Overseeding preparation techniques for fairway seashore paspalum
Overseeding practices for bermudagrass do not always work for seashore paspalum. A combination of herbicide, mowing and verticutting is key to successful transition.
D.M. Kopec, Ph.D., J. Gilbert, M.S., M. Pessarakli, Ph.D., and S.P. Nolan
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This research was funded in part by the Environmental Institute for Golf.
Research plots show a range of responses to overseed preparation treatments on seashore paspalum
at the University of Arizona’s Karsten Turfgrass Research Center in Tucson.
Photos by J. Gilbert
does not respond well to the mechanical disturbance of stolons caused by deep
divots, vertical mowing or scalping resulting from mowing. Past observations
over several years have shown that excessive regrowth periods are often
required during the summer for recovery from such events. Spring transition also
can be extremely slow and prolonged when fall vertical mowing (similar in
intensity to vertical mowing practiced on bermudagrass) is used as a
preparation technique for fall overseeding.
this in mind, a three-year field experiment was conducted on Sea Isle 1
seashore paspalum to evaluate the cultural management effects of adjusted
mowing heights; vertical mowing; and the use of a herbicide, plant growth
regulator or plant desiccant — all as management tools for preparing the turf
surface of seashore paspalum for overseeding.
Materials and methods
10-year-old stand of Sea Isle 1 seashore paspalum located at the Karsten
Turfgrass Research Center in Tucson, Ariz., was used as the test site. The turf
previously had been mowed three times weekly at 0.625 inch (1.58 centimeters)
from March until November each year. Starting in 2009, 42 treatment combinations
of preparatory mowing heights, vertical mowing (none vs. two passes at 0.375 inch
[0.95 centimeter]) and five chemical treatments (none, Finale, Scythe, Reward
or Turflon Ester; see Table 1) were repeated on the same plots for three years.
treatments were developed as follows. At eight days before overseeding, all mowing
was ceased. At the day of overseeding, plots were either mowed back to 0.625 inch
or 0.375 inch, or remained unmowed until the first mowing of the overseeded
perennial ryegrass (Lolium perenne) (Table 2).
the time of the first mowing after perennial ryegrass emergence, the unmowed
turf had reached a height of 0.875 inch (2.22 centimeters) to 1.125 inches
mowing took place immediately after mowing treatments were implemented, and all
cultivated plots had clippings removed by a rotary mower with a grass catcher
at 2 inches (5.08 centimeters).
herbicide Turflon Ester is labeled for use for overseed preparation of
bermudagrass, as are desiccants Scythe and Reward. The nonselective herbicide
Finale will produce necrotic straw, but has no effect on stolons or rhizomes
and therefore was investigated as a potential candidate for use.
applications were made five days before the overseeding mechanical treatments, which
occurred during the seashore paspalum’s elongation period.
perennial ryegrass cultivar Two Streams was seeded at a rate of 625 pounds pure
live seed/acre (700.53 kilograms/hectare). Seeding was followed by hand
brooming the plots in two directions, and a single pass with an 875-pound
(396.89-kilogram) mechanical (Brouwer) turf roller (32-inch wide × 28-inch tall
[81.28 × 71.12 centimeters]).
turf plots were irrigated for emergence and then mowed to 0.625 inch when the
majority of the plots were 0.875 inch tall. Afterward, the plots were mowed
three times weekly at 0.625 inch throughout the test. Fertility was 0.25 pound
nitrogen/1,000 square feet (1.22 grams/square meter) per month from a 15-15-15
complete water-soluble fertilizer source. Each January the turf received Sequestrene
138 chelated iron, applied at 3 ounces product/1,000 square feet (0.92 gram/ square
meter) in a solution delivery volume of 57 gallons/acre (533.17
Data collection and analysis
turf was rated for percent plot overseeding (perennial ryegrass) cover, percent
plot straw when applicable on a 1%-100% scale. Plots were also rated for
turfgrass color, density and overall turfgrass quality using the NTEP visual
assessment scale (1-9, where 1 is dead turf and 9 is the best possible). The test
was conducted in three successive years, (2009-2010, 2010-2011, 2011-2012) with
the same treatments appearing on the same plots.
treatments were analyzed as the specific combinations of preparatory mowing heights,
vertical mowing and chemical amendment additions (n = 42
treatments). Data are presented for overall turfgrass quality, which includes
the visual integration of density, smoothness and uniformity of color.
quality results are provided as an overall season mean for each year; a quality
index score (the number of rating events at which the treatment had a quality
mean score of 6.0 or greater); and the percentage of the total of yearly
ratings that achieved a mean quality score of 6.0 or greater (Table 3). In
addition, the plot composition of the turf at a noteworthy spring transition is
data show how much of the plot surface in each treatment is composed of either
living perennial ryegrass, living paspalum or necrotic straw (dead
leaves/stems) during a critical stage of spring transition.
Results and discussion
treatments reported include: group 1 — those that had the best quality means
for two or three years; group 2 — treatments that included no chemical
treatments, but received only mechanical treatments; and group 3 — treatments
that received only a chemical treatment.
three groups represent a sample of 20 of 42 total treatments that address the questions
of what the results are from (a) mechanical manipulation alone, (b) chemicals alone,
and (c) the combination of mechanical and chemical conditions that, in fact,
produced the best overall turfgrass quality and spring transition (Table 3).
1 results: Best treatments
following treatments had the greatest number of rating events that had mean
quality scores of 6.0 or greater.
19 (mowed to 0.375 inch, verticut and sprayed with Reward). This
treatment had quality mean scores of 6.0 or greater on nine of 10 dates in
2010, on six of seven dates in 2011 and on six of seven dates in 2012. This was
the only single treatment combination that consistently had high yearly mean
quality scores in all three years: 6.7 in year 1 and 7.1 in years 2 and 3
23 (mowed to 0.375 inch, verticut and sprayed with Scythe). This
treatment combination had quality scores of 6.0 or greater six of seven rating
dates in 2011, on six of seven dates in 2012, but only on five of 10 rating
dates in year 1 (2009-2010 season).
27 (mowed to 0.375 inch, verticut and sprayed with Finale). This
treatment had good quality in years 2 and 3, but was marginal in year 1.
31 (mowed to 0.375 inch, verticut, plus Turflon Ester). This
treatment had excellent quality in all three years, but had a poor-quality
transition in year 3 (with 29% straw, which lingered for several weeks), which
influenced the quality ratings for six weeks.
that received chemical applications, but were not verticut, and had generally acceptable
quality index scores included:
29 (mowed to 0.375 inch, no verticut, plus Turflon Ester). For this
treatment, half of its 2010 ratings were 6.0 or greater; either five or six of
its seven ratings were 6.0 or greater in quality in years 2 or 3.
17 (mowed to 0.375 inch, no verticut, plus Reward). This
treatment had high quality index scores in years 2 and 3, but was nominal only
in 2010 (five of 10 scores) due to having 44% plot straw at transition in 2010
(year 1). Also, this treatment had a slow start in establishment of its
overseed cover in 2010 (data not shown).
that in groups 1 and 2, most of these treatments were “prep-mowed” at 0.375 inch,
with only treatment 28 mowed at 0.625 inch. Overall, when averaged across all
verticutting and chemical treatments, the 0.375- inch mowing height produced
better-quality turf than the treatments mowed at 0.625 inch when the 0.625-inch
preparatory mowing height was also averaged over vertical mowing and chemical
2: Nonchemical (mechanical) treatments
Figure 1. Percent plot cover of seashore paspalum, straw and perennial ryegrass under four selected treatments at spring transition in three years (2010-2012) at the Karsten Turfgrass
Research Center, University of Arizona, Tucson. From left to right: Treatment 3: 0.375-inch mowing height, verticutting, no chemical treatment; Treatment 19: 0.375-inch mowing height,
verticutting, Reward; Treatment 11: no mowing, verticutting, no chemical treatment; Treatment 9: no mowing, no verticutting, no chemical treatment.
in group 2 are provided to show the effect of mechanical treatments (or none at
all) in the absence of any chemical. These treatments included treatments 11,
9, 3, 1, 7 and 5.
paspalum was left to elongate five days before overseeding (treatment 11) and was
then verticut without any other treatment, acceptable-quality turf appeared on only
50%-70% of the rating times across all three years. If paspalum was mowed to
0.375 inch in preparation for overseeding, not verticut and not treated with a
chemical (treatment 1), quality results proved inconsistent between years
(29%-71% of events had acceptable turf quality across all years).
least favorable combinations of overseed preparation without the addition of
a chemical included the following: treatment 9 (the untreated control: no
mowing until emergence, no verticutting and no chemicals). This treatment had
decreasing quality events in years 2 and 3 and mean quality scores of 5.4 in
year 1, 4.5 in year 2 and 6.2 in year 3.
single-most detrimental nonchemical treatment combination occurred for
treatment 5 (prep mowed at 0.625 inch; no verticut mowing). This treatment had
acceptable turfgrass quality index values (6.0 or more for quality), which
occurred on 40% of rating dates in year 1, 29% in year 2 and 14% in year 3.
While raising the mowing height alone before overseeding and mowing
back to the base height is often effective preparation in bermudagrass overseeding,
it was surely not the case for seashore paspalum. This treatment lacked density
in the first half of the entire overseed season in all three years of testing
(density data not shown).
of % canopy composition
Overseeded paspalum showing responses to different preparatory mowing heights, with and
without vertical mowing, when treated with Turflon Ester herbicide.
1 shows the percent canopy composition (percent plot paspalum, living perennial
ryegrass and percent straw) for comparison purposes as a simple representation
of treatments that include the untreated control (overseeded only = treatment
9); dropping the mowing height down to 0.375 inch the day of overseeding, plus
vertical mowing without a herbicide (treatment 3); vertical mowing plus mowing
to 0.375-inch plus Reward (treatment 19); and vertical mowing without a herbicide
plus no mowing at all until the emerged perennial ryegrass was first mowed
(treatment 11). Figure 1 also shows the yearly quality score and the percent of
rating dates on which each treatment had a mean quality of score of 6.0 or
the superintendent, the most desirable field condition is to have the least of
the amount of living perennial ryegrass, minimal to no straw and the most
paspalum present at transition. In general, there was more straw on all
treatments in year 2 (2011 spring); however, treatment 11 had no straw in year
treatment 9 shows a large percent of pasaplum present at transition, its
overall quality was low on too many occasions, because of poor perennial
ryegrass establishment and low density for most of the fall and winter months
(data not shown).
a herbicide was used alone, without any vertical mowing, and allowed to grow 10
days without mowing before overseeding, turfgrass quality was often not
acceptable (see treatments 33, 34, 35 and 36) (Table 1). All four herbicides in
this case had yearly quality averages of less than 6.0 in years 1 and 2, but in
year 3, Reward and Scythe had yearly quality averages of 6.2 or greater.
can draw five primary conclusions from our three-year field trial.
- Paspalum does not always have the same response as bermudagrass to mechanical overseed
and transition practices such as (a) simple verticutting alone (treatment 5: turf
quality = 3.7 for year 1, 3.4 for year 2 and 4.5 for year 3), or (b) elevating
the mowing height for leaf internode elonga tion, followed by a simple return
to the base mowing height of 0.625 inch (treatment 12: turf quality = 3.7 for
year 1, 3.4 for year 2 and 4.5 for year 3) (data not shown).
- The use of chemicals alone (without some form of mechanical canopy
manipulation) did not produce acceptable turfgrass quality. All four treatments
that included only chemicals (treatments 33, 34, 35 and 36) did not have yearly
quality score averages of 6.0 in any of the three years.
- When mowed at 0.375 inch and verticut, turf plots treated with Scythe, Turflon Ester
or Finale had quality index values of 6.0 in 57%–100% of all cases, but only in
two of the three years of the trial (see treatments 23, 37 and 31).
- When seashore paspalum was mowed back to 0.375 inch and then verticut in treatment
3 (no herbicides), yearly quality means were 6.2 in year 1, 7.3 in year 2 and 6.3
in year 3. However, in year 3, quality was only 6.0 or greater on four of the
seven (57%) rating events. In year 3, quality was reduced at transition for
- The three-way combination of the 0.375- inch preparatory mowing height,
verticut mowing and use of Reward (treatment 19) resulted in quality scores of
6.0 or greater for 86%–90% of all ratings for all three years. Treatment 19’s
overall quality means were 6.7 for year 1 and 7.1 for years 2 and 3. This
treatment produced the best season-long overall turfgrass quality, with
temporary straw production at transition (which occurred for 10 to 12 days at
most), and proved to be consistent for turfgrass quality within years and from year
authors thank the Environmental Institute for Golf (the philanthropic
organization of GCSAA) and the Golf & Environmental Foundation of Arizona
and the Cactus and Pine Golf Course Superintendents Association for providing
funding for this research.
- Duncan, R.R., and R.W. Carrow. 1999. Seashore paspalum — The environmental
turfgrass. John Wiley and Sons, Hoboken, N.J.
- Volterrani, M., S. Miele, S. Magni, M. Gaetani and G. Pardini. 2001.
Bermudagrass and seashore paspalum winter overseeded with seven cool-season turfgrasses. International
Turfgrass Society Research Journal
D.M.Kopec is an Extension specialist in turfgrass science
and culture, J. Gilbert is a senior research specialist, M. Pessarakli is a
research professor and S.P. Nolan is a student research assistant in the school
of plant sciences at the University of Arizona, Tucson.