Mineral Composition of Kentucky Bluegrass Under Effluent Water Irrigation.

Golf courses in the western United States are increasingly being irrigated with effluent water. Kentucky bluegrass (Poa pratensis L.)(KBG) is the most widely used turfgrass species in Colorado. Research was conducted on eight golf courses, including three courses in Denver after 10 years of effluent water irrigation, three courses in the nearby cities receiving effluent water for more than 10 years, and two courses receiving surface water for irrigation. Soil pH, EC, organic matter, Ca, Mg, K, Na, B, and SAR of soil saturated paste were determined. Kentucky bluegrass shoots were sampled from 25 roughs and analyzed for mineral concentration including (Na, Ca, Mg, K, Cl, B, S, P, Mn, Fe, Zn, Cu and Mo). Effluent water irrigation increased clipping sodium content by 4.3-9.9 times, chloride by 1.5 - 1.3 times, boron by 1.3 - 3.5 times, whereas tissue K/Na ratio were reduced by 74- 90%. Multiple regression analysis was conducted to identify the relationships between mineral concentration in clippings and turf quality. There was a linear relationship between turf quality and sodium content in the clippings (R²= 0.65). Soil SAR in 0-20 cm depth was highly associated with KBG shoot Na content with the logarithmic regression of R²=0.70.