<%BANNER%>

Nitrogen Leaching and St. Augustinegrass Turf Response to Lawn Maintenance Strategies.


PAGE 1

NITROGEN LEACHING AN D ST. AUGUSTINEGRASS TURF RESPONSE TO LAWN MAINTENANCE STRATEGIES By DARA MICHELLE PARK A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

PAGE 2

Copyright 2006 by Dara Michelle Park

PAGE 3

This document is dedicated to my family a nd the Behringers for their love and support during my graduate career.

PAGE 4

iv ACKNOWLEDGMENTS I express my gratitude to Dr John Cisar for his time and support. Dr. Cisar gave me the opportunity to integrate two of my passi ons: soil and water scie nce and a desire to help protect the environment. Hi s support was instrumental in a ll facets of the research. I wish to thank Drs. George Snyder, Samira Daroub, Jerry Sartain and Don Graetz for their time and their contribution on this project. I would like to acknow ledge the financial support of the Southwest Florida Water Ma nagement District, Florida Turfgrass Association, and the Florida Department of Agriculture and Consumer Services. I appreciate the support and guidance of th e SWFWMD project managers Mr. Eric DeHaven and Mr. Kyle Champion. I would also like to acknowledge the contributions of Mr. Wiley McCall and family, Environmental Tu rf, Inc., and The Toro Co. for material support. The technical support and contributions of Univer sity of Florida staff and students including Ms. Eva King, Mr. David Ri ch, Mr. Kevin Wise, Mr. John Wissenger, Mr. Kevin Mc Gowen, Mr. Gary Peders on, Dr. Raymond Snyder, and Ms. Felica Raphael-Greenberg are much appreciated. A sp ecial thanks to Karen Williams, for her technical assistance, scie ntific knowledge, and as a sounding board for ideas and reasoning. And finally to my husband Scott, th anks for his love, support and patience.

PAGE 5

v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES............................................................................................................vii LIST OF FIGURES..........................................................................................................xii ABSTRACT....................................................................................................................... xv CHAPTER 1 CONSTRUCTION OF A FIELD SC ALE FACILITY TO DOCUMENT NITROGEN LEACHING AND TURF GRASS RESPONSE FROM ST. AUGUSTINEGRASS FLORATAM MANAGEMENT STRATEGIES..................1 Introduction................................................................................................................... 1 Materials and Methods.................................................................................................5 Results and Discussion...............................................................................................11 Irrigation Uniformity...........................................................................................11 Natural Fluctuations in Percolate and Nitrate.....................................................12 Sod Establishment...............................................................................................13 Conclusions.................................................................................................................15 2 EFFECT OF IRRIGATION, N SOU RCES AND RATES ON N LEACHING, TURFGRASS QUALITY AND GROWTH FROM NEWLY ESTABLISHED ST. AUGUSTINEGRASS LAWNS...........................................................................22 Introduction.................................................................................................................22 Materials and Methods...............................................................................................24 Results and Discussion...............................................................................................29 Water Budget.......................................................................................................29 Nitrate Concentrations and Leaching..................................................................30 Ammonium Concentrations and Leaching..........................................................31 Total Inorganic Nitrogen Con centrations and Leaching.....................................33 St. Augustinegrass Quality..................................................................................36 St. Augustinegrass Growth..................................................................................37 Leaf Blade Nitrogen Concentrations...................................................................40 Nitrogen Uptake Efficiency.................................................................................42 Nitrogen Budget and Scenario Comparison........................................................43 Conclusions.................................................................................................................47

PAGE 6

vi 3 EFFECT OF IRRIGATION, N SOU RCES AND RATES ON N LEACHING, TURFGRASS QUALITY AND GROWTH FROM ESTABLISHED ST. AUGUSTINEGRASS LAWNS.................................................................................83 Introduction.................................................................................................................83 Materials and Methods...............................................................................................86 Results and Discussion...............................................................................................90 Water Budget.......................................................................................................90 Nitrate Concentrations and Leaching..................................................................92 Ammonium Concentrations and Leaching..........................................................93 Total Inorganic Nitrogen Con centrations and Leaching.....................................95 St. Augustinegrass Quality..................................................................................96 St. Augustinegrass Growth..................................................................................96 Leaf Blade Nitrogen Concentrations...................................................................99 Nitrogen Uptake Efficiency...............................................................................100 Nitrogen Budget and Scenario Comparison......................................................101 Conclusions...............................................................................................................104 LIST OF REFERENCES.................................................................................................130 BIOGRAPHICAL SKETCH...........................................................................................138

PAGE 7

vii LIST OF TABLES Table page 1-1 Mean, standard deviation and Levenes Test for Homogeneity for (a) actual percolate volumes, (b) nitrat e concentrations, and (c) ni trate leached for each of the four collection dates duri ng the stabilization period wi th only bare soil as a cover.........................................................................................................................1 7 1-2 Nitrogen inputs (g m-2) during the four month establishment period for sod with 40 g kg-1 and 100 g kg-1 SOM..................................................................................17 1-3 Comparison of mean root dry weights (g) from 40 g kg-1 and 100 g kg-1 SOM collected from cores between 0-15 cm and 15-30cm depths...................................17 2-1 (a) Explanation of experimental fact ors tested and (b) ANOVA table used for statistical differences determination.........................................................................53 2-2 Water budget from April 2001 to April 2002..........................................................54 2-3 ANOVA table for NO3-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................54 2-4 Interaction of SOM*IRR*Rate on NO3-N concentrations (mg l-1) during the DRY season. Significance values listed ar e for SOM differences within each N rate........................................................................................................................... .55 2-5 ANOVA table for total NO3-N leached for WET and DRY seasons. Significant differences are bold and italicized............................................................................55 2-6 Interaction of SOM*Rate on total NO3-N leached (g m-2) during the DRY season. Significance values listed are for SOM differences within each N rate......55 2-7 Interaction of IRR*Rate on total NO3-N leached (g m-2) during the DRY season. Significance values listed are for IRR differences within each N rate.....................56 2-8 ANOVA table for NH4-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................56 2-9 ANOVA table for total NH4-N leached for WET and DRY seasons. Significant differences are bold and italicized............................................................................57

PAGE 8

viii 2-10 ANOVA table for total inorganic-N c oncentrations for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................57 2-11 Interaction of SOM*Rate on tota l inorganic-N concentrations (mg l-1) during the DRY season. Significance values listed ar e for SOM differences within each N rate........................................................................................................................... .58 2-12 Interaction of IRR*Rate on tota l inorganic-N concentrations (mg l-1) during the DRY season. Significance values listed ar e for IRR differences within each N rate........................................................................................................................... .58 2-13 ANOVA table for total total inorgani c-N leached for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................58 2-14 Interaction of SOM*Rate on total inorganic-N leached (g m-2) during the DRY season. Significance values listed are for SOM differences within each N rate......59 2-15 Interaction of IRR*Rate on total inorganic-N leached (g m-2) during the DRY season. Significance values listed are for IRR differences within each N rate........59 2-16 ANOVA table for mean quality scores for WET and DRY seasons. Significant differences are bold and italicized............................................................................59 2-17 Interaction of SOM*Rate on turf quality scores during the WET season. Significance values listed are for SOM differences within each N rate...................60 2-18 Interaction of SOM*IRR*Source on tu rf quality scores during the WET season. Significance values listed are for SOM differences within each IRR*Source combination..............................................................................................................60 2-20 Interaction of SOM*Rate on total clippi ng yield (g m-2) during the WET season. Significance values listed are for SOM differences within each N rate...................61 2-21 Interaction of SOM*Rate on total clippi ng yield (g m-2) during the DRY season. Significance values listed are for SOM differences within each N rate...................61 2-22 ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected on 01 August 2001. Significant differences are bold and italicized.........................62 2-23 Interaction of IRR*Rate on root weight density (g m-3) within the upper 0-15 cm of the soil from cores collected 01 August 2001. Significance values listed are for IRR differences within each N rate...............................................................62 2-24 ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected on 01 August 2002. Significant differences are bold and italicized.........................63 2-25 Root weight densities (g m-3) from the 15-30 cm soil depth collected on 01 August 2002 were influenced by SOM*Sour ce*Rate interactions. Significance values listed are for SOM differences within each N Rate and N Source................63

PAGE 9

ix 2-26 ANOVA table for leaf blade N conc etrations for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................64 2-27 Nitrogen sources influenced l eaf blade N concentrations (mg g-1) during both seasons......................................................................................................................64 2-28. Interaction of SOM*Rate for N con centrations within leaf blades (mg g-1) during the DRY season. Significance values listed are for SOM differences within each N rate........................................................................................................................6 4 2-29 ANOVA table for nitrogen uptake ef ficiency for WET and DRY seasons. Significant differences ar e bold and italicized.........................................................65 2-30 Interaction of SOM*Rate on n itrogen uptake efficiency (g m-2) over the WET season. Significance values listed are for SOM differences within each N rate......65 2-31 Interaction of SOM*Rate on n itrogen uptake efficiency (g m-2) over the DRY season. Significance values listed are for SOM differences within each N rate......65 2-32 WET season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM........................................................................................................66 2-33 DRY season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM........................................................................................................67 3-1 (a) Experimental factors tested and (b ) ANOVA table of factors and interactions tested.......................................................................................................................10 7 3-2. Water budget from March 2003 to September 2004...............................................108 3-3 ANOVA table for NO3-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................109 3-4 WET season NO3-N concentrations (mg l-1) were influenced by SOM*Source* N Rate interactions. Significance values listed are for SOM differences within each N Rate and N Source......................................................................................109 3-5 ANOVA table for total NO3-N leached for WET and DRY seasons. Significant differences are bold and italicized..........................................................................110 3-6 WET season NO3-N leached (g N m-2) were influenced by SOM*Source*Rate interactions. Significance va lues listed are for SOM differences within each N Rate and N Source..................................................................................................110 3-7 ANOVA table for NH4-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................111

PAGE 10

x 3-8 WET season NH4-N concentrations (mg l-1) were influenced by IRR*Source*Rate interactions. Signi ficance values listed are for IRR differences within each N Rate and N Source........................................................111 3-9 DRY season NH4-N (mg l-1) were influenced by IRR* Source*Rate interactions. Significance values listed are for IRR di fferences within each N Rate and N Source.....................................................................................................................112 3-10 ANOVA table for NH4-N leached for WET and DRY seasons. Significant differences are bold and italicized..........................................................................112 3-11 WET season NH4-N leached (g m-2) were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source..................................................................................................113 3-12 DRY season NH4-N leached (g m-2) were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source..................................................................................................113 3-13 ANOVA table for total inorganic-N c oncentrations for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................114 3-14 ANOVA table for total inorganicN leached for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................114 3-15 ANOVA table for turfgrass quality for WET and DRY seasons. Significant differences are bold and italicized..........................................................................115 3-16 WET season quality scores were infl uenced by IRR*Source*Rate interactions. Significance values listed are for IRR di fferences within each N Rate and N Source.....................................................................................................................115 3-17 DRY season quality scores were infl uenced by IRR*Source*Rate interactions. Significance values listed are for IRR di fferences within each N Rate and N Source.....................................................................................................................116 3-18 ANOVA table for clipping yield fo r WET and DRY seasons. Significant differences are bold and italicized..........................................................................116 3-19 WET season clipping yields (g m-2) were influenced by IRR*Rate interactions...117 3-20. ANOVA table for root weight density for 0-15 cm and 15-30 cm depths from cores collected on 04 August 2003........................................................................117 3-21 ANOVA table for root weight densit y for 0-15 cm and 15-30 cm depths from cores collected on 27 April 2004. Significant differences are bold and italicized.118

PAGE 11

xi 3-22 Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were influenced by SOM*Rate*Source interactions. Cores were collected on 27 Apr 2004........................................................................................................................118 3-23 Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were influenced by SOM*IRR*Rate interac tions. Cores were collected on 04 Aug 2003........................................................................................................................119 3-24 Influence of N sources on root weight density (g m-3) of cores collected at the 15-30 cm depth on 27 April 2004..........................................................................119 3-25 Root weight densities (g m-3) from cores collected at the 15-30 cm depth on 27 April 2004 were influenced by SOM*Rate interactions........................................119 3-26 ANOVA table for pelt weight from cores collected on 27 April 2004. No significant differences were determined................................................................120 3-27 ANOVA table for leaf blade N conc entrations for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................120 3-28 WET season leaf blade N concentrations (mg N g-1) were influenced by SOM*Source interactions. Significance valu es listed are for SOM differences within each N Source.............................................................................................121 3-29 ANOVA table for nutrient uptake ef ficiency for WET and DRY seasons. Significant differences ar e bold and italicized.......................................................121 3-30 DRY season (cycle 5) nutrient upt ake efficiency (%) was influenced by IRR*Source*Rate interactions. Signi ficance values listed are for IRR differences within each N Rate and N Source........................................................122 3-31 WET season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM..........................................................................................123 3-32 DRY season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM................................................................................................124

PAGE 12

xii LIST OF FIGURES Figure page 1-1 Schematic drawing of equipment used to collect vadose zone percolate: (a) dimensions of the ceramic cup sampler, (b) connections supplying sampler with a vacuum, (c) connections for sample ex traction, and (d) ex tractor / overflow device.......................................................................................................................18 1-2 Rainfall and irrigation (mm) over the (a) stabilization and (b) establishment periods......................................................................................................................19 1-3 Nitrate concentrations (mg l-1) determined in percolate from sod containing 40 g kg-1 SOM compared to sod with 100 g kg-1 SOM during the (a) stabilization and (b) establishment periods.........................................................................................20 1-4 Nitrate leaching (g m-2) from sod containing 40 g kg-1 SOM compared to sod with 100 g kg-1 SOM during the (a) stabiliz ation and (b) establishment periods...21 2-1 Daily rainfall over the experi mental period for Experiment 1.................................68 2-2 Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass with 40 g kg-1 soil organic matter (SOM) to St. Augustinegrass with 100 g kg-1 SOM for the three N rates during the study peri od. Arrows mark fertilization events......69 2-3 Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass maintained with the FIX irrigation schedule to St. Augustinegrass maintained with the ADJ irrigation schedule for the three N rates during the study period. Arrows mark fertilization events..............................................................................70 2-4 Comparison of weekly NO3-N leached (g m-2) from St. Augustinegrass fertilized with the four N sources at the 5.0 g m-2 bimonthly rate during the study period. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark fertilization events........................................................................................................................7 1 2-5 Comparison of weekly NH4-N leached (g m-2) from St. Augustinegrass fertilized with the four N sources at the 5.0 g m-2 bimonthly rate and maintained with the ADJ irrigation schedule duri ng the (a) WET and (b) DRY seasons. Arrows mark fertilization events....................................................................................................72

PAGE 13

xiii 2-6 Mean weekly flow weighted tota l inorganic-N concentrations (mg l-1) from St. Augustinegrass fertilized w ith the three N rates and maintained with the ADJ irrigation schedule during the (a) WET and (b) DRY seasons. Arrows mark fertilization events....................................................................................................73 2-7 Mean weekly flow weighted toal inorganic-N concentrations (mg l-1) from St. Augustinegrass fertilized with the three N rates and main tained with the (a) FIX and (b) ADJ irrigation schedules dur ing the DRY season. Arrows mark fertilization events....................................................................................................74 2-8 Comparison of weekly tota l inorganic-N leached (g m-2) from St. Augustinegrass fertilized with the thr ee bimonthly N rate during the (a) WET and (b) DRY seasons. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark fertilization events...........................................................................................75 2-9 Comparison of weekly tota l inorganic-N leached (g m-2) from St. Augustinegrass fertilized with the three bimonthly N rate maintained with the (a) ADJ and (b) FIX scheduled during the DRY season. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark fertilization events......................................76 2-10 Quality scores of St. Augustinegrass associated with 40 g kg-1 and 100 g kg-1 soil organic matter (SOM) maintained at the three N rates ov er the (a) WET and (b) DRY seasons. Arrows mark fertilization events................................................77 2-11 Quality scores of St. Augustinegrass fer tilized with different N sources over the (a) WET and (b) DRY seasons. Arrows mark fertilization events...........................78 2-12 Clipping yield (g m-2) of St. Augustinegrass fertili zed with different N sources over the DRY season................................................................................................79 2-13. Comparison of leaf blad e N concentration (mg N g-1) grown with 40 g kg-1 soil organic matter (SOM) and 100 g kg-1 SOM during the (a) WET and (b) DRY seasons. Arrows mark fertilization events................................................................80 2-14 Comparison of leaf blad e N concentrations (mg N g-1) grown from the four N sources during the (a) W ET and (b) DRY seasons. Arrows mark fertilization events........................................................................................................................8 1 2-15 Comparison of cumulative ni trogen uptake efficiency (g m-2) from the four N sources during the DRY season. Arro ws mark fertilization events.........................82 3-1 Daily rainfall over the experi mental period for Experiment 2...............................125 3-2 Comparison of weekly cumulative NO3-N leached from St. Augustinegrass associated with (a) 40 g kg-1 and (b) 100 g kg-1 soil organic matter (SOM) fertilized with the four N sources at 2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events......................................................126

PAGE 14

xiv 3-3 Comparison of NO3-N leached from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly over the study period. Ar rows mark fertilization events...127 3-4 Comparison of total inorganic-N leache d from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events......................................................................................................................128 3-5 Comparison of leaf blade N concentra tions from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly for cycles 3 (WET) and 5 (DRY)..................129

PAGE 15

xv Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy NITROGEN LEACHING AN D ST. AUGUSTINEGRASS RESPONSE TO LAWN MAINTENANCE STRATEGIES By Dara Michelle Park May 2006 Chair: Samira Daroub Major Department: Soil and Water Science Home lawn fertilization has been implicated as a potential sour ce of nitrogen (N) contamination to fragile watersheds in sout hern Florida. A fieldscale study evaluating the effect of N sources and rates, and irrigation scheduling on performance and N leaching from St. Augustinegrass lawns was conducted in South Florida. Vadose zone nitrate-N and ammonium-N concentrations were determined in percolate collected from ceramic cup samplers installed 40 cm below the soil surface. Gra ss clippings and root cores were collected to assess growth. Fert ilization of N to recently established St. Augustinegrass at double the standard reco mmendation resulted in more N leaching. Conversely, reducing the recommended N ra te by half did not reduce N leaching. Controlled-release N sources did not reduce N leaching, alth ough sulfur coated urea provided better turf quality during dry s eason months. Frequency of irrigation was important in reducing N leaching during dr y season months. Water consumption was reduced by 37% during the wet season by adjust ing irrigation on a mont hly basis to meet

PAGE 16

xvi potential evapotranspiration in conjunction with usi ng a rain shut-off sensor. Nevertheless, this irrigati on scheduling was not effective in reducing N leaching. Irrigating upon visual wilt produ ced lower quality turfgrass th at eventually required more frequent irrigation. This rese arch also documented the influence of soil organic matter (SOM) harvested with sod on turf perf ormance and N leaching. Nitrate-N leaching increased after sod installation, however quick ly declined to preinstallation leaching losses. During dry season months, greater tu rf quality and growth was documented from newly established St. Augustinegrass with 100 g kg-1 SOM, however nitrate-N and total inorganic-N leaching was also greater when compared to St. Augustinegrass with 40 g kg-1 SOM. In comparison to recently estab lished St. Augustinegra ss, monitoring total inorganic-N alone was not an effective meas ure for determining maintenance strategies for reducing N leaching from established St. Augustinegrass. Best management practices could be optimized to provide quality St. Augustinegrass with minimizing the potential for N leaching by accounting for N contributions from SOM of harvested sod when determining N fertilization applications, s easonally adjusting irrigation schedules, and utilizing a rain shut-off sensor.

PAGE 17

1 CHAPTER 1 CONSTRUCTION OF A FIELD SCALE FACILITY TO DOCUMENT NITROGEN LEACHING AND TURFGRASS RESPONS E FROM ST. AUGUSTINEGRASS FLORATAM MANAGEMENT STRATEGIES Introduction As population increases in South Florida, so does the concern of water quality degradation. There is increas ing awareness for the potenti al eutrophication of lakes, springs, aquifers and bay areas due to anthropoge nic inputs. In an effort to reduce urban N pollution, identification of potential N pollution sources and determining ways to reduce their detrimental effect s are being developed. Residen tial lawn fertilization has been implicated as a potential source of elevated N concentr ations (Erickson et al., 2001). A field scale facility was built in South Florida in order to examine the influence of residential lawn management systems on N l eaching. Selection of an irrigation system, soil-water collection devices and turfg rass were decided upon the following considerations. Many of South Florida residential la wns are irrigated by using pop-up spray sprinklers or rotor sprinkle rs. For example, between January 2004 and June 2005, the Broward Soil and Water Conservation Dist ricts (BCWCD) Mob ile Irrigation Lab evaluated 79 properties using spray sprinklers and 11 properties with rotor sprinklers. By these statistics, the use of spray sprinklers is the preferred choice. The uniformity of water applied by irrigation systems can be assessed by determining the systems distribution uniformity coefficient (DU). Sp ray and rotor sprinkler DU were similar

PAGE 18

2 ranging from 50-70% (mean DU = 56.2%) for sp ray sprinklers and 50-71% (mean DU = 52.1%) for rotor sprinklers (BSWCD, 2005). Various techniques exist for monitoring soil solution. Porous cups tends to be the most frequently used in natural environm ents (Barabarick et al., 1979; Litaor, 1988; Snyder et al., 1984). Porous cups can be made of stainless steel, Teflon, cellulose, glass, fiberglass, and porcelain ceramic (Beier et al., 1992). Ceramic cup samplers have been in use for soil water collection since the early 1900 s (Briggs and McCall, 1904). Whether compared to other cup samplers or to othe r soil solution collection techniques, ceramic cup samplers tend to be the preferred material for soil solution nutrient monitoring within soil solution (Barabarick et al., 1979; Cole, 1968; Silkwort h and Grigal, 1981). Alberts et al. (1977) reported similar results for NO3-N recovery from a ceramic cup sampler and a soil core sampling technique, but favored the ceramic cup for its in situ quality. Beier and Hansen (1992) reported no differences in si x cation concentrations from a ceramic cup sampler and a polytetrofluoroethene (PTFE) cup sampler. However these authors observed that the PTFE collected less percol ate, and under dry condi tions were first to lose capillary contact. In Litaors evaluation of soil solu tion samplers (1988), he states that many of the other methods besides c up sampling require a greater amount of soil disturbance, and in some cases the removal of soil, which is not conducive for long term monitoring. More recently, other techniques such as passive wicks ha ve been used. While they may collect representative samples (Zhu et al., 2002) and additionally, some can also determine flux (Gee, 2003), wick samplers may be inadequate for shallow soils. They can collect samples from unsaturated soils when leaching may not othe rwise occur, and the apparatus can be cost prohibitive for experiments requiring multiple samplers.

PAGE 19

3 Although widely used for on site soil solu tion collection, the performance of the ceramic cup samplers for monitoring soil solution NO3-N concentration (hereafter as [NO3-N]) has been contradictory. For exam ple, both Harris and Hansen (1975) and Levin and Jackson (1977) report that ceramic cup samplers di d not collect re presentative nitrate concentrations. In comparison, Zimmerm an et al. (1978) observed high recovery rates for NO3-N and NO2-N, as well as for (NO3 + NO2)N (Nagpal, 1982). Nagpal (1982) suggested the reason for low recovery rates in previous experiments was due to the ceramic surface retaining certain ions (most commonly potassium and phosphate). Contact time and volume of sample w ill both affect ion concentrations. The potential problem of ionic absorpti on due to the cation exchange capacity (CEC) of the ceramic surface was first postu lated by Wood (1973). Yet it was not until 1988 that the effect of ceramic surface CEC was more closely examined by Debyle and others (1988). Even though ultimately the chemical makeup of the ceramics media mixture determines the CEC of the cup sample r, the CEC is relatively small and can be quickly satisfied, thus not influencing the soil solution collected (Debyle et al., 1988; Wood, 1973). If this is the case, collecting multiple soil solution samples before the onset of an experiment should satisfy the CEC and prepare the ceramic cup sampler to collect representative samples when an experiment begins. Debyle et al. (1988) also reported minimal fluctuation in K concentrations fo r ceramic cups used over a longer period of time. In previously mentioned study, the authors showed a 0.3 ppm decrease in K concentrations in a six-yea r-old cup compared to drainage water (2.5 ppm K and 2.8 ppm K, respectively). Although the authors found variability in ceramic cup solutions for diluted concentrations of Na, NO3-N and K (5.55 ppm, 1.1 ppm and 2.5 ppm,

PAGE 20

4 respectively), they state that CEC influence from the ceramic surface would be negligible for soil solutions with higher ion concentrations and this variability is small compared to natural variability from soils. Both Debyle et al. (1988) and Harris and Hansen (1975), suggest the following guidelines to reduce the variability in concen trations from soil water extracted by ceramic cups: (a) use s hort sampling intervals, (b) use uniform sampling lengths, and (c) that all samplers receive the same vacuum. For sampling vadose zone percolate it is also important that placement of ceramic cup samplers be (a) above the seasonal high water and (b) below the roots. If the ceramic cup samplers were placed within the water table, nitrogen concen trations could be influenced by saturated conditions. The ceramic cup samplers are placed below the roots to ensure that percolate past the roots would not be utilized by the plant. Ceramic cup samplers have been used to collect and monitor NO3-N movement for various turfgrass experiment s that includes reducing NO3-N leaching in bermudagrass used for home lawns in South Florid a (Snyder and Cisar, 2000), reducing NO3-N leaching in bermudagrass used on golf course s in South Florida (Snyder et al., 1984), and determining the fate of NO3-N in a Kentuc ky bluegrass and red fescue mixed turf in sandy soils in Connecticut (Starr and DeRoo, 1981). As the most commonly used lawn type, St. Augustinegrass ( Stenotaphrum secundatum ,Walt. Kuntze ) represents 64.5% of all sod in production in Florida, with 75% used for new residential landscapes (Haydu et al., 2002, 2005). The remainder is used for road medians, commercial landscapes, passive areas, and resodding of existing landscapes. While there are four cultivars of St. Augustinegrass that are commonly produced in Florida (Palmetto, Floralawn, B itterblue and Floratam), Floratam is

PAGE 21

5 the most widely produced, comprising of 75% of all St. Augustinegra ss in production. Of the St. Augustinegrass harvested, 60% came from organic soils (Histosols) located within the Everglades Agricultural Area with the remaining 40% grown on mineral soils. While the industry harvested approximately 4% more St. Augustinegrass each year compared to the previous years from 2000 to 2003, more pr oduction is shifting from organic soils to mineral soils due to loss of organic soils and thus a shift in market locations (Haydu et al., 2002, 2005). This shift to lower soil or ganic matter (SOM) attached to sod may influence NO3-N leaching and turf quality during and beyond sod establishment. The objectives of this project were to c onstruct a field scale facility capable of studying multiple turfgrass management f actors and their in teractions on St. Augustinegrass quality, growth and N leaching, and to document background N contributions prior and during sod establishm ent. The main goals of constructing the facility were to (a) make the facility capa ble of examining multiple management factors and their interactions, (b) to mimic realistic conditions of residential St. Augustinegrass lawn maintenance and (c) to be able to collect quality scientific data. Materials and Methods The site for the experimental facility was the University of Floridas Institute of Food and Agricultural Sciences, Fort Lauderd ale Research and Education Center. An area of 24 X 48 m was leveled on drained na tive Margate fine sand soil (siliceous, hyperthermic Mollic Psamnaquent). The native soil was formed in marine sediments over fractured limestone (N RCS, 2004) having 20 g kg-1 SOM within the top 38 cm of the soil surface.

PAGE 22

6 The facility was marked as a randomized sub plot design consisting of eight, 12 X 12 m main plots (isolated by 0.6 m alleys) in two columns. Within each main plot, four columns of three 4 x 3 m plots were deline ated for a total of 12 plots per main plot. Perimeter irrigation systems were installe d on each of the eigh t main plots. The irrigation system comprised of 2.4 cm diamet er Schedule 40 PVC pipe with rotor Toro EZ Adjust Sprinklers (EZ5P-60) placed in ea ch corner adjusted to spray an inward quarter circle. The sprinklers were 127 mm pop up sprinklers with a nozzle delivering 18.9 L per minute. Each main plot irriga tion system was on a separate zone and controlled by a digital irriga tion clock (Hunter ICC). Irrig ation water was supplied by a 21 m deep well fitted with a submersible pump and brought to the surface with a 10.16 cm diameter pipe. To control sp rinkler pressure, valves were installed in-line of the north end PVC pipe for each main plot. Spray di rection and global distribution uniformity ( Dug) was monitored and adjusted upon installa tion and during the st abilization period. To test for uniformity, 61 cm diameter catch can s were secured in the center of each plot by wire hooks. The top of the catch cans were at the same height as the top of the grass canopy. The irrigation test ran for 10 min per zone either during the day at which time the volumes of water within the catch cans were immediately measured, or if irrigated over night, the volumes were measur ed early the following morning. The distribution uniformity must account fo r the spatial varia tion associated both within (subplots) and between main plots. Ag ain, main plots are on separate zones, each with overlapping rotor sp rinkler heads at the four corners of the main plots. To integrate both uniformities, the following equation was derived from Clemmens and Solomons

PAGE 23

7 (1997, unpublished data) statistical procedure for determining global DU first published by Burt et al. (1997): DUg = [1(1-DUmain)2 + (1-DUsub)2] in which DUg = the global distribution uniformity for the experimental area; and DUmain and DUsub represent the distribution uniformity for the main plots and subplots as elements, respectively. Both DUmain and DUsub were calculated based on the lower quarter distribution uniformity method whic h refers to the average of th e depths that fall into the lowest quarter of all element depths divided by the average of all element depths (ACSE, 1978). In the center of each plot, ceramic-cup wa ter samplers were installed at a 40 cm depth to collect vadose zone percolate. A schematic drawing of a ceramic cup sampler can be found in Figure 1a. Ceramic cup water sa mplers were constructed of a 4 mm i.d. X 6 mm height ceramic cup (Soil Moisture E quipment Corp., California) glued to a 4 mm i.d. schedule 40 PVC body. The PVC body wa s shortened to a 15.5 mm height. A PVC end cap was glued to the top of the PVC body and contained two drilled holes in which two brass tube connectors (Swagelok, Ohio) we re installed. The first connector set-up was for collection of the vadose zone water into the sampler. It cons isted of an incoming tube (0.3 cm o.d. flexible nylon tubing) connect ed to a remote vacuum to supply suction into the sampler to collect water from the surrounding soil (Figure 1-1b). When on, the remote vacuum was regulated at 0.03 MPa in or der to ensure that only free draining water was collected. The second tube connector setup was for sample extraction (Figure 1-1c). This consists of a connector with an incomi ng tube, as well as a tube within the sampler the length of the body, sleeved in a glass tubi ng to ensure contact w ith the base of the

PAGE 24

8 cup. The incoming tube was connected to one of twelve remote sample removal stations constructed from irrigation control boxes. Each sample removal box was fitted with a valve to either open or close the sample re trieval line and a quick connect to shunt the vacuum through an extractor/overflow device. The extractor/overflow device had three lines. The first was rubber tubing that conne cted to the quick connect to supply the vacuum. The vacuum passes through an overf low chamber and was connected to a 0.3 cm o.d. nylon tube. This nylon tube connects to a rubber stopper that was placed upon the collection vial. A second nylon tube from th e stopper connects to the quick connect for a specific ceramic cup sampler. This second tube supplied the vac uum to extract and collect the water sample, and a place for exce ss sample to go so it does not go back into the vacuum line. The procedure to collect a sample was as follows: (a) Valves were set in the closed position, (b) the vacuum was turned on and wa ter was collected in the ceramic cup sampler, (c) the valves we re set in the open position, (d) the extractor/overflow device was attached to the vacuum quick connect, then the stopper was placed on the corresponding vial, (e) the sa mple was collected until the ceramic cup sampler was drained, (f) steps d-e were rep eated for all ceramic cup samplers, and (g) vacuum was turned off. In September of 2000, the ceramic cup samplers were installed, covered with soil and then allowed to equili brate. In mid-November, water samples were collected on various dates to test for natural fluctuations in soil-water N. On 3 December 2000, St. Augustinegrass Flo ratam from a mine ral sod farm in Punta Gorda was laid as a sod. Soil attached with sod was approximately 5 cm thick. Four main plots were laid with sod containing 40 g kg-1 SOM and the other 4 main plots were laid with sod containing 100 g kg-1 SOM. To determine the amount of SOM, soil

PAGE 25

9 samples from sod pieces within ea ch main block were dried at 110oC, screened through a 2 mm sieve, and ashed in a muffle furnace at 550oC for approximately 12 hours. Samples were then weighed and the weight loss on i gnition was deemed to be SOM on a weight basis. Over the following four months, esta blishment was examined by collecting percolate and monitoring turfgrass visual quality. During the es tablishment period, the turfgrass was irrigated daily to repl ace 125% potential evapotranspiration (ETp) for the first 2 weeks. Thereafter, the turfgrass was irrigated daily to replace 100% ETp. Daily ETp was retrieved from a Florida Automated Weather Network (FAWN) weather station located approximately 100 m from the experimental site. The ETp was determined by a Penman based model developed by Fares a nd Alva (1999) to determine irrigation requirements for citrus production and later adapted by the Florida Automated Weather Network. The plots were mowed as needed with a riding rotary mower set at a 7.5 cm mowing height. On 13 April 2001, a rotary pus h mower was used to collect clipping samples. A two meter long PVC pipe was used as a guide to walk the mower along in order to sample a one meter squared area repetitively. Ten centimeter diameter cores were collected to a 30 cm depth to assess the influence of SOM on below ground growth. The cores were portioned into 0-15 and 15-30 cm sections with the roots washed clean of soil. Both clipping and root samples were dried at 110oC and weighed to determine the effect of SOM on growth. Additionally, clipping samples were sent to the University of Floridas Analytical Research Laboratory for determination of total Kjeldahl N.

PAGE 26

10 Rainfall was recorded with a rain gauge located on the southeast corner of the experimental area. Periodically, [NO3-N] was determined in i rrigation and rainfall. All water samples were preserved on premises and analyzed following EPA approved methods (QuickChem #10-107-04-1-8 and 10-107-06-2-8) using an 8000 series Continuous Flow Injection Colorimetry (Hach, Colorado) at the University of Florida Belle Glade Research and Education Cent er. Daily percolate was calculated by the following equation developed by Snyder et al. (1 984): Percolate = Ir rigation + Rainfall ET. The ET used in this equation was collect ed from the FAWN website as mentioned above. The stabilization and es tablishment periods bracketed a period of dry weather. In order to collect background data even when percolate was not predicted, the sample vacuum was left on longer than would typica lly have been done in order to collect enough sample so nutrient water analysis coul d be completed. Daily nutrient loading was determined by multiplying the concentration of each nutrient found in the daily percolate sample per plot by the total quantity of perc olate calculated for the respective period. Mean [NO3-N] for the two periods were calculated as a flow weighted average (calculated as total leached divided by total calculated percolate). Turfgrass quality was visually observed and rated for each subplot on a scale from 1 to 10, with 1 = dead/ brown turf, 6 = minimally acceptable turf, and 10 = dark, green turf. Irrigation uniformity and percolate quantities, [NO3-N] and leaching during the stabilization period, and iden tification of statistically significant SOM effects for percolate, [NO3-N], leaching, and turfgrass quality scores for the establishment period were determined using the SAS proc mixed statement (SAS Institute, 1989).

PAGE 27

11 Results and Discussion Irrigation Uniformity Sprinkler base pressure was maintained at 0.3 Mpa. The lack in fluctuation in base pressure suggests that wind and spray directi on was more influential than water pressure on distribution uniformity. For four irrigation tests, the average DUmain was greater than the average DUsub (0.83 and 0.60, respectively). This suggested that the amount of irrigation applied to each of the main plots wa s fairly even, but individual subplots were receiving a variable amount of irrigation in respect to othe r subplots. Perhaps this was due to the arc of the spray or to wi nd drift. Regardless of the reason, the DUsub in this study was greater compared to the Browar d Soil and Water Conservation Districts reported DU for rotor sprinklers (as mentioned in the introduction), and greater compared to a study conducted in central Florida residential turfgrass sprinkler systems (Baum et al., 2003). These authors calculated an average DUlq of 0.48 for 17 irrigation systems that used rotor sprinklers. Baum et al. ( 2003) felt comfortable with the average DUg of 0.56 after uniformity did not improve with sp rinkler adjustments and since the value represented present irrigation uniformity for turf landscapes in South Florida. In this study, the low DUsub resulted in lower DUg than expected, ranging from 0.44 to 0.62. Mowing events may also be a factor attribut ing to changing sprinkler uniformity. After finding sprinklers moved after a mowing event, we found that checking the sprinklers by running through the zones quickly after mowing only detected defective sprinklers. A closer inspection showed sprinklers in which their orientation were slightly moved and thus the direction of the spray throw had ch anged. While it has always been a rule of thumb to not mow over the sprinkler, even pressure of the ridi ng mower close to the sprinkler tended to move a few sprinkler s in a slightly different orientation.

PAGE 28

12 Natural Fluctuations in Percolate and Nitrate Once the ceramic cup samplers were insta lled, samples were not collected from the experimental area for a 2.5 month period. This time period was to minimize influences from soil disturbance from installation on the ceramic cup samplers and to extract samples periodically to ensure that the samp ler CEC was satisfied and no air was present in the lines. After the 2.5 m onths, a stabilization period from the 14 November to 3 December 2000 followed during which percolat e was collected from all plots on four collection dates to examine the perturbations of the natural soil environment and of the ceramic cup samplers on the influence on percolate quantities and [NO3-N] and leachate. Except for 22 November, actual percolate volumes were confirmed similar by the Levenes Test for Homogeneity (Table 1-1a) ve rifying that all ceramic cup samplers were being influenced in a similar manner by the so il environment. On the first collection date (14 November 2000) no sample was collect ed from 14 cup samplers. However by 22 November 2000 all cup samplers were worki ng and collecting perc olate. Percolate volumes ranged from 0 to 23 ml over the peri od. The greater percolate volumes collected on 28 November and 01 December were most lik ely due to the one rain event of the period, occurring on 27 November and resulting in 16.5 mm of rainfall (Figure 1-2). With a mean concentration of 0.20 mg l-1, rainfall was a source of 0.06 g m-2 of NO3-N to the experimental area. Besides what was contributed by rain fall, the other source of NO3-N most likely was from the 20 g kg-1 SOM in the native soil. Assuming that for every percent of SOM a N release of 4.4 g m-2 per year based on a furrow hectare (Wolf and Snyder, 2003), approximately 0.37 g m-2 per month would be released. Except for 28 November 2000, there we re no differences among plot [NO3-N] from the percolate collected, (Table 1-1b, Figure 1-3). Nitrate con centrations attributed by the

PAGE 29

13 native soil environment ranged from 0.0 to 38.2 mg l-1 during the period. Similar to percolate and [NO3-N], NO3-N leached among the plots for each collection date did not vary (Table 1-1c, Figure 14). The amount of actual NO3-N leached was perhaps influenced by rainfall in two ways: First by qu antity of percolate a nd secondly that after a dry period the rainfall may have increased N mineralization and thus increased soluble [NO3-N]. While an immediate increase in perc olate was observed after the rain event, [NO3-N] decreased and leaching was unaffected (28 November, Table 1-1, Figures 1-3 and 1-4). Then on 01 December, more percolate was observed, as well as increased [NO3-N] (Table 1-1, Figures 1-3 and 1-4). Pe rhaps these lower and then higher [NO3-N] documented after the rain event which had fo llowed a long period of dry weather, can be attributed to immobilization and then mi neralization by the natural soil microbial community. However this is just a postulate as soil microbial p opulations were never monitored during the project. There was no calculated percolate and thus no total NO3-N leached over the stabilization period. Sod Establishment Sod establishment was during a dry period (3 December 2000 to 10 April 2001), at which time there were only twelve rain events totaling 316 mm of rainfall (Figure 1-2). Turfgrass was only irrigated 125% ETp for the first two weeks of establishment (Figure 1-2) and then 100% ETp thereafter. Irrigation totale d 417 mm with the water source having an average [NO3-N] of 0.11 mg l-1. This resulted in a total of 291 mm of calculated percolate across 16 dates. Table 2 summarizes the amount of NO3-N contributed from rainfall and irrigation, and total N from the native soil and soil attached to the two contrasting sods. The total N calculated from the soil attached to the sod was

PAGE 30

14 determined on the amount of SOM in the same manner as that of the native soil except for that the 5 cm of soil instead on 15 cm of soil was accounted for. Immediately after laying the sod, [NO3-N] spiked to over 6 and 12 mg l-1 for sod with 40 g kg-1 and 100 g kg-1 SOM, respectively (Figure 3). The subsequent gradual decline of [NO3-N] over the next month and a half wa s nearly proportional to the amount of SOM associated with the sod (Figure 3). Nitrate concen trations were significantly greater from the 100 g kg-1 SOM sod for the first month a nd a half (p<0.05, Figure 1-3). By mid-February concentrations had leve led off and were back to pre-planting concentrations for the rest of the establishmen t period (Figure 1-3). At the very end of the establishment period (23 March), a peak in [NO3-N] occurred from the sod containing 100 g kg-1 SOM which was not observed from sod containing 40 g kg-1 SOM (0.01 and 1.8 mg l-1 respectively, p = 0.0992, Figure 1-3). Rain events close to this time (19 and 20 March 2001) resulted in 151 mm of precipitation (Figure 1-2) During this time period, both sods had similar volumes of percolat e collected (mean = 16.5 and 16.0 ml for 40 g kg-1 and 100 g kg-1 SOM, respectively, P>0.1000), suggesting that percolate volume did not influence the concentrations Perhaps the increase in [NO3-N] was a result of greater amount of N present to be mineralized in th e higher SOM sod. Alternatively, the sod with 100 g kg SOM may have raised the soil moisture content to support a greater microbial population that ultimately result ed in more N mineralized. Ca sey et al. (2002) and Skopp et al. (1990) also attributed the increase in microbial activity and subsequent N mineralization to the raising of soil moisture content by irrigation. Nitrate leaching during the establishment period followed a similar trend to [NO3N]. During the two months following sod installation, NO3-N leaching from the sod with

PAGE 31

15 100 g kg-1 SOM was greater than that from the sod with 40 g kg-1 SOM on all collection dates except for the date of planting (3 December) and January 22 and 25 (P<0.05, Figure 1-4). During the remainder of th e establishment period, average NO3-N leaching for both sods were below pre-planting leaching a nd were not different (P>0.10, Figure 1-4). Actual leaching over the entire es tablishment period for the 100 g kg-1 SOM sod was 1.68 g m-2, which was greater than the 0.74 g m-2 leached from the 40 g kg-1 SOM sod (P<0.01). Calculated leaching for th e entire period from the 100 g kg-1 SOM sod (0.73 g m-2) was greater than the 0.38 g m-2 leached from the 40 g kg-1 SOM sod (P<0.01, Table 2). At the end of the establishment period, clipping samples were collected to test for the influence of SOM on turfgrass blade gr owth. The average dry weight of clippings from turfgrass with 40 g kg-1 SOM was 7.0 g m-2, which was lower (P<0.01) than the average 37.1 g m-2 from sod with 100 g kg-1 SOM. While total [N] in blades were similar for both grasses (12.9 and 16.5 mg g-1 for 40 g kg-1 and 100 g kg-1 SOM, respectively, P=0.16), the greater mass of clippings from sod with 100 g kg-1 SOM as mentioned above, resulted in a greater amount of tota l N per area basis from the sod with 100 g kg-1 SOM than the sod with 40 g kg-1 SOM (59.6 and 8.9 g m-2 respectively, P<0.01). Even though turfgrass with the 100 g kg-1 SOM had slightly more root mass at both 0-15 cm and 15-30 cm depths, SOM did not in fluence turfgrass rooting (P>0.10, Table 13). Conclusions St. Augustinegrass landscapes ha ve been implicated as a potential source of N pollution into sensitive watersheds that are important to South Floridas water supply. To determine maintenance practices that mini mize N leaching from St. Augustinegrass, a

PAGE 32

16 field scale facility was built to mimic realistic landscapes, yet at the same time be feasible to gather quality scientific data. A perf ormance evaluation of the irrigation system resulted in an average global distribution uni formity of 0.56, which was similar to others found on residential landscapes for the area. Vadose zone ceramic cup samplers were quickly primed by repetitively extracting water. Results of the stabilization and establishment periods of this facility document background N contributions from the native soil, rainfall, irrigation sour ce and soil attached to sod pieces.

PAGE 33

17 Table 1-1. Mean, standard deviation and Leve nes Test for Homogeneity for (a) actual percolate volumes, (b) nitrate concentra tions, and (c) nitrate leached for each of the four collection da tes during the stabilization period with only bare soil as a cover. Mean Standard deviation Significance (a) Actual percolate volumes (ml) 14 November 2000 10.0 6.24 0.79 22 November 2000 10.8 5.57 0.07 28 November 2000 15.3 3.93 0.28 01 December 2000 18.3 3.95 0.84 (b) N concentrations (mg l-1) 14 November 2000 1.43 0.19 0.18 22 November 2000 1.40 0.24 0.46 28 November 2000 0.94 0.19 0.05 01 December 2000 2.65 2.06 0.97 (c) Actual N leaching (g m-2) 14 November 2000 0.02 0.01 0.23 22 November 2000 0.02 0.01 0.68 28 November 2000 0.02 0.01 0.11 01 December 2000 0.05 0.04 0.68 Table 1-2. Nitrogen inputs (g m-2) during the four month establishment period for sod with 40 g kg-1 and 100 g kg-1 SOM. Inputs 40 g kg-1 SOM 100 g kg-1 SOM -----------------g m-2-----------------Rainfall 0.06 0.06 Irrigation 0.05 0.05 Native soil 0.37 0.37 Sod soil 1.00 2.48 Table 1-3. Comparison of mean r oot dry weights (g) from 40 g kg-1 and 100 g kg-1 SOM collected from cores between 0-15 cm and 15-30cm depths. SOM 0-15 cm 15-30 cm -----------------g m-2-----------------40 g kg-1 0.75 0.25 100 g kg-1 0.98 0.39 Significance 0.31 0.20

PAGE 34

18 Figure 1-1. Schematic drawing of equipment us ed to collect vadose zone percolate: (a) dimensions of the ceramic cup sample r, (b) connections supplying sampler with a vacuum, (c) connections for sa mple extraction, and (d) extractor / overflow device.

PAGE 35

19 0 1 2 3 4 5 6 14-Nov-0014-Dec-0014-Jan-0114-Feb-0114-Mar-01Irrigation (mm)0 20 40 60 80 100 120 140Rainfall (mm) Irrigation Rainfall (a) stabilization (b) establishment Figure 1-2. Rainfall and irriga tion (mm) over the (a) stabili zation and (b) establishment periods.

PAGE 36

20 0 5 10 15 14-Nov-0014-Dec-0014-Jan-0114-Feb-0114-Mar-01NO3-N concentration (mg L-1) 4% SOM 10% SOM (a) stabilization (b) establishment Figure 1-3. Nitrate c oncentrations (mg l-1) determined in percolate from sod containing 40 g kg-1 SOM compared to sod with 100 g kg-1 SOM during the (a) stabilization and (b) establishment periods.

PAGE 37

21 0.00 0.10 0.20 0.30 14-Nov-0014-Dec-0014-Jan-0114-Feb-0114-Mar-01NO3-N leached (g m-2) 4% SOM 10% SOM (a) stabilization (b) establishment Figure 1-4. Nitrate leaching (g m-2) from sod containing 40 g kg-1 SOM compared to sod with 100 g kg-1 SOM during the (a ) stabilization and (b) establishment periods.

PAGE 38

22 CHAPTER 2 EFFECT OF IRRIGATION, N SOU RCES AND RATES ON N LEACHING, TURFGRASS QUALITY AND GROWTH FROM NEWLY ESTABLISHED ST. AUGUSTINEGRASS LAWNS Introduction As it is for all plants, N is an essentia l element for growth and viability and is required in the greatest quantity for turfgr asses (Beard, 1973). Nitrogen is the constituent for amino acids and proteins and N is nece ssary for carbon metabolism (Taiz and Zeiger, 2002). Developing accurate fertilizer and ir rigation recommendations is important to maintain quality turfgrass as well as reduc ing water consumption and the potential for fertilizer waste and N contamination to watersheds (Flipse et al., 1984; FDEP, 2002). Contamination by N can lead to eutrophicati on in water bodies, ultimately resulting in a decline in water quality and death of orga nisms. Besides the potential threat to watersheds, elevated NO3-N in drinking water is consider ed a human health threat if above the standard of 10 mg l-1 (USEPA, 1976). The concern over NO3-N is because its solubility, and it is the most av ailable and mobile form of N that plants uptake (Taiz and Zeiger, 2002). However because it is an anion, it is not well retained by soil colloids. Whether on naturally occurring high ridge areas or on lots with urban fill brought in for construction, the home and home lawns in Flor ida are often on coarse sand textured soils with little physical characte ristics to retain applied N (C isar et al., 1991; Wang and Alva, 1996). In Florida, N leaching from turf home la wns has been implicated as a source of N pollution to streams, lakes, springs and bays (Erickson et al., 2001).

PAGE 39

23 Previous research on N leaching from bermudagrass ( Cynodon dactylon P ) golf course turf in Florida has shown that N rates, N sources, N application methods, and irrigation all influence the amount of N leach ing beyond the root zone, and subsequently to groundwater (Snyder, et al .,1976; Snyder, et al., 1980; Snyder, et al., 1984; Snyder, et al., 1989; Cisar, et al., 1991). However, the principal turfgrass used for home lawns in Florida is St. Augustin egrass Floratam ( Stenotaphrum secundatum, Walt. Kuntze ). In comparison to bermudagrass, St. Augustinegra ss is mowed higher, is often produced as sod on soils with high organic matter content, potentially has a deep er root system, does not have as high of a N requirement, has di fferent irrigation requirements, has more thatch from stolons and does not receive th e intensive cultivation (aerifying, verticutting and dethatching) that is used for be rmudagrass; all of which can affect NO3-N leaching. St. Augustinegrass is character ized as a stoloniferous pe rennial, rooting at nodes, with coarse-textured leaf blad es that are 6 to 8 mm wide and up to 15 cm in length (Hitchcock, 1950; Duble, 1989). In 1950, St. Augustinegrass was documented as collected in Florida, Georgia, South Carolina, Louisiana, Texas and California within the United States (Hitchcock, 1950). Since then th e pantropical species is used for lawns along the Gulf Coast States of the U.S., a nd in Southern Mexico, the Caribbean, South America, South and Western Africa, Austra lia, the South Pacific and the Hawaiian Islands (Bogdan, 1977; Duble, 1989). In the U.S., St. Augustinegrass is only native to the Gulf Coast Region of Florida and is documente d as a pioneer on the coastal shore. While the grass is grown inland, the biogeographical distributi on of St. Augustinegrass is restricted primarily to it being a subtropical C4 warm season turfgrass and thus lacking in cold tolerance (Duble,1989). It is noted by Hitchcock (1950) as being found in moist, muck soils, mostly near the coast. It is adap ted to Floridas sand soils but is less drought

PAGE 40

24 tolerant than some other warm season turfgrasses such a bermudagrass, and will not thrive unless irrigated when grown on thes e soils (Chen, 1992). While St. Augustinegrass can grow in unfertile sand soils (Chen, 1992), depending on the aesthetics and uses required, St. Augustinegrass requires fertilizatio n to maintain a healthy turfgrass stand. Physical and chemical properties of sand soils of south Florida cont ribute to the poor soil fertility. For example, within the A horiz on of Margate sand soils, saturated hydraulic conductivity ranges from 30-49.6 cm hr-1, and they have low water retention (0.01 to 0.12 cm cm-1), and low cation exchange capacity (2.4-5.6 Meq 100 g-1 of soil) with less than 16 g kg-1 SOM (Pendleton et al., 1984). Despite its common use as a residential lawn turfgrass, there has been no research on N leaching in south Florida involving a co mparison of management factors for St. Augustinegrass. This study was conducted to in vestigate the impact of a wide range of potential management parameters including re duced and excessive N fertilization, readily soluble and controlled release N sources and irrigation on N leaching from St. Augustinegrass turf. The objectives of this st udy were to (a) determine how N sources, rates and irrigation scheduling influence [N ] and leaching, turfgrass quality and growth, (b) to develop a N budget under different ma nagement scenarios, and (c) to give management strategy recommendations to minimize potential adverse impacts to the environment. Materials and Methods An experimental field cont aining eight main plots of twelve 3.0 by 4.0 m sub plots (for a total of ninety-six sub plots) was plan ted with St. Augustinegrass Floratam at the University of Floridas Fort Lauderdale Re search and Education Center to monitor turfgrass quality and N leaching in the fa ll of 2000. Ceramic-cup water samplers were

PAGE 41

25 inset in the native Margate fine sand soil (siliceous, hyperthermic Mollic Psamnaquent) in the center of each sub plot at 40 cm de pth for the purpose of collecting vadose zone water samples. St. Augustinegrass Floratam sod was planted in December 2000 with the first experiment beginning in April 2001. See Chapter 1 for specific details regarding construction, stabilization and sod establishment of th e experimental facility. The study was conducted as a balanced bloc k design with two replications, each consisting of four main plots in which each main plot had twelve sub plots. Assigned to the main plots within each replication were two 2-level factors in a factorial layout irrigation by soil organic matter. Assigned to th e 12 sub plots within each main plot were two factors in a factorial design, fertilizer source at 4 levels cr ossed with fertilizer rate at 3 levels. Soil organic matter differences brought in with sod pieces were not expected and thus treated as a random variable with ir rigation. The amount of soil organic matter harvested with the sod at the time of installation was either 40 g kg-1 or 100 g kg-1. Each main irrigation block followed eith er a fixed (FIX) or adjusted (ADJ) irrigation schedule: Fixed irri gation: irrigated at a rate equivalent to 125% maximum weekly evapotranspiration ( ET) over three irrigation app lications per week (Monday, Wednesday and Friday) regardless of rain. To determine the month with the highest ET, 10 yr monthly averages were compared from McCloud predicted ET. Adjusted irrigation: irrigating at a rate equivale nt to 125% weekly ET adjusted monthly. The 125% maximum weekly ET rate was calculated by taking th e month with the highest ET based upon the McCloud method, adding 25% and dividing by four. The 125% rate was applied to overcome any variability in application due to factors such as imme diate evaporation and by wind drift. Evapotranspiration was calculated by the McCloud method (McCloud, 1955), which was developed in Florida for grasses. Irrigation for the week was split into

PAGE 42

26 three applications per week to simulate a Phase I Water Use Restri ction by South Florida Water Management District for established residential landscapes. A Phase I Water Use Restriction allows for irrigati on to be applied three designa ted days a week (SFWMD). When rain 0.84 cm or greater occurred, the following scheduled irri gation was voided for St. Augustinegrass maintained with the ADJ i rrigation schedule (i.e. if a rain event occurred on Tuesday, then no irrigation applied until Friday). To initiate each of the six, approximate ly 2-month cycles, urea (UREA, 46% N) and / or sulfur coated urea (SCU, 38%) were us ed as one of the following four N sources applied to each subplot: liquid urea, water soluble granular urea, 50% water soluble granular urea50% controlled-release granular SCU, or controlled-release granular SCU. The fertilizer N sources provided several po tential homeowner maintenance regimes. The liquid fertilizer represente d a lawn maintenance company spraying out a completely water-soluble N source. The gra nular water-soluble N and cont rolled-release N represent those readily available for homeowners to purchase. The N rates bracketed a gene ral recommendation of 5.0 g N m-2 per application for a year total of 30 g m-2 (Cisar et al., 1991; Ruppert and Black, 1997) at one of the following three rates: 2.5, 5.0 and 10.0 g N m-2 bimonthly. Nitrogen rates also provided potential maintenance scenarios representing und er and excessive fertilizer application. A summary of experimental factors tested is found in Table 2-1a with the ANOVA table of factors and interactions tested in Table 2-1b. Since SOM was not a planned factor, SOM and irrigation schedules were not tested together for interactio ns with other factors (Table 2-1b). Fertilizer applicat ions were irrigated at the next scheduled i rrigation. This resulted in St. Augustinegrass irrigated within 24 h of fertilization. This was intentional to mimic home residents who have a professional lawn care specialist fertilizing their lawn. In

PAGE 43

27 many cases the lawn care specialist fertilizes when the customer is not home and leaves door tags informing the resident to irrigate. Phosphorous and Potassium were applied just prior to cycles 1, 3 and 5 N applications at a rate of 5.0 g m-2. The plots were mowed with a rotary pus h mower approximately every two weeks in the summer and every three weeks during th e winter. The mowing he ight was set at 7.5 cm except during the spring of 2002 when the height was raised to decrease mowing frequency. Prior to mowing events, clippings were removed from a 1m2 area from each sub plot. In August 2001 and 2002, 10 cm diameter root cores were coll ected to a 30 cm depth to determine root weight density. The cores were portioned into 0-15 and 15-30 cm sections followed by root washing to remove all soil. Both clippings and roots were dried at 110 oC and weighed to determine treatment effect on above and below ground growth. To determine N concentration (hereafter denote d as [N]) within leaf blades, all clippings were sent to University of Floridas Analytic al Research Laboratory for the determination of total Kjedahl N (EPA #351.2). To determin e N uptake efficiency (NUE), leaf blade [N] was multiplied by total cl ipping weights and then divide d N applied by fertilizer (Moll et al., 1982). Rainfall was recorded with a rain gauge located adjacent to the experimental area. Periodically, nitrate concentrati ons (hereafter denoted as [NO3-N]) and ammonium concentrations (hereafter denoted as [NH4-N]) were determined in irrigation and rainfall. All water samples were preserved on prem ises and analyzed following EPA approved methods (QuickChem #10-107-04-1-8 and 10107-06-2-8) by using Continuous Flow Injection Colorimetry (Hach, Colorado) at the University of Florida Belle Glade Research and Education Center. Daily percolate wa s calculated by the following calculation

PAGE 44

28 developed by Snyder et al. ( 1984): Percolate = Irrigation + Rainfall ET, where ET was based on the McCloud method (McCloud, 1955) using temperature logged from the FAWN weather station located approximately 100 m from the experiment. Daily nutrient loading was determined by multiplying the c oncentration of each nutrient found in the daily percolate sample per plot by the calcu lated volume of percolate for the respective period. Nutrient loading for the cycle was th e sum of all daily N lo ading. Weekly mean [NO3-N] and [NH4-N] were calculated as flow wei ghted averages by dividing weekly leachate by total weekly percolate. Turfgrass quality was visually observed a nd rated for each subplot on a scale from 1 to 10, with 1 = dead/ brown turf, 6 = minimally acceptable turf, and 10 = dark, green turf. The experiment was conducted as six 2month cycles for a total of a one-year period. Cycles were statistically separated by the total amount of ra infall during the cycle into one of two seasons: wet (WET) and dr y (DRY). Identification of statistically significant treatment effect s for average seasonal [NO3-N], [NH4-N], total inorganic nitrogen (here after denoted as [TIN]), NO3-N, NH4-N, and TIN leaching, turfgrass quality scores, clippings weights, root wei ght density, leaf blade [N], and NUE were determined using SAS MIXED model procedur es with lsmeans compared using TukeyKramer multiple comparison test (SAS In stitute, 1989). Because the strength of the analysis of the design was primarily on the s ub plot, only the highest order interactions are discussed. If no interactions were signifi cant, then significant factors are discussed separately. With a few excepti ons, only significant factor and interaction effects are discussed.

PAGE 45

29 Results and Discussion Water Budget Rainfall during the six bimonthly cycles followed general weather patterns for southern Florida, with a wet season from approximately May through October and a dry season from November through April. The e xperiment received a total of 1448 mm of rainfall for the duration of the study with 71% received during the first three cycles encompassing the majority of the wet seas on (Table 2-2, Fig 2-1). The wet season was characterized by frequent afternoon showers, however sometimes intense, with two separate rain events bringing over 10 0 mm of rainfall per event (May 30th and September 29th, 2001). The fourth, fifth and sixth cycles encompassing the majority of the dry season, received the least amount of rainfall with the majority occurring as short, infrequent yet heavy rain events. For example, 65% of the rainfall e xperienced in Cycle 6 was received in two days (February 23rd and March 7th, 2001). Over the entire study period, turfgrass maintained with the ADJ irrigation schedule r eceived 2,236 mm of irrigation, which was 58% of the 3,858 mm of water that turfgrass received from FIX irrigation. The lower amount of irrigation applie d from the adjusted schedule resulted in lower calculated percolate (1,692 mm) than tu rf maintained with the fixed irrigation (3,289 mm of percolate). As expected, hot diurnal temp eratures of the summer m onths resulted in frequent convection-based storms comprising the we t season. Although cloud cover was greatest during this time of year, calculated ET was al so the highest (Cycle 2, Table 2-2) due to the hot temperatures and optimum grow ing conditions for St. Augustinegrass. Evapotranspiration was lowest in Cycles 5 and 6 with 276 and 261 mm, respectively, most likely due to the cooler temperatures that persist during the dry season months.

PAGE 46

30 Separating the cycles into seasons by statisti cally comparing the total rainfall during each Cycle led to Cycles 1, 2 and 3 being designated as WET a nd Cycles 5, 6 and 7 as DRY (P=0.0330). Nitrate Concentrations and Leaching The season affected [NO3-N] (P<0.001). Mean [NO3-N] during the WET season was 1.51 mg l-1 and ranged from 0.05 to 13.65 mg l-1. This was approximately 80% less than mean [NO3-N] found during the DRY season (mean = 7.48 mg l-1 with a range of 0.16 to 63.07 mg l-1). Nitrate concentrations were in fluenced by rate of N applied during both seasons (Table 2-3). WET season [NO3-N] from St. Augustinegrass receiving the 2.5 and 5.0 g N m-2 bimonthly were statistically similar (0.29 and 0.48 mg l-1 respectively, P=0.7110), yet both ra tes resulted in lower [NO3-N] than the 10 g N m-2 bimonthly rate (3.75 mg l-1, P<0.01). A similar trend was observed in the DRY season (Table 2-4). Additionally, during th e DRY season, there was higher [NO3-N] in percolate from St. Augustinegrass maintained with the ADJ irrigation schedule and associated with 100 g kg-1 SOM compared to the 40 g kg-1 SOM at the high N rate (Table 2-4). Similar to [NO3-N], only N rate influenced the amount of NO3-N leached during the WET season (Table 2-5). Nitrate leachi ng from the two lower N rates were equal (0.46 and 0.77 g m-2 for 2.5 and 5.0 g N m-2 bimonthly respectively, P=0.72), with NO3N leaching from the 10 g N m-2 bimonthly rate over six times greater than the two lower rates (6.01 g m-2, P<0.01). During the DRY season, Ra te and SOM*Rate influenced NO3N leaching (Table 2-5). Over the DRY season, more NO3-N leached from the 10.0 g m-2 bimonthly N rate compared to the two lower N rates (Table 2-6). Furthermore, greater NO3-N leached from sod associated with 100 g kg-1 SOM than St. Augustinegrass with 40 g kg-1 SOM at the 10.0 g m-2 bimonthly N rate (Tab le 2-6, Figure 2-2).

PAGE 47

31 In addition to Rate*SOM influenc es, IRR*Rate also influenced NO3-N leaching during the DRY season (Table 2-5 and 2-7) While there was a trend for more NO3-N leached from the FIX irrigation schedule for each N rate level, there was greater NO3-N leaching under the FIX schedule compared to th e ADJ schedule for turf maintained at the high N rate (30.07 and 10.78 g m-2 for FIX and ADJ respectivel y, Table 2-7, Figure 2-3). Although N sources did not influence seasonal [NO3-N] and leaching totals, different sources had different nitrogen release characterist ics over the 2 month cycles (Figure 2-4). In general, the LIQ treatment had comparatively low [NO3-N] and N leaching compared to other sources (Figure 24). This may be a result of the physical form of the N source. Since fertilizers we re not irrigated until the next scheduled irrigation (which for each cycle was the next morning), there may have been considerable NH3 volatilization from the urea. Peaks of NO3-N leaching followed fertilizati on events (Figure 2-4). Nitrate leaching peaks generally did not follow large rainfall events (Figure 2-4) unless they occurred within two weeks of fertilizer applic ations (Figure 2-4, Cycle 4). It seems that less intense but continuo us rainfall during the first two weeks after fertilization was more important than heavy/intense rain events thereafter for NO3-N leaching. For example, NO3-N leaching followed rainfall patterns for the first two weeks after the third fertilization (Cycle 3). However, most of thos e rain events were not intense. For twelve days of the two-week period following the fert ilization, the continuous rainfall resulted in NO3-N leaching for a longer peri od of time compared to the other cycles (Figure 2-4). Ammonium Concentrations and Leaching Perhaps due to the quick conversion of NH4-N to NO3-N during nitrification, [NH4N] was generally low during th e study period. WET season [NH4-N] in percolate ranged

PAGE 48

32 from 0.25 to 2.24 mg l-1 with a mean concentration of 0.94 mg l-1. DRY season [NH4-N] were lower than during the WET seas on (P<0.001) ranging from 0.08 to 1.89 mg l-1 with a mean concentration of 0.60 mg l-1. During the WET season, SOM*IRR*Rate influenced [NH4-N], while no factor or intera ction influenced DRY season [NH4-N] (Table 2-8). This third orde r interaction was only significan t when comparing irrigation schedules under two specific N Rate and SOM combinations. The first was for St. Augustinegrass with 40 g kg-1 SOM and fertilized at the 10.0 g m-2 N rate, in which higher [NH4-N] were observed from the FIX irriga tion schedule in comparison to the ADJ irrigation schedule (0.67 and 1.42 0 g m-2, P<0.01). The second was for St. Augustinegrass with 100 g kg-1 SOM and fertilized at the 5.0 g m-2 N rate, in which higher [NH4-N] were observed from the FIX irriga tion schedule in comparison to the ADJ irrigation schedule (0.62 and 1.33 g m-2, P=0.02). Total WET season NH4-N leaching ranged from 0.45 to 4.18 g m-2 with a mean total leached of 1.73 g m-2. Mean total DRY season NH4-N leached was lower than during the WET season (P<0.001) ranging from 0.13 to 3.04 g m-2 with a mean total leached of 0.94 g m-2. Similar to [NH4-N], SOM*IRR*Rate influenced NH4-N leaching during the WET season, with no factor or inte raction influences during the DRY season (Table 2-9). The same third order interactions were identified as found for WET season [NH4-N]. The first was for St. Augustinegrass with 40 g kg-1 SOM and fertilized at the 10.0 g m-2 N rate, in which higher [NH4-N] were observed from the FIX i rrigation schedule in comparison to the ADJ irrigation schedule (1.24 and 2.61 0 g m-2, P=0.01). The second was for St. Augustinegrass with 100 g kg-1 SOM and fertilized at the 5.0 g m-2 N rate, in which

PAGE 49

33 higher [NH4-N] were observed from the FIX irriga tion schedule in comparison to the ADJ irrigation schedule (1.14 and 2.44 g m-2, P=0.02). Higher [NH4-N] and leaching during the WET season resulted from abundant rainfall with the addition of irrigation. These events resulted in fertilizer transported past the root zone before it was nitrified. The lack of irrigation scheduling influences and overall lowers [NH4-N] and leaching during the DRY season was likely because all NH4N applied by fertilizer was either volatilized as NH3 or had sufficient residence time within the soil profile to be nitrified to NO3-N. Although N sources did not influence seasonal [NH4-N] and leaching totals, there was a trend for more leaching from the Bl end N source during the DRY season (Figure 25 b). Total Inorganic Nitrogen Concentrations and Leaching Total inorganic nitrogen concentrations were greater during the DRY season compared to [TIN] during the WET season (5.83 and 2.21 mg l-1 for DRY and WET respectively, P<0.01). This difference was partially due to a greater range of concentrations observed during the DRY season (0.27 to 30.97 mg l-1) compared to the WET season (0.7 to 14.63 mg l-1). Regardless of all other factors, WET season [TIN] was influenced by N rate (Table 2-10). As observed with [NO3-N] and [NH4-N], average WET season [TIN] of both the 2.5 and 5.0 g m2 bimonthly N rates were statistically similar (1.29 and 1.26 mg l-1 respectively, P=0.94), with bot h mean concentrations being lower than the mean [TIN] of the high N rate of 10.0 g m-2 bimonthly (4.10 mg l-1, P<0.01, Figure 2-6a). This trend was also observed for the DRY season, with average [TIN] of both the 2.5 and 5.0 g m-2 bimonthly N rates (1.51 and 2.95 mg l-1 respectively)

PAGE 50

34 being statistically similar, and with both m ean concentrations being lower than the mean [TIN] of the high N rate of 10.0 g m-2 bimonthly (13.04 mg l-1, P<0.01, Figure 2-6b). The interactions of SOM*Rate and IRR* Rate influenced [TIN] during the DRY season (Table 2-10). Besides observing that N rates applied at the 2.5 and 5.0 g m-2 bimonthly have statistically similar [TIN] that were less than the 10.0 g m-2 bimonthly N rate, lower mean [TIN] from the St. Augustinegrass associated with 40 g kg-1 SOM was approximately 1/3 lower compared to mean [TIN] from the St. A ugustinegrass associated with 100 g kg-1 SOM (P<0.01, Table 2-11). While N rate effects were similar as previously reported for St. Augustinegrass maintained with the ADJ irrigation, analysis of IRR*Rate interactions determined a stronger separation of N rate effects under the FIX irrigation schedule during the DRY season (Table 2-12, Figure 2-7). Under the FI X irrigation schedule, mean [TIN] increased with increased N rate (Table 2-12, Figure 27 a and b). Furthermore, the ADJ irrigation schedule resulted in mean [TIN] being lower th an concentrations from the FIX irrigation schedule at 10.0 g m-2 bimonthly N rate (Table 2-12). In general, trends that were observed in average [TIN] were also observed for the average TIN leached (Tables 2-10 and 2-13) WET season TIN leaching was less than DRY season TIN leaching (4.15 and 9.62 g m-2 for WET and DRY respectively, P<0.01). Mean TIN leached during the DRY season was most likely strongly influenced by high [TIN] observed during the DRY season. WET season TIN leaching was only influenced by N rate with similar amounts of TIN leach ed from St. Augustinegrass receiving the 2.5 and 5.0 g m-2 bimonthly N rates (2.39 and 2.33 g m-2 respectively, P=0.95), and with both TIN leaching losses being lower than the TI N leached from St. Augustinegrass receiving the high N rate of 10.0 g m-2 bimonthly (7.71 g m-2, P<0.01, Figure 2-8a). N rate alone

PAGE 51

35 influenced TIN leaching during the DRY season in a similar manner as it did in the WET season (Figure 2-8b). The SOM*Rate interaction effect on TIN leaching during the DRY season paralleled trends for [TIN] (Table 2-14). Under the 10.0 g m-2 bimonthly N rate, more TIN leached from St. Augustinegrass associated with 100 g kg-1 SOM compared to the St. Augustinegrass with 40 g kg-1 SOM. However there was no influence of SOM on the 2.5 and 5.0 g m-2 bimonthly N rates (Table 2-14). Analysis of DRY season IRR*Rate interac tions determined a separation of rate effects under the FIX irrigation schedule as obs erved with [TIN] (Tables 2-12 and 2-15). Under the ADJ irrigation schedule, TI N leached was greater from the 10.0 g m-2 bimonthly N rate compared to TIN leached from the 2.5 and 5.0 g m-2 bimonthly N rates (Table 2-15, Figure 2-9). The ADJ irrigation schedule resulted in less TIN leached than leaching from the FIX irrigation schedule at the 10.0 g m-2 bimonthly N rate (Table 2-15). In contrast to conventional wisdom, th e least amount of TIN leached was during the WET season. The WET season was thought to be the time of greatest leaching because of the abundance of rainfall. However, this was also the time of active turfgrass growth. Perhaps once the St. Augustinegrass had fulfilled its N requirement, the amount of N left to be leached was minimal except at high N rates, as observed in this study. Moreover, other N fate pathways such as vol atilization and denitr ification could have been increased by high temperatures and greate r moisture and humidity. This is further discussed under the N budget se ction. Across all other fact ors, approximately 9, 7, and 16% of all N applied was leached for 2.5, 5.0, and 10.0 g m-2 bimonthly N rates respectively during the W ET season. Beyond the 5.0 g m-2 bimonthly N rate, there tends to be higher TIN concentrations and leachi ng from the sod regardless of irrigation

PAGE 52

36 schedule and amount of SOM. In the DR Y season when St. Augustinegrass was not actively growing, factors influe ncing soil moisture (irrigatio n scheduling and SOM) were governing TIN concentrations and leaching. For example, 82% of N applied as fertilizer at the 10.0 g m-2 bimonthly N rate was lost to leachi ng from St. Augustinegrass associated with 100 g kg-1 SOM in comparison to the 71% leach ing loss from the St. Augustinegrass with 40 g kg-1 SOM. St. Augustinegrass maintained with the middle and high N rates and under the FIX irrigation schedule leached 28 and 77% of N applied respectively compared to the 9.5 and 29% lost for St Augustinegrass under the ADJ irrigation schedule. The excess N loss from the St. Augustinegrass maintained under the FIX irrigation schedule could be from residual TI N from previous fertilizations. The question remains if precipitation from irrigation and/ or weather was more influential than St. Augustinegrass growth on TIN leaching. The in fluence of St. Augustinegrass growth will be addressed again after th e results of St. Augustinegra ss quality and growth are discussed. St. Augustinegrass Quality St. Augustinegrass turf quality was assessed throughout each of the six experiments. Quality scores for the WET season ranged from 5.7 to 8.9 with a mean value of 7.5. DRY season quality scores were higher than quality scores of the WET season (P<0.01) ranging from 6.0 to 9.3 with a mean score of 8.0. For both seasons, the interaction of SOM*Ra te influenced quality scores (Table 216). In the WET season, quality scores increase d with N rate applied (Table 2-17a, Figure 2-10a). The two-way interaction also documents that at every N rate, higher quality was observed from sod with 100 g kg-1 than from sod with 40 g kg-1 SOM (Table 2-17, Figure 2-10a). During the DRY season an increase in applied N also resulted in better quality

PAGE 53

37 (Table 2-17b, Figure 2-10b). However, rega rdless of SOM associated with the St. Augustinegrass, similar quality was obtaine d when fertilized with the 10.0 g m-2 bimonthly N rate in the DRY s eason (Table 2-17b, Figure 2-10b). In addition to SOM*Rate interactions during the WET season, SOM*IRR*Source also influenced quality scores (Table 2-16). Under various N Source and IRR combinations, St. Augustinegrass with 100 g kg-1 SOM had greater quality than St. Augustinegrass with 40 g kg-1 SOM (Table 2-18). Nitrogen sources influenced quality duri ng the DRY season (Table 2-16). Similar quality was observed from St. Augustinegra ss fertilized with the UREA, LIQ and BLEND (mean DRY season quality was 8.0, 7.9, and 7.9 for UREA, LIQ and BLEND treatments, P>0.10, Figure 2-11 b). However, the 100% controlled release N source (SCU) maintained better qua lity than all of the other sources (mean quality of 8.2, P<0.04, Figure 2-11). St. Augustinegrass Growth St. Augustinegrass growth was assessed by clipping yield and root mass. Total clipping yields were greater during th e WET season when St. Augustinegrass was actively growing (642 and 174 g m-2 for WET and DRY seasons respectively, P<0.01). This seasonal effect was inversely proportiona l to [TIN] and leaching, suggesting that St. Augustinegrass growth influenced [N] and leaching. The interaction between SOM*Rate resulted in a difference in clipping yield during both the WET and DRY seasons (Table 2-19). The SOM*Rate interaction during th e WET season documents an increase in clipping yield with increase in N applie d, as well as St. Augustinegrass with 100 g kg-1 SOM having greater yield at each N ra te than St. Augustinegrass with 40 g kg-1 SOM (Table 2-20). This too supports the hypot hesis that St. Augus tinegrass growth was

PAGE 54

38 influential on [TIN] and leaching and explai ns why there was no influence of irrigation and SOM treatments on [TIN] and leaching during the WET season. The trend of greater clipping yields with increases in N rate was documented in the DRY season as well (Table 2-21). However in the DRY season only at the 2.5 and 5.0 g m-2 bimonthly N rates were there greater clippi ng yields from the St. Augustinegrass with 100 g kg-1 SOM compared to the St. Augustinegrass with 40 g kg-1 SOM (Table 2-21). As was documented with turf quality ratings, N sources influenced St. Augustinegrass growth in the DRY season. Th e clipping yields from SCU and BLEND N sources were statistically si milar (mean of 192 and 191 g m-2 for SCU and BLEND respectively, P=0.91) as were clipping yiel ds from UREA and LI Q N sources (156 and 158 g m-2 for UREA and LIQ respectively, P= 0.88). However, St. Augustinegrass fertilized with the SCU and BLEND N sour ces had greater clipping yields than the UREA and LIQ sources (P<0.01, Figure 2-12). Th ese results document better turf quality in the DRY season when grass was not activel y growing from N sources that include a controlled release product. While average qua lity for both seasons was greater than the minimum acceptance criterion of 6.0 for all source s, on selected dates near the end of the DRY season, quality was less than 6.0 for UREA and LIQ when applied at the 2.5 g m-2 bimonthly N rate. At the same time, a dec line in clipping yield was observed from the UREA and LIQ treated St. A ugustinegrass, suggesting that St. Augustinegrass fertilized with these two N sources were not capable of maintaining a resource efficient plant stand (Figure 2-12). Nine months after the sod was laid and four months after th e initiation of the experiment (01 August 2001), core sample s were collected to assess below ground growth. Root weight density in the upper 15 cm was greater than root weight density in

PAGE 55

39 the lower 15 cm (2,479 and 535 g m-3 for 0-15 cm and 15-30 soil profiles respectively, P<0.001). IRR*Rate influenced root weight densities within the upper 15 cm (Table 222). From sod maintained with the 2.5 g m-2 bimonthly N rate, root weight density was greater from sod maintained with the ADJ irrigation schedule compared to sod maintained with the FIX irrigation schedule (Table 2-23). No fact or influence on root weight densities in the lower 15 cm soil profile was identified. Perhaps the lack of influence was due to time between sod instal lation and core collection was not enough for roots to have fully developed w ithin this lower soil profile. One year later (01 August 2002) root wei ght density in the upper 15 cm was still greater than root weight density in the lower 15 cm (2,148 and 382 g m-3 for 0-15 cm and 15-30 soil profiles respectively, P<0.01). Root weight densi ties decreased over the year by 13 and 28% for the 0-15 cm and 15-30 cm depths respectively (P<0.01 for both depths). Peacock and Dudeck (1985) reported a 51% increase of root mass within the upper 30 cm of the soil profile over a one-y ear period for recen tly established St. Augustinegrass (14 mo after sodding). The decrease in root weight density may be related to the time of sod installation and when cores were collected. When the first cores were coll ected, roots had only experienced part of a dry season and part of a wet season, and were most likely actively growing due to the sod esta blishing its root system. In comparison to the 2001 root weight dens ities, there was no treatment effect on densities within the upper 15 cm, with I RR and SOM*SOURCE*RATE influencing root weight densities in the 15 30 cm so il profile (Table 2-24). St. Augustinegrass maintained with the ADJ irrigation had gr eater root weight density (mean = 433 g m-3)

PAGE 56

40 compared to St. Augustinegrass maintained with the FIX irrigation schedule (mean = 331 g m-3, P=0.03). Only at the 2.5 g m-2 bimonthly N rate did N sources in fluence root weight densities in St. Augustinegrass with 40 g kg-1 SOM (Table 2-25). At this lower N Rate, UREA had the lowest root weight density, which was sim ilar to SCU but statistically less than those of the BLEND and LIQ treatments (Table 2-25 ). Except for SCU, an increase in N rate resulted in greater root weight densi ties within N sources for St. Augustinegrass associated with 40 g kg-1 SOM (Table 2-25). Rate did not influence root weight densities in St. Augustinegrass with 100 g kg-1 SOM. Nor did N sources except, at the high N rate where the BLEND source had a greater root weight density than LIQ but similar to UREA and SCU (Table 2-25). In all cases wh en significant differen ces existed between 40 g kg-1 and 100 g kg-1 SOM for a given N rate and N S ource, there was a greater root weight densities from St. Augustin egrass associated with the 40 g kg-1 SOM than with the 100 g kg-1 SOM (Table 2-25). Leaf Blade Nitrogen Concentrations Mean [N] within leaf blades were grea ter in clippings coll ected during the DRY season compared to the WET season (20.1 and 17.9 mg N g-1 for DRY and WET seasons respectively, P<0.01). Perhaps this was due to active growth during the WET season resulting in more production of leaf blades and thus a lowe r [N] within due to dilution. During the DRY season, the St. Augustinegrass was not actively growing and thus was mowed less often, resulting in more N accumula ting within the leaf blades. In the WET season, mean [N] within leaf blades were in fluenced by N sources and N rates (Table 226). Over the WET season, Leaf blade [N] were highest in the firs t clippings collected after fertilization, and the lowe st concentrations were m easured at the end of the

PAGE 57

41 fertilization cycle (Figure 213). At the beginning of each fertilization cycle, the difference in mean [N] between the 40 g kg-1 and 100 g kg-1 SOM sod was minimal, however as time since fertilization increase d, the difference between mean [N] from the two sod types increased, with St. Augus tinegrass associated with the 100 g kg-1 SOM maintaining higher leaf bl ade [N] (Figure 2-13). Increasing N rate resulted in increases in WET season mean [N] in blade tissue (total=17.3, 18.5, and 20.3 mg N g-1, P<0.01). This was contradi ctory to other findings where the percent of N found in clippings decreased for N rates above the optimum fertilization rate (Petrovic, 1990). During both seasons, N sources influenced the seasonal mean [N] found in blade tissue (Table 2-27) with the highest [N] from St. Augustin egrass fertilized with SCU (19.2 and 21.6 mg N g-1 for the WET and DRY season re spectively), bein g higher than all other sources in the WET season and hi gher than UREA and LIQ in the DRY season (20.6 and 20.4 mg N g-1, Table 2-27, Figure 2-14 a and b) Although the trend of higher [N] in leaf blades from SCU fertilized St. Augustinegrass was evident on individual clipping dates, only on 20 Feb 2002 was [N] in leaf blades from SCU statistically higher than the other N sources (Figure 2-14 b). DRY season leaf blade [N] was influenced by SOM*Rate intera ction (Table 2-26). There was an increase in leaf blade N con centrations by increasi ng the N rate applied (Table 2-28). However, only at th e lower N rate applied (2.5 g m-2 bimonthly) was there higher leaf blade [N] in St. Augustin egrass associated with the 100 g kg-1 SOM in comparison to the St. Augustineg rass associated with 40 g kg-1 SOM (Table 2-28). These values were similar to others found in the l iterature. For example, Broschat and Elliott (2004) reported 13.0 to 19.7 mg N g-1 in St. Augustinegrass maintained with 20.0 g N m2

PAGE 58

42 yr-1 using a 16-4-8 fertilizer. In comparis on, Chen (1992) reported 20-26 mg N g-1 in leaf blade clippings. Vernon et al (1993) reported 14 mg N g-1 in clippings from St. Augustinegrass var. Raleigh. Nitrogen Uptake Efficiency Cumulative NUE over the two seasons was influenced by SOM*Rate interactions (P<0.01 for both WET and DRY seasons, Table 2-29). During the WET season, cumulative NUE ranged from 51 to 57 % for a ll N rates in St. Augus tinegrass associated with 40 g kg-1 SOM (Table 2-30). St. Augustinegrass with 100 g kg-1 SOM had greater NUE at each N rate compared to the St. Augustinegrass with 40 g kg-1 SOM (Table 230). Nitrogen uptake efficiency declined with increasing N rate on St. Augustinegrass associated with 100 g kg-1 SOM (Table 2-30). At the 2.5 and 5.0 g m-2 bimonthly N rates, greater than 100% NUE was obtained sugges ting that other N inputs such as from irrigation, rainfall and mineralization from soil microbes were utilized by the St. Augustinegrass. In general, DRY season cumulative NUE was lower than those of the WET season. During the DRY season, the cumulative NUE from St. Augustinegrass fertilized at the 5.0 g m-2 bimonthly rate was greater th an at both the 2.5 and 10.0 g m-2 bimonthly rates from St. Augustinegrass associated with 40 g kg-1 SOM (Table 2-31). St. Augustinegrass with 100 g kg-1 SOM had greater NUE than St. Augustinegrass with 40 g kg-1 SOM only at the 2.5 and 5.0 g m-2 bimonthly rates (Table 2-31) As observed during the WET season, cumulative NUE decreased with increas ing N rates from St. Augustinegrass with 100 g kg-1 SOM (Table 2-31). Again, perhaps this was due to increased N mineralization from the 100 g kg-1 SOM.

PAGE 59

43 Nitrogen source also influenced cumula tive NUE, however only during the DRY season (Table 2-29, Figure 2-15). Nitrogen upt ake efficiency increased over the WET season for all N sources, suggesting once agai n N uptake from fertilizer. In the DRY season, NUE did not increase to the extent observed in the WET season, suggesting comparatively less N uptake from the St. Augustinegrass. During the DRY season SCU and Blend treatments had similar cumulative NUE (39% for both SCU and Blend, P=0.94), with both being greater than NUE from the UREA and LIQ treatments (P 0.02), of which NUE from UREA and LIQ were similar (33 and 32% for UREA and LIQ respectively, P=0.71). As the season progres sed, the difference in NUE from the SCU and Blend treatments to those of the UREA and LIQ treatments increased (Figure 2-15). This reflected the controlled release characteristics of SCU, which perhaps became more important to N uptake as the DRY season progressed. Nitrogen Budget and Scenario Comparison The mean [NO3-N] and [NH4-N] in rainfall was 0.8 and 0.2 mg l-1, respectively ( n =5) for a total year contribution of 1.4 g TIN m-2, respectively. Other than rainfall, St. Augustinegrass received N inputs from pr ecipitation through one of two irrigation schedules. Mean [NO3-N] and [NH4-N] in irrigation water was 0.9 and 0.4 mg l-1, respectively ( n =5), contributing a total of 2.9 and 5.0 g TIN m-2 for plots receiving ADJ and FIX irrigation, respectively, during the e xperimental year. Wo lf and Snyder (2003) suggested that between 2.2 4.5 g m-2 of N was released per year for every g kg-1 of SOM within an acre furrow slice. Based on th ese estimations and accounting for that approximately 5 cm of soil was attached to sod pieces, during the WET and DRY seasons, every 10 g kg-1 SOM associated with sod is equivalent to 0.25 and 0.12 g N m-2 bimonthly, respectively. Considering that N mineralization from the SOM associated

PAGE 60

44 with the St. Augustinegrass would be greate st during the wet s eason when microbial activity is highest, the calculated N mineraliz ation based on the highe r end of this scale (4.5 g N m-2 yr-1 for every g kg-1 of SOM) results in a total of 3.0 and 7.5 g N mineralized m-2 during the WET season for St. Augustinegrass with 40 and 100 g kg-1 SOM, respectively. Nitrogen minerali zation estimates would be pres umed at the lower end of the scale (2.2 g N m-2 yr-1 for every g kg-1 of SOM) during the DRY season when insufficient soil moisture limits microbial activity. Based upon this assumption, 1.5 and 3.7 g N m-2 would be mineralized during the DR Y season from St. Augustinegrass with 40 g kg-1 and 100 g kg-1 SOM, respectively. Mineralization resulted in significant N contribution. For example, sod with 100 g kg-1 SOM contributes 7.5 g N m-2 over the season, or approximately one half of what was applied by fertilizer at a general rate of 15 g N m-2 per season. The N budgets in Tables 2-32 and 2-33 summarizes seasonal N inputs from rainfall, irrigation, SOM and fertilizer rate s as well as N losses from leaching and harvested in leaf blades. With the excepti on of St. Augustinegrass associated with 100 g kg-1 SOM during the WET season, St. Augustinegra ss maintained with the greater N rate had the lowest unaccounted N balance compared to the other two N rates and reflects the greater N losses from leaching and harvests fr om the high N rate (Tables 2-32 and 2-33). Unaccounted N losses from St. Augus tinegrass associated with 100 g kg-1 SOM and fertilized with the 10.0 g N m-2 bimonthly during the WET season were greater than unaccounted losses from the 2.5 g N m-2 bimonthly rate under the ADJ irrigation schedule and greater than both lower N rates under the FIX irrigati on schedule (Table 232b). Furthermore, during this time, there wa s less unaccounted N from the FIX irrigation schedule than the ADJ schedule (Table 232b). This may suggest maximum productivity

PAGE 61

45 of the soil microbial community with a combination of the WET season and the FIX irrigation schedule. There are a couple possible reasons why there was greater unaccounted N in St. Augustinegra ss maintained with the higher N rate. Possibly more N was available than the microorganisms require d and as well as past luxury consumption. Alternatively, perhaps the extra N increased mineralization more than immobilization. During the DRY season, only 3% unaccounted N and a surplus of losses were documented from St. Augustinegrass maintained with the high N rate and FIX irrigation schedule for the 40 g kg-1 and 100 g kg-1 SOM, respectively (Tab le 2-33). During this time of year, soil microbial activity was mo st likely dependent on irrigation and N availability. Perhaps at the high N rate, mi crobial productivity increased mineralization and subsequent available N for pl ant uptake or to be leached. The high unaccounted for N balance may par tially have resulted from not sampling frequently enough during times of high percolat e. However, this is unlikely since the sampling frequency did capture pulses of N l eaching during rain events especially when they occurred within the first two weeks following fertilization. The unaccounted for N balance may be expl ained by pools that were not measured in this study. For example, wh ile the greatest [N] are typically found in leaf blades, other plant parts such as roots and verdue as well as thatch also contain N. In Petrovics review of the fate of nitrogenous fert ilizers applied to turfgrasse s (1990), he summarizes reports of anywhere from 1 to 39% N can be found w ithin these pools. Besides [N] within thatch, thatch can also cause increased NH3 volatilization, which was unaccounted for in this study. However Volk (1959) found NH3 volatilization was greater from turfgrass than from bare soil, with volatilizat ion rates up to 30%. The higher NH3 volatilization rates from turfgrass may be attributed to docume nted high urease activity in the thatch layer

PAGE 62

46 (Bowman et al., 1987). Furthermore, Petrovic (1990) reviewed various studies that documented NH3 volatilization was greater from turf grass that is not irrigated after fertilizer is applied compared to turf that was irrigated (Bowman et al, 1987; Titko et al., 1987; Sheard and Beauchamp; 1985). In this rese arch, N fertilizer was not irrigated until the next scheduled irrigation, leaving approximately 24 h for volatilization to occur. Loss of fertilizer-N may also have been through denitrification. This would have been likely during the WET season and / or under the FI X irrigation schedule when soils are near saturation or saturated. Under th ese conditions soils become anaerobic, and NO3-N is reduced by microorganisms to gaseous nitrogen compounds that are lost to the atmosphere (Brady and Weil, 2002; Cisar et al., 1991). In a 2002 study, Horgan et al. documented denitrification to account for up to 27.2 % of total fert ilizer N applied to Kentucky bluegrass ( Poa pratensis L.). Varying the coating weight (thickness) of a coated fertilizer determines the amount of N released (Peacock and DiPaola, 1992; Fr y et al., 1993). Prill lock-off occurs when the outer coating is too thick, not allowing N to be totally released from the core. Prill lock-off within SCU may have also accounted for part of the N that was not recovered. Cisar et al. (2005) reported 10% of N remaini ng in SCU prills after an 8 wk period when applied in screen packets to Tifway bermudagrass. Lastly, the unexplained balan ce of N may have also been in urea-N form which was not measured in this study. Wang and Alva ( 1996) observed urea-N losses within 5 days after applying urea based fertilizers to unc overed Central Florida sand soils that were similar to the Margate fine sand soil in th e present study. These urea -N losses attributed 27-35.5% of total N in leachate. However Urea-N losses would be expected to be less in this study since the fertilizer was applied to a turfgrass system containing thatch.

PAGE 63

47 Conclusions This study examined how management stra tegies influence [N] and leaching from recently established St. Augus tinegrass. All management factors influenced [N] and leaching and / or turfgrass quality and growt h, thus all null hypotheses were rejected. The rate of N applied and g kg-1 of SOM associated with sod influenced leaching losses the greatest. Fertilizing St. A ugustinegrass at the 10.0 g m-2 bimonthly exceeded the optimal N fertilization for St. Augustinegrass and resulted in N leaching up to 5.6 times greater than the leaching documented from the current recommendation rate of 5.0 g m-2 bimonthly. Soil organic matter was a N pool for plant uptake. Cisar et al. (1992) documented that St. Augustinegrass grown on or ganic soils (Histosols) in south Florida did not require any additional N fertilizati on due to what was supplied by the SOM. While the soil organic matter content found in so ils in this study were much less than soil organic matter within Histosols, it was ev ident that SOM was an important N pool for plant uptake. Contrary to conventional wisdom, other than when there were intense rain events or rainfall occurring shortly after a fertilizat ion event, rainfall during the WET season did not dictate [N] and leaching. Snyder and ot hers (1980) also documented greater N leaching when fertilizer was applied to berm udagrass between rainfall events in South Florida. Instead, this research documen ted that St. Augustinegrass growth (as documented by clipping yield) dictated N leaching during the WET season. During active growth, fertilizing beyond the 5.0 g m-2 bimonthly resulted in a greater abundance of NO3-N to be present within the soil profile th at was prone to leaching regardless of the amount of SOM associat ed with the sod.

PAGE 64

48 Two important interactions influenced [N ] and leaching during the dry season: (a) there was higher [N] and leaching from the St. Augustinegrass associated with 100 g kg-1 SOM than the St. Augustinegrass associated with 40 g kg-1 SOM at the high fertilization rate, and (b) there was leaching from the St Augustinegrass fertiliz ed at the 5.0 and 10.0 g m-2 bimonthly rates maintained with the FIX irrigation schedule compared to St. Augustinegrass maintained at the ADJ irrigation schedule. In both ca ses, differences in soil moisture were likely influencing [N] and leaching. Besides increasing water holding capacity, SOM influences soil structure (B rady and Weil, 2002). A lthough the microbial community was not assessed in this study, othe rs have documented the influence of soil water on N mineralization (Casey et al., 2002; Skopp et al., 1990). Furthermore, as postulated by Morton et al. (1988), excess N may be found in the root zone and potentially leach during times when plant uptake is reduced due to dormancy (dry season). The increased [N] and leaching docum ented during the DRY season in this study for St. Augustinegrass with 100 g kg-1 SOM maintained with the FIX irrigation schedule may have been under similar conditions as these previous studies documented. Perhaps the increased SOM and irrigation contributed to a greater presence of N to be mineralized and a greater water holding capacity; both of which increa sed microbial activity and ultimately increased mineralization and the amount of NO3-N within soil solution that would be potentially be availabl e for plant uptake or leached. In this study, monthly management in irrigation scheduling reduced leaching during dry season months. This can be attrib uted to less N mineralization and slower downward movement through the soil profile. Past research had documented that increasing irrigation increased N leaching (Bowman et al., 1998; Morton et al., 1988;). Morton et al. (1988) examined combinat ions of irrigation and N rate on [NO3-N] and

PAGE 65

49 leaching. The authors maintained a mixture of Kentucky bluegrass ( Poa pratensis L.) and red fescue ( Festuca rubra L.) on hydrologically separated plots with either irrigation applied to prevent drought stress and leachi ng, or over-irrigating, and fertilized with a combined readily available and controlled-release N fertilizer at rates of 0, 97, or 244 kg N ha-1 yr-1. The authors reported higher mean a nnual N concentrations and N leaching from over-watered turfgrass in comparison to the unfertilized controls, yet no differences between fertilized, scheduled irrigated turf grass and the controls. In another study by Devitt et al. (1976), the influence of irrigati on quantity was indirectly demonstrated by documenting that NO3-N movement through the soil was related to the amount of percolate. Root weight densities were strongly infl uenced by irrigation scheduling during the dry season. The greater root we ight densities in St. Augustin egrass maintained with the more conservative irrigation schedule (ADJ) re flects that plant demands were satisfied with a shallow root system. The high potential of leaching when St. Augustinegrass was excessively-irrigated during the dry season suggested that irrigation systems in S outh Florida need to have separate zones for St. Augustinegrass and ot her plants such as bedding plants planted periodically. It is common for showy flower ing annuals to be planted during the dry season which can require more irrigation than that of the St. Augustinegrass. If on the same zone, N leaching from the St. Augustinegrass could be an adverse impact to the groundwater. In this experiment, regardless of time of year, in all cycles and for all sources, [NO3-N] and leaching due to N sources peaked shortly after fert ilization and did not follow any type of consistent trend for [N ] and leaching. While some studies have found

PAGE 66

50 similar results (Petrovic, 2004; Geron, et al., 1993, Sheard et al., 1985), other studies have reported less N leaching from controll ed release products. In a previous study, Snyder, et al. (1976, 1980) demonstrated de creased N leaching from bermudagrass turf grown on sand soils fertilized with slow re lease N sources as compared to a soluble source. A variety of controlled-release materi als with different N release characteristics were compared in their study (1976). Petr ovic (2004) documented a decrease in N leached from Kentucky bluegrass when ferti lized with controlled release N products in comparison to calcium nitrate for two years out of a three-year study. However there was no difference in N leaching between the cont rolled release N products. In one study SCU released N more rapid than other controlled or slow release N s ources (Carrow et al., 2001). Perhaps the high temperatures and hum idity that persist in South Floridas environment to some extent negate the cont rolled release characteristics of different N sources. Nitrogen sources also had minimal infl uence on St. Augustinegrass quality and growth. Cisar et al. (2001) observed similar responses of ve ry few consistent quality and clipping yield differences between various controlled release and readily available N sources when applied to bermudagrass in S outh Florida. In anot her study, bermudagrass fertilized with readily available N sources had similar growth rates, N uptake rates and visual quality to bermudagrass fertilized with natural organic slow-release N sources (Sartain, 1992). While other studies have found similar results (Geron, et al., 1993), results may have been different if N sources with other N release characteristics were investigated. For example, differences can be a ttributed to different release characteristics of the N sources, and weather conditions, but ove rall their results were in agreement with results found in this study for the WET s eason, which were that no one N source out-

PAGE 67

51 performed all other N sources through out the experimental period. During the DRY season, turf quality was greater in St. Augustinegrass fertilized with the SCU source and clipping yield was greater from both the St. Augustinegrass fertilized with SCU and with the BLEND sources. Hummel and Waddington ( 1984) documented a similar response in Kentucky bluegrass fertilized with SCU. These authors observed greater N in fall clippings from turf fertilized with SCU begi nning in the previous spring. Sulfur coated urea products vary in coa tings and thus release ch aracteristics depend on the manufacturer. This experime nt tested only one SCU produc t, and other SCU products may result in different findings. As previously discussed, there are many possi ble fates of N that were not measured in this study. However, the N unaccounted for was most likely due to NH3 volatilization and denitrification. Ammonia volatilization from ammonia based and ammonia forming fertilizers was dependent on soil characteristics including soil moisture, pH and CEC, and on meteorological conditions such as rainfa ll, humidity and temperature (Ernest and Massey, 1960; OToole et al., 1982; Sigunga et al., 2002). With high temperatures, humidity and high soil pH, South Fl oridas climate is conducive to NH3 volatilization and while not measured in this study, NH3 volatilization was likely a major component of the N balance that was not quantified. Based on this study, the following manageme nt strategies for St. Augustinegrass are suggested for maintaining quality turfgra ss while reducing potential adverse impacts to the environment: (i) recen tly established St. Augustineg rass should be fertilized bimonthly at the current recommended rate of 5.0 g m-2 during the wet season, (ii) dry season fertilizer application ra tes need to account for the amount of SOM associated with the sod. (iii) irrigation should be adjusted at least on a seasona l basis if not monthly, (iv)

PAGE 68

52 void irrigations after rain fall events either manually or by using a rain shut-off sensor, and (v) make sure St. Augustinegrass and a nnual bedding plants are on separate irrigation zones.

PAGE 69

53 Table 2-1. (a) Explanation of experimental factors tested and (b) ANOVA table used for statistical differences determination. (a) Factor Treatment Description Soil Organic Matter (Main Plot) 40 g kg-1 100 g kg-1 40 g kg-1 SOM associated with sod 100 g kg-1 SOM associated with sod. Irrigation (Main Plot) Fixed Adjusted 125% maximum weekly ET over 3 applications (M-W-F). 125% weekly ET adjusted by month over 3 applications (M-W-F). Irrigation shut off when precipitation >0.84cm 24h prior scheduled irrigation. N Source (Sub Plot) Liquid urea Water-soluble urea Controlled-release Blend (Water-soluble + Controlled-release) Urea (46-0-0) dissolved in 3 liters water applied using CO2 sprayer. Granular urea (46-0-0) Granular Sulfur-coated urea [SCU] (39-0-0) 50% Urea + 50% SCU applied as granular N Rate (Sub Plot) 2.5 g m-2 bimonthly 5.0 g m-2 bimonthly 10.0 g m-2 bimonthly 15.0 g m-2 yr-1 30.0 g m-2 yr-1 60.0 g m-2 yr-1 (b) ANOVA table Source Rep Irrigation SOM SOM*IRR Main plot error Source Rate Source*Rate Irrigation*Source Irrigation*Rate SOM*Source SOM*Rate Irrigation*Source*Rate SOM*Source*Rate Irrigation*SOM*Rate Irrigation*SOM*Source Sub plot error Total df 1 1 1 1 3 3 2 6 3 2 3 2 6 6 2 3 50 95

PAGE 70

54 Table 2-2. Water budget from April 2001 to April 2002. Cycle (Date) Irrigation Regime Rainfall (mm) Irrigation (mm) Percolate (mm) ET (mm) 1 (10 Apr 01 11 Jun01) --Fixed Adjusted 238 ------677 410 --568 321 329 ----2 (12 Jun 01 13 Aug 01) --Fixed Adjusted 385 ------664 389 --619 344 423 ----3 (14 Aug 01 08 Oct 01) --Fixed Adjusted 400 ------588 410 --637 458 358 ----4 (09 Oct 01 10 Dec 01) --Fixed Adjusted 198 ------678 400 --539 271 334 ----5 (11 Dec 01 20 Feb 02) --Fixed Adjusted 148 ------649 309 --540 181 276 ----6 (12 Feb 02 24 Apr 02) --Fixed Adjusted 79 ------602 318 --386 117 261 ----Experimental period total (10 Apr 01 24 Apr 02) --Fixed Adjusted 1448 ------3858 2236 --3289 1692 1981 ----Table 2-3. ANOVA table for NO3-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 1.10 0.36 6.82 0.06 IRR 1 0.19 0.69 0.14 0.73 SOM*IRR 1 0.19 0.69 1.18 0.34 Source 3 0.61 0.62 1.52 0.22 Rate 2 27.08 <0.01 80.20 <0.01 Source*Rate 6 0.79 0.59 1.10 0.38 IRR*Source 3 0.35 0.80 1.25 0.30 IRR*Rate 2 0.24 0.79 0.07 0.94 SOM*Source 3 0.49 0.70 1.70 0.18 SOM*Rate 2 1.36 0.27 10.12 <0.01 IRR*Source*Rate 6 0.43 0.86 1.14 0.35 SOM*Source*Rate 6 0.44 0.85 1.59 0.17 SOM*IRR*Source 3 0.88 0.46 0.25 0.86 SOM*IRR*Rate 2 1.52 0.23 4.22 0.02

PAGE 71

55 Table 2-4. Interaction of SOM*IRR*Rate on NO3-N concentrations (mg l-1) during the DRY season. Significance values listed ar e for SOM differences within each N rate. N rate Irrigation 40 g SOM kg-1 100 g SOM kg-1 Within N Rate*IRR P value ADJ 0.45 b 1.90 b 1.00 FIX 0.59 b 2.38 b 1.00 2.5 g m-2 bimonthly Significance 1.00 1.00 ADJ 1.67 b 3.16 b 1.00 FIX 2.83 b 4.68 b 1.00 5.0 g m-2 bimonthly Significance 1.00 1.00 ADJ 7.68 ab 27.7 a <0.01 FIX 15.4 a 21.3 a 0.92 10.0 g m-2 bimonthly Significance 0.65 0.85 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-5. ANOVA table for total NO3-N leached for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 0.87 0.40 11.36 0.03 IRR 1 1.52 0.29 33.24 <0.01 SOM*IRR 1 0.05 0.83 0.16 0.71 Source 3 0.75 0.53 1.01 0.40 Rate 2 25.19 <0.01 120.46 <0.01 Source*Rate 6 0.80 0.57 0.63 0.71 IRR*Source 3 0.37 0.77 0.64 0.59 IRR*Rate 2 2.09 0.13 25.31 <0.01 SOM*Source 3 0.47 0.71 2.02 0.12 SOM*Rate 2 0.70 0.50 7.04 <0.01 IRR*Source*Rate 6 0.40 0.88 0.81 0.57 SOM*Source*Rate 6 0.41 0.87 1.90 0.10 SOM*IRR*Source 3 0.74 0.53 0.31 0.82 SOM*IRR*Rate 2 0.86 0.43 0.18 0.84 Table 2-6. Interaction of SOM*Rate on total NO3-N leached (g m-2) during the DRY season. Significance values listed are fo r SOM differences within each N rate. 40 g kg-1 SOM 100 g kg-1 SOM Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 0.61 a 0.61 2.61 a 2.22 0.92 5.0 g m-2 bimonthly 2.81 a 4.08 5.13 a 4.45 0.88 10.0 g m-2 bimonthly 15.1 b 12.0 25.8 b 13.9 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 72

56 Table 2-7. Interaction of IRR*Rate on total NO3-N leached (g m-2) during the DRY season. Significance values listed are for IRR differences within each N rate. ADJ FIX Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 0.70 a 0.84 2.52 a 2.23 0.95 5.0 g m-2 bimonthly 1.70 a 1.93 6.28 a 4.93 0.26 10.0 g m-2 bimonthly 10.8 b 10.12 30.1 b 9.89 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-8. ANOVA table for NH4-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY dfF value P valueF value P value SOM 1 0.00 0.97 0.00 0.97 IRR 1 31.96 <0.01 1.16 0.34 SOM*IRR 1 0.10 0.77 0.03 0.87 Source 3 0.53 0.66 0.11 0.96 Rate 2 2.48 0.09 1.58 0.22 Source*Rate 6 0.43 0.85 0.42 0.86 IRR*Source 3 0.71 0.55 0.56 0.64 IRR*Rate 2 0.07 0.93 1.31 0.28 SOM*Source 3 1.26 0.30 0.80 0.50 SOM*Rate 2 4.01 0.02 2.26 0.12 IRR*Source*Rate 6 1.39 0.24 0.84 0.55 SOM*Source*Rate 6 1.26 0.29 1.56 0.18 SOM*IRR*Source 3 0.27 0.85 0.67 0.58 SOM*IRR*Rate 2 5.10 <0.01 1.46 0.24

PAGE 73

57 Table 2-9. ANOVA table for total NH4-N leached for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY dfF value P value F value P value SOM 1 0.00 0.95 0.00 0.98 IRR 1 29.67 <0.01 1.25 0.33 SOM*IRR 1 0.11 0.76 0.04 0.85 Source 3 0.52 0.67 0.13 0.94 Rate 2 2.50 0.09 1.71 0.19 Source*Rate 6 0.42 0.86 0.42 0.86 IRR*Source 3 0.75 0.53 0.57 0.64 IRR*Rate 2 0.08 0.92 1.20 0.31 SOM*Source 3 1.23 0.31 0.77 0.51 SOM*Rate 2 3.95 0.03 2.38 0.10 IRR*Source*Rate 6 1.38 0.24 0.80 0.57 SOM*Source*Rate 6 1.26 0.29 1.52 0.19 SOM*IRR*Source 3 0.26 0.86 0.69 0.57 SOM*IRR*Rate 2 4.90 0.01 1.66 0.20 Table 2-10. ANOVA table for total inorga nic-N concentrations for WET and DRY seasons. Significant difference s are bold and italicized. WET DRY df F value P value F value P value SOM 1 0.79 0.42 8.43 0.04 IRR 1 3.73 0.13 30.34 <0.01 SOM*IRR 1 0.03 0.87 0.09 0.78 Source 3 0.97 0.42 1.04 0.38 Rate 2 26.66 <0.01 125.60 <0.01 Source*Rate 6 0.80 0.57 0.69 0.66 IRR*Source 3 0.56 0.64 0.54 0.66 IRR*Rate 2 2.26 0.12 26.62 <0.01 SOM*Source 3 0.42 0.74 1.99 0.13 SOM*Rate 2 0.34 0.72 5.34 <0.01 IRR*Source*Rate 6 0.53 0.78 0.57 0.75 SOM*Source*Rate 6 0.47 0.83 1.88 0.10 SOM*IRR*Source 3 0.64 0.59 0.25 0.86 SOM*IRR*Rate 2 1.94 0.15 0.27 0.76

PAGE 74

58 Table 2-11. Interaction of SOM*Rate on to tal inorganic-N concentrations (mg l-1) during the DRY season. Significance values lis ted are for SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 0.89 a 0.48 2.13 a 1.30 0.93 5.0 g m-2 bimonthly 2.23 a 2.75 3.67 a 2.71 0.88 10.0 g m-2 bimonthly 10.1 b 7.52 16.0 b 8.31 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-12. Interaction of IRR*Rate on to tal inorganic-N concentrations (mg l-1) during the DRY season. Significance values lis ted are for IRR differences within each N rate. FIX ADJ Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 2.10 a 1.30 0.92 a 0.54 0.95 5.0 g m-2 bimonthly 4.44 b 3.15 1.46 a 1.19 0.23 10.0 g m-2 bimonthly 19.0 c 5.86 7.05 b 5.73 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-13. ANOVA table for total total inorganic-N leached for WET and DRY seasons. Significant difference s are bold and italicized. WET DRY df F value P value F value P value SOM 1 0.78 0.43 9.67 0.04 IRR 1 3.54 0.13 29.68 <0.01 SOM*IRR 1 0.03 0.87 0.12 0.75 Source 3 0.97 0.41 1.08 0.37 Rate 2 26.27 <0.01 123.48 <0.01 Source*Rate 6 0.80 0.57 0.70 0.65 IRR*Source 3 0.55 0.65 0.61 0.61 IRR*Rate 2 2.19 0.12 24.58 <0.01 SOM*Source 3 0.42 0.74 1.92 0.14 SOM*Rate 2 0.34 0.72 6.31 <0.01 IRR*Source*Rate 6 0.52 0.79 0.71 0.64 SOM*Source*Rate 6 0.47 0.83 1.88 0.10 SOM*IRR*Source 3 0.63 0.60 0.26 0.85 SOM*IRR*Rate 2 1.92 0.16 0.30 0.74

PAGE 75

59 Table 2-14. Interaction of SOM*Rate on total inorganic-N leached (g m-2) during the DRY season. Significance values listed ar e for SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 1.44 a 0.77 3.55 a 2.24 0.93 5.0 g m-2 bimonthly 3.62 a 4.26 6.10 a 4.64 0.86 10.0 g m-2 bimonthly 16.3 b 12.2 26.7 b 13.8 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-15. Interaction of IRR*Rate on total inorganic-N leached (g m-2) during the DRY season. Significance values listed are for IRR differences within each N rate. FIX ADJ Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 3.49 a 2.22 1.49 a 0.92 0.94 5.0 g m-2 bimonthly 7.35 b 5.10 2.37 a 1.93 0.22 10.0 g m-2 bimonthly 31.2 c 9.71 11.9 b 10.11 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-16. ANOVA table for mean quali ty scores for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 141.26 <0.01 19.88 0.01 IRR 1 0.00 0.95 0.00 0.98 SOM*IRR 1 0.02 0.90 0.97 0.3811 Source 3 0.60 0.62 3.33 0.03 Rate 2 103.26 <0.01 100.61 <0.01 Source*Rate 6 1.38 0.24 0.61 0.72 IRR*Source 3 0.61 0.61 0.38 0.77 IRR*Rate 2 0.59 0.56 0.06 0.94 SOM*Source 3 0.25 0.86 0.30 0.82 SOM*Rate 2 10.54 <0.01 11.83 <0.01 IRR*Source*Rate 6 0.89 0.51 0.52 0.79 SOM*Source*Rate 6 1.00 0.43 2.00 0.08 SOM*IRR*Source 3 3.13 0.03 2.18 0.10 SOM*IRR*Rate 2 0.73 0.49 1.26 0.29

PAGE 76

60 Table 2-17. Interaction of SOM*Rate on tu rf quality scores during the WET season. Significance values listed are for SO M differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value (a) WET season 2.5 g m-2 bimonthly 6.3 a 0.3 7.5 a 0.3 <0.01 5.0 g m-2 bimonthly 7.1 b 0.3 7.9 b 0.3 <0.01 10.0 g m-2 bimonthly 7.9 c 0.3 8.3 c 0.3 0.01 (a) DRY season 2.5 g m-2 bimonthly 6.8 a 0.5 7.8 a 0.4 <0.01 5.0 g m-2 bimonthly 7.8 b 0.4 8.4 b 0.5 0.03 10.0 g m-2 bimonthly 8.5 c 0.3 8.7 c 0.3 0.95 Means with the same letter within a column and s eason are not significantly different at the 0.05 significance level. Quality was rated on a scale from 1 10, with 1 = dead, brown turf 6=minimally acceptable, 10= dark green healthy looking turf. Table 2-18. Interaction of SOM*IRR*Sour ce on turf quality scores during the WET season. Significance values listed ar e for SOM differences within each IRR*Source combination. Source Irrigation 40 g SOM kg-1 100 g SOM kg-1 Within IRR*Source P value Liquid ADJ 7.1 7.7 0.10 FIX 7.1 8.0 <0.01 Significance 1.00 0.95 Urea ADJ 7.0 8.1 <0.01 FIX 7.4 7.7 0.85 Significance 0.95 0.85 SCU ADJ 7.2 8.0 <0.01 FIX 7.1 8.0 <0.01 Significance 1.00 1.00 Blend ADJ 7.1 7.8 0.05 FIX 6.9 7.9 <0.01 Significance 1.00 1.00 Quality was rated on a scale from 1 10, with 1 = dead, brown turf 6=minimally acceptable, 10= dark green healthy looking turf.

PAGE 77

61 Table 2-19. ANOVA table for total dry cl ipping yield for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 241.37 <0.01 12.90 0.03 IRR 1 0.17 0.70 6.90 0.06 SOM*IRR 1 0.33 0.60 1.00 0.37 Source 3 0.72 0.55 5.36 <0.01 Rate 2 94.81 <0.01 114.89 <0.01 Source*Rate 6 0.53 0.79 1.52 0.19 IRR*Source 3 0.42 0.74 0.21 0.89 IRR*Rate 2 0.26 0.77 2.22 0.12 SOM*Source 3 0.66 0.58 0.46 0.71 SOM*Rate 2 3.42 0.04 6.80 <0.01 IRR*Source*Rate 6 0.23 0.97 0.25 0.96 SOM*Source*Rate 6 0.27 0.95 0.59 0.74 SOM*IRR*Source 3 1.07 0.37 0.43 0.73 SOM*IRR*Rate 2 0.31 0.74 2.92 0.06 Table 2-20. Interaction of SOM*Ra te on total clip ping yield (g m-2) during the WET season. Significance values listed are for SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 203 a 84 690 a 125 <0.01 5.0 g m-2 bimonthly 419 b 72 847 b 95 <0.01 10.0 g m-2 bimonthly 679 c 79 1014 c 146 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-21. Interaction of SOM*Ra te on total clip ping yield (g m-2) during the DRY season. Significance values listed are fo r SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 51 a 21 138 a 41 <0.01 5.0 g m-2 bimonthly 141 b 31 206 b 43 0.02 10.0 g m-2 bimonthly 249 c 61 260 c 49 0.99 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 78

62 Table 2-22. ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected on 01 August 2001. Significant di fferences are bold and italicized. 0 -15 cm 15 30 cm df F value P value F value P value SOM 1 2.24 0.14 3.76 0.12 IRR 1 0.11 0.74 1.14 0.35 SOM*IRR 1 0.15 0.70 0.06 0.82 Source 3 1.83 0.15 1.24 0.31 Rate 2 1.12 0.33 3.06 0.06 Source*Rate 6 1.21 0.31 1.35 0.25 IRR*Source 3 0.80 0.50 0.15 0.93 IRR*Rate 2 3.69 0.03 0.08 0.92 SOM*Source 3 0.44 0.72 0.48 0.70 SOM*Rate 2 0.13 0.88 0.58 0.56 IRR*Source*Rate 6 0.29 0.94 0.80 0.58 SOM*Source*Rate 6 0.86 0.53 1.91 0.10 SOM*IRR*Source 3 0.41 0.75 0.35 0.79 SOM*IRR*Rate 2 1.07 0.35 2.46 0.10 Table 2-23. Interaction of IRR*Rate on root weight density (g m-3) within the upper 0-15 cm of the soil from cores collected 01 August 2001. Significance values listed are for IRR differences within each N rate. FIX ADJ Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 2,241 a 628 2,827 a 976 0.03 5.0 g m-2 bimonthly 2,351 a 688 2,301 a 433 1.00 10.0 g m-2 bimonthly 2,767 a 722 2,385 a 568 0.65 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 79

63 Table 2-24. ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected on 01 August 2002. Significant di fferences are bold and italicized. 0-15 cm 15-30 cm df F value P value F value P value SOM 1 1.34 0.25 8.95 <0.01 IRR 1 0.26 0.62 4.90 0.03 SOM*IRR 1 1.00 0.32 0.82 0.37 Source 3 1.23 0.31 2.05 0.12 Rate 2 0.47 0.63 2.82 0.07 Source*Rate 6 0.85 0.54 1.24 0.30 IRR*Source 3 0.37 0.78 0.13 0.94 IRR*Rate 2 1.64 0.20 0.03 0.97 SOM*Source 3 0.24 0.87 0.68 0.57 SOM*Rate 2 0.17 0.84 0.64 0.53 IRR*Source*Rate 6 0.48 0.82 0.89 0.51 SOM*Source*Rate 6 0.50 0.81 2.59 0.03 SOM*IRR*Source 3 0.59 0.62 0.56 0.64 SOM*IRR*Rate 2 1.32 0.28 1.18 0.32 Table 2-25. Root weight densities (g m-3) from the 15-30 cm soil depth collected on 01 August 2002 were influenced by SOM*Sour ce*Rate interactions. Significance values listed are for SOM differences within each N Rate and N Source. 40 g kg-1 SOM 100 g kg-1 SOM Within Rate*Source P value UREA 153 a 382 a 0.16 LIQ 671 a 204 a <0.01 SCU 586 a 390 a 0.23 2.5 g m-2 bimonthly BLEND 764 a 357 a 0.01 UREA 560 a 221 a 0.04 LIQ 483 a 357 a 0.43 SCU 365 a 374 a 0.99 5.0 g m-2 bimonthly BLEND 348 a 484 a 0.39 UREA 467 a 178 a 0.07 LIQ 255 a 93 a 0.02 SCU 288 a 263 a 0.90 10.0 g m-2 bimonthly BLEND 475 a 433 a 0.79 Means with the same letter within a column compare rates within each N Source and are not significantly different at the 0.05 significance level.

PAGE 80

64 Table 2-26. ANOVA table for leaf blade N concetrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 8.07 0.05 18.9 0.01 IRR 1 1.25 0.33 0.15 0.72 SOM*IRR 1 0.20 0.68 1.75 0.26 Source 3 4.44 <0.01 5.93 <0.01 Rate 2 86.3 <0.01 105 <0.01 Source*Rate 6 1.47 0.21 0.78 0.59 IRR*Source 3 0.43 0.73 0.12 0.95 IRR*Rate 2 0.28 0.76 0.13 0.87 SOM*Source 3 1.40 0.26 0.31 0.82 SOM*Rate 2 1.72 0.19 5.45 <0.01 IRR*Source*Rate 6 0.78 0.59 0.39 0.88 SOM*Source*Rate 6 0.83 0.55 1.50 0.20 SOM*IRR*Source 3 0.52 0.67 0.63 0.60 SOM*IRR*Rate 2 0.41 0.67 3.04 0.06 Table 2-27. Nitrogen sources influenced leaf blade N concentrations (mg g-1) during both seasons. WET DRY Mean Std Dev. Mean Std Dev. UREA 18.3 b 0.19 20.6 bc 0.18 LIQ 18.6 b 0.15 20.4 c 0.23 BLEND 18.7 b 0.15 21.3 ab 0.25 SCU 19.2 a 0.18 21.6 a 0.23 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-28. Interaction of SOM*Rate for N c oncentrations within leaf blades (mg g-1) during the DRY season. Significance valu es listed are for SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 17.6 a 0.16 20.2 a 0.13 <0.01 5.0 g m-2 bimonthly 20.5 b 0.13 21.4 b 0.11 0.38 10.0 g m-2 bimonthly 22.5 c 0.07 23.6 c 0.13 0.29 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 81

65 Table 2-29. ANOVA table for nitrogen uptake efficiency for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 146 <0.01 24.2 <0.01 IRR 1 0.12 0.759 4.16 0.11 SOM*IRR 1 0.15 0.72 3.30 0.14 Source 3 1.15 0.34 4.49 <0.01 Rate 2 48.0 <0.01 26.5 <0.01 Source*Rate 6 0.65 0.69 0.34 0.91 IRR*Source 3 0.39 0.76 0.23 0.87 IRR*Rate 2 0.22 0.80 0.21 0.81 SOM*Source 3 0.86 0.47 0.97 0.41 SOM*Rate 2 46.6 <0.01 32.8 <0.01 IRR*Source*Rate 6 0.08 1.00 0.42 0.86 SOM*Source*Rate 6 0.17 0.99 1.38 0.24 SOM*IRR*Source 3 0.41 0.69 0.33 0.89 SOM*IRR*Rate 2 0.35 0.84 0.95 0.23 Table 2-30. Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the WET season. Significance values listed are fo r SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 52 a 23 184 a 36 <0.01 5.0 g m-2 bimonthly 57 a 12 122 b 17 <0.01 10.0 g m-2 bimonthly 51 a 6 78 c 11 <0.01 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 2-31. Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the DRY season. Significance values listed are fo r SOM differences within each N rate. 40 g kg-1 100 g kg-1 Mean Std Dev. Mean Std Dev. Within rate P value 2.5 g m-2 bimonthly 25 a 8 62 a 17 <0.01 5.0 g m-2 bimonthly 31 b 6 43 b 13 0.03 10.0 g m-2 bimonthly 26 a 6 30 c 8 0.37 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 82

66 Table 2-32. WET season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM. (a) 40 g kg-1 SOM ----------------ADJ-----------------------------FIX--------------Inputs Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0 Irrigation 1.6 1.6 1.6 2.5 2.5 2.5 40 g kg-1 SOM 3.0 3.0 3.0 3.0 3.0 3.0 Rain 1.0 1.0 1.0 1.0 1.0 1.0 Total 13.1 20.6 35.6 14.0 21.5 36.5 Losses accounted for Leaching 1.9 1.6 3.6 2.5 2.1 10.0 Harvested 4.5 8.1 14.1 4.4 9.4 14.8 Total 6.4 9.7 17.7 6.9 11.5 24.8 % Unaccounted 51 53 50 51 47 32 (b) 100 g kg-1 SOM ----------------ADJ-----------------------------FIX--------------Inputs Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0 Irrigation 1.6 1.6 1.6 2.5 2.5 2.5 100 g kg-1 SOM 7.5 7.5 7.5 7.5 7.5 7.5 Rain 1.0 1.0 1.0 1.0 1.0 1.0 Total 17.6 25.1 40.1 18.5 26.0 41.0 Losses accounted for Leaching 1.9 1.6 7.5 3.4 4.1 9.7 Harvested 13.9 16.6 21.4 15.0 18.3 21.8 Total 15.8 18.2 28.9 18.4 22.4 31.5 % Unaccounted 10 27 27 <1 14 23

PAGE 83

67 Table 2-33. DRY season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM. (a) 40 g kg-1 SOM ----------------ADJ-----------------------------FIX--------------Inputs Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0 Irrigation 1.3 1.3 1.3 2.5 2.5 2.5 40 g kg-1 SOM 1.5 1.5 1.5 1.5 1.5 1.5 Rain 0.4 0.4 0.4 0.4 0.4 0.4 Total 10.7 18.2 33.2 11.9 19.4 34.4 Losses accounted for Leaching 1.0 1.7 6.3 1.8 5.6 26.3 Harvested 2.1 4.5 8.6 2.3 5.1 6.9 Total 3.1 6.2 14.9 4.1 10.7 33.2 % Unaccounted 71 66 55 65 45 3 (a) 100 g kg-1 SOM ----------------ADJ-----------------------------FIX--------------Inputs Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0 Irrigation 1.3 1.3 1.3 2.5 2.5 2.5 100 g kg-1 SOM 3.7 3.7 3.7 3.7 3.7 3.7 Rain 0.4 0.4 0.4 0.4 0.4 0.4 Total 12.9 20.4 35.4 14.1 21.6 36.6 Losses accounted for Leaching 1.9 3.1 17.4 5.2 9.1 36.0 Harvested 5.2 7.7 8.6 4.4 5.4 7.9 Total 7.1 10.8 26.0 9.6 14.5 43.9 % Unaccounted 45 47 27 32 33 0

PAGE 84

68 0 20 40 60 80 100 120 04/10/0106/10/0108/10/0110/10/0112/10/0102/10/0204/10/02Experimental YearRainfall (mm day-1) Rainfall Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 Figure 2-1. Daily rainfall over the ex perimental period for Experiment 1.

PAGE 85

69 (a) WET (b) DRY Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Cumulative NO3-N leached (g m-2) 0 10 20 30 40 2.5 g N m -2 100 g kg-1 SOM 5.0 g N m -2 100 g kg-1 SOM 10 g N m -2 100 g kg -1 SOM 2.5 g N m -2 40 g kg -1 SOM 5.0 g N m -2 40 g kg-1 SOM 10 g N m -2 40 g kg-1 SOM Figure 2-2. Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass with 40 g kg-1 soil organic matter (SOM) to St. Augustinegrass with 100 g kg1 SOM for the three N rates during the study period. Arrows mark fertilization events.

PAGE 86

70 Figure 2-3. Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass maintained with the FIX irrigation schedule to St. Augustinegrass maintained with the ADJ irrigation schedule for the three N rates during the study period. Arrows mark fertilization events. (a) WET (b) DRY Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Cumulative NO3-N leached (g m-2) 0 10 20 30 40 2.5 g N m -2 FIX 5.0 g N m -2 FIX 10 g N m -2 FIX 2.5 g N m -2 ADJ 5.0 g N m -2 ADJ 10 g N m -2 ADJ

PAGE 87

71 Figure 2-4. Comparison of weekly NO3-N leached (g m-2) from St. Augustinegrass fertilized with the four N sources at the 5.0 g m-2 bimonthly rate during the study period. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark fertilization events. Study Period 04/01 06/01 08/01 10/01 12/01 02/02 04/02 NO3-N leached (g m-2) 0.0 0.2 0.4 1.0 1.2 1.4 BLEND LIQ SCU UREA Rainfall (mm d -1 ) 0 40 80 120 Rainfall

PAGE 88

72 Figure 2-5. Comparison of weekly NH4-N leached (g m-2) from St. Augustinegrass fertilized with the four N sources at the 5.0 g m-2 bimonthly rate and maintained with the ADJ irrigation sc hedule during the (a ) WET and (b) DRY seasons. Arrows mark fertilization events. (a) WET Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Cumulative NH 4 -N leached (g m -2 ) 0.0 0.5 1.0 1.5 2.0 2.5 BLEND LIQ SCU UREA (b) DRY

PAGE 89

73 Figure 2-6. Mean weekly flow weighted total inorganic-N concentrations (mg l-1) from St. Augustinegrass fertilized with the th ree N rates and maintained with the ADJ irrigation schedule during the (a ) WET and (b) DRY seasons. Arrows mark fertilization events. Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 [TN] (mg l-1) 0 10 20 30 40 50 2.5 g N m -2 bimo. 5.0 g N m -2 bimo. 10.0 g N m -2 bimo. (a) WET (b) DRY

PAGE 90

74 Figure 2-7. Mean weekly flow weighted toal inorganic-N concentrations (mg l-1) from St. Augustinegrass fertilized w ith the three N rates and maintained with the (a) FIX and (b) ADJ irrigation schedules during the DRY season. Arrows mark fertilization events. (b) ADJ 10/01 12/01 02/02 04/02 [TIN] (mg l-1) 0 20 40 60 80 100 (a) FIX [TIN] (mg l-1) 0 20 40 60 80 100 2.5 g N m -2 bimo. 5.0 g N m -2 bimo. 10.0 g N m -2 bimo.

PAGE 91

75 Figure 2-8. Comparison of weekly total inorganic-N leached (g m-2) from St. Augustinegrass fertilized with the thr ee bimonthly N rate during the (a) WET and (b) DRY seasons. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark fertilization events. (a) WET Study Period 04/01 06/01 08/01 10/01 12/01 02/02 04/02 Weekly TIN leached (g m-2) 0 1 2 3 4 5 2.5 g N m -2 5.0 g N m -2 10.0 g N m -2 Rainfall (mm d -1 ) 0 40 80 120 Rainfall (b) DRY

PAGE 92

76 Figure 2-9. Comparison of weekly total inorganic-N leached (g m-2) from St. Augustinegrass fertilized with the three bimonthly N rate maintained with the (a) ADJ and (b) FIX scheduled during the DRY season. Daily rainfall (mm d1) is on the secondary axis. Arro ws mark fertilization events. Study Period 10/01 12/01 02/02 04/02 Weekly TIN leached (g m-2) 0 1 2 3 4 5 6 7 (a) ADJ Weekly TIN leached (g m-2) 0 1 2 3 4 5 6 7 2.5 g N m -2 5.0 g N m -2 10.0 g N m -2 Rainfall (mm d -1 ) 0 25 50 75 Rainfall (b) FIX

PAGE 93

77 Figure 2-10. Quality scores of St. Augustinegrass associated with 40 g kg-1 and 100 g kg-1 soil organic matter (SOM) maintained at the three N rates over the (a) WET and (b) DRY seasons. Arrows mark fertilization events. Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Quality Score 3 4 5 6 7 8 9 10 2.5 g N m-2 100 g kg-1 SOM 5.0 g N m-2 100 g kg-1 SOM 10.0 g N m-2 100 g kg-1 SOM 2.5g N m-2 40 g kg-1 SOM 5.0g N m-2 40 g kg-1 SOM 10.0g N m-2 40 g kg-1 SOM (a) WET (b) DRY

PAGE 94

78 Figure 2-11. Quality scores of St. Augustinegrass fertilized with different N sources over the (a) WET and (b) DRY seasons. A rrows mark fertilization events. Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Quality Score 6 7 8 9 10 BLEND LIQ SCU UREA (a) WET (b) DRY

PAGE 95

79 Figure 2-12. Clipping yield (g m-2) of St. Augustinegrass fertilized with different N sources over the DRY season. DRY season 10/01 12/01 02/02 04/02 06/02 0 20 40 60 80 BLEND LIQ SCU UREA Clipping yield (g m-2)

PAGE 96

80 Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Leaf blade [N] (mg N g-1) 14 16 18 20 22 24 26 28 100 g kg-1 SOM 40 g kg-1 SOM (a) WET (b) DRY Figure 2-13. Comparison of leaf blade N concentration (mg N g-1) grown with 40 g kg-1 soil organic matter (SOM) and 100 g kg-1 SOM during the (a) WET and (b) DRY seasons. Arrows mark fertilization events.

PAGE 97

81 Figure 2-14. Comparison of leaf blade N concentrations (mg N g-1) grown from the four N sources during the (a) WET and (b) DRY seasons. Arrows mark fertilization events. Study Period 05/01 07/01 09/01 11/01 01/02 03/02 05/02 Leaf blade [N] (mg N g-1) 16 18 20 22 24 26 28 30 BLEND LIQ SCU UREA (a) WET (b) DRY

PAGE 98

82 Dry Season 10/01 12/01 02/02 04/02 Nitrogen Uptake Efficiency (%) 0 10 20 30 40 50 BLEND LIQ SCU UREA Figure 2-15. Comparison of cumulativ e nitrogen uptake efficiency (g m-2) from the four N sources during the DRY season. Arro ws mark fertilization events.

PAGE 99

83 CHAPTER 3 EFFECT OF IRRIGATION, N SOU RCES AND RATES ON N LEACHING, TURFGRASS QUALITY AND GROWTH FROM ESTABLISHED ST. AUGUSTINEGRASS LAWNS. Introduction Developing accurate fertilizer and irriga tion recommendations are important to maintain quality turfgrass, reducing water consumption, and the potential for fertilizer leaching into watersheds (Flipse et al., 1984; FDEP, 2002). Contamination by nitrogen (N) can lead to degradation of water quality. Responses in clude eutrophication, death or organisms, and shifts in plant species. Furt hermore, because south Florida wetlands are hydrologically-linked, other wetlands far fr om where the contamination originally occurred may be affected (Noe at al., 2001; Tilman et al., 1999; Davis, 1994; Ewel and Odum, 1984). Besides the potenti al threat to watersheds, el evated nitrate-nitrogen (NO3N) in drinking water is considered a cont aminant for human consumption if above the standard of 10 mg l-1 (USEPA, 1976). Nitrate-N is the preferred form of N for plant uptake (Taiz and Zeiger, 2002). However NO3-N it is an anion and it is mobile within the soil. The coarse textured sand soils characteri stic of southern Flor ida have little physical and chemical characteristics to retain N (Cisar et al ., 1991; Wang and Alva, 1996) and thus fertilizer applied to home lawns based on these sand soils have been implicated as a source of N pollution to adjacent watersheds (Cis ar et al., 2004; Erickson et al., 2001). The principal turfgrass used for home lawn s in south Florida is St. Augustinegrass Floratam ( Stenotaphrum secundatum (Walt.) Kuntze ). Previous studies have documented that St. Augustinegrass is a mode rate drought tolerant turfgrass (Qian and

PAGE 100

84 Engelke, 1999; Carrow, 1996) that is effec tive at minimizing nitrogen leaching (Bowman et al., 2002). Compared to other warm s eason turfgrasses grown in south Florida, St. Augustinegrass requires moderate fertility (Cisar et al., 1991). Current fertilizer recommendations for south Florida St. Augus tinegrass lawns is between 15 to 30 g N m-2 per year (Trenholm et al, 2002; Cisar et al., 1991). T urfgrass fertilization with a controlled or slow release N source is one way to potentially reduce N leaching (Fry et al., 1993; Sartain 1992; Petrovi c, 1990; Brown et al., 1982). Often, water-soluble urea is coated to provide a controlled release source of N (Cisar et al., 2001). Many of these coatings re lease the N fertilizer at a controlled rate by water penetrating through small micropores a nd imperfections in the coatings, or by the coating degraded by microbial activity. The release of controlled and slow re lease N sources depends on how the source releases the N, interactions in the environm ent, and cultural management (Cisar et al, 2001, Snyder et al., 1976, Snyder et al., 1980, Mo rton et al., 1988). Isobutylidene diurea (IBDU) is a slow release fertilizer that has been shown to reduce N leaching due to its uniform slow release rate (Brown et al., 1982). However, in south Florida, spring and summer intense rainfalls result in a quick N release from IBDU since its N release is controlled by dissolution, as well as for coated prills that depend on water penetrating and induce swelling of small pores (Sartain, 2001). While there are now ma ny different types of coated urea products available for turf ma nagers to choose from, sulfur coated urea (SCU) is still a main product used (Cisar et al., 2001). Sulfur coat ed urea are urea prills covered with sulfur/wax/condi tioner layers. Nitrogen sour ces controlled by microbial action such as Milorganite and ureaforma ldehyde, will quickly release N during high temperatures when microbial activity is grea test. By applying a microbial activated N

PAGE 101

85 source in the fall and early spring may ensu re a long term N release, applying them during the winter may result in insufficient amounts of N release. Quick and controlled release N sources are often blended in fertil izers to obtain a fast plant response, while supplying N for an extended period of time (Cisar et al., 2001). Morton et al. (1988) attributed the greatest N losse s from turfgrass fertilized with a blended N fertilizer during the summer when percolation events were more frequent, suggesting that the soil was often at field capacity and continuous rainfa ll events flushed N through the soil profile rapidly. Controlled release N sources also are reported to maintain acceptable quality over a longer period of time and greater yields in comparison to water soluble N sources (Snyder et al., 1980; A llen et al., 1971). Irrigation is a management fact or that is often linked to N leaching (Spalding et al., 2001; Morton et al., 1988; Peacock and Dud eck, 1985; Snyder et al., 1984). Research has suggested that determining when turfgrass needs to be irrigated can be assessed by visually recognizing when th e grass is stressed (Trenholm et al., 2003; Connellan, 2002). However to this authors knowledge, there has been no documentation on how this type of irrigation scheduling influences N leaching and turfgrass response. This study was conducted to investigate the impact of a range of potential management parameters including reduced N fertilization, readily so luble and controlled release N sources, and redu ced irrigation on N leaching from established St. Augustinegrass turf. The objectives were to determine how N sources, N rates and irrigation scheduling influence N concentra tions and leaching, turfgrass quality and growth from established St Augustinegrass, (b) to deve lop a nitrogen budget under different management scenarios, and (c) to give management st rategy recommendations to minimize potential adverse impacts to the environment.

PAGE 102

86 Materials and Methods An experimental field was constructed with St. Augustin egrass Floratam at the University of Floridas Fort Lauderdale Resear ch and Education Center to collect vadose zone percolate and monitor turfgrass quali ty in the fall of 2000. Ceramic-cup water samplers were inset in the native Margate fi ne sand soil (siliceous, hyperthermic Mollic Psamnaquent) in the center of each subplot at 40 cm depth for the purpose of collecting vadoze zone water samples. St. Augustinegra ss sod was planted in December 2000 with the first experiment beginning in April 2001. S ee Chapter 1 for specific details regarding construction, stabilization and sod establishment of the experi mental facility and Chapter 2 for discussion of management strategies for recently established St. Augustinegrass. The experiment discussed in this Chapter was initiated on 07 Marc h 2003 with treatment selection based on results from Experiment 1 and comprised of eight plots of eight 3.0 by 4.0 m sub plots (for a tota l of sixty four plots). The study was conducted as a balanced bloc k design with two replications, each consisting of four main plots in which each c onsisted of having eight sub plots. Assigned to the main plots within each REP was tw o, 2-level factors in a factorial layout Irrigation by soil organic matter. Assigned to the eight sub plots with in each main plot were two factors in a factoria l design, fertilizer source at four levels crossed with fertilizer rate at two levels. Soil organic matter differences brought in with sod pieces were not expected and thus treated as a random variable. The amount of soil organic matter within the sod when sod was installed was either 40 or 100 g kg-1 SOM. Each main irrigation block followed either an adjusted (ADJ) or wilt-only (WO) irrigation schedule: Adjusted irrigation: irrigating at a rate equivalent to 125% weekly ET adjusted monthly. The 125% maximum week ly ET rate was calculated by taking the

PAGE 103

87 month with the highest ET based upon the temperature based McCloud method (McCloud, 1955), adding 25% and dividing by four. The 125% rate was applied to overcome any variability in di stribution uniformity such as immediate evaporation and by wind drift. Irrigation for the week was split in to three applications to simulate a Phase I Water Use Restriction for established resi dential landscapes. The Phase I Water Use Restriction allows for irrigati on to be applied three designa ted days a week (SFWMD). Adjusted irrigation plots were not irrigated until the next sche duled irrigation when a rain event (0.84 cm of rain or greate r) occurred the day prior to ir rigation (i.e. if a rain event occurred on Tuesday, then no irrigation applied until Friday). Wilt-only irrigation: irrigating at a rate equivale nt to 125% weekly ET divide d by three adjusted monthly when only when wilt was observed. Eight 2-month cycles were initiated by a pplying one of four N sources to individual sub plots (Table 3-1). All N sources were granular as either 100% water-soluble N (UREA, 46-0-0), or a blend of the wate r soluble N with a slow-release N using Isobutylidene diurea (IBDU, 31-0-0). These N sources represented both what is easily available for homeowners to purchase and or wh at may be beneficial if they were to be available to the public for purchase. Based on the first experiment (Chapter 1) the high N rate of 60.0 g N m-2 yr-1 which represented twice the current ge neral recommendation of 30 g m-2 yr-1 (Ruppert and Black, 1997) resulted in NO3-N and NH4-N leaching not conducive to minimizing potential adverse effects to the environment. Based on these conclusions the N treatments applied in this trial were the recommended rate of 30 g m-2 yr-1 or half the recommended rate (15 g m-2 yr-1). A summary of experimental factors tested are found in Table 3-1(a) with the ANOVA table of fact ors and interactions tested in Table 3-1b.

PAGE 104

88 Since SOM was not a planned factor, SOM a nd irrigation schedules were not tested together for interactions with other factors (Table 3-1b). Phosphorous and potassium was applied just prior to N fertilizer applications for cycles 1, 3, 5, and 7 at a rate of 5 g m-2. The plots were mowed with a rotary push mower approximately every two weeks in the summer and every three weeks during the winter. The mowing height was set at 7.5 cm excep t during the summers of 2003 and 2004 when the height was raised to decrease mowing fr equency. Prior to mowing events, clippings were removed from a 1m2 area from each sub plot. Clippings were dried at 110 oC and weighed to determine treatment effect on below ground growth. Additionally, all clippings from a cycle for each season (cycles 3 and 5 for WET and DRY seasons, respectively) were sent to University of Fl oridas Analytical Research Laboratory for the determination of total Kj edahl Nitrogen (EPA #351.2). On two dates (04 August 2003 and 27 April 2004), 10 cm in diameter root cores were collected to a 30 cm depth. On the 27 April 2004 collection date pelts were also collected to examine factor influence on ver due and thatch collectively. The cores were portioned into 0-15 and 15-30 cm sections. R oots and pelts were washed clean of any soil. Roots and pelts were dried at 110 oC, weighed, ashed in a muffle furnace at 550 oC, and reweighed. Rainfall was recorded with a rain gauge located adjacent to the experimental area. Periodically, nitrate and a mmonium concentrations (h ere after denoted as [NO3-N] and [NH4-N], respectively) were determined in irri gation and rainfall. All water samples were preserved on premises and analyzed fo llowing EPA approved methods (QuickChem #10107-04-1-8 and 10-107-06-2-8) by using Contin uous Flow Injection Colorimetry (Hach, Colorado) at the University of Florida Belle Glade Research and Education Center and

PAGE 105

89 the Fort Lauderdale Research and Educati on Center. Daily percol ate was calculated by the following calculation developed by Snyde r et al. (1984): Perc olate = Irrigation + Rainfall ET. Daily nutrient loading was determined by multiplying the concentration of each nutrient found in the daily percolate sa mple per plot by the calculated volume of percolate for the respective period. Nutrient loading for the cycl e was the sum of all daily N loading. Weekly mean nitrate, ammonium and total inorganic nitrogen concentrations (here after denoted as [NO3-N], [NH4-N] and [TIN] respectively), were calculated as flow weighted averages by di viding weekly leachate divided by total weekly percolate. Turfgrass quality was visually observed a nd rated for each sub plot on a scale from 1 to 10, with 1 = dead/ brown turf, 6 = minimally acceptable turf, and 10 = dark, green turf. Nitrogen uptake efficiency (NUE) and N budgets were calculated for cycles 3 and 5. Nitrogen uptake efficiency was calculated as leaf blade [N] multiplied by total clippings, divided by N applied from fertilizer. The experiment was initially to be conducte d as six 2-month cycles for a total of a one-year period. However, after NO3-N analysis was found to be incorrect for the first two cycles, two additional cycles were conducted. Cycles were statistically se parated by the total amount of rainfall during the cycle into one of two seasons: wet (WET), and dr y (DRY). Identification of statistically significant treatment effect s for average seasonal [NO3-N], [NH4-N], [TIN], and NO3-N, NH4-N, TIN leaching, leaf blade [N], NUE, turfgr ass quality scores, clippings yields, root weight densities and pelt we ights were determined using SAS MIXED model procedures with lsmeans compared using Tukey-Kramer multiple comparison test (SAS Institute,

PAGE 106

90 1989). Because the strength of the analysis of the design is primarily on the sub plot, only the highest order interactions are discussed. If no interact ions were significant, then significant factors are discussed separately. On ly significant factor a nd interaction effects are discussed. Results and Discussion Water Budget South Florida is characterized as having a rainy season th at usually begins in May and ends in October followed by a dry seas on from November to April, although it is common that the seasons may start or end a month early or late. Rainfall patterns were relatively unusual. In 2003, the wet season began early with more frequent rainfall beginning in April which continued until the beginning of October when drier conditions persisted until at the end of the month when over 180 mm of rain occurred over a two week period (Cycle 1 through P4, Figure 3-1). Based on results from the first experiment (Chapter 2) in which it was concluded that fertilizer leaching potential was greatest within the first two weeks fo llowing fertilizer application, fertilizer application for initiating cycle 5 was delayed until the frequent rains were forecasted to end. After these two weeks, cycle 5 was initiated (13 Nove mber 2003), and was followed by an extended dry season which lasted through to the first we ek in July 2004 (Figure 3-1). By mid July, the frequent rains made for an unusually brie f transition to the wet season (Figure 3-1). Overall, a total of 2267 mm of rainfall occurred over the 18-month experimental period (Table 3-2). The WET season in which the experimental period included was characterized by frequent afternoon showers, sometimes intense. Rainfall in August 2003, and September 2004 was dictated primarily by weather produced by tropical

PAGE 107

91 activity including Hurricanes Charley and Franci s. The greatest rain event occurred in Cycle 2 on 27 May when over 100 mm of rain wa s recorded at the e xperimental facility (Table 3-2, Figure 3-1). Duri ng the dry season encompassing Cycles 5-7, only 15 mm of rainfall occurred during the two month peri od of Cycle 5 (Table 3-2). While 179 and 100 mm of rainfall accumulated during Cycles 6 a nd 7 respectively, the majority occurred as infrequent short yet intense rain events (F igure 3-1). For example, during Cycle 6, 67 mm of rainfall occurred on February 1st alone, comprising of 34% of the total rainfall for that cycle (Figure 3-1). Total cycl e rainfall quantities were used to statistically separate the Cycles into WET or DRY seasons. Because over a third of the rainfall total for Cycle 6 was from one rain event (01 February) statis tical separation into seasons was performed using the total minus this rain event for Cycl e 6 (total used = 112 mm). Rainfall separated Cycles 2, 3, 4 and 8 into WET (mean = 384 mm cyc-1), and Cycles 1, 5, 6 and 7 into DRY (mean = 110 mm cyc-1, P=0.04). Besides rainfall, turfgrass received wate r by scheduled irrigations. Over the 18 mo experimental period, St. Augustinegrass main tained with the WO irrigation schedule received 2,151 mm of irrigation, compared to the 3,483 mm of water that turfgrass received from ADJ irrigation (Table 3-2) By utilizing the WO irrigation schedule, between 0 85% less water was applied per cycle depending on season and time since the initiation of the experiment (Table 32). While reduced water consumption was documented from the WO irrigation schedule fo r the first four cycles, this irrigation schedule produced a plant stand that wilted more frequently and had a decreasing visual density as time progressed. Therefore, irrigation had to be increased in order to keep the St. Augustinegrass from wilting. This resulted in similar water quantities applied for the two irrigation schedules for cy cles 5-7, and then the irrigation was once again reduced for

PAGE 108

92 the St. Augustinegrass maintained with the WO irrigation in cycle 8. Moreover, the less irrigation applied from the WO schedule ove r the experimental pe riod resulted in 55% less calculated percolate compared to turf maintained with the ADJ irrigation (1,777 and 3,908 mm for WO and ADJ, respectively). As expected, hot diurnal temp eratures of the summer m onths resulted in frequent convection-based storms of the wet season, at which time total cycle ET was the highest for Cycles 2-4, and 7-8 (Table 3-2). Evapotrans piration was lowest in cycles 5 and 6 with 191 and 194 mm respectively, most likely due to the cooler temperatures that persist during the dry season months (Table 2-2). Nitrate Concentrations and Leaching The season influenced [NO3-N] (P<0.01). Mean [NO3-N] during the WET season was 1.33 mg l-1 and ranged from 0.08 to 6.01 mg l-1. This was approximately 71% lower than mean [NO3-N] found during the DRY season (mean = 4.72 mg l-1 with a range of 0.13 to 41.23 mg l-1). Nitrate concentrations were influenced by an interaction of SOM*Source*Rate during the WET season and ther e was no factor or interactions that influenced DRY season [NO3-N] (Table 3-3). Although there was a general trend for St. Augustinegrass with 100 g kg-1 SOM having higher [NO3-N] than St. Augustinegrass with 40 g kg-1 SOM, no statistical differences were determined (Table 3-4). The third order interaction effect documented greater [NO3-N] from St. Augustinegrass with 100 g kg-1 SOM fertilized with 75% UREA/25% IBDU at the high N rate in comparison to all N sources and rates from St. Augus tinegrass associated with 40 g kg-1 SOM except for the 100% UREA N source (P<0.01). Also St Augustinegrass associated with 40 g kg-1 SOM fertilized with the 100% UREA at the high N rate had higher [NO3-N] than all other N sources regardless of rate (P<0.01, Table 3-4).

PAGE 109

93 The SOM*Source*Rate also influenced the amount of NO3-N leached during the WET season (Table 3-5). Similar to [NO3-N], NO3-N leaching in general was greater from St. Augustinegrass with 100 g kg-1 SOM compared to St. Augustinegrass with 40 g kg-1 SOM. However NO3-N leaching was not greater for St. Augustinegrass with the 100 g kg-1 SOM compared to St. Augus tinegrass with the 40 g kg-1SOM (Table 3-6, Figure 3-2). The third order interac tion effect documented greater NO3-N leaching from St. Augustinegrass with 100 g kg-1 SOM fertilized with 75% UREA/25% IBDU at the high N rate in comparison to all N sources and rates from St. Augustinegrass with 40 g kg-1 SOM except for the 100% UREA N source (P<0 .03). Also St. A ugustinegrass with 40 g kg-1 SOM fertilized with the 100% UREA at the highest N rate had greater NO3-N leaching than all other N sources regardless of rate for St. Augustin egrass with the 40 g kg-1 SOM (P<0.01, Table 3-6). The rate at which fertilizer wa s applied influenced DRY season NO3-N leaching with NO3-N leaching from the 5.0 g N m-2 rate greater than NO3-N leaching from the 2.5 g N m-2 rate (2.4 and 1.0 g N m-2 respectively, P<0.01, Figure 3-3). Ammonium Concentrations and Leaching WET season [NH4-N] ranged from 0.22 to 4.49 mg l-1 with a mean concentration of 1.63 mg l-1. DRY season [NH4-N] were lower than that measured during the WET season (P<0.01) ranging from 0.17 to 2.41 mg l-1 with a mean concentration of 0.90 mg l-1. During the both seasons, the interacti on of IRR*Source*Rate influenced [NH4-N] (Table 3-7). During the WET season, there were no [NH4-N] differences between N sources and N rates from St. Augustinegra ss receiving the WO irrigation schedule (Table 3-8). At the 5.0 g m-2 fertilizer rate, higher [NH4-N] was observed from St. Augustinegrass maintained with the ADJ irrigation schedule compared to the WO irrigation schedule for

PAGE 110

94 the 25% UREA/75% IBDU source (Table 3-8). The only significant interaction for [NH4N] during the DRY season was St. Augustinegra ss fertilized with the 25% UREA/75% IBDU fertilizer at the 2.5 g m-2 bimonthly N rate. There was higher [NH4-N] from St. Augustinegrass maintained with the WO i rrigation schedule in comparison to grass maintained with the ADJ irrigation schedule (Table 3-9). Total WET season NH4-N leaching ranged from 0.13 to 2.41 g m-2 with a mean total leached of 0.89 g m-2. Mean total DRY season NH4-N leached was lower than during the WET season (P<0.01) ranging from 0.10 to 1.32 g m-2 with a mean total leached of 0.52 g m-2. Similar to [NH4-N], the interaction of IRR*Source*Rate influenced NH4-N leaching during both seasons (Table 3-10). As documented with the [NH4-N], there was no NH4-N leaching differences between N sour ces and N rates from St. Augustinegrass receiving the WO irrigation sche dule (Table 3-11). In comp aring all combinations, there were only two significant contra sts: The first was that St. Au gustinegrass maintained with the ADJ irrigation schedule had greater NH4-N leaching compared to St. Augustinegrass maintained with the WO irrigation schedul e when fertilized with the 25%UREA/75% IBDU fertilizer at a rate of 5.0 g m-2 bimonthly (1.72 and 0.22 g m-2 respectively, P=0.02, Table 3-11). In addition, St. Augustinegrass maintained with the ADJ irrigation schedule and fertilized with 50% UR EA/50% IBDU at the 2.5 g m-2 bimonthly N rate had greater leaching than St. Augustinegrass maintained on the WO irrigation schedule and fertilized with the 25% UREA/75% IBDU fertilizer at the 5.0 g m-2 bimonthly N rate (1.69 and 0.22 g m-2 respectively, P=0.03, Table 3-11). Similar to DRY season [NH4-N], no consistent trends were found for the interactions on NH4-N leaching (Table 3-12).

PAGE 111

95 Total Inorganic Nitrogen Concentrations and Leaching Mean [TIN] was greater during the DRY season compared to [TIN] during the WET season (5.63 and 2.96 mg l-1 for DRY and WET respectively, P=0.03). This was partially due to a greater range of [TIN ] observed during the DRY season (0.46 to 43.17 mg l-1) compared to the WET season (0.38 to 8.57 mg l-1). Nitrogen rates applied influenced WET s eason [TIN] while no factor influenced [TIN] during the DRY season (Table 3-13). As observed with [NO3-N] average WET season [TIN] for St. Augustinegrass fertilized at the 5.0 g m-2 bimonthly N rate was greater than St. Augustinegrass fertilized at the 2.5 g m-2 bimonthly N rate (3.54 and 2.38 mg l-1 respectively, P<0.01). WET season TIN leaching was similar to DRY season TIN leaching (2.05 and 2.22 g m-2 for WET and DRY respectivel y, P=0.58) even though there was a wider range of leaching during the DRY season (0.29 6.35 and 0.27 11.65 g m-2 for WET and DRY, respectively). During both seasons, TIN leaching was infl uenced by N rates (Table 3-14, Figure 3-4). WET season TIN leaching from St. Augustinegrass fertilized with the 5.0 g m-2 bimonthly N rates was 2.57 g N m-2, which was greater than TIN leached from St. Augustinegrass receiving the 2.5 g N m-2 bimonthly fertilizer rate (1.53 g N m-2, Figure 34). Similarly, TIN leaching dur ing the DRY season was 2.90 g N m-2 for St. Augustinegrass receiving the 5.0 g m-2 bimonthly N rate compared to 1.55 g N m-2 leached from St. Augustinegrass receiving the 2.5 g m-2 bimonthly (P<0.01, Figure 3-4). The influence of rate is only apparent for the first half of the DRY season (Figure 3-4). For the second half of the DRY season, TIN leaching was low from both N rates (Figure 3-4). Perhaps this can be explained by the ti me of year. The dry season in this year was unusually long, and although the cycles categor ized as the DRY season were based on a

PAGE 112

96 rainfall perspective, perhaps the warming te mperatures caused the St. Augustinegrass to come out of dormancy. If this is the case, than more N would be utilized by the plant for active growth, which explains the less TIN leaching. St. Augustinegrass Quality St. Augustinegrass turf quality was assessed throughout each of the eight experiments. Quality scores for the WET season ranged from 6.7 8.2 with a mean value of 7.4. DRY season quality scores were lowe r than quality scores of the WET season (P=0.03) ranging from 6.2 8.3 with a mean sc ore of 7.2. These results are in contrast of what was documented for establishing St. Augustinegrass lawns (Chapter 2) where greater quality scores were observed in the DRY season. The WO irrigation schedule increased water stress in the second experiment in comparison to the irrigations schedules tested in the first experime nt. Although significant, the difference between the means was visually similar. However, quality scores we re most likely influenced by water stress from the WO irrigation schedule. WET and DR Y season quality scores were influenced by the interaction of IRR*Source*Rate (Tab le 3-15). During the WET season, there were no significant differences in quality scores of irrigation schedules within each N source and N rate (Table 3-16). However for bot h irrigation schedules, St. Augustinegrass fertilized at the 5.0 g m-2 bimonthly rate had higher quality than grass fertilized at the 2.5 g m-2 bimonthly rate (Table 3-16). Similar tr ends were documented in the DRY season however the difference between the two fertili zation rates were not as strongly separated as in the WET season (Table 3-17). St. Augustinegrass Growth St. Augustinegrass growth was assessed by clipping yield (dry weights) and root mass (root weight density). During th e WET season a mean total of 586 g m-2 of

PAGE 113

97 clippings were collecte d (range of 121 1,180 g m-2) in comparison to the DRY season in which total clippings were less than half of what was collected during the WET season with a (mean total = 265 g m-2 of clippings, ranging from 45 461 g m-2, P<0.01). This seasonal effect was inve rsely proportional to [NO3-N] and subsequent leaching, suggesting that St. Augustineg rass growth influences [NO3-N] and leaching. The interaction of IRR*Rate and Rate resulted in significant differen ces in clipping yield during the WET and DRY seasons respectively (Table 3-18). The IRR*Rate interaction during the WET season was influenced primarily by the amount of fertil izer applied, with almost a two fold increase in clipping yield at the 5.0 g m-2 bimonthly rate compared to the 2.5 g m-2 bimonthly rate regardless of i rrigation schedule (T able 3-19). Similar to the WET season, the trend of great er clipping yields w ith an increase in N rate was documented in the DRY season as well. DRY season clipping yields were greater for St. Augustinegrass at the 5.0 g m-2 bimonthly N rate compared to the 2.5 g m-2 bimonthly N rate (353 and 176 g m-2, respectively, P<0.01). Approximately five months after the e xperiment was initiated (04 August 2003), core samples were collected to assess below ground growth. Root weight density in the 0 15 cm depth was twice the root weight de nsity found in the 15 30 cm depth (908 and 433 g m-3 for 0-15 cm and 15-30 soil profiles, re spectively, P<0.01). The interaction of SOM*Source*Rate, SOM*IRR*Rate, and IRR*S ource influenced root weight densities within the upper 15 cm (Table 3-20), however no consistent tr ends could be identified to explain the differences (data not shown). It is important to note that root cores were colleted before the WO irrigation schedule had been changed to the more freque nt irrigation equal to the ADJ irrigation schedule (which started in August). Furtherm ore, cores were colle cted during the early

PAGE 114

98 part of the WET season. So perhaps root ar chitecture was changing due to the imposed irrigation schedules and perhap s this explains why no trends were logically evident. Approximately nine months after the first root core collection (27 April 2004), root cores from the two depths were taken agai n. For this second colle ction, root weight density in the upper 15 cm was still greater than root weight density in the lower 15 cm (1,078 and 329 g m-3 for 0 15 cm and 15 30 soil profiles respectively, P<0.01). Root weight densities from the 0 15 cm depth increased by 16% (P=0.02) and decreased by 24% for the 15 30 cm depth (P=0.03) from the August cores. The difference in root weight densities may be attributed to the cha nge in irrigation schedu ling and the length of time of exposure to other experimental factors. For instance, root weight densities within the 0 15 cm depth were influenced by SOM*Source*Rate and SOM*IRR*Rate interactions (Table 3-21). Similar to r oot cores collected on 04 August 2003, no apparent trend was determine for SOM*Source*Rate in teraction (Table 3-22). Only was root density from St. Augustinegrass with 40 g SOM kg-1 and fertilized with 25% Urea/ 75% IBDU at the 2.5 g m-2 bimonthly rate (1,545 g cm-3) was greater compared to St. Augustinegrass with 100 g SOM kg-1 and fertilized with 75% Urea/ 25% IBDU at the 5.0 g m-2 bimonthly rate (645 g cm-3, P<0.01). In addition, St. Augustinegrass maintained with 40 g SOM kg-1 irrigation schedule and fertilized at the 2.5 m-2 bimonthly N rate had greater root weight density when maintained with the WO irrigation schedule co mpared to the ADJ schedule (Table 3-23). N sources influenced root weight densities within the 15 30 cm soil depth (Table 3-21). St. Augustinegrass fertilized with th e 100% UREA N source ha d the greatest root weight density among N sources and was simila r to the root weight density of the 50% UREA/50% IBDU N source (450 and 357 g m-3, Table 3-24). Root weight densities at

PAGE 115

99 the 15 30 cm depth were also influenced by SOM*Rate interactions (Table 3-21). Although fertilization rate did not increase root weight de nsity in St. Augustinegrass associated with 100 g kg-1 SOM, fertilization rate did incr ease root weight density in St. Augustinegrass associated with 40 g kg-1 SOM (Table 3-25). A dditionally, at the 5.0 m-2 bimonthly fertilization rate, greater root weight densities were observed from St. Augustinegrass associated with the 40 g kg-1 SOM compared to the 100 g kg-1 SOM (Table 3-25). Mass of pelts collected on 27 April 2004 ranged from 190 1,349 g m-2 with a mean weight of 834 g m-2. No significant treatment eff ects were observed (Table 3-26). Pelts represented aboveground plant tissue N comprised of verdue and thatch. Leaf Blade Nitrogen Concentrations Leaf blade N was analyzed for one W ET season cycle (cycle 3) and one DRY season (cycle 5). Mean [N] within leaf blades were greater in clip pings collected during the DRY season compared to the WET season (24.2 and 21.6 mg N g-1 for DRY and WET season,s respectively, P<0.01). Perhaps this can be contri buted to the active growth during the WET season causing a greater production of leaf bl ades and thus a lower [N] within. During the DRY season, the St. A ugustinegrass was not actively growing and thus was mowed less often, resulting in more N accumulating within the leaf blades. In the WET season, mean [N] within leaf blades was influenced by N rates and SOM*Sources (Table 3-27). Incr easing fertilizer rate increas ed leaf blade [N] (20.3 and 22.9 mg N g-1 for 2.5 and 5.0 g N m-2 bimonthly fertilizer rates respectively, P<0.01, Figure 3-7). Similar to the WET season, DRY se ason leaf blade [N] was influenced by N rate (Table 3-27). Increasing N rate resulte d in increases in DRY season mean [N] in blade tissue (total = 23.1 and 25.4 mg N g-1 for 2.5 and 5.0 g N m-2 bimonthly fertilizer

PAGE 116

100 rates respectively, P<0.01, Figure 3-5). Regardless of season, m ean leaf blade [N] peaked at approximately one month afte r fertilization, with the lowest concentrations measured at the end of the ferti lization cycles (Figure 3-5). A lthough significant differences were determined for SOM*Source, no trend was cons istent (Table 3-28). Neither irrigation nor the interaction of i rrigation with other f actors influenced DRY season leaf blade [N] (Table 3-27). This may be a re sult of analyzing for leaf blad e [N] in a cycle in which the irrigation applied was similar for the two irrigation schedules (cycle 5, Table 3-2). Different results may have occurred if the analysis was completed for a DRY cycle in which there were differences in irriga tion scheduling (for example cycle 1). These values were comparable to othe rs found for St. Augustinegrass in the literature. For example, Broschat and Elliott (2004) report 13.0 to 19.7 mg N g-1 in St. Augustinegrass maintained with 20.0 g N m2 yr-1 using a 16-4-8 fertilizer. In comparison, Chen (1992) documented 20-26 mg N g-1 in leaf blade clippings and [N] in clippings from St. Augustinegrass va r. Raleigh was 14 mg N g-1 (Vernon et al., 1993). Nitrogen Uptake Efficiency Nitrogen uptake efficiency was 41% during the DRY season (cycle 5) compared to 32% for the WET season (cycle 3, P<0.01) WET season NUE was influenced by IRR*Rate (Table 3-29). Nitrogen uptake effi ciency from both fertilization rates was 30 and 33% (2.5 and 5.0 g N m-2 bimonthly, respectively ) from St. Augustinegrass maintained with the WO irrigation. In compar ison, fertilization rate influenced NUE from St. Augustinegrass receiving the ADJ irriga tion schedule; with NUE = 26% from St. Augustinegrass fertilized with the 2.5 g m-2 bimonthly N rate in comparison to 39% from St. Augustinegrass fertil ized with the 5.0 g m-2 bimonthly N rate (P<0.01).

PAGE 117

101 Dry season (cycle 5) NUE was influenced by IRR*Source*Rate interactions (Table 3-32). In general, NUE was lower from St. A ugustinegrass fertilized with sources at the 5.0 g m-2 bimonthly N rate in comparison to sources fertilize d at the 2.5 g m-2 bimonthly N rate (Table 3-30). For St. Augustinegrass ma intained with the WO irrigation schedule, the 100% UREA source had the greatest NUE (66%, Table 3-30). Nitrogen uptake efficiency found in this experiment were comparable to those documented for other turfgrasses fertili zed with UREA and IBDU (Hummel and Waddington, 1981; Sheard et al, 1985; Watson, 1987). For example, NUE of 31 and 60% were determined from Lolium perenne L. Melle and Agrostis palustris Huds Penncross fertilized with Urea ( Sheard et al, 1985; Watson, 1987). Nitrogen uptake efficiencies were 37 and 46% for Poa pratensis L. Baron and Poa pratensis L. Merion fertilized with IBDU (Hummel and Wa ddington, 1981; Hummel and Waddington, 1984). Nitrogen Budget and Scenario Comparison Since leaf blade [N] was only determin ed for cycles 3 (WET) and 5 (DRY), nitrogen budgets were calculated onl y for the two cycles. The mean [NO3-N] and [NH4N] in rainfall was 0.14 and 0.19 mg l-1 respectively ( n =35) contributing 0.07 and 0.005 g TIN m-2 for cycles 3 and 5 respectively. Other th an rainfall, St. Augustinegrass received N inputs from precipitation through one of two irrigation schedules. Mean [NO3-N] and [NH4-N] in irrigation was 0.06 and 0.10 mgl-1 respectively ( n =42), contributing 0.03 and 0.08 g TIN m-2 for cycle 3, and 0.04 and 0.04 g TIN m-2 for cycle 5 for St. Augustinegrass receiving WO and AD J irrigation respectively. Wolf and Snyder (2003) suggest between 2.2 4.5 g m-2 of N is released per year for g kg-1 of SOM within an acre furrow slice. Based on these calculations and accounting for that approximately 5 cm of soil was associated with sod when it was first

PAGE 118

102 installed, during the WET and DRY seasons, every g kg-1 SOM associated with the St. Augustinegrass is equivalent to 0.25 and 0.12 g N m-2 bimonthly. Considering that N mineralization from the SOM associated with the St. Augustinegras s would be greatest during the wet season when microbial activity is highest, calcula ted N mineralization based off the higher end of this scale (4.5 g N m-2 yr-1 for every g kg-1 SOM) results in 1.0 and 2.5 g N mineralized m-2 during the WET season cycle for St. Augustinegrass with 40 and 100 g kg-1 SOM respectively. Nitrogen mine ralization estimates would be presumed at the lower end of the scale (2.2 g N m-2 yr-1 for every g kg-1 SOM) lower during the DRY season when insufficient soil moisture limits microbial activity. Based upon this assumption, 0.5 and 1.2 g N m-2 would be mineralized during the DRY season cycle from St. Augustinegrass with 40 and 100 g kg-1 SOM, respectively. The N budgets in Tables 3-31 and 3-32 summarizes seasonal N inputs from rainfall, irrigation, SOM and fertilizer rate s as well as N losses from leaching and harvested in leaf blades. For both seasons, there was a large amount of N unaccounted for (Tables 3-31 and 3-32). Nitrogen unaccount ed for ranged from 57 85 % for the WET season. In comparison, N unaccounted for wa s less during the DRY season and ranged from 24 %. With the exception of St. Augustinegrass associated with the 40 g kg SOM during the WET season, unaccounted N was similar between the two N rates (Tables 3-31 and 3-32). During the WET s eason, for each irrigation schedule, over 10% more unaccounted N was calculated from St. Augustinegrass fertili zed with the 2.5 g N m-2 N rate compared to the 5.0 g N m-2 N rate for St. Augustinegrass associated with the 40 g kg SOM (Table 3-31a). Irrigation seemed to influence the N unaccounted only during the DRY season for St. Augustinegrass associated with 100 g kg SOM. Under this management strategy,

PAGE 119

103 approximately twice as much N was unaccount ed for from St. Augustinegrass maintained with the ADJ irrigation schedule in comparis on to the WO irrigation schedule (Table 332b). As discussed in Chapter 2, the unaccounted for N balance may be explained by pools that were not measured in this study including denitr ification, ammonia volatilization, N in thatch and unmeasured forms of N such as urea. For example, while the greatest [N] are typically found in leaf blades, other pl ant parts such as roots and verdue as well as thatch also contain [N]. Although pelts comp rising of verdue and thatch were collected in this study, N within the verdue and thatch was not determined. Two main reasons lead to the specu lation of a large portion of N being within the thatch and verdue. The first is that the St. Augus tinegrass was irrigate d immediately after fertilization. Petrovic (1990) reviewed various studies that documented a decrease in NH3 volatilization from turfgrass that is irrigated after fertili zer was applied compared to turf that was not irriga ted (Bowman et al, 1987; T itko et al., 1987; Sheard and Beauchamp; 1985). However it was possible that not enough irrigation was applied to fully incorporate the fertilizer and thus some may have b een lost from volatilization. Secondly, the St. Augustinegrass may have accu mulated thatch over the years which can contain a significant amount of N. For exam ple Starr and DeRoo reported up to 21% of applied N in the thatch of a mi xed stand of Kentucky bluegrass ( Poa pratensis L.) and Red fescue ( Festuca rubra L., 1981). Thatch has also been documented as being hydrophobic in nature and attributes to a soil s water repellency (Karnock and Tucker, 1999). In addition, wetting and severe drying cycles such as what occurred on St. Augustinegrass maintained with the WO irriga tion schedule have also been reported to promote soil water repellency (Karnock a nd Tucker, 1999). When a soil becomes water

PAGE 120

104 repellent, it is harder to re-w et, and thus infiltration and wa ter efficiency is reduced. In this study, especially for St. Augustinegrass ma intained with the WO irrigation schedule, perhaps the soil became water repellent, and less water and ultimately less N was available for plant uptake. Conclusions This study examined how management strate gies influence [N] in percolate and N losses in leaching and turfgr ass response from establis hed St. Augustinegrass. All management factors individually or in comb ination influenced [N], N leaching and/or turfgrass quality and growth, thus requiri ng the null hypotheses to be rejected. The greatest influence on leaching losses and tu rfgrass response was from the rate of N applied. It was evident that SOM was an important N pool for St. Augustinegrass uptake and for N leaching for the first 16 months af ter sod was laid. However this experiment documented SOM was still influential on NO3-N leaching, root weight densities and leaf blade [N], thirty-two months after planting. This experiment documented that irrigati ng only when visual wilt was apparent had a minor influence on N leaching. However it must be noted that due to frequent water stress, this schedule was gradually increased to equal the more frequent irrigation schedule. Under certain combinati ons with N sources and rates, [NH4-N] were lower from St. Augustinegrass r eceiving the WO irrigation schedule, yet increased NH4-N leaching. Additionally, over time quality was reduced from St. Augustinegrass maintained with the WO irrigation schedule. Even with the onset of the WET season and after increasing irriga tion to the ADJ schedule, turf grass was slow to respond and increase in quality. Further decline in qua lity, differences in [N] and leaching, and

PAGE 121

105 perhaps loss of the turfgrass stand may have occurred if the WO irrigation schedule had been continued and had not been increas ed to the ADJ irrigation schedule. Reducing irrigation increased r oot weight densities. Great er root weight densities from St. Augustinegrass rece iving less irrigation was also documented during the first experiment. While others have documented the importance of rooting ability in turfgrass drought resistance and the influence of irriga tion on rooting ability (Huang et al., 1997; Qian et al., 1997; Qian et al ., 1999), there may be a threshold when irrigation reduction no longer increases rooting abil ity. For example, if the WO irrigation schedule had been followed throughout the experiment, perhaps th ere would have been different results. Regardless of irrigation schedule, this experi ment as well as Experiment 1 documents that St. Augustinegrass has a dense root syst em within 15 cm of th e soils surface, with some deeper roots (15-30 cm). This type of root architecture was optimal for N capture in sandy soils that experience a rainy season followed by dry weather (Dunbabin et al., 2003). Although many observations were influenced by management factor interactions with N sources, no trend for the N sources co uld be identified except for TIN leached. There was a weak gradual trend of more TIN leached with increasing amounts of readily available N to controlled release N within a fertilizer. However, this study only investigated Urea and IBDU as N sources. As discussed in Chapter 2, results may have been different if other N sources were investigated. This experiment documented that monito ring [TIN] and leaching alone was not an effective measure to determine management strategies on the poten tial N contamination to groundwater. While N rates and N sources were documented as influencing [TIN] and leaching, SOM, irrigation and the interactio ns of factors in which influenced [NO3-N]

PAGE 122

106 and [NH4-N] leaching did not influence [TIN] and l eaching. None the less, the fact that SOM, irrigation and the interactio ns of factors did influence [NO3-N] and [NH4-N] leaching suggests that these factors a nd interactions should not be ignored. Nitrogen leaching from the St. Augustineg rass could have an adverse impact on groundwater. Based on this study, the follo wing management strategies for St. Augustinegrass were suggested for maintaini ng quality grass while reducing potential adverse impacts to the environment: (i) es tablished St. Augustinegrass needs to be fertilized bimonthly at a rate that would be dependent on the aesthetics desirable, and (ii) irrigation should not be base d on visual assessment.

PAGE 123

107 Table 3-1. (a) Experimental factors test ed and (b) ANOVA table of factors and interactions tested. (a) Factor Treatment Description Soil Organic Matter (Whole Plot) 4% 10% 40 g kg-1 SOM associated with sod 100 g kg-1 SOM associated with sod. Irrigation (Whole Plot) Wilt-only Adjusted 125% weekly ET adjusted by month over 3 applications (M-W-F) only when wilt was observed. 125% weekly ET adjusted by month over 3 applications (M-W-F). Irrigation shut off when precipitation >0.84 cm 24h prior scheduled irrigation. N Source (Sub Plot) Water-soluble Blend (Water-soluble + Controlled-release) 100 % Urea 25% Urea + 25% IBDU 50% Urea + 50% IBDU 75% Urea + 25% IBDU N Rate (Sub Plot) 2.5 g m-2 bimonthly 5.0 g m-2 bimonthly 15.0 g m-2 yr-1 30.0 g m-2 yr-1 (b) ANOVA table Source Rep Irrigation SOM Irrigation*SOM Main plot error Source Rate Source*Rate Irrigation*Source Irrigation*Rate SOM*Source SOM*Rate Irrigation*Source*Rate SOM*Source*Rate Irrigation*SOM*Rate Irrigation*SOM*Source Sub plot error Total df 1 1 1 1 3 3 1 3 3 1 3 1 3 3 1 3 31 63

PAGE 124

108 Table 3-2. Water budget from March 2003 to September 2004. Cycle (Date) Irrigation Regime Rainfall (mm) Irrigation (mm) Percolate (mm) ET (mm) 1 (07 Mar 03 02 May 03) --Adjusted Wilt-only 144 ------297 45 --272 38 276 ----2 (03 May 03 02 Jul 03) --Adjusted Wilt-only 526 ------707 345 --622 315 411 ----3 (03 Jul 03 27 Aug 03) --Adjusted Wilt-only 314 ------507 174 --404 139 433 ----4 (28 Aug 03 26 Oct 03) --Adjusted Wilt-only 219 ------371 252 --273 172 423 ----Post-4 (27 Oct 12 Nov 04) --Adjusted Wilt-only 183 --197 133 --166 108 98 ----5 (13 Nov 03 12 Jan 04) --Adjusted Wilt-only 15 ------253 253 --208 208 191 ----6 (13 Jan 04 13 Mar 04) --Adjusted Wilt-only 179 ------225 225 --213 213 194 ----Post-6 (14 Mar 04 13 May 04) --Adjusted Wilt-only 111 --210 182 --168 162 269 ----7 (14 May 04 15 Jul 04) --Adjusted Wilt-only 100 --207 207 --161 161 470 ----8 (16 Jul 04 13 Sep 04) --Adjusted Wilt-only 476 --509 335 --401 261 456 ----Experimental period total (07 Mar 03 13 Sep 04) --Adjusted Wilt-only 2267 ------3483 2151 --2908 1777 3221 ----Cycle 5 began approximately 2 weeks after Cycle 4 due continuous rainfall. Post 4 contains data for the two-week period and is discussed only in annual data. Cycle 7 began approximately 2 months after Cycle 6 after it was determined that chemical analysis from cycles 1 and 2 were invalid. Post 6 contains data for the two month period and was included in experimental totals.

PAGE 125

109 Table 3-3. ANOVA table for NO3-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 0.95 0.39 0.06 0.82 IRR 1 0.05 0.83 2.95 0.16 SOM*IRR 1 0.67 0.46 0.09 0.78 Source 3 5.63 <0.01 1.03 0.39 Rate 1 25.85 <0.01 0.95 0.34 Source*Rate 3 3.88 0.02 1.02 0.40 IRR*Source 3 1.26 0.31 0.87 0.47 IRR*Rate 1 0.03 0.86 0.13 0.72 SOM*Source 3 4.60 <0.01 0.47 0.71 SOM*Rate 1 0.16 0.69 1.02 0.32 IRR*Source*Rate 3 0.53 0.66 1.02 0.40 SOM*Source*Rate 3 3.17 0.04 1.24 0.31 SOM*IRR*Source 3 0.52 0.67 0.46 0.72 SOM*IRR*Rate 1 1.42 0.24 1.02 0.32 Table 3-4. WET season NO3-N concentrations (mg l-1) were influenced by SOM*Source* N Rate interactions. Significance values listed are for SOM differences within each N Rate and N Source. 40 g kg-1 SOM 100 g kg-1 SOM Within Source*Rate P value 25% UREA/75% IBDU 0.42 b 0.29 b 1.00 50% UREA/50% IBDU 0.37 b 1.12 ab 1.00 75% UREA/25% IBDU 0.31 b 1.05 b 1.00 2.5 m-2 bimonthly 100% UREA 0.84 b 0.94 b 1.00 25% UREA/75% IBDU 0.70 b 1.85 ab 0.99 50% UREA/50% IBDU 0.61 b 1.01 b 1.00 75% UREA/25% IBDU 1.55 ab 4.34 a 0.11 5.0 g m-2 bimonthly 100% UREA 4.00 a 1.94 ab 0.52 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 126

110 Table 3-5. ANOVA table for total NO3-N leached for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 0.71 0.45 0.36 0.58 IRR 1 0.00 0.98 2.74 0.17 SOM*IRR 1 0.39 0.57 0.20 0.68 Source 3 5.09 <0.01 2.20 0.11 Rate 1 23.24 <0.01 16.49 <0.01 Source*Rate 3 3.31 0.03 1.76 0.18 IRR*Source 3 1.12 0.36 0.69 0.57 IRR*Rate 1 0.25 0.62 2.63 0.11 SOM*Source 3 4.04 0.02 1.18 0.33 SOM*Rate 1 0.12 0.73 0.19 0.66 IRR*Source*Rate 3 0.57 0.64 1.38 0.27 SOM*Source*Rate 3 3.05 0.04 0.31 0.82 SOM*IRR*Source 3 0.18 0.91 1.23 0.32 SOM*IRR*Rate 1 1.69 0.20 0.19 0.66 Table 3-6. WET season NO3-N leached (g N m-2) were influenced by SOM*Source*Rate interactions. Significance va lues listed are for SOM differences within each N Rate and N Source. 40 g kg-1 SOM 100 g kg-1 SOM Within Source*Rate P value 25% UREA/75% IBDU 0.39 b 0.27 c 1.00 50% UREA/50% IBDU 0.34 b 0.93 bc 1.00 75% UREA/25% IBDU 0.28 b 0.89 bc 1.00 2.5 m-2 bimonthly 100% UREA 0.72 b 0.89 bc 1.00 25% UREA/75% IBDU 0.61 b 1.58 bc 1.00 50% UREA/50% IBDU 0.55 b 0.93 bc 1.00 75% UREA/25% IBDU 1.32 b 3.71 a 0.18 5.0 g m-2 bimonthly 100% UREA 3.48 a 1.66 b 0.59 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 127

111 Table 3-7. ANOVA table for NH4-N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 0.46 0.54 1.22 0.33 IRR 1 11.25 0.03 0.49 0.52 SOM*IRR 1 0.35 0.59 0.11 0.76 Source 3 0.49 0.69 0.47 0.70 Rate 1 0.58 0.45 0.66 0.42 Source*Rate 3 1.22 0.32 0.66 0.58 IRR*Source 3 0.86 0.47 1.03 0.39 IRR*Rate 1 1.05 0.31 0.10 0.76 SOM*Source 3 0.26 0.85 0.43 0.73 SOM*Rate 1 1.31 0.26 0.06 0.81 IRR*Source*Rate 3 6.97 <0.01 5.89 <0.01 SOM*Source*Rate 3 0.31 0.82 0.06 0.98 SOM*IRR*Source 3 0.88 0.46 1.07 0.38 SOM*IRR*Rate 1 0.12 0.73 0.08 0.78 Table 3-8. WET season NH4-N concentrations (mg l-1) were influenced by IRR*Source*Rate interactions. Signi ficance values listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 1.40 a 1.29 bc 1.00 50% UREA/50% IBDU 0.87 a 3.19 a 0.08 75% UREA/25% IBDU 1.06 a 2.52 ab 0.71 2.5 m-2 bimonthly 100% UREA 0.88 a 2.54 ab 0.51 25% UREA/75% IBDU 0.40 a 3.41 a <0.01 50% UREA/50% IBDU 1.37 a 1.99 b 1.00 75% UREA/25% IBDU 1.27 a 1.19 c 1.00 5.0 g m-2 bimonthly 100% UREA 1.40 a 1.33 bc 1.00 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 128

112 Table 3-9. DRY season NH4-N (mg l-1) were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 1.48 a 0.38 b <0.01 50% UREA/50% IBDU 1.00 abc 1.28 a 0.46 75% UREA/25% IBDU 0.75 bc 0.77 ab 0.97 2.5 g m-2 bimonthly 100% UREA 0.72 bc 1.27 a 0.98 25% UREA/75% IBDU 0.46 c 0.92 ab 0.22 50% UREA/50% IBDU 0.72 bc 0.99 ab 0.48 75% UREA/25% IBDU 1.15 abc 0.72 ab 0.25 5.0 g m-2 bimonthly 100% UREA 1.36 ab 0.49 b 0.58 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 3-10. ANOVA table for NH4-N leached for WET and DRY seasons. Significant differences are bold and italicized. WET DRY df F value P value F value P value SOM 1 0.59 0.49 1.12 0.35 IRR 1 7.88 0.05 0.62 0.48 SOM*IRR 1 0.58 0.49 0.07 0.80 Source 3 0.47 0.71 0.57 0.64 Rate 1 0.69 0.41 0.57 0.46 Source*Rate 3 0.83 0.49 0.73 0.54 IRR*Source 3 0.72 0.55 1.06 0.38 IRR*Rate 1 1.07 0.31 0.18 0.67 SOM*Source 3 0.32 0.81 0.47 0.70 SOM*Rate 1 1.31 0.26 0.05 0.83 IRR*Source*Rate 3 6.84 <0.01 5.77 <0.01 SOM*Source*Rate 3 0.25 0.86 0.03 0.99 SOM*IRR*Source 3 1.15 0.35 1.12 0.36 SOM*IRR*Rate 1 0.09 0.76 0.19 0.67

PAGE 129

113 Table 3-11. WET season NH4-N leached (g m-2) were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 0.83 a 0.66 a 1.00 50% UREA/50% IBDU 0.48 a 1.69 a 0.14 75% UREA/25% IBDU 0.62 a 1.31 a 0.88 2.5 m-2 bimonthly 100% UREA 0.51 a 1.40 a 0.58 25% UREA/75% IBDU 0.22 a 1.72 a 0.02 50% UREA/50% IBDU 0.79 a 1.07 a 1.00 75% UREA/25% IBDU 0.72 a 0.66 a 1.00 5.0 g m-2 bimonthly 100% UREA 0.81 a 0.69 a 1.00 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 3-12. DRY season NH4-N leached (g m-2) were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 0.82 a 0.21 b <0.01 50% UREA/50% IBDU 0.57 ab 0.74 a 0.43 75% UREA/25% IBDU 0.44 ab 0.43 ab 0.97 2.5 m-2 bimonthly 100% UREA 0.42 ab 0.72 a 0.16 25% UREA/75% IBDU 0.27 b 0.51 ab 0.25 50% UREA/50% IBDU 0.42 ab 0.55 ab 0.54 75% UREA/25% IBDU 0.67 ab 0.42 ab 0.23 5.0 g m-2 bimonthly 100% UREA 0.80 a 0.28 b 0.02 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 130

114 Table 3-13. ANOVA table for total inorga nic-N concentrations for WET and DRY seasons. Significant difference s are bold and italicized. WET DRY df F value P value F value P value SOM 1 1.82 0.25 0.04 0.86 IRR 1 3.78 0.12 2.87 0.17 SOM*IRR 1 0.15 0.72 0.09 0.78 Source 3 1.67 0.19 0.97 0.42 Rate 1 8.86 <0.01 0.87 0.36 Source*Rate 3 1.53 0.23 1.08 0.37 IRR*Source 3 0.33 0.80 0.99 0.41 IRR*Rate 1 0.22 0.64 0.15 0.71 SOM*Source 3 1.71 0.19 0.45 0.72 SOM*Rate 1 0.15 0.70 1.06 0.31 IRR*Source*Rate 3 1.67 0.19 0.95 0.43 SOM*Source*Rate 3 1.79 0.17 1.24 0.31 SOM*IRR*Source 3 0.96 0.42 0.45 0.72 SOM*IRR*Rate 1 0.36 0.55 1.00 0.33 Table 3-14. ANOVA table for total inorga nic-N leached for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 1.41 0.30 0.43 0.55 IRR 1 1.28 0.32 2.71 0.18 SOM*IRR 1 0.11 0.76 0.16 0.71 Source 3 2.80 0.06 1.74 0.18 Rate 1 12.9 <0.01 13.97 <0.01 Source*Rate 3 1.83 0.16 1.97 0.14 IRR*Source 3 0.38 0.77 0.96 0.43 IRR*Rate 1 0.00 0.98 2.67 0.11 SOM*Source 3 2.44 0.08 0.84 0.48 SOM*Rate 1 0.04 0.85 0.22 0.65 IRR*Source*Rate 3 0.71 0.55 1.02 0.40 SOM*Source*Rate 3 2.32 0.10 0.26 0.86 SOM*IRR*Source 3 0.51 0.68 1.32 0.29 SOM*IRR*Rate 1 0.87 0.36 0.11 0.74

PAGE 131

115 Table 3-15. ANOVA table for turfgrass quali ty for WET and DRY seasons. Significant differences are bold and italicized. WET DRY df F value P value F value P value SOM 1 0.25 0.64 1.32 0.32 IRR 1 0.05 0.84 0.29 0.62 SOM*IRR 1 0.00 1.00 0.04 0.85 Source 3 1.36 0.27 1.92 0.15 Rate 1 236 <0.01 124 <0.01 Source*Rate 3 1.40 0.26 1.53 0.23 IRR*Source 3 1.69 0.19 1.19 0.33 IRR*Rate 1 1.95 0.17 1.4 0.26 SOM*Source 3 0.51 0.68 1.46 0.25 SOM*Rate 1 0.49 0.49 1.93 0.17 IRR*Source*Rate 3 4.53 0.01 5.22 <0.01 SOM*Source*Rate 3 0.83 0.49 2.12 0.12 SOM*IRR*Source 3 1.48 0.24 0.55 0.65 SOM*IRR*Rate 1 1.95 0.17 0.05 0.82 Table 3-16. WET season quality scores were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 7.2 b 7.1 b 0.41 50% UREA/50% IBDU 7.1 b 7.1 b 1.00 75% UREA/25% IBDU 6.9 c 7.3 b 0.15 2.5 m-2 bimonthly 100% UREA 7.3 b 7.1 b 0.35 25% UREA/75% IBDU 7.7 a 7.9 a 0.48 50% UREA/50% IBDU 7.6 a 7.6 a 0.90 75% UREA/25% IBDU 7.7 a 7.7 a 0.90 5.0 g m-2 bimonthly 100% UREA 7.6 a 7.7 a 0.48 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Quality scores were rated on a scale from 1 10, w ith 1 = dead, brown turf, 6=minimally acceptable, 10= dark green healthy looking turf.

PAGE 132

116 Table 3-17. DRY season quality scores were influenced by IRR*Source*Rate interactions. Significance va lues listed are for IRR differences within each N Rate and N Source. Wilt Only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 7.0 d 6.9 c 0.53 50% UREA/50% IBDU 6.9 de 6.9 c 0.75 75% UREA/25% IBDU 6.6 e 7.1 bc 0.08 2.5 m-2 bimonthly 100% UREA 7.2 cd 7.0 c 0.35 25% UREA/75% IBDU 7.5 ab 7.7 a 0.53 50% UREA/50% IBDU 7.4 bc 7.4 b 0.83 75% UREA/25% IBDU 7.6 a 7.7 a 0.83 5.0 g m-2 bimonthly 100% UREA 7.3 bc 7.8 a 0.06 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Quality scores were rated on a scale from 1 10, w ith 1 = dead, brown turf, 6=minimally acceptable, 10= dark green healthy looking turf. Table 3-18. ANOVA table for clipping yiel d for WET and DRY seasons. Significant differences are bold and italicized. WET DRY df F value P value F value P value SOM 1 1.05 0.36 7.65 0.05 IRR 1 0.03 0.86 1.12 0.35 SOM*IRR 1 0.02 0.90 0.03 0.88 Source 3 0.42 0.74 2.62 0.07 Rate 1 355 <0.01 268 <0.01 Source*Rate 3 1.17 0.34 0.35 0.79 IRR*Source 3 2.33 0.09 2.10 0.12 IRR*Rate 1 6.37 0.02 0.39 0.53 SOM*Source 3 0.01 1.00 0.84 0.48 SOM*Rate 1 0.02 0.88 0.48 0.50 IRR*Source*Rate 3 2.05 0.13 2.72 0.06 SOM*Source*Rate 3 1.30 0.29 0.03 0.99 SOM*IRR*Source 3 0.27 0.85 0.41 0.75 SOM*IRR*Rate 1 0.23 0.64 0.23 0.64

PAGE 133

117 Table 3-19. WET season clipping yields (g m-2) were influenced by IRR*Rate interactions. Wilt Only Mean St. dev. Adjusted Mean St. dev. Within Rate P value 2.5 m-2 bimonthly 395 135 359 135 0.78 5.0 g m-2 bimonthly 757 210 834 210 0.55 Within IRR P value <0.01 <0.01 Table 3-20. ANOVA table for r oot weight density for 0-15 cm and 15-30 cm depths from cores collected on 04 August 2003. Significant differences are bold and italicized. 0 15 cm 15 30 cm df F value P value F value P value SOM 1 0.18 0.69 4.09 0.11 IRR 1 0.86 0.41 8.00 0.05 SOM*IRR 1 0.00 0.97 0.65 0.47 Source 3 2.73 0.06 0.86 0.47 Rate 1 2.01 0.17 1.15 0.29 Source*Rate 3 1.24 0.31 1.83 0.16 IRR*Source 3 3.39 0.03 2.09 0.12 IRR*Rate 1 0.98 0.33 2.60 0.12 SOM*Source 3 0.44 0.73 0.72 0.55 SOM*Rate 1 0.98 0.33 0.70 0.41 IRR*Source*Rate 3 1.02 0.40 1.28 0.30 SOM*Source*Rate 3 3.73 0.02 1.51 0.23 SOM*IRR*Source 3 0.54 0.66 0.27 0.84 SOM*IRR*Rate 1 10.2 <0.01 0.34 0.57

PAGE 134

118 Table 3-21. ANOVA table for r oot weight density for 0-15 cm and 15-30 cm depths from cores collected on 27 April 2004. Significant differences are bold and italicized. 0 15 cm 15 30 cm df F value P value F value P value SOM 1 0.98 0.33 9.93 <0.01 IRR 1 5.69 0.02 0.55 0.46 SOM*IRR 1 0.05 0.83 1.19 0.28 Source 3 0.57 0.64 4.32 0.01 Rate 1 0.49 0.49 6.69 0.01 Source*Rate 3 0.73 0.54 0.70 0.56 IRR*Source 3 0.77 0.52 0.69 0.57 IRR*Rate 1 6.51 0.02 0.43 0.52 SOM*Source 3 1.35 0.27 0.78 0.51 SOM*Rate 1 0.50 0.48 5.60 0.02 IRR*Source*Rate 3 1.25 0.31 1.70 0.19 SOM*Source*Rate 3 3.19 0.04 0.39 0.76 SOM*IRR*Source 3 1.13 0.35 1.52 0.23 SOM*IRR*Rate 1 8.82 <0.01 1.08 0.31 Table 3-22. Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were influenced by SOM*Rate*Source in teractions. Cores were collected on 27 Apr 2004. Source N rate (bimonthly) 40 g SOM kg-1 100 g SOM kg-1 Within Rate*Source P value 25% Urea / 75% IBDU 2.5 g m-2 1545 a 823 a 0.45 5.0 g m-2 985 a 1333 a 0.88 Significance 0.82 0.89 50% Urea / 50% IBDU 2.5 g m-2 857 a 1027 a 1.00 5.0 g m-2 1070 a 1070 a 1.00 Significance 1.00 1.00 75% Urea / 25% IBDU 2.5 g m-2 1061 a 985 a 1.00 5.0 g m-2 1341 a 645 a 0.50 Significance 1.00 1.00 100% Urea 2.5 g m-2 1239 a 1261 a 1.00 5.0 g m-2 819 a 1053 a 1.00 Significance 0.97 1.00 No significant different were determined for Source*Rate within each SOM at the 0.05 significance level.

PAGE 135

119 Table 3-23. Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were influenced by SOM*IRR*Rate inte ractions. Cores were collected on 04 Aug 2003. 40 g SOM kg-1 100 g SOM kg-1 Within N Rate*IRR P value WO 1579 a 1138 a 0.35 ADJ 815 b 917 a 1.00 2.5 g m-2 bimonthly Significance 0.02 0.95 WO 883 ab 1180 a 1.00 ADJ 1222 a 874 a 0.65 5.0 g m-2 bimonthly Significance 0.69 0.78 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 3-24. Influence of N sources on root weight density (g m-3) of cores collected at the 15-30 cm depth on 27 April 2004. Mean Std Dev. 25% UREA/75% IBDU 270 b 170 50% UREA/50% IBDU 357 ab 246 75% UREA/25% IBDU 238 b 170 100% UREA 450 a 246 Means with the same letter within a column are not significantly different at the 0.05 significance level. Table 3-25. Root weight densities (g m-3) from cores collected at the 15-30 cm depth on 27 April 2004 were influenced by SOM*Rate interactions. 40 g kg-1 SOM Mean St. dev. 100 g kg-1 SOM Mean St. dev. Within Rate P value 2.5 m-2 bimonthly 280 170 255 187 0.47 5.0 g m-2 bimonthly 518 263 255 161 <0.01 Within IRR P value <0.01 0.84

PAGE 136

120 Table 3-26. ANOVA table for pelt weight from cores collected on 27 April 2004. No significant differences were determined. Pelts df F value P value SOM 1 0.05 0.84 IRR 1 0.17 0.70 SOM*IRR 1 0.06 0.82 Source 3 0.57 0.64 Rate 1 2.78 0.11 Source*Rate 3 0.23 0.88 IRR*Source 3 2.06 0.13 IRR*Rate 1 0.01 0.91 SOM*Source 3 1.28 0.30 SOM*Rate 1 0.27 0.56 IRR*Source*Rate 3 0.26 0.85 SOM*Source*Rate 3 0.49 0.71 SOM*IRR*Source 3 0.23 0.88 SOM*IRR*Rate 1 1.20 0.28 Table 3-27. ANOVA table for leaf blade N concentrations for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 0.32 0.60 0.01 0.92 IRR 1 0.08 0.79 0.01 0.94 SOM*IRR 1 0.66 0.46 0.10 0.76 Source 3 1.23 0.32 1.64 0.20 Rate 1 66.16 <0.01 65.22 <0.01 Source*Rate 3 1.67 0.19 0.59 0.63 IRR*Source 3 1.17 0.34 1.56 0.22 IRR*Rate 1 1.71 0.20 0.01 0.91 SOM*Source 3 3.54 0.03 0.82 0.49 SOM*Rate 1 0.21 0.65 0.87 0.36 IRR*Source*Rate 3 0.73 0.54 2.02 0.13 SOM*Source*Rate 3 0.12 0.95 0.32 0.81 SOM*IRR*Source 3 0.14 0.94 1.78 0.17 SOM*IRR*Rate 1 0.09 0.77 0.20 0.66

PAGE 137

121 Table 3-28. WET season leaf blad e N concentrations (mg N g-1) were influenced by SOM*Source interactions. Significance valu es listed are for SOM differences within each N Source. 40 g kg-1 SOM 100 g kg-1 SOM Within Source P value 25% UREA/75% IBDU 22.0 a 21.5 b 0.75 50% UREA/50% IBDU 20.4 b 22.8 a 0.16 75% UREA/25% IBDU 20.8 ab 21.8 ab 0.64 100% UREA 21.7 a 22.2 ab 0.74 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level. Table 3-29. ANOVA table for nutrient uptake efficiency for WET and DRY seasons. Significant differences ar e bold and italicized. WET DRY df F value P value F value P value SOM 1 2.30 0.20 0.30 0.61 IRR 1 0.01 0.92 0.11 0.75 SOM*IRR 1 0.04 0.85 0.11 0.75 Source 3 0.47 0.71 1.01 0.40 Rate 1 12.34 <0.01 30.28 <0.01 Source*Rate 3 1.29 0.29 1.42 0.26 IRR*Source 3 0.21 0.89 1.87 0.15 IRR*Rate 1 4.53 0.04 0.16 0.678 SOM*Source 3 0.74 0.54 0.22 0.88 SOM*Rate 1 3.15 0.09 0.40 0.53 IRR*Source*Rate 3 0.37 0.77 4.02 0.02 SOM*Source*Rate 3 0.80 0.50 1.17 0.34 SOM*IRR*Source 3 0.17 0.92 0.33 0.80 SOM*IRR*Rate 1 1.99 0.17 0.03 0.86

PAGE 138

122 Table 3-30. DRY season (cycle 5) nutrient uptake efficiency (%) was influenced by IRR*Source*Rate interactions. Signi ficance values listed are for IRR differences within each N Rate and N Source. Wilt-only Adjusted Within Source*Rate P value 25% UREA/75% IBDU 58 ab 44 bc 0.26 50% UREA/50% IBDU 35 c 47ab 0.35 75% UREA/25% IBDU 43 bc 53 a 0.30 2.5 m-2 bimonthly 100% UREA 66 a 42 ab 0.06 25% UREA/75% IBDU 37 c 36 bc 0.96 50% UREA/50% IBDU 41 c 26 c 0.22 75% UREA/25% IBDU 28 c 33 bc 0.68 5.0 g m-2 bimonthly 100% UREA 28 c 31 bc 0.81 Means with the same letter within a column are not si gnificantly different at the 0.05 significance level.

PAGE 139

123 Table 3-31. WET season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM. (a) 40 g kg-1 SOM Inputs ---------------WO ----------------------------ADJ ---------------Fertilizer 2.5 5.0 2.5 5.0 Irrigation 0.03 0.03 0.08 0.08 40 g kg-1 SOM 1.0 1.0 1.0 1.0 Rain 0.07 0.07 0.07 0.07 Total 3.60 6.10 3.65 6.15 Losses accounted for Leaching 0.08 0.22 0.58 0.99 Harvested 0.45 1.44 0.48 1.67 Total 0.53 1.66 1.06 2.66 % Unaccounted 85 73 71 57 (b) 100 g kg-1 SOM Inputs --------------WO -----------------------------ADJ ---------------Fertilizer 2.5 5.0 2.5 5.0 Irrigation 0.03 0.03 0.08 0.08 100 g kg-1 SOM 2.5 2.5 2.5 2.5 Rain 0.07 0.07 0.07 0.07 Total 5.10 7.60 5.15 7.65 Losses accounted for Leaching 0.12 0.21 0.59 0.93 Harvested 1.04 1.89 0.81 2.25 Total 1.16 2.10 1.32 3.18 % Unaccounted 77 72 74 58

PAGE 140

124 Table 3-32. DRY season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b) 100 g kg-1 SOM. (a) 40 g kg-1 SOM Inputs --------------WO ------------------------------ADJ --------------Fertilizer 2.5 5.0 2.5 5.0 Irrigation 0.04 0.04 0.04 0.04 40 g kg-1 SOM 1.0 1.0 1.0 1.0 Rain 0.005 0.005 0.005 0.005 Total 3.545 6.045 3.545 6.045 Losses accounted for Leaching 0.85 2.13 0.95 1.89 Harvested 1.13 1.54 2.07 3.46 Total 1.98 3.67 2.07 3.46 % Unaccounted 44 39 42 47 (b) 100 g kg-1 SOM Inputs --------------WO ----------------------------ADJ --------------Fertilizer 2.5 5.0 2.5 5.0 Irrigation 0.04 0.04 0.04 0.04 100 g kg-1 SOM 2.5 2.5 2.5 2.5 Rain 0.005 0.005 0.005 0.005 Total 5.045 7.545 5.045 7.545 Losses accounted for Leaching 2.42 3.63 1.25 2.07 Harvested 1.39 1.82 1.20 1.60 Total 3.81 5.45 2.45 3.67 % Unaccounted 24 28 51 51

PAGE 141

125 0 20 40 60 80 100 120 3/7/20035/6/20037/5/20039/3/200311/2/20031/1/20043/1/2004 Experimental periodRainfall (mm d-1) Figure 3-1. Daily rainfall over the ex perimental period for Experiment 2.

PAGE 142

126 Figure 3-2. Comparison of weekly cumulative NO3-N leached from St. Augustinegrass associated with (a) 40 g kg-1 and (b) 100 g kg-1 soil organic matter (SOM) fertilized with the four N sources at 2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events. 2.5 g N m -2 5.0 g N m -2 NO3-N leached (g m-2) 0 2 4 6 8 10 100% UREA 25% UREA/75% IBDU 50% UREA/50% IBDU 75% UREA/25% IBDU (a) 4% SOM Study Period 07/03 09/03 11/03 01/04 03/04 05/04 07/04 09/04 NO3-N leached (g m-2) 0 2 4 6 8 10 100% UREA 25% UREA/75% IBDU 50% UREA/50% IBDU 75% UREA/25% IBDU (b) 10% SOM

PAGE 143

127 Study Period 07/03 09/03 11/03 01/04 03/04 05/04 07/04 09/04 NO3-N leached (g m-2) 0.0 0.1 0.2 0.3 0.4 2.5 g N m-2 bimonthly 5.0 g N m-2 bimonthly Figure 3-3. Comparison of NO3-N leached from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events.

PAGE 144

128 Study Period 07/03 09/03 11/03 01/04 03/04 05/04 07/04 09/04 TIN leached (g N m-2) 0.0 0.1 0.2 0.3 0.4 2.5 g N m-2 5.0 g N m-2 Figure 3-4. Comparison of tota l inorganic-N leached from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events.

PAGE 145

129 Cycle 3 Cycle 5 07/03 08/03 09/03 10/03 11/03 12/03 01/04 02/04 Leaf blade [N] (mg N g-1) 18 20 22 24 26 28 2.5 g N m -2 5.0 g N m -2 Figure 3-5. Comparison of leaf blade N concen trations from St. Augustinegrass fertilized with 2.5 and 5.0 g N m-2 bimonthly for cycles 3 (WET) and 5 (DRY).

PAGE 146

130 LIST OF REFERENCES ACSE. 1978. Describing irriga tion efficiency and uniformity. J. Irrig. And Drain. Engng. 104(1):35-41. Alberts, E. E., R. E. Burwell, and G. E. Schuman. 1977. Soil nitrate-nitrogen determined by coring and solution extraction technique s. Soil Sci. Soc. Am. J. 41:90-92. Allen, S. E., C. M. Hunt, and G. L. Term an. 1971. Nitrogen release from sulfur-coated urea, as affected by coating weight, placem ent, and temperature. Agron. J. 63: 529533. Barbarick, K. A., B. R. Sabey, and A. Kl ute. 1979. Comparison of various methods of sampling soil water for determining ionic sa lts, sodium, and calcium content in soil columns. Soil Sci Soc. Am. J., 43:1053-1055. Baum, M. C., M. D. Dukes, and G. L. Mill er. 2003. Residential irrigation uniformity and efficiency in Florida. Written for the ASAE Florida section meeting. Paper#:FL03100. Beard, J. B. 1973. Turfgrass: Science and cu lture. Prentice-Hall, In c. Engelwood Cliffs, N.J. Beier, C., and K. Hansen. 1992. Evaluation of porous cup soil-water samplers under controlled field conditions : comparison of ceramic and PTFE cups. J. of Soil Sci. 43:261-271.Beard, J.B. 1973. Turfgrass science and culture. Prentice Hall, Englewood Cliffs, N.J. Beier, C., K. Hansen, P. Gundersen, a nd B. R. Andersen. 1992. Long-term field comparison of ceramic and poly(tetrafluor oethene) porous cup soil-water samplers. Envir. Sci. and Tech. 26:2005. Bogdan, A.V. 1977. Tropical pasture and f odder plants. Longman Inc., New York. Bowman, D. C., C. T. Cherne y, and T. W. Rufty, Jr. 2002. Fate and transport of nitrogen applied to six warm season turf grasses. Crop Sci. 42: 833-841. Bowman, D. C., D. A. Devitt, M. C. Englek e, and T. W. Rufty, Jr. 1998. The effect of root architecture on nitrat e leaching from bentgrass turf. Crop Sci. 38:1633-1639. Bowman, D. C., J. L. Paul., W. B. Davi s, and S. H. Nelson. 1987. Reducing ammonia volatilization from Kentucky Bluegrass tu rf by irrigation. Hortic. Sci. 22:84-87.

PAGE 147

131 Brady, N.C., and R. R. Weil, 2002. The nature and properties of so ils. Ed. 13. Prentice Hall. Upper Saddle River, N.J. Briggs, L. J. and J. R. McCall. 1904. An ar tificial root for indu cing capillary movement of soil moisture. Science 20:566-568. Broschat, T. K., and M. L. Elliott. 2004. Nu trient distribution and sampling for leaf analysis in St. Augustinegrass. Comm. In Soil. Sci. and Plant Anal. v.35 no.15 and 16:2357-2367. Broward Soil and Water Conservation District (BSWCD). Mobile irrigation lab results. 2005. Davie, FL. Brown, K. W., J. C. Thomas, and R. L. Duble. 1982. Nitrogen source effect on nitrate and ammonium leaching and runoff losses from greens. Agron. J. 74:947-950. Burt, C. M., A. J. Clemmens, T. S. Strlkoff, K. H. Solomon, R. D. Bliesner, L. A. Hardy, T. A. Howell, Members, ASCE, and D. E. Eisenhauer. 1997. Irrigation performance measures: Efficiency and uniformity. J. Irr. And Drain. Eng. 123(6):423-442. Carrow, R. N. 1996. Drought resistance aspects of turfgrasses in the southeast: Rootshoot responses. Crop Sci. 36:687-694. Carrow, R. N., D. V. Waddington, and P. E. Rieke. 2001. Turfgrass soil fertility and chemical problems, assessments and management. Ann Arbor Press, Chelsea, Michigan. Casey, F. X. M., N. Derby, R. E. Knight on, D. D. Steele, a nd E. C. Stegman. 2002. Initiation of irrigation effects on tempor al nitrate leaching. Vadose Zone J. 1:300309. Chen, C. P., 1992. Stenotaphrum secundatu m (Walter) O. Kuntze. p. 208-209. In: t Mannetje, L. & Jones, R.M. (Ed): Plant re sources of South-East Asia no 4. Forages. Pudoc-DLO, Wageningen, the Netherlands. Cisar, J. L., G. H. Snyder, J.J. Haydu, D. M. Park, and K. E. Williams. 2005. An evaluation of nitrogen sources on bermudagr ass color, clippings, and nitrogen release. Proc. of the 10th Inter. Turf. Res. Confer. 1:144-151. Cisar, J. L., J. E. Erickson, G. H. Snyder, J. J. Haydu, and J. C. Volin. 2004. Documenting nitrogen leaching and runo ff losses from urban landscapes. p. 266269 In Environmental impact of fertilizer on so il and water. ed. W. L. Hall and W. P. Robarge. Oxford University Press. Cary, N.C. Cisar, J. L., G. H. Snyder, J. J. Haydu, and K. E. Williams. 2001. Turf response to coated-rurea fertilizers. Proc. Fla. State Hort. Soc. 114:254-258.2001.

PAGE 148

132 Cisar, J. L., G. H. Snyder, and G. S. Swanson. 1992. Nitrogen, phosphorus, and potassium fertilization for histosol-gro wn St. Augustinegrass sod. Agron. J. 84:475479. Cisar, J. L., G. H. Snyder, and P. Nkedi-Ki zza. 1991. Maintaining quality turfgrass with minimal nitrogen leaching. p.11. Bulletin 273, University of Florida, IFAS. Gainesville, FL Cole, D.W., 1968. A system for measuring condu ctivity, acidity, and ra te of flow in a forest soil. Water Resour. Res. 4:1127. Connellan, G. 2002. Efficient irrigation: A re ference manual for turf and landscape. Burnley College Report. University of Melbourne. Davis, S. M. 1994. Phosphorus inputs and vege tation sensitivity in the Everglades. p. 419-444 In S.M. Davis and J.C. Ogden (eds.) Everglades: The ecosystem and its restoration. St. Lucie Press, Delray Beach, FL. Debyle, N. V., R. W. Hennes, and G. E. Hart. 1988. Evaluation of ceramic cups for determining soil solution ch emistry. Soil Sci. 146:30-36. Devitt, D. A., J. Letey, L. J. Lund, and J. W. Blair. 1976. Nitrate-nitrogen movement through soil as affected by soil profile characteristics. J. Environ. Qual. 5:283-288. Duble, R. L. 1989. Southern turfgrasses: Their management and use. TexScape, Inc., College Station, TX. Dunbabin, V., A. Diggle, and Z. Rengel. 2003. Is there an optimal r oot architecture for nitrate capture in leaching environmen ts? Plant, Cell ad Environ. 26:835-844. Erickson, J. E., J. L. Cisar, J. C. Voli n, and G. H. Snyder. 2001. Comparing nitrogen runoff and leaching between newly estab lished St. Augustinegrass turf and an alternative residen tial landscape. Crop Sci. 41(6):1889-1895. Ernst, J. W. and H. F. Massey. 1960. The e ffect of several fact ors on volatilization of ammonia formed from urea in the soil. Soil Sci. Soc. of Am. Proc. 24: 87 Ewel, K.C., and H.T. Odum. Editors. 1984. Cypress swamps. Univ. Press. of Fl. Gainesville. 472 pp. Fares, A., and A. K. Alva. 1999. Estimation of citrus evapotranspiration by soil water mass balance. Soil Sci. 164(5):302-310. Flipse, W. J., Jr., B. G. Katz, J. B. Linder and R. Markel. 1984. Sources of nitrate in ground water in a sewered housing developm ent. Central Long Island, New York. Ground Water. 32: 418-426. Florida Department of Environmental Pr otection. 2002. Florida water conservation initiative. Tallahassee, FL.

PAGE 149

133 Fry, J. D., D. O. Fuller, and F. P. Maier. 1993. Nitrogen release from coated ureas applied to turf. Proc. of the 7th Inter. Turf. Res. Confer. 7:533-539. Gee, G. W., Z. F. Zhang, and A. L. War d. 2003. A modified vadose zone fluxmeter with solution collection capabilit y. Vadose Zone J. 2:627-632. Geron, C. A., T. K. Danneberger, S. J. Tr aina, T. J. Logan, and J. R. Street. 1993. The effects of establishment methods and fertil ization practices on nitrate leaching from turfgrass. J. Environ. Qual. 22(1):119-125. Harris, A. R., and E. A. Hansen. 1975. A new ceramic cup soil water sampler. Soil Sci. Soc. Am. J. 39:157. Haydu, J. J., J. L. Cisar, and L. N. Satterh waite. 2005. Floridas s od production industry: A 2003 survey. in Proceedings of the 10th International Turfgrass Research Conference. 10(2):700-704. Haydu, J. J., L. N. Satterhwaite, and J. L. Cisar. 2002. An economic and agronomic profile of Floridas turf grass sod industry in 2000. Economic Rep. ER02-6, Food and Res. Economics Dep., Univ. of Florida, Gainesville, FL. 25pp. Hitchcock, A. S. 1950. Manual of the grasses of the United States. USDA Misc. Pub. No. 200. U.S. Gov. Print. Office, Washington, DC Horgan, B. P., B. E. Branham, and R. L. Mulvaney. 2002. Mass bala nce of 15N applied to Kentucky bluegrass including direct measurement of denitification. Cop Sci. 42:1595-1601. Huang, B., R. R. Duncan, and R. N. Carro w. 1997. Drought resistance mechanisms of seven warm-season turfgrasses under surface so il drying:II Root aspects. Crop Sci. 37:1863-1869. Hummel, N. W., Jr., and D. V. Waddington. 1981. Evaluation of slow-release nitrogen sources on Baron Kentucky bluegrass. Soil Sci. Soc. Am. J. 45:966-970. Hummel, N. W., Jr., and D. V. Waddington. 1984. Sulfur-coated urea for turfgrass fertilization. Soil Sci. Soc.Am. J. 48:191-195. Karnock, K. J., Tucker, K. 1999. Dry spots re turn with summer. Golf Course Mgt. May:49-52. Levin, M. J., and D. R. Jackson. 1977. A comp arison of in situ extractors for sampling soil water. Soil Sci. Soc. Am. J. 41:535-536. Litaor, M. I. 1988. Review of soil solution sa mplers. Water Resour. Res. 24(5):727-733. McCloud, D. E. 1955. Water requirements for fi eld crops in Florida as influenced by climate. Proc. Soil. Sci. Soc. Florida. 15:165-172.

PAGE 150

134 Moll, R. H., E. J. Kamprath, and W. A. Jackson. 1982. Analysis and interpretation of factors which contribute to efficiency to nitrogen utilization. Agron. J. 74:562-564. .Morton, T. G., A. J. Gold, and W. M. Sullivan. 1988. Influence of overwatering and fertilization on nitrogen losses from home lawns. J. Environ. Qual. 17:124-130. Nagpal, N. K. 1982. Comparison among and eval uation of ceramic porous cup soil water samplers for nutrient transport studies. Can. J. Soil Sci. 62:685-694. Noe, G. B, D. L. Childers, and R. D. J ones. 2001. Phosphorus biogeochemistry and the impact of phosphorus enrichment: Why is the Everglades so unique? Ecosystems 4:603-624. OToole, P., M. A. Morgan, and D. M. McAleese. 1982. Effects of soil properties, temperature and urea concentration on pattern s and rates of urea hydrolysis in some Irish soils. Irish J. of Agric. Res. 21: 185 Peacock, C. H., and J. M. Diapola. 1992. Be rmudagrass response to reactive layer coated fertilizers. Agron. J. 84:946-950. Peacock, C. H., and A. E. Dudeck. 1985. Efect of irrigation interval on St. Augustinegrass rooting. Pendelton, R. F., H. D. Dollar, L. Law, Jr., S. H. McCollum, and D. J. Belz. 1984. Soil survey of Broward County, Florida. East ern part. United States Department of Agriculture, Soil Conservation Service. U.S. Gov't Printing Off. pp. 116-119. Petrovic, A. M. 2004. Nitrogen source and timing impact on nitrate leaching from turf. 2004. Acta Horticulturae 661:427-432. Petrovic, A. M. 1990. The fate of nitrogenous fe rtilizers applied to tu rfgrass. J. Environ. Qual. 19:1. Qian, Y. L., J. D. Fry, and W. Upham. 1997. Rooting and drought avoidance of four turfgrasses in Kansas. Crop Sci. 37:905-910. Qian, Y. L. and M. C. Engelke. 1999. Perf ormance of five turfgrasses under linear gradient irrigation. HortScience 34(5):893-896. Ruppert, K.C. and R.J. Black. 1997. Florida lawn handbook (2nd edition). University of Florida, Institute of Food and Agricultu ral Sciences, Gainesville, FL. 217 pp. Sartain, J. B. 1992. Natural organic slow-releas e N sources for turfgrasses. Proc. Fla. State Hort. Soc. 105:224-226. Sartain, J. B. 2001. Soil testing and interpretatio n for Florida turfgra sses. Univ. of Fla. Coop. Ext. Serv. SL 181.Univ. of Florida, Gainesville, FL.

PAGE 151

135 Sheard, R. W. and E. G. Beauchamp. 1985. Aerodynamic measurement of ammonia volatilization from ureas applied to bluegrass-fescue turf, p. 549-556 in F. L. Lemaire (ed.),Proc. 5th Int. Turf grass Res. Conf., Avignon, France. Sheard, R. W., M. A. Haw, G. B. Johnson, and J. A. Ferguson. 1985. Mineral nutrition of bentgrass on sand rooting systems. p.469-485. in F. L. Lemaire (ed.) Proc. 5th Int. Turfgrass Res. Conf., Avignon, France. Sigunga, D. O., B. H. Janssen, and O. Oenema. 2002. Ammonia vol atilization from Vertisols. European J. of Soil Sci. 53 2:195-202 Silkworth D. R. and Grigal D. F. 1981. Fiel d comparison of soil solution samplers. Soil Sci. Soc. Am. J. 45:440. Skopp, J., M. D. Jawson, and J. W. Doran. 1990. Steady-state microbi al activity as a function of soil water content. Soil Sci. Soc. Am. J. 54:1619-1625. Snyder, G. H., and J. L. Cisar. 2000. M onitoring vadose-zone soil waterfor reducing nitrogen leaching on golf courses. Chap. 14: 243-254. in J. M. Clarcj and M. P. Kenna (eds.) Fate and management of turfgrass chemicals. Amer. Chem. Soc. Symposium Series 743. Oxford Univ ersity Press. New York, N.Y. Snyder, G. H., B. J. Augustin, and J. L. Cisar. 1989. Fertigation fo r stabilizing turfgrass nitrogen nutrition. p. 217-219 In H. Takatoh (ed.) Proc. 6th Int. Turfgrass Res. Conf. (Tokyo), Japanese Soc. Turfgrass Sci., Tokyo. Snyder, G. H., B. J. Augustin, and J. M. Davidson. 1984. Moisture sensor-controlled irrigation for reducing N leaching in be rmudagrass turf. Agron. J. 76:964-969. Snyder, G. H., E. O. Burt, and J. M. Davi dson. 1980. Nitrogen leaching in bermudagrass turf: Effect of nitrogen leach ing in bermudagrass turf: Effect of nitrogen sources and rates. p. 313-324 In R.W. Sheard (ed.) Proc. 4th Int. Turfgrass Res. Conf., Guelph, Canada. Snyder, G. H., E. O. Burt, and B. L. James. 1976. Nitrogen fertil ization of bermudagrass turf in south Florida with urea, UF, and IBDU. Proc. Fla. State Hort. Soc. 89:326330. Soil Survey Staff, Natural Resources Conserva tion Service, United States Department of Agriculture. Official Soil Series Desc riptions [Online WWW]. Available URL: "http://soils.usda.gov/technical/classi fication/osd/index.html" [Accessed 10 February 2004]. South Florida Water Management District. 2001. Commercial / recreational water use restrictions. http://www.sfwmd.gov/curre /watshort/index2.html Accessed on January 10, 2006.

PAGE 152

136 Spalding, R. F., D. G. Watts, J. S. Schepers, M. E. Burbach, M. E. Exner, R. J. Poreda, and G. E. Martin. 2001. Controlling nitrat e leaching in irrigated agriculture. J. Environ. Qual. 30:1184-1194. Starr, J. L., and H. C. DeRoo. 1981. The fate of nitrogen fertilizer ap plied to turfgrass. Crop Sci. 21:531. Statistical Analysis System Institute. 1989. SAS/STAT users guide. Ver. 6 4th ed. SAS Inst., Cary, NC. Taiz, L. and E. Zeiger. 2002. Plant physiology.3rd ed. Sinauer Associates, Inc. Sunderland, MA. Tilman, E. A., D. Tilman, M. J. Crawley, and A. E. Johnston. 1999. Biological weed control via nutrient competition: Po tassium limitation of dandelions. Ecol. Applications 9:103-111. Titko, S., III, J. R. Street, T. J. Logan. 1987. Volatilization of ammonia from granualar and dissolved urea applied to turfgrass. Agr on. J. 79:535-540. Trenholm, L. E., E. F. Gilman, G. W. Knox, and R. J. Black. 2002. Fertilization and irrigation needs for Florida lawns and la ndscapes. Univ. of Fla. Coop. Ext. Serv., ENH 860. Univ. of Fl., Gainesville, FL. Trenholm, L. E., J. B. Unruh, and J. L. Cisa r. 2003. Watering your Florida lawn. Univ. of Fla. Coop. Ext. Serv., ENH 9. Univ. of Florida, Gainesville, FL. U. S. Environmental Protection Agency. 1976. Quality criteria for water. U. S. Gov. Print. Office. Washington, DC. 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. 6:99-108. Volk, G. M. 1959. Volatile loss of ammonia fo llowing surface applications of urea to turf or bare soil. Agron. J. 75:454. Wang, F. L., and A. K. Alva. 1996. Leaching of nitrogen from slow-release urea sources in sandy soils. Soil Sci. Soc. Am. J. 60:1454-1458. Watson, C. J. 1987. The comparative effects of ammonium nitrate, urea, or a combination of nitrate/urea granular fert ilizer on the efficiency of n itrogen recovery by perennial ryegrass. Fert. Res. 11:69-78. Wolf, B., and G. H. Snyder. 2003. Sustainabl e Soils: The place of organic matter in sustaining soils and their productivity. The Hawthorn Press, Inc. Binghampton, NY. Wood, W.W., 1973. A technique us ing porous cups for water sampling at any depth in the unsaturated zone. Wa ter Resour. Res. 9:486.

PAGE 153

137 Zhu, Y., R. H. Fox, and J. D. Toth. 2002. Leach ate collection efficiency of zero-tension pan and passive capillary fiberglass wick lysimeters. Soil Sci. Am. J. 66:37-43. Zimmerman, C. F., M. T. Price, and J. R. Montgomery. 1978. A comparison of ceramic and teflon in situ samplers for nutrient pore water determination. Estuarine Coastal Mar. Sci. 7:93-97

PAGE 154

138 BIOGRAPHICAL SKETCH Dara Michelle Park is the Water/Turfg rass Management Biologist for Dr. John Cisar at the University of Floridas Fort Lauderdale Research and Education Center. Before Dara began her career at the Univer sity of Florida, sh e graduated with her undergraduate degree in biological sciences and her masters degree in environmental sciences from Florida Atlantic University. Her research interests include preventative and amelioration of soil water repellency in turfgrass systems, determining irrigation requirements for non well-watered turfgrass sy stems, reducing water consumption from irrigation by utilizing surfactants, and determin ing fertilizer best management strategies for urban turfgrass landscapes including golf cour se and sports field turfgrasses and lawn turfgrasses. Dara is the S ecretary of the Broward Chapter of the Florida Native Plant Society, is a member of the Gamma Sigma Delta Honorary Fraternity, and is active in the treasury duties for the International Turfgrass Society.


Permanent Link: http://ufdc.ufl.edu/UFE0013784/00001

Material Information

Title: Nitrogen Leaching and St. Augustinegrass Turf Response to Lawn Maintenance Strategies.
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0013784:00001

Permanent Link: http://ufdc.ufl.edu/UFE0013784/00001

Material Information

Title: Nitrogen Leaching and St. Augustinegrass Turf Response to Lawn Maintenance Strategies.
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0013784:00001


This item has the following downloads:


Full Text











NITROGEN LEACHING AND ST. AUGUSTINEGRASS TURF RESPONSE TO
LAWN MAINTENANCE STRATEGIES















By

DARA MICHELLE PARK


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


2006





























Copyright 2006

by

Dara Michelle Park

































This document is dedicated to my family and the Behringers for their love and support
during my graduate career.















ACKNOWLEDGMENTS

I express my gratitude to Dr. John Cisar for his time and support. Dr. Cisar gave me

the opportunity to integrate two of my passions: soil and water science and a desire to

help protect the environment. His support was instrumental in all facets of the research. I

wish to thank Drs. George Snyder, Samira Daroub, Jerry Sartain and Don Graetz for their

time and their contribution on this project. I would like to acknowledge the financial

support of the Southwest Florida Water Management District, Florida Turfgrass

Association, and the Florida Department of Agriculture and Consumer Services. I

appreciate the support and guidance of the SWFWMD project managers Mr. Eric

DeHaven and Mr. Kyle Champion. I would also like to acknowledge the contributions of

Mr. Wiley McCall and family, Environmental Turf, Inc., and The Toro Co. for material

support. The technical support and contributions of University of Florida staff and

students including Ms. Eva King, Mr. David Rich, Mr. Kevin Wise, Mr. John Wissenger,

Mr. Kevin Mc Gowen, Mr. Gary Pederson, Dr. Raymond Snyder, and Ms. Felica

Raphael-Greenberg are much appreciated. A special thanks to Karen Williams, for her

technical assistance, scientific knowledge, and as a sounding board for ideas and

reasoning. And finally to my husband Scott, thanks for his love, support and patience.














TABLE OF CONTENTS



A C K N O W L E D G M E N T S ................................................................................................. iv

LIST OF TA BLE S ............... ............... ................ ......... .............. .. vii

LIST OF FIGURE S ......... ..................................... ........... xii

A B S T R A C T .......................................... ..................................................x v

CHAPTER

1 CONSTRUCTION OF A FIELD SCALE FACILITY TO DOCUMENT
NITROGEN LEACHING AND TURFGRASS RESPONSE FROM ST.
AUGUSTINEGRASS 'FLORATAM' MANAGEMENT STRATEGIES ..................1

In tro d u ctio n .................................................................................................... ..... .
M materials and M methods ................................................................. ....................... 5
R results and D discussion ....................................................... .. ............ 11
Irrigation U uniform ity ............................................ ........ .. .......... .............. .. 11
Natural Fluctuations in Percolate and Nitrate ............................................. 12
Sod Establishment .................. .......................... ........ ................. 13
C o n c lu sio n s..................................................... ................ 1 5

2 EFFECT OF IRRIGATION, N SOURCES AND RATES ON N LEACHING,
TURFGRASS QUALITY AND GROWTH FROM NEWLY ESTABLISHED
ST. AU GU STINEGRA SS LAW N S ............................................... .....................22

Introduction .............. ..... ... .............. .................................. 22
M materials and M methods ....................................................................... ..................24
R results and D iscu ssion ................................. .............. ................ ..... .......... 29
W after Budget.... .......................................................... 29
Nitrate Concentrations and Leaching ...................................... ............... 30
Ammonium Concentrations and Leaching............. .....................31
Total Inorganic Nitrogen Concentrations and Leaching ...................................33
St. Augustinegrass Quality ............................................................................ 36
St. A ugustinegrass G row th........................................................ ............... 37
Leaf Blade Nitrogen Concentrations ...........................................................40
N itrogen U ptake Efficiency ....................................................... .... ........... 42
Nitrogen Budget and Scenario Comparison.................................................43
C o n clu sio n s..................................................... ................ 4 7









3 EFFECT OF IRRIGATION, N SOURCES AND RATES ON N LEACHING,
TURFGRASS QUALITY AND GROWTH FROM ESTABLISHED ST.
AU GU STINEGRA SS LAW N S. ..................................................... .....................83

In tro d u ctio n ................................................... .................. ................ 8 3
M materials and M methods ....................................................................... ..................86
R results and D iscu ssion ................................. .............. ................ ..... .......... 90
Water Budget ................................. ............................ ...........90
Nitrate Concentrations and Leaching ...................................... ............... 92
Am m onium Concentrations and Leaching ................................. .....................93
Total Inorganic Nitrogen Concentrations and Leaching ...................................95
St. A ugu stinegrass Q quality ....................................................... .....................96
St. A ugustinegrass G row th........................................................ ............... 96
Leaf Blade Nitrogen Concentrations ...........................................................99
N itrogen U ptake Efficiency ........................................ ............ ....... ........ 100
Nitrogen Budget and Scenario Comparison.................... ..................................101
C o n clu sio n s.................................................... ................ 10 4

LIST OF REFEREN CES ........................................................... .. ............... 130

BIOGRAPHICAL SKETCH ............................................................. ............... 138















LIST OF TABLES


Table p

1-1 Mean, standard deviation and Levene's Test for Homogeneity for (a) actual
percolate volumes, (b) nitrate concentrations, and (c) nitrate leached for each of
the four collection dates during the stabilization period with only bare soil as a
cov er. ................................................................................ 17

1-2 Nitrogen inputs (g m-2) during the four month establishment period for sod with
40 g kg-l and 100 g kg-1 SOM ........................................... ........................... 17

1-3 Comparison of mean root dry weights (g) from 40 g kg-1 and 100 g kg-1 SOM
collected from cores between 0-15 cm and 15-30cm depths. ................................17

2-1 (a) Explanation of experimental factors tested and (b) ANOVA table used for
statistical differences determ nation ............................................... ................... 53

2-2 W ater budget from April 2001 to April 2002. ............. ........................................54

2-3 ANOVA table for NO3-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ........................................... ............ 54

2-4 Interaction of SOM*IRR*Rate on NO3-N concentrations (mg 1-1) during the
DRY season. Significance values listed are for SOM differences within each N
rate .............................................................. ................ 5 5

2-5 ANOVA table for total NO3-N leached for WET and DRY seasons. Significant
differences are bold and italicized ................................... ............................. ......... 55

2-6 Interaction of SOM*Rate on total NO3-N leached (g m-2) during the DRY
season. Significance values listed are for SOM differences within each N rate......55

2-7 Interaction of IRR*Rate on total NO3-N leached (g m-2) during the DRY season.
Significance values listed are for IRR differences within each N rate.....................56

2-8 ANOVA table for NH4-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ........................................... ............ 56

2-9 ANOVA table for total NH4-N leached for WET and DRY seasons. Significant
differences are bold and italicized.................................................. 57








2-10 ANOVA table for total inorganic-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ........................................ ............57

2-11 Interaction of SOM*Rate on total inorganic-N concentrations (mg 1-1) during the
DRY season. Significance values listed are for SOM differences within each N
rate .............................................................. ................ 5 8

2-12 Interaction of IRR*Rate on total inorganic-N concentrations (mg 1-1) during the
DRY season. Significance values listed are for IRR differences within each N
rate ............... ..........................................................................5 8

2-13 ANOVA table for total total inorganic-N leached for WET and DRY seasons.
Significant differences are bold and italicized. ....................................... ........... 58

2-14 Interaction of SOM*Rate on total inorganic-N leached (g m-2) during the DRY
season. Significance values listed are for SOM differences within each N rate......59

2-15 Interaction of IRR*Rate on total inorganic-N leached (g m-2) during the DRY
season. Significance values listed are for IRR differences within each N rate........59

2-16 ANOVA table for mean quality scores for WET and DRY seasons. Significant
differences are bold and italicized ........................................................................ 59

2-17 Interaction of SOM*Rate on turf quality scores during the WET season.
Significance values listed are for SOM differences within each N rate...................60

2-18 Interaction of SOM*IRR* Source on turf quality scores during the WET season.
Significance values listed are for SOM differences within each IRR*Source
c o m b in atio n ..............................................................................................................6 0

2-20 Interaction of SOM*Rate on total clipping yield (g m-2) during the WET season.
Significance values listed are for SOM differences within each N rate...................61

2-21 Interaction of SOM*Rate on total clipping yield (g m-2) during the DRY season.
Significance values listed are for SOM differences within each N rate...................61

2-22 ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected
on 01 August 2001. Significant differences are bold and italicized.........................62

2-23 Interaction of IRR*Rate on root weight density (g m-3) within the upper 0-15
cm of the soil from cores collected 01 August 2001. Significance values listed
are for IRR differences within each N rate................................... ..................62

2-24 ANOVA table for root weight density for 0-15 cm and 15-30 cm cores collected
on 01 August 2002. Significant differences are bold and italicized.........................63

2-25 Root weight densities (g m-3) from the 15-30 cm soil depth collected on 01
August 2002 were influenced by SOM*Source*Rate interactions. Significance
values listed are for SOM differences within each N Rate and N Source ...............63








2-26 ANOVA table for leaf blade N concentrations for WET and DRY seasons.
Significant differences are bold and italicized ............................................. ........... 64

2-27 Nitrogen sources influenced leaf blade N concentrations (mg g-l) during both
se a so n s ................................. ........................................................... ............... 6 4

2-28. Interaction of SOM*Rate for N concentrations within leaf blades (mg g-l) during
the DRY season. Significance values listed are for SOM differences within each
N rate ............................................................ ................ 6 4

2-29 ANOVA table for nitrogen uptake efficiency for WET and DRY seasons.
Significant differences are bold and italicized ............................................. ........... 65

2-30 Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the WET
season. Significance values listed are for SOM differences within each N rate......65

2-31 Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the DRY
season. Significance values listed are for SOM differences within each N rate......65

2-32 WET season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b)
100 g kg-1 SO M ........................................................................66

2-33 DRY season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and (b)
100 g kg-1 SO M ........................................................................67

3-1 (a) Experimental factors tested and (b) ANOVA table of factors and interactions
tested ............................................................................................ 10 7

3-2. Water budget from March 2003 to September 2004. ............................................108

3-3 ANOVA table for N03-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ............. ......................... ......... 109

3-4 WET season N03-N concentrations (mg 1-1) were influenced by SOM*Source*
N Rate interactions. Significance values listed are for SOM differences within
each N R ate and N Source .......................................................................... ..... 109

3-5 ANOVA table for total N03-N leached for WET and DRY seasons. Significant
differences are bold and italicized ...................................................................... 110

3-6 WET season N03-N leached (g N m-2) were influenced by SOM*Source*Rate
interactions. Significance values listed are for SOM differences within each N
R ate an d N S ou rce .................................................................... .. .......... .. .. 1 10

3-7 ANOVA table for NH4-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized ................................ ................... 111








3-8 WET season NH4-N concentrations (mg 1-1) were influenced by
IRR*Source*Rate interactions. Significance values listed are for IRR
differences within each N Rate and N Source.................. ............... .................111

3-9 DRY season NH4-N (mg 1-1) were influenced by IRR*Source*Rate interactions.
Significance values listed are for IRR differences within each N Rate and N
S o u rc e ............................................................................................... 1 12

3-10 ANOVA table for NH4-N leached for WET and DRY seasons. Significant
differences are bold and italicized ....................................................................... 112

3-11 WET season NH4-N leached (g m-2) were influenced by IRR*Source*Rate
interactions. Significance values listed are for IRR differences within each N
R ate and N Source .................. ...................................... .. ........ .. 113

3-12 DRY season NH4-N leached (g m-2) were influenced by IRR*Source*Rate
interactions. Significance values listed are for IRR differences within each N
R ate and N Source .................. ...................................... .. ........ .. 113

3-13 ANOVA table for total inorganic-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ......................................................114

3-14 ANOVA table for total inorganic-N leached for WET and DRY seasons.
Significant differences are bold and italicized. ......................................................114

3-15 ANOVA table for turfgrass quality for WET and DRY seasons. Significant
differences are bold and italicized ....................................................................... 115

3-16 WET season quality scores were influenced by IRR*Source*Rate interactions.
Significance values listed are for IRR differences within each N Rate and N
S o u rc e ............................................................................................... 1 1 5

3-17 DRY season quality scores were influenced by IRR*Source*Rate interactions.
Significance values listed are for IRR differences within each N Rate and N
S o u rc e ............................................................................................... 1 16

3-18 ANOVA table for clipping yield for WET and DRY seasons. Significant
differences are bold and italicized ....................................................................... 116

3-19 WET season clipping yields (g m-2) were influenced by IRR*Rate interactions... 117

3-20. ANOVA table for root weight density for 0-15 cm and 15-30 cm depths from
cores collected on 04 A ugust 2003 ................................ ............. ................... 117

3-21 ANOVA table for root weight density for 0-15 cm and 15-30 cm depths from
cores collected on 27 April 2004. Significant differences are bold and italicized. 118








3-22 Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were
influenced by SOM*Rate* Source interactions. Cores were collected on 27 Apr
2 004 .............................................................................................118

3-23 Root weight densities (g cm-3) from cores collected at the 0-15 cm depth were
influenced by SOM*IRR*Rate interactions. Cores were collected on 04 Aug
2003 .............................................................................................119

3-24 Influence ofN sources on root weight density (g m-3) of cores collected at the
15-30 cm depth on 27 April 2004. .................................. ............ ..... .......... 119

3-25 Root weight densities (g m-3) from cores collected at the 15-30 cm depth on 27
April 2004 were influenced by SOM*Rate interactions ............ ...............119

3-26 ANOVA table for pelt weight from cores collected on 27 April 2004. No
significant differences were determined. .................................... .................120

3-27 ANOVA table for leaf blade N concentrations for WET and DRY seasons.
Significant differences are bold and italicized. ............. ........................ ......... 120

3-28 WET season leaf blade N concentrations (mg N g-l) were influenced by
SOM* Source interactions. Significance values listed are for SOM differences
w within each N Source. ........................ ...... ................ ............... .... .......... 12 1

3-29 ANOVA table for nutrient uptake efficiency for WET and DRY seasons.
Significant differences are bold and italicized. ............. ........................ ......... 121

3-30 DRY season (cycle 5) nutrient uptake efficiency (%) was influenced by
IRR*Source*Rate interactions. Significance values listed are for IRR
differences within each N Rate and N Source.................... .................. ................ 122

3-31 WET season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1
and (b) 100 g kg-1 SO M ..................................... ........................... 123

3-32 DRY season cycle N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and
(b) 100 g kg-1 SO M ........................ ...................... ... .. .. .... ...............124















LIST OF FIGURES


Figure page

1-1 Schematic drawing of equipment used to collect vadose zone percolate: (a)
dimensions of the ceramic cup sampler, (b) connections supplying sampler with
a vacuum, (c) connections for sample extraction, and (d) extractor / overflow
dev ice. ..............................................................................18

1-2 Rainfall and irrigation (mm) over the (a) stabilization and (b) establishment
p erio d s. ............................................................. ................ 19

1-3 Nitrate concentrations (mg 1-1) determined in percolate from sod containing 40 g
kg- SOM compared to sod with 100 g kg- SOM during the (a) stabilization and
(b) establish ent periods. ............................................................. .....................20

1-4 Nitrate leaching (g m-2) from sod containing 40 g kg-1 SOM compared to sod
with 100 g kg-1 SOM during the (a) stabilization and (b) establishment periods...21

2-1 Daily rainfall over the experimental period for Experiment 1...............................68

2-2 Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass with
40 g kg1 soil organic matter (SOM) to St. Augustinegrass with 100 g kg- SOM
for the three N rates during the study period. Arrows mark fertilization events......69

2-3 Comparison of cumulative NO3-N leached (g m-2) from St. Augustinegrass
maintained with the FIX irrigation schedule to St. Augustinegrass maintained
with the ADJ irrigation schedule for the three N rates during the study period.
Arrows mark fertilization events ................................................... ....... ....... 70

2-4 Comparison of weekly NO3-N leached (g m-2) from St. Augustinegrass fertilized
with the four N sources at the 5.0 g m-2 bimonthly rate during the study period.
Daily rainfall (mm d-) is on the secondary axis. Arrows mark fertilization
ev en ts ..............................................................................................7 1

2-5 Comparison of weekly NH4-N leached (g m-2) from St. Augustinegrass fertilized
with the four N sources at the 5.0 g m-2 bimonthly rate and maintained with the
ADJ irrigation schedule during the (a) WET and (b) DRY seasons. Arrows mark
fertilization ev ents. ............................................................. ............ ..................72









2-6 Mean weekly flow weighted total inorganic-N concentrations (mg 1-) from St.
Augustinegrass fertilized with the three N rates and maintained with the ADJ
irrigation schedule during the (a) WET and (b) DRY seasons. Arrows mark
fertilization ev ents. ............................................................. .......... ....................73

2-7 Mean weekly flow weighted toal inorganic-N concentrations (mg 1-1) from St.
Augustinegrass fertilized with the three N rates and maintained with the (a) FIX
and (b) ADJ irrigation schedules during the DRY season. Arrows mark
fertilization ev ents. ............................................................. .......... ....................74

2-8 Comparison of weekly total inorganic-N leached (g m-2) from St.
Augustinegrass fertilized with the three bimonthly N rate during the (a) WET
and (b) DRY seasons. Daily rainfall (mm d-1) is on the secondary axis. Arrows
m ark fertilization events ........................................................................... ...... 75

2-9 Comparison of weekly total inorganic-N leached (g m-2) from St.
Augustinegrass fertilized with the three bimonthly N rate maintained with the
(a) ADJ and (b) FIX scheduled during the DRY season. Daily rainfall (mm d1)
is on the secondary axis. Arrows mark fertilization events..................................76

2-10 Quality scores of St. Augustinegrass associated with 40 g kg-1 and 100 g kg-1
soil organic matter (SOM) maintained at the three N rates over the (a) WET and
(b) DRY seasons. Arrows mark fertilization events. .............................................77

2-11 Quality scores of St. Augustinegrass fertilized with different N sources over the
(a) WET and (b) DRY seasons. Arrows mark fertilization events...........................78

2-12 Clipping yield (g m-2) of St. Augustinegrass fertilized with different N sources
over the D R Y season ................................................................ .......... ....... 79

2-13. Comparison of leaf blade N concentration (mg N g-l) grown with 40 g kg-1 soil
organic matter (SOM) and 100 g kg-1 SOM during the (a) WET and (b) DRY
seasons. A rrow s m ark fertilization events..................................... .....................80

2-14 Comparison of leaf blade N concentrations (mg N g-l) grown from the four N
sources during the (a) WET and (b) DRY seasons. Arrows mark fertilization
ev en ts ..............................................................................................8 1

2-15 Comparison of cumulative nitrogen uptake efficiency (g m-2) from the four N
sources during the DRY season. Arrows mark fertilization events .......................82

3-1 Daily rainfall over the experimental period for Experiment 2 ............................125

3-2 Comparison of weekly cumulative N03-N leached from St. Augustinegrass
associated with (a) 40 g kg-1 and (b) 100 g kg-1 soil organic matter (SOM)
fertilized with the four N sources at 2.5 and 5.0 g N m-2 bimonthly over the
study period. Arrows mark fertilization events .......................................... 126










3-3 Comparison of NO3-N leached from St. Augustinegrass fertilized with 2.5 and
-2
5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization events. ..127

3-4 Comparison of total inorganic-N leached from St. Augustinegrass fertilized with
2.5 and 5.0 g N m-2 bimonthly over the study period. Arrows mark fertilization
e v e n ts ................................................................................................................ 1 2 8

3-5 Comparison of leaf blade N concentrations from St. Augustinegrass fertilized
with 2.5 and 5.0 g N m-2 bimonthly for cycles 3 (WET) and 5 (DRY)................29















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 AND ST. AUGUSTINEGRASS RESPONSE TO LAWN
MAINTENANCE STRATEGIES

By

Dara Michelle Park

May 2006

Chair: Samira Daroub
Major Department: Soil and Water Science

Home lawn fertilization has been implicated as a potential source of nitrogen (N)

contamination to fragile watersheds in southern Florida. A field-scale study evaluating

the effect of N sources and rates, and irrigation scheduling on performance and N

leaching from St. Augustinegrass lawns was conducted in South Florida. Vadose zone

nitrate-N and ammonium-N concentrations were determined in percolate collected from

ceramic cup samplers installed 40 cm below the soil surface. Grass clippings and root

cores were collected to assess growth. Fertilization of N to recently established St.

Augustinegrass at double the standard recommendation resulted in more N leaching.

Conversely, reducing the recommended N rate by half did not reduce N leaching.

Controlled-release N sources did not reduce N leaching, although sulfur coated urea

provided better turf quality during dry season months. Frequency of irrigation was

important in reducing N leaching during dry season months. Water consumption was

reduced by 37% during the wet season by adjusting irrigation on a monthly basis to meet









potential evapotranspiration in conjunction with using a rain shut-off sensor.

Nevertheless, this irrigation scheduling was not effective in reducing N leaching.

Irrigating upon visual wilt produced lower quality turfgrass that eventually required more

frequent irrigation. This research also documented the influence of soil organic matter

(SOM) harvested with sod on turf performance and N leaching. Nitrate-N leaching

increased after sod installation, however quickly declined to pre-installation leaching

losses. During dry season months, greater turf quality and growth was documented from

newly established St. Augustinegrass with 100 g kg-1 SOM, however nitrate-N and total

inorganic-N leaching was also greater when compared to St. Augustinegrass with 40 g

kg-1 SOM. In comparison to recently established St. Augustinegrass, monitoring total

inorganic-N alone was not an effective measure for determining maintenance strategies

for reducing N leaching from established St. Augustinegrass. Best management practices

could be optimized to provide quality St. Augustinegrass with minimizing the potential

for N leaching by accounting for N contributions from SOM of harvested sod when

determining N fertilization applications, seasonally adjusting irrigation schedules, and

utilizing a rain shut-off sensor.














CHAPTER 1
CONSTRUCTION OF A FIELD SCALE FACILITY TO DOCUMENT NITROGEN
LEACHING AND TURFGRASS RESPONSE FROM ST. AUGUSTINEGRASS
'FLORATAM' MANAGEMENT STRATEGIES

Introduction

As population increases in South Florida, so does the concern of water quality

degradation. There is increasing awareness for the potential eutrophication of lakes,

springs, aquifers and bay areas due to anthropogenic inputs. In an effort to reduce urban

N pollution, identification of potential N pollution sources and determining ways to

reduce their detrimental effects are being developed. Residential lawn fertilization has

been implicated as a potential source of elevated N concentrations (Erickson et al., 2001).

A field scale facility was built in South Florida in order to examine the influence of

residential lawn management systems on N leaching. Selection of an irrigation system,

soil-water collection devices and turfgrass were decided upon the following

considerations.

Many of South Florida residential lawns are irrigated by using pop-up spray

sprinklers or rotor sprinklers. For example, between January 2004 and June 2005, the

Broward Soil and Water Conservation District's (BCWCD) Mobile Irrigation Lab

evaluated 79 properties using spray sprinklers and 11 properties with rotor sprinklers. By

these statistics, the use of spray sprinklers is the preferred choice. The uniformity of

water applied by irrigation systems can be assessed by determining the systems

distribution uniformity coefficient (DU). Spray and rotor sprinkler DU were similar









ranging from 50-70% (mean DU = 56.2%) for spray sprinklers and 50-71% (mean DU =

52.1%) for rotor sprinklers (BSWCD, 2005).

Various techniques exist for monitoring soil solution. Porous cups tends to be the

most frequently used in natural environments (Barabarick et al., 1979; Litaor, 1988;

Snyder et al., 1984). Porous cups can be made of stainless steel, Teflon, cellulose, glass,

fiberglass, and porcelain ceramic (Beier et al., 1992). Ceramic cup samplers have been in

use for soil water collection since the early 1900's (Briggs and McCall, 1904). Whether

compared to other cup samplers or to other soil solution collection techniques, ceramic

cup samplers tend to be the preferred material for soil solution nutrient monitoring within

soil solution (Barabarick et al., 1979; Cole, 1968; Silkworth and Grigal, 1981). Alberts et

al. (1977) reported similar results for N03-N recovery from a ceramic cup sampler and a

soil core sampling technique, but favored the ceramic cup for its in situ quality. Beier and

Hansen (1992) reported no differences in six cation concentrations from a ceramic cup

sampler and a polytetrofluoroethene (PTFE) cup sampler. However these authors

observed that the PTFE collected less percolate, and under dry conditions were first to

lose capillary contact. In Litaor's evaluation of soil solution samplers (1988), he states

that many of the other methods besides cup sampling require a greater amount of soil

disturbance, and in some cases the removal of soil, which is not conducive for long term

monitoring. More recently, other techniques such as passive wicks have been used. While

they may collect representative samples (Zhu et al., 2002) and additionally, some can also

determine flux (Gee, 2003), wick samplers may be inadequate for shallow soils. They can

collect samples from unsaturated soils when leaching may not otherwise occur, and the

apparatus can be cost prohibitive for experiments requiring multiple samplers.









Although widely used for on site soil solution collection, the performance of the

ceramic cup samplers for monitoring soil solution N03-N concentration (hereafter as

[N03-N]) has been contradictory. For example, both Harris and Hansen (1975) and

Levin and Jackson (1977) report that ceramic cup samplers did not collect representative

nitrate concentrations. In comparison, Zimmerman et al. (1978) observed high recovery

rates for N03-N and N02-N, as well as for (NO3 + N02)N (Nagpal, 1982). Nagpal

(1982) suggested the reason for low recovery rates in previous experiments was due to

the ceramic surface retaining certain ions (most commonly potassium and phosphate).

Contact time and volume of sample will both affect ion concentrations.

The potential problem of ionic absorption due to the cation exchange capacity

(CEC) of the ceramic surface was first postulated by Wood (1973). Yet it was not until

1988 that the effect of ceramic surface CEC was more closely examined by Debyle and

others (1988). Even though ultimately the chemical makeup of the ceramic's media

mixture determines the CEC of the cup sampler, the CEC is relatively small and can be

quickly satisfied, thus not influencing the soil solution collected (Debyle et al., 1988;

Wood, 1973). If this is the case, collecting multiple soil solution samples before the onset

of an experiment should satisfy the CEC and prepare the ceramic cup sampler to collect

representative samples when an experiment begins. Debyle et al. (1988) also reported

minimal fluctuation in K concentrations for ceramic cups used over a longer period of

time. In previously mentioned study, the authors showed a 0.3 ppm decrease in K

concentrations in a six-year-old cup compared to drainage water (2.5 ppm K and 2.8 ppm

K, respectively). Although the authors found variability in ceramic cup solutions for

diluted concentrations ofNa, N03-N and K (5.55 ppm, 1.1 ppm and 2.5 ppm,









respectively), they state that CEC influence from the ceramic surface would be negligible

for soil solutions with higher ion concentrations and this variability is small compared to

natural variability from soils. Both Debyle et al. (1988) and Harris and Hansen (1975),

suggest the following guidelines to reduce the variability in concentrations from soil

water extracted by ceramic cups: (a) use short sampling intervals, (b) use uniform

sampling lengths, and (c) that all samplers receive the same vacuum. For sampling

vadose zone percolate it is also important that placement of ceramic cup samplers be (a)

above the seasonal high water and (b) below the roots. If the ceramic cup samplers were

placed within the water table, nitrogen concentrations could be influenced by saturated

conditions. The ceramic cup samplers are placed below the roots to ensure that percolate

past the roots would not be utilized by the plant.

Ceramic cup samplers have been used to collect and monitor N03-N movement for

various turfgrass experiments that includes reducing N03-N leaching in bermudagrass

used for home lawns in South Florida (Snyder and Cisar, 2000), reducing N03-N

leaching in bermudagrass used on golf courses in South Florida (Snyder et al., 1984), and

determining the fate of N03-N in a Kentucky bluegrass and red fescue mixed turf in

sandy soils in Connecticut (Starr and DeRoo, 1981).

As the most commonly used lawn type, St. Augustinegrass (Stenotaphrum

secundatum,Walt. Kuntze) represents 64.5% of all sod in production in Florida, with 75%

used for new residential landscapes (Haydu et al., 2002, 2005). The remainder is used for

road medians, commercial landscapes, passive areas, and resodding of existing

landscapes. While there are four cultivars of St. Augustinegrass that are commonly

produced in Florida ('Palmetto', 'Floralawn', 'Bitterblue' and 'Floratam'), 'Floratam' is









the most widely produced, comprising of 75% of all St. Augustinegrass in production. Of

the St. Augustinegrass harvested, 60% came from organic soils (Histosols) located within

the Everglades Agricultural Area with the remaining 40% grown on mineral soils. While

the industry harvested approximately 4% more St. Augustinegrass each year compared to

the previous years from 2000 to 2003, more production is shifting from organic soils to

mineral soils due to loss of organic soils and thus a shift in market locations (Haydu et

al., 2002, 2005). This shift to lower soil organic matter (SOM) attached to sod may

influence NO3-N leaching and turf quality during and beyond sod establishment.

The objectives of this project were to construct a field scale facility capable of

studying multiple turfgrass management factors and their interactions on St.

Augustinegrass quality, growth and N leaching, and to document background N

contributions prior and during sod establishment. The main goals of constructing the

facility were to (a) make the facility capable of examining multiple management factors

and their interactions, (b) to mimic realistic conditions of residential St. Augustinegrass

lawn maintenance and (c) to be able to collect quality scientific data.

Materials and Methods

The site for the experimental facility was the University of Florida's Institute of

Food and Agricultural Sciences, Fort Lauderdale Research and Education Center. An

area of 24 X 48 m was leveled on drained native Margate fine sand soil (siliceous,

hyperthermic Mollic Psamnaquent). The native soil was formed in marine sediments over

fractured limestone (NRCS, 2004) having 20 g kg-1 SOM within the top 38 cm of the soil

surface.









The facility was marked as a randomized sub plot design consisting of eight,

12 X 12 m main plots (isolated by 0.6 m alleys) in two columns. Within each main plot,

four columns of three 4 x 3 m plots were delineated for a total of 12 plots per main plot.

Perimeter irrigation systems were installed on each of the eight main plots. The

irrigation system comprised of 2.4 cm diameter Schedule 40 PVC pipe with rotor Toro

EZ Adjust Sprinklers (EZ5P-60) placed in each corer adjusted to spray an inward

quarter circle. The sprinklers were 127 mm pop up sprinklers with a nozzle delivering

18.9 L per minute. Each main plot irrigation system was on a separate zone and

controlled by a digital irrigation clock (Hunter ICC). Irrigation water was supplied by a

21 m deep well fitted with a submersible pump and brought to the surface with a 10.16

cm diameter pipe. To control sprinkler pressure, valves were installed in-line of the north

end PVC pipe for each main plot. Spray direction and global distribution uniformity

(Dug) was monitored and adjusted upon installation and during the stabilization period.

To test for uniformity, 61 cm diameter catch cans were secured in the center of each plot

by wire hooks. The top of the catch cans were at the same height as the top of the grass

canopy. The irrigation test ran for 10 min per zone either during the day at which time the

volumes of water within the catch cans were immediately measured, or if irrigated over

night, the volumes were measured early the following morning.

The distribution uniformity must account for the spatial variation associated both

within (subplots) and between main plots. Again, main plots are on separate zones, each

with overlapping rotor sprinkler heads at the four corners of the main plots. To integrate

both uniformities, the following equation was derived from Clemmens and Solomon's









(1997, unpublished data) statistical procedure for determining global DU first published

by Burt et al. (1997):

DUg = [1- < (1-DUmain)2 + (1-DUsub)2]


in which DUg = the global distribution uniformity for the experimental area; and DUmain

and DUsub represent the distribution uniformity for the main plots and subplots as

elements, respectively. Both DUmain and DUsub were calculated based on the lower quarter

distribution uniformity method which refers to the average of the depths that fall into the

lowest quarter of all element depths divided by the average of all element depths (ACSE,

1978).

In the center of each plot, ceramic-cup water samplers were installed at a 40 cm

depth to collect vadose zone percolate. A schematic drawing of a ceramic cup sampler

can be found in Figure la. Ceramic cup water samplers were constructed of a 4 mm i.d. X

6 mm height ceramic cup (Soil Moisture Equipment Corp., California) glued to a 4 mm

i.d. schedule 40 PVC body. The PVC body was shortened to a 15.5 mm height. A PVC

end cap was glued to the top of the PVC body and contained two drilled holes in which

two brass tube connectors (Swagelok, Ohio) were installed. The first connector set-up

was for collection of the vadose zone water into the sampler. It consisted of an incoming

tube (0.3 cm o.d. flexible nylon tubing) connected to a remote vacuum to supply suction

into the sampler to collect water from the surrounding soil (Figure 1-lb). When on, the

remote vacuum was regulated at 0.03 MPa in order to ensure that only free draining water

was collected. The second tube connector set-up was for sample extraction (Figure 1-1c).

This consists of a connector with an incoming tube, as well as a tube within the sampler

the length of the body, sleeved in a glass tubing to ensure contact with the base of the









cup. The incoming tube was connected to one of twelve remote sample removal stations

constructed from irrigation control boxes. Each sample removal box was fitted with a

valve to either open or close the sample retrieval line and a quick connect to shunt the

vacuum through an extractor/overflow device. The extractor/overflow device had three

lines. The first was rubber tubing that connected to the quick connect to supply the

vacuum. The vacuum passes through an overflow chamber and was connected to a 0.3

cm o.d. nylon tube. This nylon tube connects to a rubber stopper that was placed upon the

collection vial. A second nylon tube from the stopper connects to the quick connect for a

specific ceramic cup sampler. This second tube supplied the vacuum to extract and

collect the water sample, and a place for excess sample to go so it does not go back into

the vacuum line. The procedure to collect a sample was as follows: (a) Valves were set in

the "closed" position, (b) the vacuum was turned on and water was collected in the

ceramic cup sampler, (c) the valves were set in the "open" position, (d) the

extractor/overflow device was attached to the vacuum quick connect, then the stopper

was placed on the corresponding vial, (e) the sample was collected until the ceramic cup

sampler was drained, (f) steps d-e were repeated for all ceramic cup samplers, and (g)

vacuum was turned off. In September of 2000, the ceramic cup samplers were installed,

covered with soil and then allowed to equilibrate. In mid-November, water samples were

collected on various dates to test for natural fluctuations in soil-water N.

On 3 December 2000, St. Augustinegrass 'Floratam' from a mineral sod farm in

Punta Gorda was laid as a sod. Soil attached with sod was approximately 5 cm thick.

Four main plots were laid with sod containing 40 g kg-1 SOM and the other 4 main plots

were laid with sod containing 100 g kg-1 SOM. To determine the amount of SOM, soil









samples from sod pieces within each main block were dried at 110C, screened through a

2 mm sieve, and ashed in a muffle furnace at 550C for approximately 12 hours. Samples

were then weighed and the weight loss on ignition was deemed to be SOM on a weight

basis.

Over the following four months, establishment was examined by collecting

percolate and monitoring turfgrass visual quality. During the establishment period, the

turfgrass was irrigated daily to replace 125% potential evapotranspiration (ETp) for the

first 2 weeks. Thereafter, the turfgrass was irrigated daily to replace 100% ETp. Daily

ETp was retrieved from a Florida Automated Weather Network (FAWN) weather station

located approximately 100 m from the experimental site. The ETp was determined by a

Penman based model developed by Fares and Alva (1999) to determine irrigation

requirements for citrus production and later adapted by the Florida Automated Weather

Network.

The plots were mowed as needed with a riding rotary mower set at a 7.5 cm

mowing height. On 13 April 2001, a rotary push mower was used to collect clipping

samples. A two meter long PVC pipe was used as a guide to walk the mower along in

order to sample a one meter squared area repetitively. Ten centimeter diameter cores

were collected to a 30 cm depth to assess the influence of SOM on below ground growth.

The cores were portioned into 0-15 and 15-30 cm sections with the roots washed clean of

soil. Both clipping and root samples were dried at 110C and weighed to determine the

effect of SOM on growth. Additionally, clipping samples were sent to the University of

Florida's Analytical Research Laboratory for determination of total Kjeldahl N.









Rainfall was recorded with a rain gauge located on the southeast corner of the

experimental area. Periodically, [N03-N] was determined in irrigation and rainfall. All

water samples were preserved on premises and analyzed following EPA approved

methods (QuickChem #10-107-04-1-8 and 10-107-06-2-8) using an 8000 series

Continuous Flow Injection Colorimetry (Hach, Colorado) at the University of Florida

Belle Glade Research and Education Center. Daily percolate was calculated by the

following equation developed by Snyder et al. (1984): Percolate = Irrigation + Rainfall -

ET. The ET used in this equation was collected from the FAWN website as mentioned

above. The stabilization and establishment periods bracketed a period of dry weather. In

order to collect background data even when percolate was not predicted, the sample

vacuum was left on longer than would typically have been done in order to collect

enough sample so nutrient water analysis could be completed. Daily nutrient loading was

determined by multiplying the concentration of each nutrient found in the daily percolate

sample per plot by the total quantity of percolate calculated for the respective period.

Mean [N03-N] for the two periods were calculated as a flow weighted average

(calculated as total leached divided by total calculated percolate). Turfgrass quality was

visually observed and rated for each subplot on a scale from 1 to 10, with 1 = dead/

brown turf, 6 = minimally acceptable turf, and 10 = dark, green turf.

Irrigation uniformity and percolate quantities, [N03-N] and leaching during the

stabilization period, and identification of statistically significant SOM effects for

percolate, [N03-N], leaching, and turfgrass quality scores for the establishment period

were determined using the SAS proc mixed statement (SAS Institute, 1989).









Results and Discussion

Irrigation Uniformity

Sprinkler base pressure was maintained at 0.3 Mpa. The lack in fluctuation in base

pressure suggests that wind and spray direction was more influential than water pressure

on distribution uniformity. For four irrigation tests, the average DUman was greater than

the average DU,,b (0.83 and 0.60, respectively). This suggested that the amount of

irrigation applied to each of the main plots was fairly even, but individual subplots were

receiving a variable amount of irrigation in respect to other subplots. Perhaps this was

due to the arc of the spray or to wind drift. Regardless of the reason, the DU,,b in this

study was greater compared to the Broward Soil and Water Conservation Districts

reported DU for rotor sprinklers (as mentioned in the introduction), and greater compared

to a study conducted in central Florida residential turfgrass sprinkler systems (Baum et

al., 2003). These authors calculated an average DUiq of 0.48 for 17 irrigation systems that

used rotor sprinklers. Baum et al. (2003) felt comfortable with the average DUg of 0.56

after uniformity did not improve with sprinkler adjustments and since the value

represented present irrigation uniformity for turf landscapes in South Florida. In this

study, the low DU,,b resulted in lower DUg than expected, ranging from 0.44 to 0.62.

Mowing events may also be a factor attributing to changing sprinkler uniformity. After

finding sprinklers moved after a mowing event, we found that checking the sprinklers by

running through the zones quickly after mowing only detected defective sprinklers. A

closer inspection showed sprinklers in which their orientation were slightly moved and

thus the direction of the spray throw had changed. While it has always been a rule of

thumb to not mow over the sprinkler, even pressure of the riding mower close to the

sprinkler tended to move a few sprinklers in a slightly different orientation.









Natural Fluctuations in Percolate and Nitrate

Once the ceramic cup samplers were installed, samples were not collected from the

experimental area for a 2.5 month period. This time period was to minimize influences

from soil disturbance from installation on the ceramic cup samplers and to extract

samples periodically to ensure that the sampler CEC was satisfied and no air was present

in the lines. After the 2.5 months, a stabilization period from the 14 November to 3

December 2000 followed during which percolate was collected from all plots on four

collection dates to examine the perturbations of the natural soil environment and of the

ceramic cup samplers on the influence on percolate quantities and [NO3-N] and leachate.

Except for 22 November, actual percolate volumes were confirmed similar by the

Levene's Test for Homogeneity (Table 1-1 a) verifying that all ceramic cup samplers were

being influenced in a similar manner by the soil environment. On the first collection date

(14 November 2000) no sample was collected from 14 cup samplers. However by 22

November 2000 all cup samplers were working and collecting percolate. Percolate

volumes ranged from 0 to 23 ml over the period. The greater percolate volumes collected

on 28 November and 01 December were most likely due to the one rain event of the

period, occurring on 27 November and resulting in 16.5 mm of rainfall (Figure 1-2). With

a mean concentration of 0.20 mg 1-1, rainfall was a source of 0.06 g m2 of NO3-N to the

experimental area. Besides what was contributed by rainfall, the other source ofNO3-N

most likely was from the 20 g kg-1 SOM in the native soil. Assuming that for every

-2
percent of SOM a N release of 4.4 g m-2 per year based on a furrow hectare (Wolf and

-2
Snyder, 2003), approximately 0.37 g m-2 per month would be released.

Except for 28 November 2000, there were no differences among plot [NO3-N] from

the percolate collected, (Table 1-lb, Figure 1-3). Nitrate concentrations attributed by the









native soil environment ranged from 0.0 to 38.2 mg 1- during the period. Similar to

percolate and [N03-N], N03-N leached among the plots for each collection date did not

vary (Table 1-1c, Figure 1-4). The amount of actual N03-N leached was perhaps

influenced by rainfall in two ways: First by quantity of percolate and secondly that after a

dry period the rainfall may have increased N mineralization and thus increased soluble

[N03-N]. While an immediate increase in percolate was observed after the rain event,

[N03-N] decreased and leaching was unaffected (28 November, Table 1-1, Figures 1-3

and 1-4). Then on 01 December, more percolate was observed, as well as increased

[N03-N] (Table 1-1, Figures 1-3 and 1-4). Perhaps these lower and then higher [N03-N]

documented after the rain event which had followed a long period of dry weather, can be

attributed to immobilization and then mineralization by the natural soil microbial

community. However this is just a postulate as soil microbial populations were never

monitored during the project. There was no calculated percolate and thus no total N03-N

leached over the stabilization period.

Sod Establishment

Sod establishment was during a dry period (3 December 2000 to 10 April 2001),

at which time there were only twelve rain events totaling 316 mm of rainfall (Figure 1-2).

Turfgrass was only irrigated 125% ETp for the first two weeks of establishment (Figure

1-2) and then 100% ETp thereafter. Irrigation totaled 417 mm with the water source

having an average [N03-N] of 0.11 mg 1-1. This resulted in a total of 291 mm of

calculated percolate across 16 dates. Table 2 summarizes the amount of NO3-N

contributed from rainfall and irrigation, and total N from the native soil and soil attached

to the two contrasting sods. The total N calculated from the soil attached to the sod was









determined on the amount of SOM in the same manner as that of the native soil except

for that the 5 cm of soil instead on 15 cm of soil was accounted for.

Immediately after laying the sod, [N03-N] spiked to over 6 and 12 mg 1- for sod

with 40 g kg-1 and 100 g kg-1 SOM, respectively (Figure 3). The subsequent gradual

decline of [N03-N] over the next month and a half was nearly proportional to the amount

of SOM associated with the sod (Figure 3). Nitrate concentrations were significantly

greater from the 100 g kg-1 SOM sod for the first month and a half (p<0.05, Figure 1-3).

By mid-February concentrations had leveled off and were back to pre-planting

concentrations for the rest of the establishment period (Figure 1-3). At the very end of the

establishment period (23 March), a peak in [N03-N] occurred from the sod containing

100 g kg-1 SOM which was not observed from sod containing 40 g kg-1 SOM (0.01 and

1.8 mg 1-1 respectively, p = 0.0992, Figure 1-3). Rain events close to this time (19 and 20

March 2001) resulted in 151 mm of precipitation (Figure 1-2). During this time period,

both sods had similar volumes of percolate collected (mean = 16.5 and 16.0 ml for 40 g

kg-1 and 100 g kg-1 SOM, respectively, P>0.1000), suggesting that percolate volume did

not influence the concentrations. Perhaps the increase in [NO3-N] was a result of greater

amount of N present to be mineralized in the higher SOM sod. Alternatively, the sod with

100 g kg 1 SOM may have raised the soil moisture content to support a greater microbial

population that ultimately resulted in more N mineralized. Casey et al. (2002) and Skopp

et al. (1990) also attributed the increase in microbial activity and subsequent N

mineralization to the raising of soil moisture content by irrigation.

Nitrate leaching during the establishment period followed a similar trend to [NO3-

N]. During the two months following sod installation, NO3-N leaching from the sod with









100 g kg-1 SOM was greater than that from the sod with 40 g kg-1 SOM on all collection

dates except for the date of planting (3 December) and January 22 and 25 (P<0.05, Figure

1-4). During the remainder of the establishment period, average N03-N leaching for both

sods were below pre-planting leaching and were not different (P>0.10, Figure 1-4).

Actual leaching over the entire establishment period for the 100 g kg-1 SOM sod was 1.68

g m-2, which was greater than the 0.74 g m-2 leached from the 40 g kg-1 SOM sod

(P<0.01). Calculated leaching for the entire period from the 100 g kg-1 SOM sod (0.73 g

m-2) was greater than the 0.38 g m-2 leached from the 40 g kg-1 SOM sod (P<0.01, Table

2).

At the end of the establishment period, clipping samples were collected to test for

the influence of SOM on turfgrass blade growth. The average dry weight of clippings

from turfgrass with 40 g kg-1 SOM was 7.0 g m-2, which was lower (P<0.01) than the

average 37.1 g m-2 from sod with 100 g kg-1 SOM. While total [N] in blades were similar

for both grasses (12.9 and 16.5 mg g-1 for 40 g kg-1 and 100 g kg-1 SOM, respectively,

P=0.16), the greater mass of clippings from sod with 100 g kg-1 SOM as mentioned

above, resulted in a greater amount of total N per area basis from the sod with 100 g kg-1

SOM than the sod with 40 g kg-1 SOM (59.6 and 8.9 g m-2 respectively, P<0.01).

Even though turfgrass with the 100 g kg-1 SOM had slightly more root mass at both

0-15 cm and 15-30 cm depths, SOM did not influence turfgrass rooting (P>0.10, Table 1-

3).

Conclusions

St. Augustinegrass landscapes have been implicated as a potential source of N

pollution into sensitive watersheds that are important to South Florida's water supply. To

determine maintenance practices that minimize N leaching from St. Augustinegrass, a






16


field scale facility was built to mimic realistic landscapes, yet at the same time be feasible

to gather quality scientific data. A performance evaluation of the irrigation system

resulted in an average global distribution uniformity of 0.56, which was similar to others

found on residential landscapes for the area. Vadose zone ceramic cup samplers were

quickly primed by repetitively extracting water. Results of the stabilization and

establishment periods of this facility document background N contributions from the

native soil, rainfall, irrigation source and soil attached to sod pieces.










Table 1-1. Mean, standard deviation and Levene's Test for Homogeneity for (a) actual
percolate volumes, (b) nitrate concentrations, and (c) nitrate leached for each
of the four collection dates during the stabilization period with only bare soil
as a cover.
Mean Standard Significance
deviation
(a) Actual percolate volumes (ml)
14 November 2000 10.0 6.24 0.79
22 November 2000 10.8 5.57 0.07
28 November 2000 15.3 3.93 0.28
01 December 2000 18.3 3.95 0.84

(b) N concentrations (mg 1-1)
14 November 2000 1.43 0.19 0.18
22 November 2000 1.40 0.24 0.46
28 November 2000 0.94 0.19 0.05
01 December 2000 2.65 2.06 0.97

(c) Actual N leaching (g m-2)
14 November 2000 0.02 0.01 0.23
22 November 2000 0.02 0.01 0.68
28 November 2000 0.02 0.01 0.11
01 December 2000 0.05 0.04 0.68


Table 1-2. Nitrogen inputs (g m-2) during the four month establishment period for sod
with 40 g kg-1 and 100 g kg-1 SOM.
Inputs 40 g kg-1 SOM 100 g kg- SOM
-2
----------------g m------------------
Rainfall 0.06 0.06
Irrigation 0.05 0.05
Native soil 0.37 0.37
Sod soil 1.00 2.48


Table 1-3. Comparison of mean root dry weights (g) from 40 g kg-1 and 100 g kg-1 SOM
collected from cores between 0-15 cm and 15-30cm depths.
SOM 0-15 cm 15-30 cm
-2
------------g m-----------
40 g kg-1 0.75 0.25
100 g kg-1 0.98 0.39
Significance 0.31 0.20






18




QNs'k CramVW


ul e Overfow Flask





iiJil l
4

,-I V IVcuut zo




overf Plotw device.


(b)

tea wit CkP
j ^ ____lc
__ ~ T \ r










(a) stabilization
6


(b) establishment


140

120

100

80 E

60

40

20

0


14-Nov-00 14-Dec-00 14-Jan-01 14-Feb-01 14-Mar-01
-- Irrigation


--Rainfall


Figure 1-2. Rainfall and irrigation (mm) over the (a) stabilization and (b) establishment
periods.










(a) stabilization
15




10




5




0
14-Nov-00 14


(b) establishment


--4% SOM -10% SOM


-Dec-00 14-Jan-01 14-Feb-01 14-Mar-01


Figure 1-3. Nitrate concentrations (mg 1-1) determined in percolate from sod containing
40 g kg-1 SOM compared to sod with 100 g kg-1 SOM during the (a)
stabilization and (b) establishment periods.










(a) stabilization
0.30




0.20




0.10




0.00
14-Nov-00 1


(b) establishment


-s-4% SOM -e10% SOM


4-Dec-00 14-Jan-01 14-Feb-01 14-Mar-01


Figure 1-4. Nitrate leaching (g m-2) from sod containing 40 g kg-1 SOM compared to
sod with 100 g kg-1 SOM during the (a) stabilization and (b) establishment
periods.













CHAPTER 2
EFFECT OF IRRIGATION, N SOURCES AND RATES ON N LEACHING,
TURFGRASS QUALITY AND GROWTH FROM NEWLY ESTABLISHED ST.
AUGUSTINEGRASS LAWNS

Introduction

As it is for all plants, N is an essential element for growth and viability and is

required in the greatest quantity for turfgrasses (Beard, 1973). Nitrogen is the constituent

for amino acids and proteins and N is necessary for carbon metabolism (Taiz and Zeiger,

2002). Developing accurate fertilizer and irrigation recommendations is important to

maintain quality turfgrass as well as reducing water consumption and the potential for

fertilizer waste and N contamination to watersheds (Flipse et al., 1984; FDEP, 2002).

Contamination by N can lead to eutrophication in water bodies, ultimately resulting in a

decline in water quality and death of organisms. Besides the potential threat to

watersheds, elevated NO3-N in drinking water is considered a human health threat if

above the standard of 10 mg 1-1 (USEPA, 1976). The concern over NO3-N is because its

solubility, and it is the most available and mobile form of N that plants uptake (Taiz and

Zeiger, 2002). However because it is an anion, it is not well retained by soil colloids.

Whether on naturally occurring high ridge areas or on lots with urban fill brought in for

construction, the home and home lawns in Florida are often on coarse sand textured soils

with little physical characteristics to retain applied N (Cisar et al., 1991; Wang and Alva,

1996). In Florida, N leaching from turf home lawns has been implicated as a source of N

pollution to streams, lakes, springs and bays (Erickson et al., 2001).






23

Previous research on N leaching from bermudagrass (Cynodon dactylon P.) golf

course turf in Florida has shown that N rates, N sources, N application methods, and

irrigation all influence the amount of N leaching beyond the root zone, and subsequently

to groundwater (Snyder, et al.,1976; Snyder, et al., 1980; Snyder, et al., 1984; Snyder, et

al., 1989; Cisar, et al., 1991). However, the principal turfgrass used for home lawns in

Florida is St. Augustinegrass 'Floratam' (Stenotaphrum secundatum, Walt. Kuntze). In

comparison to bermudagrass, St. Augustinegrass is mowed higher, is often produced as

sod on soils with high organic matter content, potentially has a deeper root system, does

not have as high of a N requirement, has different irrigation requirements, has more

thatch from stolons and does not receive the intensive cultivation aerifyingg, verticutting

and dethatching) that is used for bermudagrass; all of which can affect N03-N leaching.

St. Augustinegrass is characterized as a stoloniferous perennial, rooting at nodes,

with coarse-textured leaf blades that are 6 to 8 mm wide and up to 15 cm in length

(Hitchcock, 1950; Duble, 1989). In 1950, St. Augustinegrass was documented as

collected in Florida, Georgia, South Carolina, Louisiana, Texas and California within the

United States (Hitchcock, 1950). Since then the pantropical species is used for lawns

along the Gulf Coast States of the U.S., and in Southern Mexico, the Caribbean, South

America, South and Western Africa, Australia, the South Pacific and the Hawaiian

Islands (Bogdan, 1977; Duble, 1989). In the U.S., St. Augustinegrass is only native to the

Gulf Coast Region of Florida and is documented as a pioneer on the coastal shore. While

the grass is grown inland, the biogeographical distribution of St. Augustinegrass is

restricted primarily to it being a subtropical C4 warm season turfgrass and thus lacking in

cold tolerance (Duble, 1989). It is noted by Hitchcock (1950) as being found in moist,

muck soils, mostly near the coast. It is adapted to Florida's sand soils, but is less drought






24

tolerant than some other warm season turfgrasses such a bermudagrass, and will not

thrive unless irrigated when grown on these soils (Chen, 1992). While St. Augustinegrass

can grow in unfertile sand soils (Chen, 1992), depending on the aesthetics and uses

required, St. Augustinegrass requires fertilization to maintain a healthy turfgrass stand.

Physical and chemical properties of sand soils of south Florida contribute to the poor soil

fertility. For example, within the A horizon of Margate sand soils, saturated hydraulic

conductivity ranges from 30-49.6 cm hrf1, and they have low water retention (0.01 to 0.12

cm cm-1), and low cation exchange capacity (2.4-5.6 Meq 100 g-1 of soil) with less than

16 g kg-1 SOM (Pendleton et al., 1984).

Despite its common use as a residential lawn turfgrass, there has been no research

on N leaching in south Florida involving a comparison of management factors for St.

Augustinegrass. This study was conducted to investigate the impact of a wide range of

potential management parameters including reduced and excessive N fertilization, readily

soluble and controlled release N sources, and irrigation on N leaching from St.

Augustinegrass turf. The objectives of this study were to (a) determine how N sources,

rates and irrigation scheduling influence [N] and leaching, turfgrass quality and growth,

(b) to develop a N budget under different management scenarios, and (c) to give

management strategy recommendations to minimize potential adverse impacts to the

environment.

Materials and Methods

An experimental field containing eight main plots of twelve 3.0 by 4.0 m sub plots

(for a total of ninety-six sub plots) was planted with St. Augustinegrass 'Floratam' at the

University of Florida's Fort Lauderdale Research and Education Center to monitor

turfgrass quality and N leaching in the fall of 2000. Ceramic-cup water samplers were






25

inset in the native Margate fine sand soil (siliceous, hyperthermic Mollic Psamnaquent)

in the center of each sub plot at 40 cm depth for the purpose of collecting vadose zone

water samples. St. Augustinegrass 'Floratam' sod was planted in December 2000 with the

first experiment beginning in April 2001. See Chapter 1 for specific details regarding

construction, stabilization and sod establishment of the experimental facility.

The study was conducted as a balanced block design with two replications, each

consisting of four main plots in which each main plot had twelve sub plots. Assigned to

the main plots within each replication were two 2-level factors in a factorial layout -

irrigation by soil organic matter. Assigned to the 12 sub plots within each main plot were

two factors in a factorial design, fertilizer source at 4 levels crossed with fertilizer rate at

3 levels. Soil organic matter differences brought in with sod pieces were not expected and

thus treated as a random variable with irrigation. The amount of soil organic matter

harvested with the sod at the time of installation was either 40 g kg-1 or 100 g kg1.

Each main irrigation block followed either a fixed (FIX) or adjusted (ADJ)

irrigation schedule: Fixed irrigation: irrigated at a rate equivalent to 125% maximum

weekly evapotranspiration (ET) over three irrigation applications per week (Monday,

Wednesday and Friday) regardless of rain. To determine the month with the highest ET,

10 yr monthly averages were compared from McCloud predicted ET. Adjusted irrigation:

irrigating at a rate equivalent to 125% weekly ET adjusted monthly. The 125% maximum

weekly ET rate was calculated by taking the month with the highest ET based upon the

McCloud method, adding 25% and dividing by four. The 125% rate was applied to

overcome any variability in application due to factors such as immediate evaporation and

by wind drift. Evapotranspiration was calculated by the McCloud method (McCloud,

1955), which was developed in Florida for grasses. Irrigation for the week was split into






26

three applications per week to simulate a Phase I Water Use Restriction by South Florida

Water Management District for established residential landscapes. A Phase I Water Use

Restriction allows for irrigation to be applied three designated days a week (SFWMD).

When rain 0.84 cm or greater occurred, the following scheduled irrigation was voided for

St. Augustinegrass maintained with the ADJ irrigation schedule (i.e. if a rain event

occurred on Tuesday, then no irrigation applied until Friday).

To initiate each of the six, approximately 2-month cycles, urea (UREA, 46% N)

and / or sulfur coated urea (SCU, 38%) were used as one of the following four N sources

applied to each subplot: liquid urea, water soluble granular urea, 50% water soluble

granular urea- 50% controlled-release granular SCU, or controlled-release granular SCU.

The fertilizer N sources provided several potential homeowner maintenance regimes.

The liquid fertilizer represented a lawn maintenance company spraying out a completely

water-soluble N source. The granular water-soluble N and controlled-release N represent

those readily available for homeowners to purchase.

The N rates bracketed a general recommendation of 5.0 g N m-2 per application for

a year total of 30 g m-2 (Cisar et al., 1991; Ruppert and Black, 1997) at one of the

-2
following three rates: 2.5, 5.0 and 10.0 g N m-2 bimonthly. Nitrogen rates also provided

potential maintenance scenarios representing under and excessive fertilizer application. A

summary of experimental factors tested is found in Table 2-la with the ANOVA table of

factors and interactions tested in Table 2-lb. Since SOM was not a planned factor, SOM

and irrigation schedules were not tested together for interactions with other factors (Table

2-lb). Fertilizer applications were irrigated at the next scheduled irrigation. This resulted

in St. Augustinegrass irrigated within 24 h of fertilization. This was intentional to mimic

home residents who have a professional lawn care specialist fertilizing their lawn. In






27

many cases the lawn care specialist fertilizes when the customer is not home and leaves

door tags informing the resident to irrigate.

Phosphorous and Potassium were applied just prior to cycles 1, 3 and 5 N

applications at a rate of 5.0 g m-2

The plots were mowed with a rotary push mower approximately every two weeks

in the summer and every three weeks during the winter. The mowing height was set at 7.5

cm except during the spring of 2002 when the height was raised to decrease mowing

frequency. Prior to mowing events, clippings were removed from a 1m2 area from each

sub plot. In August 2001 and 2002, 10 cm diameter root cores were collected to a 30 cm

depth to determine root weight density. The cores were portioned into 0-15 and 15-30 cm

sections followed by root washing to remove all soil. Both clippings and roots were dried

at 110 C and weighed to determine treatment effect on above and below ground growth.

To determine N concentration (hereafter denoted as [N]) within leaf blades, all clippings

were sent to University of Florida's Analytical Research Laboratory for the determination

of total Kj edahl N (EPA #351.2). To determine N uptake efficiency (NUE), leaf blade

[N] was multiplied by total clipping weights and then divided N applied by fertilizer

(Moll et al., 1982).

Rainfall was recorded with a rain gauge located adjacent to the experimental area.

Periodically, nitrate concentrations (hereafter denoted as [N03-N]) and ammonium

concentrations (hereafter denoted as [NH4-N]) were determined in irrigation and rainfall.

All water samples were preserved on premises and analyzed following EPA approved

methods (QuickChem #10-107-04-1-8 and 10-107-06-2-8) by using Continuous Flow

Injection Colorimetry (Hach, Colorado) at the University of Florida Belle Glade Research

and Education Center. Daily percolate was calculated by the following calculation






28

developed by Snyder et al. (1984): Percolate = Irrigation + Rainfall ET, where ET was

based on the McCloud method (McCloud, 1955) using temperature logged from the

FAWN weather station located approximately 100 m from the experiment. Daily nutrient

loading was determined by multiplying the concentration of each nutrient found in the

daily percolate sample per plot by the calculated volume of percolate for the respective

period. Nutrient loading for the cycle was the sum of all daily N loading. Weekly mean

[N03-N] and [NH4-N] were calculated as flow weighted averages by dividing weekly

leachate by total weekly percolate.

Turfgrass quality was visually observed and rated for each subplot on a scale from

1 to 10, with 1 = dead/ brown turf, 6 = minimally acceptable turf, and 10 = dark, green

turf.

The experiment was conducted as six 2-month cycles for a total of a one-year

period. Cycles were statistically separated by the total amount of rainfall during the cycle

into one of two seasons: wet (WET) and dry (DRY). Identification of statistically

significant treatment effects for average seasonal [N03-N], [NH4-N], total inorganic

nitrogen (here after denoted as [TIN]), N03-N, NH4-N, and TIN leaching, turfgrass

quality scores, clippings weights, root weight density, leaf blade [N], and NUE were

determined using SAS MIXED model procedures with Ismeans compared using Tukey-

Kramer multiple comparison test (SAS Institute, 1989). Because the strength of the

analysis of the design was primarily on the sub plot, only the highest order interactions

are discussed. If no interactions were significant, then significant factors are discussed

separately. With a few exceptions, only significant factor and interaction effects are

discussed.






29

Results and Discussion

Water Budget

Rainfall during the six bimonthly cycles followed general weather patterns for

southern Florida, with a wet season from approximately May through October and a dry

season from November through April. The experiment received a total of 1448 mm of

rainfall for the duration of the study with 71% received during the first three cycles

encompassing the majority of the wet season (Table 2-2, Fig 2-1). The wet season was

characterized by frequent afternoon showers, however sometimes intense, with two

separate rain events bringing over 100 mm of rainfall per event (May 30th and September

29t, 2001). The fourth, fifth and sixth cycles encompassing the majority of the dry

season, received the least amount of rainfall with the majority occurring as short,

infrequent yet heavy rain events. For example, 65% of the rainfall experienced in Cycle 6

was received in two days (February 23rd and March 7th, 2001). Over the entire study

period, turfgrass maintained with the ADJ irrigation schedule received 2,236 mm of

irrigation, which was 58% of the 3,858 mm of water that turfgrass received from FIX

irrigation. The lower amount of irrigation applied from the adjusted schedule resulted in

lower calculated percolate (1,692 mm) than turf maintained with the fixed irrigation

(3,289 mm of percolate).

As expected, hot diurnal temperatures of the summer months resulted in frequent

convection-based storms comprising the wet season. Although cloud cover was greatest

during this time of year, calculated ET was also the highest (Cycle 2, Table 2-2) due to

the hot temperatures and optimum growing conditions for St. Augustinegrass.

Evapotranspiration was lowest in Cycles 5 and 6 with 276 and 261 mm, respectively,

most likely due to the cooler temperatures that persist during the dry season months.






30

Separating the cycles into seasons by statistically comparing the total rainfall during each

Cycle led to Cycles 1, 2 and 3 being designated as WET and Cycles 5, 6 and 7 as DRY

(P=0.0330).

Nitrate Concentrations and Leaching

The season affected [NO3-N] (P<0.001). Mean [NO3-N] during the WET season

was 1.51 mg 1- and ranged from 0.05 to 13.65 mg 1-1. This was approximately 80% less

than mean [NO3-N] found during the DRY season (mean = 7.48 mg 1- with a range of

0.16 to 63.07 mg 1-1). Nitrate concentrations were influenced by rate of N applied during

both seasons (Table 2-3). WET season [NO3-N] from St. Augustinegrass receiving the

2.5 and 5.0 g N m-2 bimonthly were statistically similar (0.29 and 0.48 mg 1-
-2
respectively, P=0.7110), yet both rates resulted in lower [NO3-N] than the 10 g N m-2

bimonthly rate (3.75 mg 1-1, P<0.01). A similar trend was observed in the DRY season

(Table 2-4). Additionally, during the DRY season, there was higher [NO3-N] in percolate

from St. Augustinegrass maintained with the ADJ irrigation schedule and associated with

100 g kg-1 SOM compared to the 40 g kg-1 SOM at the high N rate (Table 2-4).

Similar to [NO3-N], only N rate influenced the amount of NO3-N leached during

the WET season (Table 2-5). Nitrate leaching from the two lower N rates were equal

(0.46 and 0.77 g m-2 for 2.5 and 5.0 g N m-2 bimonthly respectively, P=0.72), with NO3-

N leaching from the 10 g N m-2 bimonthly rate over six times greater than the two lower

rates (6.01 g m-2, P<0.01). During the DRY season, Rate and SOM*Rate influenced NO3-

N leaching (Table 2-5). Over the DRY season, more NO3-N leached from the 10.0 g m-2

bimonthly N rate compared to the two lower N rates (Table 2-6). Furthermore, greater

NO3-N leached from sod associated with 100 g kg-1 SOM than St. Augustinegrass with

40 g kg1 SOM at the 10.0 g m-2 bimonthly N rate (Table 2-6, Figure 2-2).






31

In addition to Rate*SOM influences, IRR*Rate also influenced N03-N leaching

during the DRY season (Table 2-5 and 2-7). While there was a trend for more N03-N

leached from the FIX irrigation schedule for each N rate level, there was greater N03-N

leaching under the FIX schedule compared to the ADJ schedule for turf maintained at the

high N rate (30.07 and 10.78 g m-2 for FIX and ADJ respectively, Table 2-7, Figure 2-3).

Although N sources did not influence seasonal [N03-N] and leaching totals,

different sources had different nitrogen release characteristics over the 2 month cycles

(Figure 2-4). In general, the LIQ treatment had comparatively low [N03-N] and N

leaching compared to other sources (Figure 2-4). This may be a result of the physical

form of the N source. Since fertilizers were not irrigated until the next scheduled

irrigation (which for each cycle was the next morning), there may have been considerable

NH3 volatilization from the urea.

Peaks of NO3-N leaching followed fertilization events (Figure 2-4). Nitrate

leaching peaks generally did not follow large rainfall events (Figure 2-4) unless they

occurred within two weeks of fertilizer applications (Figure 2-4, Cycle 4). It seems that

less intense but continuous rainfall during the first two weeks after fertilization was more

important than heavy/intense rain events thereafter for N03-N leaching. For example,

NO3-N leaching followed rainfall patterns for the first two weeks after the third

fertilization (Cycle 3). However, most of those rain events were not intense. For twelve

days of the two-week period following the fertilization, the continuous rainfall resulted in

NO3-N leaching for a longer period of time compared to the other cycles (Figure 2-4).

Ammonium Concentrations and Leaching

Perhaps due to the quick conversion ofNH4-N to N03-N during nitrification, [NH4-

N] was generally low during the study period. WET season [NH4-N] in percolate ranged






32

from 0.25 to 2.24 mg 1- with a mean concentration of 0.94 mg 1-1. DRY season [NH4-N]

were lower than during the WET season (P<0.001) ranging from 0.08 to 1.89 mg 1- with

a mean concentration of 0.60 mg 1-1. During the WET season, SOM*IRR*Rate

influenced [NH4-N], while no factor or interaction influenced DRY season [NH4-N]

(Table 2-8). This third order interaction was only significant when comparing irrigation

schedules under two specific N Rate and SOM combinations. The first was for St.

Augustinegrass with 40 g kg-1 SOM and fertilized at the 10.0 g m-2 N rate, in which

higher [NH4-N] were observed from the FIX irrigation schedule in comparison to the

ADJ irrigation schedule (0.67 and 1.42 0 g m-2, P<0.01). The second was for St.

Augustinegrass with 100 g kg-1 SOM and fertilized at the 5.0 g m-2 N rate, in which

higher [NH4-N] were observed from the FIX irrigation schedule in comparison to the

ADJ irrigation schedule (0.62 and 1.33 g m-2, P=0.02).

Total WET season NH4-N leaching ranged from 0.45 to 4.18 g m-2 with a mean

total leached of 1.73 g m-2. Mean total DRY season NH4-N leached was lower than

-2
during the WET season (P<0.001) ranging from 0.13 to 3.04 g m-2 with a mean total

leached of 0.94 g m2.

Similar to [NH4-N], SOM*IRR*Rate influenced NH4-N leaching during the WET

season, with no factor or interaction influences during the DRY season (Table 2-9). The

same third order interactions were identified as found for WET season [NH4-N]. The first

was for St. Augustinegrass with 40 g kg-1 SOM and fertilized at the 10.0 g m-2 N rate, in

which higher [NH4-N] were observed from the FIX irrigation schedule in comparison to


2-
the ADJ irrigation schedule (1.24 and 2.61 0 g m-2, P=0.01). The second was for St.

Augustinegrass with 100 g kg'1 SOM and fertilized at the 5.0 g m-2 N rate, in which






33

higher [NH4-N] were observed from the FIX irrigation schedule in comparison to the

ADJ irrigation schedule (1.14 and 2.44 g m-2, P=0.02).

Higher [NH4-N] and leaching during the WET season resulted from abundant

rainfall with the addition of irrigation. These events resulted in fertilizer transported past

the root zone before it was nitrified. The lack of irrigation scheduling influences and

overall lowers [NH4-N] and leaching during the DRY season was likely because all NH4-

N applied by fertilizer was either volatilized as NH3 or had sufficient residence time

within the soil profile to be nitrified to N03-N.

Although N sources did not influence seasonal [NH4-N] and leaching totals, there

was a trend for more leaching from the Blend N source during the DRY season (Figure 2-

5 b).

Total Inorganic Nitrogen Concentrations and Leaching

Total inorganic nitrogen concentrations were greater during the DRY season

compared to [TIN] during the WET season (5.83 and 2.21 mg 1- for DRY and WET

respectively, P<0.01). This difference was partially due to a greater range of

concentrations observed during the DRY season (0.27 to 30.97 mg 1-1) compared to the

WET season (0.7 to 14.63 mg 1-1). Regardless of all other factors, WET season [TIN] was

influenced by N rate (Table 2-10). As observed with [N03-N] and [NH4-N], average

WET season [TIN] of both the 2.5 and 5.0 g m2 bimonthly N rates were statistically

similar (1.29 and 1.26 mg 1- respectively, P=0.94), with both mean concentrations being

lower than the mean [TIN] of the high N rate of 10.0 g m-2 bimonthly (4.10 mg 1-1,

P<0.01, Figure 2-6a). This trend was also observed for the DRY season, with average

[TIN] of both the 2.5 and 5.0 g m-2 bimonthly N rates (1.51 and 2.95 mg 1- respectively)






34

being statistically similar, and with both mean concentrations being lower than the mean

[TIN] of the high N rate of 10.0 g m-2 bimonthly (13.04 mg 1-1, P<0.01, Figure 2-6b).

The interactions of SOM*Rate and IRR*Rate influenced [TIN] during the DRY

-2
season (Table 2-10). Besides observing that N rates applied at the 2.5 and 5.0 g m-2

bimonthly have statistically similar [TIN] that were less than the 10.0 g m-2 bimonthly N

rate, lower mean [TIN] from the St. Augustinegrass associated with 40 g kg1 SOM was

approximately 1/3 lower compared to mean [TIN] from the St. Augustinegrass associated

with 100 g kg1 SOM (P<0.01, Table 2-11).

While N rate effects were similar as previously reported for St. Augustinegrass

maintained with the ADJ irrigation, analysis of IRR*Rate interactions determined a

stronger separation of N rate effects under the FIX irrigation schedule during the DRY

season (Table 2-12, Figure 2-7). Under the FIX irrigation schedule, mean [TIN] increased

with increased N rate (Table 2-12, Figure 2-7 a and b). Furthermore, the ADJ irrigation

schedule resulted in mean [TIN] being lower than concentrations from the FIX irrigation

schedule at 10.0 g m-2 bimonthly N rate (Table 2-12).

In general, trends that were observed in average [TIN] were also observed for the

average TIN leached (Tables 2-10 and 2-13). WET season TIN leaching was less than

-2
DRY season TIN leaching (4.15 and 9.62 g m-2 for WET and DRY respectively, P<0.01).

Mean TIN leached during the DRY season was most likely strongly influenced by high

[TIN] observed during the DRY season. WET season TIN leaching was only influenced

by N rate with similar amounts of TIN leached from St. Augustinegrass receiving the 2.5

and 5.0 g m-2 bimonthly N rates (2.39 and 2.33 g m-2 respectively, P=0.95), and with both

TIN leaching losses being lower than the TIN leached from St. Augustinegrass receiving

the high N rate of 10.0 g m-2 bimonthly (7.71 g m-2, P<0.01, Figure 2-8a). N rate alone






35

influenced TIN leaching during the DRY season in a similar manner as it did in the WET

season (Figure 2-8b).

The SOM*Rate interaction effect on TIN leaching during the DRY season

paralleled trends for [TIN] (Table 2-14). Under the 10.0 g m-2 bimonthly N rate, more

TIN leached from St. Augustinegrass associated with 100 g kg-1 SOM compared to the

St. Augustinegrass with 40 g kg1 SOM. However there was no influence of SOM on the
-2
2.5 and 5.0 g m-2 bimonthly N rates (Table 2-14).

Analysis of DRY season IRR*Rate interactions determined a separation of rate

effects under the FIX irrigation schedule as observed with [TIN] (Tables 2-12 and 2-15).

Under the ADJ irrigation schedule, TIN leached was greater from the 10.0 g m-2

bimonthly N rate compared to TIN leached from the 2.5 and 5.0 g m-2 bimonthly N rates

(Table 2-15, Figure 2-9). The ADJ irrigation schedule resulted in less TIN leached than

leaching from the FIX irrigation schedule at the 10.0 g m-2 bimonthly N rate (Table 2-15).

In contrast to conventional wisdom, the least amount of TIN leached was during

the WET season. The WET season was thought to be the time of greatest leaching

because of the abundance of rainfall. However, this was also the time of active turfgrass

growth. Perhaps once the St. Augustinegrass had fulfilled its N requirement, the amount

of N left to be leached was minimal except at high N rates, as observed in this study.

Moreover, other N fate pathways such as volatilization and denitrification could have

been increased by high temperatures and greater moisture and humidity. This is further

discussed under the N budget section. Across all other factors, approximately 9, 7, and

16% of all N applied was leached for 2.5, 5.0, and 10.0 g m-2 bimonthly N rates

respectively during the WET season. Beyond the 5.0 g m-2 bimonthly N rate, there tends

to be higher TIN concentrations and leaching from the sod regardless of irrigation






36

schedule and amount of SOM. In the DRY season when St. Augustinegrass was not

actively growing, factors influencing soil moisture (irrigation scheduling and SOM) were

governing TIN concentrations and leaching. For example, 82% ofN applied as fertilizer

at the 10.0 g m-2 bimonthly N rate was lost to leaching from St. Augustinegrass associated

with 100 g kg-1 SOM in comparison to the 71% leaching loss from the St. Augustinegrass

with 40 g kg-1 SOM. St. Augustinegrass maintained with the middle and high N rates and

under the FIX irrigation schedule leached 28 and 77% of N applied respectively

compared to the 9.5 and 29% lost for St. Augustinegrass under the ADJ irrigation

schedule. The excess N loss from the St. Augustinegrass maintained under the FIX

irrigation schedule could be from residual TIN from previous fertilizations. The question

remains if precipitation from irrigation and/or weather was more influential than St.

Augustinegrass growth on TIN leaching. The influence of St. Augustinegrass growth will

be addressed again after the results of St. Augustinegrass quality and growth are

discussed.

St. Augustinegrass Quality

St. Augustinegrass turf quality was assessed throughout each of the six

experiments. Quality scores for the WET season ranged from 5.7 to 8.9 with a mean

value of 7.5. DRY season quality scores were higher than quality scores of the WET

season (P<0.01) ranging from 6.0 to 9.3 with a mean score of 8.0.

For both seasons, the interaction of SOM*Rate influenced quality scores (Table 2-

16). In the WET season, quality scores increased with N rate applied (Table 2-17a, Figure

2-10a). The two-way interaction also documents that at every N rate, higher quality was

observed from sod with 100 g kg-1 than from sod with 40 g kg-1 SOM (Table 2-17, Figure

2-10a). During the DRY season an increase in applied N also resulted in better quality






37

(Table 2-17b, Figure 2-10b). However, regardless of SOM associated with the St.

Augustinegrass, similar quality was obtained when fertilized with the 10.0 g m-2

bimonthly N rate in the DRY season (Table 2-17b, Figure 2-10b).

In addition to SOM*Rate interactions during the WET season, SOM*IRR* Source

also influenced quality scores (Table 2-16). Under various N Source and IRR

combinations, St. Augustinegrass with 100 g kg-1 SOM had greater quality than St.

Augustinegrass with 40 g kg-1 SOM (Table 2-18).

Nitrogen sources influenced quality during the DRY season (Table 2-16). Similar

quality was observed from St. Augustinegrass fertilized with the UREA, LIQ and

BLEND (mean DRY season quality was 8.0, 7.9, and 7.9 for UREA, LIQ and BLEND

treatments, P>0.10, Figure 2-11 b). However, the 100% controlled release N source

(SCU) maintained better quality than all of the other sources (mean quality of 8.2,

P<0.04, Figure 2-11).

St. Augustinegrass Growth

St. Augustinegrass growth was assessed by clipping yield and root mass. Total

clipping yields were greater during the WET season when St. Augustinegrass was

-2
actively growing (642 and 174 g m-2 for WET and DRY seasons respectively, P<0.01).

This seasonal effect was inversely proportional to [TIN] and leaching, suggesting that St.

Augustinegrass growth influenced [N] and leaching. The interaction between SOM*Rate

resulted in a difference in clipping yield during both the WET and DRY seasons (Table

2-19). The SOM*Rate interaction during the WET season documents an increase in

clipping yield with increase in N applied, as well as St. Augustinegrass with 100 g kg-1

SOM having greater yield at each N rate than St. Augustinegrass with 40 g kg-1 SOM

(Table 2-20). This too supports the hypothesis that St. Augustinegrass growth was






38

influential on [TIN] and leaching and explains why there was no influence of irrigation

and SOM treatments on [TIN] and leaching during the WET season.

The trend of greater clipping yields with increases in N rate was documented in the

DRY season as well (Table 2-21). However in the DRY season only at the 2.5 and 5.0 g

m-2 bimonthly N rates were there greater clipping yields from the St. Augustinegrass with

100 g kg-1 SOM compared to the St. Augustinegrass with 40 g kg- SOM (Table 2-21).

As was documented with turf quality ratings, N sources influenced St.

Augustinegrass growth in the DRY season. The clipping yields from SCU and BLEND N

sources were statistically similar (mean of 192 and 191 g m-2 for SCU and BLEND

respectively, P=0.91) as were clipping yields from UREA and LIQ N sources (156 and

158 g m-2 for UREA and LIQ respectively, P=0.88). However, St. Augustinegrass

fertilized with the SCU and BLEND N sources had greater clipping yields than the

UREA and LIQ sources (P<0.01, Figure 2-12). These results document better turf quality

in the DRY season when grass was not actively growing from N sources that include a

controlled release product. While average quality for both seasons was greater than the

minimum acceptance criterion of 6.0 for all sources, on selected dates near the end of the
-2
DRY season, quality was less than 6.0 for UREA and LIQ when applied at the 2.5 g m-2

bimonthly N rate. At the same time, a decline in clipping yield was observed from the

UREA and LIQ treated St. Augustinegrass, suggesting that St. Augustinegrass fertilized

with these two N sources were not capable of maintaining a resource efficient plant stand

(Figure 2-12).

Nine months after the sod was laid and four months after the initiation of the

experiment (01 August 2001), core samples were collected to assess below ground

growth. Root weight density in the upper 15 cm was greater than root weight density in






39

the lower 15 cm (2,479 and 535 g m-3 for 0-15 cm and 15-30 soil profiles respectively,

P<0.001). IRR*Rate influenced root weight densities within the upper 15 cm (Table 2-

22). From sod maintained with the 2.5 g m-2 bimonthly N rate, root weight density was

greater from sod maintained with the ADJ irrigation schedule compared to sod

maintained with the FIX irrigation schedule (Table 2-23). No factor influence on root

weight densities in the lower 15 cm soil profile was identified. Perhaps the lack of

influence was due to time between sod installation and core collection was not enough for

roots to have fully developed within this lower soil profile.

One year later (01 August 2002) root weight density in the upper 15 cm was still

greater than root weight density in the lower 15 cm (2,148 and 382 g m-3 for 0-15 cm and

15-30 soil profiles respectively, P<0.01). Root weight densities decreased over the year

by 13 and 28% for the 0-15 cm and 15-30 cm depths respectively (P<0.01 for both

depths). Peacock and Dudeck (1985) reported a 51% increase of root mass within the

upper 30 cm of the soil profile over a one-year period for recently established St.

Augustinegrass (14 mo after sodding).

The decrease in root weight density may be related to the time of sod installation

and when cores were collected. When the first cores were collected, roots had only

experienced part of a dry season and part of a wet season, and were most likely actively

growing due to the sod establishing its root system.

In comparison to the 2001 root weight densities, there was no treatment effect on

densities within the upper 15 cm, with IRR and SOM*SOURCE*RATE influencing root

weight densities in the 15 30 cm soil profile (Table 2-24). St. Augustinegrass

maintained with the ADJ irrigation had greater root weight density (mean = 433 g m-3)






40

compared to St. Augustinegrass maintained with the FIX irrigation schedule (mean = 331

g m3, P=0.03).
-2
Only at the 2.5 g m-2 bimonthly N rate did N sources influence root weight densities

in St. Augustinegrass with 40 g kg-1 SOM (Table 2-25). At this lower N Rate, UREA had

the lowest root weight density, which was similar to SCU but statistically less than those

of the BLEND and LIQ treatments (Table 2-25). Except for SCU, an increase in N rate

resulted in greater root weight densities within N sources for St. Augustinegrass

associated with 40 g kg-1 SOM (Table 2-25). Rate did not influence root weight densities

in St. Augustinegrass with 100 g kg-1 SOM. Nor did N sources except, at the high N rate

where the BLEND source had a greater root weight density than LIQ but similar to

UREA and SCU (Table 2-25). In all cases when significant differences existed between

40 g kg-1 and 100 g kg-1 SOM for a given N rate and N Source, there was a greater root

weight densities from St. Augustinegrass associated with the 40 g kg-1 SOM than with the

100 g kg-1 SOM (Table 2-25).

Leaf Blade Nitrogen Concentrations

Mean [N] within leaf blades were greater in clippings collected during the DRY

season compared to the WET season (20.1 and 17.9 mg N g-1 for DRY and WET seasons

respectively, P<0.01). Perhaps this was due to active growth during the WET season

resulting in more production of leaf blades and thus a lower [N] within due to dilution.

During the DRY season, the St. Augustinegrass was not actively growing and thus was

mowed less often, resulting in more N accumulating within the leaf blades. In the WET

season, mean [N] within leaf blades were influenced by N sources and N rates (Table 2-

26). Over the WET season, Leaf blade [N] were highest in the first clippings collected

after fertilization, and the lowest concentrations were measured at the end of the






41

fertilization cycle (Figure 2-13). At the beginning of each fertilization cycle, the

difference in mean [N] between the 40 g kg-1 and 100 g kg1 SOM sod was minimal,

however as time since fertilization increased, the difference between mean [N] from the

two sod types increased, with St. Augustinegrass associated with the 100 g kg1 SOM

maintaining higher leaf blade [N] (Figure 2-13).

Increasing N rate resulted in increases in WET season mean [N] in blade tissue

(total=17.3, 18.5, and 20.3 mg N g-1, P<0.01). This was contradictory to other findings

where the percent of N found in clippings decreased for N rates above the optimum

fertilization rate (Petrovic, 1990).

During both seasons, N sources influenced the seasonal mean [N] found in blade

tissue (Table 2-27) with the highest [N] from St. Augustinegrass fertilized with SCU

(19.2 and 21.6 mg N g1 for the WET and DRY season respectively), being higher than

all other sources in the WET season and higher than UREA and LIQ in the DRY season

(20.6 and 20.4 mg N g-1, Table 2-27, Figure 2-14 a and b). Although the trend of higher

[N] in leaf blades from SCU fertilized St. Augustinegrass was evident on individual

clipping dates, only on 20 Feb 2002 was [N] in leaf blades from SCU statistically higher

than the other N sources (Figure 2-14 b).

DRY season leaf blade [N] was influenced by SOM*Rate interaction (Table 2-26).

There was an increase in leaf blade N concentrations by increasing the N rate applied

(Table 2-28). However, only at the lower N rate applied (2.5 g m-2 bimonthly) was there

higher leaf blade [N] in St. Augustinegrass associated with the 100 g kg- SOM in

comparison to the St. Augustinegrass associated with 40 g kg- SOM (Table 2-28). These

values were similar to others found in the literature. For example, Broschat and Elliott

(2004) reported 13.0 to 19.7 mg N g- in St. Augustinegrass maintained with 20.0 g N m2






42

yr- using a 16-4-8 fertilizer. In comparison, Chen (1992) reported 20-26 mg N g-1 in leaf

blade clippings. Vernon et al. (1993) reported 14 mg N g-1 in clippings from St.

Augustinegrass var. Raleigh.

Nitrogen Uptake Efficiency

Cumulative NUE over the two seasons was influenced by SOM*Rate interactions

(P<0.01 for both WET and DRY seasons, Table 2-29). During the WET season,

cumulative NUE ranged from 51 to 57 % for all N rates in St. Augustinegrass associated

with 40 g kg-1 SOM (Table 2-30). St. Augustinegrass with 100 g kg-1 SOM had greater

NUE at each N rate compared to the St. Augustinegrass with 40 g kg-1 SOM (Table 2-

30). Nitrogen uptake efficiency declined with increasing N rate on St. Augustinegrass

associated with 100 g kg-1 SOM (Table 2-30). At the 2.5 and 5.0 g m-2 bimonthly N rates,

greater than 100% NUE was obtained suggesting that other N inputs such as from

irrigation, rainfall and mineralization from soil microbes were utilized by the St.

Augustinegrass.

In general, DRY season cumulative NUE was lower than those of the WET season.

During the DRY season, the cumulative NUE from St. Augustinegrass fertilized at the

5.0 g m-2 bimonthly rate was greater than at both the 2.5 and 10.0 g m-2 bimonthly rates

from St. Augustinegrass associated with 40 g kg-1 SOM (Table 2-31). St. Augustinegrass

with 100 g kg-1 SOM had greater NUE than St. Augustinegrass with 40 g kg-1 SOM only

at the 2.5 and 5.0 g m2 bimonthly rates (Table 2-31). As observed during the WET

season, cumulative NUE decreased with increasing N rates from St. Augustinegrass with

100 g kg-1 SOM (Table 2-31). Again, perhaps this was due to increased N mineralization

from the 100 g kg-1 SOM.






43

Nitrogen source also influenced cumulative NUE, however only during the DRY

season (Table 2-29, Figure 2-15). Nitrogen uptake efficiency increased over the WET

season for all N sources, suggesting once again N uptake from fertilizer. In the DRY

season, NUE did not increase to the extent observed in the WET season, suggesting

comparatively less N uptake from the St. Augustinegrass. During the DRY season SCU

and Blend treatments had similar cumulative NUE (39% for both SCU and Blend,

P=0.94), with both being greater than NUE from the UREA and LIQ treatments (P>0.02),

of which NUE from UREA and LIQ were similar (33 and 32% for UREA and LIQ

respectively, P=0.71). As the season progressed, the difference in NUE from the SCU

and Blend treatments to those of the UREA and LIQ treatments increased (Figure 2-15).

This reflected the controlled release characteristics of SCU, which perhaps became more

important to N uptake as the DRY season progressed.

Nitrogen Budget and Scenario Comparison

The mean [NO3-N] and [NH4-N] in rainfall was 0.8 and 0.2 mg 1-1, respectively

-2
(n=5) for a total year contribution of 1.4 g TIN m-2, respectively. Other than rainfall, St.

Augustinegrass received N inputs from precipitation through one of two irrigation

schedules. Mean [NO3-N] and [NH4-N] in irrigation water was 0.9 and 0.4 mg 1-1,

respectively (n=5), contributing a total of 2.9 and 5.0 g TIN m-2 for plots receiving ADJ

and FIX irrigation, respectively, during the experimental year. Wolf and Snyder (2003)

suggested that between 2.2 4.5 g m2 of N was released per year for every g kg1 of SOM

within an acre furrow slice. Based on these estimations and accounting for that

approximately 5 cm of soil was attached to sod pieces, during the WET and DRY

-2
seasons, every 10 g kg-1 SOM associated with sod is equivalent to 0.25 and 0.12 g N m-2

bimonthly, respectively. Considering that N mineralization from the SOM associated






44

with the St. Augustinegrass would be greatest during the wet season when microbial

activity is highest, the calculated N mineralization based on the higher end of this scale

(4.5 g N m-2 yr-1 for every g kg-1 of SOM) results in a total of 3.0 and 7.5 g N mineralized

m-2 during the WET season for St. Augustinegrass with 40 and 100 g kg-1 SOM,

respectively. Nitrogen mineralization estimates would be presumed at the lower end of

the scale (2.2 g N m-2 yr-1 for every g kg-1 of SOM) during the DRY season when

insufficient soil moisture limits microbial activity. Based upon this assumption, 1.5 and

3.7 g N m-2 would be mineralized during the DRY season from St. Augustinegrass with

40 g kg-1 and 100 g kg-1 SOM, respectively. Mineralization resulted in significant N

contribution. For example, sod with 100 g kg-1 SOM contributes 7.5 g N m-2 over the

season, or approximately one half of what was applied by fertilizer at a general rate of 15
-2
g N m-2 per season.

The N budgets in Tables 2-32 and 2-33 summarizes seasonal N inputs from

rainfall, irrigation, SOM and fertilizer rates as well as N losses from leaching and

harvested in leaf blades. With the exception of St. Augustinegrass associated with 100 g

kg-1 SOM during the WET season, St. Augustinegrass maintained with the greater N rate

had the lowest unaccounted N balance compared to the other two N rates and reflects the

greater N losses from leaching and harvests from the high N rate (Tables 2-32 and 2-33).

Unaccounted N losses from St. Augustinegrass associated with 100 g kg-1 SOM and

fertilized with the 10.0 g N m-2 bimonthly during the WET season were greater than

unaccounted losses from the 2.5 g N m-2 bimonthly rate under the ADJ irrigation

schedule and greater than both lower N rates under the FIX irrigation schedule (Table 2-

32b). Furthermore, during this time, there was less unaccounted N from the FIX irrigation

schedule than the ADJ schedule (Table 2-32b). This may suggest maximum productivity






45

of the soil microbial community with a combination of the WET season and the FIX

irrigation schedule. There are a couple possible reasons why there was greater

unaccounted N in St. Augustinegrass maintained with the higher N rate. Possibly more N

was available than the microorganisms required and as well as past luxury consumption.

Alternatively, perhaps the extra N increased mineralization more than immobilization.

During the DRY season, only 3% unaccounted N and a surplus of losses were

documented from St. Augustinegrass maintained with the high N rate and FIX irrigation

schedule for the 40 g kg-1 and 100 g kg-1 SOM, respectively (Table 2-33). During this

time of year, soil microbial activity was most likely dependent on irrigation and N

availability. Perhaps at the high N rate, microbial productivity increased mineralization

and subsequent available N for plant uptake or to be leached.

The high unaccounted for N balance may partially have resulted from not sampling

frequently enough during times of high percolate. However, this is unlikely since the

sampling frequency did capture pulses of N leaching during rain events especially when

they occurred within the first two weeks following fertilization.

The unaccounted for N balance may be explained by pools that were not measured

in this study. For example, while the greatest [N] are typically found in leaf blades, other

plant parts such as roots and verdue as well as thatch also contain N. In Petrovic's review

of the fate of nitrogenous fertilizers applied to turfgrasses (1990), he summarizes reports

of anywhere from 1 to 39% N can be found within these pools. Besides [N] within thatch,

thatch can also cause increased NH3 volatilization, which was unaccounted for in this

study. However Volk (1959) found NH3 volatilization was greater from turfgrass than

from bare soil, with volatilization rates up to 30%. The higher NH3 volatilization rates

from turfgrass may be attributed to documented high urease activity in the thatch layer






46

(Bowman et al., 1987). Furthermore, Petrovic (1990) reviewed various studies that

documented NH3 volatilization was greater from turfgrass that is not irrigated after

fertilizer is applied compared to turf that was irrigated (Bowman et al, 1987; Titko et al.,

1987; Sheard and Beauchamp; 1985). In this research, N fertilizer was not irrigated until

the next scheduled irrigation, leaving approximately 24 h for volatilization to occur.

Loss of fertilizer-N may also have been through denitrification. This would have

been likely during the WET season and / or under the FIX irrigation schedule when soils

are near saturation or saturated. Under these conditions soils become anaerobic, and

NO3-N is reduced by microorganisms to gaseous nitrogen compounds that are lost to the

atmosphere (Brady and Weil, 2002; Cisar et al., 1991). In a 2002 study, Horgan et al.

documented denitrification to account for up to 27.2 % of total fertilizer N applied to

Kentucky bluegrass (Poapratensis L.).

Varying the coating weight (thickness) of a coated fertilizer determines the amount

of N released (Peacock and DiPaola, 1992; Fry et al., 1993). Prill lock-off occurs when

the outer coating is too thick, not allowing N to be totally released from the core. Prill

lock-off within SCU may have also accounted for part of the N that was not recovered.

Cisar et al. (2005) reported 10% of N remaining in SCU prills after an 8 wk period when

applied in screen packets to 'Tifway' bermudagrass.

Lastly, the unexplained balance of N may have also been in urea-N form which was

not measured in this study. Wang and Alva (1996) observed urea-N losses within 5 days

after applying urea based fertilizers to uncovered Central Florida sand soils that were

similar to the Margate fine sand soil in the present study. These urea-N losses attributed

27-35.5% of total N in leachate. However Urea-N losses would be expected to be less in

this study since the fertilizer was applied to a turfgrass system containing thatch.






47

Conclusions

This study examined how management strategies influence [N] and leaching from

recently established St. Augustinegrass. All management factors influenced [N] and

leaching and / or turfgrass quality and growth, thus all null hypotheses were rejected. The

rate of N applied and g kg-1 of SOM associated with sod influenced leaching losses the

greatest. Fertilizing St. Augustinegrass at the 10.0 g m-2 bimonthly exceeded the optimal

N fertilization for St. Augustinegrass and resulted in N leaching up to 5.6 times greater

than the leaching documented from the current recommendation rate of 5.0 g m-2

bimonthly. Soil organic matter was a N pool for plant uptake. Cisar et al. (1992)

documented that St. Augustinegrass grown on organic soils (Histosols) in south Florida

did not require any additional N fertilization due to what was supplied by the SOM.

While the soil organic matter content found in soils in this study were much less than soil

organic matter within Histosols, it was evident that SOM was an important N pool for

plant uptake.

Contrary to conventional wisdom, other than when there were intense rain events or

rainfall occurring shortly after a fertilization event, rainfall during the WET season did

not dictate [N] and leaching. Snyder and others (1980) also documented greater N

leaching when fertilizer was applied to bermudagrass between rainfall events in South

Florida. Instead, this research documented that St. Augustinegrass growth (as

documented by clipping yield) dictated N leaching during the WET season. During active

growth, fertilizing beyond the 5.0 g m-2 bimonthly resulted in a greater abundance of

NO3-N to be present within the soil profile that was prone to leaching regardless of the

amount of SOM associated with the sod.






48

Two important interactions influenced [N] and leaching during the dry season: (a)

there was higher [N] and leaching from the St. Augustinegrass associated with 100 g kg-1

SOM than the St. Augustinegrass associated with 40 g kg-1 SOM at the high fertilization

rate, and (b) there was leaching from the St. Augustinegrass fertilized at the 5.0 and 10.0

g m-2 bimonthly rates maintained with the FIX irrigation schedule compared to St.

Augustinegrass maintained at the ADJ irrigation schedule. In both cases, differences in

soil moisture were likely influencing [N] and leaching. Besides increasing water holding

capacity, SOM influences soil structure (Brady and Weil, 2002). Although the microbial

community was not assessed in this study, others have documented the influence of soil

water on N mineralization (Casey et al., 2002; Skopp et al., 1990). Furthermore, as

postulated by Morton et al. (1988), excess N may be found in the root zone and

potentially leach during times when plant uptake is reduced due to dormancy (dry

season). The increased [N] and leaching documented during the DRY season in this study

for St. Augustinegrass with 100 g kg-1 SOM maintained with the FIX irrigation schedule

may have been under similar conditions as these previous studies documented. Perhaps

the increased SOM and irrigation contributed to a greater presence of N to be mineralized

and a greater water holding capacity; both of which increased microbial activity and

ultimately increased mineralization and the amount of NO3-N within soil solution that

would be potentially be available for plant uptake or leached.

In this study, monthly management in irrigation scheduling reduced leaching

during dry season months. This can be attributed to less N mineralization and slower

downward movement through the soil profile. Past research had documented that

increasing irrigation increased N leaching (Bowman et al., 1998; Morton et al., 1988;).

Morton et al. (1988) examined combinations of irrigation and N rate on [N03-N] and






49

leaching. The authors maintained a mixture of Kentucky bluegrass (Poapratensis L.) and

red fescue (Festuca rubra L.) on hydrologically separated plots with either irrigation

applied to prevent drought stress and leaching, or over-irrigating, and fertilized with a

combined readily available and controlled-release N fertilizer at rates of 0, 97, or 244 kg

N ha-1 yr1. The authors reported higher mean annual N concentrations and N leaching

from over-watered turfgrass in comparison to the unfertilized controls, yet no differences

between fertilized, scheduled irrigated turfgrass and the controls. In another study by

Devitt et al. (1976), the influence of irrigation quantity was indirectly demonstrated by

documenting that N03-N movement through the soil was related to the amount of

percolate.

Root weight densities were strongly influenced by irrigation scheduling during the

dry season. The greater root weight densities in St. Augustinegrass maintained with the

more conservative irrigation schedule (ADJ) reflects that plant demands were satisfied

with a shallow root system.

The high potential of leaching when St. Augustinegrass was excessively-irrigated

during the dry season suggested that irrigation systems in South Florida need to have

separate zones for St. Augustinegrass and other plants such as bedding plants planted

periodically. It is common for showy flowering annuals to be planted during the dry

season which can require more irrigation than that of the St. Augustinegrass. If on the

same zone, N leaching from the St. Augustinegrass could be an adverse impact to the

groundwater.

In this experiment, regardless of time of year, in all cycles and for all sources,

[N03-N] and leaching due to N sources peaked shortly after fertilization and did not

follow any type of consistent trend for [N] and leaching. While some studies have found






50

similar results (Petrovic, 2004; Geron, et al., 1993, Sheard et al., 1985), other studies

have reported less N leaching from controlled release products. In a previous study,

Snyder, et al. (1976, 1980) demonstrated decreased N leaching from bermudagrass turf

grown on sand soils fertilized with slow release N sources as compared to a soluble

source. A variety of controlled-release materials with different N release characteristics

were compared in their study (1976). Petrovic (2004) documented a decrease in N

leached from Kentucky bluegrass when fertilized with controlled release N products in

comparison to calcium nitrate for two years out of a three-year study. However there was

no difference in N leaching between the controlled release N products. In one study SCU

released N more rapid than other controlled or slow release N sources (Carrow et al.,

2001). Perhaps the high temperatures and humidity that persist in South Florida's

environment to some extent negate the controlled release characteristics of different N

sources.

Nitrogen sources also had minimal influence on St. Augustinegrass quality and

growth. Cisar et al. (2001) observed similar responses of very few consistent quality and

clipping yield differences between various controlled release and readily available N

sources when applied to bermudagrass in South Florida. In another study, bermudagrass

fertilized with readily available N sources had similar growth rates, N uptake rates and

visual quality to bermudagrass fertilized with natural organic slow-release N sources

(Sartain, 1992). While other studies have found similar results (Geron, et al., 1993),

results may have been different ifN sources with other N release characteristics were

investigated. For example, differences can be attributed to different release characteristics

of the N sources, and weather conditions, but overall their results were in agreement with

results found in this study for the WET season, which were that no one N source out-






51

performed all other N sources through out the experimental period. During the DRY

season, turf quality was greater in St. Augustinegrass fertilized with the SCU source and

clipping yield was greater from both the St. Augustinegrass fertilized with SCU and with

the BLEND sources. Hummel and Waddington (1984) documented a similar response in

Kentucky bluegrass fertilized with SCU. These authors observed greater N in fall

clippings from turf fertilized with SCU beginning in the previous spring. Sulfur coated

urea products vary in coatings and thus release characteristics depend on the

manufacturer. This experiment tested only one SCU product, and other SCU products

may result in different findings.

As previously discussed, there are many possible fates of N that were not measured

in this study. However, the N unaccounted for was most likely due to NH3 volatilization

and denitrification. Ammonia volatilization from ammonia based and ammonia forming

fertilizers was dependent on soil characteristics including soil moisture, pH and CEC, and

on meteorological conditions such as rainfall, humidity and temperature (Ernest and

Massey, 1960; O'Toole et al., 1982; Sigunga et al., 2002). With high temperatures,

humidity and high soil pH, South Florida's climate is conducive to NH3 volatilization and

while not measured in this study, NH3 volatilization was likely a major component of the

N balance that was not quantified.

Based on this study, the following management strategies for St. Augustinegrass

are suggested for maintaining quality turfgrass while reducing potential adverse impacts

to the environment: (i) recently established St. Augustinegrass should be fertilized

bimonthly at the current recommended rate of 5.0 g m-2 during the wet season, (ii) dry

season fertilizer application rates need to account for the amount of SOM associated with

the sod. (iii) irrigation should be adjusted at least on a seasonal basis if not monthly, (iv)







52

void irrigations after rain fall events either manually or by using a rain shut-off sensor,

and (v) make sure St. Augustinegrass and annual bedding plants are on separate irrigation

zones.









Table 2-1. (a) Explanation of experimental factors tested and (b) ANOVA table used for
statistical differences determination.
(a) Factor Treatment Description
Soil Organic Matter 40 g kg-1 40 g kg-1 SOM associated with sod


(Main Plot)

Irrigation
(Main Plot)


N Source
(Sub Plot)


N Rate
(Sub Plot)


(b) ANOVA table


100 g kg-
Fixed


Adjusted





Liquid urea


Water-soluble urea

Controlled-release


Blend (Water-soluble +
Controlled-release)
2.5 g m-2 bimonthly
5.0 g m-2 bimonthly
10.0 g m-2 bimonthly
Source
Rep
Irrigation
SOM
SOM*IRR


100 g kg-1 SOM associated with sod.
125% maximum weekly ET over 3
applications (M-W-F).

125% weekly ET adjusted by month
over 3 applications (M-W-F).
Irrigation shut off when precipitation
>0.84cm 24h prior scheduled
irrigation.
Urea (46-0-0) dissolved in 3 liters
water applied using CO2 sprayer.

Granular urea (46-0-0)

Granular Sulfur-coated urea [SCU]
(39-0-0)

50% Urea + 50% SCU applied as
granular
15.0 g m2 yr
30.0 g m2 yr1
60.0 g m2 yr1


Main plot error 3
Source 3
Rate 2
Source*Rate 6
Irrigation* Source 3
Irrigation*Rate 2
SOM*Source 3
SOM*Rate 2
Irrigation* Source*Rate 6
SOM*Source*Rate 6
Irrigation* SOM*Rate 2
Irrigation* SOM* Source 3
Sub plot error 50
Total 95






54

Table 2-2. Water budget from April 2001 to April 2002.
Irrigation Rainfall Irrigation Percolate ET
Cycle (Date) Regime (mm) (mm) (mm) (mm)
1 --- 238 --- --- 329
(10 Apr 01 11 Jun01) Fixed --- 677 568 ---
Adjusted --- 410 321 ---
2 --- 385 --- --- 423
(12 Jun 01 13 Aug 01) Fixed --- 664 619 ---
Adjusted --- 389 344 ---
3 --- 400 --- --- 358
(14 Aug 01 08 Oct 01) Fixed --- 588 637 ---
Adjusted --- 410 458 ---
4 --- 198 --- --- 334
(09 Oct 01 10 Dec 01) Fixed --- 678 539 ---
Adjusted --- 400 271 ---
5 --- 148 --- --- 276
(11 Dec 01 20 Feb 02) Fixed --- 649 540 ---
Adjusted --- 309 181 ---
6 --- 79 --- --- 261
(12 Feb 02 24 Apr 02) Fixed --- 602 386 ---
Adjusted --- 318 117 ---
Experimental period total --- 1448 --- --- 1981
(10 Apr 01 24 Apr 02) Fixed --- 3858 3289 ---
Adjusted --- 2236 1692 ---


Table 2-3. ANOVA table for NO3-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 1.10 0.36 6.82 0.06
IRR 1 0.19 0.69 0.14 0.73
SOM*IRR 1 0.19 0.69 1.18 0.34
Source 3 0.61 0.62 1.52 0.22
Rate 2 27.08 <0.01 80.20 <0.01
Source*Rate 6 0.79 0.59 1.10 0.38
IRR*Source 3 0.35 0.80 1.25 0.30
IRR*Rate 2 0.24 0.79 0.07 0.94
SOM*Source 3 0.49 0.70 1.70 0.18
SOM*Rate 2 1.36 0.27 10.12 <0.01
IRR*Source*Rate 6 0.43 0.86 1.14 0.35
SOM*Source*Rate 6 0.44 0.85 1.59 0.17
SOM*IRR*Source 3 0.88 0.46 0.25 0.86
SOM*IRR*Rate 2 1.52 0.23 4.22 0.02









Table 2-4. Interaction of SOM*IRR*Rate on N03-N concentrations (mg 1-) during the
DRY season. Significance values listed are for SOM differences within each
N rate.
Within N
Rate*IRR
N rate Irrigation 40 g SOM kg-1 100 g SOM kg- P value
2.5 g m2 ADJ 0.45 b 1.90 b 1.00
bimonthly FIX 0.59 b 2.38 b 1.00
Significance 1.00 1.00
5.0 g m2 ADJ 1.67 b 3.16b 1.00
bimonthly FIX 2.83 b 4.68 b 1.00
Significance 1.00 1.00
10.0 g m2 ADJ 7.68 ab 27.7 a <0.01
bimonthly FIX 15.4 a 21.3 a 0.92
Significance 0.65 0.85
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-5. ANOVA table for total N03-N leached for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 0.87 0.40 11.36 0.03
IRR 1 1.52 0.29 33.24 <0.01
SOM*IRR 1 0.05 0.83 0.16 0.71
Source 3 0.75 0.53 1.01 0.40
Rate 2 25.19 <0.01 120.46 <0.01
Source*Rate 6 0.80 0.57 0.63 0.71
IRR*Source 3 0.37 0.77 0.64 0.59
IRR*Rate 2 2.09 0.13 25.31 <0.01
SOM*Source 3 0.47 0.71 2.02 0.12
SOM*Rate 2 0.70 0.50 7.04 <0.01
IRR*Source*Rate 6 0.40 0.88 0.81 0.57
SOM*Source*Rate 6 0.41 0.87 1.90 0.10
SOM*IRR*Source 3 0.74 0.53 0.31 0.82
SOM*IRR*Rate 2 0.86 0.43 0.18 0.84


Table 2-6. Interaction of SOM*Rate on total N03-N leached (g m-2) during the DRY
season. Significance values listed are for SOM differences within each N rate.
40 g kg-' SOM 100 g kg-1 SOM Within rate
______Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 0.61 a 0.61 2.61 a 2.22 0.92
5.0 g m2 bimonthly 2.81 a 4.08 5.13 a 4.45 0.88
10.0 g m-2 bimonthly 15.1 b 12.0 25.8 b 13.9 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.










Table 2-7. Interaction of IRR*Rate on total N03-N leached (g m-2) during the DRY
season. Significance values listed are for IRR differences within each N rate.
ADJ FIX Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 0.70 aT 0.84 2.52 a 2.23 0.95
5.0 g m2 bimonthly 1.70 a 1.93 6.28 a 4.93 0.26
10.0 g m-2 bimonthly 10.8 b 10.12 30.1 b 9.89 <0.01
"Means with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-8. ANOVA table for NH4-N concentrations for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 0.00 0.97 0.00 0.97
IRR 1 31.96 <0.01 1.16 0.34
SOM*IRR 1 0.10 0.77 0.03 0.87
Source 3 0.53 0.66 0.11 0.96
Rate 2 2.48 0.09 1.58 0.22
Source*Rate 6 0.43 0.85 0.42 0.86
IRR*Source 3 0.71 0.55 0.56 0.64
IRR*Rate 2 0.07 0.93 1.31 0.28
SOM*Source 3 1.26 0.30 0.80 0.50
SOM*Rate 2 4.01 0.02 2.26 0.12
IRR*Source*Rate 6 1.39 0.24 0.84 0.55
SOM*Source*Rate 6 1.26 0.29 1.56 0.18
SOM*IRR*Source 3 0.27 0.85 0.67 0.58
SOM*IRR*Rate 2 5.10 <0.01 1.46 0.24











Table 2-9.


ANOVA table for total NH4-N leached for WET and DRY seasons.
giS nificant differences are bold and i d


Table 2-10. ANOVA table for total inorganic-N concentrations for WET
osaes ns Significal t differences are b d


and DRY


WET DRY
df F value P value F value P value
SOM 1 0.00 0.95 0.00 0.98
IRR 1 29.67 <0.01 1.25 0.33
SOM*IRR 1 0.11 0.76 0.04 0.85
Source 3 0.52 0.67 0.13 0.94
Rate 2 2.50 0.09 1.71 0.19
Source*Rate 6 0.42 0.86 0.42 0.86
IRR*Source 3 0.75 0.53 0.57 0.64
IRR*Rate 2 0.08 0.92 1.20 0.31
SOM*Source 3 1.23 0.31 0.77 0.51
SOM*Rate 2 3.95 0.03 2.38 0.10
IRR*Source*Rate 6 1.38 0.24 0.80 0.57
SOM*Source*Rate 6 1.26 0.29 1.52 0.19
SOM*IRR*Source 3 0.26 0.86 0.69 0.57
SOM*IRR*Rate 2 4.90 0.01 1.66 0.20


WET DRY
df F value P value F value P value
SOM 1 0.79 0.42 8.43 0.04
IRR 1 3.73 0.13 30.34 <0.01
SOM*IRR 1 0.03 0.87 0.09 0.78
Source 3 0.97 0.42 1.04 0.38
Rate 2 26.66 <0. 01 125.60 <0. 01
Source*Rate 6 0.80 0.57 0.69 0.66
IRR*Source 3 0.56 0.64 0.54 0.66
IRR*Rate 2 2.26 0.12 26.62 <0.01
SOM*Source 3 0.42 0.74 1.99 0.13
SOM*Rate 2 0.34 0.72 5.34 <0.01
IRR*Source*Rate 6 0.53 0.78 0.57 0.75
SOM*Source*Rate 6 0.47 0.83 1.88 0.10
SOM*IRR*Source 3 0.64 0.59 0.25 0.86
SOM*IRR*Rate 2 1.94 0.15 0.27 0.76









Table 2-11. Interaction of SOM*Rate on total inorganic-N concentrations (mg 1-1) during
the DRY season. Significance values listed are for SOM differences within
each N rate.
40 g kg- 100 g kg- Within rate
______ Mean Std Dev. Mean Std Dev. P value
2.5 g m-2bimonthly 0.89 a 0.48 2.13 a 1.30 0.93
5.0 g m2 bimonthly 2.23 a 2.75 3.67 a 2.71 0.88
10.0 g m2 bimonthly 10.1 b 7.52 16.0 b 8.31 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-12. Interaction of IRR*Rate on total inorganic-N concentrations (mg 1-1) during
the DRY season. Significance values listed are for IRR differences within
each N rate.
FIX ADJ Within rate
______ Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 2.10 a 1.30 0.92 a 0.54 0.95
5.0 g m2 bimonthly 4.44 b 3.15 1.46 a 1.19 0.23
10.0 g m2 bimonthly 19.0 c 5.86 7.05 b 5.73 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-13. ANOVA table for total total inorganic-N leached for WET and DRY
seasons. Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 0.78 0.43 9.67 0.04
IRR 1 3.54 0.13 29.68 <0.01
SOM*IRR 1 0.03 0.87 0.12 0.75
Source 3 0.97 0.41 1.08 0.37
Rate 2 26.27 <0.01 123.48 <0.01
Source*Rate 6 0.80 0.57 0.70 0.65
IRR*Source 3 0.55 0.65 0.61 0.61
IRR*Rate 2 2.19 0.12 24.58 <0.01
SOM*Source 3 0.42 0.74 1.92 0.14
SOM*Rate 2 0.34 0.72 6.31 <0.01
IRR*Source*Rate 6 0.52 0.79 0.71 0.64
SOM*Source*Rate 6 0.47 0.83 1.88 0.10
SOM*IRR*Source 3 0.63 0.60 0.26 0.85
SOM*IRR*Rate 2 1.92 0.16 0.30 0.74









Table 2-14. Interaction of SOM*Rate on total inorganic-N leached (g m-2) during the
DRY season. Significance values listed are for SOM differences within each
N rate.
40 g kg- 100 g kg- Within rate
____-_ Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 1.44 a 0.77 3.55 a 2.24 0.93
5.0 g m2 bimonthly 3.62 a 4.26 6.10 a 4.64 0.86
10.0 g m2 bimonthly 16.3 b 12.2 26.7 b 13.8 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-15. Interaction of IRR*Rate on total inorganic-N leached (g m-2) during the DRY
season. Significance values listed are for IRR differences within each N rate.
FIX ADJ Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 3.49 at 2.22 1.49 a 0.92 0.94
5.0 g m2 bimonthly 7.35 b 5.10 2.37 a 1.93 0.22
10.0 gm-2 bimonthly 31.2 c 9.71 11.9 b 10.11 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-16. ANOVA table for mean quality scores for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 141.26 <0.01 19.88 0.01
IRR 1 0.00 0.95 0.00 0.98
SOM*IRR 1 0.02 0.90 0.97 0.3811
Source 3 0.60 0.62 3.33 0.03
Rate 2 103.26 <0.01 100.61 <0.01
Source*Rate 6 1.38 0.24 0.61 0.72
IRR*Source 3 0.61 0.61 0.38 0.77
IRR*Rate 2 0.59 0.56 0.06 0.94
SOM*Source 3 0.25 0.86 0.30 0.82
SOM*Rate 2 10.54 <0.01 11.83 <0.01
IRR*Source*Rate 6 0.89 0.51 0.52 0.79
SOM*Source*Rate 6 1.00 0.43 2.00 0.08
SOM*IRR*Source 3 3.13 0.03 2.18 0.10
SOM*IRR*Rate 2 0.73 0.49 1.26 0.29









Table 2-17. Interaction of SOM*Rate on turf quality scores during the WET season.
Significance values listed are for SOM differences within each N rate.
40 g kg-1 100 g kg- Within rate
Mean Std Dev. Mean Std Dev. P value
(a) WET season
2.5 g m2 bimonthly 6.3 att 0.3 7.5 a 0.3 <0.01
5.0 g m2 bimonthly 7.1 b 0.3 7.9 b 0.3 <0.01
10.0 g m-2 bimonthly 7.9 c 0.3 8.3 c 0.3 0.01

(a) DRY season
2.5 g m2 bimonthly 6.8 a 0.5 7.8 a 0.4 <0.01
5.0 g m2 bimonthly 7.8 b 0.4 8.4 b 0.5 0.03
10.0 g m2 bimonthly 8.5 c 0.3 8.7 c 0.3 0.95
TMeans with the same letter within a column and season are not significantly different at the 0.05
significance level.

Quality was rated on a scale from 1 10, with 1 = dead, brown turf, 6=minimally acceptable, 10= dark
green healthy looking turf.


Table 2-18. Interaction of SOM*IRR* Source on turf quality scores during the WET
season. Significance values listed are for SOM differences within each
IRR*Source combination.
Within
IRR*Source
Source Irrigation 40 g SOM kg-1 100 g SOM kg- P value
Liquid ADJ 7.1 7.7 0.10
FIX 7.1 8.0 <0.01
Significance 1.00 0.95
Urea ADJ 7.0 8.1 <0.01
FIX 7.4 7.7 0.85
Significance 0.95 0.85
SCU ADJ 7.2 8.0 <0.01
FIX 7.1 8.0 <0.01
Significance 1.00 1.00


Blend ADJ
FIX
Significance
fQuality was rated on a scale from 1
green healthy looking turf.


7.1
6.9
1.00
10, with 1


7.8
7.9
1.00
dead, brown turf, 6


0.05
<0.01


=minimally acceptable, 10= dark









Table 2-19. ANOVA table for total dry clipping yield for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 241.37 <0.01 12.90 0.03
IRR 1 0.17 0.70 6.90 0.06
SOM*IRR 1 0.33 0.60 1.00 0.37
Source 3 0.72 0.55 5.36 <0.01
Rate 2 94.81 <0.01 114.89 <0.01
Source*Rate 6 0.53 0.79 1.52 0.19
IRR*Source 3 0.42 0.74 0.21 0.89
IRR*Rate 2 0.26 0.77 2.22 0.12
SOM*Source 3 0.66 0.58 0.46 0.71
SOM*Rate 2 3.42 0.04 6.80 <0.01
IRR*Source*Rate 6 0.23 0.97 0.25 0.96
SOM*Source*Rate 6 0.27 0.95 0.59 0.74
SOM*IRR*Source 3 1.07 0.37 0.43 0.73
SOM*IRR*Rate 2 0.31 0.74 2.92 0.06


Table 2-20. Interaction of SOM*Rate on total clipping yield (g m-2) during the WET
season. Significance values listed are for SOM differences within each N rate.
40 g kg- 100 g kg- Within rate
______ Mean Std Dev. Mean Std Dev. P value
2.5 g m-2bimonthly 203 a 84 690 a 125 <0.01
5.0 g m2 bimonthly 419 b 72 847 b 95 <0.01
10.0 g m2 bimonthly 679 c 79 1014 c 146 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-21. Interaction of SOM*Rate on total clipping yield (g m-2) during the DRY
season. Significance values listed are for SOM differences within each N rate.
40 g kg- 100 g kg- Within rate
______ Mean Std Dev. Mean Std Dev. P value
2.5 gm-2bimonthly 51 a 21 138 a 41 <0.01
5.0 g m2 bimonthly 141 b 31 206 b 43 0.02
10.0 g m2 bimonthly 249 c 61 260 c 49 0.99
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.









Table 2-22. ANOVA table for root weight density for 0-15 cm and 15-30 cm cores
collected on 01 August 2001. Significant differences are bold and italicized.
0-15 cm 15 30 cm
df F value P value F value P value
SOM 1 2.24 0.14 3.76 0.12
IRR 1 0.11 0.74 1.14 0.35
SOM*IRR 1 0.15 0.70 0.06 0.82
Source 3 1.83 0.15 1.24 0.31
Rate 2 1.12 0.33 3.06 0.06
Source*Rate 6 1.21 0.31 1.35 0.25
IRR*Source 3 0.80 0.50 0.15 0.93
IRR*Rate 2 3.69 0.03 0.08 0.92
SOM*Source 3 0.44 0.72 0.48 0.70
SOM*Rate 2 0.13 0.88 0.58 0.56
IRR*Source*Rate 6 0.29 0.94 0.80 0.58
SOM*Source*Rate 6 0.86 0.53 1.91 0.10
SOM*IRR*Source 3 0.41 0.75 0.35 0.79
SOM*IRR*Rate 2 1.07 0.35 2.46 0.10


Table 2-23. Interaction of IRR*Rate on root weight density (g m-3) within the upper 0-15
cm of the soil from cores collected 01 August 2001. Significance values listed
are for IRR differences within each N rate.
FIX ADJ Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 2,241 at 628 2,827 a 976 0.03
5.0 g m-2bimonthly 2,351 a 688 2,301 a 433 1.00
10.0 g m2 bimonthly 2,767 a 722 2,385 a 568 0.65
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.









Table 2-24. ANOVA table for root weight density for 0-15 cm and 15-30 cm cores
collected on 01 August 2002. Significant differences are bold and italicized.
0-15 cm 15-30 cm
df F value P value F value P value
SOM 1 1.34 0.25 8.95 <0.01
IRR 1 0.26 0.62 4.90 0.03
SOM*IRR 1 1.00 0.32 0.82 0.37
Source 3 1.23 0.31 2.05 0.12
Rate 2 0.47 0.63 2.82 0.07
Source*Rate 6 0.85 0.54 1.24 0.30
IRR*Source 3 0.37 0.78 0.13 0.94
IRR*Rate 2 1.64 0.20 0.03 0.97
SOM*Source 3 0.24 0.87 0.68 0.57
SOM*Rate 2 0.17 0.84 0.64 0.53
IRR*Source*Rate 6 0.48 0.82 0.89 0.51
SOM*Source*Rate 6 0.50 0.81 2.59 0.03
SOM*IRR*Source 3 0.59 0.62 0.56 0.64
SOM*IRR*Rate 2 1.32 0.28 1.18 0.32


Table 2-25. Root weight densities (g m-3) from the 15-30 cm soil depth collected on 01
August 2002 were influenced by SOM*Source*Rate interactions. Significance
values listed are for SOM differences within each N Rate and N Source.
Within
Rate*Source
40 g kg1 SOM 100 g kg1 SOM P value
2.5 g m2 UREA 153 a 382 a 0.16
bimonthly LIQ 671 a 204 a <0.01
SCU 586 a 390 a 0.23
BLEND 764 a 357 a 0.01
5.0 g m2 UREA 560 a 221 a 0.04
bimonthly LIQ 483 a 357 a 0.43
SCU 365 a 374 a 0.99
BLEND 348 a 484 a 0.39
10.0 g m-2 UREA 467 a 178 a 0.07
bimonthly LIQ 255 a 93 a 0.02
SCU 288 a 263 a 0.90
BLEND 475 a 433 a 0.79
TMeans with the same letter within a column compare rates within each N Source and are not significantly
different at the 0.05 significance level.









Table 2-26. ANOVA table for leaf blade N concentrations for WET
Significant differences are bold and italicized.


WET DRY
df F value P value F value P value
SOM 1 8.07 0.05 18.9 0.01
IRR 1 1.25 0.33 0.15 0.72
SOM*IRR 1 0.20 0.68 1.75 0.26
Source 3 4.44 <0.01 5.93 <0.01
Rate 2 86.3 <0.01 105 <0.01
Source*Rate 6 1.47 0.21 0.78 0.59
IRR*Source 3 0.43 0.73 0.12 0.95
IRR*Rate 2 0.28 0.76 0.13 0.87
SOM*Source 3 1.40 0.26 0.31 0.82
SOM*Rate 2 1.72 0.19 5.45 <0.01
IRR*Source*Rate 6 0.78 0.59 0.39 0.88
SOM*Source*Rate 6 0.83 0.55 1.50 0.20
SOM*IRR*Source 3 0.52 0.67 0.63 0.60
SOM*IRR*Rate 2 0.41 0.67 3.04 0.06


Table 2-27. Nitrogen sources influenced leaf blade N concentrations
seasons.


and DRY seasons.


(mg g-') during both


WET DRY
Mean Std Dev. Mean Std Dev.
UREA 18.3 b' 0.19 20.6 bc 0.18
LIQ 18.6 b 0.15 20.4 c 0.23
BLEND 18.7 b 0.15 21.3 ab 0.25
SCU 19.2 a 0.18 21.6 a 0.23
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-28. Interaction of SOM*Rate for N concentrations within leaf blades (mg g-')
during the DRY season. Significance values listed are for SOM differences
within each N rate.
40 g kg- 100 g kg- Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m-2bimonthly 17.6 a 0.16 20.2 a 0.13 <0.01
5.0 gm2 bimonthly 20.5 b 0.13 21.4 b 0.11 0.38
10.0 g m2 bimonthly 22.5 c 0.07 23.6 c 0.13 0.29
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.









Table 2-29. ANOVA table for nitrogen uptake efficiency for WET and DRY seasons.
Significant differences are bold and italicized.
WET DRY
df F value P value F value P value
SOM 1 146 <0.01 24.2 <0.01
IRR 1 0.12 0.759 4.16 0.11
SOM*IRR 1 0.15 0.72 3.30 0.14
Source 3 1.15 0.34 4.49 <0.01
Rate 2 48.0 <0.01 26.5 <0.01
Source*Rate 6 0.65 0.69 0.34 0.91
IRR*Source 3 0.39 0.76 0.23 0.87
IRR*Rate 2 0.22 0.80 0.21 0.81
SOM*Source 3 0.86 0.47 0.97 0.41
SOM*Rate 2 46.6 <0.01 32.8 <0.01
IRR*Source*Rate 6 0.08 1.00 0.42 0.86
SOM*Source*Rate 6 0.17 0.99 1.38 0.24
SOM*IRR*Source 3 0.41 0.69 0.33 0.89
SOM*IRR*Rate 2 0.35 0.84 0.95 0.23


Table 2-30. Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the WET
season. Significance values listed are for SOM differences within each N rate.
40 g kg- 100 g kg- Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 52 aT 23 184 a 36 <0.01
5.0 g m2 bimonthly 57 a 12 122 b 17 <0.01
10.0 g m2 bimonthly 51 a 6 78 c 11 <0.01
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.


Table 2-31. Interaction of SOM*Rate on nitrogen uptake efficiency (g m-2) over the DRY
season. Significance values listed are for SOM differences within each N rate.
40 g kg- 100 g kg- Within rate
Mean Std Dev. Mean Std Dev. P value
2.5 g m2 bimonthly 25 aT 8 62 a 17 <0.01
5.0 g m2 bimonthly 31 b 6 43 b 13 0.03
10.0 g m2 bimonthly 26 a 6 30 c 8 0.37
TMeans with the same letter within a column are not significantly different at the 0.05 significance level.









Table 2-32. WET season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and
(b) 100 g kg- SOM.
(a) 40 g kg-1 SOM
--------ADJ---------------- ---------------FIX----------
Inputs
Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0
Irrigation 1.6 1.6 1.6 2.5 2.5 2.5
40 g kg- SOM 3.0 3.0 3.0 3.0 3.0 3.0
Rain 1.0 1.0 1.0 1.0 1.0 1.0
Total 13.1 20.6 35.6 14.0 21.5 36.5

Losses accounted for
Leaching 1.9 1.6 3.6 2.5 2.1 10.0
Harvested 4.5 8.1 14.1 4.4 9.4 14.8
Total 6.4 9.7 17.7 6.9 11.5 24.8

% Unaccounted 51 53 50 51 47 32

(b) 100 g kg- SOM
--------ADJ---------------- ---------------FIX----------
Inputs
Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0
Irrigation 1.6 1.6 1.6 2.5 2.5 2.5
100 g kg- SOM 7.5 7.5 7.5 7.5 7.5 7.5
Rain 1.0 1.0 1.0 1.0 1.0 1.0
Total 17.6 25.1 40.1 18.5 26.0 41.0

Losses accounted for
Leaching 1.9 1.6 7.5 3.4 4.1 9.7
Harvested 13.9 16.6 21.4 15.0 18.3 21.8
Total 15.8 18.2 28.9 18.4 22.4 31.5

% Unaccounted 10 27 27 <1 14 23









Table 2-33. DRY season N budget (g m-2) for St. Augustinegrass with (a) 40 g kg-1 and
(b) 100 g kg- SOM.
(a) 40 g kg-1 SOM
--------ADJ---------------- ---------------FIX----------
Inputs
Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0
Irrigation 1.3 1.3 1.3 2.5 2.5 2.5
40 g kg- SOM 1.5 1.5 1.5 1.5 1.5 1.5
Rain 0.4 0.4 0.4 0.4 0.4 0.4
Total 10.7 18.2 33.2 11.9 19.4 34.4

Losses accounted for
Leaching 1.0 1.7 6.3 1.8 5.6 26.3
Harvested 2.1 4.5 8.6 2.3 5.1 6.9
Total 3.1 6.2 14.9 4.1 10.7 33.2

% Unaccounted 71 66 55 65 45 3

(a) 100 g kg- SOM
--------ADJ---------------- ---------------FIX----------
Inputs
Fertilizer 7.5 15.0 30.0 7.5 15.0 30.0
Irrigation 1.3 1.3 1.3 2.5 2.5 2.5
100 g kg- SOM 3.7 3.7 3.7 3.7 3.7 3.7
Rain 0.4 0.4 0.4 0.4 0.4 0.4
Total 12.9 20.4 35.4 14.1 21.6 36.6

Losses accounted for
Leaching 1.9 3.1 17.4 5.2 9.1 36.0
Harvested 5.2 7.7 8.6 4.4 5.4 7.9
Total 7.1 10.8 26.0 9.6 14.5 43.9

% Unaccounted 45 47 27 32 33 0







68




-Rainfall


0 Al 1 111 4 n k L Im II i L .a1A MA nn 11
04/10/01 06/10/01 08/10/01 10/10/01 12/10/01 02/10/02 C
Experimental Year

Figure 2-1. Daily rainfall over the experimental period for Experiment 1.


)4/10/02













2.5 g N m-2 100 g kg1- SOM
-- 5.0gNm-2 100 g kg- SOM
........ ....... 10 g N m 2 100 g kg -1 SOM

2.5 g N m-2 40 g kg -1 SOM
- 5.0 g N m-2 40 g kg-1 SOM
........ .... 10 g N m-2- 40 g kg-1 SOM


AAA A"
At*
A



4AAA-A

A

a~McAAAA


05/01 07/01 09/01 11/01 01/02 03/02


05/02


Study Period


Figure 2-2. Comparison of cumulative N03-N leached (g m-2) from St. Augustinegrass
with 40 g kg-1 soil organic matter (SOM) to St. Augustinegrass with 100 g kg-
1 SOM for the three N rates during the study period. Arrows mark fertilization
events.













AA AA*


2.5 g N m-2- FIX
---- 5.0 g Nm-2-FIX
...A........ 10 g N m-2 FIX
--x 2.5 g Nm-2-ADJ
- -- 5.0 g N m-2 -ADJ
.... ........ 10 g N m 2 -ADJ


AAA-AA


4,AMAAA AAAA
&u


A ,p~nM


05/01 07/01 09/01 11/01 01/02 03/02


05/02


Study Period
Figure 2-3. Comparison of cumulative N03-N leached (g m-2) from St. Augustinegrass
maintained with the FIX irrigation schedule to St. Augustinegrass maintained
with the ADJ irrigation schedule for the three N rates during the study period.
Arrows mark fertilization events.






71



1.4 0
14I I' I I --

12 40 E
1.2 IE
y Rainfall 80

E 1.0 o BLEND
S........ ....... LIQ -120
S ------ SCU
0.4 .. UREA


O 0.2 -
Z


0.0 -


04/01 06/01 08/01 10/01 12/01 02/02 04/02
Study Period

Figure 2-4. Comparison of weekly N03-N leached (g m-2) from St. Augustinegrass
fertilized with the four N sources at the 5.0 g m-2 bimonthly rate during the
study period. Daily rainfall (mm d-1) is on the secondary axis. Arrows mark
fertilization events.

















E


c--
0)


ZU
(0

z

z
(0


E
0


05/01 07/01 09/01 11/01 01/02 03/02 05/02


Study Period
Figure 2-5. Comparison of weekly NH4-N leached (g m-2) from St. Augustinegrass
fertilized with the four N sources at the 5.0 g m-2 bimonthly rate and
maintained with the ADJ irrigation schedule during the (a) WET and (b) DRY
seasons. Arrows mark fertilization events.






73



50
(a) WET (b) DRY

40 2.5 g N m2 bimo.
N 5.0 g N m-2 bimo.
30 --- 10.0 g N m-2 bimo.


S ii i il!
E 20
I I
10 -


0

I Ii l I I
05/01 07/01 09/01 11/01 01/02 03/02 05/02

Study Period
Figure 2-6. Mean weekly flow weighted total inorganic-N concentrations (mg 1-1) from
St. Augustinegrass fertilized with the three N rates and maintained with the
ADJ irrigation schedule during the (a) WET and (b) DRY seasons. Arrows
mark fertilization events.












(a) FIX


(b) ADJ


2.5 g N m-2 bimo.
5.0 g N m-2 bimo.
-O- 10.0 g N m-2 bimo.


20


0



10/01


12/01


02/02


04/02


Figure 2-7. Mean weekly flow weighted toal inorganic-N concentrations (mg 1-1) from St.
Augustinegrass fertilized with the three N rates and maintained with the (a)
FIX and (b) ADJ irrigation schedules during the DRY season. Arrows mark
fertilization events.


100


80


20


0


100


80











(a) WET


0

40 E
E
80 4
o "1o'


04/01 06/01 08/01 10/01 12/01 02/02 04/02


Study Period
Figure 2-8. Comparison of weekly total inorganic-N leached (g m-2) from St.
Augustinegrass fertilized with the three bimonthly N rate during the (a) WET
and (b) DRY seasons. Daily rainfall (mm d-1) is on the secondary axis. Arrows
mark fertilization events.


(b) DRY







76


(a) ADJ
7 -- -- -- --rp II -- 0
1 0
6 I 25 E
E

E 5
-) 2.5 g N m-2 m
-a- 75
.. 4 *+.. 5.0 g N m-2
S-A- 10.0 g N m-2
z 3



I \ I \
1- +I



0 -
7
(b) FIX

6 -

E 5 '

II
1--

_, I I I \
I I I
I I \



0)
.r_ 4 1
1 i \ \ .



10/01 12/01 02/02 04/02
Study Period
Figure 2-9. Comparison of weekly total inorganic-N leached (g m-2) from St.
Augustinegrass fertilized with the three bimonthly N rate maintained with the
(a) ADJ and (b) FIX scheduled during the DRY season. Daily rainfall (mm d-
1) is on the secondary axis. Arrows mark fertilization events.












10
(a) WET (b) DRY
A A A

S .......... .


8


5 7

6


5 --- 2.5 g N m-2 100 g kg-1 SOM
--- 5.0 g N m-2 -100 g kg SOM
A.-- 10.0 g N m-2 -100 g kg1 SOM
4 -0- 2.5g N m-2 40 g kg-1 SOM
-0- 5.0g N m-2 40 g kg-1 SOM
S**A-- 10.0g N m2 40 g kg1 SOM

05/01 07/01 09/01 11/01 01/02 03/02 05/02

Study Period



Figure 2-10. Quality scores of St. Augustinegrass associated with 40 g kg-1 and 100 g kg-1
soil organic matter (SOM) maintained at the three N rates over the (a) WET
and (b) DRY seasons. Arrows mark fertilization events.































05/01 07/01 09/01 11/01 01/02 03/02 05/02


Study Period
Figure 2-11. Quality scores of St. Augustinegrass fertilized with different N sources over
the (a) WET and (b) DRY seasons. Arrows mark fertilization events.







79




80
v BLEND
~ o LIQ
o V SCU
60 UREA

E 0

-o V
a. 40 -
0)



00
20- 6 v
8 c



10/01 12/01 02/02 04/02 06/02

DRY season


Figure 2-12. Clipping yield (g m-2) of St. Augustinegrass fertilized with different N
sources over the DRY season.






80



28
(a) WET (b) DRY
26 -

2 24
z
cJ)
E 22 -

20 -
\- 100 g kg-1 SOM
4--
2 18- 40 g kg-1 SOM

16

'1' I 1
14 ......
05/01 07/01 09/01 11/01 01/02 03/02 05/02
Study Period


Figure 2-13. Comparison of leaf blade N concentration (mg N g-l) grown with 40 g kg-
soil organic matter (SOM) and 100 g kg-1 SOM during the (a) WET and (b)
DRY seasons. Arrows mark fertilization events.






81




30
(a) WET (b) DRY

28 -- BLEND
--- LIQ
A ... SCU
S26 -


S24

z
22


-20
-j
18 -


16t t t t


05/01 07/01 09/01 11/01 01/02 03/02 05/02

Study Period
Figure 2-14. Comparison of leaf blade N concentrations (mg N g-l) grown from the four
N sources during the (a) WET and (b) DRY seasons. Arrows mark
fertilization events.






82




50



40 -


S30







z 10
Q 20 -

2 BLEND
I 10 -- -- LIQ
........ ....... S C U
--0-- UREA

0 1. 1-. .. U E
10/01 12/01 02/02 04/02

Dry Season

Figure 2-15. Comparison of cumulative nitrogen uptake efficiency (g m-2) from the four
N sources during the DRY season. Arrows mark fertilization events.














CHAPTER 3
EFFECT OF IRRIGATION, N SOURCES AND RATES ON N LEACHING,
TURFGRASS QUALITY AND GROWTH FROM ESTABLISHED ST.
AUGUSTINEGRASS LAWNS.

Introduction

Developing accurate fertilizer and irrigation recommendations are important to

maintain quality turfgrass, reducing water consumption, and the potential for fertilizer

leaching into watersheds (Flipse et al., 1984; FDEP, 2002). Contamination by nitrogen

(N) can lead to degradation of water quality. Responses include eutrophication, death or

organisms, and shifts in plant species. Furthermore, because south Florida wetlands are

hydrologically-linked, other wetlands far from where the contamination originally

occurred may be affected (Noe at al., 2001; Tilman et al., 1999; Davis, 1994; Ewel and

Odum, 1984). Besides the potential threat to watersheds, elevated nitrate-nitrogen (NO3-

N) in drinking water is considered a contaminant for human consumption if above the

standard of 10 mg I11 (USEPA, 1976). Nitrate-N is the preferred form of N for plant

uptake (Taiz and Zeiger, 2002). However NO3-N it is an anion and it is mobile within the

soil. The coarse textured sand soils characteristic of southern Florida have little physical

and chemical characteristics to retain N (Cisar et al., 1991; Wang and Alva, 1996) and

thus fertilizer applied to home lawns based on these sand soils have been implicated as a

source of N pollution to adjacent watersheds (Cisar et al., 2004; Erickson et al., 2001).

The principal turfgrass used for home lawns in south Florida is St. Augustinegrass

'Floratam' (Stenotaphrum secundatum (Walt.) Kuntze). Previous studies have

documented that St. Augustinegrass is a moderate drought tolerant turfgrass (Qian and






84

Engelke, 1999; Carrow, 1996) that is effective at minimizing nitrogen leaching (Bowman

et al., 2002). Compared to other warm season turfgrasses grown in south Florida, St.

Augustinegrass requires moderate fertility (Cisar et al., 1991). Current fertilizer

recommendations for south Florida St. Augustinegrass lawns is between 15 to 30 g N m-2

per year (Trenholm et al, 2002; Cisar et al., 1991).

Turfgrass fertilization with a controlled or slow release N source is one way to

potentially reduce N leaching (Fry et al., 1993; Sartain 1992; Petrovic, 1990; Brown et

al., 1982). Often, water-soluble urea is coated to provide a controlled release source of N

(Cisar et al., 2001). Many of these coatings release the N fertilizer at a controlled rate by

water penetrating through small micropores and imperfections in the coatings, or by the

coating degraded by microbial activity.

The release of controlled and slow release N sources depends on how the source

releases the N, interactions in the environment, and cultural management (Cisar et al,

2001, Snyder et al., 1976, Snyder et al., 1980, Morton et al., 1988). Isobutylidene diurea

(IBDU) is a slow release fertilizer that has been shown to reduce N leaching due to its

uniform slow release rate (Brown et al., 1982). However, in south Florida, spring and

summer intense rainfalls result in a quick N release from IBDU since its N release is

controlled by dissolution, as well as for coated prills that depend on water penetrating and

induce swelling of small pores (Sartain, 2001). While there are now many different types

of coated urea products available for turf managers to choose from, sulfur coated urea

(SCU) is still a main product used (Cisar et al., 2001). Sulfur coated urea are urea prills

covered with sulfur/wax/conditioner layers. Nitrogen sources controlled by microbial

action such as Milorganite and ureaformaldehyde, will quickly release N during high

temperatures when microbial activity is greatest. By applying a microbial activated N