Turf Performance Under a Linear Gradient Irrigation System in North Florida.

Periodic droughts, irrigation needs for managed turf and mandatory watering restrictions pose a challenge for turfgrass management to avoid a loss of turfgrass quality. Information regarding irrigation requirements and performance of turfgrass species used for residential and commercial landscapes, athletic fields, and golf courses in southeastern U.S. would be valuable. A Linear Gradient Irrigation System (LGIS) provides an efficient way to evaluate cultivar responses to variable moisture regimes. Eighteen commercially available cultivars and experimental lines from six turfgrass species – ‘Argentine’ bahiagrass (BH) (Paspalum notatum Flügge); ‘Common’ and ‘TifBlair’ centipedegrass (CP) [Eremochloa ophiruoides (Munro) Hack.]; ‘Captiva’, ‘Classic’, ‘Floratam’, ‘Palmetto’, ‘Raleigh’ and ‘Sapphire’ St. Augustinegrass (STA) (Stenotaphrum secundatum [Walt.] Kuntze.); ‘Celebration’, DT-1, ‘Princess 77’, T10, and ‘Common’ bermudagrass (BD) (Cynodon spp.); ‘Aloha’, ‘SeaDwarf’, and ‘Sealsle Supreme’ (SP) (Paspalum vaginatum Swartz.); and ‘Density’ buffalograss (BL) [Buchloe dactyloides (Nutt.) Engelm.] were evaluated during annually occurring dry periods in 2010 and 2011 for visual quality, color, and density; and chlorophyll index (CI). LGIS offered an irrigation gradient ranging from 0-120% of reference evapotranspiration (ET_o). At 55~80% ET_o, the species ranked in the following order for quality: CP (6.4) >BH (6.0) >BD (5.5) >STA (5.3) >SS (4.6) >BL (3.7). This trend continued as irrigation level decreased with faster decline in STA and slower decline in BD. Within each species, CP cultivars were not different under different irrigation regimes. SeaDwarf had higher CI than other SP cultivars when irrigation level was > 54% ET_o, but no differences in visual ratings were found. Among STA cultivars, Palmetto was rated lower in quality compared to Captiva, Classic, Floratam and Raleigh except at higher irrigation levels (≥80% ET_o). Sapphire had better quality compared to Palmetto under severe water deficit (3-25% ET_o), despite its lower visual quality and density ratings at high irrigation levels (≥105% ET_o). T10 performed poorest compared to other BD genotypes with lower color, quality, and density ratings, and lower CI. An experimental bermudagrass, DT-1, had higher CI than other BD genotypes (except Princess 77) when the irrigation level was < 105% ET_o, Although visual ratings provided less separation, DT-1 maintained higher quality at all irrigation levels. CP and BH persisted better than STA under little supplemental irrigation. BD had better drought performance under low irrigation levels with slower decline in turf quality. STA can perform equivalent to BH when ≥37% ET_o irrigation level was provided during periodic drought periods.