Warm-season turfgrass species: Adaptation, drought resistance and response to trinexapac -ethyl application under a Mediterranean environment

Warm-season grasses go dormant in winter months under Mediterranean conditions, but they require less water and have a higher heat and drought resistance than cool-season species. The objectives of this study were: to assess the adaptation, drought resistance, and effects of seasonal trinexapac-ethyl (TE) application (summer vs. fall) on turfgrass characteristics using 19 cultivars of six warm-season turfgrass species. The species were Cynodon dactylon L. Pers. (bermudagrass), Buchloë dactyloides Engelm. (buffalograss), Zoysia japonica Steudel (zoysiagrass), Eremochloa ophiurioides Hack. (bahiagrass), Paspalum vaginatum Swartz (seashore paspalum) and Paspalum notatum (Flügge) (centipedegrass). Festuca arundinacea Schreb. (tall fescue) was used as the cool-season control. The plots were established in two locations, the West Mediterranean Agricultural Research Institute, Antalya and the Alata Horticultural Research Institute, Mersin, located on the Mediterranean coast of Turkey in 2005. The studies were conducted for two years. For the drought study, plots were subjected to drought stress for 90 d from June 15 to September 15 and irrigation was resumed thereafter. Applications of TE were made at a 0.38 kg a.i. ha-1 rate in summer or fall where a single application was followed by zero or one sequential application at 4-wk intervals. Seashore paspalum, bermudagrasses, buffalograss, and zoysiagrass exhibited superior color and turfgrass quality throughout the growing season and the species stayed fully dormant for less than two months. Bahiagrass, bermudagrass, and buffalograss exhibited superior drought resistance. TE enhanced turfgrass color and quality in the summer and sequential application gave an added advantage. Conversely, fall TE application decreased the quality, green color retention and delayed spring green-up by 15 to 30 d. The results support the use of warm-season species in this region for summer and fall utilization when heat stress and water limitations exist, show that some of the species possess high drought resistance that can be utilized for water-efficient turf management, and support the use of sequential application of TE for reducing mowing requirements and improving turfgrass color and quality in the summer