Wear and compaction can leave youwith unsightly bare spots.BY BOB VAVREK

CAN YOUTRAFFICHOW MUCH

• • •BARE?

A well-designed net-work of paved pathscan keep the courseopen to carts duringwet weather and helpmaintain a smoothflow of traffic throughthe course. Curbingfurther enhances theeffectiveness of cartpaths - assuming,of course, that thegolfers abide by therules of the road.

Ageneral definition of traffic as it pertainsto golf turf might be the movement of peopleand vehicles across the playing suifaces.When

all is said and done, without traffic, most golfcourses would go out of business. After all, theeffects of foot and cart traffic on the turf aredirectly related to the amount of play.There is nofree golf, and green fees, membership dues, andcart revenues support golf course operations.Excessive traffic, however, can have a detrimentaleffect on the quality of the playing surfaces.

Concentrated traffic is a multi-component stressto the turf. According to Beard (1973), traffic

results in four problems: (1) turf grass wear, (2) soilcompaction, (3) soil displacement or ruts, and (4)turf removal or divots. The most apparent effectsof traffic are ruts, divots, and direct wear injury tothe turf plants. Compaction is often consideredthe hidden qJect of traffic because it affects theunderlying soil. Soil compaction may not bevisible, but it often alters the soil physical proper-ties in a manner that is detrimental to turf growth.This article discusses how compaction affects soilphysical properties, turf growth, and the quality ofplaying conditions, along with various techniquesfor relieving or preventing compaction.

JULY-AUGUST 2002

Deep-tine aeration canrelieve compactionfound beyond thereach of conventionalcore cultivationoperations.

COMPACTIONSoil compaction is defined as the pressingtogether of soil particles, resulting in a moredense soil mass with less pore space (Carrow andPetrovic, 1992). Back in Soils 101 we learned thata typical silt loam soil capable of supportinghealthy plant growth would be composed of 50%solids (45% mineral, 5% organic matter), 25% air-filled pore space, and 25% water-filled pore space.Apply pressure or compaction to this soil and thebalance between solids, air, and moisture is altered.Soil aggregates break down and individual soilparticles are squeezed and shift into closer align-ment. The ratio between small water-holdingpores and large air-filled pores increases. The soilbecomes denser and holds more water due to theincrease in small pores.

A litde compaction may actually improvegrowing conditions for turf on a sandy loam soilby increasing the moisture-holding potential ofan otherwise droughty soil. However, relativelyfew courses outside of Florida are built on sand orsandy loam soils. Most courses are built on soilsthat contain a significant amount of silt and clay.The texture of the soil is one factor that deter-mines the potential for compaction. The higherthe fraction of silt/clay in the soil, the greater thepotential for compaction.

Other factors that influence the potentialdegree of compaction for a particular soil include:• Particle size distribution - Soils that have awide particle size distribution are more susceptible

to compaction than soils that have a narrowparticle size distribution. For example, when mostof the particles of a sandy soil are about the samesize, the root zone resists compaction because theindividual sand particles touch each other and abridging action prevents a shift in the pore sizedistribution .• Soil moisture - Dry soils are more resistantto compaction than wet soils.The water acts as alubricant, and soil particles shift under pressureand orient themselves in a manner that reduceslarge pore space. As a result, the ratio of small porespace to large pore space increases .• Turf density and thatch - The amount ofliving or dead plant tissue that exists on thesurface of the soil can buffer or cushion theeffects of compacting forces. Weak, thin stands ofturf are highly susceptible to compaction.

A comprehensive review of how compactionaffects turfgrass growth can be found in Carrowand Petrovic (1992). Severe compaction affectsturfgrass growth in the following ways:• Altered root distribution and root dysfunction.Most turfgrass roots growing in heavily compactedsoils are found near the surface. The mechanicalimpedance of compacted soils to root growth ispartially to blame for the shallow rooting. Otherpotential causes of shallow root growth includethe production of ethylene by roots subjected tocompaction, resulting in the growth of shallowadventitious roots. Low oxygen levels in com-pacted soils also discourage deep rooting and limitroot water uptake.• In various studies of turfgrass growing in heavysoils, compaction has caused decreased shootdensity, rhizome/stolon development, andclipping yield. In contrast, moderate compactioncan increase top growth of turf growing in sandysoils.• Nutrient uptake is altered in compacted sitesprobably due, in part, to the effects of compactionon root growth.• Reduced water uptake can occur undercompacted conditions.• Turf growing on compacted soil can havereduced carbohydrate reserves and, in turn, haveless ability to recbver from stress.• Compacted soil has a greater capacity to holdmoisture. As a result, the soil takes longer to warmup during the spring, and the excessively moistrootzone inhibits root growth. Spring green-upcan be delayed, and soft, soggy surfaces providegolfers inconsistent playing conditions.

2 GREEN SECTION RECORD

From the golfer's viewpoint, a compacted soilequates to a less resilient playing surface. This maymean a little more roll in the fairways, but rockhard tees and greens. Golfers often complain thatthe greens don't hold when an inability to putbackspin on the ball is to blame. On the otherhand, severe compaction to a soil-based, push-upgreen can create an unfair surface that even askilled player has difficulty holding.

MINIMIZING THE EFFECTSOF SEVERE COMPACTIONIn general, two management strategies areemployed to address the myriad of problemsassociated with growing turf on compacted soil:• Alleviate the compaction that already existsthrough various cultivation techniques.• Modify the soil physical properties andreduce or redistribute traffic to prevent furthercompaction from occurring.

surfaces are not continually subject to trafficassociated with winter play. Natural processes likefreeze/thaw cycles and root growth/death aremost effective when the compacted site is leftfallow - a condition that never occurs on golfcourses. Consequently, more aggressive forms ofcultivation are required to improve growingconditions on heavily compacted sites.

HOllOW/SOLID-TINE CULTIVATIONHollow or solid-tine cultivation is the universallyrecognized maintenance practice employed toloosen compacted soils. Most golfers are intimatelyfamiliar with this operation, and some respondwith the familiar complaints regarding surfacedisruption. Practically all courses employ someform of hollow- or solid-tine aeration eachseason on greens and other areas .

Compaction caused by foot traffic, carts, ormaintenance equipment on golf courses generally

Worst-casescenario ... allowinggolf carts to roam freeon a soft, wet course.

CULTIVATIONIn some respects, the constant process of rootgrowth and dieback can be considered a passive,but important form. of cultivation. Althoughcompaction limits root growth, even a little rootgrowth through a tight soil is a step in the rightdiJection. When turf roots die and decay, thechannels often retain their integrity and helpreestablish large pore space. Microbes and the by-products of the plant decaying process are sourcesof the glue that bonds individual soil particlestogether to create relatively stable aggregates,creating more pore space.

The mechanical action of freezing and thawingalso helps relieve soil compaction, if the playing

occurs within an inch of the surface. Compactiondeeper into the soil profIle can be caused byexcessive earthmoving and grading operationswith heavy equipment during the constructionphase. However, surface compaction is, by far, amore common problem than deep compaction.

Standard punch-type coring units are designedto affect the upper 2 to 4 inches of the soil profIle.The holes enhance the movement of water intothe soil, and the holes encourage root growth.Removing aeration plugs and topdressing withsand provides an opportunity to modify thephysical properties of the soil.

Removing a core of soil from a playing surfacecannot help but reduce the bulk density of the

JULY-AUGUST 2002 3

Course design canhave a significantimpact on trafficpatterns. Thisgreenside bunkerfunnels traffic across anarrow strip of turf,resulting in a narrowstrip of dirt.

underlying soil profile. Whether or not solid- orhollow-tine aeration actually relieves compactionis debatable, based on the conflicting results fromvarious cultivation studies. Petrovic (1979) founda zone of compaction immediately surrounding ahole produced by hollow-tine cultivation. Thiscultivation-induced compaction was short livedand was generally found very close to thehole/soil interface. The greatest compactionoccurred directly under the hole, and it persistedlong after the sidewalls of the holes had collapsed.This explains how a thin zone of compaction cansometimes develop in greens that are cultivated tothe same depth year after year, a phenomenonsimilar to the plow pan that can develop inagricultural soils.

Others have found core cultivation to increasewater infiltration and root growth. Consideringthe inconsistent nature of the research results,varying the depth of cultivation penetrationwhenever possible is recommended. Standardhollow-tine cultivation of heavily traffickedplaying surfaces has been and should remain acornerstone of the foundation for any sound golfcourse maintenance program.

Vertidrain and deep-drilling cultivation makesthe process of varying the depth of penetration assimple as changing a setting on the equipment.These operations can have a beneficial effect ondeep zones of compacted soils that exist beyondthe reach of standard cultivation equipment.Water injection also can be employed to relievedeep compaction and increase the infiltration rate

of water into the soil without causing excessivedisruption to the playing surface.

Various spiking units also are available toimprove water infiltration without causingexcessive disruption. The primary advantage ofusing a spiking unit across high-use turf is thespeed at which the operation can be performed.

PREVENTING COMPACTION

COURSE DESIGNOne of the simplest ways to minimize the detri-mental effects of concentrated traffic is to designthe course in a manner that spreads the wearacross as much surface area as possible. Forexample, large bunkers, mounding, or trees thatblock the entrances and exits to greens tend toconcentrate traffic onto localized areas of thecourse.

CART PATHSA well-designed network of paved paths providesan opportunity to use carts during wet weatherwithout damaging the turf and compacting thesoil. A number of articles can be found in pastissues of the Green Section Record that describe indetail the benefits of cart paths.

MINIMIZING PLAYDURING ANDIMMEDIATELY FOllOWINGWET WEATHERAs mentioned earlier, the susceptibility of heavysoils to compaction is directly related to theamount of moisture in the soil. Motorized cartsare the primary culprits, but concentrated foottraffic across soft, wet soils can also cause com-paction. Traffic needs to be redirected away fromareas that have a history of sustaining damageduring wet weather. A combination of signs andropes/stakes helps protect these wet sites. Manycourses need to be closed to motorized carts foran appropriate period of time after heavy rainfallevents.

DRAINAGEWet soil is more vulnerable to compaction thandry soil. Consequently, improving surface andsubsurface drainage, where necessary, will reducethe potential for compaction.

IRRIGATIONControlling automatic irrigation carefully toeliminate wet areas is recommended. This may

4 GREEN SECTION RECORD

require the installation of new sprinklers, moreefficient nozzles, and new controllers, and onsome courses irrigation systems may need to becompletely replaced. Non-uniform irrigationpatterns and the resulting overwatering thatoccurs will create wet spots that are moresusceptible to compaction.

SOIL MODIFICATIONHeavy soil playing surfaces on greens, tees,and even fairways can be modified through anaggressivesand topdressing program. Routine corecultivation and core removal, followed by top-dressing to fill the holes, is one of the most wide-spread and effective maintenance practices used

Ever have an equipment vendor extol the virtueof his wares with statements such as:"The low-pressure, smooth-tread, balloon tires on this 300-gallon sprayer create a footprint no heavier than apull cart loaded with a set of clubs"?The conclu-sion you are meant to draw is that the sprayer,orany other large, heavy item of equipment outfittedwith similar turf-type tires, will cause less com-paction and wear to the turf than a pull cart.

Something about that statement alwaysbotheredme, particularly the thought of how heavy thatsprayer would be when filled with water. There isa temptation to begin a debate by challengingthat statement with a test.We both lie down onthe fairway.Someone pulls a cart with clubsacross my body and someone drives a loadedsprayer over the vendor. I win.

The fact is that a large, heavy piece of equip-ment is still large and heavy regardless of tiredesign. Granted, a fairway mower equipped withballoon tires will cause lesswear and compactionto the playing surface compared to the same unitequipped with narrow tires.The large, soft tiresspread the weight across a greater surface area andthey should be used on turf maintenance equip-ment. However, research indicates that a wide tireon a heavy unit causes deeper compaction than anarrow tire on a lighter unit, even though thefootprints are equal (Blackwell and Soane, 1981).Furthermore, spreading the weight across agreater area does just that - it subjects more areaof soil and more turf plants to traffic.

The equal footprint argument almost holds waterunder static conditions - no movement of thecart or the sprayer.Begin traveling across the turfand all bets are of[ Stopping, starting, turning, andspinning the tires will create abrasion and bruisingto the turf and impart shearing forces to theunderlying soil.

Carrow and Johnson (1989) studied the effectsof golf cart tires on turf and found that theamount of wear is significandy increased when

you turn the cart because the w~ight shifts to theoutside tires.The speeds at which you travelacross the turf and the vibration from the engineinfluence the amount of compaction that isgenerated by the tra.ffic.The fmalline in thisreference speaks volumes: "According to ourstudy, traffic distribution and the sharpness ofturns is more important than type of golf car ortire design in minimizing wear to golf courseturf"

Obviously, the more you travel over the samearea, the more wear and compaction affect theturf To distribute the weight across a greater areaand create a light footprint, more tires are placedon heavy equipment. More tires means morepassesacross the same turf and more traffic effects.

The bottom line is that turf-type tires shouldbe used on golf course maintenance equipmentwhenever possible.Tires, though, do not magicallytransform a heavy sprayer or mower into a pullcart. If you don't believe it ... take the challenge!

.' ,

Not sure how muchwear carts cause toturf? A side-by-sidecomparison of nocarts vs. heavy carttraffic leaves nodoubt.

~'11

JULY-AUGUST 2002 5II

Cart paths should bewell designed to

encourage use by thegolfers. This cart path

is too narrow andlocated too far from

the fairway.

on older push-up style soil greens to combatthe detrimental effects of traffic. Similarly, high-quality greens often are top dressed with light,frequent applications of sand throughout theseason. The intent is to develop a compaction-resistant rootzone and smooth the plaYing surface.Tees, too, are often placed on a similar cultivationand topdressing regimen.

An increasing number of courses are usingsand to topdress heavy soil fairways. Specialized,high-capacity topdressing equipment is stronglyrecommended if substantial course acreage istargeted for soil modification.

SUMMARYSoil compaction may be a hidden effect of exces-sive traffic, but the inability to see the problemdoes not lessen the detrimental effects of com-paction on turf growth and development. Con-sidering all the ways to prevent compactiondescribed in this article, the one you can taketo the bank is to limit traffic across the plaYingsurfaces when the soil is wet. Cart revenues areimportant, but allowing carts access to a soft, wetgolf course can cause short- and long-termdamage to turf and soil far greater than the valueof one day's worth of cart fees. A continuous cartpath system is an excellent investment at courseswhere wet weather regularly would limit cart use.

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How much traffic can you bare? Each courseis different due to soil type, drainage, and manyother factors. Keep the course dry, limit cart useduring wet weather, alter traffic patterns whereverpossible, and maintain an aggressive cultivationprogram to keep what you can't see, hiddencompaction, from hurting you.

REFERENCESBeard,). B. 1973. Turfgrass: Science and Culture. Prentice-Hall, Englewood CliffS, NJ.Blackwell, P. S., and B. D. Soane. 1981. A method forpredicting soil bulk density changes in field soils resultingfrom compaction by agricultural traffic.). Soil Sci. 32:51-65.

Carrow, R. N., and B.). Johnson. 1989. Turfgrass wear asaffected by golf car tire design and traffic patterns.). Amer.Soc. Hort. Sci. 114(2):240-246.

Carrow, R. N., and A. M. Petrovic. 1992. The effects oftrafflC on turfgrass. In: D. JWaddington, R. N. Carrow, andR. C. Shearman, co-editors. Turfgrass. Agronomy.32:285-330.

Petrovic, A. M. 1979. The effects of vertical operatinghollow-tine (VOHT) cultivation on turfgrass soil structure.Ph.D. diss. Michigan State University, East Lansing.

BOB VAVREK, agronomist for the North CentralRegion, wears a path to courses in Wisconsin, Michigan,and Minnesota with the intent of improving playingconditions for golfers.