Evaluation of nitrogen fertilization and irrigation on St. Augustinegrass: NO 3 -N leaching and turfgrass quality D. M. Park

Use of St. Augustinegrass ~52,000 acres harvested in 2000~52,000 acres harvested in ,775 acres for new residential starts43,775 acres for new residential starts Right-of-ways,Right-of-ways, re-sodding, recreation, re-sodding, recreation, commercial commercial From Haydu et al., 2002 Types of grass in Florida shown as a percent of total production for 2000

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

Rationale South West Florida Water Management District concerned over pollutionSouth West Florida Water Management District concerned over pollution Decline in water qualityDecline in water quality Overuse of water resourcesOveruse of water resources

Literature review: N sources No N leaching differences from different sources (Geron et al., 1993)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) 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) Comparison of coated AN versus non-coated AN in Myakka sand (Alva, 1992) N requirement by different grass species (Sartain, 1992) N requirement by different grass species (Sartain, 1992)

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

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

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

The effect of N rate on NO 3 -N leaching, St. Augustinegrass quality and clipping growth.The effect of N rate on NO 3 -N leaching, St. Augustinegrass quality and clipping growth. The effect of N sources on NO 3 -N leaching, St. Augustinegrass quality and clipping growth.The effect of N sources on NO 3 -N leaching, St. Augustinegrass quality and clipping growth. The effect of irrigation rate and frequency on NO 3 -N leaching, St. Augustinegrass quality and clipping growth.The effect of irrigation rate and frequency on NO 3 -N leaching, St. Augustinegrass quality and clipping growth. Objectives

Hypotheses N leaching will be minimized while maintaining satisfactory turf quality: H 1 = Combining of soluble and controlled release N products H 2 = Applying an optimum N rate H 3 = Applying optimum irrigation

Margate fine sand soil Margate fine sand soil siliceous, hyperthermic Mollic Psamnaquent siliceous, hyperthermic Mollic Psamnaquent

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

Install sample collection equipment Ceramic- cup sampler 40 cm

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

Grass selection Stenotaphrum secundatum (walt.) kuntze cv. ‘Floratam’ Stenotaphrum secundatum (walt.) kuntze cv. ‘Floratam’ From Haydu et al., 2002 Top four St. Augustinegrass types grown in Florida in 2000 Floratam 79% Palmetto 7% Floralawn 6% Bitterblue 3% Other 6%

Two experiments YEAR 1 (EXP.I) 2 irrigation schedules2 irrigation schedules 4 N sources4 N sources 3 N rates3 N rates YEAR 2 (EXP.II) 2 irrigation schedules2 irrigation schedules 6 N sources6 N sources 2 N rates2 N rates Six, 2 month fertilization cycles Six, 2 month fertilization cycles

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

ET p calculated (McCloud, 1955) ET P = KW (T-32) Where: K = 0.01 W = 1.07 T = mean temperature in o F. Over predicts ET during temperatures > 70 o FOver predicts ET during temperatures > 70 o F Uses a daily ET limiter of 7.6mm (Stewart and Mills, 1967)Uses a daily ET limiter of 7.6mm (Stewart and Mills, 1967)

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

Exp. I: M&M 4 N Sources Liquid Water soluble Urea (46%N) in 0.25 L H 2 0 /m 2 Granular Water soluble Urea (46%N) Granular Water soluble + controlled-release 50% Urea (46%N) + 50% SCU (39%N) GranularControlled-release SCU (39%N) UREA SCU

Exp. II: M&M 3 N Rates Applied bimonthly Year total (kg N ha -1 )

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

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

Exp. I:Observations & Measurements: 4. NO 3 -N concentrations and leaching Vadose zone pore water collected when percolate is predicted Vadose zone pore water collected when percolate is predicted Flow injection analysis using a Cd-Cu reduction column Flow injection analysis using a Cd-Cu reduction column Total cycle loadings Total cycle loadings Average cycle loadings Average cycle loadings Annual loadings Annual loadings Daily loadings = [NO 3 -N] X percolate volume Daily loadings = [NO 3 -N] X percolate volume (over 24h) (over 24h)

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

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

Exp. II: M&M N Sources No fertilizer Water soluble 100% Urea (46%N) Water soluble + controlled-release 50% Urea (46%N) + 50% SCU (39%N) Water soluble + slow-release 25% Urea (46%N) + 75% IBDU (31%N) Water soluble + slow-release 50% Urea (46%N) + 50% IBDU (31%N) Water soluble + slow-release 75% Urea (46%N) + 25% IBDU (31%N) IBDU UREA SCU

Exp. II: M&M 2 N Rates Applied bimonthly Year total (kg N ha -1 ) * 25* * = 50% UREA/ 50% SCU will not be tested at this rate.

Exp. II: Observations & Measurements: Water Budget Water Budget Visual turfgrass quality Visual turfgrass quality Growth Growth N tissue analysis N tissue analysis NO 3 -N concentrations and leaching NO 3 -N concentrations and leaching Percent N leached of applied N Percent N leached of applied N Visual turfgrass wilt Visual turfgrass wilt

Statistical analysis General linear modelGeneral linear model SAS Inc. softwareSAS Inc. software

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

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