REFINING QUALITATIVE TURFGRASS CANOPY STRESS MEASUREMENTS DURING DROUGHT

Turfgrass response to drought is often evaluated through qualitative parameters using a numerical scale of 1 to 9. As water resources become increasingly restricted for use on amenity turfgrass systems, the inability for consumers to delineate incremental drought stress relating to plant health can result in the misuse of water resources during drought conditions. Qualitative plant measurements may not precisely inventory drought stress characteristics such as turfgrass quality and leaf firing so as to apply across regions or climatic zones. A two-year drought simulation field study measured drought response of 24 warm-season turfgrass cultivars by capturing weekly images of bermudagrass (Cynodon dactylon [L.] Pers.), zoysiagrass (Zoysia spp. [Willd.]), and St. Augustinegrass (Stenotaphrum secundatum [Walter] Kuntze) plant canopies during 60 days without water. Strong correlations existed between digital image analysis and qualitative leaf firing ratings (0.90) during the 60-day drought and between digital image analysis and qualitative ground cover ratings (0.82) during the 60-day recovery period. Results demonstrate wide variability in drought response and canopy expression among the three warm-season turfgrass species.