SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
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FIELD SCIENCE 14 SportsTurf | February 2016 www.sportsturfonline.com moves out of the polymer coating into the soil. Eventually, over 8 to 52 weeks, all of the fertilizer is dissolved from inside the polymer coating. Polymer-coated sulfur-coated urea is produced with a poly- mer layer around the sulfur layer instead of a wax sealant. The polymer layer provides more protection and results in even more predictable and uniform nutrient release. Water must diffuse through the polymer coating, dissolve the urea through imperfections, micro pores and cracks in the sulfur coating and then diffuse back through the polymer coating into the soil. Another brand layers the polymer coating on the urea granule with a sulfur coating and wax sealant on the outside of the particles. With either production method, release rates are longer and less temperature dependent, and surge growth after application is reduced. LABELS All fertilizer labels will provide a Guaranteed Analysis. The Guaranteed Analysis is the manufacturer's guarantee for mini- mum percentage of nutrients claimed for the product. In the guaranteed analysis, nitrogen must be guaranteed as Total Nitrogen (N). If chemical forms of nitrogen are claimed, the forms will be shown in the Guaranteed Analysis. No particu- lar order of forms of nitrogen is required. When a fertilizer contains determinable forms of nutrients that are slowly avail- able and a slowly available claim is made, then the guarantee is shown as a footnote, rather than as a component in the guaranteed analysis. See below. To determine the slow release component or percent divide the slowly available nitrogen by the total nitrogen and multiply by 100. GUARANTEED ANALYSIS Total Nitrogen (N) x% x% Ammoniacal Nitrogen x% Nitrate Nitrogen x% Urea Nitrogen* x% Other Water Soluble Nitrogen x% Slowly Available Water Soluble Nitrogen x% Water Insoluble Nitrogen *x% Slowly available urea nitrogen from _______ (nitrogen source material) Forms of nitrogen and their sources that may appear in the Guaranteed Analysis include: Ammoniacal Nitrogen sources include monoammonium phosphate, diammonium phosphate, ammonium sulfate, ammonium nitrate, urea ammonium nitrate, ammonium polyphosphate, calcium ammonium nitrate and ammonium thiosulfate. Nitrate Nitrogen sources include urea ammonium nitrate, ammonium nitrate, potassium nitrate, calcium nitrate and sodium nitrate. Urea Nitrogen can come from sources that include urea ammonium nitrate, urea, urea triazone, sulfur coated urea and polymer-coated urea. Other Water Soluble Nitrogen can come from sources that include methylene urea, urea triazone, methylene diurea, dimethylenetriurea, dicyandiamide, triazone, ureaform and urea-formaldehyde. Slowly Available Water Soluble Nitrogen sources include methylene urea, urea triazone, methylene diurea, dimethylenetriurea, dicyandiamide, triazone, ureaform and urea-formaldehyde. Water Insoluble Nitrogen sources that include ureaform, isobutylidene diurea, urea-formaldehyde, feather meal, blood meal, corn gluten meal and other natural organic materials. So, which fertilizer source is the best? First and foremost, you must practice sound agronomic practices: perform soil and/or tissue testing, improve soil condi- tions and correct detrimental cultural practices. Plan nutrient management based on environmental and seasonal influences such as temperature, rainfall and/or irrigation, use intensity and proximity to water bodies. The type of turfgrass, expected qual- ity and budget also influences management strategy. In addition to fertilization management, you may wonder if the use of biostimulants will produce higher quality turf. Dr. Keith Karnok from the University of Georgia says turfgrass managers recognize biostimulants to be a product/ material that is non-traditional in that it is not a fertilizer or pesticide per se, but is applied to the soil or plant in hopes of improving turfgrass performance (usually roots and shoots). Humic acid, seaweed extract, salicylic acid and plant hormones are commonly used turf biostimulants. Research has shown that biostimulants may improve turfgrass response to envi- ronmental or culturally induced stress conditions; however, it needs to be applied before the stress condition. Predicting stress conditions, such as summer stress, drought or disease may be pertinent in the successful use of biostimulants. Researchers at Virginia Tech (Drs. Xunzhong Zhang and Richard Schmidt) have performed studies on turf response to various biostimulants in regard to enhanced root and shoot development, drought tolerance, salt tolerance, disease resis- tance, UV light tolerance and heat tolerance showing that biostimulants can improve turf health and stress tolerance. The consensus regarding use of biostimulants is to research products diligently, avoid products that make boastful claims without evidence from scientific studies performed by indepen- dent or university backed research, communicate with other turf managers about products that work, test on small areas prior to widespread application and do not substitute biostimu- lants for a fertilizer management plan. ■ ST Susan Haddock, B.S., MBA, is an Agent II for the University of Florida, IFAS Extension, Hillsborough County.