GB2216512A - Plant growth media - Google Patents

Abstract

A plant growth medium has a super-absorbent, in particular a cross-linked polyacrylate, mixed with particulate bulk material to provide the "soil" for the plant roots. Nutrient material may also be included in the mixture, which can be left loose or compressed to a self-cohesive solid and encased in a plastic bag. For use the bag is slit open to form a tray, and water is added in quantities to transform the mix to a gel in which seedlings can be planted. The water trapped but gradually released to the plant roots is sufficient to need only infrequent replenishment.

Description

Improvements relating to Plant Growth Media This invention relates to plant growth media.

Seeds, seedlings and small plants are often nurtured in pots containing specially prepared mixtures of soil, peat, sand, fertilisers and so on. Another popular artificial growth base is known as a Gro-Bag, which is a plastic sack filled with humus-rich material.

It is laid on the ground or a bench or shelf and the user slits it open down the middle of the uppermost side, enlarges the gap, and plants tomatoes or whatever in the material inside. This must of course subsequently be kept watered to the correct degree, avoiding over-saturation and aridity. Even if there is the time available, the job requires care and attention.

Also, the height of the growing season usually coincides with holiday absences, and watering by the neighbours is often erractic to non-existent.

Another snag with such bags is that an economical size is large, and consequently heavy and awkward to transport from garden centre to greenhouse.

It is the aim of this invention to provide a more convenient substitute, and one which considerably alleviates the watering problem.

According to the present invention there is provided a plant growth medium including a mixture of a super-absorbent and particulate bulk material to form a matrix for the plant roots.

This mixture may be bagged loose or it could be compacted into a self-cohesive solid in the form of a thick "board" or "biscuit".

A super-absorbent is a material, usually in powder form, which is able to absorb an exceptional amount of water, from several hundred to a thousand times the weight of the powder, before saturation occurs. Mixture with water produces a thixotropic jelly. The superabsorbent will generally be a cross-linked polyacrylate and sodium cross-linked polyacrylate is particularly preferred.

The matrix material may be sterile and inert, and the necessary nutrients may be provided either by additives to the water which makes the gel and/or by nutrient material being mixed with the other components at the outset. Substances envisaged for the matrix material include peat, sawdust, shredded paper, sand and even sterile earth.

The super-absorbent powder is conveniently mixed dry with the nutrient (if provided) and matrix materials, which may themselves be mixtures selected to suit the intended plant growth. As mentioned above, it may be bagged in this loose form, the bag preferrably being of moisture impervious plastics material to keep the mix dry until use.

However, it may sometimes be desired to sell the product in an even more compact form. Normally there will be sufficient moisture in the materials or the atmosphere to be absorbed by the cross-linked polyacrylate and cause it to act as a binding agent. If not, a small amount of water can be added at the mixing stage. The substance can then be compacted into cohesive blocks or pressure rolled into substantially solid sheets or boards. These may then be put into waterproof encasements, conveniently plastic bags or sacks.

The resulting blocks or boards, will be considerably smaller than an equivalent Gro-Bag and will be very much lighter. They are, however, naturally slower at taking up water than the loose-bagged material.

When being prepared for use, the bag is opened and formed into a tray or pot, depending on its basic shape.

Water is then added in vastly greater quantities than would be normal for a Gro-Bag. The material will swell up and convert to a soil or peat-like mass into which seeds and plants can easily be inserted. Despite the amount of water, they will not suffer from oversaturation, but will absorb moisture as if from a nicely damp soil. As water is taken up, a certain amount will be lost through transpiration, but on a daily basis only a small fraction of the total quantity held by the mass.

Also, as water is taken from around the plant roots, so the remainder will re-distribute and keep those roots moist. There will also be a tendency for the root ends to 'hunt' water and, since it is there in abundance with nutrients dissolved in it, rapid root development occurs. This in turn accelerates above-soil growth, flowering and fruiting.

Thus, this plant growth medium can be left untended for considerable periods (a current estimate is six weeks) while providing just as much water and nutrients as the plants require.

Claims (9)

1. A plant growth medium including a mixture of a super-absorbent and particulate bulk material to form a matrix for the plant roots.

2. A medium as claimed in Claim 1, wherein the superabsorbent is a cross-linked polyacrylate.

3. A medium as claimed in Claim 2, wherein the superabsorbent is a sodium cross-linked polyacrylate.

4. A medium as claimed in any Claim 1, 2 or 3, wherein the matrix material is sterile and inert.

5. A medium as claimed in any preceding claim, and including nutrient material mixed with the other components.

6. A medium as claimed in any preceding claim, wherein the medium has a waterproof encasement openable to provide a seed or plant pot or tray.

7. A medium as claimed in Claim 6, wherein the encasement is a plastic bag or sack.

8. A medium as claimed in Claim 7 or 8, wherein the material is contained loose in said encasement.

9. A medium as claimed in any one of Claims 1 to 7, wherein the components are compacted into a selfcohesive solid.