Ultradwarf bermudagrass is the most prevalent warm-season species used on putting greens in warm, humid regions (Hartwiger and O’Brien, 2006). Ultradwarf bermudagrasses have fine-textured leaf blades, short internodes, high shoot density, and the ability to withstand low height of cut, which provides a smooth and fast putting surface (Gray and White, 1999). However, ultradwarf bermudagrasses are rapid thatch producers that quickly generate an excessive thatch-mat layer of organic matter, which negatively affects putting green performance (Carrow, 1998; Fontanier et al., 2011; McCarty et al., 2007; Turgeon, 2005).
The United States Golf Association (USGA) putting green construction method was developed to provide near-ideal soil physical properties that result in an environment conducive for plant growth (Brady and Weil, 1999). The ideal conditions of a USGA putting green diminish over time due to the ability of ultradwarf bermudagrass to generate organic matter (Carrow, 2003). Excessive levels of thatch-mat organic matter causes many problems, including increased ball marks (Vermeulen and Hartwiger, 2005), increased pathogen and insect populations (Bevard, 2005; Christians, 1998), and reduced water infiltration rates (Bevard, 2005).
Hollow-tine aerification, also known as core aerification, is an effective practice that physically removes a soil core to improve soil physical properties. Research has shown that HT aerification improves water infiltration and reduces VWC in putting greens (McCarty et al., 2007; Rowland et al., 2009; Sorokovsky et al., 2007). Previous research has also suggested that HT aerification combined with verticutting and grooming reduced organic matter concentration more than the untreated control treatment (Atkinson et al., 2012). However, other researchers have reported HT aerification did not reduce organic matter concentration compared with non-HT aerification treatments (McCarty et al., 2007; Rowland et al., 2009; Sorokovsky et al., 2007). Hollow-tine aerification is also used to reduce compaction, which is quantified by measuring bulk density and surface firmness. Increasing the number of HT aerification events has been reported to improve bulk density (Atkinson et al., 2012; Murphy et al., 1993), whereas other researchers have noted no differences in bulk density, which have caused speculation that improvements to bulk density might be short lived (Green et al., 2001; Murphy and Rieke, 1994). As bulk density decreases, soil macroporosity increases, which promotes more efficient air and water movement throughout the soil. Atkinson et al. (2012) noted surface firmness was 4% lower when impacting 25% surface area compared with 15% surface area on a ‘TifEagle’ bermudagrass putting green. Although traditional HT aerification improves soil physical properties, it can be disruptive to the putting surface resulting in fewer rounds of golf played (Craft, 2016).
Alternative aerification practices, such as spiking, slicing, water-injection (WI) cultivation, and DI cultivation are becoming more popular because they are less disruptive to the putting surface than HT aerification. For example, previous research has shown that WI and spiking can improve water infiltration on sand-based greens with minimal surface disruption (Fontanier et al., 2011; Green et al., 2001; Murphy and Rieke, 1994; Schmid et al., 2014). A considerable amount of previous research has examined traditional aerification timing, depth, and spacing impact on soil physical properties of cool-season grasses (Landreth et al., 2008; McCarty et al., 2007; Murphy et al., 1993; Sorokovsky et al., 2007), while minimal research has concentrated on ultradwarf bermudagrass cultivars.
Determining the best combination of traditional and alternative aerification practices to maintain soil physical properties throughout the growing season while minimizing surface disruption is challenging for turfgrass managers. Despite growing interest in new aerification technology of putting greens, there is a lack of information in the literature comparing new technology with traditional methods—particularly DI. Dry-injection is a process by which high-pressure water injections create holes into the surface with sand and/or other amendments being drawn into the hole by the patented vacuum created by a burst of water (Bigelow and Soldat, 2013; Turgeon, 2012). The objective of this research was to determine the best combination of DI technology with modified traditional HT aerification programs to achieve minimal surface disruption without a compromise in soil physical properties, such as bulk density, VWC, and water infiltration.
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