Published online 1 March 2007
Published in Crop Sci 47:782-784 (2007)
© 2007 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
TURFGRASS SCIENCE
Evaluating Traffic Stress by the Brinkman Traffic Simulator and Cady Traffic Simulator on a Kentucky Bluegrass Stand
J. T. Vaninia,*,
J. J. Hendersonb,
J. C. Sorochanc and
J. N. Rogers, IIId
a New Dimensions Turf, Inc., 9 Colvin Ave., Buffalo, NY 14216
b Univ. of Connecticut, Dep. of Plant Science, 1376 Storrs Rd., Unit 4067, Storrs, CT 06269-4067
c Univ. of Tennessee–Knoxville, Ellington Plant Science Bldg., 2431 Center Dr., Knoxville, TN 37996
d Michigan State Univ., Dep. of Crop and Soil Sciences, 162 Plant and Soil Science Bldg., East Lansing, MI 48824. Funding was provided by Project GREEEN and the Michigan Turfgrass Foundation
* Corresponding author (ndturf{at}mac.com).
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ABSTRACT
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The Brinkman Traffic Simulator (BTS) has been a useful tool to simulate sports field traffic. However, rate of traffic stress produced by the BTS, a pull-behind unit with two differentially connected studded rollers, has been questioned. The Cady Traffic Simulator (CTS), a modified walk-behind core cultivation unit, was developed and tested to potentially produce more aggressive traffic stress. A comparison study was initiated between the BTS and CTS to evaluate these simulators on a Kentucky bluegrass (Poa pratensis L.) stand. Playing surface data collected were surface hardness, traction, soil moisture, bulk density, porosity, and plant counts. Higher surface hardness, lower traction, and lower plant count values resulted when the CTS applied 10 passes per week (PPW) compared with other treatments. Surface hardness, traction, and bulk density values were statistically similar when the CTS applied 2 PPW, and BTS applied 10 PPW.
Abbreviations: BTS, Brinkman Traffic Simulator • B2, 2 passes wk–1 applied with the BTS • B10, 10 passes wk–1 applied with the BTS • CTS, Cady Traffic Simulator • C2FF, one pass forward/one pass forward, respectively, applied with the CTS for a total of 2 passes wk–1 • C10FF, one pass forward/one pass forward, respectively, applied five times with the CTS for a total of 10 passes wk–1 • C2FR, one pass forward/one pass reverse, respectively, applied with the CTS for a total of 2 passes wk–1 • C10FR, one pass forward/one pass reverse, respectively, applied five times with the CTS for a total of 10 passes wk–1 • PPW, passes per week.
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INTRODUCTION
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SUBJECTING RESEARCH areas to simulated traffic is imperative when the objective is to contribute information on the effects of traffic stress on turfgrasses or playing surfaces. Turfgrass traffic stresses can be separated into two major components: turfgrass wear and soil surface disruption (Beard, 1973). Turfgrass wear can include tissue tearing, tissue bruising, and tissue removal (i.e., divoting), primarily from horizontal forces. Soil surface disruption can include soil compaction (i.e., soil displacement), which is primarily a vertical force. Once traffic stresses are imposed on a turfgrass area together, these factors mentioned above cause a deterioration of playing surface quality.
Many traffic simulators have been developed and used to create traffic stress on turfgrass areas for research purposes. Traffic simulation began in turfgrass research by driving automobiles and trucks to simulate aircraft traffic on research plots designed to test seed mixture suitability for airfields (Morrish and Harrison, 1948). Perry (1958) described the first machine designed specifically to create traffic stress on turfgrass. This machine combined the scuffing effects of feet and compactive effects of two golf spiked rollers. Goss and Roberts (1964) described a modified aerifier designed to induce scuffing and compactive effects to turfgrasses. Other researchers designed turfgrass wear simulators to induce only wear on turfgrass stands without compacting the soil for the purpose of studying turfgrass wear tolerance alone (Shearman et al., 1974; Bonos et al., 2001).
Even though these wear simulators had been specifically designed for turfgrass wear only, free-rolling studded drums were the most widely used (Van Der Horst, 1970). Free-wheeling studded drums enabled researchers to treat several plots in a relatively short period of time. However, they lacked significant horizontal force to produce adequate levels of traffic stress in few relative passes. Canaway (1976) deemed the forces produced by free-wheeling studded drums insufficient to simulate athletic activities performed on sports fields and introduced the Differential Slip Wear Machine. This simulator is widely used by the Sports Turf Research Institute in the United Kingdom and uses differentially connected studded drums to create traffic stress. Carrow et al. (2001) described a similar self-propelled machine that utilizes differentially connected studded drums that also creates traffic stress.
Other traffic simulators have also been designed and built to induce traffic stress to large plot areas in a time efficient manner (Shearman et al., 2001). These units are self-propelled units that induce turfgrass wear and soil compaction and lack the use of studded drums. One unit employs multiple free-wheeling, smooth rubber tires to induce traffic stress, and the other unit described uses smooth rubber covered steel drums that are differentially connected.
The Brinkman Traffic Simulator (BTS) is a drawn-type traffic simulator that is used widely in the United States as a sports field traffic simulator (Cockerham and Brinkman, 1989). This simulator utilizes differentially connected studded drums to create traffic stress over large plot areas very quickly. Cockerham (1989) linked the rate of wear produced by the BTS to the amount of wear produced in one National Football League game at the 40-yard line, quantitatively, measuring the number of cleat marks per square foot. However, it must be pulled over the plots, and its rate of wear has been questioned (Minner, 1989).
A new traffic simulator (a modified, self-propelled, core cultivation unit) was developed and compared to the BTS with the goal of producing a more aggressive traffic stress (Henderson et al., 2005). According to Henderson and coworkers (2005), total ground forces between the Cady Traffic Simulator (CTS) and BTS were similar using a force plate. However, the biggest difference was comparing compressive and net shear stresses produced by each simulator. The cleat surface area of the CTS (1354.9 mm2) was much smaller than the BTS (3483.9 mm2) leading to a larger force production per unit area by the CTS (Henderson et al., 2005). Research was warranted in actual field conditions.
Successful simulated traffic should encompass the following: (i) traffic should be uniform and reproducible, (ii) traffic should be similar to natural wear, and (iii) the rate of wear must be accelerated greatly over the natural rate of wear to keep the relative number of simulated passes to a minimum compared to actual wear (Younger, 1961). Previously developed traffic simulators, including the BTS, have proven to induce uniform and reproducible traffic, but traffic stress aggressiveness has been questioned.
The objective of this study was to evaluate and compare the rate of traffic stress produced by the BTS and CTS in field conditions via (i) quantifying playing surface parameters: peak deceleration, traction, divoting resistance, and plant counts and (ii) quantifying soil physical properties: volumetric soil water moisture, bulk density, and total porosity.
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MATERIALS AND METHODS
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In August 2001, a field trial was established at the Hancock Turfgrass Research Center at Michigan State University, East Lansing, MI. A randomized complete block design replicated three times was initiated to evaluate seven different traffic treatments on a Kentucky bluegrass (Poa pratensis L.) stand. Treatments are listed in Table 1. Sizes of experimental units were 1.7 by 9.0 m. The soil was a Capac loam containing 61% sand, 23% silt, and 16% clay (fine-loamy, mixed mesic Aeric Ochraqualf).
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Table 1. Description of traffic treatments evaluating the Brinkman Traffic Simulator (BTS) and Cady Traffic Simulator (CTS).
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Traffic treatments were applied with the BTS (Cockerham and Brinkman, 1989) and CTS (Henderson et al., 2005). The BTS was pulled using a John Deere 5200 tractor (Moline, IL), and weighed 571 kg when rollers were filled with water. The CTS was a modified Jacobsen Aero King 30 (A Textron Company, Charlotte, NC) self-propelled core cultivation machine and weighed 680 kg. Traffic treatments were applied from 27 August to 1 October in 2001 and 12 August to 5 September in 2002. One traffic event is defined as the total of two passes regardless of simulator type or direction of operation (BTS could only apply traffic in the forward direction compared to CTS applying traffic in both the forward or reverse directions). Traffic treatments for both simulators included one pass in one direction and the second pass in the opposite direction. Both passes were the full length of the treatment. No more than two passes were made each day regardless of traffic treatment. Treatments with two passes per week (PPW) were applied every Monday, and treatments with 10 PPW were applied every weekday. Data were collected after the traffic treatments were applied.
The study area was mowed twice per week with a Z Master mower (Toro Co., Minneapolis, MN), with a 1.58-m deck, at a height of 51 mm with clippings returned. Nitrogen fertility applied was Lebanon Country Club 18–3–18 (Lebanon, PA) at a rate 24.5 kg N ha–1 monthly April through October. Irrigation was applied daily during reestablishment and as necessary throughout the experiment to prevent wilt. No herbicides, fungicides, or insecticides were applied throughout the duration of the experiment.
On 20 May 2002, plots were vertically grooved with a Graden GS04 Verticutter (Campbellfield, VIC, Australia), with 2-mm blades and 25.4-mm spacing between blades, and the debris was dragged back in. Also, the study was slit-seeded with a Cushman slit seeder (Ransomes-Cushman-Ryan, Lincoln, NE) in two directions at 49 kg ha–1 per direction with Kentucky bluegrass 50% ‘Rugby II’ and 50% ‘Champagne’. Andersons fertilizer (19–19–19) (Maumee, OH) was applied at 49 kg N ha–1
Peak deceleration, shear resistance, divoting resistance, and plant counts were evaluated on 3, 17, and 24 September and 1 October in 2001 and 15, 19, 22, and 29 August and 5 September in 2002. Volumetric soil water content, bulk density, and porosity were only measured in 2002. The Clegg Impact Soil Tester (Lafayette Instrument Co., Lafayette, IN) was used to measure peak deceleration (Gmax) values as an indication of surface hardness. A 2.25-kg hammer was dropped randomly in three locations on each plot from a height of 0.46 m (Rogers and Waddington, 1990). Traction values (Nm) were measured by both the Eijkelkamp shear vane Type 1B (Giesbeek, the Netherlands) for shearing resistance (Rogers and Waddington, 1990) and Clegg Turf Shear Tester (Wembley DC, WA, Australia) for divoting resistance. Three measurements were recorded per plot. Plant counts were determined by extracting a soil plug with a soil probe (32-mm diameter), and individual plants were counted within the plug. Three different plugs were collected and quantified per plot. Volumetric soil water content (m3 m–3) values were measured with a portable time domain reflectometry gauge and probe. The instruments used were the Trime FM gauge and FM3 probe with 50-mm rods (Mesa Systems Co., Medfield, MA) (Topp et al., 1982). One measurement was recorded in the middle of the traffic lane.
On 24 Sept. 2002, three undisturbed soil cores (347.72 cm3) were extracted, and bulk density (g cm–3) was determined by the method described by Blake and Hartage (1986). Total porosity (%) was calculated by dividing bulk density by the average particle density (2.65 g cm–3), and this number was subtracted from one.
Data were analyzed using Agriculture Research Manager (Gylling Data Management, 2000) for a 1-way factor ANOVA. Treatment means were separated using Fisher's Protected LSD values, and calculated when the F ratio was significant at the 0.05 level.
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RESULTS AND DISCUSSION
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Peak deceleration values are listed in Table 2 and differences occurred for each sampling date in 2001 and 2002. The BTS treatments were not different from the control throughout the experiment for each year. Furthermore, the B2 (2 passes wk–1 applied with the BTS), B10 (10 passes wk–1 applied with the BTS), C2FF (1 pass forward/1 pass forward, respectively, applied with the CTS for a total of 2 passes wk–1), C2FR (1 pass forward/1 pass reverse, respectively, applied with the CTS for a total of 2 passes wk–1), and control treatments were similar in 2001. Both C10FF (1 pass forward/1 pass forward, respectively, applied five times with the CTS for a total of 10 passes wk–1) and C10FR (1 pass forward/1 pass reverse, respectively, applied five times with the CTS for a total of 10 passes wk–1) treatments had higher peak deceleration values than the control and B10 treatments with exception for 1 Oct. 2001 due to wet soil conditions and puddling of water in the traffic lanes. Soil compaction increases soil density, reduces percolation and infiltration, reduces soil aeration and porosity, increases CO2 and toxic gases, and increases water run-off and heat conductivity (Letey et al., 1966; Waddington et al., 1974; Carrow, 1980). A negative correlation between peak deceleration and soil moisture measurements was found when evaluating game and practice fields in Pennsylvania (Rogers et al., 1988). Although soil water content was not measured in 2001, puddling of water in the traffic lanes was observed for these treatments indicating a more compacted surface thus producing lower peak deceleration values for this particular date. The BTS produced minimal stress forces (Henderson et al., 2005) thus peak deceleration values were lower on these treatments compared to CTS treatments.
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Table 2. Effects of traffic treatments on peak deceleration values on a Kentucky bluegrass stand, East Lansing, MI.
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Shear resistance, divoting resistance, and plant count values are listed in Table 3. BTS treatments were not different from the control throughout the experiment for each parameter measured. Only the C10FF treatment had lower shear resistance values compared to the control for both 2001 and 2002 except for 19 Aug. 2002. Both the C10FF and C10FR treatments had lower divoting resistance values compared to the control in 2002. The C10FF and C10FR treatments had the lowest plant count values, regardless of CTS direction. On 5 Sept. 2002, the B10, C2FF, C2FR, and control treatments had lower plant counts than the B2 treatment indicating more wear or damage to the playing surface, however shear resistance values were similar. The C2FF and C2FR treatments were similar to the B10 treatments for all parameters measured (except for peak deceleration on 5 Sept. 2002 and volumetric water content on 29 August). Therefore, two passes by the CTS would be similar to 10 passes by the BTS. The CTS produces higher compressive and net shear forces when operated in either direction versus the BTS (Henderson et al., 2005). The angle the feet strike the playing surface may also explain why the CTS produced more wear. When operating the CTS in the reverse direction, the angle of the "feet" from vertical was 52° compared to 37° for studs on the rear drum of the BTS (Henderson et al., 2005). Grass plants and tufts of grass were being dislocated and flung by the "feet" coming in contact with the playing surface when operating the CTS in the reverse direction. These actions can be confirmed by the data where the C10FF and C10FR had lower plant count values compared to other treatments. The BTS did not dislodge any turfgrass from the playing surface at any given time throughout the experiment; plant counts for B2 and B10 treatments were similar to the control. This would indicate the BTS producing a less-aggressive type traffic stress compared to the CTS.
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Table 3. Effects of traffic treatments on shear resistance, divoting resistance, and plant counts for a Kentucky bluegrass stand, East Lansing, MI.
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Volumetric water content, bulk density, and calculated total porosity values are listed in Table 4. BTS treatments were not different from the control throughout the experiment for the parameters listed except for volumetric water content on 5 Sept. 2002. On 29 Aug. 2002, volumetric measurements could not be taken on C10FF and C10FR treatments because the probe could not penetrate the ground. For these two treatments, the soil appeared drier, and peak deceleration values were higher than all other treatments (Table 2). Only five treatments were analyzed on 29 August for volumetric water content. The C10FF and C10FR treatments had greater bulk density and lower total porosity values compared to B2, B10, and control treatments. These results indicate treatments C10FF and C10FR had higher soil compaction. Consequently, these soil changes can have adverse effects on growing conditions for both proper shoot and root growth (Letey et al., 1966; Van Wijk, 1980; O'Neil and Carrow, 1982). This was evident for C10FF and C10FR treatments with higher peak deceleration values and lower shearing and divoting resistance and plant count values.
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Table 4. Effects of traffic treatments on soil water content, bulk density, and calculated air porosity on a Kentucky bluegrass stand, East Lansing, MI, 2002.
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There were no differences between B2 and B10 treatments for all measured parameters except for plants counts on 5 Sept. 2002. Treatments B10, C2FF, and C2FR usually produced similar results compared to each other; there was only a difference between the B10, C2FF, and C2FR treatments for soil water content values on 29 Aug. 2002 and peak deceleration values on 5 Sept. 2002.
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CONCLUSIONS
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The BTS and CTS were both able to produce traffic stress. However, the CTS provided more turfgrass injury than the BTS. Bulk density was higher and total porosity lower (not similar) for C10FF and C10FR treatments compared to the Brinkman and Control treatments. Ten passes with the CTS increased peak deceleration and reduced traction, divoting resistance, and plant counts. Two passes with the CTS (for either treatment) provided traffic stress similar to 10 passes with the BTS. The CTS caused more turfgrass injury per pass and maybe more representative of intense turfgrass injury on high trafficked areas on sports fields.
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ACKNOWLEDGMENTS
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The authors would like to thank Project GREEEN and the Michigan Turfgrass Foundation for their generous support in funding this project.
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NOTES
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All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication August 3, 2006.
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ABSTRACT
INTRODUCTION
