SportsTurf

December 2017

SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.

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www.spor tsturfonline.com 9 December 2017 // water use and turf grown in sand- based rootzones requires more frequent irrigation due to a lack of water-holding capacity. Although sand-based rootzones have many beneficial characteristics, managing fi elds high in sand content can be challenging particularly during dry, hot conditions. Hydrophobicity (the repelling of water) is one of the most common issues of turf grown in sand and can result in 'hot spots' that tend to dry out faster compared to other turf areas. Wetting agents are commonly used to manage this situation. Although hydrophobic areas are less common in native soils or rootzones with minimal sand, wetting agents can still aid in water management of these soils. Wetting agents work by reducing the surface tension of water, allowing greater infi ltration into the soil surface and increased percolation through the soil profi le. In hydrophobic soils, wetting agents work by restoring the bond between the nonpolar organic coatings on soils and the polar water molecules. In saturated soils, wetting agents can help to increase percolation of water by reducing the attraction of water molecules to themselves; this occurs via the reduction in cohesive forces (aka surface tension) of water molecules. In the case of increasing soil moisture uniformity, a single wetting agent may be effectively making dry areas wetter and wet areas drier. Overall, this could result in decreased water use, improved water conservation and more consistent playing surface. As a water management tool, wetting agents can also indirectly result in increased rooting depth and density (in turn improving water conservation), reduced disease infection that can impact turf playability (by reducing prolonged leaf wetness duration), and improved moisture holding capacity of infield skins (which can improve playability). In addition, recent research at the University of Minnesota suggests that wetting agents may improve surface firmness and help to reduce winter damage of turf surfaces. Sports turf managers may find it challenging to translate research data supporting these claims because a majority of wetting agent research has been focused on golf course turf; however, recent finding supports the application of wetting agents to entire fi elds versus only applying to specifi c, problematic turf areas. Influence on surface firmness Over the past 4 years, researchers at the University of Minnesota have been investigating the infl uence of wetting agent applications on the firmness of sand-based putting greens. As has been shown repeatedly, there is an inverse relationship between the degree of soil wetness and fi rmness of a turf surface (i.e., more water results in a softer playing surface). Softer playing surfaces on sports fi elds may manifest several issues including increased susceptibility to damage from athletes and reduced surface stabilization, which can result in athlete injuries. In an ideal sports turf situation, using wetting agents on an entire fi eld would provide a firmer playing surface following a signifi cant rainfall event and help promote uniform wetting of turf surfaces. Under dry conditions, wetting agents may help with holding moisture at the surface, thereby improving cushioning and player safety. Our research results have demonstrated that wetting agents will impact fi rmness; some create softer surfaces and some fi rmer, depending on the chemistry, and some actually do both depending on the moisture status of the soil. Further research is needed to evaluate variations in wetting agent performance associated with environmental and climate factors. To reduce winter injury An emerging trend in turf wetting agent use has been making applications later in the season with the goal of improving winter health and spring recovery. In northern climates where irrigation systems are winterized, the strategy has been to apply a wetting just before irrigation blowout, with the anticipation that the wetting agent will be present in the soil throughout the winter months and into the spring. In southern climates, wetting agents are more commonly being applied throughout the winter months to improve soil moisture conditions during this unfavorable growth period for warm season grasses. Late fall applications in the north Winter injury of cool-season grasses is an interesting and often puzzling phenomenon. If we analyze the various mechanisms for winter injury, we fi nd that a majority of them are moisture related. Desiccation is the drying of rootzones and turf crowns to the point of death. Crown hydration and ice cover injury occur due to excessive moisture buildup on turf surfaces, and moisture Sam Bauer, University of Minnesota Extension.

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