GB2194124A

GB2194124A - Propagating trays

Info

Publication number: GB2194124A
Application number: GB08717531A
Authority: GB
Inventors: Edward Michael Leigh Manly
Original assignee: Fisons Ltd
Current assignee: Fisons Ltd
Priority date: 1986-07-26
Filing date: 1987-07-24
Publication date: 1988-03-02
Anticipated expiration: 2007-07-24
Also published as: GB2194124B; GB8618293D0; GB8717531D0

Abstract

A multicellular propagating tray contains a propagating medium which is a thixotropic gel of hectorite in water. The gel preferably contains at least 60 ppm and not more than 200 ppm calcium ions, and may contain nutrients, fungicides, pesticides and bactericides. The tray is of homopolymer polyproylene and may have a transparent or metal foil cover.

Description

SPECIFICATION Horticultural device This invention relates to a horticultural device.

In the propagation of seeds and cuttings multicellular propagating trays are used to give regular spacing and prevent inter-rooting of individual plants, which both allow for minimum root damage on transplantation and for automatic plant handling. The individual cells of the multicellular propagating trays are conventionally filled with one of the following propagating media: a form of peat compost, a soil or vermiculite. The conventional use of such propagating media in multicellular trays leads to several disadvantages.

Firstly, the filling of the multicellular propagating trays, especially when they are finely divided into propagating cells, may be difficult with the conventionally used propagating media. For example, peat has to be finely milled for adequate filling. Secondly, with the conventionally used propagating media it is difficult to achieve a uniform medium structure throughout the multicellular propagating tray.

Variation in the medium structure in the multicellular propagating tray leads to non-uniform propagation of the plants. Thirdly, the conventionally used propagating media are opaque so that it is impossible to judge when the seed has begun to germinate. Fourthly, the conventionally used propagating media have to be kept moist and so watering is necessary.

Drainage holes may have to be provided in the multicellular tray, which increases its cost of manufacture and successful propagation of the plants is dependent on the attention given by the grower.

We have now found a propagating medium which mitigates or overcomes some or all of the problems associated with the propagating media conventionally used with multicellular trays.

According to the jnvention we provide a multicellular propagating tray containing a propagating medium which is an aqueous rooting gel, which aqueous rooting gel comprises a thixotropic gel of hectorite in water.

The gel preferably contains at least 60ppm, more preferably at least 75ppm calcium ions.

The gel suitably contains not more than 200ppm calcium ions, preferably not more than 150ppm calcium ions. For a clear gel to be obtained the calcium ion concentration is preferably less than 130ppm.

The calcium ion concentration is preferably obtained by the addition of a calcium salt to the water used to prepare the gel, but other methods of incorporation may also be used, such as addition during formation of the gel.

The calcium salt should be of sufficient solubility to dissolve in the aqueous medium, and may be calcium sulphate, calcium chloride, calcium nitrate or monocalcium phosphate. It is preferred to use calcium sulphate dihydrate.

Gels with a calcium ion concentration of greater than 130 ppm which are sufficiently clear to enable visualisation of germination may be prepared by adding a calcium ion complexing agent, eg a sodium or potassium polyphosphate, to the gel. The quantity of complexing agent to be added to obtain a sufficiently clear gel will depend on the nature of the complexing agent and on the quantity of calcium ions to be complexed. However we have found that it is possible to prepare clear gels with a total calcium ion concentration of 150 ppm by adding 31Smg/litre of sodium hexametaphosphate. A clear gel having a calcium ion concentration of 200 ppm may be prepared by adding 846mg/litre sodium hexametaphosphate to the gel.

By the term hectorite is meant a trioctehedral clay which is a member of the saponite sub-group of smectites. The term hectorite has been ascribed to the natural trioctehedral clays found at Hector, California, USA. Hectorites can be represented by the general or idealised formula: (M 'pH20)(Mg3 yLiy)Si401o(0H)2 where M is an exchangeable cation, preferably sodium and where y is a number, which can be greater or less than unity. The hectorite may be of natural origin, but more usually is synthetic. The hectorite preferably comprises from 58 to 63 parts by weight SiO2, 25 to 30 parts by weight MgO, 2.2 to 2.8 parts by weight Na20, 0.65 to 0.90 parts by weight Li2O and from 0.15 to 0.40 parts by weight sulphate. It is preferably fluoride free.

It is preferred that the concentration of hectorite is in the range 1 to 5%, preferably 2 to 4% w/v.

The gel may contain one or more of the following additives; nutrients, fungicides, pesticides and bacteriocides.

Suitable nutrients include potassium, magnesium, nitrogen, iron, copper, manganese, zinc, boron and molybdenum. Suitable fungicides include tolcofos-methyl, thiophanate, methyl, metalaxyl, thiabendazole or furalaxyl.

The gel according to the invention may be prepared by any conventional method for the manufacture of a thixotropic gel. The hectorite is dispersed in water, preferably demineralised water, which contains the required amount of the calcium salt, and the gel is obtained, which is filled into the container of the propagating unit. In a typical procedure the required amount of hectorite is dispersed in water having the preferred calcium ion content, preferably at a temperature between 25 and 35"C, more preferably between 28 and 32"C, with the aid of a high energy mixer.

Provided the calcium content is restricted to below 130ppm and other additives are avoided, the gel will be transluscent, thus per mitting seed germination to be observed.

The multicellular propagating tray is preferably made of a material with a very low water transmission rate, for example, polypropylene, in particular homopolymer polypropylene.

The wall thickness of the container is preferably in the range 0.3 to 0.7, eg 0.5mm.

The multicellular propagating tray may be be provided with a cover, eg a transparent lid or preferably a metal foil cover. The metal foil cover is preferably sealed over the open face of the multicellular propagating tray after filt- ing. The foil cover may be removed entirely during use of the multicellular tray and may optionally be replaced by a transparent lid or the foil cover may be retained during use. In the latter case the metal foil may be pierced to allow insertion of the seed or cutting into the gel.

The individual cells of the multicellular propagating tray preferably have a volume in the range 0.25m1-40m1, more preferably in the range 0.25m1 16m1 and most preferably in the range 0.25m1-10ml, eg 0.5m1.

The use of a multicellular propagating tray according to the invention is found to have one or more of the following advantages; watering of the seeds or cuttings is not required, drainage holes are unnecessary, detection of propagation is facilitated, filling of the individual cells with propagating medium is facilitated, there is a uniform propagating medium structure throughout the multicellular propagating tray which leads to uniform propagation, the gel provides a sterile medium for seed and cutting growth, the root of the seedling or cutting is protected by the gel on transplantation and the use of materials with a very low water transmission rate in the manufacture of the multicellular propagating tray and the provision of a cover inhibits water loss from the gel.

According to a further feature of the invention we provide a method of plant propagation which comprises growing a seed or cutting in a multicellular propagating tray containing a thixotropic gel of hectorite in water.

According to a yet further feature of the invention we provide a thixotropic gel of- hectorite in water for use as a propagating media in a multicellular propagating tray.

Claims

1. A multicellular propagating tray containing a propagating medium which is an aqueous rooting gel, which aqueous rooting gel comprises a thixotropic gel of hectorite in water.

2. A multicellular propagating tray according to Claim 1, in which the propagating medium contains at least 60ppm calcium ions.

3. A multicellular propagating tray according to Claims 1 or 2, in which the propagating medium contains not more than 200ppm calcium ions.

4. A multicellular propagating tray according to Claims 1 or 2, in which the propagating medium contains not more than 150ppm calcium ions.

5. A multicellular propagating tray according to Claims 1 or 2, in which the propagating medium contains not more than 130ppm calcium ions.

6. A multicellular propagating tray according to any of the above claims, in which the propagating medium contains nutrients, fungicides, pesticides or bacteriocides.

7. A multicellular propagating tray according to any of the above claims, in which the multicellular propagating tray is of a material with a very low water transmission rate.

8. A multicellular propagating tray according to Claim 7, in which the multicellular propagating tray is of polypropylene.

9. A multicellular propagating tray according to Claims 7 and 8, in which the multicellular propagating tray is of homopolymer polypropylene.

10. A multicellular propagating tray according to any of the above claims which is provided with a cover.

11. A multicellular propagating tray according to Claim 10, in which the cover is a transparent lid.

12. A multicellular propagating tray according to Claim 10, in which the cover is metal foil.

13. A multicellular propagating tray according to any of the above claims, in which the individual propagating cells have a volume in the range 0.25ml--40ml.

14. A multicellular propagating tray according to any of the above claims, in which the individual cells have a volume in the range 0.25ml--16ml.

15. A multicellular propagating tray according to any of the above claims, in which the individual cells have a volume of about 0.5m1.

16. A method of plant propagation which comprises growing a seed or cutting in a multicellular propagating tray containing a thixotropic gel of hectorite in water.

17. A thixotropic gel of hectorite in water for use as a propagating media in a multicellular propagating tray.

18. A multicellular propagating tray substantially as hereinbefore described.