WO2000025569A1

WO2000025569A1 - A hydroponic grass growing system

Info

Publication number: WO2000025569A1
Application number: PCT/IB1999/001744
Authority: WO
Inventors: Edwin Michael Kruger
Original assignee: Superlawn Cc
Priority date: 1998-11-02
Filing date: 1999-10-28
Publication date: 2000-05-11
Also published as: AU6360599A

Abstract

The invention relates to a growing medium for forming a growing medium layer within a hydroponic growing system for growing grass in a sports field. The growing medium comprises particles of pine bark that have immature fractions of bark in the form of cellulose, tannins and resins separated therefrom. The pine bark particles when compacted to form a growing medium layer are extremely stable, while providing good drainage qualities and general conditions for the development of the grass roots of grass grown within the medium layer.

Description

A HYDROPONIC GRASS GROWING SYSTEM

THIS INVENTION relates to a hydroponic growing system for growing grass in a field.

The invention relates particularly to a growing medium for forming a hydroponic growing system for growing grass in a sports field.

Sports fields which require a grass playing surface have peculiar requirements when compared with ordinary, decorative grass lawns. Particularly, the grass playing surface of a sports field generally must be able to withstand substantial traffic without collapsing or tearing-up. Also, particularly for sports such as rugby union, soccer, and the like, the field must be playable in all weather conditions and effective drainage is imperative. Ideally, playing surfaces also must be resilient and not be exposed to hardening and over compacting which can expose players to injury. Still further, the playing surfaces of sports fields generally must be smooth and regular and must also be colour compatible to enhance televising of sports events.

The only known growing medium that has been generally approved for high traffic sports fields is sand. In order to provide the best results, particle size distribution within a growing medium layer and particle shapes are specified, different specifications having been identified for use in relation to sports fields for different types of sport .

The provision of sand with the required qualities for particular applications generally is very expensive and this often leads to lowering of standards. Also, sand does not create a natural growing environment insofar as it has a poor nutrient holding capability and a poor water retention capability. This can result in grass often being under stress and, therefore, being exposed to diseases. Sand, particularly when used with recommended particle sizes to provide good drainage qualities, is naturally loose, which can result in grass exhibiting inferior shear strength, thus often requiring binding with the aid of polypropylene or nylon strands, which again is very expensive. Another disadvantage or problem associated with the use of sand is that it does not harbour natural microorganisms which assist with root growth and development. Also, a sand growing medium layer results in a relatively hard playing surface which can cause injury while organic matter which is naturally produced can add to hardening and also tends to clog a growing medium layer, which can affect drainage. It is thus apparent that although sand appears to constitute the best available growing medium for grass in sports fields, it suffers from numerous disadvantages and problems .

For certain specified applications, clay is considered most suitable as a growing medium, e.g. for the playing surface of a tennis court, and the like, but because it naturally has poor drainage qualities, it will not permit playing thereon in wet conditions. Clay therefore also does not constitute an ideal growing medium.

As such, it is an object of this invention to provide a growing medium for growing grass in a sports field, in respect of which growing medium at least some of the disadvantages associated with the use of sand or clay as a growing medium are completely or partially ameliorated.

According to the invention there is provided a growing medium for forming a hydroponic growing system for growing grass in a sports field, which comprises particles of pine bark that have immature fractions of bark in the form of cellulose, tannins and resins separated therefrom.

By the removal of the immature fractions of pine bark, i.e. the cellulose of the pine bark, the remaining mature lignin part of the pine bark is rendered stable, insofar as the lignin part of pine bark does not decay, it will not degrade after compaction and after compaction it is not exposed to insect infestation. The mature lignin part of pine bark when forming a growing medium layer also will remain in tact in its originally formed particle form upon the compaction of a growing medium layer made up of such pine bark particles.

Insofar as tannins and resins are considered toxic, by their separation from pine bark used, the remaining pine bark particles will be rendered sufficiently non-toxic to serve as a growing medium for the purpose envisaged.

The particles of pine bark for forming a hydroponic growing system particularly may be obtained from a combination of different pine species. Particularly, the pine bark particles are a combination of mature pine bark particles obtained from the species pinus elliotii and immature pine bark particles obtained from the species pinus patula . By utilising such a combination of mature and immature pine bark, the separation of the immature fraction of the bark, as well as the tannins and resins can be carried out by a conventional composting process which will break down the cellulose component of the pine bark which will be linked particularly with the immature pine bark, whereas the heat generated by the composting process will serve to separate the tannins and resins associated with both the forms of pine bark.

The Applicant particularly has found that the pine bark particles provided for forming a growing medium layer within a hydroponic growing system is suitable as a growing medium for the following reasons:

1. The combination of pine bark particles described allows for an optimal blend of particles which provides for complete composting of particularly the cellulose immature fraction of the pine bark. After complete composting is achieved, the pine bark structure of the remaining lignin part of the pine bark does not change, thus becoming very stable which is important for use in a hydroponic growing system.

2. The mature lignin part of pine bark used for forming a growing medium layer has a significantly higher water retention capability than sand or other gravel based media and, as such, is particularly suitable for use in a hydroponic growing system.

3. Pine bark particles forming a growing medium layer does not easily compact beyond a compaction level which is determined particularly by the particle size of the pine bark used and, thereby, a consistent level playing surface for a sports field is ensured.

4. Because of the inherent resilient qualities of pine bark particles, a resilient playing surface having good shock absorbing qualities is provided and, thereby, possible injuries of players due to playing on a hard playing surface is largely reduced.

5. Pine bark particles forming a growing medium layer as herein envisaged also has excellent nutrient exchange abilities which allows for the optimal transfer of fertilisers to the plant root zone of grass grown in this growing medium. 6. Well composted pine bark particles also harvest friendly microorganisms such as Tricoderma and Bacillus which reduce the buildup of pathogens in plants growing therein.

7. Pine bark particles in use as a growing medium are very tolerant to over-watering.

8. In practice, as the grass roots of grass grown within a growing medium layer formed of pine bark particles will tend to grow into the bark particles, the shearing strength of the playing surface formed will be effectively improved. Damage to a playing surface even when play takes place during heavy rainfalls will thus be limited.

9. Insofar as pine bark weighs significantly less than sand, within growing systems that permit complete playing field segments to be removed and replaced, this clearly is greatly facilitated.

10. Experiment also has proven that fine organic build-up within a pine bark growing medium layer is less than that associated with such build-up in a sand growing medium layer and insofar as drainage therefore will remain very good, anaerobic conditions are unlikely to occur within a growing medium layer formed of pine bark.

11. Insofar as pine bark is dark in colour, it is associated with better winter growth insofar as it cools down significantly slower than sand. The water retention capability of pine bark also will provide for excess moisture to move upwards within a growing medium layer while heat is conducted downwards to the root zone of grass grown, thus ensuring good root development .

In practice, the superior drainage qualities of a pine bark growing medium layer within a hydroponic growing system can be combined with an effective sub-surface drainage system which can collect and recycle drained water to produce a superior hydroponic growing system. The invention extends accordingly also to a hydroponic growing system for growing grass in a sports field, which comprises a growing medium layer formed of particles of pine bark that have immature fractions of bark in the form of cellulose, tannins and resins separated therefrom. The hydroponic growing system may include a drainage system installed operatively beneath the growing medium layer, which system can collect drained water and recycle the water for subsequent irrigation of grass grown in the growing medium layer.

The growing medium of the invention can be utilised as such within various different forms of sports fields which require a stable playing surface, the resilient/hardness qualities of the playing surface being controlled by the particle size of pine bark utilised, finer particles providing for a relatively harder surface but being associated with slightly inferior drainage qualities. The invention is now described, by way of an example, with reference to the accompanying diagrammatic drawing, which illustrates schematically in cross-sectional side view a hydroponic growing system for growing grass in a sports field which has a growing medium layer formed of pine bark.

Referring to the drawing, a segment of a hydroponic growing system for growing grass in a sports field, in accordance with the invention, is designated generally by the reference numeral 10. The system 10 includes a growing medium layer 12 which is formed of pine bark particles 14 into which the roots of grass 16 grow. Operatively beneath the growing medium layer 12 there is provided a network of drainage pipes 18 (only one pipe shown) , the drainage pipes being inclined with respect to a horizontal plane and being disposed to collect water that has drained through the growing medium layer 12, i.e. that has drained through the pine bark particles 14. Water collected within the pipes 18 will flow towards one or more collector tanks (not shown) from which liquid displacement pumps (not shown) can displace the water for irrigation of the grass 16, when required. This circulation system forming a part of the hydroponic growing system 10 clearly will ensure the effective use of water for irrigation of the grass 16 growing within the associated sports field.

The pine bark particles typically is obtained from different species of pine and, by way of example, comprises a combination of mature pine bark particles obtained from the species pinus elliotii and immature pine bark particles obtained from the species pinus patula . Prior to the formation of the growing medium layer 12, the pine bark particles obtained are exposed to a composting process whereby the immature fraction of bark in the form of cellulose is decomposed, this cellulose being mainly associated with the immature pine bark particles. The heat generated by the composting process simultaneously will provide for the separation of the tannins and resins included in the pine bark particles, thus providing effectively for the removal of the toxic components of the pine bark particles.

As a result of the process as described and in combination with a mechanical breaking process, pine bark particles can be provided in a range of selected sizes, a particular range of sizes typically being specified for forming a growing medium layer 12 for a particular application. The specification for a growing medium layer in this regard is greatly variable and will be determined by the requirements of a particular sports field and, as such, the requirements of the sport to be played on the sports field.

The pine bark particles that remain, following their exposure to the composting process, will include essentially the lignin part of the pine bark, which is extremely stable and particularly when compacted to form a growing medium layer, will not be exposed to decay, degradation or insect infestation. In the formation of a growing medium layer, a predetermined volume of pine bark particles 14 will be applied on a preformed base and the particles will then be compacted to provide a desired thickness growing medium layer. In this regard it must be understood that the pine bark particles only will compact to a predetermined degree, particularly as determined by the range of particle sizes utilised, and that additional compacting will not ordinarily occur. The stability so obtained will ensure that grass grown within the growing medium layer will provide a continuous regular playing surface for the sport to be played thereon.

The further benefits associated with the use of pine bark particles 14 for forming the growing medium layer 12 are set out above and it is thus apparent that with the use of such particles to form a growing medium layer the general disadvantages and problems associated with the use of sand for forming a growing medium layer, also as set out above, are largely overcome.

It is anticipated that pine bark could be used as a growing medium layer for fields to be used in association with many different sports and that particularly by specifying a suitable particle size distribution within a growing medium layer, different hardness and stability properties can be obtained to suit the sport to be played on the associated field.

Because of the superior drainage properties of the growing medium layer 12, effective water utilisation also is provided for, particularly in combination with the remainder of the hydroponic growing system as hereinabove described. It must be understood in this regard that various different configuration drainage systems could be utilised within a hydroponic growing system which includes a growing medium layer formed of pine bark. The invention clearly extends also to all such different configuration systems .

It must be appreciated also that the use of pine bark for forming a growing medium layer will be combined with a specialized nutrient program that will deal with the peculiarities of pine bark. For example, when compared with the use of sand particles for forming a growing medium layer, higher levels of phosphates and lower levels of potassium are required in conjunction with the use of pine bark .

Claims

1. A growing medium for forming a hydroponic growing system for growing grass in a sports field, which comprises particles of pine bark that have immature fractions of bark in the form of cellulose, tannins and resins separated therefrom.

2. A growing medium as claimed in Claim 1, in which the particles of pine bark are obtained from different pine species .

3. A growing medium as claimed in Claim 2, in which the particles of pine bark are a combination of mature pine bark particles obtained from the species pinus elliotii and immature pine bark particles obtained from the species pinus patula .

4. A growing medium as claimed in any one of the preceding claims, in which the immature fractions of pine bark, tannins and resins have been removed by a conventional composting process which will have broken down the cellulose component of originally obtained pine bark, while the heat generated by the process will have provided for the separation of tannins and resins from the originally obtained pine bark.

5. A hydroponic growing system for growing grass in a sports field, which comprises a growing medium layer formed of particles of pine bark that have immature fractions of bark in the form of cellulose, tannins and resins separated therefrom.

6. A hydroponic growing system as claimed in Claim 5, which includes a drainage system installed operatively beneath the growing medium layer, which drainage system can collect water drained through the growing medium layer and recycle the water for subsequent irrigation of grass grown in the growing medium layer .

7. A growing medium for forming a hydroponic growing system for growing grass in a sports field substantially as described.

8. A hydroponic growing system for growing grass in a sports field substantially as described in the specification with reference to and as illustrated in the accompanying drawing.