REVIEWS & ANALYSES

The Role of Turfgrasses in Environmental Protection and Their Benefits to HumansJames B Beard* and Robert L. Green

ABSTRACTTurfgrasses have been utilized by humans to enhance their environ-

ment for more than I0 centuries. The complexity and comprehensive-ness of these environmental benefits that improve our quality-of-life arejust now being quantitatively documented through research. Turfgrassbenefits may be divided into (i) functional, (ii) recreational, and (ill) thetic components. Specific functional benefits include: excellent soil ero-sion control and dust stabilization thereby protecting a vital soil resource;improved recharge and quality protection of groundwater, plus flood con-trol; enhanced entrapment and biodegradation of synthetic organic com-pounds; soil improvement that includes COz conversion; acceleratedrestoration of disturbed soils; substantial urban heat dissipation-temperature moderation; reduced noise, glare, and visual pollution prob-lems; decreased noxious pests and allergy-related pollens; safety in ve-hicle operation on roadsides and engine longevity on airfields; loweredfire hazard via open, green turfed firebreaks; and improved security ofsensitive installations provided by high visibility zones. The recreationalbenefits include a low-cost surface for outdoor sport and leisure activi-ties, enhanced physical health of participants, and a unique low-cost cush-ion against personal impact injuries. The aesthetic benefits include en-hanced beauty and attractiveness; a complimentary relationship to thetotal landscape ecosystem of flowers, shrubs and trees; improved mentalhealth with a positive therapeutic impact, social harmony and stability;improved work productivity; and an overall better quality-of-life, espe-cially in densely populated urban areas.

FOR MANY CENTURIES people have been willing todevote time and resources to enhance their quality-of-life and recreational opportunities through the use ofturfgrasses (Beard, 1989a). Also, for many centuries turf-grasses have played a vital role in protecting our environ-ment, long before it became an issue of major national andinternational importance to modern societies.

The Poaceae is the most ubiquitous of the higher plantgroups found on this earth (Gould, 1968). With an esti-mated 600 genera and 7,500 species, the Poaceae ranksthird in number of genera among families of floweringplants. In respect to completeness of representation in allregions of the world and to percentage of the total world’svegetation, it surpasses all other genera. Grasses are oneof the first permanent vegetations to reappear after dis-asters, such as volcanic activity, extended droughts, floods,fires, explosions, abandoned urban ghettos, and battlefields.Without the foregiveness of the Poaceae, many ill-advised

J.B Beard, formerly Dep. of Soil and Crop Sciences, Texas A&M Univer-sity, currently International Sports Turf Institute, College Station, Texas 77843,and R.L. Green, Dep. of Botany and Plant Sciences, Univ. of California,Riverside, CA 92521. Contribution of Texas Agric. Exp. Stn. TA no. 30759.Received 29 Jan. 1993. *Corresponding author.

Published in J. Environ. Qual. 23:452-460 (1994).

construction excavations and certain agricultural activitieswould have had far more disastrous effects on one of ourmost vital natural resources, the earth’s surface soil man-fie, on which terrestrial plants and animals live.

To the botanist, grass is a member of the family Poa-ceae. To humans, grasses are the most important of allplants. The cereal grains and corn (Zea mays L.), all mem-bers of the grass family, serve as food for humans andanimals. A host of grazing ruminant animals use grassesas their major food source as forage, pasture, and preparedfeeds. Bamboo (Bambusa spp., Dendrocalamus spp., andPhyllostachys spp.) is a major building material. Also,grasses of all types represent a large source of biomassfor production of methanol, an alternate energy source.

The turfgrass species now in use evolved during the past50 million years and they have been cultured by humansto provide an enhanced environment and quality-of-life for>10 centuries (Beard, 1973). The modern turfgrass industryhas grown rapidly in the past three decades. It contributessubstantially to the national economy, with numerous em-ployment opportunities. The annual expenditure for main-taining turfgrass in the USA, including labor but exclud-ing capital expenses, was conservatively estimated to be$25 billion (Cockerham and Gibeault, 1985). This eco-nomic impact has increased substantially during the past10 yr to $45 billion. This 1993 value was based on the1985 data with adjustments for population growth andinflation. Also, the fixed assets of turf installations arevalued at many times that of the annual maintenance ex-penditures.

The functional, recreational, and aesthetic contributionsof turfgrasses than enhance the quality-of-life for humansoften are overlooked and seldom addressed in the scientificliterature. Our purpose is to document the beneficial con-tributions of turfgrasses as summarized in (Fig. 1).

TURFGRASS FUNCTIONAL BENEFITSSoil Erosion Control and Dust Stabilization

Turfgrasses are relatively inexpensive, durable groundcovers that protect our valuable, nonrenewable soil resourcefrom water and wind erosion. Agricultural operations andsimilar activities such as construction involve extensiveland disruption, in contrast to turfed land areas, which aremaintained in a long-term stable state.

Runoff water from agriculture and urban areas currentlyaccount for 64 and 5%, respectively, of the nonpointsurface-water pollution affecting the 265 485 km of riversin the USA; and 57 and 12%, respectively, of the non-point surface-water pollution affecting the 3.3 million hec-tares of lakes in the USA. Sediment and nutrients account

452

BEARD & GREEN: ROLE OF TURFGRASS 453

BENEFITS OF TURFGRASSES

FunctionalSoil erosionDust preventionHeat dissipationNoise abatementGlare reductionAir pollution controlNuisance animal reduction

RecreationalLow cost surfaces

Physical healthMental healthSafetySpectator entertainment

AestheticBeauty

Quality of lifeMental healthSocial harmonyCommunity prideIncreased property values

Compliments trees andshrubs in landscape

Fig. 1. Diagrammatic summary of benefits derived from turfs.

for 47 and 13 %, respectively, of the nonpoint surface-waterpollution in rivers and 22 and 59 %, respectively, of thenonpoint surface-water pollution in lakes. In the 1987 USDANational Resources Inventory it was estimated that the an-nual sheet and rill erosion on the 153 million hectares ofcultivated cropland in the USA was 9184 kg ha-1 (U.S.Department of Agriculture, 1989).

Gross et al. (1991) reported sediment losses of =10 60 kg ha-1 from turfgrass plots during a 30 min stormthat produced 76 mm h-1 of rainfall; soil loss for bare soilplots averaged 223 kg ha-1. .They concluded that well-maintained residential turfgrass stands should not be asignificant source of sediment entering bodies of water.It generally is recognized that a few large storms each yearare responsible for most soil erosion losses (Menzel, 1991).Other studies and reviews (Gross et al., 1990; Morton etal., 1988; Petrovic, 1990; Watschke and Mumma, 1989;Watson, 1985) have demonstrated or concluded that qual-ity turfgrass stands modify the overland flow process sothat runoff is insignificant in all but the most intense rain-fall events. The ability of grasses to function as vegetativefilter strips that greatly reduce the quantity of sedimenttransported into surface streams and rivers is welldocumented, especially when positioned downslope ofcropland, mines, and animal production facilities (Barfieldand Albrecht, 1982; Dillaha et al., 1988; U.S. Environ-mental Protection Agency, 1976; Young, 1980). A key char-acteristic of mowed turfgrasses that contributes to this veryeffective erosion control is a dense ground cover with ahigh shoot density ranging from 75 million to >20 billionshoots per hectare (Beard, 1973; Lush, 1990). Regularmowing, as practiced in turf culture, increases the shootdensity substantially because of enhanced tillering whencompared with ungrazed grasslands (Beard, 1973). Put-ring and bowling greens mowed at a 4-mm height possessup to 66 billion shoots ha-~.

The erosion control effectiveness of turfgrass is the com-bined result of a high shoot density and root mass for sur-

face soil stabilization, plus a high biomass matrix that pro-vides resistance to lateral surface water flow, thus slowingotherwise potentially erosive water velocities. Therefore,perennial turfgrasses offer one of the most cost-efficientmethods to control water and wind erosion of soil. Suchcontrol is very important in eliminating dust and mud prob-lems around homes, factories, schools, and businesses.When this major erosion control benefit is combined withthe groundwater recharge, organic chemical decomposi-tion, and soil improvement benefits discussed in the nextthree sections, the resultant relatively stable turfgrass eco-system is quite effective in soil and water preservation.

Groundwater Recharge and Surface Water QualityOne of the key mechanisms by which turfgrasses pre-

serve water is their superior capability to trap and holdrunoff, which results in more water infiltrating and filter-ing through the soil-turfgrass ecosystem. A mowed turf-grass possesses a leaf and stem biomass ranging from 1000to 30 000 kg ha-~, depending on the grass species, sea-son, and cultural regime (Lush, 1990). This biomass composed of a matrix of relatively fine-textured stems andnarrow leaves with numerous, random open spaces. Thecanopy matrix is porous in terms of the water infiltrationcapability.

Studies in Maryland conducted on the same researchsite have shown that surface-water runoff losses from a cul-tivated tobacco (Nicotiana tabacurn L.) site averaged 6.7mm ha-~ 4 wk-1 during the tobacco-growing season(May-September); whereas, the surface-water runoff lossfrom perennial turfgrass averaged only 0.6 mm ha-1 4wk-~ (Angle, 1985; Gross et al., 1990). Surface runofflosses of total N and P for tobacco were 2.34 and 0.48kg ha-1 4 wk-~, respectively. Losses of N and P from theturf averaged only 0.012 and 0.002 kg ha-1 4 wk-1,respectively. Other studies have shown a similar ability ofa turfgrass cover to reduce runoff, and therefore enhance

454 J. ENVIRON. QUAL., VOL. 23, MAY-JUNE 1994

soil water infiltration and groundwater recharge (Bennett,1939; Gross et al., 1991; Jean and Juang, 1979; Mortonet al., 1988; Watschke and Mumma, 1989). Finally, thereduced runoff volume from a turfgrass cover offers thepotential to decrease the storm-water management require-ments and costly structures used in urban development(Schuyler, 1987). Turfgrass ecosystems can support abun-dant populations of earthworms (Lumbricidae) of from 200to 300 m-2 (Potter et al., 1985, 1990a). Earthworm ac-tivity increases the amount of macropore space within thesoft, that results in higher soil water infiltration rates andwater-retention capacity (Lee, 1985).

Organic Chemical DecompositionThe runoff water and sediment that occurs from imper-

vious surfaces in urban areas carries many pollutants,(Schuyler, 1987) including metals such as Pb, Cd, Cu, andZn; hydrocarbon compounds as from oft, grease and fuels;and household and industrial hazardous wastes such as wasteoils, paint thinners, organic preservations, and solvents.Turfgmss areas can be designed for the catchment and filtra-tion of these polluted runoff waters (Schuyler, 1987). is significant that large populations of diverse soil microflomand microfauna are supported by this same soil-turfgrassecosystem. Microflora constitute the largest proportion ofthe decomposer biomass of most softs. The bacterial bi-omass component ranges from 30 to 300 g m-2, andfungi from 50 to 500 g m-2, with actinomycetes proba-bly in a similar range (Alexander, 1977). Soil invertebratedecomposer biomass ranges from 1 to 200 g m-2, withthe higher values occurring in soils dominated by earth-worms (Curry, 1986). Though soft animals play an im-portant part in the decomposition process, only 10% orless of the CO2 produced during decomposition has beenattributed to them (Peterson and Luxton, 1982).

The bacterial population in the moist litter, grass clip-pings, and thatch of a turf commonly is in the order of109 organisms cm-2 of litter surface (Clark and Paul,1970). These organisms offer one of the most active bio-logical systems for the degradation of trapped organic chem-icals and pesticides. The average microbial biomass poolis reported to be 700, 850, and 1090 kg C ha-1 for ara-ble, forest, and grassland systems, respectively (Smith andPaul, 1990). A microbial biomass of 1200 kg C ha-1 hasbeen reported for grasslands in the USA (Smith and Paul,1988). Microbial biomass values of mowed turfgrasses arenot yet available, but are probably even higher due to thehigh C biomass contained in the senescent leaves and grassclippings that accumulate near the soft surface and to amore favorable soil moisture regime due to irrigation (Smithand Paul, 1990).

The turfgrass ecosystem also supports a diverse com-munity of nonpest invertebrates. For example, a Kentuckybluegrass (Poa pratensis L.)-red fescue (Festuca rubra L.)polystand in New Jersey supported 83 different taxa of in-vertebrates including insects, mites (Acarina spp.), nema-todes (Nematoda spp.), annelids (Annelida spp.), gastro-pods (Gastropoda spp.), and other groups (Streu, 1973).Similarly, dozens of species of rove beetles, (Staphylini-dae), ground beetles (Carab/dae), ants (Formicidae), spiders

(Araneae), and other groups of invertebrates have been re-covered from turfgrass sites (Arnold and Potter, 1987;Cockfield and Potter; 1983, 1984, 1985). Earthworms,oribatid mites (Cryptostigmata), Collembola, and otherinvertebrates also are abundant in turfgrass softs (Arnoldand Potter, 1987; Potter et al., 1985, 1990a,b; Vavrek andNiemczyk, 1990).

There also is the gaseous dimension of atmospheric pol-lution control. Carbon monoxide concentrations >50 ~tLoften occur in urban environments, especially near road-sides (Jaffe, 1968). Gladon et al. (1993) reported that tain turfgrasses, such as tall rescue (Festuca arundinaceaSchreber), may be useful as an absorber of CO from theurban environment.

Soil Improvement and RestorationAn extremely important function of turfgrasses is soil

improvement through organic matter additions derived fromthe turnover of roots and other plant tissues that are syn-thesized in part from atmospheric CO2 via photosynthe-sis. A high proportion of the world’s most fertile soils hasbeen developed under a vegetative cover of grass (Gould,1968). The root depth potential ranges from 0.5 to 3 m,depending on the turfgrass species, extent of defoliation,and soft-environmental conditions. Generally, C4 warm-season turfgrasses produce a deeper, more extensive rootsystem than the C3 cool-season species (Beard, 1989b).More work has been reported on the rooting characteris-tics of Kentucky bluegrass than any other species. The rootsystem biomass of a Kentucky bluegrass lawn is in the rangeof 11 000 to 16 100 kg ha-1 (Boeker, 1974; Falk, 1976).In the upper 150 mm of the soil there are =122 000 rootsand 6.1 x 107 root hairs per liter of soft, with a combinedlength of>74 km and a surface atr~ of =2.6 mE (Dittmer,1938).

Falk (1976) estimated that the annual root system turn-over rate was 42 % for a lawn. Using Falk’s estimate, 6761kg of root biomass per hectare would be turned over intothe soft each year. This estimate is low because it did notaccount for root secretions, death and decay of fine rootsand root hairs, and consumption of roots by soil animals.The amount of root biomass annually produced and turnedover into the soft, or root net productivity, for a defoliatedgrassland is higher than the amount reported for ungrazedprairie ecosystem (Dahlman and Kucera, 1965; Sims andSingh, 1971, 1978). Similarly, the net effect of regular mow-ing on prostrate growing turfgrasses would be to concen-trate energies into increased vegetative growth, as opposedto reproductive processes, and to form a canopy of numer-ous dense, short, rapid growing plants with a fibrous rootsystem. Also, many prairie lands in the USA generally showdecreased productivity under regular defoliation, as bymowing, since most native grass species found in theseecosystems form meristematic crowns that are elevatedhigher above the soil and where removal is more likelywhen compared with turfgrass species. Dahlman andKucera (1965) estimated the time required for a centralMissouri prairie to reach 99 % soil organic matter equi-librium to be 110, 420, and 590 yr for the A~, A2, andBE SOft horizons, respectively.

BEARD & GREEN: ROLE OF TURFGRASS 455

Accelerated soil restoration of environmentally damagedareas by planting perennial grasses is employed effectivelyon highly eroded rural landscapes, burned-over lands, gar-bage dumps, mining operations, and steep timber harvestareas. These areas may then be developed as parks, golfcourses, sports field complexes, and recreational areas.

Heat Dissipation-Temperature ModerationThe overall temperature of urban areas may be as much

as 5 to 7 °C warmer than that of nearby rural areas. Throughthe cooling process of transpiration, turfgrasses dissipatehigh levels of radiant heat in urban areas. Maximum dailycanopy temperatures of a green, growing Cynodon turf wasfound to be 21 °C cooler than a brown dormant turf and39 °C cooler than a synthetic surface (Table 1; Beard andJohns, 1985). The transpirational cooling effect of greenturfs and landscapes can save energy by reductions in theenergy input required for interior mechanical cooling ofadjacent homes and buildings (Johns and Beard, 1985).

An additional asset ofa turfgrass ecosystem is the lowertotal energy input requirements for maintenance comparedwith other landscape types. A comparison of typical land-scapes used in Florida revealed a lawn was the least energyintensive at 31.5 MJ m-2 yr-~, followed by 5-yr-old treesat 87.5 MJ m-2 yr-~, and then by shrubs at 114.8 MJ m-2yr-~ (Parker, 1982). Similarly, Busey and Parker (1992)reported that the annual hours required for turf maintenancewas 1.076 h 100 m-2, while 12.37 h 100 m2 was requiredfor shrub beds, which seem to be low values. Energy in-puts for maintenance could be reduced by proper selec-tion of resource efficient, sustainable species and cultivarsof turfgrasses, trees, and shrubs.

Noise Abatement and Glare ReductionThe surface characteristics of turfgrasses function in

noise abatement as well as in multi-directional light reflec-tion that reduces glare. Studies have shown that turfgrasssurfaces absorb harsh sounds significantly better than hardsurfaces such as pavement, gravel, or bare ground (Cookand Van Haverbake, 1971; Robinette, 1972). These benefitsare maximized by an integrated landscape of turfgrasses,trees, and shrubs. Unfortunately, the proper use of turf-grasses, trees, and shrubs in concert to maximize noiseabatement has received little attention within the scientificcommunity.

Decreased Noxious Pests, Allergy-Related Pollens,and Human Disease Exposure

Closely mowed residential lawns reduce the numbersof nuisance pests such as snakes (Ophidia spp.), rodents(Rodentia), mosquitoes ( Culicidae spp.), ticks (Ixodoideaspp.; Acari order), and chiggers (Trombiculidae spp.; Acariorder). As undesirable small animals seek haven in tallergrasses, flowers, and shrubs at locations more distant fromthe house, they also are less likely to invade the house.

Allergy-related pollens can cause human discomfort andpotentially serious health concerns to susceptible individ-uals. Dense lawns typically are void of the many weedyspecies that often produce allergy-related pollens. In ad-

Table 1. Temperature comparisons offour types of surfaces onAu-gust 20 in College Station, TX.

Type of surface

Maximum Minimumdaytime nocturnalsurface surface

temperature temperature

Green growing Cynodon turf 31 °C 24 °CDry bare soil 39 °C 26 °CBrown summer-dormant Cynodon turf 52 °C 27 °CDry synthetic turf 70 °C 29 °C

dition, most turfgrasses that are mowed regularly at a lowheight tend to remain vegetative with minimal floral de-velopment, and thus have reduced pollen production; how-ever, the best solution for those who enjoy outdoor garden-ing activities is to select turfgrass species and cultivars thatdo not form flowers nor the resultant allergy-related pol-len. The turf cultural practices employed also influenceflower and pollen production.

Exposure to a number of serious human diseases is facili-tated by key insect vectors such as mosquitos and ticks.Of current concern is Lyme disease, which is spread bya tick commonly found in unmowed tall grass andwoodland-shrub habitats. A closely mowed lawn aroundresidences offers a less favorable habitat for unwanted nui-sance insects and disease vectors (Clopton and Gold, 1993).Chigger mite (T. irritens) population densities were foundto be highest at the ecotone or transition area of neighbor-ing 600-ram tall grass beyond the mowed turf. This is at-tributed to the distinct decrease in temperature and solarradiation at the ecotone.

Safety in Vehicle Operation-Equipment LongevityRoadside turfgrasses aid in highway safety, as well as

erosion control, by serving as a stabilized zone for emer-gency stoppage of vehicles (Beard, 1973). Mowed road-side turfs enhance line-of-sight visibility and views of signsand animal hazards, which are vital factors for operatorsof fast-moving vehicles. Turfgrasses are used for soil anddust stabilization around airport runways and taxiways toprolong the operating life of airplane engines (Beard, 1973).Furthermore, turfgrasses are used on small airstrips as alow-cost means to stabilize the runway surface.

Security For Vital Installations and Lower Fire HazardExpanses of green, low-growing turfs in the landscape

provide a high visibility zone that discourages unwantedintruders and vandals. Such turfs offer a low-cost approachthat is a viable security measure, especially around sensi-tive military and police installations. Also, the low fuelvalue of green, prostrate-growing turfs serves a valuablefunction as a firebreak that significantly lowers the fire haz-ard if properly positioned (Youngner, 1970). This attri-bute is especially important for homes and buildings adja-cent to extensive woodland or brush areas.

Wildlife HabitatThe ever-increasing human population of the world

results in a continuous increase in land area devoted to ur-

456 J. ENVIRON. QUAL., VOL. 23, MAY-JUNE 1994

ban development. The impact on the wildlife species nor-mally found in such areas is of concern. Certainly, properplanning of appropriate landscapes around homes, busi-nesses, industrial complexes, and public buildings canenhance the potential to support a representative wildlifecommunity that residents may enjoy. A diverse wildlifepopulation can be achieved by an integrated landscape com-posed of turfgrass, tree, shrub, and water features, suchas that found on golf courses (Green and Marshall, 1987;Maffei, 1978). A study of golf courses and parks in Cin-cinnati, OH, has shown conclusively that passerine birdsbenefit from golf courses, even to the extent that golf coursesmay be described as bird sanctuaries (Andrew, 1987).Ponds, lakes, and wetlands are very desirable features asused in parks and golf courses because they create aquatichabitats, as well as diversity in visual landscape aesthetics.Considerable preconstruction planning of golf courses,parks, and recreational areas is needed to address their im-pact on natural habitats. Properly designed urban land-scape green areas such as golf courses and parks can main-tain and even promote plant and animal diversity, naturalhabitats, and wetlands when compared to intensive agricul-ture and urban residential usage. A naturalized style of golfcourse design is unquestionably conducive to both golf reac-tion and wildlife management. Typically, 1.7 times morearea on a golf course is used for natural habitats such asroughs, woodlands, and water features than the combinedarea devoted to greens, tees, and fairways.

TURFGRASS RECREATIONAL BENEFITSTurfs provide a low-cost, safe recreational surface. Many

outdoor sports and recreational activities utilize turfgrasses,including archery, badminton, baseball, cricket, croquet,field hockey, football, golf, hiking, horse racing, horse-shoes, lawn bowling, lawn tennis, lacrosse, polo, rugby,shooting, skiing, soccer, softball, track and field, andvolleyball.

Both the enjoyment and the benefits of improved physi-cal and mental health derived from recreation and leisureactivities on turfs are vital to contemporary society, espe-cially in densely populated urban areas. Community prideand interest can be derived from quality sports fields andparks. Also, spectators derive entertainment from sport-ing competitions played on turfs.

Turfgrasses provide a unique, low-cost cushioning effectthat reduces injuries to the participants when comparedwith poorly or nonturfed soils, particularly in the moreactive contact sports like football, rugby, and soccer (Gram-ckow, 1968). In a study of 12 Pennsylvania high schoolfootball programs Harper et al. (1984) reported that 21%of injuries were classified as either definitely or possiblyfield related. Surface hardness measurements obtained witha Clegg impact soil tester (Lafayette Instrument Co.,Lafayette, IN) illustrate the substantial benefit of a properly-managed, quality turf in reducing the hardness of sportsfields (Table 2; Beard and Sifers, 1993, p. 40; Rogers etal., 1988; Rogers and Waddington, 1990, 1992). Turfs areresilient and pleasant to walk on. This resiliency can helpto protect the legs of participants, whether running orwalking.

Table 2. Impact absorption values for high school athletic fieldsversus other surfaces (Rogers et al., 1988).

Impact hammer weight

Type of surface 0.5 kg 2.25 kg

High school athletic fields 50-286~ 33-167Artificial turf 109-172 60-91Frozen practice athletic field 404 303Tiled, concrete basement floor 1440 1280Carpet and pad on tiled concrete floor 260 190Carpet and pad on hardwood floor 86 134

Sma~ = maximum deceleration (harder surfaces have greater Smax values).Good maintenance practices and field conditions generally were associatedwith lower impact values that indicated less hardness.

Home lawn owners derive the benefits of both physicalexercise and therapeutic relaxation from the stresses of thework place through activities involved in the care andgrooming of lawns. Many people find lawn maintenancean excellent opportunity to enjoy reasonable exercise anda healthy mental diversion.

TURFGRASS AESTHETIC BENEFITSFrancis Bacon, during the Renaissance in England, wrote

that next to the house there is to be a lawn, with an avenueof trees in the middle, and covered shady walks on eitherside. Respondents to a Harris-Life survey reported thatone of the things 95 % of the respondents wanted mostaround them was green grass and trees (Hooper, 1970).Turfgrasses provide beauty and attractiveness that enhancethe quality-of-life for human activities. Their aestheticbenefits are magnified when combined within an integratedlandscape of trees, shrubs, and flowers. A turf has numer-ous, important mental therapeutic benefits in addition tobeing attractive. These important dimensions that contributeto our quality of life are too often overlooked.

Improves Mental Health Via a Positive Therapeutic ImpactMost city dwellers attach considerable importance to

urban parks and forests with views of grass, trees, and openspace (Ulrich, 1986). Cities can be very dismal withoutgreen turfgrasses in parks, beside boulevards, and surround-ing homes, schools, businesses, and the workplace. Theresult can be a loss of productivity, more susceptibility toanxieties, and mental disease. For example, an outdoorview contributed to more rapid recovery for hospital pa-tients (Ulrich, 1984). Kaplan and Kaplan (1989) addressedthe role of nature, including parks, woodland areas, andlarge landscape sites in contributing to a person’s quality-of-life within urban areas. The role encompassed the op-portunity to use nature facilities in recreational activitiesas well as aesthetics, i.e., the appreciation of natural beauty.They also reported an increased sense of residential neigh-borhood satisfaction and of general well-being when therewas a nearby nature landscape. Finally, personal satisfac-tion improved if individuals were actually involved ingardening activities such as care of the landscape.

BEARD & GREEN: ROLE OF TURFGRASS 457

Contributes to Social Harmony and Improved ProductivityHow we use vegetations, such as tuffgrasses, in our sur-

roundings is basic to social stability and harmony. Ugli-ness is costly. A tufted landscape area surrounding a fac-tory or business is an asset in conveying a favorable wecare impression to employees and the general public. Theseemployees have lower levels of perceived job stress (Kaplanand Kaplan, 1989). Recent research demonstrates that vi-sual encounters with outdoor landscapes and vegetationcan be linked to health and in turn can be related to theeconomic benefits of visual quality (Ulrich, 1986). Theclean, cool, natural green of turfgrasses provides a pleas-ant environment in which to live, work, and play. Suchaesthetic values are of increasing importance to the hu-man spirit and the mental health of citizens because of rapid-paced lifestyles and increasing urbanization.

CONTEMPORARY ISSUESIn recent national headlines, there have been allegations

that turfgrass culture has a major role adversely affectingthe environment. It is important to address these allega-tions and to identify those that can be supported by soundscientific data in order to make the adjustments neededto eliminate or minimize any potential problem. At the sametime it is necessary to nullify those unfounded allegationsthat are based on speculative pseudo-scientific information.

Water ConservationConservation of water has become an issue, not only

in the arid regions of the USA, but also in many denselypopulated eastern urban areas that do not have adequatereservoir supplies as a contingency when extended droughtsoccur. Considering all our uses for water in the USA, theaverage person directly or indirectly uses between 6813and 7570 L d-1 (Rossillon, 1985). To put in perspective,this is more than applying 25 mm of water across a 929m-2 lawn each day for a year. Industry accounts for 43 %of our water use, agricultural irrigation for 47 %, and domes-tic use for cooking, bathing, sanitation, drinking, and land-scape irrigation for the remaining 10%. Decisions con-cerning the most effective programs to reduce water useshould consider these data. A primary concern that is sel-dom mentioned is the actual water leakage loss rate of mu-nicipal water distribution systems.

The original xeriscape group and others have activelypromoted the reduction ofturfgrass areas and their replace-ment with trees and shrubs as an urban water conserva-tion measure (Beard, 1993). Statements have been madein widely distributed nonscientific publications such as allturfgrasses are higher water users than trees and shrubs.There are no published scientific data available to supportthis allegation. In fact, the limited experimental data avail-able suggest the opposite position.

Very few of the many hundreds of tree and shrub spe-cies-cultivars have actually been quantitatively assessedfor their evapotranspiration rates. In contrast, a major por-tion of the turfgrass species-cultivars have been assessedfor their evapotranspiration rates. There are Cynodon cul-tivars with evapotranspiration rates of < 3 mm d-l, whose

evapotranspiration rates are 50% lower during dry-downperiods between irrigations or rain (Beard, 1990). If onecompares the evapotranspiration studies that are available,typically trees and shrubs are found to be higher water usersthan turfgrasses on a per unit land area basis (D. Devitt,1993, personal communication). This is based on the soundpremise that the evapotranspiration rate increases with leafarea when under a positive water balance (Johns et al.,1983; Kim and Beard, 1987). Note that the major grass-lands of the world are located in the semiarid regions,whereas the major forests of the world are located in thehigher rainfall areas.

Much confusion has arisen from the low water use land-scape plant lists from the xeriscape groups that have beenwidely distributed. The lists are based on the incorrect as-sumption that those plants capable of surviving in aridregions are low water users, when these plants typicallyare only drought resistant. When these species are placedin an urban landscape with drip or other forms of irriga-tion, many can become high water users. This occurs be-cause the physiological mechanisms controlling evapotran-spiration and drought resistance are distinctly different andcan not be directly correlated within a plant species or cul-tivar (Beard, 1989b).

For unirrigated landscape sites, detailed assessments havebeen conducted of drought resistance and dehydration avoid-ance for many turfgrass species and cultivars (Sifers et al.,1990). The results have shown that a number of turfgrassgenotypes possess superior dehydration avoidance and canremain green for 158 d in a high sand root zone withoutirrigation under the hot summer conditions in College Sta-tion, TX. Comparable detailed studies of dehydration avoid-ance and drought resistance among tree and shrub speciesare lacking.

When turfed areas are irrigated, the adjacent trees andshrubs also are being irrigated as a result of the multitudeof shallow tree and shrub roots that concentrate under theirrigated turf area (Whitcomb and Roberts, 1973). Thus,when a home owner is irrigating the lawn, most of the ad-jacent trees and shrubs also are being irrigated.

Numerous turfgrass species are capable of ceasinggrowth, entering dormancy, and turning brown during sum-mer drought stress, but they readily recover once rainfalloccurs (Sifers et al., 1990). Some people incorrectly as-sume that turfgrasses must be kept green throughout thesummer period to survive, and thus will irrigate. Manytrees drop their leaves during summer drought stress orduring the winter period when only brown bark remains.What then is wrong with a tan to golden-brown turf dur-ing summer droughts, if one chooses not to irrigate? If waterconservation is the goal, then a dormant turf uses littlewater whereas certain trees and shrubs may continue toremove water from lower soil depths.

Some advocates propose the replacement of turfgrasseswith a mulch cover and then planting landscape shrubswithin the mulched area as a water conservation measure.Some mulches do reduce evaporation of moisture from thesoil; however, the presence of a mulch increases the radi-ant energy load on the under side of deciduous shrubs andtrees, which have a majority of their stomata on the under

458 J. ENVIRON. QUAL., VOL. 23, MAY-JUNE 1994

sides of the leaves. This in turn substantially increases theevapotranspiration rate. For example, detailed studies re-vealed that crape myrtle (Lagerstroemia indica L.) grownon a mulched surface used 0.63 to 1.25 kg m-2 d-~ morewater than those located in a bare soil, and 0.83 to 1.09kg m-2 d-1 more water than crape myrtle located in a ber-mudagrass (Cynodon spp.) turf (Zajicek and Heilman,1991). Further, crape myrtle located on bare soil used 0.2kg m-2 d-1 more water than when growing in a bermuda-grass turf. Sensible heat and long wave radiation from themulched area increased plant temperatures and thus theleaf air vapor pressure deficit and associated transpirationrate.

In summary, there is no valid scientific basis for waterconservation strategies or legislation requiring extensiveuse of trees and shrubs in lieu of turfgrasses. Rather theproper strategy based on good science is the use of appro-priate low-water-use turfgrasses, trees, and shrubs formoderate-to-low irrigated landscapes and similarly to se-lect appropriate dehydration-avoidant and drought-resistantturfgrasses, trees, and shrubs for nonirrigated landscapeareas. The main cause for excessive landscape water usein most situations is the human factor. The waste of waterresults from improper irrigation practices and poor land-scape designs, rather than any one major group of land-scape plant materials.

What is the future? Great natural genetic diversity ex-ists among turfgrass genotypes in terms of both lowevapotranspiration rates and superior dehydration avoid-ance/drought resistance (Beard, 1989b). Applying appro-priate breeding techniques should achieve even lower wa-ter use rates among the currently used turfgrass speciesand other cultivars.

There is one caution as we strive for low evapotranspi-ration rates. One must avoid a narrow, single-issue em-phasis that ignores the potential effects of a loweredevapotranspiration rate on the total urban ecosystem. Ur-ban areas already suffer substantially higher temperaturesthan adjacent rural areas. Lowering the evapotranspirationrate through plant material selection and judicious irriga-tion will reduce transpirational cooling and increase heatloads on residences and buildings, thereby increasing energyrequirements for interior mechanical cooling. Dependingon the relative costs and availability of water vs. energy,it may be wise in certain urban areas not to strive for thelowest possible water-using landscapes. Here again, detailedscientific investigations will be required to develop appro-priate definitive strategies that take into consideration thetotal effects on all components within the urban ecosys-tem. Furth6rmore, turfgrass areas can be irrigated withreclaimed waste water. This practice has been successfullyevaluated for turfs (Anderson et al., 1981a,b; Dudeck etal., 1979; Hayes et al., 1990a,b). In this age of conserva-tion and recycling, irrigating turf and landscape sites withrecycled water has considerable merit.

Groundwater and Surface Water Quality PreservationTen percent of the turfgrass areas in the USA receive

a higher intensity of culture that involves fertilization. Ap-propriate questions must be addressed concerning the poten-

tial for these chemicals to enter groundwater by downwardleaching or surface water via runoff following intenseprecipitation.

First it has been noted previously that the perennial turf-grasses have an extensive, fibrous root system that tendsto dominate the upper 200 to 300 mm of the soil profile.This root system has an abundance of root hairs distributedalong the full length of the roots (Green et al., 1991). Sec-ond, the turfgrass ecosystem forms a very dense above-ground biomass that reduces runoff and thus allows timefor soil infiltration of water. Consequently, fertilization ofturfgrasses, according to established cultural strategies,presents a negligible potential for nutrient elements to passthrough the root zone into the groundwater or be trans-ported by runoff water into surface waters. This has beenconfirmed by a number of studies or reviews (Cohen etal., 1990; Gold et al., 1990; Gross et al., 1990; Mortonet al., 1988; Petrovic, 1990; Watschke and Mumma, 1989).Turfgrass root systems are highly efficient in the uptakeof applied nutrients. Comparatively less NO3 leaching oc-curs from turfgrasses than from row crop agriculture (Goldet al., 1990). In terms of the net effect of N fertilizer useand other factors contributing to water pollution from N,the USEPA estimated that only 1.2 % of community watersystem wells and 2.4 % of rural domestic wells nationwidecontain NO3 exceeding 10 mg L-~, which is the Maxi-mum Contaminant Level (U.S. Environmental ProtectionAgency, 1990, 1992).

Fertilizer application during a time of the year when theturfgrass is dormant or nongrowing is a potentially nega-tive situation. This is because the normally efficient nutri-ent uptake system of the roots is less operative (Petrovic,1990). Another potentially negative situation may occurduring the process of applying fertilizer. For example, ifmaterial gets on sidewalks, driveways, and streets, it maybe washed into the sewer system and eventually out intorivers and lakes. Obviously, the individual applying thefertilizer must be informed as to the need to apply all fer-tilizer to the target turf area only. In addition, fertilizerspreaders can be obtained with appropriate protective edg-ing devices to avoid throwing or dropping fertilizer ontonontarget areas. When fertilizer is applied, it is best fol-lowed by a light irrigation to move the particles into thesoil, thereby minimizing the potential of nutrients enter-ing lateral surface water flow. On the other hand, exces-sive irrigation may cause problems on course sandy soils.Excessive application rates of water-soluble N fertilizerson turfgrasses followed by over-watering on sandy soilscan cause NO3 contamination of groundwater (Brown etal., 1982; Snyder et al., 1984).

Trends in turfgrass fertilization have been toward lowerN application rates. The highest rates were used duringthe 1960s. The rates now used on professional turf areashave been reduced to one-third of those formerly used.In addition, the use of slow-release N carders has increased.In fact, the turfgrass industry has been a leader in the de-velopment of slow-release nutrient carriers, that offer in-creased environmental protection.

For the future, the breeding of turfgrasses with improvedtolerance to N stress should be emphasized. It also is crit-ical to educate the general public that the darkest green

BEARD & GREEN: ROLE OF TURFGRASS 459

turf, which many people strive for, is in feet not the healthi-est turf. A medium green turf with a moderate growth ratewill have the deepest root system with less thatching, re-duced disease and insect problems, and increased toler-ance to environmental stresses such as heat, drought, cold,and wear (Beard, 1973).

460 J, ENVIRON. QUAL., VOL. 23, MAY-JUNE 1994

Main MenuDisc 3 Table of ContentsHelpSearch