Wetting Agents to Prevent or Cure Drought Stress in a Mature, Push-Up Putting Green

Doug Karcher
Professor and Chair
Department of Horticulture and Crop Science

Background

Previous wetting agent research on putting greens has focused on sand-based greens using typical application schedules. There has been little work done on the effects of newer wetting agent products on drought stress and localized dry spot when applied on native-soil, push-up style greens, especially when applied at a single time, either as a preventative or a curative treatment.

Objective

• To determine the effects of wetting agent application timing on the prevention and cure of localized dry spot on a mature, push-up putting green.

Methods

• This experiment was initiated on June 14, 2022, on a mature push-up putting green comprised of a mixture of ‘Penncross’ creeping bentgrass and Poa annua. A rain-out shelter was constructed over the experimental area to prevent rainfall on the plots and to allow a thorough drying of the putting green root zone in the absence of irrigation.
• Each of the following five wetting agent products and an untreated control treatment were applied in four separate plots. The experimental area was irrigated with approximately 0.1 inches of water within an hour of wetting agent application.
  1. Revolution (6 fl oz / 1000 ft²)
  2. Fleet (8fl oz / 1000 ft²)
  3. Vivax (5 fl oz / 1000 ft²)
  4. Excalibur (4 fl oz / 1000 ft²)
  5. Dispatch (24 fl oz / acre)
• Wetting agent applications were made on the following dates:
  • Replicate 1 – 7 weeks prior to Field Day (June 14, 2022)
  • Replicate 2 – 6 weeks prior to Field Day (June 23, 2022)
  • Replicate 3 – 4 weeks prior to Field Day (July 7, 2022)
  • Replicate 4 – 2 weeks prior to Field Day (July 19, 2022)
• The experimental area was irrigated as follows:
  • Best management practices from the initiation of the trial through July 10.
  • After July 10, irrigation was withheld to initiate drought stress and/or localized dry spot formation.
  • Irrigation practices resumed on July 28 once the experimental area had moderate to severe drought stress symptoms.
  • Based on this schedule, Replicates 1 – 3 are considered preventative applications and Replicate 4 is considered a curative application.

Results

• Drought Stress / Localized Dry Spot
  • Evaluations were made at peak drought stress on July 28, and again on August 1, four days after recovery irrigation practices were initiated.
  • Although there were substantial differences in drought stress among treatment plots within each replication, these differences were not consistent across replications, which indicates either a high level of natural variability inherent within the mature, native soil green, or perhaps an interaction between wetting agent product and duration of preventative control, or curative ability.
  • Currently the best performing treatments at each application time are:
    • 7 weeks prior: Fleet
    • 6 weeks prior: Excalibur
    • 4 weeks prior: Excalibur
    • 2 weeks prior: Excalibur

• Turf Quality
  • Plots were rated for visual quality on the same dates used to assess localized dry spot.
  • In this trial, turf quality was highly affected by drought stress. Therefore, turf quality results were very similar to those summarized for localized dry spot above.
  • There were no statistically significant differences in turf quality among treatments
• Soil Moisture and Surface Firmness
  • Soil Moisture and Surface Firmness were measured daily during the final week of peak drought stress, from July 15 through July 28.
  • Soil moisture was assessed with a Sprectrum TDR 300 unit using a 3-inch rod depth. Measurements were taken in the center of each plot daily.
  • Firmness was assessed with a Spectrum TruFirm device. Measurements were taken in the center of each plot daily.
  • Wetting agent treatment did not affect rootzone moisture content or surface firmness on any measurement date. 

Conclusions

• Wetting agents have been shown to be highly effective in reducing localized dry spot and increasing turf quality in sand-based putting greens. This is primarily due to the high levels of water repellency that naturally develop in such systems. The native soil green used in this experiment does not have a significant sand-topdressing layer, and therefore is much less prone to developing water repellency. Wetting agents may provide some insurance against drought symptoms in a native soil turfgrass symptoms, but they are much more effective when used in sand-based systems.
• To conduct future impactful wetting agent research in Ohio, it will be important to develop sand-based, research putting greens.