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Key Takeaways

  • Superintendents and researchers have been experimenting with making multiple aeration passes in a single event as a way to maintain rootzone management goals while reducing the total number of aeration events per year.
  • The goal of this study was to compare the effect of one, two, or three aerator passes using 0.375- or 0.625-inch (diameter) solid tines during a single aeration event on cool-season putting greens.
  • Sand incorporation generally increased with tine size and with number of aerator passes. However, two or three passes with 0.375-inch tines led to the same sand incorporation as with one pass using 0.625-inch tines.
  • Total organic matter at the 0-1 inch depth ranged from approximately 6% to 9% at each golf course when the study began and only increased over the following 13 months for untreated plots.
  • Faster recovery was observed on plots with smaller tines compared to larger tines, with 0.375-inch holes healing about one week faster than 0.625-inch holes. The number of passes did not affect recovery.
     

Let’s do some word association. The prompt phrase is “putting green aeration.” The responses are likely to be predictably binary. Some will celebrate the agronomic benefits and recognize aeration as a necessary evil that is fundamental to maintaining healthy putting greens. Others will recoil at the disruption to playing conditions and question the need and the effort. At least for today, we won’t try to reconcile these views through a discussion of outcome-based rootzone management and how much aeration is needed at different points in the lifespan of a putting green. Instead, let’s start by simply acknowledging that 1) superintendents often use solid- or hollow-tine aeration to help introduce sand into putting green rootzones, 2) they do so to improve drainage and porosity characteristics by mitigating organic matter accumulation, and 3) golfers generally don’t love when they do it. Golfers’ distaste for aeration has led researchers and superintendents to experiment with various approaches to reduce the disruption while still achieving the benefits.

An increasingly common tactic involves using more-intensive aeration during a single event to reduce the total number of aeration events per year (Moeller & Lowe, 2016). A version of this concept that has gained popularity is performing multiple aerator passes in different directions over the same area during the same event, but this approach has yielded mixed results. For example, field experience and an early report from a research project in Virginia have indicated that recovery can be similar following one or two aerator passes during a single aeration event (Ervin et al., 2008; Whitlark, 2015). However, increased injury and longer recovery times have also been observed with this strategy, especially with cool-season putting greens (Ervin & Nichols, 2011; Moeller & Lowe, 2016). For these reasons, we were interested in evaluating the effects of one to three passes of solid-tine aeration on cool-season putting greens in the Pacific Northwest.

Further, superintendents commonly report and research has shown that holes from smaller tines recover faster, which made us curious about the trade-offs between surface disruption, recovery time, sand incorporation, and organic matter accumulation on greens aerated with one to three aerator passes with different-sized tines (Landreth et al., 2008). While the literature on aeration is vast, this specific topic has received little investigation. So, we designed an experiment to examine whether more passes with smaller tines could potentially introduce a similar amount of sand and similarly mitigate organic matter as when using larger tines, but with a shorter recovery time. 

Methods

Experiments were conducted at Chambers Bay Golf Course and Tacoma Country and Golf Club in Washington in 2023 and 2024. The putting green used at Chambers Bay was approximately a 50:50 mix of creeping bentgrass and annual bluegrass, whereas an annual bluegrass green was used at Tacoma Country and Golf Club. Both greens were managed in a typical manner for the region except that they only received the cultivation and sand backfill treatments in our experiments – no other aeration or topdressing was performed during the study period.

We included six aeration treatments: One (1x), two (2x), or three (3x) aerator passes with either 0.375- or 0.625-inch (diameter) tines. The aerator was set to a 3-inch depth on 2-inch centers. Additional passes for 2x and 3x treatments were offset 30 to 40 degrees from the angle of the previous pass to minimize overlapping holes. Sand was spread over plots before each aerator pass and hand-brushed to fill holes before a subsequent pass. This sequence was worth the additional effort as pilot testing taught us that many aeration holes were compromised from multiple aerator passes without the stepwise incorporation of sand.

Three aeration treatments were completed at each location: spring 2023, fall 2023 and spring 2024. The total amount of sand needed to fill aeration holes was recorded by weight in spring and fall of 2023. We also assessed total organic matter in the 0-1 inch depth and 0-3 inch depth at 0, 1, and 30 days after aeration (DAA). Data were analyzed using common statistical methods so that we could evaluate the average performance of our treatments.

Results

Sand incorporation
Approximately 600 to 1,600 pounds of sand per 1,000 square feet were required to fill aeration holes created by our treatments (Figure 1). As expected, sand requirements generally increased for larger tines and with the number of aerator passes. Up to 1,600 pounds of sand per 1,000 square feet was needed for 3x aeration with 0.625-inch tines while 2x aeration with 0.625-inch tines required about 500 pounds less sand over the same area. The 2x treatments consistently used more sand than 1x aeration with 0.625-inch tines, which was always less than 1,000 pounds.

3x aeration with 0.375-inch tines resulted in the same or more sand incorporation as with 1x or 2x aeration using 0.625-inch tines in all instances except Tacoma in spring of 2023. Interestingly, sand incorporation from 2x aeration with 0.375-inch tines was often similar to 1x aeration with 0.625-inch tines. 1x aeration with 0.375-inch tines always used the least amount of sand – less than 750 pounds per 1,000 square feet. 

Total organic matter mitigation
Total organic matter ranged from 6% to 9% in the 0-1 inch depth at both golf courses at the beginning of our experiment and only increased, statistically, for untreated plots at both golf courses (to approximately 15%) by one year later at 30 DAA in spring 2024 (Figure 2). At this time, there also were no statistical differences in total organic matter at the 0-1 inch depth among plots that were aerated during the experiment. There was almost nothing of note in total organic matter data at the 0-3 inch depth (data not shown). We were most interested in the effects of aeration treatments over time, which were not statistically significant at either golf course at this depth. When averaged over aeration treatments to explore the effect of time, total organic matter ranged from 4% to 7% at both golf courses during our experiment and was often highest in spring. It is important to remember that this was an abbreviated experiment. After one year, untreated plots appeared to be accumulating more total organic matter than plots that received aeration. Plenty of other research on this topic has shown this type of effect, but our experiment simply was too short to do so. It’s likely that more differences would eventually develop among our treatments – even among plots that were aerated.

Observations on Recovery

Although we were unable to closely track differences in turfgrass recovery in our experiments, two things were evident. First, recovery was weather-dependent. We observed a faster recovery in spring than in fall, which likely indicates that turfgrass growth potential was higher in spring during our experiments. Second, holes from 0.375-inch tines recovered more quickly (about 1 week in spring; 2 weeks in fall) than those from 0.625-inch tines (about 2 weeks in spring; 3 weeks in fall), regardless of aerator-pass frequency. This is similar to tine-size recovery differences reported by Proctor et al. (2013). Superintendents commonly report faster recovery from smaller aeration holes, which is intuitive and has also been empirically demonstrated by others (Landreth et al., 2008). In situations where recovery rate is a concern, such as late-season aeration or before a major event, we believe our data indicate that superintendents can achieve comparable sand incorporation and organic matter mitigation with multiple passes from smaller tines as with traditional “aggressive” aeration using a single pass from larger tines while potentially reducing recovery time. However, these observations should augment rather than replace traditional organic matter management programs. While making multiple passes with smaller tines in a single event can provide superintendents with greater flexibility in incorporating sand into rootzones, the strategy is not standalone and superintendents should not interpret these results as a reason to permanently supplant proper aeration intensities, frequencies, or timings, nor to replace important practices such as frequent sand topdressing throughout the growing season (Schmid et al., 2014; Whitlark & Thompson, 2019). 

Practical Conclusions

Our most important observation was that 2x or 3x aeration with 0.375-inch tines yielded as much sand incorporation as 1x (and sometimes 2x) aeration with 0.625-inch tines without statistical differences in organic matter accumulation. Although not quantitatively assessed in our experiment, we also observed quicker recovery from smaller vs. larger tines that others have experimentally quantified. Coupled with the organic matter accumulation in untreated plots, our data and observations increase our confidence in the value of using multiple passes with smaller tines to achieve sand incorporation goals and shorten recovery time compared to larger tines. However, our recovery observations were visually based and it would be interesting to further quantify this effect with estimates of ball roll distance, surface smoothness, or other surface performance metrics.

Every golf course is different, and superintendents have to develop their own targets and methods for managing putting green organic matter. What these results show is that making multiple passes with smaller tines in a given aeration event is worth considering as a way to achieve agronomic goals while minimizing the impact of aeration on playability over the course of a year.

Acknowledgement

We appreciate the cooperation of Eric Johnson, director of agronomy at Chambers Bay Golf Course, and Joel Kachmarek, golf course superintendent at Tacoma Country and Golf Club. This work would not have been possible without the support of these facilities and their leaders and staffs.

References

Ervin, E., Horvath, B., & Henderson, J. (2008). Organic matter dilution programs for sand-based putting greens. 2008 USGA Turfgrass and Environmental Research Summary. http://archive.lib.msu.edu/tic/ressum/2008/65.pdf

Ervin, E., & Nichols, A. (2011). Organic matter dilution programs for sand-based putting greens. USGA Turfgrass and Environmental Research Online, 10(8), 1-6.

Isom, C., & Thompson, C. (2025). Effects of within-event aerator-pass frequency and tine size on sand incorporation and organic matter accumulation in cool-season putting greens of the Pacific Northwest. Crop Forage & Turfgrass Management, 12, e70104. https://doi.org/10.1002/cft2.70104

Landreth, J., Karcher, D., & Richardson, M. (2008). Cultivating to manage organic matter in sand-based putting greens. Green Section Record, 46(1). https://gsrpdf.lib.msu.edu/?file=/2000s/2008/080116.pdf

Moeller, A., & Lowe, T. (2016). Managing organic matter in putting greens. Green Section Record, 54(21). https://gsrpdf.lib.msu.edu/?file=/2010s/2016/2016-11-04.pdf

Proctor, C.A., Johnston, W.J., Golob, C.T., Stahnke, G.K., & Williams, M.W. (2013). Topdressing sand color, cultivation timing, and cultivation method effects on disruption of a creeping bentgrass golf green in the Intermountain Pacific Northwest. Applied Turfgrass Science, 10(1), 1-6. https://doi.org/10.1094/ATS-2012-0166-RS

Schmid, C.J., Gaussoin, R.E., & Gaussoin, S.A. (2014). Organic matter concentration of creeping bentgrass putting greens in the continental U.S. and resident management impact. Applied Turfgrass Science, 11(1), 1-2. https://doi.org/10.2134/ATS-2014-0031-BR

Whitlark, B. (2015). Double aeration doesn’t mean double trouble. Green Section Record, 53(10). https://www.usga.org/content/usga/home-page/course-care/regional-updates/west-region/double-aeration-doesn-t-mean-double-trouble.html

Whitlark, B., & Thompson, C. (2019). Light and frequent topdressing programs. Green Section Record, 57(9). https://www.usga.org/content/usga/home-page/course-care/green-section-record/57/9/light-and-frequent-topdressing-programs.html