WO2016050594A1

WO2016050594A1 - Seedling mat

Info

Publication number: WO2016050594A1
Application number: PCT/EP2015/071927
Authority: WO
Inventors: Robin James BLAKE; Alan Stephen COCHRAN; Andrea Hawkins; David Holloway; Leslie May; Paul Edgar SEYMOUR; John Henry Nettleton-Hammond; Catherine Julia Piper
Original assignee: Syngenta Participations Ag
Priority date: 2014-10-03
Filing date: 2015-09-24
Publication date: 2016-04-07
Also published as: CN208836490U; PH22017500002Y1; MY193577A; PH22017500002U1; JP3213813U; TWM527675U; KR20190095547A; KR20170002018U; KR102339799B1

Abstract

The present invention enables/provides an improved seed/seedling mat (10), intended to optimise mat utility. The invention further provides materials with particular characteristics, and the use of such materials in seedling mats (10), as well as component layers made from such materials, and which may be incorporated into seedling mats (10). The invention further extends to methods of making such seedling mats (10), and/or component layers, and in particular to methods of making rooting substrate (06) components for use within such seedling mats (10).

Description

SEEDLING MAT

The present invention enables/provides an improved seed/seedling mat, in particular a rice seedling mat, intended to optimise mat utility. The invention further provides materials with particular characteristics, and the use of such materials in seedling mats, as well as component layers made from such materials, and which may be incorporated into seedling mats. The invention further extends to methods of making such seedling mats, and/or component layers, and in particular to methods of making rooting substrate components for use within such seedling mats.

In agriculture, and general gardening, seedlings are commonly grown initially in a specialised environment such as a nursery, glasshouse or dedicated seed-bed area. In this way certain environmental factors may be more easily controlled so as to improve the likelihood and quality of their early development. Following this, the seedlings are transplanted into a field/garden for longer-term growth.

Seed mats facilitate initial establishment and propagation of seedlings, storage and also convenient seed/seedling transfer for nursery/glasshouse and, subsequently, longer- term cultivation and growth (e.g. in a paddy field).

Mat-type products containing seeds are known in the market. WO01/60144A1 discusses problems associated with raising seedlings and discloses an example that is intended only to provide a light-weight alternative to seed-bed soil and which requires vacuum moulding for its manufacture.

In order to enhance their utility, seed/seedling mats (referred to hereafter as seedling mats) should address various aspects relevant to seed/seedling handling and propagation. For example, it is desirable to simultaneously balance seed(ling) protection and environment, mat integrity (e.g. for ease of handling and transplantation) and growth promotion/control in the mat and after transplantation.

A wide variety of mats containing seeds and different component layers exist in the prior art. Many employ aqueous glues throughout their manufacture. It has been found that the use of such adhesives can lead to a high water content in the seedling mat during production, which is disadvantageous due to (i) the time taken and/or need for specific equipment to dry the mats out, (ii) the space required to store such mats whilst drying and/or (iii) unwanted early seed germination due to the high humidity present in the mats.

The present invention addresses these issues in two ways, (i) through the use of hot melt adhesives and (ii) through the production of a seed cover component in compressed and pre-dried form, which facilitates mat assembly, minimises unwanted initiation of germination of seeds caused by a high water content in assembled prior art mats, and has unexpected beneficial effects on the growth of seeds/seedlings grown in mats incorporating such seed cover components.

Many seedling mats of the prior art utilise a soil-based substrate (referred to herein as a rooting substrate) for supporting seedling growth or alternative rooting substrates such as mineral wool. However, these suffer from a number of disadvantages, for example soil- based substrates can be bulky and/or heavy and are often difficult to handle, and mineral wool, for example, whilst a good substrate, is not readily biodegradeable and/or recyclable and is relatively expensive for large-scale use. The present invention addresses some of these drawbacks through the use of biodegradeable, self-supporting rooting substrates derived from paper-based materials, organic material that has been compressed into a self- supporting layer, or cellulose fibre material formed into a self-supporting layer. The present invention is further distinguished from the prior art in that neither the rooting substrates, nor the assembled seedling mats as described herein comprise any soil, i.e. soil is not to be found in any component of the invention.

In a first aspect, the invention thus provides a seedling mat comprising:

a generally planar rooting substrate in which seed root growth is supported and which is self-supporting, coated on one surface with a seed adhesive, for immobilising seeds in or on a top surface region of the rooting substrate, which seed adhesive is a hot melt adhesive; a seed cover component which covers the seeds and permits seedling growth therethrough; and

a plurality of seeds, distributed in or on the top surface region of the rooting substrate and adhered thereto by said seed adhesive, wherein:

the seed cover component is self-supporting and comprises organic material that has been compressed into a self-supporting layer, the organic material comprising coir, rice husk, guar gum, and/or bagasse;

the rooting substrate comprises materials selected from the group consisting of (i) paper and derivatives thereof, (ii) cellulose fibres and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer.

In a further aspect the invention provides a rooting substrate component for a seedling mat, wherein said rooting substrate component:

is self-supporting; is generally planar in form;

capable of supporting seed root growth;

comprises materials selected from the group consisting of (i) paper and derivatives thereof, (ii) cellulose fibres, and (iii) organic material selected from coir, rice husk, guar gum, /wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer; and is,

coated on one surface with a seed adhesive that is a hot melt adhesive, wherein the seed adhesive is capable of immobilising seeds in or on a top surface region of the rooting substrate component.

Given that the invention described above relates to seedling mats and components therefore, the skilled man will appreciate that the terms "rooting substrate" and "rooting substrate component" may be used interchangeably in this description, where appropriate. In some embodiments an assembled rooting substrate may contain multiple rooting substrate components as described herein. Such embodiments may be referred to as "stacked rooting substrates" or "composite rooting substrates".

As used herein with respect to any component, the term "self-supporting" means that the component as formed has a structural integrity such that it can be handled as a discrete product that maintains its shape and dimensions, and requires no further supporting elements. This differs for example, from a loose layer of mulch or soil which cannot be handled as a discrete layer without some other supporting element to prevent disintegration. Rooting substrate components and/or seed cover components of the invention are thus robust enough to be held by hand.

As stated above, the rooting substrate is self-supporting and is such that it supports seed root growth within the substrate following germination. It should allow development of roots that are preferably strong and healthy and ideally white, and which should hence be likely to become established following transplantation. It should also support the structural integrity of an assembled mat, e.g. by being continuous instead of fragmented.

Furthermore, the rooting substrate comprises materials selected from the group consisting of (i) paper and derivatives thereof, (ii) cellulose fibres and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer.

In one set of embodiments, where rooting substrates/rooting substrate components are made from paper and/or derivatives thereof, any suitable paper may be used, for example, suitable papers include airlaid papers, mulch papers, crepe papers, DRC (double re-crepe) papers, fluff papers and various commercially available filter papers. Recycled, or virgin, pulp papers and/or fibreboard derived from hard- or soft-wood sources are also suitable for use in the invention, with virgin pulp/fibres of soft-wood origin being particularly preferred.

In such embodiments, the rooting substrate component will comprise at least one optionally perforated, layer of paper/paper derivative. Any number of layers may be employed, provided that together they function as a self-supporting rooting substrate that supports seed root growth within the substrate following germination. In particular embodiments the rooting substrate component comprises 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 or 12 layers of paper/paper derivative. Where more than one layer is employed, the layers may be made from the same or from different paper/paper derivative(s). In certain preferred embodiments rooting substrate components comprise up to three layers of paper, and in particularly preferred embodiments, they comprise three layers of paper.

In further embodiments, such multi-layer components may themselves be layered atop each other to form stacked/composite rooting substrates, wherein each double or triple etc. layer rooting substrate component forms an element within the assembled composite rooting substrate.

Where a layer of paper/paper derivative is perforated, it may have holes punched through it, for example of diameter up to approximately 5mm, preferably up to about 4mm, and more preferably up to about 3mm. In particular embodiments the diameter will be in the region of 3mm, 2.5mm, 2mm, 1 .5mm, 1 mm, or smaller. Alternatively, it may contain a multiplicity of slits.

Where a layer of paper/paper derivative contains a multiplicity of slits, these will be made across the surface of the paper/paper derivative and may extend partially or fully through the depth of the paper/paper derivative. Such slits may permit the paper/paper derivative to be distorted or stretched in one or more of its dimensions, and may thus for example provide loft to the depth of the paper/paper derivative. It is important to note that whilst the slits may extend through the depth of the paper/paper derivative, they are not continuous in any other dimension. This ensures that the paper/paper derivative remains self-supporting and maintains its overall shape and structural integrity without falling apart during handling and/or assembly.

Any individual layer of paper within a rooting substrate/rooting substrate component may be infused with a polymer, such as for example PAA (polyacrylamide), SAP (super- absorbent polymer) and/or HAP (hydroxyapatite polymer), in order to optimise the water retention properties of the rooting substrate component.

Any individual layer of paper within a rooting substrate component may be substantially planar, or, it may be folded, pleated, fluted, corrugated or otherwise moulded to provide a plurality of channels which face toward the plane of the upper and/or lower surface of the rooting substrate component as incorporated in a seedling mat of the invention in use.

In one set of embodiments a rooting substrate component is comprised of corrugated paper/paper derivative. Types of corrugated papers/paper derivatives include single face, singe wall, and double wall corrugated paper/paper derivatives. In a single wall version, a flute - which is a sheet of corrugating medium (in this case paper or paper derivative) shaped into a continuous rolling wave - is adhered to a substantially planar (flat) sheet of paper/paper derivative such that one set of channels formed by the wave are enclosed by the planar sheet of paper/paper derivative (see Figure 3a).

In a single wall version, a flute is adhered to two substantially planar sheets of paper/paper derivative such the both sets of channels formed by the wave are enclosed, one set of channels by each sheet of paper/paper derivative (see Figure 3b; the flute forms the "filling" in a sandwich where the planar sheets form the "bread").

In a double wall version, a second flute is laid/adhered atop one of the planar surfaces of a single wall construct, and a further planar sheet of paper is adhered to the second flute such that exposed channels formed by the flute are enclosed (see Figure 3c).

All three types of corrugated paper/paper derivatives (e.g. card, recycled paper, recycled card) are readily available from a variety of commercial sources.

Corrugated papers/paper derivatives may be further characterised according to the amplitude of the wave of the flute, which corresponds to the depth of the corrugated construct (see Table 1 below).

Table 1 Flute characteristic for corrugated paper constructs

Flute type Wave amplitude (mm)

A-Flute 8

B-Flute 3

C-Flute 5

E-Flute 1.6

F-Flute 1 Alternatively, the paper may be formed into a cellular (e.g. honeycomb) structure, wherein the walls of the cells run perpendicular to the upper (and lower) surfaces of the rooting substrate component in use within a seedling mat of the invention.

In one set of embodiments, where a rooting substrate component comprises three layers of paper, the upper and lower layers (described with reference to their relative positions when a seedling mat of the invention is in use) are substantially planar, and either the middle layer is folded, pleated, corrugated, fluted or otherwise moulded to provide a plurality of channels which face said upper and/or lower layers, or the middle layer is of a cellular construction as described hereinbefore. In certain embodiments the plurality of channels or cells will contain (i.e. be partially or fully filled with, preferably partially filled with) a material which may enhance the water retention properties of the rooting substrate, for example, coir, vermiculate, perlite, water holding gels/pellets/crystals (for example such as those known as Seed Aide® CoverGrow™ Spread or Spray Mulching Granules obtainable from Profile Products LLC, Buffalo Grove, llinois, USA) or the like. Where the rooting substrate component comprises a corrugated paper/flute of paper, either one, or both, set(s) of channels may be partially or fully filed with such materials.

Where a rooting substrate component comprises more than one layer of paper, the layers may be adhered or affixed to each other in order to form a single self-supporting component for use as a rooting substrate. This may be through the use of adhesive or any suitable mechanical means such as, for example, stapling, stitching, clipping, pinning etc.

Where an adhesive is used for this purpose any suitable adhesive, e.g. aqueous adhesive or hot melt adhesive may be employed. Particularly suitable adhesives include the aqueous and/or hot melt adhesives described elsewhere within this specification. Preferably, hot melt adhesives will be employed, in particular hot melt adhesives as described herein with respect to seed adhesives.

In one particular embodiment a rooting substrate component comprises 3 layers of mulch paper, wherein the upper and middle layers (described with reference to their relative positions when a seedling mat of the invention is in use) are perforated, the middle layer comprises a plurality of channels which face the upper and lower layers, the upper and lower layers are substantially planar and the layers are typically adhered to each other with hot melt adhesive.

In a further particular embodiment the rooting substrate component comprises 3 layers of paper, wherein the lower and middle layers (described with reference to their relative positions when a seedling mat of the invention is in use) are mulch paper and the upper layer is a polymer infused paper, the middle layer is perforated and comprises a plurality of channels which face the upper and lower layers, the upper and lower layers are substantially planar and the layers are adhered to each other with hot melt adhesive.

In a further particular embodiment the rooting substrate component comprises 3 layers of paper wherein the upper and lower layers (described with reference to their relative positions when a seedling mat of the invention is in use) are substantially planar, and the middle layer is of a cellular construction, wherein the walls of the cells run perpendicular to the upper and lower layers and the cells are optionally partially filled with coir, and wherein the lower and middle layers are mulch paper, the top layer is a double re-crepe paper and the layers are adhered to each other with hot melt adhesive.

Rooting substrates/rooting substrate components may also be made from materials comprising cellulose fibres, for example wood fibre (in particular eucalyptus wood fibre, such as, for example, lyocell™ or tencel™), cotton fibre, jute, hemp, and the like, as well as combinations thereof. These cellulose fibres may be in the form of a woven self-supporting layer or a non-woven self-supporting layer. A non-woven self-supporting layer of cellulose fibres is one where the assembly of fibres is held together either by (i) mechanical interlocking in a random web or mat, (ii) fusing of the fibres, or (iii) bonding the fibres together with a cementing medium such as for example, starch, casein, rubber latex, a cellulose derivative, or a synthetic resin. Particularly useful cellulose fibre materials for use as rooting substrates in the invention include non-woven wood, cotton or jute fibres, in the form of a self-supporting layer with a thickness of between 0.2 to 3 cm. In certain embodiments, the rooting substrate will be formed from non-woven wood fibres, formed into a self-supporting layer of approximately 4mm or approximately 9mm thickness, for example, as used herein in the Examples. In further preferred embodiments, the rooting substrate will comprise non- woven cellulose wooden fibre material e.g. Tencel matting, such as Tencel Sure To Grow pads (The Sprout People, 170 Mendell St., San Francisco, CA94124), as used herein in the Examples. In yet a further preferred embodiment, the rooting substrate is comprised of non- woven regenerated fibre material, such as, for example that obtainable from Neaustima JSC, J. Basanaviciaus Street 103c, LT-76129 Siauliai, Lithuania, which comprises 80% cellulose fibres and 20% polyester and has a density of 120gsm.

In a further set of embodiments, the rooting substrate component will be in the form of a non-woven layer of cellulose fibres is one where the assembly of fibres (in particular jute, cotton or hemp fibres, more especially jute fibres) is held together by mechanical interlocking in a random web or mat. As an example, cellulose fibres (e.g. jute, cotton, hemp, linen) may be needle-punched through a layer of natural or synthetic film such as plastic, rubber, resin, and the like. Examples of such suitable non-woven materials are available from Anglo Recycling (Rochdale, UK) and are made from jute, cotton and the like, in particular that used herein in the Examples under the descriptor A8. A8 is a non-woven material comprising jute fibres that are needle-punched through a plastic film, The depth of A8 material is around 4- 6mm.

Rooting substrate/rooting substrate components may also be made from organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed (i.e. through the application of pressure) into a self-supporting layer. Such compressed rooting substrate components are further distinguished from materials used in the prior art in that preferably, they do not comprise soil, straw and/or cotton.

Coir may be sieved, to give a standard particle size (e.g. <2.8mm), and/or pre- washed, buffered (e.g. to pH6.0) and dried before use. Rice husk and bagasse may be milled (ground) or unmilled (unground). Suitable wood based materials include wood chips, wood shavings, and/or sawdust.

Preferably the rooting substrate component comprises as organic material (i) coir and rice husk, (ii) coir, rice husk and bagasse, or (iii) wood based material, in particular wood shavings and sawdust. More preferably the rooting substrate component consists of as organic material (i) coir and rice husk, (ii) coir, rice husk and bagasse, or (iii) wood based material, in particular wood shavings and sawdust.

Where the rooting substrate component comprises coir and rice husk a preferred weight ratio of coir to rice husk is in the region of from about 10:1 to about 1 :1 , preferably from about 5:1 to about 1 :1 and more preferably from about 4:1 to about 2:1. In one embodiment the weight ratio will be in the region of 2/3 : 1/3 coir to rice husk (i.e. 67:33).

Where the rooting substrate component comprises coir, rice husk and bagasse a preferred weight ratio of coir to rice husk to bagasse is in the region of from about 10:1 :1 , to about 1 :1 :1 , preferably from about 5:1 :1 to about 1 :1 :1 and more preferably from about 4:1 :1 to about 2:1 :1. The use of milled bagasse is preferred in these embodiments.

Optionally, the organic material of a rooting substrate component may be combined with an adhesive prior to compression. Suitable adhesives for use in the preparation of rooting substrate components include aqueous based adhesives, such as for example, VAE (vinyl acetate ethylene), polyvinyl acetate (PVA), polyvinyl alcohol (PVOH) and acrylic adhesives. PVOH adhesives, such as for example, E3443C™ (Sealock) and VAE adhesives, such as for example E1215C™ (also Sealock) are preferred, with PVOH being particularly preferred.

It is particularly preferred to include such an adhesive in rooting substrate components comprising (i) coir and rice husk, (ii) coir, rice husk, and bagasse, or (iii) wood shavings and sawdust. In such embodiments the weight ratio of organic material to adhesive is in the region of from about 5:1 to 5:2. Conveniently, the ratio is from about 4:1 to about 3:1 .

Optionally the organic material of a compressed rooting substrate component may be combined with one or more additional agent selected from a plant protection chemical, agrochemical, biological treatment and/or nutrient (such as herbicides, insecticides, fungicides, molluscicides, nematicides, safeners, plant growth regulators, micronutrient, macronutrient and/or fertilisers). In particular the organic material may be combined with a fertiliser.

The organic material of a rooting substrate component is optionally mixed with adhesive and/or additional agent as described herein, and then compressed using any suitable press, at a pressure in the region of 100-250 kgf/cm², preferably 120-220 kgf/cm². Where adhesive is incorporated, the rooting substrate component may be dried prior to storage/packaging/transport and/or subsequent use within a seedling mat as described herein.

Rooting substrate components of three main types (i.e. (i) paper/paper derivative rooting substrate components, (ii) woven or non-woven cellulose fibre rooting substrate components, and (iii) compressed organic material rooting substrate components) have been described above for use in the invention, As also described above, an assembled rooting substrate may comprise more than one rooting substrate component, and such a rooting substrate is known as a stacked rooting substrate or a composite rooting substrate, Whilst embodiments comprising more than one rooting substrate component of a the same type have also been explicitly referred to herein, the skilled man should also appreciate that the invention extends to composite rooting substrates comprising rooting substrate components of different types. For example, the invention further extends to a composite rooting substrate (as well as seedling mats containing the same, the use of such composite rooting substrates etc) comprising at least one paper/paper derivative rooting substrate component and at least one compressed organic material rooting substrate component, as well as to a composite rooting substrate comprising at least one paper/paper derivative rooting substrate and at least one woven or non-woven cellulose fibre rooting substrate component, as well as to a composite rooting substrate comprising at least one woven or non-woven cellulose fibre rooting substrate component and at least one compressed organic material rooting substrate component). Composite rooting substrates of the invention may thus comprise all three types of rooting substrate component, in any order, and may contain multiples of any given type of rooting substrate component, which may be the same or different.

A rooting substrate component (and thus any subsequently assembled seedling mat) may be of any suitable dimension for growing seeds in a nursery and subsequent transplantation to a field, but is preferably rectangular. Conveniently, the width of the rooting substrate component/seedling mat is in the region of 20-50cm, preferably about 25-40cm, and more preferably about 25-30cm (inclusive), and the length of the rooting substrate component/seedling mat is in the region of 50-100cm, preferably about 50-75cm, and more preferably about 55-60cm (inclusive). In this way, use of a mechanical transplantation machine to transplant the seedling mat may be facilitated. Further, rooting substrate components/seedling mats may be made with a greater length (e.g. in the order of multiples of the above lengths) and used initially in such a form for storage, transport and/or initial growth of seedlings in a nursery environment, before being subsequently cut to a smaller length to facilitate transplantation. Preferably the width of the rooting substrate component/seedling mat is about 25-30cm and the length of the rooting substrate component/seedling mat is about 55-60cm. In particular embodiments, the rooting substrate component/seedling mat surface area is about 28cm x 58cm.

The depth (thickness) of a rooting substrate component is in the region of 0.2 to 3 cm, preferably 0.2 to 3cm, more preferably 0.2 to 2cm, and more preferably still 0.2 to 1 cm.

In embodiments where the rooting substrate comprises more than one rooting substrate component comprised of paper/paper derivative, the maximum depth of the assembled rooting substrate component will be approximately 3 cm.

Similarly, where the rooting substrate comprises more than one rooting substrate component comprised of woven or non-woven cellulose fibres the maximum depth of the assembled rooting substrate component will be approximately 3 cm.

Where a rooting substrate component is comprised of non-woven cellulosic wood fibres, the depth as stated above, is between 0.3 to 3 cm, preferably 0.4 to 2cm, and more preferably 0.4 to l cm.Where multiple layers of such a component are assembled into a composite or stacked rooting substate, the maximum overall depth of the composite rooting substrate will be approximately 3cm. Where the rooting substrate component is comprised of compressed organic material as described supra, the depth is preferably less than 10mm, more preferably less than 5mm, and more preferably still less than 3mm. In one embodiment the depth of the rooting substrate component is in the region of 2-3mm. In a further embodiment, the rooting substrate component will comprise more than one layer of compressed organic material as decribed supra, layered atop each other. In such cases the rooting substrate component will have a depth that is the appropriate multiple of 2-3mm, and a composite or stacked rooting substrate comprising two layers of compressed organic material (i.e 2 rooting substrate components), will have a depth of 4-6mm. A composite or stacked rooting substrate comprising three layers of compressed organic material (i.e. 3 rooting substrate components) will have a depth of 6-9mm. Composite or stacked rooting substrates comprising further multiples of rooting substrate component, will increase in depth accordingly.

In a composite (or stacked) rooting substrate, combining rooting substrate components of different types, the overall depth will be the sum of the individual components employed. However, such a composite rooting substrate will in general have a minimum depth of 0.4cm and a maximum depth of 3 cm.

The skilled man will appreciate that the depth quoted applies to the rooting substrate/rooting substrate component as manufactured and/or immediately after assembly into a seedling mat as described hereinafter. In an assembled seedling mat in use i.e. when water has been applied, and/or seeds are germinating/have germinated and seedlings are growing, such processes may in some embodiments cause the depth to expand beyond the figures quoted above (e.g. in embodiments where the rooting substrate comprises organic material compressed into a self-supporting layer as described herein) or it may cause the depth to shrink/collapse to a figure smaller than that quoted above (for example in embodiments where the rooting substrate comprises paper and derivatives thereof, as described herein).

The rooting substrate is coated on one surface (which in an assembled seedling mat of the invention in use, corresponds to the uppermost surface of the rooting substrate) with a seed adhesive. By fixing seeds the seed adhesive increases the practicality of mat transport.

Suitable seed adhesives include aqueous based adhesives, in particular as described hereinafter with respect to adhesives employed in the seed cover component, as well as hot- melt adhesives. The use of a hot-melt adhesive as seed adhesive is preferred.

By hot-melt adhesive is meant a thermoplastic adhesive, which is applied in molten form at a temperature exceeding 100°C and which solidifies on cooling. Preferably the operating temperature of the hot melt adhesive will be in the range of 150°C-200°C inclusive, more preferably 155°C-190°C inclusive, more preferably 160°C-185°C inclusive, and most preferably 160°C-175°C inclusive. Examples of holt-melt adhesives suitable for use in the present invention include ethylene-vinyl acetate based adhesives, ethylene-acrylate based adhesives, polyolefin based adhesives, polyamide and polyester based adhesives, polyurethane based adhesives, styrene block copolymer adhesives (also known as styrene copolymer adhesives and rubber-based adhesives). Hot-melt adhesives which are pressure- sensitive adhesives are particularly useful in the invention, since they facilitate manufacture of a component part of the seedling mat lacking seeds. For example, the rooting substrate may be coated on one surface with such an adhesive, which maintains a degree of tack even when solidified and does not bond until pressure is applied. This is particularly advantageous as seeds may subsequently be applied when the adhesive is at a temperature which minimises or even avoids potential heat damage to the seeds, e.g. at room temperature.

Styrene copolymer and rubber-based hot-melt adhesives are thus particularly preferred, as they provide such pressure sensitivity. Examples include blends of thermoplastic rubber, resins, and plasticiser, which have a softening point in the region of 75°C to 90°C, an operating temperature of 160°C-175°C and typical viscosity of 14-20 poise at 160°C and 9-14 poise at 175°C, such as H1 125/6™, H1 155™(Sealock); blends of styrene based block copolymers and synthetic resins, which have a softening point in the region of 88°C-98°C, an operating temperature of 160°C-170°C, and a viscosity at 170°C of 6500+1700 cPs, such as D74™ (Powerbond Adhesives Ltd). Thus in one embodiment, the hot melt adhesive employed will be a blend of thermoplastic rubber, resins, and plasticiser, which have a softening point in the region of 75°C to 90°C, an operating temperature of 160°C-175°C and typical viscosity of 14-20 poise at 160°C and 9-14 poise at 175°C, and in a further embodiment the hot melt adhesive will be blends of styrene based block copolymers and synthetic resins, which have a softening point in the region of 88°C-98°C, an operating temperature of 160°C-170°C, and a viscosity at 170°C of between 48 and 82 poise.

The use of a hot melt adhesive, and in particular a pressure sensitive hot melt adhesive facilitates the production of rooting substrate as described herein, in component form, as described herein. When produced in component form (in contrast to when assembled in a seedling mat of the invention), the adhesive coated rooting substrates may additionally comprise a separation layer, to facilitate packing, storage and/or transport. Such a separation layer is removed prior to use/assembly into an intact seedling mat. Suitable separation layers include silicon paper, waxed paper, rice paper, potato starch paper and PVOH film.

In a seedling mat of the invention, seeds are sown on top of the rooting substrate and adhered thereto by the seed adhesive. Such seeds are preferably un-germinated. In certain embodiments such seeds are rice seeds. Seeds from any suitable inbred or hybrid rice varieties may be used (e.g. IR64, NK3325, Koshihikari, TR-10 and ADT-34). Prior to incorporation into a mat, seeds may be pre-treated, e.g. with an insecticide, fungicide, herbicide, nematicide, molluscicide, safener, plant growth regulator, micronutrient, macronutrient and/or fertiliser. In one embodiment, seeds are pre-treated with thiamethoxam (Cruiser^®, Syngenta). Preferably about 100-150g of seeds are used for a mat measuring approximately 58cm by 28cm. Conveniently for inbred seeds about 150g are used for such a mat and for hybrid seeds about 100g are used for such a mat. Accordingly, (rice) seed density is conveniently in the region of 1 -20 seeds/cm² (inclusive), preferably between 1 -15 seeds/cm² (inclusive) and more preferably between 1 -10 seeds/cm² (inclusive). The skilled man will appreciate that seed density will depend upon the thousand grain weight for any given variety. For example, for rice seeds of the IR64 variety, a preferred seeding density would be in the range of 1 -5 seeds/cm² (inclusive), and for rice seeds of the NK3325 variety a preferred seeding density would be in the range of 1 -7 seeds/cm² (inclusive).

In an assembled seedling mat of the invention, the seeded rooting substrate is overlaid with a compressed seed cover component. This component acts as mulch mat serving to shield seeds from environmental factors (e.g. ambient radiation, temperature, birds and insects) while promoting consistent seedling germination and growth and potentially also providing moisture and nutrition. The production of a seed cover component in compressed and pre-dried form facilitates mat assembly, minimises unwanted initiation of germination of seeds caused by a high water content in assembled prior art mats, and has unexpected beneficial effects on the growth of seeds/seedlings grown in mats incorporating such seed cover components.

Seed cover components for use in the invention are self-supporting and comprise organic material that has been compressed into a self-supporting layer, said organic material comprising (preferably consisting) coir, rice husk, guar gum, and/or bagasse.

The purposes of the seed cover component has been described above, and in order to perform those purposes and thus be suitable for use in a seedling mat, it must be capable, during use in a seedling mat, of allowing seedlings to growth through it. As stated above, the seed cover component comprises organic material comprising coir, rice husk, guar gum and/or bagasse. It is further distinguished from materials used in the prior art in that preferably, it does not comprise soil, wood pulp, straw and/or cotton.

Coir may be sieved, to give a standard particle size (e.g. <2.8mm), and/or pre- washed, buffered (e.g. to pH6.0) and dried before use. Rice husk and bagasse may be milled (ground) or unmilled (unground).

Preferably the seed cover component comprises coir, coir and guar gum, coir and bagasse, or coir and rice husk.

Where the seed cover component comprises coir and guar gum a preferred weight ratio of coir to dried guar gum is 10:1 .

Where the seed cover component comprises coir and bagasse, it may be in any weight ratio of coir to bagasse of from about 1 :1 to 9:1 . Preferred weight ratios (coir to bagasse) include: 1 :1 ; 3:2; 7:3; 4:1 , and 9:1. Particularly preferred is 3:2. The use of milled bagasse is also particularly preferred.

Where the seed cover component comprises coir and rice husk a preferred weight ratio of coir to rice husk is in the region of from about 10:1 to about 1 :1 , preferably from about 5:1 to about 1 :1 and more preferably from about 4: 1 to about 2:1 . In one embodiment the weight ratio will be in the region of 2/3 : 1/3 coir:rice husk.

Optionally, the organic material of a seed cover component may be combined with an adhesive prior to compression. Suitable adhesives for use in the preparation of seed cover components include aqueous based adhesives, such as for example, VAE (vinyl acetate ethylene), polyvinyl acetate (PVA), polyvinyl alcohol (PVOH) and acrylic adhesives. PVOH adhesives, such as for example, E3443C™ (Sealock) and VAE adhesives, such as for example E1215C™ (also Sealock) are preferred, with PVOH being particularly preferred.

It is particularly preferred to include such an adhesive in seed cover components comprising coir, coir and bagasse, or coir and rice husk. In such embodiments the weight ratio of organic material to adhesive is in the region of from about 5:1 to 5:2. Conveniently, the ratio is from about 4:1 to about 3:1.

Optionally the organic material may be combined with one or more additional agent selected from a plant protection chemical, agrochemical, biological treatment and/or nutrient (such as herbicides, insecticides, fungicides, molluscicides, nematicides, safeners, plant growth regulators, micronutrients, macronutrients and/or fertilisers). In particular the organic material may be combined with a fertiliser.

The organic material is optionally mixed with adhesive and/or additional agent as described herein, and then compressed using any suitable press, at a pressure in the region of 100-250 kgf/cm², preferably 120-220 kgf/cm². Where adhesive is incorporated the seed cover component may be dried prior to storage/packaging/transport and/or subsequent use within a seedling mat as described herein. To facilitate packing, storage and/or transport, a separation layer may be overlaid a seed cover component. Suitable separation layers include those made from, for example, silicon paper, waxed paper, rice paper, potato starch paper and PVOH film.

A seed cover component may be of any suitable dimension for subsequent use in a seedling mat, but is preferably square or rectangular. Conveniently, the width of the seed cover component is in the region of 20-50cm, preferably about 25-40cm, and more preferably about 25-30cm (inclusive), and the length of the seed cover component is in the region of 20- 100cm, preferably about 20-75cm, and more preferably about 25-60cm (inclusive). Seed cover components may be made with a greater length and/or width (e.g. in the order of multiples of the above lengths) and used initially in such a form for storage and/or transport before being subsequently cut to a smaller size to facilitate their use in seedling mats. Preferably the width of the seed component is about 25-30cm and the length of the mat is either about 25-30cm, or about 55-60cm. In certain embodiments, the seed cover component surface area is about 27cm by 28cm or 28cm x 58cm.

The depth of a seed cover component is less than 10mm, preferably less than 5mm, and more preferably less than 3mm. In one embodiment the depth of the seed cover component is in the region of 2-3mm. The skilled man will appreciate that the depth quoted applies to the seed cover component as manufactured and/or immediately after assembly into a seedling mat as described hereinafter. In an assembled seedling mat in use i.e. when water has been applied, and/or seeds are germinating/have germinated and seedlings are growing, such processes may cause the depth to expand beyond the figures quoted above.

If appropriate/desirable, the mat may comprise seed cover adhesive for attaching the seed cover component as described herein, to the layers below. Suitable seed cover adhesives include aqueous based adhesives as described supra. This is applied over the seeds. In an alternative, physical forces alone may otherwise be convenient for retaining the seed cover component. In a further alternative, the seed adhesive may also function as the seed cover adhesive.

Seed cover components as described herein, are then laid atop the seeded rooting substrate.

Preferably, the mat further comprises a root barrier structure in which, or on which, the rooting substrate is accommodated, which barrier structure is configured to inhibit lateral and/or downward root growth beyond the periphery of the rooting substrate. The root barrier structure should support the mat structure and make the mat easier to handle. The root barrier structure may be disposed peripherally of side and/or base regions of the rooting substrate. In this way seedling roots are discouraged from growing through into soil in the nursery and/or from becoming entangled with roots of seedlings in adjacent mats. In one embodiment, the root barrier structure extends peripherally around all the sides and encloses the underside of the rooting substrate.

Preferably the root barrier structure has a structural rigidity which helps support and constrain the rooting substrate, mulch and/or top cover (discussed below). In this way handling of the mat both in situ and during transport is facilitated, e.g. by preventing the mulch and/or top cover from falling off.

The root barrier structure may be considered to be discrete or integral with respect to other mat components, e.g. depending on the nature of fit and how easily the root barrier structure may be separated. For example, during/after manufacture the seedling mat may be formed/placed in, for example, a plastic tray, which could act as a root barrier structure during nursery growth and facilitate handling. Mats may then simply be removed from the plastic trays for subsequent transplantation.

The root barrier structure may be provided with a plurality of channels which face the adjacent rooting substrate. In this regard, channels may encourage roots to grow in particular directions. For example, the barrier structure may be provided with a plurality of generally parallel channels extending over the upper surface of the base region thereof. In this way, subsequent root damage when a seedling is mechanically plucked from the mat and transplanted to the field may be reduced. The channels may in general run parallel to a mat edge, for example the shorter edge of a rectangular mat. The channels may be conveniently found integrally in the barrier structure.

In one embodiment, the root barrier structure is a tray having a base region and upstanding sidewalls, which tray is preferably formed of plastics material or (structural) cardboard.

Cardboard gives a degree of flexibility which can help when mats are used with automated transplantation apparatus. Moreover, after a period of seedling growth, degradation of the cardboard may further facilitate subsequent rolling and handling of the mat for transplantation. Accordingly, the cardboard is conveniently relatively thin. The root barrier structure may also act to mitigate changes in mat humidity during storage. Optionally, the seedling mat further comprises a top cover overlaid the seed cover component. In this way the seed cover component may be protected, e.g. from pests, incidental moisture and generally while the assembled mats are being handled etc. In one embodiment, the top cover is water-soluble and/or perforated. A top cover may comprise paper or (polymeric) film, such as rice paper, potato starch paper, polyvinyl alcohol (PVOH) film or glue film. A liquid chemical coating may also be used. An aqueous adhesive (such as PVOH glue), and which may also be used elsewhere in the mat (as discussed supra), could also be used in/as a top cover.

Conveniently, top cover PVOH film may be 10-300 microns thick (inclusive). Preferably the thickness will lie in the range of about 30 microns to 45 microns, inclusive.

Top cover adhesive may be used between the seed cover component and top cover. Top cover adhesive may be the same as or different to the seed adhesive and/or mulch adhesive as appropriate/relevant. Suitable top cover adhesives include aqueous-based adhesives as described supra.

An adhesive (such as an aqueous adhesive, e.g. PVOH glue) could also be used as a top cover.

The mat may be of any suitable dimension for growing seeds in a nursery and subsequent transplantation to a field, but is preferably rectangular. Conveniently, the width of the mat is in the region of 20-50cm, preferably about 25-40cm, and more preferably about 25-30cm (inclusive), and the length of the mat is in the region of 50-100cm, preferably about 50-75cm, and more preferably about 55-60cm (inclusive). In this way, use of a mechanical transplantation machine to transplant the mat may be facilitated. Further, mats may be made with a greater length (e.g. in the order of multiples of the above lengths) and used initially in such a form for storage, transport and/or initial growth of seedlings in a nursery environment, before being subsequently cut to a smaller length to facilitate transplantation. Preferably the width of the mat is about 25-30cm and the length of the mat is about 55-60cm. In particular embodiments, the mat surface area is about 28cm x 58cm.

Conveniently, one or more seedling mat component(s) (including the rooting substrate, root barrier structure, adhesive(s), seeds, seed cover component and/or top cover), may be pre-treated with, or comprise, one or more plant protection chemical, agrochemical, biological treatment and/or nutrient (such as herbicides, insecticides, fungicides, molluscicides, nematicides, safeners, plant growth regulators, micronutrients, macronutrients and/or fertilisers). To make an embodiment of a seedling mat of the invention, a rooting substrate component is cut (if necessary) to the required size. If an integrated root barrier structure is not being used the substrate may be placed in, for example, a plastic tray. Alternatively, a rooting barrier is not employed. Seed adhesive is then applied (e.g. by spray) to the rooting substrate and pre-treated (rice) seeds are dispersed on the substrate. Optionally, a seed cover adhesive is sprayed on/over the seeds. The seed cover component is then applied over the seeds. Top cover adhesive may then be sprayed on the upper surface of the seed cover component and a top cover applied if desired. The mats are then left to dry before storage or use.

Thus, in a further aspect the invention provides a method for the preparation of a seedling mat as defined herein comprising the steps of:

(a) coating on one surface with a seed adhesive, a generally planar rooting substrate in which seed root growth is supported and which is self-supporting, wherein the rooting substrate comprises materials selected from the group consisting of (i) paper and derivatives thereof, (ii) cellulose fibres and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, and said organic material has been compressed into a self-supporting layer; and wherein the seed adhesive is a hot melt adhesive;

(b) sowing seeds onto the adhesive-coated surface of the rooting substrate component;

(c) applying a seed cover component over the top of the sown seeds, wherein the seed cover component is self-supporting and comprises organic material that has been compressed into a self-supporting layer, the organic material comprising coir, rice husk, guar gum, and/or bagasse.

Once assembled, dried mats can be stored or used to grow (rice) seedlings in a nursery/glasshouse more immediately. Mats with established seedlings can subsequently be transplanted to a (paddy) field. Commercial machinery is ordinarily used for seedling transplantation, a process which results in a small 'plug' of mat also being transplanted. The skilled man will thus appreciate that it is an important feature of rooting substrates/rooting substrate components/seedling mats of the invention, that they can pass through the transplanter machine and that seedlings can be effectively transplanted. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically indicates a basic seedling mat structure from a side-on, cross-section perspective.

The drawing shows a generally planar, rectilinear seedling mat (10). The mat includes a generally planar rooting substrate as described herein (06) having a thickness of 0.3-3cm, preferably 0.3-2.0cm. The rooting substrate (06) is accommodated in a root barrier tray (07). The tray has a flat base portion and upstanding side walls. The side walls of the root barrier tray enclose the rooting substrate (06). Rice seeds (05) are dispersed over a top surface of the rooting substrate. Seed adhesive (04), which is a hot-melt adhesive, on the top surface of the rooting substrate (06) fixes the seeds (05) to the rooting substrate. Above the seeds is seed cover component (02), which in this embodiment is adhered to the components below by virtue of the seed adhesive (04) and/or physical forces. Atop this seed cover component (02) is a protective top cover (01 ) (optional) of rice paper. Figure 2 schematically represents two embodiments, A and B, of a generally planar, rectilinear rooting substrate (09) from a side-on, cross-section perspective.

The rooting substrate component (09) of embodiment A includes a generally planar rooting substrate (06) formed of (i) paper and derivatives thereof, (ii) cellulose fibres and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer. Covering one surface of the rooting substrate (06) is a layer of hot melt adhesive (04), which serves to function as a seed adhesive (see also part B, or Figure 2). Atop the exposed surface of hot melt adhesive (04) is a separation layer (08) of silicon paper.

The rooting substrate component (09) of embodiment B includes a generally planar rooting substrate (06) formed of (i) paper and derivatives thereof, (ii) cellulose fibres and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer. Covering one surface of the rooting substrate (06) is a layer of hot melt adhesive (04), which serves to function as a seed adhesive for fixing seeds (05) to the rooting substrate Atop the exposed surface of hot melt adhesive (04) and seeds (05) is a separation layer (08) of silicon paper.

Figure 3 schematically represents three types of corrugated paper/paper derivative constructs for use in the invention (3a, 3b and 3c). In 3a, a single face corrugated paper construct is illustrated from a side-on cross- section perspective. A flute (21 ) of paper/paper derivative is adhered to a substantially planar sheet of paper/paper derivative (22) such that one set of channels (231 ) formed by the wave are enclosed by the planar sheet of paper/paper derivative. The second set of channels (232) formed by the wave of the flute are open.

The skilled man will appreciate that such a construct lends itself to embodiments where it is desirable to fill/partially fill the second set of channels with, for example, a material that enhances the water retention properties of the rooting substrate/assembled seedling mat. In such embodiments, a further sheet of paper may be laid and optionally adhered to the exposed flute (21 ) thus enclosing the second set of channels (232) and forming a single wall version (as illustrated in Figure 3b).

In 3b there is illustrated a single wall corrugated paper construct from the side-on, cross-section perspective. In a single wall construct, a flute (21 ) is adhered to two substantially planar sheets (22, 24) of paper/paper derivative such the both sets of channels (231 , 232) formed by the wave are enclosed, one set of channels by each sheet of paper/paper derivative (231 by 22, 232 by 24).

In 3c there is illustrated a double wall corrugated paper construct from the side-on, cross section perspective. In a double wall construct, a second flute (26) is adhered atop one of the planar surfaces of a single wall construct (25), and a further planar sheet of paper (27) is adhered to the exposed surface of the second flute (26).

EXAMPLES

Example 1 : Preparation of seed cover components

Seed cover components were prepared with the composition specified in Table 2 below. PVOH E3433™ glue was obtained from Sealock (Scott Close, Walworth Industrial Estate, Andover, Hampshire, SP10 5NU, UK)

Table 2 Composition of seed cover components for a component of dimensions approximately 27cm by 28cm. Coir was pre-washed, buffered to pH 6.0, dried and sieved to a particle size of <2.8mm. Bagasse, where milled, was milled

6 50g unmilled bagasse + 16g PVOH E3433™ glue

7 50g milled bagasse + 16g PVOH E3433™ glue

8 25g milled bagasse + 25g unmilled coir + 8g granular fertilizer + 16g PVOH E3433™ glue

The components were mixed and compressed at approximately 120 kgf/cm² for several minutes using an apple press. Compressed seed cover components were removed from the press and allowed to dry at room temperature overnight before subsequent incorporation in a seedling mat.

Dried seed cover components had the properties described in Table 3 below.

Table 3 Properties of dried seed cover components

Additional seed cover components were prepared with different ratios of coir:bagasse: treatment 1 : 3:2; treatment 2: 7:3; treatment 4: 4:1 ; treatment 5: 9:1 . For each treatment seed cover components were made using 50g of organic matter + 16g PVOH E3433C™ adhesive following the method described in 1.1 above. 1.2 The seed cover components described above in 1 .1 have all previously been shown in our hands to perform well when assembled into fully formed seedling mats, by laying atop a suitably prepared and seeded rooting substrate made of mineral wool. This demonstrates their applicability for use in seedling mats of the present invention EXAMPLE 2 Preparation of rooting substrate components

2.1 Paper-based rooting substrate components

Throughout these examples, where a rooting substrate component employs more than one layer (or composite rooting substrate employs more than one rooting substrate component) the relative positions of those layers are described with reference to their relative positions when within a seedling mat of the invention in use. In a composite (or stacked) rooting substrate, the components may be numbered where component 1 represents the component at the bottom of the assembled seedling mat, and the number attributed to subsequent components increases in order as the component gets closer to that bearing seeds.

The following papers/paper derivatives were used for the preparation of rooting substrate components:

(i) Blue airlaid paper (linen embossed airlaid fabric composed of virgin pulp fibres)

(ii) Brown mulch paper

(iii) Pate melange pulp board

(iv) Pate feuillus pulp board

(v) Resineaux pulp board

(vi) Eucalyptus Kraft BAHIA pulp board

(vii) Panasoft pulp board (bleached softwood Kraft pulpboard)

(viii) Double wall corrugated laminated cardboard 39 CB

(ix) Green DRC (double recrepe) paper

(x) White DRC paper

(xi) Single wall corrugated card, flute type C, made from recycled paper 90gsm

(xii) Double wall corrugated card, one flute type C, one flute type B

(xiii) Single wall corrugated paper, flute type B

(xiv) Virgin pulp paper l OOgsm. With respect to the single wall corrugated constructs, in some examples, one sheet of planar paper was removed to yield single face corrugated paper/card for use in rooting substrate construction.

These were incorporated in a variety of rooting substrate components, some of which are described in detail below for illustrative purposes, others are summarised in Table 5 in Example 4 below,

In some examples the paper/paper derivatives were perforated, in other examples they were were partially shredded, i.e. a multiplicity of slits were introduced (as described hereinbefore). Where a paper/paper derivative is referred to as "non-perforated" it is non- perforated and unshredded.

2.1.1 Triple-layer rooting substrate component made from a single type of paper

A triple-layer paper-based rooting substrate component was made from brown mulch paper. Two sheets of brown mulch paper were perforated by punching holes of

approximately 2.5mm diameter through the paper. These sheets were used to form the upper and middle layers of the rooting substrate. One of these sheets was moulded to give corrugations (i.e. a plurality of channels), and this was used to form the middle layer of the rooting substrate component. A third sheet of flat brown mulch paper (unperforated) was employed as the lower layer of the rooting substrate component.

The three sheets were stuck to each other with hot-melt adhesive (Sealock

H 1 125/26™) to provide a rooting substrate with a sandwich like structure, wherein the bottom layer is formed from a flat sheet of unperforated brown mulch paper, the middle layer is formed from corrugated perforated brown mulch paper and the top layer is formed from a flat sheet of perforated brown mulch paper. The assembled rooting substrate component was cut to the desired size (approximately 28 by 58cm).

2.1.2 Triple-layer rooting substrate component made from different types of paper

(i) A triple layer paper-based rooting substrate component was made from brown mulch paper (as used in 2.1 .1 . above) and polymer infused paper (Softcare HAP 10-15% SAP 100gsm); the bottom and middle layers were made of brown mulch paper, the top layer was made of polymer infused paper.

A sheet of brown mulch paper was perforated by punching holes of approximately 2.5mm diameter through the paper, and then moulded to give corrugations (i.e. to make a flute comprising a plurality of channels). This was used to form the middle layer of the rooting substrate component. A second sheet of flat brown mulch paper (unperforated) was employed as the lower layer of the rooting substrate component. A flat sheet of polymer- infused was used as the top layer.

The three sheets were stuck to each other with hot-melt adhesive (Sealock

H 1 125/26™) to provide a rooting substrate with a sandwich like structure, wherein the bottom layer (1 ) is formed from a flat sheet of unperforated brown mulch paper, the middle layer (2) is formed from corrugated perforated brown mulch paper and the top layer is formed from a flat sheet of polymer-infused paper (3). The assembled rooting substrate component was cut to the desired size (approximately 28 by 58cm). This rooting substrate component is an example of a single wall corrugated paper construct.

(ii) Triple-layer paper-based rooting substrate components were made from brown mulch paper (supra), cellular/honeycomb paper, and white double re-crepe (DRC) paper. In a first (iia) a flat sheet of unperforated brown mulch paper as the bottom layer (1 ), and a flat sheet of white DRC paper as the top layer (3), were employed. Sandwiched between these, was a layer of a cellular construction (2), wherein the walls of the cells run perpendicular to the upper and lower layers. All three layers were adhered to each other with hot-melt adhesive (Sealock H1 125/26™) and the assembled rooting substrate component was cut to the desired size (approximately 28 by 58cm).

In a second (iib), a flat sheet of unperforated brown mulch paper was employed as the bottom layer (1 ), and this was stuck (using hot melt adhesive as described in iia) to a layer of cellular/honeycomb paper (2; as described in (iia)). The cells were then partially filled (approximately half-filled) with sieved, washed and buffered coir (as described supra). A layer of white DRC paper (3) was then stuck (using hot melt adhesive) to the upper surface of the coir-filled cellular layer, to enclose the coir within the middle layer and complete the structure of the rooting substrate component. The assembled rooting substrate component was cut to the desired size (approximately 28 by 58cm).

A variety of rooting substrate components were made in an analgous manner using different paper/paper derivatives for each of the various layers. In further examples, the coir that was used to partially fill the honeycomb/cellular layer was substituted by vermiculite, perlite Seed Aide® CoverGrow™ Spray Mulching Granules (supra).

2.2 Cellulose fibre based rooting substrate components

Rooting substrate components were prepared by cutting them to size (57.5cm by 27.5cm) from the following materials:

(i) Non-woven wood fibre matting having a thickness of approximately 4mm;

(ii) Non-woven wood fibre matting having a thickness of approximately 9mm;

(iii) Non-woven material matting derived from eucalyptus fibres (Tencel Sure To Grow pads, The Sprout People, 170 Mendell St., San Francisco, CA94124);

(iv) Non-woven regenerated fibre matting (80% cellulose fibres, 20% polyester, density of 120gsm, supplied by Neaustima JSC, J. Basanaviciaus Street 103c, LT-76129 Siauliai, Lithuania;

(v) Non-woven jute fibre matting (A8 supplied by Anglo Recycling, Tong Lane, Whitworth, Rochdale, Lancashire, OL12 8BG, United Kingdom).

2.3 Rooting substrate components made from compressed organic material

Rooting substrate components were prepared with the composition specified in Table 4 below. PVOH E3433™ glue was obtained from Sealock (Scott Close, Walworth Industrial Estate, Andover, Hampshire, SP10 5NU, UK). Table 4 Composition for a rooting substrate component of dimensions approximately 57.5cm by 27.5cm. Coir was pre-washed, buffered to pH 6.0, dried and sieved to a particle size of <2.8mm. Bagasse, where milled, was milled to give a particle size of 180-1200μΜ. Rice husk was milled (for 2 minutes using a Robot Coupe floor standing cutter, Model R20).

The components were mixed and compressed at approximately 120 kgf/cm² for several minutes. Compressed seed cover components were removed from the press and allowed to dry at room temperature overnight before subsequent incorporation in a seedling mat. EXAMPLE 3 Assembly of a seedling mat

Rooting substrate components/substrates as described in Example 2 above were prepared with Sealock H 1 125/26™ hot melt adhesive, which was applied to the upper surface of a rooting substrate component/composite rooting substrate either using an ITW Dynatec DDS Delta Fx™ Fiberized spray applicator, or a Reka TR 60 LCD hand sprayer (Rheological Ltd., Moor Mead Road, Twickenham, Middlesex, TW1 UN, UK) and swirl jet nozzle at 3 bar pressure, to achieve an application rate of either 5g/m² of hot melt adhesive. Rice seeds (either Koshihikari or IR-64) were sown at a density of approximately 4 seeds/cm² (i.e. 150g seed for a mat of approximate dimensions 28 cm x 58cm, 63g seed for a mat of approximate dimensions 25cm x 27cm) on to the adhesive-covered surface of a rooting substrate. Seed cover components as described in Example 1 above, were laid on top of the seeded rooting substrate components, to form a fully assembled seedling mat.

EXAMPLE 4 Growth of seedlings from seedling mats

Seedling mats assembled as described in Example 3, employing rooting substrate components as described in Example 2 and seed cover components comprising coir and rice husk in weight a ratio of 67:33 as described in Example 1 were tested for their efficacy in growing rice seedlings under (i) glasshouse conditions and (ii) field/nursery conditions. Table 5 below summarises the seedling mats tested.

4.1 Glasshouse growth

For all tests the seedling mats were transported to the glasshouse and placed into a bay set at the following conditions: 28 °C day time temperature, 18 °C night time temperature, 14 hour photoperiod, 70 % relative humidity). All mats were watered immediately by overhead watering and also by flooding the trays with tap water until the surface of the water was just below the top of the rooting substrate. After twenty minutes the water was drained from the trays. Subsequently, all mats were watered every other day using this method.

4.2 Field/Nursery growth

Following production the mats were laid outside in the nursery. All mats were watered overhead with a fertiliser treatment containing 500 g basal fertiliser /m³ and 20 g ZnS0₄ /m³ at a rate of 1 litre / tray. Following fertiliser application, a single layer of black netting was placed over all the treatments to protect them from birds. The mats were flooded and drained twice per day from day 2 onwards. When the growth stage of the rice plants had reached 3.2 leaf stage, the mats were rolled up and transplanted into a pre-prepared (i.e. levelled and puddled) field using a Kubota transplanter (source: Kubota).

Table 5 Composition of seedling mats tested (representative examples). IR-64 rice seeds were adhered to the top of each rooting substrate and overlaid with a seed cover component comprising coir and rice husk in the ratio 67 coir:33 rice husk. Abbreviations: BL = bottom layer, ML = middle layer, TL = top layer (layers are described with respect to their relative position within the component when assembled into a rooting substrate in use in a seedling mat of the invention; nf = no filling; pf = partially filled with, c = coir, v = vermiculite, p = perlite, sap = Seed Aide® CoverGrow™ Spray Mulching Granules; - = component absent. The term "shredded" refers to the introduction of slits into the medium, using a paper/card shredder.

4.3 Results

4.3.1 Seedling growth

All seedling mats have been shown to support the growth of healthy rice seedlings that are suitable for transplantation. Growth was assessed after 7-10 days and seedlings had reached between the 3.0 and 3.6 (inclusive) leaf stage. Average seedling height per mat varied considerably, correlating at least in part with the growth stage and timing of assessment, but was in general good. The uniformity of growth within each mat was at least 75% and the seedlings grown from each mat were uniformly green (at least 70%). Roots were typically strong, white and well-developed.

4.3.2 Transplantability

In general seedling mats exhibited good/acceptable transplantability characteristics. They were easy to handle, loaded well into the transplanter and gave fairly consistent hills, typically with <12% missing hills. Mats comprising double wall shredded corrugated card constructs in general resulted in a slightly higher percentage of missing hills (up to 20%), as did those comprising A8 non-woven material (up to 23%).

As a generality, mats comprising a bottom layer of perforated material gave a slightly lower percentage of missing hills in comparison to those comprising a non-perforated layer of material at the bottom.

Claims

1 . A seedling mat comprising:

a generally planar rooting substrate in which seed root growth is supported and which is self-supporting, coated on one surface with a seed adhesive for immobilising seeds in or on a top surface region of the rooting substrate, which seed adhesive is a hot melt adhesive;

a seed cover component which covers the seeds and permits seedling growth therethrough; and

2 The seedling mat according to claim 1 , wherein the seed adhesive is a pressure sensitive hot melt adhesive and is selected from the group consisting of: a blend of styrene based block copolymers and synthetic resins, which have a softening point in the region of 88°C-98°C, an operating temperature of 160°C-170°C, and a viscosity at 170°C of 6500+1700 cPs; a blend of thermoplastic rubber, resins, and plasticiser, which have a softening point in the region of 75°C to 90°C, an operating temperature of 160°C-175°C and typical viscosity of 14-20 poise at 160°C and 9-14 poise at 175°C; and a blend of styrene based block copolymers and synthetic resins, which have a softening point in the region of 88°C-98°C, an operating temperature of 160°C-170°C, and a viscosity at 170°C of between 48 and 82 poise.

3. The seedling mat according to claim 1 or claim 2, wherein the rooting substrate component comprises at least one, optionally perforated, layer of paper or paper derivative.

4. The seedling mat according to claim 3, wherein the at least one layer of paper or paper derivative is substantially planar.

5. The seedling mat according to claim 3, wherein the at least one layer of paper or paper derivative is folded, pleated, corrugated or otherwise moulded to provide a plurality of channels which face toward the plane of the upper and/or lower surface of the rooting substrate component as incorporated in the seedling mat.

6. The seedling mat according to claim 3, wherein the at least one layer of paper or paper derivative is formed into a cellular structure comprising a plurality of cells wherein the walls of the cells run perpendicular to the upper and lower surfaces of the rooting substrate component in use within the seedling mat.

7. The seedling mat according to claim 5 or claim 6, wherein the plurality of channels or plurality of cells are at least partially filled with coir, vermiculite, perlite or water holding pellets.

8. The seedling mat according to any one of claims 1 to 7, wherein the rooting substrate comprises at least one layer of non-woven cellulose fibre material

9. The seedling mat according to any one of claims 1 to 8, wherein the rooting substrate comprises at least one compressed self-supporting layer of organic material wherein organic material is (i) coir and rice husk, (ii) coir, rice husk and bagasse, or (iii) wood based material.

10. The seedling mat according to any one of claims 1 -9, wherein the seed cover component comprises coir and rice husk.

1 1 . The seedling mat according to claim 10, wherein the coir to rice husk in the seed cover component are in a ratio of about 67:33 by weight.

12. The seedling mat according to any one of the preceding claims, further comprising a top cover which is optionally water-soluble and/or perforated.

13. The seedling mat according to any one of the preceding claims, further comprising a root barrier structure in which the rooting substrate is accommodated, which barrier structure is configured to inhibit lateral and/or downward root growth beyond the periphery of the rooting substrate.

14. The seedling mat according to claim 13 wherein the root barrier structure is disposed peripherally of side and/or base regions of the rooting substrate.

15. The seedling mat according to any one of the preceding claims, wherein the seeds are ungerminated rice seeds.

16. A seedling mat substantially as described herein with respect accompanying examples and figures.

17. A rooting substrate component for a seedling mat, wherein said component:

is self-supporting;

is generally planar in form;

capable of supporting seed root growth;

comprises materials selected from the group consisting of (i) paper and derivatives thereof, (ii) cellulose fibres, and (iii) organic material selected from coir, rice husk, guar gum, wood-based material and/or bagasse, wherein said organic material has been compressed into a self-supporting layer; and is,

18. A rooting substrate component substantially as described herein, with respect to the accompanying examples and figures.

19. Use of a rooting substrate component as defined in claim 17 or claim 18, in a seedling mat as defined in any one of claims 1 to 16.

20. Use of a seedling mat as defined in any one of claims 1 to 16, or a rooting substrate according to claim 17 or claim 18, for the growth of rice seedlings. A method for the preparation of a seedling mat as defined in any one of claims 1 to 16, comprising the steps of: