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Nitrogen Leaching, Water Use Rates and Turf Response of St. Augustinegrass and Bahiagrass to Irrigation and Fertilizer P...

Permanent Link: http://ufdc.ufl.edu/UFE0042127/00001

Material Information

Title: Nitrogen Leaching, Water Use Rates and Turf Response of St. Augustinegrass and Bahiagrass to Irrigation and Fertilizer Practices
Physical Description: 1 online resource (68 p.)
Language: english
Creator: Mc Groary, Pauric
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: augustinegrass, bahiagrass, evapotranspiration, fertilizer, florida, irrigation, leaching, nitrogen, turfgrass, water
Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Nitrogen Leaching, Water Use Rates and Turf Response of St. Augustinegrass and Bahiagrass to Irrigation and Fertilizer Practices In Florida, state regulators are concerned about St. Augustinegrass for both high water use and excess nitrogen (N) applications to home lawns. This has resulted in city ordinances to reduce nitrogen inputs beyond the current statewide regulations under the Urban Turf Fertilizer Rule in order to reduce N leaching. Furthermore, some municipalities have started to replace St. Augustinegrass with bahiagrass in an attempt to conserve water. However, there is limited information available on whether such practices actually help reduce N leaching and conserve water and their effect on St. Augustinegrass quality in subtropical south Florida. Consequently, two experiments were carried out 1) to determine water use rates of St. Augutsinegrass and bahiagrass under two N rates and 2) to evaluate N leaching, water conservation and St. Augustinegrass response to two irrigation regimes and four N rates. In Experiment 1 under non-limiting water and high N rates, bahiagrass cv. ?Pensacola? had comparable or higher water use rates than St Augustinegrass cv. ?Floratam?. In addition, bahiagrass may require more maintenance due to the faster growth rate in the summer months in south Florida. Additionally, N rate of 98 kg ha-1 yr-1 was able to reduced water use rates annually though it did not always produce acceptable quality. In experiment 2, applications of 196, 294 and 588 N/kg ha-1 yr-1 all produced acceptable quality. However, the applications rate of 588 kg N/kg ha-1 yr-1 produced greater amount of clippings than 196, 294 kg N/kg ha-1 yr-1 that may be an inconvenience to some homeowners. Minimum acceptable St. Augustinegrss was produced at 196 kg N/kg ha-1 yr-1. Furthermore, both low and high irrigation regimes produced acceptable quality during the experiment. However, water inputs were far greater for the high irrigation regime than the low irrigation regime. Therefore, proving to be ineffective irrigation regime for conserving water compared to the low irrigation regime. Nitrogen rates or irrigation regimes did not influence N leaching. Leaching of NO3-N never exceeded a mean flow-weighted concentration > 4 mg NO3-N L-1 during the experiment.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Pauric Mc Groary.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Cisar, John L.
Local: Co-adviser: Snyder, George H.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042127:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042127/00001

Material Information

Title: Nitrogen Leaching, Water Use Rates and Turf Response of St. Augustinegrass and Bahiagrass to Irrigation and Fertilizer Practices
Physical Description: 1 online resource (68 p.)
Language: english
Creator: Mc Groary, Pauric
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: augustinegrass, bahiagrass, evapotranspiration, fertilizer, florida, irrigation, leaching, nitrogen, turfgrass, water
Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Nitrogen Leaching, Water Use Rates and Turf Response of St. Augustinegrass and Bahiagrass to Irrigation and Fertilizer Practices In Florida, state regulators are concerned about St. Augustinegrass for both high water use and excess nitrogen (N) applications to home lawns. This has resulted in city ordinances to reduce nitrogen inputs beyond the current statewide regulations under the Urban Turf Fertilizer Rule in order to reduce N leaching. Furthermore, some municipalities have started to replace St. Augustinegrass with bahiagrass in an attempt to conserve water. However, there is limited information available on whether such practices actually help reduce N leaching and conserve water and their effect on St. Augustinegrass quality in subtropical south Florida. Consequently, two experiments were carried out 1) to determine water use rates of St. Augutsinegrass and bahiagrass under two N rates and 2) to evaluate N leaching, water conservation and St. Augustinegrass response to two irrigation regimes and four N rates. In Experiment 1 under non-limiting water and high N rates, bahiagrass cv. ?Pensacola? had comparable or higher water use rates than St Augustinegrass cv. ?Floratam?. In addition, bahiagrass may require more maintenance due to the faster growth rate in the summer months in south Florida. Additionally, N rate of 98 kg ha-1 yr-1 was able to reduced water use rates annually though it did not always produce acceptable quality. In experiment 2, applications of 196, 294 and 588 N/kg ha-1 yr-1 all produced acceptable quality. However, the applications rate of 588 kg N/kg ha-1 yr-1 produced greater amount of clippings than 196, 294 kg N/kg ha-1 yr-1 that may be an inconvenience to some homeowners. Minimum acceptable St. Augustinegrss was produced at 196 kg N/kg ha-1 yr-1. Furthermore, both low and high irrigation regimes produced acceptable quality during the experiment. However, water inputs were far greater for the high irrigation regime than the low irrigation regime. Therefore, proving to be ineffective irrigation regime for conserving water compared to the low irrigation regime. Nitrogen rates or irrigation regimes did not influence N leaching. Leaching of NO3-N never exceeded a mean flow-weighted concentration > 4 mg NO3-N L-1 during the experiment.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Pauric Mc Groary.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Cisar, John L.
Local: Co-adviser: Snyder, George H.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042127:00001


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NITROGEN LEACHING, WATER USE RATES AND TURF RESPONSE OF ST.
AUGUSTINEGRASS AND BAHIAGRASS TO IRRIGATION AND FERTILIZER
PRACTICES





















By

PAURIC C. MCGROARY


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2010

































2010 Pauric C. McGroary
































This document is dedicated to my family for all their love, help and support.









ACKNOWLEDGMENTS

I would like to thank Drs. John Cisar and George Snyder for their scientific

expertise, persistence and support. I am also indebted to my other supervisory

committee members, Drs. John Erickson, Jerry Sartain and Samira Daroub, who were

always available to answer questions and to provide guidance throughout. I am grateful

also to Drs. Alan Wright and Yigang Luo for their help and use of their lab. I would also

like to acknowledge the financial support of the Florida Department of Environmental

Protection (FDEP). The technical support of Ms. Karen Williams, Ms. Eva King, Mr. Joe

Giblin, Mr. Ajambar Rayamajhi, and Mr. Adam Michaud is much appreciated. Finally to

my fiancee Holly, for without her love, patience and support I would not have

accomplished this dream.









TABLE OF CONTENTS

page

A C KNO W LEDG M ENTS ............ ................ ........................... ............... 4

L IS T O F T A B L E S ........................ .................................................................................. 7

LIS T O F F IG U R E S .................................................................. 9

A BSTRACT ........................ ............................................. 10

CHAPTER

1 EVAPOTRANSPIRATION RATES OF ST AUGUSTINEGRASS AND
BAHIAGRASS UNDER VARYING NITROGEN RATES ............... ............ 12

Introduction ...................... ......... ............... 12
Materials and Methods............................. ............ ............... 14
Experimental Site and Design ..................................... 14
Measures of Turfgrass Quality and Clipping Growth ..................... .. 16
M measures of W ater Use........................ ....................... .................... 16
Analysis of Data .......................... ......... ......... 17
Results ................ ...... ............ ............ ................... 18
C lim ate ............... ........................ ....... ............... 18
Turfgrass Growth and Quality .............. ............ .................... 18
Turfgrass Water Use Rate .................. ................... ..... 19
D is c u s s io n ............................................................................ 1 9
C o n c lu s io n ................................................................................ ............... 2 2

2 EFFECTS OF IRRIGATION REGIMES AND NITROGEN RATES ON
NITROGEN LEACHING FROM ST. AUGUSTINEGRASS YARDS .................... 28

Introduction ...................... ......... ............... 28
Materials and Methods............................. ............ ............... 31
Experimental Site and Design ........ ........... ... ................. 31
Measure of Percolate and Nutrient Leaching ............ .................. 32
Analysis of Data .......................... ......... ......... 34
Results ................ ...... ............ ............ ................... 35
Hydrology ............... ......... .................. 35
Nitrogen Leaching ................ ........ ................. 35
D is c u s s io n .............. ..... ............ ................. ............................................. 3 7
C o n c lu s io n .............. ................. ............................................... ............... 4 0

3 EFFECTS OF IRRIGATION REGIMES AND NITROGEN FERTILIZATION ON
ST. AUGUSTINEGRASS GROWTH QUALITY AND WATER cONSERVATION... 44

Introduction .................................................................................................. ........ 44









Materials and Methods........................................... ............... 46
Turfgrass Quality .................. ..................... ......... 47
S tatistica l D esign and A na lysis..................................................... ............... 48
R e s u lts ................ ................. ................................................................................... 4 8
Turfgrass Quality .................. ..................... ......... 49
C lip p ing s Y ie ld .................................................... 5 0
Tissue N ........... ........ .. ............. ............................ 51
Nitrogen Uptake .............. .............................. 51
D discussion ............................................................................................ ............. 52
C o n c lu s io n ................................................................................ ............... 5 5
ANOVA ............................ ................. ........... ......... 58

R E FE R E N C E S .............................. ............. ....... 62

BIOGRAPHICAL SKETCH ..... ........... ......... ................. 68




































6









LIST OF TABLES


Table page

1-1 Percentage by weight of mineral particle fractions contained in the rootzone
used for construction of the field study area. ........................ ........................ 24

1-2 Total rainfall, total irrigation, total evapotranspiration and average daily air
temperature for each cycle of the trials at Ft Lauderdale, FL. .............. ............ 24

1-3 Trial 1 treatment means for dry weight of clippings of bahaiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 25

1-4 Trial 2 treatment means for dry weight of clippings of bahaiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 25

1-5 Trial 1 treatment means for turfgrass quality of bahiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 26

1-6 Trial 2 treatment means for turfgrass quality of bahiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 26

1-7 Trial 1 treatment means for water use rates of bahaiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 27

1-8 Trial 2 treatment means for water use rates of bahiagrass and St.
Augustinegrass at two N application rates............................... ... ............ 27

2-1 Percentage by weight of mineral particle fractions contained in the root zone
used for construction of the field study area............. ...... .................. 43

2-2 Analysis of variance results for drainage, flow-weighted concentration f NO3-
N, flow-weighted concentration of NH4-N quantity of NO3-N leached,
quantity of NH4-N leached and, quantity of total inorganic N leached.
Treatment means represent the average of 4 plots ............. .... ...... ........... 43

3-1 Percentage by weight of mineral particle fractions contained in the root zone
used for construction of the field study area. ............ ..... .................. 56

3-2 Total rainfall, total irrigation inputs, and reference ET for each cycle of the
stu d y ................. ................................... ........................... 5 7

3-3 Trial 1 treatment means (n = 4) for turfgrass quality for low and high irrigation
regimes and four N application rates ....... ................... ............... 58

3-4 Trial 2 treatment means (n = 4) for turfgrass quality for low and high irrigation
regimes and four N application rates ....... ................... ............... 58









3-5 Trial 1 treatment means (n = 4) for dry weight of clippings for low and high
irrigation regimes and four N application rates. .......................... ... ............... 59

3-6 Trial 2 treatment means (n = 4) for dry weight of clippings for low and high
irrigation regimes and four N application rates. .......................... ... ............... 59

3-7 Trial 1 treatment means (n = 4) for nitrogen tissue concentration for low and
high irrigation regimes and four N application rates................ ...... .............. 60

3-8 Trial 2 treatment means (n = 4) for nitrogen tissue concentration for low and
high irrigation regimes and four N application rates................ ...... .............. 60

3-9 Trial 1 treatment means (n = 4) for nitrogen uptake for low and high irrigation
regimes and four N application rates ....... ................... ............... 61

3-10 Trial 2 treatment means (n = 4) for nitrogen uptake for low and high irrigation
regimes and four N application rates ....... ................... ............... 61









LIST OF FIGURES


Figure page

2-1 Irrigation and precipitation inputs for the low and high irrigation regimes for
tria l 1 and tria l 2 (n = 32 )....................... ........ .............................. 42









Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

NITROGEN LEACHING, WATER USE RATES AND TURF RESPONSE OF ST.
AUGUSTINEGRASS AND BAHIAGRASS TO IRRIGATION AND FERTILIZER
PRACTICES

Pauric C. McGroary

August 2010

Chair: John Cisar
Cochair: George Snyder
Major: Soil and Water Science


In Florida, state regulators are concerned about St. Augustinegrass for both high

water use and excess nitrogen (N) applications to home lawns. This has resulted in city

ordinances to reduce nitrogen inputs beyond the current statewide regulations under the

Urban Turf Fertilizer Rule in order to reduce N leaching. Furthermore, some

municipalities have started to replace St. Augustinegrass with bahiagrass in an attempt

to conserve water. However, there is limited information available on whether such

practices actually help reduce N leaching and conserve water and their effect on St.

Augustinegrass quality in subtropical south Florida. Consequently, two experiments

were carried out 1) to determine water use rates of St. Augutsinegrass and bahiagrass

under two N rates and 2) to evaluate N leaching, water conservation and St.

Augustinegrass response to two irrigation regimes and four N rates.

In Experiment 1 under non-limiting water and high N rates, bahiagrass cv.

'Pensacola' had comparable or higher water use rates than St Augustinegrass cv.

'Floratam'. In addition, bahiagrass may require more maintenance due to the faster

growth rate in the summer months in south Florida. Additionally, N rate of 98 kg ha-1 yr1









was able to reduced water use rates annually though it did not always produce

acceptable quality. In experiment 2, applications of 196, 294 and 588 N/kg ha-1 yr1 all

produced acceptable quality. However, the applications rate of 588 kg N/kg ha-1 yr-

produced greater amount of clippings than 196, 294 kg N/kg ha- yr1 that may be an

inconvenience to some homeowners. Minimum acceptable St. Augustinegrss was

produced at 196 kg N/kg ha- yr1. Furthermore, both low and high irrigation regimes

produced acceptable quality during the experiment. However, water inputs were far

greater for the high irrigation regime than the low irrigation regime. Therefore, proving to

be ineffective irrigation regime for conserving water compared to the low irrigation

regime. Nitrogen rates or irrigation regimes did not influence N leaching. Leaching of

NO3-N never exceeded a mean flow-weighted concentration > 4 mg N03-N L-1 during

the experiment.









CHAPTER 1
EVAPOTRANSPIRATION RATES OF ST AUGUSTINEGRASS AND BAHIAGRASS
UNDER VARYING NITROGEN RATES

Introduction

Turfgrass landscapes provide many aesthetic and functional benefits to

residents, including opportunities for recreation. However, in order to maintain an

acceptable turfgrass landscape, irrigation inputs are required when rainfall is insufficient

(Aronson et al., 1987). In fact, the application of water to residential landscapes is a

major use of potable water (Baum, 2005). For example, water use in Florida by

residential homes accounts for 61% of the public supply category with the average

household using 71% of its total water consumption for irrigation use (Baum et al.

2005). As a result, many municipalities across the nation have enacted water

restrictions to limit residential irrigation in order to conserve potable water (e.g., South

Florida Water Management District). Some municipalities also offer programs for

replacing grass with xeriscepes in effort to reduce landscape irrigation (City of Glendale,

2010).

Turfgrass is a major component of urban vegetation and considerable work has

been done measuring its water use rates (WURs), which is the total amount of water

required for turfgrass growth plus the quantity lost by transpiration and evaporation

evapotranspirationn) (ET) from the soil and plant surfaces (Aronson et al., 1987; Beard,

1973; Fu et al., 2004; Fry and Butler, 1989; Kim and Beard, 1988; Park et al., 2005;

Youngner et al., 1981). Water loss by grass via ET is influenced by a number of factors,

includingclimate, plant morphological and anatomical factors and management

practices. Major climatic factors include wind speed (Danielson et al., 1979; Davenport,

1965), solar radiation (Feldhake et al., 1983; Shearman and Beard, 1973) atmospheric









vapor pressure, and temperature (Beard, 1973). Management practices include nitrogen

(N) fertilization rate (Barton et al., 2009; Ebdon et al., 1999; Feldhake et al., 1983;

Mantell, 1966; Shearman and Beard, 1973), fertilizer source (Saha, et al., 2005),

mowing height and frequency (Brian et al., 1981; Feldhake et al., 1983; Fry and Butler,

1989; Shearman and Beard, 1973;), use of growth regulators (Borden and Campbell,

1987) and soil water availability (Brian et al., 1981; DaCosta and Huang 2006;

Kneebone et al., 1992;) Furthermore WURs varies with turfgrass species (Aronson et

al., 1987; Fry and Butler, 1989; Fu et al., 2004; Kim and Beard, 1988; Youngner et al.,

1981) and within cultivar of the same species (Bowman and Macaulay, 1991; Ebdon

and Petrovic, 1998; Kopec et al., 1988; Shearman, 1986; Salaiz et al., 1991).

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntz] is one of the most

predominately used grass species for residential lawns in the southeastern United

States. In Florida alone, St. Augustinegrass is grown on approximately 70% of the

lawns with an additional 24,164 ha harvested annually from sod production (Busey,

2003; Haydu et al., 2005). 'Floratam' is the most extensively used cultivar due mainly to

its resistance to chinch bugs (Blissus insularis Barber) but its resistance has been

broken (Busey and Center, 1987). Recently, many state regulators in Florida have

criticized St. Augustinegrass for its high WURs, as a recent study showed that irrigation

for residential landscape accounted for 64% of total residential water use (approx. 141

mm mo-1) for homes surveyed in Central Florida (Haley et al., 2007). This has resulted

in a desire by some municipalities to substitute St. Augustinegrass with bahiagrass

(Paspalum notatum Flugge), which is commonly perceived to use less water (Lower ET)

than St. Augustinegrass under irrigated conditions. For example in Orlando, FL the









Orange County commissioners recently had one ha of St. Augustinegrass replaced with

bahiagrass in order to reduce water use in the county. However, limited data have

indicated comparable ET rates for St. Augustinegrass 'Floratam' and bahiagrass

'Penescola' in a greenhouse experiment (Miller and McCarty, 2001).

In addition to ET rates, N inputs for St. Augustinegrass lawns have also received

great interest due to environmental concerns (Erickson et al., 2001; 2008). Currently,

the recommended N rates for South Florida are 196-294 kg ha-1 yr1 for St

Augustinegrass and 98-196 kg ha- yr1 for bahiagrass (Trenholm et al., 2000). Few

studies have examined the effects of N rates on turfgrass WURs. Although Barton et al.

(2009) reported reduced ET at low N rates in Kikuyu turfgrass [Pennisetum

clandestinum (Hochst. ex Chiov)], the authors suggested that application of the

minimum N for turfgrass quality was an approach for decreasing water consumption by

turf. However, the implication of these findings for other grass species in other

environments is not well understood. Consequently, the aim of this study was to

determine the effect of different N fertilizer rates on WURs and turf quality of two warm

season grasses commonly used in residential yards in the southeastern U.S.

Materials and Methods

Experimental Site and Design

The study was conducted at the University of Florida's Institute of Food and

Agricultural Sciences, Fort Lauderdale Research and Education Center (26o03' N,

80o13' W) on stands of bahiagrass and St. Augustinegrass grown on a mined 'mason'

sand (Table 1-1) (Atlas Peat and Soil, Inc) that was low (<0.5%) in organic matter and

had a pH of 7.9 0.2. The experiment consisting of 16 turfgrass plots in a split-plot

randomized complete block design with four replications. Whole plots (8 x 4 m)









arranged in blocks consisting of either bahiagrass cv. 'Pensacola' or St Augustinegrass

cv. 'Floratam'. One of two N rates (98 and 294 N kg ha-1 yr1) was applied to sub plots

(4 x 2 m). Nitrogen rates were split equally over 6 application dates in 2006-2007 (trial

1) and again in 2007-2008 (trial 2). In 2006-2007 N was applied on 12 Oct., 12 Dec.

2006 and 15 Mar., 17 Apr., 18 June, and 16 Aug. 2007. In 2007-2008 N was applied on

the 11 Oct., 21 Dec. 2007 and 20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each

application date represented the start of a new fertilizer cycle (FC). Spray grade

granular urea (46-0-0) was used as the source (PCS Sales, Inc. Northbrook, IL) of N

and applied with a backpack C02-pressurized (30 psi) sprayer equipped with two flat-

fan TeeJet 8010 nozzles on 510 mm spacing. Immediately following N applications

turfgrass received 13 mm of irrigation to reduce N loss to volatilization and reduce burn

potential (Bowman et al., 1987). In addition to N fertilization, P and K from triple

superphosphate (0-46-0) and muriate of potash (0-0-63) were applied at the rates of

196 and 392 kg ha- yr1 to maintain acceptable soil test values. The fertilizers were split

equally every 90-days. Additionally, macro and micro-nutrients were applied as Harrell's

Max Minors containing Mg 1%, S 3.5%, B 0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6%

and Mo 0.0005% at 12 L ha- every 90-days. Throughout the duration of the experiment

plots received 2.5 mm of irrigation every day except when over 6.4 mm of precipitation

occurred. When precipitation events were > 6.4mm then irrigation for the following day

was voided. Plots were maintained using a rotary mower at a height of cut of 75 mm

and clippings were removed.









Measures of Turfgrass Quality and Clipping Growth

Turfgrass visual quality was assessed biweekly using a 1-9 scale (9 = dark green,

1 = dead/brown turf, and 6.5 = minimally-acceptable turfgrass (Carrow, 1997).

Turfgrass clipping samples for shoot growth were harvested from a 2.24 m2 area within

each plot using a rotary mower set at a height of 75 mm approximately weekly or more

frequently when necessary. Samples were oven dried at 600 C for 48 hrs to a constant

weight.

Measures of Water Use

In order to measure water use, large lysimeters were installed on top of a 300 mm

sand base in the center of each subplot. The lysimeters were constructed from plastic

drums 920 mm high, 597 mm diameter, with a 13 mm thick wall, (US Plastics

Corporation) with a flat bottom which had a threaded opening already manufactured into

the container for easy drainage pipe installations. The lysimeters were fitted with 19

mm polyvinyl chloride (PVC) drainage pipe, spliced to allow for lysimeter drainage and

individually installed on the foundation. A 90-degree elbow joint was attached to

drainage orifice, which was subsequently connected to a 10 mm section of 24 mm

diameter Schedule 40 PVC pipe that ran to a collection station. At the collection station

each pipe was allocated its own 20 L polyethylene container. Each lysimeter had a

stainless steel screen (1 mm mesh) over the orfice at the bottom of the lysimeter. This

subsequently was covered with a 100 mm layer of filter gravel (>14 mm 1%, 12-14 mm

7.5%, 9-12 mm 10.5%, 6.73-9 mm 28%, 6-6.73 mm 41%, 4-6 mm 7%, 2-4 mm 3.5%,

<2mm 1.5%) which was overlaid by 5 cm layer of choker sand (>2 mm 0.1%, 1-2 mm,

7.6%, 0.5-1.0 mm 26%, 0.25-0.5 mm 45.6%, 0.15-0.25 mm 19.1%, 0.053-0.15 1.2%,

<0.053 0.6%). Similar a layer was installed outside the lysimeter so the soil profiles









were similar. Subsequently, mason sand was packed around, between and within each

of the lysimeters to a depth of 780 mm. Furthermore, a 75 mm layer of mason sand was

spread uniformly over the top of the lysimeters. Perimeter irrigation systems were

installed on each of the main plots. The irrigation system comprised of 24 mm diameter

Schedule 40 PVC pipe with rotor Rainbird 3500 sprinklers placed in each corner

adjusted to spray an inward quarter circle.

Water use rates were determined by using the following calculation WURs =

(rainfall + irrigation)-(percolate + runoff) (Park et al., 2005). Runoff was omitted from

the equation, as it was never observed. Rainfall data was obtained from a Florida

Automated Weather Network (FAWN) station which was located within 500 m of the test

site Percolate and volumes were measured weekly and more frequently following

precipitation events exceeding 25 mm.

St. Augustinegrass and bahiagrass were sodded in their designated plots.

Additionally, berm areas were also sodded with St. Augustinegrass. Within the first

week after sod installation, a blended granular fertilizer (26-3-11) was applied to all the

plots at a rate of 50 kg N ha-1 yr- .This was followed a month later with an application of

6-6-6 at a rate of 50 kg N ha1 yr1. Before the actual initiation of the trials, grass was

allowed to establish for a period of 6 months. Throughout the first three months of the

establishment period irrigation was applied three times a week at 13 mm per

application. However, for the final three months of establishment, irrigation was adjusted

to 2.5 mm per day.

Analysis of Data

All data were analyzed for normality using the Shapiro-Wilk W test. Homogeneity

of variance was also checked graphically. Clipping yields (CYs) and WURs were totaled









for each fertilizer cycle and year. Quality ratings were averaged over each FC and trial.

Analyses were performed on individual fertilizer cycle-trial data because the length of

the fertilizer cycles varied from trial to trial. All data were subjected to analysis of

variance with PROC GLM (SAS Institute, 1999) and means were separated using

Fisher's Least Significant Difference (LSD) at the t-probability level of 0.05.

Results

Climate

Average daily temperatures ranged from 22-280C for trial 1 (14 October 2006 to

04 October 2007) and 21-280C for trial 2 (05 October 2007 to 05 November 2008)

(Table 1-2). However, in both trials air temperatures were generally lower in FC1, FC2,

and FC3 compared to FC4, FC5 and FC6. Rainfall varied slightly between trials. During

trials 1 and 2 plots received a total of 1658 mm and 1538 mm of rainfall (Table 2).

Furthermore, rainfall in both trials was generally greater during FC4, FC5, and FC6

compared to FC1, FC2 and FC3.

Turfgrass Growth and Quality

Clipping yields were affected by grass (P < 0.01) and N rate (P < 0.01) in both

trials (Table 1-3, 1-4). Clipping yields from each FC (Trial 1, FC3) were greater for

bahiagrass than St. Augustinegrass (Table 1-3; 1-4). Total clipping yields for each trial

were approximately 4 times greater from bahiagrass compared to St. Augustinegrass,

averaging 6988 and 1510 kg ha-1 for trial 1 and 4457 and 1369 kg ha- for trial 2,

respectively. In general both grasses produced the greatest CYs during FC4, F C5, and

FC6 (Table 1-3, 1-4). Additionally, the higher N rate (averaged across grasses)

significantly increased CYs by about 60% for each trial. In both trials, for each cycle









except FC1 and FC3 in trial 1 increasing the N rate from 98 to 294 kg ha-1 yr1

significantly increased clipping yields.

Both grass species and N rates produced acceptable quality (> 6.5) when

averaged across each trial. Bahiagrass quality scores were equal to or higher than St.

Augustinegrass across both trials but were only significantly different in (P < 0.05) in

three out of the 12 cycles (Table 1-5, 1-6). Although, the higher N rate always produced

higher quality scores than the lower N rate. It was only significantly higher in FC1, FC2,

FC3, and FC5 in trial 1 (Table 1-5) and FC3, FC6 in trial 2 (Table 1-6). Although the

lower N rate produced acceptable quality when averaged across trials, there were times

when quality was not acceptable, such as FC3 in trial 1 and FC2, FC3 and FC6 in trial

2.

Turfgrass Water Use Rate

Total water use rate (TWURs) was greater (P < 0.05) from bahiagrass compared

to St. Augustinegrass during trial 1, averaging 1508 and 1286 mm, respectively (Table

1-7). However, no significant difference was seen between the grasses during trial 2

(Table 1-8). In trial 1, bahiagrass showed significantly greater WURs in three out of the

six cycles, but bahiagrass WURs were only significantly greater in one cycle out of the

six cycles in trial 2 (Table 1-7, 1-8). In general, both grasses had higher WURs during

FC4, FC5, and FC6 of both trials. The high N rate (P < 0.05) increased TWURs by

about 8% in trial 1, no significant difference was found in trial 2 (Table 1-7, 1-8).

Discussion

With increasing concern over scarcity of water resources, pressure has been

placed on residents to reduce water use, especially when it comes to irrigation of

landscape areas such as yards and flower beds. While St. Augustinegrass is the most









widely used grass for home yards in Florida, it has been suggested that bahiagrass

should be used instead for its lower water use. In this study the quality, growth and

WURs of two grasses were compared under well-watered conditions utilizing two N

rates commonly applied by the lawn care industry. Results indicate that St.

Augustinegrass WURs was comparable or less than bahiagrass maintained in field

conditions.

In the current study the TWURs for St. Augustinegrass were 1,286 mm during trial

1 and 1,200 mm during trial 2, which were similar to that reported by Steward and Mills

(1967) of 1,067 mm for St. Augustinegrass. Total water use rates for both grasses was

higher during trial 1 than trial 2. A similar trend was observed in CYs, whereby yields

were greater in trial 1 than trial 2. Increased evaporative demand coupled with reduced

water inputs during trial 2 (Table 1-2) likely contributed to the lower CYs seen during

trial 2, which may explain why TWURs was lower in trial 2 compared to trial 1.

Throughout both trials WURs were generally comparable between both grasses,

and in some cases WURs were even greater for bahiagrass compared to St.

Augustinegrass (Table 1-7, 1-8). This may be explained by the fact that bahiagrass

produced significantly greater CYs than St. Augustinegrass, thus requiring more water

to support the increased growth (Barton et al., 2009; Brian et al., 1981). For example,

Barton et al. (2009) found that growth accounted for 75% of the variation in ET in kikuyu

turfgrass. Furthermore, differences in WURs between bahiagrass and St

Augustinegrass may also be explained by leaf orientation and shoot density difference

between the two grasses: St. Augustinegrass has a higher shoot density and a

substantial horizontal leaf orientation compared to bahiagrass which has a more vertical









leaf orientation and low shoot density (Kim and Beard, 1988). This vertical leaf

orientation and lower shoot density of bahiagrass leads to lower canopy resistance and

thus higher ET rates compared to a grass that has a higher canopy resistance (Kim and

Beard, 1988; Brian et al., 1981). Water use rates rates were generally higher in FC4,

FC5, and FC6 of each trial. This may be attributed to the greater canopy leaf area and

higher evaporative demand due to higher temperatures and longer photoperiod.

Throughout the duration of the experiment wilting was never observed in any of the

plots. Thus, each grass was evaluated under non deficit conditions. However, it should

be noted that even though bahiagrass used more water than St. Augustinegrass at

times in our study, bahiagrass may require less frequent and total irrigation, since

bahiagrass has a greater capacity to avoid water stress compared to St. Augustinegrass

(Miller and McCarty, 2001) and subsequently, requiring less frequent irrigation. In

addition, bahiagrass has the ability to survive periods when water is not available

through its capacity for dehydration avoidance (McCarty and Cisar, 1995) which allows

the grass to green up after watering. St. Augustinegrass does not encompass such a

mechanism. Therefore, when water becomes limiting the grass normally enters drought

and can potentially dies. Even though bahiagrass used more water under well watered

conditions in our study, it may be able to survive water deficit conditions better than St.

Augustinegrass, and thus allowing it to survive under lower and more infrequent water

inputs.

Water use rates were also affected by N fertilization rates; however these

differences were relatively modest, especially in comparison to the difference between

species. Furthermore, reducing N fertilizer rates by 67% resulted in a 5-8 % reduction









in WURs per trial. Similar results were reported for Kikulyugrass when decreasing N

rates reduced ET (Barton, et al., 2009). The reduction in WURs at low N was likely due

to the lower water use associated with reduced leaf area and clipping yield production

seen at low N (Brian et al., 1981; Barton et al., 2009). In the future if water restrictions

are heightened for home yards, manipulating of N rates may be a possible management

strategy in reducing water use rates of grasses and ultimately conserving water.

Throughout the duration of the experiment both grasses produced acceptable turfgrass

quality scores demonstrating that both grasses can be used to produce aesthetically

pleasing home yards with reduced inputs of irrigation and N However, clipping yields

showed that St. Augustinegrass (approx. 260%) responded much more to fertilization

than bahiagrass (approx. 35%), which was remarkably consistent across both trials.

Nevertheless, increasing N rates from 98 to 294 kg ha-1 yr1 improved quality in trial 1

and 2 for both grasses. Finally, clipping production varied greatly between grass

species. Bahiagrass growth rate was generally higher than St. Augustinegrass which

increased the frequency of mowing especially during FC4, FC5, and FC6 of each trial.

This may not be favored by homeowners as it may increase fuel, labor costs and waste

disposal of clippings (Fluck and Busey, 1988). Further work is needed to evaluate

bahiagrass response to lower N rates and irrigation as it may be possible to reduce N

rate without compromising turf quality. This may help in reducing WURs rates due to the

reduction in growth and the risk of N leaching.

Conclusion

While the results from this experiment varied across trials, some general

conclusions can be made regarding grasses and N management impacts on WURs

rates. First, under non-limiting water and high N rates, bahiagrass cv. 'Pensacola' had









comparable or higher WURs rates than St Augustinegrass cv. 'Floratam'. Second, both

St. Augustinegrass and bahiagrass can be used to produce acceptable quality lawns.

However, bahiagrass may require more maintenance due to the faster growth rate

especially during the warmer wetter summer months in south Florida. Finally, N rate of

98 kg ha1 yr1 was able to reduce WURs annually though it did not always produce

acceptable quality.









Table 1-1. Percentage by weight of mineral particle fractions contained in the rootzone
used for construction of the field study area.
Name Size range Weight
-------- mm------ ----%----
Fine Gravel 2.0 3.4 0
Very coarse sand 1.0 2.0 2
Coarse sand 0.5 -1.0 7
Medium sand 0.25 0.50 23
Fine sand 0.15 0.25 27
Very Fine Sand 0.05 0.15 34
Silt 0.002- 0.05 7
Clay less than 0.002 0


Table 1-2. Total rainfall, total irrigation, total evapotranspiration and average daily air
temperature for each cycle of the trials at Ft Lauderdale, FL.
Study Cycle No. Rainfall Irrigation Reference Min. Max. air Ave. air
period days ETt air temp. temp.
temp.
---------------------mm ---------------------------C-------
Trial 1 1 61 173 145 133 6 31 23
2 88 120 213 194 8 30 22
3 27 57 69 97 12 29 22
4 64 348 127 247 12 34 25
5 61 525 162 273 15 35 27
6 49 435 91 194 22 35 28
Total 350 1658 807 1138

Trial 2 1 76 210 178 179 10 32 24
2 56 142 135 113 3 30 21
3 65 157 137 220 8 32 23
4 62 158 145 291 17 35 26
5 58 439 112 257 21 35 28
6 75 432 170 244 22 32 26
Total 392 1538 877 1304 --
aTrial 1 Cycle 1, 14 October 2006 to 14 December 2006; Cycle 2, 15 December 2006 to
13 March 2007; Cycle 3, 14 March 2007 to 10 April 2007; Cycle 4, 11 April 2007 to 14
June 2007; Cycle 5, 15 June 2007 to 15 August 2007; Cycle 6, 16 August 2007 to 4
October 2007.
Trial 2 Cycle 1, 5 October 2007 to 20 December 2007; Cycle 2, 21 December 2007 to
15 February 2008; Cycle 3, 16 February 2008 to 21 April 2008; Cycle 4, 22 April 2008 to
23 June 2008; Cycle 5, 24 June 2008 to 21 August 2008; Cycle 6, 22 August 2008 to 5
November 2008.
t Reference Evapotranspiration (ET) was calculated using a modified Penman
equation.









Table 1-3. Trial 1 treatment means for dry weight of clippings of bahaiagrass and St.
Augustinegrass at two N application rates.
2006-2007
Factor C1 C2 C3 C4 C5 C6 Total
------------------------------kg ha-1----------
Grass (G)
Bahiagrass 250 205 335 1316 2463 2373 6988
St. Augustinegrass 44 89 89 233 564 492 1510
Sig. ** NS ** ** **
LSD 0.05 81 194 1005 846 586 2328
Nitrogen (N) (kg ha-1 yr-1)
98 134 99 189 567 1211 1107 3307
294 204 195 234 982 1817 1759 5191
Sig. NS NS *
LSD 0.05 66 398 544 447 1490
G X N Interaction
Bahiagrass 98 236 161 311 1051 2200 2020 5978
Bahiagrass 294 354 250 359 1581 2726 2727 7998
St. Augustinegrass 98 33 18 68 83 222 193 636
St. Augustinegrass 294 55 29 109 383 906 790 2384
Sig. NS NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001

Table 1-4. Trial 2 treatment means for dry weight of clippings of bahaiagrass and St.
Augustinegrass at two N application rates.
2007-2008
Factor C1 C2 C3 C4 C5 C6 Total
------------------------------kg ha-1----------
Grass (G)
Bahiagrass 393 ND 145 659 2066 1193 4457
St. Augustinegrass 105 ND 171 128 367 598 1369
Sig. ** NS ** ** **
LSD 0.05 146 349 780 302 1552
Nitrogen (N) (kg ha-1 yr-1)
98 186 ND 65 257 985 700 2193
294 312 ND 251 529 1449 1091 3633
Sig. ** *
LSD 0.05 74 128 141 377 322 1000
G X N Interaction
Bahiagrass 98 399 ND 102 490 1812 1039 3783
Bahiagrass 294 446 ND 188 827 2321 1346 5130
St. Augustinegrass 98 32 ND 29 24 157 360 601
St. Augustinegrass 294 178 ND 314 232 577 836 2137
Sig. NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001
ND, No data was collected during this cycle









Table 1-5. Trial 1 treatment means for turfgrass quality of bahiagrass and St.
Augustinegrass at two N application rates.
2006-2007
Factor C1 C2 C3 C4 C5 C6 Average
---------------------------------1-9---- -------------
Grass (G)
Bahiagrass 7.2 6.9 7.0 7.5 7.1 7.0 7.2
St. Augustinegrass 6.6 6.6 6.6 6.7 6.8 6.8 6.7
Sig. *** NS NS NS NS NS NS
LSD 0.05 0.3 0.6 0.5 0.7 0.3 0.7 0.4
Nitrogen (N) (kg ha-1 yr-1)
98 6.7 6.5 6.4 6.8 6.7 6.8 6.7
294 7.2 7.1 7.1 7.4 7.2 7.1 7.2
Sig. ** NS NS
LSD 0.05 0.3 0.6 0.5 0.3 0.4
G X N Interaction
Bahiagrass 98 7.0 6.8 6.6 7.3 7.0 7.0 7.0
Bahiagrass 294 7.4 7.2 7.3 7.7 7.2 7.2 7.4
St. Augustinegrass 98 6.3 6.2 6.3 6.3 6.4 6.7 6.4
St. Augustinegrass 294 7.0 7.1 6.8 7.1 7.2 7.0 7.1
Sig. NS NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001


Table 1-6. Trial 2 treatment means for turfgrass quality of bahiagrass and St.
Augustinegrass at two N application rates.
2007-2008
Factor C1 C2 C3 C4 C5 C6 Average
---------------------------------1-9---- -------------
Grass (G)
Bahiagrass 7.1 7.0 7.0 7.3 7.3 7.0 7.1
St. Augustinegrass 6.6 6.4 6.3 6.5 6.5 6.4 6.5
Sig. NS NS NS NS NS
LSD 0.05 0.5 0.7
Nitrogen (N) (kg ha-1 yr-1)
98 6.6 6.4 6.3 6.7 6.7 6.3 6.5
294 7.0 7.0 7.0 7.1 7.1 7.1 7.1
Sig. NS NS NS NS NS
LSD 0.05 0.5 0.4
G X N Interaction
Bahiagrass 98 7.0 6.8 6.8 7.1 7.0 6.7 6.9
Bahiagrass 294 7.3 7.3 7.4 7.5 7.5 7.4 7.4
St. Augustinegrass 98 6.3 5.9 5.7 6.3 6.4 5.9 6.1
St. Augustinegrass 294 6.9 6.7 6.6 6.7 6.6 6.8 6.7
Sig. NS NS NS NS NS NS NS
NS, and *, = P > 0.05, P < 0.05









Table 1-7. Trial 1 treatment means for water use rates of
Auqustinegrass at two N application rates.


bahaiagrass and St.


2006-2007
Factor C1 C2 C3 C4 C5 C6 Total
------------------------------ m-----------mm---------------------
Grass (G)
Bahiagrass 177 189 114 309 345 374 1508
St. Augustinegrass 122 159 88 238 321 360 1288
Sig. NS ** NS NS
LSD 0.05 15 116 65 80
Nitrogen (N) (kg ha-1 yr-1)
98 136 160 95 270 319 361 1341
294 162 188 106 277 347 372 1452
Sig. ** NS *
LSD0.05 15 20 11 27 10 80
G X N Interaction
Bahiagrass 98 170 192 113 326 342 373 1516
Bahiagrass 294 183 187 114 293 349 375 1501
St. Augustinegrass 98 102 128 78 214 297 349 1168
St. Augustinegrass 294 142 190 98 261 346 370 1407
Sig. NS NS NS NS NS NS NS
NS, *, and **, = P > 0.05, P < 0.05, P < 0.01


Table 1-8. Trial 2 treatment means for water use rates of
Augustinegrass at two N application rates.


bahiagrass and St.


2007-2008
Factor C1 C2 C3 C4 C5 C6 Total
-------------------------------- m ----------- ---------
Grass (G)
Bahiagrass 184 139 220 276 294 185 1298
St. Augustinegrass 159 126 205 264 265 181 1200
Sig. *
LSD 0.05 14 21 38 29 55 51 175
Nitrogen (N) (kg ha-1 yr-1)
98 165 134 208 261 267 179 1214
294 179 131 217 279 290 187 1283
Sig. NS NS NS NS NS NS
LSD 0.05 14 -
G X N Interaction
Bahiagrass 98 184 143 221 272 291 182 1293
Bahiagrass 294 185 135 219 280 297 188 1304
St. Augustinegrass 98 146 125 196 250 247 175 1139
St. Augustinegrass 294 173 127 215 278 283 186 1262
Sig. NS NS NS NS NS NS NS
NS, and *, = P > 0.05, P < 0.05









CHAPTER 2
EFFECTS OF IRRIGATION REGIMES AND NITROGEN RATES ON NITROGEN
LEACHING FROM ST. AUGUSTINEGRASS YARDS

Introduction

Nitrogen is essential for growth and function and is the mineral nutrient required in

the greatest quantity by turfgrasses (Beard, 1973). When N is maintained at sufficient

levels, N can promote vigor, visual quality, recovery from damage and overall health

(Bowman et al., 2002). Consequently, N fertilizers are frequently used to maintain or

improve density and the aesthetics of residential landscapes as the amount of N in most

soils is insufficient to support acceptable aesthetics of residential yards (Cisar et al.,

1991). When N is applied to turfgrass, it can exit the turf/soil system via gaseous losses

such as volatilization and denitrification, groundwater leaching, runoff, and clipping

removal (Petrovic, 1990). Of these processes, the regulatory and environmental groups

perceive nitrate (NO3-N) leaching as the greatest environmental threat due to its

mobility and its inability to be retained on soil colloids (Bowman et al., 2002). Nitrate is

considered one of the most widespread contaminants among the world's aquifers and

can lead to eutrophication and algal blooms in near shore environments and lakes

(Spalding and Exner, 1993). It is also considered a human health threat if NO3-N levels

exceed 10 mg L-1 in drinking water as it can cause the syndrome known as

methemoglobinemia also called "blue baby syndrome" (USEPA, 1976). In Florida, NO3-

N leaching from home lawns has been implicated as a potential source of N pollution to

streams, lakes, springs and bays (Erickson et al., 2001; Flipse et al., 1984). With

expanding residential land use and increasing urban population in Florida, greater

quantities of fertilizer may be applied, which could contribute to problems associated

with NO3-N contamination in water. In addition, residential soils in southern Florida are









generally coarse-textured with little ability to retain either N or water which may further

increase leaching of N03-N especially after excess precipitation (Cisar et al., 1991;

Erickson et al., 2008).

To date, research-examining fertilizer N leaching from turfgrass generally has

shown low potential of N leaching from turfgrass (Erickson et al., 2008; Reike and Ellis,

1974; Sheard et al., 1985; Starr and DeRoo, 1981; Mancino and Troll, 1990; Miltner et

al., 1996). However, higher N leaching losses have shown to be greatly influenced by

several management factors including N rate, N source, N frequency, N application

methods, irrigation management, turfgrass establishment, and species or cultivar

selection (Barton, et al., 2006; Bowman et al., 2002; Cisar et al., 1991; Erickson et al.,

2010; Geron et al., 1993; Reike and Ellis, 1974; Snyder et al., 1984; Snyder et al., 1989;

Petrovic, 1990). For example, soluble N fertilizer sources used at the same rates and

frequencies of slow release or organic sources tend to increase leaching (Eason and

Petrovic, 2004). Furthermore, increasing irrigation and precipitation in excess of ET has

shown to increase N leaching (Barton et al., 2006; Morton et al., 1988; Snyder et al.,

1984). For example, Snyder et al., (1984) demonstrated on bermudagrass that

scheduling irrigation on soil moisture depletion could reduce N03-N to <1% compared to

daily irrigation that resulted in losses ranging from 22 to 56%.

In 2002, Best Management Practices in Florida were developed by regulatory,

academic and industry professionals after research had shown that fertilizer

management was a major factor in reducing non-point source pollution (Gross et al.,

1990; Trenholm et al., 2002). Currently, published research for St. Augustinegrass has

examined the effects of sod type, irrigation, and fertilization on newly established St.









Augustinegarss sod, contrasting landscapes (mixed species vs. St. Augustinegrass)

and rates of quick release vs. slow release N fertilizer on ornamentals and St.

Augustinegrass NO3-N leaching (Erickson et al, 2001; Erickson et al., 2008; Erickson et

al., 2010; Saha, et al., 2005). However, there are no published data on the impact of

other management practices such as irrigation, soluble N rates and the combination of

these factors on N leaching from mature St. Augustinegrass yards.

Current state-wide regulations in Florida under the Urban Turf Fertilizer Rule has

limited N applications to 49 kg N ha-1 per application of which, the water-soluble N

portion should not exceed 34 kg N ha- (Department of Agricultural and Consumer

Services (DACS), No. 4640400, Rule 5E-1.003, 2007). Furthermore, some local

ordinances impose stricter N fertilizer guidelines than the ones under the Urban Turf

Fertilizer Rule in an attempt to further reduce N leaching. For example, the City of

Sanibel enacted Ordinance No. 07-003 (Council of the City of Sanibel, Water

Resources Department), which prohibits N fertilization during the traditional rainy

season in South Florida from June 1 through September 30, restricts annual N applied

as fertilizer to 196 kg ha-1, and further limits the per-application soluble N portion of

fertilizer to 24.5 kg ha-1. However, no research has reported that such fertilizer

practices actually needed to reduce N leaching from St Augustinegrass. In addition,

water restrictions on home yards restrict irrigation of home yards to at least three days

per week (Phase 1) to once a week (Phase 3) or none (South Florida Water

Management District, 2010) (SFWMD) depending on the ordinance and water restriction

in place to conserve water. Given that there is little data supporting the claims that

these management practices or similar ones can reduce N leaching from St.









Augustinegrass yards in south Florida, we conducted a study to determine how

irrigation regimes and N rates influence inorganic-N leaching from established St.

Augustinegrass.

Materials and Methods

Experimental Site and Design

The study was conducted at the University of Florida's Institute of Food and

Agricultural Sciences (IFAS), Fort Lauderdale Research and Education Center (26003'

N, 80013' W) on an stand of St. Augustinegrass (cv. 'Floratam'), which was initially

produced on sand soil and then grown on a mined landscape-type sand (Atlas Peat

and Soil, Inc) that was low (<0.5%) in organic matter (Table 2-1) with a pH of 7.9 0.2.

Sand was used as the rootzone media for this experiment as to demonstrate a worst

case scenario situation (Table 2-1). The experiment consisted of 32 plots in a split-plot

randomized complete block design with four replications repeated over two trials. Main

blocks (8 x 4 m) consisted of one of two irrigation regimes: 2.5 mm daily (Low) except

when daily precipitation > 6.4 mm (irrigation turned off), and 13.0 mm three times

weekly (High) simulating a Phase 1 water use restriction that is used by the South

Florida Water Management District under water shortages (SFWMD, 2010). Subplots

(2 x 4 m) consisted of four N rates (98, 196, 294 and 588 kg N ha-1 yr1). The 588kg N

ha-1 yr-, which is double the recommend rate for this geographical region by IFAS

(Trenholm et al., 2000), was included in the study as a worst-case scenario for

excessive N applications to home yards in south Florida. The 294 kg N ha- yr rate is

suggested for south Florida conditions with appreciable soil organic matter, 196 kg N

ha- yr1 is more comparable to central/north Florida with a shorter growing season and

the 98 kg rate is recommended for the University of Florida "Florida Yards and









Neighborhood" resource efficient landscapes that include turf. Nitrogen rates were split

over 6 application dates. In 2006-2007 N was applied on the 12 Oct., 12 Dec. 2006 and

15 Mar., 17 Apr., 18 June, and 16 Aug. 2007. In 2007-2008, N was applied on the 11

Oct., 21 Dec. 2007 and 20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each application

date represented the start of a new fertilizer cycle (FC). Spray grade granular urea (46-

0-0) was used as the source of N and was applied with a backpack CO2-pressurized (30

psi) sprayer equipped with two flat-fan TeeJet 8010 nozzles on 510 mm spacing as per

industry standard method of application. Immediately following N applications, plots

received 13 mm of irrigation to reduce loss by volatilization and reduce burn potential

(Bowman et al., 1987). In addition to N fertilization, P and K from triple superphosphate

(0-46-0) and muriate of potash (0-0-60) were applied to maintain acceptable soil test

values at the rate of 196 and 392 kg ha-1 yr1, split equally every 90-d, respectively.

Additionally, micro-nutrients were applied as Harrell's Max Minors containing Mg 1%,

S 3.5%, B 0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6% and Mo 0.0005% at 12 L ha-

every 90-days. Plot were maintained using a rotary mower at a height of cut of 75 mm

and clippings were removed.

Measure of Percolate and Nutrient Leaching

Drainage was measured using lysimeters inserted into each of the plots on top of

a 300 mm sand base in the center of each subplot. The lysimeters were constructed

from plastic drums 920 mm high, 597 mm diameter, with a 13 mm thick wall, (US

Plastics Corporation) with a flat bottom which had a threaded opening already

manufactured into the container for easy drainage pipe installations. The lysimeters

were fitted with 19 mm polyvinyl chloride (PVC) drainage pipe, spliced to allow for

lysimeter drainage and individually installed on the foundation. A 90-degree elbow joint









was attached to drainage orifice, which was subsequently connected to a 10 mm

section of 24 mm diameter Schedule 40 PVC pipe that ran to a collection station. At the

collection station each pipe was allocated its own 20 L polyethylene container. Each

lysimeter had a stainless steel screen (1 mm mesh) over the orfice at the bottom of the

lysimeter. This subsequently was covered with a 100 mm layer of filter gravel (>14 mm

1%, 12-14 mm 7.5%, 9-12 mm 10.5%, 6.73-9 mm 28%, 6-6.73 mm 41%, 4-6 mm 7%,

2-4 mm 3.5%, <2mm 1.5%) which was overlaid by 5 cm layer of choker sand (>2 mm

0.1%, 1-2 mm, 7.6%, 0.5-1.0 mm 26%, 0.25-0.5 mm 45.6%, 0.15-0.25 mm 19.1%,

0.053-0.15 1.2%, <0.053 0.6%). Similar a layer was installed outside the lysimeter so

the soil profiles were similar. Subsequently, mason sand was packed around, between

and within each of the lysimeters to a depth of 780 mm. Furthermore, a 75 mm layer of

mason sand was spread uniformly over the top of the lysimeters. Perimeter irrigation

systems were installed on each of the main plots. The irrigation system comprised of 24

mm diameter Schedule 40 PVC pipe with rotor Rainbird 3500 sprinklers placed in each

corner adjusted to spray an inward quarter circle. Following the completion of the

installation of the lysimeters St. Augustinegrass was planted in the designated plots.

Before the actual initiation of the experiment, grass was allowed to establish for a period

of 6 months. Thereafter, percolate water volume was measured and subsamples were

collected (20 ml scintillation vial) at least weekly, and more frequently following

precipitation events exceeding 25 mm. Additionally irrigation water and rain water

samples were collected bi weekly as well. The subsamples, irrigation and rain samples

were immediately preserved with one drop of 50% sulfuric acid to a pH < 2, refrigerated

to a temperature < 4 C and analyzed within 28 days as per Florida Department of









Environmental protection protocol. Percolate samples were analyzed by colorimetric

method for NO3-N (EPA method 353.2) using a Seal AA3 continuous flow analyzer

(Seal Analytical Mequon, WI) by the University of Florida Analytical Research

Laboratory (Gainesville, FL). In addition, percolate samples were analyzed for

ammonium (NH4-N) by colorimetric method (QuickChem method 10-107-06-2-A) using

a Lachat Flow injection analyzer (Hach Company, Loveland, CO) at the Everglades

Research and Education Center, University of Florida. All values below the minimum

detection limit (MDL) were reported as the MDL. Minimum detection limits for NO3-N

and NH4-N methods were 0.05 and 0.05 mg/L for trial 1 and 0.15 and 0.05 mg/L for trial

2, respectively. Total quantity of NO3-N and NH4-N leached and flow weighted means

concentrations (total quantity of N leached/total volume percolate) were calculated from

volume of percolate and laboratory analyses for each cycle.

Analysis of Data

All data were analyzed for normality using the Shapiro-Wilk W test. Homogeneity

of variance was also checked graphically. Percolate, NO3-N and NH4-N leached were

summed on a plot-by-plot basis for each year and analyzed on a yearly basis. In

addition, mean flow weighted concentrations were calculated for each trial. All data

were subjected to analysis of variance with PROC Mixed (SAS Institute, 1999) and

means were separated using fisher's protected Least Significant Difference (LSD) test

with alpha=0.05. Orthogonal contrasts examined linear and quadratic responses to N

rates (Gomez and Gomez, 1984).









Results


Hydrology

Annual rainfall for trial 1 and 2 averaged 1658 and 1538 mm, respectively (Figure,

2-1). Rainfall in trials 1 and 2 accounted for 67 and 46% and 65 and 43% of total inputs

for the low and high irrigation regimes, respectively. Irrigation inputs for the low and

high irrigation regime averaged 807 and 1892 mm for trial 1 and 877 and 2173 mm for

trial 2, respectively. Total water inputs varied depending on the irrigation regime. In trial

1 the high irrigation regime had a total water input of 3550 mm, which was 44% greater

than water inputs for the low irrigation (2465 mm). Similarly, in trial 2 the high irrigation

regime had 52% (3811 mm) greater water inputs than the low irrigation (2515 mm)

(Figure, 2-1). Drainage was (P <0.05) impacted by irrigation regime and N rates (Table

2-2). In both trials, the greatest drainage occurred from the high irrigation regime with

means of 1702 and 1720 mm for trials 1 and 2, respectively. The low irrigation regime

resulted in 37 and 28% less drainage than the high irrigation regime for the same trials.

Under high and low irrigation regimes 49 and 51 % of the total water inputs were lost as

drainage in trial 1 and 45 and 48% for trial 2, respectively. Furthermore, in both trials as

N increased drainage generally decreased. In trial 1 and 2 drainage decreased from

1588 to 1397 mm and 1569 to 1336 mm in response to N rates increasing from 98 to

588 kg N ha-1 yr-1 (Table 2-2).

Nitrogen Leaching

Nitrate-N and NH4-N concentrations in the rain and irrigation water were always

below the MDLs for their respective trials. Flow weighted (FW) N03-N concentrations in

the drainage were similar (P > 0.05) among both irrigation regimes and nitrogen rates

(Table 2-2). Flow weighed (N03-N) concentrations in the leachate from the low and









high irrigation treatments averaged 0.21 and 0.17 mg L-1. Similarly, FW (N03-N)

concentrations in the leachate from the N treatments ranged from 0.15-0.28 mg L-1. In

addition, FW (NH4-N) concentrations in the drainage were always lower than the FW

(N03-N) concentrations. Furthermore, increasing irrigation inputs (high irrigation

regime) or N rates did not increase (P > 0.05) FW (NH4-N) concentrations in drainage.

Flow weighted NH4-N concentrations in the drainage averaged 0.07 and 0.08 mg L1 for

the low and high irrigation regimes, respectively (Table 2-2). Flow weighted (NH4-N)

concentrations leached from the different fertilizer rates ranged from 0.07-0.09 mg L1

with FW(NH4-N) concentrations never exceeded a mean value of 1 mg L1.

Total inorganic nitrogen (TIN) leached was not (P > 0.05) affected by irrigation

regimes or N rates (Table 2-2). However, the high irrigation regime always produced

the greatest amounts of TIN leached with mean of 3.4 kg N ha-1. Additionally, the high

irrigation regime accounted for 42 % more TIN leached compared to the low irrigation

regime. Total inorganic N leached from the different fertilizer rates ranged from 2.2 to

3.8 kg N ha- (Table 2-2). The highest N rate always produced the greatest amount of

TIN leached with mean of 3.8 kg N ha-1. Under the highest N rate TIN leached

represented less than 0.6% of the total N applied. Similar to TIN leached, N03-N

leached was not (P > 0.05) affected by irrigation or N rates (Table 2-2). However, the

high irrigation regime and highest N rate produced the greatest quantity of N03-N and

NH4-N leached. Under the high irrigation regime averaged N03-N and NH4-N leached

were 1.8 and 1.1 kg N ha-1. In addition, under the highest N rate the average N03-N

and NH4-N leached were 3.1 and 0.7 kg N ha- (Table 2-2).









Discussion

Irrigation regimes and N rates were evaluated for N leaching on a sand rootzone.

A rate of 588 kg N ha-1 was included, which is twice the recommended rate for St

Augustinegrass in south Florida, to serve as a worst-case scenario. Throughout the

duration of the experiment flow weighted (N03-N) leached levels never elevated above

the EPA human health standards of 10 mg N03-N L-1. The highest FW concentration

measured in the drainage water was never > 4 mg N03-N L-1. Irrigation regimes and N

rate did impact drainage, and N rate affected FW N03-N concentrations in the drainage

(Table 2-2). However, the quantities of N03-N, NH4-N or TIN leached did not differ

among any of the treatments. These results raise questions as to whether ordinances

are really needed to reduce the N applied beyond that enforced by the Urban Turf

Fertilizer Rule, which limits N applications to 49 kg N ha- of which, the water-soluble N

portion should not exceed 34 kg N ha1.

Drainage was greatly impacted by irrigation regime, as the high irrigation regime

increased drainage by an average of 39%. However, FW N03-N and NH4-N

concentrations did not differ under the high irrigation regime. Despite greater drainage,

with the high irrigation regime, we found no differences in the quantity of N03-N, NH4-N

or TIN leached, due largely to the fact that concentrations tended to be lower in the high

irrigation regime compared to the low irrigation regime (Table 2-2). This may be

attributed to the high irrigation diluting the N03-N and NH4-N concentrations in the

drainage water especially if N03-N and NH4-N concentrations are low in the soil

solution. Furthermore, in both studies, FW N03-N concentrations were greater than

NH4-N concentrations. This may be explained by urea being rapidly converted to NO3-









N through the processes of hydrolysis and nitrification and/or by NH4-N being retained

on the cation exchange site thus, being less mobile than the N03-N.

The results in this study with regard to irrigation effects on N leaching differ from

many published studies (e.g., Morton et al., 1988; Snyder et al. 1984, and Barton et al.,

2006). For example, Barton et al. (2006) found that increasing the irrigation from 70%

to 140% of ET increased N leaching significantly. However, in this study increasing

total water inputs by 48% did not significantly increase FW NH4-N or N03-N

concentrations or quantities leached, but there was a general trend in this direction,

indicating that irrigation in the present study was not as excessive as earlier reported

research. Nitrogen rates did impact drainage and FW N03-N concentrations. Higher N

rates generally decreased drainage due to the increase in growth rates that increased

water use rates (McGroary et al., 2010) thus, decreasing the drainage volume. Barton,

(2009) found similar results when increasing N rate increased ET rates. Furthermore,

Snyder et al., 1984 showed that reducing percolate reduced N leaching from

bermudagrass. Thus, a well maintained lawn (proper irrigation and fertilization) may

actually reduce leaching due to the reduced percolate through the rootzone. In general,

as N rate increased so did FW N03-N concentrations. Again, these differences did not

result in (P > 0.05) greater FW N03-N, NH4-N or TIN leaching, due to the less drainage

observed with the high N rates. Nevertheless, there was a trend towards greater TIN

leaching at the high N rates. However, it's possible that greater quantities of the applied

N could be leached as urea or loss through gases losses. Unfortunately in this study

organic-N in percolate or gaseous losses were not measured. Thus, we were unable to

predict how much total N from urea was leached or lost to the atmosphere, but Sartain









(2010) reported that urea applications to St. Augustinegrass at 49 kg N ha-1 every 30

days for a period of 180 days did not produce urea in leachates.

Consequently, in this study we only examined the impact of N rates on TIN. Total

inorganic N leached accounted for less than 3% of the total applied N lost. This

advocates that alternative pathways in the N cycle played a more significant part in the

fate of N in this system. The amount of N leached has been found to be dependent on

soil storage/drainage, amount of N in solution, gaseous losses volatilizationn and

denitrification), immobilization, and N uptake by the vegetation. The results indicated

that St. Augustinegrass was either efficient at removing the NH4-N and N03-N from the

soil solution or at tying them up through immobilization, as soil storage in the ionic form

would have been negligible due to low cation exchange capacity of the soil.

Additionally, the N applied may have been lost to the atmosphere through volatilization

or denitrification or a combination of both pathways. In order to minimize N volatilization

losses in this study 13 mm of irrigation was applied immediately after N fertilization,

which Bowman et al. (1987), reported to reduce volatilization to less than 8% from

Kentucky bluegrass (Poa pratensis L.). However, irrigation application after N

fertilization may have not been adequate at halting volatilization completely. With the

soil having a pH 7.8 and environmental conditions (high temperature and humidity) this

would have been conducive for volatile N loss especially if irrigation was ineffective at

initially reducing volatilization (Titko et al. 1987). Plots receiving higher rates of N are

prone to higher rates of ammonium volatilization than the lower N rates (Wesley et al.,

1987). Additionally, denitrification a pathway by which facultative anaerobes reduce

NO3-N to molecular N in anaerobic soils (Coyne, 2008) may have contributed to N loss.









Horgan et al., (2002) reported 9.8 kg N ha-1 loss of applied N from Kentucky bluegrass

through denitrification. However, Barton et al. (2006) reported low denitrification rates in

sands, thus accounting for only a small amount of N loss. Immobilization, the

conversion of inorganic N to organic N, may also contribute to a large disparity between

N applied and leached. Starr and Deroo (1981) evaluated the fate of N on cool-season

grasses using labeled 15N and found that 15 21% of applied N was stored in the

organic content of the soil. However, plant uptake may have had the greatest impact of

reducing N leaching in this study. Bowman et al., (2002) reported that St

Augustinegrass was relatively efficient at reducing N03-N leaching due to its root length

density when compared to common bermudagrass [Cynodon dactylon (L.) Pers.],

'Tifway' hybrid bermudagrass (C. dactylon X transvaalensis ), centipedegrass (Erem

chloaophiuroides (Munro) Hack.), 'Meyer' zoysiagrass (Zoysia japonica Steud.), and

'Emerald' zoysiagrass (Z. japonica X intenuifolia)].

Furthermore, Bowman et al. (2002) reported that shoots, clippings and roots

accounted for up to 74% of applied N with the greatest quantity being stored in the

shoots (52%). Unfortunately, in this study, shoots were not measured but this may help

explain why little N leaching occurred.

Conclusion

Under worse case scenario conditions such as a sand rootzone and double the

recommended N rate, N leaching was negligible and did not exceed human health

standards or those thought to be of concern for environmental impact. Therefore, the

are no need to reduce N application rates beyond the current Urban Turf Fertilizer

Rules. Furthermore, the high irrigation regime (3 X week) did not significantly increase

N leaching from St. Augustinegrass. However, it produced more drainage, which









indicated that irrigating at a greater rate but reduced frequency may actually be a poor

management strategy for conserving water compared to a lower irrigation rate

increased frequency irrigation regime.







Figure 2-1. Irrigation and precipitation inputs for the low and high irrigation regimes for
trial 1 and trial 2 (n = 32).


4500
4000
3500
3000
2500
2000
1500
1000
500
0


Low


SRainfall U Irrigation


Ii


High


Low


High


Trial 2


R


Trial 1









Table 2-1. Percentage by weight of mineral particle fractions contained in the root zone
used for construction of the field study area.
Name Size range Weight
-------- mm------ ----%----
Fine Gravel 2.0 3.4 0
Very coarse sand 1.0 2.0 2
Coarse sand 0.5- 1.0 7
Medium sand 0.25 0.50 23
Fine sand 0.15 0.25 27
Very Fine Sand 0.05 0.15 34
Silt 0.002 0.05 7
Clay less than 0.002 0


Table 2-2. Analysis of variance results for drainage, flow-weighted concentration f NO3-
N, flow-weighted concentration of NH4-N quantity of N03-N leached, quantity
of NH4-N leached and, quantity of total inorganic N leached. Treatment
means represent the average of 4 plots.
Effects Drainage [N03-N] [NH4-N] N03-N NH4-N Inorganic-N
leached leached leached
(mm) (mg L-1) (mg L-1) (kg ha-1) (kg ha-1) (kg ha-1)
Irrigation (IRR)
Low 1231 0.21 0.08 1.8 0.6 2.4
High 1711 0.17 0.07 2.3 1.1 3.4
Nitrogen Rate (NR)
(kg ha-1 yr-1)
98 1579 0.15 0.07 1.6 0.6 2.2
196 1556 0.18 0.07 2.0 0.6 2.6
294 1378 0.16 0.08 1.6 0.6 2.2
588 1367 0.28 0.09 3.1 0.7 3.8
ANOVA
Source of variation
TRIAL NS NS NS NS NS NS
IRR NS NS NS NS NS
NR ** NS NS NS NS
Linear NS NS NS NS NS
Quadratic ** NS NS NS NS NS
IRR x NR NS NS NS NS NS NS
TRIAL x IRR x NR NS NS NS NS NS NS
NS, *, and ** = P > 0.05, P < 0.05, and P < 0.01, respectively. Note: Interactions not
shown were not significant.










CHAPTER 3
EFFECTS OF IRRIGATION REGIMES AND NITROGEN FERTILIZATION ON ST.
AUGUSTINEGRASS GROWTH QUALITY AND WATER CONSERVATION

Introduction

St. Augustinegrass (Stenotaphum secundatum [Walt.] Kuntze) is one of the most

widely used grass species for home lawns in the Southeastern United States. In Florida

alone, St. Augustinegrass is grown on approximately 70% of the lawns with an

additional 24,164 ha grown for sod production (Busey, 2003; Haydu et al., 2005). St.

Augustinegrass is adapted for moderate cultural practices, which include judicious

inputs of both N and irrigation (Trenholm et al., 2000). Irrigation and N are essential

components of producing quality turfgrass (Beard, 1973). At the appropriate rates, N

and irrigation have been shown to improve turfgrass color, quality, and root growth

along with many other additional benefits. However, excess N and irrigation rates

applied to turfgrass can potentially increase NO3-N leaching and degrade water quality

(Hull and Liu, 2005; Snyder et al., 1984).

In addition, many state regulators have criticized St. Augustinegrass management

both for its high water use in home yards, as a recent study showed that irrigation

accounted for 64% of residential water use (approx. 141 mm mo1) in Central Florida

(Haley et al., 2007). As a result, many municipalities across the nation have enacted

water and N fertilizer restrictions to limit residential inputs in order to conserve water

and protect water resources (e.g., SFWMD, 2010). Some municipalities even offer

rebates to remove grass and replace it with xeriscape (Glendale, 2010). For example,

in south Florida the SFWMD enforces different phases of water restrictions to

landscapes and golf courses in order to conserve water. These phases can limit









irrigation from three days per week (Phase 1) to once a week (Phase 3) or none

(SFWMD, 2010) depending on the ordinance and water restriction in place. These

efforts are intended to conserve water and result in penalties that are enforced if caught

watering outside the guidelines. Currently, the state is in mandatory Phase 1 to Phase

3 restrictions year round. Other municipalities prohibit planting of St. Augustinegrass

(Central Florida) or do not permit irrigation from installed irrigation systems in South

West Florida.

Because of concerns over anthropogenic inputs of N to threatened water bodies,

such as coastal bays and fresh water systems (Vitousek et al., 1997), current state-wide

regulations in Florida under the Urban Turf Fertilizer Rule limit N applications to 49 kg N

ha- of which, the water-soluble N portion should not exceed 34 kg N ha- (Department of

Agricultural and Consumer services (DACS), No. 4640400, Rule 5E-1.003, 2007).

However, there are no published data on whether these management practices actually

conserve water or provide sufficient N nutrition to maintain acceptable St.

Augustinegrass in South Florida that are grown primarily on sandy soils with little ability

to retain water and nutrients. Research is needed to determine if such practices can

actually conserve water and maintain St. Augustinegrass quality. Furthermore, data is

lacking on the minimum N inputs required in order to produce acceptable St.

Augustinegrass in south Florida. Consequently, research must be conducted to provide

accurate fertilizer recommendations so acceptable turfgrass quality can be maintained

with minimum impact on the environment.

Therefore, the objectives of this experiment were to 1) evaluate irrigation and

fertilizer practices and their impact on water conservation and St. Augustinegrass









growth and quality 2) to evaluate an alternative irrigation regime and to determine

minimum N requirements for the production of St. Augustinegrass in subtropical south

Florida.

Materials and Methods

The study was conducted at the University of Florida's Institute of Food and

Agricultural Sciences (IFAS), Fort Lauderdale Research and Education Center (26003'

N, 80013' W) on an established mature stand of St. Augustinegrass cv. 'Floratam' sod

initially produced on sand soil and then grown on a mined 'mason' sand commonly-used

in landscapes in south Florida. The sand was low (<0.5%) in organic matter (OM)

(Table 1) and had a pH of 7.9 0.2. The experiment consisted of 32 plots in a split-plot

randomized complete block design with four replications of each treatment. Main blocks

(8 x 4 m) consisted of one of two irrigation regimes: 2.5 mm daily (Low) except when

daily precipitation > 6.4 mm (irrigation turned off), and 13.0 mm three times weekly

(High) simulating a Phase 1 water use restriction that is implement by the South Florida

Water Management District under water shortages (SFWMD, 2010). The irrigation

system comprised of 24 mm diameter Schedule 40 PVC pipe with rotor Rainbird 3500

sprinklers placed in each corner adjusted to spray an inward quarter circle. Subplots (2

x 4 m) consisted of four N rates (98, 196, 294 and 588 kg N ha-1 yr1). The 588kg N ha-

yr-) which included in the study as a worst case scenario for excessive N applications

to home yards in south Florida which is double the recommend rate for N in this

geographical region (Trenholm et al., 2000). The 294 kg rate is suggested for south

Florida conditions with appreciable soil organic matter, and 196 kg is more comparable

to central/north Florida with a shorter growing season. The 98 kg rate is recommended

for the University of Florida "Florida Yards and Neighborhood" resource efficient









landscapes that include turf. Nitrogen rates were split equally over 6 application dates

in 2006-2007 except for (cycle two and three) in trial 1 and again in 2007-2008 trial 2.

In 2006-2007 N was applied on the 12 Oct., 12 Dec. 2006 and 15 Mar., 17 Apr., 18

June, and 16 Aug. 2007. In 2007-2008, N was applied on the 11 Oct., 21 Dec. 2007 and

20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each application date represented the

start of a new fertilizer cycle (FC). Spray grade granular urea (46-0-0) was used as the

source of N and applied with a backpack CO2-pressurized (30 psi) sprayer equipped

with two flat-fan TeeJet 8010 nozzles on 510 mm spacing as per industry standard

method of application. Immediately following N applications, plots received 13 mm of

irrigation to reduce loss by volatilization and reduce burn potential (Bowman et al.,

1987). In addition to N fertilization, P and K from triple superphosphate (0-46-0) and

muriate of potash (0-0-60) were applied to maintain acceptable soil test values at the

rate of 196 and 392 kg ha-1 yr1, split equally every 90-d, respectively. Additionally,

micro-nutrients were applied as Harrell's Max Minors containing Mg 1%, S 3.5%, B

0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6% and Mo 0.0005% at 12 L ha- every 90-

days. Plot were maintained using a rotary mower at a height of cut of 75 mm and

clippings were removed.

Turfgrass Quality

Irrigation and N response was evaluated in terms of visual quality. Visual quality

evaluations were conducted approximately every 14 days and ratings were based on a

scale of 1-9, where 1 was brown or dead grass and 9 represented dark green, dense

uniform grass. A rating of 6.5 was considered minimally acceptable (Carrow, 1997).

Turfgrass clipping samples for shoot growth were harvested from a 2.24 m2 area within

each plot using a rotary mower (Toro, Bloomington, MN) set at a height at a 75 mm









approximately bi-weekly or more frequently when necessary. Samples were oven dried

at 800 C for 48 hrs to a constant weight. Subsequently, tissue samples were ground

using a Wiley Mill and sub sampled for tissue N analysis. Nitrogen was determined

using a modification of digestion described by Wolf (1982) and analyzed for NH4-N

using a spectrometer (UNIVO 2100, Dayton, NJ) at a wavelength of 660 nm. Nitrogen

uptake was calculated by multiplying tissue N concentration (g N kg-1) by yield (kg dry

wt. ha-1), and was reported as g N ha-1. Reference evapotranspiration was calculated

using a modified penman method and was obtained from a Florida Automated Weather

Network (FAWN) station which was located within 500 m of the test site (Zazueta,

1991).

Statistical Design and Analysis

All data were analyzed for normality using the Shapiro-Wilk W test. Homogeneity

of variance was also checked graphically. Turfgrass quality, clipping yields (CYs), tissue

N concentration, and N uptake were summed on a plot-by-plot basis for each cycle and

analyzed on a year bases because of trial by treatment interactions. All data were

subjected to analysis of variance with PROC Mixed (SAS Institute, 1999) and means

were separated using Fisher's protected Least Significant Difference (LSD) test with

alpha=0.05. Orthogonal contrasts examined linear and quadratic responses to N rates

(Gomez and Gomez, 1984).

Results

Hydrology

The relative contribution of irrigation and rainfall differed depending upon the time

of year and irrigation regime (Table 3-2). For the dry season cycles (i.e., FC1, FC2, and

FC3) low and high irrigation regimes accounted for between 48 to 59 % and 67 to 77%









of the total water received by plots for trial 1 and 35 to 49% and 58 to 69% for trial 2

(Table 3-2). However, for the wet season cycles (i.e., FC4, FC5, and FC6) irrigation

inputs accounted for considerably less of the total inputs with low and high irrigation

regimes accounting for between 19 to 34% and 39 to 57% of the water received by plots

for trial 1, and 20 to 48% and 42 to 68% for trial 2 (Table 3-2). The large differences

between seasons in the percent of total inputs that irrigation accounts for can be

explained by the large precipitation event that normally occurs in the wet season in

Florida (Table 3-2). In addition, the dry season low and high irrigation regimes alone

accounted for between 65 to 109% and 147 to 251% of ET rates for trial 1 and 62 to

119% and 162 to 281% of ET rates for trial 2. However, for the wet cycles low and high

irrigation regimes account for between 49 to 50% and 126 to 138% of ET rates for trial 1

and 44 to 70% and 118 to 172% for trial 2 (Table 3-2). Irrigation inputs for the high

irrigation exceed the low irrigation regime by 144% (1162mm) and 148% (1296 mm) for

trial 1 and 2 respectively. Throughout the duration of both trials total inputs (rainfall +

irrigation) always exceeded ET demands of St. Augustinegrass. For the dry season low

and high irrigation total inputs exceed ET rates by 36 to 116% and 118 to 258% for trial

1 and 79 to 145% and 179 to 307% for trial 2. During the wet season low and high

irrigation total inputs exceed ET rates by 44 to 164% and 121 to 253% for trial 1 and 4

to 147% and 72 to 249% for trial 2.

Turfgrass Quality

St Augustiengrass visual quality was affected (P > 0.05) by irrigation regimes

though not significant in every cycle (Tables 3-3, 3-4). Both irrigation regimes did

produce acceptable quality (2 6.5) for the duration of both trials (Tables 3-3, 3-4).

Throughout the duration of trial 1, low and high irrigation regimes produced similar









turfgrass quality with an average score of 7.0 for both irrigation regimes. However, in

trial 2 the high irrigation regime produced higher visual quality rating than the low

irrigation regime with average scores of 6.7 and 6.6, respectively (Table 3-4).

Nitrogen rates affected turfgrass quality ratings with visual quality increasing with

N rate in both trials (Tables 3-3, 3-4). Among the four N rates evaluated only 98 kg N

ha-1 yr1 was unable to produced acceptable (2 6.5) visual quality for the duration of both

trials with the 588 kg N ha- yr1 always producing the highest quality with means of 7.8

and 7.6 for trial 1 and 2. Furthermore, plots receiving 294 kg N ha- yr1 always yielded

higher visual quality ratings than the 196 kg N with average scores of 7.1 and 6.7 and

6.8 and 6.6 for trial 1 and 2, respectively. The lowest quality scores were observed at

the 98 kg N ha- yr1 which had average visual scores of 6.3 and 5.8 for trial 1 and 2

which was below the acceptable (2 6.5) visual quality (Tables 3-3, 3-4).

Clippings Yield

Results for CYs were similar to those for visual quality. Clipping yields generally

increased by N rate (Tables 3-5, 3-6). Greatest CYs occurred from plots receiving 588

kg N ha-1, which typically yielded twice as much clipping as the plots receiving the next

highest N rate of 294 kg N ha- (Tables 3-5, 3-6). No differences in CYs were observed

between plots receiving 294, 196, and 98 kg N ha- when averaged over each trial.

However, statistical differences were observed between N rates within each cycle.

Plots receiving the higher N rate always produced the greatest CYs except FC4 in trials

1 and 2. Plots receiving 98 kg N ha- generally produced about 35% less clippings than

plots receiving 196 kg N ha-1. Similar CYs were observed from plots receiving 294 and

196 kg N ha-1. Irrigation regimes had no effect on CYs (Tables 3-5, 3-6).









Tissue N

Irrigation regime had no effect (P > 0.05) on tissue N concentration (Tables 3-7, 3-

8). The N concentration of clippings generally increased with increasing N fertilization

rates. However, N fertilization only affected tissue N levels in 4 cycles in trial 1 and 3

cycles in trial 2. The N rate of 588 kg N ha-1 always produced the highest N

concentration with average tissue concentrations of 21.3 and 20.5 g N kg- for trials 1

and 2, respectively. Though, tissue N did vary between cycles with N ranging from 18.9

to 26.4 g N kg and 18.0 to 24.5 g N kg for trials 1 and 2. The lowest tissue N was

always found on the plots receiving 98 kg N ha- with an average tissue N of 17.1 and

17.9 g kg- for their respective trials (Tables 3-7, 3-8).

Nitrogen Uptake

Nitrogen uptake was greatly influenced by N fertilization (Tables 3-9, 3-10). As

nitrogen rates increased so did N uptake. However, only the 588 kg N ha- rate was

statistically different from the other three N rates averaged over each trial with the 588

kg N ha- rate almost taking up double the amount of N compared to the 298 kg N ha1.

The 98 kg N ha- had the lowest N uptake with an average of 16 and 17 kg N ha- for

trials 1 and 2, respectively. In addition, plots receiving N rates of 294 and 196 kg N ha1

up took twice as much N as the 98 kg N ha-1. However, it was statistically different in

FC2 in trial 1 and FC1 and FC6 in trial 2. Similar N uptake was observed from plots

receiving 294 and 196 kg N ha-1. Nitrogen recovered in tissue based on percentage-

applied range from 14 to 16% in trial 1 and 12 to 17% of applied in trial 2. The greatest

% N recovery always occurred in the lowest N rate and the lowest recovery from the

294 kg N ha-1. Irrigation regime had no significant effect on N uptake within each trial or

when averaged across each trial (Tables 3-9, 3-10). Total N uptake for low and high









irrigation regimes were 47.7 and 44.0 kg N ha-1 for trial 1 and 39 and 41 kg N ha- for

trial 2.

Discussion

With water and N inputs to urban landscapes under scrutiny, it is essential that

both are applied to match the needs of turfgrass, as this has been shown to help

conserve water, reduce nitrogen leaching and produce aesthetically pleasing yards

(McGroary, 2010). Currently, the SFWMD enforces mandatory water restrictions,

whereby irrigation is limited between three times a week (phase 1) and once a week

(phase 3). In this study two irrigation regimes and four N rates were compared to

determine the most suitable irrigation regime and N rates to produce a visually

acceptable St. Augustinegrass lawn with minimum inputs.

In the current study, the high irrigation regime, which is a phase 1 water restriction,

did not improve growth, N uptake, and N concentrations. Barton et al. (2006) reported

similar results, as increasing irrigation from 70% to 140% replacement of pan

evaporation did not improve growth or quality of turfgrass. Under the high irrigation

regime, irrigation far surpassed water requirements for St. Augustinegrass by at least

about 65% thus, proving to be an ineffective way of conserving water as well as having

little positive impact on quality. Furthermore, the greatest difference between the

irrigation inputs and ET was observed during FC1, FC2 and FC3. Theses cycles

occurred during the dry season in south Florida where lower temperatures generally

reduced St. Augustinegrass growth and ET rate. However, under a phase one-water

restriction no reduction in irrigation inputs would be carried out, thus leading to irrigation

inputs greater than St. Augustinegrass demands with wasted water. On the other hand,

the low irrigation regime did provide irrigation inputs closer to ET demands though when









combined with rainfall did surpass water demands of the St. Augustinegrass.

Nevertheless, during the dry season this irrigation regime conserved more water without

sacrificing turfgrass quality. However, during cycles FC4, FC5 and FC6, the low

irrigation regime did not match ET requirements, which Snyder, 1984 showed improve

growth, N uptake and color of bermudagrass. When irrigation was combined with

rainfall, the total water inputs were greater than the ET demand but had an irrigation

savings of 588 and 653 mm over the high irrigation regime with still being able to

produced similar turfgrass quality scores. These results suggest that the low irrigation

regime may be a more suitable regime than the phase 3 restrictions which is enforced

by the SFWMD for maintaining acceptable St. Augustinegrass quality in south Florida

quality due to the fact that acceptable quality was able to be maintained while over 1162

and 1296 mm of irrigation water were conserved for trial 1 and 2 respectively (Table 3-

2). In addition, N concentration, N uptake and growth were not affected by irrigation

regime, indicating that neither irrigation regimes differed in the availability of N to the

plant by moving it beyond the root system, and thus increasing the risk for N to be

leached into the groundwater.

St Augustiengrass quality, N concentration, uptake and growth were greatly

influenced by N rate. Nitrogen concentration values in this study were comparable to

others found for St. Augustinegrass in the literature. For example, Broschat and Elliott

(2004) report 13.0 to 19.7 g N kg-1 in St. Augustinegrass maintained with 196kg N ha1.

In comparison, Vernon et al., (1993) documented 14 g N kg- in leaf clippings from St.

Augustinegrass var. Raleigh.









Nitrogen concentration, quality, uptake and growth increased with increasing N

rates. Nitrogen applications of 588 kg ha-1 application to St. Augustinegrass 588 kg ha-

produced the best quality, greatest N concentration and N uptake but also produced the

greatest amount of clippings compared to the other N treatments. However, this N rate

may not be favored by homeowners as it greatly increases fuel, labor costs and waste

disposal of clippings (Fluck and Busey, 1988). The N rate of 98 kg N ha- was unable to

produce acceptable quality of St. Augustinegrass for the duration of both trials, although

the quality that was produced may be acceptable to some homeowners who do not

demand their lawn to be dense and green all year round, and who do not want the extra

cost of regular mowing and waste disposal. In addition, under different soils or

management practices, such as returning clippings this N rate may be able to produce

an acceptable yard, though further research is needed to validate this question. The

minimum acceptable quality for St. Augustinegrass in South Florida could be reached

by applying 196 kg N ha- as this was the lowest N rate that was able to produce

minimum acceptable quality when average over each trial. However, this application

rate did not always provide acceptable quality in all of the cycles, which may be

unsatisfactory to some homeowners. But the N rate of 294 kg N ha- was always able

to produced quality above minimum acceptable quality for all cycles and over each trial.

Therefore, N recommendations of 196-294 kg N ha-1, as currently recommended for

South Florida (Trenholm et al., 2002), are accurate for maintaining St. Augustinegrass at

acceptable levels with clippings being removed. These recommendations may be

further reduced if clippings are returned rather than removed like in this study. Kopp and

Guillard (2002) found that returning clippings could reduce fertilizer rates by 50% in









cool-season turfgrass. Currently no such data exist for St. Augustinegrass, therefore

research is needed to determine if N inputs could be further reduced by returning

clippings to St. Augustinegrass.

In this study, the constructed soil was very low in organic matter, which can supply

appreciable N for turfgrass growth. That coupled with the source of turf being derived

from sand-based sod production probably had an effect on all measured parameters

and demonstrate the need for more N nutrition under conditions of low OM, sand-based

soil media with high saturated conductivity, and recently established turf. Over time,

with increasing OM, perhaps improved turf quality with similar inputs could be expected.

Although the irrigation rates were not excessive, since the N source was totally soluble,

N pathways such as leaching and volatile losses could have impacted turf responses

from the N fertilization. Research on more mature turf, soils with higher OM, and other

N sources and application regimes along with irrigation regimes is needed.

Conclusion

While the results from this experiment varied across trials, some general

conclusions can be drawn. The low irrigation was able to maintain St. Augustingrass

quality throughout the duration of the experiment while conserving large amounts of

water compared to the current implemented phase 1 restriction that are enforced in

Florida. Nitrogen rate of 196 and 294 N/kg ha-1 yr1 produced acceptable quality while

not producing excess growth. With minimum acceptable St Augustinegrss quality in

south Florida been able to be produced at 196 kg N/kg ha- yr'.









Table 3-1. Percentage by weight of mineral particle fractions contained in the root zone
used for construction of the field study area.
Name Size range Weight
-------- mm------ ----%----
Fine Gravel 2.0 3.4 0
Very coarse sand 1.0 2.0 2
Coarse sand 0.5 -1.0 7
Medium sand 0.25 -0.50 23
Fine sand 0.15 0.25 27
Very Fine Sand 0.05 0.15 34
Silt 0.002 0.05 7
Clay less than 0.002 0









Table 3-2. Total rainfall, total irrigation inputs, and reference ET for each cycle of the
study.
Study Irrigation Period Rainfall Irrigation Total Reference!
Period Regime Inputs ET
mm----------------------------- M -----------------------------


2006-2007
















2007-2008


Low
Low
Low
Low
Low
Low
Total

High
High
High
High
High
High
Total

Low
Low
Low
Low
Low
Low
Total

High
High
High
High
High
High
Total


97
216
86
412
248
453
1512

97
216
86
412
248
453
1512

210
142
257
158
439
432
1638

210
142
257
158
439
432
1638


142
221
79
130
130
104
806

330
508
178
330
330
292
1968

178
135
137
145
112
170
877

419
318
356
343
318
419
2173


240
437
165
541
378
557
2318

428
724
264
742
579
745
3480

388
277
394
303
551
602
2515

629
460
613
501
757
851
3811


135
202
121
258
262
211
1189

135
202
121
258
262
211
1189

179
113
220
291
257
244
1304

179
113
220
291
257
244
1304


a2006-2008 Cycle 1, 12 October 2006 to 11 December 2006; Cycle 2, 12 December
2006 to 14 March 2007; Cycle 3, 15 March 2007 to 16 April 2007; Cycle 4, 17 April
2007 to 17 June 2007; Cycle 5, 18 June 2007 to 15 August 2007; Cycle 6, 16 August
2007 to 10 October 2007;2007-2008 Cycle 1, 11 October 2007 to 20 December 2007;
Cycle 2, 21 December 2007 to 19 February 2008; Cycle 3, 20 February 2008 to 20 April
2008; Cycle 4, 21 April 2008 to 22 June 2008; Cycle 5, 23 June 2008 to 02 September
2008; Cycle 6, 03 September 2008 to 5 November 2008.
! Reference evapotranspiraton was determined using the Penman method.









Table 3-3. Trial 1 treatment means (n = 4) for turfgrass quality for
regimes and four N application rates.


low and high irrigation


Effects C1 C2 C3 C4 C5 C6 Ave

----------------------------------1-9- ------------------
Irrigation (IR)
Low 6.9 6.9 6.8 7.3 7.1 7.0 7.0
High 6.9 7.0 7.0 7.0 7.1 7.0 7.0
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 6.2c 6.0c 6.2c 6.9 6.4d 6.4c 6.3c
196 6.8b 6.6c 6.5c 6.9 6.8c 6.8bc 6.7bc
294 7.0b 7.2b 7.1b 6.8 7.3b 7.1b 7.1b
588 7.5a 7.9a 8.0a 7.9 7.9a 7.8a 7.8a
ANOVA
Source of variation
IR NS NS NS NS NS NS NS
NR *** *** *** NS *** *** ***
IRxNR NS NS NS NS NS NS NS


NS, and *** = P > 0.05, P < 0.001.
t Values within a column followed by the same
different (LSD, P< 0.05).


letter are not statistically


Table 3-4. Trial 2 treatment means (n = 4) for turfgrass quality for
regimes and four N application rates.


low and high irrigation


Effects C1 C2 C3 C4 C5 C6 Ave

----------------------------------1-9---------------------
Irrigation (IR)
Low 7.0 6.6a 6.5 6.6 6.6a 6.5 6.6a
High 6.9 6.8b 6.5 6.7 6.7b 6.7 6.7b
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 6.0c 5.4c 5.5c 5.9c 6.0b 5.6c 5.8c
196 6.8b 6.6b 6.3b 6.4bc 6.4b 6.3b 6.5b
294 7.0b 6.7b 6.6b 6.8b 6.7ab 6.8ab 6.8b
588 7.9a 8.2a 7.5a 7.5a 7.3a 7.4a 7.6a
ANOVA
Source of variation
IR NS ** NS NS NS *
NR *** *** *** ** *** ***
IRxNR NS NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not statistically different (LSD,
P< 0.05).









Table 3-5. Trial 1 treatment means (n = 4) for dry weight of clippings for low and high
irrigation regimes and four N application rates.
Effects C1 C2 C3 C4 C5 C6 Total

-----------------------------kg ha-1- ---------------
Irrigation (IR)
Low 52 113 128 363 925 742 2323
High 63 121 108 348 853 663 2156
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 36 49c 75b 121b 313c 287b 881b
196 48 82bc 104b 331b 720b 647b 1932b
294 56 124b 95b 296b 782b 651b 2004b
588 90 214a 130a 673a 1741a 1226a 4074a
ANOVA
Source of variation
IR NS NS NS NS NS NS NS
NR NS *** ** ***
IRxNR NS NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not statistically
different (LSD, P< 0.05).

Table 3-6. Trial 2 treatment means (n = 4) for dry weight of clippings for low and high
irrigation regimes and four N application rates.
Effects C1 C2 C3 C4 C5 C6 Total

------------------------------------kg ha-----------------------------------
Irrigation (IR)
Low 156 ND 307 213 595 770 2041
High 141 ND 295 276 665 806 2183
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 49c ND 65b 83b 306b 468c 971b
196 125bc ND 225b 217b 533b 745bc 1845b
294 157b ND 250b 207b 549b 814b 1977b
588 264a ND 663a 471a 1130a 1125a 3653a
ANOVA
Source of variation
IR NS ND NS NS NS NS NS
NR ** ND *** ** ** ** **
IRxNR NS ND NS NS NS NS NS
ns, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not statistically
different (LSD, P< 0.05). ND = No data was collected during this cycle.









Table 3-7. Trial 1 treatment means (n = 4) for nitrogen tissue concentration for low and


high irrigation


regimes and four


N application rates.


Effects C1 C2 C3 C4 C5 C6 Ave

----------------------------------g kg------------
Irrigation (IR)
Low 18.7 22.2 14.9 16.4 20.9 19.5 18.8
High 18.5 23.3 16.2 16.4 20.8 19.4 19.1
Nitrogen Rate (NR)
(kg ha-1 yr-1)
98 17.0 20.5b 12.6c 14.1c 19.1 19.0b 17.1c
196 18.3 20.5b 12.8c 15.3bc 21.0 19.6b 17.9bc
294 19.3 23.8ab 17.1b 17.2ab 20.8 18.9b 19.5ab
588 19.8 26.4a 19.7a 18.9a 22.4 20.4a 21.3a
ANOVA
Source of variation
IR NS NS NS NS NS NS NS
NR NS *** ** NS
IRxNR NS NS NS NS NS NS NS


NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not
different (LSD, P< 0.05).


statistically


Table 3-8. Trial 2 treatment means (n = 4) for nitrogen tissue concentration for low and
high irrigation regimes and four N application rates.

Effects C1 C2 C3 C4 C5 C6 Ave

------------------------------g kg------------------------------
Irrigation (IR)
Low 22.0 ND 21.5 16.7 17.4 16.9 18.9
High 22.0 ND 22.3 16.7 17.5 16.9 19.0
Nitrogen Rate (NR)
(kg ha-1 yr-1)
98 20.4c ND 19.7c 16.0b 16.1 16.3 17.9c
196 21.7bc ND 21.3bc 16.1b 17.5 16.3 18.6b
294 21.9ab ND 22.0b 16.1b 17.1 16.9 18.7b
588 23.2a ND 24.5a 18.0a 19.1 18.0 20.5a
ANOVA
Source of variation
IR NS ND NS NS NS NS NS
NR ND ** NS NS
IRxNR NS ND NS NS NS NS NS
NS, *, and **, = P > 0.05, P < 0.05, P < 0.01.
t Values within a column followed by the same letter are not statistically
different (LSD, P< 0.05). ND = No data was collected during this cycle.









Table 3-9. Trial 1 treatment means (n = 4) for nitrogen uptake for low and high irrigation
regimes and four N application rates.
Effects C1 C2 C3 C4 C5 C6 Total

------------------------------kg ha -1------------
Irrigation (IR)
Low 1.1 2.9 2.1 6.7 20.5 14.5 47.7
High 1.3 3.4 1.9 6.3 18.2 12.9 44.0
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 0.6 1.2c 1.0b 1.6b 6.2b 5.5b 16.1b
196 1.0 1.9bc 1.6b 5.2b 16.1b 12.0b 40.0b
294 1.1 3.4b 1.6b 6.2b 16.3b 13.0b 40.0b
588 2.0 6.1a 3.7a 13.1a 38.8a 24.0a 87.7a
ANOVA
Source of variation
IR NS NS NS NS NS NS NS
NR NS ** ** **
IRxNR NS NS NS NS NS NS NS
NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not statistically
different (LSD, P< 0.05).

Table 3-10. Trial 2 treatment means (n = 4) for nitrogen uptake for low and high
irrigation regimes and four N application rates.
Effects C1 C2 C3 C4 C5 C6 Total

----------------------------kg ha-1- ------------
Irrigation (IR)
Low 3.6 ND 7.3 3.7 11.2 13.5 39.2
High 3.1 ND 7.0 4.8 12.5 13.8 41.2
Nitrogen Rate (NR)
(kg ha1 yr-1)
98 1.0c ND 1.4b 1.4b 5.8b 7.8c 17.3b
196 2.8bc ND 5.3b 3.8b 10.1b 12.3bc 34.4b
294 3.4b ND 5.6b 3.4b 9.7b 14.0b 36.1b
588 6.2a ND 16.3a 8.4a 21.8a 20.4a 73.2a
ANOVA
Source of variation
IR NS ND NS NS NS NS NS
NR *** ND ** ** ** ** **
IRxNR NS ND NS NS NS NS NS
NS, **, and *** = P > 0.05, P < 0.01, P < 0.001.
t Values within a column followed by the same letter are not statistically
different (LSD, P< 0.05). ND = No data was collected during this cycle.









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Snyder, G.H., B.J. Augustin, and J.M. Davidson. 1984. Moisture sensor-controlled
irrigation for reducing N leaching in Bermudagrass turf. Agron. J. 76: 964-969.

Snyder, G. H., B. J. Augustin, and J. L. Cisar. 1989. Fertigation for stabilizing turfgrass
nitrogen nutrition. p. 217-219 In H. Takatoh (ed.) Proc. 6th Int. Turfgrass Res.
Conf. (Tokyo), Japanese Soc. Turfgrass Sci., Tokyo.

Spalding, R. F., and M. E. Exner. 1993. Occurrence of Nitrate in Groundwater- A
Review. J. Environ. Qual. 22:392-402.

Titko, S., J.R. Street, and T.J. Logan. 1987. Volatilization of ammonia from granular and
dissolved urea applied to turf. Agron. J. 79:535-540.









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Trenholm, L.E., E.F. Gilman, G.W. Knox, and R.J. Black. 2002. Fertilization and
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D.C.

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and fertilizer on warm-season turfgrasses. Texas J. Agri. Nat. Resour. 6:99-108.

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nutrient status. Commun. Soil Sci. Plant Anal. 13:1035-1059.

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Water use and quality of warm-season and cool-season turfgrass, p. 251-257. In
R. W. Sheard (ed.) Proceedings of the 4th International Turfgrass Research
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Canada. 19-23 July.

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Circular 750. 6 p.









BIOGRAPHICAL SKETCH

Pauric C. McGroary was born in Letterkenny, Co. Donegal, Ireland, and grew up in

Laghy, Co. Donegal, Ireland. In 1999 he graduated from St. Patrick's College with his

leaving certification and began studies at University of Central Lancashire, Preston,

England. In May 2004 he received a Bachelor of Science (Hons) in turfgrass science

from University of Central Lancashire, Preston, England. Pauric continued his

education at the University of Florida, Gainesville, FL were he joined the Entomology

and Nematology Department and obtained a Master of Science degree in spring of

2007. In summer 2007, Pauric joined the graduate Soil and Water Department program

at the University of Florida under the supervision of Dr. John Cisar in which he received

his Doctor of Philosophy in August 2010.





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1 NITROGEN LEACHING, WATER USE RATES AND TURF RESPONSE OF ST. AUGUSTINEGRASS AND BAHIAGRASS TO IRRIGATION AND FERTILIZER PRACTICES By PAURIC C. MCGROARY A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF F LORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010

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2 2010 Pauric C. McGroary

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3 This document is dedicated to my family for all their love, help and support.

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4 ACKNOWLEDGMENTS I would like to thank Drs. John Cisar and George Snyder for their scientific expertise, persistence and support. I am also indebted to my other supervisory committee members Drs. John Erickson, Jerry Sartain and Samira Daroub, who were always available to answer questions and to provide guidance throughout. I am grateful also to Drs. Alan Wright and Yigang Luo for their help and use of their lab. I would also like to acknowledge the financial support of the Florida Department of Environmental Protection (FD EP). The technical support of Ms. Karen Williams, Ms. Eva King, Mr. Joe Giblin, Mr. Ajambar Rayamajhi, and Mr. Adam Michaud is much appreciated. F inally to my fiance Holly, for without her love, patience and support I would not have accomplished this drea m.

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5 TABLE OF CONTENTS ACKNOWLEDGMENTS .................................................................................................. 4 page LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 9 ABSTRACT ................................................................................................................... 10 CHAPTER 1 EVAPOTRANSPIRATION RATES OF ST AUGUSTINEGRASS AND BAHIAGRASS UNDER VARYING NITROGEN RATES ......................................... 12 Introduction ............................................................................................................. 12 Materials and Methods ............................................................................................ 14 Experimental Site and Design .......................................................................... 14 Measures of Turfgrass Quality and Clipping Growth ........................................ 16 Measures of Water Use .................................................................................... 16 Analysis of Data ............................................................................................... 17 Results .................................................................................................................... 18 Climate ............................................................................................................. 18 Turfgrass Growth and Quality ........................................................................... 18 Turfgrass Water Use Rate ................................................................................ 19 Discussion .............................................................................................................. 19 Conclusion .............................................................................................................. 22 2 EFFECTS OF IRRIGATION REGIMES AND NITROGEN RATES ON NITROGEN LEACHING FROM ST. AUGUSTINEGRASS YARDS ........................ 28 Introduction ............................................................................................................. 28 Materials and Methods ............................................................................................ 31 Experimental Site and Design .......................................................................... 31 Measure of Percolate and Nutrient Leaching ................................................... 32 Analysis of Data ............................................................................................... 34 Results .................................................................................................................... 35 Hydrology ......................................................................................................... 35 Nitrogen Leaching ............................................................................................ 35 Discussion .............................................................................................................. 37 Conclusion .............................................................................................................. 40 3 EFFECTS OF IRRIGATION REGIMES AND NITROGEN FERTILIZATION ON ST. AUGUSTINEGRASS GROWTH QUALITY AND WATER cONSERVATION ... 44 Introduction ............................................................................................................. 44

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6 Materials and Methods ............................................................................................ 46 Turfgrass Quality .............................................................................................. 47 St atistical Design and Analysis ......................................................................... 48 Results .................................................................................................................... 48 Turfgrass Quality .............................................................................................. 49 Clippings Yield .................................................................................................. 50 Tissue N ........................................................................................................... 51 Nitrogen Uptake ............................................................................................... 51 Discussion .............................................................................................................. 52 Conclusion .............................................................................................................. 55 ANOVA ................................................................................................................... 58 REFERENCES .............................................................................................................. 62 BIOGRAPHICAL SKETCH ............................................................................................ 68

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7 LIST OF TABLES Table page 1 1 Percentage by weight of mineral particle fractions contained in the rootzone used for construction of the field study area. ...................................................... 24 1 2 Total rainfall, total irrigation, total evapotranspiration and average daily air temperature for each cycle of the trials at Ft Lauderdale, FL. ............................ 24 1 3 Trial 1 treatment means for dry weight of clippings of bahaiagrass and St. Augustinegrass at two N application rates. ......................................................... 25 1 4 Trial 2 treatment means for dry weight of clippings of bahaiagrass and St. Augustinegrass at two N application rates. ......................................................... 25 1 5 Trial 1 treatment means for turfgrass quality of bahiagrass and St. Augustinegrass at two N application rates. ......................................................... 26 1 6 Trial 2 treatment means for turfgrass quality of bahiagrass and St. Augustinegrass at two N application rates. ......................................................... 26 1 7 Trial 1 treatment means for water use rates of bahaiagrass and St. Augustinegrass at two N application rates. ......................................................... 27 1 8 Trial 2 treatment means for water use rates of bahiagrass and St. Augustinegrass at two N application rates. ......................................................... 27 2 1 Percentage by weight of mineral particle fractions contained in the r oot zone used for construction of the field study area. ...................................................... 43 2 2 Analysis of variance results for drainage, flow weighted concentration f NO3N, flowweighted concentration of NH4N quantity of NO3 N leached, quantity of NH4 N leached and, quantity of total inorganic N leached. Treatment means represent the average of 4 plots. ........................................... 43 3 1 Percentage by weight of mineral particle fractions contained in the root zone used for construction of the field study area. ...................................................... 56 3 2 Total rainfall, total irrigation inputs, and reference ET for each cycle of the study. .................................................................................................................. 57 3 3 Trial 1 treatment means (n = 4) for turfgrass quality for low and high irrigation regimes and four N application rates. ................................................................. 58 3 4 Trial 2 treatment means (n = 4) for turfgrass quality for low and high irrigation regimes and four N application rates. ................................................................. 58

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8 3 5 Trial 1 treatment means (n = 4) for dry weight of clippings for low and high irrigation regimes and four N application rates. .................................................. 59 3 6 Trial 2 treatment means (n = 4) for dry weight of clippings for low and high irrigation regimes and four N application rates. .................................................. 59 3 7 Trial 1 treatment means (n = 4) for nitrogen tissue concentration for low and high irrigation regimes and four N application rates. ........................................... 60 3 8 Trial 2 treatment means (n = 4) for nitrogen tissue concentration for low and high irrigation regimes and four N application rates. ........................................... 60 3 9 T rial 1 treatment means (n = 4) for nitrogen uptake for low and high irrigation regimes and four N application rates. ................................................................. 61 3 10 Trial 2 treatment means (n = 4) for nitrogen uptake for low and high irrigation regimes and four N application rates. ................................................................. 61

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9 LIST OF FIGURES Figure page 2 1 Irrigation and precipitation inputs for the low and high irrigation regimes for trial 1 and trial 2 (n = 32). .................................................................................... 42

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10 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy NITROGE N LEACHING, WATER USE RATES AND TURF RESPONSE OF ST. AUGUSTINEGRASS AND BAHIAGRASS TO IRRIGATION AND FERTILIZER PRACTICES Pauric C. McGroary August 2010 Chair: John Cisar Cochair: George Snyder Major: Soil and Water Science In Florida, state regulat ors are concerned about St. Augustinegrass for both high water use and excess nitrogen (N) applications to home lawns. This has resulted in city ordinances to reduce nitrogen inputs beyond the c urrent statewide regulations under the Urban Turf Fertilizer Rule in order to reduce N leaching. Furthermore, some municipalities have started to replace St. Augustinegrass with bahiagrass in an attempt to conserve water. However, there is limited information available on whether such practices actually help reduc e N leaching and conserve water and their effect on St. Augustinegrass quality in subtropical south Florida. Consequently, two experiments were carried out 1) to determine water use rate s of St. Augutsinegrass and bahiagrass under two N rates and 2) to ev aluate N leaching water conservation and St. Augustinegrass response to two irrigation regimes and four N rates. In Experiment 1 under nonlimiting water and high N rates, bahiagrass cv. Pensacola had comparable or higher water use rates than St August inegrass cv. Floratam. In addition, bahiagrass may require more maintenance due to the faster growth rate in the summer months in south Florida. Additionally, N rate of 98 kg ha1 yr1

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11 was able to reduced water use rates annually though it did not alway s produce acceptable quality. In experiment 2, applications of 196, 294 and 588 N/kg ha1 yr1 all produced acceptable quality. However, the applications rate of 588 kg N/kg ha1 yr1 produced greater amount of clippings than 196, 294 kg N/kg ha1 yr1 th at may be an inconvenience to some homeowners. Minimum acceptable St Augustinegrss was produced at 196 kg N/kg ha1 yr1. Furthermore, both low and high irrigation regimes produced acceptable quality during the experiment. However, water inputs were far greater for the high irrigation regime than the low irrigation regime. Therefore, proving to be ineffective irrigation regime for conserving water compared to the low irrigation regime N itrogen rates or irrigation regimes did not influence N leaching. L eaching of NO3N never exceeded a mean flowweighted concentration > 4 mg NO3N L1 during the experiment.

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12 CHAPTER 1 EVAPOTRANSPIRATION R ATES OF ST AUGUSTINE GRASS AND BAHIAGRASS UNDER VARYING NITROG EN RATES Introduction Turfgrass landscapes provide many aesthetic and functional benefits to residents including opportunities for recreation. However, in order to maintain an acceptable turfgrass landscape, irrigation inputs are required when rainfall is insufficient (Aronson et al., 1987). In fact, the appl ication of water to residential landscapes is a major use of potable water ( Baum, 2005). For example, water use in Florida by residential homes accounts for 61% of the public supply category with the average household using 71% of its total water consumpti on for irrigation use (Baum et al. 2005). As a result, many municipalities across the nation have enacted water restrictions to limit residential irrigation in order to conserve potable water (e.g., South Florida Water Management District). Some municipal ities also offer programs for replacing grass with xeriscepes in effort to reduce landscape irrigation (City of Glendale, 2010). Turfgrass is a major component of urban vegetation and considerable work has been done measuring its water use rates (WURs), which is the total amount of water required for turfgrass growth plus the quantity lost by transpiration and evaporation (evapotranspiration) (ET) from the soil and plant surfaces (Aronson et al., 1987; Beard, 1973; Fu et al., 2004; Fry and Butler, 1989; Kim and Beard, 1988; Park et al., 2005; Youngner et al., 1981). Water loss by grass via ET is influenced by a number of factors, includingclimate, plant morphological and anatomical factors and management practices. Major climatic factors include wind spee d (Danielson et al., 1979; Davenport, 1965), solar radiation (Feldhake et al., 1983; Shearman and Beard, 1973) atmospheric

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13 vapor pressure, and temperature (Beard, 1973). Management practices include nitrogen (N) fertilization rate (Barton et al., 2009; Ebdon et al., 1999; Feldhake et al., 1983; Mantell, 1966; Shearman and Beard, 1973), fertilizer source (Saha, et al., 2005), mowing height and frequency (Brian et al., 1981; Feldhake et al., 1983; Fry and Butler, 1989; Shearman and Beard, 1973;), use of g rowth regulators (Borden and Campbell, 1987) and soil water availability (Brian et al., 1981; DaCosta and Huang 2006; Kneebone et al., 1992;) Furthermore WURs varies with turfgrass species (Aronson et al., 1987; Fry and Butler, 1989; Fu et al., 2004; Kim a nd Beard, 1988; Youngner et al., 1981) and within cultivar of the same species (Bowman and Macaulay, 1991; Ebdon and Petrovic, 1998; Kopec et al., 1988; Shearman, 1986; Salaiz et al., 1991). St. Augustinegrass [ Stenotaphrum secundatum (Walt.) Kuntz] is on e of the most predominately used grass species for residental lawns in the southeastern United States. In Florida alone, St. Augustinegrass is grown on approximately 70% of the lawns with an additional 24,164 ha harvested annually from sod production (Buse y, 2003; Haydu et al., 2005). Floratam is the most extensively used cultivar due mainly to its resistance to chinch bugs ( Blissus insularis Barber) but its resistance has been broken ( Busey and Center, 1987). Recently, many state regulators in Florida have criticized St. Augustinegrass for its high WURs, as a recent study showed that irrigation for residential landscape accounted for 64% of total residential water use (approx. 141 mm mo1) for homes surveyed in Central Florida (Haley et al., 2007). This has resulted in a desire by some municipalities to substitute St. Augustinegrass with bahiagrass ( Paspalum notatum Flgge), which is commonly perceived to use less water (Lower ET) than St. Augustinegrass under irrigated conditions. For example in Orlando, FL the

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14 Orange County commissioners recently had one ha of St. Augustinegrass replaced with bahiagrass in order to reduce water use in the county. However, limited data have indicated comparable ET rates for St. Augustinegrass Floratam and bahiagrass Pe nescola in a greenhouse experiment (Miller and McCarty, 2001). In addition to ET rates, N inputs for St. Augustinegrass lawns have also received great interest due to environmental concerns (Erickson et al., 2001; 2008). Currently, the recommended N rates for South Florida are 196294 kg ha1 yr1 for St Augustinegrass and 98 196 kg ha1 yr1 for bahiagrass (Trenholm et al., 2000). Few studies have examined the effects of N rates on turfgrass WURs Although Barton et al. (2009) reported reduced ET at low N rates in Kikuyu turfgrass [ Pennisetum clandestinum (Hochst. ex Chiov)] the authors suggested that application of the minimum N for turfgrass quality was an approach for decreasing water consumption by turf. However, the implication of these findings for other grass species in other environments is not well understood. Consequently, the aim of this study was to determine the effect of different N fertilizer rates on WURs and turf quality of two warm season grasses commonly used in residential yards in the southeastern U.S. M aterials and M ethods Experimental Site and Design The study was conducted at the University of Floridas Institute of Food and Agricultural Sciences, Fort Lauderdale Research and Education Center (2603 N, 8013 W) on stands of bahiagrass and St. Augustinegrass grown on a mined mason sand (Table 1 1) (Atlas Peat and Soil, Inc) that was low (<0.5%) in organic matter and had a pH of 7.9 0.2. The experiment consisting of 16 turfgrass plots in a split plot randomized complete bloc k design with four replications. Whole plots (8 x 4 m)

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15 arranged in blocks consisting of either bahiagrass cv. Pensacola or St Augustinegrass cv. Floratam. One of two N rates (98 and 294 N kg ha1 yr1) was applied to sub plots (4 x 2 m). Nitrogen rates were split equally over 6 application dates in 20062007 (trial 1) and again in 20072008 (trial 2). In 20062007 N was applied on 12 Oct., 12 Dec. 2006 and 15 Mar., 17 Apr., 18 June, and 16 Aug. 2007. In 20072008 N was applied on the 11 Oct., 21 Dec. 2 007 and 20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each application date represented the start of a new fertilizer cycle (FC). Spray grade granular urea (460 0) was used as the source (PCS Sales, Inc. Northbrook, IL) of N and applied with a backpack CO2pressurized (30 psi) sprayer equipped with two flat fan TeeJet 8010 nozzles on 51 0 m m spacing. Immediately following N applications turfgrass received 13 mm of irrigation to reduc e N loss to volatilization and reduce burn potential (Bowman et al., 1987). In addition to N fertilization, P and K from triple superphosphate (0460) and muriate of potash (00 63) were applied at the rates of 196 and 392 kg ha1 yr1 to maintain acceptable soil test values. The fertilizers were split equally every 90days. Additionally, macro and micronutrients were applied as Harrells Max Minors containing Mg 1%, S 3.5%, B 0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6% and Mo 0.0005% at 12 L ha1 every 90days. Throughout the duration of the experiment plots received 2.5 mm of irr igation every day except when over 6.4 mm of precipitation occurred. When precipitation events were > 6.4mm then irrigation for the following day w as voided. Plots were maintained using a rotar y mower at a height of cut of 7 5 m m and clippings were removed.

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16 Measures of Turfgrass Quality and Clipping Growth Turfgrass visual quality was assessed biweekly using a 19 scale (9 = dark green, 1 = dead/brown turf, and 6.5 = minimally acceptable turfgrass (Carrow, 1997). Turfgrass clipping samples for shoot growth were harvested from a 2.24 m2 area within each plot using a rotary mower set at a height of 75 mm approximately weekly or more frequently when necessary. Samples were oven dried at 60o C for 48 hrs to a constant weight. Measures of Water Use In order t o measure water use, large lysimeters were installed on top of a 30 0 m m sand base in the center of each subplot. The lysimeters were constructed from plastic drums 92 0 m m high, 597 m m diameter, with a 13 m m thick wall, (US Plastics Corporation) with a flat bottom which had a threaded opening already manufactured into the container for easy drainage pipe installations. The lysimeters were fitted with 19 mm polyvinyl chloride (PVC) drainage pipe, spliced to allow for lysimeter drainage and individually insta lled on the foundation. A 90degree elbow joint was attached to drainage orifice, which was subsequently connected to a 10 m m section of 24 m m diameter Schedule 40 PVC pipe that ran to a collection station. At the collection station each pipe was allocate d its own 20 L polyethylene container. Each lysimeter had a stainless steel screen (1 mm mesh) over the orfice at the bottom of the lysimeter. This subsequently was covered with a 100 m m layer of filter gravel (>14 mm 1%, 1214 mm 7.5%, 9 12 mm 10.5%, 6.739 mm 28%, 66.73 mm 41%, 46 mm 7%, 2 4 mm 3.5%, <2mm 1.5%) which was overlaid by 5 cm layer of choker sand (>2 mm 0.1%, 12 mm, 7.6%, 0.5 1.0 mm 26%, 0.250.5 mm 45.6%, 0.150.25 mm 19.1%, 0.0530.15 1.2%, <0.053 0.6%). Similar a layer was installed out side the lysimeter so the soil profiles

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17 were similar. Subsequently, mason sand was packed around, between and within each of the lysimeters to a depth of 78 0 m m. Furthermore a 75 m m layer of mason sand was spread uniformly over the top of the lysimeters. Perimeter irrigation systems were installed on each of the main plots. The irrigation system comprised of 24 mm diameter Schedule 40 PVC pipe with rotor Rainbird 3500 sprinklers placed in each corner adjusted to spray an inward quarter circle. Water use r ates were determined by using the following calculation WURs = (rainfall + irrigation) (percolate + runoff) (Park et al., 2005). Runoff was omitted from the equation, as it was never observed. Rainfall data was obtained from a Florida Automated Weather N etwork (FAWN) station which was located within 500 m of the test site Percolate and volumes were measured weekly and more frequently following precipitation events exceeding 25 mm. St. Augustinegrass and bahiagrass were sodded in their designated plots. A dditionally, berm areas were also sodded with St. Augustinegrass. Within the first week after sod installation, a blended granular fertilizer (263 11) was applied to all the plots at a rate of 50 kg N ha1 yr--1.This was followed a month later with an application of 6 6 6 at a rate of 50 kg N ha1 yr1. Before the actual initiation of the trials, grass w as allowed to establish for a period of 6 months. Throughout the first three months of the establishment period irrigation was applied three times a week at 13 mm per application. However, for the final three months of establishment, irrigation was adjusted to 2.5 mm per day. Analysis of Data All data were analyzed for normality using the ShapiroWilk W test. Homogeneity of variance was also checked graphic ally. Clipping yields (CYs) and WURs were totaled

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18 for each fertilizer cycle and year. Quality ratings were averaged over each FC and trial. Analyses were performed on individual fertilizer cycle trial data because the length of the fertilizer cycles varied from trial to trial. All data were subjected to analysis of variance with PROC GLM (SAS Institute, 1999) and means were separated using Fishers Least Significant Difference (LSD) at the t probability level of 0.05. R esults Climate Average daily temperatures ranged from 22 28C for trial 1 (14 October 2006 to 04 October 2007) and 2128 C for trial 2 (05 October 2007 to 05 November 2008) (Table 1 2). However, in both trials air temperatures were generally lower in FC1, FC2, and FC3 compared to FC4, FC5 and FC6. Rainfall varied slightly between trials During trials 1 and 2 plots received a total of 1658 mm and 1538 mm of rainfall (Table 2). Furthermore, rainfall in both trials was generally greater during FC4, FC5, and FC6 compared to FC1, FC2 and FC3. Turfgrass Growth and Quality Clipping yields were affected by grass ( P < 0.01) and N rate ( P < 0.01) in both trials (Table 1 3 1 4). Clipping yields from each FC (Trial 1 FC3 ) were greater for bahiagrass than St. Augustinegrass ( Table 1 3 ; 1 4) Total cl ipping yields for each trial were approximately 4 times greater from bahiagrass compared to St. Augustinegrass, averaging 6988 and 1510 kg ha1 for trial 1 and 4457 and 1369 kg ha1 for trial 2, respectively. In general both grasses produced the greatest C Ys during FC4, F C5, and FC6 ( Table 1 3 1 4) Additionally, the higher N rate (averaged across grasses) significantly increased CYs by about 60% for each trial. In both trials, for each cycle

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19 except FC1 and FC3 in trial 1 increasing the N rate from 98 to 294 kg ha1 yr1 significantly increased clipping yields. Both grass species and N rates produced acceptable quality (> 6.5) when averaged across each trial. Bahiagrass quality scores were equal to or higher than St. Augustinegrass across both trials but were only significantly different in ( P < 0.05) in three out of the 12 cycles ( Table 1 5, 1 6 ) Although, the higher N rate always produced higher quality scores than the lower N rate. It was only significantly higher in FC1, FC2, FC3, and FC5 in tri al 1 (Table 1 5) and FC3, FC6 in trial 2 (Table 1 6). Although the lower N rate produced acceptable quality when averaged across trials, there were times when quality was not acceptable, such as FC3 in trial 1 and FC2, FC3 and FC6 in trial 2. Turfgrass W ater Use Rate Total water use rate (TWURs) was greater ( P < 0.05) from bahiagrass compared to St. Augustinegrass during trial 1, averaging 1508 and 1286 mm, respectively (Table 1 7). However, no significant difference was seen between the grasses during tr ial 2 (Table 1 8). In trial 1, bahiagrass showed significantly greater WURs in three out of the six cycles, but bahiagrass WURs were only significantly greater in one cycle out of the six cycles in trial 2 (Table 1 7 1 8). In general, both grasses had higher WURs during FC4, FC5, and FC6 of both trials. The high N rate ( P < 0.05) increased TWURs by about 8% in trial 1 no significant difference was found in trial 2 (Table 1 7 1 8). D iscussion With increasing concern over scarcity of water resources, pressure has been placed on residents to reduce water use, especially when it comes to irrigation of landscape areas such as yards and flower beds. While St. Augustinegrass is the most

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20 widely used grass for home yards in Florida, it has been suggested that bahiagrass should be used instead for its lower water use. In this study the quality, growth and WURs of two grasses were compared under well watered conditions utilizing two N rates commonly applied by the lawn care industry. Results indicate that St. Au gustinegrass WURs was comparable or less than bahiagrass maintained in field conditions. In the current study the TWURs for St. Augustinegrass were 1,286 mm during trial 1 and 1,200 mm during trial 2, which were similar to that reported by Steward and Mil ls (1967) of 1,067 mm for St. Augustinegrass. Total water use rates for both grasses was higher during trial 1 than trial 2. A similar trend was observed in CYs, whereby yields were greater in trial 1 than trial 2. Increased evaporative demand coupled wi th reduced water inputs during trial 2 (Table 1 2) likely contributed to the lower CYs seen during trial 2, which may explain why TWURs was lower in trial 2 compared to trial 1. Throughout both trials WURs were generally comparable between both grasses, a nd in some cases WURs were even greater for bahiagrass compared to St. Augustinegrass (Table 1 7 1 8). This may be explained by the fact that bahiagrass produced significantly greater CYs than St. Augustinegrass, thus requiring more water to support the i ncreased growth (Barton et al., 2009; Brian et al., 1981). For example, Barton et al. (2009) found that growth accounted for 75% of the variation in ET in kikuyu turfgrass. Furthermore, differences in WURs between bahiagrass and St Augustinegrass may also be explained by leaf orientation and shoot density difference between the two grasses: St. Augustinegrass has a higher shoot density and a substantial horizontal leaf orientation compared to bahiagrass which has a more vertical

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21 leaf orientation and low sh oot density (Kim and Beard, 1988). This vertical leaf orientation and lower shoot density of bahiagrass leads to lower canopy resistance and thus higher ET rates compared to a grass that has a higher canopy resistance (Kim and Beard, 1988; Brian et al., 1981). Water use rates rates were generally higher in FC4, FC5, and FC6 of each trial. This may be attributed to the greater canopy leaf area and higher evaporative demand due to higher temperatures and longer photoperiod. Throughout the duration of the experiment wilting was never observed in any of the plots. Thus, each grass was evaluated under non deficit conditions. However, it should be noted that even though bahiagrass used more water than St. Augustinegrass at times in our study, bahiagrass may requi re less frequent and total irrigation, since bahiagrass has a greater capacity to avoid water stress compared to St. Augustinegrass (Miller and McCarty, 2001) and subsequently, requiring less frequent irrigation. In addition, bahiagrass has the ability to survive periods when water is not available through its capacity for dehydration avoidance (McCarty and Cisar, 1995) which allows the grass to green up after watering. St. Augustinegrass does not encompass such a mechanism. Therefore, when water becomes l imiting the grass normally enters drought and can potentially dies. Even though bahiagrass used more water under well watered conditions in our study, it may be able to survive water deficit conditions better than St. Augustinegrass, and thus allowing it t o survive under lower and more infrequent water inputs. Water use rates were also affected by N fertilization rates; however these differences were relatively modest, especially in comparison to the difference between species. Furthermore, reducing N fer tilizer rates by 67% resulted in a 5 8 % reduction

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22 in WURs per trial. Similar results were reported for Kikulyugrass when decreasing N rates reduced ET (Barton, et al., 2009). The reduction in WURs at low N was likely due to the lower water use associated with reduced leaf area and clipping yield production seen at low N (Brian et al., 1981; Barton et al., 2009). In the future if water restrictions are heightened for home yards, manipulating of N rates may be a possible management strategy in reducing water use rates of grasses and ultimately conserving water. Throughout the duration of the experiment both grasses produced acceptable turfgrass quality scores demonstrating that both grasses can be used to produce aesthetically pleasing home yards with reduced inputs of irrigation and N However, clipping yields showed that St. Augustinegrass (approx. 260%) responded much more to fertilization than bahiagrass (approx. 35%), which was remarkably consistent across both trials. Nevertheless, increasing N rates fr om 98 to 294 kg ha1 yr1 improved quality in trial 1 and 2 for both grasses. Finally, clipping production varied greatly between grass species. Bahiagrass growth rate was generally higher than St. Augustinegrass which increased the frequency of mowing esp ecially during FC4, FC5, and FC6 of each trial. This may not be favored by homeowners as it may increase fuel, labor costs and waste disposal of clippings (Fluck and Busey, 1988). Further work is needed to evaluate bahiagrass response to lower N rates and irrigation as it may be possible to reduce N rate without compromising turf quality. This may help in reducing WURs rates due to the reduction in growth and the risk of N leaching. C onclusion While the results from this experiment varied across trials, so me general conclusions can be made regarding grasses and N management impacts on WURs rates First, under non limiting water and high N rates, bahiagrass cv. Pensacola had

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23 comparable or higher WURs rates than St Augustinegrass cv. Floratam. Second, both St. Augustinegrass and bahiagrass can be used to produce acceptable quality lawns. However, bahiagrass may require more maintenance due to the faster growth rate especially during the warmer wetter summer months in south Florida. Finally, N rate of 98 k g ha1 yr1 was able to reduce WURs annually though it did not always produce acceptable quality.

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24 Table 11. Percentage by weight of mineral particle fractions contained in the rootzone used for construction of the field study area Table 12. Total rainfall, total irrigation, total evapotranspiration and average daily air temperature for each cycle of the trials at Ft Lauderdale, FL. Study a period Cycle No. days Rainfall Irrigation Reference ET Min. air temp. Max. ai r temp. Ave. air temp. --------------------mm --------------------------------C -------------Trial 1 1 61 173 145 133 6 31 23 2 88 120 213 194 8 30 22 3 27 57 69 97 12 29 22 4 64 348 127 247 12 34 25 5 61 525 162 273 15 35 27 6 49 43 5 91 194 22 35 28 Total 350 1658 807 1138 Trial 2 1 76 210 178 179 10 32 24 2 56 142 135 113 3 30 21 3 65 157 137 220 8 32 23 4 62 158 145 291 17 35 26 5 58 439 112 257 21 35 28 6 75 432 170 244 22 32 26 Total 392 1538 87 7 1304 aTrial 1 Cycle 1, 14 October 2006 to 14 December 2006; Cycle 2, 15 December 2006 to 13 March 2007; Cycle 3, 14 March 2007 to 10 April 2007; Cycle 4, 11 April 2007 to 14 June 2007; Cycle 5, 15 June 2007 to 15 August 2007; Cycle 6, 16 August 2007 to 4 October 2007. Trial 2 Cycle 1, 5 October 2007 to 20 December 2007; Cycle 2, 21 December 2007 to 15 February 2008; Cycle 3, 16 February 2008 to 21 April 2008; Cycle 4, 22 April 2008 to 23 June 2008; Cycle 5, 24 June 2008 to 21 August 2008; Cycle 6, 22 August 2008 to 5 November 2008. Reference Evapotranspiration (ET) was calculated using a modified Penman equation. Name Size range Weight -------mm --------% ---Fine Gravel 2.0 3.4 0 Very coarse sand 1.0 2.0 2 Coarse sand 0.5 1.0 7 Medium sand 0.25 0.50 23 Fine sand 0.15 0.25 27 Very Fine Sand 0.05 0.15 34 Silt 0.002 0.05 7 Clay less than 0.002 0

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25 Table 13. Trial 1 treatment means for dry weight of clippings of bahaiagrass and St. Augustinegrass at two N application rates. Factor 2006 2007 C1 C2 C3 C4 C5 C6 Total -----------------------------kg ha 1 -----------------------------Grass (G) Bahiagrass 250 205 335 1316 2463 2373 6988 St. Augustinegrass 44 89 89 233 564 492 1510 Sig. ** NS ** ** ** LSD 0.05 81 194 1005 846 586 2328 Nitrogen (N) (kg ha 1 yr 1 ) 98 134 99 189 567 1211 1107 3307 294 204 195 234 982 1817 1759 5191 Sig. NS NS * LSD 0.05 66 398 544 447 1490 G X N Intera ction Bahiagrass 98 236 161 311 1051 2200 2020 5978 Bahiagrass 294 354 250 359 1581 2726 2727 7998 St. Augustinegrass 98 33 18 68 83 222 193 636 St. Augustinegrass 294 55 29 109 383 906 790 2384 Sig. NS NS NS NS NS NS NS NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001 Table 14. Trial 2 treatment means for dry weight of clippings of bahaiagrass and St. Augustinegrass at two N application rates. Factor 2007 2008 C1 C2 C3 C4 C5 C6 Total ----------------------------kg ha 1 -----------------------------Grass (G) Bahiagrass 393 ND 145 659 2066 1193 4457 St. Augustinegrass 105 ND 171 128 367 598 1369 Sig. ** NS ** ** ** LSD 0.05 146 349 780 302 1552 Nitrogen (N ) (kg ha 1 yr 1 ) 98 186 ND 65 257 985 700 2193 294 312 ND 251 529 1449 1091 3633 Sig. ** LSD 0.05 74 128 141 377 322 1000 G X N Interaction Bahiagrass 98 399 ND 102 490 1812 1039 3783 Bahiag rass 294 446 ND 188 827 2321 1346 5130 St. Augustinegrass 98 32 ND 29 24 157 360 601 St. Augustinegrass 294 178 ND 314 232 577 836 2137 Sig. NS NS NS NS NS NS NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001 ND, No data was collected during this cycle

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26 T able 15. Trial 1 treatment means for turfgrass quality of bahiagrass and St. Augustinegrass at two N application rates. Factor 2006 2007 C1 C2 C3 C4 C5 C6 Average --------------------------------1 9 -------------------------------Grass (G) Bahiagrass 7.2 6.9 7.0 7.5 7.1 7.0 7.2 St. Augustinegrass 6.6 6.6 6.6 6.7 6.8 6.8 6.7 Sig. *** NS NS NS NS NS NS LSD 0.05 0.3 0.6 0.5 0.7 0.3 0.7 0.4 Nitrogen (N) (kg ha 1 yr 1 ) 98 6.7 6.5 6.4 6.8 6.7 6.8 6.7 294 7.2 7.1 7.1 7.4 7.2 7.1 7.2 Sig. ** NS NS LSD 0.05 0.3 0.6 0.5 0.3 0.4 G X N Interaction Bahiagrass 98 7.0 6.8 6.6 7.3 7.0 7.0 7.0 Bahiagrass 294 7.4 7.2 7.3 7.7 7 .2 7.2 7.4 St. Augustinegrass 98 6.3 6.2 6.3 6.3 6.4 6.7 6.4 St. Augustinegrass 294 7.0 7.1 6.8 7.1 7.2 7.0 7.1 Sig. NS NS NS NS NS NS NS NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001 Table 16. Trial 2 treatment means f or turfgrass quality of bahiagrass and St. Augustinegrass at two N application rates. Factor 2007 2008 C1 C2 C3 C4 C5 C6 Average --------------------------------1 9 --------------------------------Grass (G) Bahiagrass 7.1 7.0 7.0 7.3 7.3 7.0 7.1 St. Augustinegrass 6.6 6.4 6.3 6.5 6.5 6.4 6.5 Sig. NS NS NS NS NS LSD 0.05 0.5 0.7 Nitrogen (N) (kg ha 1 yr 1 ) 98 6.6 6.4 6.3 6.7 6.7 6.3 6.5 294 7.0 7.0 7.0 7.1 7.1 7.1 7.1 Sig. NS NS NS NS NS LSD 0.05 0.5 0.4 G X N Interaction Bahiagrass 98 7.0 6.8 6.8 7.1 7.0 6.7 6.9 Bahiagrass 294 7.3 7.3 7.4 7.5 7.5 7.4 7.4 St. Augustinegrass 98 6.3 5.9 5.7 6.3 6.4 5.9 6.1 St. Augustinegrass 294 6.9 6.7 6.6 6.7 6.6 6.8 6.7 Sig. NS NS NS NS NS NS NS NS, and *, = P > 0.05, P < 0.05

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27 T able 17. Trial 1 treatment means for water use rates of bahaiagrass and St. Augustinegrass at two N application rates. Factor 2006 2007 C1 C2 C3 C4 C5 C6 Total -------------------------------mm -------------------------------Grass (G) Bahiagrass 177 189 114 309 345 374 1508 St. Augustinegrass 122 159 88 238 321 360 1288 Sig. NS ** NS NS LSD 0.05 15 116 65 80 Nitrogen (N) (kg ha 1 yr 1 ) 98 136 160 95 270 319 361 1341 294 162 188 106 277 347 372 1452 Sig. ** NS LSD 0.05 1 5 20 11 27 10 80 G X N Interaction Bahiagrass 98 1 70 192 113 326 342 373 1516 Bahiagrass 294 183 187 114 293 349 375 1501 St. Augustinegrass 98 102 128 78 214 297 349 1168 St. Augustinegrass 294 142 190 98 261 346 370 1407 Sig. NS NS NS NS NS NS NS NS, *, and ** = P > 0.05, P < 0. 05, P < 0.01 Table 18. Trial 2 treatment means for water use rates of bahiagrass and St. Augustinegrass at two N application rates. NS, and = P > 0.05, P < 0.05 Factor 2007 2008 C1 C2 C3 C4 C5 C6 Total -------------------------------mm ------------------------------Grass (G) Bahiagrass 184 139 220 276 294 185 1298 St. Augustinegrass 159 126 205 264 265 181 1200 Sig. LSD 0.05 14 21 38 29 55 51 175 Nitrogen (N) (kg ha 1 yr 1 ) 98 165 134 208 261 267 17 9 1214 294 179 131 217 279 290 187 1283 Sig. NS NS NS NS NS NS LSD 0.05 14 G X N Interaction Bahiagrass 98 184 143 221 272 291 182 1293 Bahiagrass 294 185 135 219 280 297 188 1304 St. Augustinegrass 98 146 125 196 250 247 175 1139 St. Augustinegrass 294 173 127 215 278 283 186 1262 Sig. NS NS NS NS NS NS NS

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28 CHAPTER 2 EFFECTS OF IRRIGATION REGIMES AND NITROG EN RATES ON NITROGEN LEACHING FROM ST. AUGUSTINEGR ASS YARDS Introduction Nitrogen is essential for growth and function and is the mineral nutrient required in the greatest quantity by turfgrasses (Beard, 1973). When N is maintained at sufficient levels, N can promote vigor, visual quality, recovery from damage and overall health (Bowman et al., 2002). Consequently, N fertilizers are frequently used to maintain or improve density and the aesthetics of residential landscapes as the amount of N in most soils is insufficient to support acceptable aesthetics of residential yards (Cisar et al., 1991). When N is applied to turfgrass, it can exit the turf/soil system via gaseous losses such as volatilization and denitrification, groundwater leaching, runoff, and clipping removal (Petrovic, 1990). Of these processes, the regulatory and environmental groups perceive nitrate ( NO3N ) leaching as the greatest environmental threat due to its mobility and its inability to be retained on soil colloids (Bowman et al., 2002). Nitrate is considered one of the most widespr ead contaminants among the worlds aquifers and can lead to eutrophication and algal blooms in near shore environments and lakes (Spalding and Exner, 1993). It is also considered a human health threat if NO3N levels exceed 10 mg L1 in drinking water as it can cause the syndrome known as methemoglobinemia also called blue baby syndrome (USEPA, 1976). In Florida, NO3N leaching from home lawns has been implicated as a potential source of N pollution to streams, lakes, springs and bays (Erickson et al., 2001; Flipse et al., 1984). With expanding residential land use and increasing urban population in Florida, greater quantities of fertilizer may be applied, which could contribute to problems associated with NO3N contamination in water. In addition, res idential soils in southern Florida are

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29 generally coarse textured with little ability to retain either N or water which may further increase leaching of NO3N especially after excess precipitation (Cisar et al., 1991; Erickson et al., 2008). To date, research examining fertilizer N leaching from turfgrass generally has shown low potential of N leaching from turfgrass (Erickson et al., 2008; Reike and Ellis, 1974; Sheard et al., 1985; Starr and DeRoo, 1981; Mancino and Troll, 1990; Miltner et al., 1996). However, higher N leaching losses have shown to be greatly influenced by several management factors including N rate, N source, N frequency, N application methods, irrigation management, turfgrass establishment, and species or cultivar selection (Barton, et al., 2006; Bowman et al., 2002; Cisar et al., 1991; Erickson et al., 2010; Geron et al., 1993; Reike and Ellis, 1974; Snyder et al., 1984; Snyder et al., 1989; Petrovic, 1990). For example, soluble N fertilizer sources used at the same rates and frequenci es of slow release or organic sources tend to increase leaching (Eason and Petrovic, 2004). Furthermore, increasing irrigation and precipitation in excess of ET has shown to increase N leaching (Barton et al., 2006; Morton et al., 1988; Snyder et al., 1984). For example, Snyder et al., (1984) demonstrated on bermudagrass that scheduling irrigation on soil moisture depletion could reduce NO3N to <1% compared to daily irrigation that resulted in losses ranging from 22 to 56%. In 2002, Best Management Pract ices in Florida were developed by regulatory, academic and industry professionals after research had shown that fertilizer management was a major factor in reducing nonpoint source pollution (Gross et al., 1990; Trenholm et al., 2002). Currently, publish ed research for St. Augustinegrass has examined the effects of sod type, irrigation, and fertilization on newly established St.

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30 Augustinegarss sod, contrasting landscapes (mixed species vs. St. Augustinegrass) and rates of quick release vs. slow release N fertilizer on ornamentals and St. Augustinegrass NO3N leaching (Erickson et al, 2001; Erickson et al., 2008; Erickson et al., 2010; Saha, et al., 200 5 ). However, there are no published data on the impact of other management practices such as irrigation, soluble N rates and the combination of these factors on N leaching from mature St. Augustinegrass yards. Current state wide regulations in Florida under the Urban Turf Fertilizer Rule has limited N applications to 49 kg N ha1 per application of which, the water soluble N portion should not exceed 34 kg N ha1 (Department of Agricultural and Consumer Services (DACS), No. 4640400, Rule 5E 1.003, 2007). Furthermore, some local ordinances impose stricter N fertilizer guidelines than the ones under the Urban Turf Fertilizer Rule in an attempt to further reduce N leaching. For example, the City of Sanibel enacted Ordinance No. 07003 (Council of the City of Sanibel Water Resources Department), which prohibits N fertilization during the traditional rainy seas on in South Florida from June 1 through September 30, restricts annual N applied as fertilizer to 196 kg ha1, and further limits the per application soluble N portion of fertilizer to 24.5 kg ha1. However, no research has reported that such fertilizer p ractices actually needed to reduce N leaching from St Augustinegrass. In addition, water restrictions on home yards restrict irrigation of home yards to at least three days per week (Phase 1) to once a week (Phase 3) or none (South Florida Water Management District, 2010) (SFWMD) depending on the ordinance and water restriction in place to conserve water. Given that there is little data supporting the claims that these management practices or similar ones can reduce N leaching from St.

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31 Augustinegrass yards in south Florida, we conducted a study to determine how irrigation regimes and N rates influence inorganic N leaching from established St. Augustinegrass. Materials and Methods Experimental Site and Design The study was conducted at the University of F loridas Institute of Food and Agricultural Sciences (IFAS), Fort Lauderdale Research and Education Center (2603 N, 8013 W) on an stand of St. Augustinegrass (cv. Floratam), which was initially produced on sand soil and then grown on a mined landscape type sand ( Atlas Peat and Soil, Inc ) that was low (<0.5%) in organic matter (Table 21) with a pH of 7.9 0.2. S and was used as the rootzone media for this experiment as to demonstrate a worst case scenario situation (Table 21). The experiment consi sted of 32 plots in a split plot randomized complete block design with four replications repeated over two trials. Main blocks (8 x 4 m) consisted of one of two irrigation regimes: 2.5 mm daily (Low) except when daily precipitation > 6.4 mm (irrigation tur ned off), and 13.0 mm three times weekly (High) simulating a Phase 1 water use restriction that is used by the South Florida Water Management District under water shortages (SFWMD, 2010). Subplots (2 x 4 m) consisted of four N rates (98, 196, 294 and 588 kg N ha1 yr1). The 588kg N ha1 yr1, which is double the recommend rate for this geographical region by IFAS (Trenholm et al., 2000), was included in the study as a worst case scenario for excessive N applications to home yards in south Florida. The 2 94 kg N ha1 yr1rate is suggested for south Florida conditions with appreciable soil organic matter, 196 kg N ha1 yr1 is more comparable to central/north Florida with a shorter growing season and the 98 kg rate is recommended for the University of Flor ida Florida Yards and

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32 Neighborhood resource efficient landscapes that include turf. Nitrogen rates were split over 6 application dates. In 20062007 N was applied on the 12 Oct., 12 Dec. 2006 and 15 Mar., 17 Apr., 18 June, and 16 Aug. 2007. In 20072008, N was applied on the 11 Oct., 21 Dec. 2007 and 20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each application date represented the start of a new fertilizer cycle ( F C). Spray grade granular urea (460 0) was used as the source of N and was applied with a backpack CO2pressurized (30 psi) sprayer equipped with two flat fan TeeJet 8010 nozzles on 510 m m spacing as per industry standard method of application. Immediately following N applications, plots received 13 mm of irrigation to reduce loss by volatil ization and reduce burn potential (Bowman et al., 1987). In addition to N fertilization, P and K from triple superphosphate (0 460) and muriate of potash (00 60) were applied to maintain acceptable soil test values at the rate of 196 and 392 kg ha1 yr1, split equally every 90d, respectively. Additionally, micro nutrients were applied as Harrells Max Minors containing Mg 1%, S 3.5%, B 0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6% and Mo 0.0005% at 12 L ha1 every 90days Plot were maintained using a rotary mower at a height of cut of 75 m m and clippings were removed. Measure of Percolate and Nutrient Leaching Drainage was measured using lysimeters inserted into each of the plots on top of a 30 0 m m sand base in the center of each subplot. The lysimeters were constructed from plastic drums 920 m m high, 597 m m diameter, with a 13 m m thick wall, (US Plastics Corporation) with a flat bottom which had a threaded opening already manufactured into the container for easy drainage pipe installations. The lysimeters were fitted with 19 mm polyvinyl chloride (PVC) drainage pipe, spliced to allow for lysimeter drainage and individually installed on the foundation. A 90 degree elbow joint

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33 was attached to drainage orifice, which was subsequently connected to a 10 m m section of 24 m m diameter Schedule 40 PVC pipe that ran to a collection station. At the collection station each pipe was allocated its own 20 L polyethylene container. Each lysimeter had a stainless steel screen (1 mm mesh) over the orfice at the bottom of the lysimeter. This subsequently was covered with a 100 m m layer of filter gravel (>14 mm 1%, 12 14 mm 7.5%, 9 12 mm 10.5%, 6.739 mm 28%, 66.73 mm 41%, 4 6 mm 7%, 2 4 mm 3.5%, <2mm 1.5%) which was overlaid by 5 cm layer of choker sand (>2 mm 0.1%, 1 2 mm, 7.6%, 0.5 1.0 mm 26%, 0.250.5 mm 45.6%, 0.150.25 mm 19.1%, 0.0530.15 1.2%, <0.053 0.6%). Similar a layer was installed outside the lysimeter so the soil profiles were similar. Subsequently, mason sand was packed around, between and within each of the l ysimeters to a depth of 780 m m. Furthermore, a 75 m m layer of mason sand was spread uniformly over the top of the lysimeters. Perimeter irrigation systems were installed on each of the main plots. The irrigation system comprised of 24 mm diameter Schedule 40 PVC pipe with rotor Rainbird 3500 sprinklers placed in each corner adjusted to spray an inward quarter circle. Following the completion of the installation of the lysimeters St. Augustinegrass was planted in the designated plots. Before the actual initi ation of the experiment, grass was allowed to establish for a period of 6 months. Thereafter, percolate water volume was measured and subsamples were collected (20 ml scintillation vial) at least weekly, and more frequently following precipitation events exceeding 25 mm. Additionally irrigation water and rain water samples were collected bi weekly as well. The subsamples, irrigation and rain samples were immediately preserved with one drop of 50% sulfuric acid to a pH < 2, refrigerated to a temperature < 4 C and analyzed within 28 days as per Florida Department of

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34 Environmental protection protocol. Percolate samples were analyzed by colorimetric method for NO3N (EPA method 353.2) using a Seal AA3 continuous flow analyzer (Seal Analytical Mequon, W I) by the University of Florida Analytical Research Laboratory (Gainesville, FL). In addition, percolate samples were analyzed for ammonium (NH4N) by colorimetric method (QuickChem method 10 107062 A) using a Lachat Flow injection analyzer ( Hach Company, Loveland, CO) at the Everglades Research and Education Center, University of Florida. All values below the minimum detection limit (MDL) were reported as the MDL. Minimum detection limits for NO3N and NH4N methods were 0.05 and 0.05 mg/L for trial 1 and 0.15 and 0.05 mg/L for trial 2, respectively. Total quantity of NO3N and NH4N leached and flow weighted means concentrations (total quantity of N leached/total volume percolate) were calculated from volume of percolate and laboratory analyses for each cy cle. Analysis of Data All data were analyzed for normality using the ShapiroWilk W test. Homogeneity of variance was also checked graphically. Percolate, NO3N and NH4N leached were summed on a plot by plot basis for each year and analyzed on a yearly basis. In addition, mean flow weighted concentrations were calculated for each trial All data were subjected to analysis of variance with PROC Mixed (SAS Institute, 1999) and means were separated using fishers protected Least Significant Difference (LSD ) test with alpha=0.05. Orthogonal contrasts examined linear and quadratic responses to N rates (Gomez and Gomez, 1984).

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35 Results Hydrology Annual rainfall for trial 1 and 2 averaged 1658 and 1 5 38 mm, respectively (Figure, 2 1). Rainfall in trials 1 and 2 accounted for 67 and 46% and 65 and 43% of total inputs for the low and high irrigation regimes, respectively. Irrigation inputs for the low and high irrigation regime averaged 807 and 1892 mm for trial 1 and 877 and 2173 mm for trial 2, respectively. T otal water inputs varied depending on the irrigation regime. In trial 1 the high irrigation regime had a total water input of 3550 mm, which was 44% greater than water inputs for the low irrigation (2465 mm). Similarly, in trial 2 the high irrigation regi me had 52% (3811 mm) greater water inputs than the low irrigation (2515 mm) (Figure, 2 1). Drainage was (P <0.05) impacted by irrigation regime and N rates (Table 2 2). In both trials, the greatest drainage occurred from the high irrigation regime with m eans of 1702 and 1720 mm for trials 1 and 2, respectively. The low irrigation regime resulted in 37 and 28 % less drainage than the high irrigation regime for the same trials. Under high and low irrigation regimes 49 and 51 % of the total water inputs were lost as drainage in trial 1 and 45 and 48% for trial 2, respectively. Furthermore, in both trials as N increased drainage generally decreased. In trial 1 and 2 drainage decreased from 1588 to 1397 mm and 1569 to 1336 mm in response to N rates increasing from 98 to 588 kg N ha1 yr1 ( Table 22). Nitrogen Leaching Nitrate N and NH4N concentrations in the rain and irrigation water were always below the MDLs for their respective trials Flow weighted (FW) NO3N concentrations in the drainage were similar (P > 0.05) among both irrigation regimes and nitrogen rates ( Table 22). Flow weighed (NO3N) concentrations in the leachate from the low and

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36 high irrigation treatments averaged 0.21 and 0.17 mg L1. Similarly, FW ( NO3N ) concentrations in the leachate from the N treatments ranged from 0.150.28 mg L1. In addition, FW ( NH4N ) concentrations in the drainage were always lower than the FW ( NO3N ) concentrations. Furthermore, increasing irrigation inputs (high irrigation regime) or N rates did not increase (P > 0.05) FW ( NH4N ) concentrations in drainage. Flow weighted NH4N concentrations in the drainage averaged 0.07 and 0.08 mg L1 for the low and high irrigation regimes, respectively ( Table 22). Flow weighted ( NH4N ) concentrations leached from the different fertilizer rates ranged from 0.070.09 mg L1 with FW ( NH4N ) concentrations never exceeded a mean value of 1 mg L1. Total inorganic nitrogen (TIN) leached was not (P > 0.05) affected by irrigation regimes or N rates ( Table 22). However, the high irrigation regime always produced the greatest amounts of TIN leached with mean of 3.4 kg N ha1. Additionally, the high irrigation regime accounted for 42 % more TIN leached compared to the low irrigation regime. Total inorganic N leached from the different fertilizer rates ranged from 2.2 to 3.8 kg N ha1 ( Table 22). T he highest N rate always produced the greatest amount of TIN leached with mean of 3.8 kg N ha1. Under the highest N rate TIN leached represented less than 0. 6 % of the total N app lied. Similar to TIN leached, NO3N leached was not ( P > 0.05) affected by irrigation or N rates ( Table 22). However, the high irrigation regime and highest N rate produced the greatest quantity of NO3N and NH4N leached. Under the high irrigation reg ime averaged NO3N and NH4N leached were 1.8 and 1 1 kg N ha1. In addition, under the highest N rate the average NO3N and NH4N leached were 3.1 and 0.7 kg N ha1( Table 22).

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37 Discussion I rrigation regimes and N rates were evaluated for N leaching on a sand rootzone. A rate of 588 kg N ha1 was included, which is twice the recommended rate for St Augustinegrass in south Florida, to serve as a worst case scenario. Throughout the duration of the experiment flow weighted ( NO3N ) leached levels never el evated above the EPA human health standards of 10 mg NO3N L1. The highest FW concentration measured in the drainage water was never > 4 mg NO3N L1. Irrigation regimes and N rate did impact drainage, and N rate affected FW NO3N concentrations in the drainage (Table 22). However, the quantities of NO3N, NH4N or TIN leached did not differ among any of the treatments. These results raise questions as to whether ordinances are really needed to reduce the N applied beyond that enforced by the Urban Tur f Fertilizer Rule, which limits N applications to 49 kg N ha1 of which, the water soluble N portion should not exceed 34 kg N ha1. Drainage was greatly impacted by irrigation regime, as the high irrigation regime increased drainage by an average of 39% However, FW NO3N and NH4N concentrations did not differ under the high irrigation regime. Despite greater drainage, with the high irrigation regime, we found no differences in the quantity of NO3N, NH4N or TIN leached, due largely to the fact that concentrations tended to be lower in the high irrigation regime compared to the low irrigation regime (Table 2 2). This may be attributed to the high irrigation diluting the NO3N and NH4N concentrations in the drainage water especially if NO3N and NH4N concentrations are low in the soil solution. Furthermore, in both studies, FW NO3N concentrations were greater than NH4N concentrations. This may be explained by urea being rapidly converted to NO3-

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38 N through the processes of hydrolysis and nitrificat ion and/or by NH4N being retained on the cation exchange site thus, being less mobile than the NO3N. The results in this study with regard to irrigation effects on N leaching differ from many published studies (e.g., Morton et al., 1988; Snyder et al. 1984, and Barton et al., 2006). For example, Barton et al. (2006) found that increasing the irrigation from 70% to 140% of ET increased N leaching significantly. However, in this study increasing total water inputs by 48% did not significantly increase F W NH4N or NO3N concentrations or quantities leached, but there was a general trend in this direction, indicating that irrigation in the present study was not as excessive as earlier reported research. Nitrogen rates did impact drainage and FW NO3N concentrations. Higher N rates generally decreased drainage due to the increase in growth rates that increased water use rates (McGroary et al., 2010) thus, decreasing the drainage volume. Barton, ( 2009) found similar results when increasing N rate increased ET rates. Furthermore, Snyder et al., 1984 showed that reducing percolate reduced N leaching from bermudagrass. Thus, a well maintained lawn (proper irrigation and fertilization) may actually reduce leaching due to the reduced percolate through the rootzone. In general, as N rate increased so did FW NO3N concentrations. Again, these differences did not result in (P > 0.05) greater FW NO3N, NH4N or TIN leaching, due to the less drainage observed with the high N rates. Nevertheless, there was a trend tow ards greater TIN leaching at the high N rates. However, its possible that greater quantities of the applied N could be leached as urea or loss through gases losses. Unfortunately in this study organic N in percolate or gaseous losses were not measured. Thus, we were unable to predict how much total N from urea was leached or lost to the atmosphere, but Sartain

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39 (2010) reported that urea applications to St. Augustinegrass at 49 kg N ha1 every 30 days for a period of 180 days did not produce urea in leachates. Consequently, in this study we only examined the impact of N rates on TIN. Total inorganic N leached accounted for less than 3% of the total applied N lost. This advocates that alternative pathways in the N cycle played a more significant part in t he fate of N in this system. The amount of N leached has been found to be dependent on soil storage/drainage, amount of N in solution, gaseous losses (volatilization and denitrification), immobilization, and N uptake by the vegetation. The results indica ted that St. Augustinegrass was either efficient at removing the NH4N and NO3N from the soil solution or at tying them up through immobilization, as soil storage in the ionic form would have been negligible due to low cation exchange capacity of the soil Additionally, the N applied may have been lost to the atmosphere through volatilization or denitrification or a combination of both pathways. I n order to minimize N volatilization losses in this study 13 mm of irrigation was applied immediately after N fertiliz ation, which Bowman et al. (1987) reported to reduce volatilization to less than 8% from Kentucky bluegrass ( Poa pratensis L.) However, irrigation application after N fertilization may have not been adequate at halting volatilization completel y. With the soil having a pH 7.8 and environmental conditions (high temperature and humidity) this would have been conducive for volatile N loss especially if irrigation was ineffective at initially reducing volatilization (Titko et al. 1987). Plots rece iving higher rates of N are prone to higher rates of ammonium volatilization than the lower N rates (Wesley et al., 1987). Additionally, denitrification a pathway by which facultative anaerobes reduce NO3N to molecular N in anaerobic soils (Coyne, 2008) m ay have contributed to N loss.

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40 Horgan et al., (2002) reported 9.8 kg N ha1 loss of applied N from Kentucky bluegrass through denitrification. However, Barton et al. (2006) reported low denitrification rates in sands, thus accounting for only a small amo unt of N loss. Immobilization, the conversion of inorganic N to organic N, may also contribute to a large disparity between N applied and leached. Starr and Deroo (1981) evaluated the fate of N on cool season grasses using labeled 15N and found that 15 21% of applied N was stored in the organic content of the soil. However, plant uptake may have had the greatest impact of reducing N leaching in this study. Bowman et al., (2002) reported that St Augustinegrass was relatively efficient at reducing NO3N leaching due to its root length density when compared to common bermudagrass [ Cynodon dactylon (L.) Pers.], Tifway hybrid bermudagrass ( C. dactylon X transvaalensis ), centipedegrass ( Erem chloaophiuroides (Munro) Hack.), Meyer zoysiagrass (Zoysia ja ponica Steud.), and Emerald zoysiagrass ( Z. japonica X in tenuifolia )] Furthermore, Bowman et al. (2002) reported that shoots, clippings and roots accounted for up to 74% of applied N with the greatest quantity being stored in the shoots (52%). Unfortunately, in this study, shoots were not measured but this may help explain why little N leaching occurred. Conclusion Under worse case scenario conditions such as a sand rootzone and double the recommended N rate, N leaching was negligible and did not excee d human health standards or those thought to be of concern for environmental impact. Therefore the are no need to reduce N application rates beyond the current Urban Turf Fertilizer Rules. Furthermore, the high irrigation regime (3 X week) did not signi ficantly increase N leaching from St. Augustinegrass. However, it produced more drainage, which

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41 indicated that irrigating at a greater rate but reduced frequency may actually be a poor management strategy for conserving water compared to a low er irrigatio n rate increased frequency irrigation regime.

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42 Figure 21. Irrigation and precipitation inputs for the low and high irrigation regimes for trial 1 and trial 2 (n = 32). 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Low High Low High Water inputs (mm) Rainfall Irrigation Trial 2 Trial 1

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43 Table 21. Percentage by weight of miner al particle fractions contained in the root zone used for construction of the field study area. Name Size range Weight -------mm --------% ---Fine Gravel 2.0 3.4 0 Very coarse sand 1.0 2.0 2 Coarse sand 0.5 1.0 7 Medium sand 0.25 0.50 23 Fine sand 0.15 0.25 27 Very Fine Sand 0.05 0.15 34 Silt 0.002 0.05 7 Clay less than 0.002 0 Table 22. Analysis of variance results for drainage, flow weighted concentration f NO3N, flowweighted concentration of NH4N quantity of NO3N leac hed, quantity of NH4N leached and, quantity of total inorganic N leached. Treatment means represent the average of 4 plots. NS, *, and ** = P > 0.05, P < 0.05, and P < 0.01, respectively. Note: Interactions not shown were not significant. Effects Drainage ( mm ) [NO 3 N] (mg L 1 ) [NH 4 N] (mg L 1 ) NO 3 N l eached (kg ha 1 ) NH 4 N l eached (kg ha 1 ) Inorganic N l eached (kg ha 1 ) Irrigation (IRR) Low 1231 0.21 0.08 1.8 0.6 2.4 High 1711 0.17 0.07 2.3 1.1 3.4 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 1579 0.15 0.07 1.6 0.6 2.2 196 1556 0.18 0.07 2.0 0.6 2.6 294 1378 0.16 0.08 1.6 0.6 2.2 588 1367 0.28 0.09 3.1 0.7 3.8 ANOVA Source of variation TRIAL NS NS NS NS NS NS IRR NS NS NS NS NS NR ** NS NS NS NS Linear NS NS NS NS NS Quadratic ** NS NS NS NS NS IRR x NR NS NS NS NS NS NS TRIAL x IRR x NR NS NS NS NS NS NS

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44 CHAPTER 3 EFFECTS OF IRRIGATION REGIMES AND NITROG EN FERTILIZATION ON ST. AUGUSTINEGRASS GROWT H QUALITY AND WATER CONSERVATI ON Introduction St. Augustinegrass ( Stenotaphum secundatum [Walt.] Kuntze) is one of the most widely used grass species for home lawns in the Southeastern United States. In Florida alone, St. Augustinegrass is grown on approximately 70% of the lawns with an additional 24,164 ha grown for sod production (Busey, 2003; Haydu et al., 2005). St. Augustinegrass is adapted for moderate cultural practices, which include judicious inputs of both N and irrigation (Trenholm et al., 2000). Irr igation and N are essential components of producing quality turfgrass (Beard, 1973). At the appropriate rates, N and irrigation have been shown to improve turfgrass color, quality, and root growth along with many other additional benefits. However, exces s N and irrigation rates applied to turfgrass can potentially increase NO3N leaching and degrade water quality (Hull and Liu, 2005; Snyder et al., 1984). In addition, many state regulators have criticized St. Augustinegrass management both for its high w ater use in home yards, as a recent study showed that irrigation accounted for 64% of residential water use (approx. 141 mm mo1) in Central Florida (Haley et al., 2007). As a result, many municipalities across the nation have enacted water and N fertiliz er restrictions to limit residential inputs in order to conserve water and protect water resources (e.g., SFWMD, 2010). Some municipalities even offer rebates to remove grass and replace it with xeriscape (Glendale, 2010). For example, in south Florida t he SFWMD enforces different phases of water restrictions to landscapes and golf courses in order to conserve water. These phases can limit

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45 irrigation from three days per week (Phase 1) to once a week (Phase 3) or none (SFWMD, 2010) depending on the ordinance and water restriction in place. These efforts are intended to conserve water and result in penalties that are enforced if caught watering outside the guidelines. Currently, the state is in mandatory Phase 1 to Phase 3 restrictions year round. Other municipalities prohibit planting of St. Augustinegrass (Central Florida) or do not permit irrigation from installed irrigation systems in South West Florida. Because of concerns over anthropogenic inputs of N to threatened water bodies, such as coastal bays and f resh water systems (Vitousek et al., 1997 ), current state wide regulations in Florida under the Urban Turf Fertilizer Rule limit N applications to 49 kg N ha-1 of which, the water soluble N portion should not exceed 34 kg N ha-1 (Department of Agri cultural and Consumer services (DACS), No. 4640400, Rule 5E 1.003, 2007). However, there are no published data on whether these management practices actually conserve water or provide sufficient N nutrition to maintain acceptable St. Augustinegrass in Sou th Florida that are grown primarily on sandy soils with little ability to retain water and nutrients. Research is needed to determine if such practices can actually conserve water and maintain St. Augustinegrass quality. Furthermore, data is lacking on t he minimum N inputs required in order to produce acceptable St. Augustinegrass in south Florida. Consequently, research must be conducted to provide accurate fertilizer recommendations so acceptable turfgrass quality can be maintained with minimum impact on the environment. Therefore, the objectives of this experiment were to 1) evaluate irrigation and fertilizer practices and their impact on water conservation and St. Augustinegrass

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46 growth and quality 2) to evaluate an alternative irrigation regime and to determine minimum N requirements for the production of St. Augustinegrass in subtropical south Florida. Materials and Methods The study was conducted at the University of Floridas Institute of Food and Agricultural Sciences (IFAS), Fort Lauderdale Research and Education Center (2603 N, 8013 W) on an established mature stand of St. Augustinegrass cv. Floratam sod initially produced on sand soil and then grown on a mined mason sand commonly used in landscapes in south Florida. The sand was low (<0.5%) in organic matter (OM) (Table 1) and had a pH of 7.9 0.2. The experiment consisted of 32 plots in a split plot randomized complete block design with four replications of each treatment. Main blocks (8 x 4 m) consisted of one of two irrigation regi mes: 2.5 mm daily (Low) except when daily precipitation > 6.4 mm (irrigation turned off), and 13.0 mm three times weekly (High) simulating a Phase 1 water use restriction that is implement by the South Florida Water Management District under water shortages (SFWMD, 2010). The irrigation system comprised of 24 m m diameter Schedule 40 PVC pipe with rotor Rainbird 3500 sprinklers placed in each corner adjusted to spray an inward quarter circle. Subplots (2 x 4 m) consisted of four N rates (98, 196, 294 and 58 8 kg N ha1 yr1). The 588kg N ha1 yr1) which included in the study as a worst case scenario for excessive N applications to home yards in south Florida which is double the recommend rate for N in this geographical region (Trenholm et al., 2000). Th e 294 kg rate is suggested for south Florida conditions with appreciable soil organic matter, and 196 kg is more comparable to central/north Florida with a shorter growing season. The 98 kg rate is recommended for the University of Florida Florida Yards and Neighborhood resource efficient

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47 landscapes that include turf. Nitrogen rates were split equally over 6 application dates in 20062007 except for (cycle two and three) in trial 1 and again in 20072008 trial 2. In 20062007 N was applied on the 12 Oc t., 12 Dec. 2006 and 15 Mar., 17 Apr., 18 June, and 16 Aug. 2007. In 20072008, N was applied on the 11 Oct., 21 Dec. 2007 and 20 Feb., 21 Apr., 23 June, and 3 Sept. 2008. Each application date represented the start of a new fertilizer cycle ( F C). Spray g rade granular urea (460 0) was used as the source of N and applied with a backpack CO2pressurized (30 psi) sprayer equipped with two flat fan TeeJet 8010 nozzles on 510 m m spacing as per industry standard method of application. Immediately following N applications, plots received 13 mm of irrigation to reduce loss by volatilization and reduce burn potential (Bowman et al., 1987). In addition to N fertilization, P and K from triple superphosphate (046 0) and muriate of potash (00 60) were applied to ma intain acceptable soil test values at the rate of 196 and 392 kg ha1 yr1, split equally every 90d, respectively. Additionally, micro nutrients were applied as Harrells Max Minors containing Mg 1%, S 3.5%, B 0.02%, Cu 0.25%, Fe 4%, Mn 1%, Zn 0.6% and Mo 0.0005% at 12 L ha1 every 90days Plot were maintained using a rotary mower at a height of cut of 75 m m and clippings were removed. Turfgrass Quality Irrigation and N response was evaluated in terms of visual quality. Visual quality evaluations were conducted approximately every 14 days and ratings were based on a scale of 1 9, where 1 was brown or dead grass and 9 represented dark green, dense uniform grass. A rating of 6.5 was considered minimally acceptable (Carrow, 1997). Turfgrass clipping sam ples for shoot growth were harvested from a 2.24 m2 area within each plot using a rotary mower (Toro, Blooming ton, MN) set at a height at a 75 m m

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48 approximately bi weekly or more frequently when necessary. Samples were oven dried at 80o C for 48 hrs to a c onstant weight. Subsequently, tissue samples were ground using a Wiley Mill and sub sampled for tissue N analysis. Nitrogen was determined using a modification of digestion described by Wolf (1982) and analyzed for NH4N using a spectrometer (UNIVO 2100, Dayton, NJ) at a wavelength of 660 nm. Nitrogen uptake was calculated by multiplying tissue N concentration ( g N kg1) by yield (kg dry wt. ha1), and was reported as g N ha1. Reference evapotranspiration was calculated using a modified penman method and was obtained from a Florida Automated Weather Network (FAWN) station which was located within 500 m of the test site (Zazueta, 1991). Statistical Design and Analysis All data were analyzed for normality using the ShapiroWilk W test. Homogeneity of va riance was also checked graphically. Turfgrass quality, clipping yields (CYs) tissue N concentration, and N uptake were summed on a plot by plot basis for each cycle and analyzed on a year bases because of trial by treatment interactions. All data were subjected to analysis of variance with PROC Mixed (SAS Institute, 1999) and means were separated using Fishers protected Least Significant Difference (LSD) test with alpha=0.05. Orthogonal contrasts examined linear and quadratic responses to N rates (Gomez and Gomez, 1984). Results Hydrology The relative contribution of irrigation and rainfall differed depending upon the time of year and irrigation regime (Table 32). For the dry season cycles (i.e., F C1, F C2, and F C3) low and high irrigation regimes accounted for between 48 to 59 % and 67 to 77%

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49 of the total water received by plots for trial 1 and 35 to 49% and 58 to 69% for trial 2 (Table 3 2 ). However, for the wet season cycles (i.e., F C4, F C5, and F C6) irrigation inputs accounted for considerabl y l ess of the total inputs with low and high irrigation regimes account ing for between 19 to 34% and 39 to 57% of the water received by plots for trial 1, and 20 to 48% and 42 to 68% for trial 2 (Table 32). The large differences between seasons in the perce nt of total inputs that irrigation accounts for can be explained by the large precipitation event that normally occurs in the wet season in Florida (Table 32). In addition, the dry season low and high irrigation regimes alone accounted for between 65 to 109% and 147 to 251% of ET rates for trial 1 and 62 to 119% and 162 to 281% of ET rates for trial 2. However, for the wet cycles low and high irrigation regimes account for between 49 to 50% and 126 to 138% of ET rates for trial 1 and 44 to 70% and 118 to 172 % for trial 2 (Table 32). Irrigation inputs for the high irrigation exceed the low irrigation regime by 144% (1162mm) and 148% (1296 mm) for trial 1 and 2 respectively. Throughout the duration of both trials total inputs (rainfall + irrigation ) alway s exceeded ET demands of St. Augustinegrass. For the dry season low and high irrigation total inputs exceed ET rates by 36 to 116% and 118 to 258% for trial 1 and 79 to 145% and 179 to 307% for trial 2. During the wet season low and high irrigation total inputs exceed ET rates by 44 to 164% and 121 to 253% for trial 1 and 4 to 147% and 72 to 249% for trial 2. Turfgrass Quality St Augustiengrass visual quality was affected ( P > 0.05) by irrigation regimes though not significant in every cycle (Tables 33, 3 4). Both irrigation regimes did produce acceptable quality ( 6.5) for the duration of both trials (Tables 33, 3 4). Throughout the duration of trial 1, low and high irrigation regimes produced similar

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50 turfgrass quality with an average score of 7.0 for both irrigation regimes. However, in trial 2 the high irrigation regime produced higher visual quality rating than the low irrigation regime with average scores of 6.7 and 6.6, respectively (Table 34) Nitrogen rates affected turfgrass quality ratings with visual quality increasing with N rate in both trials (Tables 33, 3 4). Among the four N rates evaluated only 9 8 kg N ha1 yr1 was unable to produced acceptable ( for the duration of both trials with the 588 kg N ha1 yr1 always producing the highest quality with means of 7.8 and 7.6 for trial 1 and 2. Furthermore, plots receiving 294 kg N ha1 yr1 always yielded higher visual quality ratings than the 196 kg N with average scores of 7.1 and 6.7 and 6.8 and 6.6 for trial 1 and 2, respectively. The lowest quality scores were observed at the 98 kg N ha1 yr1 which had average visual scores of 6.3 and 5.8 for trial 1 and 2 which was below the acceptable ( 6.5) visual quality (Tables 33, 3 4). Clippings Yield Results for CYs were similar to those for visual quality. Clipping yields generally increased by N rate (Tables 35, 3 6). Greatest CYs occurred from plots receiving 588 kg N ha1, which typicall y yielded twice as much clipping as the plots receiving the next highest N rate of 294 kg N ha1 (Tables 35, 3 6). No differences in CYs were observed between plots receiving 294, 196, and 98 kg N ha1 when averaged over each trial. However, statistical differences were observed between N rates within each cycle P lots receiving the higher N rate always produced the greatest CYs except F C4 in trials 1 and 2. Plots receiving 98 kg N ha1 generally produced about 35% less clippings than plots receiving 196 kg N ha1. Similar CYs were observed from plots receiving 294 and 196 kg N ha1. Irrigation regimes had no effect on CYs (Tables 35, 3 6).

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51 Tissue N Irrigation regime had no effect ( P > 0.05) on tissue N concentration (Tables 37, 3 8). The N concentration of clippings generally increased with increasing N fertilization rates. However, N fertilization only affected tissue N levels in 4 cycles in trial 1 and 3 cycles in trial 2. The N rate of 588 kg N ha1 always produced the highest N concentration with average tissue concentrations of 21.3 and 20.5 g N kg1 for trials 1 and 2, respectively. Though, tissue N did vary between cycles with N ranging from 18.9 to 26.4 g N kg and 18.0 to 24.5 g N kg for trials 1 and 2. The lowest tissue N was always fo und on the plots receiving 98 kg N ha1 with an average tissue N of 17.1 and 17.9 g kg1 for their respective trials (Tables 3 7, 3 8). Nitrogen Uptake Nitrogen uptake was greatly influenced by N fertilization (Tables 39, 3 10). A s nitrogen rates inc reased so did N uptake. However, only the 588 kg N ha1 rate was statistically different from the other three N rates averaged over each trial with the 588 kg N ha1 rate almost taking up double the amount of N compared to the 298 kg N ha1. The 98 kg N ha1 had the lowest N uptake with an average of 16 and 17 kg N ha1 for trials 1 and 2, respectively. In addition, plots receiving N rates of 294 and 196 kg N ha1 up took twice as much N as the 98 kg N ha1. However, it was statistically different in F C2 in trial 1 and F C1 and F C6 in trial 2. Similar N uptake was observed from plots receiving 294 and 196 kg N ha1. Nitrogen recovered in tissue based on percentageapplied range from 14 to 16% in trial 1 and 12 to 17% of applied in trial 2. The greatest % N recovery always occurred in the lowest N rate and the lowest recovery from the 294 kg N ha1. Irrigation regime had no significant effect on N uptake within each trial or when averaged across each trial (Tables 39, 3 10). Total N uptake for low and hig h

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52 irrigation regimes were 47.7 and 44.0 kg N ha1 for trial 1 and 39 and 41 kg N ha1 for trial 2. Discussion With water and N inputs to urban landscapes under scrutiny, it is essential that both are applied to match the needs of turfgrass, as this has been shown to help conserve water, reduce nitrogen leaching and produce aesthetically pleasing yards (McGroary, 2010) Currently, the SFWMD enforces mandatory water restrictions, whereby irrigation is limited between three times a week (phase 1) and once a week (phase 3 ) In this study two irrigation regimes and four N rates were compared to determine the most suitable irrigation regime and N rates to produce a visually acceptable St. Augustinegrass lawn with minimum inputs. In the current study, the high irrigation regime, which is a phase 1 water restriction, did not improve growth, N uptake, and N concentrations. Barton et al. (2006) reported similar results, as increasing irrigation from 70% to 140% replacement of pan evaporation did not improve growt h or quality of turfgrass. Under the high irrigation regime, irrigation far surpassed water requirements for St. Augustinegrass by at least about 65% thus, proving to be an ineffective way of conserving water as well as having little positive impact on qu ality. Furthermore, the greatest difference between the irrigation inputs and ET was observed during F C1, F C2 and F C3. Theses cycles occurred during the dry season in south Florida where lower temperatures generally reduced St. Augustinegrass growth and E T rate. However, under a phase onewater restriction no reduction in irrigation inputs would be carried out, thus leading to irrigation inputs greater than St. Augustinegrass demands with wasted water. On the other hand, the low irrigation regime did provi de irrigation inputs closer to ET demands though when

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53 combined with rainfall did surpass water demands of the St. Augustinegrass. Nevertheless, during the dry season this irrigation regime conserved more water without sacrificing turfgrass quality. Howev er, during cycles F C4, F C5 and F C6, the low irrigation regime did not match ET requirements, which Snyder, 1984 showed improve growth, N uptake and color of bermudagrass. When irrigation was combined with rainfall, the total water inputs were greater than the ET demand but had an irrigation savings of 588 and 653 mm over the high irrigation regime with still being able to produced similar turfgrass quality scores. These results suggest that the low irrigation regime may be a more suitable regime than the phase 3 restrictions which is enforced by the SFWMD for maintaining acceptable St. Augustinegrass quality in south Florida quality due to the fact that acceptable quality was able to be maintained while over 1162 and 1296 mm of irrigation water were conser ved for trial 1 and 2 respectively (Table 32). In addition, N concentration, N uptake and growth were not affected by irrigation regime, indicating that neither irrigation regimes differed in the availability of N to the plant by moving it beyond the root system, and thus increasing the risk for N to be leached into the groundwater. St Augustiengrass quality, N concentration, uptake and growth were greatly influenced by N rate. Nitrogen concentration values in this study were comparable to others found for St. Augustinegrass in the literature. For example, Broschat and Elliott (2004) report 13.0 to 19.7 g N kg1 in St. Augustinegrass maintained with 196kg N ha1. In comparison, Vernon et al., (199 3 ) documented 14 g N kg1 in leaf clippings from St. Augus tinegrass var. Raleigh.

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54 N itrogen concentration, quality uptake and growth increased with increasing N rates. Nitrogen applications of 588 kg ha1 application to St. Augustinegrass 588 kg ha1 produced the best quality, greatest N concentration and N upt ake but also produced the greatest amount of clippings compared to the other N treatments. However, this N rate may not be favored by homeowners as it greatly increases fuel, labor costs and waste disposal of clippings (Fluck and Busey, 1988). The N rate of 98 kg N ha1 was unable to produce acceptable quality of St Augustinegrass for the duration of both trials, although the quality that was produced may be acceptable to some homeowners who do not demand their lawn to be dense and green all year round, and who do not want the extra cost of regular mowing and waste disposal. In addition, under different soils or management practices, such as returning clippings this N rate may be able to produce an acceptable yard, though further research is needed to val idate this question. The minimum acceptable quality for St. Augustinegrass in South Florida could be reached by applying 196 kg N ha1 as this was the lowest N rate that was able to produce minimum acceptable quality when average over each trial. However this application rate did not always provide acceptable quality in all of the cycles, which may be unsatisfactory to some homeowners. But the N rate of 294 kg N ha1 was always able to produced quality above minimum acceptable quality for all cycles and over each trial. Therefore, N recommendations of 196294 kg N ha1, as currently recommended for South Florida ( Trenholm et al., 2002), are accurate for maintaining St. Augustinegrass at acceptable levels with clippings being removed. These recommendati ons may be further reduced if clippings are returned rather than removed like in this study. Kopp and Guillard (2002) found that returning clippings could reduce fertilizer rates by 50% in

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55 cool season turfgrass. Currently no such data exist for St. Augusti negrass, therefore research is needed to determine if N inputs could be further reduced by returning clippings to St. Augustinegrass. In this study, the constructed soil was very low in organic matter, which can supply appreciable N for turfgrass growth. That coupled with the source of turf being derived from sandbased sod production probably had an effect on all measured parameters and demonstrate the need for more N nutrition under conditions of low OM, sandbased soil media with high saturated conduct ivity, and recently established turf. Over time, with increasing OM, perhaps improved turf quality with similar inputs could be expected. Although the irrigation rates were not excessive, since the N source was totally soluble, N pathways such as leaching and volatile losses could have impacted turf responses from the N fertilization. Research on more mature turf, soils with higher OM, and other N sources and application regimes along with irrigation regimes is needed. Conclusion While the results from this experiment varied across trials, some general conclusions can be drawn The low irrigation was able to maintain St. Augustingrass quality throughout the duration of the experiment while conserving large amounts of water compared to the current implem ented phase 1 restriction that are enforced in Florida. Nitrogen rate of 196 and 294 N/kg ha1 yr1 produced acceptable quality while not producing excess growth. With minimum acceptable St Augustinegrss quality in south Florida been able to be produced at 196 kg N/kg ha1 yr1.

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56 Table 31. Percentage by weight of mineral particle fractions contained in the root zone used for construction of the field study area. Name Size range Weight -------mm --------% ---Fine Gravel 2.0 3.4 0 Very coarse sand 1.0 2.0 2 Coarse sand 0.5 1.0 7 Medium sand 0.25 0.50 23 Fine sand 0.15 0.25 27 Very Fine Sand 0.05 0.15 34 Silt 0.002 0.05 7 Clay less than 0.002 0

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57 Table 32. Total rainfall, total irrigation input s, and reference ET for each cycle of the study. Study a Period Irrigation Regime Period Rainfall Irrigation Total Inputs Reference! ET ----------------------------mm ----------------------------2006 2007 Low C1 97 142 240 135 Low C2 216 221 437 20 2 Low C3 86 79 165 121 Low C4 412 130 541 258 Low C5 248 130 378 262 Low C6 453 104 557 211 Total 1512 806 2318 1189 High C1 97 330 428 135 High C2 216 508 724 202 High C3 86 178 264 121 High C4 412 330 742 258 High C5 248 33 0 579 262 High C6 453 292 745 211 Total 1 51 2 1968 348 0 1189 2007 2008 Low C1 210 178 388 179 Low C2 142 135 277 113 Low C3 257 137 394 220 Low C4 158 145 303 291 Low C5 439 112 551 257 Low C6 432 170 602 244 Total 1638 877 2515 1 304 High C1 210 419 629 179 High C2 142 318 460 113 High C3 257 356 613 220 High C4 158 343 501 291 High C5 439 318 757 257 High C6 432 419 851 244 Total 163 8 2173 3811 1304 a20062008 Cycle 1, 12 October 2006 to 11 December 2006; Cycle 2, 12 December 2006 to 14 March 2007; Cycle 3, 15 March 2007 to 16 April 2007; Cycle 4, 17 April 2007 to 17 June 2007; Cycle 5, 18 June 2007 to 15 August 2007; Cycle 6, 16 August 2007 to 10 October 2007;20072008 Cycle 1, 11 October 2007 to 20 December 2007; Cycle 2, 21 December 2007 to 19 February 2008; Cycle 3, 20 February 2008 to 20 April 2008; Cycle 4, 21 April 2008 to 22 June 2008; Cycle 5, 23 June 2008 to 02 September 2008; Cycle 6, 03 September 2008 to 5 November 2008. Reference evapotranspiraton was determined using the Penman method.

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58 Table 33. Trial 1 treatment means (n = 4) for turfgrass quality for low and high irrigation regimes and four N application rates. NS, and *** = P > 0.05, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.05). Table 34. Trial 2 treatment means (n = 4) for turfgrass quality for low and high irrigation regimes and four N application rates. NS, *, **, and *** = P > 0.0 5, P < 0.05, P < 0.01, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.05). Effects C1 C2 C3 C4 C5 C6 Ave ----------------------------------1 9 -----------------------------------Irrigation (IR) Low 6.9 6.9 6.8 7.3 7.1 7.0 7.0 High 6.9 7.0 7.0 7.0 7.1 7.0 7.0 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 6.2c 6.0c 6.2c 6.9 6.4d 6.4c 6.3c 196 6.8 b 6.6c 6.5c 6.9 6.8c 6.8bc 6.7bc 294 7.0b 7.2b 7.1b 6.8 7.3b 7.1b 7.1b 588 7.5a 7.9a 8.0a 7.9 7.9a 7.8a 7.8a ANOVA Source of variation IR NS NS NS NS NS NS NS NR *** *** *** NS *** *** *** IR x NR NS NS NS NS NS NS NS Effects C1 C2 C3 C4 C5 C6 Ave ---------------------------------1 9 --------------------------------------Irrigation (IR) Low 7.0 6.6a 6.5 6.6 6.6a 6.5 6.6a High 6.9 6.8b 6.5 6.7 6.7b 6.7 6.7b Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 6.0c 5.4c 5.5c 5.9c 6.0b 5.6c 5.8c 196 6.8b 6.6b 6.3b 6.4bc 6.4b 6.3b 6.5b 294 7.0b 6.7b 6.6b 6.8b 6.7ab 6.8ab 6.8b 588 7.9a 8.2a 7.5a 7.5a 7.3a 7.4a 7.6a ANOVA Source of variation IR NS ** NS NS NS NR *** *** *** ** *** *** IR x NR NS NS NS NS NS NS NS

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59 Table 35. Trial 1 treatment means (n = 4) for dry weight of clippings for low and high irrigation regimes and four N application rates. NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.0 5). Table 36. Trial 2 treatment means (n = 4) for dry weight of clippings for low and high irrigation regimes and four N application rates. ns, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.05). ND = No data was collected during this cycle. Effects C1 C2 C3 C4 C5 C6 Total -------------------------------kg ha 1 ---------------------------------------Irrigation (IR) Low 52 113 128 363 925 742 2323 High 63 121 108 348 853 663 2156 Nitrogen Rate (NR ) (kg ha 1 yr 1 ) 98 36 49c 75b 121b 313c 287b 88 1 b 196 48 82bc 104b 331b 720b 647b 1932b 294 56 124b 95b 296b 782b 651b 200 4 b 588 90 214a 130a 673a 1741a 1226a 4 074 a ANOVA Source of variation IR NS NS NS NS NS NS NS NR NS *** ** *** IR x NR NS NS NS NS NS NS NS Effects C1 C2 C3 C4 C5 C6 Total -----------------------------------kg ha 1 ---------------------------------Irrigation (IR) Low 156 ND 307 213 595 770 2041 High 141 ND 295 276 665 806 2183 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 49c ND 65b 83b 306b 468c 97 1 b 196 125bc ND 225b 217b 533b 745bc 1845b 294 15 7b ND 250b 207b 549b 814b 197 7 b 588 264a ND 663a 471a 1130a 1125a 3653a ANOVA Source of variation IR NS ND NS NS NS NS NS NR ** ND *** ** ** ** ** IR x NR NS ND NS NS NS NS NS

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60 Table 37. Trial 1 treatment means (n = 4) for nitrogen tissue concentration for low and high irrigation regimes and four N application rates. NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.05). Table 38. Trial 2 treatment means (n = 4) for nitrogen tissue concentrati on for low and high irrigation regimes and four N application rates. NS, *, and **, = P > 0.05, P < 0.05, P < 0.01. Values within a column followed by the same let ter are not statistically different (LSD, P 0.05). ND = No data was collected during this cycle. Effects C1 C2 C3 C4 C5 C6 Ave --------------------------------g kg 1 ---------------------------------Irrigation (IR) Low 18.7 22.2 14.9 16.4 20.9 19.5 18.8 High 18.5 23.3 16.2 16.4 20.8 19.4 19.1 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 17.0 20.5b 12.6c 14.1c 19.1 19.0b 17.1c 1 96 18.3 20.5b 12.8c 15.3bc 21.0 19.6b 17.9bc 294 19.3 23.8ab 17.1b 17.2ab 20.8 18.9b 19.5ab 588 19.8 26.4a 19.7a 18.9a 22.4 20.4a 21.3a ANOVA Source of variation IR NS NS NS NS NS NS NS NR NS *** ** NS *** *** IR x NR NS NS NS NS NS NS NS Effects C1 C2 C3 C4 C5 C6 Ave ----------------------------------g kg 1 ---------------------------------Irrigation (IR) Low 22.0 ND 21.5 16.7 17.4 16.9 18.9 Hig h 22.0 ND 22.3 16.7 17.5 16.9 19.0 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 20.4c ND 19.7c 16.0b 16.1 16.3 17.9c 196 21.7bc ND 21.3bc 16.1b 17.5 16.3 18.6b 294 21.9ab ND 22.0b 16.1b 17.1 16.9 18.7b 588 23.2a ND 24.5a 18.0a 19.1 18.0 20.5a ANOVA Source of variation IR NS ND NS NS NS NS NS NR ND ** NS NS ** IR x NR NS ND NS NS NS NS NS

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61 Table 39. Trial 1 treatment means (n = 4) for nitrogen uptake for low and high irrigation regimes and four N application rates. NS, *, **, and *** = P > 0.05, P < 0.05, P < 0.01, P < 0.001. Values within a column followed by the same letter are not statistically different (LSD, P 0.05). Table 310. Trial 2 treatment means (n = 4) for nit rogen uptake for low and high irrigation regimes and four N application rates NS, **, and *** = P > 0.05, P < 0.01, P < 0.001. Values within a column followed by the same let ter are not statistically different (LSD, P 0.05). ND = No data was collected during this cycle. Effects C1 C2 C3 C4 C5 C6 Total ---------------------------------kg ha 1 -------------------------------Irrigation (IR) Low 1.1 2.9 2.1 6.7 20.5 14.5 47.7 High 1.3 3.4 1.9 6.3 18.2 12.9 44.0 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 0.6 1.2c 1.0b 1.6b 6.2b 5.5b 16.1b 196 1. 0 1.9bc 1.6b 5.2b 16.1b 12.0b 40.0b 294 1.1 3.4b 1.6b 6.2b 16.3b 13.0b 40.0b 588 2.0 6.1a 3.7a 13.1a 38.8a 24.0a 87.7a ANOVA Source of variation IR NS NS NS NS NS NS NS NR NS *** ** *** ** ** IR x NR N S NS NS NS NS NS NS Effects C1 C2 C3 C4 C5 C6 Total ------------------------------kg ha 1 -----------------------------------Irrigation (IR) Low 3.6 ND 7.3 3.7 11.2 13.5 39. 2 High 3.1 ND 7.0 4.8 12.5 13.8 41.2 Nitrogen Rate (NR) (kg ha 1 yr 1 ) 98 1.0c ND 1.4b 1.4b 5.8b 7.8c 17.3b 196 2.8bc ND 5.3b 3.8b 10.1b 12.3bc 34.4b 294 3.4b ND 5.6b 3.4b 9.7b 14.0b 36.1b 588 6.2a ND 16.3a 8.4 a 21.8a 20.4a 73.2a ANOVA Source of variation IR NS ND NS NS NS NS NS NR *** ND ** ** ** ** ** IR x NR NS ND NS NS NS NS NS

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62 REFERENCES Aronson, L.J., A.J. Gold, R.J. Hull, and J.L. Cisar. 1987. Evapotranspiration of cool season turfgrasses in the humid Northeast. Agron. J. 79:901 905. Barton, L., G. G. Y. Wan, R. P. Buck, and T.D. Colmer. 2006. Turfgrass (Cynodon dactylon L.) sod production on sandy soils: II. Effects of irrigation and fertilizer regimes on N leaching. Plant and Soil. 284:147164. Barton, L., G. G. Y. Wan, R. P. Buck, and T.D. Colmer. 2009. Nitroge n increases evapotranspiration and growth of a warm season turfgrass. Agron. J. 101:1724. Baum, M. C., M. D. Dukes, and G. L. Miller. 2005. Analysis of residential irrigation distribution uniformity. J. Irrig. Drain. Eng., 131:336 341. Beard, J.B. 19 73. Turfgrass: science and culture. Prentice Hall, Englewood Cliffs, NJ. Bowman, D.C., J.L. Paul, W.B. Davis, and S.H. Nelson. 1987. Reducing ammonia volatilization from Kentucky bluegrass turf by irrigation. HortScience 22:84 87. Bowman, D.C., and L. M acaulay. 1991. Comparative evapotranspiration rates of tall fescue cultivars. HortScience 26:122 123. Bowman, D.C., C.T. Cherney, and T.W. Rufty, Jr. 2002. Fate and transport of nitrogen applied to six warm season turfgrasses. Crop Sci. 42: 833841. Br ian, I., Bravado, I I. BushkinHarav, and E. Rawiytz. 1981. Water consumption and growth rates of 11 turfgrass as affected by mowing height, irrigation frequency, and soil moisture. Agron. J. 73:8590. Broschat, T. K., and M. L. Elliott. 2004. Nutrient distribution and sampling for leaf analysis in St. Augustinegrass. Comm unication i n Soil. Sci. and Plant Anal. v.35 no.15 and 16:23572367. Busey, P. and B. J. Center. 1987. Southern chinch bug (Hemiptera: Heteroptera: Lygaeidae) overcomes resistance i n St. Augustinegrass. J. Econ. Entomol. 80:608611. Busey, P. 2003. St. Augustinegrass. pp. 309330. In Casler, M. D., and Duncan, R. R. (eds.) Biology, breeding, and genetics of turfgrasses. John Wiley & Sons, Inc, Hoboken, NJ. Carrow, R.N. 1997. Tur fgrass response to slow release nitrogen fertilizers. Agron. J. 89:491496. Cisar, J. L., G. H. Snyder, and P. Nkedi Kizza. 1991. Maintaining quality turfgrass and minimal nitrogen leaching. Univ. of Florida., Inst of Food and Agr. Sci. 273. Universit y of Florida, Gainesville, FL.

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63 City of Glendale. 2010. Water conservation Landscape rebates Existing home conversions. Available at http://glendaleaz.com/waterconservation/ landscaperebates.cfm (verified 10 March 2010). City of Glendale City, Glendale, AZ. Council of the City of Sannibel. 2007. Ordinance No. 07003. http://www.sanibelh2omatters.com/fertilizer/PDF/Fertilizer_Ordinance.pdf. Coyne, M. S. 2008. Biological denitrification. p. 201253. In J.S. Schepers and W.R. Raun (ed.)Nitrogen in agricultural systems. Agron. Monogr. 49. ASA, CSSA, and SSSA, Madison,WI. DaCosta, M., and B. Huang. 2006. Minimum water requirements for creeping, colonial, and velvet bentgrasses under fairway conditions. Crop Sci. 46:81 89. Danielson, R. E., W.E. Hart, C.M. Feldhake, and P.M. Haw. 1979. Water requirements for urban lawns. Colo. Completion Report to OWRT Project B 035 WYO. 91 p. Davenport, D.C. 1965. V ersatility of a small grass transpirometer. Univ. of Nottingham School of Agriculture Rep. 5460 p Department of Agricultural and Consumer services, No. 4640400, Rule 5E 1.003. 2007.http://www.dep.state.fl.us/water/nonpoint/. Easton, Z.M., and A.M Petrovic. 2004. Fertilizer source effect on ground and surface water quality in drainage from turfgrass. J. Environ. Qual. 33:645655. Ebdon, J.S., and A.M. Petrovic. 1998. Morphological and growth characteristics of low and highwater use Kentucky bluegrass cultivars. Crop Sci. 38:143 152. Ebdon, J.S., A.M. Petrovic, and R.A. White. 1999. Interaction of nitrogen, phosphorus, and potassium on evapotranspiration rate and growth of Kentucky bluegrass. Crop Sci.39:209 218. Erickson, J. E., J. L. Cisa r, J. C. Volin, and G.H. Snyder. 2001. Comparing nitrogen runoff and leaching between newly established St. Augustinegrass turf and an alternative residential landscape. Crop Sci. 41:18891895. Erickson, J. E., J. L. Cisar, G. H. Snyder, D. M. Park, and K. E. Williams. 2008. Does a mixed species landscape reduce inorganic nitrogen leaching compared to a conventional St. Augustinegrass Lawn? Crop Sci. 48:15861594. Erickson, J. E., D. M. Park, J. L. Cisar, G. H. Snyder, and A. L. Wright. 2010. Effects of Sod Type, Irrigation, and Fertilization on NitrateNitrogen and OrthophosphatePhosphorus Leaching from Newly Established St. Augustinegrass Crop Sci. 50:10301036.

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64 Feldhake, C.M., R.E. Danielson, and J.D. Butler. 1983. Turfgrass evapotranspiratio n. I. Factors influencing rate in urban environments. Agron. J. 75:824 830. Flipse, W.J., Jr., B.G. Katz, J.B. Linder, and R. Markel. 1984. Sources of nitrate in ground water in a sewered housing development. Central Long Island, New York. Ground Water. 32: 418 426. Fluck, R. C. and P. Busey. 1988. Energy for mowing turfgrass. Trans. ASAE 31:13041308. Fry, J.D., and J.D. Butler. 1989. Annual bluegrass and creeping bentgrass evapotranspiration rates. HortScience 24:269 271. Fu, J., J. Fry, and B. Huang. 2004. Minimum water requirements of four turfgrasses in the transition zone. HortScience 39:1740 1744. Geron, C. A., T. K. Danneberger, S. J. Traina, T. J. Logan, and J. R. Street. 1993. The effects of establishment methods and fertilization practices on nitrate leaching from turfgrass. J. Environ. Qual. 22(1):119125. Gomez, K. A., and A. A. Gomez. 1984. Statistical Procedures for Agricultural Research, 2nd Edition. John Wiley & Sons, Inc, NY. Green, R.L., S.I. Sifers, C.E. Aitken, and J.B. Beard. 1991. Evapotranspiration rates of eleven Zoysia genotypes. HortScience 26:264 266. Gross, C. M., J.S. Angle, and M.S. Welterlen. 1990. Nutrient and sediment losses from turfgrass. J. Environ. Qual. 19: 663668. Haley, M.B, M.D. Dukes, and G.L. Miller. 2007. Residential irrigation water use in Central Florida. Journal of Irrigation and Drainage Engineering 133:427434. Haydu, J. J., J.Cisar, and L.Satterthwaite. 2005. Floridas Sod Production Industry: A 2003 Survey. International Turfgrass Soc iety Research Journal 10:700704. Horgan, B.P., B.E. Branham, and R.L. Mulvaney. 2002. Mass balance of 15N applied to Kentucky bluegrass including direct measurement of denitrification. Crop Sci. 42:1595 1601. Hull, R.J. and H. Liu 2005. Turfgrass nitro gen: physiology and environmental impacts. International Turfgrass Society Research Journal 10:962 975 Kopp, Kelly L., and Karl Guillard. 2002. Clipping management and nitrogen fertilization of turfgrass: growth, nitrogen utilization, and quality. Crop Science. 42:12251231. Kim, K.S., and J.B. Beard. 1988. Comparative turfgrass evaporation rates and associated morphological characteristics. Crop Sci. 28:328 331.

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65 Kneebone, W.R., and I.L. Pepper. 1982. Consumptive water use by subirrigated turf grasses under desert conditions. Agron. J. 74:419 423. Kneebone, W.R., D.M. Kopec, and C.F. Mancino. 1992. Water requirement and irrigation. p. 441 472. In D. Waddington (ed.) Turfgrass. Agron. Monogr. 32. ASA, CSSA, and SSSA, Madison, WI. Kopec, D.M. R.C. Shearman, and T.P. Riordan. 1988. Evapotranspiration of tall fescue turf. HortScience 23:300 301. Mancino, C. F., and J. Troll. 1990. Nitrate and ammonium leaching losses from N fertilizers applied to Penncross creeping bentgrass. HortScience 25: 194 196. Mantell, A. 1966. Effects of irrigation frequency and nitrogen fertilization on growth and water use of a Kikuyugrass lawn ( Pennisetum clandestinum Hochst.). Agron. J. 58:559 561. Miltner, E.D., B.E. Branham, A.E. Paul, and P.E. Rieke. 1996. Leaching and Mass balance of 15N labelled urea applied to a Kentucky bluegrass turf. Crop Sci. 36:14271433. Morton, T.G., A.J. Gold, and W.M. Sullivan. 1988. Influence of overwatering and fertilization on nitrogen losses from home lawns. J. Environ. Qu al. 17:124130. Miller, G.L, and L.B. McCarty. 200 1 Water relations and rooting characteristics of three Stenotaphrum secundatum turf cultivars grown under water deficit conditions. International Turfgrass Society Research Jo urnal 9:323327. McCarty, L. B. and J. L. Cisar. 1995. Bahiagrass for Florida lawns. In L. B. McCarty, K. C. Ruppert, and R. J. Black, eds. Florida Lawn Handbook. Gainesville, FL: Florida Cooperative Extension Service. McGroary, P. C. 2010. Nitro gen leaching, water use rates and turf response of S t. A ugustinegrass and Bahiagrass to irrigation and fertilizer practices. Dissertation presented to the University of Florida Graduate School, Gainesville, FL Park, D.M., J. L. Cisar, G. H. Snyder, J.E. Erickson, S.H. Daroub and K.E. Williams. 2005. Comparison of actual and predicted water budgets from two contrasting residential landscapes in south Florida. International Turfgrass Society Research Journal 10:885890. Petrovic, A.M. 1990. The fate of nitrogenous fertilizers applied to turfgrass, J. Environ. Qual. 19:114. Rieke, P.E., and B.G. Ellis. 1974. Effects of nitrogen fertilization on nitrate movement under turfgrasses. In E.C. Roberts (ed.) Proc. 2nd Int. Turfgrass Res. Conf. ASA, Madison, WI.19 21 June 1972. Blacksburg, V.A.

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66 Saha, S.K., L. E. Trenholm, and J.B. Unruh. 2005. Effect of fertilizer source on water use of St. Augustinegrass and ornamental plants. Hortscience 40:21642166. Salaiz, T.A., R.C. Shearman, T.P. Riordan, and E.J. Ki nbacher. 1991. Creeping bentgrass cultivar water use and rooting responses. Crop Sci. 31:1331 1334. Sartain, J. B. 2010. Comparative Influence of N Source on N Leaching and St. Augustinegrass Quality,Growth and N Uptake. Soil and Crop science Society of Florida Vol 67. SAS Institute. 1999. SAS Users guide. Carry, NC. South Florida Water Management District. 2010. Available at https://my.sfwmd.gov/portal/page/portal/common/pdf/splash (verified 10 March 2010). Council of the City of Sannibel. 2007. Ordinance No. 07003. http://www.sanibelh2omatters.com/fertilizer/PDF/Fertilizer_Ordinance.pdf. Shearman, R.C. 1986. Kentucky bluegrass cultivar evapotranspiration rates. HortScience 21:455 457. Shearman, R.C., and J.B. Beard. 1973. Environmental and cultural preconditioning effects on the water use rate of Agrostis palustris Huds., cultivar Pencross. Crop Sci. 13:424 427. Sheard, R. W., M. A. Haw, G. B. Johnson, and J. A. Ferguson. 1985. Mineral nutrition of bentgrass on sand rooting sys tems. In Proceedings of 5th International Turfgrass Research Conference, ed. F. Lemaire, 469 485.Avignon, France: INRA Starr, J.L., and H.C. DeRoo. 1981. The fate of nitrogen applied to turfgrass. Crop Sci. 21:531536. Stewart, E.H., and W. C. Mills.1967. Effect of depth to water table and plant density on evapotranspiration rate in south Florida. T. ASAE. 10(6):746747. Snyder, G.H., B.J. Augustin, and J.M. Davidson. 1984. Moisture sensor controlled irrigation for r educing N leaching in Bermudagrass turf. Agron. J. 76: 964969. Snyder, G. H., B. J. Augustin, and J. L. Cisar. 1989. Fertigation for stabilizing turfgrass nitrogen nutrition. p. 217219 In H. Takatoh (ed.) Proc. 6th Int. Turfgrass Res. Conf. (Tokyo), Ja panese Soc. Turfgrass Sci., Tokyo. Spalding, R. F., and M. E. Exner. 1993. Occurrence of Nitrate in Groundwater A Review J. Environ. Qual. 22:392402 Titko, S., J.R. Street, and T.J. Logan. 1987. Volatilization of ammonia from granular and dissolved urea applied to turf. Agron. J. 79:535540.

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67 Trenholm, L. E., J.L. Cisar, and J.B. Unruh. 2000. St. Augustinegrass for Florida lawns. Univ. of Fla. Coop.Ext. Serv., ENH 5. Univ. of Florida, Gainesville, FL. Trenholm, L.E., E.F. Gilman, G.W. Knox, and R.J. Black. 2002. Fertilization and irrigation needs for Florida lawns and landscapes. Univ. of Fla. Coop. Ext. Serv., ENH 860.Univ. of Florida, Gainesville, FL. United States Environmental Protection Agency. 1976. Quality criteria for water. EPA 440/9760 23. Office of Water Planning and Standards. USEPA., Washington, D.C. Vernon, J. R., D. L. Cawthon, R. G. Dubes, and L. J. Klingbeil. 1993. Effects of clippings and fertilizer on warm season turfgrasses. Texas J. Agri. Nat. Resour. 6:99108. Vitousek, P.M ., J.D. Aber, R.W. Howarth, G.E. Likens, P.A.Matson, D.W. Schindler, W.H. Schlesinger, and D.G. Tilman. 1997. Human alteration of the global nitrogen cycle: Sources and consequences. Ecol. Appl. 7:737 750. Wesely, R.W., R.C. Shearman, E.J. Kinbacher, and S.R. Lowry. 1987. Ammonia volatilization from foliar applied urea on fieldgrown Kentucky bluegrass. HortScience 22:1278 1280. Wolf, B. 1982. A comprehensive system of leaf analysis and its use for diagnosing crop nutrient status. Commun. Soil Sci. Plant Anal. 13:10351059. Youngner, V.B., A.W. Marsh, R.A. Strohman, V.A. Gibeault, and S. Spaulding. 1981. Water use and quality of warm season and cool season turfgrass, p. 251 257. In R. W. Sheard (ed.) Proceedings of the 4th International Turfgrass Rese arch Conference, Ontario Agricultural College, University of Guelph, Guelph, ON, Canada. 19 23 July. Zazueta, F.S., A.G. Smajstria, and D.Z. Hamam. 1991. Estimation of evapotranspiration by the Penman method. Institute of Food and Agriculture Service s. University of Florida. Florida Cooperative Extension Service. Circular 750. 6 p.

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68 BIOGRAPHICAL SKETCH Pauric C. McGroary was born in Letterkenny, Co. Donegal, Ireland, and grew up in Laghy, Co. Donegal, Ireland. In 1999 he graduated from St. Patric ks College with his leaving certification and began studies at University of Central Lancashire, Preston, England. In May 2004 he received a Bachelor of Science (Hons) in turfgrass science from University of Central Lancashire, Preston, England. Pauric c ontinued his education at the University of Florida, Gainesville, FL were he joined the Entomology and Nematology Department and obtained a Master of Science degree in spring of 2007. In summer 2007, Pauric joined the graduate Soil and Water Department program at the University of Florida under the supervision of Dr. John Cisar in which he received his Doctor of P hilosophy in August 2010.