The recommended N rates for St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze.) vary in Florida. This research, conducted in Fort Lauderdale, Citra, and Jay, FL, (2006–2008), aimed to determine the minimum N rate necessary for acceptable St. Augustinegrass and to determine the influence of N and irrigation rate on NO3–N leaching. Urea was applied in Fort Lauderdale, Citra, and Jay at 98, 196, 294, and 588; 49, 196, 343, and 490; and 49, 98, 196, and 294 kg N ha−1 yr−1, respectively, based on best management practices. Irrigation was 2.5 mm d–1 and 13.0 mm three times weekly in Fort Lauderdale; 13 mm twice weekly and 26 mm wk–1 in Citra and Jay. In Fort Lauderdale and Jay, lower than recommended N rates mostly produced acceptable turfgrass. Applications of 196 kg N ha−1 (Fort Lauderdale) and 98 kg N ha−1 (Jay) were the lowest rates producing acceptable turf. In Citra, 65% more N was required for acceptable turf than the recommended minimum . Leaching from all N rates was similar, except when N rates exceeded recommendations or when turfgrass exhibited herbicide stress. The high irrigation rate doubled NO3–N leaching compared to the low rate in Fort Lauderdale; irrigation frequency had no influence on leaching in Citra or Jay. The predicted minimum N rate for acceptable turf in Fort Lauderdale was <98 kg N ha−1 yr−1 (lower than in Citra; more than in Jay). In stressed turf, additional N conferred little benefit to quality and increased leaching.

Turf fertilization in Florida continues to be viewed as contributing to nonpoint‐source pollution of ground water. Continued research is needed to validate existing best management practices (BMPs). The objectives of this research were to evaluate nitrate‐N (NO3–N) leaching, turf quality, and turf growth rate from N sources applied to ‘Floratam’ St. Augustine grass [Stenotaphrum secundatum (Walter) Kuntze] and common centipede grass [Eremochloa ophiuroides (Munro) Hack.]. Research was conducted in Jay, FL, from 2008 to 2011. Nitrogen was applied in 60‐d cycles at 48 kg ha−1 as ammonium nitrate, urea, 30% slow‐release N (SRN), 50% SRN, polymer‐coated urea (PCU), and biosolid (BS) and in 120‐d cycles at 98 kg ha−1 as PCU. Nitrogen leaching was greatest during the first 6 mo following turf sodding for both species with 21.6 and 10.1 kg ha−1 leached from St. Augustinegrass and centipedegrass, respectively. Following sodding, no differences in N leached between turfgrasses were observed until 2010 when winterkill and large patch (Rhizoctonia solani Kühn) were observed on St. Augustinegrass. Turf quality of control plots was above acceptable levels in 2008 but was unacceptable by 2011. Each N source produced acceptable centipedegrass with few differences among N sources. A blend of 50% ammonium sulfate and 50% PCU resulted in higher growth rates and turf quality of St. Augustinegrass than other N sources in most years. Recommending N applications to newly sodded turf may not be necessary due to the risk of leaching during establishment.

Sulfate and glucoheptonate forms of Fe, Mn, and Mg are commonly applied to horticultural and agricultural crops. Once these metals enter the soil solution, their solubility may be limited. Glucoheptonate may prolong soil solubility, but its influence in alkaline soils has not been documented. The objective of this study was to determine the solubility of Fe, Mn, and Mg sulfates and glucoheptonates in two alkaline soils. A Tavares sand (a hyperthermic, uncoated Typic Quartzipsamment) and a Fuquay loamy sand (a loamy, kaolinitic, thermic Arenic Plinthic Kandiudult) were incubated with soluble Fe, Mn, or Mg applied as either the sulfate or the glucoheptonate. At 1 h, 4 h, 1 d, and 1, 2, and 3 wk, soils were extracted with 0.01 mol L −1 CaCl 2 and analyzed for Fe, Mn, or Mg. At 1 h, approximately 98 and 93% of applied Fe was insoluble in the Tavares sand and Fuquay loamy sand, respectively. The greatest differences between soils occurred with Mn solubility, with 54 and 20% rendered insoluble in Tavares sand and Fuquay loamy sand, respectively, at 1 h. Soluble Mg declined at 1 h by 10%, with no further reductions throughout the 3-wk incubation. Soil applications of Fe as sulfate or glucoheptonate should be avoided. Applications of Mn sulfate or glucoheptonate may lead to increased soil solubility immediately following the application but may rapidly decline. Magnesium, however, remains soluble for as much as 3 wks. Glucoheptonate did not increase the solubility of Fe, Mn, or Mg compared with sulfate in either soil. Abbreviations: EDDHA, ethylenediaminedi-o-hydroxyphenlyacetic acid; EDTA, ethylenediaminetetraacetic acid. I ron, Mn, and Mg are common components of both granular and foliar agricultural nutrient programs. In granular form, these elements are commonly applied as soluble salts (sulfates) blended with other components such as N, P, or K. In sulfate form, Fe and Mn may rapidly convert to insoluble compounds, which reduces plant uptake, leading to deficiency symptoms, particularly in high-pH soils (Petrie and Jackson, 1984; Snyder et al., 1979). Thus, metals are often applied in chelated forms that are designed to maintain solubility, especially in high-pH soils (Sommers and Lindsay, 1979). Glucoheptonate (Fig. 1) (National Center for Biotechnology Information, 2016) is a chelate relatively new to agricultural use. Glucoheptonate is typically recommended as a foliar spray. However, some applicators use glucoheptonate as a soil application or soil drench despite any evidence confirming the ability of glucoheptonate to sustain metal solubility in alkaline soils. The solubility of Fe, Mn, and Mg in soils is strongly influenced by soil pH and moisture. As transitional heavy metals, Fe and Mn respond similarly to soil pH and moisture, with both exhibiting reduced solubility as pH increases and moisture decreases (

Fertilizer bans in Florida prevent turf managers from applying nitrogen (N) fertilizers during periods of active turf growth and may encourage fertilization in fall and winter. Nutrient applications during fall or winter may pose an increased risk to nitrate N (NO3–N) leaching. A 3‐yr field lysimeter study was conducted in Jay, FL, to determine the effect of N rates on NO3–N leaching from ‘Floratam’ St. Augustinegrass (SA) [Stenotaphrum secundatum (Walter) Kuntze] and common centipedegrass (CE) [Eremochloa ophiuroides (Munro) Hack.] during turfgrass dormancy. Treatments consisted of urea applied as a foliar spray every 45 d beginning in October at rates of 0.0, 6.0, 12.5, 24.0, or 49.0 kg N ha−1. Leachate was collected weekly and analyzed for NO3–N. Elevated NO3–N levels were observed for 105 d after initiation (DAI). No differences in NO3–N leached were detected among N rates until the late winter cycle of 2008 when rainfall exceeded historic levels by 268 mm. The 49.0 kg N ha−1 treatment resulted in more NO3–N leached than untreated turf during 2008, with 12.5 and 1.3 kg NO3–N ha−1 leached, respectively. These findings suggest that N rates ≤24.0 kg ha−1 applied to dormant or semidormant warm‐season turf do not pose an increased threat of NO3–N leaching even when rainfall is excessive. Soluble N rates >24.0 kg ha−1 should be avoided during dormancy when excessive rainfall is imminent. The benefits, if any, need to be investigated further before fertilization of dormant warm‐season turf is recommended.