Lawns cover over 17 million acres in the United States (USEPA, 2012a). They offer an aesthetically pleasing environment shown to improve mental health, quality of life, and social harmony (Beard and Green, 1994). Although many homeowners manage turfgrasses solely for aesthetics, healthy turfgrass offers multiple benefits to the environment including carbon sequestration (Bandaranayake et al., 2003), temperature reductions in urban heat islands (Spronken-Smith et al., 2000), and enhanced water infiltration and erosion control (Krenitsky et al., 1998).
Over the past few decades, the home lawn care (HLC) industry has developed into a multibillion-dollar industry (Steinberg, 2006). An increased quantity of inputs applied to lawns is part of this growth, with increased emphasis on mowing, irrigation, pesticide applications, and fertilization (Harris et al., 2013). Fertilization is a critical cultural practice for both establishing and maintaining high quality turfgrasses. In particular, N fertilization is important because it is the nutrient required in the highest amount by the plant (Turner and Hummel, 1992). Nitrogen not only affects sward density and color, but also affects turfgrass vigor and health (Turgeon, 2011). However, excessive or improperly timed fertilizer applications increase the risk of NPS pollution (Law et al., 2004). Nonpoint source pollution is defined as any nondiscernable source in which pollutants are traveling, such as land runoff, precipitation, or drainage (USEPA, 2012b). Fertilizer applied off target onto impermeable surfaces such as driveways and sidewalks is a common source of NPS in the urban landscape (Arnold and Gibbons, 1996).
Nitrogen applied in highly soluble forms, such as the inorganic N form urea, and not immediately taken up by plants, can be lost by a variety of mechanisms. Nitrates in the soil solution have a high propensity to leach through the soil profile and to contaminate groundwater (Robertson and Groffman, 2007). Inorganic N sources also contribute to the NPS pollution problem as a result of runoff due to irrigation or rainfall, which ultimately moves the N to local water bodies (Law et al., 2004). Excessive concentrations of N and P fertilizers can lead to eutrophication in water bodies, a process by which algae blooms hyper proliferate, die, and decompose creating hypoxic conditions and death of other aquatic organisms (Art, 1993). The USEPA has estimated that “NPS pollution is now the single largest cause for the deterioration of our nation’s water quality” (Baird and Lawrence, 2006).
Increased NPS pollution concerns have led homeowners and lawn care operators to seek alternatives to inorganic fertilization and other inputs for maintaining lawns. One alternative to inorganic fertilizers is organic nitrogen derived from waste sources such as sewage sludge and bone meal (Law et al., 2004). Another option is to amend soil with organic compounds to improve the soil and plant health (McDonald, 1999). These organic materials, however, can have unpleasant odors and be difficult to handle and apply. Also, due to low N analyses, most organic compounds must be applied in such large amounts that they are not cost-effective and are, therefore, not a viable option compared with inorganic N sources. Furthermore, it has been shown that using organic fertilizers for reducing nitrate loss can lead to increased phosphorus levels, which are also associated with NPS pollution (Sharpley et al., 1994).
One possible alternative to inorganic N fertilization is the incorporation of legumes, such as WC, into turfgrass stands. Legumes fix atmospheric N and prior studies have reported fixation rates of between 23 and 187 kg N/ha/yr (Jørgensen et al., 1999; McCurdy et al., 2014), and even up to 545 kg N/ha/yr (Elgersma and Hassink, 1997). Some recommended N fertilization rates for a moderately maintained KBG or TF lawn is 98–147 kg/ha/yr (Kopp and Guillard, 2002; Law et al., 2004; Munshaw, 2014). If even a portion of a lawn’s yearly N needs can be supplied by WC, the reduction in fertilizer use could be significant and could reduce the amount of NPS related with the HLC industry.
‘Dutch White’ is a common variety of WC found in landscapes. It is an intermediate variety in terms of height and leaflet size. Like other WC varieties, it grows through proliferation of stolons that root at the nodes (Frame and Newbould, 1986). ‘Microclover’ is a recently released variety of WC selected to grow lower and produce smaller leaflets than other WC varieties (Heijden and Roulund, 2010), which allows it to mix well with traditional cool-season lawn grasses.
Because very little has been published concerning the best ways to establish WC in mature cool-season turf stands, this study was designed to examine the effects of three preplanting cultivation techniques and planting dates on WC establishment in two existing cool-season turfgrass lawn settings. Establishing procedures for consistent, successful establishment of WC in existing turfgrass is essential if the introduction of WC is to be widely adopted by the industry. Part of this study aimed to determine the expected time for turf recovery following WC planting, as aesthetic quality is often a priority for lawn managers.
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