Influence of Mowing Height On Quality and Stress Tolerance of Various Dwarf-Type Kentucky Bluegrass Cultivars.

Kentucky bluegrass has been used on cool-season golf course fairways for decades. As mowing heights on fairways decrease older cultivars become weakened and often weeds such as annual bluegrass become the dominant species. Newer cultivars or dwarf-type varieties have been bred to withstand very low cutting heights. However, their tolerance to stress under varying mowing heights is not well documented. Fourteen cultivars of dwarf type Kentucky bluegrass were evaluated for their tolerance to various mowing heights. Mowing height treatments included 1.25 cm, 2 cm, 2.5 cm, 4 cm and 5 cm. Data collected included susceptibility to rust infection, weed infestation, divot recovery, response to simulated wear and overall turf quality. Results indicated significant differences between cultivars across all mowing heights with respect to color and susceptibility to rust infection. Mowing height had a significant effect on color, rust incidence, weed infestation and divot recovery rate. Color ratings (based on NTEP scale) by cultivar varied from 7 to 8.8 suggesting that all cultivars produced acceptable color. Most of the cultivars had very little rust infection but 3 of the 14 cultivars tested had greater than 35% of the plot affected by rust disease. Rust incidence was also significantly greater in the plots mowed at 2 cm while there were no significant differences among the other mowing heights. Weeds were significantly lower in the plots mowed at 4 and 5 cm (< 5% total invasion) and reached levels of greater than 12% with the other three heights. Divot recovery time was also significantly greater in the plots mowed at 1.25 cm (> 60 days) than in the plots mowed at 4 and 5 cm (52 and 53 days, respectively). The results of this study suggest that although these cultivars are considered to be dwarf type varieties, they appear to be less tolerant of stress when mowed below 2 cm.