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Organics Like It Hot NaturalTurf Management, Part 6

By Marc McMullen

Since the late 1960s, when the firstreported signs of turfgrass diseaseresistance were discovered, the

turfgrass industry has been challengedto find new ways of suppressing increas-ingly resistant types ofdisease pathogens.Growing concerns about the effects ofpes-ticides on the environment have made theuse of new, improved fungicides a diffi-cult direction for the turfgrass industryto head.

A new direction the turfgrass industryis taking is in the development of diseaseresistant cultivars of turfgrasses. Anotherpath of study has led the industry tothe use of natural organic fertilizers andcomposted materials for disease sup-pression. This direction emphasizes theuse of organic fertilizers and compostedmaterials not only as a nitrogen source,but also as a way to increase in the soil"antagonistic microorganisms" that canaid in the biological control of turfgrasspathogens.Natural Organic Fertilizers

With natural organic fertilizers, youapply a nitrogen source that is containedin complexorganic compounds.These com-pounds must first be decomposed bymicroorganisms in the soilbefore they canbe used by turfgrass plants. Since thedecomposition is moisture and temper-ature dependent, it increases as soiltemperature rises.

This dependency on microorganismsto break down the organic compoundsresults in slower nitrogen release rates.Beard (1973) documented that charac-teristics commonly associated withorganic carriers include:

(a) a medium initial release rate,(b) low water solubility,(c) minimum foliar burn potential(d) higher costs per unit ofnitrog~n,(e) reduced loss by leaching,(D lower nitrogen analysis and(g) longer residual periods of four to

eight weeks.

24 sports TURF

These characteristics can be put to gooduse to control nitrogen release and burnpotential during the higher tempera-tures of the summer months.

The aim of fertilization in the summeris to maintain growth at lower rates. Inthe fall, natural organic fertilizers canuse the lower temperatures to have a slowrelease mechanism and aid in the hard-ening-off process when limited shootgrowth and maximum root growth arethe goals.

One of the reasons natural organicfertilizers are not used in large quantitiesis that they are thought to produce alower quality of turf than syntheticnitrogen sources. This can be true duringthe initial ratings and clippings yields. Inresearch done at the University of Mas-sachusetts, slow release natural organicmaterials including Hagerstown sludge(5-2-0),Milorganite (6-2-0),and Ringer TurfRestore (10-2-6)were compared to ureas(45-0-0) for quality and clipping yields.

The synthetic nitrogen carrier startedout as a superior source of growth andquality. As the experiment continuedinto mid-July, the Hagerstown sludgeproduct showed superior clipping yieldsand quality ratings. The increase inquality and clippings can be attributedto the increased nitrogen released asthe soil microorganisms decomposed theorganic compounds. The increase in yieldand quality can also be attributed tothe rise in soil temperature from earlyJune to mid-July.

Another problem associated withsome natural organic fertilizers is highlevels ofheavy metals. Realizing this, theEnvironmental Protection Agency reg-ulates the amounts of heavy metals inthese organic fertilizers.

Many other fertilizers also containthese heavy metals, but are not requiredto meet the stringent quality controlstandards like natural organic fertil-izers. Mackintosh and Cooper (1993)documented that fertilizers derived from

leather tankage material may containchromium at levels greater than 15,000ppm, compared to sludge-based fertilizersthat typically contain less than 100 ppm.Fertilizers derived from ironite havebeen found to contain more than 20,000ppm of arsenic, compared to less than tenppm in sludge-based fertilizers. Rockphosphate mined to manufacture superphosphate for blended fertilizers cancontain cadmium levels around 100 ppm,while sludges typically contain less thanten ppm of cadmium.

The thought that natural organic fer-tilizers are high in heavy metals mightbe a concern, but these heavy metalscan also show up in higher levels inmany other types of fertilizers.

The fact that these organic fertilizersare slow release can also be a positivefactor in the heat of the summer andduring hardening off in the late fall.

Disease SuppressionNatural organic fertilizers and/or

composted materials have been shownto suppress some turfgrass pathogens.This occurs due to the presence ofmicro-bial organisms. Gallant (1993) docu-mented that these microorganisms areantagonists that, when found in sufficientnumbers, can interfere with the activi-ties of plant pathogens. Compostedmaterials therefore not only strengthenturfgrass, but also provide microbialantagonists that can suppress diseases.

Organic fertilizers can lead to dis-ease suppression on many types ofgrasses. On bentgrass greens, Soikaand Sanders (1990) documented thatexcellent suppression of brown patchwas obtained with Ringer ExperimentalI, Ringer Experimental 2, Sustane andASC 66912. Ringer Experimental I andASC 66912 provided suppression ofdollar spot that was statistically dif-ferent from the check and not statisticallydifferent from the Dyrene standard.Plots treated with Dyrene and ASC

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66912 were rated highest in overall turfquality.

These reports showed that the diseaseswere not suppressed completely, but ifconditions were right, some organic fer-tilizers could suppress the dollar spot andbrown patch pathogens as well as fungi-cides.

This type of result was obtained in asimilar study at the University of RhodeIsland. Hull, Jackson, Liu and Alliare

Figure 1. Turfgrass quality inresponse to fertility programs.Arrows indicate fertilizerapplications.

(1991) documented in a test .- 8....----------------------,with eight composted organic ~ g ~~F~~ci66I~~.~. UREA

wastes and two organic g ~~:g~:~~ggg~~:~:~~LGnitrogen fertilizers that inci- g 6 • 2lbs. N/1OO0sq. ft. RIN

odence of dollar spot wasreduced somewhat by fer-tilizers having higher levelsof soluble N.

This does not necessarilyshow that organic fertilizerssuppress the dollar spotpathogen, since one ofthe cul-tural management practicesto reduce dollar spot is toincrease nitrogen. So, it is hard to saywhether the disease is reduced by the

antagonistic microorganismsproduced by the organic fer-tilizers or by the increase ofnitrogen in the soil.

But, in the case of brownpatch an increase of nitrogendoes not reduce the path-ogen. Actually, a higheramount of nitrogen canincrease the severity of thedisease. Therefore, theremay be some antagonisticmicroorganisms produced

91...---------------------.

i~....-._.. _u

.g>3:::J1-2

1OIT--------------".:----------l

o NO FERTILIZERD 1 lb. N/1ooo sq. ft. UREA62 Ibs. N/1ooo sq. ft. HAG<©> 2 Ibs. N/10oo sq. ft. MIL• 2lbs. N/10oo sq. ft. RIN

20 Jun 18 Jul 15Aug1991

12 Sep 10 Oct

T"""

---en@A"0CD>=0>2c'0..,9-<30...L..- --'

20 Jun 12 Sep 10 Oct18 Jul 15Aug1991

Figure 2. Clipping yield in responseto fertility programs. Arrows indicate

fertilizer applications.

by the organic fertilizers working toresist the brown patch pathogen.Topdressing Strategies

With more and more golf courses onfrequent topdressing programs, studieshave been done to test disease suppres-sion using either organic fertilizers or com-posted materials. As topdressing mate-rials are added frequently to tees andgreens, organic fertilizers and compostedmaterials can be incorporated into the

continued on page 26

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Organics Like It Hotcontinued from page 25topdressing to suppress diseases anddecrease the amount of fungicides neededto control these pathogens.

Nelson and Craft (1989) documentedin a study on creeping bentgrass greensthat topdressings amended with eitherRinger Compost Plus, Ringer GreensRestore or Sustane were effective insuppressing brown patch. Control ofbrown patch with these materials was asgood as a high rate of the fungicideBanner. Also, topdressing prepared froma sludge and leaf compost significantlyreduced brown patch severity as comparedwith untreated plots.

Most composts used in this studywere one year old or younger. Theseimmature composts were ineffective,particularly the sewage sludgecomposts.

A similar study also was done on anannual bluegrass putting green for dollarspot suppression. Nelson and Craft (1989)documented that only topdressingamended with Ringer Compost Plus andRinger Greens Restore significantly sup-pressed dollar spot development. Thelevel of disease control was as good as thatprovided by Banner. Topdressing

formulated with composts were ineffec-tive in suppressing dollar spot. Itwas con-cluded that some organic fertilizers mayreduce damage from dollar spot whenapplied to putting greens as a topdressing.The amount of disease suppression mayhave increased if the rates ofnitrogen wereincreased.

Another study of disease suppressionusing organic fertilizers was done on aperennial ryegrass stand. Nelson andCraft (1989) documented that topdressingamended with Sustane significantly

suppressed red thread development ascompared to untreated plots. Topdressingformulated with composts were ineffec-tive in suppressing red thread. Itwas con-cluded that some organic fertilizers mayreduce damage from red thread whenapplied as a topdressing.

Eric Nelson (1992) did an extensiveamount of research on the suppressionof diseases using topdressings amendedwith organic fertilizers and composts.There was no one product that significantlysuppressed all types of diseases. The

Table 2Biological Suppression of Various Turfgrass Diseases

With Compost-Amended Topdressinqss% Disease Control

Red ThreadTopdressing Amendment Dollar Spot Brown Patch Typhula Blight Pythium Root Rot

47.4

Brewery Compost

None

52.6*Greens Restore'SustaneSludge Compost A

Leaf CompostHorse Manure CompostSludge Compost BFungicide Standard'

65.7* 66.7* 8.5 0.030.3 75.0* 78.7* 15.234.3 41.7* 14.9 69.7*10.1 25.0 36.2 69.7*

4.5 38.9 0.00.0 0.0 0.0 54.5*0.0 8.3 0.0

97.0* 88.9* 33.3

57.9*36.8

42.1

a Determined 30, 13, 27, and 19 days post-application for Dollar Spot, Brown Patch, Red Thread and Pythium Root Rot, respectively. Gray snowmold evaluated in the spring (April), 6 months after the last fall application.

b Greens Restore is an uncomposted organic fertilizer composed of plant and animal meals.c Fungicide standard for all diseases except Pythium Root Rot consisted of Banner applied at the rate of 4 oz./1,000 ft'. For Pythium Root Rot.

Subdue was applied at the rate of 2 oz./1,000 ft'.Numbers followed by an (*) indicate statistically significant levels of disease control as compared with untreated plots.

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likely reason is that each product nurturesa different type of antagonistic micro-organism, and these microorganismsare specific to one type of disease. If thisis hue, then reproduction of these microor-ganisms could produce a biological methodof suppressing that specific disease. Also,where the organic fertilizers do sup-press diseases, they do as well if notbetter than the fungicide standard for thatdisease. Thus, if you used the rightorganic fertilizer for a specific disease, youcould reduce the amount of fungicideneeded to control it.

If the composted material is older, itseems to suppress higher amounts ofdiseases. Nelson (1991) documented thatsuppression of a number of turfgrass

diseases by composts occurs if the com-post is well aged or mature. Our researchindicates that the level of disease sup-pression inmature composts is due to theintense microbial activity associatedwith these composts.Composts Corning of Age

Composts, if managed properly, canbe a beneficial part of turfgrass man-agement. With the increased pressure onlimiting the amount of organic wastes(mostly leaves and grass clippings),compost piles can be an alternative to thelocal landfill.

If the com post pile is allowed tomature and the right microbial activityis present, compost can be a source of

Table 2Fertilizer Products Used in the Study

Product Nitrogen SourceHagerstown (5-2-0) Heat-dried sewage sludgeMilorganite (6-2-0) Heat-dried sewage sludgeRinger Turf Restore (10-2-6) Hydrolyzed poultry feather meal, blood

meal, wheat germ and bone meal.Urea (45-0-0) Synthesized from ammonia and carbon

dioxide

disease suppression and a reduction offungicide usage.

The use of natural organic fertilizerscan have many benefits in comparison tothe normal sources of nitrogen. Naturalorganic fertilizers are slow release sourcesof nitrogen with low foliar bum potential.Used at the right rates, they can give asgood, if not better, quality ratings and clip-ping yields than synthetic sources.

The amount of heavy metals thatwas once a big drawback to organic fer-tilizers is now greatly reduced. The useof some organic fertilizers and evensome mature composted materials ineither amended topdressing form or asa straight nitrogen source can be a toolin disease suppression.

As environmental concerns mountand more and more of the pesticides wetake for granted are removed from ourshelves, biological means of suppressingdiseases will need to increase. With theuse of organic fertilizer, fungicide use canbe reduced and the cost of turf manage-ment reduced.

The type of microbial activity pro-duced by organic nitrogen sources needsto be researched more, so the results indisease suppression can be more practical.Until this occurs, the use of organic fer-tilizers will remain minimal. 0'-,.

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June 1996 27