Comparative Irrigation Requirements of 28 Cultivars of Kentucky Bluegrasses and 2 Texas Bluegrass Hybrids in the Transition Zone.

Efficient use of irrigation water on turfgrasses is becoming more crucial in the U.S. Information is needed about relative irrigation rates among newly-released cultivars of turfgrasses. Twenty-eight cultivars of Kentucky bluegrass (Poa pratensis L.) and two Texas bluegrass hybrids, a cross between Kentucky bluegrass and Texas bluegrass (Poa arachnifera Torr.) were selected for this study from among and within 11 different phenotypic groups, based largely on performances in the 2004 National Turfgrass Evaluation Program (NTEP) tests. Plots, replicated three times per cultivar, were prepared and seeded under a rainout shelter in September 2006. The soil at the site was a Chase silt loam (fine, montmorillonitic, mesic, Aquic, Argiudolls). Plots were well-watered until early June 2007, after which turfgrasses were allowed to dry down without irrigation or precipitation until the first sign of wilt. Individual cultivars were evaluated daily and irrigated with 2.5 cm of water when approximately 50% of the plot area showed visible symptoms of wilt. Each plot was manually irrigated, and irrigation quantity and date was recorded. General turf performance was also evaluated daily by visually rating turf quality. The total amount of water applied to individual cultivars in the first year varied significantly, and ranged from 20 to 56 cm during the four-month period from June through September. Visual quality also varied substantially among cultivars. When considering both visual quality and water requirements, cultivars in the Compact-America, and Mid-Atlantic groups performed better (higher quality, lesser water requirements) and Common types poorer (lower quality, greater water requirements) among phenotypic groups although there was significant variability even among cultivars within each group. This study will be repeated in 2008 to integrate effects of climatic variability and to evaluate cultivars in their second year of establishment. It is anticipated that this research will result in a list of NTEP’s best-performing cultivars of Kentucky bluegrasses into categories with high, medium, and low irrigation requirements.