Mark D. Bartlett

Using the GoingStick to assess pitch quality

Mechanical behaviour of natural turf sports pitches is commonly assessed using the Clegg Impact Soil Tester and the studded disc apparatus under benchmark frameworks. Using the studded disc is time consuming and laborious, which restricts the frequency at which data on surfaces can be collected. To address this, the GoingStick® was evaluated for use as a surface assessment tool. The device was originally developed for testing horseracing tracks, and quantifies both the penetration resistance and shear resistance of the turf surface. Data were collected on three sports pitches (rugby union and football) of varying sporting level and soil texture over two seasons of sport. A laboratory experiment was also conducted assessing data from the GoingStick and the Clegg Impact Soil Tester for four soil treatments. The first season data highlighted that the maximum measurable value was too low on the device, owing to sports pitches being harder than race tracks. This issue was also found for the harder soil treatments in the laboratory study. The development of a new sports pitch calibration resolved this issue for the second season, where the entire range of resistance was successfully measured. Linear relationships were evident between penetration resistance measured with the GoingStick and impact hardness measured with the third drop of the 2.25 kg Clegg Impact Soil Tester (r2 = 0.75), and between shear resistance measured with the GoingStick and peak torque resistance measured by the studded disc (r2 = 0.88). The results of the study indicate the potential for the GoingStick to efficiently quantify the mechanical behaviour of natural turf pitches. Further work should aim to determine benchmark ranges for the measured parameters and incorporate the device within decision-support frameworks for surface management.

The effect of grass leaf height on the impact behaviour of natural turf sports field surfaces

The effect of three grass leaf height treatments (50 mm, 25 mm, < 1 mm) of two sports field rootzones (clay loam, sand) was assessed under controlled conditions using the 0.5 kg and 2.25 kg Clegg Impact Soil Testers (CIST) and the Dynamic Surface Tester (DST) device. Results were dependent upon the test device, impact energy, and drop number of the impact. The presence of grass was shown to be more important than specific grass heights in regulating impact behaviour, with no differences detected between 50 mm and 25 mm treatments. Peak deceleration was reduced (P < 0.05) by the presence of grass (50 mm and 25 mm treatments) for drop one, but not drop three of the 0.5 kg CIST missile, indicating grass leaves absorb some impact energy on lower energy single impacts but not when leaves are flattened under repeated loading. There was no difference in peak deceleration of the higher energy 2.25 kg CIST among leaf treatments for first drop, but was significantly lower (P < 0.05) for third drop on the < 1 mm treatment where the soil exhibited greater (P < 0.05) plastic displacement. Surface loading rate and energy absorption did not differ across treatments under athlete-specific impact stresses measured with the DST, suggesting grass leaves may not affect athlete impacts. Greater consideration is required for future impact testing to assess surfaces to specific impacts that occur in game situations through the use of appropriate test devices.

Development of a simplified dynamic testing device for turfed sports surfaces

The response of natural turf surfaces to loading changes with the force and loading rate applied. Quantification of surface behaviour to athlete loading is complicated by the lack of devices that replicate forces, stresses and loading rates of athletes that can be specifically used on natural turf. To address this issue, a vertical dynamic impact testing device, the DST, was developed. The DST consists of a compressed air-driven ram that vertically impacts a studded test foot on to the surface using data from biomechanical studies. The vertical dynamic stress of athlete foot strike during running is replicated, using peak force and mean boot contact area data. The ram pressure is adjustable to allow variation of the stress applied upon impact, potentially replicating a range of athlete–surface interactions. Initial laboratory testing indicated that the device was sensitive to changes in soil condition due to variations in impact data. Total penetration time and distance, and surface energy absorption were all significantly greater in prepared ‘soft’ soil treatments (p < 0.05). The loading rate in the first 50 ms after impact was significantly greater in the ‘hardest’ soil treatment (p < 0.05). Future research work will determine in situ behaviour of actual playing surfaces, compare device loading rates to those of athletes, and assess surfaces to a range of stresses.

Are golf courses a source or sink of atmospheric carbon dioxide? A modelling approach

Sports facilities have been shown to have a positive impact on local biodiversity, quality of life, and the economy. Their impact on global carbon balances is less clearly understood. Increased concentrations of atmospheric carbon dioxide (CO2) have been linked with global climate change. Currently there is a debate as to whether amenity turf is a net source or a net sink for atmospheric CO2. The turf grass of a natural sports pitch will sequester carbon through photosynthesis, but there are numerous emission sources associated with the management of turf which release CO2 into the atmosphere. These include the engines used to power mechanized operations such as mowing and spraying, the application of agrochemicals, including fertilizers, and the disposal of waste. In order to determine whether a real-world example of a sports facility was a source or sink of carbon a mechanistic mass balance model was developed. Analysis indicated that the areas of the golf course that received the most management attention were a net source of carbon emissions. The magnitude of these releases was significantly different on an equal-area basis (p < 0.01). The net carbon budget for turf grass areas across the whole golf course accounting for the sequestration by the turfgrass was −33.01 MgC/year. The mature trees that formed an integral part of the landscape of the modelled course had a significant impact on the net carbon balance, resulting in overall net sequestration of −177.3 MgC/year for the whole golf course, equivalent to −1.93 MgC/ha/year. The variability in the size, shape, and vegetation composition of different golf courses has a considerable impact on their net carbon balance, and the resultant environmental impact of sports facilities must be assessed on an individual basis.