Effects of Reclaimed Water Irrigation on Growth and Nitrogen Uptake of Turfgrass

Reclaimed water (RW) is increasingly viewed as a valuable resource for supplying irrigation water and nutrients for landscape plants growing in urban environments. A greenhouse experiment was conducted to determine if nitrogen (N) in RW contributes significantly to turfgrass plant nutrition and to measure N use efficiency and the effects of irrigation with RW on N leaching. The factorial experiment was replicated four times and conducted in a greenhouse on the University of Florida campus for 1 year using ‘Floratam’ st. augustinegrass (Stenotaphrum secundatum) and ‘Empire’ zoysiagrass (Zoysia japonica). Treatments included irrigation with tap water (control), irrigation with RW from University of Florida wastewater treatment facility, irrigation with RW with additional N supplied from ammonium nitrate to achieve 5, 9, and 13 mg L N solutions, and a dry prilled fertilizer treatment based on the recommended N application rate for turfgrass in northern Florida. The average total N and phosphorus (P) concentrations of RW, based on 1 year weekly monitoring were 3.31 mg L total N with 2.14 mg L nitrate-N and 0.46 mg L ammonium-N, and 2.00 mg L P composed of 1.92 mg L orthophosphate. Turfgrass growth responded positively (P < 0.05) to N concentration in the irrigation water. The concentration of N in the unamended university campus RW was not sufficient for optimal turfgrass growth. Grass quality and turfgrass clippings yield maximized when the total N concentration in the irrigation water was at least 5 mg L. Turfgrass receiving dry synthetic N fertilizer resulted in greater growth and 2-fold greater N leaching than with the remaining treatments for both turf types. The highest N recovery percentage for both turf types was found when the N concentration in the solution was 5 mg L.