Sand-Based Rootzone Modification with InorganicSoil Amendments and Sphagnum Peat MossCurrent player volume and maintenance practices call forresearch into changes in putting green construction materials.by CALE A. BIGELO~ DAN BOWMAN, and KEITH CASSEL

areas. A few of the more commonlyused inorganic soil amendments are theporous ceramics, diatomaceous earth,and zeolites. Some of the character-istics of these products that potentiallymake them desirable for improving theproperties of sands are a large internalporosity that results in water retention,a uniform particle size distribution thatallows them to be easily incorporated,and high cation exchange capacity thatretains nutrients. Therefore, researchexploring the suitability of newly mar-keted inorganic soil amendments thatare not subject to biological degrada-tion, but still provide water and nutri-ent retention, would be worthwhile.

composes over time. This gradual de-composition may adversely affect therootzone physical properties and this,in turn, may contribute to poor per-formance of turfgrasses grown onthese declining rootzones. Turfgrassresearchers have evaluated many in-organic soil amendments for sandrootzone construction with mixedsuccess (Waddington et a1., 1974;Schmidt, 1980; Ferguson et a1., 1986;Nus and Brauen, 1991; Kussow, 1996;Carlson et a1., 1998; McCoy andStehouwer,1998).

Renewed interest in inorganic soilamendments has resulted in manyproducts being marketed for turfgrass

Basic Principles ofSand-Based Rootzones

Since 1960, the most widely acceptedmethod of putting green constructionhas specified a high sand content root-zone. Sand is well suited for high-trafficareas like putting greens because itresists compaction, drains quickly, andmaintains good aeration properties.Also, it is relatively inexpensive andgenerally is available most anywhere.Although sand is a good substrate forputting green rootzones, it does havelimitations, most importantly poorwater retention and nutrient retention.

To correct these deficiencies, sandhas most often been amended with peatmoss (Beard, 1982). Although peatmoss may be the frequently used soilamendment for putting greens, othermaterials may also be suitable. As withany organic material, peat moss de- A wide variety of soil amendments are available for amending putting green sands.

"The pace of golf activity and trafficon golf courses is presently at a peakwhich has never been equaled. Manyof our construction methods that weresatisfactory before, will no longerproduce greens which will withstandthe wear now imposed upon them."

TIESE WERE THE WORDS thatprefaced the 1960 Green Sectionspecifications for a method of

putting green construction. Althoughwe have had a widely accepted systemfor constructing putting greens fornearly 40 years, it seems that the samewords also hold true today.

Four years ago, in an effort to furtherunderstand and improve puttinggreens, the USGA supported a series ofscientific research projects at univer-sities across the United States. One ofthe projects, entitled New Materialsand Technologies for Putting GreenConstruction, was conducted at NorthCarolina State University. In this studywe evaluated a variety of materials thatcould be used to amend sands used inputting green construction.

JULY/AUGUST 2000 7

Table 1Particle size distribution, geometric mean diameter, and particle density of three sand size classes

and five rootzone amendments used for the simulated putting green rootzone mixtures

Amendment

Fine sandMedium sandCoarse sandEcoliteGreenschoiceIsoliteProfileSphagnum peat

Particle Size------------------------------------------- mm ----------------------------------------->2.0 1.0 0.5 0.25 0.10 0.05 <0.05

___________________________________________g kg-1 -----------------------------------------

o 0 0 0 1000 0 0o 0 0 1000 0 0 0o 0 1000 0 0 0 0o <1 242 615 139 1 3o 3 871 108 11 7 <1o 5 446 534 10 5 <1o <1 0 714 272 14 <1

GeometricMean

Diametermm0.010.250.500.670.840.740.59NA

ParticleDensityMgm-3

2.622.622.622.322.15

.2.272.500.63

Considerations BeforeSelecting an Amendment

Before deciding on which amend-ment to use for improving the proper-ties of a particular sand, you shouldconsider a few questions. What effectwill the amendment have on the overallparticle size distribution of the root-zone mixture? Too many coarse or fineparticles is undesirable. What impactwill the amendment have on thechemical properties of the sand? Someamendments may dramatically changethe soil pH or contribute unwantednutrients. How stable is the amend-ment? Will it physically or biologicallydegrade and potentially clog up thedrainage pores of the rootzone mix-ture? Lastly, it is important to consideravailability and cost. An amendmentcould have the best physical andchemical properties in the world, butif it needs to be shipped across thecountry the benefits may not warrantthe cost. Since all amendments do nothave identical characteristics, an over-view of some of the major properties ofthe more commonly marketed amend-ments follows.

Types of AmendmentsThere are essentially two major

classes of amendments: 1) organicmaterials, which are derived from de-composed plant materials, ,and 2) in-organic materials, which are mineralbased.

Organic materials are typically in-expensive and, depending on theorigin, may be somewhat short-lived inthe rootzone. The benefits of addingorganic matter to most any soil are

8 USGA GREEN SECTION RECORD

numerous. It does an excellent job ofenhancing soil structure by improvingaggregation and can be an excellentsubstrate for microbial growth. Increas-ing aggregation also enhances soil aera-tion, which may ultimately improveturfgrass health.

In addition to the structural benefits,most organic matter can hold severaltimes its weight in water. When takenadvantage of in coarse-textured soils,this property can greatly improvemoisture retention. A certain amountof organic matter improves the resili-.ency or the ability of soils to withstandtraffic.

In addition to improving soil physi-cal properties, organic matter may havemoderate nutrient-holding capacities,depending on soil pH. If an organicmaterial is used for soil modification, itis important to use well-decomposedmaterials because they are more stableand less likely to negatively impactthe physical properties that you haveworked so hard to achieve.

Inorganic materials are derived'from large, naturally occurring mineraldeposits, and these products are gen-erally mined from the ground. Theseproducts range from low to high in cost,depending on the particular materialand its availability. Several inorganicmaterials have been marketed over theyears for soil modification. Some ofthe more commonly used products in-clude: calcined clays, porous ceramics,expanded shale, diatomacous earth,and the zeolites.

Calcined clays, also marketed asporous ceramics, are products thathave been heat treated at a very hightemperature (1000-18000P). This heat-

ing increases the structural integrity ofthe particles while retaining theirchemical properties. Once calcined,most products are often screened to auniform particle size that makes themwell sized for use in putting greenrootzones. Since these products areclays by nature, they also have a veryhigh inherent moisture-holding capa-city. This high moisture retention is theresult of many small internal pores.Earlier research has suggested thatparticles comprised of many smallpores may hold moisture so tightly thatit may not be available to plants (Daviset a1., 1970). Another benefit of theseclay-based minerals is that, becausethey are clays, they have some nutri-ent-holding capacity, particularly forcations like the ammonium (NH4+) ion.

Diatomaceous earth is a materialthat has been mined from deposits ofdiatom shells. Diatoms are one-celledocean organisms whose cell walls con-sist of interlocking parts and valvescontaining silica. The skeletons of thesediatoms have a high degree of internalpore structure, and thus, like the clays,retain significant quantities of water.These products have been marketedwith and without clay binders. The clayaddition certainly affects the water-holding capacity of the product. Likethe clay-based amendments, the availa-bility of water to plants and the long-term stability of these materials is notfully understood.

Zeolites are a relatively new classof amendments being widely used forturfgrass rootzones. The main attrac-tion of zeolites is that they are tremen-dous absorbers. They have long beenused in removing environmental pol-

Table 2Porosity and water retention.of three sand size

classes and five rootzone amendments

*Capillary porosity refers to water retained at -40cm**Available water holding capacity (AWHC) equals capillary water retention

minus -500cmMeans followed by the same letter in the same column are not significantly different

under Fisher's protected LSD (p = 0.05)

Rootzone ----------- Porosity ----------- ------ Water Retention ------ BulkComponent Total Macro Capillary* -20cm -500cm AWHC** Density

----------------------------- Percent (%) ------------------------------ gcm-3

Fine sand 45.0c 18.2b 26.8 bc 44.6b 2.5 c 24.4 a 1.42

Medium sand 42.9c 37.8 a 5.1 d 14.8 d 2.9 c 2.2 c 1.47

Coarse sand 38.4 c 34.7 a 3.7 d 4.7 e 0.6 c 3.1 c 1.59

Ecolite 60.6b 37.2 a 23.4 c 24.7 c 20.6b 2.8 c 0.87

Greenschoice 56.7b 32.1 a 24.6c 25.0 c 20.8b 3.8 c 0.84

Isolite 72.2 a 36.4 a 35.8b 36.1 b 34.2 a 1.6 c 0.59

Profile 73.4 a 38.0 a 35.4 b 39.6b 33.2 a 2.2 c 0.64

Peat moss 74.4 a 22.4 b 52.0 a 61.5 a 34.3 a 17.7 b 0.15

ments on creeping bentgrass establish-ment when mixed at 10% by volumein a medium-sized sand. The sandiamendment mixtures were installedinto field plots constructed accordingto USGAguidelines (USGA, 1993).Theexperimental greens were then seededto creeping bentgrass in October of1997 at the Turfgrass Field Laboratoryin Raleigh, N.C. Creeping bentgrassestablishment was rated visually bypercentage ground cover until fullcoverage was achieved. Due to spacelimitations, only a portion of the datacollected in the entire study will bepresented in this article.

Results and DiscussionPhysical Properties

Porosity and Water Retention: Sandsize significantly affected porosity andwater retention. Fine sand had thegreatest total porosity of the three sizeclasses but was not significantly differ-end from medium sand, which wassimilar to coarse sand. Although finesand was similar to medium sand fortotal porosity, the pore size distribu-tions and inherent water retention werevery different. Fine sand containedalmost 20% less macropores, or air-filled pores, than either medium orcoarse sand. Although fine sand hadless air-filled pores, it had much higher> 20% capillary water retention,measured at a -40cm tension.

Capillary water retention is a veryimportant property of a rootzone mix-ture because it represents free water

Diatomaceous earth contains manysmall diatoms that possess a largenetwork of internal pores.

The following physical propertiesof the amendments, sands, and therespective rootzone mixtures weremeasured: particle size distribution anddensity, water retention, bulk density,and saturated hydraulic conductivity(percolation rate). Nitrogen leachingwas determined using amendmentsmixed with a predominately medium-sized sand. Rootzone mixtures (12"deep) were installed in acrylic cylindersplaced above a 4" layer of gravel, satu-rated and drained for 24 hours. A liquidsolution of ammonium nitrate, equiva-lent to lIb. of N per 1,000 sq. ft., wasapplied to the surface of the rootzonemixtures and leached with distilleddeionized water. The effluent was col-lected and analyzed for the presenceof ammonium and nitrate.

In addition to the laboratory analysis,a field study was conducted to deter-mine the effect of some of the amend-

Materials and Methods

Experiments were conducted toexamine the suitability of several com-mercially available inorganic amend-ments for use in sand-based rbotzones.Specifically, amendments were testedto determine their effect on the physicalproperties of three contrasting sandsize classes and their ability to limitnitrogen leaching. A locally availablequartz sand was mechanically screenedinto three uniform size classes (fine:0.1-0.25 mm, medium: 0.25-0.50 mm,and coarse: 0.5-1.0 mm). Five amend-ments (two porous ceramics: Profileand Greenschoice; a diatomaceousearth containing a clay binder: Isolite;a clinoptilolite zeolite: Ecolite; andsphagnum peat moss) were studied.Amendments were tested at two rates(10% or 20% by volume).

lutants and in many industrial pro-cesses. Some zeolites have even beenfed directly to livestock to improvegastrointestinal performance. The useof these minerals in turf has becomepopular because they have a strongaffinity for cations. In fact, the cationexchange capacity (CEC) of somezeolites has been measured at 200cmol/kg or more (Ming and Mumpton,1989). For comparison, the CEC ofquartz sand is < 1 cmol/kg. Zeolites dohave internal porosity and hold signifi-cant amounts of moisture, but generallydo not retain as much as the clay-basedproducts.

The primary interest in using thesematerials is for improved nutrient re-tention. Several university studies havedocumented dramatic reductions infertilizer needs in zeolite-amendedsands (Nus and Brauen, 1991; Huangand Petrovic, 1994). Currently, some ofthe zeolite products are being sold "pre-charged" with fertilizers. Applicationsof these zeolites may be like applyingfertilizer and improving CEC all atonce. Theoretically, the plant is ableto use the fertilizer contained in thezeolite, and it can be "re-charged" bysubsequent fertilizer applications.

One precaution when selecting azeolite is that some of the zeolites mayhave rather high residual sodium con-tents, which is harmful to tUrfgrasses inlarge quantities. Therefore, before pur-chasing a zeolite, it is advisable todetermine how much, if any, sodiummay be present. As with the otheramendments, the long-term particlestability under turfgrass cultivation andfreeze-thaw cycles is still undefined.

JULY/AUGUST 2000 9

Table 3Percentage loss of NH4-N and N03-N in the effluent of sand amended at 20%

by volume with four inorganic soil amendments and sphagnum peat mossForm of Nitrogen in the Effluent

Soil Amendment NH4-N Loss N03-N Loss---------- Percent N Lost (%) ----------

Unamended Sand 96.2 a 98.1 aEcolite 7.8 e 99.2 aGreenschoice 69.4 b 95.4 bIsolite 63.9 b 97.8 abProfile 21.3 d 96.1 abSphagnum Peat Moss 37.7 c 95.1 bMeans in the same column followed by the same letter are not significantlydifferent under Fisher's protected LSD (p = 0.05)

that remains after gravitational drain-age stops. Thus, most of this waterfunctions as water that may be used forplant growth. As a benchmark, mostsuccessful sand-based rootzones con-tain ~ 15% water by volume (Bingamanand Kohnke, 1970). In addition tocapillary water, another importantproperty of a rootzone mixture is theavailable water-holding capacity.

For these experimental rootzonemixtures, available water was definedas the difference between water re-tained at a -40cm and a -500cm ten-sion. The -500cm tension was selectedas the theoretical "permanent wiltingpoint' because under most normal putt-ing green irrigation cycles a rootzonewould rarely be allowed to exceed thisvalue before resupplying water. Forcomparison, many soil scientists com-monly calculate available water forfield crop soils as water retained be-tween a -333cm and a -15,000cmtension. The difference between puttinggreen soils and field crop soils is thatunder natural field systems the soilsoften possess more silt and clay, aremuch deeper, and often contain amuch deeper rooted unmowed crop.Thus, the -500cm value seems moreappropriate for our shallow, coarse-tex-tured putting green rootzone system.

With that in mind, fine sand retainedsignificantly more water at all soil watertensions than any sand, and mostimportantly, had 10 times the availablewater than either medium or coarsesand alone. Further, the medium andcoarse sand had capillary water reten-tion less than 6% and a correspond-ingly very low available water status. Ifthese sands were to be considered forconstructing a sand-based putting

green rootzone, they would certainlyneed to be amended.

Comparing the amendments bythemselves to the sands showed thatthe amendments had significantlygreater total porosity than any of thesands. Total porosity for each rootzonecomponent ranked in the order: peatmoss = Profile = Isolite > Ecolite =Greenschoice > fine = medium = coarsesand. Peat moss, Profile, and Isolite hadgreater than 70% total porosity, com-pared to the sands, which had 40-45 %.Both peat moss and the inorganicamendments had 10% to 28% greatertotal porosity than the most poroussand, fine sand.

These data illustrate that in orderto have such high total porosities, theinorganic amendments must possess arelatively large internal pore space.These internal pores probably accountfor much of their water-holding capa-city. The percent air-filled pores weregenerally similar, > 30%, for all amend-ments and the medium and coarsesand. The corresponding percent capil-lary pores were highest for the inor-ganic amendments Profile and Isolite,> 35 %, and lowest in Greenschoiceand Ecolite, with < 25 %, but stillgreater than any sand.

Although porosity is an importantproperty for relatively shallow root-zones like putting greens (~ 1211

), an-other important property is the amountof water released at a relatively lowtension (-20cm tension) and how muchwater remains at the defined wiltingpoint (-500cm tension). These dataprovide information regarding overallamendment particle size, pore sizearchitecture, and possible field perfor-mance. For example, if an amendment

releases most of its water at a relativelylow tension and retains little at amoderate tension, it is probably com-posed of relatively coarse-textured par-ticles and may be of little use in analready coarse-textured medium likesand. Conversely, if an amendmentreleases little water at low tensions andretains significant amounts at hightensions, this amendment is probablycomposed of many very small pores, asituation that also may be undesirablebecause the water might not be avail-able to the plant during stress periods.

In these experiments, all sands andamendments except fine sand released28 % to 36% of their water betweensaturation and -20cm. Water releasedat this low tension is associated withgravitational drainage and generallywould not be retained in rootzones ex-ceeding 811 depth. In contrast to theserapidly draining sands and amend-ments, fine sand released only 0.4% ofits water at this low tension. Thus, thefine sand retains a rather substantialamount of water, which may be usefulas rootzone depth increases.

To further characterize the moisturerelease properties of the amendmentsand three sands, water retention datawere collected for a range of increasingsoil water tensions. Each rootzonecomponent seemed to have a charac-teristic tension where most of the waterwas released. This critical tension ap-peared to be directly related to particlesize, with finer textures requiring highertensions to release water. For example,coarse sand abruptly released most ofits water between -10cm and -20cm,medium sand between -10cm and-40cm, and fine sand between -20cmand -100cm.

Compared to the sands, the inor-ganic amendments and peat containedsignificantly more water at saturation,> 55 %, and released their water moregradually with increasing tensions upto -60cm. Once the bulk of waterwas released, the water content of theamendments leveled off and remainedrelatively constant for all four inorganicamendments out to the -15,000cm"tension. Peat moss, on the other hand,had the most gradual release of anyof the rootzone components at alltensions. This property was attributedto the wide distribution of pore sizescreated by the fibrous particles of peatmoss. For the sand/amendment mix-tures, the water release curves weregenerally similar to the curves for eachsand. The only difference was thatamended sands retained slightly more

10 USGA GREEN SECTION RECORD

Selecting properly sized sand for constructing a putting green rootzone is the first stepin providing the proper balance between rootzone moisture and aeration. Very finesands are too wet throughout the entire rootzone depth. Very coarse sands are too dryand will require significant and potentially costly quantities of soil amendments toensure they meet guidelines for putting green physical properties.

water than unamended sands at eachtension (data not shown).

Water retained at theoretical wilt(-500cm) was greatest for the amend-ments, ranging 20% to 34% by volume,and least in unamended sands, 0.6% to3%. Of all the rootzone components,available water was highest for the finesand, 24%, whereas the other sandshad less than 3% available water. Thissuggests that particle size and thearchitecture of adjacent particles whenin contact, not a high degree of internalpore space, may be a more importantdeterminant for available water.

Substantial data were generated onhow the amendments responded ineach different sized sand. However, forthe sake of brevity, a general summaryof the sand/amendment responsesfollows. Overall, amendments whenmixed with the three sands had themost predictable response on porosityand water retention in the coarse sandand the least in fine sand. Fine sandand amended fine sand mixtures werethe only rootzone mixtures that con-sistently met USGA guidelines for poresize distributions, 15% to 30% and15% to 25% for air-filled porosity andcapillary water retention, respectively(USGA,1993).

The medium and coarse sand classesfailed to meet specifications becausethey contained an excessive volume ofair-filled pores, which would promotedroughty conditions. The only excep-tion was medium sand mixed with20% peat, which also met guidelines.Although fine sand mixtures generallymet specifications, not all fine sandmixtures met guidelines. Mixtures that

. failed were 10% and 20% peat or 20%Isolite and Profile amended sands.These mixtures were unsuitable be-cause they retained too much water.Rootzones constructed with these mix-tures may be undesirable because ofexcess soil wetness. This conditionwould probably contribute to poorturfgrass rooting, inadequate soil gasexchange, and problems with ballmarking, footprinting, etc.

Bulk Density: As expected, amend-ment additions decreased bulk densityfor all three sand sizes, with peat-amended sands resulting in the lowestbulk density of all amendment mix-tures. This result was anticipated be-cause peat has the lowest particledensity of the rootzone components. Itis important to remember, though, thatbulk density values alone generally arenot an indicator of a successful root-zone mixture.

Percolation Rate: Saturated hydrau-lic conductivity, or percolation rates,were very high for all three sand sizes,> 35" per hour, and ranked in thefollowing order: coarse > medium >fine sand. All sand mixtures had per-colation rates that were much higherthan the recommended 6" to 12" perhour, probably due to the highly uni-form sands used. This observationis not unusual when working withvery uniform sands (Bingaman andKohnke, 1970).

Amendments generally decreasedthe percolation rate of the sands, butconsiderable variation occurred. Theaverage percolation rates for eachamendment across all three sandclasses ranked in the following order:Greenschoice = Ecolite ?::unamendedsand?:: Isolite ?::Profile> peat moss. Asexpected, the 20% amendment ratesignificantly decreased percolationrates more than the 10% rate. It isimportant to note that no amendmentor incorporation rate resulted in per-colation rates falling below USGAguidelines.

Nitrogen LeachingAmmonium: Amendment additions

significantly affected nitrogen leaching,most noticeably due to a wide range inammonium (NH/-N) leaching. Nitro-gen appeared rapidly in the effluent ofall rootzone mixtures, with peak con-centrations around 70 ppm occurringnear 0.5 pore volumes of leachingwater. As expected, significantly higherpeak NH4 +-N concentrations and more

cumulative NH/-N leached from un-amended sand than from 20% (v:v)amended mixtures. Leaching decreasedin the order of unamended sand >Greenschoice = Isolite > peat> Profile> Ecolite. The most effective amend-ments, Profile and Ecolite, decreasedNH4+-N leaching by 75% and 88%,respectively, compared to unamendedsand. The effectiveness of these amend-ments for decreasing NH4 +-N leachingis directly related to their relatively highCEC compared to the other products.

A second study evaluating incorpo-ration rates for Profile and Ecoliteranging from 1% to 20% by volumedemonstrated that the loss of NH/-Nand the peak concentrations decreasedin a stepwise manner, as incorporationrate increased. The highest rate, 20% byvolume, resulted in the least NH/-Nlost for each of these amendments. Thisresponse is consistent with the resultsof MacKown and Tucker (1985), whoreported decreasing NH4+-N losses withincreasing zeolite percentage in sandmixtures. In the present study, no dif-ference in leaching between Ecoliteand Profile were detected except atthe 20% rate. At this rate, significantlyless NH4 +-N leached for the Ecolite-amended sand. Although the 20%amendment rate was most effective,this quantity of product may not beeconomically practical when blendingrootzone materials for green con-struction.

A third study determined the influ-ence of amendment incorporationdepth of 10% Ecolite and Profile, and

JULY/AUGUST 2000 11

Rootzone components and sand amendment mixtures were analyzed for their abilityto retain water using a water desorption technique in a constant temperature room.

Turfgrass Establishment

Creeping bentgrass establishment onthese sand rootzone mixtures was rela-tively slow, requiring > 250 days toreach 100% coverage. This response

demonstrated that incorporation depthsignificantly affected leaching. Evenat a relatively shallow incorporationdepth of 1", these amendments de-creased cumulative NH/-N losses byalmost 25 % . Further, like the ratestudy, increasing the depth of theamendment resulted in a step-wisereduction of NH/-N leaching: Incor-poration throughout the entire 12"deep rootzone resulted in the leastNH4 +- N leaching.

Nitrate: Although Ecolite and Profilewere effective at decreasing NH4 +- Nleaching, they were without effect onnitrate (N03'-N) leaching. For all root-zone mixtures, more than 90% of theapplied nitrate was recovered in theleachate. In general, unamended sandand amended sand mixtures in allexperiments were similar regardinghigh N03'-N leaching losses.

siderably more than sphagnum peatmoss when used at the same incorpo-rate rate (Moore, 1999). This mayexplain the continued popularity ofpeat moss for amending sand-basedrootzones .

ConclusionAmending sand with inorganic

amendments or peat moss had sig-nificant beneficial effects on rootzonemixture physical properties, nitrogenleaching, and creeping bentgrass estab-lishment. Although many of the inor-ganic amendments hold considerablewater, it appears that if water reten-tion and availability are importantcharacteristics for a desirable root-zone mixture, then the most suitableamendment from both a quantitativephysical analysis and an economicstandpoint is peat moss. This fact isparticularly pertinent in coarse-tex-tured sands, where a rather substantialquantity of the amendment would berequired to effectively improve thewater retention of these sands.

Furthermore, inorganic amendmentsvary in their ability to limit nitrogenlosses. No amendment had a dramaticeffect on N03'-N leaching. However,NH4 +- N leaching losses can be sub-stantially decreased to 8% or less byvarious incorporation rates and depthsof the clinoptilolite zeolite, Ecolite, andthe porous ceramic, Profile, and to alesser extent, sphagnum peat moss.Again, N03'-N leaching continues to bea concern in sand-based putting greenmedia, particularly during turfgrassestablishment when turfgrass rootsystems are small and when solublefertilizers are used. However, it may bepossible to minimize N03'-N leachingby constructing putting greens fromsands amended with peat moss com-bined with either a zeolite or porousceramic and using an NH/-N-basedfertilizer program. The peat mosswould be beneficial for the water-holding properties and the inorganicamendment would provide nutrientretention. The use of slow-releasefertilizer products and the practice ofspoon feeding greens during establish-ment are other proven methods toreduce nutrient leaching.

Lastly, it is important to rememberthat not all amendments are suitable forevery rootzone amendment situation.Each amendment may react differentlydepending on the particle size range ofthe base sand used and the quantity ofthe amendment incorporated. Somesands may hold too much water and

may have been due to the somewhatdroughty nature of this predominatelymedium-sized sand. This sand size was'selected to best evalute the water-hold-ing benefits of the amendments tested.Although establishment was relativelyslow, the significant effects and benefitsof a rootzone amendment in thissand were obvious. Compared to un-amended sand, bentgrass establishedfaster on any of the amended sands.Rootzone mixtures ranked in orderof increasing effectiveness were: un-amended sand = Greenschoice < Pro-file = Ecolite < peat moss, with Greens-choice being similar to unamendedsand on two rating dates.

The faster establishment of theamended sands is attributed directly tothe greater water retention and, to asomewhat lesser degree, the increasednutrient retention compared to un-amended sand. Although there waslittle difference in final establishmentbetween sphagnum peat moss and theinorganic amendments Ecolite andProfile, there is a difference in costbetween these materials. In mostcases, inorganic amendments cost con-

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12 USGA GREEN SECTION RECORD

others not enough. Therefore, it is ex-tremely important to submit a potentialsand and sandi amendment rootzonemixture to an accredited laboratory forphysical analysis to determine if itmeets specifications. Finally, althoughmost of the amendments seem physi-cally stable enough for modern puttinggreens, more research needs to beconducted to determine the long-termfield performance before they can bewidely prescribed.

ReferencesBeard, J. B. 1982. Turf management for golfcourses. Burgess Publishing, Minneapolis,Minn.Bingaman, D. E., and H. Kohnke. 1970.Evaluating sands for athletic turf. Agron. J.62:464-467.Carlson, M. S., C. L. Kerkman, and W. R.Kussow. 1998. Peats and supplements forrootzone mixes. Golf Course Management.66(9):70-74.Davis, W. B., J. L. Paul, J. H. Madison, andL. y. George. 1970. A guide to evaluatingsands and amendments used for hightrafficked turfgrass. Univ. of CaliforniaAgric. Ext. AXT-n 113.

Ferguson, G. A., I. L. Pepper, and W. R.Kneebone. 1986. Growth of creeping bent-grass on a new medium for turfgrass growth:Clinoptilolite zeolite-amended sand. Agron.J. 78(6):1095-1098.

Huang, Z. T., and A. M. Petrovic. 1994.Clinoptilolite influence on nitrate leachingand nitrogen use efficiency in simulatedsand based golf greens. J. Environ. Qual.23:1190-1194.Kussow, W. R. 1996. Putting green quality asaffected by rootzone mix composition. InWisconsin Turf Research. 14:41-44.MacKown, C. T., and T. C. Tucker. 1985.Ammonium nitrogen movement in acoarse-textured soil amended with zeolite.Soil Sci. Soc. Am. J. 49:235-238.

McCoy, E. L., and R. C. Stehouwer. 1998.Water and nutrient retention properties ofinternally porous inorganic amendments inhigh sand content rootzones. J. TurfgrassManagement. 2(4):49-69.Ming, D. w., and F. A. Mumpton. 1989.Zeolites in soils. p. 874-911. In J. B. Dixonand S. B. Weed (ed.) Minerals in soil en-vironments. 2nd ed. SSSA, Madison, Wis.Moore, James F. 1999. Building and main-taining the truly affordable golf course.Green Section Record. 37(5):10-15.

Nus, J. L., and S. E. Brauen. 1991. Clinop-tilolitic zeolite as an amendment for estab-lishment of creeping bentgrass on sandymedia. Hort. Science. 26(2):117-119.Schmidt, R. E. 1980. Bentgrass growth inrelation to soil properties of typic Haplu-dalfs soil variously modified for a golfgreen. p. 205-214. In J. B. Beard (ed.) Proc.3rd Int. Turfgrass Res. Conf., Munich, WestGermany, 11-13 July 1977. ASA, Mad~son,Wis.United States Golf Association, GreenSection Staff. 1993. Specifications for amethod of putting green construction.USGA, Far Hills, N.J. 33 pages.Waddington, D. v., T. L. Zimmerman, G. J.Shoop, L. T. Kardos, and J. M. Duich.1974. Soil modification for turfgrass,areas.I.Physical properties of physically amendedsoils. Prog. Rep. 337. Pennsylvania StateUniv., College of Agriculture, Agric. Exp.Stn., University Park, Pa.

CALE A. BIGELOW is a former ExtensionAssociate; DR. DAN BOWMAN is anAssociate Professor in the Crop ScienceDepartment; and DR. KEITH CASSEL isa Professor of Soil Physics in the SoilScience Department at North CarolinaState [Jniversity.

Figure 1Water release of three sand size classes and five amendments

32.521.5log of Tension (cm)

10.5

0.1

0.8

-+- Ecolite0.7 - Greenschoice

-.-Isolite0.6 -+- Profile- -- Peat MossSu

......... -e- Fine SandS 0.5~ --6- Medium Sand-+-'s:::

--6- Coarse SandQ)-+-' 0.4s:::0u

.~lo-l

-+-'Q) 0.3S;::i

~0.2

JULY/AUGUST 2000 13