••• •• •• •• •• •

Cultivating to manageorganic matter insand-based greensAggressive verticutting removed more organicmatter from greens, but core-aerated greensrecovered more quickly.

This research was fundedin part by USGA.

Josh Landreth, M.S.Doug Karcher, Ph.D.

Mike Richardson, Ph.D.

118 GeM May 2008

Putting greens constructed according toUSGA recommendations contain a medium-to-coarse sand root zone, which provides r~pid waterinfiltration, drainage ~nd oxygen diffusion, whilemaintaining acceptable water retention (7). A golffacility makes a considerable investment to con-struct greens according to USGA recommenda-tions, so it is important that the greens are main-tained to perform as designed with regard to waterretention and drainage.

Newly constructed creeping bentgrass (Agrostisstolonifera L.) greens often perform very well dur-ing the first few years following establishment,but decline in subsequent years, especially duringperiods of high temperature and humidity. Thisdecline is likely caused by changes in the rootzone's physical properties over time, especiallynear the surface where organic matter accumu-lates. Organic matter concentrations greater than4% to 5% in a USGA root zone will decreasewater percolation through, and air movementinto, the root zone (5,6), resulting in conditionsthat are wetter than desirable. Such conditionscan ultimately lead to summer decline when tem-peratures are high and creeping bentgrass respi-ration rates (and root-zone oxygen requirements)are greater than oxygen diffusion rates into theroot zone (1).

VerticuttingNewer cultivation techniques may be effec-

tive in reducing organic matter and maintainingdesirable root-zone physical properties. Verticut-

ting equipment has been demonstrated to aggres-sivelycut channels through surface organic layersin greens, removing more organic matter than tra-ditional core-aeration treatments. However, somesuperintendents have expressed concern about thedifficulty of backfilling cultivation channels andthe slower recovery times associated with aggres-siveverticutting.

Core-aerationA recent trend in core-aeration in greens is

using more closely spaced tines, either by retrofit-ting older aeration units with adapters or by usingnew aeration units with closer tine spacing. It isimportant to note that reducing the tine spacingby half quadruples the affected area when core-aerating greens. Decreasing tine spacing should

This greens aerator has been retrofitted with tine adaptersallowing for a tine spacing of 1.25 x 1.5 inches.Photos by J. Landreth

not affect turf recovery because individual holesizes do not change. This may allow for a moreaggressive approach to controlling organic matterwithout the limitations associated with aggressiveverticu tting.

A moderately aged USGA green typically hasdesirable physical properties throughout the pro-file, except near the surface where organic mat-ter has accumulated. Therefore, it is probably notbeneficial to remove desirable root-zone sand frombelow the surface organic matter layer during aera-tion. Under such conditions, an aeration tine needsonly to be long enough to completely penetrate andremove cores from the organic matter layer. Lon-ger tines would result in excess sand debris beingpulled to the surface, increasing both the laborrequired to remove the debris and the amount ofsand needed to backfill aeration channels.

The objective of this research was to deter-mine the effects of various aggressive vertic~ttingand core-aeration treatments on removal of sur-face organic matter from a sand-based green. Weinvestigated various blade widths for verticuttingand tine diam,eters, spacings and depths for core-aeration. '

Experimental cultivation methodsA two-year experiment was initiated in spring

2003 at the University of Arkans'as Research andExtension Center in Fayetteville, on a I-year-oldPenn G-2 creeping bentgrass green built accordingto USGA recommendations (3,7). The researchgreen was mowed six days per week at a heightof 0.125 inch. Nitrogen and potassium were eachapplied at 3.5 pounds/I,OOO square feet/year, andphosphorous was applied at 0.5 pound/I,OOOsquare feet/year. Deep irrigation was applied asneeded to encourage root growth and preventdrought stress. In addition, light sand topdress-ing was applied every two weeks throughout eachgroWIng season.

The Graden GS04 verticutter is capable of cutting channelsthrough the surface organic layer of putting green root zones,

Cultivation treatments were applied usingeither a Graden verticutter (GS04 Verti-CutterlScarifier) or a Toro greens aerator (Toro Greens09120) in the spring and fall of each studyyear. Verticutting treatments were made to a l-inch (2.5-centimeter) depth to ensure completepenetration through the thatch/mat layers andincluded blade widths of 1, 2 or 3 millimeters.Core-aeration treatments included various com-binations of tine spacing (1.25 x 1.5 inches or 2x 2.5 inches [3.2 x3.8 centimeters or 5 x 6.4 cen-timeters]), tine diameter (0.25 or 0.5 inch [6.4 or1.3 centimeters]), and tine penetration depth (1.5or 2 inches [3.8 or 5 centimeters]). Cultivationtreatments were made to individual plots measur-ing 5 x 20 feet (1.5 x 6 meters), and each treat-ment was applied to four replicate plots.

The day before cultivation treatments wereapplied, in each plot, the percentage of organicmatter was measured in the top 1 inch of sur-face soil, and from 1 inch deep to the depth ofcultivation. Immediately following cultivationtreatments, scoop shovels were used to collect thedebris (sand and organic material) from each plot.Once the debris was collected, sand topdressingwas applied and brushed into the rurf until thecultivation channels were filled. The amount ofdebris removed and topdressing sand incorpo-rated into cultivation channels was recorded foreach plot. The organic matter in the cultivationdebris originating from the surface inch was cal-culated based on the distribution of organic matterfrom the surface inch to the depth of cultivation(evaluated the day before treatment applications).In addition, each plot was rated for recovery andoverall turf quality twice weekly following culti-vation treatments.

••• •• •• •• •• •research

Once the debris was collected, sandtopdressing was applied and brushedinto the turf until the cultivation chan-nels were filled. Photo by D. Karcher

May 2008 GeM 119

••• •• •• •• •• •research

':":::=::J~-.'•••••

Days after cultivation

Figure 2. Turfgrass recovery from cultivation as affected by cultivation treatment. Turf recovery is ratedon a scale of 1 to 9, where 1 is no recovery and 9 is fully recovered. Data collected September through

November 2003 in Fayetteville, Ark. Error bar represents least-significance-difference value betweentreatments within a single evaluation date.

Turfgrass recovery and qualityTurfgrass recovery evaluations following cul-

tivation are summarized in Figure 2. To improvethe clarity of Figure 2, the 2-millimeter verticut-ting treatment and core-aeration treatments with1.5-inch-deep tines were not included. However,

Organic matter removalAll of the verticutting treatments removed

more surface organic matter than any of the core-aeration treatments (Figure 1). In.fact, the 3-mil-limeter verticutting treatment removed more thanfour times the amount of organic matter removedby each core-aeration treatment. There wasnot much difference in organic matter removalbetween the 1- and 2-millimeter verticuttingtreatments.; however, they only removed abouthalf the organic matter removed by the 3-milli-meter treatment. Superintendents with sand-basedroot zones with very high organic matter contentshould consider aggressive verticutting to removeexcessive organic matter near the root-zone sur-face. Among the core-aeration treatments, thelarger-diameter, closely spaced, deeper-penetrat-ing treatment removed the most organic matterfrom near the root-zone surface.

Although it was not as effective as verticut-ting in removing large amounts of organic mat-ter from the root zone, core-aeration - especiallywith shorter tines - was more efficient in com-pletely penetrating the organic matter layer with-out bringing excess sand to the surface. Verticut-ting treatments and the deeper-penetrating hollowtines had significantly less organic matter in thecultivation debris compared to the hollow tines,which do not penetrate as deeply (Figure 1). Cul-tivation debris that was not surface organic matterwas predominately root-zone sand with desirablephysical properties.

Although verticutting treatments (left) removed more surfaceorganic matter, core-aerated plots (right) recovered significantlyfaster. Photo by J. Landreth

enc::=4-

3.0 Q)(")CD

0toQ)

2.5 ::::l0'3Q):=t:

2.0 ~(")0::::l

CD;:a.g,(")c::;:::;:<'~0'::::l

Cl..CDg-en'~

2

9

8

7

o

~6

~5CD>8 4~~ 3

Surface organic mattel7i

--CJ)

"0c::::::lo,S

"0CD>oE~CD

'EE(,)

'ccoClloCD(,)cot::::::len

1.5-inchI2.0-inchdepth depth

-,S'fliajoiaiiieter,Aj.inche~

Figure 1. Surface organic matter removed and percentage of organic matter in the cultivation debrisas affected by cultivation treatment. Data were collected May 21 , 2003, in Fayetteville, Ark. Within

evaluations, treatments with bars sharing a letter are not significantly different (capital letters are usedfor surface organic matter removed, and lowercase letters for surface content of cultivation debris).

iTurf recoverY

-+- Graden 2-millimeter blade width-8- Graden 3-millimeter blade width

Core-aerationTine diameter I_Tine s~

-+- 0.25 inch i 1.25 x 1.5 inches... I 1 .--- 0.5 Inch i .25 x 1.5 Inches

___ 0.5 inch I 2.0 x 2.5 inches

120 GeM May 2008

recovery with the 2-millimeter verticutting treat-ment was similar to recovery from the other ver-ticutting treatments, and recovery from treat-ments with the l.5-inch tine depth was similar torecovery from treatments with the 2.0-inch tinedepth.

Verticutting vs. core-aerationCultivation channels healed over more quickly

for core-aeration treatments than for verticuttingtreatments. The time required for the verticut-ting treatments to heal following cultivation wasnearly 60 days, approximately twice that neces-sary for core-aerified turf. This difference waslikely the result of the problems in backfilling cul-tivation channels with sand. Once the cultivationdebris was removed from those plots, many of theverticutting channels had partially closed, mak-ing it difficult to fill the channels with sand andsmooth the surface.

Aerification holes created by coring treat-ments were less prone to collapse and were morecompletely filled with topdressing sand, creat-ing a smoother surface, which hastened recovery.In fact, in all plots that were core-aerifie~, theamount of topdressing sand that was incorporatedback into the turf canopy was greater than 100%of the volume of the debris that was removed dur-ing cultivation. In contrast, only 70% of the vol-ume of cultivation debris could be incorporatedback into the canopy as topdressing sand for turfthat was verticut.

After this research. was completed, Gradenreleased a new verticutting unit that verticuts andbackfills channels with sand in a single operation(1). Turf recovery from aggressive verticuttingwould likely be enhanced with sand injection,although no published research has documentedthis .

Tine diameterAmong core-aeration treatments, tine diam-

eter had the greatest effect on recovery time. Turfcored with 0.25-inch-diameter tines recovered in14 days, about half the time of turf treated with0.5-inch tines. Neither tine depth nor tine spacingaffected turf recovery in this study. Consequently,a superintendent can use closer tine spacing toaffect a larger percentage of the putting surfacewithout affecting recovery time. This is a bet-ter alternative to increasing tine diameter, whichwould also increase the affected area, but woulddelay recovery time. In addition, a. shallow tineis preferable to a deeper tine (so long as the tinecompletely penetrates the surface organic layer)because shallow tines bring less debris to the sur-

••• •• •• •• •• •

face, and the amount of organic matter removedand recovery time are the same as with deepertines.

Turf qualityCultivation treatments did not affect turf qual-

ity in this trial except during periods of recoveryfrom treatment. This study was conducted ina full-sun location with considerable air move-ment, resulting in minimal disease pressure andsummer stress symptoms. Cultivation treatmentswould have been more likely to enhance turf qual-ity in an environment with limited sun exposureand air movement. Although visual quality wasnot affected by cultivation treatment in this study,untreated plots were considerably softer by theend of the study and probably had less desirableball roll characteristics. In a follow-up study onthe same plots, uncultivated turf consistently hadlower hardness values than all treated turf (2).

Organic matter contentAfter three sets of cultivation treatments and

14 months after the study was initiated, aggres-sive verticutting was most effective at minimizingorganic matter content in the surface inch of theroot zone (Figure 3). In particular, the 3-millime-ter verticutting treatment reduced the content ofsurface organic matter significantly below that ofthe untreated control and all core-aeration treat-

Surface organic matter vs. treatment

5CJ.)c 4.50N

(54e

'0.r= 3.5u.!:CJ.)u 3ce't::='en 2.5.!:CCJ.) 2C0ua; 1.5~coEu'cco

0.5Cl

Cs0

Figure 3. Organic matter content in the surface inch of the root zone as affected by cultivationtreatment. Data were collected June 21, 2004, two months after the third set of treatments wereapplied. Treatments with bars sharing a letter are not significantly different.

May 2008 GeM 121

••• •• •• •• •• •

The research says

~ Aggressive verticuttingwas more effective at removingsurface organic matter than core-aerification treatments.

~ Turf recovery from aggres-sive verticutting was much slowerthan recovery from core-aerifica-tion. Turf recovery was faster inturf treated with smaller-diametertines.

~ Tine spacing did not affectrecovery time. Closely spaced tinescan increase the affected surfacearea (and organic matter removal)without delaying recovery.

~ After three sets of treat-ments over 14 months, aggressiveverticutting resulted in a lowerorganic matter content near theroot-zone surface compared tocore-aerification.

122 GeM May 2008

ments. These results are not surprising consider-ing the large amounts of organic matter broughtto the surface by verticutting treatments.

Although all of the closely spaced core-aera-tion treatments resulted in lower content of sur-face organic matter than the control, differenceswere slight and not statistically significant afterthree sets of treatments. It is important to noteagain that this study was conducted under idealconditions (full sun and air movement) for micro-bial breakdown of organic matter. A green withlimited air movement and limited sun exposurewould probably have greater moisture content atthe root-zone surface, limiting microbial activity. -.Under such conditions, core-aeration treatmentswould be expected to significantly reduce surfaceorganic matter compared to untreated turf.

ConclusionsVerticutting treatments were more aggressive

and effective. than core-aeration treatments atremoving organic matter from the surface inchof the putting green root zone. However, the ver-ticutting treatments removed a disproportion-ately large amount of debris and recovered moreslowly. Therefore, aggressive verticutting may bemost useful when a large amount of organic mat-ter must be removed at once and recovery time isnot a primary consideration, for example, duringrenovation of a green. Core-aeration with closelyspaced tines may be better suited to more-generalmaintenance of surface organic matter for greensthat must return to a high level of quality shortlyafter cultivation.

FundingThe authors thank the USGA's Turfgrass and Environmen-

tal Research Program and the University of Arkansas Division ofAgriculture for financial support of this research.

AcknowledgmentThis paper was originally published as "Cultivating to Man-

age Organic Matter in Sand-based Putting Greens" by Josh Lan-dreth, Doug Karcher and Mike Richardson in USGA Turfgrass andEnvironmental Research Online 6 (19) :1-7.

Literature cited1. Dickson, S., K. Ross, 1Girardi and 1Bryant. 2007. Garden

with sand injection. TurfNet Monthly 14(1):6-7.2. Kauffman, J.M. 2007. Long-term cultivation effects on root-

zone properties of a sand-based putting green. M.S. thesis.University of Arkansas, Fayetteville.

3. Landreth, J.w. 2005. Cultivation techniques to maximize theefficiency of organic matter removal from sand-based puttinggreens. M.S. thesis. University of Arkansas, Fayetteville.

4. Murphy, J.w., lR.O. Field and M.J. Hickey. 1993. Age

development in sand-based turf. International TurfgrassSociety Journal 7:464:468.

5. Neylan, J. 1994. Sand profiles and their long term perfor-mance. Golf & Sports Turf Australia Aug: 22-37.

6. USGA. 1993. USGA recommendations for putting greenconstruction. USGA Green Section Record 31(2) :1-3.

Josh Landreth is a research technician; Doug Karcher,Ph.D. (karcher@uark.edu), is an associate professor; andMike Richardson, Ph.D., is a professor in the department ofhorticulture, University of Arkansas, Fayetteville.