<%BANNER%>

Role of Nitrogen and Clipping Return on Turf Growth and Nitrate Leaching in Zoysiagrass

Permanent Link: http://ufdc.ufl.edu/UFE0024923/00001

Material Information

Title: Role of Nitrogen and Clipping Return on Turf Growth and Nitrate Leaching in Zoysiagrass
Physical Description: 1 online resource (68 p.)
Language: english
Creator: Bae, Jinyong
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: clipping, empire, leaching, msr, nitrate, remove, return, zoysiagrass
Environmental Horticulture -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Increasing urbanization throughout Florida is causing concerns about potential pollution of water resources from fertilization of home lawns. Best Management Practices have been developed for the commercial lawn care service in Florida to minimize any potential adverse impacts from the fertilization and lawn care activities. The objectives of this study were to evaluate the effect of nitrogen rates and clipping management on nitrate (NO3-N) leaching of Empire zoysiagrass and to evaluate the response of N rates and clipping management on the turf quality and physiological responses. The field experiment was conducted at the University of Florida Plant Science Research and Education Center in Citra, Florida on Empire zoysiagrass. The grass was established in March 2008 in sandy loam soil (Hyperthermic, uncoated, Quartzipsamments in the Candler series) and the study was conducted from June to October 2008. This research provides information about the effect of CM and N rate on NO3-N leaching, shoot growth, TKN concentration, N uptake, quality, and chlorophyll level. Returning clippings decreased turf quality, chlorophyll content than removing clippings. Empire zoysiagrass showed higher NO3-N leaching than St. Augustinegrass from previous research (Sharma el al., 2009). Total NO3-N leachate from CRT ranged 114.6 to 7379.1 mg m-2 and 123.1 to 1537.6 mg m-2 from CRM. The average concentration of NO3-N leaching ranged 0.23 to 6.47 mg L-2. The highest N rate (294 kg N ha-1) produced significantly greater NO3-N leaching compared to the other N rates. To avoid NO3-N leaching, it is important to apply N at rates below 196 kg N ha-1 at each application. In addition, NO3-N leaching was significantly correlated with rainfall. These results would indicate that exceeding the currently recommended N fertilization rates may contribute to NO3-N leaching during raining summer season (June to Aug) in Florida. MSR data at varying wavelengths did not differ due to CM. However, responses of growth and stress indices were significant due to CM. The CRT showed less turf growth and higher stress than CRM treatment through entire experiment period. Stress indices were also lower under higher N rates throughout the experiment. Growth and stress indices such as NDVI, Stress, and IR/R showed significant and consistent linear correlation with all evaluations used in this study. These results generally contradict previous studies on CM, which reported positive results of clipping-return on NO3-N leaching in research conducted on cool-season grasses.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jinyong Bae.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Trenholm, Laurie E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024923:00001

Permanent Link: http://ufdc.ufl.edu/UFE0024923/00001

Material Information

Title: Role of Nitrogen and Clipping Return on Turf Growth and Nitrate Leaching in Zoysiagrass
Physical Description: 1 online resource (68 p.)
Language: english
Creator: Bae, Jinyong
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: clipping, empire, leaching, msr, nitrate, remove, return, zoysiagrass
Environmental Horticulture -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Increasing urbanization throughout Florida is causing concerns about potential pollution of water resources from fertilization of home lawns. Best Management Practices have been developed for the commercial lawn care service in Florida to minimize any potential adverse impacts from the fertilization and lawn care activities. The objectives of this study were to evaluate the effect of nitrogen rates and clipping management on nitrate (NO3-N) leaching of Empire zoysiagrass and to evaluate the response of N rates and clipping management on the turf quality and physiological responses. The field experiment was conducted at the University of Florida Plant Science Research and Education Center in Citra, Florida on Empire zoysiagrass. The grass was established in March 2008 in sandy loam soil (Hyperthermic, uncoated, Quartzipsamments in the Candler series) and the study was conducted from June to October 2008. This research provides information about the effect of CM and N rate on NO3-N leaching, shoot growth, TKN concentration, N uptake, quality, and chlorophyll level. Returning clippings decreased turf quality, chlorophyll content than removing clippings. Empire zoysiagrass showed higher NO3-N leaching than St. Augustinegrass from previous research (Sharma el al., 2009). Total NO3-N leachate from CRT ranged 114.6 to 7379.1 mg m-2 and 123.1 to 1537.6 mg m-2 from CRM. The average concentration of NO3-N leaching ranged 0.23 to 6.47 mg L-2. The highest N rate (294 kg N ha-1) produced significantly greater NO3-N leaching compared to the other N rates. To avoid NO3-N leaching, it is important to apply N at rates below 196 kg N ha-1 at each application. In addition, NO3-N leaching was significantly correlated with rainfall. These results would indicate that exceeding the currently recommended N fertilization rates may contribute to NO3-N leaching during raining summer season (June to Aug) in Florida. MSR data at varying wavelengths did not differ due to CM. However, responses of growth and stress indices were significant due to CM. The CRT showed less turf growth and higher stress than CRM treatment through entire experiment period. Stress indices were also lower under higher N rates throughout the experiment. Growth and stress indices such as NDVI, Stress, and IR/R showed significant and consistent linear correlation with all evaluations used in this study. These results generally contradict previous studies on CM, which reported positive results of clipping-return on NO3-N leaching in research conducted on cool-season grasses.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jinyong Bae.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Trenholm, Laurie E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024923:00001


This item has the following downloads:


Full Text

PAGE 1

ROLE OF NITROGEN AND CLIPPING-RETURN ON TURF GROWTH AND NITRATE LEACHING IN ZOYSIAGRASS ( Zoysia japonica Steud.) By JINYONG BAE A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009 1

PAGE 2

2009 Jinyong Bae 2

PAGE 3

To My Lovely Wife 3

PAGE 4

ACKNOWLEDGMENTS I express my gratitude to Dr. Laurie E. Tre nholm (chair of my supervisory committee) for her excellent guidance, time and support. Her as sistance during the course of my graduate work gave me the opportunity to reach my goal. I would like to thank my committee members, Dr. Jerry Sartain and Dr. Jason Deff man-Kruse for their advice, suppor t, and inspiration. I also would like to acknowledge Florida Department of Environmental Protection (FDEP) for funding of this research. I appreciate the support and comments of Dr. Robert McGovern, the director of Doctor of Plant Medicine (DPM) program, w ho allowed me to pursue dual degree, DPM and Masters. I would like to thank Basil Wetheri ngton for technical support of my study and for his valuable suggestions. I am gr ateful to Tommy Deberry, Ronald Castillo, Amy Cai and Shweta Sharma for their help in my research. I am deeply grateful to my parents (Mr. Bae, Duk-Chul and Mrs. Yoon, Jung-Hee) and my parents-in-law (Mr. Jung, Jong-Chul and Mrs. Kim, Kyung-Soon) for their love and moral support. I th ank my wife, Kyung-Hee Jung, for her love, encouragement and patience, and w ould like to express deep love to my lovely sons (Terang and Da-Ul). Finally, I would like to give thanks to God who has guided me with His goodness and love. 4

PAGE 5

TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES ...........................................................................................................................7 LIST OF FIGURES .........................................................................................................................8 ABSTRACT .....................................................................................................................................9 CHAPTER 1. INTRODUCTION................................................................................................................ .....11 Nitrogen Physiology in Turf ...................................................................................................11 Water and Nitrogen Leaching .................................................................................................12 Empire Zoysiagrass ................................................................................................................15 Clipping Management ............................................................................................................15 MultiSpectral Reflectance (MSR) ..........................................................................................19 2. MATERIALS AND METHODS...............................................................................................21 3. EFFECT OF CLIPPING MANAGEMENT ON NITRATE LEACHING AND TURF QUALITY AND GROWTH IN EMPIRE ZOYSIAGRASS.................................................25 Introduction .............................................................................................................................25 Materials and Methods ...........................................................................................................27 Results and Discussion ...........................................................................................................30 Nitrate Leaching ..............................................................................................................30 Shoot and Root Growth ...................................................................................................34 Tissue N concentration ....................................................................................................34 Visual Quality and Color .................................................................................................35 Chlorophyll Content (CC) ...............................................................................................36 Correlation between N rate vs. CM vs. Quality vs. Color vs. Chlorophyll Level vs. NO3-N leaching vs. Shoot Growth. ..............................................................................36 Conclusions .............................................................................................................................36 4. EFFECT OF MULTISPECTRAL RE FLECTANCE AND CORRELATION of QUALITY AND LEACHING IN EMPIRE ZOYSIAGRASS..............................................51 Introduction .............................................................................................................................51 Materials and Methods ...........................................................................................................53 Results and Discussion ...........................................................................................................55 MultiSpectral Reflectance (MSR) ...................................................................................55 Correlation between Multispectral Reflectance (MSR) vs. N rate, CM, Growth, and Quality. .........................................................................................................................56 5

PAGE 6

N Rate vs. Reflectance .............................................................................................56 CM vs. Reflectance ..................................................................................................56 Visual Quality and Color vs. Reflectance ................................................................57 NO3-N Leaching vs. Reflectance .............................................................................57 Shoot Growth vs. Reflectance ..................................................................................58 Conclusions .............................................................................................................................58 5. CONCLUSIONS........................................................................................................................62 LIST OF REFERENCES ...............................................................................................................64 BIOGRAPHICAL SKETCH .........................................................................................................68 6

PAGE 7

LIST OF TABLES Table page 3-1 N leaching (mg m-2) of Empire Zoysiagrass in re sponse to N rates and Clipping Management (CM) ..................................................................................................................38 3-2 Correlation (r2) between NO3-N leaching of 294 kg N ha-1 rate for CRT plots vs. Rainfall during trial period .....................................................................................................39 3-3 NO3-N leaching mass (mg m-2) and concentration (mg L-1) of 294 kg N ha-1 rate for CRT and Rainfall* (mm) during trial period. .........................................................................39 3-4 Percentage loss of applied fertilizer N from Zoysiagrass soil under varying N rates, and Clipping Management (CM). ..................................................................................................39 3-5 N leaching (mg L-1) of Empire Zoysiagrass in re sponse to N rates and Clipping Management (CM) ..................................................................................................................40 3-6 Turf shoot and root growth in respons e to N rates and Clipping Management (CM). ............41 3-7 Total Kjeldahl Nitrogen percentage and N uptake of Empire Zoysiagrass in response to N rates and Clipping Management. ........................................................................................42 3-8 Visual quality and color score of Empi re Zoysiagrass in response to N rates and Clipping Management (CM) in a field experiment ................................................................43 3-9 Chlorophyll Index of Empire Zoysiagr ass in response to N rates and Clipping Management (CM). .................................................................................................................44 3-10 Correlation coefficients for N rate, clippi ng management, quality, color, chlorophyll, NO3-N Leaching, and Shoot growth. ...................................................................................45 4-1 Reflectance by clipping practice and vary ing N rate 6 weeks after first fertilizer treatment (6 WAFT). ............................................................................................................59 4-2 Reflectance by clipping practice and varying N rate 1 week after second fertilizer treatment (1 WAST). ...............................................................................................................60 4-3 Correlation Coefficients for reflectance vs. N rate, clipping management, quality, color, chlorophyll, N leaching, and shoot growth. ............................................................................61 7

PAGE 8

LIST OF FIGURES Figure page 3-1 Interaction between clipping management (CM) and N rate with respect to NO3-N leaching (mg m-2) from Empire Zoysiagrass in June (a), July (b), August (c), October (d), and total (e). (NS: Not significant, ***: Significant at p =0.05 between N rates) ...........46 3-2 Comparison of monthly rainfall and nitrate (NO3-N) leaching. ..............................................47 3-3 Interaction between clipping management (CM) and N rate with respect to NO3-N leaching (mg L-1) from Empire Zoysiagrass in June (upper left), July (upper right), August (bottom left), and October (bottom right). ..................................................................48 3-4 Interaction between clipping management (C M) and N rate with respect to shoot weight (g m-2day-1) from Empire Zoysiagrass in August ...................................................................49 3-5 Interaction between clipping management (CM) and N rate with respect to N uptake (g m-2) from Empire Zoysiagrass in August ...............................................................................49 3-6 Chlorophyll level by N rate tr eatment for Empire Zoysiagrass ............................................50 3-7 Chlorophyll level by Clipping tr eatment for Empire Zoysiagrass ........................................50 8

PAGE 9

Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science ROLE OF NITROGEN AND CLIPPING-RE TURN ON N BALANCE AND NITRATE LEACHING IN ZOYSIAGRASS ( Zoysia japonica Steud.) By Jinyong Bae August 2009 Chair: Laurie E. Trenholm Major: Horticultural Science Increasing urbanization throughout Florida is causing concerns about potential pollution of water resources from fertilization of home la wns. Best Management Practices have been developed for the commercial lawn care service in Florida to minimize any potential adverse impacts from the fertilization a nd lawn care activities. The obje ctives of this study were to evaluate the effect of nitrogen rates and clipping management on nitrate (NO 3 -N) leaching of Empire zoysiagrass and to evalua te the response of N rates and clipping management on the turf quality and physiological responses. The field experiment was conducted at the Univ ersity of Florida Plant Science Research and Education Center in Citra, Florida on Empire zoysiagrass. The grass was established in March 2008 in sandy loam soil (Hyperthermic, unc oated, Quartzipsamments in the Candler series) and the study was conducted from June to October 2008. This research provides information about the effect of CM and N rate on NO 3 -N leaching, shoot growth, TKN concentration, N uptak e, quality, and chlorophyll level. Returning clippings decreased turf quality, chlorophyll content than removing clippings. Empire zoysiagrass showed higher NO 3 -N leaching than St. Augustinegrass from previous research (Sharma el al., 2009). Total NO 3 -N leachate from CRT ranged 114.6 to 7379.1 mg m -2 9

PAGE 10

and 123.1 to 1537.6 mg m -2 from CRM. The average concentration of NO 3 -N leaching ranged 0.23 to 6.47 mg L -2 The highest N rate (294 kg N ha -1 ) produced significantly greater NO 3 -N leaching compared to the other N rates. To avoid NO 3 -N leaching, it is impor tant to apply N at rates below 196 kg N ha -1 at each application. In addition, NO 3 -N leaching was significantly correlated with rainfall. These results would indicate that exceeding the curr ently recommended N fertiliza tion rates may contribute to NO 3 -N leaching during raining summer season (June to Aug) in Florida. MSR data at varying wavelengths did not differ due to CM. However, responses of growth and stress indices were significant due to CM. The CR T showed less turf growth and higher stress than CRM treatment through entire experiment period. Stress indices were also lower under higher N rates throughout the experime nt. Growth and stress indices such as NDVI, Stress, and IR/R showed significan t and consistent linear correlati on with all evaluations used in this study. These results generally contradict previous studies on CM, which reported positive results of clipping-return on NO 3 -N leaching in research conducted on cool-season grasses. 10

PAGE 11

CHAPTER 1 INTRODUCTION Nitrogen Physiology in Turf There are many sources of nitrogen (N) in our environment, some of which are available for plant use. The atmospheric is about 80% N, although it is not readily us able by plants in the element form. The N content of surface mine ral soil ranges from 0.02 to 0.5% (Brady, 1990), and may be available to plants, depending on the form in which it is stored in the soil. Nitrogen is one of the major mineral nutrients required by plants, providing the building blocks for growth and physiological functioning. Nitrogen is a component of amino acids, nucleic acids, chlorophyll, and enzymes. Nitrogen also stimulates plant shoot and root growth and development, and is essential for carbohydrate us e in plants. In general, higher rates of fertilization with N deliver better quality of turf regardless of fertilizer sources (Heckman et al., 2000). Both organic and inorga nic fertilizers have similar effects on warm-season turfgrass systems (Trenholm and Unruh, 2005b). Turfgrass absorbs N as ammonium (NH 4 + ) or nitrate (NO 3 ). Nitrate and NH 4 + are typically present at similar concentrations in so il (Hull and Liu, 2005). However, in soil water, NO 3 concentration is five to te n times higher than that of NH 4 + (Bowman et al. 1989; Hull and Liu, 2005). Because soil is nega tively charged, the cationic NH 4 + ions are attracted to cation exchange sites, and remain at a relativel y lower rate in the soil solution. The NO 3 ions move freely in the solution due to the repulsion by soil particles. T hus, turfgrass roots absorb less NH 4 + because of the immobility of NH 4 + in soil (Below, 2001) and primarily take up N as the NO 3 form. Both NO 3 and NH 4 + forms are rapidly absorbed by plan t roots. Bowman et al. (1989) demonstrated this by applying 5 g N m -2 of NO 3 and NH 4 + to separate field plots of Kentucky 11

PAGE 12

bluegrass ( Poa pratensis L.). After 24 hours, only 20 to 30% of both NO 3 and NH 4 + could be extracted from the soil-thatch phase of the turf. None of the N applied could be extracted in either form after 48 hours. Uptake of most nutrients, in cluding nitrogen, occurs mainly through root hairs, which can effectively absorb water and nutrients via their enlarged surface area (Bloom et al., 2003). Root hairs enhance root capacity to take up immobile nutrients such as phosphate and NH 4 + (Hull and Liu, 2005). A dense of fibrous ro ot, which can improve competiti on for N against soil microbes, is also an important strategy for uptake of immobile ions in so il (Jackson et al., 2008) Water and Nitrogen Leaching Water is essential for the survival and maintenance of life. Fresh water consists of surface and groundwater, the latter cons tituting 97% of the sources fo r global drinking water. According to the US Environmental Prot ection Agency (EPA), excessive nitrate concentration in drinking water has caused severe illness and even death in infants less than six months of age (EPA, 2006). Nitrate is convert ed to nitrite in the mammalian body, and this process rapidly reduces the oxygen-carrying capacity in the blood stream of children. A blue baby syndrome occurs. Thus, EPA set the drinki ng water standard at 10 ppm for nitrate and 1 ppm for nitrite (EPA, 2006). Elevated levels of nitrate in drinking water can also cause serious health issues in adults. Some of these include methemoglobinemia, cancer, neurological effects, or abortion (Gupta et al., 2008; EPA, 2006). Nitr ate levels in groundwater remain stable over time and a measurement of nitrate in water can i ndicate longer periods of exposure (Ruckart et al., 2008). Thus, this stable nature of nitrate causes a reduction in the safety of our environment and health. In addition, nitrogen is one of the nutrients most often identified in stormwater runoff, which picks up surface pollutants and carries them along as the water reenters the ground or surface water system (FDEP, 2007). In surface waters, nitrogen in stormwater can also lead to 12

PAGE 13

heavy algae growth, eutrophicat ion and low dissolved oxygen levels as a non-point source pollution (Shaver et al., 2007), which has led to the initiation of Best Management Practices (BMPs) (Trenholm et. al., 2002). The Florida Green Industries BMPs have been developed to minimize nonpoint source pollution resulting from fertilization while providing education on fertilizer management to the landscape ma intenance industries of Florida since 2003. The program funded by the Florida Department of Environmental Protection (FDEP) helped the commercial lawn and landscape industry to incr ease awareness regardi ng nutrient leaching and runoff. (FDEP, 2007; Trenholm, 2007). Fertilizers, when used properly, can maintain th e health and quality of turf. Nitrogen is the element required in greatest quantity by turf for healthy growth and functioning (Trenholm and Unruh, 2005a). In most cases, slow-release N sources can reduce the potential loss of N relative to water-soluble, quick-release N sources (Saha et al, 2007; Heckman et al., 2000). Rooting patterns (depth) can re duce the total amount of NO 3 N leachate from the soil. Deep-rooted turf absorbs N more efficiently th an shallow-rooted turf (Bowman el al. 1998). Nitrate leaching from turf has b een shown to increase as rates of applied N become excessive (Morton et al., 1988; Kopp and Gu illard, 2005; Frank et al., 2006). Lee et al. (2003) evaluated the influence of fertilization and minera lization on soil nitrate level in bermudagrass ( Cynodon spp.) systems established on 50and 70-year-old golf courses. Results indicated that NO 3 -N levels were consiste ntly low (below 4 mg kg -1 soil) and similar to the N level of an adjacent natu ral area. They also found that soil nitrate levels under different fertilization regimes were not sign ificantly different from those in adjacent, nonfertilized areas. Bowman et al. (2002) compared NO 3 -N leaching and N use efficiency among six warmseason grasses under greenhouse condition for one year. They analyzed NO 3 -N and NH 4 -N in 13

PAGE 14

samples of leachate and clippings. St. Augustinegrass ( Stenotaphrum secundatum (Walt.) Kuntze) was most efficient at minimizing NO 3 -N leaching, and Meyer Zoysiagrass ( Zoysia japonica Steud) was least efficient at minimizing NO 3 N leaching. Species selection is thus an important factor for reduction of NO 3 N leaching from turfgrass systems. The N leaching rate also depends on plant species. Erickson et al. (2001) reported the difference of N leaching between St. Augustinegrass and a mixed-species la ndscape. They concluded that N leaching loss was significantly greater on the mixed-species landscape (48.3 kg N ha -1 ) than St. Augustinegrasss (4.1 kg N ha -1 ). On the contrary, there is a study to suggest that management practices is more important than species com position for reducing N leaching from residential land use (Erickson et al., 2008). Through St. Augustinegrass (SA) and a mixed-species landscape (MS), Erickson et al.(2008) observed th at cumulative N leaching for 3 yr was 4.1 kg ha and 7.4 kg ha for the SA and MS landscapes, respectively. The MS had significantly greater inorganic-N leaching (5.2 kg ha -1 ) in year 1 of the study compared to the SA landscape (1.3 kg ha -1 ). However, after year 1, inorganic-N leaching was comparable on both landscapes, and was low (<2% of applied N) on both landscapes following establishment. The ability of grass to take up N depends on ag e. Miltner et al. (1996) examined the fate of heavy isotope 15 N applied to Kentucky bluegrass, which had been established one year before the experiment. Urea-N was applied at an annual total rate of 196 kg N ha -1 In general, the NO 3 -N in leachate was below 1 mg N L -1 and only 0.23% of applied labeled fertilizer N was collected in leachate. Frank et al. (2006) conducted an experiment similar to that of Miltner et al. (1996), but modified the design by using 10-year-old Kentucky bluegrass and two fertilizer treatments with an annual rate of 98 and 245kg N ha -1 The NO 3 -N in the leachate at the low rate (98 kg N ha -1 ) was typically below 5 mg L -1 whereas the NO 3 -N concentration at the high rate 14

PAGE 15

(245 kg N ha -1 ) was often greater than 20 mg L -1 The latter value is 2 times greater than the EPA standard for drinking water. Empire Zoysiagrass Zoysiagrass ( Zoysia spp. Willd.) originated from the Orient (Christians, 2007) with ten species, which include Korean (or Japanese) lawngrass ( Zoysia japonica Steud.), which is the most widely used species in the United States (Christians, 2007). Zoysia japonica is well adapted to use on golf courses fairways and tees as well as homelawns, because it has excellent cold tolerance (Trenholm and Unruh, 2005a), fair sh ade, and salinity tolera nce (Christians, 2007). It also grows well to traffic and droughty conditi ons while maintaining relatively low level of disease and insect damage (Christians, 2007). E mpire zoysiagrass is a native proprietary selection of Zoysia japonica It has performed well in sandy a nd clay soils with dark and green in color and a wide leaf blad e (Trenholm and Unruh, 2005a). Clipping Management Turf shoot clippings have often been consid ered a nuisance product to dispose of, although the clippings contain abundant nutrients and are a source of organic matter. Removing clipping from turf causes N loss from the system. Sta rr and DeRoo (1981) examined the various effects of clipping-return while evaluating the fate of N fertilizer with Kentucky bluegrass mix (Poa pratensis L.) and creeping red fescue ( Festuca rubra L.). The study spanned 3 years and used a suction lysimeter with 15 N labeling to trace the fate of N from clippings and fertilizer. Return of clippings to the turf increased the total N uptake of the harvested grass by 19, 41, and 74% for the 3 consecutive years of the experiment. In th e clipping returned treatment, yield and growth of the grass increased by about 30%. The tissue N concentration from clipping-removed treatment was derived equally from soil and fertilizer, whereas the tissue N concentration from clipping-returned treatment was derived from equal amounts of N from soil, fertilizer, and 15

PAGE 16

clipping-return. Nitrate-nitrogen concentratio ns in the leachate on average were 1.9 mg L -1 for clipping-removed and 2.0 mg L -1 for clipping-returned trea tment, indicating that NO 3 -N leaching was not significantly reduced by clipping treatments. To reduce nitrate leaching, re turning clipping has potential importance in turf management. Liu and Hull (2006) investigated overall gr owth and N recovery from clippings using 10 cultivars each of thr ee cool-season grasses (kentucky bluegrass (Poa pratensis L.), perennial ryegrass ( Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) under field condition. All turf was maintained unde r an N fertilization rate of 147 kg N ha -1 year -1 for two growing seasons (May through October). Cli pping yields ranged from 5,152 kg dry weight ha -1 for tall fescue and 3,680 kg ha -1 for perennial ryegrass. In terms of N recovery, Kentucky bluegrass had greater recovery th an tall fescue, and perennial ry egrass. Total N recovered from clippings exceeded the amount of N applied as fertilizer, ranging from 260 to 111 kg N ha -1 yr -1 Clippings alone were shown to be an eff ective N source for turf maintenance when clippings were provided from well fertilized turf (Bigelow et al., 2005). Tall fescue ( Festuca arundinacea 'Rebel') was treated with 0, 1, 2, 3, or 4 plot-equivalents of clippings from adjacent donor plots treated with 220 kg N ha -1 year -1 for two growing seasons. During the first year of the research, N recovery from clippings was lin ear, and all turf plots showed N deficiency, regardless of how many clippings were returned. However, in the second year, N recovery demonstrated a quadratic response, with tissue N maintained adequately in instances where clippings applications were highest. Little research has been directed towards th e clipping-return effect on turf quality or Nuse efficiency. Heckman et al. (2000) examined the effect of returning clippings to Kentucky bluegrass by using a mulching mower for 4 year s (1994-1997). Results su ggested that clipping16

PAGE 17

return treatment improved color of the turf and reduced need for N fertilization by 50%. In addition, Heckman et al. (2000) found that the use of slow-release fertiliz er reduced the problem of turf quality such as unsightly clippings or undesirable growth surge. Kopp and Guillard (2002a) examined the response of turf growth and qua lity to clipping-return at varying rates of N fertilization. Two clipping management strategi es (removed or returned) and four N fertilization rates (0, 98, 196, and 392 kg N ha -1 ) were compared. The clipping-returned treatment enhanced clipping dry matter from 30 to 72%, and increase d total N uptake from 48 to 60%. Also, N-useefficiency increased from 52 to 71%. The author s concluded that N fertilization rate could be reduced at least 50% while maintaining turf quality if grass clippings were returned. The question of whether clippings contribute to thatch was c onsidered a negative effect of clipping-return. Research has shown that thatch is accumulated not by gra ss clippings, but rather, from roots, horizontal stems (stolons and rhizomes ), and mature sheaths and blades (McCarty et al., 2007). Soper et al. (1998) found that returning clippings increased thatch by 3.4% and decreased the tiller density by 12% in Meyer Zoysiagrass ( Zoysia japonica Steud). The reduction of tiller density may be due to shadi ng effects of clippings within the turf canopy. Clipping removal was not recommended for thatch control because of the benefits provided by clippings as a nutrient so urce. (Soper et al. 1998) Qian et al. (2003) applied an eco system model, and used this to predict long-term effects of clipping management and NO 3 -N leaching. Prior to long-term prediction, 3 years of field research with Kentucky bluegrass ( Poa pratensis L.) was used to generate the predictions. Results indicated that when the clippings were returned, N fertilizer requirements would be reduced by 25% during the first of 10 years after turf establishm ent, by another 50% from 25 to 50 years, and by 60% after 50 years. 17

PAGE 18

Most studies on the effects of clipping-return have focused on cool-season grasses, with comparatively little work on warm-season gr asses. Sartain (1993) conducted a 3-year comparison of response to clipping-return by Tifway bermudagrass ( Cynodon dactylon (L.) Pers. X Cynodon transvaalensis Burtt Davy) overseeded with Pennant perennial ryegrass ( Lolium perenne L.). When clippings were returned, th e clipping yield of bot h species increased, but turf quality was enhanced only in bermudagr ass. Thatch accumulation was not affected by clipping-return (Sartain, 1993). Kopp and Guilard (2005) examined the rela tionship between clipping treatment and NO 3 N leaching over a 30-week period for creeping bentgrass ( Agrostis stolonifera L.) under greenhouse conditions. Treatments c onsisted of four rates of N fertilization (equivalent to 0, 98, 196, and 392 kg N ha -1 ), two clipping management strategies (removed or returned), and two irrigation regimes (standard or standard + precipitation). Clipping-retu rn treatments increased both NO 3 -N concentration and mass losses of N in percolating soil water. Effects were greater with increased rates of N application and irrigation. When clippings were removed, the percentage loss for applied N was 0.9 to 7.6% fo r the standard irrigation treatment, and 14.3 to 41.8% for the (standard + precipit ation) irrigation treatment. However, when clippings were returned, the percentage loss of applied N wa s 12.8 to 23.6% for standard irrigation and 39.2 to 62.9 % for the (standard + precipitation) irriga tion. The authors did not report on effects of clipping management on turfgrass quality and growth. This result was contrary to that of Starr and DeRoo (1981) who conclude d that the effect of clipping treatments on NO 3 -N leaching was negligible. The fertilizer used in the experiment by Kopp and Guillard (2005) was water-soluble inorganic NH 4 NO 3, while Starr and DeRoo (1981) 18

PAGE 19

used ureaformaldehyde, an organic, slow releas e N source. The different N sources may have contributed to the difference in NO 3 -N leached. Apparently, clipping-return can pl ay a substantial role in redu cing N fertilizer use in coolseason turfgrasses and maximizing the efficiency of N use in turf. Returning clippings to turfgrass can be a solution for more efficient, environmentally-sound fertilizer use when applied with adequate amount of N fertilizer. The majority of the research looking at clipping effects has focused on cool-season grasses rather than warm-season grasses. Thus, the objec tive of this research was to evaluate the NO 3 -N leaching, turf growth, quality, and spectral reflectan ce of Empire zoysiagrass due to N rate and clipping management. MultiSpectral Reflectance (MSR) Qualitative measurement such as quality and color are commonly utilized in turfgrass research to compare or assess turf gr owth and health (Turgeon, 1991; Heckman et al ., 2000). Recently multispectral radiometry has been used to quantitatively distinguish between stressed and non-stressed plants (Carter, 1993; Carter and Miller, 1994) including turfgrass (Trenholm et al ., 1999a and 1999b). Thus, multispectral radiometry can quantitatively provide information on overall health, growth and vigor of turfgrass. A multispectral radiometer measures the amount of light plant absorb at particular wavelengths, th ereby indicating how the plant effectively uses photosynthetically active radiation (PAR). Visible (VIS) and near infrared (NIR) regions of spectrum are useful range for determining plant response when a treatment applies. Le af reflectance of PAR ( 400 to 700nm) is highly negatively correlated (r 2 >0.97) with concentration of chlo rophyll, so a healthy plant has relatively low reflectance of PAR (Trenholm, 2000) However, more than 700nm of reflectance is positively correlated with cellular water concentr ation in the leaf cell. Thus, a stressed plant 19

PAGE 20

has high reflectance value at the PAR range, and low reflectance value above 700nm (Trenholm et al, 1999a; Trenholm, 2000). Asrar et al. (1984) showed that the ratios normalized difference vegetation index (NDVI), which computed as (R 935 -R 661 )/( R 935 +R 661 ), correlated well (r 2 =0.97) with absorbed photosynthetically active radi ation (APAR) in wheat ( Triticum aestivum L.). Trenholm et al. (1999a) reported the significance of spectral data as quantitative tool on seven seashore paspalum ( Paspalurn vaginaturn Swartz) ecotypes and three hybrid bermudagrass (Cynodon dactylon L. X C. trunsvaalensis Burtt-Davy) cultivars. They concluded that NDVI, infrared/red (IR/ R), Stress I (ST-1) (R 706 /R 760 ) and Stress II (ST-2) (R 706 /R 813 ) were highly correlated with visual quality, shoot densit y, and shoot tissue injury rating except with shoot growth (Trenholm et al. 1999a). Relatively little information is available on the spectral responses for turfgrass system. Moreover, because of lack of research on the e ffect of clipping-return in warm-season grasses, the objectives of this study were to evaluate responses of zoysiagrass to N rate and clipping treatment using spectral data and to determ ine correlation between value of multispectral radiometer and other measurements such as quality, color and shoot growth. 20

PAGE 21

CHAPTER 2 MATERIALS AND METHODS A field experiment was conducted at the Univ ersity of Florida Plant Science Research and Education Center in Citra, Fl orida on Empire zoysiagrass ( Zoysia japonica Steud.). The grass was established in March 2008 in sandy loam soil (Hyperthermic, uncoated, Quartzipsamments in the Candler series) and the study was conducted from June to October 2008. Plots measured 4.0m x 4.0m. High-density polyethylene (HDPE) lysimeters were installed in the center of each plot, approximate ly 10 cm below the soil surface. Lysimeters measured 57 cm diam. and 88 cm in height with a volume of 168 L. Lysimeters were assembled by placing cylinders into a single piece galvanized steel base unit measuring 25.4 cm in height. A bulkhead fitting was inserted into the base of each unit, to which collection tubing (0.95 cm low density polyethylene) was at tached. The tubing was run unde rground to central aboveground collection portals. Lysimeters were installed by boring and removing soil in 15.2 cm sections to a depth of 107 cm. Lysimeters were placed in holes and bases of the units were filled with washed egg rock (1.9 6.4 cm) for a volume of 38 L. The gravel was covered with fitted non-woven polyolefin cloth that was secured with a hoop of 1.3 cm HDPE tubing to reduce soil intrusion into the reservoir. Soil was replaced into the ly simeters as it had been removed from the soil profile. Soil was gently tamped w ith a tamping tool (17 kg and 858 cm 2 ) to approximate original soil bulk density. Clipping-management (CM) and nitrogen (N) fe rtilizer treatments were as follows: CM #1 consisted of clipping-retu rn, in which clippings were le ft in the experimental field after mowing with a conventional rotary mower. 21

PAGE 22

CM#2 consisted of clipping-removal, in which clippings were taken from the field by attaching a collection bag to the mower. Mowing height was set at 6.3 cm (2.5 inches). The plots were mowed once a week throughout the study period. Fertilizer treatments consisted of six levels of total N rates (equivalent to 0 lbs, 1 lbs, 2 lbs, 3 lbs, 4 lbs or 6lbs N 1,000 ft -2 yr -1 or 0 kg, 49 kg, 98 kg, 147 kg, 196 kg, or 294 kg N ha -1 yr 1 ). Treatments were applied at 2-mo intervals for a total of two treatment applications. A 50% quick-release fertilizer (QRF) and 50% slow-releas e fertilizer (SRF) of 15N-0P-15K were used. The area was irrigated to replace evapotranspiration (ET) as needed to maintain healthy turf. Turf was evaluated visually for quality a nd color, which was rated immediately after mowing. A scale of 1 to 9 was used, in which 9 represents optimal, da rk green color and 1 represents dead, brown turf. A ra ting of 6 was considered minimally acceptable for a home lawn. Soil moisture (SM), canopy temperature (CT), chlorophyll content (CC), and multispectral reflectance (MSR) were also measured. Soil moisture content was quantified weekly using a Time Domain Reflectomet er (TRD) (IMIKO Micromodule Technik GmbH; Ettingen, Germany). The CC was taken weekly using Field Scout CM-1000 Chlorophyll meter (Spectrum Technologies, Plainfield, IL). The measurement wa s taken at approximately 1.2 m from the turf canopy. This provided an evaluation of circular area approximately 144 cm 2 per measurement. The CT was also taken weekly with a Ra ytek Raynger infrared thermometer (Raytek, Santa Cruz, CA). Temperature was averaged with three random points in each plot. The MSR was measured six times at 1, 3, and 6 weeks after first N treatment, and at 1, 3, and 5 weeks after second N treatment using a Cropscan model MSR 16R (CROPSCAN, Inc., 22

PAGE 23

Rochester, MN). The radiometer was fitted with filter wavelengths to meas ure reflectance at 450, 550, 660, 694, 710, 760, 810, and 930 nm. In addition, the following growth and stress indices were evaluated: NDVI (normalized difference vegetation i ndex) growth index computed as R 930 -R 660 /R 930 + R 660 Best = highest value. IR/R (leaf area index) grow th index computed as R 930 /R 660 Best = highest value. Stress1 index computed as R 710 /R 760 Best = lowest value. Stress2 index computed as R 710 /R 810 Best = lowest value. Clippings were collected to determine shoot growth once a month and dried at 75C for 48h. They were ground in a Wiley mill and then weighed. Clippings were analyzed for total Kjeldahl nitrogen (TKN). Roots were sampled by taking three 3.8-cm diameter root cores per plot once a year. Root weight and length were measured after wa shing soil from them. Total N uptake (TNU) was also calculated from the TK N (%) and dry weight of clippings (DWC) (g m -2 ). TNU (mg m -2 ) = DWC (g m -2 ) TKN (%) 1000mg g -1 (Eq.2-1) Samples were collected by applying a vacuum to the collection tubing and withdrawing percolate from the reservoir of the lysimete r until dry. 20-ml aliquots of the leachate were transferred to collection vial s and placed on ice in the field and then frozen at 0 O C until nitrate analysis was done. Nitrate concentration was measured using an AutoAnalyzer 3 continuous segmented flow analyzer (Seal Analytical, Mequon, WI) at the UF Analytical Research Laboratory in Gainesville. Leachate volumes were also calculated for each plot. Nitrate leaching data are presented as total cumulative nitrat e-N leached over the study period and percent of applied N leached. Minimum detection limit (MDL ) for the flow analyzer was 0.05. A baseline 23

PAGE 24

leachate sample was collected prior to first treatm ent application yearly, those values were used to correct for all other N mass values for each sampling event. TNC (mg) = Nitrate concentration (mg L -1 ) Leached water volume (L). (Eq.2-2) This experiment was arranged as a nested design by CM, with fertilizer treatments randomized within. There were thre e replications. Data were an alyzed with the SAS procedure ANOVA (SAS Institute Inc., Car y, NC). Significance was determined at the 0.05 probability level. 24

PAGE 25

CHAPTER 3 EFFECT OF CLIPPING MANAGEMENT ON NITRATE LEACHING AND TURF QUALITY AND GROWTH IN EMPIRE ZOYSIAGRASS. Introduction Water is essential for survival and maintena nce of life. For humans, 97% fresh drinking water comes from a combination of surface and groundwater. However, excessive or improper use of nitrogen (N) fertilizer may incr ease nitrate leaching that could potentially lead to nonpoint source pollution of gr ound or surface waters. Nitrate-N (NO 3 -N) in water bodies causes eutrophication, which can produce detrimental toxins and lower the oxygen concentration in water (Glass, 2003). In addition, the USEPA re ports that excessive nitrate concentration in drinking water may cause severe illness and even death in infants less than six months of age (EPA, 2006). Nitrate is converted to nitrite in the body, and this conversion leads to a rapid reduction in the oxyge n-carrying capacity of blood especially in young children. A blue baby syndrome or methem oglobinemia can result. Elevated levels of nitrate in drinking water can cause serious heal th issues in adults as well such as cancer, neurological effects, or abortion. While urban turfgrass fertilization is ofte n considered a major source of potential pollution to water bodies, numerous reports indicate that a matu re turfgrass system leaches very low levels of nitrate-N (Geron et al., 1993; Lee et al., 2003; Qian et al., 2003). Nitrate leaching from turfgrass can be increased due to excessive N application rate (Morton et al., 1988; Kopp and Guillard, 2005; Frank et al., 2006) excessive irrigation or rainfall (Morton et al., 1988; Kopp and Guillard, 2005), timing (Bowman et al., 1998), N source (Snyder et al., 1984; Heckman et al., 2000 ; Guillard and K opp, 2004; Saha et al, 2007), root density (Bowman el al. 1998), soil depth (Gross et al., 1990), turf establishm ent (Geron, 1993), turf species (Bowman et al., 2002) and other factors. These reports, however, indicate that when 25

PAGE 26

fertilizer is applied at the appropriate rates, timings, and with the correct irri gation, virtually all of the N is used by the turf grass with very little lost to leaching. Gross et al. (1990) showed that there was no difference in leachi ng whether nitrogen was applied as liquid or granule. However, concerns over nitrogen leaching in Florida have le d to numerous local ordinances and a state law requiring certification and licensing of all commercial fertilizer applicators. Reducing potential nonpoint sour ce pollution from urban turfgra ss involves more than just fertilizer management. For example, turfgrass clippings may contribute to nutrient movement if left on impervious surfaces or if deposited in correctly. Clippings produced from mowed grass retain considerable levels of nut rients such as N, P, K, and ar e easily decomposed (Sartain, 2004). Decomposition rate is related to turf species due to different content of lignin and cellulose in clippings (Sartain, 2004). It is al so possible that returning clippings to turf may reduce fertilizer requirements. Research has reporte d that recycling grass clippings can help maintain high quality turf characteristics while re ducing fertilizer use in berm udagrass (Sartain, 1993 and 2004), Kentucky bluegrass (Heckman et al., 2000) and a mixture of Kentucky bluegrass ( Poa pratensis L.)-perennial ryegrass ( Lolium perenne L.)red fescue (Festuca rubra L.) (Kopp and Guillard, 2002a). Empire zoysiagrass (Zoysia japonica Steud.) is increasingly used as a home lawn grass throughout Florida. Recommendations from the University of Florida for fertilization of zoysiagrass vary, depending on location in Florida, from 147 to 294 kg N ha -1 yr -1 (Unruh et al., 2006). In north Florida, 147 to 245 kg N ha -1 yr -1 is recommended, while in central and south Florida 147 to 294 kg N ha -1 yr -1 and 196 to 294 kg N ha -1 yr -1 respectively, are recommended (Unruh et al., 2006). However, research (Trenholm and Unruh, 2009) has 26

PAGE 27

indicated that the cultivar Em pire may perform best with lower rates of N than those suggested in the official reco mmendations. There are currently no other published reports on responses of Empire to fertilization rates. The Florida Green Industries Best Manageme nt Practices (BMPs) were developed in 2002 to minimize nonpoint source pollution result ing from fertilization and to provide education on fertilizer management to the landscape maintenance industries of Florida. Use of grass clippings may represen t a source of critical nutrients and can also provide organic matter. Due to lack of informa tion regarding the effect of c lipping-return on nitrate leaching in Empire zoysiagrass, the objectives of this study were to determine the effects of N rate and clipping management on NO 3 -N leaching and turf quality of Empire zoysiagrass. Materials and Methods The field experiment was conducted at the Univ ersity of Florida Plant Science Research and Education Center in Citra, Florida on Empire zoysiagrass. The grass was established in March 2008 in sandy loam soil (Hyperthermic, unc oated, Quartzipsamments in the Candler series) and the study was conducted from June to October 2008. Plots measured 4.0m x 4.0m. High-density polyethylene (HDPE) lysimeters were installed in the center of each plot, approximately 10 cm below the soil surface. Lysimeters measured 57 cm diam. and 88 cm in height with a volume of 168 L. Lysimeters were assembled by placing cylinders into a single piece galvanized steel base unit measuring 25.4 cm in height. A bulkhead fitting was inserted into the base of each unit, to which collection tubing (0.95 cm low density polyethylene) was at tached. The tubing was run unde rground to central aboveground collection portals. Lysimeters were installed by boring and removing soil in 15.2 cm sections to a depth of 107 cm. Lysimeters were placed in holes and bases of the units were filled with washed egg rock (1.9 6.4 cm) for a volume of 38 L. The gravel was covered with fitted non-woven 27

PAGE 28

polyolefin cloth that was secured with a hoop of 1.3 cm HDPE tubing to re duce soil intrusion into the reservoir. Soil was replaced into the ly simeters as it had been removed from the soil profile. Soil was gently tamped w ith a tamping tool (17 kg and 858 cm 2 ) to approximate original soil bulk density. Clipping-management (CM) and nitrogen (N) fe rtilizer treatments were as follows: CM #1 consisted of clipping -return (CRT), in which cl ippings were left in the experimental field after mowing with a conventional rotary mower. CM#2 consisted of clipping-removal (CRM), in which clippings were taken from the field by attaching a collection bag to the same rotary mower. Mowing height for both management strategies was set at 6.3 cm (2.5 inches). The plots were mowed once a week during the growing season. Fertilizer treatments consisted of six levels of total N rates applied over the study period that were equivalent to 0 lbs, 1 lbs, 2 lbs, 3 lbs, 4 lbs or 6lbs N 1,000 ft -2 (0 kg, 49 kg, 98 kg, 147 kg, 196 kg, or 294 kg N ha -1 ). Treatments were applied at 2-mo intervals for a total of two treatment applications. A 50% sl ow-release N fertilizer (Urea N) with an analysis of 15N-0P15K was used. The area was irrigated to replace ev apotranspiration (ET) as needed to maintain good quality turf. Turf was evaluated visually for quality and color, immediately after mowing every week. A scale of 1 to 9 was used, in which 9 represents optimal, dark green color and 1 represents dead, brown turf. A rating of 6 was considered minimally acceptable for a home lawn. Soil moisture (SM), canopy temperature (CT), and chlorophyll content (CC) were also measured. The SM was quantified weekly usin g a Time Domain Reflectometer (TRD) (IMIKO Micromodule Technik GmbH; Ettingen, Germany). 28

PAGE 29

Chlorophyll content of the leaf tissue was measured weekly using a Field Scout CM-1000 Chlorophyll meter (Spectrum Technologies, Plai nfield, IL). The measurement was taken at approximately 1.2 m from the turf canopy Turf CT was also taken weekly with a Ra ytek Raynger infrared thermometer (Raytek, Santa Cruz, CA). Temperature wa s averaged from reading of th ree random points in each plot. Clippings were collected to determine shoot growth once a month and dried at 75C for 48h. They were ground in a Wiley mill and then weighed. The total N concentration was analyzed with 0.2 g of dried clippings by the to tal Kjeldahl N (TKN) procedure. Roots were sampled by taking three 3.8-cm diamet er root cores per plot once a year. Root weight and length were measured after washing them free of soil. Total N uptake (TNU) was also calculated from the TKN (%) and dry weight of clippings (DWC) (g m -2 ). Nitrate-N leachate samples were collected by applying a vacuum to the collection tubing and withdrawing percolate from the reservoir of the lysimeter until dry. 20-ml aliquots of the leachate were transferred to collection vials and placed on ice in the field and then frozen at 0 O C until nitrate analysis was done. Nitrate concentration was measured using an AutoAnalyzer 3 continuous segmented flow analyzer (Seal An alytical, Mequon, WI) at the UF Analytical Research Laboratory in Gainesville. Leachate volume s were also calculated for each plot. Nitrate leaching data are presented as total cumulative NO 3 -N leached over the study period and percent of applied NO 3 -N leached. Minimum detection limit (M DL) for the flow analyzer was 0.05. A baseline leachate sample was collected prior to first treatment applicat ion yearly, with those values used to correct for all other N mass values for each sampling event. This experiment was arranged as a nested design by CM, with fertilizer treatments randomized within. There were thre e replications. Data were an alyzed with the SAS procedure 29

PAGE 30

ANOVA (SAS institute Inc., Cary. NC) and means were separated by Tukeys method. Significance was determined at the 0.05 probability level. Results and Discussion Nitrate Leaching In all evaluation periods, ther e were differences due to N rates (Table 3-1). Greater amounts of NO 3 -N leached from the 294 kg N ha -1 rate than from the other rates. High N rate has previously been shown to increase nitrate-N leaching (Morton et al., 1988; Kopp and Guillard, 2005; Frank et al., 2006) in othe r grass species. The highest rate applied here (294 kg N ha -1 ) represents a 3-fold increase in recommended app lication rates from the University of Florida. Even at the next highest rate of 196 kg N ha -1 nitrate-N leaching did not differ from the lower rates or from the control. There were also differences in NO 3 -N leaching due to CM and the interaction of N rate and CM for all month with exceptions of Aug and Sep (Table 3-1 and Fig 3-1). The amount of NO 3 -N leaching for CRT plots drama tically increased at 294 kg N ha -1 rate during June to Aug. There was no increase in NO 3 -N leaching from CRM plots, regard less of N rate during June to Aug. In contrast to this, in Oct there wa s no difference between N rates for CRT and NO 3 -N leached in CRM plots increased remarkab ly over CRT plots (Fig 3-1). These results of high NO 3 -N leached for the highest N rate in CRT plots were correlated with the amount of monthly rainfa ll (Table 3-2). The peak of NO 3 -N leaching was in June (2867.7 mg m -2 ) and the lowest was in October (84.2 mg m -2 ) (Table 3-3, Fig 3-2) This is positively correlated with rainfall during this study period ( r 2 =0.372, p=0.0157) (Table 3-2), with approximately 78% of the rain r eceived was during the first three months (June to Aug) (Table 33). Heavy rainfall has previously been shown to increase leaching (Kopp and Guillard, 2005). This shows that heavy rainfall in Fl orida can accelerate the risk of NO 3 -N leaching combined 30

PAGE 31

with high N rate. This field was established 3 mont hs before this research. Root system of the zoysiagrass was not fully estab lished and grown during June to Aug, when N from CRT may be mobilized quickly under rainfall. There was no correlation in NO 3 -N leaching (mg m -2 ) at any N rate for CRM (Data not shown). Starr and DeRoo (1981) re ported no response of NO 3 -N leaching due to CM in a mixture of Kentucky bluegrass and creepi ng red fescue. They applied N fe rtilizer at a rate of 195 kg N ha -1 in the first 2 years and 180 kg N ha -1 in the 3 rd year. Their research result was similar to this research when compared with the rate of 194 kg N ha -1 or less in this research. There were differences in the percent of tota l applied N that leached over the trial period due to N rate and interaction between CM and N rate (Table 3-4), with means ranging from 0 to 11.97% for CRT and 0.09 to 2.16 % for CRM. Percentage loss of applied fertilizer N was less than 0.84 and 2.08 %, respectively, for CRT and CRM except at the 294 kg N ha -1 which had leaching percentages of 11.97 and 2.16, respectively. Nitrate-N leaching by concentration (mg L -1 ) also peaked at the highe st N rate (Table 3-5), similar to NO 3 -N leaching (mg m -2 ). The concentration of NO 3 -N leached ranged from 0.15 to 28.1 mg L -1 These NO 3 -N concentrations were less than th e USEPA drinking water standard of 10 mg L -1 (10 ppm) with the exception of the highest N rate in June (28.1 mg L -1 ), July (18.5 mg L -1 ) and August (11.0 mg L -1 ) only for CRT plots. There were differences in concentration of NO 3 -N leached due to N rate and CM (Table 3-5) The interaction between N rate and CM was also significant in June ( p=0.0007), July ( p=<.0001), August (p=0.0003) and October ( p=0.0027). The concentration of NO 3 -N leachate dramatically increased when the highest N rate (294 kg N ha -1 ) was combined with CRT treatment dur ing June to August, resulting in NO 3 -N leaching exceeding the USEPA standard (Fig. 3-3). 31

PAGE 32

There are a limited number of studi es on the effect of N rate on NO 3 -N leaching in warmsseason grasses. Sharma et al. ( 2009) observed very low levels of NO 3 -N leaching in healthy St. Augustinegrass even at the highest N rate of 296 kg N ha -1 At four different N rates (75, 147, 222, and 294 kg N ha -1 ), there were no differences in NO 3 -N leaching due to N rate during the first and second fertilizer cycle (FC) because of the healthy condition of the turf. However, during the third FC, when there wa s injury due to mite and scal e insects, higher N rate caused higher NO 3 -N leaching. The NO 3 -N concentrations of percolate ranged from 0.58 to 66.95 g N m -2 and an average of 0.08 to 0.40 % of applied N leached. The range of application rates of N fertilizer used in this previous research study was similar to this study s; however, the previous research was done on St. Augustinegrass, rather than zoysiagrass. The reduction in NO 3 -N leaching previously reported in St. Augustineg rass may be due to the deeper and better developed root system of. St. Augustineg rass as compared to zoysiagrass. Saha et al. (2007) compared nitrate leach ing from Floratam St. Augustinegrass with a mix of common Florida ornament als, including canna ( Canna generalis L.H. Bailey), nandina ( Nandina domestica Thunb.), ligustrum ( Ligustrum japonicum Thunb.), and allamanda ( Allamanda cathartica L.). Less NO 3 -N leached from St. Augustinegrass than from ornamentals, and more NO 3 -N leached from quick-release fertilizer th an from slow-release fertilizer when applied at a rate of 294 kg N ha The -1 NO 3 -N concentration from t he turf ranged from 0.11 to 0.21 mg L and from ornamentals ranged 0.23 to 0.52mg L -1 -1 Erickson et al. (2001) observed that a greater amount of NO 3 -N was leached from ornamentals (1.46 mg L -1 ) in comparison to newly established turf (<0.2 mg L -1 ) when a fertilizer was applied at a rate of 300 kg N ha -1 for turf and 150 kg N ha -1 for ornamentals. In 2008, Erickson et al. (2008) reported that NO 3 -N concentration of ornamental (0.44.12 mg L 32

PAGE 33

1 ) was higher than St. Augus tinegrass (0.05 0.01 mg L -1 ). In all of these previous reports, less nitrate-N leached from St. Augustinegrass th an was reported here from zoysiagrass, Kopp and Guillard (2005) also reported that there were interactions between CM and N rate on NO 3 -N leaching in creeping bentgrass. They a pplied N fertilizer at a rate of 0 to 392 kg N ha -1 Clipping-return plots (CRT ) had greater nitrate-N leachi ng than clipping-remove plots (CRM) as N rate increased. Cumulative NO 3 -N mass losses from the creeping bentgrass were 1.9 to 85.4 mg L -1 when clippings were removed, and 10.1 to 171mg L -1 when clippings were returned. Results reported here are similar to NO 3 -N leaching results in cool-season grasses. In creeping bentgrass (Kopp and Guillard, 2005) a nd Kentucky bluegrass (Morton et al., 1988; Frank et al., 2006), the amount of NO 3 -N leached increased as N rate increased. Morton et al. (1988) observed that the average NO 3 -N concentration in leachate for three N rates (0, 97, and 244 kg N ha -1 ) was 0.51, 087, and 1.24 mg L -1 with scheduled irrigation, and 0.36, 1.77, and 4.02 mg L -1 with overwatered irrigation in average. Frank et al. ( 2006) used two N rates (98 and 245 kg N ha -1 ) to investigate NO 3 -N leaching of mature Kentucky Bluegrass. They reported that NO 3 -N concentration for 98 kg N ha -1 were typically below 5 mg L -1 and for 245 kg N ha -1 were often greater than 20 mg L -1 In creeping bentgrass, NO 3 -N concentration ranged from 0.13 to 21.0mg L -1 for four N rates of 0, 98, 196, and 392 kg N ha -1 and the percent of applied N lost due to nitrate-N leaching ranged from 0. 9 to 63% (Kopp and Guillard, 2005). There were differences in NO 3 -N leaching (mg L -1 ) at 294 kg N ha -1 rate for CRT plots by month (Table 3-5). The peak of NO 3 -N leachate was in August (28.1 mg L -1 ) and the lowest was in September and October (0.8 to 1.2 mg L -1 ) This is directly correlated with rainfall during this study period ( r 2 =0.331, p=0.0307) (Table 3-2). This pattern of NO 3 -N leaching (mg L -1 ) at 33

PAGE 34

the highest N rate for CRT was similar to that of mass of NO 3 -N leaching (mg m -2 ) (Table 3-2 and 3-3). There was no correlation in NO 3 -N leaching (mg L -1 ) at any N rate for CRM (Data not shown). Shoot and Root Growth There were differences in shoot growth due to N rate for all months and the average of the harvests (Table 3-6). In July, Aug, and Sept there were differences in shoot growth due to CM, with more clippings in July and Sept when clippings were removed. The response in July and Sept are most probably due to N treatment application 2 wks prior to harvest, while in Aug, there was no N treatment application. The res ponse may also have been related to limited rainfall during Sept and Oct (Table 3-3). Less rainfall resulted in less NO 3 -N leaching, which resulted in production of maximum shoot growth in Oct (Table 3-1 and 3-6). There was an interaction of N rate and CM in Aug (Fig 3-4). CRT treatment produced greater clippings than CRM treatment as N rates increased. These results were similar to previous reports on shoot growth in cool-season grasses. Shoo t growth from CRT treatment exceeded the amount of clippings from CRM (L iu and Hull, 2006; Kopp and Guillard, 2002a). Ten cultivars of three cool-s eason grasses produced clippings ranged from 515g dry weight m -2 for tall fescue and 368g m -2 for perennial ryegrass while applied 15g N m -2 in a year for two growing season (Liu and Hull, 2006). CRT treatme nt enhanced clipping dry matter from 30 to 72%, and increased total N uptake from 48 to 60% with a cool-season gra ss mixture for 2-year (Kopp and Guillard, 2002a). There was no differen ce in root weight due to any treatment effect. Tissue N concentration Leaf TKN differed due to N rate in Sept and Oct and due to CM in Oct only (Table 3-7). This may indicate that CRT increasingly affects ti ssue N concentration over time. There were no interactions for TKN. There were differences of N uptake due to N rate in every month and for 34

PAGE 35

the average of the trial period and due to CM in July, Aug, and Sept. There was an interaction for N uptake between N rate and CM in Sept (Table 3-7; Fig. 3-5). Both CRT and CRM treatment increased N as N rates increased. However, N uptake was steeply increased in CRT plots. Visual Quality and Color Turf visual quality and color differed due to N rate for each month and when averaged over the entire trial period (Table 3-8). Averag e quality ranged from 6.75 to 8.20, and average color from 6.67 to 7.92, with higher scores as N rate incr eased. There were also differences in quality due to CM in June through Aug and for color in June and July, where CRM plots had better quality and color than CRT plots. Average qua lity was 7.41 for CRT and 7.67 for CRM. This result was contrary to Sartain (1993 and 2004), who found increased visual quality of bermudagrass when clippings were returned ov er a 3-yr period. The author reported no difference of quality for ryegrass due to CM. Similar results were reported by Kopp and Guillard (2002a, 2002b) with a bluegrassryegrassfescue mixture, and Heckman et al. (2000) with Kentucky bluegrass. Turf color was ge nerally better where cli ppings were returned (Heckman et al., 2000). Kopp and Guillard (2002) also reported th at clipping-return may reduce more than 50% of N fertilization use without negative effect on turf quality. The reason that quality and color rating decr eased may be from clipping size, which can cause delay of clipping decom position. The rotary mower used in this research had less efficiency to chop clippings rather than th e mulching mower used by Heckman et al. (2000). Bigger clippings remain on the turf surf ace longer, covering the surface and reducing photosynthesis activity of turf. Th is is likely to reduce quality and color as well as chlorophyll level in shoot. 35

PAGE 36

Chlorophyll Content (CC) Chlorophyll index ranged from 216.8 to 303.1 (Table 3-9; Fig 3-6), with higher levels occurring at the higher N rates. There were also differences due to CM for Sept, Oct, and when averaged over the trial period (Table 3-9). Hi gher chlorophyll level was found when clippings were removed (Fig.3-7). Chlorophyl l level is related to photosynthe sis activity in leaf tissue. Photosynthesis may be reduced due to shading effect of clippings left on l eaf tissue, resulting in lower CC levels observed here. Use of a mulc hing mower may reduce this shading effect and increase CC. Correlation between N rate vs. CM vs. Qual ity vs. Color vs. Chlorophyll Level vs. NO 3 -N leaching vs. Shoot Growth. Nitrogen rate was correlated with quality, color, chlorophyll, NO 3 -N leaching, and shoot growth (Table 3-10). The strongest associations (r values ranging from 0.736 0.875) occurred in correlation with quality, co lor, chlorophyll and shoot growth (Table 3-10). There was no significant correlation between CM and other eval uations (Table 3-10). The strongest correlation (r = 0.93) occurred between visual qualit y and color ratings (Table 3-10). Chlorophyll level was positively correlated w ith N rate, quality, color and shoot growth (Table 3-10). Correlation of chlorophyll level and shoot growth were generally high (r = 0.645) with significantly correlated evaluations. NO 3 -N leaching was also correlated with N rate, quality, color, and shoot growth. When shoot growth increased, the NO 3 -N leaching decreased in general. This not surprising, as more shoot growth provides more ground cover more tissue to absorb applied N. Conclusions This research provides information about the effect of CM and N rate on NO 3 -N leaching, shoot growth, TKN concentration, N uptak e, quality, and chlorophyll level. 36

PAGE 37

37 Returning clippings resulted in lower turf quality and chlorophyll index than removing clippings. Total NO 3 -N leached from CRT range d from 114.6 to 7379.1 mg m -2 while the range was from 123.1 to 1537.6 mg m -2 under CRM. The average concentration of NO 3 -N leached ranged 0.23 to 6.47 mg L -2 with significantly higher NO3-N leached From the highest N rate (294 kg N ha -1 ). From the results of this research, it is im portant to apply N at rates below 196 kg N ha -1 per application to avoid NO 3 -N leaching in Empire zoysiagra ss. The potential for leaching was greater under a combination of CRT and high N ra tes, particularly unde r heavy rainfall. These results generally contradict previous st udies on clipping-return effect, which showed reduced NO3-N leaching under CRT in cool-season grasses. Thus, further research is required to verify verify the effect of clipping management and N rate on NO3-N leaching and turf quality in Empire zoysiagrass.

PAGE 38

38 Table 3-1. N leaching (mg m -2 ) of Empire Zoysiagrass in response to N rates and Clipping Management (CM) June July Aug Oct Total N-rate (kg ha -1 ) CRT CRM CRT CRM CRT CRM Sep CRT CRM CRT CRM 0 9.8b 20.5 3.7b 5.6 3.5b 11.2b 1.6 b 0.8b 2.7b 114.6 b 242.5 b 49 5.7b 12.8 2.3b 3.2 4.6b 3.7b 1.3 b 3.7b 1.3b 121.2 b 123.1 b 98 10.0b 12.8 1.9b 7.5 3.1b 5.2b 2.6 b 4.2b 9.2b 131.0 b 261.5 b 147 20.1b 16.0 2.1b 18.1 4.6b 6.8b 2.0 b 2.6b 5.5b 146.3 b 363.0 b 196 85.8b 75.6 11.7b 7.6 16.9b 3.1b 2.1 b 5.1ab 13.6b 530.2 b 412.6 b 294 1307.7a 32.3 225.4a 30.5 206.6a 50.9a 12.6 a 9.6a 60.6a 7379.1 a 1537.6 a ANOVA N-rate (N) 0.0067 <.0001 <.0001 <.0001 0.0010 <.0001 CM 0.0220 0.0375 NS NS 0.0247 NS N CM 0.0073 <.0001 0.0160 NS 0.0218 0.0061 Means followed by the same letter within ea ch column for each N rate and clipping ma nagement are not sign ificantly different at P=0.05. NS= not significant CRT-Clippings returned. CRM-clippings removed.

PAGE 39

39 Table 3-2. Correlation (r 2 ) between NO 3 -N leaching of 294 kg N ha -1 rate for CRT plots vs. Rainfall during trial period Rainfall r 2 p-value mg m -2 0.372 0.0157* NO 3 -N Leaching mg L -1 0.331 0.0307* *, **, *** Significant at the 0.05, 0.01, and 0.001 probability levels, respectively. Table 3-3. NO 3 -N leaching mass (mg m -2 ) and concentration (mg L 1 ) of 294 kg N ha -1 rate for CRT and Rainfall* (mm) during trial period. Jun Jul Aug Sep Oct (mg m -2 ) 2867.7 2493.3 1812.3 121.6 84.2 NO 3 -N leaching (mg L -1 ) 28.1 a 18.5 ab 11.0 ab 1.2 b 0.8 b Rainfall (mm) 91.9 102.6 116.1 44.5 43.9 *Data from Florida Automated Weat her Network (FAWN) were edited Means followed by the same letter within each column for each N rate and clipping management are not signifi cantly different at P=0.05. Table 3-4. Percentage loss of applied fertilizer N from Zoysiagrass soil under varying N rates, and Clipping Management (CM). Percentage Loss of Applied N N Rate CRT CRM Kg N ha -1 % 49 -0.19 0.09 98 -0.01 2.08 147 0.26 1.97 196 0.84 1.47 294 11.97 2.16 ANOVA N-rate (N) 0.0037 CM NS N CM 0.0119

PAGE 40

Table 3-5. N leaching (mg L -1 ) of Empire Zoysiagrass in response to N rates and Clipping Management (CM) Jun Jul Aug Oct N-rate (kg ha -1 ) CRT CRM CRT CRM CRT CRM Sep CRT CRM Average 0 0.21 0.92 0.52 1.01 0.22 0.56 0.15 b 0.15 0.37 0.41 b 49 0.18 0.36 0.31 0.23 0.21 0.15 0.17 b 0.41 0.15 0.23 b 98 0.29 0.26 0.19 0.83 0.15 0.22 0.30 b 0.81 1.37 0.52 b 147 0.45 0.44 0.28 1.74 0.18 0.51 0.25 b 0.32 0.68 0.53 b 196 2.52 4.12 1.06 0.88 0.71 0.19 0.31 b 0.73 1.19 0.73 b 294 28.07 1.81 18.50 3.29 10.96 2.30 1.75 a 1.18 8.47 6.47 a ANOVA N-rate (N) 0.0003 <.0001 <.0001 0.0003 <.0001 0.0002 CM 0.0065 0.0038 0.0337 NS 0.0168 NS N CM 0.0007 <.0001 0.0003 NS 0.0027 NS Means followed by the same letter within ea ch column for each N rate and clipping ma nagement are not sign ificantly different at p=0.05. NS= not significant 40

PAGE 41

Table 3-6. Turf shoot and root growth in resp onse to N rates and Clipping Management (CM). Shoot growth (g m -2 day -1 ) N-rate (kg ha -1 ) Jul Aug Sep Oct Average Root Weight (g) 0 3.26 c 0.91 d 3.31 d 8.37 c 3.96 d 1.03 49 6.55 c 1.65 d 6.67 cd 17.18 bc 8.01 cd 0.62 98 7.83 c 2.38 cd 11.04 c 22.48 bc 10.93 bcd 0.80 147 23.13 b 3.77 bc 19.74 b 28.94 b 18.89 b 0.72 196 16.14 b 4.37 ab 19.52 b 27.72 b 16.94 bc 0.77 294 41.84 a 5.88 a 29.65 a 47.32 a 31.18 a 0.53 CM Return 11.11 b 4.52 a 12.42 b 24.39 13.11 0.69 Remove 21.81 a 1.80 b 17.55 a 26.29 16.86 0.80 ANOVA N-rate (N) <0.0001 <0.0001 <0.0001 0.0050 <0.0001 NS CM <0.0001 <0.0001 0.0062 NS NS NS N CM NS 0.0026 NS NS NS NS Means followed by the same letter within ea ch column for each N rate and clipping ma nagement are not sign ificantly different at P=0.05. NS= not significant 41

PAGE 42

Table 3-7. Total Kjeldahl Nitrogen percentage and N uptake of Empire Zoysiagrass in response to N rates and Clipping Management % TKN N uptake (mg m -2 ) N-rate (kg ha -1 ) Jul Aug Sep Oct Average Jul Aug Sep Oct Average 0 1.55 1.70 1.48 b 1.43 ab 1.54 50.5 d 13.9 d 50.8 c 127.9 c 60.8 c 49 1.73 1.67 1.53 ab 1.37 b 1.58 102.2 cd 25.7 d 104.7 c 268.2 bc 125.2 bc 98 1.72 1.69 1.53 ab 1.42 ab 1.59 123.7 cd 37.8 cd 174.7 bc 354.1 bc 172.6 bc 147 1.45 1.78 1.58 ab 1.45 ab 1.57 365.8 b 58.3 bc 313.1 b 447.4 b 296.1 b 196 1.62 1.83 1.75 ab 1.41 ab 1.65 264.6 bc 74.9 ab 322.6 b 457.6 b 279.9 b 294 1.59 1.79 1.80 a 1.59 a 1.70 709.3 a 99.9 a 503.9 a 804.2 a 529.3 a Clipping Management Return 1.56 1.74 1.57 1.52 a 1.60 182.3 b 74.4 a 202.9 b 398.4 214.5 Remove 1.66 1.75 1.65 1.38 b 1.61 356.4 a 29.1 b 287.0 a 421.4 273.5 ANOVA N-rate (N) NS NS 0.0185 0.0233 NS <0.0001 <0.0001 <0.0001 0.0033 <0.0001 Clipping (C) NS NS NS 0.0004 NS <0.0001 <0.0001 0.0142 NS NS N C NS NS NS NS NS NS 0.0035 NS NS NS Means followed by the same letter within ea ch column for each N rate and clipping ma nagement are not sign ificantly different at P=0.05. N uptake (mg m -2 ) = Dry Shoot growth % TKN 42

PAGE 43

43 Table 3-8. Visual quality and color score of Empire Zoysiagrass in response to N rates and Clipping Manageme nt (CM) in a field experiment Quality Color N-rate (kg ha -1 ) Jun Jul Aug Sep Oct Average Jun Jul Aug Sep Oct Average 0 5.78d 6.55d 7.03d 7.01c 7.32d 6.75d 6.02d 6.57c 6.83d 7.01d 6.87d 6.67c 49 6.40c 7.05c 7.68bc 7.57b 7.95c 7.33c 6.43c 7.10b 7.47c 7.70c 7.30c 7.18b 98 6.32c 7.03c 7.65c 7.80b 8.02bc 7.35c 6.45c 7.23b 7.62bc 7.90b 7.50bc 7.33b 147 7.10b 7.72b 8.07a 8.10a 8.28ab 7.87b 7.13b 7.87a 7.88ab 8.20a 7.70ab 7.73a 196 6.63c 7.75ab 8.02ab 8.12a 8.30ab 7.75b 6.77bc 7.88a 7.87ab 8.17a 7.72ab 7.68a 294 7.90a 8.13a 8.25a 8.28a 8.43a 8.20a 7.65 a 8.05a 7.93a 8.22a 7.73a 7.92a CM Return 6.57b 7.17b 7.58b 7.78 7.98 7.41 b 6.60 b 7.28 b 7.58 7.89 7.52 7.36 Remove 6.81a 7.57a 7.98a 7.87 8.12 7.67 a 6.88 a 7.62 a 7.62 7.86 7.42 7.48 ANOVA N-rate (N) *** *** *** *** *** *** *** *** *** *** *** *** CM *** *** NS NS ** ** NS NS NS NS N CM NS NS NS NS NS NS NS NS NS NS NS NS *, **, *** Significant at the 0.05, 0.01, and 0.001 probability levels, respectively. / NS: Not Significant Means followed by the same letter within ea ch column for each N rate and clipping ma nagement are not sign ificantly different at P=0.05. NS= Not Significant at P=0.05

PAGE 44

44 Table 3-9. Chlorophyll Index of Empire Zoysia grass in response to N rates and Clipping Management (CM). Chlorophyll Index N-rate (kg ha -1 ) Jul Aug Sep Oct Average 0 236.5 c 220.50 d 213.2 c 197.2 c 216.8 d 49 306.3 b 271.8 bc 253.4 b 209.8 bc 260.2 c 98 323.5 b 299.92 a 273.1 ab 227.1 ab 280.9 b 147 374.8 a 285.0 ab 276.9 ab 230.5 a 291.8 ab 196 381.2 a 303.08 a 287.27 a 240.6 a 303.1 a 294 381.9 a 257.08 c 274.4 ab 231.0 a 286.1 ab CM Return 330.01 a 279.1 a 238.9 b 212.8 b 265.2 b Remove 338.04 a 266.5 a 287.2 a 232.6 a 281.1 a ANOVA N-rate (N) <0.0001 <0.0001 <0.0001 0.0015 <0.0001 CM NS 0.0509 <0.0001 0.0015 0.0047 N CM NS NS NS NS NS Means followed by the same letter within ea ch column for each N rate and clipping management are not significan tly different at P=0.05.

PAGE 45

Table 3-10. Correlation coefficients for N rate, clipping management quality, color, chlorophyll, NO 3 -N Leaching, and Shoot growth. N-rates CM Quality Color Chlorophyll NO 3 -N Leaching Shoot growth r 0.000 0.858 0.875 0.736 0.519 0.812 N-rates P 1.000 <0.0001 <0.0001 <0.0001 0.0012 <0.0001 r 0.000 -0.255 -0.128 -0.247 0.24 -0.183 CM P 1.000 0.134 0.4557 0.1472 0.1587 0.286 r 0.858 -0.255 0.93 0.823 0.382 0.866 Quality P <0.0001 0.134 <0.0001 <0.0001 0.0214 <0.0001 r 0.875 -0.128 0.93 0.824 0.443 0.859 Color P <0.0001 0.4557 <0.0001 <0.0001 0.0069 <0.0001 r 0.736 -0.247 0.823 0.824 0.082 0.645 Chlorophyll P <0.0001 0.1472 <0.0001 <0.0001 0.6358 <0.0001 r 0.519 0.24 0.382 0.443 0.082 0.51 NO 3 -N Leaching P 0.0012 0.1587 0.0214 0.0069 0.6358 0.0015 r 0.812 -0.183 0.866 0.859 0.645 0.51 Shoot growth P <0.0001 0.286 <0.0001 <0.0001 <0.0001 -0.0015 45

PAGE 46

0 200 400 600 800 1000 1200 1400 0 49 98147196294NO3-N (mg m-2)(a) (NS) (NS) (NS) (NS) (NS) ( *** ) 0 50 100 150 200 250 0 49 98147196294NO3-N (mg m-2) (NS) (NS) (NS) (NS) (NS) ( *** ) (b) 0 50 100 150 200 250 0 49 98147196294 N rate (kg ha-1 yr-1)NO3-N (mg m-2) CRT CRM (NS) (NS) (NS) (NS) (NS) ( *** ) (c) 0 10 20 30 40 50 60 70 0 49 98147196294 N rate (kg ha-1 yr-1)NO3-N ( m g m-2 ) CRT CRM (NS) (NS) (NS) (NS) (NS) ( *** ) (d) 0 1000 2000 3000 4000 5000 6000 7000 8000 0 49 98147196294 N rate (kg ha-1 yr-1)NO3-N (mg m-2) CRT CRM (NS) (NS) (NS) (NS) ( *** ) (NS) (e) Figure 3-1. Interaction between clipping management (CM) and N rate with respect to NO 3 -N leaching (mg m2 ) from Empire Zoysiagrass in June (a), July (b), August (c), October (d), and total (e). (NS: Not significant, ***: Significant at p=0.05 between N rates) 46

PAGE 47

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00 June July Aug Sep Oct 0 20 40 60 80 100 120 140 Nitrate leaching (mg m-2) Rainfall(mm) Fig. 3-2. Comparison of monthl y rainfall and nitrate (NO 3 -N) leaching. 47

PAGE 48

` 0 2 4 6 8 10 12 14 16 18 20 0 49 98 147196294 N rate (Kg ha-1 yr-1) 0 5 10 15 20 25 30 04998147196294 N rate (Kg ha-1 yr-1)Concentration (mg L-1) of NO3-N leaching June July August October Figure 3-3. Interaction between clipping management (CM) and N rate with respect to NO 3 -N leaching (mg L1 ) from Empire Zoysiagrass in June (upper left), July (upper right), August (bottom left), and October (bottom right). 0 2 4 6 8 12 10 04998147196294 N rate (Kg ha-1 yr-1)Concentration (mg L-1) of NO3-N leaching 0 2 4 6 8 10 0 49 98 147 196 294 N rate (Kg ha-1 yr-1) CRT CRM CRT CRM 48

PAGE 49

0 5 10 15 20 25 30 35 04998147196294 N rate (kg ha-1)Shoot Weight (g m-2) Clipping-return Clipping-remove Figure 3-4. Interaction between clipping mana gement (CM) and N rate with respect to shoot weight (g m2 day -1 ) from Empire Zoysiagrass in August 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00 04998147196294 N rate (kg ha-1)N uptake (mg m-2) Clipping-return Clipping-remove Figure 3-5. Interaction between clipping manageme nt (CM) and N rate with respect to N uptake (g m2 ) from Empire Zoysiagrass in August 49

PAGE 50

150 170 190 210 230 250 270 290Chlorophyll level N rates Control 49 kg N ha-1 98 kg N ha-1 147 kg N ha-1 196 kg N ha-1 294 kg N ha-1D AB B C AB A Figure 3-6. Chlorophyll level by N rate tr eatment for Empire Zoysiagrass 255 260 265 270 275 280 285Chlorophyll level Clipping Management Clipping-Remove Clipping-RemoveA B Figure 3-7. Chlorophyll level by Clipping tr eatment for Empire Zoysiagrass 50

PAGE 51

CHAPTER 4 EFFECT OF MULTISPECTRAL RE FLECTANCE AND CORRELATION OF QUALITY AND LEACHING IN EMPIRE ZOYSIAGRASS Introduction Turfgrass research typically uses qualitativ e visual measurements to compare effects of treatments. These measurements include over all turf quality and may often include related parameters such as tu rf color, density, percent green or injured, etc. While these ratings may produce solid statistical data, technology has been developed to determine ability to quantify these subjective ratings. Use of multispectral reflectance has been used by a number of researchers in turf system s. Trenholm et al. (1999a) observed that reflectance at particular wavelengths th roughout the visible sp ectrum was highly correlated with visual turf quality scores, shoot density, and shoot tissue injury in seashore paspalum ( Paspalum vaginatum Swartz.) and hybrid bermudagrass ( Cynodon dactylon x C. transvaalensis Burtt-Davy). Reflectance at 661 and 813 nm had the strongest correlations, as did se veral growth and stress indi ces using both visual spectrum and near infrared (NIR) wavelengths. Tre nholm et al. (1999b) further observed that reflectance could be reliably used to disc riminate between wear injury. Spectral reflectance was also used to distinguish betw een N application, herb icide stress, and C3 vs. C4 grasses (Trenholm et al., 2000). Higher reflectance in the vi sible range (400-700 nm) indicates less plant light attenuation and utilization at those wavelengths and has been associated with stress or nutritional deficiency. Growth indices NDVI (normalized difference vegetation index)and LAI (leaf area index) have been associated with crop growth and yield (Asrar et al., 1984) and with healthy turfgr ass growth and shoot density (Trenholm, et al., 1999). Higher values i ndicate optimal performance, and Stress1 (reflectance at wavelength 710/wavelength 760) and Stress2 (reflectance at wavelength 51

PAGE 52

710/wavelength 810) indices are associated with turf stress response, where lower values indicate lower stress levels and better performance. There are at least 10 sp ecies of zoysiagrass ( Zoysia spp. Willd.), all of which have originated from the Orient (Christians, 2007). They in clude Korean (or Japanese) lawngrass ( Zoysia japonica Steud.), which is the most wide ly used species in the United States (Christians, 2007). Zoysia japonica is well adapted to use on golf courses fairways and tees and some cultivars appear to be well suited to home lawn use (Trenholm and Unruh, 2005a), fair shade, and sa linity tolerance (Chris tians, 2007). It also stands up well to traffic and has been repor ted to tolerate drought while maintaining relatively low levels of disease and insect damage (Christians, 2007). Empire zoysiagrass is a native pr oprietary selection of Zoysia japonica It has performed well in trials in Florida and appears to require less nitrogen than other zoysiagrass cultivars (Trenholm and Unruh, 2009). It is currently being used increasingly in home lawns throughout Florida. Turf shoot clippings have often been c onsidered a nuisance pr oduct to dispose of, although the clippings contain a bundant nutrients and are a source of organic matter. Removing clippings from turf causes N loss from the system. Starr and DeRoo (1981) examined the various effects of clipping-return while evaluating the fate of N fertilizer with Kentucky bluegrass mix ( Poa pratensis L.) and creeping red fescue ( Festuca rubra L.). The study spanned 3 years a nd used a suction lysimeter with 15 N labeling to trace the fate of N from clippings and fert ilizer. Return of clippings to the turf increased the total N uptake of the harvested gra ss by 19, 41, and 74% for the 3 consecutive years of the experiment. In the clipping returned treatme nt, yield and growth of the grass increased 52

PAGE 53

by about 30%. The tissue N concentration from clipping-re moved treatment was derived equally from soil and fertilizer, whereas the tissue N concentration from clippingreturned treatment was derived from equa l amounts of N from soil, fertilizer, and clipping-return. No information is available on the spectral responses for turfgrasses due to clipping management. Therefore, the objectives of th is study were to evaluate responses of zoysiagrass to N rate and clipping treatme nt using spectral reflectance data and to determine the degree of associ ation between reflectance valu es and other measurements such as nitrate leaching, quality, colo r and shoot growth. Materials and Methods The field experiment was conducted at th e University of Florida Plant Science Research and Education Center in Citr a, Florida on Empire zoysiagrass ( Zoysia japonica Steud.). The grass was established in March 2008 and the study was conducted from June to October 2008. Clipping-management (CM) and nitrogen (N) fertilizer treatments were as follows: CM #1 consisted of clippi ng-return, in which clippi ngs were left in the experimental field after mowing with a conventional rotary mower. CM#2 consisted of clipping-removal, in which clippings were taken from the field by attaching a collection bag to the mower. Mowing height was set at 6.3 cm (2.5 inches ). The plots were mowed once a week throughout the study period. Fertilizer treatments consisted of six levels of total N rates (equivalent to 0 lbs, 1 lbs, 2 lbs, 3 lbs, 4 lbs or 6lbs N 1,000 ft -2 or 0 kg, 49 kg, 98 kg, 147 kg, 196 kg, or 294 kg 53

PAGE 54

N ha -1 ). Treatments were applied at 2-mo intervals for a total of two treatment applications. A 50% quick-release fertilizer (QRF) and 50% slow-release fertilizer (SRF) of 15N-0P-15K were used. The area was irriga ted to replace evapotranspiration (ET) as needed to maintain healthy turf. Turf was evaluated visually for quality and color, which were rated immediately after mowing. A scale of 1 to 9 was used, in which 9 represents optimal, dark green color and 1 represents dead, brown turf. A rating of 6 was considered minimally acceptable for a home lawn. Soil moisture (SM), canopy temperature (CT), chlorophyll content (CC), and multispectral reflectance (MSR) were also measured. Soil moisture content was quantified weekly using a Time Domain Reflectometer (TRD) (IMIKO Micromodule Technik GmbH; Ettingen, Germany). Multispectral reflectance readings were taken every 7-10 days with a Cropscan MSR16 radiometer (Cropscan, Inc., Rocheste r, MN); The radiometer was fitted with filter wavelengths to measure reflectance at 450, 550, 660, 694, 710, 760, 810, and 930 nm. In addition, the following growth and stress indices were evaluated: NDVI (normalized difference vegetation i ndex) growth index computed as R 930 R 660 /R 930 + R 660 Best = highest value. IR/R (leaf area index) grow th index computed as R 930 /R 660 Best = highest value. Stress1 index computed as R 710 /R 760 Best = lowest value. Stress2 index computed as R 71 0/R 810 Best = lowest value. Nitrate leaching and shoot grow th collection methodologies were previously described in Chapter 3. 54

PAGE 55

This experiment was arranged as a nested design by CM, with fertilizer treatments randomized within. There were three replicat ions. Data were analyzed with the SAS procedure ANOVA or CORR (SAS institute Inc., Cary. NC). Significance was determined at the 0.05 probability level. Results and Discussion MultiSpectral Reflectance (MSR) There were few differences in reflectance scores due to CM f in the weeks following the first fertilizer treatment (WAFT) (Table 4-1). There were differences in reflectance at all wavelengths and in all indices (P<0.001) at 1 week after second treatment (WAST), with better values occurring in CRM plots (Table 4-2), which means that CRT plots had more stress than CRM plot s (Table 4-2). At 3 WAST, stress indices also showed that the CRT plots had more st ress than the CRM plots (data not shown). Reflectance at 450 nm at 5 WAST consisten tly showed that the CRT plots had more stress than the CRM plot s (data not shown). In general, N treatment had significant difference at PAR range (450-710) and growth (NDVI, and IR/R) and stress (ST-1, an d ST-2) indices at between 1 WAFT and 1 WAST (Table 4-1). At 3 WAST, stress indices showed that lower N rate plots had higher reflectance and therefore less ability to assimilate and use light at the various wavelengths measeured than higher rate plots (data not shown). Throughout the evaluation period, higher N rate plots generally had lower reflectance than lower N rate (Table 4-1 and 4-2). Similar results we re reported by Trenholm et al. (2000). They observed that there were consis tent differences due to N ra te throughout the visible range wavelengths. The reflectance was consistently greater at the lowest N. 55

PAGE 56

Correlation between Multispectral Reflecta nce (MSR) vs. N rate, CM, Growth, and Quality. N Rate vs. Reflectance N rate was correlated with spectral reflectance at 450 and 550 nm and the ratios NDVI, ST-1, ST-2, and IR/R (Table 4-3). Highest r values (0.490-0.638) were obtained from 450 nm, NDVI, ST-1, ST-2, IR/R (Table 4-3). Lower N rate indicated higher reflectance and stress (ST-1, and ST-2) caused by N deficiency (Table 4-3). CM vs. Reflectance There was no correlation between any of the wavelengths evaluated and CM (Table 4-4). However, response of CM to growth and stress indices was significant (r = 0.383-0.458), with lowest vales seen with IR/R and highest with NDVI (Table 4-4). The negative correlation between CM and grow th indices (NDVI and IR/R) and positive correlation between CM and Stress indices im plies that CRT had less turf growth and higher stress than CRM treatment (Table 4-4). This was different from the result of Heckman et al.(2000) who reported a productive effect of CRT on shoot growth and turf quality. There are several possibilities about the effect of CRT on turf health. First possibility was evaluation timing for MSR, which was evaluated immediately after mowing event. Clippings in CRT plots possibly affected reflectance readings. Second, for zoysiagrass, CRT may require longer time periods for satisfactory effect on turf growth and health due to th eir physiological difference from cool-season grasses. Sartain (1993) repor ted that the clipping yield a nd quality of one warm-season grass (Tifway bermudagrass) species and one cool-season grass (Pennant perennial ryegrass) increased when clippings were returned for three years. The other possibility 56

PAGE 57

may result from mower difference. Regular ro tary mower was used rather than mulching mower Heckman et al (2000) used. In general, warm -season grasses grow faster and more active in summer than cool-season gra sses. We mowed weekly with cutting height of 6.3 cm regardless of growing status. Clippings may cover turf effectively from sunlight while reducing chlo rophyll level of tissue. NDVI is related to chlorophyll concentration (Filella et al ., 1995). The NDVI index (-0.458) showed that CRT treatment had less chlorophyll concentration (Table 4-3). Visual Quality and Color vs. Reflectance Similar responses were seen for visual quality and color at varying reflectance. Quality and color were negatively correlated with reflectance at 450 and 660 nm, (Table 4-3). The correlation coefficient ranged fr om -0.358 to -0.702 for quality, and -0.335 to 0.627 for color (Table 4-3). Turf quality and co lor were highly correlated with all growth and stress indices (Table 4-3). Correlation coefficients all showed a high degree of association with quality ( 0.698-0.804) and color (0.639-0.762); relations were positively associated for growth indices NDVI and IR/R and were negatively for the stress indices (Table 4-3). NO 3 -N Leaching vs. Reflectance Reflectance was not correlated with NO 3 -N leaching data at any individual wavelength or indices (Table 4-3). This is somewhat surprising, since NO 3 -N leaching was positively correlated with N rate, quality, color, and chlorophyll level ( r =0.382 to 0.519) (Table 3-9) and it could be speculated that stronger, more de nse grass associated with increased N rate, quality, and color would reduce leaching. 57

PAGE 58

58 Shoot Growth vs. Reflectance Reflectance at 450 nm was correlated with shoot growth (Table 4-3). In this study, highest values were found in reflectan ce at wavelength 450nm, NDVI, ST-1, ST-2, and IR/R ( r = -0.529, 0.548, -0.655, -0.656, and 0.661, re spectively) (Table 4-3). Conclusions This research provides information about th e effect of CM and N rate on spectral reflectance responses of Empire zoysiagrass. There was very little response to any reflectance values to CM, except for the va lues taken the week following the second fertilizer application. Reflectance values did va ry due to N rate and showed several strong associations with other measured parameters. From the results of this research, it appear s that CM has little effect on turf light attenuation through the visible range wavelengths and that it has little effect on the associated physiological functions. Results also indicate that it is not practical to use this methodology to predict nitrate leach ing from Empire zoysiagrass Further research should be done to de termine if multiple years will provide similar results regarding nitrate leaching a nd spectral reflectance correlations and responses.

PAGE 59

Table 4-1. Reflectance by clip ping practice and varying N rate 6 weeks after first fertilizer treatment (6 WAFT ). Wavelength (nm) N-rate (kg ha -1 ) 450 550 660 694 710 NDVI Stress-1 Stress-2 IR/R 0 4.5a 13.5a 7.1a 10.0 a 19.4 a 0.81 b 0.37 a 0.33 a 9.2 b 49 3.9bc 11.5b 5.8bc 8.2 bc 16.5 b 0.83 ab 0.33 bc 0.30 bc 11.1 a 98 3.8bc 11.0bc 5.6 b-d 7.8 cd 15.8 bc 0.84 ab 0.32 bc 0.29 bc 12.3 a 147 3.7bc 10.6cd 5.5cd 7.8 cd 15.5 bc 0.84 ab 0.32 bc 0.29 bc 11.3 a 196 3.6c 10.2d 5.1d 7.1 d 14.7 c 0.85 a 0.30 c 0.27 c 12.6 a 294 4.1ab 11.1bc 6.3b 8.7 b 16.6 b 0.81 b 0.35 ab 0.32 ab 9.3 b CM Return 3.9 11.1 b 5.8 8.1 16.0 b 0.83 0.33 0.30 10.7 Remove 4.0 11.5 a 6.0 8.4 16.8 a 0.83 0.33 0.30 10.9 ANOVA N-rate (N) <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 0.0016 0.0001 0.0001 <0.0001 CM NS 0.0017 NS NS 0.0016 NS NS NS NS N CM NS NS NS NS NS NS NS NS NS WAFT: Week(s) After First Treatment Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. *** Significant at the 0. 001 probability level. NS= not significant 59

PAGE 60

Table 4-2. Reflectance by clipping practice and varying N ra te 1 week after second ferti lizer treatment (1 WAST). Wavelength (nm) N-rate (kg ha -1 ) 450 550 660 694 710 NDVI Stress-1 Stress-2 IR/R 0 4.3 a 13.8 a 8.4 a 12.2 a 22.1 a 0.75 0.43 a 0.41 a 6.3 b 49 3.6 b 11.5 b 6.8 ab 10.1ab 18.9 b 0.77 0.40 ab 0.38 ab 7.7 ab 98 3.4 b 10.6bc 6.7 ab 9.7 b 17.9 bc 0.77 0.40 ab 0.37 ab 8.0 ab 147 3.3 b 10.1b-d 6.3 b 9.0 b 16.8 b-d 0.78 0.37 ab 0.35 ab 8.5 ab 196 3.0 b 9.3 d 5.4 b 7.9 b 15.2 d 0.81 0.33 b 0.31 b 10.1 a 294 3.3 b 9.6 d 6.2 b 8.7 b 15.7 cd 0.78 0.37 ab 0.34 ab 9.1 a CM Return 3.8 a 11.5 a 7.5 a 10.8 a 19.2 a 0.74 b 0.43 a 0.41 a 6.8 b Remove 3.2 b 10.2 b 5.7 b 8.4 b 16.3 b 0.81 a 0.33 b 0.31 b 9.7 a ANOVA N-rate (N) <.0001 <.0001 0.002 0.0003 <.0001 NS 0.050 0.0266 0.004 CM 0.0002 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 N CM NS NS NS NS NS NS NS NS NS Significant at the 0.05 probability level. ** Significant at the 0.01 probability level. *** Significant at the 0. 001 probability level. NS= not significant 60

PAGE 61

Table 4-3. Correlation Coefficients for reflectance vs. N rate, clipping management, quality, co lor, chlorophyll, N leaching, a nd shoot growth. 61 Wavelength (nm) 450 550 660 694 760 810 NDVI Stress-1 Stress-2 IR/R N-rates -0.545 (0.0006) -0.344 (0.040) -0.304 (NS) -0.190 (NS) 0.226 (NS) 0.243 (NS) 0.490 (0.002) -0.626 (<0.0001) -0.638 (<0.0001) 0.561 (0.0004) CM 0.249 (NS) -0.021 (NS) 0.199 (NS) 0.105 (NS) -0.253 (NS) -0.245 (NS) -0.458 (0.005) 0.418 (0.011) 0.397 (0.017) -0.383 (0.021) Quality -0.702 (<0.0001) -0.358 (0.032) -0.417 (0.011) -0.254 (NS) 0.338 (0.044) 0.364 (0.029) 0.698 (<0.0001) -0.795 (<0.0001) -0.804 (<0.0001) 0.771 (<0.0001) Color -0.627 (<0.0001) -0.335 (0.046) -0.358 (0.032) -0.207 (NS) 0.342 (0.041) 0.368 (0.027) 0.639 (<0.0001) -0.750 (<0.0001) -0.762 (<0.0001) 0.726 (<0.0001) Chlorophyll -0.760 (<0.0001) -0.479 (0.003) -0.554 (0.0005) -0.404 (0.015) 0.226 (NS) 0.265 (NS) 0.737 (<0.0001) -0.830 (<0.0001) -0.839 (<0.0001) 0.812 (<0.0001) N-leaching -0.017 (NS) 0.094 (NS) 0.219 (NS) 0.242 (NS) 0.188 (NS) 0.159 (NS) -0.105 (NS) -0.010 (NS) -0.015 (NS) -0.042 (NS) Shoot Yield -0.529 (0.0009) -0.222 (NS) -0.262 (NS) -0.134 (NS) 0.338 (0.044) 0.350 (0.037) 0.548 (0.0005) -0.655 (<0.0001) -0.656 (<0.0001) 0.661 (<0.0001) ( ): p-value NS= not significant

PAGE 62

CHAPTER 5 CONCLUSIONS Six different N rates and two clipping manage ment (return vs. remove) were studied for their effects on NO3-N leaching, shoot growth, TKN concentration, turf visual quality and color, chlorophyll content, and multispectral reflecta nce (MSR) in Empire zoysiagrass in 2008. There were differences in NO3-N leaching, shoot growth, turf visual quality and color, and chlorophyll content due to N rate. Inte restingly, however, ther e were no significant difference in NO3-N leaching, shoot growth, TKN concentr ation, and turf visual color between CRT and CRM treatment. Even CRM had higher score in turf visual quality and chlorophyll content than CRT treatment. However, there was significant interaction for NO3-N leaching between CM and N rate treatment during all trial periods except Sep. The NO3-N leachate dramatically increased when the highest N rate (294 kg N ha -1 ) was combined with more CRT treatment than CRM, resulting in nitrate-N leaching exceeding the USEPA standard. This result implies that N returned from clippings increases in condition of high N rate. Thus, if to maintain N environmentally safe is a goal through avoiding NO3-N leaching, it is important to abstain from applying high N rate (over 196 kg N ha -1 ) combined with returning c lippings to turf. If turf grass clippings are returned, fertilizer rates should be reduced in high N rate. These results are well supporte d through MSR data, in which any reflectance at varying wavelengths had no differences with CM. Howeve r, responses of CM to growth and stress indices were significantly differe nt. The CRT showed less turf growth and higher stress than CRM treatment through entire expe riment period. Consistent results were also shown that higher N rate plots generally had less stress than lower N rate. Growth and stress indices such as NDVI, St ress, and IR/R showed the significant and consistent linear correlation with all evaluations used in this study.

PAGE 63

In sum, we conclude that CRT treatment cau sed higher stress and le ss turf health than CRM treatment for Empire zoysiagrass in 2008. Th is may result from clipping size, which can cause delay of clipping decomposition, by using ro tary mower. Bigger clippings remain on the turf surface longer, covering the surface and redu cing photosynthesis activity of turf. This is likely to reduce quality and color as we ll as chlorophyll level in shoot. Because of different conclusions from previ ous research about the effect of CM, and because of physiological or inter-species differe nce from other turf system, further studies on mower effect of CM and other warm-season grasses are needed.

PAGE 64

LIST OF REFERENCES 1. Asrar, G., M. Fuchs, E.T. Kanemasu, and J.L. Hatfield. 1984. Estimating absorbed photosynthetic radiation and leaf area index from spectral refl ectance in wheat. Agron. J. 76:300-306. 2. Below, F.E. 2001. Nitrogen metabolism and crop productivity In Pessarakli, M (Ed.). Handbook of Plant and Crop Physiology, 2nd Ed. New York: Marcel Dekker, Inc. pp385406. 3. Bigelow, C.A., D.W. Waddill, and D.R. Chalmers. 2005. Turf-t ype tall fescue lawn turf response to added clippings. Int. Turfg rass Soc. Res. J. 10:916-922. 4. Bloom, A.J., P.A. Meyerhoff, A.R. Taylor and T.L. Rost. 2003. Root development and absorption of ammonium and nitrate from the rhizosphere. J. Plant Growth Regul. 21:416-431. 5. Bowman, D.C., J.L. Paul, W.B. Davis, and S.H. Nelson. 1989. Rapid depletion of nitrogen applied to Kenturky bluegrass turf. J. Am. So c. Hortic. Sci. 114:229-233. 6. Bowman, D.C., D.A. Devitt, M.C. Engelke, and T.W. Rufty Jr. 1998. Root architecture affects nitrate leaching from bent grass turf. Crop Sci. 38:1633-1639. 7. Bowman, D.C., C.T. Cherney, and T.W. Ruft y, Jr. 2002. Fate and transport of nitrogen applied to six warm-season turf grasses. Crop Sci. 42:833-841. 8. Brady, N.C. 1990. The Nature and Propertie s of Soils, 10th ed. New York: Macmillan Publishing. pp.315-338. 9. Carter, G.A. 1993. Responses of leaf spectral reflectance to plant stress, Am. J. Bot. 80:230-243 10. Carter, G.A. and R.L. Miller. 1994. Early de tection of plant stress by digital imaging within narrow stress-sensitive wavebands. Remote Sens. Environ. 50:295-302. 11. Christians, N.E. 2007. Fundamentals of turfgrass management 3rd Ed. Hoboken, NJ: John Wiley & Sons, Inc. pp 9-12. 12. Environmental Protection Agency (EPA). 2006. National primary drinking water regulations: Technical factsheet on: Nitrate/nitrite. http://www.epa.gov/ogwdw000/dwh/tioc/nitrates.html (verified 18 September, 2008) 13. Erickson, J.E., J.L. Cisar, J.C. Volin, and G. H. Snyder. 2001. Comparing nitrogen runoff and leaching and between newly established St. Augustinegrass turf and an alternative residential landscape. Crop Sci.41: 1889-1895.

PAGE 65

14. Erickson, J.E., J.L. Cisar, G.H. S nyder, D.M. Park, K.E. Williams. 2008. Does a mixed-species landscape reduce inor ganic-nitrogen leaching compared to a conventional St. Augustinegrass lawn?. Crop Sci. 48: 1586-1594 15. Filella, I., L. Serrano, J. Serra and J. Pe uelas. 1995. Evaluating wheat nitrogen status with canopy reflectance indi ces and discriminant anal ysis. Crop Sci. 35:1400-1405. 16. Florida Department of Environmental Protection (FDEP). 2007. Best Management Practices for the enhancement of environmental quality on Florida golf courses. 17. Frank, K.W., O'Reilly, K. M., Crum, J. R., and Calhoun, R. N. 2006. The fate of nitrogen applied to a mature Kentucky bluegrass turf. Crop Sci. 46:209-215. 18. Geron, C.A., T.K. Danneberger, S.J. Traina, T.J. Logan, and J.R. Street. 1993. The effect of establishment methods and fertilization pr actices on nitrate leaching from turfgrass. J. Enriron. Qual. 22:119-125. 19. Glass, A.D.M. 2003. Nitrogen use efficiency of crop plants: Physio logical constraints upon nitrogen absorption. Crit. Rev. Plant Sci. 22:453-470. 20. Gross, C.M., J.S. Angle, and M.S. Welterl en. 1990. Nutrient and sediment losses from turfgrass. J. Environ. Qual. 19:663-668. 21. Guillard, K., and K.L. Kopp. 2004. Nitrogen fer tilizer form and associated nitrate leaching from cool-season lawn tu rf. J. Environ. Qual. 33:1822-1827. 22. Gupta, S.K., R.C. Gupta, S.K. Chhabra, S. Eskiocak, A.B. Gupt a, and R. Gupta. 2008. Health issues related to N pollution in water and air. Current Sci. 94:1469-1477. 23. Heckman, J.R., H. Liu, W. Hill, M. DeM ilia, and W.L. Anastasia. 2000. Kentucky bluegrass responses to mowing practice and nitrogen fertility management. J. Sustain Agr. 15:25-33. 24. Hull, R.J., and H. Liu. 2005. Turfgrass nitroge n: Physiology and environmental impacts. Int. Turfgrass Soc. Res. J. 10:962-975. 25. Jackson, L.E., M. Burger, and T.R. Cavagnaro. 2008. Roots, nitrogen transformations, and ecosystem services. A nnu. Rev. Plant Biol. 59:341-363. 26. Kopp, K.L., and K. Guillard. 2002a. Clipping mana gement and nitrogen fertilization of turfgrass: Growth, nitrogen utiliz ation, and quality. Crop Sci. 42:1225-1231. 27. Kopp, K.L., and K. Guillard. 2002b. Adjusti ng nitrogen rates when clippings are returned: Returning clippings to fairways and roughs boosts natural nitrogen levels and reduces the need for inputs. Golf Course Management. 70(10): 60-64.

PAGE 66

28. Kopp, K.L., and K. Guillard. 2005. Clipping c ontributions to nitrate leaching from creeping bentgrass under vary ing irrigation and N rates ba ckground. Int. Turfgrass Soc Res. J. 10:80-85. 29. Lee, D.J., D.C. Bowman, D.K. Cassel, C.H. Peacock, and T.W. Rufry, Jr. 2003. Soil inorganic nitrogen under fertilized be rmudagrass turf. Crop Sci. 43:247-257. 30. Liu, H. B., and R.J. Hull. 2006. Comparing cult ivars of three cool-s eason turfgrasses for nitrogen recovery in clippings. HortScience. 41:827-831. 31. McCarty, L.B., M.F. Gregg, and J.E. Toler. 2007. Thatch and mat management in an established creeping bentgrass go lf green. Agron. J. 99:1530-1537. 32. Miltner, E.D., B.E. Branham, E.A. Paul and P.E. Rieke. 1996. Leaching and mass balance of 15N-labeled urea applied to Kent urky bluegrass turf. Crop Sci. 36:1427-1433. 33. 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. 34. Qian, Y. L., W. Bandaranayakea, W. J. Pa rtonb, B. Mechamc, M. A. Harivandid and A. R. Mosiere. 2003. Long-term effects of clippi ng and nitrogen manage ment in turfgrass on soil organic carbon and nitrogen dynamics: The CENTURY m odel simulation. J. Environ. Qual. 32:1694-1700. 35. Ruckart, P.Z., A.K. Henderson, M.L. Black, and M.D. Flanders. 2008. Are nitrate levels in groundwater stable over time?. J. Expo. Sci. Env. Epid. 18:129-133. 36. Saha, S.K., L.E. Trenholm, J.B. Unruh. 2007. Effect of fertilizer source on nitrate leaching and St. Augustinegrass turfgrass quality. HortScience. 42:1478-1481. 37. Sartain, J.B. 1993. Interrelationships among turf grass, clipping recycling, thatch, and applied calcium, magnesium, and potassium. Agron. J. 85:40-43. 38. Sartain, J.B. 2004. Returning clippings reduces fertilizer losses. Grounds Maintenance. 39(4): 12-23. 39. SAS Institute. 2002-2003. SAS Statistic program. 9 th ed. SAS Inst., Cary, NC. 40. Sharma, S. 2009. Effect of nitrogen rates a nd mowing heights on nitrogen leaching, turf quality and spectral reflectance in Flor atam St. Augustinegrass. Masters Thesis. University of Florida. 41. Shaver, E., R. Horner, J. Skupien, C. Ma y, and G. Ridley. 2007. Fundamentals of urban runoff management. Technical and Institutional Issues. 2 nd Ed. Madison, FL. North American Lake Management Society. pp 44-52. 42. Snyder, G.H., B.J. Augustin, and J.M. Davidson. 1984. Moisture sensor-controlled irrigation for reducing N leaching in bermudagrass turf. Agron. J. 76:965-969.

PAGE 67

43. Soper, D.Z., J.H. Dunn, D.D. Minner, and D.A. Sleper. 1988. Effects of clipping disposal, nitrogen, and growth retardants on thatch a nd tiller density in Z oysiagrass. Crop Sci. 28:325-328. 44. Starr, J.L., and H.C. DeRoo. 1981. The fate of nitrogen applied to turfgrass. Crop Sci. 21:531-536. 45. Trenholm, L.E., R.N. Carrow, and R.R. Duncan. 1999a. Relationship of multispectral radiometry data to qualitative data in turfgrass research. Crop Sci. 39:763-769. 46. Trenholm, L.E., R.R. Duncan, and R.N. Carrow. 1999b. Wear tolerance, shoot performance, and spectral reflectance of s eashore paspalum and bermudagrass. Crop Sci. 39:1147-1152. 47. Trenholm, L.E. 2000. Spectral analysis: A valu able tool for selec ting stress-tolerant turfgrasses and managing sta nds. Diversity. 16(1/2): 57-58. 48. Trenholm, L.E., M.J. Schlossberg, G. Lee, and W. Parks. 2000. An evaluation of multispectral responses on selected turfgrass species. Int. J. Remote Sens. 21:709-721. 49. Trenholm, LE., E.F. Gilman, G.W. Knox, a nd R.J. Black. 2002. Fertilizatation and irrigation needs for Florida lawns and landscap es Univ. of Fla. Coop. Ext. Serv., ENH 860. Univ. of Florida, Gainesville, FL. 50. Trenholm, L.E., and J.B. Unruh. 2005a. The Florida Lawn Hanbook: Best Management Practices for your home lawn in Florida. Gain esville, FL: University Press of Florida. pp45-53 51. Trenholm, L.E., and J.B. Unruh. 2005b. Warm-s eason turfgrass response to fertilizer rates and sources. J. Plant Nutr. 28:991-999. 52. Trenholm, L.E. 2007. Florida's green industrie s Best Management Practices educational program. Abstracts: 2007 International Annual Meetings [ASA/CSSA/SSSA]. p. 1. 53. Trenholm, L.E., and J.B. Unruh. 2009. Nitrate leaching during turf es tablishment: sodded St. Augustinegrass and Zoysiagrass. Abstracts: 2009 International Annual Meetings [ASA/CSSA/SSSA]. 54. Turgeon, A. 1991. Turfgrass management. Prentice-Hall, Eaglewood Cliffs, NJ. 55. Unruh, J.B. L.E. Trenholm, and J.L. Cisar. 2006. Zoysiagrass in Fl orida (Fact Sheet ENH 11). Florida Cooperative Extensi on Service, Institute of Food and Agricultural Sciences, University of Florida.

PAGE 68

BIOGRAPHICAL SKETCH Jinyong Bae was born in 1976 in Seoul, South Ko rea. He completed his undergraduate from Seoul National University, South Korea in 1998. After graduating, he served at Air Force as an officer of Nuclear, Biological, and Chemi cal Defense (NBC) for seven years. After he was honorably discharged from military service, he jo ined the Doctor of Plant Medicine program in the University of Florida in fall 2006 and added his M.S. degree process from fall of 2008 at Environmental Horticulture department. He gr aduated with M.S. de gree in environmental horticulture in 2009. After graduating he w ill join the U.S. Army in September 2009.