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90 GOLF COURSE MANAGEMENT 07.14 The year was 1993. Lee Janzen won the U.S. Open; the Dallas Cowboys were Super Bowl XXVII Champions; and "Jurassic Park" was the top-grossing movie. And Dr. Jim Mur - phy, with his advisor Dr. Paul Rieke, published the results of his Ph.D. research at Michigan State University. Many other researchers had previously ex - amined the impact of turfgrass cultivation on water infltration and thatch, but few had stud - ied how cultivation affected the soil and the turf itself. This was important, as we typically core-aerify to relieve soil compaction and en - courage root growth, among other benefts. A 3-year-old Penneagle creeping bentgrass green was used. The treatments were: (1) level of soil compaction (none and compacted); (2) hollow- or solid-tine aeration (both ~½ inch di - ameter); and (3) soil water content ("moist" or "wet") at the time of compaction. Cores from the hollow-tine treatments were reincorpo - rated; treatments were not further topdressed. The treatments were applied six times: in June, July and August of each year. Relatively easy measurements like turf color or quality may not provide much information, so you have to collect data like bulk density (a measure of how much soil solid is crammed into a given volume, with a higher bulk density indicating greater compaction); porosity (how much of the soil is flled with air holes, ~50%); and pore size distribution (the relative num - ber of small pores to big pores; a 50:50 mix is good). You need these numbers to determine if core cultivation really did anything to the soil. So Murphy measured soil bulk density, porosity and pore-size distribution. He also measured the ability of water to fow through the green, both in the laboratory (saturated hydraulic conductivity) and in the feld (dou - ble-ring infltrometer). Last, he measured soil compaction with a soil penetrometer, and he collected turf quality, root and shoot responses. This research provided some concrete data about the effects of compaction. Compaction increased soil bulk density, reduced water infl - tration and reduced the macropores, convert- ing them to micropores, which created wetter soils that did not drain as effectively. The most effective treatment for restoring macropores was use of hollow-tine coring, not solid tine. Soil resistance (as measured by the pene- trometer) was also affected by the coring treat- ments. Hollow tines were better for relieving soil compaction, and the effect lasted longer. With solid tines, any relief of soil compaction was gone after three weeks (as compared to the control), indicating that aerifcation with solid tines might have to be frequent if used to re - lieve soil compaction. Be careful, however, as it was noted that constant aerifcation at the same depth could result in the subsurface develop - ment of a cultivation pan. Overall, hollow-tine aerifcation was the best method for increasing soil macroporos - ity, improving water conductivity and relieving soil compaction. Cultivation when the soil was "wet" or "moist" was a little hard to sort out. In general, there seemed to be a little more turf injury when the soil was allowed to dry. Also, drying the soil before cultivation may limit the development of a cultivation pan. Not surprisingly, compaction reduced root growth. Perhaps surprisingly, root weight was not increased by cultivation, and summer cul - tivation did not increase root development. This was an intense aerifcation schedule (three times in summer), and analysis of root growth well after the aerifcation period may have pro - vided more information about root response. We need more work in this area. Should you aerify? Yes. This paper clearly showed that hollow-core cultivation tines in - creased water infltration and macroporosity and decreased soil compaction. But, long-term and frequent use requires careful consideration, and the depth of effective aerifcation should be altered to avoid the development of a compac - tion pan. Avoid tine aeration if your soil is not compacted. This work saw the benefts of culti - vation on compacted soils, but not on the non- compacted plots in the study. Source: Murphy, J.A., P.E. Rieke and A.E. Erickson. 1993. Core cultivation of a putting green with hollow and solid tines. Agronomy Journal 85:1-9. Beth Guertal, Ph.D., is a professor in the department of agronomy and soils at Auburn University in Auburn, Ala., and the editor-in-chief for the Agronomy Society of Amer - ica. She is a 17-year member of GCSAA. Beth Guertal, Ph.D. firstname.lastname@example.org twitter: @AUTurfFert Poke some holes in this (verdure) It was noted that constant aerifcation at the same depth could result in the subsurface development of a cultivation pan. 090-091_July14_Verdure.indd 90 6/17/14 2:33 PM