Virginia Turfgrass Council – The Turfgrass Water Conservation Alliance Supports Virginia Tech Efforts in Identifying Drought Tolerant Turfgrasses
Virginia Turfgrass Journal – Mike Goatley, Jr., Ph.D., Professor and Extension Turfgrass Specialist, Virginia Tech School of Plant and Environmental Sciences
Virginia Tech Turfgrass Research team is excited to partner with the Turfgrass Water Conservation Alliance (TWCA) in conducting turfgrass variety research under controlled drying conditions in order to evaluate superior drought tolerance. In previous trials at other locations, varietal differences of up to 26 day delays in the onset of drought stress have been observed in bluegrasses and fescues, a variable of extreme importance at a time when turfgrass scientists and breeders are exploring ways to both reduce and better utilize water resources. In the mid-Atlantic, adequate supplies of water are often not a major concern in the production of a healthy turfgrass, but drought seasons such as the summer of 2019 remind the green industry that water is our most precious resource that not only requires protecting, it requires conserving as much as possible. TWCA partners with several universities around the country in sponsoring controlled-environment studies in the field that identify drought tolerant standard varieties currently available to the industry, as well as yet to be named experimental varieties that might warrant eventual release as named cultivars.
TWCA provides all cooperators a rainout shelter (ROS), a light box and associated powerpacks, and a camera for digital image collection. The lightbox and camera provide consistent light conditions for capturing images of turfgrasses as they experience dry down and turf recovery conditions. The digital analysis of these images provides objective rather than subjective data that can readily be compared within and across research locations. Another great benefit of the cooperative research program is that TWCA donates the ROS to the cooperating site in support of future water conservation research activities.
A key to TWCA trials is to conduct them under as controlled of an environment as possible but in a field setting so that light, soil, regular maintenance practices, etc. are similar to a standard turfgrass management program. The factor being controlled is soil moisture and this is managed by restricting any effects of rainfall and only providing supplemental irrigation at a rate and timing dictated by the research protocol. The ROS is covered in a thick translucent plastic that blocks rainfall but still allows adequate sunlight to pass to drive photosynthesis; the ends and and bottom sides of the shelter remain uncovered to provide air circulation so as to not promote disease. At Virginia Tech, 59 Kentucky bluegrasses were seeded in the field at the Turfgrass Research Center in replicated 3 ft by 3 ft plots in September 2018. The trial includes a number of grasses deemed drought tolerant or drought susceptible in previous research so that these varieties can be used for comparative evaluations of drought tolerance. The site used for the trial was carefully selected prior to the construction of the ROS in summer 2019, utilizing a relatively flat site with still enough slope for surface drainage, and an orientation for the structure that minimized the likelihood of wind damage from storms. VT Turfgrass Research Center manager Jon Dickerson was invaluable in organizing and leading the construction and final installation of the structure in the summer of 2019 (Figure 1).
Prior to initiating the drought stress the research block was soaked with 2 inches of irrigation water applied over 2 days to bring the area to uniform soil moisture (field capacity). Then the dry-down phase of the trial began and continued until all plots fell below 25% green turf cover (approximately 5 weeks for our site, Figure 2) when the entire experimental area was once again irrigated with 2 inches of irrigation to initiate drought recovery. Thereafter the experiment received supplemental irrigation in order to replenish 100% evapotranspiration rates. Digital images were regularly collected throughout the dry down and recovery periods to assess plant response to drought and returned moisture.
As seen in Figure 2 and from the recovery evident when the plots were shown at the August VT Turfgrass Research Landscape Field Day (Figure 3), there are clearly significant differences in drought tolerance among Kentucky bluegrass varieties. Drought tolerant standards such as Bedazzled and Bewitched performed well, whereas a drought susceptible variety like Geronimo went dormant quicker and recovered slower than others. However, what is most promising is that many experimental varieties performed quite well in the first year of the trial in terms of both turfgrass quality during dry-down and then in recovery. With any Kentucky bluegrass trial, patience is a must because many varieties perform differently over time based on their maturity; it is far too early in the research to deem ‘winners and losers’ now, but we are confident that there will soon be a significant number of Kentucky bluegrasses that will not only meet our overall field performance requirements in NTEP and supplemental variety trials to gain posting on the Virginia/Maryland Recommended Variety List, some will also be noted for their drought tolerance. This information will be very important in the selection and maintenance of bluegrasses under limiting moisture conditions, and will be very important for the selection and management of varieties that can maintain higher visual quality and turf performance during drought conditions.
Special thanks to Jack Karlin and the entire TWCA Board for the support and opportunity to participate in this research, Whitnee Askew for the attention to detail in data collection and reporting, and Jon Dickerson for the oversight and planning in constructing the ROS (Figure 4). It’s another example of the value of teamwork that we hope our industry clientele recognizes as a defining characteristic of belonging to the VT Turf Team. We hope that you will attend the August 2020 Turf and Landscape Research Field Day to see how this trial progresses toward allowing us to offer recommendations to you regarding the highest quality, most drought tolerant Kentucky bluegrasses on the market.READ THE ISSUE