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Wetting Agents And Winter Injury May 4, 2018 By USGA Green Section

  • Early fall or late-winter applications of wetting agents may mitigate winter injury related to crown tissue desiccation of ultradwarf bermudagrass putting greens.
  • Wetting agents applied during early fall or late winter may persist in the soil during dry winters, reducing hydrophobic conditions and improving green up.
  • Research has shown that deploying permeable putting green covers is the most effective method to minimize the effects of extreme low-temperatures.
  • Using wetting agents with permeable covers is an excellent combination to minimize winter injury.

Localized dry spot (LDS) is a common problem that occurs during dry weather when isolated areas of soil become water repellent. In moderate to severe cases, LDS can lead to significant turf decline and heavy irrigation. Localized dry spot is easily identified on turf during summer and symptoms are often alleviated with wetting agent applications. However, LDS on dormant ultradwarf bermudagrass greens during winter is difficult to identify and may increase the likelihood of desiccation injury. Researchers from the University of Arkansas are trying to determine if late-fall to early winter wetting agent applications can enhance the positive effects permeable covers have on the survival of ultradwarf bermudagrass putting greens during winter.

The researchers made a single late-fall application of three commonly used wetting agents to TifEagle, Champion, and MiniVerde ultradwarf bermudagrass cultivars. Soil moisture, water droplet penetration time (WDPT) – i.e., the wettability of the soil – and percent green turf cover was collected to determine the effect of wetting agents on the ultradwarf bermudagrass cultivars.

Inconsistent weather likely played a role in variable results during the 2015-2016 and 2016-2017 winters. Both winters were unseasonably warm, which limited opportunities for winter injury.

In 2016, two of the three wetting agents reduced WDPT in the top 2 inches of the soil profiles when measured in April of the following spring. The reduction in WDPT indicates that wetting agents alleviated hydrophobic conditions and restored waters ability to move into the soil pore space.

In 2017, reduced WDPT was not observed after the January measurement date. The consistent precipitation that occurred throughout the winter likely reduced differences between untreated plots and those treated with wetting agents. Doubling the wetting agent application rates did not impact WDPT when measured in April for both years.

Percent green turf cover was significantly higher in plots treated with two of the three wetting agents in 2016 but not in 2017. The difference was likely due to more frequent precipitation during the winter of 2016-2017. Doubling the wetting agent application rate did not increase percent green turf cover during either year.

Despite the inconsistent results, late-fall to early winter wetting agent applications provide superintendents with a potential insurance policy against winter desiccation. These applications in conjunction with deploying permeable covers can help lessen the negative effects of dry conditions and low-temperature on ultradwarf bermudagrass putting greens. This research has been repeated during the 2017-2018 season and will hopefully yield more information on this important topic.