winter protection of annual bluegrass golf greens

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Winter Protection of Annual Bluegrass Golf Greens How protective covers can reduce winter damage to putting greens. by JULIE DIONNE TI E QUALITY of putting sur- faces is one of the most important criteria by which golf courses are evaluated. Extensive winter-kill on annual bluegrass golf greens is a major concern in Canada and the northern United States, where damage can dis- rupt play for many weeks in the spring and result in significant losses of in- come. Winter damage is caused by a wide range of environmental stresses, including rapid exposure to cold tem- peratures, prolonged exposure to cold temperatures, desiccation, freeze-thaw cycles, extended snow cover, ice en- casement, and disease. Golf course superintendents utilize various types of protective covers to reduce winter damage to putting greens. The covers can be invaluable tools for protecting golf greens against freezing temperatures, ice encasement, and desiccation injury. There is a wide array of winter covers available for use. However, many superintendents report inconsistent results with the use of the protective covers, and there are few precise recommendations for their use and almost no data comparing their effectiveness in northern climates. The Horticultural Research Center of Laval University, Quebec City, estab- lished a research program to answer some of these questions. The Canadian Turfgrass Research Foundation pro- vided funding for the project. The project's objectives were to evaluate the effectiveness of different winter covers and develop improved protection prac- tices for annual bluegrass golf greens. Research Methods The study was conducted over a seven-year period at Laval University's experimental green located in Quebec City and on greens at Montreal Country Club, Royal Montreal Country Club, and Royal Quebec Country Club. The golf courses were selected in part because of the wide variation in winter climates between sites. The principal objective of this research was to evalu- ate the impact of different winter pro- tective covers on soil temperature and on winter survival of annual bluegrass on golf greens. During the winter of 1994-95, eight different winter protection treatments were tested. Covering systems with different permeability and insulating .characteristics were selected. The pro- tection systems in the project included: • Permeable covers • Impermeable covers (Evergreen brand covers from Hinspergers Poly Industries Ltd.) • A curled wood shavings mat (American Excelsior Company) protected with an impermeable cover • A straw mulch system (consisting of a permeable cover with 15cm Research plots at Montreal Country Club seven days after the winter protection covers were removed. The type of cover used had a significant influence on soil temperatures and turf injury under severe winter conditions. SEPTEMBER/OCTOBER 2000 11

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Page 1: Winter Protection of Annual Bluegrass Golf Greens

Winter Protection ofAnnual Bluegrass Golf GreensHow protective covers can reduce winter damage to putting greens.by JULIE DIONNE

TIE QUALITY of putting sur-faces is one of the most importantcriteria by which golf courses are

evaluated. Extensive winter-kill onannual bluegrass golf greens is a majorconcern in Canada and the northernUnited States, where damage can dis-rupt play for many weeks in the springand result in significant losses of in-come. Winter damage is caused by awide range of environmental stresses,including rapid exposure to cold tem-peratures, prolonged exposure to coldtemperatures, desiccation, freeze-thawcycles, extended snow cover, ice en-casement, and disease.

Golf course superintendents utilizevarious types of protective covers toreduce winter damage to puttinggreens. The covers can be invaluabletools for protecting golf greens againstfreezing temperatures, ice encasement,and desiccation injury. There is a widearray of winter covers available for use.

However, many superintendents reportinconsistent results with the use of theprotective covers, and there are fewprecise recommendations for their useand almost no data comparing theireffectiveness in northern climates.

The Horticultural Research Center ofLaval University, Quebec City, estab-lished a research program to answersome of these questions. The CanadianTurfgrass Research Foundation pro-vided funding for the project. Theproject's objectives were to evaluate theeffectiveness of different winter coversand develop improved protection prac-tices for annual bluegrass golf greens.

Research MethodsThe study was conducted over a

seven-year period at Laval University'sexperimental green located in QuebecCity and on greens at MontrealCountry Club, Royal Montreal CountryClub, and Royal Quebec Country Club.

The golf courses were selected in partbecause of the wide variation in winterclimates between sites. The principalobjective of this research was to evalu-ate the impact of different winter pro-tective covers on soil temperature andon winter survival of annual bluegrasson golf greens.

During the winter of 1994-95, eightdifferent winter protection treatmentswere tested. Covering systems withdifferent permeability and insulating.characteristics were selected. The pro-tection systems in the project included:

• Permeable covers• Impermeable covers (Evergreen

brand covers from HinspergersPoly Industries Ltd.)

• A curled wood shavings mat(American Excelsior Company)protected with an impermeablecover

• A straw mulch system (consistingof a permeable cover with 15cm

Research plots at Montreal Country Club seven days after the winter protection covers were removed. The typeof cover used had a significant influence on soil temperatures and turf injury under severe winter conditions.

SEPTEMBER/OCTOBER 2000 11

Page 2: Winter Protection of Annual Bluegrass Golf Greens

of straw covered by animpermeable cover)

• A 3mm felt material (TexelIncorporated) protected by animpermeable cover

• A 10mm felt material (TexelIncorporated) protected by animpermeable cover

• A 5cm air space (created with a. wooden frame covered with an

impermeable cover)• A non-protected control

treatmentIn 1994, winter covers were installed

on 3m-by-3m plots on November 24,prior to the first snow cover at LavalUniversity and on November 30 at theMontreal Country Club. A fungicideand rodent repellent were applied be-fore the covers were installed. Winterprotective covers were removed onApril 7 at Laval University and onMarch 21 at the Montreal CountryClub. Soil temperatures under thecovers and climatological data, includ-ing air temperature, thickness of snowcover, rainfall, and snowfall, were re-corded daily during the winter. Annualbluegrass quality and recovery in thespring were also evaluated.

Soil Temperatures andTurfgrass Winter Survival

Soil temperature is more critical thanair temperature for the winter survivalof annual bluegrass. Temperatures inthe surface soil affect the crown portionof the plant. Surface soil temperature isalso a determinant in turfgrass diseasedevelopment. Winter air temperaturesin both Quebec City and Montrealoften reach values of -30°C (-22°P).Annual bluegrass cannot tolerate ex-posure to such low temperatures, andits winter survival is linked to the in-sulating protection of snow or artificialcovers.

12 USGA GREEN SECfION RECORD

Effects of Deep Snow CoverSnow cover was deep and lasting at

the Quebec City plots. Soil tempera-tures remained around O°C (32°P)throughout the winter season underthe different protective covers and onuncovered control plots. The thick andcontinuous snow cover was a verygood natural insulating material andprevented soil temperatures that couldbe fatal to the turf. However, the deepsnow cover and constant soil tempera-ture also were favorable for snow molddiseases. Consequently, most winterdamage observed on the experimentalgolf green at Quebec City was causedby snow mold rather than by freezingtemperatures. These results emphasizethe importance of disease managementand appropriate use of fungicides priorto installing the covers.

Effects of Intermittent Snow CoverIn contrast to the Quebec City ex-

perimental site, the plots at MontrealCountry Club had thin snow cover,and, as a result, the soil temperatureswere lower, even though air tempera-tures at the sites were similar. In addi-tion, high rainfall completely meltedthe snow cover in December 1994 andJanuary 1995. The type of cover usedhad a significant influence on soil tem-peratures and the resulting turf injuryunder these severe winter conditions.

Insulating covers like straw, thecurled wood mat, and the 5 cm air spacereduced soil temperature fluctuationsat the crown level, minimizing theimpact of freezing air temperaturesand thin snow cover. Minimum soiltemperatures at the crown level wererecorded at -1°C (300P) under straw,-2°C (28°F) under curled wood mat,and -6°C (21°F) under the air space.Straw, the curled wood mat, and the5 cm air space provided adequate in-

sulation, and the annual bluegrassoverwintered successfully. Turf qualitywas excellent immediately upon re-moval of the straw and curled woodmat covers. Minor damage was ob-served under the cover that providedthe 5 cm air space, but the turf was fullyrecovered within two weeks followingthe removal of the covers.

The thick felt material (10mm) coverdid not provide as much insulation asstraw, the curled wood mat, or air spacetreatments. The soil temperature atcrown level under the felt dropped toa minimum of -10°C (14°F) and con-siderable winter damage was observedon turf under those covers. Recoverywas complete and turf quality wasexcellent on April 26, more than amonth after winter protection removal.

Very cold minimum soil tempera-tures were recorded under the thin feltmaterial (3mm) covers, permeable andimpermeable covers used alone, and onturf without protection. Minimum soiltemperature at crown level reached-15°C (SOP)under permeable and im-permeable covers and -17°C (1°F)under thin felt material covers and onthe uncovered control plots. The coldsoil temperatures at the plant crownsand the large temperature variationswere responsible for the severe damageobserved for the four treatments.

Annual bluegrass under thin feltmaterial, permeable and impermeablecovers, and on the uncovered controlplots was entirely dead following theremoval of the covers. Spring recoveryeventually resulted from germination ofannual bluegrass seed present in thegreen soil seed bank.

Annual bluegrass seedlings were ap-parent on damaged plots in mid-April,and turfgrass quality improved asannual bluegrass growth progressed.Spring turfgrass quality on control plotsand under thin felt material, permeable,

Page 3: Winter Protection of Annual Bluegrass Golf Greens

and impermeable covers remained sig-nificantly inferior to that observedunder the better-insulating covers forseveral weeks following the removal ofthe covers. Annual bluegrass on theseseverely damaged plots was not suitablefor play until May 17,about one monthfollowing the Montreal Country Clubgolf course opening (April 16). Fromthe level of damage observed on theseplots and from other winter protectionexperiments, we have determined thata critical minimum crown level tem-perature of -10°C (14°F) is required todamage annual bluegrass greens.

Practical Steps ForWinter Protection

The use of insulating winter protec-tive covers improved turfgrass qualityand surface conditions earlier in thespring in our tests. That may be goodnews for golf course superintendentsand for golfers in northern climates.There are some practical steps for op-timizing the winter protection of yourgolf greens:

• A preventive fungicide for snowmold disease control must be appliedbefore the installation of winter protec-tive covers. Temperature and moistureconditions under covers are very favor-able for disease activity, and fungicideprotection is therefore imperative.

• Consider local winter conditionsand snow cover. It is not necessary touse a heavy insulating material if snowcover is deep and continuous. How-ever, if snow cover is thin, the use ofinsulating protective covers is highlyrecommended. They decrease tem-perature fluctuations at crown leveland minimize the impact of freezingtemperatures.

• Always use impermeable protectivecovers to keep the insulating materialdry and reduce injury from ice encase-ment and crown hydration.

• Monitor the temperature profileunder winter protective covers. Tem-perature provides information on themodifications of the insulating proper-ties of the covers and will be helpfulfor determining when to remove thecovers in spring.

• Install and remove the winter pro-tective covers at the right time. Install-ing covers too early may interfere withhardening of the plant and lead toexcessively warm temperatures underthe covers. It is important to installcovers as late as possible in fall, ideallyafter the plant has hardened off.Removing covers too early in the springcan expose turf to frost damage and

desiccating winds, while late removalcould result in snow mold damagebecause fungicide effectiveness is low atthe end of winter.

• Spring permeable covers should beused after the winter protective covershave been removed. These light covermaterials provide protection againstlate frosts and desiccation.

• Winter protective covers are avaluable tool for preventing winterkillof annual bluegrass golf greens. How-ever, the covers will be most successfulwhen used together with a sound turf-grass management plan. Proper mow-ing practices and a sound fall fertili-zation program are very important tomaximize energy reserves and opti-mize cold hardening of turf, and con-sequently improve winter survival ofannual bluegrass golf greens. Turf grow-ing in full sun also will reach a greaterdegree of cold temperature hardiness.

Current Research ProgramsThe first series of experiments con-

firmed that winter protective covers arean effective and practical way to miti-gate winter damage on annual blue-grass golf greens in northern climates.Additional trials to look at differentinsulating materials and coveringsystems also are required. We currentlyare working on atmospheric compo-sition under winter protective covers,particularly under impermeable covers.These covers are very effective in pre-venting excess water at the plant crownlevel and keeping insulating materialsdry, thereby increasing plant toleranceto winter stresses. However, annualbluegrass winter damage not related to

low temperatures' has been observedunder impermeable covers on certaingolf greens. It is hypothesized thatthis damage may result from themodification of the atmosphere at theplant level due to the presence of thecovers.

We have recently documented thatCO2 concentration under covers in-creases as a result of oxygen consump-tion, exposing plants to anoxic condi-tions for long periods of time duringwinter. The objectives of our ongoingresearch on winter protection are toidentify soil and/or plant factors asso-ciated with the occurrence of anoxiaunder winter protective covers, and toevaluate passive or forced ventilationsystems for reducing anoxic conditionsand toxic gases on recurrent winter-damaged annual bluegrass golf greens.

Principal Collaborators on the ProjectDr. Yves Desjardins, Laval University,

QuebecDr. Philippe Rochette, Agriculture and

Agri-Food Canada, QuebecEric Dugal, Laval University, QuebecNormand Bertrand, Agriculture and

Agri-Food Canada, QuebecPierre Dufort, Superintendent,

Montreal Country ClubBlake McMaster, Superintendent,

Royal Montreal Golf ClubMichel Tardif, Superintendent,

Royal Quebec Country ClubThis research is funded by the Canadian

Turfgrass Research Foundation

JULIE DIONNE is a research associate atthe Horticultural Research Center, LavalUniversity, Quebec, Canada.

SEPTEMBER/OcrOBER 2000 13