A PLANT CULTIVATOR AND A METHOD FOR ITS MANUFACTURE

Abstract: Device for cultivating plants on air spaces comprising a cultivating body of hydrophilic particles of a dense microporous material comprising cellulose fibers derived from the chemical digestion of coniferous wood, the interspaces between the particles forming macropores and being such as to enable air to pass through the body even when the body is saturated with water. The cultivating body has substantially the same form in both wet and dry states. The cultivating body is embraced by a casing which fits tightly against the surface of the cultivating body and which prevents moisture from leaving the body.

Description: A PLANT CULTIVATOR AND A METHOD FOR ITS MANUFACTURE I I The present invention relates to a plant cultivator preferably a cultivator for cultivating conifer plants, such as spruce and pine plants, comprising a body of cultivating substrate having a surface which can be placed on a substratum. Such plant cultivators form part of the prior art. The cultivating-substrate body normally comprises compress ed peat, and in particular so-called Sphagnum-peat, in the form of .a slab in which seeds can be planted for sub¬ sequent germination. ' One disadvantage with such plant cultivators is that the compressed-peat cultivating body does not retain its shape or form when coming into contact - with water, particularly water used to initiate germinat¬ ion of the seed. This instability of the cultivating body also presents a problem when handling the cultivating bodies mechanically, both in conjunction with their manu¬ facture and when placing out the cultivating bodies with plants rooted therein. It has now been found that these disadvantages can be eliminated or substantially reduced when the cultivat¬ ing body incorporates hydrophilic microporous particles of relatively high density, such that the water with which the material is brought into contact is taken up in the icropores of the material and forms colloidal solutions while swelling. The spaces between the particles of micro¬ porous material form macropores which render the body permeable to air even when saturated with water, such as to enable the roots, of the plant to penetrate the culti¬ vating medium. It has been found that a microporous mate¬ rial which, fulfils these requirements is one in which the micropores have a mean particle size of between 10 um and 30 um, and in which the macropores forming the particle interspaces have a mean particle size of between 30 and 300 ju . Particles which exhibit these characteristics afford an extremely high suction effect and consequently a high water-retention factor. At the same time, the macro¬ pores in the,particle interspacing create an' ' air capacity sufficient for nurturing the roots of a plant. One very important advantage afforded by the invention is that it enables, without undue prior experimental work, a culti¬ vating media to be built-up which will produce optimal results when cultivating a given type of tree and when cultivating for special purposes. On the basis of the aforegoing the invention relates to improved plant cultivators of the kind mentioned in the introductory paragraph. The improved cultivator is charac¬ terized in that the cultivating body comprises hydrophilic particles of a relatively dense microporous material, in which the micropores have a mean particle size between 10 and 30 j im and the spaces between the particles form macro¬ pores of a mean particle size between 30 and 300 jum. A common usage to " which bodies of cultivating sub¬ strate of the aforesaid kind are put is the so-called air¬ space cultivation of plants. In this case the cultivating ° ^body is covered with a thermoplastic casing, there being provided an opening on each side of the body. The one opening facing towards the upper side of the body is in¬ tended to leave room for the forestry plant to sprout from the substrate subsequent to germination, while the other opening serves 'the purpose of cultivating the plant on so-called air spaces, the purpose of the latter being to .prevent the roots formed upon germination of the seed from growing out from the. underside. Once the substrate has - been watered, the seed planted therein germinates quite quickly. The moisture-retaining casing embracing the cul¬ tivating substrate also serves, inter alia, as a heat- absorption means, to increase the temperature of the sub¬ strate, or as a heat-reflecting means, to lower the tem¬ perature of the substrate to a level beneath ambient tem- perature, the alternative chosen depending upon prevailing climatic conditions. Consequently, on the basis of the aforegoing, a cultivating body of the afore-described kind is characte¬ rized in that it is embraced by a casing whiph prevents, undesirable release of moisture from the body. When the plant cultivator is intended for the so-called cultivation of plants on air spaces, the aforesaid casing does not cover, or only partially covers that surface of the plant cultivator which rests against a substratum subsequent to setting the plant grown on air spaces - to enable cultivat ion on air spaces and to permit the roots to penetrate down into the ground subsequent to placing-out the plant on the ground. In the manufacture of plant cultivators of the kind mentioned in the introduction, serious difficulties- have been encountered hitherto in enclosing the cultivating body of, for example, compressed peat, in a coating of material which prevents the release of moisture from the body, due to the mechanical instability of the body with respect to shape and form. Hitherto it has been necessary to encase the body in a casing of larger inner volume than the external volume of the cultivating body. The present invention affords a plant cultivator whose cultivating body will retain, its shape and form and which will not change in volume when in use by more than about 10%. When cultivating forestry plants, the cultivation of-plants on air spaces suitably takes place in a nursery, whereafter the young plants are transported to the region in which, they are intended to grow. During this cultivat¬ ion period in the nursery, the cultivating substrate tends to dry out, with, the subsequent risk of inhibiting plant growth.. It is therefore necessary to water the cultivating substrate. It has been discovered that subsequent to dry¬ ing out once or twice it is extremely difficult to water compressed-peat cultivating substrate with sufficient speed or to a sufficient extent. It is difficult to say why this is so, but can be assumed that resins are present in the peat, or are formed therein, and result in a change in direction towards hydrophobization of_the material. which in turn makes it more difficult to wet the material. This has-been found to constitute a significant drawback. • > Another disadvantage with peat is that the material is heavily compressed in order to prevent its dense port- ions from swelling expressively when a cultivating body is subsequently watered, thereby reducing the air perme¬ ability of the material at times to an extent in which the air permeability is too low. • It has now been found in accordance with the invent ion that these and other disadvantages can be reduced or substantially avoided by using a cellulosic material obtained from non-humified wood. A particular suitable material is one which com¬ prises cellulose fibres derived from the chemical digest- ion of softwood or coniforous wood, i.e. primarily spruce and pine. The wood may have been digested in accordance with sulphate method or the sulphite method. Such a material may be formed into substrate bodies by heavily compressing a felt of cellulose fibres, for example fibres of the kind obtained as residue in the manufacture of paper, at a pressure of, for example, 2 20 kg/ , to form a relatively dense fibre cloth, which is then cut with, the aid of a suitable cutting tool into chips of suitable length, for example between 2 and 50 mm, and suitable width., for example between 0.5 and 5 mm, depending upon the type of plant to be grown and the pre¬ vailing climatic conditions, whereafter the chips are collected to form a block having the same dimensions as a desired cultivating body. The block is then enclosed in a thermoplastic foil casing-to form a cultivating body, which is provided with openings on two large surfaces, one to accomodate the plant which sprouts subsequent to germination, and one which, when cultivating on air spaces, prevents the roots from passing out on the side facing the ground. The possibility of providing a cultivating body which retains its shape and substantially its initial volume, both in a wet and a dry state, enables the body" to be provided with a stable casing in accordance with ~ - f various alternative methods. ( • In accordance with one method, the casing can be 5 applied in the form of a tightly fitting and/or adhering . film, adhesive layer or the like. The film or adhesive layer can suitably be applied with the aid of a solution or emulsion of a polymeric plastic or a thermoplastic melt. In accordance with another method, the protective 0 casing for the cultivating body may be covered with a film or foil in a manner similar .to that in which diffe¬ rent kinds of goods are packed (skin packing method). Another conceivable method is one of injection moulding the casing and then bringing the casing to embrace the 5 cultivating body. When the casing has the form of a foil or an adhesive layer, the casing may suitably be applied by immersing the cultivating body in a bath of molten thermoplastic film-forming or adhesive-layer forming material. 0 The cultivating body normally comprises a square, preferably quadrangular plate. It will be understood, how¬ ever, that the cultivating body may also be given other shapes, such, as a circular shape. A circular shape affords the advantage of enabling the casing to be fitted tightly 5 more readily. In accordance with, the invention, the film-forming solution or emulsion applied to form a protective casing on a cultivating body, or the actual film or foil itself, placed around the cultivating body, may be pigmented. When 0 the cultivating plates are intended for use in regions of cold climate for example in the north and midlands, of Sweden, there may suitably be used a black pigment, so as to impart heat-radiation absorbing properties to the film or foil, thereby influencing the germination process in a 5 positive sense. In warmer countries on the other, it may be advantageous to use light-coloured or white pigment, - thereby causing germination to take place at a temperature lower than the temperature of the ground. A further development of the invention enables plants to be propagated in a manner which has proved to be more successful than those methods hitherto applied. In 5 this further embodiment of the invention, a small culti¬ vating body is taken from the upper side of a large culti¬ vating body, therewith leaving a corresponding recess in the larger body. The smaller cultivating body co ' ntains the seed from which the plant is grown. The seed is germinated 10 by watering the smaller cultivating body. As soon as the seed has germinated and a plant has sprouted, the smaller cultivating body, together with the rooted plant, is bedd¬ ed for continued growth of the plant. The possibility of cutting-out shape-retaining "plugs", facilitates handling 5 and enables the work involved to be more readily mechaniz¬ ed. Although the invention can be applied in the culti¬ vation of many different types of plant, it has been found particularly advantageous in respect of the cultivation 0 of forestry plants, primarily coniferous plants, such as spruce and pine plants. The plant cultivator according to the invention simplifies the cultivation of such plants, which is often undertaken on a large scale, and the use of the cultivator represents a considerable rationalizat- 5 ion. The invention will now be described in more detail with reference, to the accompanying drawings, in which ' Figure 1 is a cross-sectional view in perspective of a cultivating body according to the invention? and 0 Figure 2 illustrates the cultivating body of Figure 1 enclosed in a protective casing of an adhering film material. The embodiment illustrated in. Figure 1 comprises a body 1 of material suitable for plant cultivating pur- 5 poses and a seed 3 planted in a hole in the body. The seed has been germinated in a plant nursery, by adding water — - and fertilizer to the body 1, thereby to-produce a plant 5 and roots 6, which penetrate towards the underside ' of the body 1. When the cultivating body is transported to* 2 - a planting site and placed thereon, there is/formed a thin layer of moisture at the border zone of the pressed body 1 adjacent the ground, which causes th ' ' roots 6 to 5 grow and penetrate out through the underside of the body 1 , and to work down into the ground while the plant con¬ tinues to grow and root itself in the ground. The cultivating medium 7 comprises compre-ssed aggregates of cellulose fibre obtained from coniferous • 10 trees. The dimensions of the aggregate is adapted so that the cultivating medium composed thereof obtains a given porosity with pores having a mean poor size of between 30 and 300 μm. The cellulose fibre cloth has a denseness such that the mean pore size of the inner pores lies at 15 about 10-30 um. Because of the extent to which the mate¬ rial is compressed and as a result of the inherent pro¬ perties of the material, the ability of the cultivating body to take-up water is restricted, so that the culti¬ vating medium retains its structure even when watered 20 heavily, at the same time as sufficient water is retained in the smaller pores without preventing air from reach¬ ing the roots to any appreciable extent. The larger pores have substantially non-capillary dimensions and thus form a suitable drainage system, enabling adequate replenish- 25 ent of the water in the substrate used for root develop¬ ment. An important feature of the invention resides in the combination of long-term, water-absorption ability, through the capillary and colloidal system of the dense part of the cultivating body, and the ability- to replenish 30 water through the system of larger pores, while substan¬ tially retaining the shape and form of the cultivating body. Figure 2 illustrates the cultivating body 1 of Figure 1 enclosed in a protective casing in the form of 35 an adhering thermoplastic film. The protective casing 2 is provided with an opening 4, through which the seed 3 •• - is inserted into a hole in the body 1. The plant culti- vator comprising the body 1 of cultivating medium and Sie protective casing 2, has been placed on an air space andr watered, causing the seed 3 to germinate and a plant 5 to grow, said plant sprouting through the opening 4. The protective casing 2 is intended to reduce the risk of the cultivating medium drying out, while being permeable to water vapour at the same time. As shown in broken lines, the protective casing 2 does not cover, or only " partially covers the undersurface of the cultivating body 1. This prevents the roots of the plant from growing outwardly from the undersurface of the plant cultivator during cul¬ tivation on an air space. Subsequent to being placed on intended growing sites, the roots are able to penetrate into the ground and enable the plant to root therein.

Claims: CLAIMS 1. A device for cultivating plants on air spaces comprising a body of cultivating substrate comprising particles of a relatively dense microporous material, the micropores having a mean pore size of between 10 and 30 μm and the spaces between the particles forming throughout macropores having a mean pore size of between 30 and 300 μm and which body is embraced by a casing which prevents the release of moisture and which is provided on the upper side with an opening through which a formed plant can grow, characterized in that the casing is provided on the under¬ side thereof with an opening which prevents outward pene¬ tration of the roots when cultivating on air spaces; and in that the microporous particles comprise substantially cellulose fibres derived from the chemical, digestion of coniferous wood. 2. A device according to Claim 1, characterized in that the hydrophilic particles comprise compressed fibre chips. 3. A device according to Claim 1 or 2, characterized in that the casing embracing the cultivating body comprises thermoplastic foil, which is optionally pigmented. 4. A device according to Claim 1, characterized in that the casing embracing the cultivating body comprises an adhering layer of film or an adhesive, which are optionally pigmented. 5. A method for producing a device according to Claim 4 characterize -in that. the film or the glue is applied from a solution or an emulsion of the film-forming material or adhesive material, or by applying a melt of respective materials. 6. A method according to Claim 5, characterized in that the film or adhesive layer is applied by immersing the cultivating body in a bath of molten thermoplastic, film- forming or adhesive-layer forming material.

Inventors: HEINSTEDT DAVID, HEINSTEDT, DAVID
Applicants: HEINSTEDT DAVID, HEINSTEDT, DAVID
Application year: 1985
Main classification: A01G9
IPC codes: A01G9