TechNotes are provided by Syngenta GreenCast.
Thatch control in ultradwarfs
"Ultradwarf” bermudagrass greens produce considerable amount of thatch compared to the older green varieties of Tifgreen (328) and Tifdwarf. Controlling thatch in these new cultivars is challenge. Deep vertical mowing (depth 0.5 to 1 inch depth) is common practice to extract thatch from the turf. Research has found that frequent verticutting to these depths is detrimental to the quality of an ultradwarf green. Deep verticutting may take up to 6 weeks for the turf to recover.
As a general rule of thumb, the ultradwarfs probably require two or less deep verticuttings in a growing season. More frequent applications result in a decline in the overall quality of the turf. From a recovery standpoint a deep spring verticutting should be timed to coincide with active turf growth. Average daily soil temperatures greater than 75 F (2 to 4 inch depth) might be a good key for spring verticutting.
Regarding topdressing, the consensus is light frequent topdressing is desirable for thatch control. When actively growing, weekly topdressings are considered desirable, while less frequent (once every 2 to 3 weeks) applications are applied during spring and fall during periods of slower growth. I would be remiss to not mention that variable results have occurred with topdressing studies. In some cases heavy topdressing may disperse the thatch deeper in the profile, thus not decreasing the overall thatch amount.
Topdressing alone for controlling thatch does not appear to be enough. Coring and subsequent topdressing to fill the holes is important. Impacting 20 to 25 percent of the surface area during the season through coring is the desired goal. This may require 3 to 6 corings per year. The tine size and spacing can be adjusted depending on the time of the years but the overall goal is to get 20 to 25 percent of the surface area.
Nitrogen fertilization is often mentioned as a contributor ultradwarf thatch accumulation. Nitrogen is applied within the desired range of growth, and not excessively, does not appear to contribute to thatch. Nitrogen applied between 0.5 to 1.5 lb nitrogen per 1000 square feet per growing month is the desirable range. Also, have of this nitrogen should be in the form of a slow release source.
