less than 5% passing the 100 sieve screen drain freely...

SportsTurf 11www.stma.org

less than 5% passing the 100 sieve screen(see photo 7).

Big-Roll Sod. Look for sod that ismature (1 to 1-1/2 years old) and grownon soil that is similar to the native soil ofthe field. If it’s available (and especially ifthe drainage system described above isinstalled), use sod with sandy soil. If it’snot available at this time, use native soilsod. Aerating and topdressing with sandwill begin next year and provide betterrooting and better drainage.Before the sod is installed, apply

starter fertilizer recommended by soiltest results and go over the surface with afinishing tractor attachment like a powerrake. This attachment removes small de-bris and provides a flat, smooth surfaceto prepare the soil for sod.Then install the big-roll sod using

Kentucky bluegrass in the north andbermudagrass in the south (see photo 9).

YEARLY RENOVATIONCreate a 3 to 4 inch sand-cap over a

10-year period with this yearly renova-tion program starting the year after thesod is installed. The sand layer will allowsurface water to drain quickly into theunderdrains (if installed). The field willget better each year.Aerate and topdress with 3/8” of the

sand that was recommended for the sub-surface drainage trenches. You will needabout 75 tons to topdress the field (goalpost to goal post and sideline to sidelineincluding the bench areas). This processshould be done every spring betweenApril and May for cool season grassesand between May and June for warmseason grasses. The results are betterrooting, thicker turf that will hold up tomore events, and improved drainage.Use a solid-tine vibrating aerator unlessyou can remove the cores that a hollow-tine core aerator leaves behind. Mixingthe topsoil cores with the coarse sandwill contaminate the sand and preventdrainage (see Photo 10).Don’t worry about creating a perched

water table that will prohibit drainage bytopdressing with a different materialthan already exists on the field. In fact,the opposite is true; placing coarse mate-rial over fine material allows water to

drain freely through the coarse materialand into the fine textured soil below andeventually into the underdrains (if in-stalled). A perched water table is createdby placing fine material over coarse ma-terial preventing water from drainingthrough the fine material until it reachesalmost 100% capacity. USGA puttinggreens and high profile sports fields arebuilt using a perched water table withthe intent of keeping the sand moist.After 10 years of when the sod was

installed, replace the sod as you wouldthe carpet on an artificial turf field. Let’sface it, nothing lasts forever.This time you won’t be able to use a

plow to remove the grass. Use a big-rollsod cutter or other conventional ma-chine to physically remove the sod andthe thatch layer to dispose of off-site.Remove some of the sand at this time

leaving about 1-1/2” to 2” of the sandbelow. This will allow for yearly top-dressing with sand for the next 10 years.Install sod that is grown on a coarse

sand soil or washed sand to prevent aperched water table (placing fine overcoarse texture).Beginning in the spring of the follow-

ing year, start topdressing with about ¼”if sand yearly (50 tons of sand). That willbring the sand layer back to 4” before it’stime to replace the sod again. Then startall over by removing the sod and 2” ofsand and so on and so forth.

ESTIMATED BUDGETInitial reconstruction cost to remove

the grass, grade, and sod: $60,000Optional: full field irrigation $32,500Optional: subsurface drainage in-

stalled on 20 ft centers. $32,500Yearly renovation: $8,000After ten years replace the sod:

$60,000The total for a 10 year commitment

program: $124,000 (excluding irrigationand drainage). n

Jim Puhalla is the president of SportS-cape International, Inc. in Boardman, OHspecializing in Sports Field Design, Con-sulting, and Construction Supervision andcoauthor of 3 sports field books.

12 SportsTurf | July 2013 www.sportsturfonline.com

FieldScience | By Pamela J. Sherratt

THE QUALITY ANDLONGEVITY of an athleticfield is directly related to thedrainage capability of the soil.How fast water drains into

and through the soil (infiltration rate, KSat)is the best indicator of how many gamescan be played and how the field will reactduring a rain game. Ideally, fields shouldhave a minimum infiltration rate of 1inch/hr., but it is not uncommon to seesoils with infiltration rates of 0.01inches/hr. or less.

The infiltration rate of a soil is influ-enced by the soil texture and the level ofcompaction the soil is subjected to. Fieldswith low infiltration rates create very poorplaying conditions. When wet, they turn tomud, when dry they turn to concrete (Fig-ure 1). Turf plants will not grow in thesesoil conditions and so the field gets takenover by weeds like prostrate knotweed,

clover, dandelions and Poa annua. Turfgrowth is so poor that nutrients are nottaken up, so the turf becomes chlorotic/yel-low and does not recover from wear. Slowturf growth is more susceptible to diseaseslike red thread and rust. It is also impossibleto get seed established on hard, compactedsoils (Figure 2). Improving the infiltrationrate of the soil therefore is the key to im-proving field conditions.

There are short term fixes to improve in-filtration. These include using aerationequipment like a core aerator, spiker, deep-tiner or verti-drain. These machines punchholes in the soil, allowing water to enterand O2 and CO2 to enter and exit. After aperiod of a couple of weeks or less however,those holes seal over and the previous con-ditions return.

A long-term fix is to amend the soil witha material that improves the infiltrationrate, namely sand. As well as improving in-

filtration rates, topdressing evens out theplaying surface and fills holes that couldcause athlete injury (Figure 3). Applying 50tons of sand to a field per year via topdress-ing appears to be an effective rate. It is pos-sible to apply higher rates of 60-100 tons,especially if the sand is applied in two incre-ments (spring & fall). The sand is either ap-plied alone or in combination with soil orcompost. The soil &/or compost typicallymakes up 10-30% of the mix. Adding com-post to the mix is a good way to get someorganic material into the soil if it is lacking.Compost improves the soil health (in-creased oxygen, reduced bulk density, in-creased water holding capacity) and alsoadds nutrients. The soil component in atopdressing mix helps to maintain surfacestability (sand alone does not have goodshear strength) and also retains moisture,which is important for seed establishment.

Improving Native Soil Fields

The soil &/or composttypically makes up 10-30%of the mix. Adding compostto the mix is a good way toget some organic materialinto the soil if it is lacking.

Figure 1

Figure 2

Figure 3

The sand component of the mix should ideally bemedium-coarse in size and uniform. In many situations,the sand component of the mix does not meet this spec-ification and it is not unusual to see sand mixes thatcontain large amounts of silt and clay or gravel. Silt andclay particles are very fine and they clog a soil system.Air spaces are blocked and the soil becomes prone tocompaction. When dry, silt and clay soils are rock-hard,but they turn to a quagmire when wet. For these rea-sons, very fine sand, silt and clay are generally restrictedin mixes to less than 15% of the total mix.

There are no set guidelines for the amount of gravelallowed on a sports field but there is a landscape recom-mendation. ASTM D 5268-92 “Standard Specificationfor Topsoil Used for Landscaping Purposes” suggests thatno more than 5% deleterious material (rock, gravel etc.)be included in a topsoil mix. Gravel is not a suitable ma-terial to improve soil physical or chemical properties andon a playing surface it can disrupt play and possibly causeplayer injury. In addition, gravel on the surface coulddamage mower blades and be very difficult to grow grassor seed in. For a whole multitude of reasons then, gravelshould not exceed 3-10% of the total mix.

Unfortunately, this has not been the case in many sit-uations. Site visits to sports fields over the years haveshown that many topdressing mixes contain far toomuch gravel. In one notable instance, a college soccerfield was constructed with a material that contained44% gravel. That particular field had also been gradedand then leveled with a vibratory roller, making it ashard and impenetrable as a parking lot. The ultimate


FieldScience

Figure 5: Hand-texture test. The flowchart is easy to follow and results in a betterunderstanding of what a silty, clay or sandy soil feels like.

Figure 6: The textural triangle. To plot sand, find the per-cent sand along the bottom and follow the line diagonally left.To plot clay, find the percent clay along the left edge and fol-low the line horizontally across from left to right. To plot silt,find the percent silt along the right edge and follow the line di-agonally left. Example: Soil containing 30% sand, 30% clayand 40% silt would be a “Clay Loam.”

Figure 4


goal of topdressing with sand is to achieveat least 70% sand by weight in the root-zone. At this point, the sand particlesbridge, creating macropores and reducingparticle density. Without a doubt, initiatinga sand topdressing program significantlyimproves native soil field quality andlongevity.

One way to ensure that topdressing ma-terial contains the right amount of sand,silt, clay and gravel is to carry out someDIY quality control. There are several easyways to do this:

Firstly, avoid the temptation to acceptany sand, just because it’s free or cheap.Dressing fields with high amounts of gravelor silt and clay will probably make the fieldsperform a lot worse than before

Get familiar with what the sizes looklike. Being able to distinguish betweengravel and coarse sand can be helpful whentaking delivery of an order (Figure 4)

Send a sample away to a soil testing labto have a textural analysis done on the sandcomponent. The lab will furnish results thatstate clearly the percent of fine, mediumand coarse sand and gravel.

Carry out a hand-texture test (Figure 5).While not precise, it offers an idea of thetype of soil in hand and it helps for the turfmanager to become accustomed to whatdifferent soils feel like.

Perform a soil settlement test, sometimescalled a “Jar test” (a good practice for base-ball infield mixes too):

Take a small soil sample.Quarter fill a water bottle or mason jar

with the soil.Add tap water until the bottle is three-

quarters full. Replace the lid and shake until the water

and soil are thoroughly mixed.Leave to settle for 2-3 daysAfter 2-3 days, the soil will have settled

out into discreet layers, with the gravel andsand on the bottom, then the silt, and thenthe clay (being the smallest particle, claysettles last).

Measure the total thickness of the soil,then each individual layer, to determinewhat percentage sand, silt, and clay is pres-ent. For example, if the total mineral layer is2 inches thick and the sand layer is 1-inchthick, there is 50% sand.

The sand, silt and clay components canbe plotted against the soil textural triangleto determine soil texture (Figure 6)

One of the main issues with starting atopdressing program is that a topdresser isneeded to apply the material, unless an out-side contractor is paid to make the applica-tion. Also, the program is not a “one time”occurrence, but must take place each year,

ideally in conjunction with aeration, whichwill take time and money. However, inevery instance where a sand topdressingprogram has been adopted, the results havebeen so dramatic and the fields have im-proved so significantly that school boardsand administrators usually look for extrasources of funding to try to start topdress-ing programs on additional fields.


FieldScience

It may take a couple of years to see thebenefits of dressing with sand. Obviously,the more sand applied, the faster the desired70% by weight goal will be reached. It isnot a good idea to apply more than 0.25inch at any one time as the sand can beabrasive to both turf equipment and thegrass, but two or three applications couldbe made each year, outside of the playingseason. If there is money and manpoweravailable, a new “fast-track” sand build-upsystem could be employed. This system wasrecently developed by Michigan State Uni-versity and can be accessed through theirwebsite.In addition to improving the rootzone

soil, there are several drainage options forfields:

Surface Drainage refers to the ability ofwater to shed or run off the surface due tothe installation of a slope or crown. Theseverity of the slope or crown depends uponthe amount of sand in the rootzone. Finetextured soils with <45% sand should havecrowns/slopes of 1.5 - 2 % while rootzoneswith >70% sand can have smallercrowns/slopes of 0.75 – 1.0 %. For a moredetailed guideline on this, refer to ASTMWK37583 – New Guide for Constructionor Renovation of Native-soil Athletic Fields.

Internal Pipe Drain: The origin of thistype of installation is in agriculture and it isrelatively cheap to install. It consists of agrid of piping below the surface of the sub-soil. The benefits are (1) the gradual lower-ing of the water table and (2) shorter dryingtime. However, this system is not accus-tomed to dealing with high volumes ofwater in short periods of time, such as dur-ing a game. Also the area affected by thedrainage pipes is usually restricted to withina few feet or so of the pipes. The main ob-jectives of pipe drainage is to lower watertables, control or cut off flow of extraneouswater, and drain any surface water directedto them.. The disadvantages to this systemare that the water must flow to the drains inorder for them to be effective.

Slit Drains: Slit-drained fields are de-signed so that surface water bypasses the na-tive soil, and the local soil has less of aninfluence on drainage rate. A commonspecification is to install sand slits 1-incheswide, 10-inches deep, on 3 ft. spacing (Fig-

ure 7). Most importantly, the slits musttransmit surface water through the nativesoil surface to a more permeable materialunderneath - such as a gravel layer or per-meable fill over pipe drains. The slits runperpendicular to the pipe drains. Two prob-lems can occur with slit drained fields: (1)when the permeable material does notcome into contact with the sand slit (i.e.there is a soil layer between the sand slitand the underlying permeable material), or(2) when the slit is not kept directly at thefield surface and the slit is sealed off by ad-jacent native soil. This can occur rapidly,even during one game if field conditions arevery wet. To prevent the latter, a heavy an-nual sand topdressing program has to beinitiated to make sure that the slits are not“capped off ” over time. Research by theSTRI has indicated that these types of fieldcan accommodate 6 hours adult play perweek (95-125 events per season). In addi-tion, they have suggested that, if managedcorrectly, a slit-drained field should lastabout 7 years before needing to be slitagain.

Suspended Water Table (USGA, PATsystem or similar): By far the most expen-sive of the options to install and maintain,the suspended water table (SWT) construc-tion consists of internal drain pipe, a gravelblanket and a sand rootzone. The biggestbenefit is that it resists compaction and hasvery high infiltration rates. The challengesare that they require greater input (water,fertilizer) and they can lose grass coverquickly from over-use if the sand is not sta-ble, or if regular over-seeding and topdress-ing is not performed. Organic matteraccumulation is also a challenge. Switchingfrom a native soil field to a SWT field isnot economically viable in many cases andcan only really be justified from a financialpoint of view if play has to be guaranteedirrespective of the weather (except snow andfrost).

OTHER NATIVE SOILFIELD IMPROVEMENTSMoving on from discussing the intrica-

cies of removing water quickly from soilfields, adding water to soil fields is also animportant part in native soil field improve-ment. Irrigation is undoubtedly the mostunderused management practices on native

soil fields, especially during renovations oroverseeding/sodding operations. It is highlyunlikely that turf will recuperate from wearor that new seedlings will survive if supple-mental water is not added to the field dur-ing drought (Figure 8). Even in Ohio, with40-inches of precipitation per year, it is notuncommon to have drought conditionsJune, July and August.Adding water to a field does more than

grow healthy grass, but can significantly re-duce surface hardness on fine textured, dryand compacted soils. Dry and compactednative soil fields can have Gmax (hardness)readings in excess of 400, which is fourtimes harder than recommended for athletesafety. And with the CDC reporting that135,000 children between the ages of 5 and18 are treated each year for concussion andother head injuries, it is best to make surethat the playing surface is not one of thecontributing factors. Guidelines for best management prac-

tices on native soil fields, like mowing, reg-ular and timely applications of fertilizer,over-seeding etc. can be found through theSTMA website or University turfgrass pro-gram website. For example, Ohio State hasa free factsheet entitled “Standard Guide forMaintaining Sports Fields and RecreationalTurf in Ohio.” n

Pamela J. Sherratt is the sports turf exten-sion specialist for the turf program at TheOhio State University in Columbus.

Figure 8: This new field was constructed inthe spring and then not irrigated during thesummer. The football season then had to beplayed at another location.

Figure 7


Problem: Stadium field has lines of melted snowfrom end to endTurfgrass area: Major league soccer stadiumLocation: TurkeyGrass Variety: Bluegrass/ryegrass mix

Answer to John Mascaro’s Photo Quiz on Page 33

Can you identify thissports turf problem?

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John Mascaro’s Photo QuizJohn Mascaro is President of Turf-Tec International


FieldScience | By Andy McNitt, PhDmela J. Sherratt

I’VE HEARD IT OVER ANDOVER AGAIN from those in theturf business: “If I could mow atone inch, I’d be able to have pris-tine looking turfgrass like in all

these NFL stadiums.” I politely reply that ifthose kinds of skills and knowledge existedanywhere, there would already be lots ofsmart people using them to improve thesesurfaces.

Let’s review a few facts that aren’t alwaysin our frontal lobe while we watch an NFLgame from the comfort of our homes on alate November Sunday.

First, it’s November. It’s getting seriously

cold now and the light levels are extremelylow. Think about the effects of “winterplay” on a golf course.

Yes, most of the NFL’s northern fieldshave an ethylene glycol heating system run-ning under the sand rootzone. The heatingsystems provide some benefit by extendingthe growing season further into the fall andlimiting frost development on areas that re-quire painting; however, light is still limit-ing. The sun is low in the sky and thestadium seating is being placed as close tothe playing surface as possible. This meansvery steep seats and significant shade. Yes,south facing endzones are sometimes built

lower or more open but there are manyfields where the sun never hits the fieldfrom the endzone through the 20 yard linein November.

In the fall direct sunlight is very limitingand if the heating system is used to pushthe turfgrass excessively, the turf becomesseverely etiolated. Also, the heating systemcan push moisture to the soil surface. Intheory, the ideal set up for an NFL footballgame on a sand rootzone is to have amplemoisture in the rootzone but have it a littledry in the top half inch or so. When theheating system is running during coldweather, moisture in the rootzone is vapor-

Issues and technologies usedon NFL playing surfaces


ized. It moves up through the sand andeventually encounters the cold air tempera-ture where it condensates. This flips themoisture strata where now it is wet on thesurface and dryer further down in the root-zone.While a tremendous help, the heating

systems are not a silver bullet for growingturf in cold conditions. Light is a truly limiting factor in the fall

and in some stadia throughout the season.Artificial lighting systems have been devel-oped and are being used in Lambeau Fieldin Green Bay. Here at Penn State, we’vebeen experimenting with a rollable lighttarp. This system contains a series of LEDlights in the wavelengths needed for opti-mal growth. The wavelengths can be variedto provide optimal growth conditions forparticular species and in some instances forparticular cultivars. We continue to work toget this system commercialized. Besides limitations of light and heat well

into the fall and winter, it’s important to re-alize the tremendous amount oftraffic/damage that occurs to these surfaces.Football fields look big when watching thegame on TV. When you attend an NFLgame the stadium is large and bigger thanlife. This subconsciously makes us multiplythe size of the field. The field looks im-mense. Really, the majority of the game isplayed on a small area. Research has shownthat for most games about 80% of the traf-fic occurs between the numbers and be-tween the 20-yard lines. The area receiving80% of the damage is about 15,800 squarefeet, or the size of about two and a half golfgreens. Think about that for a moment. Most stadia, save three, in the NFL are

used for multiple and varied revenue gener-

ating and charity events. There are the NFLevents, college football games, high schoolfootball games, the FOP versus the FOFcharity event. Lacrosse championships, soc-cer tournaments and professional soccerevents dot the schedule. Then in summerwhen the temperatures are sometimes ex-treme, the stadium hosts between one andthree summer concert events and/or mon-ster truck rallies where at least parts of theturfgrass may be covered for up to 7 days

and other parts must accommodate largecranes, and countless passes with forklifts,trucks and other utility vehicles.Considering the amount and kinds of

events held on these surfaces, it’s a testa-ment to the field managers that they areable to provide a safe and playable surfaceweek in and week out. Remember, there areno frost delays. Unlike baseball nobody stopsplaying for a little rain or even snow. For those of you managing high school

Left: THE SUN is low in the sky and the stadium seating is being placed as close to the playing surface as possible. This means very steep seats andsignificant shade. Middle: Artificial lighting systems have been developed and are being used in Lambeau Field in Green Bay. Right: Most stadia, savethree, in the NFL are used for multiple and varied revenue generating and charity events that can find parts of the turfgrass covered for up to 7 days.

fields that host well over 100 events peryear, the pure number of events may lookunimpressive. You should realize that thekinds of events do differ. To give you apoint of reference, when I evaluate theamount of damage caused by a Division Ifootball game on a Saturday to an NFLgame on a Sunday, it like the difference Iobserve on a high school field between a7th grade game and a varsity football game.Seriously, the difference is dramatic. It’s thesize and speed of the players (Energy =Mass x Velocity). It’s not how strong theplayers are, it’s how fast they can move verylarge bodies. And when these large bodieshave momentum and want to change direc-tion, the shear forces on the turf system aretremendous. On these higher-end sand-based sys-

tems, grinding out of the turf through abra-sion is a secondary damage of the turfbehind divoting. So the management phi-losophy of an NFL field manager and ahigh school field manager are different.A high school turf manager caring for a

native soil field receiving many, many eventsper week is trying to limit, and more impor-tantly trying to constantly recover from weardue to abrasion and soil compaction. Thus,the turfgrass needs ample nitrogen to help itrecover and should have a higher cuttingheight to help reduce the effects of abrasion.Aeration is done to reduce soil compaction. On these higher-end NFL and college

fields that have lower numbers of events, per-

haps only two per week, but where the eventsare at a much higher intensity, maintenancepractices vary. Research on Kentucky blue-grass grown on sand indicates that withinreason a lower mowing height results in lessdamage due to divots. In the past, Beaver Sta-dium at Penn State was mowed as low as7/8” and typically exhibited a low amount ofdivoting. A common mowing height forKentucky bluegrass in the NFL is 1.25 inchesalthough some are mowed at a lower heightyear round.During summer months, before the begin-

ning of the football season, some nitrogen andwater is withheld in order to “harden off” thebluegrass. Stressing the plants somewhat hasproven to reduce divots compared to havingsucculent plants heading into the season.When the weather cools, additional nitrogenis applied in order to stimulate growth. Also,significant spring nitrogen applications aresuggested during any cultivation or renova-tion procedures. Cultivation followed by coreharvesting on sand rootzones is done to re-duce organic matter buildup in the rootzone.


FieldScience

ORGANIC MATTER accumula-tion in the top couple inches ofthe surface can begin to act likesilt and clog the macropores thatconduct air and drainage water.

ALL BUT A HANDFUL of natural grass NFLstadia resod at least 1.5 times per year and asmany as four times per year, bermudagrassfields included.

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