Impact of Nitrogen Fertilization and Irrigation on St. Augustinegrass Quality and NO3-N Leaching

1. Evaluation of nitrogen fertilization and irrigation on St. Augustinegrass: NO3-N leaching and turfgrass quality D. M. Park

2. Use of St. Augustinegrass • ~52,000 acres harvested in 2000 • 43,775 acres for new residential starts • Right-of-ways, re-sodding, recreation, commercial Types of grass in Florida shown as a percent of total production for 2000 From Haydu et al., 2002

3. Sun-Sentinel Sep 26, 1999 Palm Beach Post May 17, 1998 The Orlando Sentinel May 9, 1998

5. Rationale • South West Florida Water Management District concerned over pollution • Decline in water quality • Overuse of water resources

6. Literature review: N sources • No N leaching differences from different sources (Geron et al., 1993) • Cultural practices: (ex. irrigation and mowing) (Snyder et al., 1976, 1980) (Cisar et al., 1991) • Comparison of coated AN versus non-coated AN in Myakka sand (Alva, 1992) • N requirement by different grass species (Sartain, 1992)

7. Literature review: N rates • Increase N rate, increase N leaching (Brown et al., 1977) (Cisar et al., 1991)

8. Literature review: Irrigation • Scheduled irrigation reduced [N] and leaching(Morton et al., 1988) • Increased N leaching from sand soils from initial simulated rainfall events(Wang and Alva, 1996)

9. Literature review: St. Augustinegrass • Focus on cool season grasses and bermudagrass • Minor information on St. Augustinegrass • Greater root density (Bowman et al., 2002) • Only field scale study in South Florida (Erickson et al., 2001) • 0.4% N loss of applied (Erickson et al., 2001)

10. Objectives • The effect of N rate on NO3-N leaching, St. Augustinegrass quality and clipping growth. • The effect of N sources on NO3-N leaching, St. Augustinegrass quality and clipping growth. • The effect of irrigation rate and frequency on NO3-N leaching, St. Augustinegrass quality and clipping growth.

11. Hypotheses N leaching will be minimized while maintaining satisfactory turf quality: H1 = Combining of soluble and controlled release N products H2 = Applying an optimum N rate H3 = Applying optimum irrigation

12. Margate fine sand soil • siliceous, hyperthermic Mollic Psamnaquent

13. Experimental design: Split Plot Repeated Measure Irrigation treatments (main plot) X N sources X (subplots) N rates X 4 Reps

14. 40 cm Ceramic- cup sampler Install sample collection equipment

15. Location of ceramic-cup samplers, tubing, and sprinklers Cup samplers Vacuum & sample lines Sprinkler heads

16. Grass selection Top four St. Augustinegrass types grown in Florida in 2000 Palmetto 7% Floralawn 6% Bitterblue 3% Other 6% Floratam79% From Haydu et al., 2002 • Stenotaphrum secundatum (walt.) kuntze cv. ‘Floratam’

17. YEAR 1 (EXP.I) 2 irrigation schedules 4 N sources 3 N rates Two experiments YEAR 2 (EXP.II) • 2 irrigation schedules • 6 N sources • 2 N rates • Six, 2 month fertilization cycles

18. EXP. I: M&M Irrigation treatments (2) Excessive: 125% maximum weekly ETp over three applications per week (M-W-F). Conservative: 125% weekly ETp adjusted by month, over three applications per week (M-W-F). • If rain event = 8.4mm of rain, then next irrigation was voided.

19. ETP = KW(T-32) Where: K = 0.01 W = 1.07 T = mean temperature in oF. • Over predicts ET during temperatures > 70 oF • Uses a daily ET limiter of 7.6mm (Stewart and Mills, 1967) ETp calculated (McCloud, 1955)

20. Comparison of methods for calculating ETp for Miami, Florida ET Models M= McCloud P= Penman T= Thornwaite From Augustine, 1983

21. Exp. I: M&M UREA SCU

22. Exp. II: M&M

23. Exp. I:Observations & Measurements: • 1. Water budget: • Irrigation • Rainfall • ETp • Percolate Percolate = Rainfall + Irrigation – ET (Snyder et al., 1984)

24. 3. Growth: • Dry weights • Clippings from a 2m2 area • Tissue N analysis • 0-15cm and 15-30cm cores Exp. I:Observations & Measurements: • 2. Visual turfgrass quality: • Scale from 1-10

25. Exp. I:Observations & Measurements: • 4. NO3-N concentrations and leaching • Vadose zone pore water collected when percolate is predicted • Flow injection analysis using a Cd-Cu reduction column • Daily loadings = [NO3-N] X percolate volume • (over 24h) • Total cycle loadings • Average cycle loadings • Annual loadings

26. Exp. I:Observations & Measurements: • 5. Percent N leached of applied N • Cycle • Annual

27. EXP. II: M&M Irrigation treatments (2) Excessive: 125% weekly ETp adjusted by month, over three applications per week (M-W-F). • If rain event = 8.4mm of rain, then next irrigation was voided. Conservative: Irrigate as above when visual wilt is present.

28. Exp. II: M&M IBDU SCU UREA

29. Exp. II: M&M * = 50% UREA/ 50% SCU will not be tested at this rate.

30. Exp. II:Observations & Measurements: • Water Budget • Visual turfgrass quality • Growth • N tissue analysis • NO3-N concentrations and leaching • Percent N leached of applied N • Visual turfgrass wilt

31. Statistical analysis • General linear model • SAS Inc. software

32. Anticipated Results Different combinations will result in different N leaching amounts and turfgrass quality

33. Implications • Less demand on water supply • Greater water use efficiency • Reduce risk of contamination to ground water supply • Basis for new BMP’s for St. Augustinegrass in South Florida

34. Questions?