ponsored Research You Can Use Rootzone Amendments for Putting Green Construction So many greens, so many soils, so many soil amendments. Making sense of it all. BY JAMES A. MURPHY S andy, infertile soils have long been recognized as highly suitable for golf courses since the earliest days of golf course development on the links land bordering the sea in Scotland (Alister Mackenzie, 1995). Such land provides good drainage and low to moderate turf growth, both conducive to playing the game of golf As interest in the game expanded, golf courses were built in locations lacking sandy, infertile soil. Thus, the need arose for specifications to guide the construction of rootzones (soil), particularly for putting greens, that were suitable for the game. The USGA Green Section first published guidelines on rootzone construction in 1960, with the most recent update being completed in 2004. These guidelines primarily describe the physical parameters for constructing a rootzone that will create a well-drained playing surface. Research has demonstrated that the range of properties described in the guidelines is large enough to provide a notable range in the behavior of the rootzone (that is, requirements for water and nutrient management). Thus, particular combinations of sand and amendment(s) can be selected to produce a specific influence on the vigor of the turf, which, as previously mentioned, is often intended to be low to moderate for good playing conditions. The selection of amendment(s) for a sand mix varies throughout the United States and other parts of the world, 8 GREEN SECTION RECORD and it is often based on the biases of individuals involved in the design, construction, and future management of new or rebuilt putting greens. Regardless of personal biases, it is important to understand that sand and amendments should be selected based on climatic and other environmental and management conditions that can limit putting green performance. Peat continues to be the most widely used amendment for sand-based rootzone construction; however, a number of materials have been proposed and used over the years as a replacement for peat in sand-based rootzones. Many involved in the design and construction of putting greens do not realize that considerable insight has been gained from recent research on putting green rootzone materials. This article sum- marizes major findings from a nine- year field study of rootzone amend- ments conducted by the Rutgers Center for Turfgrass Science and draws from the findings of others as well.
Transcript
ponsored
Research You Can Use
Rootzone Amendments forPutting Green ConstructionSo many greens, so many soils, so many soil amendments.Making sense of it all.BY JAMES A. MURPHY
Sandy, infertile soils have long beenrecognized as highly suitable forgolf courses since the earliest days
of golf course development on the linksland bordering the sea in Scotland(Alister Mackenzie, 1995). Such landprovides good drainage and low tomoderate turf growth, both conduciveto playing the game of golf As interestin the game expanded, golf courseswere built in locations lacking sandy,infertile soil. Thus, the need arose forspecifications to guide the constructionof rootzones (soil), particularly forputting greens, that were suitable forthe game. The USGA Green Sectionfirst published guidelines on rootzoneconstruction in 1960, with the mostrecent update being completed in2004. These guidelines primarilydescribe the physical parameters forconstructing a rootzone that willcreate a well-drained playing surface.Research has demonstrated that therange of properties described in theguidelines is large enough to provide anotable range in the behavior of therootzone (that is, requirements forwater and nutrient management).Thus, particular combinations of sandand amendment(s) can be selected toproduce a specific influence on thevigor of the turf, which, as previouslymentioned, is often intended to below to moderate for good playingconditions.
The selection of amendment(s) for asand mix varies throughout the UnitedStates and other parts of the world,
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and it is often based on the biases ofindividuals involved in the design,construction, and future managementof new or rebuilt putting greens.Regardless of personal biases, it isimportant to understand that sand andamendments should be selected basedon climatic and other environmentaland management conditions that canlimit putting green performance. Peatcontinues to be the most widely usedamendment for sand-based rootzoneconstruction; however, a number of
materials have been proposed andused over the years as a replacementfor peat in sand-based rootzones. Manyinvolved in the design and constructionof putting greens do not realize thatconsiderable insight has been gainedfrom recent research on putting greenrootzone materials. This article sum-marizes major findings from a nine-year field study of rootzone amend-ments conducted by the RutgersCenter for Turfgrass Science and drawsfrom the findings of others as well.
Image I. Profile samples of nine-year-old rootzone plots visually indicate that very little organic matter has accumulated within the original rootzone (noteyellow sand color of 100%sand profile on left) compared to the large amount of organic matter above the rootzone (note brown colored thatch-mat layer ofboth profile samples). Profile on right is from an 80:20 (v/v) sand-peat rootzone mix, which has a similar accumulation pattern.
100%SAND CONSTRUCTION(NO AMENDING)Constructing putting greens with100% sand (non-amended) is popularwith some architects, builders, andsuperintendents. The cost savings inconstruction associated with notblending an amendment into the sandis typically the primary justificationused by advocates for straight-sandconstruction. However, often over-looked are the increased long-termcosts associated with maintenance ofthese putting greens, discussed later.Construction with 100% sand is alsorationalized with the misconceptionthat problems associated with theaccumulation or organic matter (thatch)
will be reduced by this type of root-zone. Advocates argue that accumulat-ing organic matter "amends" the sandrootzone over time, therefore elimi-nating the need to amend the sand atthe time of construction (Hurdzan,2004). Research has proven that thisconcept is flawed. Measurements oforganic matter accumulation in fieldstudies clearly indicate that the vastmajority of organic matter additionis not in the rootzone (Table A andImage 1). Rather, the majority oforganic matter accumulates above therootzone in the form of thatch or mat,which is thatch plus topdressing. It isthe thatch-mat layer above the root-zone that reduces water infiltration and
increases water retention at the surfaceof putting greens, not the underlyingrootzone. A rootzone of 100% sanddoes not become "amended" overtime and will continue to have verylow (too low) water and nutrient reten-tion. The end result is putting greenturf that requires frequent, intensivemanagement inputs to avoid droughtstress and maintain adequate plantnutrition.
On the other hand, experiencedemonstrates that the dry, infertilecondition of 100% sand constructiondoes gradually alleviate over time asthe developing thatch-mat layerbecomes thick enough to improvewater and nutrient availability. Never-
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Table AConcentration of organic matter and saturated hydraulic conductivity of surface layers of putting green rootzonesafter nine years of growth of L-93 creeping bentgrass maintained as putting green turf in North Brunswick, N.J.
Organic Matter Concentration' Saturated Water Conductivity2
Thatch-Mat layer above the rootzone(1.3 inches thick for sand)(1.4 inches thick for 90: 10 sand-peat)
0- to 3-inch depth of the rootzone
4.52
0.22
% by Weight
5.38
0.40
7.8
32.1
Inches per Hour
8.3
28.5
'Organic matter concentration determined by combustion (360° C) of 3-inch-diameter cores taken from the respective layer of therootzone plots in 2006.
2Saturated water conductivity determined from undisturbed 3-inch-diameter cores taken from the respective layer of the rootzone plotsin 2006.
]Type of peat is sphagnum.
theless, our field trial experience indi-cates that there are meaningful differ-ences between a rootzone of 100%sand and a sand-peat rootzone evenafter nine years (Figure 1). Turf perfor-mance on 100% sand plots frequentlywas poorer than turf grown on sand-peat rootzones. Also, hand-wateringneeds were sometimes greater (morefrequent) on 100% sand rootzones thansand-peat rootzones (Figure 2). Theauthor and numerous USGA agrono-mists have worked with many superin-tendents in every region of the countrywho struggle with water managementon 100% sand putting greens duringdry weather, even during late wintermonths when evapotranspiration islow. Thus, it is unreasonable to expectthatch-mat layer development on 100%sand rootzones to match the perfor-mance of putting greens constructedof a sand-peat mix without an increasein maintenance costs. Moreover, therewill be opportunity costs incurred bythe superintendent and staff; that is,the additional time managing 100%sand putting greens will take timeaway from other management needson the golf course. Eventually, theunending need to assess and tweak themanagement program of 100% sandputting greens can shift from anintriguing mental challenge for the
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superintendent to a seemingly infinitefrustration.
INORGANICAMENDMENTSVarious mineral sources - includingclay, diatomaceous earth, clinoptilolite(zeolite), and volcanic rock - are usedto produce inorganic amendments(IAs), which are comprised of hard,porous (lightweight) sand-sized par-ticles. The internal pores of IAs increaseeffective surface area within the root-zone and are small enough to retainwater against the pull of gravity(capillary) as well as increasing cationexchange capacity (surface chemistry).The amount of CEC depends on themineral source of the IA; generally,zeolites have the greatest CEC.
The improved nutrient retention ofa sand-I A mix can improve turf vigorand quality, especially during establish-ment of new turfs when ample amountsof water and fertilizers are being applied(Murphy et al., 2004). However, thelonger-term effects of sand-IA mixeson turf vigor and quality are not asconsistent as those observed duringestablishment (Figure 1). The differ-ences in turf performance betweenestablishment and maintenance pro-grams on sand-IA rootzones are oftenattributed to water availability. Despite
greater water retention for sand-IAmixes, we only observed sand mixeswith AxisTMand Isolite™ to reduce theneed for hand watering compared to100% sand rootzones (Figure 2). Sand-IA mixes with Profile';MGreenschoice;Mand ZeoPrdM typically requiredsimilar hand-watering as 100% sandrootzones. At various times during thetrial, localized dry spot developed insome plots of 100% sand, 90:10 sand-IA mixes of Profile™ and Greens-choice;M and 95:5 and 80:20 sandmixes with loam. Putting greens ongolf courses constructed of sand-IAmixes have also been observed to sufferdroughty conditions and localized dryspot. Reasons for these observationscontinue to be studied, but it is likelythat changes in the structure of macro-pores (air-filled porosity) versus micro-pores (capillary porosity) within therootzone profile contribute to perfor-mance issues related to water. Thus,our experience indicates that mediumsand mixed with IAs will be very welldrained and aerated, but some sand-IAmixes can suffer from droughtyconditions.
The fact that IAs do not decomposeis another purported benefit. Sinceorganic matter can undergo decompo-sition, it is argued that organic amend-ments in a rootzone will degrade into
finer particles and contribute to thechallenges of managing organic matterin a rootzone. Focus on the rootzoneprofile is one important flaw in thisrationalization. Our research and othersclearly show that it is the accumulationof organic matter above the rootzonethat is the site of declining physicalconditions, not the rootzone mix itself(Table 1). The physical changes in therootzone of a sand-peat or sand-com-post mix are relatively small and oflittle consequence compared to thechanges occurring above the rootzonemix. This observation, combined withthe fact that turf performance on sand-IA mixes most typically does notexceed that of sand-peat or sand-com-post mixes, indicates that the agro-nomic value of a non-decomposingamendment in the rootzone profile isvery limited. Moreover, high-qualitypeat amendments are typically humi-fied; that is, the organic matter hasbeen microbially altered into relativelystable organic matter.
Thus, other benefits may be neededto justify the greater cost of construct-ing putting green rootzones with IAs.There are some advantages to IAs thatmay be important. The better IAproducts are very uniform and there-fore make quality control easier, unlikepeat and compost, which can varyconsiderably in water content, otherphysical attributes, and chemical prop-erties during the blending operation.Inorganic amendments are very dryand flowable, making blending mucheasier and more consistent. Inorganicamendments will displace a significant
volume within a mix with sand, where-as peat does not. For example, blending7,000 cubic yards of a 90:10 sand-IArootzone mix will require approxi-mately 10% less sand than a 90:10sand-peat mix. This 10% reduction insand (700 cubic yards) will significantlyreduce shipping costs. If peat were tobe used, you will still need to haul all7,000 cubic yards. Nelson (2003)discussed this in a cost analysis ofmaterials for constructing 140,000 sq.ft. (3.2 acres) of putting green root-zones using either peat or IAs. Thisanalysis demonstrated that use of a
Figure I. Average annual turf quality ratings for L-93 creeping bentgrass grown on rootzone plots in North Brunswick, N.j.. from 1999 to 2005. Allamendments were mixed at 10% by volume with medium sand that conformed to USGA guidelines. Error bars represent the least significant differenceamong means (P < 0.05); that is. mean differences greater than the error bar are statistically different.
MAY-JUNE 2007 II
Figure 2. Total water applied to rootzone plots by sprinkler irrigation and hand-held hose based onvisual wilt stress and low soil water content measurements from April to October of 200 I and 2002.Hand watering was done to avoid overwatering plots that were able to retain a greater amount ofplant-available water and reduce the frequency of watering. Sprinkler irrigation applied 8.7 inches ofwater in 200 I and 8.8 inches in 2002. Error bar for 2002 represents the least significant differenceamong means (P < 0.05); that is, mean differences greater than the error bar are statistically different.No differences were observed among root zones in 2001.
Compost should be free of objection-able odors. Nutrient content can vary,but compost used to amend sandshould be slightly acidic (pH 6.2-6.8),relatively low in salts (EC<10dS/m,preferably <5dS/m), and low inchemical (arsenic, cadmium, lead,zinc, etc.) and biological (pathogens,weed seed) contaminants. Compostsshould not contain visible refuse orother physical contaminants, substancestoxic to plants, or sufficient fine par-ticles such that the specifications forparticle size distribution and otherphysical properties of a sand-compostmix cannot be met. Blending opera-tions will proceed more easily and bemore uniform if the compost is moistbut not excessively wet (not clumpy)and capable of passing through a screen.Certainly, there should be no visiblewater or dust produced when handlingcompost. More information on com-post specifications can be viewed at theU.S. Composting Council Web page:http:// compostingcouncil. org/pdf!fgcu 4-Characteristics- Parameters. pdf
The composts evaluated in our trialshave generally improved soil fertility,particularly phosphorus and micro-nutrient content. Turf performance ona 90:10 sand-compost mix was as goodas or better than sand-peat mixes(Figure 1), and hand-watering needswere similar to 90:10 sand-peat mixes(Figure 2).
These research findings, alongwith an ample supply of consistentand high-quality composts within theNY /NJ/PA region, have encouragedmore blenders and suppliers of sandmixes to offer compost as a componentof construction mix products. Itcannot be overemphasized that thequality of compost is essential forsuccess. There are unfortunateexamples where use of an improperlycomposted material had disastrousresults. Thus, buyers should confirm(test) the quality and consistencyof composts or sand-compostmixes available in your regionbefore using.
biological qualities of compost willvary depending on the source material(feedstock) as well as the compostingprocess itself Unlike fertilizer products,there are limited government regula-tions or certification standards in placethat provide a guaranteed analysis forcompost. Thus, the onus of document-ing compost quality and consistency(quality control) often falls to thebuyer.
High-quality composts for amend-ing sand rootzones are produced byaerobic decomposition of organic mat-ter and should be mature, stable, andweed free. Examples of organic mattersources for compost (feedstock) includeagricultural, food or industrial residuals,class A biosolids, yard trimmings, orsource-separated municipal solid waste.Composted biosolids should meet allapplicable USEPA CFR, Title 40, Part503 Standards for Class A biosolids.
Table 2Data pertaining to Figure 2 (Water input, inches)
COMPOSTCompost is a very popular organicamendment among those interested in"organic" or "natural organic" methodsto manage turf and other plants. Unfor-tunately, the quality and consistency ofcomposts can vary widely, presenting asignificant challenge when selectingcomposts. The physical, chemical, and
sand-IA (90:10 by volume) mix wouldincrease material cost by $86,000 onaverage compared to a sand-peat(90:10) mix. The analysis used modestvalues for shipping cost compared totoday's costs, and thus would be asignificant underestimate. A savingsin shipping cost may be a substantialfactor for some regions in the UnitedStates where high-quality sands and/ororganic amendments are not readilyavailable, particularly considering therecent increase in fuel costs.
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FINER-TEXTURED SOILSand can also be amended with afiner-textured soil to subtly increasethe organic matter and fine particlesize content (silt and clay) of a mix,which is intended to improve nutrientand water retention. We observed thatsand-loam mixes were effective atimproving nutrient retention and turfquality in our trials; however, wecould not demonstrate improvementsin water availability by amending sandwith loam. Moreover, we found thatamending sand with excessive amountsofloam (too much silt and clay) resultedin a more compacted rootzone andturf that was very sensitive to droughtstress.
Putting green construction usingfiner-textured soil native to the sitewas very common during the earlyyears of golf course construction; thistype of construction is often referredto as "push-up" greens. These nativesoils were often mixed with smallamounts (relative to today's standards)of sand and/or an organic mattersource such as manure, compost, orpeat. Additionally, many "push-up"greens have been aerated and top-dressed for numerous years, developingas much as 6 inches of an improvedrootzone over the original soil profile ..This improved rootzone in the upper-most profile is generally much closerto current USGA construction mixguidelines than the original underlyingsoil base.
Many older golf courses in coolertemperate climates have outstandingputting greens originally constructedand managed in this way. However,repositioning, expansion, or recontour-ing of putting greens is sometimesnecessary to update older golf coursesand accommodate modern playingstandards. Use of sand-based construc-tion in these cases can produce signifi-cant inconsistencies in playability andturf management that are undesirable.As a result, there is interest in mimick-ing push-up construction on older golfcourses.
Our research corroborates fieldobservations of excellent putting greensmaintained on sand-topdressed push-up greens. However, mimicking push-up construction has two major chal-lenges: developing a successful profiledesign and identifying a builderexperienced in construction means andmethods compatible with manipulatingand layering of finer-textured soil.Detailed specifications for this type ofconstruction are not available due to
Dr. Jim Murphy describes results of the compre-hensive root zone mix project at the RutgersField Day in August 2005. The USGA, GCSAA,and other state and regional associations helpedfund this landmark nine-year study.
the wide variation in soil textures andlayering used to construct and manageputting greens on older golf courses.Thus, it is essential to work with aqualified agronomist who can assist inrootzone design and the interpretationof physical property tests of potentialconstruction materials (soils).
Inclusion of an improved sand-basedlayer in the uppermost part of the pro-file is an essential design element inthis type of construction. Care mustbe taken to avoid working the nativefiner-textured soil when it is too wetor too dry. It is essential that thebuilder have an understanding of howto till and firm the soil so that excessivesettling is avoided, yet prevent excessivecompaction during the constructionprocess. Lightweight equipment withlow p.s.i. tracks or turf tires must beused to avoid excessive compaction ofthe soil. These can be difficult chal-lenges for inexperienced builders, sodiligence in selection is critical.
SUMMARYResearch clearly documents the bene-fits of properly anlending sand for con-struction of putting green rootzones.Justifications for not amending sandare clearly based on short-term costsavings and not improvements in long-term management or costs. While IAscan improve some characteristics of asand mix, a cost-benefit analysis shouldbe considered since IAs are not typicallycost effective in a sand mix where high-quality sand and organic amendmentsare readily available at moderate ship-ping costs. Compost can also be ahighly effective anlendment in a sandmix; however, it is critical that a high-quality and consistent supply of com-post be identified before selecting.Push-up putting green constructionmay be appropriate in situations requir-ing expansion, recontouring, or move-ment of greens on older golf courses.Push-up construction requires a thor-ough understanding of finer-texturedsoil and layering (i.e. a skilled agrono-mist) as well as an experienced builderto be successful.
REFERENCESHurdzan, M. J. 2004. Golf Greens: History,Design, and Construction. John Wiley & Sons,Hoboken, N.J.Mackenzie, A. 1995. The Spirit of St. Andrews.Sleeping Bear Press, Chelsea, Mich.Murphy, J. A., H. Samaranayake, J. A. Honig,T. J. Lawson, and S. L. Murphy. 2004. Creep-ing bentgrass establishment on sand-basedrootzones varying in amendment. Turfgrassand Environmental Research Online 3(10).http://usgatero.msu.edu/v03/n10.pdf.Nelson, M. 2003. Dollars and "sense" toimprove soil properties. USGA Green SectionRecord. 41(3):10-13.USGA Green Section Staff 1960. Specificationsfor a method of putting green construction.USGAJournal and Turf Management.13(3):24-28.USGA Green Section Staff. 2004. USGARecommendations for a method of puttinggreen construction. Available online at http://www.usga.org/turf!course construction/green articles/USGA RecommendationsFor a Method of Putting GreenConstruction. pdf.
JAMESA. MURPHY,PH.D., is extensionspecialist in tutjgrass management at Rutgers,The State University ifNew Jersey.
