The Impacts of Athletic Field Paint on Light Spectral Quality, Turfgrass Photosynthesis, and Transpiration in Painted Turfgrass Canopies

Athletic field paints are applied to turf surfaces with little or no acute injury. However, field managers often notice chronic declines in turfgrass health after repeated applications. This study examines the impacts of athletic field paint on light spectral quality, photosynthesis, and transpiration in painted turfgrass canopies. Athletic field paints produce various colors through selective reflection, transmission, and absorption of visible light (400--700 nm). However, photosynthetically active radiation (PAR) also exists at these wavelengths, and as a result it was hypothesized that alterations in visible light to produce specific colors would lead to reductions in photosynthetically active radiation (PAR) and total canopy photosynthesis (TCP). Athletic field paints may also impact transpiration by obstructing gas exchange at the leaf surface, which could potentially lead to reductions in TCP and transpiration as well as increases in canopy temperature above optimal ranges.;Lab experiments using a spectroradiometer and integrating sphere examined the impacts of athletic field paint color and dilution on reflection, transmission, and absorption of PAR as well as wavelengths within PAR. Subsequent growth chamber experiments were used to examine how these impacts related to turfgrass photosynthesis and transpiration. Photosynthesis was evaluated in 'Palmer V' perennial ryegrass (Lolium perenne L.) using a gas exchange system 24 h after application of red and white athletic field paint at two dilutions as well as in 'Tifway' bermudagrass [ Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] 24 h after application of ten colors. Transpiration of Tifway as a result of six paint colors was evaluated using mass balance methods. Canopy temperature was measured in all experiments using an infrared digital thermometer immediately prior to measurements of photosynthesis and transpiration.;Spectroradiometry analyses revealed the significant effects of paint color (P ≤ 0.001) and dilution (P ≤ 0.0001) on reflection, transmission, and absorption of PAR. Lighter colors including white, yellow, orange and red reflected 47--92% of PAR, while darker colors including green, black, and dark blue absorbed 87--95% of PAR. Accompanying gas exchange measurements revealed that all treatments reduced TCP based upon color (P ≤ 0.0001) and dilution (P ≤ 0.0001). Values for TCP were most negatively correlated with absorption of PAR (r = -0.959; P ≤ 0.001) and was positively correlated with reflection and transmission of PAR. Transpiration in Tifway canopies was reduced by paint application (P ≤ 0.0001) where lighter colors yellow and white reduced transpiration the least while black and blue reduced transpiration the most. Canopy temperature was affected by paint color (P ≤ 0.0001) in all growth chamber experiments and was most positively correlated with PAR absorption (r = 0.872; P ≤ 0.001) over the range of the ten colors examined. Black and blue resulted in the largest increases in canopy temperature (39.6 and 40.5°C), which is above the optimal range of 27--35°C, potentially resulting in heat stress.;The results presented in these experiments reveal the color-dependent relationship between available PAR, TCP, and transpiration in painted turfgrass canopies. The overlap of visible light and PAR results in secondary impacts on turfgrass growth including shading, stomatal obstruction, and heat stress. These factors clearly indicate that damage to turfgrasses with long-term painting will be difficult to avoid, and this is particularly true with darker colors of paint.