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Published in Crop Sci 39:1431-1434 (1999)
© 1999 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
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Crop Science 39:1431-1434 (1999)
© 1999 Crop Science Society of America

TURFGRASS SCIENCE

Top Growth and Rooting Responses of Tall Fescue Cultivars Grown in Hydroponics

Kyoung-Nam Kima, Robert C. Shearmanb and Terrance P. Riordanb

a Samsung Joong-Ang Development Co., Ltd., Kyungki-Do, South Korea 435-020
b Dep. of Horticulture, 377 Plant Science, University of Nebraska, Lincoln, NE 68583-0724 USA

rshearman1{at}unl.edu


   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 
Use of turf-type tall fescue (Festuca arundinacea Schreb.) as a reduced-input and drought-resistant turfgrass species has increased in recent years. Several growth types of tall fescue have been identified. Concerns have been expressed about the rooting responses of cultivars classified as turf type and dwarf type. Turf- and dwarf-type tall fescues may lack the potential drought-avoidance characteristics associated with cultivars like Kentucky 31. This study was conducted in hydroponics under greenhouse conditions to determine whether potential differences in top and root growth responses exist among tall fescue cultivars, experimental lines, and growth types. Sixteen cultivars and experimental lines, representing four growth types (i.e., dwarf, turf, intermediate, and forage) were evaluated. Tall fescue cultivars, experimental lines, and growth types differed in top growth and rooting responses. All cultivars and lines, except `Jaguar' and `Kenhy', produced roots to the 600- to 750-mm sampling depth. Dwarf- and turf-type cultivars and lines had the best responses for total root production and distribution under the conditions of this study. `Silverado', `Eldorado', `Trailblazer', and 516 had relatively high verdure yields ranging from 5.3 to 5.7 g, low clipping yields ranging from 3.6 to 3.9 g, and a clipping yield to verdure ratio (CY/V) of 0.7. Results from this study refute concerns expressed by some persons in the turfgrass industry regarding the potential for reduced depth and extent of rooting in dwarf- and turf-type tall fescues. These data further support the presence of genotypes with abilities to express deep, extensive root systems and favorable characteristics for drought avoidance potential.

Abbreviations: CY/V, clipping yield to verdure ratio • ET, evapotranspiration, FRL, final root length • IRL, initial root length • RGR, root growth rate • VER, vertical elongation rate


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
Materials and methods
 Results and discussion
 REFERENCES
 
TURFGRASS SPECIES and cultivars with drought-resistance characteristics could play an important role in turfgrass management and water conservation. Levitt (1980) recognized three forms of drought resistance: avoidance, tolerance, and escape. Youngner (1985) felt that drought avoidance was the most important form of turfgrass drought resistance. Beard (1989), Simpson (1981), and Youngner (1985) reported deep, extensive root systems and reduced evapotranspiration (ET) as important turfgrass drought-avoidance components. Shearman (1986, 1989) demonstrated the importance of canopy resistance mechanisms for reduced ET in Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.). Turfgrass quality and ET rates have been studied in relation to drought resistance (Aronson et al., 1987; Beard, 1989; and Carrow 1995, 1996). Researchers have reported differences among turfgrass species in regard to rooting responses and drought-avoidance mechanisms (Kim and Beard, 1988; Kopec et al., 1988; Lehman et al., 1993; Marcum et al., 1995; Salaiz et al., 1991; Shearman, 1986 and 1989).

Tall fescue use as a turfgrass species has increased since the introduction of turf-type cultivars (Funk et al., 1981, 1984). Beard (1973) and Turgeon (1985) reported tall fescue had better high temperature tolerance and drought resistance than other cool-season turfgrasses. Erusha (1986) and Kopec (1985) reported tall fescue clonal differences for top growth and rooting responses, but did not study differences among cultivars. Carrow (1996) and Qian et al. (1997) reported on tall fescue rooting responses and drought-avoidance characteristics.

The difficulty of evaluating turfgrass root growth under field conditions has prompted some researchers to use hydroponics as a method of root growth evaluation (Arnott et al., 1974; Erusha, 1986; Howard and Watschke, 1984; Kopec, 1985; Spomer, 1975). In this study we investigated top growth and rooting responses of tall fescue cultivars, experimental lines, and growth types grown in hydroponics under greenhouse conditions.


   Materials and methods
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 Materials and methods
Results and discussion
 REFERENCES
 
Tall fescue cultivars were selected on the basis of consultation with turfgrass breeders and observed differences from field trials. Based on this information, selections were arbitrarily classified as dwarf, turf, intermediate, or forage growth types (Table 1) .


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  		Table 1 Tall fescue cultivars and experimental lines classified on the basis of growth types.{dagger}

 
Seeds of each cultivar or line were germinated in petri dishes in a controlled-environment chamber with a 14-h photoperiod and a day and night temperature of 30 and 20°C. Seedlings were transferred to 38-mm-diameter by 210-mm-deep plastic conetainers 1 wk after germination. The conetainers were filled with washed, silica sand, and plants were placed in the greenhouse. A quarter-strength Hoagland's nutrient solution (Hoagland and Arnon, 1950) was applied every other day, and distilled water was applied weekly to leach the profile and minimize potential salt accumulation. Plants were clipped weekly at 50 mm.

Root growth reached the bottom of the conetainers 6 wk after transplanting. Root systems were washed to remove silica sand. Six plants with similar top and root growth development were selected from each cultivar or experimental line. These plants were transferred to the hydroponics system in the greenhouse. The system was previously described by Erusha (1986). Hydroponics containers were constructed from 102-mm-o.d. by 750-mm-long polyvinyl chloride (PVC) pipe. Each container was capped on the bottom with 102-mm-i.d. sewer pipe caps, which were sealed with silicone sealant to prevent leakage. Tops were made with 19-mm-thick styrofoam, and were cut to tightly fit the inside diameter at the top of the container. A center hole (25-mm diameter) was cut in the top to allow insertion of plants. The cap was painted with white latex paint. The containers were painted on the outside with black latex paint to reduce light penetration. A coat of white latex paint was added to cover the black surface and reduce potential heat buildup. The system was filled with a quarter-strength Hoagland's nutrient solution. Cultivars and experimental lines were arranged in a randomized complete block design with treatments replicated six times.

Plants were allowed to equilibrate in the hydroponics system for 2 wk prior to starting the study. Light intensity measurements ranged from 325 to 760 Wm-2 and temperatures ranged between 22.5 and 28.0°C during these experiments.

The nutrient solution was changed weekly to maintain concentrations and reduce the potential for salt accumulation. The solution was replaced to the level of draw-down resulting from ET for each treatment. This method exposed the cultivars and lines to declining water levels. Sullivan (1983) used this method, when studying sorghum [Sorghum bicolor (L.) Moench] to identify genotypes that exhibited greater root growth distribution values associated with decreasing water levels.

The study was terminated 8 wk after its initiation. Procedures were the same for each of two experiments conducted. The first experiment was initiated in February and the second in March.

Root growth rates (RGR) were measured weekly, and were determined on the basis of the differences between initial root length (IRL) and final root length (FRL) after 8 wk of growth. Results were reported as millimeters of growth per week. Plants were mowed weekly at 50-mm and clippings were collected, dried at 70°C for 72 h, and weighed. Verdure was collected at the termination of the study, dried, and weighed with the same procedure used for clippings. Clipping yield and verdure were reported on a dry weight basis. Top growth was determined as total clipping yield plus the verdure. Clipping yield to verdure ratios were calculated by dividing clipping yield by verdure. Relative shoot density was assessed using a 1 to 6 rating scale, where 1 = very low and 6 = very high.

At the termination of the study, plants were removed from the system, severed at the crown, and roots were separated from the verdure. The roots were separated into 150-mm segments (extending from 0 to 750 mm), dried at 70°C for 72 h, and weighed. Data were subjected to analysis of variance. Root lengths at the initiation of the study were not uniform within the cultivars and lines. Analysis of covariance was used to eliminate this initial variability in the treatment comparisons. Data were combined from the two experiments after comparing mean square error terms and determining less than a twofold difference (Steel and Torrie, 1980). Means were separated using LSD at the 0.05 probability level.


   Results and discussion
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
REFERENCES
 
Tall fescue cultivars and experimental lines differed in total root production (Table 2) . Total root production varied by as much as 31% when comparing 516 with Kenhy, the highest and lowest producing entries, respectively. There was no evidence of reduced root production or distribution for those selections classified as dwarf or turf types when compared with the intermediate or forage types.


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  		Table 2 Root production, root distribution, and root growth rate (RGR) for tall fescue cultivars grown in hydroponics.{dagger}

 
Total root production is of interest, but root distribution is of greater interest where drought avoidance mechanisms are concerned. A turfgrass may produce high root-production values with most of its rooting restricted near the soil surface. This rooting response would limit soil moisture extraction to the upper portion of the soil profile (Salaiz et al., 1991; Shearman, 1986; Sullivan, 1983; Youngner, 1985). Root distribution varied among the cultivars and experimental lines tested in this study (Table 2). Jaguar and Kenhy were the only cultivars that did not produce roots to 600 to 750 mm. There were no significant differences in root growth distribution beyond the 600-mm depth. However, the fact that 5-EGR, Eldorado, `Arriba', `Bonsai', Silverado, and 516 did produce roots beyond the 600-mm depth is of biological interest. Root growth rates varied among cultivars and lines by 44%. The experimental line, 5-EGR, had the fastest root growth rate with a mean of 86 mm wk-1, while Kenhy had the slowest rate with a mean of 60 mm wk-1 (Table 2).

Since root lengths at the initiation of the study were not uniform within the cultivars and lines, analysis of covariance was used to eliminate this initial variability in the treatment comparisons. The response to final root length was associated with initial root length, as indicated by a coefficient of determination, . The adjusted root length at the termination of the study differed among cultivars and experimental lines. These results provide evidence that genetic variation does exist for total root production, distribution, and growth rate among tall fescues grown in the same environment.

`Mesa', `Monarch', `Arid', and `Shortstop II' had high total root production, but had limited root production beyond the 600-mm depth (Table 2). Bonsai, 516, and Eldorado produced extensive root production beyond the 600-mm depth. `Maverick', 5-EGR, and Arriba had well-distributed root systems, but produced intermediate total root production values. Among the cultivars and lines tested, Eldorado, Bonsai, and 516 exhibited desirable root growth characteristics, based on their ability to produce roots and redistribute them as solution levels declined. Using the same screening technique, Kopec (1985) screened vegetative clones of tall fescue for rooting responses. He verified the responses obtained from the hydroponics with rooting in a field. Kopec conducted his research with vegetative clones as opposed to the heterogeneous cultivars used in this study. One might expect similar responses under field conditions from the cultivars and lines used in this study, but testing under field conditions is needed to substantiate this potential.

Cultivars and experimental lines differed for all top growth parameters measured (Table 3) . Verdure varied by as much as 40% among cultivars and lines. Those classified as dwarf and turf types produced the greatest amount of verdure, while Kentucky 31, the intermediate type, and Kenhy, the forage type, produced the least verdure. Mesa yielded 44% more clippings than the dwarf types, 5-DD and Bonsai. Shortstop II, Bonsai, and 5-DD produced the least clippings. These selections were classified as dwarf types. Monarch also had low clipping yields, as did Arriba, Trailblazer, Eldorado, and Silverado, when compared with other entries tested. Clipping yield to verdure ratio ranged from 0.6 to 1.2. Kenhy and Kentucky 31, forage and intermediate types, had CY/V values >1, while dwarf types, like 5-DD, Shortstop II, and Bonsai, had values of 0.6. Values of less than one were considered to be desirable, since they indicated reduced vertical elongation rate (VER). Shearman (1986, 1989) reported a positive correlation between VER and ET rates for Kentucky bluegrass and perennial ryegrass cultivars.


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  		Table 3 Verdure, clipping yield, shoot density, clipping yield to verdure ratio (CY/V), and top growth for tall fescue cultivars grown in hydroponics

 
Top growth varied by as much as 25% among the cultivars and lines tested. Eldorado, Silverado, Monarch, Trailblazer, and 516 had the highest relative shoot density values, while Kentucky 31 and the Kenhy had lowest values. Johns et al. (1983) found St. Augustine grass [Stenotaphrum secundatum (Walt.) Kuntze] ET to be influenced most by canopy resistance. Kim and Beard (1988) reported that grasses with comparatively low ET rates were characterized by high shoot density, horizontal leaf orientation, slow vertical leaf extension rate, and narrow leaves. The dwarf-type and turf-type tall fescues used in this study exhibited high verdure and shoot density values, low clipping yield, and low CY/V values. These characteristics support an increased potential for canopy resistance and reduced ET rates, similar to those reported for other grasses by Johns et al. (1983) and Shearman (1986, 1989).

Cultivars with deep, extensive root systems and high canopy resistance would be desirable when water conservation is a primary concern. This study demonstrated that dwarf- and turf-type tall fescues were ideally suited to express these characteristics. Dwarf types were not found to have a reduced root production or depth. The experimental line, 5-DD, might be an exception, but even so, it had roots distributed throughout the profile. Dwarf and turf types expressed desirable characteristics for drought avoidance, while the forage-type response was poor when maintained under turf conditions. Kopec et al. (1988) found similar results in their experiment relative to ET and rooting responses in tall fescue turf.

Results from this study support the potential for maintenance of quality, drought-avoidant turfs based on cultivar selection within tall fescue. Studies with Kentucky bluegrass (Shearman, 1986), tall fescue (Kopec et al., 1988), and perennial ryegrass (Shearman, 1989) demonstrated ET reductions based on cultivar selection. Verdure, shoot density, clipping yields, and clipping yield to verdure ratio are important turfgrass morphological characteristics, influencing potential canopy resistance and ET rate. Turfgrass breeders interested in water conservation might use these characteristics as selection criteria, while turfgrass managers might use them to select cultivars with the potential for reduced water use.


   NOTES
TOP
 NOTES
ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 
Journal Series no. 9476, Agric. Res. Division, University of Nebraska-Lincoln.

Received for publication May 15, 1998.


   REFERENCES
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 




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K. S. Erusha, R. C. Shearman, T. P. Riordan, and L. A. Wit
Kentucky Bluegrass Cultivar Root and Top Growth Responses When Grown in Hydroponics
Crop Sci., May 1, 2002; 42(3): 848 - 852.
[Abstract] [Full Text] [PDF]

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