Golf Course Management

JUL 2017

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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72 GOLF COURSE MANAGEMENT 07.17 of dallisgrass was uniform across mowing re- gimes, with average reductions of 38% (year one) and 45% (year two), regardless of the mowing height/frequency treatment. Basi - cally, for bahiagrass, the lower the mowing height, the more lateral spread was reduced. For dallisgrass, any mowing reduced lateral spread (compared with the unmowed control), but spread was not reduced more by continued reductions in mowing height. Similar results were observed with the fresh weight of rhizomes. Because rhizomes are stems, they are capable of producing growth, and thus plants with greater rhizomes would potentially have better growth and recovery. For bahiagrass, any mowing regime reduced the fresh weight of rhizomes, with decreases measured with each decrease in mowing height. Fresh weight of bahiagrass rhizomes was reduced by 71% when mowed at ½ inch, three times weekly. Fresh weight of dallisgrass rhizomes was reduced when mowed at any of the three heights, but mowing lower or more frequently did not further affect rhizome fresh weight. The treatments (mowing height/frequency) that are typical for a bermudagrass fairway sig - nificantly reduced the spread and viability of bahiagrass, and the treatment with most fre - quent mowing at the lowest height was more effective. This result helps explain why bahia - grass may be more prevalent in areas main- tained as a rough. Growth of dallisgrass was less affected by mowing height/frequency, and it still exhibited lateral spread and rhi - zome growth under the mowing conditions typically used for a bermudagrass fairway. It was also noted that in the "real world," com - petition from bermudagrass would be present, which would likely result in further reductions in lateral spread and rhizome growth from these two problematic weeds. Source: Henry, G.M., M.G. Burton and F.H. Yelverton. 2007. Effect of mowing on lateral spread and rhizome growth of troublesome Paspalum species. Weed Science 55(5):486- 490. Beth Guertal, Ph.D., is a professor in the Department of Crop, Soil and Environmental Sciences at Auburn Univer - sity in Auburn, Ala., editor-in chief for the American Soci- ety of Agronomy, and president-elect of the Crop Science Society of America. She is a 20-year member of GCSAA. Beth Guertal, Ph.D. Twitter: @AUTurfFert (verdure) Bahiagrass and dallisgrass are two trouble- some Paspalum species in bermudagrass. With their spreading lateral growth, tall seedheads and overall unattractiveness, these species can play havoc with a fairway. Current chemical control methods are sometimes not efficient, and they may not be cost-effective. Given this, the folks at North Carolina State — Fred Yelverton, Ph.D., and Gerald Henry, Ph.D. (now at the University of Geor - gia) — decided to explore how something as simple as a mowing regime (in this study, a combination of height and frequency) affected the growth of these weeds, in particular their lateral spread and stem growth (rhizomes). For two years, intact plugs of bahiagrass and dallisgrass were collected and transplanted into bare soil. After one month of growth to ensure establishment, transplants were mowed following regimes similar to those used for bermudagrass fairways and roughs. In year one of the study, the mowing regimes were ½ inch (1.3 cm) three times a week or 3 inches (7.6 cm) twice a week. In the second year, a third height/frequency treatment was added: 2 inches (5.2 cm) twice a week. There was also a non-mowed check. All the mowing treat - ments were applied from June through No- vember. Mowing heights were reduced gradu- ally before the start of the experiment so that the lowest mowing heights did not scalp the turf. All plant growth was measured in plots that were maintained as weed-free, so that growth of the two Paspalum species was ob - served without competition. The growth of the bahiagrass and dallisgrass was measured as a change from the initial diameter of the planted plugs. Collected data included plant diameter at monthly intervals and above- ground biomass and fresh weight of rhizomes (the underground stem tissue) at five months after the start of the experiment. Bahiagrass and dallisgrass growth were different as the mowing regime changed. Any mowing reduced the lateral spread of the bahiagrass, but reduction was greatest at the lowest mowing height (½ inch). In year one, lateral spread of bahiagrass was reduced by 44%, and in year two, it was reduced by 62% in the plots that were mowed at ½ inch three times weekly when compared with spread in the control plots. When the bahiagrass was mowed at a 3-inch height twice weekly, the lateral spread was reduced by only 25% over both years. In comparison, the lateral spread For bahiagrass, the lower the mowing height, the more lateral spread was reduced. For dallisgrass, any mowing reduced lateral spread. Mow low to push out Paspalum

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