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Published online 20 June 2006
Published in Crop Sci 46:1772-1778 (2006)
© 2006 Crop Science Society of America
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TURFGRASS SCIENCE

Nitrogen Rate and Mowing Height Effects on TifEagle Bermudagrass Establishment

E. A. Guertala,* and D. L. Evansb

a Agronomy and Soils, Auburn Univ., AL, 36849
b DOW AgroScience, LLC, 9330 Zionsville Rd., Indianapolis, IN 46268

* Corresponding author (eguertal{at}acesag.auburn.edu)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
In the southeastern United States, ‘TifEagle’ hybrid bermudagrass [Cynodon dactylon (L). Pers. x C. transvaalensis Burtt Davy] has become a selected cultivar for renovated or new bermudagrass putting greens, and its use has increased in popularity. However, there is limited research which examines TifEagle establishment, especially when cultural practices such as mowing height are included in the experimental design. The objective of this research was to evaluate the impact of N rate and mowing height on the percentage ground cover, shoot density, color, total nonstructural carbohydrate (TNC) content, and soil nitrate (NO3–N) and ammonium (NH4–N) content of TifEagle hybrid bermudagrass putting greens throughout three establishment years (2002, 2003, and 2004). Weekly applications of N were applied at 0.3, 0.6, 1.2, 2.4, and 4.8 g N m–2 wk–1, and mowing height applied at 3.2, 3.9, and 4.8 mm. Almost every agronomic measure (percentage ground cover, shoot density, root or rhizome and stolon mass, color) responded to increased applications of N, with maximum ground cover and shoot density reached at N rates from 3.4 to 4.3 g N m–2 wk–1. Turf mowed under the lowest mowing height often had reduced turfgrass color and rhizome and stolon mass, compared with that mowed at 3.9 or 4.8 mm. Soil pH and residual NO3–N and NH4–N were almost always affected by N rate, but not by mowing height. For rapid establishment without significant reductions in shoot density, rhizome and stolon mass, and TNC, the highest N rate of 4.8 g N m–2 wk–1, as used in this study, was not needed.

Abbreviations: TNC, total nonstructural carbohydrate • WAS, weeks after sprigging


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
FOR THE PAST 40 YEARS the hybrid bermudagrass cultivar Tifdwarf has been the predominate choice for warm-season putting greens (Burton, 1966; Moncrief, 1975). Within 10 yr, patches of off-type bermudagrass began to appear in Tifdwarf putting greens (Moncrief, 1975), and these patches were often phenotypically different from the original sprigged Tifdwarf (Caetano-Anolles et al., 1995). Superior off-types, with shorter internodes and higher shoot densities (Gray and White, 1999; Hollingsworth et al., 2005) were released as new cultivars. TifEagle, an irradiated mutant of Tifway II, is an example of a cultivar with such growth characteristics (Hanna and Elsner, 1999). In the southeast United States, TifEagle has become a frequent selection for renovated or new bermudagrass putting greens, and its use has increased in popularity.

Putting green management research has typically focused on the two major species for putting greens: (i) hybrid bermudagrass (Brown et al., 1977; Goatley et al., 1994; Snyder and Cisar, 2000; Hollingsworth et al., 2005) or, (ii) creeping bentgrass (Agrostris palustris Huds.) (Salaiz et al., 1995; Bell and Danneberger, 1999; McCarty et al., 2005). These researchers evaluated treatment responses on established greens, and not during the establishment period, when management practices might differ from those used on an established green.

In established ultradwarf hybrid bermudagrass turf, recent research has examined light requirements of TifEagle (Bunnell et al., 2005a, 2005b), and N source and cultivation effects on four ultradwarf cultivars (Hollingsworth et al., 2005). Another study evaluated N and K, and length of photoperiod on growth and TNC content of ‘FloraDwarf’ in a glasshouse experiment (Trenholm et al., 1998).

When turf establishment on a putting green was studied, typical treatments included variations in the root-zone mix (Murphy et al., 2005, 2001; Bigelow et al., 2001), P and K rates (Rodriguez et al., 2002), and mycorrhizal inoculation (Podeszfinski et al., 2002). One study used ultradwarf cultivars (Floradwarf and TifEagle, Rodriguez et al., 2002); the others evaluated creeping bentgrass. In the ultradwarf bermudagrass study, highest cover rates were reached when plots were fertilized at a 1.0–0.4–0.8 N–P–K ratio, with the N rate based on a weekly N application of 49 kg ha–1. In some treatments, applying P in excess of a 1.0–0.4 N–P ratio decreased coverage rate. The N part of the ratio remained constant across all treatments, with only P and K rates changing (Rodriguez et al., 2002).

Although the ultradwarf hybrid bermudagrasses are being sprigged on new and renovated putting greens, little research exists which examines best management practices for establishment, especially when cultural practices such as mowing height are included in the experimental design. Golf course superintendents desire grow-in information, as managing turf during this critical phase affects the time of course opening and agronomic costs. The objective of this research was to evaluate the impact of N rate and mowing height on the establishment, shoot density, color, TNC content, and soil nitrate (NO3–N) and ammonium (NH4–N) content of TifEagle hybrid bermudagrass putting greens throughout the establishment period.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
The 3-yr study was conducted in 2002, 2003, and 2004 at the Auburn University Turfgrass Research Unit, located at Auburn, AL. The study was conducted on a Marvyn loamy sand (fine-loamy, kaolinitic, thermic Typic Kanhapludult) native soil putting green. In each year the following was performed: existing turfgrass was removed and the area was fumigated with methyl bromide–chloropicrin at a rate of 390 kg a.i. ha–1. Two weeks after fumigation the area was tilled to 15-cm and prepared to receive sprigs. Sprigs were applied by hand at a rate of 0.01 m3 m–2. Sprigs were partially incorporated to 0.5 cm via a hand-pushed disk harrow, and topdressed with a 3.2-mm layer of topdressing sand. Sprigs were planted on 20 Aug. 2002, 23 June 2003, and 17 June 2004.

Nitrogen was applied weekly beginning 2 wks after sprigging (WAS) at 0.3, 0.6, 1.2, 2.4, and 4.8 g N m–2 wk–1, applied as granular urea (46–0–0 N–P–K) using a ground-driven 1.2-m-wide drop fertilizer spreader (Gandy Co., Gwatonna, MN). Plots were mowed 6 d wk–1 at a height of cut of 3.2, 3.9, and 4.8 mm, with a walk mower without grooming attachments (Toro Co., Bloomington, MN), beginning 3 WAS.

To counteract changes in pH caused by yearly N treatments, dolomitic lime (Ca·MgCO3) was applied to each mow height–N rate treatment when the pH measurement was below 5.8, and lime was applied to bring to soil to a pH of 6.5 (Adams et al., 1994). Lime was hand applied to each mow height and N rate treatment combination each fall (November), and not incorporated. Any remaining surface lime was incorporated when the plots were tilled each spring in preparation for sprigging. Spring pH measurements showed that differences due to treatment effect had been removed, as there was no significant difference in soil pH due to N rate or mowing height in any year of spring sampling.

Agronomic management other than mowing height and N rate was applied uniformly to the research area. Fertilizer applications (other than N) were applied according to yearly soil test recommendations, which are discussed in the Results section of this paper. Yearly soil tests (0- to 7.6-cm sampling depth) were conducted by removing 20 to 25 soil cores randomly from the research area. Collected cores were bulked, extracted, and analyzed for soil nutrients using standard analytical techniques (Adams et al., 1994). Plots were irrigated to maintain a moist soil surface for the first 2 WAS. After that, irrigation was applied daily as needed to supply {approx}2.5 cm water wk–1.

The following data was collected in each year of the study: (i) establishment via line transect counts; (ii) shoot counts after line transect data exceeded 90% establishment; (iii) weekly qualitative color ratings, including spring greenup; (iv) fall dry mass of roots (2002) or rhizomes or stolons (2003 and 2004); and (v) fall and spring TNC content.

Beginning 3 WAS, percentage ground cover was determined in each plot by placing four marked strings the length (3.7 m) of each plot. Each week the strings were replaced in the same spot; and were not placed randomly across the plot. Each string had 25 marks, and if a piece of green turf tissue touched the string it was counted as a hit. The number of hits for the four strings was totaled for each plot, and reported as percentage ground cover (establishment). Ground cover data was collected weekly from 20 Sept. until 11 Oct. 2003, 13 July until 5 Aug. 2004, and 7 July until 2 Sept. 2005.

Shoot density was determined using a destructive sampling technique, beginning when line transect data indicated that 90% ground cover was obtained in a majority of treatments. This occurred at 9, 7, and 10 WAS for 2002, 2003, and 2004, respectively. In each plot, three 5.7-cm-diam. cores were removed from each plot. Cores were taken to the laboratory, where every distinct shoot (a shoot was considered a node that produced leaf tissue) was hand-separated, counted, and recorded. In 2002, shoots counts were taken on 3 October and in the following spring (9 Apr. 2003). In 2003, shoot counts were taken weekly from 6 August until 23 September. In 2004, shoot counts were taken on 2 and 13 September. Shoot counts were taken each week until a frost pushed the TifEagle into dormancy.

Qualitative color ratings were performed using a 1-to-9 visual rating scale, with 1 = completely brown turf and 9 = lush, dark green turf. Color ratings were taken each week beginning 4 WAS and continued until the end of the experiment. In February and March following each year's test, spring greenup data was collected using the same 1-to-9 visual rating scale.

Using the abovementioned collection procedure as described for shoot density, cores were harvested from each plot to determine the mass of roots, rhizomes, and stolons. Root tissue was harvested by removing roots from crowns, stolons, and rhizomes, washing free of sand, and drying in a forced air oven at 70°C for 48 h. Dry mass of rhizome and stolons was determined by removing all roots and leaf tissue from harvested rhizomes and stolons, washing free of sand, and drying in a forced air oven at 70°C for 48 h. Root, rhizome, and stolon data were collected on 25 Oct. 2002, 22 Sept. 2003, and 23 Sept. 2004.

The same collection procedure used for shoot density was used for TNC determination, with the following modifications. First, all collected plant material was immediately placed in plastic bags, and then on ice while in the field. All plant material was kept chilled during transport, cleaning, and separation into roots, shoots, rhizomes, and stolons. All roots, rhizomes, and stolons were analyzed for TNC following the procedures described by Smith (1981). The TNC data was collected on 22 Sept. 2003 and 22 March 2004 for the 2003 study, and on 23 Sept. 2004 and 20 March 2005 for the 2004 study.

Soil NO3–N, NH4–N, and pH data were collected from each plot in the fall (20 Oct. 2002, 21 Oct. 2003, and 16 Sept. 2004) and spring (4 Apr. 2003, 30 Mar. 2004, and 10 Mar. 2005). Ten soil samples (6.35-cm-diam. cores, 15-cm deep) were collected from each plot, and the cores were consolidated into one sample per plot. Soil nitrate and ammonium content were measured by extracting a subsample with 2M KCl and determining nitrate-N and ammonium-N via a colorimeteric method (Sims et al., 1995). A second subsample was analyzed for soil pH, using a 1:1 soil–water ratio.

The study was a 3 x 5 factorial with four replications, with the treatments arranged in a strip design. Main plots were mowing height, with each plot measuring 3.7 x 24 m, and the split was N rate, with those plots measuring 1.2 x 3.7 m. Each year the treatment randomization was different, ensuring that N rate and mowing height treatments were not in the same location.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
General Soil Test Results
During May 2002, a general soil test reported K at 12 mg kg–1, P at 38 mg kg–1, and a pH of 5.9. To fulfill soil test recommendations (Adams et al., 1994), K was applied in June 2002 as potassium sulfate (0–0–41 N–P–K) at a rate of 200 kg ha–1. No P, Ca, Mg, or lime was recommended. In May 2003, a general soil test reported K at 10 mg kg–1, P at 16 mg kg–1, and a pH of 6.5. To fulfill soil test recommendations, K was applied as potassium sulfate at 200 kg ha–1, and P was applied at 134 kg ha–1 as triple superphosphate (0–20–0 N–P–K). In 2004, the spring soil test reported K at 20 mg kg–1, P at 55 mg kg–1, and a pH of 6.2. To fulfill 2004 soil test recommendations, K was applied as potassium sulfate at a rate of 180 kg ha–1. No additional P was recommended.

Although P and K were applied as recommended to the entire plot area each spring, dolomitic lime was applied on a treatment-by-treatment basis each fall, at the completion of all data collection since both N rate and mowing height treatments significantly affected soil pH. There was never a significant mowing height x N rate interaction on soil pH. In every year, pH decreased as N rate increased. At the highest rate of N fertilization, average fall pH was 5.6 while the average pH at the lowest rate of N fertilization was 6.0. In every year, plots mowed at 4.8 mm had a significantly greater pH (5.9) than those mowed at 3.2 or 3.9 mm (5.7).

Percentage Ground Cover via Line Transect and Shoot Counts
TifEagle growth response, as measured via line transect, was different in 2002 than in 2003 and 2004. In 2002 there was a significant N rate x mowing height interaction at every sampling date, while in 2003 and 2004 there was never a significant interaction. Figure 1 illustrates a typical data set; in this case, for data collected 6 WAS (4 wk of N rate and 3 wk of mowing height treatments had been applied at this date). In 2002, percentage ground cover significantly decreased at the two highest mowing heights as N rate increased. At the lowest mowing height (3.2 mm), percentage ground cover was unaffected by N rate. Such a response was observed in every week of the 2002 data collection.


Figure 1
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  		Fig. 1. Percentage ground cover of TifEagle hybrid bermudagrass as affected by N rate (bottom) and the interaction of N rate and mowing height (top) at 6 wk after sprigging at Auburn, AL.

 
In 2003 and 2004, only N rate affected percentage ground cover with a significant curvilinear response to N rate at every sampling date (Fig. 1). When the first derivative of regression equations was taken, ground cover was greatest at N rates from 3.6 to 4.3 g N m–2 wk–1. Optimal N rates observed here are similar to that used (4.4 g N m–2 wk–1) to establish TifEagle and Floradwarf ultradwarf hybrid bermudagrasses on high-sand putting greens (Rodriguez et al., 2002). Bunnell et al (2005a) demonstrated that both N rate and mowing height affected lateral regrowth of TifEagle (measured June–Aug.), with regrowth increasing 5% when mowing height was raised from 3.2 to 4.7 mm, and increasing when additional N was applied.

Differences in 2002, as compared with 2003 and 2004, are likely due to the late 2002 sprigging date (20 Aug 2002). It has been shown that photoperiod may affect growth of bermudagrass, with daylength correlated with growth and yield (Lovvorn, 1945; Schmidt and Blaser, 1969; Burton et al., 1988). Although cultivar dependant, researchers have shown that bermudagrass will often produce longer leaves under longer daylengths (Marousky et al., 1992). It has also been shown that bermudagrass leaf blades were shorter under reduced light (Gaussoin et al., 1988). Topgrowth produced under shorter days could be stimulated with higher rates of N, however (Lovvorn, 1945). In our study, bermudagrass mowed at 3.9 and 4.8 mm, receiving higher rates of N, would be more likely to have excessive topgrowth, with reduced rhizome and stolon growth and reduced rates of establishment as a result. Such an effect would be more pronounced as daylengths grew shorter, a byproduct of the August sprigging date.

A significant mowing height x N rate interaction did not occur for shoot density, and the main effect of mowing height never affected shoot density in any year of the study. In comparison, the main effect of N rate affected shoot density at every sampling in every year. Figure 2 illustrates shoot population counts as affected by N rate at the first sampling date in every year of the study. Shoot population responded in this same general curvilinear fashion at every sampling date, with shoot population maximized at N rates ranging from 4.8 g N m–2 wk–1 (2002) to 2.9 g N m–2 wk–1 (2003). The average N rate at which shoot density was maximized was 4.8, 3.4, and 4.3 g N m–2 wk–1 in 2002, 2003, and 2004, respectively. Shoot population ranged from 2.9 to 9.0 shoots cm–2, with lower populations measured earlier in each year. These shoot densities were similar to those measured on a renovated 2-yr-old TifEagle putting green (Hollingsworth et al., 2005).


Figure 2
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  		Fig. 2. Shoot density of TifEagle hybrid bermudagrass collected 9, 7, and 10 wk after sprigging in 2002, 2003, and 2004, respectively, as affected by N rate at Auburn, AL.

 
Root, Stolon, and Rhizome Dry Weight
When the mowing height x N rate interaction term was not significant (2002 and 2004, Fig. 3 and 4) both main effects of N rate and mowing height significantly affected the dry weight of harvested roots (2002) and rhizomes and stolons (2004). In 2002 a curvilinear response to increasing N and mowing height occurred, with root weight maximized at an N rate of 2.9 g N m–2 wk–1 and a mowing height of 4.6 mm (Fig. 3). Other researchers who measured root growth found both quadratic and linear responses to increasing N rate, with the response a function of cultivar (Tifdwarf or FloraDwarf) (Trenholm, et al., 1998). For the cultivar FloraDwarf, root growth was maximized at the highest N rate of 2.5 g N m–2 wk–1, while Tifdwarf exhibited a quadratic response, with root growth maximized at {approx}2.0 g N m–2 wk–1 (Trenholm et al., 1998). In other research with a cool-season turfgrass, root density increased as mowing height increased from 3.2 to 4.8 mm (Salaiz et al., 1995).


Figure 3
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  		Fig. 3. Root dry mass of TifEagle hybrid bermudagrass as affected by the main effects of mowing height (top) and N rate (bottom) at Auburn, AL, in 2002.

 

Figure 4
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  		Fig. 4. Mass of dry stolons and rhizomes of TifEagle hybrid bermudagrass as affected by the main effects of mowing height (top) and N rate (bottom) at Auburn, AL, in 2004.

 
In 2004, the dry weight of rhizomes and stolons was maximized at an N rate of 3.6 g N m–2 wk–1, while rhizome and stolon dry weight increased linearly as mowing height increased (Fig. 4).

In 2003, when the mowing height x N rate interaction was significant, the dry weight of rhizomes and stolons at the two highest mowing heights (3.9 and 4.8 mm) had a similar response to an increasing N rate. As N rate increased, the dry weight of rhizomes and stolons increased to an N rate of 2.8 and 3.6 g N m–2 wk–1 for the 3.9- and 4.8-mm mowing heights, respectively (Fig. 5 ). In comparison, at the lowest mowing height (3.2 mm) the dry weight of stolons and rhizomes was maximized at a much lower N rate (1.6 g N m–2 wk–1), and their weight decreased with any additional inputs of N (Fig. 5). Additional leaf tissue at the higher mowing heights likely provided additional photosynthetic leaf area (Krans and Beard, 1985) which could utilize higher rates of N, promoting greater stolon and rhizome growth for turf mowed at 3.2 and 3.9 mm.


Figure 5
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  		Fig. 5. Mass of dry stolons and rhizomes of TifEagle hybrid bermudagrass as affected by the interaction of mowing height and N rate at Auburn, AL, in 2003.

 
Total Nonstructural Carbohydrate
In the two years that TNC data were collected, there was never a significant mowing height effect or a significant mowing height x N rate interaction. However, at every sampling, both fall and spring, TNC was significantly affected by N rate (Fig. 6 ). In 2003–2004, application of higher rates of N negatively affected both fall (September 2003) and spring (March 2004) TNC levels, as TNC decreased with increasing N rate in the spring sampling, and TNC was maximized at an N rate of 2.4 g N m–2 wk–1 in the fall sampling. Results were different in 2004–2005, as both fall and spring TNC levels generally increased with increasing rates of N. In the fall (Sept., 2004) it was a curvilinear response, with TNC maximized at an N rate of 4.4 g N m–2 wk–1, and in the spring (March, 2005) TNC concentration increased linearly with increasing N rate. Both linear and quadratic effects in TNC response to rates of N have been shown previously, with maximum TNC obtained at an N rate of 5.9 g N m–2 mo–1, and with variation due to daylength (Trenholm et al., 1998).


Figure 6
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  		Fig. 6. Total nonstructural carbohydrate content of TifEagle hybrid bermudagrass as affected by N rate in 2003 and 2004 tests at Auburn, AL.

 
Color
Color ratings taken during each year's experiment were often affected by the interaction of N rate and mowing height, while spring greenup ratings were affected by both mowing height and N rate, but not their interaction. When the interaction was significant, turf mowed at the lowest height was less green than turf mowed at 3.9 or 4.8 mm (Table 1). Differences were most evident at the highest rates of N application, indicating that increases in N fertilization did not compensate for the poorer color ratings that were a result of the lowest mowing height.


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  		Table 1. Relative color ratings of TifEagle hybrid bermudagrass as affected by N rate, mowing height, and year, at Auburn, AL.

 
If the N rate x mowing height interaction was not significant, the main effects of mowing height and N rate significantly affected turf color at every rating during the months in which the study was conducted (Table 1). Turf color increased with increasing rates of N, with turf color maximized at N rates between 3.3 and 4.8 g N m–2 wk–1. Differences due to mowing height alone usually occurred because turf mowed at 3.2 mm had less green color than that mowed at 3.8 or 4.8 mm.

Spring greenup of the research plots was only affected by N rate, but not by mowing height or the mowing height x N rate interaction. In every case, spring greenup was quicker, and the plots were darker green for those receiving the highest rates of N application (from the previous year's test). Improved spring greenup was not a function of spring residual NH4–N or NO3–N, as N rate did not significantly affect soil NH4–N or NO3–N concentrations in the April 2003, March 2004, or March 2005 soil samples (data not shown). Thus, greenup was more a function of healthier turf breaking dormancy earlier in the spring, as opposed to differential N uptake and spring greening due to differences in residual N, which did not exist. Average soil NH4–N and NO3–N in April 2003 was 0.8 and 2.3 µg g–1, respectively. In March 2004 average soil NH4–N and NO3–N was 2.9 and 1.1 µg g–1, respectively, and during March 2005 average soil NH4–N and NO3–N was 0.9 and 3.1 µg g–1, respectively.

2 M KCl Extractable NH4–N and NO3–N
In the fall, samplings N rate almost always affected soil NH4–N and NO3–N content. Mowing height had less of an impact on soil NH4–N and NO3–N, with only soil NH4–N significantly affected, and only in the October 2002 sampling. In every case more soil NH4–N was measured in plots maintained at the lowest mowing height (3.2 mm) than at the two greater heights.

In every year of sampling, soil NH4–N and NO3–N exhibited a significant curvilinear response to increasing N rate, with maximum NH4–N and NO3–N measured in plots receiving the highest rate of N (Fig. 7 ). There was one exception to this finding, which was that in 2004 soil NH4–N was maximized at an N rate of 3.7 g N m–2 wk–1. Even at the highest rates of N application, none of the residual levels of NH4–N and NO3–N were particularly high, with highest levels of soil NO3–N ranging from 2.3 to 3.0 µg g–1. Lowest levels of soil NO3–N occurred at N application rates of 1.0 g N m–2 wk–1 (2003 and 2002) and 2.0 g N m–2 wk–1 (2004). This indicates that much of the N applied at lower rates of N application was being utilized by the growing turfgrass plants. It has been shown that inorganic N is rapidly used by growing turf (Allen et al., 1978; Mancino and Troll, 1990) and, in some cases, depleted within 2 to 4 d, primarily by biological immobilization (Bowman et al., 1989).


Figure 7
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  		Fig. 7. Fall soil extractable NO3–N (top) and NH4–N (bottom) content as affected by N rate in 2002, 2003, and 2004.

 

   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
For a loamy sand native soil putting green as used in this study, the highest N rate of 4.8 g N m–2 wk–1 was not needed to achieve optimal ground cover and establishment of a TifEagle bermudagrass putting green. Plots, on average, had 90% ground cover (as measured via line transect) at 9, 7, and 10 WAS for 2002, 2003, and 2004, respectively. Although not a specific research objective in this study, turf that was sprigged late in the growing season (August 2002) responded differently to N rate and mowing treatments when compared with turf sprigged in June (2003 and 2004). Late summer sprigging and its effects on bermudagrass establishment should be further evaluated.

Greatest dry weight of roots, stolons, and rhizomes and greatest shoot density were obtained at N rates from 3.4 to 4.3 g N m–2 wk–1. Mowing height had less of a significant impact, although turf color and rhizome and stolon weight were often reduced at the lowest mowing height. For this study, applying N at 3.4 to 4.3 g N m–2 wk–1, and mowing at 3.9 or 4.8 mm appears to produce rapid grow-in with minimal negative impact on stolon, rhizome, or root dry weights, TNC content, residual soil nitrate levels, and turf color. For establishment of sprigged turfgrass, turf managers should avoid overapplication of N. In addition to possible negative environmental affects, N overapplication reduced rhizome and stolon weights, root dry weight, and TNC content, possibly affecting long-term turf performance.

Received for publication January 5, 2006.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 





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