If you've ever attended your favorite highschool's Friday night football game andlooked at the center section of the field,you've probably seen some sparse turfWhether on golf courses, sports fields orplaygrounds, no turf area is immune to the

devastating effects of compaction.You'll also find compaction around

the goal on a soccer field, the paththat always appears between thesame two bunkers every time peo-ple walk from their golf car to thegreen or just where people takethat proverbial shortcut throughthe grass to the sidewalk. Theseare only the visible signs - the"tip of the iceberg" - of compac-tion problems that are really pres-ent in your soil.

Once you know it's there, youknow it must be remedied. Superin-tendents relieve compaction primarily

through mechanical cultivation, namelyaeration. You can choose many meth-

ods of aerifying for the differing condi-tions and situations in a given area, and

each will yield a different result. Whichmethod is best: deep or shallow tines,

coring or sofid tines, slicing blades orvertical linear aeration (deep powerslicing)?

After more than 20 years in the aeration business and visitsto thousands of golf courses, athletic complexes and sportsfields in the U.S., Canada and Mexico, I've found that whilethe problems are all the same, the options have clear advan-tages and disadvantages.

Deep tines vs. shallow tinesFor turf managers, the age-old question is, "Should I deep tine or shallow tine?"

Several years ago, the late Houston Couch, Ph.D., spoke on the subject of deep-tineaeration, and I heard a superintendent ask, "My old aerifier went 3 inches deep andthe root system stopped there. My next aerifier went 4 inches deep and the rootsstopped there. Now I started deep-tine aerifying and my roots seem to be stoppingthere. What can I do now?" Couch looked perplexed and responded, ''And what's theproblem with lO-inch roots?"

That remark encompasses my view in a nutshell. Given the choice, go deep. It'strue that the root system usually stops where aeration tines stop. But at 10 inches deep,the root system will support a healthy stand of turf. I've even seen lO-inch Poa annuaroots in golf greens.

With a deeper root system from deep-tine aerification you lengthen irrigation in-tervals, fertilizer applications last longer and you introduce more oxygen into the soil.Some golf courses have completely amended the top 12 inches of their greens' soilprofile through the creation of deep sand tunnels from topdressing after using largetines and up to 1Y2 tons of sand per 1,000 square feet. This amounts to virtually re-building the green from the inside out without taking it out of play and saves thou-sands of dollars.

The old rolling-type shallow aerifier is still cheap and fast, but offers minimal com-paction relief and generally produces tufting around the holes. The newer deep-tineheaving machines are faster (more than 2 acres/hour), so deep-tine aeration is nowmore economically feasible for multiple athletic complexes and golf course fairways.

Before you start a deep-tine program, make sure the irrigation lines and wires aredeeper than the aerifying depth. I've seen lots of "scenic fountains" pop up unexpect-edly during deep aerification.

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Deep-tine aerification promotes a deeper root systemand allows superintendents to lengthen irrigation inter-vals. Photo courtesy of Wiedenmann Ltd.

Straight up-and-down vs.heaving

Another question to answer iswhether to choose a machine with"straight up-and-down" (SUD) tine ac-tion or heaving action. I recommend aheaving-action aerifier for most appli-cations. With the SUD action of con-ventional aerifiers, compaction relief be-tween the holes is minimal at best. SUDaerifiers, although still manufactured,are a bit out of date given the neweraerification technologies. Even the ver-tical drilling machines produce little tono compaction relief between the holes.I recommend choosing an aerifier witha positive heaving action that breaks upthe compacted soil between the holes.This introduces needed oxygen, willincrease the total cation exchange ca-pacity, and can improve drainage bothhorizontally and vertically throughoutthe soil profile. Plus, at the bottom ofeach stroke, the heaving tine is movinghorizontally as it is moving vertically,adding a slicing action to the lifting ac-tion in the turf.

This motion minimizes the creationof a hardpan layer caused by the tradi-tional pounding action of the old SUDaerifiers. Rather than compressing thesoil and actually adding to the compac-tion problem, the process of heaving dis-places the soil upward, raising the play-ing surface from "not noticeable at all" toY2 to % of an inch, depending on how themachine is adjusted. Matching the extentof the heave for the given soil conditionscan be critical in producing good results.For example, after using needle tines, theputting surface should be smooth with-out using any topdressing and shouldputt smoothly even after using largertines and a light topdressing.

Solid tines vs. coring tinesHere is another brainteaser: Should

you use solid or coring tines? The an-swer depends on what you're trying toaccomplish. Although solid tines areavailable in either SUD or heave-;ctionaerifiers, I recommend using a heavingmachine when choosing solid tines be-cause an SUD aerifier with solid tines

Use a combination of knives and spoon tines to aerateand improve drainage. Photo by Seth Jones

can do more damage than good.SUD aerifiers with solid "shatter

tines" will break up the soil, but only ifthe conditions are desert-like - rockhard or bone dry. Consequently, the aeri-fier has a hard time driving the tines intothe ground to any considerable depthwithout causing undue damage to theturf and the machinery. You can useSUD aerifiers with solid tines as shal-low pin spikers (possibly on hydrophobicgreens or "in season" athletic fields), butthey're really only good for opening thethatch surface during high-stress times,allowing for quick water and air pen-etration with minimal disturbance tothe surface or subsurface. Again, this isonly opening the surface, not relievingcompaction.

Using this method too much causesan even more serious problem. The SUDaerifier will create a "sheep's-foot roller"effect and a really bad hardpan layer inthe soil profile. I've seen hardpan layersso severe that not only was there a toxicgas buildup underneath but the soil alsohad a toxic chemical layer.

So when using SUD aerifiers, whethergoing deep or shallow, avoid using solidtines and stick to coring tines for com-paction relief. You can use solid tines

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Most peoplethink you have

to pull a core forthatch removal,

but that processonly provides 5

percent of the total

Lthatchremovalnecessary.

effectively with deep-tine heaving-typeaerifiers with little or no damage to theturf. They will relieve the shallow hard-pan and toxic layer created by the SUDmachines. With solid tines ranging from31i6 inch to 1 inch in diameter and 6 to16 inches in length, the ground doesn'tneed to be bone dry but only needs suf-ficient moisture for optimal penetrationand compaction relief. Don't choose anaerifier that merely pokes a hole (deep orshallow) with no heaving action, as thoseare just "shatter tining" and can contrib-ute to compaction.

Almost all aerifiers offer some type of

coring tine. Most people think you haveto pull a core for thatch removal, butthat process only provides 5 percent ofthe total thatch removal necessary. On agreen, about 95 percent of thatch controlcomes from verticutting and topdress-ing. The 5 percent of thatch that isn'tremoved with solid tines instead of cor-ing tines can cause trouble during hot,high-stress times when the green surfacecan become hydrophobic and repel ir-rigation water. Ironically, most ath-letic field managers would love to havesome thatch in the middle of a footballfield to protect the crowns of the plantsand keep the players from making a

I muddy "pig pen" of the field during wetconditions.

Turf managers who opt to use no-mess solid tines on a golf course shouldadd an extra verticutting and topdress-ing. Your turf will love you for it, andthe channels you create with the deeptine make a permanent chimney of sandallowing water and roots to penetratewith ease and flourish.

I Vertical linearvs. reciprocating

Another choice for compaction reliefis the relatively new method of deep-power slicing, called vertical linear aera-tion (VLA). The soil-loosening capabil-ity of this machine is similar to that ofthe deep-tine heaving machines. Thedifference is in the consequences of theVLA's use of blades rather than tines.VLAs aerate by driving long 10- to 16-inch blades through the soil. They aremounted on a rotating shaft and pow-ered by a chain drive from the PTO-driven gearbox. These blades are off-set in their mounting to penetrate theground in alternating fashion and cre-ate a side-to-side "wave" action to loosenthe turf. They do not bring any soil tothe surface but do provide a considerabledegree of compaction relief.

VLA machines produce a continu-ous slit in the ground, which exposesthe turf to drying or desiccation alongthe edges of the slice and requires in-creased irrigation during the healing.time. Given the same soil conditions,

I VLA machines usually can penetratedeeper than a reciprocating deep aerator.The VLA machines use far fewer mov-ing parts and are easy and less expensive

to maintain. I recommend this methodfor heavily compacted soils that may beextra hard or rocky and more difficult fora deep-tine aerator to penetrate. Thesemachines can also be equipped with sandhoppers that will gravity-feed sand intothe slits for improved drainage.

Rolling slicerThe slicing roller, yet another aera-

tion choice, sounds simple because itis. Slicing, although not really intendedfor compaction relief, can be beneficialto turfgrasses that produce stolons and/or rhizomes, such as bluegrass, zoysia-grass or bermudagrass. Slicing the sto-

Vertical linear aeration does not bring soil to the surfacebut provides compaction relief by loosening the turf.Photo by Seth Jones

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Ions and rhizomes creates new motherplants that send out new rhizomes andstolons with a vertical growth pattern. AVLA machine also accomplishes this, aswill - to a lesser degree - any of theaforementioned techniques. The soil-loosening effects generally are minimal.In fact, with extended use you may in-crease compaction through the "sheep's-foot roller" effect, so some kind of com-paction relief program will be necessary.

Some slicing models are designedwith twisted or angled heaving knivesto provide some compaction relief.These have some loosening capabilitiesbut may cause damage to the turf. It's a

cheap way to aerify if you can afford thehealing time.

Oscillating solid tinesWhile a little too aggressive for fine

turf areas such as golf course greens,these machines are a good choice forfairway, rough and athletic field ap-plications. They do an excellent job ofloosening the top 4 to 6 inches of thesoil profile. They use only solid tinesand don't pull out or destroy any of theexisting turf. This type of aerifier ranksamong the highest tested for compac-tion relief in the soil's top 5 inches in aUniversity of Georgia study. They alsocan be fitted with a seed box for seeding

while aerifying.

Water injectionWater injection can be a useful mode

of aerifying in certain situations. Thistype of aerifier works by injecting waterunder high pressure into the soil. Thiscan be especially helpful when the turfbecomes hydrophobic during summerstress. You must have access to a watersource through a quick coupler.

These injection machines create al-most no surface disturbance and thegrounds can be returned to playing sta-tus immediately after treatment.

Slicing, although notreally intended forcompaction relief,can be beneficial

f to turfgrasses thatproduce stolons and/or rhizomes, such asbluegrass,zoysiagrass orbermudagrass.

Dry material injectionThe dry material injection machines

work on the same theory as the water in-jection. They inject water, but dry mate-rial also is pulled by siphon effect froma hopper mounted above the injectors.Various soil amendments can be addedin this manner for a variety of plantneeds.

Drill and fillThe "drill and fill" machines have

been on the market since the mid-1980sand have been useful in many cases

I for amending turf areas with poor soil.These machines can go as deep as someof the deep-tine machines on the mar-

This type of aertor injects water under high pressureinto the soil, creating almost no surface disturbance.Photo courtesy of Toro

ket, and in some situations can be usedwith less surface disturbance. This typeof aerifier has several drawbacks:

• They are slow when compared toreciprocating deep-tine machines(about a fourth of the speed, de-pending on soil type and depth).

• Keeping the material hoppers filledcan be labor intensive.

• The drill makes a hole, but doesminimal, if any, loosening betweenthe holes.These machines create minimal dis-

turbance to the surface of the turf, andplayability afterwards is very good.

·Micro tiningMicro tining is performed primar-

ily on golf course putting greens. Verysmall, solid or coring tines, J.A inch indiameter or smaller, can be used to ef-fectively dethatch and/or ventilate aputting green surface. Micro tining doesnot decompact the soil since these tinesonly penetrate the thatch surface andshouldn't get into the soil.

Maximum micro-tining depth isgenerally 1Yzinches. With the small tinediameter and shallow depth, the green isunder very little stress as the oxygen andgas exchange takes place (thus the term"ventilating"). The spacing of these

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holes should be no farther apart than 3inches by 3 inches.

During the growing season, I've seenthese holes heal over by the next day.The "micro cores" can be blown off bya leaf blower or mowed up with a greensmower. Since they are not getting intothe soil, this generally doesn't impose abedknife wear issue.

Preventive V5. curativeSuperintendents frequently ask how

often they should deep-aerify. My an-swer is that turf managers must firstunderstand deep aeration as a means ofpreventing compaction rather than re-lieving it.

As a superintendent, I deep-aerifiedgreens every spring and fall, and nee-dle-tined greens during summer. I alsodeep-aerified my bermudagrass fairwaysduring the summer, all with a deep-heaving machine. In this way, the prob-lems associated with compaction weregreatly reduced and my turf generallyflourished, even in hot weather.

If you are responsible for main-taining sports fields, you could adopta pro gum of deep aerating as often asdesired, but a tight budget may deter-mine the frequency of your aerificationprogram. For example, if you own a ma-chine, a program of ongoing use doesn'tcost much more than the occasional use,except for additional topdressing, tinesand labor. If you choose the ongoing

program, you'll find that the tremen-dous savings in applied chemicals, irri-gation water and greens rebuilding willmore than offset the purchase price of adeep aerator.

For those with limited budgets, fi-nancing a machine is a way to expandyour aerification program and receivethe accompanying savings. Many cus-tomers hire a contractor to get the jobdone. They have a couple of reasons forcontracting the job out: They are rely-ing on the experience of the personneland want to see results before they maketheir purchase. Also, just a spring and/or a fall deep-tine aerification programyields unparalleled results comparedwith conventional aerifying and is rea-sonably priced by many contractors.

Choose a company that uses the bestaeration equipment and employs expe-rienced operators who will make cor-rect decisions for your turf conditions.Knowing the proper machine adjust-ments, hole spacing, tine choice, soil!turf tolerance and weather conditionswill greatly affect customer satisfactionin terms of healing time and playability.

It's impossible to discuss every brandand type of aerifier on the market, but Ihope this overview helps when makingaerification decisions. Whether you'repurchasing an aerifier or hiring a con-tractor, choosing the proper machineand operator, combined with the propertines or blades for the desired applica-tion, can make the difference betweensatisfaction and disappointment.

Remember: Don't be too radical atanyone time. The main things to keepin mind for a successful aerifying jobare to not force the machine beyondits capabilities and not to use too largeof a tine or a spacing that's too closefor the conditions. The soil didn't getcompacted overnight, and rarely cancompaction be completely alleviated inone treatment. The best route to opti-mal improvement is making all the rightchoices, and now, hopefully it's easierdone than said.

Bryan Wood (bryan@greensmowertools.com) is aformer superintendent and the owner of CommercialTurf and Tractor, an equipment and contract serviceprovider for the golf course and sports turf indus-tries in Chillicothe, Mo.