Published online 19 September 2005
Published in Agron J 97:1438-1442 (2005)
DOI: 10.2134/agronj2004.0302
© 2005 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
Turfgrass
Effects of Misting and Subsurface Air Movement on Bentgrass Putting Greens
Ian R. Rodrigueza,
Lambert B. McCartya,* and
Joe E. Tolerb
a Dep. of Hortic., D-136 Poole Agric. Cent., Clemson Univ., Clemson, SC 29634-0319
b Dep. of Appl. Econ. and Stat., Clemson Univ., Clemson, SC 29634-0319
* Corresponding author (bmccrty{at}clemson.edu)
Received for publication December 7, 2004.
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ABSTRACT
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Preferential use of creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)] on golf putting greens has expanded into the hotter, more environmentally stressful regions of the southeastern United States where turfgrass decline is problematic during summer months. Methods of reducing temperatures in the putting green microclimate would enhance bentgrass survival under heat stress conditions. The objectives of this study were to evaluate the bentgrass putting green microclimate under combined misting and/or subsurface fan systems with surface fans. Field studies were conducted in the summers of 2001 and 2002 on a ‘Crenshaw’ creeping bentgrass putting green located in Clemson, SC. Treatments consisted of surface fan only, surface fan plus misting, surface fan plus subsurface fan, and surface fan plus misting and subsurface fan. Fan treatments were applied from 1100 to 1500 h on days when temperatures were 
29.5°C, there was no visible cloud cover, and wind speed < 1.0 m s–1. Surface fan plus misting treatments reduced putting green canopy, soil surface, and soil temperatures by as much as 9, 7, and 6°C, respectively, while increasing canopy relative humidity and soil moisture content. Benefits were generally observed over a range of 5 m from the fan. These treatments demonstrate great potential for improving canopy and soil microclimate conditions influencing bentgrass survival in a heat stress environment. Surprisingly, the use of subsurface fans did not enhance the cooling effect provided by surface fans. Fan/mist systems should be investigated further to determine possible disease occurrence during extended use periods.
Abbreviations: USGA, United States Golf Association
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INTRODUCTION
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CREEPING BENTGRASS is native to central Europe and is adapted to the cool, humid environments in the northeastern and northwestern United States (McCarty, 2005). Preference for the superior putting surface of bentgrass has led to its use in the hotter, more humid regions of the United States where turfgrass decline is problematic during summer months. Much of the decline has been attributed to a reduction in photosynthesis and an increase in root respiration at ambient temperatures greater than 30°C, leading to a reduction in overall carbohydrate accumulation (Huang et al., 1998; Huang and Gao, 2000).
The extent of leaf cooling is directly proportional to air velocity (Brown and Wilson, 1905), but only a few studies have examined effects of artificial air movement on bentgrass greens. One study noted fan-induced air movement (at 1.79 m s–1) reduced creeping bentgrass mat temperature by more than 7°C and soil temperature at 5 cm by 5.5°C compared with no air movement (Duff and Beard, 1966).
Applying light, frequent amounts of water (syringing) is a management practice often utilized on bentgrass putting greens under heat stress conditions. This practice is based on the concept of evaporative cooling. Syringing creeping bentgrass has been shown to produce modest (1 to 2°C) turf mat temperature reductions (Duff and Beard, 1966) or no reduction unless the turf had already wilted (DiPaola, 1984). No information is available on the use of water mist in a fan's air stream to reduce canopy and soil temperatures.
Forcing air into a USGA (United States Golf Association) green rootzone through subsurface drain lines has been shown to reduce soil temperatures. A preliminary study noted forcing air into the rootzone reduced soil temperatures 2 to 3°C at a depth of 5 cm in the afternoon (Dodd et al., 1999). Similar experiments also reported soil temperature reductions as great as 2.5°C at 10-cm depth in USGA bentgrass greens (Bigelow et al., 2001).
Using misting and/or subsurface fans with surface fans may provide effective means of reducing plant and soil temperatures of bentgrass putting greens in the southern United States. The objective of this study was to evaluate, under heat stress conditions, the effects of misting and/or subsurface air movement on the bentgrass putting green microclimate when used in combination with surface fans.
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MATERIALS AND METHODS
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A field study was conducted in the summers of 2001 and 2002 in Clemson, SC, to examine the benefits of combining misting and/or mechanically induced subsurface air movement with surface air movement for reducing heat stress effects on a USGA creeping bentgrass green. This study was conducted on a Crenshaw creeping bentgrass research green established from seed in September of 1997. The green was constructed with 10 individually drained 190-m2 cells separated by PVC walls, permitting use of two 5.59-kW (7.5-hp) subsurface air pumps and two cells at one time (SubAir Model ES1867, SubAir, Inc., Deep River, CT). The same two cells were used as the experimental plots throughout the 2-yr study. Air pumps were connected to 20-cm-diam. drain lines which traverse through an air/water separator vault into a 15-cm-diam. drain running to gate valves at each individual green cell. When open, the gate valves allowed for positive pressure into a cell at 4 cm of water pressure via the 9-cm drain lines. Turf was maintained at normal golf course standards by mowing daily at 4 mm with clipping removal. Irrigation was applied twice weekly at 1.9 cm per event, and a standard preventive fungicide program was applied every 14 d throughout the study.
Two blower type, 1.12-kW (1.5-hp) surface electric fans (WhisperBreeze, Precision Small Engine Co., Pompano Beach, FL) were each equipped with two microirrigation mist nozzles (AF3M, Agrifim, Fresno, CA) that applied a fine mist of water to the fan air stream at a rate of 14.8 L h–1 per nozzle. Each fan was mounted on a custom rolling trailer with air outlets 0.75 m above the putting green surface. Electricity was provided to each fan by a 220-V extension cord, and water was supplied to misters via quick-coupler hose outlets adjacent to the green. Fans were placed facing east–southeast to minimize interference from prevailing winds.
A 2 x 2 factorial experiment was used to examine the effects of two levels of misting (with and without) and subsurface fans (with and without) when applied along with surface fans. Therefore, the study included four treatment combinations: surface fan only, surface fan plus misting, surface fan plus subsurface fan, and surface fan plus misting and subsurface fan. Since only two treatment combinations could be evaluated at a time, the treatments were scheduled according to a balanced, randomized incomplete block design with three replications per run and with an additional restriction that the same treatment would not be applied to the same plot on consecutive days. Each 6-d cycle constituted one run, and four runs were conducted (two in 2001 and two in 2002). Pressure mode was used with subsurface fan. To minimize confounding effects from ambient environmental conditions, treatments were applied on days with air temperatures 29.5°C, no visible cloud cover, and air movement < 1.0 m s–1 at a height of 3 cm above the putting green surface. Treatments were initiated at 1100 h and ended at 1500 h.
Data were collected on air velocity, canopy temperature and relative humidity, soil temperatures, and soil moisture. Soil moisture readings were taken at 1100 and 1500 h. Additional data were collected on all remaining variables at 1200 and 1400 h. Ambient relative humidity and canopy, surface, and soil temperatures were taken in an area outside of the treated areas at 1200 and 1400 h, which were used to calculate relative humidity and temperature changes. Soil moisture readings were obtained after completion of the treatments at 1500 h. Readings were collected for all variables at 1-m increments from the surface fan to a distance of 11 m from the fan. Air velocity was measured 3 cm above the green surface using a hot-wire anemometer (Extech Model 407123, Extech Instruments, Waltham, MA). Canopy temperatures of the turfgrass surface were obtained with an infrared thermometer (Raynger ST2, Raytek, Santa Cruz, CA). Two soil temperatures were recorded using a T-type thermocouple inserted at depths of 2 mm ("soil surface temperature") and 13 mm ("soil temperature"). A small relative humidity meter (605-H1, Testo Inc., Flanders, NJ) was used to collect relative humidity measurements 0.5 cm above the putting green surface. An average of soil moisture content from the upper 5.7 cm was obtained using a dielectric soil moisture probe (Vitel Hydra Logger, Stevens Water Monitoring Systems, Beaverton, OR). Three measurements were taken for each data type at each 1-m increment (one directly ahead of the fan and one at 1 m to each side of the centerline) and averaged. Statistical analysis of results from the incomplete block design using interactions between treatments and incomplete blocks as the error term (Cochran and Cox, 1964) was conducted with SAS (SAS Inst., 1987), and hypothesis testing was performed at the 0.05 level of significance.
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RESULTS AND DISCUSSION
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No significant treatment x year interactions were detected; therefore, results were combined for the 2 yr. Treatment effects were consistent for all response variables at 1200 and 1400 h (Table 1), so results have been averaged across sampling times for presentation and discussion. Air velocity over the range of distances observed was comparable for all treatments, increasing to a maximum of 4.7 m s–1 at 3 m from the fan and then declining to 1.2 m s–1 at 11 m (Fig. 1)
. The low air velocity at 1 m can be attributed to fan design, as the fan exhaust duct was located 0.75 m above the putting green surface. While air velocity was similar at 1 m and the 7- to 8-m range, temperatures were more dramatically affected at the 1-m distance. This may be attributed to the fact that excess spray settled in the ranges closest to the nozzles.
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Table 1. Probability values for main and interaction effects from analysis of variance of air velocity; temperature changes of creeping bentgrass canopy, soil surface, and soil at 13-mm depth; relative humidity; and soil water content change in a bentgrass microenvironment following surface and subsurface fans with and without misting, 2001–2002.
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Fig. 1. Effect of distance from a surface fan on the velocity of mechanically induced air movement at 3 cm across a creeping bentgrass putting green, 2001–2002 (SE = standard error of the mean).
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Canopy temperature was not affected by subsurface air movement, but a significant misting x distance interaction was detected (Table 1). Misting reduced canopy temperatures an average of 2.5°C over a 5-m range from the fan while no differences were detected from 6 to 11 m (Fig. 2)
. Surface fans provided temperature reductions averaging 5°C over this range; therefore, the combined effects of surface fan plus misting reduced canopy temperatures an average of 7.5°C over the 5-m range. The greatest reduction in canopy temperature for surface fan plus misting (9°C) was observed at 2 m, and the cooling effect of surface fans, with and without misting, steadily declined to <1°C at 11 m. The reductions in canopy temperature provided by surface air movement and misting were consistent with results reported by Duff and Beard (1966) using surface fans and syringing.
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Fig. 2. Effect of misting in conjunction with surface fan on canopy temperature change relative to untreated turf measured at 1-m intervals across a creeping bentgrass putting green, 2001–2002 (* and NS denote significance at the 0.05 probability level and not significant, respectively; SE = standard error of the mean).
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Soil surface temperature at 2 mm below the turfgrass canopy was not affected by subsurface air movement, but a significant misting x distance interaction was detected (Table 1). Misting reduced soil surface temperatures an average of 1.5°C over a 5-m range from the fan while no differences were detected from 6 to 11 m (Fig. 3)
. Surface fans provided temperature reductions averaging 4.3°C over this range; therefore, the combined effects of surface fan plus misting reduced soil surface temperatures an average of 5.8°C over the 5-m range. The greatest reduction in soil surface temperature for surface fan plus misting (7°C) was observed at 2 m, and the cooling effect of surface fans, with and without misting, steadily declined to <1°C at 9 m from the fan.
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Fig. 3. Effect of misting in conjunction with surface fan on 2-mm-deep soil surface temperature change relative to untreated turf measured at 1-m intervals across a creeping bentgrass putting green, 2001–2002 (* and NS denote significance at the 0.05 probability level and not significant, respectively; SE = standard error of the mean).
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Soil temperature at 13-mm depth was affected by misting and subsurface air movement, but significant interactions with distance from the fans were detected for both factors (Table 1). Misting reduced soil temperature an average of 1.1°C over a 5-m range from the fan while no differences were detected from 6 to 11 m (Fig. 4A)
. Surface fans provided temperature reductions averaging 3.8°C over this range; therefore, the combined effects of surface fan plus misting reduced soil temperatures at 13-mm depth an average of 3.9°C over the 5-m range. The greatest reduction in soil temperature for surface fan plus misting (6°C) was observed at 2 m, and the cooling effect of surface fans, with and without misting, steadily declined to <1°C at 9 m. The reductions in soil temperature provided by surface air movement and misting were comparable with results reported by Duff and Beard (1966) and Guertal and Han (2002) using surface fans and syringing.
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Fig. 4. Effect of (A) misting and (B) subsurface air movement in conjunction with surface fan on soil temperature change at 13-mm depth measured at 1-m intervals relative to untreated turf across a creeping bentgrass putting green, 2001–2002 (* and NS denote significance at the 0.05 probability level and not significant, respectively; SE = standard error of the mean).
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Interestingly, subsurface air movement did not decrease soil temperatures and actually had an average of 0.6°C higher soil temperature at 13-mm depth over a 9-m range from the fan while no differences were detected at 10 or 11 m (Fig. 4B). Although previous research has shown soil temperature reductions from subsurface fans (Dodd et al., 1999; Bunnell et al., 2004), the cooling effect was evident at greater soil depths than sampled in this study. Furthermore, Bunnell et al. (2004) noticed air injection can increase or have minimal effects on soil temperature. This depends on the depth and length of the subsurface pipe and ambient air temperature (time of day) during treatment. Deeper and longer runs potentially reduce subsurface pipe air temperatures while warmer ambient air temperature at the time of treatment increases soil temperature.
Relative humidity at the canopy surface was not affected by subsurface air movement, but a significant misting x distance interaction was detected (Table 1). Misting increased relative humidity over a range of 10 m from the fan, but the greatest impact occurred in the first 5 m (Fig. 5)
. Relative humidity increased an average of 39% from 1 to 5 m with misting but rapidly declined to a difference of only 4% at 10 m. The accumulation of water droplets on the turf canopy was consistently observed to a distance of 6 m from the fan during misting applications.
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Fig. 5. Effect of misting in conjunction with surface fan on canopy relative humidity change measured at 1-m intervals relative to untreated turf across a creeping bentgrass putting green, 2001–2002 (* and NS denote significance at the 0.05 probability level and not significant, respectively; SE = standard error of the mean).
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Soil water content was not affected by subsurface air movement, but a significant misting x distance interaction was detected (Table 1). Misting increased soil water content over a range of 7 m from the fan with no differences observed from 8 to 11 m (Fig. 6)
. In the upper 5.7 cm of soil, misting increased water content by 13.2 cm3 cm–3 at 1 m, but the effect of misting on soil moisture rapidly declined to <2 cm3 cm–3 at 6 m. Moisture loss for treatments without misting was generally consistent across the 11-m range and averaged 3.7 cm3 cm–3. This suggests that the air velocities induced by surface fans in this study did not reduce soil water content to detrimental levels, even at close proximity to the fan.
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Fig. 6. Effect of misting in conjunction with surface fan on moisture content change in the top 5.7 cm of the soil measured at 1-m intervals across a creeping bentgrass putting green, 2001–2002 (* and NS denote significance at the 0.05 probability level and not significant, respectively; SE = standard error of the mean).
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These results demonstrate that surface air movement can significantly reduce heat stress conditions in a bentgrass putting green microclimate and that its impact can be amplified by addition of mist to the fan's air stream. Benefits were generally observed over a range of 5 m from the fan, which may limit the usefulness of this method of cooling on larger golf greens. The failure of subsurface air movement to contribute additional benefits by decreasing soil temperature was unexpected based on previous research. The effects of subsurface air movement on soil temperatures at depths below 13 mm should be investigated. While surface fans plus misting may reduce canopy and soil temperatures by as much as 9 and 6°C, respectively, these temperature reductions may not be sufficient to avoid a carbohydrate deficit in bentgrass under extreme heat stress. Carbohydrate deficit has been shown to occur at an ambient temperature of 30°C (Huang and Gao, 2000) while summer temperatures in the Southeast may exceed 38°C. The focus of this study did not provide information on possible long-term effects of using surface fans and misting on a bentgrass putting green. Extended use of misting would create ideal conditions for development of algae and disease, so additional research is needed to determine whether limitations on its use may exist. In summary, surface fans, and especially surface fans with the addition of a mist system, show great potential for improving canopy and soil microclimate conditions that can affect bentgrass survival in a heat stress environment.
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NOTES
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Technical Contribution no. 5090 of the Clemson Univ. Agric. Exp. Stn., Clemson, SC.
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REFERENCES
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- Bigelow, C.A., D.C. Bowman, D.K. Cassel, and T.W. Rufty. 2001. Creeping bentgrass response to inorganic soil amendments and mechanically induced subsurface drainage and aeration. Crop Sci. 41:797–805.[Abstract/Free Full Text]
- Brown, H.T., and W.E. Wilson. 1905. On the thermal emissivity of a green leaf in still and moving air. Roy. Soc. London, Proc. 76B:122–137.
- Bunnell, B.T., L.B. McCarty, and H.S. Hill. 2004. Soil gas, temperature, matric potential, and creeping bentgrass response to subsurface air movement on a sand-based golf green. HortScience 39:415–419.
- Cochran, W.G., and G.M. Cox. 1964. Experimental designs. 2nd ed. John Wiley & Sons New York.
- DiPaola, J.M. 1984. Syringing effects on the canopy temperatures of bentgrass greens. Agron. J. 76:951–953.[Abstract/Free Full Text]
- Dodd, R.B., S.B. Martin, and J.J. Camberato. 1999. Subsurface cooling and aeration. Golf Course Manage. 67:71–74.
- Duff, D.T., and J.B. Beard. 1966. Effects of air movements and syringing on the microclimate of bentgrass turf. Agron. J. 58:495–497.[Abstract/Free Full Text]
- Guertal, E., and D. Han. 2002. Fans and syringing for cooling creeping bentgrass putting greens. Golf Course Manage. 70:57–60.
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- Huang, B., X. Liu, and J.D. Fry. 1998. Shoot physiological responses of two bentgrass cultivars to high temperature and poor soil aeration. Crop Sci. 38:1219–1224.[Abstract/Free Full Text]
- McCarty, L.B. 2005. Best golf course management practices. 2nd ed. Prentice-Hall, Inc., Upper Saddle River, NJ.
- SAS Institute. 1987. SAS user's guide: Statistics. 6th ed. SAS Inst., Inc., Cary, NC.
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ABSTRACT
INTRODUCTION
