eOrganic Amendments - Soil Elixir or More Snake Oil?DR. BRIAN uou- PROFESSOR EMERITUS, UNIVERSITY OF sc- lAMORNA ENTERPRISES lTD.

The maintenance of high qualitysports turf under intensive useand management is an on-going

challenge. The exploitation of various de-signs of sand or amended sand root zoneswas initiated primarily to address issuesrelated to drainage and compaction, par-ticularly in regions with high rainfall andperiods of significant winter play. Never-theless, the sand-based root zone bringsits own challenges - effective water andnutrient management is essential for anyturf, but can be particularly critical on thesand base. It is not an uncommon experi-ence to see the investment of significantcapital resources in new field constructionprovide inadequate performance and poorreturns on investment as a consequenceof insufficient provision for subsequentmaintenance resources.

In addition to their more conventionaluses, modern recreational sports turf isoften subjected to a diversity of other ac-tivities, including festivals and concerts.

The impact of stage construction, vehicletraffic, 25,000 rambunctious fans and an-cillary requirements for concessions andportable toilets can result in excessivewear. Communication of the conse-quences of severe traffic and wear to usergroups is often a significant challenge. Wehave found the following conversion ofwear from conventional soccer play intoa per metre expression of foot traffic to bean effective means of communicating thepotential for damage to the turf.

On a soccer field, 70% of the play oc-curs on 30% of the field. Each player trav-els approximately 10 km/game - thatproduces 250,000 foot imprints per game(excluding the referee and goalies). At 42foot imprints per square metre per game,a 100 game season results in 4,200 footimprints per square metre! Given the ad-ditional impact of the referee, linesmen,goal tending pressures and other sidelineactivity, the real surprise is the ability tomaintain any turf under this kind of traffic.

Holistic ManagementIn assessing management options to

improve the performance of sports turf,there has been considerable interest in or-ganic amendment and supplementation ofsand-based turf in particular. In additionto the range of materials that are availablefor new construction, there are many ad-ditional products available for fertilization,topdressing and supplementation. Organicamendment use should be part of a moreholistic approach to turfgrass managementreflected in the concept of Integrated Cul-tural Management (ICM) - "the processof managing sports turf by considering andanalyzing all environmental factors, pests,maintenance processes and player-appliedstresses which affect the health of theturfgrass culture" (Puhalla, Krans andGoatley. Sports Fields; A Manual for De-sign, Construction and Maintenance.Sleeping Bear Press 1999).

In this article, I will review briefly someof the underlying principles of organic

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SPORTS TURF MANAGER • 9

amendment use and factors to consider inassessing the selection and application ofa particular amendment type.

Much of the interest in organic amend-ments is derived from:• Increased construction and use of sand-

based turf systems and increased use(and degradation) of soil-based fields.

• Greater societal emphasis on "organic"approaches to turfgrass management inthe context of "going green."

• The production of organic materialsthrough a variety of recycling pathwaysand waste streams and regulatory andcommercial pressure that perceivesturfgrass as a desirable route for the re-introduction of these materials into theecosystem.

• Increased understanding of the role andnatural benefits of soil organic matter.

• Literature that attributes multiple ben-efits to organic amendments in the turfecosystem, including provision of nutri-ents, improved soil structure, enhancedplant growth, higher stress tolerance, im-proved ability to recover from diseaseor insect damage, enhanced beneficialsoil microbial populations and diseasesuppression.The key to any good sports turf begins

with a suitable growing medium and goodturf management. A "typical" native soilincludes solid components (mineral andorganic matter) and pore space (air andwater). Levels of approximately 3% arecommonly quoted for the organic matter(OM) content of such "typical" soils. Thephysical properties of a good root zoneinclude total porosity of 35-55% distrib-uted between air-filled and capillary po-rosity, with a saturated hydraulicconductivity of 15-30 cm/hr and moistureretention of~2.5 cm/30 em depth (Sheard,R.W. Understanding Turf Management,Sports Turf Association of Ontario 2000).These basic characteristics reflect the im-portance of physical composition and per-formance characteristics of the soil profile.Based on the figures above, it might bepresumed that organic matter (OM) is arelatively insignificant component of theroot zone mix. In fact, organic mattermakes a disproportionate contribution tothe soil-plant relationship. The signifi-cance of naturally occurring OM in water

10 • MARCH 2002

On a soccer field, 70% of the play occurs on 30% of the field. Each playertravels approximately 10 km/game - that produces 250,000 foot imprints pergame (excluding the referee and goalies). At 42 foot imprints per square metreper game, a 100 game season results in 4,200 foot imprints per square metre!

relations and in stabilizing soil aggregatesand nutrient cycling has led to consider-able interest in the use of organic soilamendments, especially for sand-basedturf.

Assessing OrganicsWhat are some of the issues that need

to be considered in relation to an assess-ment of organic materials and their appro-priate use in turfgrass management?

The keys to this assessment includeevaluation of:• C/N ratios of the starting material• Soil O2 levels and gas exchange• Soil microbial populations• Physical and chemical nature of the ma-

terial, including formulation• Continuity and quality control of supply• Independent substantiation of product

claimsOrganic amendments include peat, soil,

peanut shells, sawdust, composted urbanwaste, composted sewage sludge(biosolids), organic fertilizers derivedfrom a variety of sources (including com-posts), humates and biostimulants of vari-ous types. These diverse materials arecomposed of various amounts of sugarsand starches, amino acids and proteins,cellulose, hemicellulose, lignins, fats andwaxes. It is not surprising, therefore, thatorganic sources differ markedly in physi-cal and chemical composition, rates of

decomposition and contribution to theplant-soil ecosystem.

Organic matter decomposition involvesreaction with microbes in an aerobic en-vironment to produce humus, carbon di-oxide and microbial biomass.Decomposition rates are influenced by C/N ratios, the physical and chemical for-mulation of the material and the soil con-ditions - particularly water and oxygen(good gas exchange is an essential featureof effective organic matter turnover). Formaterial with the same surface area (par-ticle size), the higher the C/N ratio of theorganic material, the slower the decom-position process will occur. High C/Nmaterials may also result in temporaryimmobilization of soil N, making it una-vailable for plant growth in the absenceof adjustments to the fertility program.Compacted or waterlogged soils will alsohave significantly poorer OM decompo-sition, and are more prone to developingmicrobial communities that include del-eterious bacterial species.

CompositionMajor interest in organic amendments

has been focused on the increasing avail-ability of compost and compost-based fer-tilizer products in the market place. In anative soil, good quality compost shouldincrease particle aggregation, improvepermeability, reduce surface compaction

and contribute to nutrient re-cycling. Thematerial should be highly organic and de-composed (or manufactured from suchmaterials). Material high in recognizablewood chips may have higher CIN ratiosand slower decomposition rates. Moisturecontents of 30-50% are generally desir-able. At levels above 60% the material ishard to handle and clumps; below 25% itmay be excessively dusty. Moisture lev-els can be critical to effective spreadingandlor ease of incorporation.

The reaction (pH) of the materialshould be between 6 and 8. In soil, pH isunlikely to be a significant issue; however,on a sand base, incorporation of compostmay influence the overall pH and couldaffect nutrient availability. Because of thehighly variable input sources that can beused for composting, it is also essential toobtain a measure of the salt content - someproducts are sufficiently high in salts tocreate additional soil problems. Composts,as with most organic materials, provideslow release, low analysis fertilizer inputsto the turfgrass system. In particular, therelease of some materials may be particu-larly low in the first year. At higher appli-cation rates, this may lead to nitrogenimmobilization. This uncertainty can be aparticular challenge for the "unprocessed"composts that tend to be more variable incomposition and less defined in terms ofrelease rates than fertilizers that have beenmanufactured from composted sources.

Other organic amendments includematerials such as humates and a range ofbiostimulants products such as kelp ex-tracts, microbial inoculants and other bio-logically derived materials. Humicsubstances are "naturally-occurring,

highly decomposed organic substanceswith very complex structures." They nor-mally include humic acid, fulvic acid andhumins, which are distinguished on thebasis of their solubility characteristics.Many of the characteristics attributed tonatural soil OM have also been associatedwith humic substances - they are not fer-tilizers, but have been correlated with in-creased mineral nutrient absorption,enhanced soil microbial populations, re-duced aluminum toxicity, increased planthormone activity, etc. The challenge withhumic substances is that because they aredefined on the basis of solubility, materi-als with similar solubility may be fromvery different sources, have differentchemical structure and properties, andhave a very different effect on plantgrowth. With such materials, it is clearlycritical to have specific and dependableevidence for the performance claims of thespecific source material.

That category of materials known asbiostimulants is probably the most chal-lenging group of products to assess. Theyare diverse in origin and offer a similarrange of benefits to other organics - nu-trient uptake enhancement, beneficial mi-crobial activity, soil structural benefits,stress tolerance, etc. Our experience withsome of these kinds of products is that theyare generally more likely to be efficaciousunder stress conditions - when growingconditions are near optimal, often littlebenefit is observed. As with any othergroup of products, independent evidenceto substantiate claims is an important partof the assessment. As James Baird of theUSGA pointed out at the recent OntarioTurfgrass Symposium, red flags should be

raised when product claims are precededby the statement "this product is so good,it didn't need any research." It is also es-sential that there be a clear rationale forthe inclusion of these organic materialsinto the management program.Biostimulants, or any other organicamendment, are not substitutes for goodturtgrass management.

Putting Organics to UseIn a sand-based sports field, and for

soils in which OM deficits are clearlyproblematic, a strong argument can bemade for the use of organic amendmentsin the initial design! construction phase,andlor as part of the long-term mainte-nance strategy. As product availability in-creases, the ability to make an informedchoice becomes more challenging. Par-ticular attention should be paid to the ba-sic rationale for including an organicamendment, to the properties of the ma-terial relative to the intended use, to ap-propriate incorporation of the material intothe overall management strategy, and par-ticularly to the scientific evidence used tosubstantiate the claims made for the prod-uct. If organic amendments have been in-corporated into your managementprogram, don't assume that is the end ofthe process. Continue to monitor the turfand its response to inclusion of any neworganic amendment and to review the out-come in the context of your overall cul-tural management. Organic amendmentsmay not be the elixir of life for your turf,but careful selection of materials withdemonstrated potential can form an im-portant part of an integrated cultural man-agement program. •

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