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© 2006 Plant Management Network.
Accepted for publication 27 March 2006. Published 31 May 2006.

Comparison of the USGA and Airfield Sand Systems for Sports Turf Construction

Xi Xiong, Department of Agronomy, University of Florida, Gainesville 32611, Gregory E. Bell and Michael W. Smith, Department of Horticulture and Landscape Architecture, and Bjorn Martin, Department of Plant and Soil Sciences, Oklahoma State University, Stillwater 74078

Corresponding author: Xi Xiong. xixiong@ufl.edu

Xiong, X., Bell, G. E, Smith, M. W., and Martin, B. 2006. Comparison of the USGA and airfield sand systems for sports turf construction. Online. Applied Turfgrass Science doi:10.1094/ATS-2006-0531-02-RS.

Abstract

The purpose of this research was to compare the Airfield system with a USGA system for soil factors that affect ‘Tifsport’ bermudagrass (Cynodon dactylon L. × C. transvaalensis Burtt-Davy) growth and to determine if the drainage in these systems was sufficient to maintain consistent gravimetric water content throughout the system regardless of relative elevation along a 2% slope. Canopy temperature and root and soil properties were evaluated monthly from May to October in 2003 and 2004. The two systems did not differ in soil temperature, canopy temperature, soil gravimetric water content, and root density in the 7.7- to 15.2-cm soil layer but the USGA system had higher root density in the 0.0- to 7.6-cm soil layer. Both systems retained more water and drained more poorly as elevation decreased from high to middle to low along a 2% slope. Root density was significantly greater at the lowest elevation compared with the middle elevation and significantly greater in the middle elevation compared with the highest elevation. The composite results suggested that the Airfield system was not substantially different from the USGA system.

Introduction

One goal of professional sports field managers is to maintain firm, smooth, and well drained turfgrass playing surfaces. Sand, with its ideal physical characteristics, relatively consistent particle size, better compaction resistance, substantial porosity, and high infiltration rate, is considered one of the best growing mediums for turfgrass playing surfaces. By 1960, the USGA Green Section recommended using sand-based root zones to construct putting or playing surfaces that tolerate traffic while resisting compaction (6).

The USGA system usually consists of a 9:1 sand-peat root zone (v/v) 30 cm deep with a perched water table resulting from the placement of the sand-peat mix over 10 cm of pea gravel. In this system, the root zone mix must be at or near saturation before water enters the coarser pea gravel for vertical drainage. Excess water drains through pipes in the sub-base below the gravel layer. The USGA system effectively increases drainage while providing an adequate amount of water holding capacity. However, during humid warm summers, the extra moisture available in the perched water table may have a negative affect. With extra water stored, the root zone has less air-filled porosity. Also the water acts as an insulator, resulting in root zones with high soil temperature (1). High soil temperature and less oxygen availability imply greater root stress during warm summer temperatures.

Due to these concerns and the high price of construction, several non-USGA systems have been developed. The Airfield system (Airfield Systems, Edmond, Oklahoma) consists of a porous sand root-zone mix placed over a geotextile fabric that allows the downward migration of water and fine particles from the root zone to a composite grid support structure below. The support structure provides a 2.5-cm layer of space that encourages rapid drainage and constant air exchange. The support structure rests on an impervious liner against the sub grade that slopes to perimeter drains where water is collected and moved away. According to the distributor, the Airfield system reduces construction time that contributes to a lower system cost.

The Airfield system is currently used at several sites with generally favorable reports but independent studies of this system are not available. The purpose of this research was to compare the Airfield system with a USGA system for soil factors that affect turf growth and to determine if the drainage in these systems was sufficient to maintain consistent gravimetric water content throughout the system regardless of relative elevation along a 2% slope.

Site Construction

This study was conducted at the Oklahoma Turfgrass Research Center, Stillwater, OK. The experimental site was constructed by the founder of Airfield Systems in the summer of 2000 and consisted of two Airfield systems built by the founder to his specifications and two USGA systems. The USGA system construction was supervised by researchers to make certain that the construction conformed to USGA recommendations. Each system was 7.0 m × 3.5 m. The Airfield system consisted of a 28-cm root zone of United States Department of Transportation concrete specification sand. This sand met USGA specifications for particle size, except for a larger than recommended component of coarse particles (Table 1). The USGA specifies that no more than 10% of the root zone consist of particles that range from 1.0 to 3.4 mm (7). In the concrete sand used for airfield construction 14.4% of the particles fell into the 1.0 to 3.4 mm range. The root zone sand was placed over a Lutradur geotextile filter fabric (Freudenburg Spunweb, Durham, NC) that prevented the migration of root zone particles into the Draincore2 (Invisible Structures, Inc., Golden, CO) composite grid support structure below (Fig. 1). The Lutradur spunbonded polyester filter fabric had sufficient porosity to allow the downward migration of fine particles (e.g., silt, clay, and organic materials) from the root zone into the support structure presumably to be carried away in drainage. The Draincore2 structure was 2.5 cm thick and rested on a 30-µm polyvinylchloride impervious liner (Colorado Lining International, Parker, CO) against a firm subgrade that sloped to a perimeter drain where water was collected and moved away. The system required an excavation 31 cm deep, 9 cm less that the excavation for the USGA systems and did not require additional excavation for drain pipes below the subgrade.

Table 1. Specifications for Airfield and USGA root zone sands and the particle distribution of the root zone sands used for the study site.

 ^w Year 2005 recommendations available by request from Airfield Systems, Edmond, OK.

 ^x Year 1993 USGA Green Section recommendations (7)

 ^y The total of the 1.0- to 2.0-mm fraction + the 2.0- to 3.4-mm fraction should not exceed 10%

 ^z The 0.00 to 0.15 fraction should not exceed 10%

Fig. 1. Cross sectional view of the Airfield system used in the study.

The USGA construction consisted of a 30-cm root zone of USGA specification sand with no organic component (Table 1). The root zone rested on 10 cm of washed pea gravel over firm subsoil. Approximately 3% of this gravel consisted of particles that ranged in size between 9.0 and 12.0 mm, 70% of the particles were between 6.0 and 9.0 mm, 27% of the particles were between 2.0 and 6.0 mm, and less than 1% ranged in size from 1.0 to 2.0 mm. The particle distribution of the root zone compared with the particle distribution of the pea gravel met USGA recommendations for construction with no intermediate sand layer between the root zone and gravel. Drainage was provided by a single 10-cm diameter drain pipe located in the sub-grade below the gravel that extended down the middle of the plot for its entire length and emptied into a perimeter drain. The absence of an organic component in the root zone was the only factor that differed from a typical USGA installation. To lower construction expenses and to promote root zone consistency, organic components were not added to the root zone sand. The root zone sand for the USGA system cost $13 per ton. The concrete specification sand used for the Airfield construction cost $7 per ton, a savings of 46% compared with the USGA root zone sand.

The ‘Tifsport’ bermudagrass in both systems was maintained at 2.5 cm tall and fertilized at 240 kg N per ha per growing season. Pre-emergent herbicide, 0.897 kg prodiamine per ha (2, 6-dinitroaniline), was applied each spring to control summer annual weeds. A nonselective herbicide, 0.46 kg glyphosate (N-phosphonomethyl glycine) per ha, and a broadleaf herbicide, 0.92 kg 2, 4-D amine (2, 4-dichlorophenoxy acetic acid) per ha, were applied each winter to control cool-season weeds.

Methods of Assessment

The study site had a 2% slope from west to east to accommodate both surface and subsurface drainage flow. To determine if residual soil water differed by elevation, the main plots consisting of Airfield and USGA system construction were each divided into three subplots by elevation. Each subplot was 2.3 m × 3.5 m and was classified high, middle, or low depending on its location along the 2% slope of the main plot. The experiment was conducted as a split block design with repeated measures. The treatment structure was a 2×3 factorial with two system treatments (Airfield and USGA) and three location treatments based on surface and subsurface drainage flow direction from high to middle to low. Sampling was performed monthly from May through October in 2003 and 2004.

Soil temperature was measured using a bimetal thermometer (Reotemp Instruments, San Diego, CA) that produced a direct measurement of soil temperature at a depth of 5 cm. The canopy and concurrent air temperatures were measured using an infrared thermometer (ST27 Turf Monitor; Standard Oil Engineered Materials, Solon, Ohio). Soil and canopy temperatures were measured three times within each experimental unit at random locations and a mean calculated for analysis.

Soil water content was measured by collecting soil samples using a standard soil probe (2.5 cm diameter). Samples consisted of 15 randomly selected cores removed from the 0.0- to 7.6-cm soil layer within each experimental unit. The shoots and thatch layer were removed from each core and the soil and roots used for analysis. All 15 cores were mixed for one measurement. An additional 15 cores were collected at a depth of 7.7 to 15.2 cm and handled in the same manner. After collection, the soil sample fresh weight was measured prior to drying at 50°C to constant weight to determine dry weight. The difference between the dry soil weight and the fresh soil weight was used to determine the soil gravimetric water content (kg/kg). After collecting soil samples, the holes were filled with the same sand used in construction of the corresponding systems, and the same holes were not sampled again during the following months.

After the soil moisture was determined, the roots were washed free of soil under tap water and collected in U.S. Standard Sieves (Fisher Scientific Company, Pittsburgh, PA). A combination of three sieves was used to separate the roots from the soil under running water. The opening sizes of the sieves were 6.35 mm, 2.54 mm, and 1.00 mm in order from top to bottom. The roots from the 0.0 to 7.6 cm samples were also separated from the rhizomes. The roots were collected from each sieve and dried in an oven at 50°C. The root mass was determined after the roots were dried to constant weight. Once the dry weight was determined, root density (mg/cm³) was calculated.

Visual ratings for turf quality were conducted during the 2004 growing season using a 1-to-9 scale (9 = best quality, all plants were healthy and green; 1 = worst quality, all plants were dead or brown).

The main effects of sand system, location, and date of measurement, and their interactions pooled from two years data were determined by analysis of variance (ANOVA) according to the general linear model of Statistical Analysis System (SAS Institute Inc., Cary, NC). A prior analysis including year as a variable, indicated no year × treatment interaction. In fact, no significant interactions were detected in this study. The means of significant major effects were separated using Fisher’s protected least significant difference LSD (P = 0.05).

Soil and Canopy Temperature Responses

Soil temperatures were similar for the Airfield and USGA systems (Table 2). Soil temperature differed significantly by month. From May to August, the mean (n = 12) monthly soil temperature increased from 25 to 30°C and then decreased in September and October to 20 and 22°C, respectively.

Table 2. Soil temperature, canopy temperature, and visual turf quality rating of bermudagrass grown in the Airfield and USGA systems in 2003 and 2004. Main effect means for system, location and month are presented.

 ^x Visual ratings were made in 2004 only.

 ^y Means in the same column and category followed by the same letter do not differ significantly (LSD; P < 0.05).

 ^z No visual ratings were made in September.

The canopy temperature of bermudagrass in the Airfield and USGA systems was similar during the two growing seasons (Table 2). The canopy temperature trend by month was similar to the soil temperature. From May to August, the mean (n = 12) monthly canopy temperature increased from 33 to 37°C, then decreased in September to 17°C, and increased again to 32°C in October.

Canopy temperatures in both of the systems were consistently higher than the surrounding air temperatures in each month (Fig. 2). The canopy temperature averaged 4°C higher than the air temperature at solar noon. The result implied that during midday, temporary drought stress reduced the transpirational cooling of the turf. A similar condition was observed in Corn (Zea mays L.) (5). Under a well-watered condition, the difference between canopy and air temperature was near zero but when visible drought stress appeared, the canopy-air temperature difference could be higher than 10ºC.

Fig. 2. Mean (n = 12) canopy temperature (°C) and mean air temperature (°C) in different months collected on bermudagrass in 2003 and 2004.

Soil Water Content

Gravimetric water content was similar for the two systems in each soil layer tested (Table 3). The gravimetric water content in the 0.0- to 7.6-cm layer of soil and in the 7.7- to 15.2-cm layer of soil consistently increased along the locations of drainage from high to middle to low. Consequently, the gravimetric water content in the 0.0- to 15.2-cm layer also increased from high to low elevation.

Table 3. Soil gravimetric water content in the Airfield and USGA systems in 2003 and 2004. Main effect means for system, location and month are presented.

 ^x Means in the same column and category followed by the same letter do not differ significantly (LSD; P < 0.05).

Root Density

Root density was 16% greater in the 0.0- to 7.6-cm soil layer of the USGA system than in this layer in the Airfield system (Table 4). The root density was less in the 7.7- to 15.2-cm layer than in the 0.0- to 7.6-cm layer in both systems and averaged 0.65 mg/cm³. The overall mean root density in the 0.0- to 15.2-cm layer of sand in the Airfield system (0.79 mg/cm³) was significantly less than the USGA system (0.87 mg/cm³) due to the difference in density in the upper soil layer. In both systems, the roots in the 0.0- to 15.2-cm soil layer had the highest root density in the lowest elevation. The root density in the highest location (0.69 mg/cm³) was significantly (P < 0.05) less than in the lowest location (0.94 mg/cm³) even though water availability was greatest at the lowest elevation (Table 4). There were more roots per unit of soil in locations where soil water was more abundant. Similarly, Huang and Fry (2) found that under dry soil conditions, tall fescue (Festuca arundinacea Schreb) produced finer roots than in a well watered control. Dryer conditions increased root length and reduced root mass per unit soil volume.

Table 4. Bermudagrass root density in the Airfield and USGA systems in 2003 and 2004. Main effect means for system, location, and month are presented.

 ^x Means in the same column and category followed by the same letter do not differ significantly (LSD; P < 0.05).

Roots were most plentiful in the 0.0- to 7.6-cm layer during September followed by October (Table 4). Root density in this layer during May through August was similar and less than September or October. The root density in the 7.7- to 15.2-cm layer was higher in May and June than in July, August, September, and October. The overall root density in the 0.0- to 15.2-cm layer was greatest in September and October. The lowest root density occurred in August.

For bermudagrass, the best adapted shoot growth temperatures are believed to be 35 to 38°C. For root growth, the best soil temperatures are believed to be 18 to 27°C (4). A comparison of root density and soil temperature suggested that root density decreased when the soil temperature reached 28°C. Regression analysis suggested that root density was significantly (P < 0.05) affected by soil temperature in each soil layer evaluated. The linear relationship between soil temperature and root mass in the 0.0- to 7.6-cm soil layer (r² = 0.32) was stronger than the relationship between soil temperature and root mass in the 7.6- to 15.2-cm layer (r² = 0.06), suggesting that the upper root mass was more sensitive to soil temperature than the lower. In this study, root density demonstrated a summer decline and a fall increase. This pattern has been reported in cool-season grasses (3), but not in warm-season grasses. Root growth in bermudagrass is generally believed to increase over the summer. These results suggested that high soil temperatures in excess of 28°C may cause a decline in bermudagrass root growth during summer.

Visual Rating

No differences were detected in visual turf quality in 2004 between the two systems (Table 2). Although the root density in the 0.0- to 7.6-cm layer was significantly higher in the USGA than in the Airfield system, the visual quality assessment implied that the difference between systems was not large enough to affect shoot quality.

Conclusion

The Airfield system and USGA system did not differ in soil temperature, canopy temperature, soil gravimetric water content, and root mass in the 7.7- to 15.2-cm soil layer. Bermudagrass root density in the 0.0- to 15.2-cm soil layer was higher in September and October compared to other months. Both systems retained more water and drained more poorly at lower elevations. Both systems also encouraged increasing root growth at lower elevations. Results suggested that both systems produced similar bermudagrass turf quality. Therefore, economics may be the dominant factor for determining which system to use.

Acknowledgment

Approved for publication by the Director of the Oklahoma Agricultural Experiment Station. Funding provided by the Oklahoma Turfgrass Research Foundation grant number AG-89-RS-140, and The Oklahoma Agricultural Experiment Station project number OKLO 2392.

Literature Cited

1. Ervin, E. H., Ok, C., and Fresenburg, B. S. 1999. Amendments and construction systems for improving the performance of sand-based greens. Online. 1999 Turfgrass Res. & Infor. Rep., Turfgrass Res. Center, Univ. of Missouri, Columbia.

2. Huang, B., and Fry, J. D. 1998. Root anatomical, physiological, and morphological responses to drought stress for tall fescue cultivars. Crop Sci. 38:1017-1022.

3. Huang, B., and Liu, X. 2003. Summer root decline: Production and mortality for four cultivars of creeping bentgrass. Crop Sci. 43:258-265.

4. Duble, R. L. 1996. Turfgrasses: Their Management and Use in the Southern Zone, 2nd Ed. Texas A&M University Press, College Station, TX.

5. Sadler, E. J., Bauer, P. J., Busscher, W. J., and Millen, J. A. 2000. Site-specific analysis of a droughted corn crop: II. Water use and stress. Agron. J. 92:403-410.

6. USGA Green Section. 1960. Specifications for a method of putting green construction. USGA Green Sect. Record 13:24-28.

7. USGA Green Section. 1993. USGA recommendations for a method of putting green construction. USGA Green Sect. Record 31:1-3.