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1996 A Physiological Study of Common Carpetgrass (Axonopus Affinis) Subjected to Cultural and Environmental Stress. Edward Wayne Bush Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Bush, Edward Wayne, "A Physiological Study of Common Carpetgrass (Axonopus Affinis) Subjected to Cultural and Environmental Stress." (1996). LSU Historical Dissertations and Theses. 6300. https://digitalcommons.lsu.edu/gradschool_disstheses/6300

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A PHYSIOLOGICAL STUDY OF COMMON CARPETGRASS (AXONOPUS AFFINIS) SUBJECTED TO CULTURAL AND ENVIRONMENTAL STRESS

A Dissertation

Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in

The Department of Horticulture

by Edward Wayne Bush B.S., Southeastern Louisiana University, 1983 M.S., Louisiana State University, 1986 December 1996

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION Dedicated to my wife, Lisa LeBlanc Bush, and son Nathan.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS I wish to express my gratitude and appreciation to Dr.

Dennis Shepard and Dr. Paul Wilson for serving as co-major professors during the course of study. The willing and

helpful advice of the examining committee, Dr. David Blouin, Dr. Robert Edling, Dr. William Young, and Dr. Thomas Lawson

was greatly appreciated. I am also indebted to my colleagues, Ms. Amy Blanchard and Ms. Gloria McClure, for their support and guidance, and departmental staff and faculty for their support. I would like to express my appreciation to Dr.

Dennis Shepard and Gloria McClure (Chapter 2) , Dr. Dennis

Shepard and Dr. Wayne Porter (Chapter 3), Dr. Robert Edling and Dr. Mary Musgrave (Chapter 4) , Dr. David Blouin (Chapter

5) , and Dr. Dennis Shepard (Chapter 6) . I would like to especially thank my parents Patsy and Joseph E. Bush for their support during this study.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

DEDICATION ...... ii

ACKNOWLEDGEMENTS ...... iii LIST OF T A BL ES ...... vii

LIST OF FIGURES ...... X

ABSTRACT ...... xii CHAPTER 1 INTRODUCTION ...... 1 Introduction ...... 2 Benefits of turfgrass ...... 2 Turfgrass characteristics ...... 2 Characteristics of common carpetgrass ...... 4 Taxonomy and genetics ...... 4 Geographical distribution ...... 5 Herbicide tolerance ...... 6 Insect and disease tolerance ...... 7 Shade tolerance...... 8 Seed germination ...... 9 Seedhead suppression ...... 10 Water stress ...... 11 Low temperature tolerance ...... 12 Cultural practices ...... 12 Research needs ...... 13 Research objectives ...... 14 References to Chapter 1 ...... 15

2 SEED GERMINATION ENHANCEMENT OF COMMON CARPETGRASS AND CENTIPEDEGRASS...... 18 Introduction ...... 19 Priming grass s e e d ...... 19 Warm-season grasses...... 20 Materials and Methods ...... 21 Results and Discussion ...... 24 Common carpetgrass ...... 24 Centipedegrass...... 27 Carpetgrass and centipedegrass ...... 28 Summary and conclusions...... 3 0 References to Chapter 2 ...... 31 3 COMMON CARPETGRASS SEEDHEAD SUPPRESSION USING MEFLUIDIDE, SETHOXYDIM, SULFOMETURON, TRINEXAPAC-ETHYL, AND FLUAZASULFURON...... 33 Introduction ...... 34 PGR selection...... 34 Materials and Methods ...... 36 iv

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Results and Discussion ...... 39 Phytotoxicity ratings ...... 3 9 Seedhead control ...... 41 Turf quality ...... 44 Vegetative growth ...... 44 Grass clipping reduction and turfgrass quality ...... 48 Summary and conclusions...... 50 References to Chapter 3 ...... 51 4 COMMON CARPETGRASS AND CENTIPEDEGRASS NUTRIENT COMPOSITION AND GROWTH RESPONSE TO SOIL WATERLOGGING ...... 53 Introduction ...... 54 Soil waterlogging...... 54 Iron and manganese plant accumulation...... 55 Grass waterlogging response ...... 55 Turfgrass flooding ...... 56 O b j e c t i v e s ...... 56 Materials & Methods ...... 56 Results and Discussion ...... 59 Common carpetgrass nutrient analysis ...... 59 Common carpetgrass growth measurements .... 62 Centipedegrass nutrient analysis ...... 64 Centipedegrass growth measurements ...... 64 Common carpetgrass and centipedegrass ...... 67 Summary and conclusions...... 68 References to Chapter 4 ...... 68 5 LOW TEMPERATURE SURVIVAL OF COMMON CARPETGRASS IN RELATIONSHIP TO CARBOHYDRATE PARTITIONING .... 71 Introduction ...... 72 Winter hardiness ...... 72 Low temperature tolerance ...... 73 Materials and Methods ...... 74 Results and Discussion ...... 76 Carbohydrate analysis ...... 76 Survivability...... 80 Summary and conclusions...... 84 References to Chapter 5 ...... 85

6 INFLUENCE OF MOWING HEIGHT AND NITROGEN RATES ON COMMON CARPETGRASS TURF QUALITY ANDGROWTH RATE . .87 Introduction ...... 88 Nitrogen requirements...... 88 Mowing response ...... 89 Weed competition ...... 89 Materials and Methods ...... 90 Results and Discussion ...... 93 Cumulative vegetative g r o w t h ...... 93 Turfgrass quality ...... 97 v

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Weed competition ...... 100 Summary and conclusions...... 104 References to Chapter6 ...... 105 7 SUMMARY AND CONCLUSIONS ...... 107 A P P E N D I X ...... 113 V I T A ...... 126

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES Table 1. Germination performance of common carpetgrass seed following 21 days incubation at 15, 20, 25, or 30C ...... 25 Table 2. Germination performance of centipedegrass seed following 21 days incubation at 15, 20, 25, or 30C ...... 26

Table 3 The influence of plant growth regulator application on common carpetgrass phytotoxicity (%) 2, 4, and 6 weeks after treatment in 1994 and 1995 . . 40 Table 4 Seedhead suppression and height reduction of nonmowed common carpetgrass treated with plant growth regulators 2, 4, and 6 weeks after treatment in 1994 42

Table 5 Seedhead suppression and height reduction of nonmowed common carpetgrass treated with plant growth regulators 3 and 6 weeks after treatment in 1995 . . . 43 Table 6. The influence of plant growth regulators on turf quality of common carpetgrass 6 weeks after application ...... 45 Table 7 The effect of plant growth regulator applications on cumulative vegetative growth (cm) for nonmowed common carpetgrass over a 6 week period ...... 46 Table 8. The effect of plant growth regulator applications on cumulative vegetative growth (cm) for mowed common carpetgrass over a 6 week period ...... 47

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 9. Clipping yield reduction and mowing frequency of common carpetgrass 6 weeks after plant growth regulator applications ...... 49 Table 10 Iron and manganese leaf, root, and stolon tissue composition for common carpetgrass ...... 60 Table 11, Iron and manganese leaf, root, and stolon tissue composition for centipedegrass...... 63 Table 12 Common carpetgrass vertical growth and clipping weight influenced by soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, LA, 1995 ...... 65 Table 13 Centipedegrass vertical growth and clipping weight influenced by soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, LA, 1995 66

Table 14 The estimated stolon total nonstructural carbohydrate composition (TNC) and Ltso of four acclimated warm-season lawngrasses ...... 81 Table 15 Common carpetgrass cumulative vegetative growth contrast comparing nitrogen rates by mowing height and year .... 94 Table 16 Mean common carpetgrass mowing frequency as influenced by fertilizer rates and maintenance treatments during a two year growing period (1993- 1994) at Burden Research Plantation, Baton Rouge, LA. . 98

Table 17, Mean common carpetgrass turfgrass quality as influenced by fertilizer rates and maintenance treatments during a two year growing period (1993- 1994) at Burden Research Plantation, Baton Rouge, LA. . 99

V l l l

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 18. Mean common carpetgrass turfgrass color as influenced by fertilizer rates and maintenance treatments during a two year growing period (1993- 1994) at Burden Research Plantation, Baton Rouge, LA. . 101

Table 19, Mean common carpetgrass turfgrass coverage as influenced by fertilizer rates and maintenance treatments during a two year growing period (1993-1994) at Burden Research Plantation, Baton Rouge, LA...... 102

Table 20 Occurrence of annual bluegrass on February 29, 1994 as influenced by mowing height and N fertilizer rates...... 103

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES Figure 1. Thermogradient table schematic for seed enhancement experiments where shaded block represents randomization of seed enhancement treatments ...... 23 Figure 2. Plant growth regulator field plot plan located at Burden Research Plantation, Baton Rouge, L A ...... 37 Figure 3. Microplot schematic layout for turfgrass waterlogging experiment located at the Louisiana State University Hill Farm, Baton Rouge, L A ...... 57 Figure 4. Partitioning of starch (A) and sucrose (B) within common carpetgrass in the 1993-1994 sampling period ...... 77 Figure 5 . Partitioning of reducing sugars (A) and total nonstructural carbohydrates (B) within common carpetgrass in the 1993-1994 sampling period ...... 79

Figure 6. Mean common carpetgrass stolon survival after one hour exposure to freezing temperatures in a 1:1 ethylene glycol:water bath...... 82

Figure 7. Mean atmospheric maximum and minimum temperature measured in Baton Rouge, LA., during the 1993-1994 experimental sampling p e r i o d ...... 83 Figure 8. Fertility and maintenance treatment experimental plot design located at Burden Research Station, Baton Rouge, LA, for 1993-1994 91

Figure 9. Annual cumulative growth of common carpetgrass fertilized with four nitrogen rates during the 1993 growing s e a s o n ...... 95 x

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 10. Annual cumulative growth of common carpetgrass fertilized with four nitrogen rates during the 1994 growing season . . .

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Common carpetgrass (Axonopus affinis Chase) is a low maintenance stoloniferous grass widely distributed throughout

the southern coastal plains of the United States. This study investigated seed germination enhancement, seedhead

suppression, waterlogging tolerance, winter hardiness, and maintenance practices for common carpetgrass. Pre-soaking common carpetgrass and centipedegrass

{Eremochloaophiuroid.es [Munro.] Hack.) seed was beneficial at the 30C germination temperature. Priming seed in KN03

solutions significantly accelerated seed germination of both centipedegrass and carpetgrass at 30C, and increased total germination percentage of centipedegrass. At 20 and 25C, seed priming significantly improved mean time of germination for

both grass species and total germination percentage of common carpetgrass. Neither pre-soaking nor priming resulted in germination enhancement at 15C for either species. Plant growth regulators significantly reduced seedhead number, cumulative growth and clipping yield. Trinexapac- ethyl (0.48 kg'1), f luazasulfuron (0.054 kg ha'1) and

sulfometuron (0.63 kg ha'1) were effective in reducing nonmowed seedhead growth and increasing turfgrass quality.

Applications of trinexapac-ethyl (0.32 and 0.48 kg ha'1) significantly improved turfgrass quality and color of mowed common carpetgrass.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Soil waterlogging significantly increased Fe and Mn tissue nutrient levels of carpetgrass and centipedegrass. Common carpetgrass and centipedegrass survived 6 weeks of

continuous waterlogging in the summer heat. Data suggested that retention of high Fe and Mn levels within or on root

tissue may have served as an adaptive mechanism. Nonstructural carbohydrate (NSC) partitioning and node survival increased during winter acclimation. Sucrose and starch were the predominate NSC in leaves, roots and stolons. An estimated Lt50 range of -2 to -4C for node survival was established for common carpetgrass.

As nitrogen rates increased from 0 - 196 kg ha'1 common carpetgrass quality and mowing frequency increased within plots mowed at 3.8 and 7.6 cm. There was little or no benefit

to fertilizing nonmowed common carpetgrass. The data indicated that mowing at 3.8 or 7.6 cm would provide acceptable lawn quality.

Common carpetgrass is an acceptable low maintenance lawn or utility grass. Common carpetgrass geographic adaptability seems to be limited by the lack of winter hardiness.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1

INTRODUCTION

1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 Introduction Benefits of turfgrass. The benefits of turfgrass are diverse and far reaching into today's urban society. Turfgrass

reduces environmental pollution, glare, erosion, noise, and carbon monoxide providing beneficial oxygen and soil

enrichment (Beard, 1973). Recreational uses of turfgrasses create safe playing surfaces suitable for children and adults alike. The pleasing aesthetic qualities of turfgrass provide

a desirable soft, green buffer in the harsh urbanistic

landscape. The maintenance of turfgrass in the landscape serves as a therapeutic activity relieving mental stress and promoting physical exercise. The existence of turfgrass in

the landscape reduces psychological stress and increases social harmony (Beard and Green, 1994).

The turfgrass industry provides an estimated 45 billion dollars in the United States economy (Beard and Green, 1994). Important areas of usage for turfgrass include airports, cemeteries, education, erosion abatement, fire breaks, golf

courses, parks, recreational fields, research endeavors, seed production, slope stabilization, sod production, right-of-way, and lawn care industries. These uses of turfgrass provide a multitude of job opportunities worldwide (Beard, 1973).

Turfgrass characteristics. Criteria for turfgrass selection are dependent upon site characteristics and planned usage. Environmental factors, soil characteristics, and management practices all effect turfgrass growth and quality. Optimum

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. characteristics for any particular turfgrass may include: dark green, dense foliage with fine leaf texture, pest resistance,

and tolerance to moisture, temperature, shade, herbicide, and

traffic stresses. The capacity of a grass to maintain uniform turf with the ability to recuperate from damage is an essential trait.

Few if any turfgrass species reflect all of the characteristics previously mentioned. Turfgrass species chosen for golf course playing surfaces must conform to rigid

standards exemplifying the best characteristics of turfgrass.

These grasses require frequent maintenance and specialized mowers, topdressers, aerators, spray equipment, and intense maintenance practices to a much greater extent than lawngrasses. Warm-season lawngrasses such as bahiagrass,

(Paspalum notatum Flugge.) common bermudagrass (Cynodon dactylon L.) , centipedegrass (Eremochloa ophiuroides [Munro.] Hack.), common carpetgrass (Axonopus affinis Chase), St. Augustinegrass (Stenotaphrum secundatum (Waltz.) Kuntz.) and zoysiagrass (Zoysia japonica Willd.) are more practical choices for homeowners in the southern gulf coastal plain

region of the United States due to their lower maintenance and equipment requirements. The qualities of lawngrasses are often lower than golf course grasses, but well managed lawns provide many of the benefits of turfgrass to the homeowner and the environment.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Characteristics of common carpetgrass. Common carpetgrass is the only turfgrass species recommended for wet sites. Burton (1992) suggested that the usage of carpetgrass in place of

bermudagrass where water accumulates would eliminate the need for drainage tile. A selection of plant genotypes adapted to

various environmental stresses is horticulturally a good decision. Common carpetgrass can easily be established from either seed or vegetative parts. Carpetgrass is adapted to a wide pH (pH 4.1 - 7.1) range and soil types (Heath et al.,

1985; Musser, 1962). Nitrogen requirements are low compared

to other warm-season grasses (Koske, 1991). Beard (1973) lists few pests associated with the culture of common carpetgrass. Tolerance to pests is essential in environments where disease pressure is high. Common carpetgrass cold tolerance is documented as "very poor" (Beard, 1973) ; however, a common carpetgrass plant preserved in the Missouri Botanical Garden Herbarium was collected as far north as

Memphis, Tennessee. The use of common carpetgrass on golf course fairways at the Louisville Country Club, Louisville,

MS, is an example of the versatility of this grass species. The low maintenance aspects of common carpetgrass, pest resistance, and its adaptability to moist soil conditions make it a desirable turfgrass species in the southeastern coastal plains of the United States.

Taxonomy and genetics. A botanical survey of Central and South America documented at least 110 species and 3 0 varieties

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. classified in the genus Axonopus (Hickenbick et al., 1975) . Species within this genus range from diploid (2n = 10) to

decaploid (2n = 50) . Common carpetgrass is an octoploid with

a basic chromosome number of 5 (2n = 40) (Hickenbick et al., 1975) .

Common carpetgrass forms a dense, stoloniferous sod, with light green, coarse textured (6.0 - 8.0 mm) leaf blades. Leaves of common carpetgrass are short, blunt tipped, smooth,

and folded in the bud (Radford et al., 1983) . Seedheads have

heights ranging from 15-30 cm, with two to three branch-form raceme (4 - 6 cm long) with filiform seedstalks, solitary spikelets, subsessile, yielding brownish to gray seed about 3 mm in length (Heath et al., 1985; Bailey and Bailey, 1976).

Geographical distribution. Common carpetgrass is currently

being cultured within Australia, Central America, Malaysia, North America, South America, South Korea, and West Africa. Indigenous populations of common carpetgrass have been identified throughout Central America, South America, and the West Indies. The introduction of common carpetgrass into North America

during the 19th century was thought to have occurred through the port of New Orleans. Common carpetgrass soon became a chief component of unimproved pasture lands in the gulf south United States (Heath et al., 1985). Carpetgrass is well adapted to the southeastern coastal plains of the United

States near the Gulf of Mexico, growing in a wide variety of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. soil textures ranging from infertile sands to imperfectly- drained clays (Heath et al., 1985; Radford et a l ., 1983). Common carpetgrass is referred to by New Orleaneans as

"Louisianagrass" or "petit gazon" meaning "small lawn" (Wise,

1961) . It is adapted to the humid sub-tropical region of the United States (Turgeon, 1991).

Herbicide tolerance. Tolerance to pre- and post-emergence herbicides is an important turfgrass characteristic for

species that are cultured for sod production and home lawns.

Acceptable turf quality of carpetgrass followed applications

of atrazine (2.2 kg ha'1), bentazon (2.2 kg ha'1), dicamba (0.6 kg ha'1), imazaquin (0.4 and 0.6 kg ha'1), mecoprop (1.1 kg ha' x) , metsulfuron, (0.2 kg ha'1), trichlopyr (0.6 kg ha'1), 2,4-D (1.1 kg ha'1) , and herbicide combinations including 2,4-D plus

dicamba (0.8 + 0.3 kg ha'1) and 2,4-D plus trichlopyr (0.3 + 0.2 kg ha'1) (McCarty and Colvin, 1991). Johnson (1975)

reported selective smutgrass [Sporobolus poiretii (R. & S.) Hitchcock] control in common carpetgrass with two applications of atrazine at 2.2 kg ha'1. Repeat applications of atrazine

selectively controlled smutgrass without significant phytotoxicity or reduction in common carpetgrass quality.

Sethoxydim (0.6 kg ha'1) treated common carpetgrass recovered to a level similar to the control four weeks after application

(McCarty and Colvin, 1991). Asulam (8.0 kg ha'1), bromocil (2.2 kg ha"1), and dalpon (8.0 kg ha'1) caused a decrease in carpetgrass yield (Martin,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1983) . Common carpetgrass was severely injured by MSMA

(monosodium methanearsonate) applied at 2.2 kg ha'1. Bromocil in combination with diuron (1.1 + 1.1 kg ha'1) severely injured carpetgrass. McCarty and Colvin (1991) reported asulam (2.2 kg ha'1) MSMA (1.1 and 2.2 kg ha'1), and sethoxydim (0.6 kg

ha'1) resulted in unacceptable turf quality two weeks after application.

Several herbicides are available to maintain weed free quality common carpetgrass without unacceptable phytotoxicity. Atrazine (2.2 kg ha'1), bentazon (2.2 kg ha'1), dicamba (0.6 kg

ha'1), imazaquin (0.4 and 0.6 kg ha'1), mecoprop (1.1 kg ha'1), metsulfuron, (0 .2 kg ha'1) , trichlopyr (0.6 kg ha"1) , 2,4-D (1.1

kg ha'1), and herbicide combinations including 2,4-D plus

dicamba (0.8 + 0.3 kg ha'1) and 2,4-D plus trichlopyr (0.3 + 0.2 kg ha'1) were effective controlling weeds without causing

unacceptable phytotoxicity (McCarty and Colvin, 1991) . The availability of these selective herbicides is essential for

the culture of common carpetgrass.

Insect and disease tolerance. Insects and diseases are not reported as a major problem associated with common

carpetgrass. Lawn caterpillars, mole crickets (Gryllotalpidae sap.), and spittlebugs (family-Cercopidae) may cause damage if not controlled (McCarty et al., 1992) . Turfgrass grown in a stressful environment is predisposed to pest damage (Fitter

and Hay, 1989). Although common carpetgrass is considered to have fewer pest problems compared to other lawngrass species,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 fall armyworms can decrease turfgrass quality. In a

controlled experiment, fall armyworms {Spodoptera frugiperida J. E. Smith) consumed common carpetgrass and bermudagrass 6 to 1 over centipedegrass (Wiseman et al., 1982).

Disease pathogens can also cause significant damage to

managed turfgrass. Brown patch (Rhizoctonia solani Kuhn.) is a pathogenic disease found commonly on St. Augustinegrass that can affect common carpetgrass (Beard, 1973). The prevalence of brown patch on common carpetgrass is much less than St. Augustinegrass.

Proper fertility and cultural practices will help decrease disease outbreaks. Many pest problems are compounded by improper fertilization and irrigation management (Turgeon,

1991). Comparatively, common carpetgrass has fewer pest problems than most cultured lawn grasses.

Shade tolerance. Selecting shade tolerant turfgrass species is necessary for many home lawns in the gulf coast region of the United States. Warm-season grasses grown in a low light environment can become stressed, thus reducing cold, disease, drought, insect, and traffic tolerances (Turgeon, 1991) . St. Augustinegrass is one of the most shade tolerant warm-season grasses. Busey and Davis (1991) hypothesized that the critical natural sunlight level for turfgrass survival ranges from 10% - 40% of natural sunlight, with bermudagrass barely persisting at a higher percentage (20 - 40%) and St. Augustinegrass barely persisting at a lower percentage (10 -

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20%) . St. Augustinegrass responds to shade with decreased number and length of stolons and decreased vegetative cover,

while individual leaf area, leaf length, and number of plugs without stolons increase (Peacock and Dudeck, 1993). Kumai et

al. (1977) reported that tropical grasses within the same

genus as common carpetgrass maintained twice as much C02 assimilation as temperate grasses; however, common carpetgrass and St. Augustinegrass were similar to tall fescue, (27-31 mg C02 dm'2 h'1) a moderately shade tolerant cool-season grass.

Tropical carpetgrass (Axonopus compressus [Swarty] Beauv.) has exhibited similar shade tolerance as St. Augustinegrass

(Samarakoon et al. , 1990) , which is considered one of the most shade tolerant warm-season turfgrass species (Winstead and Ward, 1974) . St. Augustinegrass and tropical carpetgrass were

similar in top growth, leafiness, percentage leaf matter and shade response (Samarakoon et al., 1990). LeBlanc (1996)

reported that common carpetgrass had similar shade tolerance

to several cultivars of St. Augustinegrass. Collectively this research suggests that common carpetgrass is adapted for home lawns having partially shaded areas.

Seed germination. Seed establishment is generally the least expensive and burdensome method of turfgrass establishment. Common carpetgrass can be established by seeding at the rate of 98 - 196 kg pure live seed ha"1 for turfgrass establishment (McCarty et al. , 1992). Common carpetgrass is often mixed with more expensive centipedegrass seed to serve as a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10

companion grass during turfgrass establishment. A

commercially packaged seed mixture of common carpetgrass and centipedegrass is being sold throughout the Gulf Coast region. Common carpetgrass germinates and establishes quickly, reducing the potential of seed washing and erosion.

Centipedegrass germination was enhanced using seed treatments (Delouche, 1961). Presoaking and priming techniques (KN03) have enhanced seed germination and reduced mean time of germination of several grass species (Brede and Brede, 1989). Heavy rainfalls, water stress, and pest infestations are

prevalent in the United States gulf south region. Seasonal

precipitation in New Orleans is heaviest from December - August, encompassing the optimum establishment time for warm- season grasses (Calhoun and Frois, 1995) . Expedient turfgrass establishment in the gulf coast region of the United States is essential to reduce soil erosion, seed washing, and pest competition. Seed treatments accelerate germination rates,

imbibition, and reduce light requirements. There has been no previous research studying the benefit of seed priming with common carpetgrass seed. Seedhead suppression. Prominent seedhead formation ranging

from 15 - 30 cm is an objectionable feature of common carpetgrass. Plant growth regulators (PGRs) can be used successfully to reduce unsightly seedhead formation of common carpetgrass with phytotoxicity ranging from slight to severe (Fry and Wells, 1990). Commercially available PGRs offer a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 means of reducing seedhead height and plant growth while

reducing mowing frequency and improving turfgrass quality. Reducing seedhead formation of common carpetgrass would greatly expand its usage as a lawngrass. Newly developed

chemicals with PGR attributes could reduce seedhead production, vegetative growth, and increase turfgrass quality

(Dingwall, 1993; Porter and Shepard, 1995).

Water stress. Common carpetgrass has been reported to tolerate high water tables and soil moisture (Heath et a l ., 1985) . Common carpetgrass and centipedegrass are both used as lawn grasses in the coastal plains states. Lawngrass mixtures

consisting of common carpetgrass and centipedegrass are

commonplace due to their similar color, texture, and

appearance. Excessive precipitation, poor internal and surface soil drainage, and irrigation mismanagement can lead to periodic flooding and waterlogging of soils. The gulf south region of the United States receives an average annual

precipitation in excess of 127 cm. In 1991, New Orleans

received in excess of 246 cm of precipitation causing widespread flood damage (Calhoun and Frois, 1995). Flooding and waterlogging tolerance research of lawngrass species has been limited. Fry (1991) determined that centipedegrass was the least flood tolerant compared to bermudagrass, St.

Augustinegrass, and zoysiagrass. Common carpetgrass was not included in this experiment. Studying the waterlogging tolerances of centipedegrass and common carpetgrass and their

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12 adaptive mechanisms could expand our knowledge base concerning waterlogging stress.

Low temperature tolerance. Beard (1973) classified cold tolerance of common carpetgrass as "very poor". The lethal temperature at which 50% of a common carpetgrass plant

population is killed due to low temperature has not been established by quantitative research (Lt50) . Severe freezing in December 1989 in Louisiana, followed by above normal temperatures (>6C) in January 1990 exemplifies the cyclic

weather fluctuations in the Gulf South encountered during winter acclimation and spring transition (Calhoun and Frois,

1995) . Structural and non-structural carbohydrates have been associated with an increase in low temperature acclimation in turfgrass species (Fry et al., 1993). The role of

carbohydrate partitioning in carpetgrass during winter acclimation has not been studied.

Cultural practices. Native grasses are more frequently being established as low maintenance lawngrass with the increased

popularity of integrated pest management (Wu et al., 1989). Native plants are often capable of withstanding harsh conditions where cultivated species cannot survive. Stephens (1942) makes reference to common carpetgrass as a "native pasture grass" in Georgia. Although common carpetgrass is native to the West Indies and South America, it has naturalized in the southeastern coastal plains where high temperatures, and abundant rainfall are prevalent. The term

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13

"native pasture grass" is in reference to its ability to

invade abandoned infertile pasture lands where few domesticated grasses will survive. Common carpetgrass is adapted to a wide range of soil types ranging from clays to infertile sands (Heath et al., 1985). Cultural

recommendations suggest a 2.5 - 5.0 cm mowing height and

applications of 49 - 98 kg N ha'1 annually. However, an extensive literature review revealed no published research studying the influence of fertilizer applications and mowing heights for turfgrass management of common carpetgrass. The

establishment of mowing heights and fertility rates is

essential for the management of any turfgrass species (Beard, 1993) .

Research needs. Turfgrass managers have little information in which to make informed decisions concerning common carpetgrass management. Seed establishment, mowing practices, and fertility management are currently based on pasture research

published in the 1940's or field observations. The control of

common carpetgrass seedheads without phytotoxicity would be an essential component of managing carpetgrass as a turfgrass. Two newly developed PGRs, trinexapac-ethyl and flurasulfuron, could offer a turfgrass manager chemical control of seedhead production. Research investigating waterlogging tolerance of

common carpetgrass or centipedegrass has not been documented. Comparing and determining the mechanism in which common carpetgrass and centipedegrass adapts to wet soils could be of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 benefit in the future development of turfgrass species. The winter hardiness and nonstructural carbohydrate composition of

common carpetgrass has not yet been determined. Nonstructural carbohydrate composition has been associated with winter hardiness. Research pertaining to low temperature tolerance, response to winter acclimation, and nonstructural carbohydrate

composition would be original. Mowing and fertility research could provide more accurate data for the management of common

carpetgrass as a turfgrass.

Research objectives. The following research objectives were established to:

1) investigate the influence of pre-soaking and priming on common carpetgrass and centipedegrass seed germination and mean time of germination

2) determine the efficacy and phytotoxicity of plant growth regulators on seedhead suppression, vegetative growth, and turfgrass quality of common carpetgrass 3) compare the effects of waterlogging on vegetative growth and nutrient composition of common carpetgrass and centipedegrass 4) characterize carbohydrate partitioning of common carpetgrass during low temperature acclimation and node survival

5) determine the influence of mowing height and nitrogen rates on vegetative growth, turfgrass quality, and mowing frequency of common carpetgrass. Efforts to accomplish these research objectives are discussed in Chapters 2 - 6. A brief summary of research results is contained in Chapter 7 (Summary and Conclusions) .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 References to Chapter 1 Bailey, L. H. , and E. Z. Bailey. 1976. Hortus Third. MacMillian Publishing Co., Inc., 866 Third Ave., New York, NY. 10022. p. 131. Beard, J. B. 1973. Turfgrass Science and Culture. Prentice- Hall, Inc. Englewood Cliffs, N.J.

Beard, J. B. 1993. Turfgrass recuperative potential. Grounds Maintenance. 4:42, 111.

Beard, J. B., and R. L. Green. 1994. The role of turfgrasses in environmental protection and their benefits to humans. J. Environ. Qual. 23:452-460.

Brede, J. B., and D. Brede. 1989. Seed priming. Grounds Maintenance. 4:42, 46, 48.

Burton, G. W. 1992. Breeding improved grasses. Turfgrass. ed. D.V. Waddington, R.N. Carrow, and R.C. Sherman, p. 759. Busey, P., and E. H. Davis. 1991. Turfgrass in the shade environment. Proceedings of the Florida State Horticulture Society. 104:353-358.

Calhoun, M. , and J. Frois. 1995. Louisiana Almanac (1995-96). Pelican Publishing Co., Gretna, LA. pp. 129-133. Delouche, J. C. 1961. Effect of gibberellin and light on germination of centipedegrass seed (Eremochloa ophiuroides) . Proc. of the Assoc, of Official Seed Analyst. 51:147-150.

Dingwall, J. G. 1993. Key chemical inputs to new herbicides intermediates, processes, and mechanistic investigations. Pest. Sci. 41:259-267.

Fitter, A. H. , and K. M. Hay. 1989. Environmental Physiology of Plants. Academic Press, San Diego, CA. pp. 1-423. Fry, J. D. 1991. Submersion tolerance of warm-season turfgrasses. HortScience. 26(7):927. Fry, J. D., and D. W. Wells. 1990. Carpetgrass seedhead suppression with plant growth regulators. HortScience. 25 (10) :1257-1259 . Fry, J. D., N. S. Lang, R. Clifton, and F. P. Maier. 1993. Freezing tolerance and carbohydrate content of low temperature-acclimated and non-acclimated centipedegrass. Crop Sci. 33:1051-1055.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16 Heath, M. E., R. F. Barnes, and D. S. Metcalfe. 1985. Forages: The Science of Grassland Agriculture. Iowa State University Press, IA. pp. 255-265. Hickenbick, M. C., J. F. Vails, F. M. Salzano, and M. I. Fernandes. 1975. Cytogenetic and evolutionary relationships in the genus Axonopus (Graminae). Cytologia. 40:185-204. Johnson, B. J. 1975. Smutgrass control with herbicides in turfgrasses. Weed Sci. 23(2):87-90. Koske, T. P. 1991. Louisiana Lawns: Facts Sheet. Louisiana State University Agricultural Center, Baton Rouge, LA. pp. 1- 6 . Kumai, S., T. Sato, and K. Taji. 1977. On differences in photosynthetic rate in tropical and temperate grasses. J. of Jap. Soc. of Grassl. Sci. 23 (2) :108-113. LeBlanc, M. R. 1996. The influence of tree shade on the establishment of St. Augustinegrass cultivars. A Thesis. Louisiana State University, Baton Rouge, LA. pp. 1-55. Martin, R. J. 1983. Improvement of carpetgrass pasture by fertilization and oversowing with the aid of selective herbicides. Weed Res. 43:77-83.

McCarty, L. B., and D. L. Colvin. 1991. Carpetgrass response to postemergence herbicides. Weed Tech. 5:563-565. McCarty, L. B., R. J. Black, and K. C. Ruppert. 1992. Florida Lawn Handbook. Florida Cooperative Extension Bulletin-SP 45, University of Florida, Gainesville, FL. 32611. p.11., pp.51- 52 .

Musser, H. B. 1962. Turfgrass Management. Revised ed. McGraw- Hill Book Co., New York.

Peacock, C. H., and A. E. Dudeck. 1993. Response of St. Augustine cultivars [Stenotaphrum secundatum (Waltz.) Kuntze] to shade. Int. Turf. Soc. Res. J. 7:657-663. Porter, W. C., and D. P. Shepard. 1995. Postemergence control of green kylinga (Kylinga brevifolia) in bermudagrass turf. Proceedings, Southern Weed Science Society. 408:103. Radford, A. E., H. E. Ahles, and C. R. Bell. 1983. Manual of the Vascular Flora of the Carolinas. The University of North Carolina Press. Chapel Hill, NC. pp. 139-140.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 Samarakoon, S. P., J. R. Wilson, and H. M. Shelton. 1990. Growth, morphology and nutritive quality of shaded Stenophrum secundatum, Axonopus compressus and Peimisetum cladestinum. J of Agr. Sci. 114(2):161-169.

Stephens, J. L. 1942. Pastures for the coastal plains of Georgia, Bulletin 27. pp. 1-57.

Turgeon, A. J. 1991. Turfgrass Management, Third ed. Prentice Hall Regents, Englewood Cliffs, NJ. pp. 1-418.

Winstead, C. W., and C. Y. Ward. 1974. Persistence of southern turfgrasses in a shade environment, pp. 221-230. In E.C. Roberts (ed.) Proc. Second International Turfgrass Res. Conf., Blacksburg, Va., June, 1973. Agronomy Journal, Madison, W I . Wise, L. N. 1961. The Lawn Book. Bowden Press Inc., Decatur, GA. pp. 47-49.

Wiseman, B. R., R. C. Gueldner, and R. E. Lynch. 1982. Resistance in common centipedegrass to the fall armyworm. J. of Econ. Entom. 75:245-247.

Wu, L., D. R. Huff, and M. A. Harivandi. 1989. Buffalograss as a low maintenance turf. Calif. Agric. 43(2):23-25.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2

SEED GERMINATION ENHANCEMENT OF COMMON CARPETGRASS AND CENTIPEDEGRASS

18

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19 Introduction Quiescent seed and a suitable environment are necessary for rapid establishment of turfgrass sod. Centipedegrass

lEremochloa ophuiroides Munro. (Kunz.)] and common carpetgrass

(Axonopus affinis Chase), both warm-season lawngrasses, are frequently established by sowing individual species or as a

seed mixture. Common carpetgrass is frequently used as a companion grass with centipedegrass to reduce establishment

time. Establishing warm-season grasses from seed during the

early spring months when soil temperatures are cold can be

challenging. Priming of seed prior to planting has been used

extensively to accelerate germination, overcome dormancy requirements, and improve germination rate and uniformity at sub-optimum temperatures. Seed priming is a controlled- hydration treatment in which seeds are exposed to an external water potential sufficiently low to prevent radical protrusion

and yet stimulate physiological and biochemical activities. Potassium nitrate (KN03) has been used successfully in many horticultural crops to control seed hydration (Bradford, 1986; Heydecker and Coolbear, 1977).

Priming grass seed. Priming with KN03 significantly advanced the rate of germination of perennial ryegrass (Lolium perenne L.) , browntop (Agrostis capillaris L.) , and Kentucky bluegrass (Poa pratensis L.) (Lush and Birkenhead, 1987). Maguire and Steen (1971) reported that KN03 accelerated grass seed germination rate. Additionally, perennial ryegrass primed

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. with PEG at -1.0 MPa increased seed germination by 35%

(Danneberger et al., 1992) . Adegbuyi et al. (1981) determined

that priming of cool-season grass species [sheep fescue

(Festuca ovina L.), ryegrass, and rough bluegrass (Poa trivialis L.)] with priming salts (-1.0 to -1.4 MPa) resulted in a significant advancement in speed of seed germination at

sub-optimum temperatures. Hardegree (1994) demonstrated that priming Great Plain native perennial grass seeds (-1.0 to -2.5

MPa) significantly accelerated germination by 4-8 days.

Priming wheat (Triticum durum L.) and oat (Avena fatua L.) seeds (-1.0 MPa) accelerated speed of germination thereby improving seedling competitiveness against weed competition (Akalehiywot and Bewley, 1977) .

Warm-season grasses. Although priming has been used

extensively to improve germination performance of cool-season turfgrass, priming warm-season grass seeds has not been

thoroughly investigated. Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] burrs presoaked in water significantly increased germination percentage by one week (Fry et al.,

1993). Toole and Toole (1939) observed an increased common carpetgrass seed germination rate by moistening germination

paper with a 0.2% KN03 solution in petri dishes. Centipedegrass seeds presoaked in water resulted in a 7% germination increase in petri dishes (Walker, 1976). Common carpetgrass germination (Association of Official Seed

Analysts, 1994) recommendations include moistening germination

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 filter paper with 0.2% KN03/ exposing seeds to at least eight hours of cool white fluorescent light (81 - 135 lum/sq. m) , 15/25C alternating temperatures. These recommendations for common carpetgrass are unreferenced. There are no seed

testing recommendations established for centipedegrass by the Association of Official Seed Analysts (1994).

These experiments tested the hypothesis that priming and pre-soaking treatments would improve common carpetgrass and centipedegrass seed germination at sub-optimum (<30C) temperatures. The relationship between priming solution water

potential and germination performance was evaluated at 15, 20, 25 or 30C.

Materials and Methods This experiment consisted of two grass species (common carpetgrass and centipedegrass), four isothermic germination temperatures (15, 20, 25, and 30C) , and 6 seed enhancement treatments (distilled water; 1%, 2%, 3%, and 4% KN03 solutions; and an untreated control).

Centipedegrass and common carpetgrass (Lot # U4/410, Pennington Seed, LA) seeds were soaked for 48 hrs in aerated distilled water (-0.06 MPa) or primed with KN03 [1% (-0.5 MPa), 2% (-0.9 MPa), 3% (-1.3 MPa) or 4% (-1.7 MPa)] solutions maintained at 25C. The osmolality of priming solutions (Wescor, Vapor Pressure Osmometer) was measured prior to and following the 48 hour treatment period. Each solution was aerated using a standard aquarium pump. Cool, white

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22 fluorescent lights provided continuous illumination (135 lum/ sq. m) during seed enhancement treatment period. Following treatments, seeds were rinsed with copious amounts of water,

transferred to paper towels, and air dried for one hour.

Fifty seeds of each seed enhancement treatment were placed into separately labeled 6.0 cm petri dishes lined with Whatman

#42 filter papers moistened with two milliliters of distilled water. A control treatment (untreated seed) was also included. Seeds were misted with distilled water as needed to prevent desiccation.

The two grass species and 6 seed enhancement treatments were evaluated separately. A thermogradient table (Scientific Systems Corp., Baton Rouge, La.) with isothermic temperature lanes calibrated at 15, 20, 25, or 3 0C was sectioned into two blocks (Figure 1) . A block consisted of 6 seed treatment petri dishes randomized within each temperature lane. Cool,

white fluorescent lights (135 lum/sq. m) provided 14 hours of daily illumination as determined by preliminary experiments

(Appendix A.l) . Two time periods were needed to establish four replications for each grass species and germination

temperature. Germination counts (radicle protrusion) were taken daily for 21 days and germinated seed discarded. Mean time of germination (MTG) and germination percentage of primed seeds were calculated and compared to nonprimed seeds (control). Mean time of germination was calculated as follows:

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23

Time Period Cl) Time Period (2) Block I / Block III © © © © O o o o 0 © © © O o o o © © © © o o o o © © © © o 0 o o © © © © o 0 o o © © © © o o o o Block II Block IV o O o o o o o o o O o 0 o 0 o o 0 O o o o 0 o o o O o 0 o 0 o o o O o 0 o 0 o o o O o o o o o o 15C 20C 25C 30C 15C 20C 25C 3 OC Figure 1. Thermogradient table schematic for seed enhancement experiments where shaded block represents randomization of seed enhancement treatments. Characters within circles (petri dishes) represent seed enhancement treatments as follows: C = control, nonprimed; 0 = presoaking; 1 = 1% KN03; 2 = 2% KN03; 3=3% KN03; 4 = 4% KN03.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 MTG = (S Ti Ni ) / G Where Ti is the day of germination, Ni is the number of seeds

germinating on Ti and G is the total number of germinated

seeds (Hartmann et al., 1990) . A tetrazolium test was used to determine the viability of ungerminated seeds (AOSA, 1994) .

Seed viability was calculated based on the summation of germinated seed/summation of viable seed and germinated seeds. The experimental design used for both grass species and

temperature was a randomized complete block with four replications. Analysis of Variance (ANOVA) was performed

separately on each grass species and germination temperature, using the SAS statistical package (SAS Institute, 19 91).

Means were separated using Duncan's New Multiple Range Test (DNMR) at the 0.05 level.

Results and Discussion Preliminary research established that optimum seed germination for both common carpetgrass and centipedegrass

was 30C for this experiment (Appendix A.l) . Water potential of KN03 solutions remained unchanged following the 48 hrs of priming (data not shown). Neither presoaking in distilled water nor priming improved germination performance of either grass species at 15C (Tables 1 and 2) . The effect of priming on germination performance was dependent on species and germination temperature above 15C.

Common carpetgrass. There was no significant benefit to priming common carpetgrass seed and germinating seed at 20C.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to U1 * 30C 2.9 b 2.2 2.2 c 2.1 c 2.0 c 4.4 a 2.1 c 0 .1 0 .1 0 3.2 3.2 c 3.6 3.6 be ** 8.3 b 12.5 7.1 b 3.4 c 15C 20C 25C Mean time to germination (d) Performance ns ns 95.9 15.3 8.0 b 4.0 b 99.5 97.6 13.6 98.1 15.0 7.5 b 3.3 c 97.0 14.6 7.2 b 95.1 12.3.2 10 a 5.6 a a a a * 1.3 1.2 0.4 0.5 96.6 a 96.9 96.0 98.5 99.0 a 87.9 b a abz a a b Germination % * 20C 25C 30C 64.6 83.7 85.6 49.3

3.4 3.5 5.5 65.6 ab 6.1 15C 6 . 0 . 6 4.1

o

o 1 -0.5 -0.9 -1.3-1.7 2.1 4.7 82.7 3 Treatment Germination solution ¥ (MPa) k n o 0 3 1 2 4 Significance ns the 5% level of probability as determined by Duncan's Multiple Range Test, SE zMeans followed by the same letter within a column are not significantly different at Control at at 15, 20, 25, or 30C. ns.* = Nonsignificant or significant at P=0.05, respectively. priming Table 1. Table 1. Germinationperformance common of carpetgrass seed following days21 incubation Aerated

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to CTl b 0.4 ab 3.6 b 25C 30C 0.4 5.7 4 . 6 b. 4 3.2 b 5.7 ab 2.8 b a 8.6 a 5.5 a c a 5.4 b 3.1 b be *** 8 . 0 . 8 9.4 ns 16.7 15C 20C Mean time to germination (d) a.3 14 9.3 be * 2.5 1.1 0.4 33 .0 33 d 15.0 11.4 62.0 be 17.0.3 10 ab 6.4 ab.1 3 72.0 b.4 13 73 . 6 b . 73 57.0 c6 . 14 11.0 a b b b b ■k 25C 30C 34.5 36.4 35.0 58 .3 58 30.0 33 . 5 b. 33 87.5 20C 36.6 Germination % 2.2 3.3 3.1 5 . 0 . 5 21.0 15C 11. 0 11. -0.5.1 12 32.8 -1.3-1.7 0 . 4 26.7 -0 . 9 . -0 6.0 29.0 -0.06 Treatment GerminationPerformance 1 0 3 2 4 Aerated KN03 5% 5% level of probability as determined by Duncan's Multiple Range Test, Significance “Means followed by the same letter within a column are not significantly different at the ns ns SE Control 5.0 22.2 20, 20, 25, or 30C. ns, ns, * = Nonsignificant or significant at P=0.05, respectively. priming solution ^ (MPa) Table 2. Table 2. Germinationperformance of centipedegrass seed following days21 incubation at 15,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27 Presoaking common carpetgrass seeds in distilled water improved overall germination performance at 25 and 3 0C (Table 1) . At 25C, presoaking or priming significantly-

increased common carpetgrass germination percentage by approximately 8% in comparison to the nonprimed control. Additionally, MTG at this temperature was significantly

reduced by approximately 2 days. Seed germination percentage at 30C was not increased by pre-soaking, however; MTG was reduced by approximately two days. Common carpetgrass germination percentage at 20C was

significantly increased by at least 33% when primed in 2, 3, and 4% KN03, and MTG was significantly decreased by

ca. two days in comparison to nonprimed seeds (Table 1) . Seed primed with KN03 (1, 2, 3, and 4%) and germinated at 25C significantly increased germination percentage, and significantly decreased MTG. Although germination

percentage at 30C was not improved by priming, MTG was reduced by approximately two days (Table 1).

Centipedegrass. Centipedegrass seeds pre-soaked in distilled water or primed in KN03 solutions increased seed germination percentage at 25 and 3 0C, and decreased MTG at 20, 25, and 30C (Table 2) . Neither presoaking nor priming significantly increased centipedegrass germination percentage at 20C.

Mean time of germination for the 20C temperature treatment was significantly accelerated by at least two

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 days after soaking in distilled water. There was no

benefit to pre-soaking centipedegrass seed when germinating seed at 25C. The highest germination percentage for centipedegrass (87%) resulted from the

pre-soaking seed in distilled water and a germination temperature of 3 0C. Mean time of germination was also decreased by more than 2.5 days.

Priming centipedegrass seed in a 2% KN03 solution significantly increased germination percentage by 23% at the 25C germination temperature. Mean time of germination was also significantly reduced by three days

for seeds primed in either 1 or 4% KN03 compared to nonprimed seeds. Primed centipedegrass seed germination

percentages at 30C were significantly greater than nonprimed seeds (>29%) and MTG was reduced by ca. two days.

Carpetgrass and centipedegrass. The overall germination percentage of nonprimed centipedegrass after 21 days was low in comparison to common carpetgrass (Tables 1 and 2) . Centipedegrass and common carpetgrass germination percentage for treated seeds at 15C was not significantly different from nonprimed seeds (Tables 1 and 2) . Both

nonprimed and presoaked seed germination percentage at 20C was at least eight times greater for common carpetgrass and ca. four times greater for centipedegrass in comparison to seed germination at 15C. This may

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 indicate a minimum temperature at which seed enhancement

treatments become ineffective. Seed germination

percentage was highest and MTG the quickest at 30C. The overall influences of pre-soaking and priming for common carpetgrass and centipedegrass were

temperature and species dependent (Tables 1 and 2) . Presoaking and/or priming common carpetgrass and centipedegrass seeds have the potential for improving seed germination. These data support the hypothesis that pre-soaking and priming improves grass seed germination percentage and MTG at sub-optimum temperatures (Tables 1 and 2) . Improved seed germination may be the result of

physiological changes occurring during imbibition at low temperatures (McClure, 1995).

Priming grass seed for early spring plantings when soil temperatures are sub-optimum and the threat of heavy rainfalls are prevalent may be beneficial. At 20 and 25C, a seed mixture of common carpetgrass and

centipedegrass would benefit most (germination % and MTG) from a 2% KN03 priming treatment (Tables 1 and 2) . Previous priming studies have shown an increased germination rate at temperatures considered suboptimal for germination (Brede and Brede, 1989; Hardegree, 1994; Murray, 1990) . Pre-soaking seed in distilled water was the best seed treatment when germinating at 30C. These results concur with Walker (1976) and Delouche (1961)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30 indicating that pre-soaking grass seed accelerates MTG

and increases germination percentage. Also, Fry et al. (1993) reported that pre-soaking buffalograss seeds

increased field seed germination percentage. These results suggest that seed priming or presoaking of common carpetgrass and centipedegrass will

increase germination percentage and decrease MTG at 20, 25 and 30C. Increased germination percentage and

decreased MTG could reduce seed washing in geographical regions of the United States that receive heavy rainfalls such as the southeastern coastal plains. Seed enhancement treatments should be selected on the basis of

species and germination temperature. Further evaluation

of field performance of primed and presoaked common carpetgrass and centipedegrass seed is being proposed. Summary and conclusions. These research results indicate that both presoaking and priming common carpetgrass and

centipedegrass seeds can be beneficial at optimum and

sub-optimum temperatures. The effect of pre-soaking and

priming is dependent on species and temperature. The optimum seed germination temperature for both warm-season grass species was 30C. Priming common carpetgrass or centipedegrass seeds at greater than 2% KN03 concentration had no added benefit on germination

percentage, or mean time of germination (MTG). Higher KN03 concentrations were in some cases detrimental.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 There was no significant increase in overall germination percentage, or decreased MTG at 15C.

Priming or presoaking in the early spring when soil temperatures are sub-optimum and the threat of heavy

rainfalls is prevalent may be beneficial. At 20 and 25C, a seed mixture of common carpetgrass and centipedegrass would benefit from a 2% KN03 priming treatment. Pre- soaking common carpetgrass and centipedegrass seeds germinated at 30C was the most efficient seed enhancement

treatment. Further field research is needed to determine the full benefits of priming and pre-soaking in the field.

References to Chapter 2 Adegbuyi, E., S. R. Cooper, and R. Don. 1981. Osmotic priming of some herbage grass seed using polyethylene glycol (PEG). Seed Science and Technology. 9:867-878. Akalehiywot, T., and J. D. Bewley. 1977. Promotion and synchronization of cereal grain germination by osmotic pretreatment with polyethylene glycol. Journal of Agricultural Science, Cambridge. 89:503-506. Association of Official Seed Analysts (AOSA) . 1994. Rules for testing seeds. Journal of Seed Technology. 16:1-113. Bradford, K. J. 1986. Manipulation of seed water relations via osmotic priming to improve germination under stress conditions. HortScience. 21:1105-1112. Brede, J. , and A. D. Brede. 1989. Seed priming. Grounds Maintenance. 4:42, 46, 48. Danneberger, T. K. , M. B. McDonald Jr., C. A. Geron, and P. Kumari. 1992. Rate of germination and seedling growth of perennial ryegrass seed following osmoconditioning. HortScience. 27(l):28-30.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32 Delouche, J. C. 1961. Effect of gibberellin and light on germination of centipedegrass seed (Eremochloa ophiuroides) . Proceedings of the Association of Official Seed Analysts. 51:147-150. Fry, J. D. , W. Upham, and L. Leuthold. 1993. Seeding month and seed soaking affect buffalograss establishment. HortScience. 28 (9) : 902-903.

Hardegree, S. P. 1994. Matric priming increases germination rate of Great Basin native perennial grasses. Agronomy Journal. 86:289-293.

Hartmann, H. T., D. E. Kester, and F. D. Davies, Jr. 1990. Plant Propagation: Principles and Practices, 5th Ed.

Heydecker, W. , and P. Coolbear. 1977. Seed treatments for improved performance: Survey and attempted prognosis. Seed Science Technology. 5:353-425. Lush, W. M. , and J. A. Birkenhead. 1987. Establishment of turf using advanced ('pregerminated’) seeds. Australian Journal of Experimental Agriculture. 27:323-337. Maguire, J. D., and K. M. Steen. 1971. Effects of potassium nitrate on germination and respiration of dormant and nondormant Kentucky bluegrass (Poa pratensis L.) seed. Crop Science. 11:48-50. McClure, G. 1995. Sweet C o m Seed Reserve Changes During Imbibition in Relation to Germination at Low Temperature. A Thesis. Louisiana State University, Baton Rouge, LA. Murray, G. 1990. Priming sweet com seed to improve emergence under cool conditions. HortScience. 25(2):231. SAS Institute. 1991. SAS Users Guide. SAS Institute, Inc., Cary, N.C. Toole, E. H . , and V. K. Toole. 1939. Notes: Germination of carpetgrass seed. Journal of the American Society of Agronomy. 31 (6) : 566-567. Walker, J. T. 1976. Centipedegrass seed treatments and light-temperature effects on germination. Plant Disease Reporter. 60 (5) :393-397.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3

COMMON CARPETGRASS SEEDHEAD SUPPRESSION USING MEFLUIDIDE, SETHOXYDIM, SULFOMETURON, TRINEXAPAC-ETHYLf AND FLUAZASULFURON

33

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 Introduction Common carpetgrass (Axonopus affinis Chase) is a low

maintenance lawngrass well adapted to the gulf coast region of the United States (Heath et al., 1985). It is

preferably used as a low maintenance home lawngrass or utility sod mowed between 3.75 - 7.50 cm in height

(McCarty et al., 1992). Numerous seedheads can be an unsightly problem associated with the maintenance of

common carpetgrass, increasing mow frequency. The use of plant growth regulators (PGRs) offers an economical means

of reducing maintenance costs and unsightly seedheads (Nielsen, 1992) .

PGR selection. Efficacy, phytotoxicity, longevity, and

cost are factors in the selection of PGRs. Common

carpetgrass PGR research efforts have focused on sethoxydim, mefluidide, and sulfometuron. Fry and Wells (1990) applied PGRs to reduce common carpetgrass seedhead development with minimal phytotoxicity. Sethoxydim (0.11 kg ha"1) and sulfometuron (0.6 kg ha'1) significantly

reduced seedhead development by 88% and 86%, respectively, 21 days after treatment. Common carpetgrass seedhead formation was restricted up to 6 weeks after sethoxydim was applied at 0.17 and 0.22 kg ha'1. Sethoxydim (0.05 and 0.1 kg ha'1) significantly reduced seedhead production with moderate phytotoxicity (Wells, 1984) . As sethoxydim rates were increased from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.28 - 1.12 kg ha'1, there was a gradual increase in phytotoxicity and reduction in grass stand; however, there was a significant growth rate reduction after 7

weeks. Fry (1988) concluded that sequential applications of sethoxydim (0.07 and 0.14 kg ha'1) inhibited seedhead

elongation. Wells (1984) also reported that sethoxydim (0.07 and 0.14 kg ha'1) was an effective PGR reducing mowing frequency. Mefluidide enhanced rooting and quality later that same season. Green et al. (1990)

reported that mefluidide affected leaf extension rate,

evapotranspiration rates, and turfgrass quality of St.

Augustinegrass [Stenophrum secundatum (Waltz.) Kuntze.]. They concluded that for maximum PGR benefits to occur, irrigation should be managed carefully.

New PGRs are being used to manage turfgrass growth and suppress seedhead formation with improved turf

quality (Dingwall, 1993). According to the label, trinexapac-ethyl can increase turfgrass density, color, and turf quality, while decreasing mowing frequency and grass clippings (Anonymous, 1994). Trinexapac-ethyl

suppressed seedhead formation for 2 weeks at 0.4 kg ha'1 and vegetative growth of nonmowed common and 'Tifway’ bermudagrass (Cynodon dactylon [L.] Pers. X Cynodon transvaalensis Burtt-Dawy 'Tifway’) for 8 weeks at 0.2 kg ha'1 (Johnson, 1992) . Fluazasulfuron (ASC-67040) is a new selective sulfonylurea herbicide developed by ISK

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36 Biotech being evaluated in warm-season grasses. Early results indicate that it is very effective as a herbicide on sedges and has PGR properties on turfgrass (Porter and Shepard, 1995).

The objective of this research was to compare the efficacy and phytotoxicity of fluazasulfuron

(experimental herbicide) and trinexapac-ethyl to standard PGR treatments for both low and high maintenance common carpetgrass.

Materials and Methods This experiment consisted of two maintenance treatments {low(nonmowed) and high (mowed-5.1 cm) } and 12

PGR treatments as follows:

Plant Growth Rate Plant Growth Rate Regulator kg ha'1 Regulator kg ha'1 l=control 7=sulfometuron 0.63 2=trinexapac-ethyl 0.16 8=sethoxydim 0.084 3=trinexapac-ethyl 0.32 9=sethoxydim 0.11 4=trinexapac-ethyl 0.48 10=sethoxydim 0.22 5=mefluidide 0.14 ll=fluazasulfuron 0.027 6=mefluidide 0.28 12=fluazasulfuron 0.054

Plant growth regulator common and chemical names are

listed in Appendix B.l. A plot of naturalized common carpetgrass growing in an Olivier silt loam soil (fine silt, mixed, thermic Aquic Fragiudalf, pH 6.2, OM 1.1 meq/L) located on the Burden Research Plantation, Baton Rouge, Louisiana was partitioned into four sub-plots (Figure 2) . Each sub­ plot was divided into two columns where maintenance

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37

Block I Block II Mowed2 Nonmowed Nonmowed Mowed

iwvw V }

ivwwS

!vvv / v . w ^ . v v. - 5* a ?mwfflWwmwm'.W'SW?w!->

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Block III Block IV Mowed Nonmowed Nonmowed Mowed

Figure 2. Plant growth regulator field plot plan located at Burden Research Plantation, Baton Rouge, LA. Shaded block represents randomization of maintenance strips and PGR treatments. Maintenance strips were as follows: mowed at 5.1 cm and nonmowed = unmowed.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 strips were established. The 12 PGR treatments were assigned to rows within each column. Maintenance strips were mowed at 5.1 cm with a

rotary mower (14 SZ, John Deere) prior to the start of the experiment for both low and high maintenance plots. On July 21, 1994 unfertilized 1.5 m x 3.0 m plots were established. New plots (1.5 m x 3.0 m) were established on July 13, 1995 and were fertilized with 87 kg N/ha"1 of

a 21-5-10 slow release turfgrass fertilizer. Treatments were applied with a C02 pressure sprayer in 188 L of

water ha'1 at 240 kPa on July 21, 1994 and July 14, 1995. Turfgrass height measurements were taken weekly using a measuring device described by Parish et al. (1994). Common carpetgrass plots exceeding 7.0 cm (>40% base mowing height) were mowed to the base mowing height of

5.1 cm. All plots were harvested at base cutting height for a final harvest and seedhead count. Seedhead heights

were measured at 2, 4, and 6 weeks after treatment application (WAT) in 1994 and at 3 and 6 WAT in 1995. Data collected included: weekly height measurement; mowing frequency; seedhead height and seedhead number/sq.

m. Clipping yield was measured using a Mettler AE 240 balance following each required mowing and 6 WAT. Harvested grass clippings were dried using a forced air drier (VWR 1600, Scientific, Inc.) at 65C for 5 days. Nonmowed plots were harvested and dry weight measured at

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39 the conclusion of the study. Plots were rated weekly for

phytotoxicity using a visual 1 - 9 scale, where 1 = brown, unhealthy turfgrass, 6 = acceptable for home lawns, and 9 = dark green, healthy turfgrass. Turfgrass quality ratings were a combination of color, density,

uniformity, and vigor. A scale of 1 - 9 where 1 = discolored, unhealthy turfgrass, 6.0= acceptable for home lawns, and 9 = dark green, dense, uniform, healthy turfgrass was utilized. Weather data was recorded over

the two year experimental period (Appendices C .2, C .3, and C .4).

Data for each maintenance treatment and year were statistically analyzed separately. Data were subjected

to analysis of variance, and means separated using Duncan's multiple range test (0.05 level) (SAS Institute, 1991).

Comparisons between PGR treatments and the control were made using contrasts. Analysis of variance was performed using the General Linear Model procedure in the Statistical Analysis Systems for cumulative vegetative growth data (SAS Institute, 1991).

Results and Discussion Phytotoxicity ratings. There were no phytotoxicity symptoms 6 weeks following PGR applications (Table 3). Common carpetgrass phytotoxicity 2 and 4 WAT ranged from no damage to severe foliage discoloration. The lower

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. o 0 0 0 0 0 0 ns ns 1995 * 7 7 be 3 3 ab 0 0 4 4 ab 0 00 4 ab 5 b 0 0 0 0 0 0 a 0 0 0 0 a 0 0 0 ns 6 6 wks 2 wks 4 wks 6 wks 1 1 a 0 5 ab 0 0 3 3 a 0 4 ab 0 0 8 8 be 0 4 ab 0 a 0 0 13 cd 0 0 0 11 11 cd 0 15 15 d 0 18 d 0 ** 0 0 ay 0 a 2 2 wks 4 wks 38 38 e 13 13 b 3 a 18 be 32 32 de 24 cd ---- Rate 0.110 0.220 0.027 0.054 26 cd 0.280 12 b 1 a 0. 084 0. 1 b 4 ab 0 .140 0 0.160 8 ab 0 a 0.320 8 ab 1 a 0 0 a 0.480 13 b kg ha'1 1994 5% 5% level of probability as determined by Duncan's Multiple Range Test, zThe zThe increase of phytotoxicity compared (%) to the control. Fluazasulfuron Significance Control yMeans yMeans followed by the same letter within a column are not ns, significantly * = Nonsignificant different or significantat the at P=0.05, respectively. Sulfometuron 0.630 Trinexapac-ethyl Sethoxydim Treatment Mefluidide Table 3. phytotoxicity 2, The (%) 4, and 6 weeks influence after treatment of plant in 1994 and 1995z. growth regulator application on common carpetgrass

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rates of trinexapac-ethyl (0.16 and 0.32 kg ha'1) caused no significant phytotoxicity over both years tested. The high

rate (0.48 kg ha'1) of trinexapac-ethyl 2 and 4 WAT in 1994 resulted in slight (8%) yellowing of common carpetgrass leaf

blades. Mefluidide (0.14 and 0.28 kg ha'1) also caused yellow discoloration of leaf blades accounting for a significant

increase in phytotoxicity ratings 2 WAT in 1994 (Table 3) . However, in 1995, neither mefluidide treatment caused significant phytotoxicity symptoms. Sulfometuron (0.63 kg ha' x) , and sethoxydim (0.11 and 0.22 kg ha'1) plots incurred

significant phytotoxicity (browning) 2 WAT for both 1994 and 1995 (Table 3) . Turfgrass phytotoxicity 2 WAT with

sulfometuron (0.63 kg ha'1), sethoxydim (0.22 kg ha"1), and fluazasulfuron (0.027 and 0.054 kg ha'1) exceeded acceptable

levels (>20%) in 1994. Damaged plots successfully recovered over the remaining 4 weeks. Sulfometuron (0.63 kg ha'1)

phytotoxicity ratings decreased to an acceptable (15%) level

4 WAT in 1994, and eventually no phytotoxicity 6 WAT. Moderate phytotoxicity is tolerable if temporary quality

reductions result in overall improvement of turfgrass quality.

Seedhead control. Sulfometuron (0.63 kg ha'1) and sethoxydim (0.11 and 0.22 kg ha'1) were the only treatments to

significantly increase seedhead control (47 - 65%) 6 WAT for both years (Table 4 and 5) . These data confirm previous data conclusions by Fry and Wells (1990).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to a-d cde f def a def def 25.9 24 .1 24 31.2 30.7 a 23.9 e a be a 20 .3 20 11. 9 11. 32 . 0 . 32 17.8 cd 21.1 cd 15.5 d 26.7 b-e d ab 29.0d 17.5 cd 23.6 ef cd 13.2 19.1 10.9 13 .5 13 ab a-d 10.4 d a 20.6 a abc 6 6 wks wks 2 4 wks 6 wks 47 bed abcabc 30 a-d 19 ab 15.5 be 15.2.1 c 24 b 21.1 24.1 be a 0 a 20.3 a7 a. 28 30.2 abc ab 16 ab a 0 be 58 cd 14.0 cd.1 22 b 26.2 cde 0 65 c 65 d9 10. a 12 ee 53 e 55 be 34 cde 35 a 0 1 0 0 ay 2 wks 4 wks 82 34 bed69 23 abc 16 ab 15.8 be.1 23 b 28.2 77 57 , 160 , 31 abc 34 .320 ,480 65 e 37 abc 29 .280 .630.084 110 . 63 de 18 abc . 220 . .027 72 e 45 abc 12 . . Rate 0. 0..140 0 0 , 0. 0 0,,054 0. 0 . the 5% level of probability as determined by Duncan's Multiple Range Test. Sethoxydim FluazasulfuronzSeedhead percentage reduction compared to the 0. control. treated with plant growth regulators 2, 4, and 6 weeks after treatment in 1994. Control Sulfometuron Trinexapac-ethyl 0. yMeans yMeans followed by the same letter within a column are not significantly different at Table 4. Seedhead suppression and height reduction of nonmowed common carpetgrass Treatment kg ha"1 Seedhead control2 (%) Seedhead height (cm) Mefluidide

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. u 51.3 a 6 6 wks 35.3 ef 33.8 f ht. ht. (cm) 26.9 cde 44.5 be 32.5 be 49.3 ab 24.4 cde 6 6 wks 3 wks control2 (%) Seedhead 84 84 b 52 cd 18.0 e 41.2 cde 58 58 b 15 a 63 b 28 bed 0 a 47 cd 38.4 ab 44.2 a 19.8 de 49.5 ab 69 69 b 89 b 61 b 47 cd 60 d 48 cd 30.0 be 29.7 d 53.1 a 40.4 cde 61 61 b 70 b 11 abc 0 ab 28.5 cd 36.6 ef 73 73 b 0 ab 3 3 wks Rate 0.054 0.140 0.280 0.630 0.084 .110 0 0.220 0.160 0.320 0.480 kg ha'1 Seedhead Fluazasulfuron 0.027 82 b 44 bed 23.9 cde 42.4 cd treatment in 1995. Sulfometuron Sethoxydim zSeedhead percentage reduction compared to the control. different at the 5% level of probability as determined by Duncan's Multiple carpetgrass treated with plant growth regulators 3 and 6 weeks after Control 0 ay 0 a 46.0 a 54.6 a Treatment Range Test. Trinexapac-ethyl Table 5. Seedhead suppression and height reduction of nonmowed common Mefluidide yMeans yMeans followed by the same letter within a column are not significantly

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44 Trinexapac-ethyl (0.32 and 0.48 kg ha'1) , sethoxydim (0.11

and 0.22 kg ha'1), sulfometuron (0.63 kg ha'1), and fluazasulfuron applications significantly reduced seedhead height 6 WAT for both years (Tables 4 and 5) . Mefluidide treatments did not effectively inhibit seedhead number or height.

Turf quality. Common carpetgrass turfgrass quality was significantly improved by PGR applications (Table 6) . The two high rates of trinexapac-ethyl significantly increased turfgrass quality for both years and maintenance treatments.

The highest turfgrass quality ratings for mowed common carpetgrass were enhanced by high rate applications of

trinexapac-ethyl. Trinexapac-ethyl plots were generally uniform, dark green, and maintained a dense sward of common carpetgrass. Trinexapac-ethyl (0.16, 0.32 and 0.48 kg ha'1), sulfometuron (0.63 kg ha'1), sethoxydim (0.22 kg ha'1), and fluazasulfuron (0.027 and 0.054 kg ha'1) maintained

significantly improved turfgrass quality for nonmowed common turfgrass (Table 6) . Seedhead height, seedhead number, and

cumulative vegetative growth inhibition accounted for increased turfgrass quality 6 WAT. Numerous seedheads in the control and mefluidide plots were objectionable, especially when lodging occurred.

Vegetative growth. Mefluidide cumulative vegetative growth reduction of common carpetgrass was inconsistent over both time and maintenance treatment (Tables 7 and 8) . Cumulative

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in common 5.3 5.3 ab 5.6 5.6 a 5.2 5.2 ab 3.9 e 3.7 e 4.4 cd 1995 4.9 abc 4.9 be 5.1 5.1 ab 5.0 be4.6 a-d 3.8 de 4.3 b-e turf quality of 6.8 6.8 c 6.6 6.6 c 6.9 c 7.0 be 4.8 abc 5.1 ab 6.6 6.6 c 4.0 cde 4.9 be 6.9 c 4.8 abc 7.5 7.5 a 5.3 a regulators on Mowed Nonmowed 1994 1995 1994 6.5 6.5 cd 6.4 de6.1 e 6.5 c 6.5 c 3.8 de 4.1 de 6 .6 bcdy.6 6 6.6 c 3.5 e Rate 0 . 054 . 0 6.4 de 6.0 c 4.6 bed 5.2 ab 0.220 6.1 e 0.110 6.5 cd 0.160 6.7 ab 0.140 0.280 0.630 0.084 6.8 abc 0.320 7.0 a 7.4 ab 0.480 7.0 a kg ha'1 fluazasulfuron 0.027 6.5 cd the 5% level of probability as determined by Duncan's Multiple Range Test. zTurf zTurf quality l=poor quality; 9=dark green, uniform turfgrass. Sulfometuron Sethoxydim yMeans followed by the same letter within a column are not significantlydifferent at carpetgrass 6 weeks after application.2 Control Treatment Trinexapac-ethyl Table 6. The influence of plant growth Mefluidide

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46

Table 7. The effect of plant growth regulator applications on cumulative vegetative growth (cm) for nonmowed common carpetgrass over a 6 week period. Rate Treatment kg ha'1 1994 WK 2 WK 4 WK 6 control 3.8 5.6 10 .1 trinexapac-ethyl 0.160 2.1** 3.5** 8.1 0 .320 2.4** 3.0** 7.3* 0.480 1.8** 2.7** 6.8** mefluidide 0 .140 3.6 5.9 8.6 0 .280 3 . 0 5.2 9.9 sulfometuron 0.630 0.3** 3.8** 8.9 sethoxydim 0 . 084 2.1** 4.9 9.4 0.110 1.8** 4.5 8.7 0 .220 0.7** 4.1** 9.4 fluazasulfuron 0.027 0.5** 3.5** 8.7 0 . 054 0.3** 3.6** 7.8* 1995 WK 2 WK 4 WK 6 control 9 . 9 17.3 32 .4 trinexapac-ethyl 0.160 4.9** 10.7** 24 .1* 0.320 4.7** 12 . 1* 24 .8* 0 .480 3.8** 8.2** 20.0** mefluidide 0.140 7.5 12 .4* 26.5 0 .280 8.6 16.7 27.6 • * 00 o sulfometuron 0.630 2.2** 11.1 H sethoxydim 0 . 084 5.0** 11.2* 22 .5* 0 .110 3.2** 11.5* 17.4** 0 .220 6.0** 14 .4 21.0** fluazasulfuron 0.027 3.0** 12 .4* 22.8* 0.054 2.4** 10.5** 20.5** *, ** = Significant at the 0.05 and 0.01 probability levels, respectively, other comparisons nonsignificant.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47

Table 8. The effect of plant growth regulator applications on cumulative vegetative growth (cm) for mowed common carpetgrass over a 6 week period. Rate Treatment kg ha*1 1994 WK 2 WK 4 WK 6 control 4.7 6.9 11.7 trinexapac-ethyl 0.160 3.3** 6.1 9.5* 0.320 2.5** 4.1** 6.4** 0.480 1.9** 3.7** 6.3** mefluidide 0.140 2.7** 5.3 9.1* 0.280 2.8** 6.5 10.6 sulfometuron 0.630 0.4** 4.7* 9.3** sethoxydim 0.084 1.9** 5.6 10.0 0.110 1.5** 6.7 11.1 0.220 0.7** 4.8* 10 .2 fluazasulfuron 0.027 0.4** 5.8 9.9 0.054 0.3** 4.9* 7.9** 1995 WK 2 WK 4 WK 6 control 12 .6 23 .0 30.5 trinexapac-ethyl 0.160 9.2* 17.2* 22 . 9* 0.320 7.2** 17.6* 23.2* 0.480 5.1** 11.5** 16.7** mefluidide 0.140 12.1 23.2 29.6 0.180 13 .4 25.6 32.6 * to sulfometuron 0 .630 3.2** 15.3** to -j sethoxydim 0.084 7.8** 18 .4 25.4 0.110 5.2** 18.6 21.2* 0.220 7.8** 19 .4 21.1* fluazasulfuron 0.027 6.2** 20.4 22.9* 0.054 3.1** 17.7* 20.6* *, ** = Significant at the 0.05 and 0.01 probability levels, respectively, other comparisons nonsignificant.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 vegetative growth of mowed plots treated with trinexapac- ethyl (0.16 kg ha'1) was significantly reduced 6 WAT for both treatment years. Trinexapac-ethyl (0.32 and 0.48 kg ha'1) and sulfometuron (0.63 kg ha'1) consistently reduced cumulative vegetative growth of nonmowed and mowed common

carpetgrass in 1994 and 1995 (Tables 7 and 8) . Fluazasulfuron (0.054 kg ha'1) significantly reduced cumulative vegetative growth of nonmowed grass plots. Fluazasulfuron (0.054 kg ha'1) also significantly reduced cumulative vegetative growth of mowed turfgrass in 1994 and 1995 (Table 8) . Sethoxydim resulted in inconsistent cumulative vegetative growth reduction. The two higher rates reduced CVG significantly after 6 weeks. Sulfometuron (0.63 kg ha'1) consistently reduced cumulative vegetative growth in nonmowed plots.

Grass clipping reduction and turfgrass quality. There were no significant clipping yield reductions either year for nonmowed PGR treatments (data not shown) . Mefluidide had no significant influence on clipping yields or mowing frequency (Table 9) . There were, however, significant clipping yield and decreased mowing frequency over both years when trinexapac-ethyl (0.48 kg ha'1), sulfometuron (0.63 kg ha'1), and fluazasulfuron (0.054 kg ha'1) were

applied to common carpetgrass (Table 9) . Sethoxydim (0.22 kg ha'1) significantly decreased clipping yields

for both years, but only marginally decreased mowing

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1995 5.5 5.5 ab 5.8 5.8 ab 5.5 5.5 ab 6.0 a 6.0 a 4.5 c 6.0 6.0 a 4.5 c e de bed 4.3 c e bed a be 1994 3.8 3.8 3.3 de 3.0 3.5 cde 6.0 a 4.8 a 4.8 abc 3.3 abc0 . abc 4 4.0 be 6.0 a a bed 3.0 a-d 1995 15 20 a-d c 10 cc 28 cd 25 bed 4.3 ab 5.3 b ca 38 d 15 ab 5 ab c axc 0 18 1994 4 52 61 61 c 26 bed 58 11 62 58 c 24 36 be 49 43 0.027 0.054 0.630 0.084 .110 0 .220 0 0.480 0.140 0.320 0.280 Rate Clipping yield the 6 weeks. Fluazasulfuron zClipping yield reductions by (%) weight in comparison to the control over Sulfometuron yNumber of mowings over the 6 weekxMeans followed testing by period. the same letterdifferent within at a the column 5% level areRange of not probabilityTest. significantly as determined by Duncan's Multiple Control 0 Sethoxydim carpetgrass 6 weeks after plant growth regulator applications. Table 9. Clipping yield reduction and mowing frequency of common Treatments kg ha'1 Mefluidide reduction2 Mowing frequencyy Trinexapac-ethyl 0.160

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 frequency. The greatest clipping yield reductions 6 WAT were attained using trinexapac-ethyl (0.48 kg ha"1) , sulfometuron (0.63 kg ha"1), sethoxydim (0.11 and 0.22 kg ha"1) and

fluazasulfuron (0.027 and 0.054 kg ha"1) (Table 9). The high rate of trinexapac-ethyl (0.48 kg ha"1) significantly reduced mowing frequency 1.5 mowings over a six week period. Trinexapac-ethyl (0.48 kg ha'1) improved common carpetgrass quality by consistently reducing mowing frequency,

clipping yield percentage, and seedhead height with marginal

to no phytotoxicity over both mowing heights and years (Table 9). Sethoxydim (0.22 kg ha'1) inhibited seedhead formation significantly improving the turfgrass quality of nonmowed common carpetgrass. Mefluidide caused significant turfgrass

discoloration with minimal PGR benefits (Table 9) . Unacceptable phytotoxicity 2 WAT could decrease the aesthetics of highly visible turfgrass locations.

Summary and conclusions. Trinexapac-ethyl and fluazasulfuron were effective PGRs when applied to common carpetgrass. The high rates of both PGRs provided acceptable vegetative growth

reductions. The higher rates of trinexapac-ethyl improved turfgrass quality and consistently reduced common carpetgrass vegetative growth. Previous research and these results suggest that mefluidide has little or no PGR activity on common carpetgrass.

Trinexapac-ethyl, sethoxydim, sulfometuron and fluazasulfuron applications significantly reduced seedhead

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 height 6 WAT for both years. Applying plant growth regulators increases turfgrass quality, decreases mowing frequency, and reduces unsightly seedhead production of common carpetgrass.

References to Chapter 3 Anonymous. 1994. Turf & Ornamental Chemical Reference, 3rd ed. Chemical and Pharmaceutical Publishing Corporation, pp. L65- L66. Dingwall, J. G. 1993. Key chemical inputs to new herbicides: Intermediates, processes, and mechanistic investigations. Pesticide Science. 41:259-267. Fry, J. D. 1988. Sequential sethoxydim applications for season-long carpetgrass seedhead suppression. Progress Report: Louisiana Agricultural Experiment Station, Hammond, Louisiana. 38:33-35.

Fry, J. D., and D. W. Wells. 1990. Carpetgrass seedhead suppression with plant growth regulators. HortScience. 25 (10) :1257-1259 .

Green, R. L., K. S. Kim, and J. B. Beard. 1990. Effects of flurprimidol, mefluidide, and soil moisture on St. Augustinegrass evapotranspiration rate. HortScience. 25(4):439-441.

Heath, M. E., R. F. Barnes, and D. S. Metcalfe. 1985. Forages: The Science of Grassland Agriculture. Iowa State University Press, IA. pp. 255-265.

Johnson, B. J. 1992. Response of bermudagrass (Cynodon spp.) to CGA 163935. Weed Technology. 06:577-582. McCarty, L. B., R. J. Black, and K. C. Ruppert. 1992. Florida lawn handbook. Florida Cooperative Extension Bulletin-SP 45, University of Florida, Gainesville, Fla. 32611. pp. 11, 51, 52.

Nielsen, S. 1992. Pricing challenges. Grounds Maintenance. 11:12-16. Parish, R. , E. W. Bush, and D. P. Shepard. 1994. A simplified turfgrass height-measuring device. HortTechnology. 4(1) :49-50 .

Porter, W. C., and D. P. Shepard. 1995. Postemergence control of green kylinga (Kylinga brevifolia) in bermudagrass turf. Proceedings, Southern Weed Science Society. 408:103.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52 SAS Institute. 1991. SAS Users Guide. SAS Institute, Inc., Cary, NC.

Wells, D. W. 1984. Carpetgrass response to plant growth regulators, Progress Report: Louisiana Agricultural Experiment Station, Hammond, Louisiana. 34:68-69.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4

COMMON CARPETGRASS AND CENTIPEDEGRASS NUTRIENT COMPOSITION AND GROWTH RESPONSE TO SOIL WATERLOGGING

53

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54

Introduction Common carpetgrass (Axonopus affinis Chase) and centipedegrass [Eremochloa ophuiroid.es Munro. (Kunz.)] are lawngrasses grown in the southeast coastal plains of the

United States where excessive periods of rainfall cause soil waterlogging for prolonged periods. Currently a seed mixture including seed of both grass species is being sold in the gulf coastal plains of the United States. Little information is documented concerning

waterlogging tolerance of lawngrasses. Adaptation of common

carpetgrass in areas with high water tables has been noted by

Heath et al. (1985) and Beard (1973); however, no research has studied waterlogging tolerance of lawngrasses.

Soil waterlogging. Waterlogging is regarded as the saturation of soil pore space without covering grass stolons or leaves. Waterlogging occurs generally as a result of excessive rainfall, irrigation mismanagement, and/or poor soil drainage. Slow diffusion of atmospheric oxygen into waterlogged soils may cause anaerobic soil conditions (Kawase, 1981). Decreasing availability of soil oxygen causes hypoxia (reduced oxygen diffusion) and eventually anoxia (anaerobic

conditions). Soil waterlogging can cause a chemically-reduced state in soils (Grineva et al., 1989). The relationship between waterlogging and nutrient toxicity has been established. As

soils drain allowing gaseous diffusion, there is increased

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 solubility of potentially toxic Fe and Mn compounds (Grass et al., 1973) . Submerged soils reduced Mn (IV) oxides to Mn (II) , increasing water soluble Mn*2 and precipitating manganous

carbonate (Ponnamperuma, 1972) . Manganese and Fe soil concentrations increased following as few as 7 days of

waterlogged conditions (Adams and Akhtar, 1994).

Iron and manganese plant accumulation. Jones (1971) reported that increased accumulation of Fe and Mn within or on roots reduced toxic shoot levels. Jones (1972) proposed that roots

of many waterlogging species serve as a protective system

preventing toxic levels of Fe from accumulating in leaf tissue. Less is known about Mn, however there seems to be a

similar response with waterlogging tolerant plants. Hypoxia can lead to morphological and physiological disturbances within a plant. Metabolic changes in plants have been measured as soon as 12 hours after soil waterlogging

(Daugherty and Musgrave, 1993). Morphological changes in

flooded corn plants led to decreased physiological activity and plant death after two days (Grineva et al., 1989). Respiration in the roots and stem base decreased, while leaf respiration increased.

Grass waterlogging response. Agrostis stolonifera L. and Festuca rubra L. grass species grown in waterlogged soils resulted in an increase in Fe and Mn plant tissue (Jones, 1972) . The greatest increases of these elements were in root tissue. Jones (1972) hypothesized that roots may serve as a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 protective system preventing excessive Fe uptake by leaves. Immobilization of Fe in or on roots has been noted in

waterlogging tolerant plants (Jones and Etherington, 1970) .

Turfgrass flooding. Fry (1991) studied the effect of submersion on five warm-season lawngrass species reporting that all were living after 55 days. Centipedegrass was the only grass not surviving after 93 days of submersion.

Objectives. A study was established to determine the influence of waterlogging on nutrition composition and growth of common carpetgrass and centipedegrass.

Materials & Methods This experiment consisted of two grass species (common carpetgrass and centipedegrass), two waterlogging treatments (waterlogging and control), and four harvest treatments [3

(3C) and 6 weeks (6C) of continuous waterlogging, and two 3 week recovery periods following 3 (3R) and 6 (6R) weeks of continuous waterlogging] .

This experiment was performed in an open-ended microplot structure located on the Louisiana State University Hill Farm, Baton Rouge, LA. There were 8 independent butyl-lined

compartments paired together to form four blocks (Figure 3). Each block consisted of a control and waterlogging compartment. Each compartment contained 8 plastic nursery containers (24 cm wide x 20 cm deep) filled with a Lintonia silt loam soil having pH 6.2, 1.1% OM. Four of the filled

nursery containers were planted with common carpetgrass, and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. -j m © © © © © © ©© © © WAT WAT Control © ©©© © © © © © © Control © ©© © © © ©©© © © © © © © © ©©© © © © © ©© © © © © Control WAT ® ® © ® © ® A E A E Control • • il il # Block I Block II Block III Block IV WAT E A i> i> # m m m 3* E A IP BfcWSS • Figure 3. Microplot schematic layout 3for turfgrass = waterlogging 3 experimentweeks continuous located + at a waterlogging; the 3 week recovery 6 = 6 weeksperiod. continuous An experimental waterlogging; = waterlogged block 3R is = compartment3 comprisedweeks of of and both control a waterlogged = drainedand compartment. A=common carpetgrass, and LouisianaState University Hill Farm, Baton Rouge, LA. Shadedareas representcontinuous waterloggingthe following: week a + 3 recoveryperiod; weekscontrol 6R = 6 compartment.of continuous waterlogging Thewaterlogging two treatments were representedE=centipedegrass.bythe following: WAT

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58

the remaining four with centipedegrass. Established

common carpetgrass and centipedegrass containers were assigned separately to half of each compartment. The harvest treatments were assigned across species and waterlogging treatments for each block.

Common carpetgrass and centipedegrass sod was

harvested and soil washed from the roots. Washed sod was planted into nursery containers and allowed to establish for six weeks prior to the start of the experiment. Fertilizer nutrients during establishment were supplied by a 400 ppm weekly application of 21-5-20 analysis water

soluble fertilizer (Peters All-Purpose Fertilizer).

Waterlogging treatments were imposed on July 10, 1995. Water levels were maintained using a flotation valve switch. Water levels for waterlogged treatments were maintained evenly with the soil surface. Leaf blades and stolons remained above the water level.

Control plants were subirrigated to maintain adequate soil moisture by allowing water to cover half of the container drain hole allowing water consumption as needed. The recovery treatments (3R and 6R) were maintained under the same conditions as the control during the three week recovery period. Weekly vertical growth was measured using a modified turfgrass disc meter (Parish et al., 1994). Grass clippings were harvested weekly, forced air dried at 65C for 5 days and weighed.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59 Sod was destructively harvested for nutrient analysis at

the termination of each treatment. Common carpetgrass leaves, roots, and stolons were hand harvested and washed. Tissue was analyzed (N, P, K, Ca, Mg, S, Fe, Mn, Cu, Cl, Mo, B, Mo, and Zn) by the LSU Feed and Fertilizer

Laboratory, Baton Rouge, LA. Daily maximum and minimum atmospheric temperatures were measured (Appendix C .3).

The experimental design was a randomized complete block design with four replications. Analysis of variance was performed separately on each species,

waterlogging treatment, and harvest treatment using the

statistical analysis systems (SAS, Institute, 1991).

Results and Discussion Common carpetgrass nutrient analysis. The overall nutrient analysis of common carpetgrass leaves, roots, and stolons was measured (Appendix D.l, D.2, and D.3) . Root Fe and Mn composition was considerably higher than

leaf and stolon tissue (Table 10) . There is currently no published data concerning optimum Fe and Mn levels in common carpetgrass. Iron and Mn were inherently high within all plant parts compared to other lawngrasses (McCrimmon, 1996) . According to Foong et al. (1982) , the

Fe content in tropical carpetgrass (Axonopus compressus (Schwartz) Beauv.) leaves ranged from 137.5 - 249.1 ppm. Levels measured during this experiment were measurably higher.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. o

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plant tissue analysis revealed significant changes

occurring within leaves, roots, and stolons as a result of waterlogging (Table 10) . Common carpetgrass leaf

tissue Fe and Mn levels were significantly effected by waterlogging. A significant increase in leaf tissue Mn was measured for common carpetgrass after 3 weeks of waterlogging and recovery period. Root Fe and Mn content following 3 weeks of waterlogging nearly doubled (Table 10). Ashraf and Yasmin (1991) indicated that the roots

of Leptochloa fusca (L.) Kunth., a waterlogging tolerant grass plant, immobilize reduced forms of Fe and Mn in or on roots. Leaf and stolon tissue Fe and Mn levels

significantly increased following 6 weeks of waterlogging and recovery period. Grass et al., (1973) noted that oxidation of flooded soils releases soluble forms of Mn and Fe which can become toxic. Significantly high levels of stolon Fe and Mn could have been caused by high

external concentrations of Fe*2 and Mn"2 (Jones and Etherington, 1970) . Stolon Fe and Mn content in grass plants subjected to waterlogging and a recovery period were significantly increased. Waterlogging intolerant species often are incapable of decreasing the Fe and Mn content in leaf vs. root tissue (Ashraf and Yasmin, 1991). Common carpetgrass Fe content within root tissue

was twice as high as shoots. Manganese root tissue

levels were ca. 3.5 times higher than leaf tissue after

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62

3 weeks of waterlogging. The root:leaf ratio of Fe for

common carpetgrass averaged above 2:1 over all harvest treatments. The 3C treatment was the only waterlogged

treatment to maintain greater than a 2:1 Mn root:shoot ratio for common carpetgrass. Andrew and Hegarty (1969)

suggested that exclusion of Mn within or on root tissue

may reduce leaf tissue levels. Toxic leaf manganese levels of several pasture legumes ranged from 550 - 1600

ppm. Manganese content in roots of Stylosanthes humulis, a Mn tolerant legume, was maintained at higher levels in root tissue compared to shoots (Andrew and Hegarty, 1969).

Common carpetgrass growth measurements. Common carpetgrass vertical growth and clipping dry weight significantly increased after one week of waterlogging (Table 11). There were however, significant reductions in vertical growth following 4 and 6 weeks of constant

waterlogging. Clipping weight was also significantly

reduced after 4 weeks of continuous waterlogging. Etherington (1984) indicated that clipping waterlogging tolerant species under waterlogged conditions may influence their ability to adapt over time. Grass plants recovering from 3 weeks of waterlogging resumed normal growth within one week. These results coupled with

nutrient data indicate that short-termed waterlogging during the summer months had limited effects on common

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CTl u> ns ns 0.11 * 2 3 (cm) 1 ns 3.4 2.5 2.0 0 .48 0 0.35 (g) Weeks after waterlogging * 6 ns ns ns 0.3466 . 0 .47 0 0.39 0.17 ns ns 2.8 2.5 4.1 3.0 2.5 0 .46 0 * * 4 5 Clipping dry weight 4 . 0 . 4 Turfgrass vertical growth ns ns 3.5 2.70 . 2 0.7 0.92 0.67 2 3 ns ns 4.3 1. 00 1. Weeks after treatment * ■k 1 4.4.1 4 3.9 1.5199 0. 0.61 0.26 0.33 Control 0.76 Significance ns = Nonsignificant, * = significant at the P=<0.05 level. influencedby soil waterlogging located at Louisiana State UniversityHill Significance Farm, Farm, Baton Rouge, LA, 1995. Control Waterlogged Treatment Waterlogged 5.3 Table 11. Common carpetgrass vertical growth and clipping weight I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. carpetgrass (Tables 10 and 11) . Stephens (1942) observed that common carpetgrass was well adapted to areas enduring short periods of inundation. Common carpetgrass

tolerated both waterlogging conditions and severe heat stress. The capability of common carpetgrass to tolerate extended waterlogging makes it an excellent turfgrass

choice for wet soils and areas having high water tables. Centipedegrass nutrient analysis. The overall nutrient

analysis of centipedegrass leaves, roots, and stolons was measured (Appendices D.4, D.5, and D.6). Centipedegrass root Fe content was higher than leaves (Table 12). There was a general increase in Fe tissue content from 3 to 6

weeks. Leaf and stolon Fe and Mn contents were similar. There was however, a significant increase in stolon Fe levels following 3 weeks of waterlogging and a recovery period. As with Fe, stolon Mn levels were significantly

higher in the waterlogging treatment for the 3R treatment (Table 11) . The root:leaf ratio of Mn and Fe for

centipedegrass was greater than 2:1 for all harvest treatments.

Centipedegrass growth measurements. There were significant vertical growth increases measured at 1, 2,

and 6 weeks for waterlogging treatments (Table 13) .

There was, however, a decline in growth over the 6 week experiment. Increasing temperatures and leaf content Mn

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CT\ 01 ** 0.03 ns ns 0.28 0.12 ns ns ns ns ns ns 0.03 0.33 0.07 * ns .38 0.10 0.61 0.11 ** ns ns ns ns ns ns ns 0.981.59 0.35 0.54 0.18.20 0 0.20 0.32 0.09 0.19 0.881.33 .27 .37 0.0507 . 0 0.22.27 0 06 . .12 0 0 1.11 0.32 0.07 0.21 0.09 1.32 0.12 Root Stolon Leaf Root Stol< Iron dwt) (% Manganese dwt) (% * .41 .19 .11 0.40 1.8 Leaf Significance Control Significance ns Control Significance ns ns Waterlogged .39 Control Control Significance ns Waterlogged .14 Waterlogged .13 Waterlogged 0.13 1.3 .41 6 6 wk continual 6 6 wk continual + 3 wk recovery P=<0.01 level + + 3 wk recovery 3 3 wk continual ns = Nonsignificant, * = significant at the P=<0.05 level. ** = significant at the 3 3 wk continual waterlogging centipedegrass. Table 12. Iron and manganese leaf, root, and stolon tissue composition for waterlogging

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cn CTi * 0.25 ** * 2 3 2.1 1.6 0.39 0.46 Weeks after waterlogging * •k 0.23 0.23 0.34 0.24 ns 0.24 0.34 0.57 0.19 Clipping dry weight (g) Turfgrass vertical growth (cm) ns ns 0.49 0.37 •k 3.1 2.6 2.8 2.4 2.6 3.79 . 2 8 . 2 0.51 Weeks after treatment * 1 2 3 4 5 6 1 3.1 2.4 3.0 2.6 2.5 1.8 2.5 0 . 84 . 0 0.61 0.60 0.30 Significance ns ns ns ns ns ns ns ns = Nonsignificant, * = significant at the P=<0.05 level. Control Significance Control soil waterlogging located at Louisiana State University Hill Farm, Baton Waterlogged 0.69 Treatment Rouge, Rouge, LA, 1995. Waterlogged 3.7 Table 13. Centipedegrass vertical growth and clipping weight influenced by

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67 and Fe levels were measured over time (Table 12 and Appendix C.3). Clipping yields also decreased sharply

over the 6 week period. Centipedegrass maintained growth

throughout the 6 week period. Centipedegrass vertical

measurements and weights were consistently greater than control treatments following 3 weeks of waterlogging and 2 and 3 weeks of the recovery period (Table 13).

Common carpetgrass and centipedegrass. Common carpetgrass and centipedegrass responses to waterlogging were different. Common carpetgrass leaf Fe tissue content remained lower than centipedegrass tissue after 6 weeks of continuous waterlogging. Root Fe levels for both grasses were greater than leaf and stolon tissue.

Accumulation of Fe within or on root tissue is an

adaptive mechanism of waterlogging tolerant plants (Ashraf and Yasmin, 1991). Stolon Fe tissue content was often similar to leaf tissue for common carpetgrass; however, in centipedegrass, levels were slightly higher. Centipedegrass stolons may exclude toxic elements in the

same manner as roots by reducing leaf tissue Fe and Mn content (Table 12). Common carpetgrass leaf and root Mn levels were considerably higher than centipedegrass. After 6 weeks waterlogging and a recovery period, Mn levels exceeded 0.75 % Mn compared to 0.20% for centipedegrass. Common

carpetgrass did exclude Mn within roots following 3 weeks

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 of continuous waterlogging (Table 10) . Waterlogging greater than three weeks may have exceeded the capacity of common carpetgrass roots to exclude high levels of Mn from accumulating in leaf tissue.

Summary and conclusions. Common carpetgrass and centipedegrass both survived 6 weeks of continuous

waterlogging during the intense summer heat. Waterlogging tolerance was linked to the capability of

grass plants to exclude Fe and Mn. Accumulation of Fe and/or Mn in or on the root tissue reduces leaf tissue

concentrations. Common carpetgrass and centipedegrass

retained large concentrations of Fe in or on root tissue. Centipedegrass leaf tissue Mn levels were much lower than

common carpetgrass following 3 and 6 weeks of waterlogging. The ratio of root:leaf Mn and Fe levels was greater than 2:1 throughout this experiment. These

data results suggest the survival of grass plants under

waterlogging conditions may involve root exclusion of leaf Fe and Mn uptake below toxic levels. Iron and Mn tissue levels were exceptionally high throughout this experiment. Further research is needed to determine the range of Fe and Mn toxicity for common carpetgrass and centipedegrass. References to Chapter 4 Adams, W. A., and N. Akhtar. 1994. The possible consequences of waterlogging compacted pasture soils. Plant and Soil. 162:1-17.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 Andrew, C. S., and M. P. Hegarty. 1969. Comparative responses to manganese excess of eight tropical and four temperate pasture legumes species. Aust. J. Agric. Res. 20 -.661-696. Ashraf, F., and H. Yasmin. 1991. Differential waterlogging tolerance in three grasses of contrasting habitats: Aluropus langopoides (L.) Trin., Cynodon dactylon (L.) Pers. and Leptochloa fusca (L.) Kunth. Environmental and Experimental Botany. 31(4) :437-445 . Beard, J. B. 1973. Turfgrass Science and Culture. Prentice-Hall, Inc. Englewood Cliffs, N.J. Daugherty, C. J., and M. E. Musgrave. 1993. Characterization of populations of rapid-cycling Brassica rapa L. selected for differential waterlogging tolerance. Journal of Experimental Botany, 45(272):385-392. Etherington, J. R. 1984. Relationship between morphological adaptation to grazing, carbon balance and waterlogging tolerance in clones of Dactylis glomerata L. New Phytol. 98:647-658. Foong, T. W. , C. S. Ong, and S. A. Bakar. 1982. Induced deficiency symptoms of nitrogen, phosphorus, potassium, magnesium, and iron in Axonopus compressus cultured in sand. Garden Bulletin, Singapore. 35(l):33-44. Fry, J. D. 1991. Submersion tolerance of warm-season turfgrasses. HortScience, 26(7):927. Grass, L. B., A. J. MacKenzie, B. D. Meek, and W. F. Spencer. 1973. Manganese and iron solubility changes as a factor in tile drain clogging: I. Observations during flooding and drying. Soil Science Society of America Proceedings. 37:14-17.

Grineva, G. M., T. V. Bragina, A. F. Garkavenkova, and A. M. Polotskii. 1989. Physiological and structural characteristics of c o m seedlings under conditions of complete flooding. Fiziologiya Rastenii. 35 (6) :1189-1197. Heath, M. E., R. F. Barnes, and D. S. Metcalfe. 1985. Forages: The Science of Grassland Agriculture. Iowa State University Press, IA. pp. 255-265. Jones, H. E. 1971. Comparative studies of plant growth and distribution in relation to waterlogging II. An experimental study of the relationship between transpiration and the uptake of iron in Erica cinera L. and E. tetralix L. J. Ecol. 59:167-178.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70 Jones, R. 1972. Comparative studies of plant growth and distribution in relation to waterlogging. J. Ecol. 60:131-139.

Jones, H. E., and J. R. Etherington. 1970. Comparative studies of plant growth and distribution in relation to waterlogging. I. The survival of Erica cinera L. and E. tetralix L. and its apparent relationship to iron and manganese uptake in waterlogged soils. J. Ecol. 58:487- 496.

Kawase, M. 1981. Anatomical and morphological adaptation of plants to waterlogging. HortSci. 16(l):30-34. McCrimmon, J. 1996. The chemical composition of several lawngrass species. Louisiana State University, Dept, of Hort., Baton Rouge, LA. Unpublished.

Parish, R., E. W. Bush, and D. P. Shepard. 1994. A simplified turfgrass height-measuring device. HortTechnology. 4(l):49-50.

Ponnamperuma, F. N. 1972. The chemistry of submerged soils. Adv. Agron. 24:29-96. SAS Institute. 1991. SAS Users Guide. SAS Institute, Inc., Cary NC.

Stephens, J. L. 1942. Pastures for the coastal plains of Georgia, Bulletin 27. pp. 1-57.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 5

LOW TEMPERATURE SURVIVAL OF COMMON CARPETGRASS IN RELATIONSHIP TO CARBOHYDRATE PARTITIONING

71

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72 Introduction Winter hardiness is a major limiting factor for most warm-season turfgrasses. The adaptation zone for most warm-season turf grass species in the United States ranges from the transitional zone to the southern coastal states

where temperatures less than -IOC are infrequent. Common

carpetgrass (Axonopus affinis Chase) is a low maintenance stoloniferous lawngrass grown in the southern Gulf Coast region of the United States (McCarty et.al, 1992). The

low temperature tolerance (Lt50) of common carpetgrass

has been reported as very poor; however, there has been

no quantitative research (Beard, 1973) .

Winter hardiness. Several factors that influence the adaptability of a grass species include cultural practices, botanical characteristics, growth stage, pests, and environmental factors (Beard, 1973). Low temperature acclimation, environmental conditions,

turfgrass species, and cultural practices have been associated with turfgrass winter hardiness. The acclimation process for warm-season grasses begins as night temperatures approach IOC (West, 1973) . Warm-

season turf growth slows, photosynthetic rates decrease, and subsequent leaf discoloration occurs due to loss of

pigmentation. St. Augustinegrass [Stenotaphrum secundatum (Waltz.) Kuntze.] and bermudagrass responded to increased chilling stress with rapid and continual

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73

reduction in nighttime carbon dioxide exchange rate (Kamok and Beard, 1983) . Carbohydrates are stored in plant tissue during the winter acclimation process (Ito

et al., 1985). A positive correlation (r=0.78) between

acclimated centipedegrass [Eremochloa ophiuroid.es (Munro) Hack.], stolon sucrose concentrations, and freezing

tolerance was established (Fry et al. , 1993).

Nonstructural carbohydrates have been correlated to increased cold tolerance of warm-season grasses. Acclimated bermudagrass increased protein synthesis, subsequently increasing Ltso by as much as -5C (Gatschet et al., 1994). Increased centipedegrass stolon sucrose

concentrations were correlated to improved cold tolerance (Fry et al., 1993).

Low temperature tolerance. Several warm-season lawngrass species have been evaluated for cold hardiness.

Centipedegrass, bahiagrass (Paspalurn notaturn Flugge) , and St . Augustinegrass are characterized as having very poor low temperature hardiness (Beard, 1973). Bermudagrass

(Cynodon dactylon [L.] Pers.) and zoysiagrass (Zoysia japonica Steud.) have poor and medium low temperature hardiness, respectively. Studies have shown that St. Augustinegrass has a low temperature tolerance range of -4 to -6C without significant damage; however, at lower temperatures significant damage can occur (Maier et al.,

1994; Robbins and Pharr, 1988). The first visual symptom

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74 of chilling temperatures in St. Augustinegrass is wilting

leaf blades, followed by water soaked lesions, and leaf necrosis (Kamok and Beard, 1983) . In contrast, zoysiagrass is infrequently damaged by low temperatures.

Rogers et al. (1975) determined that the accumulation of

nonstructural carbohydrates during fall acclimation decreased Ltso values. Further research establishing the complex mechanisms of low temperature tolerance would be beneficial.

The objectives of this research were to determine the Ltso of common carpetgrass and nonstructural

carbohydrate partitioning during winter acclimation. Materials and Methods

Four plots of naturalized common carpetgrass were fertilized with 49.5 kg N ha'1 on April 15, and June 15,

1993 at Burden Research Plantation. Grass plugs were

harvested for tissue analysis and stolon node survivability studies on August 26, September 23, October 21, November 12, and December 16, 1993 and January 13, February 10, and March 8, 1994. Six grass plugs 10 cm in diameter were randomly harvested from each plot monthly, washed, and partitioned into either leaves, roots, or

stolons. Nonstructural (starch, sucrose, glucose, fructose) carbohydrate analysis was determined following the procedures described by Fry et al. (1993) using high performance liquid chromatography (HPLC). Sugars were

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 identified and quantified using a Supelco column (Bio- Rad, Richmond, Calif.). Starch concentrations were

determined enzymatically by detecting released glucose using a Lambda 4 spectrophotometer (Perkins-Elmer Corp., Oak Brook IL) (Fry et al., 1993).

Node survival of common carpetgrass was performed by harvesting, washing, and then acclimating stolons at 1C

overnight in a low temperature incubator (C1213, Curtis Matheson, Scientific, Houston). One node cuttings were individually wrapped in moistened paper towels. Ten

individually wrapped nodes in moistened paper towels were placed into a test tube for each of the temperature treatments (1, 0, -2, -4, -6, or -8C) with four

replications. A chip of ice was placed into each test tube to encourage ice nucleation and reduce tissue supercooling. Additional stolons with inserted probes

were placed randomly in test tubes to monitor internal stolon tissue temperature. All nodes were contained in test tubes, placed into the 1:1 ethylene glycol:water bath (Model RM 20, Brinkman Instruments, Westbury, N.Y.) , and allowed to remain at their respective temperature treatments for one hour. Following temperature treatments, nodes were allowed to thaw in a refrigerated

chamber, set at 1C overnight. Grass nodes were then unwrapped and placed in labeled petri dishes lined with moistened filter paper under grow lights maintained at

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76 28C for six weeks. Labeled petri dishes were arranged into a completely randomized design. A shoot emerging from a stolon after six weeks was considered node survival. The estimated Ltso range is defined as the two temperatures between which node survival drops below 50%

(Maier, 1993) .

Analysis of variance was used to determine differences between leaf, root, and stolon nonstructural

carbohydrate composition for each sampling month independently, using the general linear model procedure

(SAS, Institute, 1991).

The experimental design for temperature exposure treatments was a completely randomized design. Analysis of variance was used to determine statistical differences between low temperature treatments within each month with the general linear model procedure (SAS, 1991) for node survival. Mean separation using the Least Square

Differences analysis at the 0.05 probability level was performed within each month (SAS, Institute, 1991).

Results and Discussion

Carbohydrate analysis. The main nonstructural carbohydrate present in plant tissue was sucrose, followed by starch concentrations (Figure 4) . Common carpetgrass total nonstructural carbohydrate (TNC) composition of stolons was similar to St. Augustinegrass; however, sucrose was the dominant nonstructural

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77

Leaves Roots Stolons

sz 2 as (IS

120

O) 100 O) £ 80 CD CO O o as

AUG OCT NOV DECSEPT JAN FEB MAR Months

Figure 4. Partitioning of starch (A) and sucrose (B) within common carpetgrass in the 1993-1994 sampling period.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. carbohydrate in common carpetgrass (Figure 4). Starch was the predominant nonstructural carbohydrate stored in

St. Augustinegrass stolons (Fry et al., 1991). There was a gradual increase in TNC during fall acclimation for leaves, stolons and roots. Rogers et al. (1975) suggests that declining temperatures causes decreased respiration, resulting in the accumulation of export sugars. Stolon sucrose and starch levels gradually increased from August

- November (Figure 4) . Stolon reducing sugars were found

in similar concentrations as St. Augustinegrass and responded similarly to winter acclimation (Fry et al. ,

1993) (Figure 5) . Stolons are important carbohydrate

storage organs manufactured during the fall hardening period (Dunn and Nelson, 1974). Stolon TNC began to decrease following the resumption of vegetative growth in March (Figure 5) . Stolon sucrose levels were significantly greater than root tissue over the entire period. Leaf sucrose levels were significantly less than

stolons August - November. The statistical trend for both leaf and stolon sucrose levels was similar for the months of January, February, and March. Leaf and root sucrose increased from August to February four fold, before decreasing in March.

Plant tissue starch levels ranged from 8.0 - 33.5

mg/g. Leaf starch gradually increased during the autumnal months, before sharply increasing in March with

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79

35 ! Leaves Roots Stolons ! !-•------.A . |

(5 20 o>

05

3 10 T3

O)

150

100

AUG OCT NOVDECSEPT JAN FEB MAR Months

Figure 5. Partitioning of reducing sugars (A) and total nonstructural carbohydrates (B) within common carpetgrass in the 1993-1994 sampling period.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80

the resumption of active growth. As leaf sucrose levels

began to decrease in March, leaf starch levels rose.

There has been evidence that starch accumulates in chloroplasts of a grass plant subjected to 10C night temperatures (West, 1973). Leaf and stolon starch increases could be attributed to spring transition. As

sink sources such as roots and stolons are decreased,

increased TNC would accumulate in leaves. This research combined with previously published data suggests an association between stolon TNC and increasing node survival (Table 14) . Autumnal acclimation is essential for the accumulation of TNC,

which increases cold tolerance. Rogers et al. (1975)

suggest that the high starch content of zoysiagrass during the winter months contributes to its superior cold

hardiness in comparison to other warm-season grasses. Survivability. Node survival at 0 and -2C remained above 50% the entire season. Node survival at -4C peaked with >48% in December (Figure 6) . The estimated Lt50 for common carpetgrass ranged from -2 to -4C following winter acclimation. There was a slight decrease in node survival in January compared to December. Cyclic temperature patterns exceeding 20C in late November and early January may have caused deacclimation of common carpetgrass stolons (Figure 7) . Unseasonably high temperatures during winter can cause deacclimation to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81

Table 14. The estimated stolon total nonstructural carbohydrate composition (TNC) and Ltso of four winter acclimated warm-season lawngrasses. Warm-season Estimated Estimated Literature Turfgrass stolon TNC Lt50 Range Citation (mg/g) (C) zoysiagrass 375 - 550 -10 to -12 (Rogers et (Z. japonica) al., 1975) centipedegrass 170 - 200 -7 to -9 (Fry et (E. ophiuroides) al., 1993) St. Augustinegrass 140 - 188 -5 to -6 (Fry et (S. secundaturn) al., 1991) common carpetgrass 130 - 160 -2 to -4 (A. affinis)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 00 to MAR FEB JAN Months OC -2C AUG SEPT OCT NOV DEC 20 60 80 40 100 D U) 0) O (0 > £ T3 temperatures a 1:1 ethylenein glycol:waterlevel.bath. Vertical bars represent LSD at the 0.05 Figure 6. Mean common carpetgrass stolon survival after one hour exposure to freezing

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. JAN MARFEB Months Min Max NOVDEC SEPT AUGOCT 30 40 Q. CO o E a) k. 3 a o CD a> a> 20 CO E 3 +* £ H / • " • s o Figure 7. Mean atmospheric maximum and minimum temperature measured in Baton Rouge, LA., during the 1993-1994 experimental sampling period.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84 occur (Rogers et al., 1975) . Johnston and Dickens (1977)

reported that centipedegrass loses cold tolerance in the

lower south due to fluctuating warm temperatures in

winter. The capability of warm-season grass to remain physiologically dormant in the deep south is paramount to surviving low temperature damage. St. August inegrass and centipedegrass growth response to warming temperatures

was found to reduce winter damage (Reeves and McBee, 1972; Johnston and Dickens, 1977) . The influence of

winter acclimation and nonstructural carbohydrates appears to effect the cold tolerance of common carpetgrass.

Summary and conclusions. Common carpetgrass TNC were primarily composed of sucrose and starch, respectively.

The TNC composition was similar to St. August inegrass. This research confirms previous reports that common carpetgrass cold tolerance is very poor, and its culture may be limited to moderate winter temperatures. Winter acclimation improved low temperature tolerance. The

estimated -2 to -4C Ltso range of common carpetgrass was established after field acclimation. Winter acclimation

influenced both nonstructural carbohydrate composition and partitioning, and node survivability over sampling months. The greatest survival (48%) of nodes at subjected -4C was measured in December.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85 Common carpetgrass may be limited to the

geographical southeastern coastal plains of the United States due to its lack of cold tolerance. These data do not fully explain the distribution as far north as Memphis, Tennessee. Further research is needed to determine the influence of winter acclimation on winter hardiness.

References to Chapter 5 Beard. J. B. 1973. Turfgrass Science and Culture. Prentice-Hall, Inc. Englewood Cliffs, NJ. Dunn, J. H., and C. J. Nelson. 1974. Chemical changes occurring in three bermudagrass turf cultivars in relation to cold hardiness. Agronomy Journal 66:28-31. Fry, J. D., N. S. Lang, and R. Clifton. 1991. Freezing resistance and carbohydrate composition of ' Floratam' St. Augustinegrass. HorLScience 26:1537-1539. Fry, J. D., N. S. Lang, R. Clifton, and F. P. Maier. 1993. Freezing tolerance and carbohydrate content of low temperature-acclimated andnon-acclimated centipedegrass . Crop Science. 33:1051-1055. Gatschet, M. J., C. M. Taliaferro, J. A. Anderson, D. R. Porter, and M. A. Anderson. 1994. Cold acclimation and alterations in protein synthesis in bermudagrass. Journal of American Society of Horticulture Science. 119 (3) :477- 480.

Ito, K., H. Numaguehi, and M. Inosaka. 1985. Relation of non-structural carbohydrate concentration in autumn to wintering ability of several tropical grasses in Southern Kyushi. Proceedings of the XV International Grasslands Conference. 15:363-365. Johnston, W. J . , and R. Dickens. 1977. Cold tolerance evaluation of several centipedegrass selections. Agronomy Journal. 69:100-103.

Kamok, K. J., and J. B. Beard. 1983. Effects of gibberellic acid on the C02 exchange rates of bermudagrass and St. Augustinegrass when exposed to chilling temperatures. Crop Science. 23:514-517.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 Maier, F. P. 1993. Intraspecific Differences in St. Augustinegrass Freezing Tolerance. A Thesis. Louisiana State University, Baton Rouge, LA. pp. 37-49. Maier, F. P., N. S. Lang, and J. D. Fry. 1994. Evaluation of an electrolyte technique to predict St. Augustinegrass freezing tolerance. HortScience. 29(4):316-318. McCarty, L. B., R. J. Black, and K. C. Ruppert. 1992. Florida lawn handbook. Florida Cooperative Extension Bulletin-SP 45, University of Florida, Gainesville, FL. 32611. p.11., pp.51-52. Reeves, S. A., and G. G. McBee. 1972. Nutritional influences on cold hardiness St. Augustinegrass (Stenotaphrum secundatum) . Agronomy Journal. 64:447-450. Robbins, N. S., and D. M. Pharr. 1988. Effect of restricted root growth on carbohydrate metabolism and whole plant growth. Cucumis sativus L. Plant Physiology. 87 :409-413. Rogers, R. A., J. H. Dunn, and C. J. Nelson. 1975. Cold hardening and carbohydrate composition of 'Meyer' zoysia. Agronomy Journal. 67:836-838.

SAS Institute. 1991. SAS Users Guide. SAS Institute, Inc., Cary, N.C. West, S. H. 1973. Carbohydrate metabolism and photosynthesis of tropical grasses subjected to low temperatures. In: Plant Response To Climatic Factors, Proceedings Uppsala Symposium.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 6

INFLUENCE OF MOWING HEIGHT AND NITROGEN RATES ON COMMON CARPETGRASS TURF QUALITY AND GROWTH RATE

87

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88 Introduction

Common carpetgrass (Axonopus affinis Chase) is a low maintenance lawngrass well adapted to the southeastern

coastal plains of the United States. Abandoned pasture lands are invaded by common carpetgrass due to its

capability to thrive in infertile sandy soils (Heath et al., 1985). Stephens (1942) refers to carpetgrass as ubiquitous in low fertility pasture soils. Cultural requirements are low compared to many warm-season

turfgrasses (Koske, 1991).

Nitrogen requirements. Nitrogen recommendations for carpetgrass range from 3 9 - 78 kg N ha'1 annually (McCarty et al . , 1992), but no formal research has addressed the nutritional requirements of common

carpetgrass in a lawn situation. There have been reports that indicate high N rate applications in common

carpetgrass pastures actually reduced grass stands. Common carpetgrass was eliminated within one year from pasture plots fertilized with 24 or 48 kg N ha'1 (Gartner, 1969). Excessive nitrogen rates reduce lateral

stem development and meristematic node development of

grasses, consequently decreasing shoot initiation (Beard, 1993) . In contrast to Gartner (1969) , Blaser and Stokes (1942) observed a 7-fold increase in common carpetgrass yield when a complete fertilizer was applied to a pasture soil deficient in N, P, K, and Ca. Although limited N

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89 fertilizer research has focused on common carpetgrass, a hydroponic experiment studied the effects of nitrogen deficiency on a closely related species. Tropical

carpetgrass (Axonopus compressus [Swarty] Beauv.)

nitrogen deficiency symptoms resembled a complete omission of nutrients causing reduced inflorescence, root

tillering, and dry matter production (Foong et al., 1982) .

Mowing response. Establishing the proper mowing height is a major factor in the overall growth and development

of turfgrasses. Each turfgrass species has an optimum

recommended mowing height at which photosynthesis and carbohydrate storage are favored (Beard, 1993). Mowing

lower than the optimum mowing height decreases aesthetics, recuperative ability, and predisposes turfgrass to pests. Previous research results concluded

that heavy grazing of common carpetgrass pastures was required to maintain purity (Wolters, 1975). This would

suggest that mowing frequency would have a significant effect on turfgrass quality.

Weed competition. Common blue violet (Viola papilionacea

Willd.) and Indian mockberry [Duchesnea indica (Andr.) Focke] broadleaf weeds were controlled in established tall fescue through timely fertilization and mowing practices (Gray and Call, 1993) . A low mowing height (4 cm) reduced weed infestations. Conversely, Dernoeden et

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. al. (1993) indicated that a high mowing height (8.8 cm) was the best management strategy for weed control compared to N fertilizer rate and herbicidal control of

smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb. ] . Tall fescue mowed at a low mowing height

(1.9 cm) and fertilized with a high rate (244 kg N ha'1

yr*1) of N fertilizer was invaded by bermudagrass

(Cynodon dactylon L.); however, when mowed at a high mowing height (5.7 cm), there was minimal bermudagrass invasion (Brede, 1992). Determining the interaction between N fertilizer and mowing height is essential for

the culture of a quality common carpetgrass lawngrass.

The objective of this research was to establish proper mowing height and N fertility requirements to maintain a quality common carpetgrass lawn.

Materials and Methods This experiment consisted of three mowing treatments (nonmowed, 3.8 cm, and 7.6 cm) and five fertilizer treatments (0, 49, 98, 147, and 196 kg N ha'1) .

A naturalized common carpetgrass plot at Burden Research Plantation was sectioned into four blocks on June 15, 1993 for a two year experimental period (Figure 8) . Mowing strips were partitioned into three columns within each block. The mowing strips were divided into rows, in which fertilizer treatments were assigned.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91

Nonmowed 3.8 7.6 ■ B E SliBIBj EBBHi i i i i i i IliliiliBil lllllliMllllilliWilllillliiMMIMIl

l i i i i i i i — 3.8 7.6 Nonmowed 7.6 Nonmowed 3.8

Figure 8. Fertility and maintenance treatment experimental plot design located at Burden Research Station, Baton Rouge, LA, for 1993-1994. Shaded block represents randomization of maintenance and N fertilization, treatments. Maintenance treatments were as follows: nonmowed = Control; 3.8 = mowed at 3.8 cm; 7.6 = mowed at 7.6 cm. Nitrogen fertilizer treatments were as follows: 0 = 0 kg N ha'1; 1 = 49 kg N ha'1; 2 = 98 kg N ha'1; 3 = 147 kg N ha'1; 4 = 196 kg N ha'1.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Nitrogen (34-0-0) was broadcasted over grass plots

in four split applications on June 15, July 15, August 23, and September 20, 1993. Turfgrass growth was measured by monitoring weekly grass height using a measuring device described by Parish et al. (1994). A

grass plot was mowed when the average of three sub-sample

measurements exceeded 40% of the base mowing height. Weekly turfgrass height measurements were used to determine cumulative vegetative growth of common carpetgrass. Turfgrass quality ratings were taken at the initiation of the study, August 18, and September 19,

1993, and June 17, August 24, and September 19, 1994. Turfgrass color ratings were recorded at the initiation of the experiment and August 18, 1993. Weed competition was measured on February 29, 1994. Turfgrass plots were mowed following evaluation on March 30, 1994 and

maintained at 3.8 cm. Plots remained intact for N fertilizer re-applications on June 17, July 17, August 17, and September 16, 1994. Turfgrass color ratings occurred on January 9, June 17, and December 24, 1994. Weather data was recorded over the two year experimental period (Appendices C .1, C .2, and C .4). A 3 x 5 factorial experiment arranged within a

randomized block design with four replications was established. Analysis of variance (ANOVA) for both mowing treatments and each year was performed separately

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93

for cumulative vegetative growth using the general linear

model procedure (SAS, Institute, 1991). Statistically, mowing treatments and years were analyzed separately. An

ANOVA using the general linear model procedure was utilized (SAS, Institute, 1991). Means were separated using Duncan's New Multiple Range Test (DNMR) at the 0.05

level.

Results and Discussion Cumulative vegetative growth. Nonmowed common carpetgrass cumulative vegetative growth (CVG) was not

significantly influenced by N fertilizer applications

(Table 15) . Common carpetgrass mowed at 3.8 and 7.6 cm

did have significant increases in CVG during the 1993 and

1994 growing seasons. There was a gradual CVG increase as N rates increased for both mowing heights (Figures 9 and 10) . There were highly significant CVG increases in

1993 when 3.8 cm mowed plots were fertilized with at least 98 kg ha'1 N fertilizer. Cumulative vegetative growth maintained an increase in CVG at the highest N rate. During the 1993 growing season CVG was significantly increased at the high rate. Applications

of 98 kg N ha'1 fertilizer were sufficient to provide significant CVG for common carpetgrass (Table 15). Mowed plots fertilized with 98 - 147 kg N ha'1 provided increased CVG both years. Mean CVG differences were dependent on year. These differences could be

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94

Table 15. Common carpetgrass cumulative vegetative growth contrast comparing nitrogen rates by mowing height and year. N Rate 1993 1994 kg ha-1 nonmowed 3.8 7.6 nonmowed 3.8 7.6 0 v s . 49 ns * ns ns ns ns

0 v s . 98 ns ** k ns * **

0 v s . 147 ns ** k k ns ** ** 0 v s . 196 ns ** k k ns ** ** 49 v s . 98 ns * * ns ns ns * 49 v s . 147 ns ** k ns ns * 49 v s . 196 ns •k k k k ns ** 98 v s . 147 ns ns ns ns ns ns 98 v s . 196 ns ns k k ns * ns 147 v s . 196 ns ns k k ns ns ns *, ** = Significant at the 0.05 and 0.01 probability levels, respectively, ns = nonsignificant.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 196 147

A — • — ▲ Nonmowed 3.8 cm 7.6 cm Nitrogen Rate (kg/ha) A 49 98 0 • - • A

22 28 30 32 38 36

ca ca 26 3 C C □ E □ 0 > O E o < 24 o JS <5 -C 34 Figure 9. Annualrates duringcumulative the 1993 growth growing of commonseason. carpetgrass fertilized with four nitrogen

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■ A 196 A 147 98 — • — A Nonmowed 3.8 cm 7.6 cm Nitrogen Rate (kg/ha) 49 0

25 55 60 C C 30 C3 3 3 40 3 E Q) 45 Q) o E < ^35 U 50 _ca 0 SI Figure 10. Annual cumulativerates growthduring the of common 1994 growing carpetgrass season. fertilized with four nitrogen

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97 attributable to decreased rainfall during August and

early September in 1994 (Appendix C.4) .

Mowing frequency generally increased with fertilizer rate (Table 16) . Common carpetgrass fertilized with 149 kg N ha'1 significantly increased mowing frequencies for both mowing heights and years. Plots mowed at 7.6 cm were mowed ca. 30% less frequently than 3.8 cm plots (Table 16) . High N fertilizer rates significantly increased mowing frequency.

Turfgrass quality. Nonmowed turfgrass quality ratings were lower than mowed plots following the first mowing (Table 17) . As fertilizer rates increased there was a

slight increase in quality after the first season. Increased fertilizer rates did significantly increase turfgrass color and quality during the 1993 growing season. There was no significant increase in turfgrass quality the second growing season for nonmowed grass. As expected, nonmowed grass plots maintained lower turfgrass

quality than either mowing treatment. Mowed turfgrass quality significantly increased with N rates (Table 17). Nitrogen fertilizer rates of 98 kg N ha'1 or greater applied to plots mowed at 7.6 cm were significantly greener than control plots in January; however no significant effects occurred December 24, 1994. The low mowing height resulted in significantly greener leaf blades at the termination of the experiment

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98

Table 16. Mean common carpetgrass mowing frequency as influenced by fertilizer rates and maintenance treatments during a two year growing period (1993- 1994) at Burden Research Plantation, Baton Rouge, LA. 1993 1994 N Rate ------kg ha'1 3.8 cm 7.6 cm 3.8 cm 7.6 cm 0 9.25 bz 5.00 b 14.00 b 9.00 b 49 10.50 a 5.50 b 16.00 a 10.50 ab 98 12.00 a 5.75 b 16.00 a 11.00 a 147 12.50 a 6.00 b 17.00 a 11.50 a 196 12.75 a 7.50 a 17.00 a 12.00 a zMeans followed by the same letter within a column are not significantly different at the 5% level of probability as determined by Duncan's Multiple Range Test.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vo cm be be ★ 6.5 a 5.8 6.8 7.6 a a 6.5 a b 6.0 b cm b b b 5.8 d b 6.5 c -94 ** * 7.1 6.5 7.0 6.4 6.3 6.3 3.8 9-16 b 6.8 4.9 5.1 5.0 5.0 b 5.0 b 4.9 ** 7.6 7.6 cm nonmowed 5.5 5.5 abc 5.5 abc 6-17-94 8-23-93 9-20 -93 5.9 4.8 5.3 6.0 6.0 b 3.8 3.8 cm ** 3 . 8 . 3 6 . 2 0 . 6 5.0 5.0 5.0 b 3.8 5.69 . 4 5.5 5.6 c 5.4 c ns ns ns ns 4.0 cy 5.0 c 4.8 c 4.8 b 5.8 b nonmowed ha'1 0 98 49 lawngrass quality. ^ 196 2.3 6.3.1 6 98 significance 147 2.5 6.0 5.1 zMeans zMeans followed by the same letterdifferent within at thea column 5% level are of not probability significantly as determined by Duncan's 147 5.3 ab 7.0 a 6.0 ab8 b. 4 6.8 b 7.3 ab 0 196significance 5.8 a 7.0 a 6.3 a 5.8 a 7.5 a 7.8 a ns Nonsignificant,= * = Turfgrasssignificant quality at the ratings: P=s0.05utility level. quality; <5.0 6.0 = acceptable = unacceptable, lawngrass 5.0 = quality;acceptable >6.5 = excellent fertilizer rates and maintenance maintenance rates year during and growing a treatments fertilizer two 49 Multiple Range Test. kg Table 17. Mean Table quality carpetgrass common 17. by turfgrass as influenced period (1993-1994) period Burden Research Rouge, Baton at LA. Plantation, (1993-1994) N Rate

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 (Table 18) . There was concern of low temperature damage resulting from active growth during winter months; however, no winter damage was observed. Both 1993 and

1994 were considered moderate to mild winters. Deacclimation of grasses during the winter months has

been reported in the United States gulf coast region for warm-season grasses (Johnston and Dickens, 1977). There was a significant increase in turfgrass coverage measured

March 9, 1994 for grass plots mowed at 3.8 cm (Table 19) . Nonmowed plots responded inconsistently to increased N

fertilizer rates. There were no significant differences in turfgrass coverage within each mowed treatment on December 24, 1994. However, there were slight

differences between each mowing regime with the 3.8 cm mowing height having the highest percentage fertilized turfgrass coverage (Table 19).

Weed competition. Natural annual bluegrass weed invasion into common carpetgrass was measured February 29, 1994

(Table 20). Nonmowed plots were virtually weed free due most probably to dead leaf and seedhead litter

accumulation shading the soil. There was no significant fertilizer effect for nonmowed common carpetgrass. Common carpetgrass mowed at 3.8 cm was heavily infested with annual bluegrass. A low mowing height coupled with adequate moisture and fertility is conducive to annual bluegrass establishment (Dest and Allinson,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 ab cm 4.5 ab 4.9 ab 7.6 4.5 4 . 0 . 4 4.5 ns 4.2 ** ★ 5.0 5.0 b 3.6 3.6 d 4.8 b 4.5 be significantly different ns 2.6 5.9 ab 5.6 a 3.3 4 .1 4 a column are not c b b 3.8 7.3 c7.9 3.9 4.3 be ns ns ■k ** 3 . 8 8 cm . 3 7.6 cm nonmowed 3.8 cm 8/18/94 12/24/94 8/16/93 1/9/94 7.0 7.0 be 6.8 2.5 7.5 7.5 be 8.5 a 7.0 7.0 c 7.0 6.9 8.0 a 7.4 6.9 7.0 8.0 a 7.1 3.1 6.3 a 5.4 6.8 7.4 b 7.3 3.0 5.9 ab 6.3 6.5 c 6.5 2.3 5.0 b 4.3 b 6.9 8.5 a 8.4 a 4.2 5.4 a8 . 4 ns 6 . 8 . 6 6.9 7.8 b 7.8 6.3 ns nonmowed by the same letter ’within 1 0 0 98 49 98 49 6.9 147 196 = = Nonsignificant, * = significant 1 = brown, at the 9 = darkP=<0.05 green. level. Turfgrass color ratings: Significance zMeans zMeans followed at the 5% level of probability as determined by Duncan's Multiple Range Test. ns 196 147 Significance kg ha rates and maintenance treatments during a two year growing period (1993-1994) maintenance year growing period during treatments and a two rates at (1993-1994) Table 18. Mean by common as color carpetgrass Table fertilizer influenced turfgrass 18. Burden Research Plantation, Rouge, Baton Research Burden LA. Plantation, N Rate

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 ns 7.6 7.6 i 90 87.5 90 85.0 90 87.5 3.8 3.8 cm ns a ab ab * 17.5 b 95 87.5 17 .5 17 b 85 85.0 37.5 25.0 nonmowed ns 85.0 83 .8 83 86.3 81.3 a a * 3.8 cm 7.6 cm 91.3 ab 87.5 b2 11.3 94.8 16.3 96.3 28.8 26.3 91.3 ab8 . 83 35.0 17.5 nonmowed 0 98 49 196 147 respectively. zMeans zMeans followed by the same different letter within at a the column 5% level are of not probabilitysignificantly as determined by Duncan's fertilizer rates and maintenance treatments maintenance year and growing during rates treatments fertilizer a two Multiple Range Test, ns, * = Nonsignificant or significant at P=0.05, Significance ns kg ha'1 kg ha'1 3/9/94 12/24/94 Table 19. Table 19. Mean carpetgrass common coverage turfgrass by as influenced period (1993-1994) Burden period at Rouge, Plantation, Research LA. Baton (1993-1994) N Rate

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103

Table 20. Occurrence of annual bluegrass on February 29, 1994 as influenced by mowing height and N fertilizer rates. Weed Coverage % N Rate ------kg ha'1 nonmowed 3.8 cm 7.6 cm 0 6.3 15.0 cz 5.0 b 49 8.8 26.3 be 9.3 ab 98 7.5 22 .5 be 4.3 b 147 11.3 41.3 ab 8.8 ab 196 8.8 48.8 a 16.3 a Significance ns * * zMeans followed by the same letter within a column are not significantly different at the 5% level of probability as determined by Duncan's Multiple Range Test. ns, * = Nonsignificant or significant at P=0.05, respectively.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104

1981). Weed coverage encompassed greater than 40% of plots when N was applied at 147 kg N ha'1 or greater (Table 20) . The high N rate applied to carpetgrass mowed

at 7.6 cm significantly increased annual bluegrass occurrence by 11% compared to the control. Although the

annual bluegrass populations were striking, common carpetgrass soon thereafter began active growth and recovered with little or no permanent damage.

Summary and conclusions. Common carpetgrass mowed at 3 .8

or 7.6 cm and fertilized with at least 98 kg N ha'1 maintained acceptable to excellent lawngrass quality

during the 1993 and 1994 growing seasons. Turfgrass coverage, color, and CVG were greatest for mowed plots

fertilized with 98 - 196 kg N ha'1 fertilizer. The lower mowing height did increase mowing frequency. During the

summer months common carpetgrass mowed at 3.8 cm required weekly mowing. The 7.6 cm mowing treatment required mowing every two weeks. Seedheads were an unsightly problem in the nonmowed plots following three weeks after the beginning of the experiment. Seedheads were not a problem associated with mowed plots. The high nitrogen

applications extended vegetative growth into autumn months providing greener turfgrass. The results of this

experiment indicate that mowing common carpetgrass at 3 .8 or 7.6 cm, and fertilizing with 98 - 196 kg N ha'1 fertilizer will provide acceptable lawngrass quality. As

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 mowing height decreases and N rates increase, higher

maintenance practices may be required.

References to Chapter 6 Beard, J. B. 1993. Turfgrass recuperative potential. Grounds Maintenance. 4:42, 111. Blaser, R. E., and W. E. Stokes. 1942. The chemical composition, growth, and certain deficiency symptoms of carpetgrass, Axonopus affinis, as affected by lime and fertilizer mixtures. Agronomy Journal. 34(8):765-768. Brede, A. D. 1992. Cultural practices for minimizing bermudagrass invasion into tall fescue turf. Agronomy Journal. 84 (6) : 919-922.

Dest, W. M., and D. W. Allinson. 1981. Influence of nitrogen and phosphorus fertilization on the growth and development of Poa annua L. (annual bluegrass) . Proceedings of the International Turfgrass Research Conference. 4:325-332.

Dernoeden, P. H., M. J. Carroll, and J. M. Krouse. 1993. Weed management and tall fescue quality as influenced by mowing, nitrogen, and herbicides. Crop Science. 33:1055- 1061. Foong, T. W., C. S. Ong, and S. F. Bakar. 1982. Induced deficiency symptoms of nitrogen, phosphorus, potassium, magnesium, and iron in Axonopus compressus cultured in sand. Garden Bulletin, Singapore. 35(l):33-44. Gartner, J. A. 1969. Effect of fertilizer nitrogen on a dense sward of kikuyu, paspalum and carpetgrass. 1. Botanical composition, growth and nitrogen uptake. Queensland Journal of Agricultural and Animal Science. 26:21-33 .

Gray, E., and N. M. Call. 1993. Fertilization and mowing of Indian mockberry (Duchesnea indica) and common blue violet (Viola papilionacea) in tall fescue (Festuca arundinaceae) lawn. Weed Science. 41:548-550. Heath, M. E., R. F. Barnes, and D. S. Metcalfe. 1985. Forages: The Science of Grassland Agriculture. Iowa State University Press, IA. pp. 255-265.

Johnston, W. J., and R. Dickens. 1977. Cold tolerance evaluation of several centipedegrass selections. Agronomy Journal. 69:100-103.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106 Koske, T. J., 1991. Louisiana Lawns: Fact Sheet. Louisiana State University Agricultural Center, Baton Rouge, LA. pp. 1-6.

McCarty, L. B., R. J. Black, and K. C. Ruppert. 1992. Florida lawn handbook. Florida Cooperative Extension Bulletin-SP 45, University of Florida, Gainesville, FL. 32611. p.11., pp.51-52. Parish, R., E. W. Bush, and D. P. Shepard. 1994. A simplified turfgrass height-measuring device. HortTechnology. 4(l):49-50. Stephens, J. L. 1942. Pastures for the coastal plains of Georgia, Bulletin 27. pp. 1-57. SAS Institute. 1991. SAS Users Guide. SAS Institute, Inc., Cary, N.C.

Wolters, G. L. 1975. Production and persistence of common carpetgrass in relation to site and harvest frequency. Journal of Rangeland Management. 25 (5) :360-364.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 7

SUMMARY AND CONCLUSIONS

107

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108 Common carpetgrass (Axonopus affinis Chase) is well

adapted to the southeastern coastal region of the United States. Seed establishment, plant growth regulator availability, waterlogging tolerance, cold tolerance, and

low maintenance requirements enable homeowners in this region of the United States to establish and maintain a

common carpetgrass lawn with minimal input. Pre-soaking (distilled water) and priming (1, 2, 3,

and 4% KN03) common carpetgrass and centipedegrass

[Eremochloa ophuiroides Munro. (Kunz.)] seed was beneficial at optimum (30C) and sub-optimum (20 and 25C) germination temperatures measured on a thermogradient table. Pre-soaked seeds germinated at 30C maintained a

significantly higher mean time of germination (MTG) rate

compared to the nonprimed control. Priming common carpetgrass and centipedegrass in a 2% KN03 solution significantly increased seed germination percentages and MTG germinated at 20 and 25C. Priming common carpetgrass or centipedegrass seeds at greater than 2% KN03 concentrations had no added benefit for germination percentage or MTG, and in some cases was detrimental. Priming or presoaking common carpetgrass and centipedegrass seed may be beneficial in the early spring when soil temperatures range from 20 to 3 0C. There were no differences measured in germination percentage or MTG

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109 rate for primed or pre-soaked seeds of either species

germinated at 15C.

The efficacy and phytotoxicity of several plant growth regulators applied to mowed (5.1 cm) and nonmowed

common carpetgrass was evaluated over a six week period

in the summers of 1994 and 1995. Plant growth regulators

significantly reduced seedhead number and height,

cumulative vertical growth (CVG), clipping yields, and mowing frequency. Trinexapac-ethyl (0.48 kg'1), fluazasulfuron (0.054 kg ha'1), and sulfometuron (0.63 kg

ha'1) were effective in reducing nonmowed seedhead

growth, and increasing turfgrass quality. Trinexapac-

ethyl (0.48 kg'1), fluazasulfuron (0.054 kg ha'1), and

sulfometuron (0.63 kg ha'1) consistently reduced CVG of

nonmowed and mowed maintenance treatments. Sethoxydim (0.11 and 0.22 kg ha'1) significantly reduced clipping yields and seedhead number and height in 1994 and 1995

experiments. Phytotoxicity ratings 2 weeks after

treatment (WAT) for fluazasulfuron (0.027 and 0.054 kg

ha'1), sulfometuron (0.63 kg ha'1), and sethoxydim (0.22 kg ha'1) in 1994 were unacceptable (>20%) . The following year sulfometuron (0.63 kg ha"1), and sethoxydim (0.084, 0.11, and 0.22 kg ha'1) caused significant, but

acceptable phytotoxicity 2 WAT. No phytotoxicity symptoms were measured 6 WAT for either year. Applications of trinexapac-ethyl (0.32 and 0.48 kg ha'1)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110 in 1994 and 1995 significantly improved turfgrass quality

and color for mowed and nonmowed common carpetgrass. Nonmowed common carpetgrass turfgrass quality was also enhanced by the application of trinexapac-ethyl (0.16 kg ha'1) , sulfometuron (0.63 kg ha'1) , sethoxydim (0.22 kg ha'

x) , and fluazasulfuron (0.054 kg ha'1) both experimental years. Low phytotoxicity ratings, decreased cumulative vegetative growth, reduced clipping yields and seedhead height, and increased turfgrass quality ratings followed application of trinexapac-ethyl (0.48 kg ha'1) to common

carpetgrass.

Common carpetgrass and centipedegrass waterlogging

tolerance was evaluated over a 6 week period during the summer of 1995. Common carpetgrass and centipedegrass both survived 6 weeks of continuous waterlogging. Waterlogging tolerance may be associated with root

exclusion of Fe and Mn, reducing leaf tissue levels.

Common carpetgrass and centipedegrass retained large quantities of Fe within or on root tissue. Centipedegrass leaf tissue Mn levels were much lower than common carpetgrass following 3 and 6 weeks of waterlogging. The data suggest the survival of grass plants under waterlogging conditions may involve their capacity to decrease leaf Fe and Mn uptake. The nonstructural carbohydrate composition and node survival of common carpetgrass was established from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ill August 26, 1993 - March 8, 1994 sampling period. Common carpetgrass total nonstructural carbohydrate (TNC) composition was primarily composed of sucrose, starch, and reducing sugars (glucose and fructose) , respectively. The Ltso was established by field harvesting stolons and subjecting individual nodes to several temperature

treatments (1, 0, -2, -4, -6, and -8C) . Node survival gradually increased from August through December. The

highest survival (48%) rate of common carpetgrass nodes

subjected to -4C in an ethylene glycol bath was measured in December. This research indicates that the low temperature tolerance of common carpetgrass is very poor, and its culture may be limited to geographical regions with mild winters.

Common carpetgrass mowed at 3.8 or 7.6 cm and fertilized with at least 98 kg N ha'1 maintained

acceptable to excellent lawngrass quality during the 1993 and 1994 growing seasons. Turfgrass coverage, color, and

cumulative vegetative growth were highest for mowed plots

fertilized with 98 - 196 kg N ha"1 fertilizer. The 3.8 cm mowing height increased mowing frequency. During the summer months common carpetgrass mowed at 3.8 cm required weekly mowing, and the 7.6 cm mowing height bi-weekly

mowing. Seedhead production within mowed plots was not a problem. The higher nitrogen rates extended vegetative

growth into autumn months providing greener turfgrass

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 into winter. The results of this experiment indicate that mowing common carpetgrass between 3.8 and 7.6 cm,

and fertilizing with 98 - 196 kg N ha'1 fertilizer will

provide acceptable lawngrass quality. As mowing height was decreased from 7.6 to 3.8 cm and N rates increased from 0 - 196 kg N ha'1, higher maintenance practices were required.

Common carpetgrass can be easily established from

late spring through the warm summer months. Several herbicide and plant growth regulators are available for the management of common carpetgrass. A maj or advantage to growing common carpetgrass is the limited number of pests associated with its culture. The versatility of

common carpetgrass is attributable to its adaptability

to a wide range of soil types and pH, pest tolerance, low maintenance, and soil waterlogging. Common carpetgrass is an attractive warm-season stoloniferous lawn or utility grass well suited for the warm, humid, gulf coastal region of the United States.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX

113

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 * 5.0 4.2 4.7 4.3 4.7 ns 4.5 MTG 6.1 6.1 c 11.2 b a a a a b b ★ 5.5 0.2 9.8 39.5 48 .3 48 37.8 74.7 k ★ * 3.6 3.6 a 49.2 a 0.3 1.8 0.3 4.4 d.5 73 a 5.0 d c 19.1 a 10.0 c 17.8 a b 9.8 b.3 66 . Carpetgrass. Centipedegrass k k 0.8 46.5 Common 0y 30.5 b 3.1 c 68 96.0 a 94.5 a 3.3 be 3.3 abc 10 95.5 a 3.5 ab 120 a . 94 14 98.2 a 3.4 ab 55.0 a 15z 20 25 85.7 a 6.2 c 308 a . 93 experiment. Significance zLight zLight exposure was 14 hrs dailyduration (135 of lum/sq the m) experiment. for the Standard Error 2.2 0.1 Significance yTemperature exposure was set at 30C for the duration of the Standard error exDosure Licrht 4.4 carpetgrass and centipedegrass seed germination as influenced by temperature and light exposure. Treatment Temperature (C) Germination MTG Germination Appendix A.I. Preliminary experimental results for common

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 [methyl [methyl 2-[[[[(4,6-dimethyl-2-pyrimidinyl) amino]carbonyl] amino] 1-(4,6-dimethoxypyrimidin-2yl)-3-[3-trifluoromethyl-pyridinsulphonyl] urea 2-yl) sulfonyl]benzoate)] cyclohexen-1-one) Chemical Name acid ethylester] methyl)sulfonyl]amino]phenyl]acetamide] Regulator fluazasulfuron sethoxydimsulfometuron (2-[1-(ethoxyimino) butyl-5-[2-ethylthio)propyl]-3-hydroxy-2- Plant Growth trinexapac-ethyl [4(cyc1opropy1-x-hydroxy-methy1ene)-3,5 dioxcyclohexane- carboxylic mefluidide [N-2,4-dimethyl-5-[[(trifluoro- by their proper chemical names. Appendix B.l Plant growth regulator chemicals applied to common carpetgrass described

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 NOVDEC Min SEPTOCT Months Max AUG JUL JUN 30 20 40 -10 01 v- Q. <0 O k. 0) (0 O E ■ M M sz I- o in in 1993. Appendix C.l. Mean atmospheric maximum and minimum temperature measured in Baton Rouge, LA., Rouge, Baton in measured temperature minimum and maximum atmospheric Mean C.l. Appendix i

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 Months Max Min JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC 30 20 40 -10 3 c5 a> a Q. (0 u. a> 0) E O Xm a) (0 O E C.2. C.2. Mean atmospheric maximum and minimum temperature measured in Baton Rouge, LA. £ o 5 in in 1994. Appendix I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 Months Max Min JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC 10 20 40 -10 a. 3 Q. E (D 0) CO (0 <5 = o E o .c H o in in 1995. Appendix C.3. Mean atmospheric maximum and minimum temperature measured in Baton Rouge, LA. Rouge, Baton measured in minimumtemperature and maximum atmospheric Mean C.3. Appendix t

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119

Appendix C.4. Monthly precipitation measurements (cm) recorded in Baton Rouge, Louisiana for 1993, 1994, and 1995. 1993 1994 1995 January 33 .71 18.18 14 .05 February 8.53 9.67 7.80 March 12.75 9.49 28.58 April 25.93 13.86 21.79 May 9.35 15.44 16.61 June 11.53 19.71 5.36 July 8.94 15.92 7.11 August 13 .26 9.82 15.22 September 2.95 6.14 4 .72 October 15.24 8.05 14.61 November 7.72 5.25 20 .02 December 9.63 7.28 19.71

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 120 29.9 29.7 ns ns ns ns ns ns Zn Cu 77.0 27.9 80.0 35.1 63.9 ppm * * * * * * 9.2 57.0 24.6 41.1 17.6 77.0 31.1 20.3 76.0 26.6 18 . 5 . 18 80.8 30.0 ns Na B 0.79 90 . 0 0.72 82 . 0 ns ns ns ns ns ns ns ns ns ns ns s 0 .17 0 .21 0 1c * ★ ★ ★ Mg ns ns 0.64 0.19 0.17 0.52 17.7 0 .43 0 .16 0 .20 0 1.05.4 15 115.0 0.50 0.43 0.19 0.52 0.21 percentage dwt ** 0.30 0.98 0.26 0.22 0.80 1.07 0.25 P K Ca 0.23 0.21 1.10 0.48 0.18 0.18 0.647 . 16 0.28 0.90 0.23 0.95 0.43 0.14 Significance ns Control.20 0 Significance ns ns ns Waterlogged Control 0.2497 53. 0 . 0 0.21 0.19 Significance ns ns Significance nsz ns ns Control Control Waterlogged.27 0 Waterlogged 0.24 0.86 Treatment Waterlogged Week waterlogging waterlogging 6 6 wk continual 6 6 wk continual 3 3 wk continual 3 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, zns, *, ** Nonsignificant (ns) or significant at the 5% or (*) 1% (**) level. soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, LA, LA, 1995. Rouge, Baton Farm, Hill University State Louisiana at located waterlogging soil Appendix D.l. Appendix D.l. analysis of Mean by as carpetgrass tissue nutrient influenced common leaf

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121 * 59.0 46.0 59.4 51.3 50.5 47 .4 47 Zn Cu 88.9 95.2 60 .3 60 ppm 77.7 71.5 ns ns ns 7.9 7.2 60.3 41.9 13.5 59.5 57.2 0.33 6.2 65.4 S Na B ns ns ns ns ns ns ns ns ns ns ns 0.12 0.26 0.14 0.30 12.6 ns ns Mg 0.13.13 0 0.11 0.12 ns ns 0.41 0.12 0.13 0.32 17.4 0.44 0.13.14 0 0.33 percentage dwt K Ca ns ns ns ns ns ns ns ns ns ns ns 0.22 0.46 0.40 0.34 0.13 0.15 0.39 11.3 0.24 0.70 0.30 0.34 0.31.44 0 92 . 0 0.28 0.13.11 0 0.31 P ns2 ns ns 0.23 0.20 0.18 0.14 0.20 Significance ns Control 0.16 Significance ns Control Waterlogged Significance ns Significance Control Control22 . 0 Waterlogged 0.19 0.30 0.38 0.12 0.13 0.29 7.5 Treatment Waterlogged Waterlogged Week waterlogging waterlogging 6 6 wk continual 6 6 wk continual 3 3 wk continual 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, * = Nonsignificant (ns) Nonsignificant or significant at the = 5% level. * (ns) (*) zns, 1995. by soil waterlogging located at Louisiana State University Hill Farm, waterlogging Universityat Louisiana Baton Hill State by Rouge, Farm, located soil LA, Appendix D.2. D.2. Appendix Mean nutrient analysis of tissue root carpetgrass common as influenced

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 122 ns ns 19.4 8 . 19 20 .0 20 .4 22 22.8 31.1 22.0 ns ns Zn Cu ns ns ns ns 60.0 ppm 78.7 55.69 . 28 62 .2 62 73.9 78.0 * ns ns 7.2 7.7 5.7 12.0 15.1 74.9 11.9 ns ns ns 0.54 6.08 . 63 0.37 0.42 0.52 0.34 0.33 'k ns ns .16 0.16 0.17 0.15.42 0 4.3 0.15 ns ns ns ns nsns ns Mg S Na B 0.12 0.14 0.50 0.14 0.15 0.10 0.11 ns Ca ns ns 0 .52 0 0.39 0.40 0 .34 0 0.11 percentage dwt * ns ns ns ns 0.33 0.45 0.33 0.39 0.37 0.12 0.18 * PK ns 0.13 0.13.44 0 0.35 0.11 0.14 0.11 0.12 Significance ns Control.14 0 .23 0 0.52 Significance Control 0.12 0.36 0.39.12 0 Significance ns Waterlogged 0.15 0.16 Significance Control Waterlogged Control Waterlogged Treatment Waterlogged Week waterlogging waterlogging 6 6 wk continual 6 6 wk continual 3 3 wk continual 3 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, * = Nonsignificant (ns) at Nonsignificant or the significant 5% = level. * (*) (ns) zns, influenced influenced by soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, LA, LA, Rouge, 1995. Baton Appendix Appendix D.3. Mean stolon tissue nutrient analysis of common carpetgrass as

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123 ★ ns 26 . 0 . 26 18.9 19.7 22 . 9 . 22 ns 39.9.4 20 54.1.2 20 ppm 48 .0 48 27.3 ns ns ns ns ns ns ns ns ns 8.5 46.6 14.2 47.7 14.9 22.5 12.0 11.5 41.6 21.9 16 .3 16 46.1 * •k ** ** Na B Zn Cu 0 . 28 . 0 10.3.2 42 * ns ns ns 0.12 0.35 0.12 0.56 0.12 0.35 0.14 0.35 0.14 * * ns 0.17 0 .16 0 0.13 0.66 0.14.11 0 0.66 0.17 0.17 0.14 0.11 0.41 0.17 0.17 * ns Ca Mg S 0 .34 0 0.26 0.28 0.24 percentage dwt ** K 0.89 1.13 0.36 1.28 0.33 1.37 P ns ns ns ns ns 0.17 0.16 0.18 1.47 0.17 0.21 1.65 Significance Significance Waterlogged Significance nsz Control 0.20 1.42 0.27 Significance ns ns ns ns Waterlogged Control 0.19 1.25 0.33 Waterlogged Waterlogged Treatment Week waterlogging waterlogging 6 6 wk continual Control 6 6 wk continual Control.18 0 3 3 wk continual 3 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, *, ** Nonsignificant (ns) Nonsignificant or at the or 1% significant 5% level. *, ** (ns) (*) (**) zns, 1995. soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, University State Hill at Louisiana waterlogging Rouge, LA, Baton Farm, located soil Appendix D.4. Appendix D.4. Mean by analysis tissue nutrient of as centipedegrass leaf influenced

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (O ns Cu ns 50.4 29 . 9 . 29 40.1 * * ns ns ppm 55.5 59.8 50.1 59.29 . 54 73 .7 73 63 .3 63 55.7 41.0 ns ns ns 2.0 9.1 4.1 2.0 ns ns ns ns ns 0 .26 0 10.1 0.26 S Na B Zn ns ns ns ns ns 0.07 0.07 ns ns ns ns Mg 0.07 0.65 0.39 0 .12 0 0.09 0.29 0.07 ns ns ns 0.19 0.28.10 0 0.07 0.20 percentage dwt * K Ca ns ns ns ns ns 0 .21 0 .26 0 .06 0 0.06.19 0 1.5 0.18 0.29 0.26 0.10 0.28 0.23 0.25 0.290.27 0.11 0.06 0.17 12.0.4 84 48.8 P 0.10 0.10 0.16 0.3932 . 0 0.13 0.16 0.12 Significance ns Significance ns Control Significance ns Control Control Waterlogged.15 0 Waterlogged 0.14 0.32 0.36 0.12 0.10 0.30 5.1 73.6 32.2 Control Significance nsz Waterlogged Waterlogged Treatment Week waterlogging waterlogging 6 6 wk continual 6 6 wk continual 3 3 wk continual 3 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, Nonsignificant or = at * significant the 5% level. (ns) zns, (*) soil waterlogging located at Louisiana State University Hill Farm, Baton Rouge, waterlogging State Universityat Louisiana Hill soil LA, located Rouge, Baton Farm, 1995. Appendix D.5. Appendix D.5. Mean analysis nutrient root tissue by of centipedegrass as influenced

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to un H ns ns 13.6 15.5 15.6 13 .7 13 13 .5 13 14.5 ns ns ns ns ns ns Zn Cu ppm 38.9 38.3 37.7 41.2 17.1 36.3 5.1 47.1 6.3 3.7 38.8 4.1 34.1 19.9 14.4 ns ns 04.6 6.3 04.1 * ns ns ns 0.12.46 0 ns ns ns ns ns ns ns ns ns ns 0.10 0.11 0 . 09 . 0 * percentage dwt ns ns ns ns ns ns ns 0.37 0.28 0.12 0.12 0.45 0.39 0 .47 0 0.29 0 .46 0 0.30 0.09 0.11 0.38 0 . 98 . 0 0.21 0.09 0.10 0.34 P K Ca Mg S Na B ns ns 0.10 0.10 0.09 0.10 0.10 0.48 0.28 0.10 0.11 0.33 11.3 Treatment Significance ns Significance nsz Control 0.09.45 0 0.36 0.12 0.11 0.35 10.2 Significance Significance Control Control 0.09 Waterlogged Waterlogged Waterlogged Waterlogged 0.10.46 0 .34 0 0.10 0.12 0.31 Week waterlogging waterlogging 6 6 wk continual Control 6 6 wk continual 3 3 wk continual 3 3 wk continual + + 3 wk recovery + + 3 wk recovery zns, * = Nonsignificant (ns) Nonsignificant or significant at 5% level. = the * (ns) (*) zns, 1995. soil waterlogging located at Louisiana State University Hill Farm, UniversityLouisiana Rouge, Hill State at waterlogging Baton LA, located Farm, soil Appendix D.6. Appendix D.6. Mean nutrient of stolon as centipedegrass analysis tissue by influenced

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA Edward W. Bush, son of Joseph E. and Patsy J. Bush,

was born in New Orleans, Louisiana, on August 4, 1962.

A graduate of Jesuit High School, he entered Southeastern Louisiana University in August of 1980 and was graduated from there in December of 1983 with a Bachelor of Science degree in Plant Science.

In January, 1984 he enrolled in the graduate school of Louisiana State University and was graduated in August of 1986 with a Masters of Science in Ornamental Horticulture. Mr. Bush managed an industrial based GreenCare business for six months prior to accepting a research associate position at Calhoun Research Station.

He became project leader of the woody ornamental and

turfgrass project in 1989. He accepted an instructional position in the Louisiana State University Department of Horticulture in January, 1992.

Mr. Bush is a candidate for the degree of Doctor of Philosophy in Horticulture at Louisiana State University.

126

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DOCTORAL EXAMINATION AND DISSERTATION REPORT

Candidate: Edward Wayne Bush

Major Field: Horticulture

Title of Dissertation: A Physiological Study of Cornnon Carpetgrass (Axonopus affinis) Subjected to Cultural and Environmental Stress

Approved:

Major ofessor and Chairman

Dean or the Graduate School

EXAMINING COMMITTEE:

c /sL

Date of Examination:

June 24, 1996

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.