Ready to roll?
Michigan State University’s “Doctor of Green Speed” offers his top 10 reasons why lightweight rolling is good for your greens.
Thomas A. Nikolai, Ph.D.
Read this story in GCM's digital edition
Photos by Montana Pritchard
When I initiated my first lightweight rolling putting green
study at Michigan State University in 1993, I had no idea I would still be
researching the mechanical practice nearly 20 years later.
In the ’90s, the initial objective of lightweight roller
research was to gather data to determine whether the practice was safe.
Concerns included the limitation of rolling frequency due to the increased
possibility of compaction, tissue bruising and the more prevalent movement of
diseases that are spread by mechanical means.
Just 10 years ago lightweight rolling was primarily used to
alleviate frost heaving, prep seed beds or increase green speed for tournaments
— if it was used at all. Today, because of surprising results from research,
lightweight rolling has been embraced as a means of creating healthy turfgrass and
increasing customer satisfaction.
Because of my extensive research with the practice, I have
been asked time and again to create a list of “The Top 10 Reasons to Lightweight
Roll.” I’ll admit to originally scoffing at the idea, but the truth is, I was
the perfect individual to create such a list, so I finally gave in to the
requests. What follows are my top 10 reasons to lightweight roll.
Alleviate heaving and minimize scalping when climatic conditions dictate
As recently as 10 years ago, superintendents were limiting rolling frequency due to their concerns about compaction, tissue bruising and spreading disease.
The numerous freeze/thaw cycles that occur in temperate
regions of the world result in soil frost heaving, which leads to bumpy soil
surfaces in the spring. It is customary to roll turfgrass surfaces before the
first spring mowing to minimize the potential of scalping. Similarly, when heavy
rains are followed by hot humid weather, thatch can swell, creating puffy turf
that is prone to scalping. Under these climatic conditions, rolling before
mowing can decrease the potential of scalping.
Seed bed preparation
Rolling is important during the establishment of turfgrass
sites for several reasons. First of all, on high-value areas, it is imperative
to roll the site multiple times before seeding to compress the root zone and
reduce or eliminate soil settling during or following establishment. Second,
numerous turfgrass books rightfully preach the importance of having good
seed-to-soil contact during the establishment of turfgrass sites, and the best
way to have good seed-to-soil contact is to roll the site immediately after
seeding. Additionally, in a putting green establishment study performed at
Michigan State University, plots rolled multiple times per week filled in
quicker and were ready for play sooner than putting green plots that were not
Broadleaf weed, moss, algae reduction
No research plots have ever been designed to examine the
impact of lightweight rolling on broadleaf weeds, moss or algae encroachment, yet
related research has documented that lightweight rolling decreases each of
them. In a study performed at Michigan State University in 1996, putting greens
rolled three times per week had fewer broadleaf weeds and less moss than greens
that were not rolled. Furthermore, in 2008, University of Arkansas master’s
degree student Jay Richards reported that lightweight rolling decreased algae
encroachment. Exactly why regular lightweight rolling would decrease these
pests is not known, but it is hypothesized that increased turfgrass density
reduces all of them.
Decreased localized dry spot
Studies at Michigan State University and the University of Arkansas have shown that lightweight rolling decreases localized dry spot.
Photos courtesy of T. Nikolai
A lightweight rolling study performed at Michigan State
University from 1995 to 2000 revealed that greens rolled three times per week displayed
significantly less localized dry spot than greens that were never rolled. Soil
samples from the study showed that rolled plots retained more moisture and had
more root mass than root zones that were not rolled. Obviously, increased soil
moisture content and root mass could lead to less localized dry spot on the turfgrass
In the past several years it has become easier for
researchers and golf course superintendents alike to measure volumetric soil
moisture content because time domain reflectometry (TDR) technology has been
vastly improved. TDR measurements taken for lightweight rolling studies
performed at Michigan State and the University of Arkansas have consistently shown
that lightweight rolling does increase soil volumetric moisture content.
Height of cut raised and green speed retained
Figure 1 shows green speed measurements from the very first
mowing height/rolling study. Plots mowed at 0.187 inch were rolled three times
per week and were compared to plots that were not rolled and were mowed at 0.156
inch. In the beginning of the study, plots maintained at the higher height of
cut had slower green speeds compared to plots mowed at the lower height of cut.
However, after a week and a half of rolling, plots maintained at the higher
height of cut achieved green speeds as fast as (and in some cases faster than)
plots mowed at the lower height. Interestingly, rolling resulted in enough
residual green speed that the higher height of cut maintained the green speed
of plots at the lower height of cut the day after rolling. Since that original
study, several other studies have been performed that validate those findings.
Furthermore, Rutgers University has documented that rolling and increasing the
height of cut decreases anthracnose while Michigan State University has
observed decreases in brown patch.
Decreased cutworm activity — maybe!
OK. This might be a stretch, but bear with me and, if
nothing else, you’ll learn I am an honest individual. At the Hancock Turfgrass Research
Center at Michigan State, we usually do not get enough black cutworms to
warrant an insecticide spray. However, over a period of years I had observed
cutworms, along with their unmistakable chewing damage, on my plots that
coincided with increased bird feeding. Therefore, I hypothesized that the birds
were going after the cutworms. The three years this happened I counted
bird-beak holes in the turfgrass before mowing/rolling. Plots rolled three
times per week had significantly fewer bird-beak holes (and therefore fewer
cutworms). Interestingly enough, the decrease in bird-beak holes was between 55
percent and 60 percent in each of the years, which seems pretty consistent. I
now feel comfortable stating that I think rolling decreases cutworm activity,
but in all truth I did not count cutworms, so I cannot say it with 100 percent
confidence. I’ll leave that up to you until a turfgrass entomologist performs a
Improved topdressing Incorporation
In 2006 Michigan State University performed a lightweight
roller/sand incorporation study on creeping bentgrass putting green plots.
Treatments included control plots that were never topdressed with sand,
topdressed plots with the sand brushed in when dry, and plots that were brushed
and then received a single pass with the True-Surface vibratory roller.
The day after topdressing, the plots were mowed with a
walk-behind mower, the debris was collected into buckets and put into paper bags
that were placed into an oven at 104 F to boil off water. Then the debris was
poured into a bucket of water, in which the sand sank while the clippings
floated. Clippings were collected with a net and the sand was poured onto a
very fine screen, returned to the oven and weighed. The result was
approximately 40 percent less topdressing sand was collected in the buckets when
plots were rolled after brushing (Figure 2). These plots also had a faster
green speed several days after topdressing and decreased organic matter content
at the end of the season.
John Sorochan, Ph.D., performed a similar study on
bermudagrass greens at the University of Tennessee and reported an 80 percent
decrease in the amount of sand after a single pass with the True-Surface
vibratory roller. To my knowledge, no university research study has tested
whether non-vibratory rollers increase sand incorporation after topdressing.
Decreased dollar spot
Research greens that are rolled frequently show
significantly less dollar spot disease.
In 1995 I noticed that research greens rolled three times
per week had less dollar spot than greens that were not rolled. None of the
data was statistically significant, and I was certain I would never make a
similar observation. The following year, the rolled plots on my research greens
had significantly less disease each time a dollar spot outbreak occurred. To
say I was surprised would be an understatement. Since then I have made similar
observations year after year in my lightweight rolling studies. Additionally, in
2011 Paul Giordano, a Michigan State graduate student, reported that increasing
the frequency of rolling significantly decreased the incidence of dollar spot.
The obvious question is, “Why does rolling decrease dollar spot?” The answer is
lengthy and a bit elusive, and heck, this is just a top-10 list. The important
fact is that regular use of lightweight rolling does decrease dollar spot.
It’s the economy (rolling/mowing frequency programs)
I published the results of my dollar spot observations in a
scientific journal in 2001, and understandably many of my peers seemed skeptical.
In 2002, I gave a presentation on the subject at the GCSAA Education Conference
in Orlando, and several roller companies were so delighted that they have
continued to fund my lightweight rolling research to date. Support from those
companies (and the Michigan Turfgrass Foundation) has allowed us to study the
effects of various rolling/mowing frequency programs over the years, including
the three listed below.
- Alternating daily mowing and rolling. In 2004 Michigan State initiated the first mowing/rolling
frequency study by comparing mowing every day with alternating mowing and
rolling on a daily basis. On research greens, alternating mowing and rolling
improves turfgrass wear tolerance and produces green speed measurements equivalent
to mowing daily. If you are thinking this might result in an economic saving,
you are correct. University of Tennessee graduate student Dan Strunk performed
a cost-analysis study comparing daily mowing to alternating mowing and rolling
on a daily basis and concluded that alternating mowing and rolling could save the
average golf course in Tennessee approximately $13,000 annually. This can be a very
nice economic option, especially when heat stress is high on cool-season
grasses or cold stress is high on warm-season grasses.
- Mow and roll every day. We
certainly are not considering saving money with this option; however, results
indicate that both mowing and rolling every day produces consistent green
speeds from day to day, possibly allows raised mowing heights for better
turfgrass health and wear tolerance, and results in significantly more dollar
spot control than mowing every day and rolling every other day.
- Roll every day and mow every other. That’s
right, rolling every day and mowing every other day. Of all the mowing/rolling
frequencies I have researched, this one results in the most consistent green
speeds from day to day, very good wear tolerance compared to mowing alone, and
better dollar spot control than mowing every day and rolling every other day.
Depending upon your current rolling program, this option could result in some
economic savings as well.
With all the programs listed above I have never observed an
increase in compaction; however, all my research plots have been on frequent
sand-topdressing programs (every two to three weeks). An additional caution:
When I rolled plots every day of the week, I always used the lightest rollers available
on the market (TruTurf, DMI Speed Roller and True-Surface vibratory rollers)
because they have been continuous supporters of my research. I don’t want to
imply that rolling seven days per week with a roller heavier than 550 pounds
would cause compaction and therefore weaker turf, I am just cautioning that we
do not know whether heavier rollers used daily would result in compaction or
not. Although I am a big advocate of lightweight rolling and encourage every
superintendent to roll greens, I am even a bigger advocate of proceeding with
caution when making any changes to a putting surface.
Increased customer satisfaction
The author cites studies using lightweight rollers and cautions superintendents to proceed with caution when using rollers
heavier than 550 pounds.
Photo by Scott Hollister
Golfer survey after golfer survey indicates that the
condition of the putting surface is the No. 1 thing golfers care about.
Lightweight rolling produces smoother putting surfaces, which result in truer
ball roll and faster green speeds. No other cultural or mechanical practice can
increase customer satisfaction as much as frequent use of a lightweight roller.
Finally, no other mechanical practice allows the superintendent the possibility
to adjust the green speed to make his clientele happy. To quote Walter S.
Harbin from 1922, “I cannot conceive how a perfect putting surface can be
developed or maintained without rolling.” I think Mr. Harbin would be happy
with the conditions on the putting surface today, due in part to the use of
Nikolai, Ph.D., is the “Doctor of Green Speed” in the department of crop and
soil sciences at Michigan State University, East Lansing, Mich., and the author
of the bimonthly column “Up to speed” in GCM.