Dollars and "Sense" toImprove Soil PropertiesMake rootzone amendment cost comparisonsbefore the final purchase order is signed. BY MATT NELSON

For the past 40 or 50 years, golfcourse putting greens have beenconstructed with predominately

sand rootzones. Sand resists compac-tion, provides rapid drainage, and main-tains good aeration porosity. Limitingfactors of sand as a growth mediuminclude low nutrient and water reten-tion. To overcome these limitations,sands are commonly amended withorganic material. Laboratory testing ofthe sand and various amendmentchoices identifies the proper ratio ofeach component for optimal perfor-mance and reduces the potential riskfor problems. Over the past few decades,inorganic soil amendments have piquedthe interest of turf grass managers andscientists. Performance criteria and costare important factors when choosingthe proper soil amendment.

The most commonly marketedinorganic soil amendments are porousceramics, diatomaceous earth, andzeolites. These materials have highwater-holding capacity due to internalpore space, and some have a high cationexchange capacity (CEC) for nutrientretention. These are attractive attributes,but a research review is prudent todetermine if these qualities actually re-sult in improved turfgrass performanceas compared to organic amendments.The next step is to determine if thebenefits are cost-effective.

PERFORMANCE CRITERIA:WATER-HOLDING CAPACITYInorganic soil amendments are charac-terized by having a large volume ofinternal pore space that confers a highwater-holding capacity. Evidence sug-gests that much of this water is held too

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tightly and thus remains unavailable forplant use,I.4.24although McCoy showedthat water held by calcined clay anddiatomaceous earth might be moreavailable than previously thought. 12Thiscould be important during periods ofextreme moisture stress, but would beless apparent under normal maintenanceconditions. Studies by Bigelow et al. in-dicate that sand particle size and archi-tecture playa more important role inwater availability than the internal porespace of soil amendments. 1Bowmanshowed that peat retained more waterthan any inorganic amendment testedand, comparatively, released water moregradually at all tensions.1.4

Anecdotal evidence from the fieldsuggests that inorganic amendments areuseful to alleviate localized dry spotwhen incorporated into the upper soilprofile via core aeration and topdressing.This has yet to be substantiated withreplicated, independent research atmultiple sites. A topdressing study con-ducted at Iowa State University showedthat none of the inorganic amendmentstested had a significant effect on theamount of dry patch compared to thesand/peat control,13 while researchers atMissouri found that topdressing withporous ceramic clay reduced dry spotincidence and facilitated turf recovery. 14An Auburn University study demon-strated a negative effect on rootingwhen a calcined clay product was addedto a creeping bentgrass rootzone viaaeration and topdressing. 8

NUTRIENT RETENTIONAnother important aspect of amend-ments to sand is nutrient retention.Sands have low cation exchange capa-

city (CEC), and amendments are usedto hold more nutrients in the rootzone.This is especially important duringturfgrass establishment when nutrientleaching potential is greatest. Severalstudies have shown that none of theinorganic amendments available todayare any more effective at reducingnitrate leaching than peat moss.1.4,19.21Zeolites have very high CEC and havebeen shown to improve potassiumretention in the rootzone,10.16.22yetresearch also has shown that peat wasmore effective at improving nitrogenand potassium recovery in the plantcompared to zeolite.19 Sodium retentionmay present a problem in sites wheresalinity and sodicity are issues.2°Withrespect to preventing leaching lossesand retaining nutrients for plant growth,it appears that organic matter amend-ments remain superior or equal toinorganic products.

TURFGRASS ESTABLISHMENTAs mentioned previously, sands are mostprone to nutrient loss from leachingduring turfgrass establishment. As theturfgrass stand matures, plant produc-tivity results in an increase of soilorganic matter and a correspondingincrease in both nutrient retention andwater-holding capacity. Unamendedsands typically present challenges forturfgrass establishment, requiring morewater and fertilizer than amended sand.Several studies have indicated that peatmoss as an amendment is superior toinorganic materials with respect toestablishment rate.2.3.4.26Conflictingreports exist regarding the influence ofzeolites on the rate of turf grass estab-lishment.17.21Zeolite and sphagnum peat

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Building putting greens is a costly endeavor, involving specified materials and several construction steps.Soil amendment selection can significantly affect the bottom line.

were found to have similar microbialcommunity structure, thus refuting theclaim that zeolite will promote earlymicrobial activity in a sand rootzonecompared to traditional organic matteramendments.6

LONG-TERM QUALITYThe long-term effects of using aninorganic amendment in putting greenconstruction remain largely unknown,and additional studies are needed. Themechanical and chemical stability ofinorganic soil amendments is a concern,as breakdown of these materials couldconceivably result in reduced porosityand performance. More long-termstudy is needed to evaluate the effects ofamendment breakdown and physicalperformance of the rootzones and turf.However, a five-year rootzone studyat Rutgers University indicates thatturf grass quality differences between

amendment treatments are becomingless apparent with time. 16 A likelyexplanation is that as the turf matures,the developing thatch/mat layer be-comes the limiting factor with respectto water infiltration, gas exchange inthe rootzone, and correlating turfgrassvigor.16

•21 Proponents of inorganic

amendments argue that the benefits ofan inorganic amendment will last overtime as compared to peat, which de-composes rapidly. There is no researchevidence that demonstrates rapiddegradation of peat in the rootzone, butrather evidence that suggests peat willlast much longer than other organicmatter sources.24 Organic matter alsoaccumulates in the rootzone as the turfmatures. Look around the maintenancefacility and take note of how manytools are designed for organic matterremoval! Water-holding capacity andnutrient retention are rarely problems

for established greens; thus,. soil amend-ments appear to be less important afterthe first few years of establishment.Gibbs et al. did not demonstrate thatzeolites encouraged deeper rooting overthe long term.7

DOLLARSAND SENSEThe soil amendment debate essentiallycan be reduced to cost-effectiveness.Recent university research shows quiteclearly that none of the inorganic soilamendments evaluated provide anysignificant agronomic benefit as com-pared to peat. 1.2.4.16.21.26 There seems to bean inherent desire for bigger, better,faster,or more sophisticated products in almostevery facet of our industry. While in-organic amendments may appear attrac-tive based upon certain attributes andproduction methods, research has yetto validate any major performance

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A long-term rootzone study at Rutgers University is addressing the role of various organic andinorganic soil amendments in turfgrass quality and performance.

advantage over traditionally used organicamendments. And when it comes timeto put pencil to paper for a construc-tion project, the type of amendmentselected can significantly influence thebottom line.

The following example of a golfcourse construction project is basedupon average costs for sand, inorganicamendments, peat, and blending. Obvi-ously, trucking costs significantly alterthese figures, depending on where theinorganic amendment must be shipped.The cost of peat varies less (range ofapproximately $80 to $110 per 4 cu. yd.bale of sphagnum peat) than most in-organic soil amendments throughoutthe country; thus, transportation costsare not as significant. This exampleproject requires 6,000 cu. yd. of root-zone mixture, which assumes approxi-mately 140,000 sq. ft. of putting greenswith a 12 in. deep rootzone, plus awaste factor of 10-20%.

Assuming a 90: 10 rootzone construc-tion blend of sand:peat by volume, 600

cu. yd. of peat is needed since peat doesnot displace any significant amount ofsand when mixed (you still need 6,000cu. yd. of sand). We assume the cost ofsphagnum peat is $105 for a 4 cu. yd.bale. If 150 bales are required for thisproject, the total cost of peat is $15,750.Sand weighs approximately 1.35 tonsper cu. yd; thus, 8,100 tons of sand areneeded. Dividing $15,750 by 8,100tons of sand equals a cost of$1.95 ofsphagnum peat per ton of mix. Usingreed sedge peat could increase the costof peat to as high as $4.50 per ton ofmix. Laboratory testing is a criticalcomponent of the construction processto identify the most suitable organicmatter amendment for the sand used inconstruction.

An average blending cost of materialsranges from $2.50 to $3.50 per ton.The cost is the same, regardless of theamendment type. Blending costsapproximately $24,300 in this example,using an average blending cost of $3per ton.

Sales tax is another important con-sideration, and for this example we willassume a sales tax of 5%. If the deliveredcost of the sand is $25 per ton at 8,100tons, peat is $105 per bale at 150 bales,and blending cost is $3 per ton for8,100 tons, the tax would be $10,125,$788, and $1,215, respectively ($12,128total tax). Thus, the total cost of materialsfor this putting green constructionproject utilizing a 90: 10 blend of sandto sphagnum peat moss is $254,678($212,625 for sand + $16,538 for peat +$25,515 for blending).

If, instead of peat moss, an inorganicsoil amendment is selected for thisproject, the calculation to determinethe cost of the materials is as follows.We assume again that this putting greenconstruction project will encompass140,000 sq. ft. of putting surface with a12 in. deep rootzone. The cost of sandand blending remains the same ..

A recent phone survey of the majorinorganic soil amendment suppliersrevealed an average cost of approxi-mately $200 per cu. yd. (the range was$180 to $225 per cu. yd.). This is anaverage cost of commonly marketedporous ceramic, diatomaceous earth,and zeolite products before delivery.This number is subject to variation dueto trucking costs, and the delivered costcould be higher than reported in thisexample. For the sake of this example,we will use a 90: 10 ratio of sand toinorganic amendment by volume.

Unlike peat moss, inorganic soilamendments displace sand on a 1:1ratio. Thus, only 5,400 cu. yd. of sandand 600 cu. yd. of inorganic amend-ment are necessary to achieve 6,000 cu.yd. of rootzone mix. If 5,400 cu. yd. ofsand is equal to 7,290 tons, then the costof sand at $25 per ton is $182,250.Thecost for the inorganic soil amendmentat $200 per cu. yd. for 600 cu. yd. is$120,000.

The weight per cu. yd. of theinorganic soil amendments ranges from675 to 1,350 lbs. For the sake of thisexample, we will use an average weightof 1,000 lbs. per cu. yd. to estimate

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blending cost.Therefore, 600 cu. yd. ofinorganic soil amendment weighs 300tons.The blender will therefore blend7,290 tons of sand with 300 tons ofinorganic amendment for a cost of$22,770 (7,590 tons X $3).

Assuming the same 5% salestax, thetax on the sand at $25 per ton for 7,290tons, inorganic amendment at $200 percu. yd. for 600 cu. yd., and blendingcost of$22,770 is $9,113,$6,000, and$1,139, respectively ($16,252 total tax).Thus, the total cost for the materials inthis putting green construction projectutilizing a 90:10blend sand to inorganicamendment is $341,272 ($191,363 forsand + $126,000 for inorganic amend-ment + $23, 909 for blending). Remem-ber, this total could increase significantly,depending on location and truckingcosts.

CONCLUSIONIn this fictitious 18-hole putting greenconstruction example, the cost ofmaterials increased by $86,594 when anaverage inorganic soil amendment wasused at a 90:10 sand-to-amendmentratio by volume as compared to usingsphagnum peat moss at the same ratio.Based upon independent research con-ducted at several leading universitiesacross the nation, it would be difficultto justify the added expense agronomi-cally.Organic matter consistently isdocumented as the best amendment forsand-based rootzones for performancecriteria and cost.

Currently, the USGA guidelines forputting green construction do notrecommend the use of inorganic soilamendments.23 The upcoming revisions(2003) to the guidelines will likely statethat with proper laboratory testing it issafe to use certain inorganic soil amend-ments and still comply with specifica-tions; however, each course should lookat cost effectiveness as an importantcriterion. In any case,put pencil topaper at the outset of any plannedconstruction project and comparedollars and sense.

LITERATURE CITED1.Bigelow, C A., 0. C Bowman, and K. Cassel.

2000. Sand-based rootzone modificationwith inorganic soil amendments andsphagnum peat moss. USGA Green SectionRecord. 38(4):7-13.

2. Bigelow, C A., 0. Bowman, 0. K. Cassel, andT.W Rufty,Jr. 2001. Creeping bentgrassresponse to inorganic soil amendments andmechanically induced subsurface drainageand aeration. Crop Sdence. 41:797-805.

3. Bigelow, CA., 0. Bowman, and 0. K. Cassel.1999. Germination and establishment withrootzone amendments. Golf CourseManagement. 67(4):62-71.

4. Bowman, 0. 1998. Evaluation of new tech-nologies in construction and maintenance ofgolf course greens. USGA Tuifgrass andEnvironmental Research Summary. p. 13-14.

5. Brauen, S.E., and G. K. Stahnke. 1995.Leaching of nitrate from sand putting greens.USGA Green Section Record. 33(1):29-32.

6. Gaulin, E., and R. L.Tate III. 2000. Microbialcommunity development in greens mixesand its role in manageability of golf greens.Proceedings if the 9th annual Rutgers tuifgrasssymposium. Jan. 13-14. Cook College.

7. Gibbs, R.J., C Liu, M.Yang, and M. P.Wrigley. 2001. Effect of rootzone composi-tion and cultivation/aeration treatment onthe physical and root growth performance ofgolf greens under New Zealand conditions.International Tuifgrass Sodety Research journal.9(2):506-517.

8. Hart,W]., R. H.Walker, and E.A. Guertal.2000. Regulator, amendment, cultivars inter-act in heat-stress environment. Golf CourseManagement. 68(11):61-65.

9.Joo,Y K.,J P. Lee, N. E. Christians, and 0. 0.Minner. 2001. Modification of sand-basedsoil media with organic and inorganic soilamendments. International Tuifgrass SodetyResearch journal. 9(2):525-531.

10. Kussow,W R. 1996.Jump starting microbeactivity in sand-peat rootzone mixes. TheGrass Roots. 24(3):44-45.

11. Li, D., N. E. Christians, M.Volterrani, and0. 0. Minner. 2002. Freeze-thaw cycles andsoil amendments. Golf Course Management.70(10):110-113.

12. McCoy, E. L., and R. C Stehouwer. 1998.Water and nutrient retention properties ofinternally porous inorganic amendments inhigh sand content rootzones.journal if Turf-grass Management. 2(4):49-69.

13. Minner, 0. D., and N. E. Christians. 2000.Managing bentgrass stress on putting greenslopes - 2000 report. Iowa State Universitytuifgrass reports. http://tuifgrass.hort.iastate.-edu/pubs/turfrptI2001/32-putting.html.

14. Minner, 0. D.,J. H. Dunn, S. S.Bughrara, andB. E Fresenburg. 1997.Effect of topdressingwith "Profile M" porous ceramic clay onputting green quality, incidence of dry spotand hydraulic conductivity. InternationalTuifgrass Research journal. 8(2):1240-1249.

15. Moore,]. E 1999. Building and maintainingthe truly affordable golf course. USGA GreenSection Record. 37(5):10-15.

16. Murphy,J.,JA. Honig, H. Samaranayake,T.J.Lawson, S.L. Murphy, and B. B. Clarke. 2001.Assessing rootzone mixes for putting greensover time under two environmental condi-tions. Progress report to GCSAA, USGA, Tri-state researchfoundation. New Brunswick, N.J.

17. Nus,]. L., and S.E. Brauen. 1991. Clinoptilo-litic zeolite as an amendment for establish-ment of creeping bentgrass on sandy media.Hort Sdence. 26:117-119.

18. Nus,J L. 1994. Soil amendments. Golf CourseManagement. 62(8):54-58.

19. Petri, A., and A. M. Petrovic. 2001. Cationexchange capacity impacts on shoot growthand nutrient recovery in sand based creepingbentgrass greens. International Tuifgrass SodetyResearch journal. 9(1):422-427.

20. Qian,Y L.,A.]. Koski, and R.Welton. 2001.Amending sand with Isolite and Zeoliteunder saline conditions: leachate compositionand salt deposition. Hort Sdence. 36(4):717-720.

21. Robinson, M., and]. N eylan. 2001. Sandamendments for turf construction. GolfCourse Management. 69(1):65-69.

22. Shaw,].W, and R. 0.Andrews. 2001. Cationexchange capacity affects greens' turf growth.Golf Course Management. 69(3):73-77.

23. USGA. 1993. USGA recommendations for amethod of putting green construction.USGA Green Section Record. 26(2):1-3.

24.Waddington,D.V 1992. Soil mixtures andamendments. P. 331-383. In D.VWaddington,R. N. Carrow, and R. C Shearman (ed.)TurfgrassAgron. Monogr. 32.ASA, CSSA,and SSSA,Madison, Wis.

25.Waltz, C, S.Burnett,V Quisenberry, andB. McCarty. 2000. Soil amendments affectcompaction, soil strength. Golf CourseManagement. 68(11):49-55.

26.Waltz, C, and B. McCarty. 2000. Soilamendments affect turf establishment rate.Golf Course Management. 68(7):59-63.

MATT NELSON isan agronomist in theGreen Section ~Northwest Region.

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