St. Augustinegrass is a widely used warm-season turfgrass for home lawns throughout the south. St. Augustinegrass prefers moderate cultural practices (Cisar et al., 1992) with a fertility requirement of 10 to 30 g·m−2·yr−1 N (Trenholm et al., 2000a). In residential areas, lawn fertilization is often cited as a major contributor to nonpoint source pollution, which may lead to elevated levels of NO3 − in groundwaters. Petrovic (1990) demonstrated that NO3 − has the potential to leach through soils and contaminate groundwater if not properly applied, although other research has shown that properly applied fertilizer is assimilated by the grass (Erickson et al., 2001; Snyder et al., 1984). Proper fertilizer management, including appropriate rates, sources, application timing, and proper irrigation after fertilizing, have all been shown to influence NO3 − leaching (Gross et al., 1990).
Controlled-release fertilizers have been shown to reduce fertilizer leaching from turfgrass (Killian et al., 1966). Brown et al. (1982) observed nitrate losses of 8.6% to 21.9% in golf course greens (bermudagrass, perennial ryegrass, Kentucky bluegrass, tall fescue, and creeping bentgrass) fertilized with ammonium nitrate. When slow-release sources such as isobutylidene diurea and ureaformaldehyde were used, only 0.2% to 1.6% NO3 − was leached. Sulfur-coated urea is often found in turfgrass fertilizers and it is less likely to leach than noncoated urea (Allen et al., 1971).
The typical landscape is comprised of both turfgrass and ornamentals, which often makes it difficult to separate fertilization and irrigation regimes between species. Although research has been done on turfgrass fertilization and its effect on environmental quality, little information is available on effects of turfgrass fertilizer formulations on ornamental plants or the effects of ornamental fertilizer formulations on turfgrass. In a nutrient management study comparing St. Augustinegrass and a mixed landscape planting, Erickson et al. (2001) observed that a greater amount of NO3 − was leached from ornamentals (1.46 mg·L−1) than from turfgrass (less than 0.2 mg·L−1). More than 30% of the applied nitrogen was leached from the ornamentals and less than 2% from the turfgrass.
The objectives of this study were: a) to evaluate qualitative and growth responses of turfgrass and ornamentals to different fertilizer sources, 2) to evaluate NO3 − leaching from different fertilizer sources, and 3) to compare nutrient leaching of turfgrass versus ornamentals.
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