Performance Testing on Bermudagrass Athletic Fields.

            Athletic fields at various levels of sport receive intense amounts of foot traffic during a full season resulting in a loss of turf coverage and compaction.  Surface hardness is normally collected using a Clegg Impact Soil Tester, but recent trends in sports turf are to use the E missile.  Forty traffic events were applied to ‘Tifway’ bermudagrass grown in an ASTM constructed sand root zone and a silt loam soil on the Center for Athletic Field Safety at the University of Tennessee.  A F355-E surface hardness testing device was used to measure G_max and head impact criteria (HIC) for both root zones after every eight traffic events.  Head Impact Criteria values were regressed to drop height to calculate critical fall height (CFH) for both root zones.  Critical fall height is the maximum height an athlete can fall from where the surface meets the impact attenuation performance criteria.  A life-threatening head injury would not be expected to occur from a drop height less than the CFH.  Critical fall height of the ASTM constructed sand root zone was 2.3 m, while CFH of the silt loam soil was 2.0 m.  The differences in critical fall heights were due to soil compaction.  After forty traffic events, the average soil bulk density of the ASTM constructed sand root zone was 1.3 g/cm³, and the silt loam was 1.4 g/cm³.  A 2.3 m CFH of the ASTM root zone occurred during the initial testing, before the loss of green turf coverage.  A loss of green turf coverage resulted in a higher CFH due to sand dispersion.  A 2.0 m CFH of the silt loam soil was calculated after forty traffic events.  HIC values for both root zones were significantly changed as a result of traffic.