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© 2008 Plant Management Network. Sod Production Utilizing an Improved Seeded Bermudagrass Cultivar John McCalla, Jr., Michael Richardson, Douglas Karcher, Josh Landreth, and Aaron Patton, Department of Horticulture, 316 Plant Sciences Building, University of Arkansas, Fayetteville 72701 Corresponding author: Michael Richardson. mricha@uark.edu McCalla, J., Jr., Richardson, M., Karcher, D., Landreth, J., and Patton, A. 2008. Sod production utilizing an improved seeded bermudagrass cultivar. Online. Applied Turfgrass Science doi:10.1094/ATS-2008-0118-01-RS. Abstract Improved, seeded bermudagrass (Cynodon spp.) cultivars have the potential to be used for sod production, but there has been no research to determine appropriate methods for this application. The objective of this study was to determine the effects of sod netting and the growth regulator, trinexapac-ethyl (TE), on the time required to harvest sod using a seeded bermudagrass. The experimental design of this study was a strip-plot with sod netting being the whole plot treatment and TE treatments (0.059 lb ai/acre every 2 weeks and 0.118 lb ai/acre every 4 weeks) as the sub-plot treatment. ‘Riviera’ bermudagrass (C. dactylon var. dactylon) was seeded at a rate of 43.5 lb/acre during the first week of June in 2005 and 2006. A commercially-available sod netting product was randomly applied to half of the whole plot area in each replicate immediately after seeding and TE treatments were initiated at 6 weeks after planting (WAP). A strip of sod containing twelve 18- × 30-inch pads was harvested from each sub-plot at 10, 12, 14, and 16 WAP. At each harvest date, the following parameters were measured: (i) harvestable sod as the percentage of pads that were able to be handled without damage, and (ii) sod tensile strength was measured on a subsample of 5 harvested pads. Netting allowed 100% of the sod to be harvested as early as 10 WAP, while a complete harvest was never obtained with the non-netted sod up to 16 WAP. The growth regulator, TE, had a positive effect on both percentage harvested sod and tensile strength of the sod, suggesting it can be used to hasten the harvest of bermudagrass sod when established from seed. Introduction The production of commercially available sod began around 1920 in the United States (10). Although many turfgrass species are commercially produced as sod, bermudagrass (Cynodon spp.) continues to be the major turfgrass species grown for sod across the southern United States and throughout the transition zone. The majority of sod is produced from vegetatively-propagated hybrid [C. dactylon (L.) Pers. Var. dactylon × C. transvaalensis Burtt Davy] cultivars such as ‘Tifway’ and ‘Midlawn’ and recently with newer hybrids such as ‘Tifsport’ and ‘Patriot.’ In the past two decades, several new seeded bermudagrass cultivars have appeared in the market and these have many desirable characteristics compared to older types of common bermudagrass. In the 1997 National Turfgrass Evaluation Program bermudagrass trial, the seeded cultivars, ‘Princess-77’ and ‘Riviera’ (C. dactylon var. dactylon), ranked at the top of the trial for both seeded and vegetative types of bermudagrass (11). These grasses are being primarily used in situations where turf areas can be directly planted with seed. However, they also have the potential to impact the sod industry by offering a seeded bermudagrass option, which may increase the production volume of warm-season sod farms or decrease production costs. In addition, there are many instances where sod establishment is preferred over seeding due to time constraints or the need to stabilize areas with a mature turf. Seed propagation is the primary establishment method for sod production of cool-season grasses such as perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), and tall fescue (Festuca arundinaceae Schreb.) (2,6,15). Rhizomatous Kentucky bluegrass seedlings are able to knit together and a harvestable crop can be produced in approximately 6 months under good conditions (14). However, bunch-type grasses such as perennial ryegrass and tall fescue require a binding agent to produce a harvestable crop in this same time frame (5). This is typically accomplished by either adding a spreading species such as Kentucky bluegrass to the seed mixture (5,6) or by applying a synthetic reinforcement material immediately after planting (1,3). Other studies have investigated the use of chemical treatments to enhance sod strength. Although results have been inconsistent, positive effects of plant growth regulators, such as trinexapac-ethyl (TE), have been observed (7,8,9). Trinexapac-ethyl applied at 28 days after seeding increased Kentucky bluegrass turfgrass density and sod strength (9). In addition, Heckman and co-workers (8) also observed increased sod strength from TE applications to mature (over 2 years old) Kentucky bluegrass sod. There have been no studies that have tested the effects of TE on warm-season grass sod production. In preliminary studies, a full stand of bermudagrass could be established from seed in as little as 6 weeks (J. H. McCalla, unpublished). However, it is uncertain whether this juvenile stand has the tensile strength to be harvested as sod, as there have been no studies using seeded bermudagrass for sod production. The goal of this research was to assess the potential use of improved seeded bermudagrass for sod production. Effects such as sod netting and trinexapac-ethyl application were also evaluated for decreasing sod production duration. Sod Establishment and Evaluations This study was conducted at the University of Arkansas Research and Extension Center in Fayetteville, AR (36°0'N, 94°10'W). The soil type was a Captina silt loam (fine-silty, mixed, mesic Typic Fragiudult) with an average pH of 6.2. Prior to planting, the site was fumigated with methyl bromide (67%) and chloropicrin (33%) at 350 lb/acre. Riviera bermudagrass was seeded at a rate of 43.5 lb pure live seed (PLS) per acre during the first week of June in 2005 and 2006. The seed were obtained as coated seed from Johnston Seed Co. of Enid, OK and each year of the trial was established with seed harvested from the previous year’s seed crop. The seed were lightly raked and then rolled using the rubber wheels on a 3-wheeled sand rake. Immediately after planting, whole plot treatments (sod netting) were applied to a 15- × 75-ft plot areas and similar plots were established as a non-netted control (Fig. 1). The sod netting used in this study was a plastic fiber with a 0.75- × 1.04-inch mesh size (SodNet, R04035, Conwed Plastics Inc., Minneapolis, MN) and was applied to half of the whole plots in each of four replicates.
Proper soil moisture levels were maintained during the establishment period to promote germination and seedling vigor. In the absence of rainfall, the test area was irrigated at a rate of approximately 1.0 inch of water per week to promote vigorous growth and prevent drought stress. A soil test was conducted prior to seeding each year and phosphorous and potassium levels were adjusted to attain a soil test value of 100 lb P per acre and 250 lb K per acre. Nitrogen was applied as urea every two weeks at a rate of 65 lb N per acre. Plots were mowed twice weekly throughout the experiment, beginning at 4 weeks after planting. The mowing height was 1.25 inches using a triplex mower and clippings were returned. At 6 weeks after planting, TE was applied to 15- × 25-ft sub-plots within each netting treatment. Two rates of TE, 0.059 lb ai/acre and 0.118 lb ai/acre, were applied every 14 or 28 days, respectively, until the end of the study (16 weeks after planting) and compared to an untreated control. Sod was harvested at 10, 12, 14, and 16 weeks after planting (WAP) and harvest date was considered a third split for data analysis. Data collected at harvest included percent harvestable sod and sod strength. Sod was harvested as 18- × 30-inch pads from each sub-plot using a walk-behind sod harvester (Ryan Jr. Sod Cutter, CGC Inc., Johnson Creek, WI) set to a depth of 0.75 inch at each harvest. The plot size provided enough area so that 12 pads could be harvested from each net × TE plot on each harvest date. Percent harvestable sod was determined by lifting each sod piece by hand from the soil and placing the sod on a cart for transport. Sod that could be moved from the soil to the cart without breaking was considered harvestable sod. Sod tensile strength was measured at each harvest date using a device patterned after a similar machine designed at Michigan State University (13,16). The machine operates by initiating a lateral pull on an immobile pad of sod and recording the maximum shear force required to break an individual piece of sod (Fig. 2). Within each net × TE × harvest date plot, five intact pads were collected (if available) and analyzed with the sod stretching device.
Significant Treatment Effects Riviera attained full canopy cover at 6 WAP for both years of the study (data not shown). Year, netting, TE, and WAP all had significant effects on both % harvestable sod and sod strength (Table 1). In addition, there were several interactions, including a year*netting*TE*WAP interaction on percent harvestable sod (Table 1). Therefore, the percent harvestable sod data will be presented and discussed specifically on this interaction. For sod strength, there was also a significant year*WAP interaction (Table 1), so data on sod strength will be presented based on this interaction and the main effects of TE and netting. Table 1. Analysis of variance results, testing the main effects and
Percent Harvested Sod All netting treatments produced 100% harvestable sod at all harvest dates across both growing seasons of this trial (data not shown). Non-netted, control plots produced less harvestable sod than those that received netting, especially at the earlier harvest dates (Fig. 3). At 12, 14, and 16 WAP in 2005, control plots that were treated with the growth regulator were not statistically different from the netted plots for percent harvestable sod (Fig. 3). The TE treatments improved percent harvestable sod at the 10, and 12 WAP harvests in 2005 compared to the untreated control, but were not different from the untreated control at 14 or 16 WAP (Fig. 3). Although trends were similar in 2006, the TE treatments were better than the controls at the 12, 14, and 16 WAP treatments (Table 1). There was only one date (16 WAP in 2006) where there was a significant difference between the two rates of TE.
There was also a significant year effect on percent harvestable sod (Table 1) and it was clear that sod development in the non-netted plots was less in 2006 compared to 2005 (Fig. 3). Environmentally, there were no apparent differences in temperatures between the two seasons (Fig. 4), especially during the first 10 weeks of establishment. It is unclear why there were such striking differences between the two years of the study, but this variability further justifies the use of netting, as the netted plots had excellent harvest percentages in both years of the trial.
These results clearly demonstrate that netting is a superior method to quickly harvest bermudagrass sod when planting from seed, enabling a sod producer to harvest a crop of seeded bermudagrass in as little as 10 weeks after planting. Carrow and Sills (3) and Beard et al. (1) reported similar results with tall fescue and bluegrass sod that had been harvested with and without net after a shortened establishment period. However, the use of the growth regulator, TE, also improved the handling characteristics of bermudagrass sod and may be more economically feasible than the use of net. In addition, the netting used for sod production has a very long decay period and some turf situations, such as athletic fields, may not accept sod with netting, as this creates a potential hazard for athletes. Sod Strength There was a significant main effect of both TE and netting on the sod shear strength (Table 1). Plots that were netted after seeding had an approximately two-fold increase in sod strength compared to non-netted plots (Fig. 5). Similar increases in sod strength have been observed when netting was used for cool season grasses (1,3).
Across both years and all harvest dates, TE also had a significant effect on sod strength measurements (Table 1). Both rates of TE increased the peak force to break the sod by approximately 15% compared to the untreated control (Fig. 5). Similar increases in sod strength were observed by Hall and Bingham (7) when TE was applied to Kentucky bluegrass at either a rate of 0.6 or 0.78 lb ai/acre. Although there are numerous studies that have demonstrated the positive effects of TE on bermudagrass performance (4,12), this is the first report demonstrating its usefulness in bermudagrass sod production. Although not documented in the present study, previous studies have demonstrated a significant increase in stolon number in TE-treated bermudagrass (4). This increase in stolon density would likely explain the increase in sod strength observed in the present research. Future studies investigating the effects of TE on sod production of seed- and vegetatively-propagated bermudagrass cultivars would be worthwhile. Sod strength generally increased with harvest date in both 2005 and 2006 (Fig. 6). In 2005, the 10 WAP harvest date produced sod that was significantly weaker than the 12 and the 16 WAP harvest dates, but not statistically different from the 14 WAP (Fig. 6). In 2006, the 14 and 16 WAP harvest dates had significantly higher sod strength than the 10 and 12 WAP dates, which were not different from each another.
Conclusions This is the first report demonstrating that an improved seeded bermudagrass such as Riviera can produce a harvestable sod crop in 10 weeks with minimal waste if plastic netting is used for production. If a grower desires to seed without netting, it will likely take 16 weeks or longer to reach a similar level of maturity. Similar results have been observed, with successful production occurring from both netted and non-netted practices, with the only difference being the duration until first harvest (Russ Nicholson, Pennington Seed Co., Madison, GA, personal communication). Although this is the first report on sod production using a seeded bermudagrass, earlier reports demonstrated that vegetative hybrids such as Tifway were capable of producing a sod crop in approximately 16 weeks (10), so the differences between propagation methods relative to production interval may not be of economic significance if netting is not used. However, when netting was employed, a marketable crop was produced in 10 WAP in both years of the study. The use of a growth regulator such as trinexapac-ethyl was also effective at reducing the harvest interval and improving sod handling characteristics of a seeded bermudagrass. Acknowledgments The authors wish to thank Turfgrass Producer’s International for their financial support of this project. Literature Cited 1. Beard, J. B., Martin, D. P., and Mercer, F. B. 1980. Investigation of net-sod production as a new technique. Int. Turfgrass Soc. Res. J. 3:353-360. 2. Beard, J. B., Rieke, P. E., and King, J. W. 1969. Sod production of Kentucky bluegrass. Int. Turfgrass Soc. Res. J. 1:509-513. 3. Carrow, R. N., and Sills, M. 1980. Tall fescue sod production with plastic netting. HortScience 15:818-820. 4. Fagerness, M. J., Yelverton, F. H., Livingston, D. P., III, and Rufty, T., Jr. 2002. Temperature and trinexapac-ethyl effects on bermudagrass growth, dormancy, and freezing tolerance. Crop Sci. 42:853–858. 5. Hall, J. R., III, and Taylor, L. H. 1989. Impact of companion crop and fertilization on tall fescue sod production. Int. Turfgrass Soc. Res. J. 6:259-261. 6. Hall, J. R., III. 1980. Effect of cultural factors on tall fescue - Kentucky bluegrass sod quality and botanical composition. Int. Turfgrass Soc. Res. J. 3:367-377. 7. Hall, J. R., III, and Bingham, S. W. 1993. Impact of growth regulators on Kentucky bluegrass sod management and installation parameters. Int. Turfgrass Soc. Res. J. 7:701-707. 8. Heckman, N. L., Horst, G. L., Gaussoin, R. E., Frank, K. W. 2001. Storage and handling characteristics of trinexapac-ethyl treated Kentucky bluegrass sod. HortScience 36:1127-1130. 9. Henderson, J. J., Sorochan, J. C., Crum, J. R., and Rogers, J. N., III. 1999. Effects of trinexapac-ethyl and wetting agent on establishment rate of Kentucky bluegrass in sand-based root zones. Page 136 in: 1999 Agronomy Abstracts. ASA, CSSA, and SSSA, Madison, WI. 10. Mitchell, C. H., and Dickens, R. 1979. Nitrogen fertilization and mowing height effects on tensile strength of bermudagrass sod. Agron. J. 17:1061-1062. 11. Morris, K. N. 2000. National Turfgrass Evalutation Program, 1997 National Bermudagrass Test. NTEP No. 00-4, USDA, Beltsville, MD. 12. Richardson, M. D. 2002. Turf quality and freezing tolerance of ‘Tifway’ bermudagrass as affected by late-season nitrogen and trinexapac-ethyl. Crop Sci. 42:1621–1626. 13. Rieke, P. E., Beard, J. B., and Hansen, C. M. 1968. A technique to measure sod strength for use in sod production studies. Page 60 in: 1968 Agronomy Abstracts. ASA, CSSA, and SSSA, Madison, WI. 14. Rieke, P. E., and Beard, J. B. 1969. Factors in sod production of Kentucky bluegrass. Int. Turfgrass Soc. Res. J. 1:514-521. 15. Shildrick, J. P. 1982. Mixtures and seed rates for sod production. J. Sports Turf Res. Inst. 58:76-95. 16. Sorochan, J. C., Calhoun, R. N., and Rogers, J. N., III. 2001. Apparatus to measure turfgrass sod strength. CD-ROM. Annual Meetings Abstracts. ASA, CSSA, and SSSA, Madison, WI. |
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