EP0331692A1

EP0331692A1 - Cultivation substrates based on mineral wool

Info

Publication number: EP0331692A1
Application number: EP19880907336
Authority: EP
Inventors: Kenneth Roy Dunn
Original assignee: Saint Gobain Isover SA France
Current assignee: DUNN, KENNETH, ROY
Priority date: 1987-08-28
Filing date: 1988-08-12
Publication date: 1989-09-13
Also published as: WO1989001736A1; CA1338795C

Abstract

Le substrat pour culture hors-sol, selon l'invention est à base de feutre de fibres minérales et conditionné sous forme de pains (10) capables de supporter une pluralité de plants. Ce substrat est caractérisé en ce que la structure des pains est telle qu'en position d'utilisation les fibres sont disposées essentiellement suivant des plans verticaux (9). Le substrat selon l'invention permet d'améliorer la production des plants. Abstract A substrate for cultivation without soil is based on mineral fibre felt and packaged into the form of cakes (10) capable of supporting a plurality of plants. The structure of the cakes is such that in the position of use the fibers are arranged essentially in vertical planes (9). Plant production is improved by the invention.The substrate for above-ground cultivation according to the invention is based on felt of mineral fibers and packaged in the form of breads (10) capable of supporting a plurality of plants. This substrate is characterized in that the structure of the loaves is such that in the position of use the fibers are arranged essentially along vertical planes (9). The substrate according to the invention makes it possible to improve the production of plants. Abstract A substrate for cultivation without soil is based on mineral fiber felt and packaged into the form of cakes (10) capable of supporting a plurality of plants. The structure of the cakes is such that in the position of use the fibers are arranged essentially in vertical planes (9). Plant production is improved by the invention.

Description

CROP SUBSTRATES BASED ON MINERAL WOOL

10

The invention relates to mineral wool substrates used for above-ground cultivation.

The use of mineral wool, in particular rock wool (based on volcanic rocks or blast furnace slag) or glass wool for what is commonly called the above-ground culture 0 has experienced a great expansion in recent years. These products indeed have very interesting characteristics. They are relatively inexpensive, easy to implement and ^* offer for culture itself, interesting properties: safety for plants, sterilized medium, good water retention ...

" ₅ The mineral wool substrates used hitherto are products directly derived from those intended for thermal insulation. These are products in the form of felts, the fibers of which are maintained by ut) binder product based on resin. With respect to traditional insulation felts, the main difference

30 rence is due to the fact that the substrates must be easily wettable by aqueous solutions used for hydration and nutrition of plants. For this purpose it is common to incorporate in these substrates surfactants promoting the penetration of water. Apart from this possible modification, we have tried

35 for reasons of economy, to ensure that the insulation products and those intended for above-ground cultivation are as similar as possible. This allows in particular to use the same production facilities for felts.

We also know that the mode of production determines for an important part the structure of the felt. In general, the feu¬ tres are made from fibers coming directly from the drawing from molten material. These fibers are transported by gas streams to a gas permeable receiving conveyor. On this conveyor the fibers are retained while the gases are evacuated. The felt is gradually formed by the accumulation of fibers on top of each other. Experience shows that the fibers are arranged in a privileged manner along planes parallel to the receiving conveyor. For felts intended for Insulation this arrangement is advantageous insofar as it corresponds to good thermal resistance.

The "horizontal" arrangement of the fibers is found in the soilless growing substrates that have been proposed so far. The substrates are marketed and used in the form of "breads", that is to say parailélépipédiques blocks whose dimensions, and in particular the width, are determined by the cultivation techniques. Users want to be able to have breads whose width varies according to the case but can exceed 200 mm or even 300 mm. To obtain these dimensions on felts ordinarily conditioned to the dimensions of the insulation products, it has been the practice to cut the loaves so that the fibers during use are arranged substantially horizontally, that is to say ie approximately parallel to the ground or to the support on which the bread rests. Furthermore, still in the field of growing substrates made of mineral fibers, there are commercially available "cubes" or clods intended for plant growth. When the plant has reached a sufficient size, these cubes are placed on the culture bread itself. The cubes are usually made of the same material as bread, but their dimensions are much smaller, they are of the order of 100 mm per side.

Contrary to what is found for breads, the cubes are often prepared so that the fibers in the position of use lie in substantially vertical planes. The reason for this difference is also due to the packaging method of these cubes. These are obtained from felts cut first into transversa¬ bands and then these bands themselves cut in their width to the dimensions of the desired cubes. To limit the loss of material and above all facilitate the sheathing operation of the cubes, as will be explained in more detail below with reference to the accompanying drawings, we are led to this vertical arrangement of the fibers in the cubes, without, ble- t-11, it has been found a particular influence of this dispo¬ sition on the results of the culture.

The object of the invention is to provide a culture substrate in the form of breads, that is to say substrates on which the culture is completed, in contrast to the cubes used only for the growth of plants, substrate having new properties compared to those of traditional breads, properties which improve the conditions for plant growth. The breads according to the invention consist of mineral fiber felts and are characterized by the fact that the fibers are placed essentially in vertical planes in the position of use. It is remarkable, as will be seen in the examples, to note that this modification of arrangement results in a substantial improvement in crop yields. The reasons for this improvement are not yet fully understood. It is however possible to compare this result with the particularities observed in the "vertical" use of the fibers, in particular with regard to the water retention properties of these substrates. In the search for mineral fiber substrates, we first focused on their inertial qualities and their ability to retain the water necessary for growth. However, it is known that the water content of the substrate is not the only condition to be monitored to ensure good plant growth. It is also necessary to ensure good ventilation, which requires a balance which is difficult to maintain satisfactorily. It seems that it is not very favorable for plant growth to keep parts of the substrate saturated with water. The study of fibrous substrates in which the fibers are arranged horizontally would tend to show a non-uniform distribution of water (or nutrient solutions) in the height of the bread, the lowest areas being the most loaded. Under these conditions, even for an adequate overall solution content, the distribution of this solution may not be satisfactory.

By using substrates according to the invention, the fibers of which are arranged in vertical planes, it can be seen that the distribution of the solutions in the height of the substrate is much more homogeneous, and that in particular saturation is avoided even in the lowest parts. In other words, the crop breads according to the invention provide better drainage. This better control of the distribution of solutions does not only eliminate the risk of saturation, it also allows, for example, a good distribution of nutritive constituents and in particular avoids the accumulation of localized salts. The tests carried out also show that the roots develop and penetrate more easily from the cube into the bread. The reason for this better passage of the roots when the fibers of the bread are in vertical planes probably comes from the very texture of the felts which constitute them. It is thus known that in the manufacture of felts from which the culture loaves are drawn, the lower and upper surfaces form a tighter network of fibers and of the edge as a result of the "lissage" which takes place during the dimensioning in the oven of the lant. It thus appears on the two faces of the felt a sort of "crust" that the roots of the plants have a certain difficulty in crossing. When, according to the invention, breads are used which present the fibers in vertical planes, the "crusts" are located on the lateral faces of the bread, the roots are therefore not hindered in their growth from the cube to the bread.

The use of fibers in vertical plies still has the advantage of better mechanical strength, especially since the felt has a lighter density. For the lightest traditional products, for example those whose density is less than 30 kg / m ³ or even less than 20 kg / m ³ their resistance to crushing is relatively low to the point that when they are soaked from liquid there is a certain tendency to crash under their own weight and that of the liquid. The arrangement of the fibers in the vertical planes, on the other hand, gives the products according to the invention a much higher compressive strength in the direction of these planes. For this reason, the products according to the invention do not show any tendency to sag even when they are of low density.

In the alternative, the culture breads according to the invention also make it possible to minimize the difficulties encountered when the ground or the support on which the bread is placed is not perfectly horizontal. The use of traditional substrates with horizontal fibers requires a support which is also very horizontal, otherwise the solutions tend to saturate the lower parts, neglecting the upper parts, leading to a complete imbalance in the hydration of the plants. The substrates according to the invention are much less sensitive to these level variations.

The mineral fiber substrates according to the invention are produced from felts obtained under usual conditions. In other words, the felts from which the loaves are cut have fibers in planes substantially parallel to the faces of the felts. To obtain the breads according to the invention, the cutting of the felt is made so that the edges, or if the thickness is desired, become the upper and lower faces of the cultivation bread.

The production conditions from felt tends to limit their thickness. As we have indicated, these felts are obtained by collecting fibers conveyed by a gas stream, on a conveyor serving as a filter. To facilitate the deposition of fibers and the elimination of carrier gases it is necessary to maintain an energetic suction under the conveyor. The energy required for this suction is all the more important as the gases have more difficulty in filtering through the conveyor and the mass of fibers already deposited. It is understood under these conditions that in order to be able to operate economically, it is necessary to limit the thickness of the felt being formed on the conveyor. For this reason and also because in uses as an insulator, the thickness is determined by compliance with very precise standards, felts more than 300 mm thick are not usually produced and the the most usual thicknesses are of the order of 75, 100 and 150 mm. In the case of felts of which the thickness is insufficient to constitute the loaves whose width is suitable for the crops envisaged, it is of course proceeded to the assembly of several thicknesses by bringing the parts corresponding to the upper faces into contact. ¬ felt felt. The assembly can have two or more parts depending on the desired width. All combinations are obviously possible starting from elements coming from the same felt and therefore of the same thickness or from several felts of different thicknesses.

Traditional mineral fiber substrates are usually presented wrapped in a sheath formed from a film of plastic material. The role of this sheath is varied. It protects the breads during their transport and also prevents contamination by foreign products during transport or storage. It also plays a role in the management of the culture by avoiding too intense evaporation of the water from the nutritive solutions. Generally, however, this sheath is not kept sealed. We do enco- to ensure some drainage. Anyway in these dif¬ ferent functions, the sheath of tradi ional products is relatively thin and does not need to be adjusted. On the contrary, a certain amount around the bread may be preferred to facilitate drainage. - According to the invention it is proposed, when several thicknesses of felts must be assembled to constitute a loaf, to develop them in a sheath sufficiently resistant and adjusted to maintain the various elements constituting the loaf in position. This support function can be combined with those recalled above 0 for traditional products.

It goes without saying that if you wish to use an unsheathed substrate it is possible to replace the sheath indicated above by links or any other assembly means leaving almost all of the faces of the loaves free. 5 In the case of a sheathing of the products, it is convenient to ensure a "tightening" of the sheath on the felt elements to use a sleeve made of a film of heat-shrinkable plastic material. In this case, the elements being introduced into a sleeve of dimensions slightly greater than the assembly of the elements. 1 join together, and the assembly 0 is passed through an oven to retract the film which comes to apply in close contact with the elements.

The invention is described in more detail in the following, with reference to the attached plates in which:

FIG. 1 is a diagram showing the arrangement of the fibers in a traditional substrate,

FIG. 2 schematically shows the succession of steps leading to the formation of a cube for growing plants in which the fibers are arranged vertically,

FIG. 3 schematically shows the structure of a bread according to the invention,

FIG. 4 schematically shows the structure of a bread formed from several juxtaposed elements,

- Figure 5 shows the two stages leading to the assembla¬ ge of two elements by means of a sheath of a shrinkable material.

3. The mode of cultivation on traditional substrate is illustrated in FIG. 1. The substrate (1) rests flat on the ground or a support (not shown) which is substantially horizontal. The culture can be directly done on the substrate (1) but more usually we proceed in two stages. The plans are developed in a first step on cubes (2) and when their growth is sufficient and requires a volume of additional substrate, the cubes are placed on the substrate (1) in which the roots are propagated. This culture method often uses other elements, not shown, such as nutrient solution supply systems, tanks on which the substrates (1) are deposited to recover the excess drained liquids ...

In FIG. 1, the unsheathed substrate (1) has been shown to show the arrangement of the fibers along traditionally substantially horizontal planes (3). It is common to coat the loaves of substrate with an envelope as indicated above.

Figure 1 also shows the cubes (2) coated with a sheath. For these elements, the use of a protective film without being absolutely dispensable is very general and is due to the way in which they are usually produced, which is illustrated in FIG. 2. In 2a, the transverse cutting of a felt strip (4) from production. As previously in this strip of felt, the fibers are oriented in parallel planes, to the faces of this strip.

The transverse cutting can be carried out for example using a circular saw (5) as shown diagrammatically or by any other equivalent traditional means for cutting the felts of mineral fibers. There, the first cutting of the strip results in the production of long parallé¬ lepipeds (6). These parallelepiped elements must then be cut into smaller elements. Due to their relative fragility, the cubes are, as indicated, coated with a plastic film. The sheathing operation for obvious reasons of convenience is advantageously carried out on the elements (6). Likewise, the sheathing makes it possible to properly maintain the cubes (7) during their formation by cutting out the elements (6) as shown in 2a. As can be seen, this succession of operations results in the production of cubes (7) sheathed on four sides. The sheathed faces are shown hatched. The two free faces (8) are normally used to place the plants. Under these conditions it is understood that according to the most convenient technique abou¬ tit cubes in which the fibers are arranged in vertical planes, but this arrangement owes nothing to considerations concerning the culture itself.

FIG. 3 shows the arrangement and the structure of a culture loaf (10) according to the invention. The use of this bread is analogous to that indicated in connection with FIG. 1. The fundamental difference the resides in the arrangement of the fibers. This has been shown diagrammatically so that the vertical planes appear, for example in (9).

Figure 3 shows a monobloc bread obtained by cutting a felt thick enough to give a sufficient width to this bread, the thickness of the felt constituting the width of the bread. When it is not possible to obtain the necessary thickness, one proceeds as shown in FIG. 4, to the union of several elements (11, 12). Figure 4 shows the two identical elements meeting, it is possible the same way to bring together elements of differentiated thicknesses thy or more than two elements to arrive at a full range of ^'lar¬ geur breads.

As mentioned above, the faces of the felts (4) may have a surface layer which is denser in fibers and therefore less permeable to liquids or even to the roots. If this surface layer constitutes too great an obstacle, it is preferable to remove it in the assemblies such as that represented in FIG. 4 at least on the faces of the elements 11 and 12 brought into contact in (13). This removal is done by peeling equivalent to cutting the felt in its thickness and can be carried out for example by means of suitably arranged band saws.

When several elements (11, 12) are used to form a loaf as shown in FIG. 4, it is necessary to join them together. A mode of assembly is shown in Figure 5. This involves joining the two elements (11, 12) by means of a sheath (14). To obtain a very stable assembly, it is proposed, for example, to form the sheath by means of a film of heat-shrinkable plastic material. In this case the two elements (11) and (12) are arranged in a sleeve (15) of the chosen film (FIG. 5a). This installation is very easy, the section of the sleeve being very large compared to that of the two elements. The assembly is spent a few moments in a heat treatment enclosure and the sheath retracts against the elements which it keeps tightly pressed against each other (FIG. 5b).

The sheath used is usually black or white. The black color is preferably used when it is necessary to limit the heat losses at the level of the substrate. This is particularly the case for winter crops. When on the contrary it is necessary to preserve the substrate against an excessive temperature, white films are preferred.

The advantages of the culture substrates according to the invention have been demonstrated in tests carried out in the greenhouse for cultivation cucumbers. The tests were carried out simultaneously on traditional breads having a horizontal arrangement of the fibers and on breads according to the invention. In both cases, the loaves were pro¬ ducts â from the same rock wool felt whose chemical composition is ₅ wt.

Si 2 41.8% FeO, Fe2Û3 0.8%

CaO 41% S 0.3%

AI2O3 11% Tiθ2 0.4%

MgO 3.7% MnO 0.5%

20 The density of the felt is approximately 40 kg / m ³ .

The dimensions of the traditional breads (A) and according to the invention (B, C) are as follows: length width thickness

A 900 mm 150 mm 75 mm n II II II

15 ^B

C "" 110 mm

The development of the plants is carried out on "cubes" of the same material as the substrate of the loaves and of dimensions 100 × 100 × 65 mm. The variety used is Brucona (Bruinsma). It is sown on

July 10 on the cubes and planted on the breads on July 27 because of 2 plants per loaf. The breads are arranged randomly at a spacing corresponding to 1.2 plants per square meter.

The irrigation and temperature nutrition conditions “5 are those traditionally implemented by the station. Harvesting takes place between September 1 and September 30.

The average crop results at the end of the harvest are as follows:

1) number of fruits per plant:

30 to ^{12 ”50}

B 14.25

C 14.50 or an increase of about 15% for the plants grown on the breads according to the invention.

35 2) fruit weight:

A 348.4 g

B 405.0 g

C 413.7 g, an increase in order of 17.5%. 3) weight of fruit harvested per plant:

A. 4.36 kg

B 5.77 kg

C 5.99 kg

- an increase of around 35%.

The improvement observed in production can be explained by a better rooting of the plants itself resulting from a better environment, that is to say from a better adapted substrate.

Physical measurements on the breads are appraître _Q air / water higher in the substrates of the invention condui¬ health â better aeration of the roots.

Analysis of the breads after cultivation also shows a more regular distribution of the roots and greater growth in the breads according to the invention. 5

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Claims

1. Substrate for above-ground cultivation, based on felt of mineral fibers conditioned in the form of breads (10) capable of supporting a plurality of plants, characterized in that the structure of the breads is _ς such that in the position of use the fibers are arranged essen¬ tially along vertical planes (9).

2. Substrate according to claim 1 formed by the meeting of several elements (11, 12), the thickness of the original felts (4), whereby these elements from being individually insufficient to ₀ provide a suitable width bread .

3. Substrate according to claim 2 wherein the different elements (11, 12) gathered to form the bread of suitable width are held in position against each other by means of a sheath (14). 4. The substrate according to claim 3, in which the elements are held tight by retraction of a heat-shrinkable sheath (14). 5. Substrate according to claim 2 to 4 wherein when several elements are combined to form a bread of suitable width, these elements are previously rid of the surface layers of the original felts at least on the faces bringing into contact two elements.

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