...Using Science to Benefit Golf

Turfgrass and EnvironmentalResearch Online

Volume 7, Number 12June 15, 2008

University of California (Davis) scientists discuss the development of a model plant systemthat allows for the rapid screening of foliar chemicals. This system has been used to deter-mine the relative efficacy and efficiency of a range of widely available foliar zinc products.Zinc was selected for these studies as it is the most widely used micronutrient in US agri-culture but has largely been ignored in turfgrass production.

PURPOSE

The purpose of USGA Turfgrass and Environmental Research Online is to effectively communicate the results ofresearch projects funded under USGA’s Turfgrass and Environmental Research Program to all who can benefitfrom such knowledge. Since 1983, the USGA has funded more than 350 projects at a cost of $29 million. The pri-vate, non-profit research program provides funding opportunities to university faculty interested in working on envi-ronmental and turf management problems affecting golf courses. The outstanding playing conditions of today’sgolf courses are a direct result of using science to benefit golf.

Editor

Jeff Nus, Ph.D.1032 Rogers PlaceLawrence, KS 66049jnus@usga.org(785) 832-2300(785) 832-9265 (fax)

Research Director

Michael P. Kenna, Ph.D.P.O. Box 2227Stillwater, OK 74076mkenna@usga.org(405) 743-3900(405) 743-3910 (fax)

Permission to reproduce articles or material in the USGA Turfgrass and Environmental Research Online (ISSN 1541-0277) isgranted to newspapers, periodicals, and educational institutions (unless specifically noted otherwise). Credit must be given tothe author(s), the article title, and USGA Turfgrass and Environmental Research Online including issue and number. Copyrightprotection must be afforded. To reprint material in other media, written permission must be obtained fom the USGA. In anycase, neither articles nor other material may be copied or used for any advertising, promotion, or commercial purposes.

USGA Turfgrass and Environmental Research Committee

Steve Smyers, ChairmanJulie Dionne, Ph.D.

Ron DodsonKimberly Erusha, Ph.D.

Ali Harivandi, Ph.D.Michael P. Kenna, Ph.D.

Jeff Krans, Ph.D.Brigid Shamley Lamb

James MooreJeff Nus, Ph.D.

Paul Rieke, Ph.D.James T. Snow

Clark Throssell, Ph.D.Ned Tisserat, Ph.D.Scott Warnke, Ph.D.

James Watson, Ph.D.Chris Williamson, Ph.D.

The Essential Nutrients for Turgrass Growth:Where's the Zinc?

Fourteen elements (excluding C, H, O)are known to be essential for plant growth: N, P,K, Ca, Mg, S, Fe, Cu, Mn, Zn, Mo, Cl and Ni.While the concentration of these essential ele-ments in plant tissues varies by a ratio of morethan 10 million to 1 from nitrogen to nickel, all areessential and plant growth will decline if they arenot present in adequate amounts.

In turfgrass management, however, onlyN, P, K, S and Fe are routinely applied; Ca and Mgare occasionally applied; and the micronutrientsZn, Mn, B, Cl, Ni are rarely applied as a targetedtreatment (7, 13). The lack of targeted applicationof Zn, in particular, is striking given that zinc isthe most widely used micronutrient in US agricul-ture (Figure 1) and is the most common micronu-trient deficiency worldwide (3). The cereal grass-es rice, wheat, and corn are particularly sensitiveto Zn deficiency and the majority of all cereal pro-duction now receives Zn as a routine practice (1).Over the past decade, there has also been a promi-nent and growing use of Zn in agronomic and hor-ticultural crops across the US.

Zinc performs a wide array of functions inplants (2) including functioning as an essentialcomponent of gene transcription and translation, astructural and functional component of a widerange of enzymes including many associated withphotosynthesis and membrane stability, and a crit-ical element for temperature, light, and heat stresstolerance (4). While all of these functions are crit-ical for turfgrass growth and development, Hull(7), has further emphasized the importance of Znfor processes of specific importance to turf pro-duction including waterlogging tolerance, hightemperature and light stress resistance, mainte-nance of photosynthesis in warm climate speciesand protection against fungal diseases.

Development of a Model System to Test FoliarFertilizers for Use in the Turfgrass Industry

Patrick H. Brown and David Burger

SUMMARY

Foliar fertilization has become a standard practice ofmany turfgrass managers. However, our understanding ofthis important class of products is remarkably poor, and forthe majority of foliar fertilizers, there is very little informa-tion on their effectiveness. This lack of information is aconsequence of both the great difficulty in conductingresearch with foliar fertilizers and a general paucity ofresearch in micronutrients in turfgrass production. Here wediscuss the development of a model plant system thatallows for the rapid screening of foliar chemicals. This sys-tem has been used to determine the relative efficacy andefficiency of a range of widely available foliar zinc (Zn)products. Zinc was selected for these studies as it is themost widely used micronutrient in US agriculture but haslargely been ignored in turfgrass production. Additionalexperiments to develop a model grass system to test a rangeof foliar products on turfgrass species are underway. Thekey observations and findings are:

Foliar fertilizers are a critical component of modern turfmanagement and yet there is a paucity of information ontheir use. Foliar Zn nutrition has not been examined in turf-grass.

The model plant test system developed here is a power-ful approach to screening large numbers of materials undercontrolled conditions and provides essential preliminaryinformation to guide subsequent field testing.

Foliar Zn formulations vary greatly in their efficacy andefficiency. The solubility of the chemical form of zinc in thefertilizer product is a primary determinant of efficiency ofthe product.

The specialty foliar Zn complexed and chelated productssold as liquids vary from moderate to excellent efficacy andwere generally more efficient than non-complexed Zn salts.

Zinc has been overlooked as a component of turfgrassfertility management and further research and field testingis warranted. Foliar fertilizers can play an important role inZn management, however not all foliar fertilizers are equal-ly effective.

PATRICK H. BROWN, Ph.D., Professor of PlantNutrition; and DAVID BURGER, Ph.D.,Professor of Plant Science; Department of PlantSciences, University of California, Davis, CA

1USGA Turfgrass and Environmental Research Online 7(12):1-10.TGIF Record Number: 137274

In agricultural crops, Zn deficiency occursmost prominently in high pH soils, but also occursin soils with high levels of reactive organic matterand in coarse-textured, sandy soils of low mineralnutrient content. Zinc deficiency in US agricultureis observed more frequently in the predominantlycalcareous soils of the western and mountainstates, the north central region, and in the acid,coarse textured soils of the southeastern andsouthern states like Florida. Globally, it is thegrass species, wheat, rice, and corn that utilize thegreatest amounts of fertilizer zinc. Zinc seed andstarter fertilizers are now utilized in much of thecorn production in the US and in a large percent-age of global rice and wheat production (1).

Environmental conditions and fertilizermanagement can also result in Zn deficiency. Incorn and in a range of horticultural species, Zndeficiency can occur in early spring when plantgrowth has initiated, but soil temperatures are low

and/or the soil is saturated with water. In rice,lack of soil oxygen, excess levels of soil Fe caninduce Zn deficiencies while in many species,high temperatures and high light levels canincrease the metabolic demand for Zn andincrease the impact of a latent deficiency (4). Thechoice of nitrogen source can also exacerbate theoccurrence of Zn deficiencies with the use of coat-ed urea materials having a significant negativeeffect on Zn deficiency in rice (11). The applica-tion of excess phosphorus is also well known toinduce Zn deficiency in a wide range of croppingsystems (9).

The State of Knowledge Regarding Zinc inTurfgrass

The functions of Zn in plants, its specificimportance for grass species and the conditionsunder which modern greens are managed all sug-

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Figure 1. Total Micronutrient consumption for select micronutrients over the period 1995 to 2004. This data issourced from fertilizer tonnage sales reported to respective state agencies and Plant Food Control Officers in eachstate. Values shown are gross total nutrient consumed and do not consider form of the element or respective nutri-ent solubility. Micronutrients incorporated into bulk blended, finished fertilizers and other specialty fertilizers are notincluded in these data. Data courtesy of the American Association of Plant Food Control Agents (AAPFCO).

gest that Zn nutrition should be of concern for golfcourse superintendents. There are, however, veryfew scientific reports of turfgrass response to fer-tilizer Zn additions (13) and little to no informa-tion on the identification and correction of Zndeficiencies can be found in the widely cited turf-grass management publications (8, 9, 10). Thislack of published proof of a benefit of fertilizer Znon turf production, however, should not be inter-preted as proof that there is no need for fertilizerzinc (7).

Though the experimental data is lacking, itis generally accepted that Zn is required in turf-grass leaves at concentrations of from 30 to 80parts per million (microgram per gram dry matter)depending upon cultivar (7). The true relevance ofthese 'typical' concentrations for optimal plantproductivity remains unknown. In agriculturalspecies, symptoms of Zn deficiency includereduced growth and vigor, often associates with ashortening of the internodes (distance betweenleaves) resulting in a shortened brushy appearanceof emerging tillers (Figure 2). Plants may showyellowing and interveinal chlorosis (Figure 3) ,

patchy necrosis or leaf bleaching (Figure 4).Occurrence of a deficiency in a field or turf areacan often be irregular, corresponding to changesin soil type, waterlogging, or localized high heatand high light stress.

While visual symptoms can be used tohelp identify a nutrient deficiency, it should berecognized that the goal of a good agronomist,horticulturalist, or superintendent is to avoid theoccurrence of any deficiency. Once a deficiencyis severe enough to be identified by visual symp-toms, invariably growth, aesthetic appearance,and stress resistance have all been compromised.To ensure optimal productivity, it is essential thatnutrients removed from the ecosystem in clip-pings or harvested yield, leaching, and erosion bereplaced.

The likelihood that an element such as Znwill become deficient can also be determined withthe help of soil and plant testing. While specificguidelines do not exist for the interpretation ofsoil and plant tests in turfgrass, there are certainconditions including high soil pH (>8), high sandcontent, and declining tissue Zn concentrationsthat are known to exacerbate the occurrence of Zndeficiency. Given the lack of any alternative, thetissue and soil standards established for corn maybe used as a guide for Zn management in turf-grass.

Given the known functions of Zn in plants,the soil and environmental conditions that resultin Zn deficiency and the widespread occurrence ofZn deficiencies in US agriculture, it is perhapssurprising that Zn deficiency has not been morewidely reported in the US turfgrass industry. Thismay in part be a consequence of the lack of cleardescription of Zn deficiency in turfgrass species,particularly at marginal levels of deficiency, and iscomplicated further by interactive effects of heatstress, cold temperatures, and water logging onthe expression of Zn deficiency.

Zinc is well known to have beneficialeffects on plant tolerance to stress conditions (4),so it is probably not a coincidence that many ofthe foliar products sold on the basis of their 'bios-timulant' or 'stress protection' function actuallycontain significant levels of Zn in addition to a

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Figure 2. Zinc deficiency in corn showing interveinalchlorosis, bleaching and shortening of internodesresulting in stunted compact growth. (photo courtesyof J.E.Sawyer http://extension.agron.iastate.edu/soil-fertility/photos/photossdef.html)

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Material Name1 Manufacturer or Concentration Overall CommentsDistributor2 (ppm)3 Ranking4

EleMax Super Zinc FL 1-0-0 Yara 500 1 40% Zn as zinc oxide. Miscible in water, solubility limited.

Neutral Zinc MontereyAgChem 400 1 52% zinc oxide and sulfate.

RNA Microphos RNA Corporation 400 3 52% Zn as phosphate/oxide mixture. Miscible in water, solubility limited.

Zinc Fulvic Acid Wilbur Ellis 400 4 7% zinc fulvic acid complex. Moderate effectiveness

Zinc sulfate 400 5 36% zinc sulfate.

Krystal Klear Zn Lidochem Inc. 400 6 9% synthetic chelated Zn. Moderate and consistent response.

Zinc Lignosulfonate Wilbur Ellis 400 6.5 7 - 10% zinc sulfate ignosulfonate. Moderate effectiveness, some variability in response.

Bio-link ZN Westbridge 400 6.6 8% Zn, hydroxy-carboxylic, amino acidcomplex. Consistent and effective.

RNA Zinc nitrate 400 7.0

RNA Microphos RNA Corporation 5,000 7.2 52% Zn as phosphate/oxide mixture. Miscible in water, solubility limited.

BioMin Zn JH Biotech 400 7.3 7% zinc sulfate, citric acid, glycine. Consistent and effective.

Zn Metalosate Albion 400 7.3 7% Metalosate amino complexed Zn. Consistent and very effective.

BioNutrient Zn+ Wilbur Ellis 400 7.3 8% zinc. Consistent and very effective.

Zinc EDTA 400 8 10% EDTA complexed Zn. Very effective and very consistent.

Neutral Zinc Monterey AgChem 1,860 8 52% zinc oxide and sulfate.

Zinc sulfate 1,500 8 36% zinc sulfate. Good effectiveness.

Foli-GroNZn Wilbur Ellis 400 8.4 5% Zn as Zn nitrate with urea and urea ammonium nitrate. Very effective and very consistent.

FloratineZicron-F FloratineBiosci 400 8.6 6% zinc carbon complex. Very effective and consistent.

Zinc Manniplex Brandt Chemicals 400 9 7% zinc carbon complex. Highly effective very consistent response.

11 = no significant difference from water control; 2-4 = measurable but small increase in tissue Zn; 5-7 = consistent and significant increase in tissue Zn, goodeffectiveness; 8-10 = consistent and very significant increase in tissue Zn, superior effectiveness.

2 Mention of a product trade name or commercial enterprise does not imply endorsement of this product or commercial enterprise by the author or theUniversity of California, Davis. If a distributor is not identified then the product can be assumed to be widely available.

3 Materials were applied to foliage only, at either a standard 400 ppm concentration in spray solution . Where 400 ppm Zn was not the approximate field appli-cation rate, experiments were repeated at the higher field rate. Experiments were conducted in a non-grass system and products and rates listed may not belabeled or appropriate for turfgrass use.

4 Products shown with numerical rankings that differ by 0.9 or greater are significantly different at the 0.05% level of significance.

Table 1. Ranking of various foliar zinc products in common commercial use

host of other compounds of less certain physio-logical function.

With the widespread adoption of theUSGA sand green, the development of higher den-sity, faster growing turfgrass cultivars, theenhanced stress caused by lower cutting heightsand the potential effects of global warming, Znmanagement in turf should be re-examined.

Supply of Zinc to Turf and the Evidence for theUse of Foliar Fertilizers

Whereas the majority of Zn fertilization inagronomic crops occurs as a soil or seed applica-tion, increasingly in horticultural and other highvalue species, Zn is applied as a foliar fertilizer.Foliar chemicals are used widely in horticulturefor a number of reasons, the most common ofwhich is a perceived advantage in control of appli-cation timing to match crop demand (3). Foliarsare also superior for the correction of deficienciesin high pH, Zn-fixing soils and may be advanta-geous in supplementing excessive nutrientdemand during rapid plant growth (spring andearly summer flushes), during periods of impairednutrient uptake due to low temperature or soilflooding (early spring), or as a consequence ofreduced nutrient uptake during periods of limitedroot growth (summer stress in cool-season grasses).

While foliar fertilizers have gained accept-ance in turfgrass management, our understandingof the principles that determine the efficacy offoliar nutrients is extremely poor. The factors thatultimately determine the nutrient use efficiency(NUE) of a foliar formulation are quite compli-cated and are dependent upon many physical, bio-logical, and environmental factors including:

The physicochemical characteristics of the formu-lation:

Effect of drying time, crystallization, solubilityand deposition uniformity (concentration) on thequantity and distribution of applied nutrient ele-ment on the leaf surface

Effect of chemical formulation and physicalproperties on penetration and distribution of nutri-

ent element within sub-cuticular tissuesEffect of formulation on biological utilization

of absorbed elementEffect of formulation on short- and long-dis-

tance transport of the element away from the siteof application.

Environmental and biological condition present atapplication:

Leaf temperature, relative humidity, windspeed, sun exposure, application techniques

Species, leaf age, leaf structure and composi-tion, and leaf damage

Drought, disease, nutrient status, phenologicalstage

Biological complexation, transport processes,compartmentation, sequestration, etc.

The great complexity of factors that influ-ence the effectiveness of a foliar fertilizer makesthe conduct of field experiments extremely diffi-cult to perform and interpret, and misleadingresults can easily be obtained. Studies of foliar Znproducts are particularly difficult to interpret sinceZn has a tendency to adhere irreversibly to leafsurfaces making it impossible to distinguishbetween surface adhering (non-functional) Zn andfunctional Zn that has entered the leaf. To over-come these problems and to provide a robust andinterpretable test of fertilizer, test systems areneeded that avoid the complications of environ-

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Figure 3. Zinc deficiency induced interveinal chloro-sis and bleaching in warm season grass species.

ment and Zn contamination while simultaneouslyallowing for a determination of the degree towhich the applied product is absorbed by the leafsurface, transported within the plant, and utilizedfor metabolic activities.

In the following, we describe the develop-ment of two model test systems to address theseissues. The first of these systems uses a non-grassspecies (Arabidopsis thaliana) that is the mostwidely used species in plant nutritional, biochem-ical, and genetic research. This species is selectedas it has a short 45-60 day life cycle (cultivardependent) and a very distinct vegetative/floraltransition period which allows for the applicationof materials to leaf tissue with subsequent recov-ery of the applied element in the floral tissues thus

avoiding the potential for contamination. Thesmall size of the plant also allows for large num-bers of replications to be conducted.

In the second model system, we utilizeannual bluegrass (Poa annua L.) and creepingbentgrass (Agrostis stolonifera L.) grown in anartificial solid media and use a repetitive cuttingapproach to determine Zn uptake and transportrates.

Materials and Methods

Model System 1

Arabidopsis thaliana seeds were plantedin trays of eight, 1 inch x 1 inch seedling pots in asoil mixture consisting of 80% fine quartz sand,20% potting soil mixture. Each tray representsone replicate and all treatments were replicated atleast 6 times in each experiment. The entireexperiment was then replicated 6 times.

A total of 18 common commercial inor-ganic salt and liquid zinc formulations were testedduring the 6 replicate experiments. Within a sin-gle experiment, all treatments were replicated atleast 5 times with a total of at least 30 plants. Thenumber of replicate experiments, however, variedwith treatment from a single replicate experiment(field rate applications) to as many as 6 replicateexperiments for some materials (control, 400 ppmZn sulfate, and 400 ppm NZn).

Control, 400 ppm Zn sulfate and 400 ppmNZn treatments were included in all trials to rep-resent non-effective, intermediate, and highlyeffective products and to provide for internal stan-dardization across all experiments. Rankings ofeach material in comparison with these standardsand in comparison with other materials includedin the same experiment, were then integrated intoa final summary table (Table 1).

Each formulation was applied at day 25-35. At this time, all plants were in the vegetativestage of growth, and any early reproductive tis-sues were removed. Spray applications wereapplied to leaves to runoff using a controlled mistapplication with the addition of Silwet L-77

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Figure 4. Zinc deficiency in wheat showing charac-teristic necrosis and chlorosis. (Photograph courtesyof CIMMYT http://wheatdoctor.cimmyt. org/index.php?o p t i o n = c o m _ e a s y g a l l e r y & a c t = p h o t o s & c id=271&Itemid=33)

spreader. The soil surface was protected fromdirect contamination with plastic and lanolin bar-riers. Independent tests using the tracer ion, rubid-ium, confirmed that no foliar spray materialsentered the soil.

Two experimental approaches were used:1) application of all materials at a 400 ppm Zn inthe final application solution, or 2) application ofthe material at the specified field application rate.

Fourteen to 18 days after spray applicationas plants commenced senescence, reproductivetissues were collected and analyzed. The leaf tis-sue that had received the foliar spray was notincluded, as these leaves would have been con-taminated with non-functional residual Zn. Thestructure of the Arabidopsis plant, growth condi-tions and the manner in which the experiments

were conducted make direct contamination ofreproductive tissues by leaf-applied Zn extreme-ly unlikely. Increases in tissue Zn as a result offoliar application observed in these trials representZn that has been both absorbed by leaves andtransported to the reproductive tissue.

Model System 2

The following system is under develop-ment and has not yet been utilized for trials offoliar fertilizers.

Seeds of annual bluegrass (Poa annua L.)and creeping bentgrass (Agrostis stolonifera L.)were placed on the surface of Oasis® Horticube®Growing Medium blocks that measured 3.8 cmwide x 3.8 cm deep x 1.3 cm tall. The blocks had

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Figure 5. Model growth system designed for testing of foliar fertilizer and non-fertilizer products. System allowsfor repeated cutting and resampling of each 1.5 x 1.5-inch experimental unit.

been washed in running deionized water for atleast 60 minutes and drained via vacuum beforeuse. Once seeds had been sown, the blocks wereplaced in 7.5 cm x 7.5 cm x 10 cm tall boxes and50 ml of the test solution was added. Lids wereplaced on the Magenta box and placed in an incu-bator kept at 20°C with a 16/8 hour light/darkphotoperiod. An example of this system is provid-ed in Figure 5.

Results and Discussion

Results of the six replicate experiments areprovided in Table 1. The data shown represents anintegrated assessment of the ranking of each mate-rial in contrast to the water (control), 400 ppmzinc sulfate (intermediate effectiveness) and 400ppm NZn (high effectiveness) standards. Resultsillustrate that the efficacy of spray materials variessignificantly between materials and is stronglyinfluenced by concentration of Zn present in thespray solution.

Solubility Matters

The relative efficiency with which a spe-cific product enhances Zn in the model plant canbe determined from experiments in which thematerials were provided at a standard concentra-tion of 400 ppm. Here we selected 400 ppm asthis standard value as it represents the applicationrate used in the majority of the liquid foliar for-mulations. Using these criteria, it can be seen thatmaterials that are largely insoluble miscible sus-pensions of Zn oxides and phosphates includingEleMax, Neutral Zn, RNA Microphos, are inef-fective or only marginally effective at the 400ppm rate. These materials all result in the depositof a characterisitic white powder on the surface ofthe leaves which is unacceptable for turfgrassapplications.

Among the liquid foliar materials, all wereeffective at significantly increasing tissue Zn con-centrations. Efficacy varied from moderate for Znsulfate- and Zn lignosulfonate-based materials togood (KrystalKlear, Bio-link), and very good

(BioMin, Metalosate, BioNutrient) for the materi-als containing amino acids and other synthetic ornatural complexers. Several sugar- and polysac-charide-based Zn formulations (Floratine Zicron-F and Brandt Manniplex Zn) were shown to beconsistently superior across all experiments.Additionally, NZn, which does not contain anyorganic complex or chelate material, also per-formed at a superior level.

Efficiency Does Not Equal Efficacy

Several of the foliar materials tested hereutilize field application rates that are substantiallyhigher than 400 ppm. These materials are all inor-ganic forms of Zn (zinc sulfate, zinc oxide, zincphosphate, and mixes thereof) that are generallynot provided as liquids (unless solubilized by avendor), and none contain any putative chelator orcomplexing molecule. Field rates of these materi-als range from 1,500 to 5,000 ppm or 4- to 12-foldhigher than the 400 ppm typically used for spe-cialty liquids. On a cost basis, these materialsmay still be cheaper than the liquid formulationseven when applied at substantially higher rates.When applied at field rates, however, all of thesematerials improved performance.

Zinc Microphos, a Zn phosphate/oxide-based material improved significantly when pro-vided at 5,000 ppm, however it was still deemedan unacceptable product for turfgrass use as it lefta heavy white precipitate on the leaf surface thatpersisted for several days. Both Neutral Zn andZn sulfate improved dramatically in performancewhen concentration was increased from 400 ppmto 1,860 and 1,500 ppm, respectively. Theimprovement in performance of Neutral Zn mighthave been a consequence of the zinc sulfate con-tained in that product.

The Bottom Line

The development of this model system hasallowed us to contrast 18 materials in a series of 6experiments over a 6-month period and has pro-vided reproducible and valuable results. Thiscould not have been accomplished in a field set-

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ting and illustrates the utility of this approach.These results must be considered in light of thefact that experiments were not conducted on turf-grass under playing conditions, and we cannot notguarantee that identical results will be achievedunder 'real' conditions.

However, on the basis of literature and ourexperience, it is expected that materials rankedsuperior in these trials have the greatest potentialefficacy, and we hypothesize that these superiormaterials will never be less effective than thosematerials ranked lower in the accompanying table.We are now developing a model system basedupon grass species and will be replicating this Zntrial and commencing additional trials with Fe andother non-fertilizer products in the comingmonths.

Results of these trials suggest that many ofthe foliar Zn materials available for use in themarketplace work to varying degrees and thatmany of the higher priced liquid products, espe-cially those 'complexed' with sugar and polysac-charide molecules are highly effective.

While it is apparent from this research thatthe use of a heavy dose of an inorganic, low solu-bility product can result in effective supply of Znto plants at a competitive price, managers mustalso consider issues of ease of use, aesthetics, andbe concerned with the total amount of Zn that isadded to the environment.

Given the importance of Zn to all agricul-tural cereals and the conditions under which mod-ern turfgrass is managed, it would be surprising ifZn deficiency is not more widely prevalent in theturfgrass industry than is currently recognized.The presence of substantial amounts of Zn inmany foliar blends including 'biostimulant' and'stress response' materials is perhaps the clearestevidence that there could be benefit to the turgrassindustry of a targeted study of the management ofZn in turfgrass productivity.

Acknowledgements

The authors wish to thank USGA’sTurfgrass and Environmental Research Programfor financial support of this project.

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