Effect of Irrigation Frequency on Turf Quality, Shoot Density, and Root Length Density of Five Bentgrass Cultivars

The culture of creeping bentgrass ( Agrostis palustris Huds.) at low mowing heights on putting greens in the hot humid region of the USA presents numerous water management problems. Frequent irrigation of greens to prevent water stress has been credited with producing shallow rooted turf with reduced tolerance to environmental stress. The present study was conducted to determine the relationship between irrigation frequency and turf quality, shoot density, and root length density for five cultivars of creeping bentgrass grown on a sand‐based root zone and maintained to putting green standards. A total of 81 plots, 1.5 by 1.5 m each, were established on a USGA‐type root zone mixture and organized into nine irrigation cells of nine plots each. Each irrigation cell could be irrigated individually. One plot in each irrigation cell was planted to the following bentgrass cultivars: A‐4, Crenshaw, Mariner, L‐93, and Penncross. The remaining four plots in each irrigation cell were also planted with bentgrass but were not a part of this study. Irrigation frequency treatments of 1‐, 2‐, and 4‐d were imposed on three irrigation cells each. After establishment, measurements of turf quality, shoot density and root length density were made over a 2‐yr period. In both years, Crenshaw and L‐93 had the best turf quality. At the end of the study, shoot densities for Crenshaw, L‐93, and A‐4 were 37 to 42% greater than Mariner and Penncross. Because of frequent rainfall events in 1997, there were no significant ( P ≤ 0.05) effects of irrigation frequency on shoot density or root length density. However, in 1998, turf was more dependent on irrigation and bentgrass irrigated every 4 d had significantly greater turf quality, shoot density, and root length density than that watered every 1 or 2 d. The data show that even under putting green management conditions, reduced irrigation frequency of bentgrass produces a larger and deeper root system resulting in greater overall plant health, turf quality, and shoot density.