1998 Iowa Turfgrass Research Report
The Effect of Topdressing with Rubber Buffings on Intensely Trafficked Football Turf - 1996-97 data
Jeffrey J. Salmond and David D. Minner
The rubber recycling industry was introduced to the turfgrass industry about 15 years ago. Since then, ways have been improved for the incorporation of the rubber into the soil profile. Crumb rubber is typically the rubber particle used for topdressing turf. The spherical crumb rubber particle shape allows for easier incorporation of the material into core aerification holes. Buffing rubber has a length-to-width aspect ratio of 7:1. Buffing rubber, therefore, is not used as often for two reasons. One, the number of passenger retreads have decreased (U.S. EPA and PES, 1993) and two, the longer buffings do not filter into the turf canopy or core holes very easily. Other research reported in this publication indicates that turf injury was less when topdressed with buffing rubber compared to crumb rubber.
Traffic studies usually consist of a machine simulating a traffic pattern (i.e. Brinkman and Brouwer traffic simulators). Our goal was to use football players to apply live traffic to buffing rubber. The objectives of the two-year study were to evaluate buffing rubber as a topdressing and to determine its effects on seed germination.
Materials. A study was initiated in the summer of 1996 at the Ames High School football field in Ames, Iowa to evaluate the effects of buffings rubber on a intensely trafficked football turf for a two-year study. The data were collected during a 5-day football training camp in August of 1996 and August of 1997. The experimental plots were arranged on a mature stand of common Kentucky bluegrass (Poa pratensis L.) overseeded with perennial ryegrass (Lolium perenne L.) in an area just off the playing field. Overall plot size was 1.8 m x 6.1 m (6 ft. x 20 ft.) with individual plots being 0.9 m x 0.6 m (2 ft. x 3 ft.) for a total of 18 plots, 2 rows of 9 plots each (Table 1). Each rubber treatment was adjacent to a non-rubber control plot. The three medium buffing (MB) treatments were arranged in a randomized complete block design. The rubber treatments were placed at 0.6, 1.3, 2 cm depths, (1/4", 1/2" and 3/4" respectively), and replicated three times. The overall plot was mowed at 1.5 cm and core aerified with 1.3 cm diameter hollow tines and topdressed with the rubber treatments. Topdressing with the 2 cm treatment was excessive, therefore a remaining amount of rubber was added later, after settling had occurred, to achieve the desired amount.
The particle size of the medium buffing rubber ranged from 1.0 mm diameter (18 mesh) to 0.5 mm diameter (35 mesh). The average ratio of length to width for the longest shreds in the buffing rubber was approximately 7:1.
Percent turfgrass cover was used to assess turf injury from traffic. Temperatures were recorded within the grass canopy and at a 2.5 cm depth. The surface temperature was measured using a hand-held infrared probe (Cole-Parmer, Type J, model # H-39652-00, Niles, IL) plugged into a thermocouple thermometer held at a height of 61 cm above the plot. The effective diameter cone measured was 15 cm with an area of 182.6 cm2. The 2.5 cm depth temperature was measured with a 30.5 cm, 0.64 cm diameter heavy-duty penetration probe (Cole-Parmer, Type T, model # H-93601-26, Niles, IL).
Surface hardness was measured with the Brüel and Kj' r 2515 Vibration Analyzer (Br el and Kj' r, Decatur, GA) (Table 2).
The experimental plot was measured to the size of a football exercise apparatus called 'ropes'. The object of the exercise is to develop balance of the athlete and to teach foot and eye coordination. Human athletes, wearing 1 cm high-density plastic cleats, were used to uniformly apply traffic to the plots during the football practice exercise. The athlete runs through the ropes by placing his foot into the desired square sector. The coach can instruct the athlete to do various exercises such as a criss-cross, bunny-hop, side step, diagonal and others. The 1.8 m x 6.1 m apparatus was placed over the experimental plot area such that each square of the apparatus was over the top of the 0.9 m x 0.6 m treatments and controls. The number of feet to hit each plot was calculated with a hand-held counter and later recorded to find the total number of feet placed into each individual plot.
Data were analyzed by using the general linear model (GLM) procedure of SAS (SAS Institute, 1990). Data collected from the two-year experiment were pooled and analyzed using the method for multiple year, single location as described by Steel and Torrie (1980). Fisher's least significant difference (LSD) test was used to compare main effect over-all treatment means for each collection day and for the temperatures (P ¾ 0.05).
The analysis showed no overall differences between the two years. The number of feet trafficked into each plot increased from 1996 (Table 3) to 1997 (Table 4). Differences between the rubber treatments and the untreated control were not apparent on three of the five collection days. The rubber treatments, however, had a higher percentage of living turfgrass cover throughout the traffic period than the controls (Table 5). The 0.6, 1.3, and 2 cm depths of medium buffing rubber showed a 57, 71, and 82% increase in turf cover compared to their respective untreated controls by the end of the traffic treatments, respectively. On the fifth collection day, the medium buffing at 2 cm depth had an average percent turf cover of 33 and the control had 6% turf cover. Likewise, the 1.3 cm depth of rubber had an average turf cover of 32% and the control had 9% turf cover. The 1.3 and 2.0 cm depths showed a 50% increase in turf cover compared to the 0.6 depth of rubber by the end of the traffic treatments (Table 5). The 0.6 cm depth of rubber had 15% turf cover compared to 32% and 33% turf cover for the 1.3 and 2 cm depths, respectively. The 2 cm depth of rubber provided more turfgrass cover on four of the five collection days (Table 5).
Rubber treatments did not result in a significant difference between subsurface temperatures compared to control treatments. Surface temperature increased 0.4 to 2.4 ° C for the rubber treatments versus the controls (Table 6). Subsurface temperatures verify that the rubber treatments are slightly cooler than the controls. Subsurface temperatures of the rubber treatments were slightly cooler (0.4 to 0.9 ° C) than the control plots (Table 6).
Table 1. Treatments and the arrangement of treatments in the experimental plots.
Depths
1. 1/4" medium rubber buffings (0.635 cm)
2. 1/2" medium rubber buffings (1.27 cm)
3. 3/4" medium rubber buffings (1.9 cm)
C = control
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ISU Horticulture:Publications:1998 Turfgrass Report | College of Agriculture |