Most soils supporting turfgrassgrowth contain a very active anddiverse microbial population. Somepeople have alleged that the use of syn-thetic fertilizers and pesticides reducesor eliminates the microbial communityby altering the pH of the soil or causingdirect and indirect toxicity to organ-isms. Except for the presence of inertingredients in some emulsifiable con-centrate formulations that have causedtoxicity, preliminary results from oneongoing study indicate that pesticidesdo not adversely affect most non-targetmicroorganisms (16).

Due to the high productivity andrapid turnover of turfgrass roots, as wellas the high lignin content in the stemsand leaves, organic matter and micro-bial habitat are rarely deficient in turf-grass systems (12). The one system thatmay limit microbial activity due to alack of favorable habitat is a newlyconstructed high-sand-content root-zone, likely due to reduced nutrient-and water-holding capacity. Keep inmind, however, that the advent of thesand rootzone system and sand top-dressing arose to address severe agro-nomic difficulties, namely soil com-paction and poor drainage of native soilgreens. Sand-based rootzones havecreated physical characteristics thatallow golf course superintendents toprovide superior playing conditionsand also maintain an oxygenated root-zone. Microbial populations generallywill stabilize 3-5 years after establish-ment, so amendments to the sand thatcan facilitate a more rapid colonizationof the rhizosphere should lend stabilityto the system (6). These amendmentswould include various organic types,including composts and/or inorganicamendments. The challenge of estab-lishing turfgrass on new, sand-basedrootzones could be due in part to thelack of sufficient microbial activity tobuffer the system from environmentalextremes and harmful pathogens.

Soil Management andMicrobial EnhancementTesting for Soil Microbes

Undisputed is the important rolemicroorganisms play in plant and soilhealth. The difficulty is in quantifyingand qualifying that role. Recent ad-vances in molecular testing capabilitieshave enabled fairly accurate quantifi-cation of the microbial component insoils. While this will not yield a clearunderstanding of the diverse functionand interaction of the various organ-

2 USGA GREEN SECTION RECORD

isms, it is a beginning point for assess-ing microbial health in soils. Keep inmind that microbial populations fluc-tuate widely across sites and over thecourse of a season, however, so test-ing for microbial activity may producesomewhat confusing results until alarge enough database can be assimi-lated. This currently may not be feasibleor cost effective, and it will certainlytake time. However, microbial testingmay provide comparisons of soil thatsupports healthy turf versus soilstruggling to support turf. Be sure toaccount for other factors that may belimiting growth, such as sunlight, aircirculation, drainage, fertility, trafficflow, etc. (13). Soil testing for microbesmay help assess whether microbialactivity is influencing turfgrass quality.

BiostimulantsBiostimulant is a loose term that

includes microbial inoculum, energysources for microbes, soil conditioners,plant hormones, and other non-nutri-tional growth-promoting substances.In recent years, products containingboth biostimulants and fertilizers havefurther muddled this definition. Thismakes differentiating between fertilizerresponse and biostimulant responsedifficult, if not impossible. No doubtthis is precisely what the manufacturersof such products have intended, sincethe non-nutritional component alonemay not elicit a plant response.

One group of biostimulants is planthormones. These products may containone or more of the following: cyto-kinins, gibberellins, auxins, abscisicacid, and ethylene. When growingunder normal conditions, plants haveadequate levels of hormones for nor-mal growth and development. Mostphysiological processes in plants in-volve an interaction of several hor-mones, and individual hormones haveseveral functions. Further, many hor-mones have different functions indifferent plant species (8).

Normal hormone production canbe influenced by environmental andcultural stress. Different species ofplants, growing in different environ-ments, with different stresses, at differ-ent times of the year are quite likely toreact in different ways. One of thesedifferent reactions will undoubtedly bewith hormone regulation, and this isconsistent with the variability in plantresponse to hormone applications inresearch results and field trials acrossthe country. There currently is no evi-dence to suggest that applications of

plant hormones will yield favorableor consistent results with respect toimproved plant health. Furthermore,adding hormones to plants beyond nor-mal levels may produce an inhibitory orundesirable effect. Without researchinformation to identify and quantifytreatment regimes, it may be wise toavoid tampering with plant hormonalactivity (7). Anecdotal evidence andtestimonials have been the substitutefor independent research results re-peated at multiple locations.

Another type of growth stimulantavailable on the market containshumate or humic acid. These are natu-rally occurring organic compoundsthat are the end products of biologicaldecomposition. Accordingly, they areextremely resistant to further decom-position. Products containing humatesclaim to increase cation exchangecapacity, increase microbial activity,and chelate micronutrients. Kussowreviewed manufacturer recommenda-tions for amending a sand-peat root-zone mix with humate and found it tobe a very expensive means of increas-ing the CEC by 13% (9). His reviewfurther concluded that iron, copper,manganese, and zinc are rarely defi-cient in turfgrass soils, thus enhancingmicronutrient availability may onlyprovide negligible benefits. Anotherstudy clearly demonstrated that sincehumates are the end result of decom-position and thus resistant to furtherbreakdown, they do not stimulateincreased microbial activity (25). Yetanother study reviewed the effects ofsix non-traditional growth-promotingproducts on the establishment of creep-ing bentgrass in high-sand-contentrootzones. Only one of the productsproduced significant differences fromthe control, and the product containedhumate. Upon chemical nutrientanalysis of the product, however, it wasdiscovered to contain 6% N, 5% P, 2%K, 4% S, and 4% Fe. Using this productat the recommended application ratewas equivalent to applying an addi-tional 0.75 pound N, 1.3 pounds of P,and 0.34 pound of K per 1,000 squarefeet per month (27). Itmay well be thatthis response could have been dupli-cated with conventional fertilizer, andit would seem to request an indepen-dent nutrient analysis of any growth-stimulating products you intend to try.

Finally, there have been studies thatindicate humates and humic acids canreduce the efficacy of pesticides byreducing their absorption by plantsand pathogens (9). It is also reported

Some microorganisms found in certaincomposts can inhibit turfgrass diseasessuch as Pythium. Biological control ofturfgrass diseases has proven successfulin laboratory studies, but has not beenconsistently successful in field trials.

that the fulvic acid component ofhumates can actually increase thesolubility of pesticides and possiblyincrease mobility (25). Most of thestudies that claim any benefit fromadding humates were in either nutrientculture or sand culture systems, not infield situations. The variation in humicsubstances from different sources andlack of research that supports their useon turfgrasses currently do not justifytheir use in turf management.

Carbohydrate fertilizers, another bio-stimulant, have not been proven toimprove turfgrass stress tolerance orhave any lasting impact on soilmicrobial populations. Again, researchon turfgrass and carbohydrate applica-tion is lacking, but observations acrossthe country indicate no observablebenefits. Any stimulation of microbialactivity is likely to be very short-lived.

MicrobiallnoculantsVarious microbial inoculants have

been formulated for use on turfgrass,with claims of accelerated organic mat-ter decomposition, improved nutrientuse efficiency and availability, soil con-ditioning, disease control, mycorrhizalassociations, and others. The success ofthese inoculants has been limited for anumber of reasons. At this point, youshould be aware that the microbialcommunity is a very diverse andcomplex set of organisms. The degreeof natural competition, antagonism,and predation limits the successfulestablishment of introduced species.Persistence of applied organisms isfurther hindered by the continualtemporal and spatial fluctuation ofmicroorganism populations (6). For-mulation and delivery of the organismspresent even more problems for micro-bial inoculation (15). If the organismscan be kept alive until application,

many are sensitive to UV light andmust be applied frequently (in somecases nightly) to establish sufficientpopulations. Although there have beenefforts to apply microorganismsthrough irrigation systems, the resultsremain largely inconsistent (2). Finally,some companies will not even list whatorganisms they have formulated, be-cause they are proprietary. Withoutknowing what is being applied, it isimpossible to gauge the potentialbenefits. These organisms could bedetrimental to your turf by actuallycompeting with the beneficial organ-isms already present in your soil (7)!

CompostsWith little doubt, the most promising

method of managing and enhancingthe activity of soil microbes is withcomposted organic matter in wastesand other materials. Ironically, this isalso one of the oldest agriculturalpractices ..Composts have been shownto add an active microbial componentto soils and to stimulate those microbesalready present in the soil (14). Well-decomposed organic matter providesexcellent habitat and energy sourcesfor soil microbes, and will provide morepermanent benefit than inoculationwith microorganisms. Composts willeffectively enhance soil aggregation,provide nutrients, reduce compaction,and improve soil porosity. Sandy soilsamended with compost will exhibitgreater nutrient- and water-holdingcapacity (10). While limited evidenceexists, there is some data to suggestamending sand-based rootzones withcompost can offer improved establish-ment and disease control over com-monly used peat amendments (5, 14).

The use of composts in turfgrassmanagement presents a viable means ofrecycling municipal and industrialwastes while improving turfgrassquality. Composts can vary con-siderably, however, depending on theirsource. Commonly used compostsinclude brewery sludge, yard wastes,poultry litter, animal manure, munici-pal wastes, and food wastes. It isrecommended to have composts testedfor organic matter content, ash con-tent (especially if used as a topdres-sing), moisture content, pH, nutrients,metals, and soluble salts (10). On-sitecomposting operations should followguidelines to ensure that the materialhas been properly and sufficiently com-posted (14, 20, 28). The disease-sup-pressive characteristics of compostswill be discussed in the next section.

Biological Pest ControlIn recent years, considerable focus

has been placed on the biological sup-pression or control of various turfgrasspests, including diseases, insects, andweeds. Reducing the pesticide load onthe environment is the primary impetusbehind such study. While researchhas proven effective pest control withvarious biological entities in the labo-ratory, few have proven consistentlyeffective in field studies.

Biological control operates on fivebasic interactions with the turfgrass-soilcommunity: competition, antagonism,predation, parasitism, and patho-genicity (1).The two ways of exploitingthese interactions include microbialinoculants and organic amendments.While dozens of organisms withpotential as inoculants for diseasecontrol have been studied (17, 18,24),few have demonstrated any efficacy inthe field, and only one product (Biotrek22G, Trichoderma harzianum) hasbeen registered for disease control onturf (11, 15). Biological control ofinsects has been somewhat successfulin recent years with such organisms asentomogenous nematodes, soil bac-teria and fungi, although registeredproducts are still limited (21,26).

Serious shortcomings exist in theunderstanding of the pest controlmechanisms themselves, relationshipswith other organisms in the commu-nity, and formulation and deliverytechnology. Furthermore, foliar diseasecontrol with inoculants is limited dueto UV sensitivity of the organisms andwide fluctuations of environmentalparameters in the turfgrass canopy.The difficulty in delivering organisms tothe roots has preempted much successin controlling root diseases. Becausesuccessful pest control typically de-pends on the establishment of highpopulation levels, frequent (and argu-ably unsustainable) applications be-come necessary. Injecting organismsthrough irrigation systems has yet tobe proven as an effective method ofuniform and consistent microorganismapplication. Keep in mind that 1)popu-lation interactions within the soil aredynamic and interrelated, 2) intro-duced organisms are slow to colonizehabitat and generally fail to persist, and3) it is unclear whether the introductionof microbes in the environment willproduce a lasting change and if theintroduction will be beneficial in thelong run (1, 15).

Organic soil amendments and addi-tives, particularly compost, have per-

JULY/AUGUST 1998 3

, Evaluating Independent Research• Who (principal investigator) did the research?• Where was the work done (lab or field, sand or soil)?• Look for replication, good comparative treatments, and statistically

significant differences.

• Have the results been duplicated at another site by another independentresearcher?

• Have the results been published in a refereed journal?• Slick brochures can be confusing!!! Don't be fooled by sales techniques.

~Site Testing Protocol• Test products at s~verallocations representing different conditions on the

golf course. '

• Replicate at each site for best results.• Use controls (no product) to establish comparisons.• At least two years of field data are necessary to obtain an accurate

assessment.• Rate the plots monthly to track differences (color, disease, stress tolerance,

rooting, etc.).

• Conduct an independent nutrient analysis of new products. You may beseeing a fertilizer response!

• Be honest! Is it the product or favorable weather, better cultivation, animproved growing environment, or other changes in managementstrategies?

haps a greater potential for effectivebiological control of diseases than doinoculants. Well-composted material(2-3 years) often exhibits disease-sup-pressive characteristics (14). Studies atCornell University have demonstratedsignificant and lasting disease suppres-sion of Pythium root rot, dollar spot,and snow mold when composts wereused as amendments or topdressing(14). Continued research in this areato reveal the microbiological mysteriesshould help develop more reliable andpredictable composts for disease sup-pression and soil conditioning. Asalluded to earlier, proper compostingtechniques and laboratory testingcoupled with on-site testing will revealwhat to expect from composts.

New ProductsNever before has the turfgrass in-

dustry had as many commercially avail-able products for use. Financial respon-sibility and sound management dictatethat product purchasing decisions areof extreme importance. So how doesone choose between the good, the bad,and the ugly?

The first place to start is with theproduct label. There are products thathave been registered with the EPA andcan legally justify the claims of theproduct. These are products that con-tain active ingredients (29). There areunregistered products marketed forvarious uses, some of which are sup-ported by independent research. Thenthere are products marketed for varioususes without supportive research.These products use testimonials andfancy marketing to make a sale, andoften can be classified as snake oils.

Let's be sure we understand the in-dependent, scientific research thatsupports product use. Be sure youknow who conducted the research,where, under what conditions, and therelevancy to turfgrass systems. Also,look for replication in the study, good

comparative treatments, and least sig-nificant differences. Check closely tosee that the results have been dupli-cated at another site by another inde-pendent researcher, and that resultshave been published in a refereed jour-nal. Make no mistake, slick brochuresand displays can be confusing! Oneproduct advertisement I recently re-viewed claimed the product wouldcause no grow-in layer, extend the use-fullife of greens, reduce grow-in time,eliminate the possibility of nitrite (yes,they said nitrite, not nitrate!) andphosphate leaching, and reduce labor,among other things. This companymay need legal counsel as much asscientific counsel. Finally, call the re-searchers and ask technical represen-tatives what the active ingredients areand what are their modes of action(29). University extension personneland USGA agronomists can also pro-vide valuable information.If a product you are interested in

passes this initial screening, it isstrongly recommended to conduct on-site testing at your golf course. Manyof these products are not cheap, and

good management involves an eco-nomic analysis. Test the material atseveral locations on the golf courserepresentative of different conditions,replicate (meaning include repeatedtreatments at each site), and use un-treated controls and other treatmentsin side-by-side comparisons. All toooften, new products are tried all overthe golf course without a control; thus,it is impossible to determine whateffect, if any, the new product has.Perceived benefits could be a result offavorable weather or other manage-ment techniques (7, 13). Take consis-tent, monthly ratings of the plots forcolor, disease, and rooting depth andmass, and note stress tolerance differ-ences. Good tests require at least twoyears of field data. Because a productwill cause no harm is not reason touse it, and such a decision is repre-sentative of poor management.

ConclusionTurfgrass management is a continu-

ally evolving science, and as ourunderstanding of the microbial com-munity in turfgrass systems improves,new products will routinely hit themarket. Some of these products will beuseful, and many others will not. Inde-pendent research will be essential tothe development of effective products.Perhaps companies marketing bio-logical products would be wiser to fundsome research than to purchase full-page ads in popular trade magazines(if they have faith in their products)!If completely organic management

is ever realized, it will certainly bethrough a gradual phase-out of syn-thetic products. Along with the adventof biological products, golf course

4 USGA GREEN SECTION RECORD

Soil Microbes

Bacteria Single-celled organisms without a nucleus. Perform animportant role in organic matter decomposition, nutrientcycling, soil aggregation, competition with pathogens,production of phytohormones. Also form symbioticassociations with plants.

Actinomycetes Filamentous bacteria. Decompose complex organicmatter molecules like chitin and cellulose, produceantibiotics, and regulate bacterial populations.

Fungi Very good degraders of organic matter. Mycorrhizal andendophytic fungi form beneficial associations with plants.Most turfgrass pathogens are fungi.

Algae Autotrophic organisms. Some fix nitrogen. Excessnutrients can result in an unwanted bloom.

Protozoa Important in nutrient cycling and organic matterdecomposition. Feed on bacteria and control bacterialpopulations.

superintendents must also keep them-selves apprised of advances in syntheticchemistry. Many new products havebeen developed from synthesizedorganic compounds that are effectiveat very low levels of active ingredients,have low water solubility, short half-lives, and a strong binding potentialwith soil and organic matter. The newsynthetic chemistries are better for theenvironment than many of the olderchemistries.

The importance of a strong microbialcommunity cannot be questioned. Theeffectiveness of various products avail-able to stimulate microbial activity canbe questioned. Become familiar withsoil microbiology and processes, checkfor duplicated independent research tosupport product claims, and test thematerial yourself to be sure it is effectiveand makes good economic sense. Butwhatever you do, don't forget thebasic tenets of successful turfgrassagronomy: adequate sunlight, drainage,air circulation, proper fertility, goodwater management, traffic control, andcultivation.

MATT NELSON is an agronomist inthe Northeast Region of the USGA GreenSection. He "bugs" superintendents totake a close look at product purchasing.

Literature Cited1. Berndt, W L. 1996. Population inter-

actions: the key to unlocking naturalpest control. The Turf Letter. 1(3):1-8.

2. Bresnahan, J. 1998. Bioject: results of1997 research trials. Presented at NewEngland Regional Turfgrass Confer-ence and Show. Providence, RI. March4,1998.

3. Chiariello, N., J. C. Hickman, and H. A.Mooney. 1982. Endomycorrhizal rolefor interspecific transfer of phosphorusin a community of annual plants.Science. 3:941-943.

4. Dernoeden, P. H. 1987.Management oftake-all patch of creeping bentgrasswith nitrogen, sulfur, and phenylmercury acetate. Plant Disease. 71(3):226-229.

5. Hall, R. 1996. Composts vs. peats:composts win. Landscape Manage-ment.35(8):14.

6. Holl, F. B. 1997. The mysterious worldof the turfgrass root zone. TurfgrassTrends. 6(11):1-8.

7. Isaac, S. 1998. Bio-stimulants and allthat! International Turfgrass Bulletin.199:9-10.

8. Karnok, K. J. 1989. The use of planthormones as non-nutritional turfgrassgrowth enhancers. Golf Course Man-agement. 57(7):28-38.

9. Kussow, W. R. 1994. Humate andhumic acid. The Grass Roots. 22(2):18.

10. Landschoot, P. 1998. Using composts toimprove turf performance. TurfgrassManagement in the Pacific North-west. 1(1):32-34.

11. Lo, C. T., E. B. Nelson, and G. E.Harman. 1996. Biological control ofturfgrass diseases with a rhizospherecompetent strain of Trichodermaharzianum. Plant Disease. 80(7): 736-741.

12. Loomis, R. S., and D. J. Connor. 1992.Crop ecology. Cambridge UniversityPress, New York, NY.

13. Moore, J. F. 1997. Let's give creditwhere credit is due. USGA GreenSection Record. 35(2):20.

14. Nelson, E. B. 1996. Enhancingturfgrassdisease control with organic amend-ments. Turfgrass Trends. 5(6):1-15.

15. Nelson, E. B. 1997. Biological controlof turfgrass diseases. Golf CourseManagement. 65(7):60-69.

16. Nelson, E. B. 1998. Turfgrass pesticidesand biological disease control: are theycompatible? CUTT. 8(4):7-9.

17.Nelson, E. B., and C. M. Craft. 1991.Introduction and establishment ofstrains of Enterobacter cloacae in golfcourse turf for the biological control ofdollar spot. Plant Disease. 75:510-514.

18. Powell, J. F., M. G. Nair, and J. M. :'Vargas, Jr. 1994. Utilization of abacterial metabolite for the manage-ment of dollar spot disease of cr:~epingbentgrass (Agrostis palustris). Phyto-pathology. 84(10):1077.

19. Roberts;. E. C. 1998. T1Jl'f"ie~earch:nature, needs, and net results. TurfgrassTrends. 7(1):1-9.

20. Senseman, R. Y. 1995. Composting:turn your eyesore into black gold.USGA Green Section Record. 33(3):8.

21. Shetlar, D. J. 1996. Field testing of bio-logical pesticides. Turfgrass Trends.5(8):1-9.

22. Stockwell, C. T., E. B. Nelson, and C.M. Craft. 1994. Biological control ofPythium graminicola and other soil-borne pathogens of turfgrass withactinomycetes from composts. Phyto-pathology. 84:1113.

23. Thompson, D. C., B. B. Clarke, J. R.Heckman, and J. A. Murphy. 1994.Suppression of summer patch in turfwith acidifying nitrogen fertility pro-grams. Phytopathology. 84(10):1085.

24. Thompson, D. C., B. B. Clarke, and D.Y. Kobayashi. 1996. Evaluation ofbacterial antagonists for reduction ofsummer patch symptoms in Kentuckybluegrass. Plant Disease. 80(8):856-862.

25. Varshovi, A. 1996. Humates and theirturfgrass applications. Golf CourseManagement. 64(8) :53-56.

26. Villani, M. G. 1996. Biorational controlagents for Japanese beetle management.CUTT. 7(1):1-1

27. Wegner, T. 1997. Bentgrass response tonon-traditional soil additives. TheGrass Roots. 25(4):58-61.

.'28. Zontek, S: 1974. Composting: alchemyin action. USGA Green SectionRecord. 12(3):9-11.

29. Zontek, S. 1997. Buyer ... beware.USGA Green Section Record. 35(1):17.

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