Periodic drought, irrigation requirements, and the enforcement of mandatory watering restrictions have posed a challenge for homeowners and landscape managers to maintain acceptable turf quality during dry periods. Information regarding irrigation requirements and performance of common turfgrass species used for residential and commercial landscapes in the southeastern United States would be valuable. A Linear Gradient Irrigation System (LGIS) provides an efficient way to measure cultivar responses to variable moisture regimes. Nine commercially available cultivars from three turfgrass species: ‘Argentine’ bahiagrass (BH) (Paspalum notatum Flügge); ‘Common’ and ‘TifBlair’ centipedegrass (CP) [Eremochloa ophiruoides (Munro) Hack.]; ‘Captiva’, ‘Classic’, ‘Floratam’, ‘Palmetto’, ‘Raleigh’, and ‘Sapphire’ st. augustinegrass (STA) [Stenotaphrum secundatum (Walt.) Kuntze.] were evaluated during naturally occurring dry periods in 2010 and 2011 for visual quality, color, and density and chlorophyll index. An irrigation gradient ranging from 0% to 120% of reference evapotranspiration (ETo) was provided by LGIS. Centipedegrass and BH had less demands on supplemental irrigation to maintain acceptable quality during periodic drought compared with STA. ‘Argentine’ BH performed similar to ‘Common’ CP for its visual quality except at the irrigation level of 40% ETo. Among STA cultivars, ‘Palmetto’ performed poorest in its relative drought response than other cultivars. ‘Sapphire’ STA needs further study to better characterize its drought response. The irrigation level of 120% ETo decreased turf quality except for ‘Argentine’ BH, and the irrigation replacement at 40% to 80% ETo, depending on turfgrass species and cultivar, may provide enough supplemental moisture to maintain acceptable turf quality during short-duration drought (≈2 weeks) in north Florida regions.
Jing Zhang, J. Bryan Unruh, and Kevin Kenworthy
Subhrajit K. Saha, Laurie E. Trenholm, and J. Bryan Unruh
Due to increasing consumption of water in landscapes and concern over conservation of water resources, this study was conducted to determine the effect of fertilizer source on water consumption of turf and ornamentals and to compare total water use (WU) of st. augustinegrass and ornamentals. The experiment was performed in a climate-controlled greenhouse at the G.C. Horn Turfgrass Field Laboratory at the University of Florida in Gainesville. `Floratam' st. augustinegrass (Stenotaphrum secundatum Walt. Kuntze) was compared to a mix of common Florida ornamentals including canna (Canna generalis L.H. Bailey), nandina (Nandina domestica Thunb.), ligustrum (Ligustrum japonicum Thunb.), and allamanda (Allamanda cathartica L.). All plants were grown in 300-L plastic pots in Arredondo fine sand. There were three fertilizer treatments [quick-release fertilizers (QRF) 16–4–8 and 15–0–15, and slow-release fertilizer (SRF) 8–4–12] applied at 4.9 g N/m2 every 60 days. Water was applied as needed to maintain turgor and turfgrass pots were mowed weekly. Experimental design was a randomized complete block design with four replications. Visual quality ratings and time domain reflectometry (TDR) data were collected weekly. Both turf and ornamentals consumed less water and had higher water use efficiency (WUE) when treated with SRF. Ornamentals consumed from 11% to 83% more water than turf, depending on season. These results may have implications in future research on irrigation management to verify WUE between turf and ornamentals in an urban landscape.
Subhrajit K. Saha, Laurie E. Trenholm, and J. Bryan Unruh
As a result of the coexistence of turfgrass and ornamentals in traditional landscapes, it is often impractical to separate fertilization and irrigation management among species. Furthermore, limited information is available on effects of turfgrass fertilizer on ornamental plants and vice versa. This research studied effects of two quick-release fertilizers (QRF) and one slow-release fertilizer (SRF) on quality and growth of turfgrass and ornamental plants and nutrient leaching. ‘Floratam’ St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) was compared with a mix of common Florida ornamentals, including canna (Canna generalis L.H. Bailey), nandina (Nandina domestica Thunb.), ligustrum (Ligustrum japonicum Thunb.), and allamanda (Allamanda cathartica L.). All plants were grown in 300-L plastic pots in Arredondo fine sand. Less nitrate (NO3 −) was leached from turfgrass than from ornamentals and more NO3 − leached from QRF 16N–1.7P–6.6K than from SRF 8N–1.7P–9.9K. Quick-release fertilizers produced higher plant quality. This controlled environment research provides preliminary data on which in situ research may be modeled. Further research is required to verify how nutrient release rate affects turfgrass and ornamental quality and nitrate leaching in an urban landscape.
George Hochmuth, Terril Nell, J. Bryan Unruh, Laurie Trenholm, and Jerry Sartain
Degraded inland and coastal water quality is a critical statewide concern in Florida and other states. Nutrients released from land-based human activities are present in water bodies resulting in algal blooms and increased eutrophication that impairs water bodies for their intended uses. There are differing approaches to addressing eutrophication, including voluntary adoption of current best management practices (BMPs) for nutrients, state regulation, or local county or municipal ordinances. The local ordinance, some including a summer (or so-called “wet season”) fertilizer ban or “blackout,” has been the chosen approach in some Florida counties and municipalities to address local water quality issues. Many components of these ordinances follow published BMPs, and there is agreement in the literature on the effectiveness of these practices for preventing nutrient losses from the landscape. However, there has been disagreement among stakeholders regarding the inclusion of a total fertilizer ban in a local ordinance. Regulators are asking about the best approach to controlling urban pollution and if banning fertilizer in the growing season would achieve the desired environmental protection and whether there are any potential unintended consequences associated with removing fertilizer from turfgrass growing in the summer months. The scientific literature documents the nature and scope of the water pollution problem, and numerous research reports have addressed fertilizer BMPs to prevent nutrient losses from the landscape. This article discusses the increased rate of eutrophication and reviews the pertinent national literature regarding managing urban landscape fertilization to protect water quality. Particular attention is given to fertilization practices during the active landscape plant (especially turfgrass) growth period that corresponds to the summer fertilizer bans in some Florida local ordinances. Therefore, special attention is paid to the question of what information is in the scientific literature and whether a fertilizer ban is the best way of achieving the goal of improving urban water quality. Research summarized in this review points to potential unintended consequences of increased nutrient losses from urban landscapes, particularly turfgrass, when proper, recommended fertilization and irrigation practices are not followed.
Christopher D. Ryan, J. Bryan Unruh, Kevin E. Kenworthy, Alexa J. Lamm, John E. Erickson, and Laurie E. Trenholm
Every county and municipality in Florida can adopt its own unique ordinance regulating the fertilization of lawns and landscapes. With increased concern for eutrophication to state waterbodies, many have chosen to implement seasonal fertilizer restrictive periods prohibiting the application of nitrogen and phosphorus fertilizers, typically during the rainy summer months. These fertilizer “blackout” policies have been the subject of controversy among environmental activists, university scientists, and policy decision makers, with their efficacy being called into question. A Foucauldian discourse analysis was undertaken to trace the dynamics of the controversy, and survey research was conducted with Florida residents and with Florida decision makers to compare their lawncare maintenance practices, sentiments surrounding turfgrass, their trust in landscape science, as well as their awareness of policy in the city or county in which they reside. Differences were found between the two populations in terms of how many respondents fertilized, used automated irrigation systems and hand-pulled weeds. Although both populations had very neutral sentiments around turfgrass with no significant differences, Florida decision-maker respondents had a higher mean response for trust in landscape science. Only 32% of Florida resident respondents were able to accurately identify if their city or county had a blackout ordinance, compared with 81% of decision-maker respondents. Increasing civic science may be the best way for reducing this discrepancy, while also giving power to citizens in environmental policy adoption.