TURF BASED SPORTS GROUNDS

Abstract

A grass sports ground is produced by mixing man-made vitreous fibres into soil having relatively high loam levels at a rate in the range 0.5 to 50 parts by weight per 100 parts soil (dry weight), preferably in the presence of moisture to separate the fibres and distribute them among soil particles, and then growing grass. The soil/fibre mixture has desirable moisture management properties as well as good mechanical characteristics providing extended use characteristics even in cold, wet or hot and dry conditions.

Claims

1. A plant growth medium comprising soil that comprises 1 to 10% loam wherein loam is the fraction of soil that passes through a sieve with 0.063 mm openings, at least 0.5% organic matter and has particulate size distribution having a M50 value in the range 100-500 m and having at least 95% by weight particle size less than 4 mm, further comprising man-made vitreous fibres (MMVF), wherein the man-made vitreous fibres are present in an amount of from 0.5 to 50 parts by weight per 100 parts soil, on a dry matter basis, and wherein the fibres are present in loose form distributed in the soil particulate matter.

2. A plant growth medium according to claim 1, wherein the MMVF are present in an amount in the range 1 to 30 parts per 100 parts by weight soil, preferably 2 to 20 parts, more preferably 4-10 parts, per 100 parts soil.

3. A plant growth medium according to claim 1, having a moisture content in the range 5 to 50 parts by weight per 100 parts soil dry matter, preferably 10 to 25 parts by weight

4. A plant growth medium according to claim 1, wherein the MMVF are stone fibres, preferably having content of oxides as wt % as follows: TABLE-US-00009 SiO.sub.2 35 to 50, preferably 38 to 48 Al.sub.2O.sub.3 12 to 30, preferably 15 to 28 TiO.sub.2 up to 2 Fe.sub.2O.sub.3 2 to 12 CaO 5 to 30, preferably 5 to 18 MgO up to 15, preferably 1 to 8 Na.sub.2O 0 to 15 K.sub.2O 0 to 15 P.sub.2O.sub.5 up to 3 MnO up to 3 B.sub.2O.sub.3 up to 3.

5. A plant growth medium according to claim 1, wherein the fibres have length at least 2000 microns, preferably at least 2500 microns, more preferably at least 3000 microns, most preferably at least 3500 microns.

6. A plant growth medium according to claim 1, wherein the diameter of the fibres is in the range 3 to 15 m.

7. A plant growth medium according to claim 1, in the form of a layer 10 to 30 cm thick supported on a sub-layer of ground preferably provided with water-drainage means.

8. A plant growth medium according to claim 1, further having plants growing thereon.

9. A plant growth medium according to claim 8, wherein the plants are grass plants.

10. A plant growth medium according to claim 8, wherein the plant growth medium and plants cover a sports ground, preferably selected from a soccer pitch, a baseball pitch, a field hockey pitch, a rugby pitch, a polo pitch, a horseracing track, a golf course, tennis court, equestrian arena, or a multi-use area

11. A method of producing a stratified field for growth of plants comprising a substratum and a top layer, wherein the substratum comprises water drainage means and the top layer comprises a mixture of soil and MMVF, comprising the steps: providing a layer of soil, comprising 1-10% by weight loam, wherein loam is the fraction of soil that passes through a sieve with 0.063 mm openings, at least 0.5% by weight organic matter, and having a M50 value in the range 100-500 m and at least 95% by weight particle size less than 4 mm, on said substratum at a thickness in the range 5-30 cm, controlling the moisture level of the soil to a level in the range 5 to 50%, applying flocks of entangled MMVF to the layer of soil, optionally application of water to the MMVF, comprising compressing the flocks of MMVF, and, mixing the compressed MMVF and layer of soil by application of energy so as to separate the entangled fibres in the flocks and distribute the separated fibres among soil particles.

12. A method according to claim 11 wherein the fibres in the product are loose, preferably wherein the product is a plant growth medium according to claim 1.

13. A method of providing a plant growth medium according to claim 1, comprising low shear mixing of soil and flocks of MMVF in amounts to provide a preselected proportion of MMVF to soil based on dry mass, said mixing being carried out in the presence of moisture present in an amount in the range 10 to 50 parts per 100 parts soil based on dry weight, whereby the MMVF fibres are distributed among soil particulates.

14. A method according to claim 13, wherein the MMVF is contacted with moist soil in the form of flocks of entangled fibres and the low shear mixing is carried out for a time sufficient to separate the entangled fibres of the flocks so that flocks are no longer visible to the naked eye.

15. A method according to claim 13, wherein the flocks of entangled fibres are primarily formed by separating a bale of MMVF wool into flocks and the flocks are contacted with soil.

16. A method according to claim 15, wherein the flocks are compressed, optionally after addition of water, before being subjected to low shear mixing with the soil.

17. The method according to claim 16, wherein the compressing increases the bulk density of the flocks by a factor of at least 1.5.

18. A method according to claim 16, wherein the compression is carried out in situ on the ground after distribution of flocks, preferably using an agricultural roller.

19. A method according to claim 13, wherein the low shear mixing is carried out in situ on the ground by means of a harrow, for instance a power harrow, preferably a harrow which penetrates between 5 and 30 cm into the soil.

20. A method according to claim 13, wherein the soil is distributed onto a sub-layer, MMVF fibre is distributed onto the soil in the form of flocks, and low shear mixing is applied in situ.

21. A method according to claim 20, wherein MMVF flocks are applied to the soil at a value of 5-20 kg/m.sup.2, preferably in the range 8-15 kg/m.sup.2.

22. A method according to claim 11, wherein the MMVF are stone fibres, preferably having content of oxides as wt % as follows: TABLE-US-00010 SiO.sub.2 35 to 50, preferably 38 to 48 Al.sub.2O.sub.3 12 to 30, preferably 15 to 28 TiO.sub.2 up to 2 Fe.sub.2O.sub.3 2 to 12 CaO 5 to 30, preferably 5 to 18 MgO up to 15, preferably 1 to 8 Na.sub.2O 0 to 15 K.sub.2O 0 to 15 P.sub.2O.sub.5 up to 3 MnO up to 3 B.sub.2O.sub.3 up to 3, further wherein the fibres have length of at least 2000 m, and number average diameter in the range 3 to 15 m.

23. Use of the plant growth medium according to claim 1, to cultivate and grow plants.

24. Use according to claim 23, wherein the plants are grown from seed sown into the plant growth medium.

25. Use according to claim 23 or 24, wherein the plants are grass plants.

26. Use according to claim 25, wherein the grass surface is utilised as a sports ground.

27. Use according to claim 26, wherein the sports ground is located in a frost prone location.

28. Use according to claim 26 or 27, wherein the sports grounds is a soccer pitch.

29. A sports ground comprising grass growing on a grass support layer 5 to 30 cm thick in which roots of growing grass are supported, said grass support layer comprising soil containing 1-10% by weight loam, wherein loam is the fraction of soil that passes through a sieve with 0.063 mm openings, at least 0.5% by weight organic matter, and having a particulate size distribution having M50 value in the range 100 to 500 m and having at least 95% by weight particle size less than 4 mm, intermingled with 1 to 30 parts by weight per 100 parts soil based on dry matter MMVF fibres, having content of oxides as wt % as follows: TABLE-US-00011 SiO.sub.2 35 to 50, Al.sub.2O.sub.3 12 to 30, TiO.sub.2 up to 2 Fe.sub.2O.sub.3 2 to 12 CaO 5 to 30, MgO up to 15, Na.sub.2O 0 to 15 K.sub.2O 0 to 15 P.sub.2O.sub.5 up to 3 MnO up to 3 B.sub.2O.sub.3 up to 3.

30. A sports ground according to claim 29, wherein the MMVF are substantially free of fibre binder.

31. A sports ground according to claim 29, wherein the MMVF are stone fibres, preferably having content of oxides as wt % as follows: SiO.sub.2 35 to 50, preferably 38 to 48 Al.sub.2O.sub.3 12 to 30, preferably 15 to 28 TiO.sub.2 up to 2 Fe.sub.2O.sub.3 2 to 12 CaO 5 to 30, preferably 5 to 18 MgO up to 15, preferably 1 to 8 Na.sub.2O 0 to 15 K.sub.2O 0 to 15 P.sub.2O.sub.5 up to 3 MnO up to 3 B.sub.2O.sub.3 up to 3, further wherein the fibres have length at least 2000 microns, preferably at least 2500 microns, more preferably at least 3000 microns, most preferably at least 3500 microns; further wherein the diameter of the fibres is in the range 3 to 15 m.

32. A sports ground according to any of claim 29, which is a soccer pitch.

Description

EXAMPLE 1PRODUCTION OF PLANT GROWTH MEDIUM

1. Experimental Set-Up

1.1 Top Soil Properties

[0056] The top soil material was supplied as suitable for a natural grass soccer sport pitch. The specification of the soil including granulometry from species tests is shown in the following Table 1.

TABLE-US-00003 Properties Weight % Loam 6.1% Organic component 2.5% [<4 mm] fine gravel 100% [<2.0 mm] very coarse sand 99% [<1.0] coarse sand 96% [<0.500 mm] medium sand 85% [<0.355 mm] medium sand 74% [<0.250] fine sand 57% [<0.180] fine sand 38% [<0.125] very fine sand 24% Fraction <2 m 2.3%

Other

[0057]

TABLE-US-00004 TABLE 1 Structure closed M50 number 234 Texture rough Shape Round, angular and moderate angular

1.2 Variation of Parameters

[0058] Parameters (content of fibres to soil, binder presence and fibre length are varied to find the most suitable content of fibre product to optimize the performance and water management in top soil/fibre compositions (plant growth media).

1.3 Mixing Equipment, Conditions & Procedure

[0059] Appropriate mixing equipment, mixing conditions and mixing procedure are defined and given in the tables below.

TABLE-US-00005 TABLE 2 Mixing equipment, conditions & procedure Mixing conditions Mixing equipment Stephan mixer Mixing time 60 sec Total, of which 30 sec (without moisture) 30 sec (with moisture) Mixing speed 1500 rpm Moisture content 15 wt. % Mix batches 3000 gram Amount of batches per mix 2

1.4 Test Methods

[0060] The test methods for determination of the performance (mechanical tests) and water management (water behavior) of the plant growth medium are given in the next table. The tests are carried out on samples of the soil/fibre blend forming the plant growth media, subjected to conditions to simulate application to the ground, by filling into open-topped boxes and subjecting to compression at a pressure corresponding to an agricultural roller.

TABLE-US-00006 TABLE 3 Summary of test methods (mechanical tests, water behavior, frost and soil condition Property Test method Description Mechanical Vertical ball Deformation of the soil by using a 5 kg tests deformation ball, dropped from 100 cm (average of 3). Penetration Force that is needed to penetrate the resistance medium on a depth of ca. 10 mm using a pocket penetrometer (average of 5). Torsion Shear stress [kg/cm.sup.2] of the medium at a resistance surface of minimal 25 mm in diameter. Tensile testing Force (N/mm.sup.2) against 15 mm of deformation using the tensile testing machine. Water Water content Moisture content of the soil in volume behavior percentage. Drying the soil Drying the medium at 110 5 C. Water buffer Time [sec] to store an amount of water capacity [ml] into the medium. Water Water loss [%] by evaporation in time. evaporation Frost Frost time Time to reach the medium a temperature of 0 C. Soil pH value pH value of the medium. condition

[0061] The soil and fibre combinations are set out in Table 4. The granulate comprises flocks (or granules) of stone wool fibres free of binder. The fibres with binder are chopped flocks of Grodan Vital plant growth medium, i.e. fibres bound by hydrophilic binder. Batches of fibre and soil are subjected to mixing in a

[0062] Stephan mixer with soil at 1500 rpm for 60 s, of which 30 s is carried out without addition of water, the final 30 s after addition of water (15%). A preliminary step of tumbling the chopped bound fibre alone was conducted to separate the fibres in the flocks. The following mixtures were subjected to the tests described below:

TABLE-US-00007 TABLE 4 Mass Moisture Moisture Example Type of Fibre Fibre Mass fibres content content No fibres length load soil batch (wt. %) (gram) 01 Reference 3000 15 wt. % 450 (no fibres) gram 02 Granulate 4000 m 2 wt. % 3000 60 gram 15 wt. % 459 gram 03 Granulate 4000 m 5 wt. % 3000 150 gram 15 wt. % 472.5 gram 04 Fibres with ND 2 wt. % 3000 60 gram 15 wt. % 459 binder gram 05 Fibres with ND 5 wt. % 3000 150 gram 15 wt. % 472.5 binder gram 06 Synthetic 30 mm 0.1 wt. % 3000 3 gram 15 wt. % 454.5 fibres gram

[0063] Torsion resistance is carried out using a pocket value tester (C101 device). After compressing the plant growth medium sample in a suitable box, the device is set to 0, and is then held against the surface until the C101 part is completely pushed into the soil. The device is then turned until the surface crashes. The value of torsion at which the surface crashes is determined. The test is repeated three times, after each time mixing and recompressing the sample. The mean value is determined and the average torsion resistance is calculated.

[0064] The tensile deformation testing is carried out on the compressed sample in a suitable open topped box. A compression device having a head with surface area of 25 cm.sup.2 is positioned at the surface and is then pushed into the surface with a preload of 10 N to a depth of 15 mm. The resistance to compression at the point 15 mm is determined. When the preload is gone (when the soil comes out of the box or cracks the test was stopped. The test is performed three times, before each test the soil is mixed and compressed as per the standard technique.

[0065] The water content of the plant growth media are determined using a standard moisture meter, taking care that the sensors are fully covered by plant growth medium in compressed form. The test is repeated three times and the mean taken.

[0066] The water-buffer capacity is the capacity of the plant growth medium to absorb a predetermined amount of water when the starting moisture content is low, around 5 volume %, and when the moisture content is high, around 25 volume %. Plant growth medium having the specified moisture content is filled into an open ended, vertically arranged pipe having cross section around 12 cmdiameter, by sequentially placing portions into the pipe and compressing them, until a depth of around 20 cm of plant growth medium in compressed form is reached. The amount of material used is weighed. 100 ml water is poured into the top of the pipe, at T=0. The time at which the surface is dry, that is once the water has soaked into the surface, is determined. Further 100 ml aliquots of water are poured in, with the time determined for the surface to dry after each addition. Furthermore, the amount of water added before the total volume starts to drain from the base, judged by observation of water passing through a filter paper located across the open end, is determined.

[0067] The drain capacity, which is related to moisture buffer capacity, is the capacity of saturated plant growth medium to drain 1 I of water. This test is carried out in a plastic pipe containing compressed plant growth medium prepared as for the water buffer capacity measurement. 1500 is added to the soil to saturate it. Once the medium is no longer draining water from the base, the amount of plant growth medium and water in the pipe is weighed. Then 1000 ml water are added to the soil at T=0. The time taken for the surface to dry again, that is for the 1000 ml water to drain through the surface, is determined. The time taken for 1000 ml water to drain from the lower end of the pipe is determined.

[0068] The water evaporation measurement is relevant for determining the rate of evaporation from the plant growth medium in hot climates. It would be desirable for the rate of evaporation to be as low as possible. The technique is carried out by positioning an open box containing compressed plant growth medium having known moisture content (around 25-30 vol. %), stored in an oven at 40 C. and ventilated with air of humidity of 40%. The soil is measured hourly until the weight stabilises.

[0069] The time taken to freeze the plant growth medium with an air temperature of 18 C. is determined. Compressed plant growth medium in an open topped box, having a known moisture content (around 25-30 vol. %.) is placed in a freezer, which is switched from ambient to freeze. Sensors positions 4 cm below the surface of the plant growth medium are set to record the temperature change, as the temperature within the freezer is reduced to 18 C. The time at which all the sensors reach 5 C. is determined.

[0070] The results of some of the tests are shown in Table 5 below. The results of the water-buffering, drainage properties and water evaporation tests are shown in FIGS. 1 to 4.

TABLE-US-00008 TABLE 5 Test Results Example Test 1.01 1.02 1.03 1.04 1.05 1.06 Vertical ball 4.0 3.1 2.7 3.2 2.9 2.8 deformation (cm) Penetration 0.3 0.75 1.05 0.7 1.0 0.55 resistance pin (kg/cm.sup.2) Coin (kg/cm.sup.2) 2.7 3.9 4.8 3.8 4.7 3.6 Torsion 0.85 1.25 1.75 1.55 1.83 1.77 resistance (kg/cm.sup.2) Tensile 0.62 0.39 0.38 0.39 0.34 0.54 modulus (N/mm.sup.2) Smax 0.22 0.35 0.25 0.30 0.25 0.41 (N/mm.sup.2) Fmax % 30 30 30 30 30 30 Time to 320 340 370 340 380 320 freeze (min) pH 8.5 8.5 8.5 8.5 8.5 8.1

CONCLUSIONS

[0071] The presence of stone wool material decreases the vertical ball deformation of the soil in the falling ball method. The use of flocks of unbound fibres at the same level provides improved deformation resistance compared to bound wool samples. The higher level of incorporation of stone wool provides additional resistance to deformation. Penetration resistance is similarly improved by the presence of stone wool fibres, for both the pin and the coin. Again the use of unbound wool provides improved resistance to penetration. The presence of stone wool materials also increases the torsion resistance of the soil, which indicates a resistance to damage on use of the playing surface. The higher level of incorporation provides improved torsion resistance. In the tensile testing results indicate that the stone wool fibres disturb the packaging of sand and loam particles. Soils containing significant levels of loam and larger particles normally tend to high packing levels and high compression and thus density. Addition of the fibres, especially loose fibres, is shown in these experiments to disturb the packaging for integration between the large and the small particles with the result that the plant growth medium is less stiff. This means that the use of fibres in the plant growth medium in the surface of a sports pitch can support the energy restitution of a sports pitch for the improved comfort and safety of the players.

[0072] The various tests on the water-buffer capacity of the plant growth media indicate that the presence of stone wool fibres significantly improves the buffering capacity, both when the soil is dry (simulating summer) and when it is wet (simulating winter). Also the water evaporation rate appears to decrease with the presence of stone wool. This is likely to be due to reduced levels of water close to the surface due to improved drainage, and thus reduction of the tendency of water to be available for evaporation.

[0073] The freezing time results show that the presence of stone wool reduces the rate at which plant growth medium reaches low temperatures in the presence of cold air temperatures. The reduction is proportional to the amount of fibre incorporated. This indicates that sports pitches used in winter should be usable for as much as one hour longer in evenings, increasing available training time.

[0074] The pH values are not influence by the presence of stone wool.

[0075] The comparative results using synthetic fibre in place of stone wool fibre, which is a commercially available treatment, indicates that equivalent properties may be achieved for stone wool incorporation. The method of production of the plant growth medium by mixing soil and fibre is significantly improved compared to use of synthetic fibre, however. There are difficulties with mixing using available mixers and application procedures for the synthetic fibres, in that incorporation of levels more than 0.1% by weight leads to problems mixing, so that inhomogeneities are observed and difficulties with providing level ground on application.

EXAMPLE 2GROWTH OF PLANTS ON MEDIA

[0076] This Example compares the influence of fibres, when incorporated in flock form or distributed in loose form into soil, used as a plant growth medium for growing grass.

[0077] For all of the tests, a top-soil, similar to that used in Example 1, is mixed with stone wool fibre, at four levels, 2.5, 5, 7.5 and 10% by weight. Batches of 300 g soil are mixed with stone wool in the form of flocks. For tests where the fibre is to be broken up so that fibres are distributed in the plant growth medium, mixing is carried out in a Stefan Mixer, mixed at 1500 rpm for 2 minutes. For tests where the fibre is to remain in the form of flocks, mixing is done in a concrete mixer for 15 minutes, after which flocks of fibre could still be seen in the mixed medium.

[0078] Two lots of trials were conducted. Field trials were conducted where flocks of the medium were laid onto test fields and compressed, with grass seed being sown in a normal manner. The results show that the presence of fibre flocks in soil seems to disrupt the ability of grass to grow and reduces the density of grass. However where fibres are fully dispersed into the soil by harrow, grass growth is changed only to a small extent by the presence of fibres, these reducing the density of grass to a small extent.

[0079] For pot trials, grass was grown in pots, which were watered by rain after grass seed was sown. Moisture determinations using moisture meters were determined weekly. The moisture in the pot trials, the grass density is improved compared to the reference by the presence of loose fibres, at both 2.5 and 5% by weight. Also the presence of fibres leads to better moisture retention after dry periods, so that grass colour is improved for both 5% and 7.5% by weight fibres.

[0080] A comparison of the roots following a period of growth shows that the roots of grass grown in plant growth medium with loose fibres distributed amongst the soil particles gives improved root structure. Where flocks of stone wool are incorporated, the development of roots appears to be disrupted.

[0081] From the experiments, when stone wool fibres are used in soil with a growing grass medium, the moisture content can be increased. The moisture content increases with increasing fibre content, both during wet and dry weather conditions, using loose fibres and fibre flocks in soil. However the presence of loose fibre content improves the covering ability and density of the grass whereas flocks provide a deterioration of the density of the grass. A higher fibre content of loose fibres can keep the grass green for a longer period of time during dry and warm weather conditions due to increase of moisture content retention with higher levels of fibre. Loose fibres in the plant growth medium seem to improve the structure of roots. During measuring of the moisture content, it was noted that the resistance to penetration by the moisture metering equipment is higher when more fibres are used, which is due to fibres improving the strength of grass roots in the soil.