Materials and methods

The study was conducted at two locations in Turkey, the West Mediterranean Agricultural Research Institute in Antalya (lat. 36°52'N, long. 30°43'E) and the Alata Horticultural Research Institute in Mersin provinces (lat. 36°37'N, long. 34°42'E). Soil on the Antalya site was a silty clay loam (Paralithic Xerortent) with a 1.4% organic matter (OM) content, electrical conductivity (EC) of 0.24 dS·m⁻¹, pH 8.4, phosphorus (P) level of 22 mg·kg⁻¹, and potassium (K) level of 117 mg·kg⁻¹. The Mersin site was a sandy soil (Typic Xerofluvent) with a 1.2% OM, EC of 0.17 dS·m⁻¹, pH 8.3, P level of 12 mg·kg⁻¹, and K level of 102 mg·kg⁻¹. Warm-season turfgrass species and cultivars studied were bermudagrass cultivars SWI-1044, Contessa (SWI-1045), Princess 77, Riviera, Mohawk, Sultan, NuMex Sahara, and Blackjack; buffalograss cultivars Cody, Bowie, SWI-2000, Bison and Texoka; zoysiagrass cultivars Zenith and Companion; bahiagrass cultivars Argentina and Pensacola; seashore paspalum cultivar Sea Spray; and centipedegrass cultivar Tifblair. ‘Eldorado’ tall fescue was included as a cool-season species.

The seeding rates of the species were 15 g·m⁻² for bermudagrass and buffalograss, 5 g·m⁻² for centipedegrass and seashore paspalum, 10 g·m⁻² for zoysiagrass, and 30 g·m⁻² for bahiagrass. The seeding dates were 15 July and 12 Aug. 2005 for the Mersin and Antalya locations, respectively. Tall fescue was seeded at 50 g·m⁻² on 15 Oct. at both locations. The experimental sites were raked and then rolled with a cultipacker after seeding to improve seed-to-soil contact. Irrigation was provided three times daily for 4 weeks at 7 mm to encourage germination and enhance establishment. Subsequently, turf was irrigated to prevent visual wilt symptoms. Starter fertilizer (15N–6.6P–12.5K) was applied at 5 g·m⁻² N at the time of seeding. After establishment, turfs received 17.5 g·m⁻² N per growing season with applications made as 5 g·m⁻² N in May, June, and July and 2.5 g·m⁻² N in August using a slow release (33N–0P–0K) fertilizer in both locations. In addition, 17.5 g·m⁻² K per season was applied along with the N for the Mersin location. For tall fescue, applications were made as 5 g·m⁻² N in May, 2.5 g·m⁻² N in June, and 5 g·m⁻² N in October and November. Soil samples were taken in Apr. 2006 and 2007 before fertilizer applications, and soil tests indicated P (41 and 38 mg·kg⁻¹, respectively) and K (102 and 108 mg·kg⁻¹, respectively) levels in Antalya and P (12 and 28 mg·kg⁻¹, respectively) levels in Mersin were sufficient, whereas K (44 and 81 mg·kg⁻¹, respectively) levels in Mersin were not sufficient. Foliar sprays of 0.6 g·m⁻² ferrous sulfate (FeSO₄) were applied from mid-April to mid-October with a backpack sprayer in both locations to alleviate iron chlorosis. Plots were hand-weeded in both locations. Turfs were mowed weekly at 50 mm with clippings removed.

Turfgrass establishment, quality, color, and green cover were rated weekly from Aug. 2005 to May 2008. Turfgrass establishment, spring green-up, and percentage of turfgrass groundcover were based on a visual estimate scale of 0% to 100%, where 0% = no green vegetation cover and 100% = 100% green vegetation cover. Spring green-up was measured until all species reached 100% green cover in the spring from March through May. Turfgrass quality ratings were based on National Turfgrass Evaluation Program (NTEP) guidelines using a 1–9 visual rating scale, where 1 = poorest, 6 = acceptable, and 9 = best (NTEP, 2010). Turfgrass color was based on a 1–9 visual rating scale, where 1 = straw brown, 6 = light green, and 9 = dark green. Quality ratings were based on combination of color, density, uniformity, texture, weed, and disease infestation or sensitivity to environmental stress. Each species had its own standard.

The climate for both locations was strongly Mediterranean with dry, hot summers and mild, wet winters. Mean monthly maximum and minimum air temperatures in °C were determined for each location (Table 1). Daily GDD were calculated for 18 weeks beginning with seeding days for both the Antalya and Mersin locations by subtracting a 5 °C base temperature from the difference of daily maximum and minimum temperatures (Frank et al., 1998; Gilmore and Rogers, 1958; Patton et al., 2004; Pruess, 1983; Unruh et al., 1996).

Table 1.

Meteorological parameters during the study period in 2006 and 2007 from weather stations located ≈1200 and 200 m (3937.0 and 656.2 ft) from the field sites in Antalya and Mersin, Turkey, respectively.

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The experimental design was a split plot with species as whole-plot treatments arranged in a randomized complete block and cultivars within species as subplots (Federer, 1955). Species within a replicate were randomized and cultivars were nested and randomized within species. The main plots were 5.5 × 12.5 m and subplots were 1.5 × 1.5 m with a 0.3 m bare soil alleyway between each plot. Hartley's F max test (Hartley, 1950) was performed to determine homogeneity of variance between the first and second year and between the Antalya and Mersin locations. Treatment differences were tested using analysis of variance procedures with PROC MIXED (SAS release 8.0; SAS Institute, Cary, NC). Means were separated using Fisher's protected least significant difference procedure at P ≤ 0.05.

Results and discussion

Hartley's F max test (Hartley, 1950) between the Antalya and Mersin locations indicated that variance is different at the two locations and so are analyzed separately. There were significant interactions for turfgrass color, quality, and green cover between years and species on some evaluation dates at both locations (Table 2). However, the warm-season species showed similar trends for both years and therefore data are not reported separately.

Table 2.

Analysis of variance for turfgrass color, quality, and green cover in Antalya and Mersin, Turkey, for combined data of 2006 and 2007.

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Significant differences were detected in establishment among species and cultivars at both locations (Table 3). Bermudagrass, bahiagrass, and seashore paspalum reached 95% coverage at 1095 GDD (Table 3); buffalograss and centipedegrass at 1436 GDD in Antalya; and ‘Zenith’ and ‘Companion’ zoysiagrass had 90% and 84% coverage at Antalya after accumulating 2031 GDD. Although, zoysiagrass was established with 25% less GDD in Mersin than that of in Antalya, bermudagrass showed a similar establishment at both locations. However, buffalograss, seashore paspalum, and centipedegrass established (>80% coverage) within 3 weeks and bahiagrass 11 weeks later in Mersin than in Antalya, which could be due to the differences in soil type, GDD, or the factors that influence GDD for the two locations (Table 3). The establishment rate of bermudagrass and seashore paspalum was more rapid than that of buffalograss, zoysiagrass, and centipedegrass in both locations. Croce et al. (2001) also found that bermudagrass and seashore paspalum cultivars established faster than zoysiagrass and buffalograss cultivars in Italy. Bermudagrass establishment was faster than zoysiagrass requiring 1100 and 1900 GDD, respectively, to reach 95% coverage. This data agrees with earlier research by Patton et al. (2004), with 950 and 1750 GDD for bermudagrass and zoysiagrass, respectively. Frank et al. (1998) reported that buffalograss required at least 1000 GDD for successful establishment. However, in this study, buffalograss required 1436 and 1928 GDD for establishment in Antalya and Mersin, respectively. The higher mean daily temperatures in Antalya and Mersin locations than the species requirement for germination and establishment may have led to the higher GDD values for establishment in our study compared with the sites of the reported studies during establishments.

Table 3.

Mean percentage of turfgrass coverage (establishment) for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Antalya and Mersin, Turkey, taken after seeding in 2005.

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Mean percentage of turfgrass cover values among bermudagrass cultivars differed in the first 5 weeks in Antalya and in the first 7 weeks in Mersin. ‘Blackjack’, ‘Sultan’, ‘Sahara’, and ‘Mohawk’ established significantly faster than ‘SWI-1044’, ‘SWI-1045’, ‘Princess 77’, and ‘Riviera’ (Table 3). The buffalograss cultivars were significantly different for their establishment rate throughout the establishment period. Overall, ‘SWI-2000’ established faster than other cultivars and ‘Cody’ was the second best. ‘Bison’ established relatively slowly in the sandy soil in Mersin (Table 3). Zoysiagrass and bahiagrass cultivars did not show significant intralocation variation (Table 3).

Using the growing degree model (Unruh et al., 1996), bermudagrass, bahiagrass, and seashore paspalum could be seeded as late as 1 Sept.; centipedegrass and buffalograss on 15 Aug.; and zoysiagrass on 1 Aug. in Antalya and still have acceptable establishment. In Mersin, bermudagrass could be seeded as late as 1 Sept.; seashore paspalum on 10 Aug.; centipedegrass on 1 Aug.; and bahiagrass, buffalograss, and zoysiagrass on 15 July in the Mediterranean region and still achieve >95% coverage before winter dormancy.

Significant differences in turfgrass quality and color throughout the growing season were detected among the turfgrass species (Table 2) and cultivars (Tables 4–7). The mean turfgrass quality of the species from May to December ranked from highest to lowest was as follows: seashore paspalum > bermudagrass > zoysiagrass > buffalograss = centipedegrass > bahiagrass > tall fescue. Volterrani et al. (1997) in Italy and Geren et al. (2009) in Turkey reported similar results, where seashore paspalum exhibited the greater turfgrass quality, but zoysiagrass had the lowest quality rating among the warm-season species tested (Geren et al., 2009).

Table 4.

Mean turfgrass quality throughout the growing period for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Antalya, Turkey, averaged over 2006 and 2007.

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Table 5.

Mean turfgrass quality for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Mersin, Turkey, averaged over 2006 and 2007.

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Table 6.

Mean turfgrass color for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Antalya, Turkey, averaged over 2006 and 2007.

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Table 7.

Mean turfgrass color for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Mersin, Turkey, averaged over 2006 and 2007.

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Zoysiagrass and buffalograss cultivars exceeded the acceptable turfgrass quality of 6 by mid-April at Mersin. By mid-May, all species except bahiagrass were above the acceptable quality level at both locations. The duration of mean turfgrass quality of the species above the acceptable level varied from 6 to 7.5 months (from mid-April to December). Bermudagrass maintained acceptable turfgrass quality for 6 months, centipedegrass for 6.5 months, seashore paspalum for 7 months, and zoysiagrass for 7.5 months at both locations. Buffalograss maintained above-acceptable quality for 6 months at Antalya and 7 months at Mersin. Bahiagrass failed to provide acceptable quality on most of the evaluation dates and tall fescue had the lowest quality throughout the study. Significant differences in turfgrass quality and color were detected among the bermudagrass cultivars throughout the growing season (Tables 4–7). Seasonal color and quality ratings of the bermudagrass cultivars SWI-1044, SWI-1045, Princess 77, and Riviera were significantly higher than the cultivars Mohawk, Sultan, Sahara, and Blackjack during most of the growing seasons. These differences were due to a substantially finer leaf, denser turfgrass stand, and darker green color of the former group of cultivars.

Of the buffalograss cultivars, Cody was the first to reach to acceptable quality by mid-April and provided the highest quality throughout growing season, followed by cultivars Bowie, SWI-2000, Bison, and Texoka (Tables 4–5). In the NTEP trial (2000), ‘Cody’ demonstrated the best color and quality throughout the growing season. All the buffalograss cultivars declined in quality below the acceptable level by early November in both locations. Buffalograss is adapted to a wide range of soil types and exhibits a high alkaline soil tolerance (Turgeon, 1999). Wenger (1943) reported that buffalograss preferred heavy, not sandy soil types; however, results indicate that turf-type buffalograss cultivars performed equally well in the sandy soil at Mersin.

‘Zenith’ zoysiagrass exhibited superior color and quality when compared with ‘Companion’ throughout the growing season at both locations. Similarly, ‘Zenith’ had better color and a higher quality than ‘Companion’ in the southeastern United States (NTEP, 2006a).

‘Argentine’ bahiagrass exhibited a darker green color but similar quality to ‘Pensacola’. These cultivars rarely reached acceptable quality, with a mean rating of 5.5 during their active growth period. Busey (2003) reported that bahiagrass turfs exhibited a relatively open growth habit, had a poor ability to survive in high (over 7.5) soil pH, and showed iron chlorosis in the spring under such conditions in Florida. We observed open growth habit and such chlorosis at both locations on ‘Argentine’ and ‘Pensacola’ bahiagrass post-green up in spring and summer months. The poor density and chlorosis contributed to the lower quality ratings of bahiagrass.

The buffalograss cultivars Bison and Cody were reported to have a satisfactory establishment in the first 2 years of establishment in Italy (Croce et al., 2001). However, weed invasion reduced the quality and made them unacceptable as a turf in the same study. We observed a very successful establishment and satisfactory color and quality of the buffalograsses over the 2-year period at both locations. Vegetatively propagated seashore paspalum cultivars are reported to have comparable quality levels with the best of vegetatively propagated bermudagrass and zoysiagrass cultivars in Italy (Croce et al., 2001). Although all the cultivars used in our study were seeded types, we also observed that seeded-type ‘Sea Spray’ seashore paspalum performed better in overall quality and ranked with the best bermudagrass cultivars.

Differences in fall color retention among species and cultivars were detected (Tables 6–9). Turfgrass color retention for warm-season grasses in the fall is a desirable character. Growth of the warm-season species slowed in November. All the warm-season species began to show significant color decline when the mean minimum air temperatures dropped below 10 °C (Table 1). Overall fall color retention of the warm-season species was ≈15 d longer at Antalya than at Mersin. This delay was likely due to differences in mean minimum air temperatures ranging from 9 to 13 °C in Antalya and 5 to 8 °C in Mersin during November (Table 1). The green cover of buffalograss cultivars at both locations and the bermudagrass and zoysiagrass cultivars in Mersin was less than 50% by the end of November. Centipedegrass dropped below 50% by mid-December and seashore paspalum by late-December. Bahiagrass exhibited the best fall color retention with greater than 50% green cover until the end of December at both locations. The species order for fall color retention was buffalograss < zoysiagrass < centipedegrass < bermudagrass <seashore paspalum < bahiagrass. Geren et al. (2009) reported a similar order for fall color retention of the species in western Turkey.

Table 8.

Mean percentage of turfgrass green cover for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Antalya, Turkey, averaged over 2006 and 2007.

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Table 9.

Mean percentage of turfgrass green cover for bermudagrass, buffalograss, zoysiagrass, seashore paspalum, centipedegrass, bahiagrass, and tall fescue species and their cultivars in Mersin, Turkey, averaged over 2006 and 2007.

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There were differences among the cultivars of bermudagrass for fall color retention with ‘SWI-1044’, ‘SWI-1045’, and ‘Princess 77’ retaining their color longer than the other bermudagrass cultivars (Tables 6–7). ‘SWI-1044’ and ‘SWI-1045’ provided over 50% and 40% green cover on 15 Dec. in Antalya and Mersin, respectively (Tables 8–9). ‘SWI-1044’ and ‘SWI-1045’ exhibited superior fall color retention compared with the other bermudagrass cultivars in the southeastern United States from 2002 to 2006 (NTEP, 2006b). Dudeck and Peacock (1985) and White and Schmidt (1989) also reported growth cessation and discoloration responses among bermudagrasses to chilling temperatures (0 to 10 °C). Buffalograss cultivars responded similarly to declines in air temperature with a loss of 50% to 66% of their green color and green cover in November at both locations. No differences were detected for fall color among the zoysiagrass cultivars. The zoysiagrass cultivars performed similarly to most of the bermudagrass cultivars. All species and cultivars demonstrated a turfgrass color measurement of 6 or above at the end of October in both locations, but by the end of November, Argentine bahiagrass was the only cultivar with a color value of 6 in Antalya (Tables 6–7). Of all the warm-season cultivars, ‘Argentine’ and ‘Pensacola’ bahiagrass demonstrated the best fall color retention, followed by ‘Sea Spray’ seashore and ‘SWI-1044’ and ‘SWI-1045’ bermudagrass in mid-December (Tables 6–7). ‘Pensacola’ is reported to have better frost tolerance than ‘Argentine’ (Burton, 1946), which may help to explain the better winter color of ‘Pensacola’ in both locations.

All the warm-season species stayed fully dormant with a straw brown color for ≈6 to 8 weeks from mid-December to the end of February at both locations. The buffalograsses and zoysiagrasses entered dormancy in early December, followed by bermudagrass and centipedegrass, then seashore paspalum, and finally bahiagrass. Tall fescue did not go dormant at any time but discolored during summer heat stress.

The turfgrass species and cultivars differed in their spring green-up response at both locations (Tables 8–9). Intra and interspecific variations have been reported to exist in base spring green-up temperatures for growth in warm-season turfgrass species (Madakadze et al., 2003; Unruh et al., 1996). Spring green-up began in mid- to late February and was completed in late April in both locations. Zoysiagrass exhibited the best spring green-up at 80%, followed by buffalograss and centipedegrass at 70% by mid-March. Centipedegrass has been reported to have a higher basal temperature requirement and higher growth rate constant than other warm-season turfgrasses (Unruh et al., 1996). However, centipedegrass had a similar green-up to zoysiagrass and buffalograss and greened up earlier than seashore paspalum and bermudagrass in our study. All the species exceeded 90% green cover by the end of April with a mean GDD of 983. Seashore paspalum and bermudagrass exhibited the slowest spring green-up among the warm-season species. However, Geren et al. (2009) reported that ‘Sea Spray’ seashore paspalum and ‘Bowie’ buffalograss exhibited the earliest and latest spring green up in another study conducted at Izmir, located at western Turkey. The species order for spring green-up was zoysiagrass > buffalograss > centipedegrass > bahiagrass > seashore paspalum > bermudagrass.

Bermudagrass cultivars differed in their spring green-up response between the two locations, with ‘Riviera’ at both locations and ‘Mohawk’ and ‘Sahara’ in Mersin demonstrating better spring green-up than the other bermudagrass cultivars. They exhibited a superior spring green-up with over 80% green cover when compared with ‘Princess 77’, ‘SWI-1044’, and ‘SWI-1045’, which had less than 55% green cover at the end of March. Our results agree with that of NTEP (2006b), in which ‘Riviera’ showed better spring green-up than ‘SWI-1045’. Croce et al. (2001) reported a relatively slow spring green-up rate for ‘Princess 77’ in Italy. In general, bermudagrass cultivars with better fall color retention demonstrated delayed spring green-up (Tables 8–9).

Buffalograss cultivars began spring green-up in late February and completed it by mid-April in Mersin and late April in Antalya. ‘Cody’ was superior to the other buffalograss cultivars in both locations throughout the spring green-up period. ‘Cody’ also showed superior early-spring green-up in NTEP trials (2000). The zoysiagrass cultivars Zenith and Companion showed similar spring green-up. The bahiagrass cultivar Pensacola exhibited better spring green-up than ‘Argentine’. When all the cultivars were evaluated, ‘Companion’ and ‘Zenith’ zoysiagrass, ‘Pensacola’ bahiagrass, and ‘Tifblair’ centipedegrass initiated the earliest spring green-up in both locations, with a 20% to 26% green cover at Antalya and 32% to 45% at Mersin by the end of February. By the end of March, the zoysiagrass cultivars Companion and Zenith and the buffalograss cultivar Cody demonstrated over 90% green cover at Antalya and over 95% at Mersin. All the cultivars, except SWI-1045 and Princess 77 bermudagrass at Mersin showed over 90% spring green-up by the end of April in both locations (Tables 8–9).

The warm-season species retained 95% to 100% green cover throughout the summer (Tables 8–9). Tall fescue had the poorest color and quality ratings and lowest percentage of green cover when all warm-season grasses were actively growing during the summer and early fall. Cool-season turfgrasses showed reduced turfgrass quality and green cover in response to high temperature stress in previous studies (Baker and Jung, 1968; Wehner and Watschke, 1981). Tall fescue's green cover declined after 15 July until October and recovered only partially to reach 70% in December at Antalya, while it failed to recover at Mersin, requiring reseeding in fall (Tables 8–9). Surviving tall fescue plants in the plots retained their green color during winter months with a turfgrass color measurement of 5 or better in Antalya.

In conclusion, this research identified several warm-season species and cultivars that have great potential for summer and fall utilization in the Mediterranean region. Based upon our research findings, these warm-season turfgrasses may perform better than cool-season species that are commonly used in this region and provide a quality turf with reduced water-use requirements. These results will be helpful to turfgrass managers and adviser seeking to manage and recommend suitable warm-season turfgrass species and cultivars for the Mediterranean region. Turfgrass breeders and companies would also have a better understanding of response of their cultivars in the target environment. Future research on the long-term performance of the species under different fertilization, mowing height, and irrigation regimes should also be considered to develop specific maintenance recommendations for a given species under a Mediterranean environment.