Spatial Impact of Turf Fans On Creeping Bentgrass Putting Greens.

Heat stress of creeping bentgrass [Agrostis stolonifera L. var palustris (Huds.)] is one of the most limiting factors of successful putting green management in the Southeastern and Mid-Atlantic regions of the US. Turf fans are one of the tools utilized by golf course superintendents to improve air circulation and increase transpiration during prolonged heat stress and high humidity situations. Despite increased popularity of turf fans, there is limited scientific literature available to support claims of improved creeping bentgrass performance during heat stress. The objectives of this research are to 1) spatially quantify benefits of turf fans on the overall health of creeping bentgrass putting greens and 2) determine optimal activation timing to maximize creeping bentgrass health. The study was a 3 x 6 split plot design, with each main plot consisting of a putting green with a unique fan application (no fan, initiate fan at 21°C, and initiate fan at 27°C). Sub-plots consisted of six collection points aligned 3m apart at increasing distances from the fan. Six in-play creeping bentgrass (Penn A1/A4) putting greens equipped with permanent 5hp oscillating turf fans (TurfBreeze TB-50 Premium) and compared against three comparable putting greens without fans. Fans were activated when daily soil temperature at 4cm averaged 21°C (10 May 2013) and 27°C (28 May 2013).  Each fan treatment was replicated on three greens and for each green, three subsamples were collected every 3m between 6m and 21m. Measurements included soil moisture (4cm), root zone temperature (4cm), canopy temperature, rooting depth, and wind speed at turf canopy. Turf quality from each sampling point and across green was determined using geo-referenced reflectance data (NIR/VR). In August 2013, rooting depth, root zone temperature, and canopy temperatures were positively impacted by fans, regardless of activation date. Impact was most apparent for 12m. Wind speed ranged from 12mph (6m) to 4mph (21m), compared to a relatively constant 2mph on greens with no fans. Soil moisture was highly variable and appeared to be influenced by many extraneous factors, thereby limiting detection by fans.  Rooting depth was greatest when fans were activated when soil temperatures reached 21°C, suggesting that running earlier in the season may benefit the turf throughout the summer.