ABSTRACT
Creeping bentgrass (Agrostis stolonifera L.) grows under very stressful conditions during hot, humid summers in the southern and eastern United States. The practice of hand-watering and syringing has been utilized for many years as a management tool during this stress period. The objectives of this study were to determine the effect of hand-watering and syringing on leaf water potential, canopy temperature, soil temperature, and turf quality of a creeping bentgrass green. A mature ‘Penncross’ creeping bentgrass green grown on a United States Golf Association specification root zone was treated with a syringing rate of 1.3 mm of water or a hand-watering rate consisting of 5.1 mm of water at 1300h on days when canopy temperatures were greater than 35 °C. Treatment areas were replicated eight times on 1.5 X 1.5 m plots. Leaf water potential, canopy temperature, and soil temperature was measured before, and at 30, 60, and 120 minutes after treatment application. Hand-watering plots consistently had higher leaf water potentials than the syringed and control plots. Additionally, syringed plots also had significantly higher leaf water potentials than the control plots. Typical ranges in mean leaf water potentials recorded for treatment dates were: hand-watered plots (−0.6 to −1.0 MPa), syringed plots (−0.9 to −1.3 MPa), and control plots (−1.2 to −1.7 MPa). There were immediate reductions in canopy temperature after hand-watering and syringing (2 to 5 °C, 5 minutes after application). However, 30 minutes after application, canopy temperatures were back to control plot levels. Therefore, hand-watering and syringing treatments do not provide an extended cooling of the turf canopy, but rather improve water status of creeping bentgrass, as indicated by higher leaf water potentials. Soil temperatures were not affected by hand-watering or syringing in any year. Turf 611quality on both hand-watered and syringed plots was significantly higher than the control plot levels for both years.
Creeping bentgrass (Agrostis stolonifera L.) continues to be the dominant turfgrass species for golf course greens in the United States. However, creeping bentgrass grows under very stressful conditions during hot, humid, summers in the southern and eastern United States. Stress factors on this turf include close, frequent mowing, shallow rooting, high evapotranspiration rates, and high air and soil temperatures. Subsequently, during periods of high evapotranspiration, an internal plant water stress develops because water loss by evapotranspiration exceeds water uptake through the root system (Beard, 1995). Wilt and even desiccation can occur within a matter of hours on close cut bentgrass greens having a limited root system (Beard, 1973). Creeping bentgrass grown on a United States Golf Association (USGA) specification putting green, where soil moisture retention is only 15 to 25 percent, may need frequent irrigation for turfgrass survival. Golf course superintendents find supplemental irrigation is crucial to enhancing summer turf survival on golf greens.
Cool-season turfgrasses are particularly susceptible to high temperature effects given their poor performance with a shallow root system (Beard and Daniel, 1965, 1966). Midday wilt even with sufficient soil moisture is common with bentgrasses and annual bluegrass, especially where close mowing is practiced (Turgeon, 1996). Presently, superintendents encounter pressure from golfers to keep greens at extremely low mowing heights, even during periods of summer stress and heavy traffic. This results in a shallow root system that can’t utilize water held deeper in the root zone.
Creeping bentgrass greens often need supplemental irrigation as a maintenance practice to survive periods of summer stress. Syringing is the application of 0.25 cm or less of water primarily to the turfgrass leaves, and is used to correct plant water deficits (Beard, 1995), reduce canopy temperatures, and remove substances from the leaves (Turgeon, 1996). Hand-watering is a similar practice but involves higher rates that penetrate the canopy and enter the soil surface. This positions the water in the shallow root zone of the bentgrass. Both syringing and hand-watering are proving to be vital management tools for bentgrass during the summer months. However, there is little information on creeping bentgrass response to supplemental irrigation during periods of summer stress. This research was conducted to determine how syringing and hand-watering affect creeping bentgrass survival during the summer.
The following experimental objectives were formulated to address the effects of syringing and hand-watering on bentgrass water relations. Determine how supplemental irrigation affects: 1) leaf water potential, 2) canopy temperature, 3) soil temperature, and 4) turf quality of creeping bentgrass grown under golf green conditions.
