Wetting agents are commonly used on golf course bermudagrass (Cynodon sp.) putting greens to manage soil moisture. Turfgrass quality on putting greens can be restricted if hydrophobic conditions arise, and wetting agents have been used to alleviate this hydrophobicity and increase turfgrass quality (Aamlid et al., 2009). However, some wetting agent manufacturers posit wetting agents also increase putting green surface firmness and ball roll distance (commonly referred to as putting green speed). These claims may originate from the assumption that wetting agents have differing abilities to move water deeper into the root zone, which may, in turn, result in a drier, firmer surface. This has resulted in many turfgrass managers applying wetting agents not only to manage moisture, but also to manage golf ball roll distances without any confirmatory evidence. Because wetting agents can account for a substantial portion of a turfgrass manager’s budget, it is essential that the influence wetting agents have on golf ball roll distance be determined.
Some researchers report wetting agents influence the VWC of sand-based putting greens, whereas others report no influence. Soldat et al. (2010) reported that wetting agents resulted in lower VWC than well-irrigated plots during both years of their 2-year study. However, Soldat et al. (2010) reported the distribution uniformity was greater in wetting agent-treated plots than in the reduced-irrigation control plot, which indicates the volume of water near the putting green surface may be reduced by using wetting agents but the remaining water is distributed more uniformly when compared with reduced-irrigation plots. Similar results have been reported for warm-season turfgrasses. Schiavon et al. (2014) investigated the influence of wetting agents on ‘Princess 77’ bermudagrass (Cynodon dactylon) maintained under deficit irrigation and reported that soil moisture was more uniform as a result of one of the two wetting agents tested during their 3-year study. In south Florida, Cisar et al. (2000) reported that soil water repellency of a ‘Tifdwarf’ hybrid bermudagrass (C. dactylon × C. transvaalensis) putting green was reduced following the application of wetting agents. Other studies have also provided similar moisture uniformity results when using wetting agents on sand-based putting greens (Aamlid et al., 2009; Kostka et al., 2008). However, Bauer et al. (2017) investigated the influence of 13 wetting agents or wetting agent combinations on an 88:12 (sand:peat) putting green in Minnesota and reported that the VWC of the top 12 cm was not influenced by wetting agents when compared with untreated turfgrass on any rating date during the 2-year study. Bauer et al. (2017) speculated that the lack of difference in VWC may have been a result of the lack of water repellency over the trial area.
Soil VWC has been correlated with putting green surface firmness. Linde et al. (2011) measured VWC and putting green surface firmness on 50 golf courses in New Zealand and reported the relationship was significant (P < 0.001) and linear, with a coefficient of determination of 0.44. When they measured VWC and surface firmness from individual golf courses, the relationship was also significant (P < 0.001), but the variability resulted in a range of coefficients of determination (0.19–0.7). Linde et al. (2011) speculated that the variability could be a result of a number of factors unrelated to VWC, such as turfgrass species, soil texture, and soil bulk density. Other researchers have also reported similar results. Baker et al. (1996) sampled 147 putting greens on 74 golf courses in Great Britain and reported a weak relationship (r2 = 0.28) between VWC and surface firmness.
Ball roll distance is an important and commonly measured variable of putting greens. As a matter of perspective, amateur golfers may struggle if the ball roll distance is greater than 300 cm, whereas professional golfers commonly play on putting greens with ball roll distances greater than 365 cm. Thus, ball roll distance is an important variable that superintendents must manage. Because prior research has indicated that wetting agents influence VWC, and VWC and surface firmness are correlated, speculation exists that wetting agents, in turn, influence golf ball roll distance. Munoz (2016) claimed that the application of a wetting agent will result in a “firm and fast” surface as a result of the increased downward movement of moisture. McCarty (2016) classified wetting agents as soil penetrants and soil water retainers, and identified soil penetrants as wetting agents that move water rapidly through the soil profile and provide uniform moisture distribution leading to a “firm and fast” surface. The implication that drier, firmer surfaces lead to greater ball roll distances may be accurate, but evidence supporting this assumption is lacking.
Each of the aforementioned studies measured the influence of wetting agents on various soil and turfgrass dynamics. However, none of the studies measured the influence of wetting agents on golf ball roll distance. Therefore, the hypotheses of this study were that wetting agents influence the VWC, increase surface firmness, and increase golf ball roll distance on sand-based putting greens.
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