Genetic Characteristics and Environmental Parameters for Growing Turfgrass
in Closed and Retractable Dome Stadiums
Bruce Bugbee and P. Johnson
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Our analysis indicates that electric lighting
for turfgrass growth is highly cost effective, if it is coupled with
appropriate genetic and environmental changes.
Inadequate light levels for vigorous turf growth
is the key challenge associated with growing turf in enclosed and
retractable dome stadiums. The light levels of closed stadiums are
too low to maintain vigorous plant growth that can quickly recover
from the damage caused by athletic events. As a solution, retractable-dome
stadiums have been built. However, even with the roof open, light
levels in these stadiums are less than half of natural sunlight because
of shading from the side walls of the stadium. As such, maintaining
an attractive, uniform playing field has been difficult.
Vigorous plant growth without sunlight is routinely
achieved in commercial hydroponic lettuce and tomato production using
electric lamps. This same technology can be used to maintain live
turf grass in closed athletic stadiums. It can also be used to supplement
natural sunlight in retractable roof stadiums. The challenge is to
determine the optimal combination of genetic characteristics and environmental
parameters to grow turf in a closed stadium using artificial light
and to quantify the benefits of supplemental lighting in retractable
The research and development needed to achieve
vigorous turf growth under the low light conditions of enclosed and
retractable dome stadiums can be accomplished in four phases, which
Develop stadium design requirements for vigorous
turf growth in enclosed and retractable dome stadiums based on a
thorough feasibility study of current state-of-the-art for turf
production in low light.
Quantifying the response of the two most promising
turf grass species (Zoysiagrass C4, warm temperatures or
Poa supina C3, cool temperatures) to low light and determining
the value of growth regulators, CO2 enhancement,
temperature, etc. for enhancing growth under low light.
Examine all promising turf grass species and
the genetic variation within each species to enhance vigorous turf
growth under ever diminishing light levels (10 to 1 mol m-2
d-1), and initiate preliminary evaluation
of turfgrass species and critical levels of secondary inputs (i.e.,
growth regulators, CO2, temperature, nutrients,
etc.) in stadiums.
Implement full-scale testing of turfgrass on
indoor athletic fields in direct collaboration with stadium engineers
and field managers.
Following we review the current state-of-the-art
for turf production in low light and discuss in detail the research
needed to achieve healthy, live turf on indoor playing fields.
STADIUM TECHNOLOGY AND TURFGRASS MANAGEMENT ISSUES
The management of live grass on athletic fields presents an extraordinary
challenge to plant physiologists. Athletic fields are regularly damaged
by intense activity and are expected to continuously look as good as
artificial turf. TV exposure, demands of coaches, and high salaries
of professional athletes all contribute to high expectations. These
same fields are also often used for other events such as music concerts
and other revenue generating activities for the stadium. These many
demands, combined with the desire to attract more fans to sporting events,
have created many changes in stadium field technology.
Artificial vs. Natural Turf
Artificial turf was extensively used in stadiums
until about 10 years ago to reduce maintenance and increase the use
of a venue. However, many outdoor fields are now being converted to
natural turf, and most new stadiums are installing natural grass fields.
Natural turf fields provide cooler playing conditions, and provide
psychological benefit to both players and fans. The spectator experience
has become a critical part of stadium design in recent years. Camden
Yards in Baltimore and Jacobs Field in Cleveland are shining examples
of spectator stadiums. Part of this experience is the natural grass.
Even more importantly, natural grass
offers a safer playing surface for athletes. Natural turf is usually
softer than artificial turf and protects joints and muscles from damage.
A recent survey of NFL Players found that 92% believe playing on artificial
turf leads to shortened careers, 90% feel that artificial turf will
worsen their quality of life after football, and 96% say that artificial
turf adds to their soreness after games. Natural turf is softer and
offers more give than artificial turf. When a player turns quickly,
their cleats tear at the turf. If the strain is too great, the turf
gives way. This feature is much like a shear pin protecting a motor
on a piece of equipment.
Natural turf has many
benefits but requires high light levels for good growth. Artificial
turf has thus been the only choice for domed stadiums.
The Houston Astrodome, built in 1965, demonstrated
that domed stadiums could prevent weather-related delays and cancellations
of events. Domed stadiums are now popular around the world, but the
surroundings are considered sterile, partly because of the artificial
turf. Turfgrasses can be grown in many stadiums, but the light levels
are too low to maintain vigorous plants that can recover from the
damage caused by athletic events. As a compromise between domes and
open-air stadiums, retractable-dome stadiums are now being built.
The first retractable dome stadium was the SkyDome in Toronto, built
in 1989. The Skydome provided an open air feeling, potential to use
real grass, and prevented weather delays. Numerous retractable dome
stadiums are now being built worldwide. These include Safeco Field
in Seattle (opened July 1999), Miller Park (under construction), Enron
Field in Houston, and fields in Japan (Oita Sports Park, and the Sapporo
Dome). In fact, retractable-dome stadiums are being proposed and built
in the hope of attracting a professional sports team. The Harris County
Stadium is being proposed to attract a football team back to Houston
The first retractable
domed stadium to use natural turf is the BankOne Ball Park in Phoenix,
Arizona. This field has been in use for two seasons. In spite of the
retractable dome, low light conditions limit the growth and durability
of the turf, especially if post-season baseball games are played into
October. These problems would be exacerbated in more northerly areas
where the dome would be closed more often due to weather, and there
would be greater shading due to the lower sun angle.
To further add to the reduction in light, the roof at BankOne Ball Park
has been closed more than originally planned because of the priority
for fan and player comfort. Thus far, retractable-dome stadiums have
only been used for baseball. Football presents a new challenge, especially
where the roof would likely be shut the majority of the time to facilitate
heating during the cool fall weather.
A unique combination of natural turf and a domed
stadium was used during the 1994 World Cup soccer games played at
the Pontiac Silverdome in Pontiac, Michigan. The Silverdome has a
fabric roof and has an artificial grass field. Prior to the World
Cup, turf was grown in large interlocking containers that were moved
into the stadium for the games. These containers were then moved out
after the events. The turf was in the stadium for up to 10 days at
a time and provided a high quality playing field for the matches viewed
around the world. In a similar and even more temporary situation,
thick rolls of sod were laid on the floor of the Louisiana Super Dome
for a football game and removed shortly after the game.
To date, no stadium has successfully grown natural turfgrass for extended
periods in a completely enclosed stadium with a roof that does not
transmit sunlight. Even retractable dome stadiums have inadequate
light levels for vigorous turf growth.
The challenges is to determine the optimal combination of genetic
characteristics and environmental parameters to grow turf in a closed
stadium using artificial light and to quantify the benefits of supplement
light in a retractable dome stadium.
GENETIC CHARACTERISTICS OF
A "start with the grass" approach will
improve chances of successfully engineering enclosed turfgrass stadium
The most commonly used turf in cool-season athletic fields (northern
half of the U.S.) is Kentucky bluegrass (Poa pratensis). Bermudagrass
(Cynodon dactylon) is the most commonly used turf in warm-season
athletic fields (southern half of the U.S.). However, neither Kentucky
bluegrass nor Bermudagrass are tolerant of low light levels. The grass
species most tolerant of low light levels are Poa supina and
zoysiagrass (Zoysia japonica). These two speices have excellent
potential for indoor stadiums.
Poa supina is relatively new to the U.S.
turf industry. It has been studied for use as an indoor athletic turf
in translucent roof stadiums and has been consistently the best performing
cool-season turfgrass in those conditions.
It is very useful on athletic fields because it has aggressive lateral
growth by stolons, which helps it recover from athletic damage. One
of the first aspects of growth impacted by low light is lateral growth
and damage recovery.
Zoysiagrass is used extensively in the
southern U.S. for lawns and athletic fields. Zoysiagrass grows
slowly, but is rugged and resistant to damage because of an extensive
network of underground stolons. It also is one of the most shade-tolerant
of warm-season grasses. Zoysiagrass was used at the Bank One
Ballpark in Phoenix, Arizona because of its ability to tolerate the
hot summer temperatures yet still survive in the shadiest areas of
the stadium. It is well adapted to the warm, humid conditions.
Alhough both Poa supina and Zoysiagrass are classified
as shade tolerant, there is very little quantitative data on the low-light
level limit, how other environmental factors affect low-light tolerance,
and most importantly, the wear tolerance characteristics.
Types of wear
Three general types of damage occur on athletic
Abrasion damage is present most anywhere the
turf is used.
Divots, or tearing of the turf, are the most
common. Athletes cleats tear the turf and remove part of it
leaving a divot or void.
Soil compaction in the most frequently used
areas of the fields. Compaction can be greatly reduced by management
practices and proper field construction.
Both Poa supina and
Zoysiagrass are tolerant to abrasion and both resist or repair
divots. Additional methods of replacing large areas of turf and supplementing
the surface soil with plastic fibers can also increase tolerance to
tearing wear using currently available technology (See below: Supplemental
management and construction techniques).
Research methodology to determine wear tolerance
A number of methods have been developed to simulate wear on turfgrass
plots. These methods usually involve pulling a unit with two drums with
numerous cleats or spikes inserted. The two drums turn at slightly different
rates causing a tearing action on the turf. We have the experience necessary
to adapt these methods to a small scale for greenhouse or growth chamber
plots. Other devices can replicate divots or holes. Since all root-zones
in sports fields are man-made, these can be replicated in pots or boxes
enabling many treatments within one growth chamber or greenhouse.
High quality athletic fields are built with a root zone composed of
about 90% sand and 10% peat. This provides a porous soil that is resistant
to compaction. Underlying construction of gravel and drainage tiles
further improves drainage of the rootzone. The profile of 6 to12 inches
of sand/peat over a 2 inch layer of fine gravel keeps the sand moist.
A lower layer of coarse gravel and drain tile and allows excess water
to move down and away in the drainage tiles. This construction is similar
to USGA specification for golf greens. Some fields also incorporate
pumps and fans into these sub-soil systems to push water into the profile
from underneath and to introduce air into the rootzone.
Plant growth regulators
Turfgrass growth and quality, especially in shady
conditions, can be significantly improved with the use of plant growth
regulators (PGRs). The most commonly used regulators block the production
of gibberellic acid (GA) in the plants, which slows vertical growth
and creates a darker green color. PGRs also increase carbohydrate
production, which increases abrasion tolerance and wear resistance.
PGRs are especially useful in shady conditions because plants grown
under low light usually produce higher amounts of GA, which causes
tall, spindly growth. Applications of anti-GA PGRs in shade-grown
turf help reduce this elongation and results in a more robust plant.
Supplemental management and construction techniques
SportGrass is a hybrid between artificial turf
and natural grass. It is composed of a loosely woven nylon mat with
long vertical fibers. The vertical fibers are top-dressed with sand
to create a sand root zone interspersed with the nylon fibers. The
fibers help create a tougher turf and increase the lateral stability.
The SportGrass turf still "gives" like natural turf, but
fewer large divots are removed during athletic events.
SquAyres and Netlon rootzone fibers are used together
in a system. Netlon fibers are mixed with the rootzone mix to provide
additional sod strength. The SquAyres system is designed to move large
pieces of sod within the field or between nursery fields outside of
the playing fields. This system allows replacement of damaged turf
from the most frequently used parts of the field with turf from areas
that experience very little traffic.
FACILITIES AND PERSONNEL
The Utah State University
Crop Physiology Laboratory is primarily supported by NASA
and most research is directed towards optimizing growth of plant species
and bio-regenerative life support systems. Much of this research includes
hydroponics, elevated carbon dioxide and light levels and the development
and testing of models and sophisticated new sensors for monitoring
and control. This work has equipped the laboratory to carry out research
projects on the production of crops in enclosed facilities, such as
an athletic stadium.
Bruce Bugbee (Ph.D. Horticulture
Crop Physiology, Pennsylvania State University), Director of
the Crop Physiology Laboratory, brings extensive expertise in effects
of radiation (photons of light) quality, intensity and duration on
photosynthesis and growth, nutrient management in recirculating hydroponic
culture, sensors and methods for plant growth analysis, and plant/soil
systems. He has served on several NASA and American Association of
Biological Sciences peer review panels. Dr. Bugbee will lead the biological
aspects of this research effort.
Paul Johnson (Ph.D. Horticulture Turfgrass Science,
University of Minnesota), brings basic and applied expertise on the
growth, culture, and genetics of turfgrasses. He is the Utah State
Turfgrass Extension Specialist and has consulted on many athletic
fields around the nation. Dr. Johnson also has served as Turfgrass
Biotech Consultant to the Monsanto Corporation.