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03.15 GOLF COURSE MANAGEMENT 91 The three cool-season species — Kentucky bluegrass, perennial ryegrass and tall fescue — followed similar trends in carbon dioxide fux across most measurement dates. Carbon dioxide fux data within species but across cultivars of varying growth rates showed few differences. Grass clipping management played a minor role in greenhouse gas fux, as returning grass clippings resulted in greater carbon diox - ide fux than collecting clippings on only one of the six measurement dates. Nitrous oxide fux was not different among main treatment effects (species, cultivar and clipping manage - ment) during the experiment, and there was not a measurable methane fux. Differences in labile and total soil carbon were realized between turfgrass species after three years of growth post-planting, with tall fescue having 9.9% more labile soil carbon and 4.5% more total soil carbon than Ken - tucky bluegrass. After two years under differ- ent mowing practices, plots where grass clip- pings were returned had 3.3% more labile soil carbon, 4.2% more total soil carbon and 4.6% more total soil nitrogen than those where clip - pings were collected. Planting slower-growing turfgrasses re - sulted in fewer annual mowing events: Ken- tucky bluegrass required fewer annual mow- ing events than tall fescue, and slow-growing cultivars needed to be mowed less than the moderate-growing cultivars, which were mowed fewer times than the fast-growing cul - tivars (Table 1). Mowing by the one-third rule also reduced mowing requirements (Table 1). Returning clippings increased the num - ber of annual mowings by about 2 compared to plots where clippings were collected when mowed by the one-third rule (Table 1), but returning grass clippings was benefcial as it increased tissue nitrogen concentration in clippings as well as total soil nitrogen concen - tration and total and labile soil carbon. This project is one of many current proj - ects being conducted by turf scientists around the country so that we can continue to learn and better understand how turf management infuences soil carbon sequestration. The re - sults of this study highlight the importance of turfgrass selection and mowing practices on the carbon and nitrogen dynamics and bio - geochemical cycling in a turfgrass system. Aaron Patton (firstname.lastname@example.org) is an associate pro- fessor, Quincy Law is a graduate research assistant, and Dan Weisenberger is a research agronomist in the depart - ment of horticulture and landscape architecture, and Jon Trappe is a graduate research assistant and Ron Turco is a professor in the department of agronomy at Purdue Uni - versity, West Lafayette, Ind. Number of mowing events Weekly One-third rule Cultivar Species Growth rate † Collected Returned Collected Returned Gazelle II tall fescue slow 28.25 29 16 17.75 Tar Heel II tall fescue medium 29 29.25 17.25 21.25 Endeavor tall fescue fast 28.75 29.5 21 24.25 Prosperity Kentucky bluegrass slow 19.75 24 12.25 14.25 Moonshine Kentucky bluegrass medium 27.5 28 15.5 17.5 Thermal blue Kentucky bluegrass fast 27.75 28 20 22.5 † Cultivars were selected for this experiment based on their growth rate in preliminary trials and their similar appearance and stress tolerance in previous field trials in West Lafayette, Ind. (data not shown). Table 1. The number of recorded mowing events with clippings collected and returned for each treatment in 2013. Recorded mowing events in 2013 Reducing annual bluegrass in fairways Zac Reicher, Ph.D. Matt Sousek David Minner, Ph.D. Andrew Hoiberg, Ph.D. Annual bluegrass (Poa annua) is the most (Report) troublesome weed on golf courses wherever cool-season grasses are grown. On fairways in particular, populations can quickly approach 50% or more if aggressive control measures are not initiated shortly after establishment. Furthermore, diffcult summers can cause sig - nifcant thinning or widespread death of an- nual bluegrass. In response, superintendents will overseed in late August to early September to help the stand recover from summer. However, an - nual bluegrass germination and competition is highest in the fall, and thus it can overtake the desired turf and the cycle starts over. Mini - mizing annual bluegrass and maximizing the desired cool-season turf could help break this cycle. Seeding early in the summer before the almost inevitable annual bluegrass thinning could allow the desired turf to establish while the annual bluegrass is thinning. Addition -