Science in Action: Synthetic Play Surfaces in the Desert

Artificial turfgrass surfaces, in
the past, were viewed as expensive playing surfaces relegated to professional
sports fields and not meant for municipal or backyard applications. Now, faced
with limited resources and an ever expanding user population, organizations and
public entities are interested in finding ways to reduce costs and maximize
athletic field capacity. Natural grass playing surfaces are being successfully challenged
by these improved artificial surfaces in many different applications.

Golf course turfgrass and irrigation ponds add the equivalent of about a 70 ton air conditioner per acre to the local environment and water loss from leaf surfaces keep the surface temperature at right around 95F even when air temperatures hit 120F

            There has
been an evolution in synthetic playing surfaces since the 1960’s during which
AstroTurf^TM became a household name. Due to clever marketing,
AstroTurf^TM was tied to the image of “space age” technology
and domed stadiums like the Huston Astrodome for which it was named and Minneapolis’ Metrodome. Untreated
nylon and polyurethane grass and mat surfaces were highly susceptible to
decomposition by UV light and not very durable, with high maintenance costs.
These surfaces were replaced on an average of every five years, certainly not
within the budgets of municipalities and homeowners.

            But
AstroTurf^TM had numerous other problems as well which included
its poor drainage characteristics, impact on ball roll and bounce, alteration
in the speed of players on the field affecting play, increase in minor injuries
to players and finally the players just didn’t like it. Instead of addressing
the problems, Monsanto and other competing firms with similar products, suggested
things like elbow pads and special turf shoes when playing on artificial
turfgrass.

            The
original AstroTurf^TM no longer exists on any NFL fields as these types
of products eventually evolved to newer and improved artificial surfaces
(AstroPlay^TM, FieldTurf^TM, Sportexe Momentum
Turf^TM,
RealGrass^TM,
and others) or in some cases fields were converted back to natural grass.
A quick review of the artificial turfgrass evolution might be interesting.

            During the
1970’s little was done to improve the artificial turfgrass industry as Monsanto
dominated the market with the exit of competing products from companies like 3M
and Biltrite. AstroTurf^TM was the only artificial turfgrass available,
they had captured the market and so R and D came to a standstill.

            During the
early 1980’s engineers attempted to correct the problems of ball roll and
drainage problems still associated with artificial turfgrass. The ball roll
problem was solved by “texturizing” the nylon grass fibers, making them kinked
instead of smooth.

            During the late 1980’s new products
began to emerge that attempted to combine natural and synthetic surfaces into
one playing field hoping to capitalize on the best attributes of both. Surfaces
such as the original sportsgrass^TM emerged which used polypropylene grass blades held
together with a woven backing that was applied to an amended layer of sand.

            Natural grass was grown by seeding
or sprigging into this synthetic layer in hopes of preventing damage to the
crown and root systems from heavy play. Roots
could grow through the woven backing and into the sand below. Since grass roots
grow down through the synthetic fibers and backing, the crown and roots of the
plant would be protected. Complaints
emerged in some parts of the country that the playing surface became hard from
compaction and extensive play damaged the synthetic backing. This type of
damage led to an unstable playing surface which in turn hampered regrowth of
the natural grass.

            Engineers in the sports field
industry also tackled the player injury and stability problem by paving the
soil under the turfgrass with asphalt and adding a layer of PVC foam for
cushioning. Outside fields subjected to heavy rains were “crowned”, making the
center of the field 16 to 25 inches higher than the sides so that water would surface
drain off of the field.

            Porous
asphalt, a technology developed in England, was incorporated into the
engineering of artificial turfgrass to improve internal drainage. First the soil
of the field was leveled and then covered with a layer of crushed rock several
inches thick. A layer of porous asphalt was laid on top of the gravel followed
by a shock-absorbing pad and finally followed by the turf. After installation,
the turf was glued to the pad and holes were punched through the foam pad for
drainage.

            Things
changed in the 1990’s when strong and soft polyethylene was chosen by
artificial turfgrass manufacturers to replace the stiff but durable nylon of
the past. The fibers were UV resistant and long compared to previous artificial
turfgrass fibers. These fibers were “tufted” into a mat in a process similar in
appearance to a shag rug. Once the “sod carpet” was in place, it was topdressed
with “infill” which could be recycled rubber called “crumb” or a mixture of this
rubber and sand. Recycled rubber has been a source of controversy as to its
potential for damaging the environment and human health concerns. An average
football field might require up to 400 tons of infill applied to its surface.

In most recent years, two groups of artificial turfgrasses
have emerged with infill systems (NeXturf^TM, AstroPlay^TM and FieldTurf^TM). These products carried
claims that they realistically duplicated natural grass color and playability,
allowed for more play, and provided a ten year life before replacement. If
true, this was a significant improvement over previous generations of
artificial turf and placed it with the budgetary reach of nonprofessional
sports turf and municipal budgets. But the part that caught the eye of
municipalities and managers of nonprofessional sports fields with smaller
budgets were the claims that these surfaces lowered long term maintenance costs
(no water, no chemicals, decreased labor), were more environmentally friendly (no
pesticides or fertilizers) while at the same time reduced major injuries to players.

            During the early years
of AstroTurf^TM, players complained of numerous minor injuries such as
“turf toe” (a ligament sprain in the big toe that was exacerbated by
artificial turf), “turf burn” (skin abrasions like rug burn), foot blisters,
and bruised toes. Since then numerous studies have been conducted to evaluate
the safety and playability of synthetic surfaces. Mechanical devices have been
devised to simulate human movement across a playing surface, injury from
concussions, and the type and number of injuries occurring to athletes during
events were counted and recorded.

Reports and studies are numerous that
demonstrated fewer serious player injuries on artificial turfgrass compared to
natural grass (NFL, NCAA, reports by the University of Nebraska, and the
Amarillo Independent School District) while claims of minor injuries (such as
“turf burn”) still persisted. 
Researchers have suggested that the reason for fewer player injuries on
artificial grass might be due to a more even and predictable playing surface
and the accessibility of these fields to frequent and timely practices which
were not possible on natural grass surfaces that needed repair after heavy play.

The rationale for switching to
artificial turfgrass since that first installation has varied based on site
location and user needs. Reasons have included: increasing playability during
inclement weather, lower maintenance costs, and perhaps most relevant to the
southwestern United States,
the conservation of water. However, a potentially significant undesirable
characteristic of artificial turfgrass is the elevated surface temperatures (approaching
170 F) which restricts play during the summer months and human health concerns
for players.

Communities like Las Vegas have spent millions of dollars
replacing turfgrass on recreational sporting fields with artificial turfgrass,
with the goal of reducing maintenance costs, increasing play time while saving
significant amounts of money by eliminating irrigation. Although the rapid
increase in surface temperature in the presence of sunlight has been known for
decades little research has been published on the subject, especially related
to the controlling forces behind the rise in temperature. The majority of
information currently available on elevated surface temperature of artificial
turfgrass has come from unpublished studies available from internet web sites.

Research at the University of Nevada
in Las Vegas examined
the factors that influence surface temperature rise of artificial turfgrass. The
data collection included surface temperatures, spectral reflectance, solar
radiation and air temperatures associated with different landscape covers and
artificial turfgrass components; and, an assessment of energy balance and heat
transport through artificial turfgrass.