Sports Field Aerification: (an you afford not to do it? DALE GETZ, CSFM, THE TORO COMPANY Aerify, aerify, aerify and when you're done, aerify some more. This is the man- tra we've heard for the last 20 years and longer. But what does aerification really do for the turf and for the soil? How does it help sports turf? Is there a "best" method? Is there a "best time" to aerify? Can I afford aerification? Can I afford not to aerify? These are the questions I hope to answer. erification is one of the most im- portant cultural activities you can do for turfgrass manage- ment and sports turf in particular. Let's look at what we are really asked to do for the sake of sports and how aerification can help. You, as sports turf managers, have to take care of a living, breathing (respiring), growing entity that is 35 times shorter than a six foot human and hundreds of times lighter than a 200 pound human and make it not only survive, but thrive, while being played on, tromped on, overused and abused in many ways. We want our sports fields to play safely, look great and perform well under a vari- ety of environmental conditions. If you can do all of the previously mentioned under these conditions, you are a genius. Before you get too disappointed and de- pressed, however, there are some answers, some techniques you can use to help you win the battle. While I can't address all the issues in this article, we can ad- dress one of the most important - aerification. Aerification Basics What does aerification really do? Es- sentially, aerification breaks up soil aggregates that have become severely compacted. Aggregates are soil particles that have adhered forming larger clumps or peds. A well-aggregated loamy soil, for example, will consist of 50% pore space and 50% solids. Through compaction, suc- cessive periods of wetting and drying and the chemical processes of soil particles, these aggregates become harder and denser, limiting the ability of water and roots to penetrate them and extract needed nutrients. These compacted aggregates 6 SUMMER 2003 I Sports TurfManager also hinder the ability of the roots to pen- etrate deeper into the soil where adequate nutrients and moisture may exist. So what does aerification really do? • Relieves compaction • Improves water infiltration • Promotes deeper rooting • Improves nutrient availability & uptake • Improves toxic gas exchange • Improves drying of the soil Aerification also has additional benefits related to the overall health of the turf. Aerifying can be used to modify the root zone soils. By picking up or harvesting the cores during core aerification and then topdressing with a coarser material such as sand or a sand/peat mixture, you can improve the texture of the root zone soil so it is not as prone to compaction in the first place. Aerifying and topdressing or drag- ging in the cores can help control the thatch layer. Finally, aerification can provide one of the best seedbeds for overseeding purposes. Impediments to a Solid Plan With all the advan- tages of aerification for the development of healthy turfgrass, it's hard to imagine someone not having an aggressive aerification plan. But what about the disadvan- tages - there actually are some. The biggest, of course, is the cost. The cost of equipment purchases, labour and time. But don't let this deter you. Equipment can be pur- chased, leased or rented, or the entire service can be contracted. Aerification is such an important practice it cannot be ig- nored if you want to have healthy turfgrass. Another disadvantage is that aerification can bring weed seeds to the surface and promote their germination. Finally, if done at the wrong time of the year, aerification can cause desiccation to the turfgrass around the hole and cause surface disruption which could impede play. Sports turf management presents unique challenges in that most sports are played more intensively in pockets or con- centrated areas of the field. For example,
Transcript
Sports Field Aerification: (an you afford not to do it?DALE GETZ, CSFM, THE TORO COMPANY
Aerify, aerify, aerify and when you're done, aerify some more. This is the man-tra we've heard for the last 20 years and longer. But what does aerificationreally do for the turf and for the soil? How does it help sports turf? Is there a"best" method? Is there a "best time" to aerify? Can I afford aerification? Can Iafford not to aerify? These are the questions I hope to answer.
erification is one of the most im-portant cultural activities youcan do for turfgrass manage-ment and sports turf inparticular. Let's look at what we
are really asked to do for the sake of sportsand how aerification can help. You, assports turf managers, have to take care ofa living, breathing (respiring), growingentity that is 35 times shorter than a sixfoot human and hundreds of times lighterthan a 200 pound human and make it notonly survive, but thrive, while beingplayed on, tromped on, overused andabused in many ways.
We want our sports fields to play safely,look great and perform well under a vari-ety of environmental conditions. If youcan do all of the previously mentionedunder these conditions, you are a genius.Before you get too disappointed and de-pressed, however, there are some answers,some techniques you can use to helpyou win the battle. While I can't addressall the issues in this article, we can ad-dress one of the most important -aerification.
Aerification BasicsWhat does aerification really do? Es-
sentially, aerification breaks up soilaggregates that have become severelycompacted. Aggregates are soil particlesthat have adhered forming larger clumpsor peds. A well-aggregated loamy soil, forexample, will consist of 50% pore spaceand 50% solids. Through compaction, suc-cessive periods of wetting and drying andthe chemical processes of soil particles,these aggregates become harder anddenser, limiting the ability of water androots to penetrate them and extract needednutrients. These compacted aggregates
6 SUMMER 2003 I Sports TurfManager
also hinder the ability of the roots to pen-etrate deeper into the soil where adequatenutrients and moisture may exist. So whatdoes aerification really do?
• Relieves compaction• Improves water infiltration• Promotes deeper rooting• Improves nutrient availability & uptake• Improves toxic gas exchange• Improves drying of the soil
Aerification also has additional benefitsrelated to the overall health of the turf.Aerifying can be used to modify the rootzone soils. By picking up or harvestingthe cores during core aerification and thentopdressing with a coarser material suchas sand or a sand/peat mixture, you canimprove the texture of theroot zone soil so it is notas prone to compaction inthe first place. Aerifyingand topdressing or drag-ging in the cores can helpcontrol the thatch layer.Finally, aerification canprovide one of the bestseedbeds for overseedingpurposes.
Impediments to aSolid Plan
With all the advan-tages of aerification forthe development ofhealthy turfgrass, it'shard to imagine someonenot having an aggressiveaerification plan. Butwhat about the disadvan-tages - there actually aresome. The biggest, of
course, is the cost. The cost of equipmentpurchases, labour and time. But don't letthis deter you. Equipment can be pur-chased, leased or rented, or the entireservice can be contracted. Aerification issuch an important practice it cannot be ig-nored if you want to have healthyturfgrass. Another disadvantage is thataerification can bring weed seeds to thesurface and promote their germination.Finally, if done at the wrong time of theyear, aerification can cause desiccation tothe turfgrass around the hole and causesurface disruption which could impedeplay.
Sports turf management presentsunique challenges in that most sports areplayed more intensively in pockets or con-centrated areas of the field. For example,
in baseball the area in front of the pitch-er's mound and the outfield positionlocations get more use. In football, it's thearea between the hash marks and the side-lines that gets the most concentrated useand in soccer and lacrosse, it's the goalmouth. This is both a blessing and a curse.A curse is the fact that: I) These areas aresuper compacted, 2) They cannot bemoved from week to week in most cases,and, 3) They are overused so finding timeto promote good turf growth is limited.
The blessing is that these areas are rela-tively small in size so what may seem likea daunting task can actually take less timeand budget dollars to complete than origi-nally anticipated. In other words, you canconcentrate your efforts on the areas thatneed your attention the most.
Aerification MethodsCore aerification is the process by
which actual cores or plugs of turf and soilare pulled up and brought to the surface.This is by far the most beneficial type ofaerification for the turf. By doing this youactually decrease the bulk density of thesoil. You can then drag or break up thecores allowing the soil to refill the holesin a less compacted state. You can also pickup the cores and topdress with sand (ma-sonry sand works very well for this and isreadily available but it is wise to have yoursoil and sand tested to determine compat-ibility).
The downside to core aerification is thesurface disruption and the time it takes fordragging, topdressing and cleaning up but,once again, concentrating on small areascan go relatively quickly. Also, choosingsmaller tine sizes can minimize the dis-ruption; however, it will also minimize thebeneficial effects you are trying to achieve.The other downside is that the surface dis-ruption can affect play and surfacestability, especially in sand based soils, sotiming is very critical. Do not core aerifywithin two weeks of major events on yourfield. This will give time for the turfgrassto heal and the surface to stabilize.
Solid tine aerification simply pokesholes into the soil. This can be beneficialwhen there is a need to aerify during theplaying season. For example, you maywant to aerify after a game or event thathas been played in wet conditions and you
need to loosen the surface to aid in gasexchange or water infiltration (be sure toallow time for the soil to adequately drybefore aerifying). The surface disruptionis much less and there is no need for cleanup with solid tines. Solid tines are avail-able in many different sizes dependingupon the situation at hand. One caution,though, is that because you don't actuallyremove cores from the soil, repeated solidtine aerification can cause compaction atthe hole depth and some evidence evensuggests that glazing of the sides of theholes can inhibit water infiltration, particu-larly when soil moisture is high.
Water injection aerification is anothervaluable tool at your disposal. In thismethod, water is injected into the soil at600 mph (5,000 psi). Each burst of waterleaves a surface hole of less than 1/4" butcan affect up to a 3" diameter of soil be-low the surface. Water injectionaerification causes virtually no surfacedisruption and can even be used prior tosporting events. Water injection is used
adequate job in large open areas where thesoil is not too compacted but severalpasses may be needed to get the spacingyou want. Depth of aerification is highlydependent on soil moisture and type. Also,since the tines are mounted on a drum orroller, they have a tendency to tear the turfand disrupt the soil much more than othertypes.
Reciprocating aerifiers are designed sothe tine enters the soil vertically. Thisleaves a much cleaner hole and the downpressure guarantees a uniform depth. Re-ciprocating aerifiers come in many sizesfrom walking units to large 80-inch unitspulled behind tractors. Reciprocating unitshave a wide variety of tine sizes; some aredesigned to aerify as deep as 12". Walk-ing reciprocating aerifiers do an excellentjob on the smaller areas discussed earlier.They are very maneuverable, relativelyinexpensive, have many tine options andare self-contained so you don't need an-other piece of equipment to pull them with.
Finally, there are drill type aerifiers that
quite extensively in the southern portionsof the United States to alleviate localizeddry spots or hydrophobic soils. Whenmanaging cool season turfgrasses, waterinjection aerification is an excellent wayto aerify during the summer months whenother types of aerification may damageyour turf.
Aerification EquipmentThere is a plethora of aerification equip-
ment on the market today. The type youchoose will depend upon what you wantto accomplish, how much ground youneed to aerify, what your budget will with-stand and what your current soil andturfgrass conditions are today.
Drum or towing type aerifiers are rela-tively inexpensive and cover a largeamount of ground in a short period of time.They are available in either a pull type orthree-point hitch mounted. They do an
use carbide tipped bits to drill a hole intothe soil up to 12" deep and I" in diameter.There are even attachments that can auto-matically fill the holes with topdressingmaterial after they have been drilled. Drilltype aerifiers are very expensive but thereare many companies that provide this serv-ice on a contract basis.
Aerification TimingProper timing of aerification is impor-
tant to achieve the desired results. I willaddress timing both in terms of theweather and in terms of which sport isplayed on the field. Obviously weatherplays an important part in the quality ofaerification. Aerifying during periods ofheat and/or drought stress can negativelyimpact your results, especially with coolseason turfgrasses. You will further stressthe turf and recovery can take longer.There is also a chance of turfgrass desic-
cation around each hole. This does notmean you can not or should not aerify inthe summer but it does mean you shouldmonitor the weather closely and if you seea period when weather conditions im-prove, plan your aerification. You shouldalso consider using smaller tines. Periodsof drought or heat stress are also a goodtime to consider water injection aerification.
Late fall or early winter can also presentaerification challenges. Leaving openholes can cause turf desiccation aroundthem. On the other hand, if you drag inthe cores and/or topdress, the desiccationis minimized and subsequent freeze andthaw cycles of winter can actually helploosen the soil further. Late fallaerification is often performed on footballfields after the season has ended becauseany desiccation that may occur over win-ter will heal prior to the next season.
Soil moisture also plays a part in deter-mining when to aerify. The soil should bemoderately wet but not at full field capac-ity. If it is too wet, the cores will not breakup easily and more glazing can occur. Onthe other hand, if the soil is too dry, thecores will break up easier but hole depthmay vary and the turfgrass around the holewill be more prone to desiccation. Expe-rience with your own soil types will beyour best teacher.
Scheduling aerification with regard tosports or events on your sports fields isanother challenge. For those of you fortu-nate enough to have separate fields foreach different sport this issue is mucheasier. For those managing multiple-usefields, finding a time to aerify can be ex-tremely challenging.
In general, aerifying immediately afterthe season or after periods of heavy use is
the best. For football and soccer, thismeans late fall in most parts of the coun-try. For the spring sports of baseball andsoftball, this means late spring. If you havespecial events such as concerts, picnicsor large tournaments on your fields,aerifying immediately afterward is alsohelpful.
Finally, with regard to timing, howmany times should you aerify? This is thethousand-dollar question. Once is betterthan not at all. Twice is better than onceand so on. Remember, however, it is notuncommon to aerify the worst areas of asports field five or six times each year.
Aerification StrategyCommit to a three-year aerification pro-
gram to achieve maximum results. Thisprogram should be well thought out andin writing. Write a separate plan for eachof your sport fields. Consider game andpractice schedules (as well as when thepreferred time to aerify would be) andwhat areas of the field you want toaerify.
Following is an aerification plan for atypical high school football field. The fieldis cool season turfgrass used for 18 homegames and some practices in the fall andpractices in the spring and late summer.
e November (after last game)Aerify entire field, drag cores, seed,topdress and fertilize
e Late April (after spring practice)Aerify entire field, drag cores, seed,topdress and fertilize
eMidMayAerify between hash marks, sidelinesand painted end zones, drag cores,topdress
e Early to Mid JuneAerify only bad areas, drag cores,topdress
e Early July (weather permitting)Aerify only bad areas, drag cores,topdress
Can I or Can I Not Afford to Aerify?I firmly believe you can not afford not
to aerify. It is such a powerful tool in yourarsenal of weapons against field use andabuse that aerification must be a part ofyour overall turf management strategy. Becreative, though. If you have to rent anaerifier, do only the necessary areas. Manygolf courses are willing to let schools bor-row equipment because their children maygo to school there. Contracting aerificationservices is a way to get aerification donewithout owning equipment.
Develop a plan of action to improveyour sports fields with aerification andtake that plan through the budgeting proc-ess to obtain equipment dollars. Above all,strive to make your sports fields better andsafer through active turfgrass manage-ment. •
- Reprinted with the permission of the NationalFederation of State High School Associations
ReferencesChristians, Nick, Fundamentals of TurfgrassManagement. Chelsea, Michigan: AnnArbor Press, Inc., 1998, 301 pp.
Emmons, Robert D., Turfgrass Science andManagement, 3rd Edition. Albany, NewYork: Delmar Publishers, 2000, 528 pp.
Turgeon, A. J, Turfgrass Management, 4th
Edition. Upper Saddle River, New Jersey:Prentice Hall, Inc., 1980, 393 pp.
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