THE RESEARCH PLAYBOOK
Spring dead spot is one of the most common diseases of bermudagrass in regions where the grass experiences winter dormancy , such as throughout the transition zone . The fungal pathogen Ophiosphaerella infects the turfgrass in the fall while soil temperatures are between 50 ° F and 75 ° F ; however , symptoms are not present until the spring after green-up occurs ( hence the name ). The disease appears as a patch of dead turfgrass that varies in size . It creates a sunken surface in the turfgrass canopy , leading to significant variability in field uniformity . Winterkill is not technically a disease ; it is caused by severe temperature fluctuations during winter months , leaving large areas of completely dead turfgrass following spring green-up . Both spring dead spot and winterkill are common on athletic fields , and their presence creates an obvious uneven surface within the turfgrass canopy .
Our research objective was to quantify the effects of spring dead spot and winterkill on field performance and athlete safety using various metrics . We hypothesized that spring dead spot and winterkill will create adverse playing conditions , such as increased surface hardness and decreased foot traction , causing athlete safety concerns on these inconsistent surfaces .
RESEARCH METHODOLOGY Spring dead spot and winterkill were present on several athletic fields throughout southwestern Virginia ( and many other transition zone locations ) during the spring and summer of 2023 . Data were collected at four locations : two fields in Blacksburg and two in Roanoke . The fields in Roanoke were of particular interest because they were used by my summer league team at the time , and my teammates and I could physically feel the differences between areas of asymptomatic turfgrass versus areas with spring dead spot and winterkill while practicing .
A 2.25 kg Clegg hammer was used to measure surface hardness , a FieldScout TDR 350 to measure soil moisture , a Turf-Tec Shear Strength Tester ( shear vane ) to measure the rotational shear strength of the turfgrass , a ball rebound device to record the bounce height of a FIFA-grade soccer ball when released from two meters , and a FLEX testing device to simulate an athlete ’ s stopping or accelerating motion . The shear vane measures the rotational resistance of the turfgrass by simulating an athlete ’ s cleat planting and changing direction . It measures the force ( Nm but converted to inch-pounds for this article ) required to ‘ shear ’ the surface . The shear vane used was about 80 pounds . The FLEX device was created by University of Tennessee ’ s professor John Sorochan , Ph . D . and Kyley Dickson , Ph . D .
Winterkill ( taken May 2023 ).
It is portable and was designed to simulate the foot strike of an athlete when stopping or accelerating . It takes four separate measurements in one strike :
1 . Vertical force : hardness of the surface experienced at the ankle . 2 . Rebound : energy restitution of the surface or recoil . 3 . Displacement : stability of the surface . 4 . Horizontal force : horizontal traction force .
At each field location , data were collected from 20 spring dead spot patches and 20 areas with winterkill and compared against adjacent asymptomatic matched pairs . Additionally , 10 of the 20 spring dead spot patches and asymptomatic areas tested were irrigated with 0.25 inches of water to see if an increase in soil moisture from potential rainfall or planned irrigation would worsen the effects of the disease . The decision to irrigate was made due to results from a previous study in which the impacts of spring dead spot were more drastic on a field with higher soil moisture than on nearly fields with lower soil moisture .
Data were analyzed using JMP 16 ( version , SAS institute , Cary , N . C .), where means were separated using the Each pair Student ’ s t-test when appropriate ( a = 0.05 ).
RESULTS SURFACE HARDNESS Overall , spring dead spot did not impact surface hardness before or after irrigation in our locations . Gmax values ranged from 75.8 inside of spring dead spots to 73.5 in asymptomatic regions prior to irrigation , and from 66.6 to 69.5 in the same areas immediately following irrigation . Both spring dead spot and asymptomatic turfgrass were within the 60-80 Gmax range for acceptable playing conditions , whether irrigated or not . As expected , irrigation caused Gmax values for both spring dead spot and sportsfieldmanagementonline . com August 2024 | SportsField Management
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