be relied upon to give

acceptable turf quality and are most likely to require herbicide applications.

10 September 2008 www.sportsturfonline.com

y Mike Winkenhofer and Jeff Haag

----11----- he goal of every sportsturf manager is to not only provide asafe playable surface, but to also provide aesthetically pleas-ing green turfgrass. To achieve the latter involves a reciprocalbalance between soil, fertility, moisture, temperature, humid-ity, grass species used, mowing techniques, cultural practices,

preventing reactive oxygen species (free radicals) damage from occurring, andcooperation from Mother Nature. This article discusses what free radicals are,factors that cause free radical damage, and mechanisms you can use to pre-vent development and alleviate their existence if they do develop.

What are free radicals?Most turfgrass managers know that research has shown that free radi-

cals, if not quickly converted to water and ground-state oxygen byantioxi-dants, can bleach chlorophyll, and can damage lipids, proteins, and DNAinside cells of the turf grass plant.

So exactly what are free radicals? Typically, stable molecules containpairs of electrons. When a chemical reaction breaks the bonds that hold thepaired electrons together, free radicals are produced. Free radicals containan odd number of electrons, which make them unstable, short-lived, andhighly reactive. As they combine with other atoms that contain unpairedelectrons, new radicals are created, and a chain reaction begins. This chainreaction or accumulation of reactive oxygen species in plants is generallyascribed to several possible sources, which can be attributed to environmen-tal causes such as drought, heat, ultraviolet light, airborne photo oxidants, orchemicals such as herbicides. Accumulation of reactive oxygen species iscentral to plant response to several pathogens. The free radicals (reactiveoxygen species) are singlet, hydroxyl, superoxide, and hydrogen peroxide.

There is a catch-22 to light. We know that light is necessary for photo-synthesis to occur but it can also playa part in free radical formation. Whenphotosynthetic organisms are exposed to ultraviolet radiation, significant,irreversible damage to important metabolic processes within the cell mayoccur (such as lesions in DNA and inhibition of photosynthesis). Throughthese reactions and others, radical forms of oxygen are often created. Manystudies suggest that this damage is due to oxidative stress resulting fromeither UV-A or UV-B or both.

The major effect of ultraviolet- B light on the thylakoid proteins is the

12 September 2008

breakdown of the reaction centre Dl protein. One must question whetherultraviolet- B radiation will become an even more serious factor in the yearsto come. The depletion of the stratospheric ozone is causing renewed con-cern about the increased level of ultraviolet- B radiation reaching the Earth'ssurface, and it is known that exposure to environmental ozone can cause sig-nificant damage to turfgrass by imposing oxidative stress.

Photosynthetic light absorption and energy use must be kept in balanceto prevent formation or reactive oxygen species in one important compo-nent of the turf grass cell where chlorophyll is developed, the chloroplast. Inthe case of drought for example, it causes stomatal closure, which limits thediffusion of carbon dioxide to chloroplasts and thereby causes a decrease inCO? assimilation in favor of photorespiration that produces large amountsof hydrogen peroxide.

Under these conditions the probability of singlet oxygen production atPhotosystem II and superoxide production of Photosystem I is increased.These may cause direct damage, or induce a cell suicide program. We sus-pect this to be the case as well since we are currently seeing a gradualincrease in yearly temperatures across the world, and an increase in skincancers in humans. How it affects turf grass plants in the years to comeremains to be seen.

Defense mechanisms: antioxidantsThe antioxidants a-tocopherol (Vitamin E), ascorbic acid (Vitamin C),

carotenoids (B-Carotene), vitamin B6, and mannitol contained in somebiostimulants all playa vital role in scavenging free radicals. Applications ofbiostimulants, which supplement plant hormones, have been shown toenhance the presence of various antioxidants in the leaves, reducing stressand promoting faster recovery from injury. Applying this type ofbiostimu-lant product to sports fields several weeks before the beginning of play andfollowing up with regular applications during the season can enhance thepresence of antioxidants for stress reduction and recovery.

Carotenoids (B-Carotene). In terms of its antioxidant properties,carotenoids can protect Photo system I and Photosystem II in one of fourways: by reacting with lipid peroxidation products to terminate chain reac-tions; by scavenging singlet oxygen and dissipating the energy as heat; byreacting with triplet or excited chlorophyll molecules to prevent formation

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dissipation of excess exci-ough the xanthophyll cycle.

ophylls function as accessory pigmentsesting light at wavelengths that chloro-

yll cannot, and transfer the light energy tochlorophyll, but they also absorb excess lightenergy and dissipate it in order to avoid damagein what is termed the xanthophyll cycle.

a-tocopherol (Vitamin E). This is considered amajor antioxidant in chloroplasts in at least twodifferent, but related roles: it protectsPhotosystem II from photoinhibition, and thy-lakoid membranes from photooxidative damage.The antioxidant properties of Vitamin E are theresult of its ability to quench both singlet oxygenand peroxides, although Vitamin E is a less effi-cient scavenger of singlet oxygen than B-Carotene, it may function in the thylakoid mem-brane to break carbon radical reactions by trap-ping peroxyl radicals.

Vitamin E also has the ability to donate twoelectrons, which results in opening of the chro-manol ring to form the corresponding toco-quinone derivative. These combined molecularcharacteristics allow Vitamin E to protectpolyunsaturated fatty acids from lipid peroxida-tion by scavenging lipid peroxyl radicals thatpropagate lipid peroxidation chain reactions inmembranes.

Ascorbic Acid(Vitamin C). It is generallybelieved that maintaining a high ratio of ascorbicacid is essential for the scavenging of free radi-cals, and is needed in high concentrations in thechloroplasts to be effective in defending the tur-fgrass against oxidative stress. Although ascorbicacid can directly scavenge the free radicals super-oxide and singlet oxygen, probably the main ben-efit that ascorbic acid plays in the prevention offree radicals is that it is an excellent scavenger ofthe hydroxyl radicaL The hydroxyl radical is dan-

14 September 2008

gerous to turfgrass because idioxide assimilation by inhibiting several Calvincycle enzymes.

Vitamin B6. Apart from its function as acofactor, Vitamin B6 is also thought to act as aprotective agent against reactive oxygen species(free radicals), such as singlet oxygen. VitaminB6 is also the master vitamin in processingamino acids, and plays a very important role indeveloping proteins specifically designed to helpchloroplasts, thylakoid membranes, PhotosystemI, and Photo system II to function properly.

Mannitol. The antioxidant mannitol has theability to protect, and quench, two damaging freeradicals: singlet oxygen, and hydroxyL Singletoxygen is damaging because it can react with pro-teins, pigments, and lipids, and is thought to bethe most important species of light-induced lossof Photo system II activity, as well as the degrada-tion of the Dl protein, which we will discuss later.It has further been demonstrated that when man-nitol is present in the chloroplasts, it can protectturfgrass against oxidative damage by the hydrox-yl radicals. The Senn, Senn, and Senn Companymanufactures a biostimulant called N.O.G.(Natures Organic Growth) that contains andexcellent source of mannitol, along with the otherantioxidants mentioned.

Amino Acids. As we know, amino acids are thebuilding block of proteins. Under optimal condi-tions proteins are able to perform the normalphysiological function to synthesize amino acids,but intensively manicured turf grass such assports turf are rarely operating under normal con-ditions due to low mowing heights and trafficstress placed upon them.

The topical application of amino acids plays anextremely important part in developing the pro-teins specifically designed to help chloroplasts,thylakoid membranes, Photosystem I, and

nction properly. These pro-teins are known as Dl, D2, CP43 , CP47, andcytochrome b559. Of special importance is the Dlprotein because it exhibits the highest turnoverrate of all the thylakoid proteins, and is also high-ly vulnerable to the free radical singlet oxygen.

Humic acids are another compound that hasshown to contain antioxidant properties thatpromote the scavenging of free radicals. Theadded benefits are that they also increase theavailability of micronutrients, phosphate, andpotassium to the plant, and enhance the chloro-phyll content of turfgrass. Humic acid also hasbeen shown to stimulate root initiation due tothe auxin-like activity they contain, which ismost likely due to their ability to inhibitindoleacetic acid (IAA) oxidase breakdown.

There is new evidence that carbon now playsa role in the overall development of the turfgrassplant leaf, that a reduction in carbon also reducesphotosynthetic activity which reduces carbohy-drate availability to the turfgrass plant, and thereis also new evidence to suggest without properamounts of carbon in the chloroplast that properdevelopment of the turfgrass plant cannot occur.

There is also further evidence to suggest that,if there is an abundant source of carbon in the thy-lakoid membranes inside the chloroplasts, it canbe mobilized for use as an energy source duringsenescence. As we discussed earlier, light absorp-tion by the enzyme pheophorbide an oxygenase,the key enzyme in the pathway to chlorophylldegradation to senescence, can cause the develop-ment of the free radical singlet oxygen.•

Mike Winkenhofer is sportsturf manager and JeffHaag is assistant sportsturf manager for theUniversity of Louisville. For a list of referencefromthis article, seewww.sportsturfonline.com.3-D Molecule illustration courtesy of istockphoto.com

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FIELD SCIENCE

Hybrid bluegrass vs. Kentucky blueand tall fescue in transition zone

By Dale J. Bremer, Kemin Su, Steven J. Keeley, and Jack D. Fry

c

Bill Snyder Family Stadium, courtesy Kansas State University Athletic Department

Insome areas of the United States, Kentucky bluegrass and tall fes-

cue are subjected to frequent drought, which results in heat anddrought stress symptoms, and irrigation is required to maintainacceptable quality. Kentucky bluegrass (KEG) commonly goesdormant during periods of high temperature and drought. Tall fes-

cue (TF) has good drought avoidance because of its relatively deep rootingsystem, but some turfgrass managers prefer the finer texture and recupera-tive capacity that KEG offers.New hybrid bluegrass (HBG) cultivars, which are genetic crosses

between KEG and native Texas bluegrass, have the appearance of KEG butmay be able to withstand higher temperatures and extended drought with-out going dormant. In warm climates HBG may stay green all year long.Furthermore, HBG may use less water than other cool-season species whilemaintaining their green color. This is especially important given the increas-ing competition for water and the rising costs of irrigation.In our 2-year study, two HBG were compared with KEG and TF in the

stressful climate of the transition zone. The objectives were to evaluateKEG (Apollo), TF (Dynasty), and two cultivars of HBG (Thermal Blue(HBG1) and Dura Blue (HBG2)) for: 1) canopy establishment rates afterfall seeding; 2) visual quality and growth characteristics of canopies; and 3)drought resistances under different irrigation regimes and deficits.The study was conducted from September 2002 to October 2004 at the

Rocky Ford Turfgrass Research Center near Manhattan, KS. The soil at the

I

16 September 2008

site was Chase silt loam (fine, smectitic, mesic-Aquertic, Argiudolls).Thirty-six subplots were established in a split-plot design. Two irrigationtreatments and a control, replicated three times each, were applied to wholeplots arranged in a Latin square design. Four species or cultivars of turf-grasses were established in the subplots. One species/ cultivar of each turf-grass was planted once within each whole plot; species/cultivar was ran-domly assigned to subplots within each whole plot. Therefore, each irriga-tion-by-species/cultivar treatment combination was replicated three timesin the entire study.Irrigation treatments included the replacement of 100 and 60% of the

water lost from plants and soil via evapotranspiration (ET), and controlplots received only natural precipitation. Water was applied twice weeklythrough a fan spray nozzle attached to a hose; a meter was attached toensure proper application rate. To determine irrigation requirements, evap-otranspiration (ET) was calculated by using the Penman-Monteith equa-tion, and climatological data were obtained at a weather station located atRocky Ford.In 2003, irrigation treatments were not applied because of a moderate

billbug infestation that affected a number of plots of KEG, HBG1, andHBG2 despite insecticide applications. Plots in 2003 were irrigated every3-4 days, providing 40 mm of water per week in the absence of rain, to min-imize stress related to billbug damage. Therefore, irrigation treatments wereapplied for only one year (2004) of the study.

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Canopy evaluationsTurfgrass canopy establishment was evaluated visually after seeding,

from 17 December 2002 to 20 July 2003. Establishment was estimated aspercentage of the ground surface covered by turfgrass canopies within eachplot (0 to 100%).

All plots were evaluated biweekly for visual turf grass quality, which wasrated on a scale from 1 (dead, brown turf) to 9 (optimum uniformity, den-sity, and color) and 6 was considered acceptable quality for a horne lawn; allevaluations in each year were conducted by the same person. Turfgrass den-sity and color were also evaluated visually in each plot independent of, albeitless frequently than, quality during the same periods in 2003 and 2004.

Clippings were collected every 3 weeks, or 4 times from 5 August to 10October in 2003, with a walk-behind rotary mower equipped with a modi-fied collection bag that allowed for complete capture of clippings from eachplot. Clipped biomass was determined gravimetrically after samples hadbeen dried in a forced-air oven for 48 hours at 65 degrees C.

Tests of differences in canopy establishment, visual quality, canopy colorand density, clipping biomass, vertical growth rates, and irrigation effectsamong treatments were conducted with the mixed linear model procedureofSAS.

Plot maintenanceAll plots were mowed with a walk-behind rotary mower at a height of

2.5 inches once or twice weekly as needed to prevent removing more than1/3 of the canopy height. All plots were fertilized with approximately 225kg urea N ha?l yr?l in 2003 and 2004, in split applications in September,November, May, and July. Because bluegrass billbug had infested some blue-grass plots at the research center in previous years, plots were treated in2003 with 0.36 kg a.i. ha?l ofimidacloprid (1-(6-chloro-3-pyridylmethyl)-N -nitroimidazolidin- 2-ylideneamine, 1- [(6-chloro- 3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine) on 7 June and 0.09 kg a.i. ha?l ofbifenthrin(2-methyl-1, 1-biphenyl-3-y1)-methyl-3-(2-chloro-3,3,3-trifluoro-1-

propenyl)- 2,2-dimethyl cyclopropanecarboxylate) on 1August, and in 2004 with 0.44 kg a.i. ha?l ofimidacloprid on19 April, 0.125 kg a.i. ha?l ofbifenthrin on 27 May, and 1.69kg a.i. ha?l of halofenozide (Benzoic acid, 4-chloro-, 2-ben-zoyl-2-(1,1-dimethylethyl)hydrazide) on 9 July.Preemergence herbicide applications included 0.56 kg a.i.ha?l of dithiopyr (IS, S/?-dimethyl 2-difluoromethyl-4-isobutyl-6-trifluoromethylpyridine- 3,5 -dicarbothioate) on17 May 2003 and 27 May 2004. Broadleaf pests were treatedas needed, and no fungicides were applied during the study.

Establishment was most rapid in TF, which was at 90%cover by 17 December 2002 and reached 100% by 7 May2003. Both KEG and HBG 1 established more slowly thanTF and were similar to each other; HBG 1 reached 99% coverby 13 June and KEG by 28 June. The HBG2 was slowest toestablish, reaching 96% cover by 19 July. Percentage cover forHBG2 was lower than for TF, KEG, and HBG 1 during theentire period of establishment evaluations. Establishment inTF was 99% complete 37,52, and more than 73 days fasterthan in HBG1, KEG, and HBG2, respectively.

Visual quality was generally lower in the bluegrasses thanin TF during 2003 and 2004. Mean quality, when averaged over the season,ranked TF>KEG>HBGhHBG2 both years; all differences in mean qual-ity among species or cultivars during the season were significant in bothyears, except between KEG and HBG1 in 2003.

The ranking of visual quality among species was, in part, a function ofdifferences in canopy density and color. For example, canopy density washighest in TF and generally similar between KEG and HBG 1 in both years,but a lighter color in HBG 1 resulted in its lower quality rating in a numberof instances. In 2003, quality in HBG2 was consistently lower among plotsearly in the growing season because of its slower establishment. Slowerestablishment in HBG2 resulted in a lower canopy density than in TF,KEG, and HBG1 up to 11 July 2003. Canopy density also was consistent-ly lowest in HBG2 during 2004. Higher seeding rates may be required forHBG2 to obtain an adequate stand.

Vertical growth rates of HBG 1 were similar to TF in 2003 and 2004,

Vertical growth rates were measured biweekly to monthly from 14 Julyto 21 October in 2003 and biweekly from 14 June to 12 August in 2004.Daily vertical growth rates were calculated as the increase in canopy heightsbetween consecutive mowing events, divided by the number of daysbetween mowing. Canopy heights were measured immediately after mow-ing at two randomly selected locations within each plot; each location wasmarked with a flag that remained until the next mowing date. Before thenext mowing, canopy heights were measured a second time at the same(marked) locations. Canopy heights were measured by placing a circularpiece oflightweight cardboard over the canopy and centered on the flag; thecardboard was rigid enough to hold its shape but lightweight enough tominimize the bending of the canopy by its weight. The height of the canopywas then measured at four perpendicular spots around the circumference ofthe cardboard. The flags were then removed before mowing and then rein-serted at new, random locations for the next measurements.

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and were higher than KEG on three of fourmeasurement dates in 2003 and on the last twodates in 2004. Averaged across the season, ver-tical growth rates of HBG 1 were higher thanthose of KEG in 2003 and higher than those ofKEG and HBG2 in 2004. It is clear thatHBG 1 shows little promise of reduced mowingfrequency, compared with conventional cool-season species. The vertical growth rate ofHBG2, by contrast, was more similar to KEGin both years. Averaged across the season, thevertical growth rate of HBG2 was lower thanthat ofTF in 2003 and 2004 (albeit not signif-icantly in 2004). Thus, there is potential forreduced mowing frequencies with HBG2 (andperhaps future cultivars of HBG), comparedwith TF.

Effects of water deficitIn 2004, frequent, above-average rainfall

from May through August minimized theimpact of water-deficit treatments; precipita-tion between June and August 2004 was 18.42inches, which was 5.82 inches above normal.Drier (albeit cooler) weather during a 52-dayperiod in September and October of 2004allowed for a stronger comparison amongspecies and cultivars under drought conditions;precipitation was 1.02 inches duringSeptember, which was 2.63 inches below nor-mal, and only 0.27 inches occurred in earlyOctober before the study ended.

Visual quality ratings were similarly highamong species and cultivars in well-wateredplots at the end of the dry period in Septemberand October 2004. Visual quality in the 60%ET treatment was significantly lower in HBG2than in KEG, and quality in HBG1 and HBG2

was below the rating of 6 determined as accept-able for home lawns. In the control, whichreceived only natural precipitation during thisperiod (i.e., no irrigation), the quality of allbluegrasses was below 6 and ratings of KEGand HBG 1 were significantly lower than thoseofTF. Visual quality in TF declined only from8 to about 6.5 to 7 in the reduced-irrigation andcontrol plots, indicating that TF was not sub-stantially affected by drought in this study.

The lack of response of TF to water deficitmay have been caused by a combination of deepsoils at the research site and deep roots typical ofTF that may extract soil water from lower in theprofile. Higher quality in KEG than in HBG2at 60% ET, and the lack of differences betweenKEG and HBG 1 and HBG2 in the control, arein contrast to results from a study that reportedhigher quality in a HBG (Reveille) than in KEG(Bensun [A-34]) during prolonged dry down.The latter study also determined that the HBGhad greater root length density and root mass inthe 0- to 60-cm profile than the KEG had, andthat greater dehydration avoidance was observedin the HBG than in KEG. Significant variationin drought resistance has been observed amongcultivars of KEG and HBG however, and suchdifferences among species and cultivars mayhave contributed to the contrasting resultsobserved in our study .•

Dale J Bremer, Kemin Su, Steven J Keeley,and Jack D. Fry, are with the Department ofHorticulture, Forestry & Recreation Resources,Kansas State University. This research was firstreported in Applied Turfgrass Science inJune 2006.Acknowledgements and Literature Cited are avail-able at www.sportsturfonline.com.

What it means to youOur results indicate that tall fescue (TF) may be better suited than hybrid bluegrass

(HBG)in areas of the transition zone where soils are deep, especially if drought resistanceis a priority. Susceptibility of HBGto bluegrass billbug in this study also suggests that itsmaintenance costs may be higher than in TF,although other HBGcultivars not tested inthis study may be more resistant to bill bug damage. Because some cultivars of HBGalsomay exhibit higher drought resistance than others, further research is needed using newor different cultivars of HBG and in areas with different soils to more completely deter-mine the potential for the use of HBG in the transition zone.

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FIELD SCIENCE

Pros and cons of usingperennial ryegrass for sports turfBy Dr. John Street and Pam Sherratt

I . ~ erennial ryegrass Lolium perenne is the most predominantIt cool-season sports turf grass. It is also used by many warmseason turf managers as the overseeding grass of choice inthe fall.

While perennial ryegrass is revered in Europe, it issomewhat "suffered" in the United States, with cool-season turf managersmuch preferring to use Kentucky bluegrass Poapratensis, even if the chanceof success is minimal. The distaste for perennial ryegrass as a sports turfgrass has always perplexed me, since we know that most fields are alreadycomposed of ryegrass and I know just how great it can perform as a sportssurface. It does have its issues and some of those can lead to majorheadaches, but its "pros" far outweigh its "cons," as listed here in a Point-Counterpoint format:

22 September 2008

Point: It is a bunch-type grass and therefore does not have the capabil-ity to spread laterally. Counterpoint: Ryegrass is a prolific producer of tillers,particularly if mowed at the lower end of the preferred height of cut (1-1.5"). In studies conducted at Ohio State over the past several years, ryegrasshas had as good recuperative potential as Kentucky bluegrass or tall fescueunder traffic. In addition to its recuperative ability it is very wear tolerant,and so persists during heavy traffic.

Point: Because it is a bunch-type grass, fields must be overseeded con-stantly. Counterpoint: There is no such thing as an athletic field that does-n't need constantly overseeding, regardless of turf type. On native soils,where traffic and compaction are commonplace, all cool-season turfgrassesneed regular overseeding to keep fields safe.

Point: It is "slippery." Counterpoint: It is "shiny" on the underside of the

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leaf, which makes it look wet from a distance.Point: It has poor heat, drought, and cold tol-

erance. Counterpoint: Like bluegrass and tall fes-cue, it is a cool-season grass and so prefers airtemperatures of 60-75F (15-24C) and soil tempsof 50-65F (10-18C). In extreme conditions, itmay not be as heat and drought tolerant as tallfescue, or as cold tolerant as bluegrass, but it willsurvive in most areas.

Point: It is susceptible to grubs. Counterpoint:Like many other turf grasses , it is susceptible togrub attack. However, many perennial ryegrasscultivars contain "endophytes" (microscopic fungiin the plant cells) that prevent attack from surfaceinsect pests, such as bluegrass billbugs, chinchbugs and sod webworms.

Point: Lignin in the leaf produces leaf tissueso strong that the leaves "tear" rather than cutcleanly, resulting in poor mowing quality.Counterpoint: In every instance we have seen thisphenomenon, dull mower blades were the culprit.

Point: In fall and spring, ryegrass does not mix

well with other grasses. The color is different andthe clumps of ryegrass stand out. Counterpoint:Ryegrass staying green longer into the fall/earlywinter and greening up quickly in spring is amajor advantage for sports turf managers withfall or spring sports. Masking color differencescan be helped by applications of iron or nitrogen,choosing bluegrass cultivars with short winterdormancy or painting the field with a green dyein early spring. Some turf managers may alsocover the field with a growth blanket, to promotespring growth of all the grasses. In Europe, rye-grass cultivars are much lighter green, to mask thePoa annua that invariably encroaches on sportsfields.

Point: Ryegrass takes over the field like aweed. Counterpoint: The number one reason itdoes so well is its ability to germinate and estab-lish so quickly. The ability to grow quickly meansit shades out the bluegrass and prevents seed ger-mination and establishment. Athletic fields arenot perennial stands of grass like lawns, they are

in a constant state of renovation and as such thekey to success is "quick" grass.

Point: Perennial ryegrass is susceptible to awhole host of turf grass diseases. Counterpoint:Yes, it is. No arguing on this point. If the condi-tions are favorable for a disease attack, ryegrass isprone to get it. Turf managers need to beextremely vigilant with irrigation and nitrogenand choose cultivars that have shown betterresistance. Where possible, especially on gamefields, preventative applications of fungicide maybe required. As a side note however, because it isso quick to grow it can sometimes "outgrow" adisease like damping off much more successfullythan slower-growing species. •

FIELD SCIENCE

John Street is an associateprofessor in the OhioState Department of Horticulture & Crop Science.Pamela Sherratt is a sports turf extension specialist atOhio State. This information first appeared April16, 2008 in the "International Sports Notes" sectionof www.buckeyeturfosu.edu.

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