Evaluation of Warm- and Cool-Season Turfgrass Species and Mixes Under Deficit Irrigation in Southern California.

Identification of species, cultivars and mixes with improved tolerance to drought and heat stress is important to the sustainability of turfgrasses in California amidst declining water resources and increasing water use restrictions on lawns and landscapes. A study was conducted in 2015 and 2016 at the University of California, Riverside turfgrass research facility to compare drought tolerance of three tall fescue (Festuca arundinacea Schreb.)cultivars (‘Kentucky 32’, ‘Escalade’, and ’04-DUST’), seven cool-season species mixes (‘Contractor’s Choice’, ‘Drought Buster’, ‘Drought Buster Plus’, ‘Premium Mixture’, ‘Rapid Turf 600’, ‘Rapid Turf 600 TF’, and ‘Slope Control’), three cool- and warm-season species mixes (‘Sport Mix #1’, ‘Sport Mix #2’, and ‘Sport Mix #3’), and two bermudagrasses [(Cynodon dactylon (L.) Pers.) blend (‘Double Play’, and ‘Top Tier’). The trial was seeded in April 2015, established successfully with sufficient water, and subsequently went through a 21-d dry down cycle in the summer of 2015. In 2016, from June 1 until October 31, plots were hand watered at 60% ET₀ to assess long term performance under deficit irrigation. ‘Double Play’ and ‘Top Tier’ bermudagrasses blend retained the highest green cover during the dry down cycle, never dropping below 75%. In 2015, no statistical differences were found among cool-season species and mixes, although ‘Rapid Turf 600’ had the lowest green cover at the end of the drought period. In 2016, the best results were achieved by the cool- and warm-season species mixes. Sport Mix #2 and #3 were the top performers in the trial, showing the highest quality, cover and NDVI during the summer months. Nevertheless, no mix showed quality consistently higher than an acceptable level of 6 when irrigated at 60% ET₀ through the summer. Overall, these results supported previous research findings that warm-season turfgrasses are best adapted to inland Mediterranean climates like Riverside. In addition, our findings warrant further examination of warm- and cool-season mixes for achieving a combination of summer drought tolerance and winter color.