STABILIZED TURF FOR ATHLETIC FIELD

Abstract: A stabilized turf (10) particularly suitable for athletic fields includes a mat (18) interposed between upper (24) and lower (16) layers of growth media, the mat (18) having a horizontally disposed, substantially biodegradable backing (22) and generally upwardly extending non-biodegradable fibers (20) secured thereto, wherein the fibers (20) extend above the upper layer (24) of growth media. Natural grass plants (26) extend upwardly above the upper layer (24), with the roots extending down through the backing (22) and into the lower layer (16). The mat (18) stabilizes root growth, particularly during initial grow in. The substantial biodegradability of the backing (22) results in a loss of all or most of its horizontal structural integrity within a predetermined time period. The backing (22) may be treated with a decomposition agent to control the predetermined time period. Aerating helps to reorient and distribute the non-biodegradable fibers (22) within a subsurface vertical band (22a) greater in vertical dimension than the fibers (22) themselves. The stabilized turf (10) can also be topdressed. Thus, this turf (10) is adapted to accommodate both aeration and topdressing, two well-recognized and advocated turf management practices.

Description: STABILIZED TURF FOR ATHLETIC FIELD FIELD OF THE INVENTION This invention relates to a natural turf for athletic fields, and more particularly to a natural turf which is stabilized via fibers and a growth media such as sand BACKGROUND OF THE INVENTION Since Robey U S Patent No 4,023,506, it has been known that a flat layer of artificial fibers disposed below the ground can be used to enhance the stability of a natural turf located thereabove, by providing enhanced holding power for the root system of the natural grass Thereafter, U S Patent Nos 4,044,179 and 4,337,283, issued to Haas, Jr , disclosed a surface compnsing an artificial composite having a horizontal backing and upπght fibers, with sand filled m to provide lateral support for the fibers The primary purpose of the mventions disclosed in these Haas patents was to provide a stable, maintenance free surface for a vaπety of uses, such as a landing area for golf ball driving ranges, or even golf courses European patent application EP 0403 008 Al discloses a combination of natural grass and artificial fibers which extend upwardly from a horizontally disposed artificial backing to stabilize the natural grass The roots of the natural grass extend downwardly through the backing, the grass extends upwardly above the fibers, and the artificial fibers are supported laterally by a fill layer, such as sand U.S Patent Nos 5,489,317 and 5,586,408, issued to Bergevin, disclose and claim a structure similar to these pπor disclosures, but with the specific feature of the sand fill layer terminating at the same vertical level as the tops of the artificial fibers. This results in an above-ground playing surface which is entirely natural grass, because the fibers do not extend above the sand As indicated in the Bergevin patents and in the prosecution histones thereof, a relatively thick layer of sand is necessary to fill the fibers to their upper ends, to uniformly hold down the horizontal backing, and also to initiate natural plant growth at a vertical level which is very near to the top ends of the artificial fibers Such a substantial sand fill layer atop the horizontal layer and surrounding the artificial fibers forms a tight, uniformly compacted playing surface of natural grass However, because of the height of the sand, l e , to the tops of the fibers, the ground surface tends to become slick and hard once the natural turf begins to wear The reason for this problem requires a discussion of the importance of turf management practices It is a commonly understood turf management practice to apply peπodic layers of "topdressmg," usually sand, on a natural turf athletic surface, such as a ball field or golf course putting green or tee The peπodically applied layers of topdressmg provide stability and some degree of firmness to the ground, but more importantly they create and help maintain an environment conducive to healthy plant growth and rapid recovery from use Most well kept athletic surfaces for sport purposes are maintained in such a way that the grass clippings are collected, rather than simply allowed to disperse on the surface However, with natural grass plants, particularly under the intense maintenance regimes common for professional and collegiate facilities, even if clippings are collected there is still considerable production and decomposition of plant and root matter which can quickly build up and form a thatch layer This decomposing plant matter will eventually form a thick orgamc layer if not managed Agronomically, this orgamc layer has severe negative effects on dramage and movement of nutπents and pesticides into the root system From an athletic playabi ty standpomt, footing, surface speed, wear tolerance, ball roll and bounce, can be adversely affected The orgamc layer can result m a condition known m the industry as "black layer," whereby the orgamc matter becomes anaerobic due to poor drainage and a loss of capacity for gas exchange This condition can severely limit root growth and overall plant health It is well recognized that the peπodic application of "topdressmg," (l e , a layer of growth media, usually sand or sand based, with a thickness m the range of about 0 125-0 25 inches), helps to prevent the forming of an orgamc layer of this type Topdressing also ameliorates these harmful conditions if such a layer should begin to develop Topdressmg is typically applied 1-3 times per year The number of applications depends to some extent on the availability of the field The surface cannot be used immediately after topdressmg because topdressmg creates a loose layer on the playing surface, which adversely affects footing in the short term With respect to the turf disclosed m the Bergevm patents, the application of the first layer of topdressmg would immediately result in completely burying the upπght artificial fibers, so that the fibers would be dimmished m their ability to perform the mtended purpose of providing lateral stability for the turf Thus, the owner of the field must choose between the lesser of two evils, I e , completely burying the stabilizing fibers with the first application of topdressmg or risking the possibility that an adverse "black layer" may eventually form at the ground surface It is applicant's understanding that the wπtten turf management guidelines for the Bergevm turf product specifically emphasize that topdressmg should not be applied to the turf because it would negate the beneficial aspects of the product Stated another way, this product forces the owner of an athletic field to disregard the well known turf mamtenance practice of applying topdressmg Thus, the wear of the turf eventually causes shckness, but one of the normal turf management steps for ameliorating this condition is discouraged Another commonly recommended and practiced turf management strategy involves aerating a natural turf As with applying topdressmg, aeratmg is peπodically performed to decrease the build-up of orgamc matter on the surface, decrease compaction, keep the surface well drained and to maintain a vigorous natural turf canopy Typically, aeratmg is done with the same frequency or m conjunction with topdressmg, due to scheduling, although additional aerations without topdressing may provide further agronomic benefits But agam, the frequency depends on field availability and scheduling Aeratmg is usually done by inserting and removing into the turf hollow tines which are 0 375-0 75 mches m width In order to penetrate an entire thatch layer and the uppermost root zone area of the natural turf it is typically necessary to aerate to a depth of three mches or greater Unfortunately, with the vaπous pnor art natural grass/artificial fiber turfs descπbed above, it can become difficult to aerate down to the desired depth because of the structural density of the honzontal backing which holds the artificial fibers This is particularly true if aeratmg is done with hollow aeratmg tmes, which are preferred over solid pointed tmes Also, if aerated too many times, the backing would no longer be able to achieve its stated purpose of holding the fibers With the product constructed m accordance with the Bergevin patents, the management guidelines recognize this problem, and the turf management manual states that aeration should not be implemented Thus, while this structure initially provides increased stability for the natural turf surface, the honzontal backing hinders the performance of one of the most basic turf management practices, namely aeratmg with hollow tmes The athletic field owner is agam forced to disregard an advantageous turf management principle The honzontal backing can also act as a flow barπer between the layers of growth media located above and below This can adversely affect dramage or subimgation of the field This concern aπses particularly with respect to subsurface dramage, imgation and heating systems, and controls therefor, as disclosed in applicant's PCT Application Nos PCT/US95/11891 and PCT/US96/02207 In essence, the honzontal backmg and/or the orgamc surface layer can create a "perched water table" above the underlying growth media, a condition which is readily understood by those skilled in the art By creatmg a perched water table at the top of the root zone, downward movement of water and nutrients and upward movement of water by capillary action ("wicking") during sub-irπgation and the natural phenomenon of evapo- transpiration are sigmficantly inhibited In essence, the subsurface mateπals above the backmg are isolated from those below it Thus, the relatively recent developments in combining artificial fibers with natural grass plants have produced only limited advances in achieving a stabilized natural turf athletic field, particularly but not exclusively for natural turfs which are constructed of soils high in sand content The relatively slow market acceptance of these stabilized turfs to date indicates that there is room for improvement, pπmaπly from an agronomic standpoint A stabilized natural turf may be initially grown on a sod farm, on top of a plastic layer, until it is ready to be cut and then transported to the ultimate site where it is to be used Since the transporter will typically pay transportation costs which are directly proportional to the weight of the material being transported, it is desirable to minimize the overall weight of the components which make up the stabilized athletic turf grown at the sod farm Large layers of sand atop the honzontal backing are counter-productive m this regard SUMMARY OF THE INVENTION It is an object of the invention to improve upon the stability of a natural turf, particularly for athletic fields, while at the same time allowing the natural turf to be compatible with readily accepted turf management practices such as aeration and topdressmg It is another object of the invention to achieve a stable natural turf with minimal orgamc residue at the surface thereof and improved dramage capability It is still another object of the invention to achieve a stable natural turf which is more compatible with state of the art subsurface control systems for dramage and imgation It is still another object of the invention to achieve a stabilized natural turf wherem the stabilizing fibers do not become buned with the first application of topdressmg It is still another object of the invention to achieve a stabilized natural turf which is more efficiently harvested at a sod farm without waste, and then economically and convemently transported from the sod farm to another site, such as a stadium The present invention achieves the above-stated objects by utilizing, in conjunction with natural grass plants, an improved stabilizing mat having non-biodegradable fibers secured to a substantially biodegradable backmg When the backmg is disposed honzontally, the fibers are generally upnght A stabilizing upper layer of growth media, such as sand, supports the bottom portions of the generally upright fibers The upper portions of the fibers extend above the upper layer of growth media Thus, the backmg is only temporary, because it eventually goes away The substantial biodegradmg, l e , decomposing, of the backmg promotes dramage and subimgation, by eliminating any barner effects As the backmg substantially decomposes and the grass plants mature, aeration will cause the upnght fibers to vertically disperse somewhat, thereby increasmg the vertical dimension of the stabilized ground beyond the vertical dimension of the individual fibers This occurs as a result of the mteraction of the aeratmg tmes and the fibers Because the fibers initially extend well above the upper layer, the stabilized turf of this mvention can be topdressed without burymg the fibers on the first application of topdressmg, or even within the first few applications The biodegradmg of the backmg makes it easy for the hollow aeration tines to move vertically therethrough to allow aeration of the natural turf down to optimal depths, to promote healthy maturation of the natural grass plants Because the stabilized turf of this invention can be aerated and topdressed when needed, the turf has excellent drainage capabilities with minimal opportunity of "black layer" formation. Additionally, the invention contemplates treating the biodegradable backing so as to accelerate or decelerate the biodegrading process, as desired. Normally, an untreated homogenous woven backing of jute, for instance, will decompose completely within about one year or so, but it will lose its structural integrity much sooner than that, i.e., within several months. These time periods to some extent depend on the climate, i.e., temperature and wetness. The substantial decomposition time period should be determined and correlated to the time it takes for stable root growth for the natural grass plants. Stated another way, once a suitable grow in period is determined for the natural grass plants for the athletic field in question, the backing can be made and/or treated to substantially biodegrade within about that same time period. Once the backing has substantially decomposed, there is no longer any hindrance to normal drainage or even vacuum-assisted drainage, a type of drainage which is common with some of the more sophisticated state of the art control systems for athletic fields around the world. Also, the non-biodegradable fibers are able to reorient from generally upright positions and even to migrate vertically in response to aeration of the turf. As a result, the fibers become distributed over a stabilizing band which is greater in vertical dimension than the fibers themselves. Despite decomposition of the backing, the non-biodegradable fibers continue to provide stabilized support for the natural grass plants, because their performance of that function does not require the continued presence of the backing. Moreover, this vertical redistribution of the fibers niinimizes the possibility that subsequent applications of topdressing will eventually bury all of the fibers. According to a first prefened embodiment of the invention, the mat comprises non-biodegradable artificial fibers made of polypropylene secured in upright orientation to a homogenous honzontal backmg woven out of jute The prefened manner of securement is by tufting The backmg is "finished" on both sides by applymg a secondary coating thereto in liquid form, such as an acrylic latex suspended m a dispersing agent such as water The first finishing step occurs on the upper surface of the backmg before securement of the non-biodegradable fibers, while the second finishing step, 1 e , the backside application, occurs after fiber securement These secondary backings, as known m the carpet backmg industry, help to secure the fibers to this backmg In affect, they serve as temporary stabilizing agents They are temporary because they decompose several weeks after the mat has been underground To some extent, and dependmg on the matenal, the stabilizing agent may affect decomposition Additionally, a decomposition agent, specifically an anti-microbial such as zmc omadme, may also be mcluded in the liquid dispersion m an effective amount to slow the rate of degradation of the woven portion of the backmg If grown in at a field site, the mat, I e , the backing with the fibers secured generally upnght thereto, is laid upon a lower fill layer of growth media, such as sand, then an upper fill layer is applied thereto Preferably, the upper fill layer of growth media extends only about halfway to two thirds of the way up the fibers Thereafter, the upper fill layer is seeded, spngged or m some cases, covered with a sod which has been pressure washed, or any other form of turfing After the grow in penod, natural grass plants extend upwardly above the upward layer, alongside and eventually above the tops of the upnght fibers, with roots that extend downwardly through the backmg and mto the lower layer of growth media If the stabilized turf is grown at a remote site such as a sod farm, then there is no lower layer of sand used at the sod farm The mat is placed directly on a sheet of plastic Everything above remams the same Because the total matenal transported to the installation site mcludes only a relatively thin upper layer of growth media, this invention minimizes the vertical dimension and the overall weight of the turf to be transported Since the upnght fibers extend above the sand, the playmg surface compπses natural grass plants and upnght fibers, with the tops of the fibers generally located below the tops of the natural grass plants The location of the fibers above the top of the upper layer of growth media helps to maintain good footmg and minimum shckness of the playmg surface as the natural grass plants decompose The use of an upper fill layer which resides below the upper ends of the artificial fibers also allows the application of topdressmg to the natural turf surface Because the topdressmg layers usually have a vertical dimension of about 0 125 to 0 25 inches, and because some settling may occur after the application of topdressmg, none of the first few applications of topdressing will bury the fibers By allowing this turf management practice of penodically applying topdressing, this invention helps to eliminate or at least to sigmficantly reduce the undesired build up of homogenous orgamc residue at the surface Thus, the playmg surface of the stabilized turf does not become slick or slippery as the natural turf begms to wear Also, because the fibers still extend above the ground surface even after several applications of topdressmg, they continue to provide some degree of added surface friction to the ground This helps to assure contmued sure footmg on the playmg surface, and athletic play on the field can be resumed relatively soon after applying topdressmg Advantageously, the substantially biodegradable backmg absorbs and holds moisture and soluble nutnents, unlike the artificial non-biodegradable backmg matenals of pπor art stabilized turfs This moisture and nutnent holding capability is particularly beneficial in the turf establishment penod If desired, a fertilizing agent can also be incorporated mto the backmg, to further assist natural plant growth Also, once moisture-laden, the backmg becomes heavier and less likely to slide laterally relative to the underlymg layers Applicant believes this feature to be particularly true for a woven jute backing This also helps to minimize the possibility of differential shift of different sections of a turf athletic field The substantially biodegradable backmg also provides important advantages m both turf stability and economics for turf grown at a sod farm Specifically, the backmgs of adjacent sections can be secured, 1 e , sewn or stapled, together to provide a seamless turf This securement together of adjacent backmg sections is particularly advantageous pnor to transport from a turf farm to a site, particularly for end to end seams of rolled turf sections residmg m a single row As the turf is rolled up along the row, it may tend to separate or tear along the transverse seam Securement of the transverse end to end seams eliminates this problem As an alternative to the above-descnbed embodiment, the backmg can be supplemented with a synthetic matenal, such as polypropylene, and woven therein to provide reinforcement and added strength, and to slow the overall decomposition rate, so that substantial degradation is delayed This reinforcement may compnse the longitudinal or the transverse fibers of the backmg As yet another embodiment of the invention, the backmg may be reinforced with a layer of relatively lightweight mesh, having open cells or a relatively high degree of openness, thereby to form a non-biodegradable layer of the backmg It is believed that a composite backmg having a first "primary" layer of woven jute reinforced with a second "primary" layer of mesh would not necessanly need to be treated with a decomposition agent to decelerate substantial biodegradmg nor a stabihzmg agent to assist in temporarily holding the fibers Alternatively, at least one of the above-descnbed finishing applications could be omitted The reinforcement layer of mesh aids in laterally stabihzmg the turf after the biodegradable backmg has substantially decomposed Nevertheless, this mesh layer is of such a light weight and such an open cell construction as to permit vertical flow therethrough of water and nutnents and also to permit relatively easy aeration therethrough with hollow tmes Even if such an aerating tine should contact the mesh, the mesh is sufficiently thin so as to be frangible, or breakable under such a force With this embodiment, the non-degradable mesh layer and the biodegradable layer of the backmg, l e , the two "pπmary" backmgs, are simultaneously run through a tufting machine, which tufts the non-biodegradable fibers thereto Thus, with this construction the honzontal portion of the mat is substantially biodegradable, but not completely biodegradable These and other features of the mvention will be more readily understood m view of the following detailed descnption and the drawing BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a cross-sectional view of a stabilized natural turf m accordance with a first preferred embodiment of the invention Figure 2 is a cross-sectional view of the stabilized turf shown m Fig 1 , but after the backing 22 has substantially biodegraded and the stabilized turf has subsequently been aerated Figure 3 is a perspective view of a turf stabihzmg mat constructed in accordance with another preferred embodiment of the invention Figure 4 is a side view of the mat shown m Fig 3 Figure 5 is a plan view which schematically shows parallel rows of the stabilized turf of the invention during growth at a sod farm DETAILED DESCRIPTION OF THE DRAWING Figure 1 shows, in cross-section, a stabilized natural turf surface or stabilized turf 10 in accordance with a first preferred embodiment of the mvention In the context of this application, the terms stabilized natural turf surface and stabilized turf are used interchangeably When in place, the surface 10 mcludes a compacted subsurface 12, which is typically graded to a desired level with a desired degree of uniformity If desired, a barner 14 may reside on the subsurface 12, the barner 14 supporting one or more dramage components 15 for draining, subirπgating or heating the surface 10, as disclosed m applicant's PCT Patent Application Senal Nos PCT US95/11891 and PCT/US96/02207, which are expressly incorporated by reference herem m their entirety Alternatively, the natural turf surface 10 may be installed over sand or soil fields which may or may not have a prepared or compacted subsurface and installed dramage or imgation components Typically, a lower fill layer 16 of growth media, such as sand, soil or the like, resides above the subsurface 12, at a depth which vanes depending upon the application Typically, sand sports fields are constructed with about 6-12 mches of fill layer 16 A stabihzmg mat 18 rests on the lower layer 16 The mat 18 has generally upnght fibers 20 which extend generally upwardly from a honzontally disposed backmg 22 These fibers 20 are non- biodegradable and preferably have a length dimension above the backmg 22 which is in the range of about 1-2 mches, although the length could be lesser or greater, and a target denier m the range of about 7,600-10,000 Typically the fibers 20 are made from a tape which is fibπllated, and then spun mto a thread at a rate of 3/4 twist/ inch, although those skilled in the art readily understand that this is only one of several methods of manufacturing the non-biodegradable fibers 20 The fibers 20 may be made of synthetic matenal, such as polypropylene, polyethylene, nylon, polyester, or they could even be made of a natural material which is either inherently non- biodegradable or treated so as to be non-biodegradable The fibers 20 are secured to the backmg 22 preferably at a density of 11 5 stitches per 3 inch section and a stitch gauge of 3/8" to 5/8" This is preferably done by tuftmg the fibers 20 to the backmg 22 m a zig zag pattern The backmg 22 is substantially biodegradable, so that it will substantially decompose within a predetermined time penod Applicant has found that woven jute is a suitable material for the backmg 22 This is similar to what was previously done with respect to the manufacture of pnmary backmgs for carpet, before the standardized use of synthetic matenals for that purpose However, whereas the jute backmg of carpet represented a disadvantage, because the jute was susceptible to moisture retention if the carpet became wet, m this application the jute backmg 22 provides an agronomic advantage m that the moisture retention promotes growth of the natural grass plants 26 The natural jute backmg 22 preferably has a weave density of 15 threads by 13 threads per square inch, resultmg m a weight of approximately 9 oz per square yard and a sheet width in the range of 12-15 feet Such a backmg 22, as shown m Fig 1, is completely biodegradable over a sufficient penod of time However, as descπbed above, "complete" decomposition is not necessary, only decomposition such that the backmg 22 has little or no remaining honzontal structural integπty At this point, water flow is ummpeded and the fibers 20 are free to migrate vertically m response to contact with aerating tmes With the backmg 22 of jute as descπbed immediately above, it is believed that complete decomposition will occur within about 8-12 months However, the honzontal structural integrity will severely dimmish within as few as two months, particularly in warmer and wetter climates such as Florida Once that occurs, the backmg 22 has "substantially biodegraded " For the embodiment of Fig 1, the stabilized turf 10 can be aerated at any time it makes agronomic sense to do so It is not necessary for the backmg 22 to completely decompose in order for the aeratmg tines to pass therethrough and extend therebelow In the context of this application, the phrase "substantially biodegradable" refers to somethmg which is sufficiently biodegradable, within a given tune penod, to lose all or most of its honzontal structural integrity At that point, water and nutnents flow readily in a vertical direction through the space previously occupied by the backmg 22 With the backing 22 substantially biodegraded, there is no impeding effect at all on the aeratmg tmes, and these tmes cause vertical movement of the fibers 20 Other substantially biodegradable materials such as cotton, flax, hemp, cycel, burlap (sometimes called jute) or the like could also be used for the backmg 22 Even more recent man-made biodegradable matenals could also be used Applicant believes that such matenals cuπently exist and are used m the diaper makmg mdustry Accordmg to the first embodiment, the backing 22 is woven, with transversely and longitudmally extendmg strands of the same matenal, such as jute, so that the backmg 22 is homogenous The backmg 22 could also be stitched or knitted The fibers 20 are held to the backmg 22 by stitching, l e , tufting, preferably in a zig-zag pattern With this embodiment, two secondary backmgs help to temporanly hold the fibers 20 to the backmg 22 One secondary backing is applied pπor to tufting the fibers 20 to the jute backmg 22, and the second secondary backmg is applied thereafter Each of these secondary backmgs is applied by usmg a liquid-coating "finishing" technique recognized in the carpet-making mdustry The possible matenals for the secondary backmg mclude but are not limited to acrylic latex, starch, calcium carbonate and urea, applied m a dispersing agent and then heated to achieve a desired coating The amount of coatmg is usually quantified m dry weight per umt area Accordmg to the first embodiment, acrylic latex was used to produce a dry weight on the primary of about 1 5-4 0 ounces per square yard, with a dry weight of 3 ounces per square yard being preferable These secondary backmg matenals are all considered biodegradable Within a penod of weeks, they will decompose due to subsurface conditions Their primary function is to temporanly assist in holding the fibers 20 during handling and installation In essence, these matenals serve as agents for temporary securement of the fibers Yet, to some extent they may have an effect on biodegradation time, because they provide a protective coatmg for the backmg 22 Applicants believe that a coating of acrylic latex of this type will extend, or decelerate, substantial biodegradmg to about 5-8 months, but that agam depends on other factors Also, a decomposition agent, specifically zmc omadine, an anti-microbial, was included in the liquid dispersion in a range of about 0-10 parts per million to decelerate decomposition of the backmg 22 Applicant used zinc omadine 48% FPS, provided by Olm under product code CPE00306#, m a quantity of about 4 parts per million If desired, a natural grass growth agent such as a fertilizer or a pesticide may also be mcluded m the liquid dispersion Some of the above-identified stabihzmg agents also can serve as growth agents, such as calcium carbonate The decomposition agent is used because in most climates substantial biodegradmg occurs too soon, I e , within two to three months This usually will not be long enough for sufficient maturation of the root system Thus, for the woven jute backmg 22 according to the first embodiment, the treatment with a specific decomposition agent, such as zmc omadine, causes substantial biodegradmg to be delayed up to several years if desired The amount of the decomposition agent, the type of decomposition agent and the manner of application will depend upon the climate and wetness at the site, the soil conditions at the site, the density and matenal of the backmg 22, the other agents used on the backmg 22, and how soon the field needs to be ready for play, among other things There may be other instances where it is desirable to accelerate decomposition Agam, this will depend on the conditions identified above, such as the matenal and density of the backing 22, and the climate Other than treatmg the backmg 22, another possible method of accelerating the decomposition rate would be to inoculate, prior to placement of the mat 18, the backmg 22 or the fill layer 16 with biological agents which use cellulose from the jute backing 22 for energy The pnor art Bergevin patents disclose the general concept of a secondary backmg, i e , a coating such as latex, on a primary backmg which is non-biodegradable, wherem the secondary backmg helps to hold the artificial fibers to the backing for about 1-3 weeks but biodegrades thereafter However, this is the only disclosed backmg matenal which biodegrades The primary remams intact over tune In contrast, this mvention represents an improvement because the backmg 22, which m this case is of homogenous woven jute transversely (weft) and longitudmally (warp) extendmg biodegradable fibers, substantially biodegrades within a predetermined time period Once substantially biodegraded, the backing 22 is no hindrance to water or nutnent flow, 1 e , it does not create any barner effect, and it also promotes aeration The substantial biodegradation is selectively controlled, preferably via the decomposition agent, so that the honzontal structural integnty of the mat 18 remams intact during the important grow- in penod An upper fill layer 24 is located above the stabihzmg mat 18 Agam, as with the lower layer 16, the upper layer 24 of growth media may be of sand, or any other particulate matenal which promotes plant growth and provides stabilization and cushion, such as diatomaceous matenal, calcmed clay, crumbed rubber or other orgamc or inorganic additives The upper layer 24 resides within and sunounds the fibers 20 of the stabihzmg mat 18, to laterally support the fibers 20 in a generally upnght position and to provide stabilization for the turf surface 10 Preferably, the upper layer 24 extends about halfway to two-thirds of the way up the vertical lengths of the fibers 20, to allow sufficient room for initial application of topdressmg, and to reduce the overall weight, which is particularly advantageous m the case of sod farm production In the first preferred embodiment, the layer 24 preferably resides at least about 0 50" below the tops of the fibers 20, with the fibers 20 extending about 1 50" above the backmg 22 Natural grass plants 26 extend upwardly through the upper layer, with the tops 28 of the grass plants 26 extending above the fibers 20 The natural plants 26 also extend downwardly through the backmg 22 and mto the lower layer 16 Thus, the tops 28 of the grass plants 26 are above the tops of the fibers 20, and the crowns of the grass plants 26 reside within the upper layer 24, while the roots 30 extend through the backing 22 and termmate m the lower layer 16 The playing surface, l e , the matenal residing above the upper layer 24 of growth media, compnses both natural grass 26 and non-biodegradable fibers 20 The upper layer 24 and/or the lower layer 16 may be inoculated with microbes to establish a beneficial population of micro-organisms, since sand is typically stenle, pπor to sodding the upper layer 24 with grass plants 26 In a sense, these microbes could be considered a decomposition agent and a growth agent, because depending on their composition and distnbution, they could accelerate biodegradmg of the backmg 22 and also promote growth of the grass 26 To that extent, these effects need to be taken mto account in determining the time penod for substantial biodegradmg The grass plants 26 can be generated by seeding, spπggmg or even laymg down sod which has been jet washed to remove undesired soil and particulate It is anticipated that exposmg approximately the upper portions of the fibers 20 above the upper layer 24 will result m the "ballooning" of the tips of the fibers 20 Ballooning, as will be understood by one of ordinary skill m the art, results when the exposed tips of the fibers 20 fray and or fluff, which is beneficial to the turf system 10 because it will promote fibπllation and movement of the fibers 20 throughout the depth of the turf 10 in response to normal wear, aeration and or other standard turf mamtenance procedures It also provides a less slick playmg surface m the event natural turf is worn away Fig 2 shows the backmg 22 after substantial biodegradation has occuπed, and after topdressmg 24a has been applied In contrast to Fig 1, where the fibers 22 occupied only a vertical band which conesponded to upper layer 24, Fig 2 shows the fibers 20 vertically distπbuted within a vertical band 20a This band 20a is greater m vertical dimension than the fibers 20 themselves, because the fibers 20 have migrated vertically This migration occurs m response to movement of the aerating tines downwardly through the turf 10 during aeration This migration effectively produces this subsurface stabihzmg band 20a Thus, aeratmg of the turf 10 not only produces the commonly known agronomic benefits, it also assures contmued stabilization of the turf 10 long after installation, by contmumg to redistπbute the fibers 20 These advantages are possible only because the backmg 22 is substantially biodegradable within a predetermined time penod As noted above, the backing 22 may be woven, knitted or tufted The backmg 22 may also be reinforced for added strength for certain applications The reinforcement may be done by mcreasmg the thickness of the transverse and or longitudinal fibers, or by adding a synthetic strand, fiber or filament such a polypropylene These added strands could be laced into the weave of the backmg 22 or perhaps substituted for the transverse or the longitudinal fibers However, it is important that the backmg 22, even if it is a composite of this type and not homogenous, be substantially biodegradable Fig 3 shows a second prefeπed embodiment of this invention A turf 10 made accordmg to this embodiment would be identical to the turf 10 of Figs 1-2 except that the mat 118 is different More specifically, mat 118 includes a backmg 122 with a non-biodegradable open cell web 122a for reinforcement Stated another way, the backmg 122 is a composite which has two "primary" backmgs, or layers The first is a completely biodegradable layer 122b, of a matenal such as jute, and the second is a non-biodegradable layer 122a, such as a synthetic web Preferably, the web 122a is made of non-biodegradable polypropylene, to provide some minimal ongoing lateral structural integπty for the mat 118 However, the cells of the web 122a are sufficiently open and the longitudinal and transverse strands are sufficiently thin that the composite backmg 122 is still considered substantially biodegradable This is because there is sufficient openness to allow passage therethrough of water and nutnents and there is no barner effect created Also, the fibers 120 are relatively free to migrate m response to contact with aerating tines The individual strands of the web 122a will break if they happen to be contacted by hollow tmes during aeration For the mat 118, the composite backmg 122 mcluded a layer 122a made from polypropylene, with a strand count of 5 x 5 and a weight of 1 728 ounces per yard This layer 122a is commercially available from Conwed Plastics of Roseville, Minnesota, and identified as Product No R07821-002 The "strand count" refers to the number of "cells" per square mch A stand count of 5 x 5 refers to a mesh with 25 cells per square mch, m 5 rows and 5 columns Applicant believes that a strand count as low as 2 x 2 would also work, but that a strand count with larger openmgs would possibly cause problems with aeration tmes due to thickness of matenal To make a mat 118 which has a composite backmg 122 of a first layer 122b of homogenous woven biodegradable matenal and a second layer 122a of non-biodegradable mesh, the layers 122a and 122b are simultaneously run through a tufting machine to secure the non- biodegradable fibers 120 thereto Thus, other than the tufted fibers 120, there is nothing holding the layers 122a and 122b together The fibers 120 are tufted m a predetermined density, by stitching with a 5/8" gauge, in an acute zig zag pattern to maximize the amount of matenal on the underside of the backmg 122 This manner of fiber securement provides additional initial horizontal strength for the mat 118 and mcreases the ability of the turf 10 to vertically redistnbute the fibers 120 through the rootzone dunng aeration (Fig 3) With this reinforcement layer 122a, it may not be necessary to treat the backmg 122 with a decomposition or a stabihzmg agent because of the added lateral stability provided by the mesh Thus, the need to apply one or more secondary coatmgs in finishing steps may be eliminated On the other hand, it may be desirable to apply one "finishing" treatment on the backside of the mat 118 to mclude one or more of the following agents a decomposition agent, a stabihzmg agent and a growth agent With either mat 18 or mat 118, the benefits of the invention result from the ability to practice standard agronomic mamtenance prmciples for the turf 10, I e , aerating and topdressing, whenever desired after installation As noted previously, prior stabilized turfs either did not recommend these practices, or resulted in other disadvantages if these turf mamtenance practices were used If the stabilized turf 10 is initially grown at a remote site such as a sod farm, m preferably 12 to 15 feet wide sections of any desired length, the mat 18 (or 118) is rolled out on a synthetic barner of some sort, such as plastic The plastic barner inhibits root growth mto the ground below, thereby eliminating the need to cut the turf 10 at the roots prior to transport The structure of the turf 10 thereabove remams the same as shown in Fig 1 except that the grass 26 has not yet grown in and there is no lower layer 16 That is, the upper layer 24 of growth media is filled in around the fibers 20 (or 120), preferably leavmg at least about 0 5 mches of the fibers 20 extendmg thereabove The upper layer 24 is then seeded, spπgged or planted with power washed sod, or other known turfing method Once a sufficient growing time period has passed and there has been sufficient growth of the roots 30 into and through the backmg 22 (or 122), the natural turf 10 is ready to be cut longitudmally and rolled m desired lengths for transport to a site for use, such as an athletic stadium In Fig 5, the lmes 34 show longitudinal seams extendmg along adjacent rows ofsections ofturf 10 Reference lmes 36 show transverse seams Reference numerals lOa-lOf show the locations of individual sections of turf 10 Sections 10a and 10b are m one row, while sections 10c and lOd and lOe and 1 Of are m the next two rows, respectively Sections 10c and lOd have been rolled up, while the other sections are shown m place The individual sections of the turf 10 may be jomed to adjacent sections by securement of the edges of the coπesponding backings 22 (or 122) This can be done by sewing with a fabπc thread such as jute or a synthetic thread such as polypropylene It can also be done by stapling the backmgs 22 together Thin metal staples typically degrade by rusting within about 8 months Securmg the adjacent sections of turf 10 is beneficial whether the turf 10 is initially installed on-site or grown at a sod farm For turf 10 grown at a sod farm, it is particularly advantageous along the transverse, or butt jomts, of sections residing m a single row This is because rolling of the turf 10 for transport to a remote site generates a stretchmg force on the turf 10 This stretchmg force can cause separation of the turf 10, particularly along the transverse seams of adjacent sections, for instance along the seam between rolled sections 10c and lOd (Fig 5) Securing the transverse edges together eliminates the nsk of the turf 10 pulling apart during rolling Securement of adjacent turf sections together also helps at the field site, whether grown m initially or moved thereto from a sod farm With some prior turfs, including those with artificial backmgs, it was sometimes necessary to provide a reinforced foundation underlying ad j oining turf sections, to minimize differential settling or vertical shifting of one section relative to an adjacent section On the other hand, when the stabihzed turf 10 of this invention is installed on-site at the athletic facility, the stability of the turf 10 is sigmficantly increased because the secured together adjacent sections neither shift relative to one another nor become exposed The following examples refer to grow-in installations EXAMPLE I According to the first preferred embodiment of this mvention, a laser graded surface is covered with a stabihzed synthetic, sand-filled mat 18 constructed of 100% polypropylene fibers 20 (10,000 demer, 75 twist, approx 970g/m 2 ), stitched (tufted) m a chevron pattern mto a woven backmg 22 made of natural and biodegradable fibers The fiber mat 22 has a plain weave, with a fiber count of 15 x 13 count, a face weight of approx 340g/m 2 and is manufactured m 4 6m widths It is treated with a stabilizing agent and a decomposition agent, as descnbed previously, to extend the time required for biodegradation once placed m the field and to help secure the fibers 20, as descπbed previously The backmg 22 mcludmg this coatmg has a minimum weight of 408 g/m 2 The polypropylene fibers 20 tufted mto the mat 18 extend 38mm above the surface in a vertical onentation The manufactured mat 18 has a minimum total weight of 1 375kg/m 2 The mat 18 is rolled onto a laser graded sand surface, adjacent rolls abutted and the seams secured together to create a contmuous, seamless "carpet" across the entire playmg surface Once installed, the vertically stitched fibers 22 are filled to approximately 65% of their height (I e , slightly less than 25 mm) with the same specified sand as was used to create the rootzone The sand is applied m lifts and broomed into the mat to assure the synthetic fibers 20 remain upnght After all the sand has been spread the surface is planted with top quality, nursery grown hybnd Bermudagrass spngs, such as GN-1 , or similar The grow-in penod begms immediately following completion of the spnggmg process and is expected to last about eight weeks, and possibly longer EXAMPLE II This example is identical to Example I, except that mat 118 is used mstead of mat 18 This means that the backmg 122 includes two pnmanes, one 122b bemg biodegradable jute and the other 122a bemg a polypropylene mesh with a strand count of 5 x 5 The fibers 120 are tufted thereto Also, the treatment for the backmg 118 may differ, because no decomposition agent nor any stabilizing agent for the fibers 120 may be necessary, or at least only one side may need to be coated The stabilized natural turf 10 of this invention provides a stable playmg surface with a stable base and a completely natural turf look and feel, with the playmg surface comprising natural grass 26 and, to some extent, the upper ends of the fibers 20 (or 120) Eventually, the fibers 20 become buned due to topdressmg applications But by then the backmg 22 (or 122) has substantially biodegraded By then the fibers 20 (or 120) have also vertically migrated and reonented These results are produced because common turf management practices, namely topdressing and aeration, can be repeatedly used with this stabilized turf 10 These practices can be used after the initial grow m pnmaπly because of the relative height of the upper layer 24 with respect to the fibers 20 and because the backing 22 is substantially biodegradable. While prefeπed embodiments of the invention have been described, it will be readily understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention. For instance, there may well be other materials for making the backing 22 of the mat 18 substantially biodegradable. Moreover, for such other materials, the weave density or the fiber thickness may be subject to variation. Moreover, depending upon the growth environment and the agronomic conditions, the relative thickness of the lower layer, and the upper layer relative to the non-biodegradable fibers may change. These factors may also depend upon the type of grass being used. We claim:

Claims: 1 A stabilized turf compnsing a mat including a substantially biodegradable backmg oriented horizontally and a plurahty of non-biodegradable fibers held by the backmg and extendmg generally upnght therefrom, an upper layer of growth media located above the mat, natural grass plants having roots and crowns, the roots extendmg downwardly through the upper layer and through the backmg and the crowns located above the backing, the tops of the grass plants and the fibers extendmg above the upper layer, whereby the backmg substantially biodegrades within a predetermined time penod, thereby to promote vertical migration of the fibers m response to aeration 2 The stabilized turf of claim 1 wherem the substantially biodegradable backmg includes a woven primary layer 3 The stabilized turf of any of the previous claims wherem the backmg compnses one of the following matenals, jute, burlap, hemp, flax, cycel 4 The stabilized turf of any one of the previous claims wherem the substantially biodegradable backing mcludes a reinforcmg primary layer of non-biodegradable mesh 5 The stabilized turf of any one of the previous claims wherem the artificial fibers have a length m the range of about 1 25" to about 1 75," and or a width m the range of about 7,500 to about 10,000 demer 6 The stabilized turf of claim 1 wherein the backing is woven, with a density of about 15x13 threads per square inch and a weight of about 9 oz per square yard 7 The stabilized turf of any one of the previous claims wherem the fibers are tufted to the backmg 8 The stabilized turf of any one of the previous claims wherem the backmg or the growth media mcludes a decomposition agent to control the predetermined tune penod for substantial biodegradmg 9 The stabilized turf of any one of the previous claims wherem the backmg mcludes at least one secondary layer, with at least one of the following agents a stabihzmg agent, a decomposition agent and a growth agent 10 A method of installing the stabilized turf of any one of the previous claims, compnsmg cutting and removing the stabilized turf from a growth site and planting it at an installation site such as a stadium 11 The stabilized turf of any one of claims 1 -9 wherem the stabilized turf mcludes a plurahty of like sections of the stabilized turf aπanged end to end m rows, the backmgs of adjacent sections secured together 12 The stabilized turf of claim 11 wherem the sections are secured together by sewing or by stapling 13 A method of maintaining a stabilized turf accordmg to any one of claims 1 -9 compnsmg aerating the stabilized turf by movmg tmes downwardly beyond the level of the backmg after the backing has substantially biodegraded, thereby causmg at least some of the fibers to vertically disperse within the upper layer of growth media, and topdressmg the stabilized turf 14 A stabilizer for stabihzmg a natural turf compnsmg a backmg which is substantially biodegradable, the backmg bemg of sufficient openness that when onented honzontally beneath natural grass plants it permits downward growth therethrough of the roots of the natural grass plants, the composition of the backmg being selectively controlled to cause substantial biodegrading within a predetermined time period; and non-biodegradable fibers secured to the backing and oriented substantially upright when the backing is disposed horizontally, the fibers adapted to provide stabilization for natural grass plants so that the roots thereof can extend downwardly through the backing. 15. The stabilizer of claim 14 wherein the substantially biodegradable backing has at least one primary layer which is woven and of homogenous composition. 16. The stabilizer of claim 14 or 15 wherein the backing is made of one of the following materials: jute, burlap, hemp, flax, cycel. 17. The stabilizer of any of claims 14-16 wherein the backing includes at least one secondary layer with at least one of the following agents: a stabilizing agent, a decomposition agent and a growth agent. 18. The stabilizer of any of claims 14-17 wherein the non-biodegradable fibers are tufted to the backing. 19. The stabilizer of any of claims 14-18 wherein the non-biodegradable fibers are artificial. 20. The stabilizer of any of claims 14-19 wherein the backing includes a reinforcement of non-biodegradable material. 21. The stabilizer of claim 20 wherein the reinforcement comprises a primary layer of mesh. 22. The stabilizer of claim 21 wherein the non-biodegradable fibers are tufted to the non-biodegradable primary layer and to the rest of the backing. 23. A stabilized natural turf comprising: (a) a bottom support surface; (b) a lower layer of growth media located above the support surface; (c) a mat supported on the lower layer, the mat having a substantially biodegradable backing oriented horizontally and non-biodegradable fibers extending generally upwardly therefrom, the backing including a primary and a secondary, the secondary including a stabilizing agent to assist in holding the fibers to the backing and a decomposition agent to promote substantial biodegradation of the backing within a predetermined time period; (d) an upper layer of growth media located above the mat; and (e) natural grass plants having roots and crowns, the roots extending downwardly through the upper layer and through the backing and the crowns located above the backing, the tops of the grass plants and the fibers extending above the upper layer. 24. The stabilized turf of claim 23 wherein the primary backing comprises a homogenous woven material, and the fibers are tufted to the backing. 25. The stabilized turf of claim 23 wherein the decomposition agent decelerates biodegrading of the backing. 26. A stabilized natural turf comprising: (a) a bottom support surface; (b) a lower layer of growth media located above the support surface; (c) a mat supported on the lower layer, the mat having a substantially biodegradable backing oriented horizontally and non-biodegradable fibers extending generally upwardly therefrom, the backing including a first substantially biodegradable primary and a second non-biodegradable primary, the second primary being an open cell mesh, the first primary being selected to have a composition, weight and density to substantially biodegrade within a predetermined time period; (d) an upper layer of growth media located above the mat; and (e) natural grass plants having roots and crowns, the roots extending downwardly through the upper layer and through the backing and the crowns located above the backing, the tops of the grass plants and the fibers extending above the upper layer. 27. The stabilized turf of claim 26 wherein the fibers are tufted to the first and second primaries. 28. The stabilized turf of claim 26 wherein the backing further includes a secondary layer with at least one of the following: a decomposition agent, a fiber stabilizing agent and a growth agent. AMENDED CLAIMS [received by the International Bureau on 12 November 1998 (12.11.98); original claims 1-28 replaced by amended claims 1-23 (4 pages)] 1. A stabilized turf comprising: a compacted subsoil; a first layer of growth media located above the subsoil; a mat supported on the first layer, the mat including a first primary backing which is biodegradable and oriented horizontally and a plurality of non- biodegradable fibers held by the first primary backing and extending generally upright therefrom; an upper layer of growth media located above the mat; natural grass plants having roots and crowns, the roots extending downwardly through the upper layer and the first primary backing and into the first layer, and the crowns located above the first primary backing, the tops of the grass plants and the fibers extending above the upper layer; whereby the first primary backing substantially biodegrades within a predetermined time period, thereby to facilitate aeration down to the first layer and to promote vertical migration of the fibers, and the first primary backing or the growth media includes a decomposition agent to control the predetermined time period for substantial biodegrading of the first primary backing. 2. The stabilized turf of claim 1 wherein the first primary backing is woven. 3. The stabilized turf of any of the previous claims wherein the primary backing comprises one of the following materials, jute, burlap, hemp, flax, sisal. 4. The stabilized turf of any one of the previous claims wherein the mat further includes a second reinforcing primary backing of non-biodegradable mesh. 5. The stabilized turf of any one of the previous claims wherein the artificial fibers have a length in the range of about 1.25" to about 1.75," and/or a width in the range of about 7,500 to about 10,000 denier. 6 The stabilized turf of claim 2 wherem the first primary backmg is woven and has a density of about 15x13 threads per square mch and a weight of about 9 oz per square yard 7 The stabilized turf of any one of the previous claims wherem the fibers are tufted to the first primary backmg 8 The stabihzed turf of any one of the previous claims wherem the first primary backmg is of homogenous composition 9 The stabilized turf of any one of the previous claims wherem the first primary backmg mcludes at least one secondary layer, with at least one of the following agents a stabihzmg agent, a decomposition agent and a growth agent 10 The stabilized turf of claim 4 wherem the fibers are secured to both of the primary backmgs 11 The stabihzed turf of any one of the previous claims 1 -9 wherem the stabilized turf mcludes a plurahty of like sections of the stabilized turf aπanged end to end in rows, the backmgs of adjacent sections secured together, as by sewing or by stapling 12 The stabilized turf of claim 10 wherem the fibers are secured by tufting 13 A method of maintaining a stabilized turf, compnsmg aeratmg the stabilized turf, wherem the turf mcludes a compacted subsoil, a first layer of growth media located above the subsoil, a mat supported on the first layer, the mat mcludmg a biodegradable primary backmg onented hoπzontally and a plurality of non-biodegradable fibers held by the primary backmg, an upper layer of growth media located above the mat, and natural grass plants having roots and crowns, the roots extendmg downwardly through the upper layer and below the backmg and mto the first layer, and the crowns located above the primary backmg, the tops of the grass plants extending above the upper layer, the aeratmg occurring by moving tmes downwardly below the level of the first primary backmg after the first primary backmg has begun to biodegrade, thereby causmg at least some of the fibers to vertically disperse and reonent within the lower and upper layers of growth media, and topdressmg the stabilized turf 14 A stabilizer for stabihzmg a natural turf, made accordmg to the process compnsmg creating a first primary backmg which is biodegradable, the first primary backmg bemg of sufficient openness that when onented hoπzontally beneath natural grass plants it permits downward growth therethrough of the roots of the natural grass plants, applymg to the first primary backmg a secondary layer which mcludes a stabilizing agent and a decomposition agent to cause substantial biodegradmg within a predetermined tune penod, and secuπng non-biodegradable fibers to the first primary backmg to be onented substantially upnght when the first primary backmg is disposed honzontally, the fibers adapted to provide stabilization for the roots and crowns of natural grass plants 15 The stabilizer of claim 14 wherem the first primary backmg is woven and of homogenous composition 16 The stabilizer of claim 14 or 15 wherem the first primary backmg is made of one of the following mateπals jute, burlap, hemp, flax, sisal 18 The stabilizer of any of claims 14-16 wherem the non-biodegradable fibers are tufted to the backmg 19 The stabilizer of any of claims 14-16, 18 wherem the non-biodegradable fibers are artificial 21 The stabilizer of claim 18 and further compnsmg a secondary primary layer of reinforcing mesh 22. The stabilizer of claim 19 wherein the non-biodegradable fibers are tufted to both primary backings. 23. A method of maintaining a stabilized turf comprising: growing natural grass plants having roots and crowns, the roots extending downwardly through an upper layer of growth media, through a biodegradable primary backing of a stabilizing mat and further downwardly into a lower layer of growth media located below the primary backing, the primary backing being oriented horizontally and having fibers secured thereto, the crowns of the natural grass plants located above the primary backing within the upper layer, the tops of the grass plants and the fibers extending above the primary backing; and aerating the stabilized turf by moving tines downwardly below the level of the first primary backing and into the lower layer, thereby causing at least some of the fibers to vertically disperse and reorient within the lower and upper layers of growth media. STATEMENT UNDER ARTICLE 19 Amended claim 1 now expressly includes reference to the compacted subsoil and the first layer of growth media located above the subsoil. It refers to a biodegradable primary backing with fibers held thereto, and the primary backing also includes a decomposition agent so that the primary backing substantially biodegrades within a predetermined time period. This feature facilitates aeration of the natural turf down to the depth of the first layer of growth media and promotes vertical migration of the fibers. Amended claim 1 now includes the features of original claim 8, and therefore original claim 8 has been cancelled. Claims 2, 3, 4, 6 and 7 have been amended for clarification, primarily to conform with amended claim 1 by now referring to the "primary" backing and also to correct the spelling of "sisal" in claim 3. Added claim 8 recites the "homogenous" feature (for the primary backing) which was originally in claim 24. Added claims 10 and 12 relate to details of the embodiment recited more broadly in amended claim 4. Amended claims 10 and 12 relate to the subject matter of cancelled claim 27. Original claim 10 was deemed unnecessary, and original claim 12 has been combined with claim 11, enabling original claims 10 and 12 to be cancelled. Amended claim 13 combines the features of original claim 1 and original claim 13, but amended claim 13 is now presented in independent form. It clarifies that the tines move downwardly below the backing, to cause vertical dispersion of the fibers within the lower and the upper layers of growth media. Amended claim 14 is now a product by process claim. The first step involves creating a first primary backing which is biodegradable and has sufficient openness to be root permeable. The second step involves applying a secondary layer which includes a stabilizing agent and a decomposition agent to cause substantial biodegrading within a predetermined time period, as referred to in original claim 17. The third step involves securing fibers to the first primary backing. Amended claim 14 incorporates the subject matter of original claims 14 and 17, but in product by process form. Claims 15 and 16 refer to a primary backing. Claims 18 and 19 omit reference to cancelled claim 17. Claims 21 and 22 were amended for clarity and to conform to amended claim 14. Original claim 20 has been cancelled, as have original claims 23-28. The amendment to claim 1 and the addition of new claims 8, 10 and 12 enabled original claims 23-29 to be cancelled. Added claim 23 relates to a method of maintaining a stabilized turf, which involves growing a stabilized turf of the type recited in claim 1 and aerating the turf to a depth below the primary backing. The application now includes four independent claims (claims 1, 13, 14, and 23) and 21 claims in total. The numbered claims skip numbers 17 and 20. The amended claims emphasize the features regarded as patentable. Amended independent claims 1 and 14 emphasize a first primary backing which is biodegradable to facilitate aeration and a decomposition agent to control the predetermined time period for biodegrading. In essence, the biodegradable primary backing is only temporary. It eventually goes away so that the fibers can migrate vertically and reorient, in response to aeration. Proper turf management plays an important role in maintaining a natural grass field, whether the field is all natural turf or a stabilized turf which combines natural grass and artificial fibers. Claims 13 and 23 emphasize turf management practices by expressly including reference to "aerating." The stabilized turf claimed in the application accommodates the important turf management principals of aeration and top dressing, because the first primary backing substantially biodegrades within a predetermined time period to permit passage therethrough of downwardly moving aeration tines. Because the first primary backing substantially biodegrades, the stabilizing mat of this invention does not create an agronomic barrier between the upper and lower layers of growth media. Because the fibers migrate vertically and reorient in response to aeration, the invention produces a root stabilization zone of vertical dimension greater than the initial upper layer of growth media. These features and advantages are described in more detail in the specification. The amendments do not go beyond the disclosure of the international application as filed.

Inventors: HEINLEIN MARK A, LINVILLE STEVE, MOTZ JOSEPH E, HEINLEIN, MARK, A., LINVILLE, STEVE, MOTZ, JOSEPH, E.
Applicants: HEINLEIN MARK A, LINVILLE STEVE, MOTZ GROUP, MOTZ JOSEPH E, HEINLEIN, MARK, A., LINVILLE, STEVE, MOTZ, JOSEPH, E., THE MOTZ GROUP
Application year: 1998
Main classification: E01C13
IPC codes: A01G1, E01C13