Irrigation Water Quality and Fertilizer Source Effects on Nitrogen Uptake Efficiency of Bermudagrass.

As availability of potable water for irrigation of turfgrass systems declines, turfgrass must increasingly be managed using lower-quality water sources, which are often characterized by elevated pH, salts and/or sodium.  While irrigation chemistry has been shown to directly impact plant growth and soil physical properties, there has been little research aimed at determining impacts of water chemistry on nitrogen uptake efficiency of turfgrass.  Nitrogen is the pacemaker of plant growth, and therefore, is the nutrient applied in greatest quantities on managed turf.  Previous research has shown that foliar N source can have a significant effect on N uptake in creeping bentgrass, but little is known regarding the influence of N source on warm-season putting green turf.  Given environmental and economic consequences of reduced N uptake efficiency, there is considerable practical importance in better understanding these dynamics.  Therefore, objective of this research was to determine the influence of water quality and N source on foliar and root N uptake by 'Champion' bermudagrass (Cynodon dactylon x C. transvaalensis) and 'Tifway' bermudagrass (Cynodon dactylon x C. transvaalensis germplasma) putting green turf.  Washed sod was planted atop a USGA specified root zone sand in 10 cm diam. x 30 cm deep lysimeters in a greenhouse at Texas A&M University.  After a 6-week acclimation period of irrigating with either reverse osmosis, sodic potable, or saline 2.5, 5, 10 dS m^-1 irrigation water, N applications [¹⁵N-labeled urea (NH₂CONH₂), ammonium sulfate (NH₄)₂SO₄), and potassium nitrate (KNO₃)] were foliar-applied at a rate of 0.5 kg N ha^-1.  Following an 8-hr uptake period, turf/soil cultures were harvested and analyzed via mass spectrometry to determine percent of applied N taken up by plant tissue and amount remaining in soil/thatch.  Effects of both water quality and N source on N uptake efficiency were observed, demonstrating the importance of water quality considerations and appropriate N selection during foliar fertilization events.