Deficit Irrigation of Seashore Paspalum and Bermudagrass

We compared the responses of 16 mm tall ‘Tifsport’, ‘Tifway 419’, ‘Tifgreen 328’, and ‘MidIron’ bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Davy], and ‘SeaSpray’, ‘SeaDwarf’, and ‘Sea Isle 1’ seashore paspalum (Paspalum vaginatum Swartz) to variable rates of irrigation applied using a linear gradient irrigation system in the semiarid Southwest. Target irrigation levels were 100, 80, 60, and 40% (2009) and 100, 80, 70, 60, and 40% (2010) of standardized reference evapotranspiration (ETos). Actual water applied (including rainfall) was 100, 83, 66, and 49% of ETos in 2009 and 100, 83, 75, 66, and 49% in 2010. Canopy temperatures increased as much as 15°C, quality (rated on a scale of 1–9) decreased from values of 6 or greater in turf irrigated with 100% ETos to 1.25 to 4.35 in turf irrigated with 40% ETos in July and August 2010, while dry matter production declined between 1.3 and 15.8 g m⁻² d⁻¹. Water application rates required to maximize turfgrass quality ratings across all turfgrasses ranged from 75 to 83% of ETos. Lower application rates were required for acceptable quality turfgrass (with quality ratings ≥6.0) and ranged from 66 to 75% of ETos for bermudagrass, and 75 to 80% of ETos for seashore paspalum. Spring green-up was delayed by deficit irrigation, approximately 2 wk with 80% ETos, 4 wk with 70% ETos, and 6 wk with 60% ETos. Bermudagrass, particularly MidIron, maintained higher quality ratings than seashore paspalum under accumulated water stress conditions.