Growing Degree Days to Predict Warm Season Turfgrass Establishment From Seed Under Saline and Subsurface Drip Irrigation.

A growing scarcity of potable water in the southwestern United States sets limits on its availability for nonessential uses such as turfgrass irrigation. Low quality ground water and recycled water have been identified as alternatives to potable water for irrigation. Both types of water can exhibit higher salinity levels than potable water and the resulting salt build-up in the turfgrass rootzone requires a change in species selection in transition zones from traditional cool season grasses to salt tolerant warm season grasses. However using warm season grasses in high altitude desert locations has been challenging, because the growing season for the warm season grasses can be relatively short and salinity stress can further slow down growth and establishment.  A study was conducted at New Mexico State University in Las Cruces, NM in 2008 and 2009 to determine the Accumulated Average Daily Soil Temperature (AADST) necessary to establish bermudagrass [Cynodon dactylon (L.)] cultivar Princess 77 and seashore paspalum [Paspalum vaginatum (Swartz)] cv. Sea Spray.  The grasses were irrigated at 100% potential ET with both with saline (1500 ppm TDS) and potable (500 ppm) water under 2 irrigation systems (sprinkler vs. subsurface-drip). In 2008 grasses were planted early March [dormant] and early June [standard]) and in 2009 grasses were seeded every 15^th day of each month from March to June. Response of percent ground cover to AADST was fitted to linear regression equations. In 2008 early seeded plots established faster than late seeded plots regardless of irrigation type and water quality. With the exception of saline drip irrigated plots, all late seeded treatments required fewer heat units (AADST) to reach 50% ground cover than early seeded plots. AADST strongly predicted percent ground cover for all treatments.