Impact of Soil Water Content on Bermudagrass Athletic Field Performance

Soil water content (SWC) influences the consistency and performance of athletic field surfaces. Two studies were conducted at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) to determine how SWC affects wear tolerance of hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis, Burtt-Davy, ‘Tifway’] on root zones comprised of either silt loam (cohesive) or sand meeting USGA specifications (non-cohesive). Soil water content treatments for cohesive root zones averaged 0.10 m3/m3 (+/0.035), 0.17 m3/m3 (+/0.035), 0.26 m3/m3 (+/0.035), and 0.35 m3/m3 (+/0.005); comparatively, SWC on non-cohesive averaged 0.08 m3/m3 (+/0.03), 0.16 m3/m3 (+/0.03), and 0.25 m3/m3 (+/0.05). Plots were subjected to 50 traffic events annually with the Baldree traffic simulator. Green turfgrass cover (GTC) was reduced four times faster at 0.35 m3/m3 SWC than the 0.10 m3/m3 and 0.17 m3/m3 SWC treatments on cohesive soil. All SWC treatments on non-cohesive lost GTC at a similar rate. Surface hardness increased as SWC decreased for both root zones, while a minimum surface hardness of 50 GMAX is suggested for optimal athletic field performance based on the combined impact GTC and shear strength values. Turfgrass shear strength decreased with traffic for all treatments on cohesive soils, particularly at 0.35 m3/m3 SWC. Soil water content of 21 non-cohesive did not compound the effect of traffic on turfgrass shear strength. The optimal mean SWC ranges to maximize hybrid bermudagrass wear tolerance on cohesive soils were 0.10 m3/m3 to 0.17 m3/m3, and 0.08 m3/m3 to 0.16 m3/m3on non-cohesive soils. INTRODUCTION There are greater than 2.7 million ha-1 of athletic fields in the United States (U.S.) ranging from local parks and recreational fields to professional stadiums (STMA, 2003). In the U.S., over 40 million athletes participate in organized sports annually (Micheli, 2000). Annual medical expenses for sports related injuries were estimated to be over $1.3 billion (Hergenroeder, 1998). A survey of high school football injuries in Pennsylvania found that up to 21% of sports related injuries could have been linked to surface conditions of athletic fields (Harper et al., 1984). Surface consistency is key for reducing injuries. However, accumulation of traffic events creates inconsistent surfaces as a result of wear (Carrow and Petrovic, 1992). Many athletic fields in the U.S. are built with native soils compared to constructed sand root zones such as those developed according to the United States Golf Association (USGA; USGA Green Section Staff, 2007). Native soils high in silt and clay tend to have greater soil water contents (SWC) and slower water infiltration rates compared to constructed sand root zones (Pitt et al., 2008). The inherently slow water infiltration rates of cohesive soils (i.e., nonsand soils) are potentially problematic when precipitation occurs prior to athletic events. Cohesive soils with SWC are subject to extreme decreases in viscosity, shear modulus, and yield stress, compromising soil stability and decreasing playability (Ghezzehei and Or, 2001). Soils containing high amounts of silt and clay are significantly affected by water content because water acts as a lubricant decreasing solid-solid friction (Israelachvili and Adams, 1978; Schoen et al., 1987). The Atterberg limits of a soil define changes in soil behavior and consistency