stages of deacclimation. Tey did this by harvesting cores from a 6-year-old stand of bermudagrass from the field in February, taking the cores to a greenhouse, and exposing them to warm conditions (e.g. 80-85 degrees F) for 0, 2, 4, and 8 days, and then separating groups of 10 stolons from the cores. Te stolons were then subject to roughly 38 degrees F for 24 hours. Following this cooling period, stolons were subject to approximately 32-, 28-, 24-, and 20-degrees F. Sub-sets of these samples were then placed in flats at several time periods, allowed to green up, and the percentage of stolons that greened up was counted. Tis was conducted at either 0, 45, or 90 days after deacclimation. What they found was that “below-freezing temperatures and prolonged dormancy after freezing hindered bermudagrass survival.” By contrast, short deacclimation periods before freezing did not.
Based on this knowledge, other researchers began to explore how mineral nutrition affected winter hardiness, with a focus on N inputs applied later in the growing season. To evaluate late-season N effects, Dr. Goatley conducted several experiments. One such experiment conducted in Mississippi on ‘Tiflawn’ and Arizona Common bermudagrass evaluated the effect of both water-soluble and controlled release (e.g. sulfur coated, methylene-urea, etc.) N-sources applied on September 28. Over three years, these sources were applied at a rate of two pounds of N per 1000 square feet. Tis rather high (unrecommended rate) N-rate and late timing were used to focus on a worst-case scenario that might induce winter injury. A one-pound N rate applied about four weeks earlier during more active growth would be preferred. To determine plant response, turf color data across the late-fall, winter, and spring green-up, along with plant carbohydrate status, was determined. Tey reported that carbohydrate levels of rhizomes were higher with ammonium nitrate and IBDU than for the methylene- urea, biosolid, or unfertilized control. Further, generally, the bermudagrass held green color longer into the autumn and greened up earlier than the unfertilized control and at no time was there any indication that N predisposed bermudagrass to winter-kill.
Lastly, a two-year study was conducted in Lexington, Kentucky (Munshaw et. al., 2001) to evaluate how grow- in urea-N applications might affect the establishment and “fitness” of ‘Mirage’ seeded bermudagrass stolons when planted in early June on a silt-loam at 0.25, 0.5, 0.75, and 1 pound of pure live seed. Te entire area received one pound of N per 1000 square foot at planting, and an additional one pound at 30, 14, or 7 days after planting until 10 September. Tese N applications totaled 1, 4, 8, or 12 total pounds. Te researchers measured stolon size, internode length, and carbohydrate status in October following seeding. Tey found that stolon size was larger with a lower seeding rate but that did not affect
TPI Turf News May/June 2024
Tese turf plots show cultivar differences for winterkill. Photo courtesy of Dr. Cale Bigelow
carbohydrate status. N applied at 4 or 8 pounds had higher carbohydrates than 12 pounds. While no winterkill was observed in either year of the study, previous research has shown that “fit” stolons (e.g. larger) with higher carbohydrates are important for winter survival.
Collectively, this information indicates that N can play a significant role in winter survival, especially in promoting plant health (e.g. carbohydrates) and green color. Future studies should be conducted on more contemporary cold- hardy cultivars. When it comes to bermudagrass nutrition some of the best advice comes from the Goldilocks fairy tale… “Not too much, Not too little, but just right.”
References Beard, J.B. 1982. An assessment of late season nutritional strategies on C-4 warm-season grasses. p. 81-98. In: Symposium on turfgrass fertility: Advances in turfgrass fertility, Columbus, OH. 20-21 Oct. 1982. Ohio Turfgrass Council.
Chalmers, D.R. and R.E. Schmidt. 1979. Bermudagrass survival as influenced by deacclimation, low temperatures and dormancy. Agron. J. 71:947-949.
Chalmers, D.R. 1986. Bermudagrass management to reduce winter injury – Pay now or pay later. USGA Green Sec. Rec. 43(3):8-10.
Goatley, J.M. Jr., V.L. Maddox and K.L. Hensler. 1998. Late-season applications of various nitrogen sources affect color and carbohydrate content of ‘Tiflawn’ and Arizona common bermudagrass. HortSci. 33:692-695.
Munshaw, G.C., D.W. Williams, and P.L. Cornelius. 2001. Management strategies during the establishment year enhance production
and fitness of seeded bermudagrass stolons. Crop Sci. 41:1558-1564.
Cale Bigelow, PhD, is a professor of Turfgrass Science and Ecology in the Department of Horticulture and Landscape Architecture at Purdue University in Indiana. Mike Fidanza, PhD, is a professor of Plant and Soil Science at Pennsylvania State University, Berks Campus. They are teaming to provide a Rooted in Research article for each issue of Turf News.
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