Rolling during golf tournaments is a common practice to maximize greenspeedand improve putting quality.

The Ups and Downsof Rolling Putting Greens

A practical guide tor developing a rolling program.by CHRIS HARlWIGER

HISTORY has an uncanny abilityto repeat itself. Nowhere is thismore apparent than in the turf-

grass management practice of rollingputting greens. Once an important toolin a superintendent's management pro-gram in the early' 1900s, the practice ofrolling has endured periods of popu-larity and disdain. Nevertheless, rollingputting greens has received consider-able attention during the early 1990s,and its merits are being debated atmany golf courses.

The attitudes toward rolling varywidely today. Some golf course super-

intendents view rolling as a means ofimproving putting quality, while othersbelieve rolling is just another stressthat makes putting green managementjust that much more difficult. While thedebate over rolling continues, a largeportion of the golf course managementindustry is interested in revisiting thisold maintenance practice and learningabout its potential for use today.

This article will serve as a guide todeveloping an agronomically appro-priate greens rolling program throughcareful consideration of several factors.To accomplish this, a brief history of

rolling and the advantages and disad-vantages associated with greens rollingwill be reviewed. Next, research resultson the effects of rolling putting greenswill be presented in order to under-stand appropriate frequencies of rollingputting greens. Finally, the differenttypes of rollers available today will bereviewed, and methods to comparedifferent rollers will be offered.

Rolling HistoryHistorically, superintendents used

rolling as a supplement to mowing toimprove the smoothness of putting

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Historically, golf course superintendents used rolling as a mowing supplement inturfgrass management programs.

greens. The mowing equipment, turf-grass varieties, and cultural practicesfor putting greens during the early1900s were much less sophisticatedthan those available today, and thepractice of rolling provided an imme-diate improvement in putting con-ditions. As golf course managementevolved, the attitudes about rollingchanged too. New bentgrass varietiesand improved mowers allowed super-intendents to make major improve-ments in putting quality. Also, turfgrassscientists discovered the negativeeffects of compaction on turfgrassgrowth and development. Needless tosay, many rollers were relegated to theback comer of the equipment storagefacility.

Several events have occurred duringthe last 20 to 30 years that have madesuperintendents reconsider the prac-tice of rolling putting greens. The firstis the proliferation of high-sand-con-tent putting greens, which are lesssusceptible to compaction. Also, manyequipment manufacturers haveintroduced new lightweight rollersdesigned specifically to provide anefficient and reliable means of rollinggreens. A final consideration is theincreasing pressure being placed onsuperintendents to provide faster andsmoother putting surfaces.

Rolling PerceptionsWith the renewed interest in roll-

ing, is is important to understand thepotential advantages and disadvan-tages associated with an appropriateputting green rolling program. Underreasonable mowing heights, rollingwill increase green speed. Accompany-ing the benefit of green speed is animprovement in smoothness anduniformity. After rolling, improvedsmoothness is readily apparent,especially to golfers. Some superin-tendents roll greens in conjunctionwith mowing, while others roll as asubstitute for mowing. This approachreduces the stress associated withmowing and can smooth spike marks,remove dew, and provide an immediateimprovement in smoothness.

While golf's Scottish ancestors con-sidered inconsistent greens a challenge,the demands of today's players dictatea consistent surface from the first greenthrough the 18th green. Rolling all 18greens can improve the uniformity andconsistency of speed among greens.

Aerification is a practice that's essen-tial for high-quality putting greens, butunfortunately golfers have a poor

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understanding of this practice. Somesuperintendents are using rolling as away to minimize the surface disruptioncaused by aerification and improvepost-aerification putting quality forgolfers.

Equipment used to maintain turf-grass has limitations, and rollers areno different. Over the years, severalareas of concern with rolling havearisen. Turf scientists have demon-strated that compaction hinders turf-grass growth, and some fear that rollingincreases compaction. Along with thischange, some believe that rolling maycause a decrease in the infiltration ratethat could hinder oxygen and wateravailability to the roots. Also, there is aconcern that rolling may result in wearinjury or bruising of the turfgrass onthe putting green.

Until recently, researchers had notinvestigated these concerns, and the re-sult was a cautious approach to rollingby superintendents. For example, someuse rollers prior to a tournament orspecial event and use it sparingly atother times. Two major forces aredriving this conservative approach.The first is a lack of research on theeffects of rolling. Additionally, superin-tendents do not want to raise golfers'expectations without knowing moreabout the negative effects of rolling.

The Effects of RollingIf the practice of rolling is to find its

place in the future of putting greenmanagement programs, several impor-tant issues need to be resolved. First,

the practice of rolling appears toincrease green speed, but both theimmediate effects on green speed andthe residual effects on green speed arenot understood completely. Also, turfmanagers are aware of the negativeeffects associated with compaction,but no one has determined if the newlightweight rollers compact puttinggreen soils. Finally, examples of rollersinjuring turf through abrasion havebeen observed, but little is knownabout what conditions and frequenciesof rolling can cause this injury.

In 1992, I identified these questionsand initiated a research project atNorth Carolina State University underthe guidance of Drs. Joe DiPaola,Charles Peacock, Leon Lucas, and BillCassel. The goal of this project was toevaluate the effects of lightweight roll-ing on green speed, compaction, andturf quality. This experiment was con-ducted on bentgrass greens constructedwith a USGA specification rootzoneand a native soil rootzone. The initialstudy was conducted for 10 weeks inthe summer of 1993 and was repeatedin the summer of 1994. Rolling fre-quencies on the bentgrass test plotswere either 0, 1,4, or 7 times per week.

Outlined below is a.brief summary ofthe results of this research.

Green Speed - The experimentsperformed on green speed revealed twoimportant points. First, green speedmeasurements taken one to two hoursafter rolling were 10to 15percent fasterthan an untreated area. Also, a residualeffect was observed. Approximately 48

Research at North Carolina State University demonstrated that rollingonce a week did not decrease turf quality. Turf quality declined after rollingthe turf four or seven times per week after a period of three to five weeks.

hours after rolling, the plots receivingthe rolling treatment had green speedsapproximately 2 to 4 percent fasterthan untreated plots ..

Bulk Density - Bulk density mea-surements were used to assess the levelof compaction of both the USGA andnative soil rootzones. On the USGAspecification green, no change in com-paction was detected in either of thetreatment years for any of the rollingfrequencies. In essence, rolling as muchas seven times per week for ten weeksdid not produce a measurable changein bulk density.

On the native soil green, mixed re-sults were observed. In the 1993 experi-ment, rolling frequencies of four orseven times per week produced anincrease in bulk density. No change inbulk density was noted for the plotsreceiving zero or one rolling treatmentper week. In the second year, nochange in bulk density was detectedregardless of rolling frequency.

TurfQuality - Results of the studyindicated that, depending on the roll-ing frequency, turfgrass thinning anddecreased turf quality can result fromrolling. At a frequency of rolling onetime per week, no decrease in turfquality was evident when comparedto an untreated plot. However, rollingfrequencies of four or seven times perweek did result in turfgrass thinningafter approximately three to four weeks

of rolling treatments. When thinningdid appear, it began in isolated areasand increased as treatments continued.Rolling four or seven times per weekdid reduce turf quality, but only ifpracticed for several consecutiveweeks. Therefore, superintendents canroll at low frequencies for extendedperiods of time and at high frequenciesfor short durations.

Types of RollersThere are three primary types of

rollers available for putting greens. Thedrum roller is the oldest type of rollerin use today. Drum rollers have beenused for many years and they vary insize, shape, and weight. Typically, theseunits were constructed by a creativegolf course mechanic. During opera-tion, drum rollers are pulled behind autility vehicle.

The second type of roller is called atriplex attachment. These rollers areattachments substituted for the reels ona triplex mower. The actual operationof these units is virtually identical tomowing a green with a triplex mower.As a result, little operator training isneeded for effective use. A differencebetween these units and the other twocategories is that tires of the triplex,and not the rollers themselves, are thelast part of the unit to impact the turf.

Dedicated lightweight rollers are thethird category of roller available today.

These units have been receiving themajority of the publicity surroundingthe renewed interest in rolling.Designed only to roll putting greens,these models come in a variety of sizes,shapes, and weights. The major differ-ences between various models of dedi-cated lightweight rollers are the numberand size of actual rollers on the unit,the presence or absence of hydraulics,and the weight of the unit. A dedicatedlightweight roller usually has two orthree rollers underneath the unit. Thepresence of hydraulics, which is asource of concern to superintendentswho worry about hydraulic leaks, isfound on some of the models, whileothers have a belt -only drive systemwith no hydraulics.

Comparing RollersChoosing the type of roller for your

golf course is an important decisionthat involves several factors. The costof the roller is a key consideration.Typically, drum rollers are least expen-sive, followed by triplex attachmentsand dedicated lightweight rollers. Theneed for operator training must beexamined closely. Triplex attachmentrollers require the least amount ofoperator skill, while dedicated light-weight rollers are the most difficult tooperate. The terrain of the greens andsurrounds can dictate the level ofoperator skill needed. The more un-dulations or steep slopes present, thegreater the need for operator skill andthe capability of a roller to handle theseconditions.

The amount of force per unit areathat a roller imparts on the green isanother important consideration. His-torically, measures such as pounds persquare inch (PSI) or pounds per lateralinch (PLI) have been used to determinethe force applied to a green by a pieceof turf equipment. Unfortunately, bothPSI and PLI are difficult to apply torollers. PSI and PLI will be reviewedto understand their limitations, and aformula called the Roll Factor willbe presented as a means to comparethe compaction potential of differentrollers.

In simple terms, PSI can be calcu-lated by dividing the weight of the rollerby the area of surface contact. Often,the technical specifications for theroller will contain the weight, but notthe areas of surface contact. On aconcrete floor, the surface area is easyto determine. Unfortunately, rollers areused on a putting green and not onconcrete. When a roller is placed on a

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Compaction potential of various roller units can be compared by calculating the rollfactor,which includes the unit weight, length of the rollers, and the diameter of therollers in the equation.

525 7505 x (36 x 3) 8 x (36 x 3)

0.97 0.87

In the example, Roller B has a rollfactor value of 0.87, while Roller A hasa roll factor value of 0.97. Based on thehigher roll factor value, Roller A has agreater potential for compaction thanRoller B. Remember that the roll factordoes not offer a measure of force perunit area, but is a method to rank therelative potential for compaction of twoor more rollers. This formula is easyto use and all the information neededis readily available. By using the rollfactor, a superintendent has an excel-lent means to compare rollers and

other turf equipment used on the golfcourse.

CHRIS HARIWIGER is an agronomist inthe USGA Green Section's Southeasternand Florida Regions.

The "Do's and Don'ts" of RollingNow that we have reviewed the

effects of rolling on the putting surface,the types of rollers available, and amethod to compare rollers, some finalthoughts on developing a rolling pro-gram are in order.

Realize that a roller is a tool and nota quick fix or a substitute for a goodagronomic program. As demonstratedthrough research, proper frequencies ofrolling can improve the smoothnessand speed of a green. Generally, lowrates of rolling, such as once or twicea week during non-stress periods, canbe practiced without detriment to theturf. Higher rates of rolling can bepracticed for short durations only.When injury occurs, it is gradual anddoes not happen overnight. However,high frequencies of rolling, such asfour or seven times per week for anextended period, may result in dimin-ished turf quality.

Rolling does not always have to beused as a means to improve existinggreen speed. During the off-season,when clipping production is minimal,rolling greens is an excellent means toremove dew and provide a putting sur-face comparable to a freshly mowedgreen. Rolling also can be used afteraerification as a way to minimize thesurface disruption associated with thispractice.

The education of golfers and courseofficials is essential to any rolling pro-gram. Spoiling golfers with continualrolling may help create a standard thatno one can sustain. lt is important tomake a distinction between the properand improper use of a roller. There aretimes when rolling can be practicedand time when rolling is not advised.The more these groups understand theprinciples of a proper rolling program,the more successful the superintendentwill be.lt is not known whether the practice

of rolling will continue to follow aroller coaster of popularity. What isknown is that superintendents nowhave more information about theeffects of rolling and a wider choice ofrolling equipment. This informationcan be used to develop an agro-nomically appropriate greens rollingprogram that will benefit those whoenjoy golf.

8 in.

36 in.

5 in.

36 in.

paring rollers, all hope should not belost. There is a formula called the rollfactor that can be used effectively tocompare different pieces of turf equip-ment, including putting green rollers.As we have noted above, the importantfactors to consider when evaluatingrollers are the weight of the unit, thelength of the rollers, and the diameterof the rollers. The formula for the rollfactor takes all of these factors intoaccount as noted in the followingformula: Roll Factor = Weight of Unit-:- (Diameter of Rollers x Length ofRollers).

To illustrate how this formula works,consider the following example:Specification Roller A Roller BRollerWeight 5251bs. 7501bs.Number of 3 3RollersLength ofRollersDiameter ofRollersRoll FactorFormulaRoll FactorValue

Introducing the Roll FactorWhile neither of the two methods

above appears to be effective in com-

putting green, there is some amountof depression into the putting surface,which changes the area of contact. Tocomplicate matters, the area of contactis not linear but circular, and the weightof the unit is not distributed equallyat all surface points. The amount ofdepression into a green can vary withthatch levels, mowing height, soilmoisture, rootzone construction, andother factors. As a result, PSI can beextremely variable and difficult todetermine. In determining PSI, it isunlikely that each manufacturer hasused the same assumptions, leavingthe superintendent to try and compareapples to oranges.

Another popular method of com-paring rollers is to measure pounds perlateral inch. The PLI equation is cal-culated by dividing the weight of a unitby the lateral inches of all the rollers onthe unit. For example, a roller weigh-ing 525 pounds With three rollers of 36inches each would have the followingPLI measurement: 525 -:-(36x 3) =8 PLI.While this method is certainly easy tocompute, it does not take into accountthe diameter of the rollers. Theo-retically, two different models eachcould weigh 525 pounds with threerollers 36 inches long, but with differentroller diameters. In theory, the modelwith the larger roller diameter wouldhave a larger area of surface contactand would affect the turf differently. Bynot taking roller diameter into account,the PLI equation is limited and is nota good method to compare rollers.

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