Plant husbandry – Seed tape or mat – method or apparatus
Reexamination Certificate
2000-11-21
2002-09-10
Poon, Peter M. (Department: 3643)
Plant husbandry
Seed tape or mat, method or apparatus
Reexamination Certificate
active
06446386
ABSTRACT:
This invention relates to a seed germination medium for encouraging the germination and establishment of seeds, especially in hostile environments, where water, nutrients, climate, chemical contamination and soil conditions may be limiting factors.
Desertification, salination and soil erosion are significant and increasing problems in many parts of the world. They are typically caused by climatic change, rapidly increasing population, shortage of water and loss of agricultural land to development. This process often places unprecedented pressure for increased productivity from a diminishing and non-renewable land resource. This often leads to contamination of the soil with salts (from contaminated irrigation water and fertiliser use) which eventually makes it impossible to grow food or even cover crops. This in turn accelerates soil degradation and leads to desertification.
One of the few ways to reverse salination is to irrigate contaminated soils with clean water to wash-out the saline contaminants. This is often not possible due to the lack of pure water. An alternative is to establish salt tolerant species (e.g. pistachio, barley and sugar beet), then to minimise water use, and subsequently to ‘soak-up’ salts in the harvested crops. This is a gradual process which will allow a wider range of less tolerant crops to be grown in the longer term.
Various proposals have been made for providing seed germination media which provide the seeds with water, nutrients and protection during the germination phase.
U.S. Pat. No. 5,189,833 discloses an arrangement in which lawn grass seeds are germinated in a thin layer of growing medium sprayed over a mat of non-woven polypropylene lying on top of an impermeable membrane. After a few days of germination, the mat carrying the seed-bearing medium can be lifted, rolled and then spread over an appropriately conditioned and prepared lawn bed. It will be appreciated that such an arrangement is neither intended nor suitable for growing crops in adverse environmental conditions.
Australian Patent Application AU-A-81394/75 discloses a seed bearing mat comprising upper and lower layers bonded together with a latex adhesive, seeds being bonded between the layers. The lower layer is a water permeable material such as straw, coconut fibres, peat moss or wood shavings whilst the upper or covering layer is formed from material of a finer texture than the lower layer such as coconut fibre dust or sawdust bonded together by latex. The seed bearing mat of AU-A-81394/75 is described as being particularly useful in preparing lawns.
French Patent Application FR-A-2505607 discloses a seed germination medium comprising a folded layer of a transparent plastics material such as polyethylene having bonded to the underside thereof bands of a water-soluble or degradable seed-bearing medium such as paper. In use, the seeds germinate beneath the transparent plastics layer and, as the seedlings grow, they lift the transparent layer away from the water-soluble/degradable medium. Thus the transparent layer is gradually unfolded and carried upwards by the growing seedlings and therefore remains in place over the top of the plants to maintain a greenhouse effect.
French Patent Application FR-A-2440438 discloses a peat-based seed bearing medium comprising a lower layer formed of a water-permeable fibrous material such as cellulose fibres or muslin cloth, an intermediate layer of peat comprising seeds and any additives; and optionally an upper layer which is also water-permeable and can be formed from a material such as muslin. Although FR-A-2440438 discloses that the media are envisaged as being economical for large scale use such as plantations in arid regions e.g. deserts, it is also emphasised that an advantage of the peaty medium, compared with polyethylene sheets, is that it allows the penetration of rain water.
International Patent Application WO-A-96/28010 discloses a seed germination medium in sheet form having upper and lower layers and seeds disposed therebetween. The upper and lower layers are preferably formed from a biodegradable paper material. In order to assist anchoring of the medium in the underlying soil or, in the case of desert areas, sand, the medium is slit longitudinally to enable it to be stretched laterally to form an open lattice. However, it has been found that a problem with the lattice arrangement disclosed in WO-A-96/28010 is that it has a tendency to dry out too quickly. In particular, when stretched to open out the lattice, the edges of the lattice openings lift exposing the lower layer of the medium and increasing water loss. Also, the lifting of the edges of the lattice results in the seeds being lifted away from the soil which acts to inhibit germination of the seedlings, possibly through build up of ethylene in the medium.
It is an object of the present invention to provide a seed germination medium which avoids the problems inherent in many known media and which enables seeds to be germinated effectively in a range of different types of environment, particularly arid and semi-arid areas and areas in which soil salination and desertification has taken hold.
Accordingly, in a first aspect, the invention provides a seed-germination medium comprising an upper layer formed from a biodegradable material which is permeable to gases but substantially impermeable to water in liquid form; a lower layer formed from a water-absorbent biodegradable material; seeds being disposed beneath the upper layer; and the upper layer having a plurality of perforations therein to enable seedlings germinating from the seeds to grow therethrough.
The lower layer is also preferably provided with a plurality of perforations to enable roots emerging from the seeds to grow therethrough.
The biodegradable material from which the upper layer is formed can be partially permeable to water vapour but should nevertheless provide some barrier properties with respect to water vapour. A major function of the upper layer is to minimise loss of water from the medium through evaporation, and to hold seeds in position when exposed to wind, rain or harsh irrigation.
The biodegradable material of the upper layer is preferably a biodegradable polymer. The polymer can be one which contains a biodegradable element and a non-biodegradable element. For example, the polymer can contain, as the non-biodegradable element, a polymer which, in its pure form is impermeable to water, for example polymers such as polyolefins, e.g. polyethylene and polypropylene; polyesters, polyamides, and chlorinated polymers such as polyvinylchloride (PVC). The upper layer can be made of a transparent polymeric material or it can be non-transparent.
The biodegradable element can function as a binder for the non-biodegradable element. Preferably the biodegradable polymer is one which is at least partially degraded by microbial means. For example, the biodegradable polymer can be a material such as a polysaccharide, e.g. starch, a phosphatide, or a glyceride, e.g. a mono-, di- or triglyceride or mixtures thereof such as a vegetable oil, one example of a vegetable oil being soya oil.
One example of a biodegradable material which can be used in the medium of the present invention is a composite material formed from PVC and soya bean oil sold by Linpac, France under the trade name “Degradyl”. Another example of a suitable biodegradable polymer is a starch based polymer available from I.C.I. under the trade name “Bioplast”.
In an alternative embodiment, the upper layer can be formed predominantly from a biodegradable water permeable material treated to render the upper surface thereof impermeable to liquid water, but partially permeable to water vapour, an example of such a material being a waxed paper.
The lower layer is an absorbent layer which can be made from a wide range of bio-degradable materials including air-laid paper e.g. an air-laid latex bonded paper, for example a paper formed from fluff pulp and a latex binder; waste or recycled paper; or other fibre-based or waste products. The selection of a suit
Gellner Jeffrey L.
Lahive & Cockfield LLP
Poon Peter M.
LandOfFree
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