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Soil Compaction and Goosegrass Infestation in Bermudagrass Turf

HIDE
 Title Page
 Dedication
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Abstract
 Introduction
 Goosegrass infestation and soil...
 Goosegrass infestation and soil...
 Goosegrass and bermudagrass root...
 Goosegrass and bermudagrass root...
 Conclusions
 References
 Biographical sketch
 

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1 SOIL COMPACTION AND GOOSEGRASS IN FESTATION IN BERMUDAGRASS TURF By CLAUDIA B. ARRIETA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006

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2 Copyright 2006 by Claudia B. Arrieta

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3 To my parents.

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4 ACKNOWLEDGMENTS I would like to give my sincere thank to my supervisory committee members: Dr. Philip Busey, for trusting in me and giving me the opport unity and his support to achieve this study; Dr. Samira Daroub, for her guidance and assistance du ring the course of my graduate work; Dr. Sabine Grunwald, for her advice and support; and Dr. Grady Mill er, for his input and opinions. I would also like to th ank faculty and staff of the Fort Lauderdale Research and Education Center who lent me equipment and space during th e different steps on my project. I want to express my gratitude to Diane Johnson who assist ed me in getting organized at the beginning of the study; and Dr. George Snyder and Irena Ogne vich who helped me do the soil analysis. In addition, I want to say thank to Robert Klitz, general manager at Orangebrook Golf Country Club; Juan Perez, superintendent at Arrowhead Golf Club; and Angela Simmons, superintendent at Pine Island Ridge Country Club where some of the data for the study were collected. Also, I want to say thank you to Michael Brutto, the park foreman at Plantation Sunset Park, who allowed me collect data on three of th e fields. Finally, I am deeply grateful to my husband Ruben, my daughter Lia, and my sister Laura for their help, love, and encouragement.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES................................................................................................................ .........8 ABSTRACT....................................................................................................................... ..............9 CHAPTER 1 INTRODUCTION..................................................................................................................11 Bermudagrass..................................................................................................................12 Goosegrass..................................................................................................................... ..12 Herbicides and Goosegrass Control................................................................................13 Cultural Management of Goosegrass..............................................................................14 Soil Compaction..............................................................................................................17 Soil Physical Propertie s and Penetrometers....................................................................19 Objectives..................................................................................................................... ...20 2 GOOSEGRASS INFESTATION AND SOIL PROPERTIES IN TRAFFIC AND NOTRAFFIC AREAS IN GOLF COURSES..............................................................................22 Introduction................................................................................................................... ..........22 Materials and Methods.......................................................................................................... .23 Field Sites.................................................................................................................... ....23 Experimental Design.......................................................................................................24 Data Collection................................................................................................................24 Soil Properties Analysis..................................................................................................26 Sample Processing...........................................................................................................26 Statistical Analysis..........................................................................................................28 Results and Discussion......................................................................................................... ..29 Goosegrass Infestation.....................................................................................................29 Penetration Resistance and Soil Moisture.......................................................................29 Soil Properties................................................................................................................ .31 Correlation between Parameters......................................................................................32 Conclusions.................................................................................................................... .........33 3 GOOSEGRASS INFESTATION AND SOIL PENETRATION RESISTANCE IN TRAFFIC AND NO-TRAFFIC AREAS IN SOFTBALL AND BASEBALL FIELDS.......43 Introduction................................................................................................................... ..........43 Materials and Methods.......................................................................................................... .44 Goosegrass Infestation.....................................................................................................45

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6 Penetration Resistance and Soil Moisture.......................................................................45 Statistical Analysis..........................................................................................................45 Results and Discussion......................................................................................................... ..46 Goosegrass Infestation.....................................................................................................46 Penetration Resistance and Soil Moisture.......................................................................46 Conclusions.................................................................................................................... .........47 4 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION (GLASSHOUSE STUDY).....................................................................................................54 Introduction................................................................................................................... ..........54 Materials and Methods.......................................................................................................... .56 Statistical Analysis..........................................................................................................59 Results and Discussion......................................................................................................... ..60 Conclusions.................................................................................................................... .........62 5 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION, FERTILIZATION, AND CANOPY REMOVAL (GLASSHOUSE STUDY)......................66 Introduction................................................................................................................... ..........66 Materials and Methods.......................................................................................................... .68 Statistical Analysis..........................................................................................................70 Results and Discussion......................................................................................................... ..70 Conclusions.................................................................................................................... .........72 CONCLUSIONS.................................................................................................................... ........76 LIST OF REFERENCES............................................................................................................. ..78 BIOGRAPHICAL SKETCH.........................................................................................................83

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7 LIST OF TABLES Table page 2-1 United States Golf Association specifica tions for physical proper ties of root zone mixes for golf greens.........................................................................................................35 2-2 Management practices on tee slopes on each golf course..................................................35 2-3 Variables measured and numbers of samp les per each tee slope and in the three golf courses........................................................................................................................ ........36 2-4 Particle density values for the differe nt classes of total organic carbon (TOC) encountered in the three golf courses.................................................................................37 2-5 Goosegrass plants and c over, gravimetric water cont ent, and soil penetration resistance (SPR) and ANOVA table. Means of 30 observations.......................................38 2-6 Means of soil parameters measured on the tee slopes on the uppe r depth. Means of 30 observations................................................................................................................ ..39 2-7 Correlation coefficients (r) among soil pr operties and soil penetration resistance (SPR). Means of 30 observations.......................................................................................39 3-1 Variable measured and numbers of sample s per experimental unit in the three ball fields......................................................................................................................... ..........48 3-2 Goosegrass plants and c over, gravimetric water cont ent, and soil penetration resistance and ANOVA table. Means of 12 observations..................................................49 4-1 Dry weight of bermudagrass and goose grass roots and shoot s at different soil compaction levels in the first run when both species were growing separately................63 4-2 Dry weight of bermudagrass and goose grass roots and shoot s at different soil compaction levels in the second run when both species were growing separately...........63 5-1 Management of the pots from establishm ent to harvest when both species were growing together............................................................................................................... .73 5-2 Goosegrass emergence and tillers, root and shoot dry weight of goosegrass and bermudagrass by treatments and ANOVA table. Means of 16 observations....................74

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8 LIST OF FIGURES Figure page 2-1 Undisturbed soil core sample used to determine bulk density, saturated hydraulic conductivity, and capillary porosity......................................................................................40 2-2 Goosegrass canopy cover and soil penetrati on resistance at shallo w depth at three golf courses.* Significant differences between tr eatments at P<0.05 and ns, no significant differences between treatment..............................................................................................41 2-3 Gravimetric water content and soil penetra tion resistance at the shallow depth (average 2.5 and 5 cm) for all three golf courses. (n=600).................................................................42 3-1 Overview of the fields with the study areas (2 plots) marked in each of them..................50 3-2 Baseball field number six with the sampling grid. White cells indicate the traffic area which is marked with the black line from home pl ate to dugout..........................................51 3-3 Soil penetration resistance values versus gravimetric water content for the three ball fields. (n=180)................................................................................................................ .......52 3-4 Goosegrass canopy cover and penetration resistance by traffic treatment and field study.......................................................................................................................... .........53 4-1 Device used to produce compaction in the pots.................................................................64 4-2 Goosegrass roots growing in pot of medium compaction treatment (Db= 1.29 gcm-3) indicate the property for the roots to remain shallow...........................................................65 5-1 Bermudagrass root dry we ight for compaction and mowi ng treatments combinations. Means of eight replications...................................................................................................7 5

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9 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science SOIL COMPACTION AND GOOSEGRASS INFE STATION IN BERMUDAGRASS TURF By Claudia B. Arrieta December 2006 Chair: Samira Daroub Cochair: Philip Busey Major Department: Soil and Water Science The weed goosegrass is believed to infest turf grass compacted by traffi c. Objectives were to determine whether goosegrass ( Eleusine indica ) infestation in bermudagrass ( Cynodon spp.) turf occurs more in traffic areas and whether soil compaction explains it. Field studies in bermudagrass golf and softball fields compared goosegrass infestation and soil properties in adjacent traffic versus no-traffic areas. The gol f field study was a randomized complete block design on three golf courses with 15 blocks each consisting of a tee with two slopes assigned to either the traffic treatment next to the cart path, or the no-traffic treatment opposite the cart path. The softball field study was a randomized complete block design on three fields with six blocks each consisting of a foul area with traffic and no-traffic treatments assigned to quadrats according to player traffic. Traffic effect was measured as soil penetration resistance and goosegrass cover and plant density. Water conten t, hydraulic conductivity, capillarity porosity, bulk density, and total organic carbon were measured only on golf tees, from undisturbed soil cores. Two controlled greenhouse studies determin ed the effect of artif icial soil compaction on growth of bermudagrass and goosegrass. Greenh ouse studies used a Margate series soil (siliceous, hyperthermic Mollic Ps ammaquent) in rigid cylindrical pots 19.5-cm inside diameter

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10 and 22.8-cm deep. Compaction treatments were created, before planting grasses, by varying numbers of drops onto the soil surface, from 42. 0-cm height, of a 13.5-Kg weight. The first greenhouse experiment evaluated over 43 days the growth of goosegrass and bermudagrass growing separately under three levels of soil compaction, low (3 drops, 1.14 g cm-3 bulk density), medium (10 drops, 1.24 g cm-3), and high (42 drops, 1.33 g cm-3). The second greenhouse experiment evaluated from 70 to 75 da ys the growth of goosegrass, and over 203 to 206 days the growth of bermudagrass growing toge ther under two levels of soil compaction, low (3 drops, 1.07 g cm-3 bulk density) and high (42 drops, 1.26 g cm-3). Other treatment factors were nitrogen fertilization rate, 288 and 144 Kg ha-1 y-1, and mowing height, 25.4 and 12.7 mm. Goosegrass seedling emergence was also measur ed. Goosegrass plant de nsity and cover were larger (P<0.05) on traffic areas of golf tees a nd softball foul areas, compared with no-traffic areas. Soil penetration resistan ce was increased by traffic (P<0.05) at shallow (2.5 to 5.0 cm) depth on golf tees slopes, but not softball fields There was no effect of traffic on other soil properties. While goosegrass infested traffic ar eas more than no-traffic areas, it was not associated with soil compaction. In the fi rst greenhouse experiment, bermudagrass biomass showed no effect of soil compaction, but gooseg rass root biomass was decreased (P<0.05) by increasing soil compaction. In the second greenhouse experiment, goosegrass emergence was increased (P<0.001) by low mowing height and was decreased (P <0.01) by high soil compaction. Goosegrass biomass was not affected by any tr eatment, but bermudagrass root biomass was reduced (P<0.01) by soil compaction, and shoot and root biomass were reduced (P<0.01 and 0.001, respectively) by low mowing he ight. Controlled compaction so metimes reduced growth of either bermudagrass or goosegrass. Low mo wing height, which simulated canopy removal effects of wear, increased goosegrass seedling emergence.

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11 CHAPTER 1 INTRODUCTION As weeds become established in thin and weak turf areas, the best de fense against weeds is to have a dense vigorous turf (McCarty and Murphy, 1994; Watschke and Engel, 1994). Competition between any crop and weeds is more intense when they have similar growth habits and demand similar resources (Rao, 2000). In turfgrass and grass weed competition, for example, both have their growing points close to the soil surface allowing them to survive close mowing (Watschke and Engel, 1994). Goosegrass infestation has been suggested as a consequence of traffic-caused compaction (Carrow and Petrovic, 1992). This may be consistent with the fact that compaction is associated with low soil oxygen conditions (Waddington, 1992) which goosegrass tolerates (Waddington and Baker, 1965). However, there are no data to document the asso ciation of goosegrass infestation and traffic or to ve rify that traffic-caused compaction is the mechanism and how it promotes goosegrass occurrence. Recreational turf areas are exposed to frequent vehicular and foot traffic, which results in both wear of the turf and soil compaction. Defi ned by Carrow and Petrovic (1992), wear is the injury from pressure, scuffing, or tearing directly of the turfgr ass tissue. Soil compaction is the re-arranging of soil particles resulting in a mo re dense soil mass with less pore space which reduces root growth, soil aer ation, and water infiltration (B rady and Weil, 2002). If trafficcaused soil compaction is the mechanism to expl ain goosegrass infestation, then it might operate by differentially decreasing bermudagrass growth and as a result increasing competition from goosegrass.

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12 Bermudagrass Bermudagrass hybrid cultivars have been the predominant turfgrasses in use on golf courses and athletic fields thr oughout the southern USA and in warm climates areas worldwide. Hybrid bermudagrasses ( Cynodon dactylon L. Pers. X C. transvaalensis Burtt-Davy and reciprocal) are both naturally and artificially occurring in terspecific hybrids of common bermudagrass ( C. dactylon ) and African bermudagrass ( C. transvaalensis ) (Turgeon, 2005). While hybrid bermudagrass cultivars provide high quality and dense cover for recreational turf, they require a regular maintenance program with intense mowing and high levels of fertilizer to maintain required standards (Beard, 2002). Regular mowing at the proper height, which varies depending on the use of the field and cultivar used, is necessary to reach acceptable field conditions (Beard, 2002; Turgeon, 2005). In additi on, proper fertilization rates and timing are essential for wear resistance, qui ck turf recovery from traffic damage, and aesthe tics (Miller and Cisar, 2005). A range of total nitrogen 230 to 320 Kg ha-1 y-1 and total potassium 140 to 230 Kg ha-1 y-1 is generally required for bermudagrass main tenance (Miller and Cisar, 2005; Sartain and Miller, 2002). Goosegrass Goosegrass, a summer annual seed-dispersal weed, is a serious problem in bermudagrass golf and sports turf in warm climates. Goosegra ss has a bunch-type (non-creeping) growth habit where the adventitious roots orig inate from the basal nodes of the main axis and from the tillers (Brown, 1979). It is a prolific seed producer with most of the seed germinating in the first year and little thereafter (Hawton a nd Drennan, 1980). Since goosegrass seed germination responds to fluctuating temperatures, greatest emergence of goosegrass occurs on bare ground, in scalped and thin turf where maximum diurnal fluctuati ng temperatures would be expected (Nishimoto

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13 and McCarty, 1997). Busey (2004b) defined goosegrass as a gap colonist weed because seed quickly germinate in an open turf canopy due to the presence of divots, inse ct injury and wear. Herbicides and Goosegrass Control Goosegrass control mostly re lies on preand postemergence herbicides. Preemergence herbicides kill goosegrass seedlings after they ha ve germinated, but before they have emerged from the ground. Common goosegrass preemergence herbicides are the chemicals dithiopyr (trade name, Dimension), metolachlor (Pennant ), oxadiazon (Ronstar), oryzalin (Surflan), pendimethalin (Halts, Pre-M, Pendulum, and Southern Weedgrass Control), prodiamine (Barricade and RegalKade) and their combinations (Johnson, 1993, 1996, and 1997). Preemergence herbicide application begins in sp ring (March in northern temperate areas) and continues through summer dependin g on rate of application, the ha lf-life of the herbicide, and considerations of economics and goosegrass population density (Busey, 2004b). Broadcast postemergence herbicides kill weed plants after they have germinated. Two disadvantages of using postemergence herbicides fo r goosegrass control are that they are not always effective on mature plants and they may weaken the desired turf (Busey, 2004a). Common postemergence herbicides are MSMA or monosodium methan earsonate (many brands), diclofop-methyl (Illoxan), metribuzin (Sencor), and foramsulfu ron (Revolver) and their mixtures (Busey, 2004a; Johnson, 1980; Johnson, 1997; McCarty, 1991; Mu rdoch and Ikeda, 1974; Murdoch and Nishimoto, 1982; Nishimoto and Murdoch, 1999). Monosodium methanearsonate (MSMA), an orga nic arsenical product, has been used in warm-season turf largely for goosegrass control. It has been mostly applied on athletic fields, golf courses and parks. In August, 2006, the Envi ronmental Protection Agency determined that all uses of MSMA are ineligib le for re-registration (USEPA, 2006). Several monitoring studies in Florida golf course ponds f ound total annual mean arsenic c oncentrations at individual ponds

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14 as high as 64 ppb. Additionally, from 2003 to 2005, at least 5% of Florida drinking water compliance monitoring samples exceeded 3 ppb arseni c. These detections are not proven to be caused by organic arsenical herbic ide use, but they exceed the typical background values of < 2 ppb; therefore, they are likely explained by some kind of anthropogenic input. In addition, monitoring in shallow wells beneath golf courses detected arsenic in groundwater at 9 of 14 Florida golf courses test ed, with detections of up to 120 ppb in shallow wells (<12 ft depth) and up to 11 ppb in deeper wells (<28 ft depth). This represents expos ure that might be expected in worst case scenarios when maximum labeled rate s are applied in the most vulnerable sites. Although there are uncertainties in the mode ling, available monitoring data support the conclusion that typical use of organic arseni cals may result in drinking water exposure to inorganic arsenicals that exceed levels of concern (USEPA, 2006). As a consequence of high arsenic levels associated with sites where MSMA has been applied, alternative herbicides and cultural practices can be considered worthwhile alternatives to organic arsenical herbicides. Mechanically removing goosegrass involves ha nd weeding whereby roots are cut or removed below the ground to avoid disturbance of the surface appearance It is impractical on large turfgrass areas, but it is useful in controlling isolated mature goosegrass plants. Spot treatment of individual plants of goosegrass, with nonselectiv e postemergence herbicides such as glyphosate (Roundup) applied in the center of plan ts, has been shown to be an effective alternative to broadcast app lication (Baerson et al., 2002). Cultural Management of Goosegrass Cultural management of weeds in turfgra ss is poorly documented, and there is no documentation on cultural management practices to prevent goosegrass infestation (Busey, 2003). Periodic cultural practices that can contribute to control of goosegrass, based on the comments of turfgrass managers, are the use of fertilization, irrigation, cultivation and traffic

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15 control (Busey, 2004b). Bermudagra ss is a relatively rapid grow ing grass (Busey and Myers, 1979), and its growth responds strongly to increase d fertilization. Nitrogen at the rate of 48 Kg ha-1 per growing month (Sartain and Miller, 2002; Turgeon, 2005) helps regrow turf canopy into areas damaged by traffic (Busey, 2004b). Since high li ght intensity is required for germination of goosegrass, increasing turf density will prevent light from reaching the soil surface (Busey, 2004b; McCarty and Murphy, 1994). Cultivation (core aer ation) is used to alleviate compaction. In addition, wear is decreased by redirecting and/ or avoiding traffic in some circumstances, e.g. after rain. It has been suggested that goosegrass infests trafficked areas, and the reason for that is still unclear. Maintaining proper soil moisture through irriga tion and soil drainage encourages vigorous turf growth. Excessive irrigati on and poor soil drainage result in low oxygen levels (McCarty and Murphy, 1994). Also, the effect s of irrigation practices in c onjunction with soil compaction can be more detrimental to turfgrass roots. Agnew and Carrow (1985) re ported that rates of oxygen diffusion rate (ODR) fell below 20 x 10-8 g cm-2 min-1, the critical value of ODR for common crops such as cotton, sunflower, and co rn, for 143 hours on compacted turf, but for only 26 hours on uncompacted turf. Daily irrigation of turf, especially on golf cour ses, is need because of the shallow root system resulting from the necessary close mo wing. However, daily irrigation at excessive application rates may leave the soil more susceptible to compaction effect of traffic, which could decrease root growth and consequently result in higher wilting tende ncy (Turgeon, 2005). Turf density decreases with compaction. Goos egrass as well as annual bluegrass ( Poa annua L ), prostrate knotweed ( Polygonum aviculare L ), and various sedges ( Cyperus spp.) may invade because they can tolerate these conditions (McCarty and Murphy, 1994).

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16 A greenhouse study was conducte d (Waddington and Baker, 1965) to determine the influence of soil aeration on root growth of three grass species: Kentucky bluegrass ( Poa pratensis L.), creeping bentgrass ( Agrostis palustris ) and goosegrass. The study was conducted using flooding so that aeration, and not mechanical impedance or fertility, would be the limiting factor in the growth of the grass plants. Each grass produced thicker roots with fewer laterals under conditions of poor aeration. Kentucky bluegra ss root growth was reduced at ODR below 5 x 10-8 to 9 x 10-8 g cm-2 min-1. In comparison, roots of creeping bentgrass and goosegrass grew well in soil having ODR below 3 x 10-8 g cm-2 min-1. Cultural practices promoting vigorous, dens e turf are the most important and least recognized means of preventing weed establishment and encro achment (McCarty and Murphy, 1994). In a review of cultural management practi ces of weeds in turfgrass, Busey (2003) stated that mowing height is one of the most studied cultural factors aff ecting weed population on turfgrass. When there was a significant effect within the mowing height studies, the lower mowing height is always associated with mo re weeds in turfgrass such as crabgrass ( Digitaria spp), green killinga ( Killinga brevifolia Rottb.), and annual bluegrass. In the same review, Busey reported that higher rates of n itrogen fertilization reduce crabgr ass populations and also suppress broadleaf weeds, probably because of stimulation of the turfgrass to grow more rapidly and be more competitive. However, annua l bluegrass infestation may be increased by a higher rate of nitrogen fertilization (Busey, 2003). In the past, existing native soil fields had provided adequa te sports playing surfaces. However, as intensity of use has increased, sa nd-based fields were installed for improving playability (Puhalla et al., 1999). The sand field offers several advantages that cannot be provided by a native soil field. Primary among these advantages of a sand-ba sed root zone is its

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17 high water permeability, which allows for rapid surface water removal by internal drainage (Turgeon, 2005), and a second advantage is that a sand-based root zone will protect against compaction. Correctly specified and tested sand will not compact to levels that can limit its internal drainage properties by reducing macropores. Macropore s allow water to be drawn downward by gravity. When selectin g the sand it is important to know sand size classes, shape, particle size distribution, and sand particle stability b ecause they will affect the soil physical properties of the field (Puhalla et al., 1999). The United States Golf Association (US GA) has recommended putting greens to be comprised of a sand-based root zone mix. Soil phys ical properties of the root zone mix (total porosity, air-filled porosity, capillary porosit y, and saturated hydraulic conductivity) are evaluated and used to predict the performance of a root zone mix (United States Golf Association, 2004). A root zone soil must meet the physical speci fications found in Table 2-1 to meet USGA specifications. Soil Compaction Compaction in turfgrass typically occurs in the first few centimeters of the soil surface (Sills and Carrow, 1983; ONeil and Carrow, 1983; and Carrow and Petrovic, 1992). As soil is compressed, bulk density increases, pore volume d ecreases, and pore distribution shifts toward smaller pores. This result in a compacted soil characterized as having lower aeration, slower permeability, and higher mechanical impedance to root growth (Brady and Weil, 2002). Bulk density and Soil Penetra tion Resistance (SPR) measurements can be used to assess soil compaction and soil strength. Bulk density is expressed as the oven mass of soil per volume of soil (Blake and Hartge, 1986). An increase in bulk density also indicates that movement of air and water within the soil is reduced. The collec tion of cores for determin ing bulk density within the laboratory is time consuming. However, equipment for core sampling is relatively

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18 inexpensive and durable for field usage (Mille r et al., 2001). In comparison, penetrometers are easier and quicker to operate, do not disturb the ground and give an instant result. Furthermore, in a study conducted by Vazquez et al. (1991), SPR measurements were ten times more sensitive than bulk density measurements for indicati ng soil compaction on sand soils (Arrendondo fine sand) in Florida. A penetrometer reading is one way to quantify soil strength, the property of the soil that causes it to resist deformati on (Brady and Weil, 2002). Pene trometers measure the physical constraint exerted by soil on plant root growth by simulating the pressure a root encounters when growing into a soil (Brady and We il, 2002). Roots penetrate the soil by pushing into pores. If the pore is too small, the root must push the soil particles aside and enlarge the pore. Therefore, increased density of the soil (bulk density) restrict s root growth. In addition, root penetration is limited by soil strength. The most common use of penetrometers in agriculture has been for assessing soil compaction under wh eels and tillage. Penetrometer s are useful in estimating compaction below tractor wheels in agricultural crops Also, they have been used to evaluate the ability for root growth in the soil after diffe rent tillage treatments (Campbell and OSullivan, 1991). However, there is no documentation on th e use of penetrometers to indicate soil compaction levels in turfgrass areas. Penetrometer values are commonly reported as the cone index (CI) which is the shear resistance of the soils. Cone index is calcula ted as in Eq. 1-1 (Ra ndrup and Lichter, 2001), CI= F/ (d/2)2 Eq.1 1 where F is total pressure needed to force the penetrometer into the soil in newtons (N), the denominator is the base area of the cone, and d is diameter of the cone. Cone indices are reported as Kg cm-2, KPa, MPa, and psi (Randrup and Lichte r, 2001). Cone indices depend on soil and

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19 probe characteristics such as base diameter of the cone, cone angle, and surface roughness of the cone, as well as moisture content, bulk densit y, organic matter, and texture of the soil (Bradford, 1980; Perumpral, 1987). In a wet soil, the penetration pressure is dependent on the interaction between the resistance of the probe and the soil water tension, which means that readings should be taken at similar moisture content if they are to be compared. This effect will be more important in less penetrable soils with a high content of silt and clay (Randrup and Lichter, 2001). Soil Physical Properties and Penetrometers Factors that influence the degree of soil co mpaction are soil texture, soil structure, moisture content, particle size distribution, and fo ot and vehicular traffic. According to Carrow and Petrovic (1992) foot and vehi cular traffic are the more important soil compacting forces on most recreational turfgrass sites. Foot traffic is influenced by the speed of the traffic event (walking vs. running), and the magn itude of the compacting force, which is a function of surface contact area and weight. Vehicula r traffic is a function of the lo ad of the wheel, the shear stress resulting from wheel slippage, and vibration transmitted from the engine through the tire. However, wheel slippage (rapid starting, stoppin g, and turning) can co mpact soil to a much greater degree than by increasing the load. In addition, the degree of soil compaction cr eated by traffic is a function of both soil texture and soil moisture. As soil moisture content increases to saturation, a corresponding linear or exponential reduction in porosity occurs (C arrow and Petrovic, 1992). However, the adverse effects of compaction on soil physic al properties are less evident in coarse-textured soils than in fine-textured soils. Even though sandy soils may compact, the degree of compaction is limited to the bridging between the sand partic les, which prevents the elimin ation of most of the larger pores (Carrow and Petrovic, 1992). This is the r eason that makes sandy soils most desirable for

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20 sports fields and golf course. In addition, coarse sands with a very uniform particle size distribution are most desirable because they have better infiltration rates than sands with a wide particle size distributi on (Stitt et al., 1982). Several researchers have worked on the rela tionship between soil penetration resistance, bulk density, and water content. A study of fact ors affecting mechanical impedance of tillageinduced pans in coarse-textured soils in the Atla ntic coastal plai n found that the best model for explaining the measured mechanical impedance included soil water content, surface roughness of soil particles, and bulk density (Stitt et al., 1982). Si milar results were obtained by Ayers and Perumpral (1982) who found a direct relations hip between penetrati on resistance and bulk density, and an inverse relations hip between penetration resistan ce and water content for various mixtures of sand and clay. Ley and Laryea ( 1994) observed that doubling the water content reduced the penetration resistance by 56-87% in th e topsoil (0 to 15 cm depth). However, Ayers and Perumpral (1982) found that in soils compacted at the same level the highest bulk density and the highest cone index values were achieved at two distinctly differe nt moisture contents. Besides, for soils with 100 percent sand the cone index-bu lk density relationship was independent of moisture content. Due to the re lationship between compaction and soil moisture, it is desirable to measure gravimetric water content in the soils in which SPR measurements are taken (Campbell and OSullivan, 1991). Additiona lly, penetration resistance and soil water content are affected by particle size. Warnaars and Eavis (1972) re ported that in finer grade sand, penetration resistance decreased w ith increasing in moisture cont ent occur; however, in coarse sand it was relatively unaffected by moisture. Objectives The objectives of this study were to determin e if goosegrass infestation occurs more often in traffic areas, and whether soil compaction or some other mechanism w ould explain this. There

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21 are three main hypotheses: (1) traffic areas s how higher goosegrass infestation than no-traffic areas; (2) traffic areas have higher soil compaction levels, 3) in response to soil compaction, bermudagrass growth decreases more than goosegrass growth.

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22 CHAPTER 2 GOOSEGRASS INFESTATION AND SOIL PROP ERTIES IN TRAFFIC AND NO-TRAFFIC AREAS IN GOLF COURSES Introduction The game of golf consists of playing a ball acr oss a grassed course of typically 18 holes by successive strokes with a club, starting from the "teeing ground," or tee (USGA, 2004). For purposes of this discussion, the "hole" will refe r to one of the typically 18 complexes of one teeing ground and associated putting green, where the hole is located, and the intervening area between the tee and the putting green which is called the fairway. The fairway is bordered by uncut grass or less intensely ma intained grass known as rough. Foot traffic on golf courses is concentrated on tees, greens, and next to cart paths throughout the golf course. Golf courses are ofte n built on level areas with poor drainage. To alleviate poor drainage, greens and tees are often elevated, sometimes with fill material, but foot traffic and sometimes even cart traffic is intens e on the sloped side of the tee nearest the cart path, as golf players step up to the tee. Traffic is essentially ab sent on the sloped side of the tee opposite the cart path. The symmetri cal design of the elevated tee, with a traffic side and a notraffic side, provides a structure to experimentally measure the e ffect of traffic on golf courses. The teeing ground, which is an important area where traffic occurs, may comprise one or more rectangular areas totaling 9 to 18 m2 per 1,000 rounds of golf a nnually (Beard, 2002); if there are multiple tees within the teeing ground to provide accessibility for different player strengths, they may be designated forward, midd le, and back. Tee markers are generally moved daily to different positions with in the tee, to make the game of golf more interesting, and to spread out the traffic throughout the teei ng ground and associated sloped sides. Goosegrass has been observed as the most seri ous weed problem in golf and sport turf in southern Florida (Busey, 2001), and it has b een largely controlled by MSMA, a postemergence

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23 arsenical herbicide, which use has been determ ined ineligible for re -registration (USEPA, 2006). Therefore, it is important to learn the factor s that promote goosegrass infestation, as this knowledge may be applied in the use of cultural practi ces that can prevent its infestation. The objective of this study wa s to test the hypotheses that traffic areas show higher goosegrass infestation and higher so il compaction level compare to no -traffic sides of golf course tees. Data were collected to: (1 ) compare goosegrass infestation a nd SPR in traffic and no-traffic areas; (2) compare soil properties in traffic and no-traffic areas; and (3) measure the association among goosegrass infestation, SPR, and soil properties. Materials and Methods Field Sites The study was conducted on three golf courses located in Broward County, Florida. The 18-hole golf course at Arrowhead Golf Club is 36 years old and has approximately 50,000 rounds of golf played per year. Raised areas (g reens and tees) were c onstructed partly with Udorthents soil which consists of heterogeneous geologic material that has been excavated from ponds and canals. The golf course at Pine Isla nd Ridge Country Club is also 36 years old, has 18 holes, and has approximately 33,000 rounds of golf played per year. The golf course also has been constructed with Udorthents soil, and it is on a ridge with higher and better drained soils (Pendleton et al., 1984). Orange brook Golf and Country Club is 71 years old, contains two courses with 18 holes each, and has approximate ly 85,000 rounds of golf pl ayed between the two courses per year. The golf course has been constructed over Pennsuco series (Coarse-silty, carbonatic, hyperthermic, Typic Fluvaquents), Marg ate series (Siliciceo us, hyperthermic, Mollic Psammaquents), and Dade series (Hyperthermic uncoated Spodic Quartzipsamments; Pendleton et al., 1984). In 2001, the golf courses at Ora ngebrook were renovated us ing native soil to reshape the course. Composite samples from A rrowhead and Pine Island Golf course tees

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24 showed that they have sandy soils with a pH of 6.9 and 6.6; and average organic carbon content of 2.31 and 1.64% respectively. A composite sample from Orangebrook Golf and Country Club showed tees having loamy sand soil with 10 % si lt and 4% clay, 7.4 pH, and total organic carbon 2.59%. Table 2-2 describes the common management practices done by the superintendents for the three golf courses. Experimental Design The experimental design was a randomized comp lete block with 15 blocks each consisting of a tee, with five tees selected from each of th e three golf courses. Within each block there was two plots consisting of the two t ee slopes parallel to the longest ax is. The tee slope next to the cart path, from which golfers walked up onto the t ee, was the "traffic" pl ot and the tee slope opposite the cart path was the "no-traffic" plot. On each golf course, five tees were selected based on dimensions of the tee slopes to pick the largest sampling areas. Except as indicate d, the back tees were selected; the numbers represent the progressive position of the selected tees with reference to the normal direction of play. In Arrowhead tees 5, 6, 10, 12 and 16 were se lected; at Pine Island Ridge tees 1 (middle), 5, 12, 13, and 18 were selected; and at Orangebro ok east side tees 4, 7, 10, 18 (middle), and 18 were selected Data Collection The dimensions of traffic and no-traffic samp ling area were each defined to be 27.4 m long by 2.7 m wide for each tee slope, which conforme d approximately to the length of tee slopes adjacent to the flat tee tops. In cases of s horter tees, the sampling area was broadened to maintain the same area and sampling density. With in each traffic and no-traffic area, goosegrass cover (%) and the number of plants present we re determined visually in fifteen randomly

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25 distributed quadrats (0.25 m2) within the respective sampling areas. Observations were done between July and September, 2005. For each traffic and no-traffic tee slope, twenty Soil Penetration Resistance (SPR) readings were randomly taken along with soil core sample s to determine gravimet ric soil water content. Soil cores were collected adjacent to the SPR meas urements points. The penetrometer used was a Field Scout SC-900 (Spectrum Technologies, Plainfiel d, IL), which digitally displays readings in KPa in 2.5 cm increments of soil depth. It is designed to American Society of Agricultural Engineers standards. The instrument error was 103 KPa for SPR and 1.25 cm for depth (Spectrum Technologies). At each of the 20 point s, SPR measurements were recorded at 2.5, 5.0, 7.5, 10 and 12.5 cm depths. Due to the presence of stones, SPR measurements were not collected at the 12.5 cm depth on tee number four on Oran gebrook Golf Club. The presence of stones may result in non-representative SPR measurements (O Sullivan et al., 1987). Cone indices reported as shallow were an average of the 2.5 a nd 5.0 cm depth SPR measurements. Cone indices reported as all depths were an averag e for all depths from 2.5 to 12.5 cm. Soil cores were separated into two sectio ns, upper, 1.5 7.5 cm and lower, 7.6 12.5 cm, depth, to measure soil moisture status. The three upper sections of cone index (2.5, 5, and 7.5 cm depth) corresponded with the upper sections for wa ter content, and the two lower sections of cone index (10 and 12.5 cm depth) correspond with the lower sections for water content. Soil from each section, 15 to 20 g, was dried to a consta nt weight at 105 C, at which time a final dry weight was measured. Relative gravimetric wate r content was calculated by weighing the soil core from the field under moist condition (fresh wt.) and weighing again after drying in an oven until its weight remained constant (dry wt.). The weight loss during drying represented soil water, and its percentage composition is expressed as Eq. 2-1 (Gardner, 1986).

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26 Relative soil water content (%) = ((fres h wt. dry wt.)/ dry wt.) x 100 Eq.1 2 Soil penetration measurements and water conten t samples were collected on the same day. The tee slopes at Arrowhead, Pine Island Ridge and Orangebrook we re sampled between February and October, 2005. Variables measured and numbers of samples collected on each tee slopes are illustrated in Table 2-3. Soil Properties Analysis Four undisturbed soil cores were collected fr om traffic and no-traffic areas. Soil cores were collected using a hammer driven core sample r 5.1 cm diameter to a depth of 9 cm (Fig. 21). The top 1.5 cm containing turf verdure, crowns, rhizomes, st olons, thatch was cut off and discarded, leaving soil cores 7.5 cm deep for th e analysis. The soil was analyzed for saturated hydraulic conductivity, pore space content, po re distribution (macro and micro), and bulk density, using methods described by the United St ates Golf Associati on (Hummel, 1993), except that the samples were not artificially compacte d. Samples were collected from the beginning of January to the end of February, 2006. Table 2-3 summarizes the soil analysis number of samples per treatment and the total numbers of samples in the three golf courses. Sample Processing After a soil core was collected from the fiel d, it was saturated and then placed in a permeameter where water flowing through the core was maintained at a constant hydraulic head (measured from the bottom of soil column to wate r level above the soil) fo r four hours, at which time percolate aliquots were collected. Satura ted hydraulic conductiv ity was calculated according to Eq. 2-2 (Hummel, 1993), Ksat = QL/hAt Eq.2 2 where Ksat = hydraulic conductivity (cm hr-1) Q = quantity of water collected (cm3) in period of time (t)

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27 L = length of soil column (cm) h = hydraulic head (cm) A = cross sectional area of the soil core (cm2) t = time required to collect Q (hr) After Ksat was determined, the soil core was placed on a tension table, set to remove water at 40 cm of tension. When the soil core weight reached equilibrium (after 18 to 30 h), this last weight was recorded. The core was oven drie d at 105C until constant weight was obtained. Capillary porosity, amount of pores retaini ng water at -0.004 MPa (40 cm tension) which represents field capacity, was calculated on an oven dried basis, and bulk density was calculated from the soil weight and volume. Capillary por osity (microporosity) was determined according to Eq. 2-3 (Hummel, 1993), Cp = ((Mw Md)/ V) x 100 Eq. 3 2 where Cp = capillary porosity on dry weight basis (%) Mw = net wet soil wt. at 40 cm tension of the core (g) Md = net dry soil wt of the core (g) V= volume of the core= x r2 x L (cm3) L= length of soil column The value of dry soil weight was also used to calculate bulk density of the soil core, and from this value of bulk density total porosity was determined (Hummel, 1993). Total Porosity= (1 (Db/Dp)) x 100 Eq.4 2 where Db= bulk density (g cm-3) Dp= particle density (g cm-3) Air filled porosity (macroporosity) was calculate d by subtracting percentage of capillary porosity from total porosity. Total organic carbon (TOC) was determined using the Nelson and Sommers (1996) procedure. Chromic acid oxidation with sulfuric acid measures easily oxidizable organic carbon. This easily oxidizable organic carbon is multiplied by a recovery factor of 77% to convert it to

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28 total organic carbon. Easily oxidizable organic ca rbon content was analyzed from the same soil cores (upper and lower depths) used to determine water content. Particle density was calculated from the same soil cores used to determine TOC. However, since soil bulk density was only determined on the top 7.5 cm of the soil pr ofile, particle density was calculated at the same depth with no distin ction between traffic an d no-traffic treatments. The purpose of measuring particle density was to assure an accurate estimation of porosity. Each of the 30 soil cores available was assigned to a class interval depending on the % TOC, and then a sub-sample of each class interval was taken an d particle density calculated. Interval classes were based on the number of samples and closeness of TOC value. The value of particle density was matched to the value of to tal organic carbon per each tee and then total porosity was calculated for each tee. Particle density was calculated by dividing mass over volume of the sample. The volume of solid particles was calcu lated by subtracting volume of the water from total volume of volumetric flask (Hummel, 1993). Particle density for each sub-sample of TOC is listed in table 2-4. Pa rticle density was not correlated with TOC (r=-0.56, P=0.117)) In comparison, Dr. G.H. Snyder (personal communication) has found particle density values of about 2.55 g cm-3 for sand soils on different golf courses in Broward County. Calculation of porosity for e ach tee was performed using particle density assumed as 2.55 g cm-3 and particle density determined from the soil samples (Table 2-4). However, the porosity means values were the same; on the no-traffic slopes of the tees 50.9% vs. 50.8% respectively; and on the traffic slopes 50.1% vs. 49.6% respectively. Statistical Analysis Data were analyzed by ANOVA us ing SAS software (SAS Institute, Cary NC). However, GLM (general linear model) was used for the co mbined analysis of three golf courses in order partition variation and degrees of freedom within golf course s versus among golf courses.

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29 Results and Discussion Goosegrass Infestation Goosegrass infestation, measured as goosegrass plants and cover, was higher (P<0.05) on the traffic sides of the tee slopes (Table 25). For example, goosegra ss cover was 1.86% on the traffic side, compared with 0.82% on the no-traf fic side. When each golf course was analyzed separately there was no effect of traffic except percent goosegra ss cover at Pine Island Ridge Golf Course was higher (P=0.043) on the traffic side (Fig. 2-2). Preemergence herbicides were not used in Arrowhead Golf Course which may have caused the higher g oosegrass infestation in both sides of the tees slopes compared with Pine Island Ridge and Orangebrook. Penetration Resistance and Soil Moisture Soil Penetration Resistance (SPR) showed an eff ect of traffic at the shallow depth (P<0.05) but not for all depths (Table 2-5). The coefficien t of variation for SPR at the shallow depth was 18%, and 25% for SPR average at all depth. These values were similar to values obtained by OSullivan and Ball (1982), 18 to 50%, dependi ng on the numbers of SPR measurements. The values of penetration re sistance (SPR) for all the depths m easured did not reach the limit value cited by Lipiec and Hatano (2003) of 3 MPa at whic h penetration resistance becomes critical for root growth. When the analysis was done by location, onl y Arrowhead Golf Course showed a highly significant effect of traf fic (P<0.01) for shallow depths (Fig. 2-2) and all depths. At shallow depth, SPR for the traffic side of Arrowhead wa s approximately 30% higher than SPR at the notraffic side, 775.5 KPa vs. 597.3 KPa, respectivel y. These results agree with results from Vazquez et al. (1991) who found a 30% increase in SPR in the upper 20 cm of the soil on traffic sites compared to no-traffic sites.

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30 The high SPR values at Arrowhead could have been caused by the high numbers of rounds of golf per year compared with the other two golf courses; also, this golf course has never been renovated. High SPR values can be e xplained by differences in text ure, bulk density, and organic matter (Campbell and OSullivan, 1991; Perumpral, 1987). As an example, Orangebrook Golf course had the highest SPR with the higher grav imetric water content which could have been explained by the 10% of silt and 4% of clay in the root zone mix. There was no difference in gravimetric water content between traffic and no-traffic slopes of the tees. There was a difference (P<0.01) be tween the upper and lower depths explained by the higher content in total organi c carbon in the upper de pth allowing the soil to hold more water. The variability of gravimetric water was high with coefficients of variation between 38 to 56 % for upper depth and lower depth respectively. The aim of measuring water content was to corre ct penetration resistan ce by water content. However, this was not accomplished because there was no correlation (P>0.05) between gravimetric water content and penetration resi stance for any of the depth (Fig. 2-3). Many researchers (Ayers and Perumpral, 1982; Perump ral, 1987; Ley and Laryea, 1994) have found an inverse relationship between pene tration resistance and water cont ent for various mixtures of sand and clay. The low correlation (r= -0.155, P= 0.413) and lack of significance between SPR values and gravimetric water content at the shallo w depth may be related to other factors such as particle size distribution. In all the three golf courses the sand frac tion analysis showed that tees have high percentage of very coarse sand and fine gravel (from 29.5 to 43.2%) while low percentage of coarse sand and medium sand (from 40.2 to 33.1%) Results from Warnaars and Eavis (1972) indicated that in fi ner sands grades, penetration resi stance decreases with increasing moisture content; however, in coarse sands it was relatively unaffected by moisture.

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31 However, our results are similar to Ehlers et al. (1983) where the rate of change of soil penetration resistance with water conten t was less at low bulk density (1.3 g cm-3) than at high bulk density (1.5 g cm-3). At high moisture content, bulk density had minimal effect on penetration resistance. In our study the average bulk density was 1.24 g cm-3 (Table 2-6) with a range from 1.42 to 0.88 g cm-3 and the gravimetric soil moisture content was more than 0.25g g-1 in the upper depth. Similar results were obtained by Smith et al. (1997) where for a range of bulk densities, only small differences in SPR occurre d at water contents approaching field capacity and wetter. In a loamy sand soil, only small di fferences in strength development were noted across a wide range of water contents. This can be primarily related to the contribution of frictional rather than cohesion forces to SPR. One of the difficulties in the study was to co llect the SPR with similar soil moisture contents for all the golf courses. The goal was to collect soil moisture samples and penetrations resistance when the soil was at field capacity or after 24 hours irrigation or rain trying to avoid big differences in soil water conten t. However, it was difficult to achieve this because of changes in irrigation schedules or weather conditions that could not be avoided such as rain. Soil Properties Soil properties measured included bulk densit y, capillary porosity, hydraulic conductivity, and TOC while total porosity and air-filled porosity were calculated. There was no effect of traffic on any soil parameter. Table 2-6 shows mean for each treatment and p-values for these parameters. Most of the values of bulk dens ity were low for sandy soils, which could be explained by the high organic matter content in th e upper depth of these tees. Total porosity was within ranges of what USGA recommends. However, capillary porosity is higher than what the USGA recommends while air-filled poros ity is lower (Table 2-6, Table 2-1).

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32 Hydraulic conductivity was highly variable within treatments. The mean values of each treatment were lower than what USGA consider s the acceptable range of saturated conductivity of 15 to 30 cm hr-1 (Table 2-1). However, these values fo r hydraulic conductivity are in the range to the geometric mean values for soils classifi ed according to USDA soil texture classes 18.19 to 9.14 cm hr-1 for sandy soil and 14.13 to 10 cm hr-1 for fine sandy soil (Rawls et al., 1998). These results reflect the large spatial variability of hydraulic conductivit y measured in the field, which has encouraged scientists to develop models to estimate satu rated hydraulic conductivity from other easily measured soil physical properties such as particle size dist ribution, bulk density, and particle shape (Sperry and Peirce, 1995; Jabro, 1992). Total organic carbon content showed no differen ce between traffic and no-traffic areas of the tees. There was a difference between th e upper depth, 2.30 and 2.07 and the lower depth, 1.70 and 1.64, respectively (P<0.05). Roots were pr esent in the upper surface. Bellow the 7.5 cm, most of the time in the pure sand, no roots were present. Correlation between Parameters Goosegrass cover and plant density were not correlated with any soil property or penetration resistance at differe nt depths. Correlation coeffici ents among soil properties and penetration resistance are presen ted in Table 2-7. The following in terpretations are based on the sign, magnitude, and significance of the respect ive coefficients. The table shows correlation among independent variables where the variables have been measured directly (bulk density, capillary porosity, gravimetric water conten t, hydraulic conductivity, TOC, and SPR). There are two main empirical behaviors in so il properties responses that were expected. First, bulk density was associated with capilla ry porosity, soil gravimetric water content and TOC (P<0.001); and capillary poros ity was associated with soil gravimetric water content and TOC (P<0.001). Higher bulk densit y resulted in decreased capillary porosity and gravimetric

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33 water content. This was expected as increasing in bulk density decreases pore space, which may decrease gravimetric water content. Also, an inverse relationship should be expected between bulk density and TOC since organic matter will al so increase pore space in the soil (Brady and Weil, 2002; McCoy, 1998). Second, capillary porosity shows slightly significant inverse relation with hydraulic conductivity and SPR (P<0.05). Ev en though hydraulic conduc tivity and capillary porosity were not different between traffic and no-traffic sides of the tees; a negative relationship existed between these two parameters, which should be expected. Because saturated hydraulic conductivity is the measure of a soils ability to transmit wate r under saturated conditions, and air-filled porosity is responsible for the saturated movement of the water in the soil, an increase in capillary porosity will be associated with reduced hydr aulic conductivity of the soil (Henderson et al., 2005; Brady and Weil, 2002). Conclusions This research provides information on goosegra ss infestation and its relationship with soil properties measured in traffic a nd no-traffic areas in three diffe rent golf courses. Goosegrass plant density and cover were highe r on traffic areas. Due to the high soil moisture content, at the time when SPR were taken, and being coarse sa ndy soils, the study did no t detect correlation between soil water content and SPR as described by other researchers. The combined analysis that included all three golf c ourses showed higher values of SPR on the traffic areas at the shallow depth. However, this result was driven for the significant differen ces present in one of the golf course for all the depths. Soil bulk density values did not show significant differences between treatments; nevertheless SPR may have been more sensitive in detecting soil compaction than bulk density in the case of that golf course in particular. This study provides preliminary data in the use of penetrometr in situ done in a turfgrass situation to determine compaction levels in th e field which may no be useful in sandy soils.

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34 However, penetrometer measurement will be more useful if done in controlled environmental situation with controlling soil moisture content. The results from the study show that goosegrass infestation was higher on the traffic slopes, whic h validates the first hypothesis. However, soil compaction was not encountered for most of th e traffic areas, which invalidates the second hypothesis that soil compaction o ccurs in traffic areas. Conseque ntly soil compaction is not the mechanism that explains goosegrass infestation.

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35 Table 2-1. United States Golf A ssociation specifications for physic al properties of root zone mixes for golf greens. Characteristic Acceptable Range 15 25% 15 30% Capillary porosity (at 40 cm tension) Air-filled porosity (at 40 cm tension) Total porosity 35 55% Saturated hydraulic c onductivity 15-30 cm h-1 USGA, 2004. Table 2-2. Management practices on tee slopes on each golf course. Golf course Practice Arrowhead Orangebrook Pine Island Ridge Mowing height 3.81cm 3.18cm 5.08cm Nitrogen fertilization rate 48 Kg ha-1 48 Kg ha-1 48 Kg ha-1 Fertilization frequency ten times/yr four times/yr six times/yr Irrigation, winter 5 d/wk 15 min cycle 3 times/wk to 1/8 inch water applied 25 min every 3 days as needed Irrigation, summer every other day 10 min cycle 3 times/wk to 1/8 inch water applied 35 min every day until rainy season starts Weed control Postemergence herbicides Preemergence and spot spray with postemergence herbicide Preemergence and spot spray with postemergence herbicide Overseed on slope No Yes, perennial ryegrass No

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36Table 2-3. Variables measured and numbers of samples per each tee slope and in the three golf courses. Variables Goosegrass plants and cover Soil penetration resistance Gravimetric water content Saturated hydraulic conductivity, capillarity porosity, and bulk density Total organic carbon Particle density Treatments No.quadrats No.Readings Upper depth No-traffic 15 20 40 4 2 1 Traffic 15 20 40 4 2 1 Total number sample/tee x five tees x three golf courses 450 600 1200 120 60 30 Gravimetric water content and total organic carbon we re also measured at lower depth (7.6 to 12.5 cm) Readings from 2.5 to 12.5 cm depth Upper depth= 1.5 to 7.5 cm depth

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37 Table 2-4. Particle density values for the di fferent classes of total organic carbon (TOC) encountered in the three golf courses. Class interval Soil samples Mean TOC Particle density (% TOC) (Number) (%) (g cm-3) 0.80-1.10 4 0.96 2.53 1.11-1.70 3 1.44 2.47 1.71-1.90 6 1.80 2.50 1.91-2.05 3 2.00 2.46 2.06-2.10 3 2.08 2.55 2.11-2.60 1 2.26 2.44 2.61-2.80 3 2.75 2.48 2.81-3.10 3 3.06 2.46 3.11-3.80 4 3.68 2.44 Total samples=30 Average= 2.48

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38 Table 2-5. Goosegrass plants and cover, gr avimetric water content, a nd soil penetration resistance (SPR) and ANOVA table. Mean s of 30 observations. Goosegrass Gravimetric water SPR Plants Cover Upper Shallow All depths Number % g g-1 KPa No-traffic 0.40 0.82 0.28 683.04 1003.51 Traffic 0.92 1.86 0.26 788.23 1121.07 Statistical analysis Source of variation df Mean squares Location 2 3.90* 15.39* 163.53NS 49372.73 NS 33873.80NS Error a (tees within locations) 12 0.602.41165.40 21224.73 46818.45 Traffic 1 2.03* 8.09* 36.64NS 82996.14 103651.94NS Traffic and Location 2 0.40 1.08 39.28NS 11251.68NS 33211.23NS Error b (tees x traffic) 12 0.28 1.00 57.26 19095.43 77611.33 Significant at P=0.05 or NS, not significant. F-test from analysis of variance. Water content measured from 1.5 to 7.5 cm depth. Shallow depth is the average value for SPR measured at 2.5 and 5 cm depth Number of plants per 0.25 m2

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39 Table 2-6. Means of soil parameters measured on the tee slopes on the uppe r depth. Means of 30 observations. Soil properties Bulk density Capillary porosity Air-filled porosity Total porosity Saturated conductivity Total organic carbon g cm-3 % cm h-1 % No-traffic 1.22 40.75 10.10 50.81 12.78 2.07 Traffic 1.24 40.52 9.11 49.63 11.36 2.30 Significance (P) 0.68 0.16 0.90 0.51 0.66 0.48 P is the probability level of significan ce from F-test analysis of variance. Table 2-7. Correlation coefficients (r) among soil properties and soil penetration resistance (SPR). Means of 30 observations. Capillary porosity Gravimetric Water content Hydraulic conductivity Total organic carbon SPR shallow Bulk density -0.906 *** -0.828*** 0.255-0.759*** 0.349 Capillary porosity 0.719*** -0.450* 0.647*** -0.426* Gravimetric water content -0.3340.805*** -0.154 Hydraulic conductivity -0.279 0.341 Total organic carbon -0.035 Soil penetration resistance (SPR) Shallow depth is the average value for SPR measured at 2.5 and 5 cm depth *, **, *** Significant at the 0.05, 0.01 and 0.001 level respectively

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40 Figure 2-1. Undisturbed soil core sample used to determine bul k density, saturated hydraulic conductivity, and capillary porosity.

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41 Figure 2-2. Goosegrass canopy cover and soil pene tration resistance at sh allow depth at three golf courses.* Significant differences be tween treatments at P<0.05 and ns, no significant differences between treatment.

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42 Figure 2-3. Gravimetric water content and soil penetration resistance at the shallow depth (average 2.5 and 5 cm) for all three golf courses. (n=600)

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43 CHAPTER 3 GOOSEGRASS INFESTATION AND SOIL PE NETRATION RESISTANCE IN TRAFFIC AND NO-TRAFFIC AREAS IN SOFTBALL AND BASEBALL FIELDS Introduction The purpose of this study was to test the second hypothesis again, th at high-traffic areas show higher goosegrass infestation associated with higher soil compaction levels. However, this study was set up in baseball and softball sport fields with different charac teristics than in the prior golf course study, but both games having in common small areas with high traffic from the players. Baseball and softball ar e the only major sports that are played on fields that have both turf and exposed soil for a playing surface and about 66% of the game is played on the infield, or skinned" areas (Miller, 2001). Th e skinned area is the exposed so il portion of the field where defensive players are standing. In this area, condi tioners are mixed into th e soil to soak up extra water during wet conditions, retain water on dr y conditions, and minimize compaction (Puhalla et al., 1999). The infield, where the four bases ar e, is the area enclosed by the foul lines and it has the pitchers mound as the highest point in the field. The pitchers mound and batters box are recommended to be built on clay-based soils to withstand weather and continuous excavation by pitchers (Puhalla et al., 1999). Baseball is a game made up of two teams. The team at bat is known as the offensive team, and its objective is to have its batters become base runners an d its runners to advance touching all bases. When this is done, a run is scored. Th e team in the fixed positions in the field is known as the defensive team, and its objective is to prevent offensive players from becoming base runners and advancing around the bases. When th ree offensive players are legally put out, the teams change from the offensive to the defensive and from defensive to offensive. The objective of each team is to score more runs than its opponents (National Collegiate Athletic Association, 2005). The dugout is where a team's bench is lo cated. There are two dugouts, one for the home

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44 team and one for the visitor team, located in fr ont of the first and third bases, respectively. Players go from the dugout to home plate to begi n playing. Since bases are numbered counterclockwise from the first base, home pl ate is also the final base a play er must touch to score. From the dugout, players will go to the home plate most of the time in a concentrated path with some traffic on the rest of the field due to players coming back from the bases or outfield to the dugout. The foul area, where traffic was clearly defined between home pl ate and dugout, was the area of this study. The objective of this second study was to compare goosegrass infestation and soil penetration resistance between tra ffic and no-traffic areas on a sport field. Materials and Methods The study was conducted on three baseball/softball fi elds at Sunset Park located in the City of Plantation, Broward County, Florid a. Fields number 2, 3 (softball fields) and 6 (baseball field) were chosen for the study due to the pres ence of goosegrass infestation in the foul areas between the dugouts to the foul lines (Fig. 3-1). On each field, the area of study began at 4.3 m from home plate along a direction parallel to the foul line, and 1.5 m from the foul line into the foul area. From this initial point a rectangle 30 m l ong and 9 m wide was marked and gridded at 3x3 m. The same area, between the dugouts to the foul line was marked on both sides of the field (home and visitor) sides which we re called plot 1 and 2. Figure 3-2 shows the arrangement of the grids on one of the fields which was the same for all. To define the traffic area a line was drawn from the dugout gate to the home plate, and all the cells within 1 me ter of either side of the line were marked as the traffic area (10), and the rest of the cells were defined as notraffic (20).

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45 Goosegrass Infestation Within each cell (3x3 meters) a sub cell (1x1 me ter) was randomly selected to determine goosegrass cover and the number of plants present. Therefore, there were 30 points measured per plot. Observations were determined on 17 July 2006. Penetration Resistance and Soil Moisture For each sub cell, one soil penetration resistan ce (SPR) reading was taken within the center of the sub cell along with soil core samples to determine grav imetric soil water content (Table 31). Soil cores were collected adjacent to the SPR measurements. The penetrometer used was a Field Scout SC-900 (Spectrum Tec hnologies, Plainfield, IL); the same device used in the study on the golf courses. Due to presen ce of stones, SPR measurements were collected only to 7.5 cm depth. At each of the 30 points, SPR measuremen ts were recorded at 2.5, 5.0, and 7.5 cm depths. Soil penetration resistance values were reporte d as an average of the 2.5, 5, and 7.5 cm depths. Soil cores (1.5 to 7.5 cm) were collected to meas ure soil moisture status. Each soil penetration resistance value corresponded w ith a soil core for water cont ent. Soil water content was determined by gravimetric analysis done by wei ghing soil samples before and after drying and expressed as a percent of the oven dry weight of the soil (Gar dner, 1986). Fifteen to twenty grams of soil was dried to a constant weight at 105 C, at which time a final weight was measured. Soil penetration measurements and wate r content samples were collected on the same day. The fields were sampled on 17 and 18 July 2006. Statistical Analysis The experimental design was a randomized comp lete block with 6 replications (2 foul areas x 3 fields) and one treatment factor, traffi c vs. no-traffic. Data were analyzed by ANOVA and correlations among variables were determined using SAS software (SAS Institute, Cary NC).

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46 Results and Discussion Goosegrass Infestation Number of goosegrass plants and cover diffe red (P<0.05) between traffic and no-traffic areas and varied differently (P<0.001) among fi elds. Traffic areas showed more cover and numbers of goosegrass plants with low coefficien ts of variance (21 to 26%, respectively). Penetration Resistance and Soil Moisture The gravimetric water content as well as so il penetration resistance showed no difference between traffic and no-traffic gr ids. However, gravimetric wa ter showed differences (P<0.05, Table 3-2) among fields while SPR did not. The co efficient of variation for gravimetric water was lower (6%) than the coefficient of variati on measured for the tee slopes (38%) in the previous study, while the coefficient of variation for SPR was almost the same as the coefficients of variation measured for the t ee slopes (12% vs. 18%, respectiv ely). Because soil gravimetric water content was measured during a period of two days in this study, the coefficient of variation was much lower than on th e tee slopes study sites. Soil penetration resistance values were not correlated (r=-0.268) w ith gravimetric water content (Fig. 3-3). The aim of measuring water co ntent was to correct so il penetration resistance by water content. However, this was not accomplished because there was no significant correlation between gravimetric wa ter content and penetr ation resistance as opposed to most of the articles reviewed (Ayers and Perumpral, 198 2; Ley and Laryea, 1994; Perumpral, 1987). As already discussed in results in chapter 2, these results could be explaine d by the high gravimetric water content in the soil at the moment of coll ection of SPR and the fact it is a sandy soil where 53% of the sand fraction is very coarse sand and fine gravel. When the correlation analysis was done among a ll the variables for a ll the fields (n=180) penetration values at 5 cm dept h were correlated with cover a nd numbers of plants of goosegrass

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47 (P<0.01respectively); ho wever, both correlations were lo w (r=0.24 and r=0.22, respectively). Penetration values at 7.5 cm de pth were correlated only with go ssegrass cover (P<0.01) with a similar coefficient of correlation (r=0.20). Goosegrass canopy cover and plants number wa s higher on the baseball and softball fields than in the golf course tees (Fig. 3-4). However, the penetration resistance was very similar for both studies. Therefore, we can conclude that soil compaction did not determine goosegrass infestation. On the baseball and softball fields bare ground was more ofte n seen in the traffic path, while it did not happened most of the tim e in the traffic slopes of golf course tees. The larger presence of bare ground might determine th e larger infestation of goosegrass. In addition, large mature goosegrass plants (fro m the prior year) were more ofte n seen on the ball fields than on the golf course tees, probably due to a less intense management on theses sites. Conclusions Goosegrass plant density and cover was higher on the traffic sides, which validate the first hypothesis again. However, high soil compacti on was not found on the traffic area, which invalidates the second hypothesis of this research. Wear and tear of the turfgrass may explain goosegrass infestation in high-tra ffic areas, but it is not explai ned by the occurrence of higher soil compaction which goosegrass may tolerate.

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48 Table 3-1. Variable measured a nd numbers of samples per experi mental unit in the three ball fields. Treatments Goosegrass plants and cover Soil penetration resistance Water content No. quadrats No. readings No. soil cores No-traffic 10 10 10 Traffic 20 20 20 Total n= sample /block x 2 block/field x 3 fields 180 180 180

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49Table 3-2. Goosegrass plants and cover, gr avimetric water content, and soil penetration resistance and ANOVA table. Means of 1 2 observations. Goosegrass Cover Plants Gravimetric water Soil penetration resistance % number/m2 g g-1 KPa No-traffic 4.57 7.37 0.32 811.78 Traffic 7.58 11.46 0.30 848.60 Statistical analysis Source of variation df Mean squares Block 5 86.36 *** 140.41*** 19.97* 17166.39NS Traffic 1 27.11 50.32* 10.19NS 4066.40NS Error 5 2.45 3.92 3.74 9215.47 *, **, ***, and NS; Significant at the P<0.05, P<0.01, P<0.001, and not si gnificant at P<0.05. F-test fr om analysis of variance

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50 Figure 3-1. Overview of the fields with the st udy areas (2 plots) marked in each of them

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51 Figure 3-2. Baseball field number six with the sampling grid. White cells indicate the traffic area which is marked with the black line from home plate to dugout.

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52 Figure 3-3. Soil penetration resist ance values versus gravimetric water content for the three ball fields. (n=180).

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53 Figure 3-4. Goosegrass canopy cove r and penetration resistance by traffic treatment and field study.

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54 CHAPTER 4 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION (GLASSHOUSE STUDY) Introduction Changes to the soil physical properties due to compaction were ev aluated on three golf courses and results are described in Chapter 2. In this chapter the focus is on the effect of soil compaction on goosegrass and bermudagr ass root and shoot growth. Common responses of a crop root system to in creasing compaction are decreased root size, retarded root penetration and smaller rooting de pth (Glinski and Lipiec, 1990). These are mostly due to excessive mechanical impedance and insufficient aeration depending on soil wetness (Lipiec and Hkansson, 2000). Turfgrass gr own in a compacted soil is subject to both stresses. Carrow and Petrovic (1992) discussed whether mech anical impedance or aeration decreases root growth. They suggested that soil aeration is the primary influen ce on root growth at moderate compaction, while at heavy compaction both mechan ical impedance and aeration are important. When the compacted zone is present at sha llow depth, soil strength that prevents root penetration or reduces root el ongation rates may reduce plant deve lopment and yields if water uptake by the plants depends only on precip itation (Unger and Kaspar 1994). Mechanical impedance decreases the rate of root elonga tion, which is often accompanied by thickening (radial expansion) of the root axes (Bengough and Mullins, 1990; Atwell, 1992). Both elongation rate and the degree of thickening of the root depend on particular ex perimental conditions (Atwell, 1992). Total root volume and mass are not necessarily reduced by soil strength because the shorter root axes are of ten proportionately thicker. Studies on the effect of compaction on warm-s eason grasses have been limited. In a study on the responses of three cool-season grasse s to compaction, Carrow (1980) reported that compaction decreased visual quality with tall fescue ( Festuca arundinacea Schreb.) the most,

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55 while perennial ryegrass ( Lolium perenne L.) was the least influenced ; shoot density and verdure decreased the most in Kentucky bluegrass ( Poa pratensis L.), while tall fescue and perennial ryegrass were not affected. Root weight was re duced in Kentucky bluegrass and tall fescue but increased in perennial ryegrass. ONeil and Ca rrow (1983) reported that compaction reduced visual quality and clipping yield of perennial ry egrass, affected root di stribution after 12 weeks but did not reduce root weights. However, another study conducted by Sills and Carrow (1983) using the same species (perennial ryegrass) at di fferent levels of nitrogen fertilization showed that compaction decreased visual quality and cli ppings but did not affect verdure. Root weight was decreased by compaction and a greater decreas e occurred in the higher nitrogen rate. In a similar study, Agnew and Carrow (1985) reported th at shoot growth of Kentucky bluegrass is affected by soil compaction by reducing clippings yield, visual quality and verdure. Also, compaction reduced root growth at lower depths while rooting increased in the 0-5 cm depth range. However, total root growth did not decline, which the author s attributed to an increase in surface roots due to ethylene-promoted adventitious roots (Atwell, 1992). No studies have been conducted on the sepa rate effects of wear and compaction on bermudagrass, since traffic studies include these two effects jointly. Dunn et al. (1994) observed that the combination of spring and fall traffic wa s too intensive for bermudagrass in mixture with cool-season grasses. Kentucky bl uegrass and perennial ryegrass dominated the mixtures with bermudagrass after 3 years, and showed good tolera nce to simulated traffi c. Carrow et al. (2001) evaluated turf coverage of seven seashore paspalum ( Paspalum vaginatum Swartz.) ecotypes and three bermudagrasses ecotypes to simulated traffic at near soil saturation and at field capacity. Grasses with the greatest traffic stress toleran ce in terms of turf cove rage, regardless of soil moisture, were Tifway and TifSport berm udagrasses and Temple 1 seashore paspalum.

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56 These results have been explained by different wear tolerances mechanisms for each species (Trenholm et al., 2000). This research will co ntribute to improving our understanding of goosegrass and bermudagrass growth under compacted soils without the in fluence of wear. The objective for this experiment was to test the la st hypothesis of this st udy that soil compaction decreases bermudagrass growth more than goosegra ss growth. The aim of the experiment was to determine the effect of controlled levels of soil compaction on shoot and root growth of goosegrass and bermudagra ss growing separately. Materials and Methods Two glasshouse experiments were conducte d from 26 May to 19 Sept. 2005 at the University of Florida, Fort Lauderdale Resear ch and Education Center Davie, Florida. A factorial experiment was utilized to evaluate the growth of goosegrass and bermudagrass grown under different levels of soil compaction. The same experiment was done in two runs. There were four replicates and five replicates for the first and second runs of the experiment, respectively. The experiment was set up in PVC pipe cyli nder pots. Pots had 0.8 cm wall thickness and an inside diameter of 19.5 cm. They were cut to 22.8 cm lengths, and were joined with a cement solvent to a 0.635 cm thick PVC square sheet (2 5.4 by 25.4 cm) used as the bottom of the pot. Fifty holes, 0.635 cm diameter, were drilled in the sheet. A vector-virus mesh, 0.24 mm thread size, was placed at the bottom of each pot to prevent soil from migrating out of the pot. Pots were filled with Margate fine sand (s iliceous, hyperthermic Mo llic Psammaquent), a native soil at the Fort Lauderdal e Research and Education Center The surface of an undisturbed area was cleared of grass and roots and the firs t 8 cm (horizon A) of soil was dug out from the site. The soil was sieved through an ASTM no.1 0 (American Society fo r Testing Materials) sieve, which allows passing particle sizes less th an 2 mm in diameter. So il was dried at 60 C for

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57 24 hours to get consistent water co ntent in the soil, and then mixe d with water to an estimated 0.25 g g-1 of water content. Soil and water were mixed in an electrical soil mixer in batches large enough to fill eight pots at one time. From each batch of soil, two samples were collected and oven dried to determine water content. The pe rcentage of water varied from 0.25 to 0.27 g g-1. Total organic carbon (TOC) was analyzed from a co mposite sample from the soil used in both runs. Total organic carbon was determined by us ing the Nelson and Sommers (1996) procedure. In the first run the soil contained on averag e 4.19 % TOC while in the second run the soil contained 7.80 % TOC. A PVC ring 7.5 cm high was joined with a clam p to the top of each pot before compaction. Then, the pot was filled with so il already mixed with the water to the top of the ring. Because soil after compaction subsided 3 to 6 cm, the ring permitted adding more soil into the pot as compaction reduced the level, and still getting th e same level of soil for all pots. Soil was compacted by dropping a 13.5 Kg weight from a he ight of 42.0 cm onto a piece of wood cut to fit the inside of the pot, before planting gra sses. A special device wa s built to achieve the different compaction levels. The device consisted of 4 rods, 12 mm diameter and 155 cm height which held a base and a secondary platform 38 cm from the base. The pot wa s placed at the base where the compaction was applied. A solid shaft wa s attached in the center of the secondary platform, and a tube, which rode over the center shaft held the weight that went up and down hitting the piece of wood cut to co mpress the soil (Figure 4-1). Treatments were low compaction (3 drops), medium compaction (10 drops), and high compaction (42 drops). Initially a zero compac tion treatment was incl uded but later removed from the experiment because there was diffi cult establishing bermudagrass stolon in this treatment. Some of the bermudagrass stolons dr ied and died in some of the no compacted pots

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58 probably because of an insufficient contact betw een soil and roots. The high pore content of the soil did not retain enough water near the roots. After dropping the weights on each pot according to each treatment, pots were weighed and volum e was calculated to determine bulk density. To calculate bulk density, the height of soil and weight in each po t was measured after they had been compacted. The volume occupied by soil on each pot was calculated using the following equation: Volume pot = x r2 x h Eq.1 4 where = 3.1416 r = inside radius of the pot h = height of the soil in the pot Then, wet soil weight in each pot was calcula ted by subtracting the weight of the empty pot from the total weight of the pot plus the we t soil. The dry soil in ea ch pot was calculated by multiplying the wet soil weight by the percentage of water content. The percent of water content was estimated by a sample per each batch of so il mixed. Finally, bulk density was determined according to Eq. 4.2. Db= dry soil estimated per each pot/ volume of soil in each pot Eq. 2 4 where Db= bulk density of the soil (g cm-3). The number of drops resulted in slightly diffe rent bulk density values for each pot. Values were averaged per treatment. The average valu es of bulk density for the first run were 1.19, 1.29, and 1.37 g cm-3 for the low, medium, and high compacti on treatments respectively, with eight observations per treatment. In the second run, th e average values of bulk density were 1.08, 1.18, and 1.28 g cm-3 for the low, medium and high levels of soil compaction respectively. The average for the two runs was 1.14, 1.24, and 1.33 g cm-3 for low, medium, and high treatment respectively.

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59 Goosegrass plants were germinated in the gr eenhouse, and transplanted to the already compacted pots. Six seedlings of goosegrass with 2 to 3 leaves per each seedling were placed in each pot. Tifway sod was used to obtain bermudagra ss stolons. Four stolons were placed in each pot. To accommodate roots of both plants, small hol es were made on the pot with a tooth pick where roots were placed. In the first run, two replicates were plante d on 26 May 2005, and the other two replicates on June 1. After 8 days, all pots were fertilized with a soluble 36-6-6 (N-P2O5-K2O) fertilizer at nitrogen rate of 144 Kg ha-1, and a second fertilization at nitrogen rate of 48 Kg ha-1 was done 30 days from the date of planting. In the sec ond run, all pots were pl anted on 8 August 2005, and then fertilized two times as the first run at 8 and 30 days from the date of planting. Before harvest, each pot with goosegrass was thinned to three plants per pot in the first run, and four plants per pot in the second run. All pots were watered regularly not allowing them to wilt. Plants were harvested 14 July 2005, in the first run and 19 Sept. 2005, in the second run. Shoot (included leaves and stol ons) and root growth was calculated as dry weight of washed samples harvested 43 days from the day of planting for both runs. Aboveground plant portions were separated from roots; dried at 60 C for 24 hours, and weighed to de termine shoot and root growth. Roots were washed and passed through a se ries of sieves to remove as much soil as possible before placing in bags for drying in the oven. Statistical Analysis Data were analyzed by ANOVA to determine treatment differences at 0.05 significance level and means were separated with Fishers LSD, and regression of goosegrass dry weight and compaction were determined using SAS software (SAS Institute, Cary NC).

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60 Results and Discussion Bulk density values obtained from each leve l of soil compaction in the second run were lower than those values obtained in the first run. The coefficients of variation of the bulk density were low and the same (4, 4, and 3%) for each of the compaction treatments low, medium, and high, in first and second run respectively. In both r uns, soils were sampled from the same area at the Fort Lauderdale Research and Education Ce nter; however, the TOC content differed between the two soils. In the second run the soil had 8% TOC compared to 4 % TOC level in the soil of the first run. The TOC differences are consistent with the differences in bulk density achieved. Root and shoot growth response to compacti on differed between the two species. In the first run (Table 4-1), there was a significant block effect for r oots (P<0.01) and shoots (P<0.001) of goosegrass, which were higher in the last two replicates planted. In both the first and second runs (Table 4-2), goosegrass root dry weight was decreased by compaction. In the two runs, goosegrass root dry weight was decreased 53% (first run) and 26% (second run), under high compaction compared with low compaction (P <0.05). In the high compaction pots, most goosegrass roots were distributed around the wall of the pot wh ere the compaction probably was least. Root distribution was not measured; however it was observed that roots were abundant in the upper surface of the pots and fewer roots were seen in the lower depth for both high and medium compaction pots (Figure 4-2). These resu lts are similar to results obtained for Agnew and Carrow (1985) and ONeil a nd Carrow (1983) where Kentuc ky bluegrass and perennial ryegrass roots were distributed on the first 5 cm of the soil. However, total root growth did not decline, which the authors attributed to an in crease in surface roots due to ethylene-promoted adventitious roots. In the pres ent study, compaction reduced tota l root growth, which coincides with results obtained by Sills and Carrow (1983) in perennial ryegrass roots. Therefore, higher

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61 mechanical impedance in the surface of the soil c ould impede root growth rate and result in fewer roots in the lower soil zones. Goosegrass shoot dry weight was decreased (P <0.01; Table 4-1) by co mpaction only in the first run; goosegrass shoot dry weight was decreased 23% under high compaction, compared with low compaction. The detrimental effect on goosegrass shoot and root growth observed the first run may be partially explained by the hi gh bulk density level reached in the pots. For bermudagrass, no differences were obser ved in root and s hoot growth due to compaction treatments; however, there was a tr end for reduced bermudagrass root and shoot growth in both runs at higher compaction (Table 4-1 and 4-2). No studi es have been conducted on the effect of soil compaction on bermudagrass si nce traffic studies have included also wear effects. Dunn et al. (1994) obs erved that the combination of spring and fall traffic was too intensive for bermudagrass in mixture with cool season grasses. But these results do not apply to the present study, since this study was done durin g the summer, the main growing season for bermudagrass. Another study by Carrow et al. (2001) evaluated traffi c effects on different grasses and cultivars. Grasses with the best traffic stress tolera nce in terms of turf coverage regardless of soil moisture conditions were Ti fway and TifSport bermudagrasses and Temple 1 Seashore paspalum. From these results one can in fer that some bermudagrass cultivars can be tolerant to traffic situat ions; however, the degree of soil compaction is not known. Regression analysis relating goosegrass growth and compacti on was significant for root growth (P<0.01), but not for shoot growth in the fi rst run. The analysis showed that an increase in compaction predicted a decrease in goosegrass roots according to the regression formula Y= 7.89 1.73X where Y was the predicted goosegrass root dry weight and X was the level of compaction. Compaction explained 74% of the va riability observed on root growths. The

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62 regression analysis relating goosegrass root a nd compaction, in the second run, was also significant (P<0.05; Y= 17.5 2.02X), and comp action explained 63% of the variability observed on root growths. However, the coefficient of variation in the second run was lower than the coefficient of variation of the first run, 16 % and 36%, respectively. Conclusions Goosegrass root growth was significantly decreased by compaction, while shoot growth was reduced only in the first r un possibly due to the higher bulk density values. As already explained in the introduction, if soil compaction is associated with low soil oxygen, goosegrass will tolerate this condition and we should not exp ect a decrease in root growth. Root growth was decreased at the highest level of compaction; however, since oxygen diffusion rate was not measured in the pots, it was unknown if mechani cal impedance and/or soil oxygen deficiency was affecting goosegrass root growth. Even though bermudagrass establishment was slow and highly variable, root and shoot dry weight were not affected by compaction in this study. Theref ore, the hypothesis that soil compaction decreases bermudagrass growth mo re than goosegrass growth has not been demonstrated. However, bermudagrass stolons ma y not have had enough time to develop and be affected by compaction. It is worth noting th at both species were not mowed during the experiment, and there was no competition effect as the two species were separated in different pots, possibly affecting results.

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63 Table 4-1. Dry weight of bermudagrass and goosegrass r oots and shoots at different soil compaction levels in the first run when both species were growing separately. Bermudagrass Goosegrass Compaction level Roots Shoots Roots Shoots g/pot Low 0.98 7.07 6.13a 21.39a Medium 0.65 6.03 4.11b 19.96a High 0.68 5.14 2.89b 16.40b Statistical analysis Source of variation df Mean squares Blocks 1 0.05 NS 9.76NS 26.79** 1011.64*** Compaction level 2 0.13 NS 3.75NS 10.71* 26.39** Error mean square 8 0.28 11.46 1.28 2.02 Means of two replicates for each of two planting dates analyzed as blocks. Means followed with the same letter within the same column are not different according to LSD test (P<0.05). *, **, ***, NS; Significant at P<0.05; P<0.01; P<0.001; not si gnificant at P<0.05. Table 4-2. Dry weight of bermudagrass and goosegrass r oots and shoots at different soil compaction levels in the second run when both species were growing separately. Bermudagrass Goosegrass Compaction level Roots Shoots Roots Shoots g/pot Low 0.48 3.16 15.66a 42.59 Medium 0.32 2.08 13.16ab 41.09 High 0.21 1.70 11.62b 41.79 Statistical analysis Source of variation df Mean squares df Mean squares Compaction 2 0.07 NS 2.12NS 220.84* 2.81NS Error mean square 9 0.06 2.25 124.92 44.12 Means of five replicates, not blocked, for each treatment except there were three missing values for bermudagrass. Means followed with the same le tter within the same column are not different according to LSD test (P<0.05). *, **, ***, NS; Significant at P<0.05; P<0.01; P<0.001; not si gnificant at P<0.05.

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64 Figure 4-1. Device used to pr oduce compaction in the pots.

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65 Figure 4-2. Goosegrass roots growing in pot of medium compaction treatment (Db= 1.29 gcm-3) indicate the property for the roots to remain shallow.

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66 CHAPTER 5 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION, FERTILIZATION, AND CANOPY REMOVAL (GLASSHOUSE STUDY) Introduction Goosegrass control relies on the use of pre and post-emergen ce herbicides and there is little documentation on cultural management practices to prevent gooseg rass infestation. Preemergence herbicides are effective if applied pr ior to weed seed germin ation since they lose effectiveness when applied too early or after the weeds have emerged (McCarty and Murphy, 1994). The most important environmental factors governing weed emergence are soil temperature and soil moisture. A study done by Masi n et al. (2005) evaluating the use of a model to predict goosegrass emergence showed th at goosegrass emergence predictions were underestimated and delayed because of higher base temperatures in which goosegrass germinates in the field. Additionally, the effect of soil co mpaction on the germinati on and establishment of goosegrass seeds has not been evaluated. Adequate seed-soil contact is a prerequisite for rapid emergence as it provides a route through which soil water can enter a seed. Seed-soil contact is depe ndent on soil conditions such as texture, aggregate size dist ribution, and level of compaction. Brown et al. (1996) attempted to model the seed-soil contact areas using rigid spheres representing seeds, and spheres of modeling clay, that were used to form artificial aggreg ates. Results showed that as compression reduced macroporosity, the area of contact on all faces of the artificial seeds increased. The investigation suggested that minimal reduction in macroporosity to produce a given degr ee of seed-soil contact can be achieved when seed and soil aggregates ar e of closely similar size. However, reduction in aggregate size during rolling could lead to aerati on problems at low matric potentials (Brown et al., 1996).

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67 The physical properties of a seedbed have a ma jor influence on emergence and early root growth. Germination and shoot a nd root growth are affected by temperature and matric potential and do not occur below or above critical temperat ures or below a critical matric potential (Nabi et al., 2001). Seed germination commences after a period of imbibition, during which the seed takes up sufficient water to initiate growth. G oosegrass does not germinate if water potential is less than -1.21 MPa (Masin et al., 2005). Ismail et al. (2002) f ound that goosegrass germination is inhibited by a water potential of -0.80MPa. High soil strength reduces the rate of shoot and root growth, delaying and sometimes preventing emergence. Nasr and Selles (1995) report ed that at every level of bulk density (0.9 to 1.7 gcm-3) the resistance to penetration of the se edbed was higher in coarse than in fineaggregated seedbeds due to c ohesion and friction within aggreg ates is higher than among aggregates. In the Nasr and Selles (1995) study, in creases in bulk density and aggregate size of the seedbed delayed emergence and reduced the number of seedlings of wheat ( Triticum aestivum L. c.v. Lancer) that emerged. Although the es timates of speed or rate of emergence were highly correlated with indicators of the phys ical conditions of the seedbed, final emergence appeared not to be affected by bulk density a nd aggregate size (Nasr and Selles, 1995). The results suggested that when seed-soil contact is adequate, the physical conditions of the seedbed affect primarily the speed and time at which s eedlings emerge from the soil, and the final emergence is affected not only by physical conditi ons of the seedbed, but also by other factors, probably related to seed si ze and other seed characteris tics (Nasr and Selles, 1995). The objective of this experiment was to te st the third hypothesis that soil compaction decreases bermudagrass growth more than gooseg rass growth when both species were growing together. Along with testing soil compaction effect on bermudagrass and goosegrass growth,

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68 fertilization and mowing treatments were adde d to the experiment. The purpose of the low mowing height treatment was to simulate canopy removal produced by wear on a field situation. The objectives of this study were: 1) To determine whether compaction, canopy removal, and fertilization influence goosegrass emergence when it was interp lanted into a bermudagrass stand. 2) To evaluate whether compaction, canopy rem oval, and fertilization influence shoot and root growth of goosegrass and bermudagrass growing together. Materials and Methods A glasshouse study was conducted from 14 Feb. to 9 Sept. 2006 at the University of Florida, Fort Lauderdale Research and Education Center, Davie, Florida. The experiment was set up in the same cylinder PVC pipe pots as in th e prior glasshouse experiment using the same native soil (Margate fine sand). Two levels of soil compaction, low bulk density (3 drops, 1.07 gcm-3) and high bulk density (42 drops, 1.26 gcm-3), done in the same way as the prior experiment, were randomly assigned to pots Tifway bermudagrass stolons were plante d in the pots on 14 and 15 Feb. 2006 and pots were placed in the greenhouse. Information about the management of the pots is given in Table 5-1. Turf was mowed by a hand-held, battery-pow ered grass shear at the specified height described in Table 5-1. Clippings were harves ted, dried at 60C for 24 hours, and weighed on three dates before goosegrass seeds were added to the pots. Pots were assigned to different blocks depending on their total bermudagrass dry matter per pot. There was no difference between low and high compaction treatments in the total clippings collected in three mowing episodes. On 19 June 2006, four month from the date of bermudagrass planting, when bermudagrass stand had covered the surface of the pots, mowing height and fertilization treatments were

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69 assigned to the pots. Treatments factors were 2.54 and 1.27 cm mowing height, corresponding to high and low mowing respectively; and 96 and 48 Kg ha-1 nitrogen fertilization rate to correspond to high and low rate respectively. Both treatments factors were assigned randomly to pots. Goosegrass was seeded in all pots (app roximately 600 seeds per pot). After June 19 clippings were not collected because both spec ies were growing together. The mowing height treatments were done weekly and the fertilization rate s treatments were done monthly. The last mowing was done on August 23 and after 14 days without mowing harvest of the pots began. Bermudagrass grew in the pots for 203 to 206 days from the time stolons were transplanted, and goosegra ss plants grew between 70 to 76 days from the time seeds were planted to the moment of harvest. All pots were watered regularly not allowing them to wilt. During two weeks, after goosegrass seeds were placed in the pots, pots were watered every day to assure a period of imbibition of the seeds. Plant emergence of goosegrass was determined by counting the number of seedlings in each pot, 10, 11, 14, 16, 18, 21, 24, and 29 days from the date seeds were seeded in the pots. On day 36, most of the pots had six seedlings of gooseg rass; however, since a few did not reach this number on day 43 (1 August 2006) all the pots we re thinned to five seedlings. In addition, numbers of seedlings of goosegra ss that had tillers were counted per pot before harvesting. At harvest, pots were cut with a circular saw to make it easier to get soil and plants from the pot. Bermudagrass and goosegrass plants were separated, and shoots, including leaves and stolons, were separated from roots; both were dried at 60 C for 24 hours, and weighed to determine root and shoot growth. Roots were wash ed and passed through a series of sieves to remove as much soil as possible before placing in bags for the oven. Root and shoot dry weight was registered by treatment and species.

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70 Statistical Analysis Experimental design was a randomized complete block with four replications. Data was analyzed by ANOVA using SAS software to de termine treatment diff erences at the 0.05 significance level (SAS Institute, Cary NC). Results and Discussion Goosegrass emergence was highly different fo r mowing height and compaction treatments (Table 5-2). In the high mowing treatment goos egrass emergence was reduced 58% compared with the lower mowing, probably due to a decrea se in light exposure on the seed. Additionally, in the high compaction treatment goosegrass emer gence was reduced 41% compared to the low compaction (Table 5-2). Nasr and Selles (1995) suggest ed that when seed-soil contact is adequate, the physical conditions of the seedbed affect primarily the sp eed and time at which seedlings emerge from the soil and the final emergence with time is not infl uenced by physical conditions of the soil at the moment of planting. Probably, in this study the lower final emergence on the high compaction treatment was due to a poor seed-soil contact. Numbers of tillers per seedli ng of goosegrass differed only for mowing treatments (Table 5-2). The low mowing height treatments had a large number of seedlings with tillers (50%), compared with the high mowing treatments ( 16.5 %). The interception of light reaching the crown of the gossegrass seedlings as a result of light interception by the leaves of the bermudagrass probably reduced tilleri ng. This result implies that in a golf course or sports field mowing low could enhance goosegrass tille ring and consequently shoot density. No differences were found in goosegrass shoot and root mass for any of the treatments. In the present study goosegrass root growth was not affected by soil compaction, whereas in the prior glasshouse experiment they were highly decreased by compaction. In the present study,

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71 even when plants were growing in the pots for 76 to 70 days, a longer pe riod than in the prior experiment, they were smaller probably becau se they were mowed every week, and were affected by bermudagrass competition. In the prev ious glasshouse study, goosegrass plants were grown in the pot for 43 days without restri cted by mowing or bermudagrass competition. Bermudagrass root mass was reduced by hi gh compaction and low mowing treatments respectively (P<0.01; Table 5-2). Since root distribution was not observed in this study, it is unknown at which depth root growth was more a ffected. Knowing root di stribution could have helped understand which factors mechanical impeda nce at shallower depth or root dieback at deeper depth (Agnew and Carrow, 1985; Carrow, 1980) could have explained the results observed. Research has shown that reducing mowi ng height results in de creasing root growth (Turgeon, 2005; Duble, 1989). Root mass decreased the most in the lo w fertilization and low mowing treatment; therefore, higher fertilization could alleviate so me of the root growth reduction caused by low mowing. In addition, root mass was enhanced when the soil was not compacted and bermudagrass was mowed high (Fig.5-1); therefore, high mowing treatment may not alleviate the effect of high compaction in bermudagrass roots growth. Greater bermudagrass shoot mass was observe d for high fertiliza tion (P<0.05) and high mowing treatment (P<0.001; Table 5-2). After mo wing, the rate of growth (leaf and tiller production) in turfgrass is depe ndent on the levels of carbohydrat es in the leaves, stem, and crown of the tiller. Therefore, th e rate of regrowth after mowing is greater when carbohydrates are high. Consequently high mowing height treatments, which had a greater residual leaf area, had a faster rate of regrowth in the conditions of this study (Duble, 1989). However, the mowing treatments in this study (12.7 and 25.4 mm) we re higher than mowing heights recommended for

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72 bermudagrass tees (6.4 to 13 mm), while nitr ogen fertilization ra tes (48 to 96 Kg ha-1) were near the range (25 to 60 Kg ha-1) recommended per month (Beard, 2002). Bermudagrass shoot dry weight decreased the most in high compaction a nd low fertilization treatments; therefore, higher fertilization may alleviate the effect of soil compaction on bermudagrass shoots. Conclusions Goosegrass seedling emergence and number of tillers were increased by lower mowing. In this study, bermudagrass was more affected than goosegrass, which agreed with what was stated in the hypothesis. Bermudagrass shoot mass was increased with high fe rtilization and mowing, and root mass was decreased by high compaction and low mowing. Even when bermudagrass roots were decreased at higher co mpaction it neither reflects a decr ease in the shoot mass nor an increase in goosegrass growth. Consequently mowing, a principal cultural pr actice could have more significance on the emergence and infestation of goosegrass in bermudagrass than comp action. In addition, fertilization may alleviate soil compaction e ffects on bermudagrass shoots growth, and may alleviate low mowing effects on berm udagrass root growth. Results ob tained in this research may vary in a field situation, but it creates new thoughts on the need to evaluate the discussed cultural practices in the cont rol of goosegrass.

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73Table 5-1. Management of the pots from establishment to harvest when both species were growing together. Operation Date Details Bermudagrass sprigged 14 and 15 February 4 stolons/pot Before treatments: Nitrogen Fertilization 6 March 48 Kg ha-1 13, 20 March, 27 April 144 Kg ha-1 4 May and 9 June 48 Kg ha-1 3 and 24 May 3.81 cm height Mowing 13 June 2.54 cm height After treatments: Goosegrass seed planted 19 June 600 goosegrass seeds/pot Goosegrass thinned 1 August 5 seedlings/pot Mowing 19 June; weekly 1.27 and 2.54 cm height Nitrogen Fertilization 19 June; monthly 96 and 48 Kg ha-1 Watering Three times per week As required 22 March Abamectin to control aphids (Homoptera) 9 June Abamectin to control mites (Acari) Insecticides 11 and 19 July Acephate to control mealybug (Homoptera ) Harvest 6 to 9 September Root and shoot separated by species

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74Table 5-2. Goosegrass emergence and tillers root and shoot dry weight of goosegrass and bermudagrass by treatments and ANOVA table. Means of 16 observations. Goosegrass Bermudagrass Treatments Levels Emergence Tillers Roots Shoots Roots Shoots (seedlings/pot) (no./ plants) (g/pot) Low 87 1.19 0.310.96 5.68 13.88 Compaction (C) High 51 1.62 0.331.15 4.26 12.92 Low 65 1.50 0.310.96 4.71 12.86 Fertilization (F) High 74 1.31 0.331.15 5.24 13.93 Low 98 2.00 0.311.09 4.46 11.22 Mowing (M) High 41 0.81 0.331.02 5.48 15.58 Statistical analysis Source of variation df Mean squares Block 3 6770.13 0.091.11 4.53 4.32 Compaction 1 10368** 0.06 0.000.28 16.03** 7.27 Fertilization 1 5780.01 0.000.29 2.26 9.13* Mowing 1 26450*** 0.45* 0.000.03 8.37** 151.51*** C x F 1 280.00 0.010.06 2.70 9.39* C x M 1 20800.00 0.020.29 8.56** 0.01 F x M 1 1900.01 0.000.01 8.39** 0.08 Error 22 9670.06 0.020.39 0.91 1.74 CV (%) 44.7093.60 49.2059.40 19.20 9.86 Surface area of the pot: 298.6 cm2. *, **, *** significant at P<0.05; P< 0.01; and P<0.001, respectively.

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75 Figure 5-1. Bermudagrass root dr y weight for compaction and mo wing treatments combinations. Means of eight replications.

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76 CONCLUSIONS This research studied the e ffect of traffic on goosegrass in festation and soil compaction, and the growth of bermudagras and goosegrass pl anted in compacted soil. Goosegrass cover and plant density were higher on traffic areas of ball fields and golf course tees than on adjacent notraffic areas. Therefore, the first hypothesis wa s accepted that goosegrass infestation was greater on traffic areas. However, traffic areas had no impact on soil penetrati on resistance or bulk density values. In addition, other soil properties measured related to soil compaction were not affected by traffic. Although in one out of se veral instances there wa s increased penetration resistance associated with tra ffic the hypothesis was rejected th at soil compaction was higher on traffic areas compared to non-traffi c areas in golf courses and sports fields. In addition, the soil penetration resistance values did not reach the limit value at which penetration resistance becomes critical for root growth. Soil compaction affected both goosegrass and bermudagrass root gr owth. In the first glasshouse experiment, goosegrass root grow th decrease with so il compaction while bermudagrass was not affected. However, in the second glasshouse experiment, the opposite result occurred. Bermudagrass root growth d ecreased with soil compaction while goosegrass was not affected. Therefore, the third hypothesis was accepted that both species were affected by compaction. Low mowing increased the germination and ti llering of goosegrass. Therefore, cultural practices such as mowing, fer tilization, and irrigation that pr omote vigorous, dense turf and improve turfgrass wear tolerance should be cautiously planned to prevent goosegrass establishment.

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77 Further research is required to verify the mechanisms that impart wear tolerance to goosegrass. Knowledge of these characteristics will assist in developing cultural practices that favor turfgrass more than goosegrass growth.

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78 LIST OF REFERENCES Agnew, M.L. and R.N. Carrow. 1985. Soil compac tion and moisture stress preconditioning in Kentucky Bluegrass. I. Soil aeration, water use, and root resp onses. Agron. J. 77:872878. Atwell, B.J. 1992. Response of roots to mechan ical impedance. Environ. Exp. Bot. 33:27-40. Ayers, P.D. and J.V. Perumpral. 1982. Moisture and density effect on cone index. Trans. ASAE 25:1169-1172. Baerson, S.R., D.J. Rodriguez, M. Tran, Y. Feng, N.A. Biest, and G.M. Dill. 2002. Glyphosateresistant goosegrass: Identification of a mutation in the target enzyme 5enolpyruvylshikimate-3-phosphate synt hase. Plant Physiol. 129:1265-1275. Beard, J.B. 2002. Turf management for golf cour ses. 2nd ed. United States Golf Association. Ann Arbor Press, Chelsea, Michigan. Bengough, A.G. and C.E. Mullins. 1990. Mechanical impedance to root growth: A review of experimental techniques a nd root growth responses. J. Soil Sci. 14:341-358. Blake, G.R. and K.H. Hartge. 1986. Bulk density. p. 363-375. In A. Klute (ed.) Methods of soil analysis. Part 1. Physical and mineralogi cal methods. 2nd ed. Agron. Monogr. 9 ASA and SSSA, Madison, WI. Bradford, J.M.1980. Penetration resistance in a soil with well defined structural units. Soil Sci. Soc. Am. J. 44:601-606. Brady, N.C. and R.R Weil. 2002. The nature and pr operties of soils. 13th ed. Pearson Education, Singapore, India. Brown, A.D., A.R. Dexter, W.C.T. Chamen, a nd G. Spoor. 1996. Effect of soil macroporosity and aggregate size on seed-soil contact. Soil Tillage Res. 38:203-216. Brown, L. 1979. Grasses: An identificati on guide. Houghton Mifflin Company. Boston. Busey, P. 2001. Goosegrass most difficult weed in South Florida. Fla. Turf Digest 18:24-27. Busey, P. 2003. Cultural management of weeds in turfgrass: A review. Crop Sci. 43:1899-1911. Busey, P. 2004a. Goosegrass ( Eleusine indica ) control with foramsulfuron in bermudagrass ( Cynodon spp.). Weed Technol. 18:634-640. Busey, P. 2004b. Managing goosegrass1.Preventi on. Golf Course Manage. 72 (1):199-202. Busey, P. and B.J. Myers. 1979. Growth rates of turfgrasses propagated vegetatively. Agron. J. 71:817-821. Campbell, D.J. and M.F. OSullivan. 1991. The cone penetrometer in relation to trafficability, compaction, and tillage. p. 399-429. In K.A. Smith and C.E. Mullins (ed.) Soil analysis: Physical methods, 1st ed. Marcel Dekker, New York. Carrow, R.N. 1980. Influence of soil compacti on on three turfgrass sp ecies. Agron. J. 72:10381042.

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79 Carrow, R.N., R.R. Duncan, J.E. Worley, a nd R.C. Shearman. 2001. Turfgrass traffic (soil compaction plus wear) simulator: Response of Paspalum vaginatum and Cynodon spp. Int. Turfgrass Soc. Res. J. 9:253-258. Carrow, R.N. and A.M. Petrovic. 1992. Effects of traffic on turfgrasses. p. 285-330. In D.V. Waddington et al. (ed.) Turfgrass. Agr on. Mongr. 32. ASA, CSSA, and SSSA, Madison, WI. Duble, R. 1989. Southern turfgr asses: Their management and use. TexScape, Inc. College Station, TX. Dunn, J.H., D.D. Minner, B.F. Fresenburg, a nd S.S. Bughrara. 1994. Bermudagrass and coolseason turfgrass mixtures: Response to simulated traffic. Agron. J. 86:10-16. Ehlers, W., U. Kpke, F. Hesse, and W. Bhm. 1 983. Penetration resistance and root growth of oats in tilled and untilled loess soil. Soil Tillage Res. 3:261-275. Gardner, W.H. 1986. Water content. p. 493-544 In A. Klute (ed.) Methods of soil analysis. Part 1. Physical and minerological methods 2nd ed. Agron. Monogr. 9 ASA and SSSA, Madison, WI. Glinski, J. and J. Lipiec. 1990. Soil physical c onditions and plant roots. CRP Press, Inc. Boca Raton, FL. Hawton, D. and D.S. Drennan. 1980. Studies on th e longevity and germination of seed of Eleusine indica and Crotalaria goreensis Weed Res. 20:217-223. Henderson, J.J., J.R. Crum, T.F. Wolff, and J.N. Rogers. 2005. Effects of particle size distribution and water content at compacti on on saturated hydraul ic conductivity and strength of high sand content root zone materials. Soil Sci. 170:315-324. Hummel, N.W., Jr. 1993. Laboratory methods for evaluation of putti ng green root zones mixes. USGA Green Section Record March/April. p. 23-27. Ismail, B.S., T.S. Chuah, S. Salmajah, Y.T. Teng, and R.W. Schumacher. 2002. Germination and seedling emergence of glyphosate-resistan t and susceptible biotypes of goosegrass (Eleusine indica [L.] Gaertn.) Weed Biol. Manag. 2:177-185. Jabro, J.D. 1992.Estimation of saturated hydrau lic conductivity of soils from particle-size distribution and bulk density data. Trans. ASAE 35:557-560. Johnson, B.J. 1980. Goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ) turf. Weed Sci. 28:378-381. Johnson, B.J. 1993. Sequential herbicide treatments for large crabgrass ( Digitaria sanguinalis ) and goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ) turf. Weed Technol. 7:674-680. Johnson, B.J. 1996. Reduced rates of preemergence and postemergence herbicides for large crabgrass ( Digitaria sanguinalis ) and goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ). Weed Sci. 44:585-590. Johnson, B.J. 1997. Reduced herbicid e rates for large crabgrass ( Digitaria sanguinalis ) and goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ). Weed Sci. 45:283-287.

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80 Ley, G.J. and K.B. Laryea. 1994. Spatial variability in penetration resistance of a hardsetting tropical alfisol. Soil Tillage Res. 29:367-381. Lipiec, J. and I. Hkansson. 2000. Influences of degree of compactness and matric tension on some important plant growth fact ors. Soil Tillage Res. 53:87-94. Lipiec, J. and R. Hatano. 2003. Quantification of compaction effects on soil physical properties and crop growth. Geoderma 116:107-136. Masin, R., M.C. Zuin, D.W. Archer, and G. Za nin. 2005. WeedTurf: A predictive model to aid control of annual summer weeds in turf. Weed Sci. 53:193-201. McCarty, L.B. 1991. Goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ) turf with diclofop. Weed Sci. 39:255-261. McCarty, L.B. and T.R. Murphy. 1994. C ontrol of turfgrass weeds. p. 209-244. In A.J. Turgeon (ed.) Turf weeds and their contro l. ASA and CSSA, Madison, WI. McCoy, E.L. 1998. Sand and organic amendment influe nces on soil physical properties related to turf establishment. Agron. J. 90:411-419. Miller, G.L. 2001. Baseball field layout and construction. Florida Cooperative Extension Service, Institute of Food and Agricultura l Sciences, University of Florida ENH159 series. [Online]. Available at edis.ifas.ufl.edu/pdffiles/EP/EP09200.pdf (verified 10 Oct. 2006). University of Florida, IFAS Extension, Gainesville, Florida. Miller, G.L. and J.L. Cisar. 2005. Maintaining at hletic fields. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida Bull. 262 [Online]. Available at edis.ifas.ufl.edu/LH065 (verified 10 Oct. 2006). University of Florida, IFAS Extension, Gainesville, Florida. Miller, R.E., J. Hazard, and S. Howes. 2001. Precisi on, accuracy, and efficiency of four tools for measuring soil bulk density or strength. USDA Forest Service, Pacific Northwest Research Station. 16p. Murdoch, C.L. and D. Ikeda. 1974. Goosegrass cont rol in bermudagrass turf with combinations of MSMA and s -triazines. Agron. J. 66:712-714. Murdoch, C.L. and R.K. Nishimoto. 1982. Dicl ofop for goosegrass control in bermudagrass putting greens. HortScience 17:914-915. Nabi, G., C.E. Mullins, M.B. Montemayor, a nd M.S. Akhtar. 2001. Germination and emergence of irrigated cotton in Pakistan in relation to sowing depth and physical properties of the seedbed. Soil Tillage Res. 59:33-44. Nasr, H.M. and F. Selles. 1995. Seedling emerge nce as influenced by aggregate size, bulk density, and penetration resistance of the seedbed. Soil Tillage Res. 34:61-76 National Collegiate Athletic Association. 2005. Baseball 2006: Rules and interpretations. [Online] Available at www.ncaa.org/library/rules/2006/2006_baseball_rules.pdf (verified 10 October 2006). NCAA, Indianapolis, IN. Nelson, D.W. and L.E. Sommers. 1996. Total Carbon, Organic Carbon, a nd Organic Matter. p 961-1010 In D.L. Sparks (ed.) Methods of soil an alysis, Part 3. Chem ical methods. SSSA Book Ser. 5. SSSA and ASA, Madison, WI.

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81 Nishimoto, R.K. and C.L. Murdoch. 1999. Mature goosegrass ( Eleusine indica ) control in bermudagrass ( Cynodon dactylon ) turf with a metribuzin-d iclofop combination. Weed Technol. 13:169-171. Nishimoto, R.K. and L.B. McCarty. 1997. Fluctu ating temperature and light influence seed germination of goosegrass ( Eleusine indica ). Weed Sci. 45:426-429. ONeil, K.J. and R.N. Carrow. 1983. Perennial ryegrass growth, water use, and soil aeration status under soil compaction. Agron. J. 75:177-180. OSullivan, M.F. and B.C. Ball. 1982. A comparison of the five instruments for measuring soil strength in cultivated and uncultivated cereal seedbeds. J. Soil Sci. 33:597-608. OSullivan, M.F., J.W. Dickson, and D.J. Camp bell. 1987. Interpretation and presentation of cone resistance data in tillage and traffic studies. J. Soil Sci. 38:137-148. Pendleton, R.F., H.D. Dollar, L. Law, Jr., S.H. McCollum, and D. J. Belz. 1984. Soil Survey of Broward County: Eastern Part. Florid a. USDA-Soil Conservation Service. Perumpral, J.V. 1987. Cone penetrometer app lication: A review. Trans. ASAE 30:939-944. Puhalla, J., J. Krans, and M. Goatley. 1999. Spor t fields: A manual for design, construction and maintenance. John Wiley & Sons, Inc., New Jersey. Randrup, T.B. and J.M. Lichter. 2001. Measur ing soil compaction on construction sites: A review of surface nuclear gauges and pe netrometers. J. Arboric. 27(3):109-114. Rao, V.S. 2000. Principles of weed science. 2nd ed. Science Publishers, Inc. Enfield, NH. Rawls, W.J., D. Gimenez, and R. Grossman. 1998. Use of soil texture, bul k density, and slope of the water retention curve to predict satu rated hydraulic conduc tivity. Trans. ASAE 41:983-988. Sartain, J.B. and G.L. Miller. 2002. Recommendati ons for N, P, K and Mg for golf course and athletic field fertilization based on Mehlich I extractant [Online] Available at edis.ifas.ufl.edu/pdffiles/SS/SS40400.pdf (verified 10 Oct 2006). Soil and Water Science Department, Florida Cooperative Extension Se rvice, Institute of Food and Agricultural Sciences, University of Florida. Sills, M.J. and R.N. Carrow. 1983. Turfgrass grow th, N use, and water use under soil compaction and N fertilization. Agron. J. 75:488-492. Smith, C.W., M.A. Johnston, and S. Lorentz. 1997. The effect of so il compaction and soil physical properties on the mechanical resi stance of South African forestry soils. Geoderma 78:93-111. Sperry, J.M. and J.J. Peirce. 1995. A model for estimating the hydraulic conductivity of granular material based on grain shape, grain size, and porosity. Ground Water 33:892-898. Stitt, R.E., D.K. Cassel, S.B. Weed, and L. A. Nelson. 1982. Mechanical impedance of tillage pans in Atlantic coastal pl ains soil and relati onship with soil physical, chemical, and mineralogical properties. SSSA J. 46:100-106. Trenholm, L.E., R.N. Carrow, and R.R. Dun can. 2000. Mechanisms of wear tolerance in seashore paspalum and bermudagrass. Crop Sci. 40:1350-1357.

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82 Turgeon, A.J. 2005. Turfgrass management. 7th ed. Pearson Prentice Hall, Upper Saddle River, NJ. Unger, P.W. and T.C. Kaspar. 1994. Soil compac tion and Root growth: A review. Agron. J. 86:759-766. USEPA-Office of Prevention, Pesticides and Toxic Substances. 2006. Revised reregistration eligibility decision for MSMA, DSMA, CAMA, and cacodylic acid [Online] Available at www.epa.gov/oppsrrd1/REDs/organic_arsenicals_red.pdf (accessed 10 Aug. 2006; verified 9 Oct. 2006). USEPA-OPPTS, Washington, DC. United States Golf Association. 2003. The rules of golf and the rules of amateur status. USGA, Far Hills, NJ. United States Golf Association. 2004. Reco mmendations for a method of putting green construction [Online] Available at www.usga.org/turf/cours e_construction/green_ articles/USGA_Recommendations_For_a_M ethod_of_Putting_Gree n_ Construction.pdf (verified 10 Oct 2006). USGA, Far Hills, NJ. Vazquez, L., D.L. Myhre, E.A. Hanlon, and R. N. Gallaher. 1991. Soil pe netrometer resistance and bulk density relationships after long term no tillage. Commun. Soil Sci. Plant Anal. 22(19-20):2101-2117. Waddington, D.V. 1992. Soils, soil mixt ures, and soil amendments. p. 331-383. In D.V. Waddington et al. (ed) Turfgrass. Agron. ser. 32. ASA, CSSA, and SSSA, Madison, WI. Waddington, D.V. and J.H. Baker. 1965. Influenc e of aeration on grass species. Agron. J. 57:253-258. Warnaars, B.C. and B.W. Eavis. 1972. Soil physical conditions affecting seedling root growth. II mechanical impedance, aeration and moisture av ailability as influenced by grain-size distribution and moisture content in silica sands. Plant Soil 36:623-634. Watschke, T.L. and R.E. Engel. 1994. Ecology of turfgrass weeds. p. 29-36. In A.J. Turgeon (ed.). Turfgrass Weeds and Their Co ntrol. ASA and CSSA, Madison, WI

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83 BIOGRAPHICAL SKETCH Claudia B. Arrieta was born in 1966 in a sma ll city Durazno in Uruguay. She grew up in a cattle and sheep operation and she ro de her horse every day to a one room rural school where she completed her elementary school years. She fini shed high school in Durazno, and in 1985 she moved to the country ca pital Montevideo to join the F aculty of Agriculture. In 1992, after receiving her bachelors degree Ingeniero Agronomo she became an Agronomy Extension Agent advising dairy farmers for 4 years. In 1997, she married and moved to the United States where her husband was working. She finished an Asso ciate in Science in Wetland Management at Broward Community College with the objective of broadening her job expectations. She worked on different horticultural nurseries for two y ears until in 2004 she learned about the Fort Lauderdale Research and Education Center in Davie and the possibility of doing a masters degree as a distance education student. She join ed the University of Florida in 2004 and will graduate with a Master of Science degree in the Soil and Water Science Department in 2006. Upon graduation she would like to continue using her knowledge and skills in turfgrass and soil science as a research assistant at e ither a public or private institution.


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Title: Soil Compaction and Goosegrass Infestation in Bermudagrass Turf
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Copyright Date: 2008

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Title: Soil Compaction and Goosegrass Infestation in Bermudagrass Turf
Physical Description: Mixed Material
Copyright Date: 2008

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Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
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Table of Contents
    Title Page
        Page 1
        Page 2
    Dedication
        Page 3
    Acknowledgement
        Page 4
    Table of Contents
        Page 5
        Page 6
    List of Tables
        Page 7
    List of Figures
        Page 8
    Abstract
        Page 9
        Page 10
    Introduction
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
    Goosegrass infestation and soil properties in traffic and no-traffic areas in golf courses
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
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    Goosegrass infestation and soil penetration resistance in traffic and no-traffic areas in softball and baseball fields
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    Goosegrass and bermudagrass root and shoot growth evaluated at different degrees of soil compaction
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    Goosegrass and bermudagrass root and shoot growth evaluated at different degrees of soil compaction, fertilization, and canopy removal
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    Conclusions
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    References
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    Biographical sketch
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Full Text






SOIL COMPACTION AND GOOSEGRASS INFESTATION IN BERMUDAGRASS TURF


By

CLAUDIA B. ARRIETA














A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2006

































Copyright 2006

by

Claudia B. Arrieta



































To my parents.









ACKNOWLEDGMENTS

I would like to give my sincere thank to my supervisory committee members: Dr. Philip

Busey, for trusting in me and giving me the opportunity and his support to achieve this study; Dr.

Samira Daroub, for her guidance and assistance during the course of my graduate work; Dr.

Sabine Grunwald, for her advice and support; and Dr. Grady Miller, for his input and opinions.

I would also like to thank faculty and staff of the Fort Lauderdale Research and Education

Center who lent me equipment and space during the different steps on my project. I want to

express my gratitude to Diane Johnson who assisted me in getting organized at the beginning of

the study; and Dr. George Snyder and Irena Ognevich who helped me do the soil analysis.

In addition, I want to say thank to Robert Klitz, general manager at Orangebrook Golf

Country Club; Juan Perez, superintendent at Arrowhead Golf Club; and Angela Simmons,

superintendent at Pine Island Ridge Country Club where some of the data for the study were

collected. Also, I want to say thank you to Michael Brutto, the park foreman at Plantation Sunset

Park, who allowed me collect data on three of the fields. Finally, I am deeply grateful to my

husband Ruben, my daughter Lia, and my sister Laura for their help, love, and encouragement.









TABLE OF CONTENTS



A C K N O W L E D G M E N T S ..............................................................................................................4

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

LIST OF FIGURES ............................................. .. .......... ...........................8

A B S T R A C T .................................................................................................................... ......... .. 9

CHAPTER

1 INTRODUCTION .................................. .. ........... ............................. 11

B e rm u d ag ra ss ................................................................................................................. 12
G o o seg rass ............................................... ....................................................... ....... .. 12
H erbicides and G oosegrass C control ........................................................... ............... 13
Cultural M anagem ent of G oosegrass ......................................................... ................ 14
S o il C o m p action n ................ .... ................................................................................ 17
Soil Physical Properties and Penetrom eters ............................................... ................ 19
O bj ectiv es ........................................................................................................ ........ .. 2 0

2 GOOSEGRASS INFESTATION AND SOIL PROPERTIES IN TRAFFIC AND NO-
TRAFFIC AREAS IN GOLF COURSES .........................................................................22

In tro du ctio n ............................................................................................................ ........ .. 2 2
M materials and M methods .............. .............................................................................. 23
F field S ite s ........................................................................................................ ........ .. 2 3
E xperim mental D design .................................................. ............................................. 24
D ata C o lle ctio n ............................................................................................................... 2 4
Soil Properties A analysis ................................................. .............. ................ 26
S am ple P processing .................................................... ............................................... 2 6
S statistical A n aly sis .......................................................................................................... 2 8
R results and D iscu ssion .................................................... ............................................... 29
G oo segrass Infestation ........................................................... ..................... ................ 2 9
Penetration R resistance and Soil M oisture.................................................. ................ 29
S o il P ro p e rtie s ................................................................................................................ 3 1
Correlation betw een Param eters.................................... ....................... ................ 32
C o n clu sio n s............................................................................................................. ........ .. 3 3

3 GOOSEGRASS INFESTATION AND SOIL PENETRATION RESISTANCE IN
TRAFFIC AND NO-TRAFFIC AREAS IN SOFTBALL AND BASEBALL FIELDS .......43

In tro du ctio n ............................................................................................................. ........ .. 4 3
M materials and M methods .............. .............................................................................. 44
Goosegrass Infestation ...................... ........... .....................................45









Penetration R resistance and Soil M oisture.................................................. ................ 45
S statistical A n aly sis .......................................................................................................... 4 5
R results and D iscu ssion .................................................... ............................................... 46
G oo segrass Infestation ........................................................... ..................... ................ 4 6
Penetration Resistance and Soil Moisture..................................................................46
C o n clu sio n s............................................................................................................. ........ .. 4 7

4 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH
EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION
(G L A S SH O U SE ST U D Y ) .....................................................................................................54

In tro du ctio n ............................................................................................................. ........ .. 54
M materials and M methods .............. .............................................................................. 56
S statistical A n aly sis .......................................................................................................... 5 9
R results and D iscu ssion .................................................... ............................................... 60
C o n clu sio n s............................................................................................................. ........ .. 6 2

5 GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH
EVALUATED AT DIFFERENT DEGREES OF SOIL COMPACTION,
FERTILIZATION, AND CANOPY REMOVAL (GLASSHOUSE STUDY) ......................66

In tro du ctio n ............................................................................................................. ........ .. 6 6
M materials and M methods .............. .............................................................................. 68
S statistical A n aly sis .......................................................................................................... 7 0
R results and D iscu ssion .................................................... ............................................... 70
C o n clu sio n s............................................................................................................. ........ .. 7 2

C O N C L U SIO N S ......................................................................................................... ....... .. 76

L IST O F R EFER EN CE S ............................................................................................. 78

B IO G R A PH IC A L SK E T C H .............. ...................................................................... 83









LIST OF TABLES


Table page

2-1 United States Golf Association specifications for physical properties of root zone
m ix es for g olf green s. ............................................................................................... 3 5

2-2 Management practices on tee slopes on each golf course.............................................35

2-3 Variables measured and numbers of samples per each tee slope and in the three golf
co u rse s............................................................................................................ . ....... .. 3 6

2-4 Particle density values for the different classes of total organic carbon (TOC)
encountered in the three golf courses............................................................ ................ 37

2-5 Goosegrass plants and cover, gravimetric water content, and soil penetration
resistance (SPR) and ANOVA table. Means of 30 observations..................................38

2-6 Means of soil parameters measured on the tee slopes on the upper depth. Means of
3 0 o b serve atio n s. ................................................................................................................ 3 9

2-7 Correlation coefficients (r) among soil properties and soil penetration resistance
(SPR ). M eans of 30 observations........................................ ....................... ................ 39

3-1 Variable measured and numbers of samples per experimental unit in the three ball
fi eld s .............................................................................................................. . ....... .. 4 8

3-2 Goosegrass plants and cover, gravimetric water content, and soil penetration
resistance and ANOVA table. Means of 12 observations.............................................49

4-1 Dry weight of bermudagrass and goosegrass roots and shoots at different soil
compaction levels in the first run when both species were growing separately .............63

4-2 Dry weight of bermudagrass and goosegrass roots and shoots at different soil
compaction levels in the second run when both species were growing separately. ..........63

5-1 Management of the pots from establishment to harvest when both species were
g ro w in g to g eth er ............................................................................................................... 7 3

5-2 Goosegrass emergence and tillers, root and shoot dry weight of goosegrass and
bermudagrass by treatments and ANOVA table. Means of 16 observations .................74









LIST OF FIGURES


Figure page

2-1 Undisturbed soil core sample used to determine bulk density, saturated hydraulic
conductivity, and capillary porosity....................................... ....................... ................ 40

2-2 Goosegrass canopy cover and soil penetration resistance at shallow depth at three golf
courses.* Significant differences between treatments at P<0.05 and ns, no significant
differences betw een treatm ent ................................................................... ................ 41

2-3 Gravimetric water content and soil penetration resistance at the shallow depth (average
2.5 and 5 cm ) for all three golf courses. (n=600) ............................................ ................ 42

3-1 Overview of the fields with the study areas (2 plots) marked in each of them ..................50

3-2 Baseball field number six with the sampling grid. White cells indicate the traffic area
which is marked with the black line from home plate to dugout................................... 51

3-3 Soil penetration resistance values versus gravimetric water content for the three ball
fi eld s. (n= 180).................................................................................................... ....... .. 52

3-4 Goosegrass canopy cover and penetration resistance by traffic treatment and field
stu dy .......................................................................................................... 53

4-1 D evice used to produce com action in the pots............................................ ................ 64

4-2 Goosegrass roots growing in pot of medium compaction treatment (Db= 1.29 gcm-3)
indicate the property for the roots to remain shallow ..................................... ................ 65

5-1 Bermudagrass root dry weight for compaction and mowing treatments combinations.
M eans of eight replications ......................................................................... ................ 75









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

SOIL COMPACTION AND GOOSEGRASS INFESTATION IN BERMUDAGRASS TURF


By

Claudia B. Arrieta

December 2006

Chair: Samira Daroub
Cochair: Philip Busey
Major Department: Soil and Water Science

The weed goosegrass is believed to infest turfgrass compacted by traffic. Objectives were

to determine whether goosegrass (Eleusine indica) infestation in bermudagrass (Cynodon spp.)

turf occurs more in traffic areas and whether soil compaction explains it. Field studies in

bermudagrass golf and softball fields compared goosegrass infestation and soil properties in

adjacent traffic versus no-traffic areas. The golf field study was a randomized complete block

design on three golf courses with 15 blocks each consisting of a tee with two slopes assigned to

either the traffic treatment next to the cart path, or the no-traffic treatment opposite the cart path.

The softball field study was a randomized complete block design on three fields with six blocks

each consisting of a foul area with traffic and no-traffic treatments assigned to quadrats

according to player traffic. Traffic effect was measured as soil penetration resistance and

goosegrass cover and plant density. Water content, hydraulic conductivity, capillarity porosity,

bulk density, and total organic carbon were measured only on golf tees, from undisturbed soil

cores. Two controlled greenhouse studies determined the effect of artificial soil compaction on

growth of bermudagrass and goosegrass. Greenhouse studies used a Margate series soil

(siliceous, hyperthermic Mollic Psammaquent) in rigid cylindrical pots 19.5-cm inside diameter









and 22.8-cm deep. Compaction treatments were created, before planting grasses, by varying

numbers of drops onto the soil surface, from 42.0-cm height, of a 13.5-Kg weight. The first

greenhouse experiment evaluated over 43 days the growth of goosegrass and bermudagrass

growing separately under three levels of soil compaction, low (3 drops, 1.14 g cm-3 bulk

density), medium (10 drops, 1.24 g cm-3), and high (42 drops, 1.33 g cm-3). The second

greenhouse experiment evaluated from 70 to 75 days the growth of goosegrass, and over 203 to

206 days the growth of bermudagrass growing together under two levels of soil compaction, low

(3 drops, 1.07 g cm-3 bulk density) and high (42 drops, 1.26 g cm-3). Other treatment factors were

nitrogen fertilization rate, 288 and 144 Kg ha-1 y1, and mowing height, 25.4 and 12.7 mm.

Goosegrass seedling emergence was also measured. Goosegrass plant density and cover were

larger (P<0.05) on traffic areas of golf tees and softball foul areas, compared with no-traffic

areas. Soil penetration resistance was increased by traffic (P<0.05) at shallow (2.5 to 5.0 cm)

depth on golf tees slopes, but not softball fields. There was no effect of traffic on other soil

properties. While goosegrass infested traffic areas more than no-traffic areas, it was not

associated with soil compaction. In the first greenhouse experiment, bermudagrass biomass

showed no effect of soil compaction, but goosegrass root biomass was decreased (P<0.05) by

increasing soil compaction. In the second greenhouse experiment, goosegrass emergence was

increased (P<0.001) by low mowing height and was decreased (P<0.01) by high soil compaction.

Goosegrass biomass was not affected by any treatment, but bermudagrass root biomass was

reduced (P<0.01) by soil compaction, and shoot and root biomass were reduced (P<0.01 and

0.001, respectively) by low mowing height. Controlled compaction sometimes reduced growth of

either bermudagrass or goosegrass. Low mowing height, which simulated canopy removal

effects of wear, increased goosegrass seedling emergence.









CHAPTER 1
INTRODUCTION

As weeds become established in thin and weak turf areas, the best defense against weeds is

to have a dense vigorous turf (McCarty and Murphy, 1994; Watschke and Engel, 1994).

Competition between any crop and weeds is more intense when they have similar growth habits

and demand similar resources (Rao, 2000). In turfgrass and grass weed competition, for

example, both have their growing points close to the soil surface allowing them to survive close

mowing (Watschke and Engel, 1994).

Goosegrass infestation has been suggested as a consequence of traffic-caused compaction

(Carrow and Petrovic, 1992). This may be consistent with the fact that compaction is associated

with low soil oxygen conditions (Waddington, 1992) which goosegrass tolerates (Waddington

and Baker, 1965). However, there are no data to document the association of goosegrass

infestation and traffic or to verify that traffic-caused compaction is the mechanism and how it

promotes goosegrass occurrence.

Recreational turf areas are exposed to frequent vehicular and foot traffic, which results in

both wear of the turf and soil compaction. Defined by Carrow and Petrovic (1992), wear is the

injury from pressure, scuffing, or tearing directly of the turfgrass tissue. Soil compaction is the

re-arranging of soil particles resulting in a more dense soil mass with less pore space which

reduces root growth, soil aeration, and water infiltration (Brady and Weil, 2002). If traffic-

caused soil compaction is the mechanism to explain goosegrass infestation, then it might operate

by differentially decreasing bermudagrass growth and as a result increasing competition from

goosegrass.









Bermudagrass

Bermudagrass hybrid cultivars have been the predominant turfgrasses in use on golf

courses and athletic fields throughout the southern USA and in warm climates areas worldwide.

Hybrid bermudagrasses (Cynodon dactylon L. Pers. XC. transvaalensis Burtt-Davy and

reciprocal) are both naturally and artificially occurring interspecific hybrids of common

bermudagrass (C. dactylon) and African bermudagrass (C. transvaalensis) (Turgeon, 2005).

While hybrid bermudagrass cultivars provide high quality and dense cover for recreational turf,

they require a regular maintenance program with intense mowing and high levels of fertilizer to

maintain required standards (Beard, 2002). Regular mowing at the proper height, which varies

depending on the use of the field and cultivar used, is necessary to reach acceptable field

conditions (Beard, 2002; Turgeon, 2005). In addition, proper fertilization rates and timing are

essential for wear resistance, quick turf recovery from traffic damage, and aesthetics (Miller and

Cisar, 2005). A range of total nitrogen 230 to 320 Kg ha-1 y-1 and total potassium 140 to 230 Kg

ha-1 y-1 is generally required for bermudagrass maintenance (Miller and Cisar, 2005; Sartain and

Miller, 2002).

Goosegrass

Goosegrass, a summer annual seed-dispersal weed, is a serious problem in bermudagrass

golf and sports turf in warm climates. Goosegrass has a bunch-type (non-creeping) growth habit

where the adventitious roots originate from the basal nodes of the main axis and from the tillers

(Brown, 1979). It is a prolific seed producer with most of the seed germinating in the first year

and little thereafter (Hawton and Drennan, 1980). Since goosegrass seed germination responds to

fluctuating temperatures, greatest emergence of goosegrass occurs on bare ground, in scalped

and thin turf where maximum diurnal fluctuating temperatures would be expected (Nishimoto









and McCarty, 1997). Busey (2004b) defined goosegrass as a "gap colonist" weed because seed

quickly germinate in an open turf canopy due to the presence of divots, insect injury and wear.

Herbicides and Goosegrass Control

Goosegrass control mostly relies on pre- and postemergence herbicides. Preemergence

herbicides kill goosegrass seedlings after they have germinated, but before they have emerged

from the ground. Common goosegrass preemergence herbicides are the chemicals dithiopyr

(trade name, Dimension), metolachlor (Pennant), oxadiazon (Ronstar), oryzalin (Surflan),

pendimethalin (Halts, Pre-M, Pendulum, and Southern Weedgrass Control), prodiamine

(Barricade and RegalKade), and their combinations (Johnson, 1993, 1996, and 1997).

Preemergence herbicide application begins in spring (March in northern temperate areas) and

continues through summer depending on rate of application, the half-life of the herbicide, and

considerations of economics and goosegrass population density (Busey, 2004b). Broadcast

postemergence herbicides kill weed plants after they have germinated. Two disadvantages of

using postemergence herbicides for goosegrass control are that they are not always effective on

mature plants and they may weaken the desired turf (Busey, 2004a). Common postemergence

herbicides are MSMA or monosodium methanearsonate (many brands), diclofop-methyl

(Illoxan), metribuzin (Sencor), and foramsulfuron (Revolver) and their mixtures (Busey, 2004a;

Johnson, 1980; Johnson, 1997; McCarty, 1991; Murdoch and Ikeda, 1974; Murdoch and

Nishimoto, 1982; Nishimoto and Murdoch, 1999).

Monosodium methanearsonate (MSMA), an organic arsenical product, has been used in

warm-season turf largely for goosegrass control. It has been mostly applied on athletic fields,

golf courses and parks. In August, 2006, the Environmental Protection Agency determined that

all uses of MSMA are ineligible for re-registration (USEPA, 2006). Several monitoring studies

in Florida golf course ponds found total annual mean arsenic concentrations at individual ponds









as high as 64 ppb. Additionally, from 2003 to 2005, at least 5% of Florida drinking water

compliance monitoring samples exceeded 3 ppb arsenic. These detections are not proven to be

caused by organic arsenical herbicide use, but they exceed the typical background values of < 2

ppb; therefore, they are likely explained by some kind of anthropogenic input. In addition,

monitoring in shallow wells beneath golf courses detected arsenic in groundwater at 9 of 14

Florida golf courses tested, with detections of up to 120 ppb in shallow wells (<12 ft depth) and

up to 11 ppb in deeper wells (<28 ft depth). This represents exposure that might be expected in

worst case scenarios when maximum labeled rates are applied in the most vulnerable sites.

Although there are uncertainties in the modeling, available monitoring data support the

conclusion that typical use of organic arsenicals may result in drinking water exposure to

inorganic arsenicals that exceed levels of concern (USEPA, 2006). As a consequence of high

arsenic levels associated with sites where MSMA has been applied, alternative herbicides and

cultural practices can be considered worthwhile alternatives to organic arsenical herbicides.

Mechanically removing goosegrass involves hand weeding whereby roots are cut or

removed below the ground to avoid disturbance of the surface appearance. It is impractical on

large turfgrass areas, but it is useful in controlling isolated mature goosegrass plants. Spot

treatment of individual plants of goosegrass, with nonselective postemergence herbicides such as

glyphosate (Roundup) applied in the center of plants, has been shown to be an effective

alternative to broadcast application (Baerson et al., 2002).

Cultural Management of Goosegrass

Cultural management of weeds in turfgrass is poorly documented, and there is no

documentation on cultural management practices to prevent goosegrass infestation (Busey,

2003). Periodic cultural practices that can contribute to control of goosegrass, based on the

comments of turfgrass managers, are the use of fertilization, irrigation, cultivation and traffic









control (Busey, 2004b). Bermudagrass is a relatively rapid growing grass (Busey and Myers,

1979), and its growth responds strongly to increased fertilization. Nitrogen at the rate of 48 Kg

ha-1 per growing month (Sartain and Miller, 2002; Turgeon, 2005) helps regrow turf canopy into

areas damaged by traffic (Busey, 2004b). Since high light intensity is required for germination of

goosegrass, increasing turf density will prevent light from reaching the soil surface (Busey,

2004b; McCarty and Murphy, 1994). Cultivation (core aeration) is used to alleviate compaction.

In addition, wear is decreased by redirecting and/or avoiding traffic in some circumstances, e.g.

after rain. It has been suggested that goosegrass infests trafficked areas, and the reason for that is

still unclear.

Maintaining proper soil moisture through irrigation and soil drainage encourages vigorous

turf growth. Excessive irrigation and poor soil drainage result in low oxygen levels (McCarty

and Murphy, 1994). Also, the effects of irrigation practices in conjunction with soil compaction

can be more detrimental to turfgrass roots. Agnew and Carrow (1985) reported that rates of

oxygen diffusion rate (ODR) fell below 20 x 10- g cm-2 min-1, the critical value of ODR for

common crops such as cotton, sunflower, and corn, for 143 hours on compacted turf, but for only

26 hours on uncompacted turf.

Daily irrigation of turf, especially on golf courses, is need because of the shallow root

system resulting from the necessary close mowing. However, daily irrigation at excessive

application rates may leave the soil more susceptible to compaction effect of traffic, which could

decrease root growth and consequently result in higher wilting tendency (Turgeon, 2005). Turf

density decreases with compaction. Goosegrass as well as annual bluegrass (Poa annua L.),

prostrate knotweed (Polygonum aviculare L.), and various sedges (Cyperus spp.) may invade

because they can tolerate these conditions (McCarty and Murphy, 1994).









A greenhouse study was conducted (Waddington and Baker, 1965) to determine the

influence of soil aeration on root growth of three grass species: Kentucky bluegrass (Poa

pratensis L.), creeping bentgrass (Agrostispalustris) and goosegrass. The study was conducted

using flooding so that aeration, and not mechanical impedance or fertility, would be the limiting

factor in the growth of the grass plants. Each grass produced thicker roots with fewer laterals

under conditions of poor aeration. Kentucky bluegrass root growth was reduced at ODR below 5

x 10-8 to 9 x 10-8 g cm-2 min-1. In comparison, roots of creeping bentgrass and goosegrass grew

well in soil having ODR below 3 x 108 g cm-2 min1.

Cultural practices promoting vigorous, dense turf are the most important and least

recognized means of preventing weed establishment and encroachment (McCarty and Murphy,

1994). In a review of cultural management practices of weeds in turfgrass, Busey (2003) stated

that mowing height is one of the most studied cultural factors affecting weed population on

turfgrass. When there was a significant effect within the mowing height studies, the lower

mowing height is always associated with more weeds in turfgrass such as crabgrass (Digitaria

spp), green killing (Killinga brevifolia Rottb.), and annual bluegrass. In the same review, Busey

reported that higher rates of nitrogen fertilization reduce crabgrass populations and also suppress

broadleaf weeds, probably because of stimulation of the turfgrass to grow more rapidly and be

more competitive. However, annual bluegrass infestation may be increased by a higher rate of

nitrogen fertilization (Busey, 2003).

In the past, existing native soil fields had provided adequate sports playing surfaces.

However, as intensity of use has increased, sand-based fields were installed for improving

playability (Puhalla et al., 1999). The sand field offers several advantages that cannot be

provided by a native soil field. Primary among these advantages of a sand-based root zone is its









high water permeability, which allows for rapid surface water removal by internal drainage

(Turgeon, 2005), and a second advantage is that a sand-based root zone will protect against

compaction. Correctly specified and tested sand will not compact to levels that can limit its

internal drainage properties by reducing macropores. Macropores allow water to be drawn

downward by gravity. When selecting the sand it is important to know sand size classes, shape,

particle size distribution, and sand particle stability because they will affect the soil physical

properties of the field (Puhalla et al., 1999).

The United States Golf Association (USGA) has recommended putting greens to be

comprised of a sand-based root zone mix. Soil physical properties of the root zone mix (total

porosity, air-filled porosity, capillary porosity, and saturated hydraulic conductivity) are

evaluated and used to predict the performance of a root zone mix (United States Golf

Association, 2004). A root zone soil must meet the physical specifications found in Table 2-1 to

meet USGA specifications.

Soil Compaction

Compaction in turfgrass typically occurs in the first few centimeters of the soil surface

(Sills and Carrow, 1983; O'Neil and Carrow, 1983; and Carrow and Petrovic, 1992). As soil is

compressed, bulk density increases, pore volume decreases, and pore distribution shifts toward

smaller pores. This result in a compacted soil characterized as having lower aeration, slower

permeability, and higher mechanical impedance to root growth (Brady and Weil, 2002).

Bulk density and Soil Penetration Resistance (SPR) measurements can be used to assess

soil compaction and soil strength. Bulk density is expressed as the oven mass of soil per volume

of soil (Blake and Hartge, 1986). An increase in bulk density also indicates that movement of air

and water within the soil is reduced. The collection of cores for determining bulk density within

the laboratory is time consuming. However, equipment for core sampling is relatively









inexpensive and durable for field usage (Miller et al., 2001). In comparison, penetrometers are

easier and quicker to operate, do not disturb the ground and give an instant result. Furthermore,

in a study conducted by Vazquez et al. (1991), SPR measurements were ten times more sensitive

than bulk density measurements for indicating soil compaction on sand soils (Arrendondo fine

sand) in Florida.

A penetrometer reading is one way to quantify soil strength, the property of the soil that

causes it to resist deformation (Brady and Weil, 2002). Penetrometers measure the physical

constraint exerted by soil on plant root growth by simulating the pressure a root encounters when

growing into a soil (Brady and Weil, 2002). Roots penetrate the soil by pushing into pores. If the

pore is too small, the root must push the soil particles aside and enlarge the pore. Therefore,

increased density of the soil (bulk density) restricts root growth. In addition, root penetration is

limited by soil strength. The most common use of penetrometers in agriculture has been for

assessing soil compaction under wheels and tillage. Penetrometers are useful in estimating

compaction below tractor wheels in agricultural crops. Also, they have been used to evaluate the

ability for root growth in the soil after different tillage treatments (Campbell and O'Sullivan,

1991). However, there is no documentation on the use of penetrometers to indicate soil

compaction levels in turfgrass areas.

Penetrometer values are commonly reported as the cone index (CI) which is the shear

resistance of the soils. Cone index is calculated as in Eq. 1-1 (Randrup and Lichter, 2001),

CI= F/7t (d/2)2 Eq.[1 1]

where F is total pressure needed to force the penetrometer into the soil in newtons (N), the

denominator is the base area of the cone, and d is diameter of the cone. Cone indices are reported

as Kg cm-2, KPa, MPa, and psi (Randrup and Lichter, 2001). Cone indices depend on soil and









probe characteristics such as base diameter of the cone, cone angle, and surface roughness of the

cone, as well as moisture content, bulk density, organic matter, and texture of the soil (Bradford,

1980; Perumpral, 1987). In a wet soil, the penetration pressure is dependent on the interaction

between the resistance of the probe and the soil water tension, which means that readings should

be taken at similar moisture content if they are to be compared. This effect will be more

important in less penetrable soils with a high content of silt and clay (Randrup and Lichter,

2001).

Soil Physical Properties and Penetrometers

Factors that influence the degree of soil compaction are soil texture, soil structure,

moisture content, particle size distribution, and foot and vehicular traffic. According to Carrow

and Petrovic (1992) foot and vehicular traffic are the more important soil compacting forces on

most recreational turfgrass sites. Foot traffic is influenced by the speed of the traffic event

(walking vs. running), and the magnitude of the compacting force, which is a function of surface

contact area and weight. Vehicular traffic is a function of the load of the wheel, the shear stress

resulting from wheel slippage, and vibration transmitted from the engine through the tire.

However, wheel slippage (rapid starting, stopping, and turning) can compact soil to a much

greater degree than by increasing the load.

In addition, the degree of soil compaction created by traffic is a function of both soil

texture and soil moisture. As soil moisture content increases to saturation, a corresponding linear

or exponential reduction in porosity occurs (Carrow and Petrovic, 1992). However, the adverse

effects of compaction on soil physical properties are less evident in coarse-textured soils than in

fine-textured soils. Even though sandy soils may compact, the degree of compaction is limited to

the bridging between the sand particles, which prevents the elimination of most of the larger

pores (Carrow and Petrovic, 1992). This is the reason that makes sandy soils most desirable for









sports fields and golf course. In addition, coarse sands with a very uniform particle size

distribution are most desirable because they have better infiltration rates than sands with a wide

particle size distribution (Stitt et al., 1982).

Several researchers have worked on the relationship between soil penetration resistance,

bulk density, and water content. A study of factors affecting mechanical impedance of tillage-

induced pans in coarse-textured soils in the Atlantic coastal plain found that the best model for

explaining the measured mechanical impedance included soil water content, surface roughness of

soil particles, and bulk density (Stitt et al., 1982). Similar results were obtained by Ayers and

Perumpral (1982) who found a direct relationship between penetration resistance and bulk

density, and an inverse relationship between penetration resistance and water content for various

mixtures of sand and clay. Ley and Laryea (1994) observed that doubling the water content

reduced the penetration resistance by 56-87% in the topsoil (0 to 15 cm depth). However, Ayers

and Perumpral (1982) found that in soils compacted at the same level the highest bulk density

and the highest cone index values were achieved at two distinctly different moisture contents.

Besides, for soils with 100 percent sand the cone index-bulk density relationship was

independent of moisture content. Due to the relationship between compaction and soil moisture,

it is desirable to measure gravimetric water content in the soils in which SPR measurements are

taken (Campbell and O'Sullivan, 1991). Additionally, penetration resistance and soil water

content are affected by particle size. Warnaars and Eavis (1972) reported that in finer grade sand,

penetration resistance decreased with increasing in moisture content occur; however, in coarse

sand it was relatively unaffected by moisture.

Objectives

The objectives of this study were to determine if goosegrass infestation occurs more often

in traffic areas, and whether soil compaction or some other mechanism would explain this. There









are three main hypotheses: (1) traffic areas show higher goosegrass infestation than no-traffic

areas; (2) traffic areas have higher soil compaction levels, 3) in response to soil compaction,

bermudagrass growth decreases more than goosegrass growth.









CHAPTER 2
GOOSEGRASS INFESTATION AND SOIL PROPERTIES IN TRAFFIC AND NO-TRAFFIC
AREAS IN GOLF COURSES

Introduction

The game of golf consists of playing a ball across a grassed course of typically 18 holes by

successive strokes with a club, starting from the "teeing ground," or tee (USGA, 2004). For

purposes of this discussion, the "hole" will refer to one of the typically 18 complexes of one

teeing ground and associated putting green, where the hole is located, and the intervening area

between the tee and the putting green which is called the fairway. The fairway is bordered by

uncut grass or less intensely maintained grass known as rough.

Foot traffic on golf courses is concentrated on tees, greens, and next to cart paths

throughout the golf course. Golf courses are often built on level areas with poor drainage. To

alleviate poor drainage, greens and tees are often elevated, sometimes with fill material, but foot

traffic and sometimes even cart traffic is intense on the sloped side of the tee nearest the cart

path, as golf players step up to the tee. Traffic is essentially absent on the sloped side of the tee

opposite the cart path. The symmetrical design of the elevated tee, with a traffic side and a no-

traffic side, provides a structure to experimentally measure the effect of traffic on golf courses.

The teeing ground, which is an important area where traffic occurs, may comprise one or

more rectangular areas totaling 9 to 18 m2 per 1,000 rounds of golf annually (Beard, 2002); if

there are multiple tees within the teeing ground to provide accessibility for different player

strengths, they may be designated forward, middle, and back. Tee markers are generally moved

daily to different positions within the tee, to make the game of golf more interesting, and to

spread out the traffic throughout the teeing ground and associated sloped sides.

Goosegrass has been observed as the most serious weed problem in golf and sport turf in

southern Florida (Busey, 2001), and it has been largely controlled by MSMA, a postemergence









arsenical herbicide, which use has been determined ineligible for re-registration (USEPA, 2006).

Therefore, it is important to learn the factors that promote goosegrass infestation, as this

knowledge may be applied in the use of cultural practices that can prevent its infestation.

The objective of this study was to test the hypotheses that traffic areas show higher

goosegrass infestation and higher soil compaction level compare to no-traffic sides of golf course

tees. Data were collected to: (1) compare goosegrass infestation and SPR in traffic and no-traffic

areas; (2) compare soil properties in traffic and no-traffic areas; and (3) measure the association

among goosegrass infestation, SPR, and soil properties.

Materials and Methods

Field Sites

The study was conducted on three golf courses located in Broward County, Florida. The

18-hole golf course at Arrowhead Golf Club is 36 years old and has approximately 50,000

rounds of golf played per year. Raised areas (greens and tees) were constructed partly with

Udorthents soil which consists of heterogeneous geologic material that has been excavated from

ponds and canals. The golf course at Pine Island Ridge Country Club is also 36 years old, has 18

holes, and has approximately 33,000 rounds of golf played per year. The golf course also has

been constructed with Udorthents soil, and it is on a ridge with higher and better drained soils

(Pendleton et al., 1984). Orangebrook Golf and Country Club is 71 years old, contains two

courses with 18 holes each, and has approximately 85,000 rounds of golf played between the two

courses per year. The golf course has been constructed over Pennsuco series (Coarse-silty,

carbonatic, hyperthermic, Typic Fluvaquents), Margate series (Siliciceous, hyperthermic, Mollic

Psammaquents), and Dade series (Hyperthermic, uncoated Spodic Quartzipsamments; Pendleton

et al., 1984). In 2001, the golf courses at Orangebrook were renovated using native soil to

reshape the course. Composite samples from Arrowhead and Pine Island Golf course' tees









showed that they have sandy soils with a pH of 6.9 and 6.6; and average organic carbon content

of 2.31 and 1.64% respectively. A composite sample from Orangebrook Golf and Country Club

showed tees having loamy sand soil with 10 % silt and 4% clay, 7.4 pH, and total organic carbon

2.59%. Table 2-2 describes the common management practices done by the superintendents for

the three golf courses.

Experimental Design

The experimental design was a randomized complete block with 15 blocks each consisting

of a tee, with five tees selected from each of the three golf courses. Within each block there was

two plots consisting of the two tee slopes parallel to the longest axis. The tee slope next to the

cart path, from which golfers walked up onto the tee, was the "traffic" plot and the tee slope

opposite the cart path was the "no-traffic" plot.

On each golf course, five tees were selected based on dimensions of the tee slopes to pick

the largest sampling areas. Except as indicated, the back tees were selected; the numbers

represent the progressive position of the selected tees with reference to the normal direction of

play. In Arrowhead tees 5, 6, 10, 12 and 16 were selected; at Pine Island Ridge tees 1 (middle),

5, 12, 13, and 18 were selected; and at Orangebrook east side tees 4, 7, 10, 18 (middle), and 18

were selected

Data Collection

The dimensions of traffic and no-traffic sampling area were each defined to be 27.4 m long

by 2.7 m wide for each tee slope, which conformed approximately to the length of tee slopes

adjacent to the flat tee tops. In cases of shorter tees, the sampling area was broadened to

maintain the same area and sampling density. Within each traffic and no-traffic area, goosegrass

cover (%) and the number of plants present were determined visually in fifteen randomly









distributed quadrats (0.25 m2) within the respective sampling areas. Observations were done

between July and September, 2005.

For each traffic and no-traffic tee slope, twenty Soil Penetration Resistance (SPR) readings

were randomly taken along with soil core samples to determine gravimetric soil water content.

Soil cores were collected adjacent to the SPR measurements points. The penetrometer used was a

Field Scout SC-900 (Spectrum Technologies, Plainfield, IL), which digitally displays readings in

KPa in 2.5 cm increments of soil depth. It is designed to American Society of Agricultural

Engineers standards. The instrument error was + 103 KPa for SPR and 1.25 cm for depth

(Spectrum Technologies). At each of the 20 points, SPR measurements were recorded at 2.5, 5.0,

7.5, 10 and 12.5 cm depths. Due to the presence of stones, SPR measurements were not collected

at the 12.5 cm depth on tee number four on Orangebrook Golf Club. The presence of stones may

result in non-representative SPR measurements (O'Sullivan et al., 1987). Cone indices reported

as "shallow" were an average of the 2.5 and 5.0 cm depth SPR measurements. Cone indices

reported as "all depths" were an average for all depths from 2.5 to 12.5 cm.

Soil cores were separated into two sections, upper, 1.5 7.5 cm and lower, 7.6 12.5 cm,

depth, to measure soil moisture status. The three upper sections of cone index (2.5, 5, and 7.5 cm

depth) corresponded with the upper sections for water content, and the two lower sections of

cone index (10 and 12.5 cm depth) correspond with the lower sections for water content. Soil

from each section, 15 to 20 g, was dried to a constant weight at 105 C, at which time a final dry

weight was measured. Relative gravimetric water content was calculated by weighing the soil

core from the field under moist condition (fresh wt.) and weighing again after drying in an oven

until its weight remained constant (dry wt.). The weight loss during drying represented soil

water, and its percentage composition is expressed as Eq. 2-1 (Gardner, 1986).









Relative soil water content (%) = ((fresh wt. dry wt.)/ dry wt.) x 100 Eq. [2 1]

Soil penetration measurements and water content samples were collected on the same day.

The tee slopes at Arrowhead, Pine Island Ridge and Orangebrook were sampled between

February and October, 2005. Variables measured and numbers of samples collected on each tee

slopes are illustrated in Table 2-3.

Soil Properties Analysis

Four undisturbed soil cores were collected from traffic and no-traffic areas. Soil cores

were collected using a hammer driven core sampler 5.1 cm diameter to a depth of 9 cm (Fig. 2-

1). The top 1.5 cm containing turf verdure, crowns, rhizomes, stolons, thatch was cut off and

discarded, leaving soil cores 7.5 cm deep for the analysis. The soil was analyzed for saturated

hydraulic conductivity, pore space content, pore distribution (macro and micro), and bulk

density, using methods described by the United States Golf Association (Hummel, 1993), except

that the samples were not artificially compacted. Samples were collected from the beginning of

January to the end of February, 2006. Table 2-3 summarizes the soil analysis number of samples

per treatment and the total numbers of samples in the three golf courses.

Sample Processing

After a soil core was collected from the field, it was saturated and then placed in a

permeameter where water flowing through the core was maintained at a constant hydraulic head

(measured from the bottom of soil column to water level above the soil) for four hours, at which

time percolate aliquots were collected. Saturated hydraulic conductivity was calculated

according to Eq. 2-2 (Hummel, 1993),

Ksat= QL/hAt Eq. [2 2]

where Ksat = hydraulic conductivity (cm hr-1)
Q = quantity of water collected (cm3) in period of time (t)









L = length of soil column (cm)
h = hydraulic head (cm)
A = cross sectional area of the soil core (cm2)
t = time required to collect Q (hr)

After Ksat was determined, the soil core was placed on a tension table, set to remove water

at 40 cm of tension. When the soil core weight reached equilibrium (after 18 to 30 h), this last

weight was recorded. The core was oven dried at 1050C until constant weight was obtained.

Capillary porosity, amount of pores retaining water at -0.004 MPa (40 cm tension) which

represents field capacity, was calculated on an oven dried basis, and bulk density was calculated

from the soil weight and volume. Capillary porosity (microporosity) was determined according

to Eq. 2-3 (Hummel, 1993),

Cp ((Mw Md)/ V) x 100 Eq. [2- 3]

where Cp = capillary porosity on dry weight basis (%)
Mw = net wet soil wt. at 40 cm tension of the core (g)
Md = net dry soil wt of the core (g)
V= volume of the core= 7t x r2 x L (cm3)
L= length of soil column

The value of dry soil weight was also used to calculate bulk density of the soil core, and

from this value of bulk density total porosity was determined (Hummel, 1993).

Total Porosity= (1 (Db/Dp)) x 100 Eq. [2 4]

where Db= bulk density (g cm-3)
Dp= particle density (g cm-3)

Air filled porosity (macroporosity) was calculated by subtracting percentage of capillary

porosity from total porosity.

Total organic carbon (TOC) was determined using the Nelson and Sommers (1996)

procedure. Chromic acid oxidation with sulfuric acid measures easily oxidizable organic carbon.

This easily oxidizable organic carbon is multiplied by a recovery factor of 77% to convert it to









total organic carbon. Easily oxidizable organic carbon content was analyzed from the same soil

cores (upper and lower depths) used to determine water content.

Particle density was calculated from the same soil cores used to determine TOC. However,

since soil bulk density was only determined on the top 7.5 cm of the soil profile, particle density

was calculated at the same depth with no distinction between traffic and no-traffic treatments.

The purpose of measuring particle density was to assure an accurate estimation of porosity. Each

of the 30 soil cores available was assigned to a class interval depending on the % TOC, and then

a sub-sample of each class interval was taken and particle density calculated. Interval classes

were based on the number of samples and closeness of TOC value. The value of particle density

was matched to the value of total organic carbon per each tee and then total porosity was

calculated for each tee. Particle density was calculated by dividing mass over volume of the

sample. The volume of solid particles was calculated by subtracting volume of the water from

total volume of volumetric flask (Hummel, 1993).

Particle density for each sub-sample of TOC is listed in table 2-4. Particle density was not

correlated with TOC (r=-0.56, P=0.117)) In comparison, Dr. G.H. Snyder (personal

communication) has found particle density values of about 2.55 g cm-3 for sand soils on different

golf courses in Broward County. Calculation of porosity for each tee was performed using

particle density assumed as 2.55 g cm-3 and particle density determined from the soil samples

(Table 2-4). However, the porosity means values were the same; on the no-traffic slopes of the

tees 50.9% vs. 50.8% respectively; and on the traffic slopes 50.1% vs. 49.6% respectively.

Statistical Analysis

Data were analyzed by ANOVA using SAS software (SAS Institute, Cary NC). However,

GLM (general linear model) was used for the combined analysis of three golf courses in order

partition variation and degrees of freedom within golf courses versus among golf courses.









Results and Discussion


Goosegrass Infestation

Goosegrass infestation, measured as goosegrass plants and cover, was higher (P<0.05) on

the traffic sides of the tee slopes (Table 2-5). For example, goosegrass cover was 1.86% on the

traffic side, compared with 0.82% on the no-traffic side. When each golf course was analyzed

separately there was no effect of traffic except percent goosegrass cover at Pine Island Ridge

Golf Course was higher (P=0.043) on the traffic side (Fig. 2-2). Preemergence herbicides were

not used in Arrowhead Golf Course which may have caused the higher goosegrass infestation in

both sides of the tees slopes compared with Pine Island Ridge and Orangebrook.

Penetration Resistance and Soil Moisture

Soil Penetration Resistance (SPR) showed an effect of traffic at the shallow depth (P<0.05)

but not for all depths (Table 2-5). The coefficient of variation for SPR at the shallow depth was

18%, and 25% for SPR average at all depth. These values were similar to values obtained by

O'Sullivan and Ball (1982), 18 to 50%, depending on the numbers of SPR measurements. The

values of penetration resistance (SPR) for all the depths measured did not reach the limit value

cited by Lipiec and Hatano (2003) of 3 MPa at which penetration resistance becomes critical for

root growth.

When the analysis was done by location, only Arrowhead Golf Course showed a highly

significant effect of traffic (P<0.01) for shallow depths (Fig. 2-2) and all depths. At shallow

depth, SPR for the traffic side of Arrowhead was approximately 30% higher than SPR at the no-

traffic side, 775.5 KPa vs. 597.3 KPa, respectively. These results agree with results from

Vazquez et al. (1991) who found a 30% increase in SPR in the upper 20 cm of the soil on traffic

sites compared to no-traffic sites.









The high SPR values at Arrowhead could have been caused by the high numbers of rounds

of golf per year compared with the other two golf courses; also, this golf course has never been

renovated. High SPR values can be explained by differences in texture, bulk density, and organic

matter (Campbell and O'Sullivan, 1991; Perumpral, 1987). As an example, Orangebrook Golf

course had the highest SPR with the higher gravimetric water content which could have been

explained by the 10% of silt and 4% of clay in the root zone mix.

There was no difference in gravimetric water content between traffic and no-traffic slopes

of the tees. There was a difference (P<0.01) between the upper and lower depths explained by

the higher content in total organic carbon in the upper depth allowing the soil to hold more water.

The variability of gravimetric water was high with coefficients of variation between 38 to 56 %

for upper depth and lower depth respectively.

The aim of measuring water content was to correct penetration resistance by water content.

However, this was not accomplished because there was no correlation (P>0.05) between

gravimetric water content and penetration resistance for any of the depth (Fig. 2-3). Many

researchers (Ayers and Perumpral, 1982; Perumpral, 1987; Ley and Laryea, 1994) have found an

inverse relationship between penetration resistance and water content for various mixtures of

sand and clay. The low correlation (r= -0.155, P=0.413) and lack of significance between SPR

values and gravimetric water content at the shallow depth may be related to other factors such as

particle size distribution. In all the three golf courses the sand fraction analysis showed that tees

have high percentage of very coarse sand and fine gravel (from 29.5 to 43.2%) while low

percentage of coarse sand and medium sand (from 40.2 to 33.1%) Results from Warnaars and

Eavis (1972) indicated that in finer sands grades, penetration resistance decreases with increasing

moisture content; however, in coarse sands it was relatively unaffected by moisture.









However, our results are similar to Ehlers et al. (1983) where the rate of change of soil

penetration resistance with water content was less at low bulk density (1.3 g cm-3) than at high

bulk density (1.5 g cm-3). At high moisture content, bulk density had minimal effect on

penetration resistance. In our study the average bulk density was 1.24 g cm-3 (Table 2-6) with a

range from 1.42 to 0.88 g cm-3 and the gravimetric soil moisture content was more than 0.25g g1

in the upper depth. Similar results were obtained by Smith et al. (1997) where for a range of bulk

densities, only small differences in SPR occurred at water contents approaching field capacity

and wetter. In a loamy sand soil, only small differences in strength development were noted

across a wide range of water contents. This can be primarily related to the contribution of

frictional rather than cohesion forces to SPR.

One of the difficulties in the study was to collect the SPR with similar soil moisture

contents for all the golf courses. The goal was to collect soil moisture samples and penetrations

resistance when the soil was at field capacity or after 24 hours irrigation or rain trying to avoid

big differences in soil water content. However, it was difficult to achieve this because of changes

in irrigation schedules or weather conditions that could not be avoided such as rain.

Soil Properties

Soil properties measured included bulk density, capillary porosity, hydraulic conductivity,

and TOC while total porosity and air-filled porosity were calculated. There was no effect of

traffic on any soil parameter. Table 2-6 shows mean for each treatment and p-values for these

parameters. Most of the values of bulk density were low for sandy soils, which could be

explained by the high organic matter content in the upper depth of these tees. Total porosity was

within ranges of what USGA recommends. However, capillary porosity is higher than what the

USGA recommends while air-filled porosity is lower (Table 2-6, Table 2-1).









Hydraulic conductivity was highly variable within treatments. The mean values of each

treatment were lower than what USGA considers the acceptable range of saturated conductivity

of 15 to 30 cm hr-1 (Table 2-1). However, these values for hydraulic conductivity are in the range

to the geometric mean values for soils classified according to USDA soil texture classes 18.19 to

9.14 cm hr-1 for sandy soil and 14.13 to 10 cm hr-1 for fine sandy soil (Rawls et al., 1998). These

results reflect the large spatial variability of hydraulic conductivity measured in the field, which

has encouraged scientists to develop models to estimate saturated hydraulic conductivity from

other easily measured soil physical properties such as particle size distribution, bulk density, and

particle shape (Sperry and Peirce, 1995; Jabro, 1992).

Total organic carbon content showed no difference between traffic and no-traffic areas of

the tees. There was a difference between the upper depth, 2.30 and 2.07 and the lower depth,

1.70 and 1.64, respectively (P<0.05). Roots were present in the upper surface. Bellow the 7.5 cm,

most of the time in the pure sand, no roots were present.

Correlation between Parameters

Goosegrass cover and plant density were not correlated with any soil property or

penetration resistance at different depths. Correlation coefficients among soil properties and

penetration resistance are presented in Table 2-7. The following interpretations are based on the

sign, magnitude, and significance of the respective coefficients. The table shows correlation

among independent variables where the variables have been measured directly (bulk density,

capillary porosity, gravimetric water content, hydraulic conductivity, TOC, and SPR).

There are two main empirical behaviors in soil properties responses that were expected.

First, bulk density was associated with capillary porosity, soil gravimetric water content and

TOC (P<0.001); and capillary porosity was associated with soil gravimetric water content and

TOC (P<0.001). Higher bulk density resulted in decreased capillary porosity and gravimetric









water content. This was expected as increasing in bulk density decreases pore space, which may

decrease gravimetric water content. Also, an inverse relationship should be expected between

bulk density and TOC since organic matter will also increase pore space in the soil (Brady and

Weil, 2002; McCoy, 1998). Second, capillary porosity shows slightly significant inverse relation

with hydraulic conductivity and SPR (P<0.05). Even though hydraulic conductivity and capillary

porosity were not different between traffic and no-traffic sides of the tees; a negative relationship

existed between these two parameters, which should be expected. Because saturated hydraulic

conductivity is the measure of a soil's ability to transmit water under saturated conditions, and

air-filled porosity is responsible for the saturated movement of the water in the soil, an increase

in capillary porosity will be associated with reduced hydraulic conductivity of the soil

(Henderson et al., 2005; Brady and Weil, 2002).

Conclusions

This research provides information on goosegrass infestation and its relationship with soil

properties measured in traffic and no-traffic areas in three different golf courses. Goosegrass

plant density and cover were higher on traffic areas. Due to the high soil moisture content, at the

time when SPR were taken, and being coarse sandy soils, the study did not detect correlation

between soil water content and SPR as described by other researchers. The combined analysis

that included all three golf courses showed higher values of SPR on the traffic areas at the

shallow depth. However, this result was driven for the significant differences present in one of

the golf course for all the depths. Soil bulk density values did not show significant differences

between treatments; nevertheless SPR may have been more sensitive in detecting soil

compaction than bulk density in the case of that golf course in particular.

This study provides preliminary data in the use of penetrometr in situ done in a turfgrass

situation to determine compaction levels in the field which may no be useful in sandy soils.









However, penetrometer measurement will be more useful if done in controlled environmental

situation with controlling soil moisture content. The results from the study show that goosegrass

infestation was higher on the traffic slopes, which validates the first hypothesis. However, soil

compaction was not encountered for most of the traffic areas, which invalidates the second

hypothesis that soil compaction occurs in traffic areas. Consequently soil compaction is not the

mechanism that explains goosegrass infestation.









Table 2-1. United States Golf Association specifications for physical properties of root zone
mixes for golf greens.


Characteristic


Acceptable Range


Capillary porosity (at 40 cm tension) 15 25%
Air-filled porosity (at 40 cm tension) 15 30%
Total porosity 35 55%
Saturated hydraulic conductivity 15-30 cm h-1


USGA, 2004.

Table 2-2. Management practices on tee slopes on each golf course.
Golf course
Pine Island
Practice Arrowhead Orangebrook Ridge


Mowing height


Nitrogen
fertilization rate
Fertilization
frequency


Irrigation,
winter



Irrigation,
summer



Weed control


3.81cm


48 Kg ha-1


ten times/yr



5 d/wk 15 min
cycle



every other day
10 min cycle



Postemergence
herbicides


3.18cm


48 Kg ha-1


four times/yr



3 times/wk 14 to
1/8 inch water
applied


3 times/wk 14 to
1/8 inch water
applied


Preemergence and
spot spray with
postemergence
herbicide


5.08cm


48 Kg ha-1


six times/yr



25 min every 3
days as needed



35 min every
day until rainy
season starts


Preemergence
and spot spray
with
postemergence
herbicide


Overseed on
slope


Yes, perennial
ryegrass









Table 2-3. Variables measured and numbers of samples per each tee slope and in the three golf courses.

Variables
Saturated
hydraulic
conductivity,
Goosegrass Gravimetric capillarity Total
plants and Soil penetration water porosity, and organic Particle
cover resistance content bulk density carbon density


Treatments No. quadrats No.Readings j Upper depth

No-traffic 15 20 40 4 2 1
Traffic 15 20 40 4 2 1

Total number
sample/tee x five
sample/tee x five 450 600 1200 120 60 30
tees x three golf
courses
tGravimetric water content and total organic carbon were also measured at lower depth (7.6 to 12.5 cm)
Readings from 2.5 to 12.5 cm depth
Upper depth= 1.5 to 7.5 cm depth









Table 2-4. Particle density values for the different classes of total organic carbon (TOC)
encountered in the three golf courses.
Class interval Soil samples Mean TOC Particle density
(% TOC) (Number) (%) (g cm-3)
0.80-1.10 4 0.96 2.53
1.11-1.70 3 1.44 2.47
1.71-1.90 6 1.80 2.50
1.91-2.05 3 2.00 2.46
2.06-2.10 3 2.08 2.55
2.11-2.60 1 2.26 2.44
2.61-2.80 3 2.75 2.48
2.81-3.10 3 3.06 2.46
3.11-3.80 4 3.68 2.44
Total samples=30 Average= 2.48











Table 2-5. Goosegrass plants and cover, gravimetric water content, and soil penetration resistance (SPR) and ANOVA table. Means
of 30 observations.
Goosegrass Gravimetric water SPR
Plants Cover Uppert Shallowj All depths
Number %- gg-1 KPa
No-traffic 0.40 0.82 0.28 683.04 1003.51
Traffic 0.92 1.86 0.26 788.23 1121.07


Statistical analysis
Source of variation df Mean squares
Location 2 3.90 15.39 163.53 NS 49372.73 NS 33873.80 NS
Error a (tees within 12 0.60 2.41 165.40 21224.73 46818.45
locations)
Traffic 1 2.03 8.09 36.64 NS 82996.14 103651.94 NS
Traffic and
Location 2 0.40 1.08 39.28 NS 11251.68 NS 33211.23 NS
Error b (tees x
traffic) 12 0.28 1.00 57.26 19095.43 77611.33
Significant at P=0.05 or NS, not significant. F-test from analysis of variance.
t Water content measured from 1.5 to 7.5 cm depth.
$ Shallow depth is the average value for SPR measured at 2.5 and 5 cm depth
Number of plants per 0.25 m2









Table 2-6. Means of soil parameters measured on the tee slopes on the upper depth. Means of 30
observations.
Total
Soil Bulk Capillary Air-filled Total Saturated organic
properties density porosity porosity porosity conductivity carbon
g cm-3 0- cm h-1 o
No-traffic 1.22 40.75 10.10 50.81 12.78 2.07
Traffic 1.24 40.52 9.11 49.63 11.36 2.30
Significance
(P) 0.68 0.16 0.90 0.51 0.66 0.48
P is the probability level of significance from F-test analysis of variance.

Table 2-7. Correlation coefficients (r) among soil properties and soil penetration resistance
(SPR). Means of 30 observations.
Gravimetric Total
Capillary Water Hydraulic organic SPR
porosity content conductivity carbon shallow

Bulk density -0.906 *** -0.828 *** 0.255 -0.759 *** 0.349

Capillary porosity 0.719 *** -0.450 0.647 *** -0.426 *

Gravimetric water -0.334 0.805 *** -0.154
content
Hydraulic -0.279 0.341
conductivity
Total organic -0.035
carbon
Soil penetration
resistance (SPR)
t Shallow depth is the average value for SPR measured at 2.5 and 5 cm depth
*, **, *** Significant at the 0.05, 0.01 and 0.001 level respectively


































Figure 2-1. Undisturbed soil core sample used to determine bulk density, saturated hydraulic
conductivity, and capillary porosity.











0

CL
0





0)
U

4.



to
0


0
s:

0
Co
(0


UO
2

U)
0
U,



0
A)
0C
0


0


U/)



CU
.0

C
0)
0.


a


Arrowhead


Orangebrook


ns


Pine Island Ridge


Golf Course

Figure 2-2. Goosegrass canopy cover and soil penetration resistance at shallow depth at three
golf courses.* Significant differences between treatments at P<0.05 and ns, no
significant differences between treatment.


[ Traffic
l No Traffic
T -------


ns


ns


ns


0

1000 -


800


600


400 -


200


0










3000


0. 2500


2000 -


1500 *


O 1000

C 500


0 I I
0.0 0.2 0.4 0.6 0.8

Gravimetric water content (g/g)



Figure 2-3. Gravimetric water content and soil penetration resistance at the shallow depth
(average 2.5 and 5 cm) for all three golf courses. (n=600)









CHAPTER 3
GOOSEGRASS INFESTATION AND SOIL PENETRATION RESISTANCE IN TRAFFIC
AND NO-TRAFFIC AREAS IN SOFTBALL AND BASEBALL FIELDS

Introduction

The purpose of this study was to test the second hypothesis again, that high-traffic areas

show higher goosegrass infestation associated with higher soil compaction levels. However, this

study was set up in baseball and softball sport fields with different characteristics than in the

prior golf course study, but both games having in common small areas with high traffic from the

players. Baseball and softball are the only major sports that are played on fields that have both

turf and exposed soil for a playing surface and about 66% of the game is played on the infield, or

"skinned" areas (Miller, 2001). The skinned area is the exposed soil portion of the field where

defensive players are standing. In this area, conditioners are mixed into the soil to soak up extra

water during wet conditions, retain water on dry conditions, and minimize compaction (Puhalla

et al., 1999). The infield, where the four bases are, is the area enclosed by the foul lines and it

has the pitcher's mound as the highest point in the field. The pitcher's mound and batter's box

are recommended to be built on clay-based soils to withstand weather and continuous excavation

by pitchers (Puhalla et al., 1999).

Baseball is a game made up of two teams. The team at bat is known as the offensive team,

and its objective is to have its batters become base runners and its runners to advance touching

all bases. When this is done, a run is scored. The team in the fixed positions in the field is known

as the defensive team, and its objective is to prevent offensive players from becoming base

runners and advancing around the bases. When three offensive players are legally put out, the

teams change from the offensive to the defensive and from defensive to offensive. The objective

of each team is to score more runs than its opponents (National Collegiate Athletic Association,

2005). The dugout is where a team's bench is located. There are two dugouts, one for the home









team and one for the visitor team, located in front of the first and third bases, respectively.

Players go from the dugout to home plate to begin playing. Since bases are numbered counter-

clockwise from the first base, home plate is also the final base a player must touch to score. From

the dugout, players will go to the home plate most of the time in a concentrated path with some

traffic on the rest of the field due to players coming back from the bases or outfield to the

dugout. The foul area, where traffic was clearly defined between home plate and dugout, was the

area of this study. The objective of this second study was to compare goosegrass infestation and

soil penetration resistance between traffic and no-traffic areas on a sport field.

Materials and Methods

The study was conducted on three baseball/softball fields at Sunset Park located in the City

of Plantation, Broward County, Florida. Fields number 2, 3 (softball fields) and 6 (baseball field)

were chosen for the study due to the presence of goosegrass infestation in the foul areas between

the dugouts to the foul lines (Fig. 3-1). On each field, the area of study began at 4.3 m from

home plate along a direction parallel to the foul line, and 1.5 m from the foul line into the foul

area. From this initial point a rectangle 30 m long and 9 m wide was marked and gridded at

3x3 m. The same area, between the dugouts to the foul line was marked on both sides of the field

(home and visitor) sides which were called plot 1 and 2. Figure 3-2 shows the arrangement of

the grids on one of the fields which was the same for all. To define the traffic area a line was

drawn from the dugout gate to the home plate, and all the cells within 1 meter of either side of

the line were marked as the traffic area (10), and the rest of the cells were defined as no- traffic

(20).









Goosegrass Infestation

Within each cell (3x3 meters) a sub cell (lxi meter) was randomly selected to determine

goosegrass cover and the number of plants present. Therefore, there were 30 points measured per

plot. Observations were determined on 17 July 2006.

Penetration Resistance and Soil Moisture

For each sub cell, one soil penetration resistance (SPR) reading was taken within the center

of the sub cell along with soil core samples to determine gravimetric soil water content (Table 3-

1). Soil cores were collected adjacent to the SPR measurements. The penetrometer used was a

Field Scout SC-900 (Spectrum Technologies, Plainfield, IL); the same device used in the study

on the golf courses. Due to presence of stones, SPR measurements were collected only to 7.5 cm

depth. At each of the 30 points, SPR measurements were recorded at 2.5, 5.0, and 7.5 cm depths.

Soil penetration resistance values were reported as an average of the 2.5, 5, and 7.5 cm depths.

Soil cores (1.5 to 7.5 cm) were collected to measure soil moisture status. Each soil penetration

resistance value corresponded with a soil core for water content. Soil water content was

determined by gravimetric analysis done by weighing soil samples before and after drying and

expressed as a percent of the oven dry weight of the soil (Gardner, 1986). Fifteen to twenty

grams of soil was dried to a constant weight at 105 C, at which time a final weight was

measured. Soil penetration measurements and water content samples were collected on the same

day. The fields were sampled on 17 and 18 July 2006.

Statistical Analysis

The experimental design was a randomized complete block with 6 replications (2 foul

areas x 3 fields) and one treatment factor, traffic vs. no-traffic. Data were analyzed by ANOVA

and correlations among variables were determined using SAS software (SAS Institute, Cary NC).









Results and Discussion


Goosegrass Infestation

Number of goosegrass plants and cover differed (P<0.05) between traffic and no-traffic

areas and varied differently (P<0.001) among fields. Traffic areas showed more cover and

numbers of goosegrass plants with low coefficients of variance (21 to 26%, respectively).

Penetration Resistance and Soil Moisture

The gravimetric water content as well as soil penetration resistance showed no difference

between traffic and no-traffic grids. However, gravimetric water showed differences (P<0.05,

Table 3-2) among fields while SPR did not. The coefficient of variation for gravimetric water

was lower (6%) than the coefficient of variation measured for the tee slopes (38%) in the

previous study, while the coefficient of variation for SPR was almost the same as the coefficients

of variation measured for the tee slopes (12% vs. 18%, respectively). Because soil gravimetric

water content was measured during a period of two days in this study, the coefficient of variation

was much lower than on the tee slopes study sites.

Soil penetration resistance values were not correlated (r=-0.268) with gravimetric water

content (Fig. 3-3). The aim of measuring water content was to correct soil penetration resistance

by water content. However, this was not accomplished because there was no significant

correlation between gravimetric water content and penetration resistance as opposed to most of

the articles reviewed (Ayers and Perumpral, 1982; Ley and Laryea, 1994; Perumpral, 1987). As

already discussed in results in chapter 2, these results could be explained by the high gravimetric

water content in the soil at the moment of collection of SPR and the fact it is a sandy soil where

53% of the sand fraction is very coarse sand and fine gravel.

When the correlation analysis was done among all the variables for all the fields (n=180)

penetration values at 5 cm depth were correlated with cover and numbers of plants of goosegrass









(P<0.01respectively); however, both correlations were low (r=0.24 and r=0.22, respectively).

Penetration values at 7.5 cm depth were correlated only with gossegrass cover (P<0.01) with a

similar coefficient of correlation (r=0.20).

Goosegrass canopy cover and plants number was higher on the baseball and softball fields

than in the golf course tees (Fig. 3-4). However, the penetration resistance was very similar for

both studies. Therefore, we can conclude that soil compaction did not determine goosegrass

infestation. On the baseball and softball fields bare ground was more often seen in the traffic

path, while it did not happened most of the time in the traffic slopes of golf course tees. The

larger presence of bare ground might determine the larger infestation of goosegrass. In addition,

large mature goosegrass plants (from the prior year) were more often seen on the ball fields than

on the golf course tees, probably due to a less intense management on theses sites.

Conclusions

Goosegrass plant density and cover was higher on the traffic sides, which validate the first

hypothesis again. However, high soil compaction was not found on the traffic area, which

invalidates the second hypothesis of this research. Wear and tear of the turfgrass may explain

goosegrass infestation in high-traffic areas, but it is not explained by the occurrence of higher

soil compaction which goosegrass may tolerate.









Table 3-1. Variable measured and numbers of samples per experimental unit in the three ball
fields.


Goosegrass
plants and cover


Soil penetration
resistance


Water content


No. quadrats No. readings No. soil cores
No-traffic 10 10 10
Traffic 20 20 20

Total n= sample
/block x 2
/blockdx32 180 180 180
block/field x 3
fields


Treatments









Table 3-2. Goosegrass plants and cover, gravimetric water content, and soil penetration resistance and ANOVA table. Means of 12
observations.
Goosegrass Gravimetric Soil penetration
Cover Plants water resistance
% number/m2 --g g1- -KPa-
No-traffic 4.57 7.37 0.32 811.78
Traffic 7.58 11.46 0.30 848.60


Statistical analysis
Source of variation df Mean squares
Block 5 86.36 *** 140.41 *** 19.97 17166.39 NS
Traffic 1 27.11 50.32 10.19 NS 4066.40 NS
Error 5 2.45 3.92 3.74 9215.47
*, **, ***, and NS; Significant at the P<0.05, P<0.01, P<0.001, and not significant at P<0.05. F-test from analysis of variance.










Field 6


Field 3
- AS


Field 2


Figure 3-1. Overview of the fields with the study areas (2 plots) marked in each of them



















Foul line




riinnmit


/I1


Home
plate


Figure 3-2. Baseball field number six with the sampling grid. White cells indicate the traffic area
which is marked with the black line from home plate to dugout.










1800

1600

1400 -

1200

1000 -

800

600

400

200 -

0
0.0 0.1


0.2 0.3 0.4 0.5 0.6

Gravimetric water (g/g)


Figure 3-3. Soil penetration resistance values versus gravimetric water content for the three ball
fields. (n=180).


0.7 0.8









.O k, 10 -------------
%- 10
N": Traffic
W_ No Traffic
> 8 -
O

6 -


4-




0 0

S1000

n "s
800 -









0 200




Baseballlsoftball fields Golf course tees

Study

Figure 3-4. Goosegrass canopy cover and penetration resistance by traffic treatment and field
study.









CHAPTER 4
GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT
DIFFERENT DEGREES OF SOIL COMPACTION (GLASSHOUSE STUDY)

Introduction

Changes to the soil physical properties due to compaction were evaluated on three golf

courses and results are described in Chapter 2. In this chapter the focus is on the effect of soil

compaction on goosegrass and bermudagrass root and shoot growth.

Common responses of a crop root system to increasing compaction are decreased root size,

retarded root penetration and smaller rooting depth (Glinski and Lipiec, 1990). These are mostly

due to excessive mechanical impedance and insufficient aeration depending on soil wetness

(Lipiec and Hikansson, 2000). Turfgrass grown in a compacted soil is subject to both stresses.

Carrow and Petrovic (1992) discussed whether mechanical impedance or aeration decreases root

growth. They suggested that soil aeration is the primary influence on root growth at moderate

compaction, while at heavy compaction both mechanical impedance and aeration are important.

When the compacted zone is present at shallow depth, soil strength that prevents root

penetration or reduces root elongation rates may reduce plant development and yields if water

uptake by the plants depends only on precipitation (Unger and Kaspar, 1994). Mechanical

impedance decreases the rate of root elongation, which is often accompanied by thickening

(radial expansion) of the root axes (Bengough and Mullins, 1990; Atwell, 1992). Both elongation

rate and the degree of thickening of the root depend on particular experimental conditions

(Atwell, 1992). Total root volume and mass are not necessarily reduced by soil strength because

the shorter root axes are often proportionately thicker.

Studies on the effect of compaction on warm-season grasses have been limited. In a study

on the responses of three cool-season grasses to compaction, Carrow (1980) reported that

compaction decreased visual quality with tall fescue (Festuca arundinacea Schreb.) the most,









while perennial ryegrass (Lolium perenne L.) was the least influenced; shoot density and verdure

decreased the most in Kentucky bluegrass ( Poapratensis L.), while tall fescue and perennial

ryegrass were not affected. Root weight was reduced in Kentucky bluegrass and tall fescue but

increased in perennial ryegrass. O'Neil and Carrow (1983) reported that compaction reduced

visual quality and clipping yield of perennial ryegrass, affected root distribution after 12 weeks

but did not reduce root weights. However, another study conducted by Sills and Carrow (1983)

using the same species (perennial ryegrass) at different levels of nitrogen fertilization showed

that compaction decreased visual quality and clippings but did not affect verdure. Root weight

was decreased by compaction and a greater decrease occurred in the higher nitrogen rate. In a

similar study, Agnew and Carrow (1985) reported that shoot growth of Kentucky bluegrass is

affected by soil compaction by reducing clippings yield, visual quality and verdure. Also,

compaction reduced root growth at lower depths while rooting increased in the 0-5 cm depth

range. However, total root growth did not decline, which the authors attributed to an increase in

surface roots due to ethylene-promoted adventitious roots (Atwell, 1992).

No studies have been conducted on the separate effects of wear and compaction on

bermudagrass, since traffic studies include these two effects jointly. Dunn et al. (1994) observed

that the combination of spring and fall traffic was too intensive for bermudagrass in mixture with

cool-season grasses. Kentucky bluegrass and perennial ryegrass dominated the mixtures with

bermudagrass after 3 years, and showed good tolerance to simulated traffic. Carrow et al. (2001)

evaluated turf coverage of seven seashore paspalum (Paspalum vaginatum Swartz.) ecotypes and

three bermudagrasses ecotypes to simulated traffic at near soil saturation and at field capacity.

Grasses with the greatest traffic stress tolerance in terms of turf coverage, regardless of soil

moisture, were 'Tifway' and 'TifSport' bermudagrasses and 'Temple 1' seashore paspalum.









These results have been explained by different wear tolerances mechanisms for each species

(Trenholm et al., 2000). This research will contribute to improving our understanding of

goosegrass and bermudagrass growth under compacted soils without the influence of wear. The

objective for this experiment was to test the last hypothesis of this study that soil compaction

decreases bermudagrass growth more than goosegrass growth. The aim of the experiment was to

determine the effect of controlled levels of soil compaction on shoot and root growth of

goosegrass and bermudagrass growing separately.

Materials and Methods

Two glasshouse experiments were conducted from 26 May to 19 Sept. 2005 at the

University of Florida, Fort Lauderdale Research and Education Center, Davie, Florida. A

factorial experiment was utilized to evaluate the growth of goosegrass and bermudagrass grown

under different levels of soil compaction. The same experiment was done in two runs. There

were four replicates and five replicates for the first and second runs of the experiment,

respectively.

The experiment was set up in PVC pipe cylinder pots. Pots had 0.8 cm wall thickness and

an inside diameter of 19.5 cm. They were cut to 22.8 cm lengths, and were joined with a cement

solvent to a 0.635 cm thick PVC square sheet (25.4 by 25.4 cm) used as the bottom of the pot.

Fifty holes, 0.635 cm diameter, were drilled in the sheet. A vector-virus mesh, 0.24 mm thread

size, was placed at the bottom of each pot to prevent soil from migrating out of the pot.

Pots were filled with Margate fine sand (siliceous, hyperthermic Mollic Psammaquent), a

native soil at the Fort Lauderdale Research and Education Center. The surface of an undisturbed

area was cleared of grass and roots and the first 8 cm (horizon A) of soil was dug out from the

site. The soil was sieved through an ASTM no. 10 (American Society for Testing Materials)

sieve, which allows passing particle sizes less than 2 mm in diameter. Soil was dried at 60 C for









24 hours to get consistent water content in the soil, and then mixed with water to an estimated

0.25 g g-1 of water content. Soil and water were mixed in an electrical soil mixer in batches large

enough to fill eight pots at one time. From each batch of soil, two samples were collected and

oven dried to determine water content. The percentage of water varied from 0.25 to 0.27 g g-1.

Total organic carbon (TOC) was analyzed from a composite sample from the soil used in both

runs. Total organic carbon was determined by using the Nelson and Sommers (1996) procedure.

In the first run the soil contained on average 4.19 % TOC while in the second run the soil

contained 7.80 % TOC.

A PVC ring 7.5 cm high was joined with a clamp to the top of each pot before compaction.

Then, the pot was filled with soil already mixed with the water to the top of the ring. Because

soil after compaction subsided 3 to 6 cm, the ring permitted adding more soil into the pot as

compaction reduced the level, and still getting the same level of soil for all pots. Soil was

compacted by dropping a 13.5 Kg weight from a height of 42.0 cm onto a piece of wood cut to

fit the inside of the pot, before planting grasses. A special device was built to achieve the

different compaction levels. The device consisted of 4 rods, 12 mm diameter and 155 cm height

which held a base and a secondary platform 38 cm from the base. The pot was placed at the base

where the compaction was applied. A solid shaft was attached in the center of the secondary

platform, and a tube, which rode over the center shaft held the weight that went up and down

hitting the piece of wood cut to compress the soil (Figure 4-1).

Treatments were low compaction (3 drops), medium compaction (10 drops), and high

compaction (42 drops). Initially a zero compaction treatment was included but later removed

from the experiment because there was difficult establishing bermudagrass stolon in this

treatment. Some of the bermudagrass stolons dried and died in some of the no compacted pots









probably because of an insufficient contact between soil and roots. The high pore content of the

soil did not retain enough water near the roots. After dropping the weights on each pot according

to each treatment, pots were weighed and volume was calculated to determine bulk density. To

calculate bulk density, the height of soil and weight in each pot was measured after they had

been compacted. The volume occupied by soil on each pot was calculated using the following

equation:

Volume pot = 7 x r2 x h Eq. [4 1]

where t = 3.1416
r = inside radius of the pot
h = height of the soil in the pot

Then, wet soil weight in each pot was calculated by subtracting the weight of the empty

pot from the total weight of the pot plus the wet soil. The dry soil in each pot was calculated by

multiplying the wet soil weight by the percentage of water content. The percent of water content

was estimated by a sample per each batch of soil mixed. Finally, bulk density was determined

according to Eq. 4.2.

Db= dry soil estimated per each pot/ volume of soil in each pot Eq. [4 2]

where Db= bulk density of the soil (g cm-3).

The number of drops resulted in slightly different bulk density values for each pot. Values

were averaged per treatment. The average values of bulk density for the first run were 1.19, 1.29,

and 1.37 g cm-3 for the low, medium, and high compaction treatments respectively, with eight

observations per treatment. In the second run, the average values of bulk density were 1.08, 1.18,

and 1.28 g cm-3 for the low, medium and high levels of soil compaction respectively. The

average for the two runs was 1.14, 1.24, and 1.33 g cm-3 for low, medium, and high treatment

respectively.









Goosegrass plants were germinated in the greenhouse, and transplanted to the already

compacted pots. Six seedlings of goosegrass with 2 to 3 leaves per each seedling were placed in

each pot. Tifway sod was used to obtain bermudagrass stolons. Four stolons were placed in each

pot. To accommodate roots of both plants, small holes were made on the pot with a tooth pick

where roots were placed.

In the first run, two replicates were planted on 26 May 2005, and the other two replicates

on June 1. After 8 days, all pots were fertilized with a soluble 36-6-6 (N-P205-K20) fertilizer at

nitrogen rate of 144 Kg ha-1, and a second fertilization at nitrogen rate of 48 Kg ha-1 was done 30

days from the date of planting. In the second run, all pots were planted on 8 August 2005, and

then fertilized two times as the first run at 8 and 30 days from the date of planting. Before

harvest, each pot with goosegrass was thinned to three plants per pot in the first run, and four

plants per pot in the second run. All pots were watered regularly not allowing them to wilt.

Plants were harvested 14 July 2005, in the first run and 19 Sept. 2005, in the second run.

Shoot (included leaves and stolons) and root growth was calculated as dry weight of washed

samples harvested 43 days from the day of planting for both runs. Aboveground plant portions

were separated from roots; dried at 60 C for 24 hours, and weighed to determine shoot and root

growth. Roots were washed and passed through a series of sieves to remove as much soil as

possible before placing in bags for drying in the oven.

Statistical Analysis

Data were analyzed by ANOVA to determine treatment differences at 0.05 significance

level and means were separated with Fisher's LSD, and regression of goosegrass dry weight and

compaction were determined using SAS software (SAS Institute, Cary NC).









Results and Discussion

Bulk density values obtained from each level of soil compaction in the second run were

lower than those values obtained in the first run. The coefficients of variation of the bulk density

were low and the same (4, 4, and 3%) for each of the compaction treatments low, medium, and

high, in first and second run respectively. In both runs, soils were sampled from the same area at

the Fort Lauderdale Research and Education Center; however, the TOC content differed between

the two soils. In the second run the soil had 8% TOC compared to 4 % TOC level in the soil of

the first run. The TOC differences are consistent with the differences in bulk density achieved.

Root and shoot growth response to compaction differed between the two species. In the

first run (Table 4-1), there was a significant block effect for roots (P<0.01) and shoots (P<0.001)

of goosegrass, which were higher in the last two replicates planted. In both the first and second

runs (Table 4-2), goosegrass root dry weight was decreased by compaction. In the two runs,

goosegrass root dry weight was decreased 53% (first run) and 26% (second run), under high

compaction compared with low compaction (P<0.05). In the high compaction pots, most

goosegrass roots were distributed around the wall of the pot where the compaction probably was

least. Root distribution was not measured; however, it was observed that roots were abundant in

the upper surface of the pots and fewer roots were seen in the lower depth for both high and

medium compaction pots (Figure 4-2). These results are similar to results obtained for Agnew

and Carrow (1985) and O'Neil and Carrow (1983) where Kentucky bluegrass and perennial

ryegrass roots were distributed on the first 5 cm of the soil. However, total root growth did not

decline, which the authors attributed to an increase in surface roots due to ethylene-promoted

adventitious roots. In the present study, compaction reduced total root growth, which coincides

with results obtained by Sills and Carrow (1983) in perennial ryegrass roots. Therefore, higher









mechanical impedance in the surface of the soil could impede root growth rate and result in

fewer roots in the lower soil zones.

Goosegrass shoot dry weight was decreased (P<0.01; Table 4-1) by compaction only in the

first run; goosegrass shoot dry weight was decreased 23% under high compaction, compared

with low compaction. The detrimental effect on goosegrass shoot and root growth observed the

first run may be partially explained by the high bulk density level reached in the pots.

For bermudagrass, no differences were observed in root and shoot growth due to

compaction treatments; however, there was a trend for reduced bermudagrass root and shoot

growth in both runs at higher compaction (Table 4-1 and 4-2). No studies have been conducted

on the effect of soil compaction on bermudagrass since traffic studies have included also wear

effects. Dunn et al. (1994) observed that the combination of spring and fall traffic was too

intensive for bermudagrass in mixture with cool season grasses. But these results do not apply to

the present study, since this study was done during the summer, the main growing season for

bermudagrass. Another study by Carrow et al. (2001) evaluated traffic effects on different

grasses and cultivars. Grasses with the best traffic stress tolerance in terms of turf coverage

regardless of soil moisture conditions were Tifway and TifSport bermudagrasses and Temple 1

Seashore paspalum. From these results one can infer that some bermudagrass cultivars can be

tolerant to traffic situations; however, the degree of soil compaction is not known.

Regression analysis relating goosegrass growth and compaction was significant for root

growth (P<0.01), but not for shoot growth in the first run. The analysis showed that an increase

in compaction predicted a decrease in goosegrass roots according to the regression formula Y=

7.89 1.73X where Y was the predicted goosegrass root dry weight and X was the level of

compaction. Compaction explained 74% of the variability observed on root growths. The









regression analysis relating goosegrass root and compaction, in the second run, was also

significant (P<0.05; Y= 17.5 2.02X), and compaction explained 63% of the variability

observed on root growths. However, the coefficient of variation in the second run was lower than

the coefficient of variation of the first run, 16 % and 36%, respectively.

Conclusions

Goosegrass root growth was significantly decreased by compaction, while shoot growth

was reduced only in the first run possibly due to the higher bulk density values. As already

explained in the introduction, if soil compaction is associated with low soil oxygen, goosegrass

will tolerate this condition and we should not expect a decrease in root growth. Root growth was

decreased at the highest level of compaction; however, since oxygen diffusion rate was not

measured in the pots, it was unknown if mechanical impedance and/or soil oxygen deficiency

was affecting goosegrass root growth.

Even though bermudagrass establishment was slow and highly variable, root and shoot

dry weight were not affected by compaction in this study. Therefore, the hypothesis that soil

compaction decreases bermudagrass growth more than goosegrass growth has not been

demonstrated. However, bermudagrass stolons may not have had enough time to develop and be

affected by compaction. It is worth noting that both species were not mowed during the

experiment, and there was no competition effect as the two species were separated in different

pots, possibly affecting results.









Table 4-1. Dry weight of bermudagrass and goosegrass roots and shoots at different soil
compaction levels in the first run when both species were growing separately.
Bermudagrass Goosegrass
Compaction level Roots Shoots Roots Shoots
g/pot
Low 0.98 7.07 6.13 a 21.39 a
Medium 0.65 6.03 4.11 b 19.96 a
High 0.68 5.14 2.89 b 16.40 b

Statistical analysis
Source of variation df Mean squares
Blocks 1 0.05 NS 9.76 NS 26.79 ** 1011.64 ***
Compaction level 2 0.13 NS 3.75 NS 10.71 26.39 **
Error mean square 8 0.28 11.46 1.28 2.02
Means of two replicates for each of two planting dates analyzed as blocks. Means followed with
the same letter within the same column are not different according to LSD test (P<0.05).
*, **, ***, NS; Significant at P<0.05; P<0.01; P<0.001; not significant at P<0.05.


Table 4-2. Dry weight of bermudagrass and goosegrass roots and shoots at different soil
compaction levels in the second run when both species were growing separately.
Bermudagrass Goosegrass
Compaction level Roots Shoots Roots Shoots
g/pot
Low 0.48 3.16 15.66 a 42.59
Medium 0.32 2.08 13.16 ab 41.09
High 0.21 1.70 11.62 b 41.79

Statistical analysis
Source of variation df Mean squares df Mean squares
Compaction 2 0.07 NS 2.12 NS 2 20.84 2.81 NS
Error mean square 9 0.06 2.25 12 4.92 44.12
Means of five replicates, not blocked, for each treatment except there were three missing values
for bermudagrass. Means followed with the same letter within the same column are not different
according to LSD test (P<0.05).
*, **, ***, NS; Significant at P<0.05; P<0.01; P<0.001; not significant at P<0.05.





























. ....


- m U -


U. -


qi i Y I -


... ....


Figure 4-1. Device used to produce compaction in the pots.
























64


... ...... .


........ ......
Jflll,


.. .. ....













.. ...... ..





... ......


. .. ..... .... ... .. ....






































Figure 4-2. Goosegrass roots growing in pot of medium compaction treatment (Db= 1.29 gcm-3)
indicate the property for the roots to remain shallow.









CHAPTER 5
GOOSEGRASS AND BERMUDAGRASS ROOT AND SHOOT GROWTH EVALUATED AT
DIFFERENT DEGREES OF SOIL COMPACTION, FERTILIZATION, AND CANOPY
REMOVAL (GLASSHOUSE STUDY)

Introduction

Goosegrass control relies on the use of pre and post-emergence herbicides and there is little

documentation on cultural management practices to prevent goosegrass infestation. Pre-

emergence herbicides are effective if applied prior to weed seed germination since they lose

effectiveness when applied too early or after the weeds have emerged (McCarty and Murphy,

1994). The most important environmental factors governing weed emergence are soil

temperature and soil moisture. A study done by Masin et al. (2005) evaluating the use of a model

to predict goosegrass emergence showed that goosegrass emergence predictions were

underestimated and delayed because of higher base temperatures in which goosegrass germinates

in the field. Additionally, the effect of soil compaction on the germination and establishment of

goosegrass seeds has not been evaluated.

Adequate seed-soil contact is a prerequisite for rapid emergence as it provides a route

through which soil water can enter a seed. Seed-soil contact is dependent on soil conditions such

as texture, aggregate size distribution, and level of compaction. Brown et al. (1996) attempted to

model the seed-soil contact areas using rigid spheres representing seeds, and spheres of modeling

clay, that were used to form artificial aggregates. Results showed that as compression reduced

macroporosity, the area of contact on all faces of the artificial seeds increased. The investigation

suggested that minimal reduction in macroporosity to produce a given degree of seed-soil contact

can be achieved when seed and soil aggregates are of closely similar size. However, reduction in

aggregate size during rolling could lead to aeration problems at low matric potentials (Brown et

al., 1996).









The physical properties of a seedbed have a major influence on emergence and early root

growth. Germination and shoot and root growth are affected by temperature and matric potential

and do not occur below or above critical temperatures or below a critical matric potential (Nabi

et al., 2001). Seed germination commences after a period of imbibition, during which the seed

takes up sufficient water to initiate growth. Goosegrass does not germinate if water potential is

less than -1.21 MPa (Masin et al., 2005). Ismail et al. (2002) found that goosegrass germination

is inhibited by a water potential of-0.80MPa.

High soil strength reduces the rate of shoot and root growth, delaying and sometimes

preventing emergence. Nasr and Selles (1995) reported that at every level of bulk density (0.9 to

1.7 gcm-3) the resistance to penetration of the seedbed was higher in coarse than in fine-

aggregated seedbeds due to cohesion and friction within aggregates is higher than among

aggregates. In the Nasr and Selles (1995) study, increases in bulk density and aggregate size of

the seedbed delayed emergence and reduced the number of seedlings of wheat (Triticum

aestivum L. c.v. Lancer) that emerged. Although the estimates of speed or rate of emergence

were highly correlated with indicators of the physical conditions of the seedbed, final emergence

appeared not to be affected by bulk density and aggregate size (Nasr and Selles, 1995). The

results suggested that when seed-soil contact is adequate, the physical conditions of the seedbed

affect primarily the speed and time at which seedlings emerge from the soil, and the final

emergence is affected not only by physical conditions of the seedbed, but also by other factors,

probably related to seed size and other seed characteristics (Nasr and Selles, 1995).

The objective of this experiment was to test the third hypothesis that soil compaction

decreases bermudagrass growth more than goosegrass growth when both species were growing

together. Along with testing soil compaction effect on bermudagrass and goosegrass growth,









fertilization and mowing treatments were added to the experiment. The purpose of the low

mowing height treatment was to simulate canopy removal produced by wear on a field situation.

The objectives of this study were:

1) To determine whether compaction, canopy removal, and fertilization influence

goosegrass emergence when it was interplanted into a bermudagrass stand.

2) To evaluate whether compaction, canopy removal, and fertilization influence shoot and

root growth of goosegrass and bermudagrass growing together.

Materials and Methods

A glasshouse study was conducted from 14 Feb. to 9 Sept. 2006 at the University of

Florida, Fort Lauderdale Research and Education Center, Davie, Florida. The experiment was set

up in the same cylinder PVC pipe pots as in the prior glasshouse experiment using the same

native soil (Margate fine sand). Two levels of soil compaction, low bulk density (3 drops, 1.07

gcm-3) and high bulk density (42 drops, 1.26 gcm-3), done in the same way as the prior

experiment, were randomly assigned to pots

Tifway bermudagrass stolons were planted in the pots on 14 and 15 Feb. 2006 and pots

were placed in the greenhouse. Information about the management of the pots is given in Table

5-1. Turf was mowed by a hand-held, battery-powered grass shear at the specified height

described in Table 5-1. Clippings were harvested, dried at 600C for 24 hours, and weighed on

three dates before goosegrass seeds were added to the pots. Pots were assigned to different

blocks depending on their total bermudagrass dry matter per pot. There was no difference

between low and high compaction treatments in the total clippings collected in three mowing

episodes.

On 19 June 2006, four month from the date of bermudagrass planting, when bermudagrass

stand had covered the surface of the pots, mowing height and fertilization treatments were









assigned to the pots. Treatments factors were 2.54 and 1.27 cm mowing height, corresponding to

high and low mowing respectively; and 96 and 48 Kg ha-1 nitrogen fertilization rate to

correspond to high and low rate respectively. Both treatments factors were assigned randomly to

pots. Goosegrass was seeded in all pots (approximately 600 seeds per pot). After June 19

clippings were not collected because both species were growing together. The mowing height

treatments were done weekly and the fertilization rates treatments were done monthly. The last

mowing was done on August 23 and after 14 days without mowing harvest of the pots began.

Bermudagrass grew in the pots for 203 to 206 days from the time stolons were

transplanted, and goosegrass plants grew between 70 to 76 days from the time seeds were

planted to the moment of harvest. All pots were watered regularly not allowing them to wilt.

During two weeks, after goosegrass seeds were placed in the pots, pots were watered every day

to assure a period of imbibition of the seeds.

Plant emergence of goosegrass was determined by counting the number of seedlings in

each pot, 10, 11, 14, 16, 18, 21, 24, and 29 days from the date seeds were seeded in the pots. On

day 36, most of the pots had six seedlings of goosegrass; however, since a few did not reach this

number on day 43 (1 August 2006) all the pots were thinned to five seedlings. In addition,

numbers of seedlings of goosegrass that had tillers were counted per pot before harvesting.

At harvest, pots were cut with a circular saw to make it easier to get soil and plants from

the pot. Bermudagrass and goosegrass plants were separated, and shoots, including leaves and

stolons, were separated from roots; both were dried at 60 C for 24 hours, and weighed to

determine root and shoot growth. Roots were washed and passed through a series of sieves to

remove as much soil as possible before placing in bags for the oven. Root and shoot dry weight

was registered by treatment and species.









Statistical Analysis

Experimental design was a randomized complete block with four replications. Data was

analyzed by ANOVA using SAS software to determine treatment differences at the 0.05

significance level (SAS Institute, Cary NC).

Results and Discussion

Goosegrass emergence was highly different for mowing height and compaction treatments

(Table 5-2). In the high mowing treatment goosegrass emergence was reduced 58% compared

with the lower mowing, probably due to a decrease in light exposure on the seed. Additionally,

in the high compaction treatment goosegrass emergence was reduced 41% compared to the low

compaction (Table 5-2).

Nasr and Selles (1995) suggested that when seed-soil contact is adequate, the physical

conditions of the seedbed affect primarily the speed and time at which seedlings emerge from the

soil and the final emergence with time is not influenced by physical conditions of the soil at the

moment of planting. Probably, in this study the lower final emergence on the high compaction

treatment was due to a poor seed-soil contact.

Numbers of tillers per seedling of goosegrass differed only for mowing treatments (Table

5-2). The low mowing height treatments had a large number of seedlings with tillers (50%),

compared with the high mowing treatments (16.5 %). The interception of light reaching the

crown of the gossegrass seedlings as a result of light interception by the leaves of the

bermudagrass probably reduced tillering. This result implies that in a golf course or sports field

mowing low could enhance goosegrass tillering and consequently shoot density.

No differences were found in goosegrass shoot and root mass for any of the treatments. In

the present study goosegrass root growth was not affected by soil compaction, whereas in the

prior glasshouse experiment they were highly decreased by compaction. In the present study,









even when plants were growing in the pots for 76 to 70 days, a longer period than in the prior

experiment, they were smaller probably because they were mowed every week, and were

affected by bermudagrass competition. In the previous glasshouse study, goosegrass plants were

grown in the pot for 43 days without restricted by mowing or bermudagrass competition.

Bermudagrass root mass was reduced by high compaction and low mowing treatments

respectively (P<0.01; Table 5-2). Since root distribution was not observed in this study, it is

unknown at which depth root growth was more affected. Knowing root distribution could have

helped understand which factors mechanical impedance at shallower depth or root dieback at

deeper depth (Agnew and Carrow, 1985; Carrow, 1980) could have explained the results

observed. Research has shown that reducing mowing height results in decreasing root growth

(Turgeon, 2005; Duble, 1989).

Root mass decreased the most in the low fertilization and low mowing treatment;

therefore, higher fertilization could alleviate some of the root growth reduction caused by low

mowing. In addition, root mass was enhanced when the soil was not compacted and

bermudagrass was mowed high (Fig.5-1); therefore, high mowing treatment may not alleviate the

effect of high compaction in bermudagrass roots growth.

Greater bermudagrass shoot mass was observed for high fertilization (P<0.05) and high

mowing treatment (P<0.001; Table 5-2). After mowing, the rate of growth (leaf and tiller

production) in turfgrass is dependent on the levels of carbohydrates in the leaves, stem, and

crown of the tiller. Therefore, the rate of regrowth after mowing is greater when carbohydrates

are high. Consequently high mowing height treatments, which had a greater residual leaf area,

had a faster rate of regrowth in the conditions of this study (Duble, 1989). However, the mowing

treatments in this study (12.7 and 25.4 mm) were higher than mowing heights recommended for









bermudagrass tees (6.4 to 13 mm), while nitrogen fertilization rates (48 to 96 Kg ha-1) were near

the range (25 to 60 Kg ha-1) recommended per month (Beard, 2002). Bermudagrass shoot dry

weight decreased the most in high compaction and low fertilization treatments; therefore, higher

fertilization may alleviate the effect of soil compaction on bermudagrass shoots.

Conclusions

Goosegrass seedling emergence and number of tillers were increased by lower mowing. In

this study, bermudagrass was more affected than goosegrass, which agreed with what was stated

in the hypothesis. Bermudagrass shoot mass was increased with high fertilization and mowing,

and root mass was decreased by high compaction and low mowing. Even when bermudagrass

roots were decreased at higher compaction it neither reflects a decrease in the shoot mass nor an

increase in goosegrass growth.

Consequently mowing, a principal cultural practice could have more significance on the

emergence and infestation of goosegrass in bermudagrass than compaction. In addition,

fertilization may alleviate soil compaction effects on bermudagrass shoots growth, and may

alleviate low mowing effects on bermudagrass root growth. Results obtained in this research may

vary in a field situation, but it creates new thoughts on the need to evaluate the discussed cultural

practices in the control of goosegrass.









Table 5-1. Management of the pots from establishment to harvest when both species were growing together.
Operation Date Details
Bermudagrass sprigged 14 and 15 February 4 stolons/pot
Before treatments:
Nitrogen Fertilization 6 March 48 Kg ha-1


13, 20 March, 27 April
4 May and 9 June

3 and 24 May
13 June


Mowing


144 Kg ha-1
48 Kg ha-1

3.81 cm height
2.54 cm height


After treatments:

Goosegrass seed planted

Goosegrass thinned

Mowing

Nitrogen Fertilization

Watering

Insecticides




Harvest


19 June

1 August

19 June; weekly

19 June; monthly

Three times per week

22 March
9 June
11 and 19 July

6 to 9 September


600 goosegrass seeds/pot

5 seedlings/pot

1.27 and 2.54 cm height

96 and 48 Kg ha-1

As required

Abamectin to control aphids (Homoptera)
Abamectin to control mites (Acari)
Acephate to control mealybug (Homoptera)

Root and shoot separated by species









Table 5-2. Goosegrass emergence and tillers, root and shoot dry weight of goosegrass
table. Means of 16 observations.


and bermudagrass by treatments and ANOVA


Treatments

Compaction (C)

Fertilization (F)

Mowing (M)


Levels Emergence
(seedlings/pott)
Low 87
High 51
Low 65
High 74
Low 98
High 41


Goosegrass
Tillers
(no./plants)
1.19
1.62
1.50
1.31
2.00
0.81


Roots Shoots


0.31
0.33
0.31
0.33
0.31
0.33


0.96
1.15
0.96
1.15
1.09
1.02


Bermudagrass
Roots Shoots
(g/pot)
5.68 13.88
4.26 12.92
4.71 12.86
5.24 13.93
4.46 11.22
5.48 15.58


Statistical analysis


Source of variation
Block
Compaction
Fertilization
Mowing
CxF
CxM
FxM
Error


677
10368 **
578
26450 ***
28
2080
190
967


0.13
0.06
0.01
0.45 *
0.00
0.00
0.01
0.06


CV (%) 44.70 93.60
t Surface area of the pot: 298.6 cm2.
*, **, *** significant at P<0.05; P<0.01; and P<0.001, respectively.


-Mean squares-
0.09 1.11
0.00 0.28
0.00 0.29
0.00 0.03
0.01 0.06
0.02 0.29
0.00 0.01
0.02 0.39


49.20 59.40


4.53
16.03 **
2.26
8.37 **
2.70
8.56 **
8.39 **
0.91
19.20


4.32
7.27
9.13
151.51
9.39
0.01
0.08
1.74
9.86












- Mowed 2.54 cm
Mowed 1.27 cm


Compaction, P<0.001
Mowing height, P<0.01
Compaction x mowing, P<0.01

T


High


Figure 5-1. Bermudagrass root dry weight for compaction and mowing treatments combinations.
Means of eight replications.


"f




0
0


Low


Compaction









CONCLUSIONS

This research studied the effect of traffic on goosegrass infestation and soil compaction,

and the growth of bermudagras and goosegrass planted in compacted soil. Goosegrass cover and

plant density were higher on traffic areas of ball fields and golf course tees than on adjacent no-

traffic areas. Therefore, the first hypothesis was accepted that goosegrass infestation was greater

on traffic areas. However, traffic areas had no impact on soil penetration resistance or bulk

density values. In addition, other soil properties measured related to soil compaction were not

affected by traffic. Although in one out of several instances there was increased penetration

resistance associated with traffic the hypothesis was rejected that soil compaction was higher on

traffic areas compared to non-traffic areas in golf courses and sports fields. In addition, the soil

penetration resistance values did not reach the limit value at which penetration resistance

becomes critical for root growth.

Soil compaction affected both goosegrass and bermudagrass root growth. In the first

glasshouse experiment, goosegrass root growth decrease with soil compaction while

bermudagrass was not affected. However, in the second glasshouse experiment, the opposite

result occurred. Bermudagrass root growth decreased with soil compaction while goosegrass was

not affected. Therefore, the third hypothesis was accepted that both species were affected by

compaction.

Low mowing increased the germination and tillering of goosegrass. Therefore, cultural

practices such as mowing, fertilization, and irrigation that promote vigorous, dense turf and

improve turfgrass wear tolerance should be cautiously planned to prevent goosegrass

establishment.









Further research is required to verify the mechanisms that impart wear tolerance to

goosegrass. Knowledge of these characteristics will assist in developing cultural practices that

favor turfgrass more than goosegrass growth.









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BIOGRAPHICAL SKETCH

Claudia B. Arrieta was born in 1966 in a small city Durazno in Uruguay. She grew up in a

cattle and sheep operation and she rode her horse every day to a one room rural school where she

completed her elementary school years. She finished high school in Durazno, and in 1985 she

moved to the country capital Montevideo to join the Faculty of Agriculture. In 1992, after

receiving her bachelor's degree Ingeniero Agronomo she became an Agronomy Extension Agent

advising dairy farmers for 4 years. In 1997, she married and moved to the United States where

her husband was working. She finished an Associate in Science in Wetland Management at

Broward Community College with the objective of broadening her job expectations. She worked

on different horticultural nurseries for two years until in 2004 she learned about the Fort

Lauderdale Research and Education Center in Davie and the possibility of doing a master's

degree as a distance education student. She joined the University of Florida in 2004 and will

graduate with a Master of Science degree in the Soil and Water Science Department in 2006.

Upon graduation she would like to continue using her knowledge and skills in turfgrass and soil

science as a research assistant at either a public or private institution.