Golf Course Management

JUL 2019

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

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58 GOLF COURSE MANAGEMENT 07.19 summer aerification in the Mid-Atlantic and Northeast regions. In years such as 2018, late August and September aerification caused notable damage, regardless of which method (hollow tines vs. solid tines vs. aggressive spik- ing) was used. Even waiting until early October is no guarantee for success: 2018 was unusually hot and wet, and those environmental stresses re- sulted in extremely slow recovery from aerifi- cation. Another consideration at that time of year is the shortening of daily sunlight, which can lead to frosts, which slow turf growth sig- nificantly. In some years, August may be a great time to aerate, but it only takes one event of ex- treme turf stress to cause superintendents to rethink when and how they aerify. „e injury from aerification in 2018 (and other years) varied among courses and from green to green on those courses. Many times, shaded greens or greens that lacked air movement were most severely damaged. Recipes for success „ere is not a single recipe for successful aerification timing and methods that is appli- cable to every golf course. Some golf courses experience little golf from Halloween until late spring, for example, and these courses potentially have fewer issues with aerifica- tion timing because they have more flexibility. Some golf courses have a core group of 20 to 30 players who will play almost every day of the year, including winter, as long as they can access the golf course. Every course is unique in regard to golfing schedule, budget, labor, grass species and growing environments. For many, you can add seasonal concerns, a heavy tournament schedule, or the agendas of club professionals or owners to the mix. It's hard to say which of those factors is the most impor- tant, but it varies from course to course, and the superintendent on the ground at those fa- cilities will know the landscape best and how to make an informed decision. „e most common time to aerify is late summer, and that's also widely thought to be the best time to aerate, agronomically speak- ing, because holes heal quickly, and greens typically have recovered before any late-sum- mer or autumn golf tournaments. I agree that mid-to-late August and early September do provide a good time for quick healing. How- ever, if the weather is not ideal at the time of aerification, as well as over the next few weeks during recovery, greens will not heal as quickly as they do during favorable weather. Poa problems? Many argue that aerifying in late autumn encourages Poa annua germination. Poa germination patterns can vary widely based on many factors. A field research study in Maryland found this to be partially true, but field observations I've made after visiting many of the same golf courses for more than 10 years have illustrated that if you aer- ate after the Poa germinates, you naturally may be able to mitigate this problem in late autumn. Research at two golf courses in Maryland between late September and the middle of October found that the majority (50%-70%) of Poa had germinated by that time, and most germination ended by early November (1). The research found that, on average, 24% of all Poa seedlings emerged between November and May. My field observations line up with this data, and I have seen significantly more Poa in greens aerated before Nov. 1 in most years in the Mid-Atlantic and Northeast regions. I also have seeded Poa (collected seedheads in spring and cleaned and dried them for the following autumn) for research trials, and we have struggled to get it to germinate after the middle of October in fumigated soils with no competition. Is there a higher risk of Poa invasion into greens when they are thin from aerification damage in August or September, since 50%-70% of the total Poa germinates in late September or October in Maryland? Or is there a higher risk of Poa encroachment with aerification late into the year? Although there is no exact research on this question, a lot of nearly pure creeping bentgrass greens are aerified in late autumn each year. Many other components besides aerification — use of plant growth regulators, shade, Poa seed bank, existing populations of bentgrass and Poa — also factor into this issue. Literature cited 1. Kaminski, J.E., and P.H. Dernoeden. 2007. Seasonal Poa annua L. seedling emergence patterns in Maryland. Crop Science 47(2):773-779. doi:10.2135/cropsci2006.03.0191 — S.M.

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