Physiological response of two turfgrass species to varying ratios of soil matric and osmotic potentials

Plants grown under saline conditions can experience elevated matric and osmotic stress between irrigation events. Research was conducted to assess the physiological response of tall fescue (Festuca arundinacea Schreber 'Monarch') and common bermudagrass (Cynodon dactylon L. 'Numex Sahara') to varying combinations of soil matric (psi(M)) and osmotic potentials (psi(U)). Two line-source gradient experiments were conducted, using municipal water with an electrical conductivity (EC) of 1.1 dS m(-1) or saline aquifer water blended with municipal water (EC of 6.0 dS m(-1)). Turf temperature, leaf xylem water potential (psi(L)), tissue osmolality (psi(N-TISS)), yield, evapotranspiration (ETa), percent cover, turf color, and tissue ion concentrations were monitored during a 68-d drydown period during the summer of the second year of experimentation. The total soil water potential (psi(T)) was highly linear with distance from the line source with no significant difference between fresh and saline treatments within each species (bermudagass, Adj r(2) = 0.867**; tall fescue, Adj r(2) = 0.810*). Significantly lower soil osmotic potentials were recorded under the saline treatment, while lower soil matric potentials were recorded under the fresh treatment for both species. Turf temperature, yield, ETa, turf color, and canopy cover responded to psi(M) and psi(N) in an additive fashion. The psi(L), psi(U-TISS) and tissue ion concentrations in bermudagrass and psi(N)-(TISS) and tissue ion concentrations in tall fescue responded in a nonadditive fashion, however. Our results suggest that water with a salinity level of 6.0 dS m(-1) could be used as a supplemental irrigation source for both tall fescue and bermudagrass if irrigation practices were designed to minimize water deficit.