Spatial Impact of Turf Fans on Creeping Bentgrass Putting Greens.

The physiology of creeping bentgrass CBG [Agrostis stolonifera L. var palustris (Huds.)] is negatively impacted during periods of stress, decreasing the efficiency of many vital functions. CBG optimal growth occurs between 10°C and 18°C. Root development slows as the soil temperature rises above 27°C, with a loss of functionality at temperatures above 30°C. To mitigate environmental stresses to CBG, turf fans are used on many golf courses to improve airflow and increase transpiration. With limited data available that does not address improved fan technologies with higher output, we designed our research to quantify the potential benefits of turf fans on putting greens. The objectives of this research are to 1) spatially quantify benefits of turf fans on the overall health of CBG putting greens and 2) determine optimal activation timing to maximize CBG performance during summer stress. The study was a 3 x 6 split plot design, with each main plot consisting of an entire putting green with a unique fan application (no fan, activate fan at 21°C, and activate fan at 27°C). Each fan treatment was replicated on three greens and for each green, three subsamples were collected every 3m between 6m and 21m. Six in-play creeping bentgrass (Penn A1/A4) putting greens were equipped with permanent 5hp oscillating turf fans (TurfBreeze TB-50 Premium) and compared against three comparable putting greens without fans. The study was repeated once, with data collection in 2013 and 2014. Fans were activated when daily soil temperature at 4cm averaged 21°C (10 May 2013 and 06 May 2014) and 27°C (28 May 2013 and 12 June 2014). Once activated, each fan ran continuously throughout all data collections. Measurements included soil moisture (4cm), root zone temperature (4cm), canopy temperature, rooting depth, and wind speed at turf canopy. Regression analysis by distance was performed for each variable. Turf quality from each sampling point and across green was determined using geo-referenced reflectance data (RVI = NIR760nm/VR670nm). Root depth, root zone temperature, and canopy temperatures were positively impacted by fans, regardless of activation date, and were strongly correlated to surface wind speed. Impact was most apparent for 12m. Air flow ranged from 5.4 m s^-1 (6m) to 1.5 m s^-1 (21m), compared to 0.9 m s^-1 on greens with no fans. Duration between fan activation dates was 18 days in 2013 and 36 days in 2014. Rooting depth was greatest when fans were activated early, suggesting CBG may benefit during peak summer stress.