A method for producing continuous lengths of propagation plugs or rods

Abstract

The present invention relates to the production of propagation plugs, primarily blocks of growth medium for the growing of cuttings and seed plants, and of the type consisting of a cylindrical block having an envelope of sheet material and an associated filling of sphagnum or a corresponding substrate material. The sheet material is here a netting or mesh, preferably biodegradable, having a mesh size within the range of 0.1 to 1.5 mm.

Description

A method for producing continuous lengths of propagation plugs or rods, and propagation plugs or rods produced by such methodTechnical field of the inventionThe present invention relates to the production of propagation plugs or rods, primarily blocks with growth medium, for the growing of cuttings and seed plants, and of the type consisting of a cylindrical block or rod having an envelope of sheet material and an associated filling of growth medium.Background of the inventionThe production of plant pots from non-woven paper combined with a growth medium, like sphagnum, presents an innovative approach to sustainable horticulture. Non-woven paper, known for its versatility and environmental friendliness, serves as an ideal candidate for creating biodegradable plant pots. This material, typically made from medium to long fibres bonded mechanically, thermally, or chemically, is not only sturdy but also breathable, which is crucial for plant growth.The integration of sphagnum as a growth medium complements the non-woven paper by providing excellent water retention properties and promoting healthy root development. Sphagnum moss, often used in horticulture, helps maintain moisture and nutrients, offering a conducive environment for roots to thrive.For these pots to be effective, the non-woven paper must be perforated. Perforation of the paper is critical as it allows roots to penetrate the walls of the pot, thereby allowing for air pruning of the plant roots. Air pruning functions by allowing the surrounding dry air to disturb or prune the penetrating (through the sheet material) tip of the roots. Once the roots are air pruned, they lose their dominance, and many secondary roots develop to replace them. These are then in turn also air pruned and again they are replaced by even more roots. Air pruning therefore results in a root system with a very large quantity of young vigorous roots that are needed for a subsequent transplanting operation where the larger number of roots quickly grow outwards, giving the plant a great head start.The manufacturing process involves designing the paper to be durable enough to hold the growth medium and the developing plant while ensuring it will break down in the soil without leaving harmful residues. This biodegradability is a key feature, reducing plastic use and waste in gardening and commercial agriculture.By using such biodegradable pots, gardeners and farmers can transplant the entire pot directly into the soil, minimizing root disturbance and labour involved in transplantation.However, the production of the nonwoven paper is production intensive, and the perforation process takes time.Therefore, there exists a need for an improved biodegradable nonwoven sheet material to produce propagation pots, which has sufficient degradation time, while also providing low moisture retention properties, better hydrophobicity, as well as sufficient tear strength and bending stiffness.Description of the inventionIt is an object of the present invention to provide a sheet material for producing continuous lengths of propagation plugs or rods.The inventor of the present invention has developed a sheet netting or mesh that is compatible with the current methods of producing paper plant pots, such that the sheet or mesh netting can merely be used in stead of the nonwoven paper. At the same time, the netting or mesh have been found to need a mesh size within the range of 0.1 to 1.5 mm to allow for appropriate air pruning of the plant roots while still being able to retain the growth medium that it supports.A first aspect relates to a method of manufacturing a continuous length of propagation pots or rods comprising:- suctioning sphagnum or a corresponding substrate material through a pipe into a suction chamber for deposition and compaction within the suction chamber by suction applied through a perforated tube in the suction chamber;- forming a plug of the compacted sphagnum or a corresponding substrate material in an outlet conduit of the suction chamber as part of compacting the sphagnum or a corresponding substrate material within the suction chamber;- introducing a netting or mesh sheet material through an aperture in the pipe; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm; and- joining the edge area of the lining hose by conveying the lining hose containing the compacted sphagnum or a corresponding substrate material through a heating station, such that thereafter the netting or mesh sheet material is stabilized in its hose shape for further advancing inside the pipe.A second aspect relates to a propagation plug or rod produced by the method according to the first aspect.A third aspect relates to a propagation plug or rod comprising a growth medium held in a netting or mesh sheet material having a mesh size within the range of 0.1 to 1.5 mm.The term “continuous lengths of propagation plugs or rods” refers to the production of growth medium plugs or rods, which is made in a continuous line as e.g., disclosed in WO9203914. The length of growth medium is thereafter cut into pieces of suitable size (length relative to the diameter), corresponding to the desired size of a propagation pot or rod. The term “propagation plug” also covers the term “plant pot”. The propagation pots and rods may e.g., be used for seedlings, seeds, flowers, and trees.The term “growth medium” refers to physical support for plant growth, or the germination of a seed to take place, providing water retention, aeration, and optionally nutrient supply. Non-limiting examples of growth medium may e.g., be mosses in general, sphagnum, peat moss, soil, composted bark, potting mixes, bark, vermiculite, stone wool, polymeric foam, or a corresponding substrate material.In the present context, the terms “netting” and “mesh” may be used interchangeably. However, in meshes are typically evaluated based on their ability to allow passage of air and liquids through precisely defined and uniform openings, and are typically made by weaving, or welding wires or fibres together. Nets generally refers to a fabric-like material made by knotting a thread or cord at intersections, creating a grid that can be elastic or fixed, and evaluated more for their physical properties and ability to contain objects, with various sizes and types of openings depending on the specific use.The mesh sizes of the netting or mesh sheet material is between 0.1 to 1.5 mm, preferably within the range of 0.2-1.4 mm, such as within the range of 0.3-1.3 mm, e.g., within the range of 0.4-1.2 mm, such as within the range of 0.5-1.1 mm, e.g., within the range of 0.6-1.0 mm, such as within the range of 0.7-0.9 mm.Preferably, the netting or mesh sheet material is biodegradable. In the present context, the term “biodegradable” means that the referred substance or object is capable of being decomposed by bacteria or other living organisms. The netting or mesh sheet material is in some embodiments made from biodegradable polymers, preferably from polylactic acid (PLA), preferably combined with polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), or polycaprolactone (PCL).In one or more embodiments, the method further comprises cutting the continuously produced length of propagation plugs into individual lengths of propagation plugs or rods. Typically, the length of the propagation rod may preferably be within the range of 0.5-20 meters, such as within the range of 1-18 meters, e.g., within the range of 2-16 meters, such as within the range of 3-14 meters, e.g., within the range of 4-15 meters, such as within the range of 5-14 meters, and even more preferably within the range of 5-10 meters. Typically, the length of the propagation plug may preferably be within the range of 1-49 cm, such as within the range of 5-45 cm, e.g., within the range of 10-40 cm, such as within the range of 15-35 cm, e.g., within the range of 20-30 cm. Both the propagation plugs and rods are preferably tubular.In one or more embodiments, the netting or mesh sheet material exhibits an open area within the range of 15% to 40%, e.g., within the range of 20-35%, such as within the range of 25-30%. This configuration allows the netting or mesh sheet material to be air permeable.In one or more embodiments, the netting or mesh sheet material may have air permeability of at least 75 l / m²*s, preferably of 100 to 5000 l / m²*s. An air permeability of at least 75 l / m²*s, and preferably of at least 100 l / m²*s, enables the netting or mesh sheet material to provide the propagation plug or rod with a sufficient breathability to enable the growth of a plant disposed in this propagation plug or rod. Furthermore, an air permeability of more than 5000 l / m²*s may lead to a too open structure and the retention of the growth medium used to fill the propagation plug might not be ensured. The air permeability is measured according to ISO Standard 9237 at 196 Pa and reported in liter per square meter per second (l / m²*s).In one or more embodiments, the netting or mesh sheet material experiences an elongation in the Cross Direction of within the range of 3-15%, preferably within the range of 5-10 %. The elongation may e.g., be measured according to ISO 13934-2.In one or more embodiments, the netting or mesh sheet material experiences an elongation in Machine Direction of within the range of 3-15%, preferably within the range of 5-10 %. The elongation may e.g., be measured according to ISO 13934-2In one or more embodiments, the netting or mesh sheet material has a bending stiffness in the Cross Direction of within the range of 3-20 N / m, preferably within the range of 5-15 N / m. The bending stiffness may e.g., be measured according to ISO 2493.In one or more embodiments, the netting or mesh sheet material has a bending stiffness in Machine Direction of within the range of 3-20 N / m, preferably within the range of 5-15 N / m. The bending stiffness may e.g., be measured according to ISO 2493.In one or more embodiments, the netting or mesh sheet material has a weight of within the range of 15-50 grams per square meter. In one or more embodiments, the netting or mesh sheet material has a grammage within the range of 15 to 40 g / m², preferably within the range of 20 to 35 g / m², and preferably a thickness of 50-300 micrometres at 100 kPa, measured according to ISO Standard 534:1988.In one or more embodiments, the netting or mesh sheet material has a thickness of within the range of 60-500 microns at 100 kPa, measured according to ISO Standard 534:1988.In one or more embodiments, the netting or mesh sheet material has a thickness of within the range of 60-500 microns.The netting or mesh sheet material may comprise additives conventionally employed in netting or mesh, preferably as long as they are biodegradable. If present, these additives may be included in amounts of less than 10 wt%, preferably less than 5 wt%, based on total weight of the (biodegradable) netting or mesh.In one or more embodiments, the netting or mesh sheet material is formulated with an additive adapted for enhancing the biodegradability thereof, such as enzymes (e.g., a PET hydrolase), transition metal salts (e.g., cobalt or manganese salts), biodegradable plasticizers, photodegradable additives (e.g., UV-sensitive additives), and peroxides.The netting or mesh sheet material will typically and preferably exhibit a degradation time of at least 30 days, preferably 40 days, in soil.Due to the advantageous properties of the netting or mesh sheet material, such as long degradation time in soil, good bending stiffness, and water resistance, the netting or mesh sheet material disclosed herein may be employed for forming (biodegradable) propagation plugs, such as plant plugs, such as propagation plugs for flowers and trees.In one or more embodiments, the method further comprises the step of conveying the lining hose containing the compacted sphagnum or a corresponding substrate material from the suction chamber by gripping the lining hose and moving the gripped lining hose.Another aspect relates to a netting or mesh sheet material supplied on a reel, the sheet material being for producing continuous lengths of propagation plugs; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm.Yet another aspect relates to a netting or mesh sheet material supplied on a reel; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm.The netting or mesh sheet material is preferably made from a thermoplastic polymer, preferably a biodegradable thermoplastic polymer.If production conditions do not allow for joining of the edge area of the lining hose in the heating station, the netting or mesh sheet material may be coated with a hotmelt adhesive.Before or during the process of manufacturing continuous lengths of propagation plugs, the netting or mesh sheet material may preferably be provided with a hot-melt adhesive. This embodiment allows for an easier joining of the edge area of the lining hose in the heating station.As used herein, "hot-melt adhesive" refers to a thermoplastic polymer or copolymer (e.g., polyhydroxybutyrate, polyhydroxyvalerate, or polyhydroxyalkanoate) that is heated to obtain a liquid of flowable viscosity, and, after application, cooled to obtain a solid. Generally, the molecular weight of the adhesive is tailored to provide good rheology as a melt and sufficient strength as a solid to resist shearing forces experienced in the application. The primary feature of hot-melt adhesives is the ability of the thermoplastic material (e.g., polyhydroxybutyrate, polyhydroxyvalerate, or polyhydroxyalkanoate) to flow above a certain temperature, and to provide a strong bond at the normal use temperature. Upon cooling, the material hardens, either through passing through the glass transition temperature or the crystallization temperature. This hardening provides physical integrity to the bond.The hot melt may be coated on the entire face, or on both faces, of the biodegradable (and preferably air permeable) composite sheet material. Preferably, the hot melt is coated only on the one or two side edge areas (in the longitudinal direction) of the composite sheet material, since only the joining edge area needs fixation.In one or more embodiments, the hot melt adhesive comprises or consists of one or more biodegradable polymers selected from the group consisting of poly(lactic acid), aliphatic biopolyesters, polyhydroxybutyrate, polyhydroxyvalerate, polyhydroxyalkanoate, cellulose-based polymers, polycapreolactone, and mixtures thereof.Especially, polyhydroxyalkanoates have shown also to function as soil conditioner. The term soil conditioner implies compounds, which favourably alter the physical and / or chemical properties of soil. The concept of using polymer materials as soil conditioners is not new. Natural polymers such as polyuronic acids, alginic acids, agar, gum, pectin, starch, etc. have been successfully used in the past for soil conditioning. In one or more embodiments, the hot melt adhesive comprises or consists of polyhydroxyalkanoates.The polyhydroxyalkanoates (PHAs) are synthesized by soil microbes for use as intracellular storage material. Hence, nonwoven sheet material made from the polymers are generally recognized by soil microbes as a food source.In one or more embodiments, the hot melt adhesive comprises or consists of one or more biodegradable polymers selected from the group consisting of a poly(3-hydroxybutyrate) homopolymer, a poly(3-hydroxybutyrate-co-4-hydroxybutyrate), a poly(3-hydroxybutyrate-co-3-hydroxyvalerate), a poly(3-hydroxybutyrate-co-5-hydroxyvalerate), a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and mixtures thereof.Preferably, the hot melt adhesive comprises or consists of one or more biodegradable polymers of non-GMO (genetically modified organism) origin.The hot melt adhesive may comprise at least 50% w / w of one or more biodegradable polymers, such as at least 55% w / w, e.g., at least 40% w / w, such as at least 65% w / w, e.g., at least 70% w / w, such as at least 75% w / w, e.g., at least 80% w / w, such as at least 85% w / w, e.g., at least 90% w / w, such as at least 95% w / w, e.g., at least 99% w / w. Other components may be inorganic fillers or biodegradable organic fillers.In one or more embodiments, hot melt adhesive comprises a reactive filler component, such as an aluminium compound, a magnesium compound, a calcium compound, a barium compound or a mixture thereof. Preferred are these compounds that react with acidic functional groups, for example carboxylic acid groups, carboxylic acid anhydride groups, hydroxyl groups, acidic amine groups, sulfonic acid groups, phosphonic acid groups, etc. The reactive filler may be, for example, in the form of oxides, hydroxides, silicates, etc., or a mixture thereof. Some exemplary compounds include, for example, aluminum oxide (AI203), aluminum hydroxide (AI(OH)3), magnesium oxide (Mg0), magnesium hydroxide (Mg(OH)2), calcium oxide (Ca0), calcium hydroxide (Ca(OH)2), barium oxide (Ba0), barium hydroxide (Ba(OH)2), aluminometasilicates, fluoroaluminosilicates and mixtures thereof. Aluminium compounds are particularly preferred, especially aluminium compounds that react with acidic functional groups.Aluminium oxide, aluminium hydroxide, aluminium silicate, aluminium metasilicate and mixtures thereof are of particular note.The reactive filler may be present in the hot-melt adhesive composition in any suitable amount. Of particular note is an amount of about 5% to about 50% by weight, or, of about 10% to about 45% by weight, or, of about 15% to about 40% by weight, based on the weight of the hot-melt adhesive composition. Use of reactive filler in the amounts noted above helps to bring characteristics of the adhesive composition closer to those of the biodegradable and air permeable nonwoven sheet material in terms of thermal expansion, deformation, stiffness, etc.The amounts noted above also lead to less shrinkage due to consolidation thus reducing internal stress in the adhesive, to less stress concentration in a joint formed with the adhesive, to better fatigue resistance in the joint, and to decreased sensitivity of the adhesive composition to moisture.Another aspect relates to a netting or mesh sheet material supplied on a reel, the sheet material being of the type used for producing continuous lengths of propagation plugs; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm; and wherein the netting or mesh sheet material comprises a hot melt adhesive comprising one or more biodegradable polymers; wherein the hot melt adhesive is supplied to at least a part of a face of the composite sheet material.Further features and advantages of the present technology will appear from the following description of specific embodiments.As used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and / or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about", it will be understood that the particular value forms another embodiment.It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.Brief description of the figuresFigure 1 shows a perspective view of a system performing the method in accordance with various embodiments of the invention.Detailed description of an embodiment of the inventionThe following description is to be seen as non-limiting examples of the production of propagation plugs and rods and composite sheet material according to various embodiments of the present invention.In the present context, the term “in general” when used when mentioning a feature relating to the present invention, it must be understood that the feature may be used with all embodiments of the invention, even if the mentioning is made in the detailed part of the document.Production of biodegradable netting or mesh sheet materialIn general, producing biodegradable sheet netting or mesh with mesh sizes between 0.1 to 1.5 mm may e.g., involve an extrusion process that utilizes a blend of biodegradable polymers, such as polylactic acid (PLA) combined with other materials like polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), or polycaprolactone (PCL). These materials are selected to enhance the biodegradation rate and the environmental compatibility of the final product.Poly(lactic acid) (PLA) stands out as a promising biodegradable polymer due to its renewable origin from corn starch or sugarcane, and mechanical properties resembling those of conventional plastics. However, PLA’s slow degradation rate in certain environments, such as soil, necessitates enhancement strategies to expedite its breakdown.One effective strategy involves blending PLA with other biodegradable polymers such as polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), or polycaprolactone (PCL). These blends leverage the complementary properties of different polymers to achieve desirable degradation kinetics. PHA, for instance, is renowned for its biodegradability and can accelerate the breakdown of PLA due to its microbial susceptibility. When combined, PHA enhances the overall degradation rate of the blend in soil environments.Similarly, incorporating PBS into PLA blends contributes to faster degradation kinetics. PBS possesses favourable mechanical properties and is biodegradable under various environmental conditions, including soil. Blending PLA with PBS not only accelerates degradation but also offers improved flexibility, expanding the applicability of the resulting materials.PCL, another commonly used biodegradable polymer, complements PLA by enhancing its biodegradation rate. PCL exhibits slow degradation kinetics on its own but can synergistically interact with PLA to expedite degradation. By blending PLA with PCL, the resulting material benefits from PCL’s biodegradability while retaining PLA’s strength and stiffness.The success of biodegradable polymer blends in expediting degradation relies on careful selection and optimization of blend compositions. Balancing the properties of individual polymers to achieve desired mechanical strength, degradation kinetics, and environmental compatibility is crucial. Additionally, factors such as polymer compatibility, phase morphology, and processing techniques play significant roles in determining the performance of these blends.Overall, biodegradable polymer blends based on PLA, supplemented with PHA, PBS, or PCL, offer a promising solution to mitigate plastic pollution by accelerating degradation in soil and other environments. Through continued research and development efforts, these blends hold tremendous potential for widespread adoption in various applications, contributing to a more sustainable future.The manufacturing process begins with the preparation of these biodegradable polymers, which are typically supplied in pellet form. These pellets might include a mix of PLA and another biodegradable polymer, such as PHA, to optimize the netting’s mechanical properties and degradation rate. The mix can be tailored with additives that promote stability, UV resistance, or facilitate the biodegradation process, depending on the intended application of plant pot.Once the raw materials are prepared, they are fed into an extruder where they are heated until they melt into a homogenous, viscous fluid. This process requires precise control over temperature and pressure to prevent any thermal degradation of the sensitive biopolymers. The molten biopolymer blend is then forced through a die specifically engineered to create netting with fine mesh sizes as discussed above.Following extrusion, the netting or mesh undergoes a cooling process, typically in a controlled air or water bath, to solidify the netting or mesh while preserving its intricate structure. This stage is critical to ensure that the net retains its dimensional stability and mesh uniformity.After cooling, the netting or mesh might be subjected to a stretching process. This orientation step is crucial for aligning the polymer chains, thereby enhancing the bending stiffness and mechanical integrity of the biodegradable netting or mesh. This makes the netting more robust and suitable for practical applications while maintaining its biodegradability.The final product is then either wound onto spools or cut into sheets.By utilizing a blend of biodegradable polymers like PLA and PHA, manufacturers can produce eco-friendly netting or mesh that degrades more quickly and effectively in natural environments, reducing the impact on ecosystems and promoting a more sustainable approach to plant pot horticulture.Production of propagation plugs or rodsFigure 1 shows a perspective view of a system performing the method in accordance with various embodiments of the invention. In the right-hand side of the figure is shown an amount of sphagnum or a corresponding substrate material 2 supplied on a conveyor belt 4 forwardly conveying towards the end of a suction funnel 6. The suction funnel 6 projects into a first part 8 of a conveyor pipe. It is not decisive how the sphagnum is supplied to the first part 8 of the conveyor pipe, as long as it is a continuous delivery. The first part 8 of the conveyor pipe extends into a folding zone 12, in which the netting or mesh sheet material 14 according to the present invention is supplied from a storage reel 16 and successively wrapped about the first part 8 of the conveyor pipe and continues into a second part 20 of the conveyor pipe. The netting or mesh sheet material 14 continues into the second part 20 of the conveyor pipe through a narrow annular slot 18 (holding means 26 is arranged for fixing of the pipe parts in this area) to form an inner lining hose in the second part 20 of the conveyor pipe. The netting or mesh sheet material 14 is a thermoplastic material. The thermoplastic material is activated in a heating station 24, whereby the netting or mesh sheet material 14 is stabilized in its hose shape for further advancing inside the second part 20 of the conveyor pipe.The length of growth medium is thereafter cut into pieces of suitable size (length relative to the diameter), corresponding to the desired size of a propagation pot or rod.Disintegration testing based on tensile strength Machine Direction (MD)PBS PHBV PBS / PHBH (70 / 30) New 38.61 36.39 31.6814 days 28.59 13.61 36.4721 days 22.35 11.09 27.1235 days 24.47 8.59 13.2449 days 22.24 8.25 4.5870 days 24.11 7.84 4.7198 days 20.4 9.55147 days 17.29 9.0125175 days 17.78 9.075217 days 18.15 6.07350 days 6.8 6.91The polybutylene succinate (PBS) trial showed that the netting or mesh sheet material was generally intact after 217 days. After 350 days, one sample was completely disintegrated, and two others were damaged. The tensile strength was generally stable from day 14 to day 217.The polyhydroxyalkanoate (PHA) trial (here specifically testing poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV) resulted in the netting or mesh sheet material to still be fully intact after 350 days. After 14 days, the tensile strength of the netting or mesh sheet material made from PHBV was generally lower than when made from PBS.Mixing the two polymers provided a faster degradation time, and after 70 days, disintegration made it impossible to perform further tensile strength measurements.References2 Sphagnum or a corresponding substrate material4 Conveyor belt6 Suction funnel8 First part of a conveyor pipe12 Folding zone14 Air permeable composite sheet material16 Storage reel18 Annular slot20 Second part of a conveyor pipe24 Heating station26 Holding means

Claims

Claims1. A method of manufacturing a continuous length of propagation pots or rods comprising:- suctioning sphagnum or a corresponding substrate material through a pipe into a suction chamber for deposition and compaction within the suction chamber by suction applied through a perforated tube in the suction chamber;- forming a plug of the compacted sphagnum or a corresponding substrate material in an outlet conduit of the suction chamber as part of compacting the sphagnum or a corresponding substrate material within the suction chamber;- introducing a netting or mesh sheet material, preferably biodegradable, through an aperture in the pipe; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm; and- joining the edge area of the lining hose by conveying the lining hose containing the compacted sphagnum or a corresponding substrate material through a heating station, such that thereafter the netting or mesh sheet material is stabilized in its hose shape for further advancing inside the pipe.

2. The method according to claim 1, further comprising cutting the continuously produced length of propagation plugs into individual lengths of propagation plugs or rods.

3. The method according to any one of the claims 1-2, wherein netting or mesh sheet material exhibits an open area within the range of 15% to 40%.

4. The method according to any one of the claims 1-3, wherein the netting or mesh sheet material has a bending stiffness in the Cross Direction of within the range of 3-20 N / m, preferably within the range of 3-15 N / m.

5. The method according to any one of the claims 1-4, wherein the netting or mesh sheet material has a bending stiffness in Machine Direction of within the range of 3-20 N / m, preferably within the range of 5-25 N / m.

6. The method according to any one of the claims 1-5, wherein the netting or mesh sheet material has a weight of within the range of 15-50 grams per square meter.

7. The method according to any one of the claims 1-6, wherein the netting or mesh sheet material has a thickness of within the range of 60-500 microns.

8. The method according to any one of the claims 1-7, wherein the netting or mesh sheet material exhibits a degradation time of at least 30 days, preferably at least 40 days, in soil.

9. The method according to any one of the claims 1-8, wherein the netting or mesh sheet material is made from polylactic acid (PLA), preferably combined with polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), or polycaprolactone (PCL).

10. A propagation plug, or rod produced by the method according to any one of the claims 1-9.

11. A propagation plug or rod comprising a growth medium held in a netting or mesh sheet material having a mesh size within the range of 0.1 to 1.5 mm.

12. A netting or mesh sheet material supplied on a reel, the sheet material being for producing continuous lengths of propagation plugs; wherein the netting or mesh sheet material has a mesh size within the range of 0.1 to 1.5 mm.