Search Results
You are looking at 1 - 6 of 6 items for :
- Author or Editor: Jerry B. Sartain x
- HortTechnology x
Florida's citrus (Citrus spp.), vegetable, and turfgrass industries must improve nitrogen (N) and phosphorus (P) fertilizer use efficiency to remain sustainable in an era of emerging environmental policies designed to protect water quality. Producers have traditionally used water-soluble N and P fertilizers because they are plentiful and economical. Improving nutrient use efficiency (NUE) is being addressed through implementation of best management practices (BMPs) such as nutrient management planning, proper fertilizer material selection, better application timing and placement, and improved irrigation scheduling. Emerging technology that will aid in this effort includes increased use of enhanced efficiency fertilizers (EEFs), organic soil amendments, fertigation, and foliar fertilization. However, any new technology shown to improve NUE must be economically feasible before it can be considered a BMP. Future research in this area will aim to improve the economics of EEFs and precision fertilizer application.
Best management practices (BMPs) for Florida's green industries have been established since 2002. BMPs for nonagricultural industries such as commercial lawn care were developed in 2002 by the Florida Department of Environmental Protection (FDEP), the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), and other parties. The BMP educational program, delivered primarily by UF/IFAS extension in partnership with the FDEP, began in 2003 as a voluntary program. As a result of increasing concerns regarding lawn fertilization and potential harmful effects on ground and surface waters, several local governments throughout the state require commercial fertilizer applicators to have a certificate of completion in a BMP educational program. The BMP program emphasizes appropriate fertilization practices to reduce nonpoint source pollution, including proper rates, timings, and application of fertilizers. Research done on fate of fertilizer applied to turfgrass demonstrates that a properly maintained lawn provides an effective means for uptake of nutrients. Some of the factors that have been shown through research to increase the opportunity for nutrient leaching include nitrogen (N) application at higher than recommended rates, excess rainfall after fertilization, and fertilization at a time when turf is not actively growing. Research results vary regarding N source and the difference in nitrate leaching resulting from N source. To provide concise research-based information for lawmakers and elected officials in Florida, there is currently a large research project underway to further quantify nutrient leaching under a variety of circumstances. Results of this research should form the basis for future regulations regarding fertilizer applications.
Slow-release fertilizers marketed to the public usually include a claim that nutrient release will last for a specific time period (e.g., 6, 9, or 12 months). However, no official laboratory method exists that can verify these claims. A long-term (180 days) incubation method has been developed that produces constants for an exponential model that characterizes nutrient release as a function of time. In addition, a relatively short-term (74 h) extraction method has been developed to assess nutrient release under accelerated laboratory conditions. Through regression techniques, release constants established for individual slow-release nutrient sources by the incubation method are used in conjunction with the laboratory extraction data to verify the release claims of slow-release fertilizers. Nutrient release for selected single materials has been predicted with greater than 90% accuracy in previous studies. Nutrient release from mixtures of slow-release products has been more variable. It is typical for water-soluble and slow-release fertilizers to be mixed in commercial products. Ultimately, it is intended that these methodologies will be accepted as an official method to verify nutrient release claims placed on slow-release fertilizers.
Applying water-soluble nitrogen (N) fertilizer to Florida citrus (Citrus spp.) trees on deep sandy soils may lead to poor nutrient use efficiency and possible nitrate contamination of groundwater if rainfall or irrigation is excessive. Controlled-release fertilizer (CRF) is a possible alternative to increase N uptake efficiency and minimize losses to the environment, but current grower acceptance is limited as a result of lack of experience with CRF performance and its high relative cost. The objective of this study was to measure the N release characteristics of a CRF blend (CitriBlen®) designed for mature Florida citrus trees and its three CRF components [Agrocote® Type A, Agrocote® Type C(D), and Agrocote® Poly-S®] under laboratory and field conditions. We first characterized N release from these CRF materials using a 270-day laboratory soil incubation. The quantity of N released was influenced by CRF material used; after 270 days, cumulative leached N recoveries were 90%, 82%, 85%, and 69% of the total N applied as CitriBlen®, Agrocote® Type A, Agrocote® Type C(D), and Agrocote® Poly-S®, respectively. We then measured the N release patterns of the fertilizers in a 1-year field evaluation and developed their N release curves. Studies were simultaneously conducted in central and southwestern Florida. Mesh bags containing 3.5 g of elemental N from each source were placed on the soil surface within the irrigated zone under a citrus tree canopy to estimate N release rates from the fertilizers. Despite differential N release rates between locations, at 1 year, the rank of N release was Type A > CitriBlen® > Poly-S® > Type C(D). CitriBlen® N release patterns matched well with the current University of Florida, Institute of Food and Agricultural Sciences citrus fertilization strategy recommended as a best management practice.
Urban watersheds include extensive turfgrass plantings that are associated with anthropocentric attitudes toward landscapes. Native and construction-disturbed urban soils often cannot supply adequate amounts of nitrogen (N) and phosphorus (P) for the growth and beauty of landscape plants. Hence, fertilization of landscape plants is practiced. Mismanaged fertilization and irrigation practices represent a potential source of nutrients that may contribute to water quality impairment. This review focuses on turfgrass fertilization practices and their impacts on urban water quality. Research results show that fertilization during active growth periods enhances turfgrass nutrient uptake efficiencies. The major concern regarding the fertilization of turfgrass and landscape plants in urban watersheds, therefore, is selecting the proper combination of fertilizer rate, timing, and placement that maximizes nutrient utilization efficiency and reduces the risk for nutrient loss to water bodies. Encouraging individuals to adopt best management practices (BMPs) is a priority for watershed managers. Research has found that educational programs are an important part of changing fertilization habits and that education needs to be thorough and comprehensive, which is beyond the scope of many seminars and fact sheets currently in use.
Urban water quality management is becoming an increasingly complex and widespread problem. The long-term viability of aquatic ecosystems draining urban watersheds can be addressed through both regulatory and nutrient and water management initiatives. This review focuses on U.S. regulatory (federal, state, and local) and management (runoff, atmospheric deposition, and wastewater) impacts on urban water quality, specifically emphasizing programs in Florida. Because of rapid population growth in recent decades, and projected increases in the future, appropriate resource management in Florida is essential. Florida enacted stormwater regulations in 1979, before the U.S. Environmental Protection Agency (USEPA) amended the Clean Water Act (CWA) to regulate stormwater discharges. However, in the United States, more research has been conducted on larger structural best management practices (BMPs) (e.g., wet ponds, detention basins, etc.) compared with smaller onsite alternatives (e.g., green roofs, permeable pavements, etc.). For atmospheric deposition, research is needed to investigate processes contributing to enhanced deposition rates. Wastewater (from septic systems, treatment plants, and landfills) management is especially important in urban watersheds. Failing septic systems, elevated nutrient concentrations in discharged effluent, and landfill leachate can all potentially degrade water quality. Proposed numeric nutrient criteria from the USEPA and innovative technologies such as bioreactor landfills are emergent regulatory and management strategies for improved urban water quality.