Influence of Plant Growth Regulators on Core Cultivation Recovery Time of Annual Bluegrass Putting Green Turf
Influence of Plant Growth Regulators on Core Cultivation Recovery Time of Annual Bluegrass Putting Green Turf
Chas Schmid, Alec Kowalewski, Brian McDonald and Emily Braithwaite
Department of Horticulture
Oregon State University
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Summary Points:
• Spring applications of ethephon (Proxy) help annual bluegrass putting greens recover quicker from core cultivation, whereas fall applications slow recovery
• Increased turfgrass growth observed in Gibberellic acid treatments initially increased the percent recovery compared to other treatments; however, scalping caused reduced turfgrass cover, and increased recovery time.
• Trinexapac-ethyl (Primo Maxx) timing had little effect on cultivation recovery time in 2021, regardless of season.
Introduction
Organic matter (OM) management with core cultivation is one of the most important management practices for golf course putting greens, and one of the most disruptive to golfers. Core cultivation is done in the spring and fall on actively growing cool-season turfgrasses to minimize recovery time (Beard, 1973). However, this is also the time of year when golf courses experience the most play. In a USGA report of the top 10 questions frequently asked by golfers, three questioned need for core cultivation of putting greens (Maloy, 2002). Thus, there is a need to reduce recovery time post core cultivation to limit disruption to golfers.
Plant growth regulators (PGR) are commonly used on golf courses to manage vertical growth and to improve turf stand density (Beasley and Branham, 2007; Ervin and Koski, 1998; Fagerness and Yelverton, 2000). Golf course managers apply PGRs routinely on a calendar based schedule or using growing degree day (GDD) models (Krueser and Soldat, 2011) to limit post-inhibition growth enhancement (aka “rebound effect”). Plant growth regulator applications to cool-season turfgrass are most commonly applied in the spring and fall when shoot and root growth are maximal (Johnson, 1989). In contrast, there has been a trend with sports field managers to use post-inhibition growth enhancement to recover from events that damage turfgrass, such as concerts (Polimer, 2020). On golf courses, core cultivation is one of the most damaging events to occur, but no research currently exists that demonstrates the effect of PGRs on recovery from core cultivation or if plant hormones such as gibberellic acid can be used to reduce recovery time. It may be possible to use post-inhibition growth enhancement to decrease recovery time.
OBJECTIVES:
1) Determine the effect of trinexapac-ethyl application timing on core cultivation recovery
2) Determine if ethephon treatments applied in the spring for annual bluegrass seedhead control influence cultivation recovery time
3) Evaluate the effect of gibberellic acid (GA3) on core cultivation recovery
MATERIALS AND METHODS
This three-year field trial will begin March 2021 with evaluations ending October 2023. The trial will be conducted on a sand-based annual bluegrass research green. The putting green will be mowed Monday through Friday at 0.110 inches with a Jacobsen Eclipse 322 mower. Irrigation will be applied to provide moderately moist soil to encourage recovery from cultivation treatments. The green will be core cultivated in the spring and fall (approximately May 15th and September 15th) with ½” inside diameter hollow tines (2 x 2” spacing). A complete fertilizer (Anderson’s 28-5-18) will be applied 2-d prior to cultivation to all plots at a rate of 0.25 lbs N/1000 ft2.
Treatments will be arranged as a randomized complete block design with four replications. Plot size for the trial will be 4’ x 4’ (16 ft2). Treatments are listed below:
Treatments
1. Untreated control
2. TE¥ applied 400 GDDɎ prior to cultivation
3. TE applied 400 GDD prior to cultivation + ethephon↑
4. TE applied 400 and 200 GDD prior to cultivation
5. TE applied 400 and 200 GDD prior to cultivation + ethephon
6. TE applied 400, 200 and 10 GDD prior to cultivation
7. TE applied 400, 200 and 10 GDD prior to cultivation+ ethephon
8. GA3 applied 10 GDD prior to cultivation at 0.05 oz RyzUp /Acre
9. GA3 applied 10 GDD prior to cultivation at 0.1 oz RyzUp/Acre
¥ All trinexapac-ethyl (TE) applications will be applied at 5.5 fl oz of Primo MAXX/Acre
ɎCumulative GDD model will be calculated as the summation of the daily mean air temperature (°C) with a base of 0°C following the most recent TE application.
↑All ethephon applications will be at 218 fl oz of Proxy/Acre 400 and 200 GDD prior to cultivation.
Treatments will be applied with a CO2-pressured backpack sprayer equipped with 4 TeeJet flat fan 80015 nozzles applied at 35 psi using a carrier volume of 1.8 gallons per 1,000 sq. ft. The first treatment application in the spring will be initiated at first sign of annual bluegrass plants in the “boot” stage, and subsequent applications and cultivation timing will be made based on a growing degree day model. Routine applications of trinexapac-ethyl will continue throughout the summer months on all plots (except non-treated control and GA plots) every 14 days.
Digital photos will be taken at the same location in each plot, daily during the recovery period, using a lightbox to track recovery over time. Digital images will be analyzed using Sigmascan to determine percent recovery over time. Plots were periodically rated for visual turf quality and turf color throughout the growing season, and intensively rated for the 10-14 day period post core cultivation, in both spring and fall. Turfgrass leaf clippings were collected 5 and 14 days post cultivation treatments to measure the amount of vertical growth (i.e. rebound effect). Soil samples will be collected at the conclusion of the study to determine the effect of PGRs on total organic matter. Soil samples were collected prior to the initiation of the study using methods described by Lockyer (2008) and analyzed using the loss on ignition method (Nelson and Sommers, 1996). Additional soil samples will be collected at the conclusion of the trial in Oct 2023. Response variables will be analyzed with analysis of variance (ANOVA) and the means separated using LSD at the 5% alpha level.
Findings:
Results from the spring of 2021 indicate that the main effect of ethephon treatments had the greatest effect on cultivation recovery time, with plots receiving ethephon recovering quicker than plots that received no ethephon (Fig. 1). The main effect of TE timing was only significant on one date in the spring of 2021, where the last app of TE applied 400 GDD prior to cultivation had greater percent recovery 5-d after cultivation compared to TE applied 10 GDD prior to cultivation (data not shown).
Results from the fall cultivation event also indicated that the main effect of ethephon treatment had the greatest effect on cultivation recovery time; however, during this season plots receiving ethephon were slower to recover than plots that received no ethephon (Fig 1). Trinexapac-ethyl timing had no effect on cultivation recovery time in the fall of 2021.
Interestingly, plots treated with GA at 0.05 or 0.1 oz/A initially had increased turfgrass growth (Fig 2) and rapid recovery from core cultivation 3-5 days after cultivation (Table 1 & 2; Fig 3). However, scalping from excessive turfgrass growth slowed recovery time overall. A higher rate of nitrogen (0.5 lbs N/ 1000 ft2 in Fall compared to 0.3 lbs N/ 1000 ft2 in spring) applied prior to the fall cultivation event seem to reduce the negative effect of the GA treatments long-term. It may be possible to limit the negative effect of excessive turfgrass growth by mowing more frequently and/or applying higher rates nitrogen prior to GA applications. Further research is needed to better understand how PGR applications influence cultivation recovery
LITERATURE CITED
Beard, J.B. 1973. Turfgrass science and culture. Prentice Hall, Englewood Cliffs, NJ.
Beasley, J.S. and B.E Branham. 2007. Trinexapac-ethyl and paclobutrazol affect Kentucky bluegrass single-leaf carbon exchange rates and plant growth. Crop Sci. 47:132-138.
Ervin, E.H, and A.J Koski. 1998. Growth response of Lolium perenne L. to trinexapac-ethyl. HortSci. 33:1200-1202.
Fagerness, M.J., and F.H. Yelverton. 2000. Tissue production and quality of ‘Tifway’ bermudagrass as affected by seasonal application patterns of trinexapac-ethyl. Crop Sci. 40:493-497.
Johnson, B.J. 1989, Response of tall fescue (Festuca arundinacea) to plant growth regular application dates. Weed Technol. 3:408-413.
Kreuser, W.C., and D.J. Soldat. A growing degree day model to schedule trinexapac-ethyl applications on Agrostis stolonifera golf greens. Crop Sci. 51:2228-2236.
Lockyer, J. 2008. STRI-testing for organic matter. Turfgrass Bulletin. 242:13-16.
Maloy, B. 2002. What are golfers thinking?: The top ten questions frequently asked of the USGA Green Section. USGA Green Sec. Rec. 40:13-16.
Nelson, D.S. and L.E. Sommers. 1996. Total carbon, organic carbon, and organic matter. in: Sparks, D.L., et al., editors, Methods of Soil Analysis, Part 3. SSSA Book Ser. 5. SSSA, Madison, WI. p. 961-1010.
Polimer, B. (2020). Why every sports field manager should consider using PGRs (SportsField Management). Retrieved from https://sportsfieldmanagementonline.com/2020/05/11/why-every-sports-field-manager-should-consider-using-pgrs/11506/
Table 1. Plant growth regulator effect on core cultivation recovery time in the spring of 2021
† DAC = days after core cultivation
‡ TE = Trinexapac-ethyl (Primo Maxx)
* GA = Gibberellic acid (RyzUp smartgrass®)
Table 2. Plant growth regulator effect on core cultivation recovery time in the fall of 2021
† DAC = days after core cultivation
‡ TE = Trinexapac-ethyl (Primo Maxx)
* GA = Gibberellic acid (RyzUp smartgrass®)
Figure 1. The main effect of ethephon (Proxy) on the percent recovery from core cultivation over time, in the spring (A) and fall (B) of 2021. Error bars above or below a rating date indicates a significant difference between treatments. The size of the error bar represents the LSD value.
Figure 2. The effect of PGR treatments on clipping yield, 7 days after cultivation and 14 days after cultivation in the spring of 2021. Upper-case letters indicate differences between treatments 7 day after cultivation and lower-case letter indicate differences between treatments 14 days after cultivation.
Figure 3. Cultivation recovery 4 days after fall coring event in plots treated gibberellic acid (GA) at 0.1 oz/A 10 GDD prior to cultivation (L) and the non-treated control (R).