Urban Turfgrass Fertilization and Irrigation Best Management Practices

Urban Turfgrass Fertilization and Irrigation Best Management Practices for Reducing Impairment of Florida's Water Resources J. Bryan Unruh 1, Laurie E. Trenholm 1, John L. Cisar 1, Jerry B. Sartain 1, and Michael Thomas 2 1 University of Florida and 2 Florida Department of Environmental Protection Abstract There approximately 2. 2 million hectares of home lawns in the state of Florida, most of which are maintained with some level of fertilization throughout the year. Fertilization of home lawns is often believed to be a significant source of nitrates or phosphates reported in ground or surface waters. Because the sandy soils found throughout much of Florida have a tendency to leach nitrates, and due to the abundance of ground and surface water in the state, it is imperative that fertilization regimes be designed to minimize environmental impact. A more thorough understanding of how fertilization and irrigation practices can influence nitrogen leaching and overall turfgrass health may serve to reduce this source of potential contamination. Development of the Florida Green Industries Best Management Practices (BMPs) has raised industry awareness of the need for caution when applying lawn fertilizers to reduce potential environmental impacts. Prior to enforcement of the BMPs under Florida statutes, research data are needed to support the most environmentally sound recommendations for lawn maintenance throughout the state. A five-year, three-location (north, central, and south Florida) project was developed to gain understanding of nitrate and phosphate leaching from warm-season turf (centipedegrass, St. Augustinegrass, zoysiagrass, and bahiagrass) receiving varying application rates of fertilizers and irrigation. Additionally, warm-season turfgrass phosphorus requirements, the influence of nitrogen source and timing on nitrate leaching, and the nitrate leaching potential of fertilizer applied to dormant/semi-dormant grasses are being studied. Results from this work will result in state-wide fertilizer recommendations for maintenance of the highest quality turf with minimal environmental impact. These recommendations will be used by county extension faculty, Florida Department of Environmental Protection, and state or local governmental agencies. Research Project Methodology/Construction All field studies involve a single bucket lysimeter installed in each sub-plot. The lysimeters have a surface area of ~ 0. 25 m 2 and are one meter deep. Lysimeters are constructed of a heavy grade plastic with a leachate evacuation port located on the bottom of each lysimeter. Plastic tubing attached to each lysimeter runs beneath the plots to a central collection point. Leachate collection is conducted a minimum of two times per week unless rainfall events dictate a more frequent schedule. Gainesville and Milton use vacuum evacuation and Ft. Lauderdale employees a gravity fed system. Turfgrass visual data collection occurs every two weeks throughout the growing season. Additionally, establishment data, root and shoot growth estimates, and pest incidence are recorded periodically. Nitrogen Research Project Summaries Phosphorus Research Project Summaries Fertilization During Establishment of Lawn Grasses – Ft. Lauderdale, Gainesville, Jay The establishment portion varies between the locations to best answer multiple questions pertaining to establishment recommendations. Gainesville will address state-wide issues relating to establishment of two grass species – St. Augustinegrass and zoysiagrass. Milton will address more regional issues dealing with establishment method and fertilization of centipedegrass from both seeded and sodded sources. Ft. Lauderdale will address issues relating to sod source (organic vs. mineral soils) and the effect on establishment recommendations. Phosphorus Requirement of Florida Lawn Grasses - Gainesville Glasshouse Phase - The objective of this Gainesville-based study is to identify the critical phosphorus requirement of the St. Augustinegrass and zoysiagrass lawn grasses using solution culture techniques. Six levels of phosphorus will be established in solution (0, 1. 2, 6. 2, 31. 0, 155. 0, and 775. 0 ppb) and replicated five times. Fertilization of Established Lawn Grasses – Ft. Lauderdale, Gainesville, Jay In the portion dealing with established lawn grasses, all locations will test St. Augustinegrass, the standard lawn grass used throughout Florida. Different additional grasses (zoysiagrass - Gainesville; centipedegrass - Jay, and bahiagrass - Ft. Lauderdale) have been chosen for each location to generate more information on the other lawn grasses. Experimental procedures are similar in these projects, with variation in nitrogen treatment rates occurring due to differences in growing season lengths between locations or differences in fertilization needs of the different species. Each study also has two irrigation regimes yielding the same net amount of applied water either applied once per week or split into two applications. Field Phase – The objective of this Gainesville-based study is to determine the phosphorus fertilization level as it relates to the critical tissue phosphorus level of St. Augustinegrass and zoysiagrass lawn grasses grown under field conditions. Five phosphorus fertilization levels based on information gained from solution culture studies will be established on St. Augustinegrass and zoysiagrass grown on a soil low in Mehlich 1 extractable phosphorus. By obtaining glasshouse data on the exact phosphorus requirement, the critical level of phosphorus in the tissue of the two lawn grasses commonly grown in central Florida will be established. These critical levels can then be verified in field studies. BMP Development History In July 2000, the University of Florida hosted a meeting of industry leaders, government regulators, and university faculty to start the process of addressing the rising concern over the increasing number of local governmental ordinances aimed at limiting maintenance practices on turf. In Florida, preemptory laws only pertain to pesticides and not fertilizers (with the exception of fertilizer bag labeling). As such, individual municipalities were enacting regulations that differed from their neighboring communities or counties. These ordinances, largely devoid of any scientific merit, were creating burdensome logistical problems for landscape maintenance companies who provided services across these geopolitical boundaries. Several months later another meeting was held to start the process of developing the Florida Green Industry Best Management Practices (BMPs) for Protection of Water Resources in Florida. The BMP manual was jointly developed by the Florida Department of Environmental Protection, Florida Department of Agriculture and Consumer Services, Florida Department of Community Affairs, Florida water management districts, the University of Florida, and many private industry partners. During the development of the manual, it became abundantly clear that scientifically derived data to support the recommendations being made were lacking. University of Florida turf faculty met and developed landscape fertilizer “interim measures”; recommendations based on reasonable expectations and extrapolations from research conducted on non-landscape turf and from other states. In June 2002, the BMP manual was in final form and went to print. Since 2002, Dr. Laurie Trenholm has developed a comprehensive training program aimed at educating commercial landscape managers on the BMPs. Major BMP topics include: Best Management Practices for Design and Installation of Landscapes; Irrigation Best Management Practices; Mulching, Mowing, and Pruning; Fertilization, and Pest Control. Securing the Funding As the BMP manual was being developed, discussions ensued with industry leaders and regulatory officials about the need to garner significant funding to support research to determine the most appropriate fertilization rates and practices on a statewide basis. Florida has a diverse climate ranging from temperate in the north to tropical/sub-tropical in south. Additionally, soil types range from marl, deep sands, to heavier sandy loams. Water tables range from a few centimeters below grade to many meters. Though the common lawn grasses grow in all regions of Florida, growing seasons differ – ranging from seven months in north Florida to year-round in south Florida. All of these conditions pointed to the need for developing regional recommendations based on sound science. Nitrogen Source and Timing Studies – Ft. Lauderdale Lawn care companies find themselves applying fertilizers during times of limited grass growth in order to accommodate all customers in a route-based business. This research will help to determine whether or not this is an acceptable practice and which fertilizer types are best suited for these applications. In Ft. Lauderdale, fertilizer sources include Nitamin ®, Polyon® + urea, and Milorganite® at rates equaling either 48, 97, 147 kg N ha-1 applied in single applications either two, three, or six times per year to give a total of 293 kg N ha-1 per season. In January 2004 a five-year task-assignment contract between the Florida Department of Environmental Protection and UF was signed. This contract specified that UF would conduct research with the following objectives: 1. 2. 3. to provide data on best fertilization and irrigation regimes on various grasses during establishment in different locations of the state; to provide nitrate and ortho-phosphate leaching data on various species at the fertilization levels in these studies; and to provide recommendations to the commercial lawn care industry for BMP fertilization rates that can be applied statewide. This massive research project involves four UF professors, graduate students, chemists, biologists, and student labor. The studies are conducted at three locations in Florida: Ft. Lauderdale, Gainesville, and Jay. The grant also included funding to purchase a Bran & Luebbe Segmented Flow Analyzer dedicated to this project and a chemist to conduct the analysis. Impact of Fertilizer Applications to Semi-Dormant and Dormant Lawn Grasses on Environmental Quality Many lawn care services operate on a route-based business cycle. In order to service all clientele in a timely fashion and keep lawns looking green, they are often forced to apply fertilizers outside of the optimum growing season. Little documentation exists on the fate of fertilizer applied to grasses that are at some degree of dormancy. The objective of this project is to document turfgrass response (Milton - centipedegrass; Gainesville - St. Augustinegrass) and nitrogen leaching when fertilizer is applied during the winter months. All nitrogen is applied as urea in a liquid solution. Fertilizer is applied every 45 days beginning early to mid-September and ending around April 1. The Effect of Soil-Test Phosphorous on Turfgrass Quality, Growth and on Phosphorous Leaching - Ft. Lauderdale Phosphorous leaching is an environmental concern in urban landscapes adjacent to natural water bodies and hydrologicallylinked ecosystems like the Florida Everglades. In order to reduce phosphorus leaching and runoff, homeowners are encouraged to avoid excessive phosphorus fertilization and minimize phosphorus levels in the soil. Soils generally serve as a reservoir of phosphorus that becomes available over time. However, when excessively loaded with phosphorus, leaching can occur. Thus, use of phosphorus-free fertilizers is being mandated for urban turfgrass. The effects of these practices have not been subjected to scientific scrutiny. Since soil phosphorus can be monitored by soil testing, the objective of this study is to both examine the effect of levels of soil-test phosphorus on turfgrass quality, growth, and phosphorus leaching. Using a mined quartz sand initially low in phosphorus, three levels of soil-test phosphorus will be established corresponding to the low, medium, and high categories provided by the University of Florida Soil Testing Laboratory. A preliminary incubation study will be conducted to determine the amount of phosphorus that is needed to establish the three soil-test phosphorus levels. Various amounts of triple superphosphate will be added to the sand soil. After incubating in plastic containers in a field-moist state for one month, samples of the soil mixes will be analyzed for phosphorus. Using the phosphorus application vs. soil-test phosphorus curves generated with these data, the low, medium, and high levels of phosphorus will be established in mixes that will be used in the field. A fourth treatment containing no added phosphorus will be included in the study. The mixes will be added to field plots containing lysimeters from which percolate samples can be obtained. Sod, washed free of soil, will be established on the field plots. The turf will be maintained with phosphorus free fertilizers. Homeowner Phosphorus Soil Test Kit Investigation – Ft. Lauderdale A selection of homeowner phosphorus soil test kits will be used to analyze an assortment of turfgrass lawn soils from across Florida to compare the homeowner kit results with results from the University of Florida Soil Testing Laboratory in Gainesville.