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© 2005 Plant Management Network. Recovery of Zoysiagrass Varieties from Divot Injury Douglas E. Karcher, Michael D. Richardson, Joshua W. Landreth, and John H. McCalla, Jr., Department of Horticulture, University of Arkansas, 316 Plant Sciences Building, Fayetteville 72701 Corresponding author: Douglas E. Karcher. karcher@uark.edu Karcher, D. E., Richardson, M. D., Landreth, J. W., and McCalla, J. H., Jr. 2005. Recovery of zoysiagrass varieties from divot injury. Online. Applied Turfgrass Science doi:10.1094/ATS-2005-0728-01-RS. Abstract Although zoysiagrasses (Zoysia japonica Steud., Z. matrella (L.) Merr, and Z. tenuifolia Willd.) provide an excellent golf course fairway or tee surface, their use in areas of intense play may be limited because of their relatively slow recuperative potential. The objective of the following research was to identify zoysiagrass varieties with improved recuperative potential that may be adapted to such situations. Divot injury was simulated in 2003 and 2004 on 24 zoysiagrass varieties maintained under golf course fairway conditions. A digital image of each divot was collected on the day of injury and regularly thereafter until full recovery was reached. Divot images were analyzed for percent green turf cover using digital image analysis to quantify recovery percentages. In both years, ‘Crown,’ ‘Palisades,’ and ‘Zorro’ were among the fastest varieties to recover from injury. ‘El Toro’ had very rapid recovery in 2003, but not in 2004. ‘Meyer’ and ‘Emerald’ were consistently the slowest to recover from injury. Introduction Zoysiagrasses are often used in transition-zone environments due to their improved cold and shade tolerance, and relatively low maintenance requirements, compared to bermudagrass (Cynodon spp.). In addition, zoysiagrass forms a rigid turf (14) with superior load-bearing capacity (3), which provides an excellent surface for golf course fairways or tees with clean, tight lies (1). However, the relatively slow growth rate of zoysiagrass translates to poor recuperative potential, which often precludes its use for football or soccer fields where injury from traffic is inevitable (2). “Par three” golf tees and fairways that receive high volumes of play or that have limited landing areas are also subjected to extensive injury through divoting. Zoysiagrass varieties that recover relatively quickly from divot injury would be well-suited to such situations. Although it is commonly accepted that zoysiagrass has relatively poor recuperative potential (7), minimal research effort has focused on differences among zoysiagrass varieties regarding their recovery from injury. The National Turfgrass Evaluation Program (NTEP) has been the predominant means by which zoysiagrass varieties are tested throughout North America, but evaluations have not traditionally included a measure of recuperative potential (9). In previous NTEP zoysiagrass trials, differences in establishment vigor have been reported, which suggests that differences in recuperative potential may exist among current zoysiagrass varieties. If recuperative data were available in addition to the standard evaluation data resulting from NTEP trials, better choices could be made when selecting a zoysiagrass variety for use where injury is likely to occur. The objective of the following research was to determine if there are significant differences in recovery from divot injury among zoysiagrass varieties. Measuring Divot Injury Recovery Rates Twenty-four varieties, including those in the 2002 NTEP National Zoysiagrass Test (8) in addition to ‘Cavalier,’ ‘Crowne,’ ‘El Toro,’ and ‘Palisades’ were planted on 2 July 2002 in a silt loam soil (Captina silt loam soil, typic hapludult) at the University of Arkansas Research and Extension Center in Fayetteville. The four additional varieties were selected because they are well adapted to the transition zone and are frequently used as golf course tee and fairway turf. Each variety was planted in three replicate plots, each measuring 2.4 by 2.4 m. Vegetative cultivars were planted as 5-cm diameter plugs on 30-cm spacings within the plots, while seeded cultivars were broadcast planted at a seeding rate of 48 kg/ha. Following establishment, plots were maintained under typical golf course fairway or sports field conditions, with a mowing height of 12 mm and monthly nitrogen applications at the rate of 24 kg/ha from April through October. During months when divot recovery was evaluated, nitrogen applications were made seven days prior to divot injury. Phosphorous and potassium applications were made each March to maintain fertility status as recommended by soil test results. Irrigation was initially applied as needed to promote establishment and subsequently to prevent the development of wilt (applied twice weekly at a 1.3-cm depth during periods of no rainfall). Divot injury was simulated on the zoysiagrass varieties on 1 August in 2003
and 6 August in 2004. Standardized divots, each measuring 5 cm wide by 10 cm
long by 1.25 cm deep, as measured from the turf surface, were cut from each plot
using a modified edger (4) and then completely backfilled with topdressing sand.
The particle size of the sand was predominately in the ‘medium’ size class (0.25
to 0.50 mm). Although the same plots were used in both years, different areas of
the plot were evaluated in each year to ensure that divot injury in 2003 did not
affect recovery in 2004. Recovery was evaluated using methods described by Karcher et al. (6). Digital images were collected semiweekly for each divot,
beginning on the day of injury and continuing until full recovery was reached. A
red metal frame with a 10- by 15-cm opening was placed around each divot when
collecting images so that for every divot, the same area of turf was measured
each time an image was collected. The frame interior of each image was analyzed
for percent green turf cover using SigmaScan Pro (13) software and techniques
described by Richardson et al. (11). Percent recovery for an individual divot
was calculated from the following: A scatter plot of the zoysiagrass recovery data versus days after injury (DAI) revealed a strong nonlinear relationship. Moreover, the data fit well (variety R2 values ranging from 0.74 to 0.99) to the one-phase exponential association model, [ recovery = 1 - exp(-K * DAI) ], where DAI equals the number of days after divot injury and K is an estimated model parameter such that recovery equals 50% when DAI equals (0.6932 / K) (10). With this model, recovery begins at zero and increases rapidly initially, but progresses asymptotically towards 100%. A sum of squares reduction F-test was used to determine if zoysiagrass varieties significantly affected recovery (10). The F-test compared the sum of squares from a global model (all varieties share a K value) against the cumulative sum of squares from models where K values were determined separately for each variety. If the sum of squares were reduced significantly (P < 0.05) using separate K values, variety effects were determined to be significant. Pairs of varieties were determined to be significantly different if the 95% confidence intervals associated with their predicted K values did not overlap. Nonlinear regression analysis of the recovery data was performed using GraphPad Prism version 4.0 for Windows (GraphPad Software, San Diego, CA). Differences in Divot Injury Recovery Among Zoysiagrass Varieties In both 2003 and 2004, recovery from divot injury was significantly affected by zoysiagrass variety (Table 1). The one phase exponential association model provided a good fit to the data as variety R2 values ranged from 0.74 to 0.99 in 2003 and from 0.88 to 0.98 in 2004 (Table 2). As higher K values translate to more rapid recovery, ‘Palisades’ and ‘Crown’ were consistently among the quickest varieties to recovery; however, ‘El Toro’ was the fastest variety to recover in 2003 but was among the slowest recovering varieties in 2004 (Table 2). The relatively slow recovery of ‘El Toro’ in 2004 was unexpected since this variety is well-documented as having a rapid lateral growth rate (5,7,12). Among the commercially available varieties, ‘Meyer’ had the slowest recovery from injury in both years. Table 1. Hypothesis test summaries for 2003 and 2004 zoysiagrass
x K values determine recovery percentage according to the formula: Table 2. Nonlinear regression results for predicting zoysiagrass variety recovery from injury. Varieties are sorted by average K value (fastest to slowest recovery).
x S = seeded, V = vegetative. y K values determine recovery percentage according to the formula: [1-exp(-K * DAI)] where DAI = days after injury. Higher K values indicate faster recovery from injury. Recovery curves for commercial varieties in 2003 and 2004 are shown in Figs. 1 and 2 respectively. In 2003 the most rapidly recovering variety (‘El Toro’) reached 75% recovery approximately 15 days faster than the slowest recovery variety (‘Meyer). In 2004, the difference between the fastest (‘Palisades’) and slowest (‘Meyer’) varieties to reach 75% recovery was smaller at approximately 5 days.
Confidence intervals (95%) of the mean DAI to reach 50% recovery for the commercially available varieties are illustrated in Figs. 3 and 4, for 2003 and 2004, respectively. Varieties with non-overlapping confidence interval bars are significantly different (P = 0.05). ‘Crowne,’ ‘Palisades,’ and ‘Zorro’ were the only varieties to be among the fastest to reach 50% recovery in both years, while ‘Meyer’ and ‘Emerald’ were the only varieties to be among the slowest in both years.
The effect of propagation on recovery from injury was significant in 2003, but not in 2004 (Table 1). The DAI needed to reach 50% recovery was significantly greater for seeded than vegetatively propagated varieties in 2003 (Fig. 5). However, in 2004 the DAI for seeded varieties to reach 50% recovery decreased compared to 2003 and was similar to vegetatively propagated varieties. Since the varieties only had one year of growth in 2003, the seeded varieties probably did not have well developed lateral stems from which to recover into divoted areas. An increase in lateral stem development in 2004 among seeded varieties likely resulted in more rapid recovery from injury. In a similar study on bermudagrass (6), seeded varieties consistently had faster recuperative rates compared to vegetative hybrids, but the relationship between propagation type and recuperative potential in zoysiagrass is less clear.
For vegetatively propagated varieties, recuperative potential was closely related to reported establishment vigor. Among the 20 varieties evaluated in the 1991 NTEP Zoysiagrass trial, ‘El Toro,’ ‘Crown,’ and ‘Palisades’ had the highest establishment ratings, while ‘Emerald’ and ‘Meyer’ were among the lowest rated varieties (12). In addition, ‘DALZ 0102’ was rated highest in percent establishment in the 2002 NTEP Zoysiagrass Trial (8). For seeded varieties, seedling vigor and percent establishment ratings were marginal predictors of recuperative potential. ‘Companion’ was rated highest for seedling vigor and percent establishment in the 2002 NTEP Zoysiagrass Trial (8) while it ranked near the bottom among seeded varieties for recuperative potential in this study. In another study, seedling vigor was found to be a poor predictor of recuperative potential for bermudagrass varieties (6). Recuperative potential is an important trait when selecting a zoysiagrass variety for intensively used turf areas; however, other criteria should be considered. Characteristics such as disease resistance, genetic color, density, leaf texture, and overall quality should also weigh into variety selection, with their relative importance dependent on the local environment, management intensity, and user expectations. Acknowledgments The authors thank Golf Course Superintendents Association of America and the National Turfgrass Evaluation Program for the financial support of this research. Literature Cited 1. Bevard, D., Foy, J., Lowe, T., and White, B. 2005. Alternative grasses: Panacea or problem? USGA Green Section Record 43:26-28. 2. Duble, R. L. 1996. Turfgrasses: Their Management and Use in the Southern Zone. 2nd ed. Texas A&M University Press, College Station, TX. 3. Erusha, K. S., Shearman, R. C., and Wit, L. A. 1999. A device to measure turfgrass load bearing capacity under field conditions. Crop Sci. 39:1516-1517. 4. Fry. L. R. 2004. Zoysiagrass recovery from divot injury. M.S. thesis. Univ. of Arkansas, Fayetteville. 5. Gibeault, V. A., and Cockerham, S. T. 1988. ‘El Toro’ zoysiagrass. Calif. Turf. Cult. 38:1. 7. McCarty, L. B. 2004. Best Golf Course Management Practices. 2nd ed. Pearson Prentice Hall, Upper Saddle River, NJ. 8. Morris K. N. 2004. 2002 National Zoysiagrass Test- 2002-03 Data. Progress Report NTEP No. 04-2. 9. Morris K. N. 2001. 1997 National Zoysiagrass Test. Final Report NTEP No. 01-15. 10. Motulsky, H. J. and Christopoulos, A. 2003. Fitting models to biological data using linear and nonlinear regression: A practical guide to curvefitting. GraphPad Software, Inc. San Diego, CA. 11. Richardson, M. D., Karcher, D. E., and Purcell, L. C. 2001. Quantifying turfgrass cover using digital image analysis. Crop Sci. 41:1884-1881. 12. Shearman, R., and Morris, K. N. 1996. National Zoysiagrass Test. Final Report NTEP No. 96-15. 13. SPSS Inc. 1998. Sigma Scan Pro 5.0. SPSS Science Marketing Department, Chicago, IL. 14. Turgeon, A. J. 2005. Turfgrass Management. 7th ed. Pearson Prentice Hall. Upper Saddle River, NJ. |
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