Green Industries Best Management Practices manual

influences the activity of the soil microbial population,these materials release N more slowly and are less effectiveduring the cool season.Particle size and rate of hydrolysis control the N releasefrom IBDU; thus, this product should not be used duringperiods of heavy rainfall. However, it is one of the moreeffective materials in the cool season when precipitationlevels decrease.N release from sulfur-coated urea (SCU) products is controlledby the coating thickness and the degree of imperfectionin the coating. SCU products typically induce asomewhat mottled appearance when used during the coolseason, but are generally very effective during the highrainfall,warm-season growth period. Because of the fragilenature of the sulfur coating on most SCU materials,they should not be applied using a drop-type spreader.Other products include polymer-coated, controlledreleasefertilizers that use a polymer coating to encapsulatenutrient granules. A polymer membrane is chemicallybonded to the substrate resulting in a fertilizer withrelease governed largely by soil temperature, providedadequate moisture is present. The release mechanism isosmotic diffusion. Some systems consist of multiplelayers of polymer, and may include other intermediatecoatings. Product longevity may be controlled by coatingthickness and blending ratios.Organic fertilizers are another source of nitrogen that isslowly made available through microbial degradation.In this case, the release rates depend on nature of theproduct and the prior treatment that it has received aswell as temperature and moisture. Organic fertilizers,including biosolids from wastewater treatment plants,generally have low N:P 2 O 5 ratios, which means that it isdifficult or impossible to meet the nitrogen needs of theturf without exceeding the annual maximum allowableP 2 O 5 , unless other nitrogen sources are added. Somemanufacturers do blend in other N sources to overcomethis and provide a more balanced product that preservesthe benefits of nutrient recycling.In conclusion, a wide variety of slow-release materials isavailable. Under typical Florida conditions, slow-releaseN sources are likely to leach less than an equal amountof soluble N sources. However, leaching can still takeplace and some slow-release products may be subject torunoff of the nutrient-containing slow release particles.Judicious use of professional judgment and a mixture ofsoluble and slow-release N sources are recommended.For more information on N sources for lawn fertilization,see IFAS Publication CIR-1262, Selected Fertilizers Usedin Turfgrass Fertilization, at http://edis.ifas.ufl.edu/SS318,or Publication SP141, Florida Lawn Handbook: AnEnvironmental Approach to Care and Maintenance of YourLawn, Second Edition.Nitrogen Rate and FrequencyThe rate of nutrient application, particularly N,depends on a number of factors: turfgrass species,turfgrass maintenance level goals, the location in thestate where the turfgrass is being grown, time of year,and type of fertilizer source being used (soluble orslow release). Thus, a single rate of application cannotbe recommended. The frequency of fertilization alsodepends on all the factors listed above for N rate. Tolimit the environmental impact of your fertilizationprogram, it is recommended that no more than 0.5pounds of water-soluble N per 1,000 square feet beapplied in a normal application. Total N should belimited to 1 lb./1000 ft 2 , per the Urban Turf Rule.Table 5 is from the Florida Fertilizer Rule, 5E-1.003(2).In areas irrigated with reclaimed water, check with thereclaimed water supplier for estimates of the N appliedper year in the reclaimed water, and recommendationsto adjust the fertilization. A study for the Tampa BayEstuary program (April 2008) estimated 0.6 to 5.3 lbN/1000ft 2 was applied annually to lawns from severaldifferent wastewater treatment systems.For a detailed fertilization guide for Florida turfgrasses,see IFAS Publication SL-21, General Recommendationsfor Fertilization of Turfgrasses on Florida Soils, athttp://edis.ifas.ufl.edu/LH014.Table 5: Fertilization guidelines for established turfgrass lawns in three regions of FloridaNitrogen recommendations (lbs N / 1000 ft 2 / year)*Species North Central SouthBahia 2-3 2-4 2-4Bermuda 3-5 4-6 5-7Centipede 1-2 2-3 2-3St. Augustine 2-4 2-5 4-6Zoysia 3-5 3-6 4-6* North Florida is north of Ocala. Central Florida is defined as south of Ocala to a line extending from Vero Beach to Tampa. South Floridaincludes the remaining southern portion of the state.Department of Environmental Protection – Revised DECEMBER 200829