Description

The present invention relates to a growth substrate that is suitable for use in soilless plant cultivation, such as vertical farming, the growth substrate comprising a carrier material comprising one or more plant seeds. The present invention further relates to methods for providing the growth substrate and the use of the growth substrate in vertical farming of soilless plant cultivation.

Due to increasing food demand and decreasing land area to cultivate and produce food crops, vertical farming and/or soilless growing and farming of plants and food crops, including horticulture are evolving rapidly, increasing in scale. In vertical farming and/or soilless growing use is made of growing substrates in which the plants and crops are being cultivated. Cultivation of plants and especially young plants is often performed using various types of growth substrates such as plant plugs, cultivation mats and blocks. Cultivating young plants using such growth substrates have shown to improve yields and produce healthy plants at locations that have a limited space for plant growth in soil. It also provides an easier system for cultivation of seedlings that are difficult to cultivate, since the growth substrate has a potentially greater capacity to withstand pests, disease and drought due to the more contained and controlled environment during plant cultivation. This soilless culture uses less to none fertilizer, pesticide, herbicides and insecticide due to the contained and controlled environment.

The market for propagating young plants or plant seedlings continuously requires improvement of the substrate system in which young plants are cultivated in limited space, such as with vertical farming. For example, the propagation or cultivation substrate is continuously adapted because the market is increasing awareness to reduce carbon footprint, in combination with strict environmental and health legislation, reduction of chemicals and consumers increasingly demand alternative green biodegradable substrates.

In vertical farming and/or soilless growing farming plants and food crops are being cultivated without the use of the actual soil. Seeds are being provided or sown on top of a plant growth substrate in plant holders or plant trays. However, seeds are easily detached and fall off the growth substrate when not attached firmly to the growth substrate, especially when used for vertical farming purposes. To attach the seeds to the growth substrate, in general inorganic glue or additives used are less environmentally friendly and less suitable to obtain a fully biodegradable and compostable product.

Furthermore, in many vertical farming and soilless plant cultivation, inorganic substrates such as mineral wool are being used. Mineral wool is made from stone melted in furnaces. Stone is not a recycled or sustainable material. It is extremely energy-intensive to produce and has high embodied energy. For example, the Dutch production facility for mineral wool produces 142.000.000 kg CO2 per year and uses almost 92.000.000 kWh of electricity. Mineral wool is difficult to recycle and has few reuse applications. It does not decompose or break down when disposed of in landfills.

Considering the above, there is a need in the art for fully biodegradable and compostable growth substrates ready for use and suitable for soilless cultivation of plants such as vertical farming. In addition there is a need in the art for a method for providing a biocompatible, biodegradable growth substrate for plants suitable for soilless plant cultivation.

It is an object of the present invention, amongst other objects, to address the above need in the art. The object of present invention, amongst other objects, is met by the present invention as outlined in the appended claims.

Specifically, the above object, amongst other objects, is met, according to a first aspect, by the present invention by a plant growth substrate for soilless cultivation, such as vertical farming, comprised of a carrier material comprising one or more plant seeds, wherein the plant seeds are attached to the carrier material via at least one layer of a biological adhesive composition comprised of latex and at least one bio-stimulatory compound.

The growth substrate of present invention is comprised of a carrier that is composed of natural material of vegetal origin, preferably jute fiber, or a biopolymer, preferably polylactic acid (PLA). These fibers are 100% compostable once the growth substrate has been used. It can end up in the green waste without any problems and also can be given a second life as a fertilizer product by composting it, providing a ready-to-use ecosystem to complement and enhance soil biology. Jute fibres are composed primarily of the plant materials cellulose and lignin. The Jute fibres are derived from the stem and ribbon (outer skin) of the jute plant. PLA is comprised of thermoplastic polymers of lactic acid and is biodegradable, biocompatible and produced from processed vegetable raw materials, such as PLA is therefore a green alternative to traditional plastics for example derived from chemical polyethylene, polypropylene or polystyrene.

According to a preferred embodiment, the present invention relates to the plant growth substrate, wherein the carrier material is comprised of natural material of vegetal origin or a biopolymer, or combinations thereof, preferably one or more selected from the group consisting of Corchorus fibre, jute fiber, seagrass, elephant grass, sisal, arm, hemp and kapok, polylactic acid (PLA) or combinations thereof, preferably Corchorus fibre or jute fiber.

According to another preferred embodiment, the present invention relates to the plant growth substrate, wherein the growth substrate is further comprised of a wetting agent of plant origin, preferably saponin. Preferably the wetting agent, such as Saponin, is included in the growth substrate by mixing the adhesive composition and the wetting agent, preferably at most 0.5 to 2 wt%, more preferably 0.75 to 1.5 wt% on the basis of the weight of the mixture of adhesive composition with the wetting agent. By including a wetting agent as part of the growth substrate, the water surface tension is being reduced resulting in a facilitated water update of the growth substrate, more specifically a more facilitated water update by the carrier material. Saponins are phytochemical, nonionic surfactants of plant origin with various biological activities. It is found in various plants and is isolated for its various properties. The amphipathic nature of saponins gives them activity as surfactants. Saponins are found in the botanical family Sapindaceae, including soapberry or soapnut and chestnut, and in the families Aceraceae (maples) and Hippocastanaceae.

According to another preferred embodiment, the present invention relates to the plant growth substrate, wherein the carrier material comprises a fibre density of between 200 to 1.600 g/m2, preferably 500 to 900 g/m2, most preferably 600 to 800 g/m2. In case the carrier material comprises a fibre density that is below 200 g/m2 there is a higher chance the seeds that are to be provided on the carrier material will “fall” through the carrier material and therefore result in losses of plant seeds. In case the density of the carrier material will be too high, i.e. above 1.600 g/m2, the density becomes too high to be able to efficiently and economically produce the carrier material. Furthermore, a too dense carrier material will affect seed germination, plant development and the easy flow through of nutrients and water in the carrier material.

According to yet another preferred embodiment, the present invention relates to the plant growth substrate, wherein the at least one biostimulatory compound is present in the biological adhesive composition in an amount of at least 0.5 wt%, preferably at least 1 wt%, more preferably at least 10 wt%, based on the weight of the biological adhesive composition. The biostimilatory effect is already observed at 0.5 wt%, below this amount the effect on the plants and seeds is not observed. Above 10 wt%, the effect does not outweigh the costs of the biostimulatory compound.

According to a preferred embodiment, the present invention relates to the plant growth substrate, wherein the biostimulatory composition is a plant growth biostimulant composition extracted from algae, preferably compound BYAS-A601. BYAS-A601 (Back of the Yards algae sciences Inc.) is a potent microalgae based bio-stimulant that acts on cellular level which accelerates plant growth, improves plant biomass yield. BYAS has been tested in comparative trials on lettuce, basil, pepper and tomato. It is a proven natural accelerator of plant growth and phytochemical production and is very suitable for vertical farming purposes, both indoor and outdoor.

According to another preferred embodiment, the present invention relates to the plant growth substrate, wherein the biological adhesive composition has a dynamic viscosity of between 50 to 200 mPa s, preferably 75 to 125 mPa s. Higher viscosity of the adhesive composition resulted in increased film formation by the composition and too quick dry out effects of the glue characteristics, therefore high viscosities (i.e. above 200) are undesirable. Furthermore, the adhesive composition is preferably applied by spray coating on the carrier, therefore should have sufficient low viscosity. Typically, the viscosity is in the range of 75 to 125 mPa s at about 25 °C, as determined by capillary viscometer or microfluidic rheometers. Dynamic viscosity is measured by comparing the differential flow rates, the viscosity of the reference material, and the position of the interface between the two fluids within the microfluidic channel, such as by using a capillary viscometer or microfluidic rheometers.

According to another preferred embodiment, the present invention relates to the plant growth substrate, wherein the one or more seeds is selected from the group consisting of parsley, chives, lettuce, basil, pepper and tomato.

According to yet another preferred embodiment, the present invention relates to the plant growth substrate, wherein said one or more seed has a weight of at most 20 gram/seed, preferably at most 15 g/seed, more preferably at most 10 g/seed, most preferably at most 7.5 g/seed. If the seed weight is exceeding 20 gram there is an increased chance that the seed will not attach properly or withstand the gravitational forces when the plant growth substrate is used in vertical farming.

According to a preferred embodiment, the present invention relates to the plant growth substrate, wherein the growth substrate is fully biodegradable and compostable and/or reusable as fodder, vegetable mould, or humus for gourmet mushrooms (cantharellen). The growth substrate of present invention is 100% compostable because it is fully comprised of organic matter that can be completely broken down to provide a nutrient rich compost. The growth substrate is fully biodegradable by for example bacteria, fungi or microbes to be reabsorbed by the surrounding environment, ideally without causing any pollution or leaving a carbon footprint. Furthermore, the growth substrate, after being used in soilless plant cultivation, the substrate is reusable as fodder, vegetable mould, or humus for gourmet mushrooms.

The present invention, according to a second aspect, relates to a method for providing a plant growth substrate as described herein, comprised of the steps; a) Providing a carrier material comprised of natural material of vegetal origin, preferably jute fiber, or a biopolymer, preferably polylactic acid (PLA) or combinations thereof, preferably Corchorus plants that are comprised of jute fiber. b) Providing at least one layer of a biological adhesive composition onto said carrier material, preferably by airless spraying techniques, directly followed by applying one or more seeds on the surface of the carrier material provided with the biological adhesive composition such that the seeds will adhere to the carrier material, c) Optionally providing a finishing layer on the carrier material comprising the one or more seeds.

Before applying the finishing layer, the seeds that have been applied to the surface of the carrier material are left to dry for at most 30 seconds at a temperature of at most 50 °C, to ensure optimal adhesion of the seeds to the carrier material. According to a preferred embodiment, the present invention relates to the method, wherein the at least one layer of a biological adhesive composition are two layers, preferably three layers, more preferably 4 layers. The use of more than one layer of adhesive composition provided onto the carrier material resulted in an increased contact of the seeds provided onto the surface of the carrier material, resulting in reduced losses when the growth substrates (for example the bio-matts) are being transported and/or handled. Furthermore, apart from the adhesive and protective role, the adhesive composition comprises a biostimulatory compound (or biostimulant) providing an improved seed germination and plant growth.

According to another preferred embodiment, the present invention relates to the method, wherein the finishing layer in step c is comprised of a composition that is identical to the biological adhesive composition. The finishing layer further improved seed protection as well as biostimulation of these seeds resulting in improved seed germination and biomass yield.

The present invention, according to a further aspect, relates to the use of a plant growth substrate as disclosed herein in vertical farming, soilless plant cultivation or vertical plant cultivation.

The present invention will be further detailed in the following examples and figures wherein:

Figure 1: (A) Shows a plant growth substrate (bio-mat) according to present invention close up, wherein plant seeds are attached to the carrier material of jute fiber via a layer of a biological adhesive composition comprised of latex, wherein the adhesive composition comprises a biostimulatory compound, providing a blueish color to the growth substrate. (B) Shows a plant growth substrate (bio-mat) according to present invention suitable for soilless cultivation comprised of a carrier material of jute fiber comprising plant seeds attached to the carrier material via a layer of a biological adhesive composition comprised of latex. The seeds stick and remain fixed to the carrier material when lifted upright.

Figure 2: Shows Parsley (A, B) and Chives (C, D) plants about 40 days after sowing on plant growth substrate (bio-mat) according to present invention (Figures B and D), and the control group (Figures A and C), i.e. plant growth substrates without a biological adhesive composition comprised of latex, comprising a biostimulatory compound and wetting agent. The biomass growth was significantly improved in the plants using the plant growth substrate of present invention. Examples

Example 1 - improved biomass yield and seed germination using a biostimulant

A plant growth substrate according to present invention was prepared comprised of a jute fiber (700 g/m2) as carrier material comprising plant seeds attached to the carrier material via one layer of a biological adhesive composition comprised of latex and BYAS-A601 (1 wt%) biostimulatory compound. As comparison an identical plant growth substrate was prepared, but without biosimulatory compound. It was concluded that the plant growth substrate according to present invention significantly improved seed germination and plant growth over time, as determined by visual inspection.

Example 2 — improved effect using a wetting agent in the biomat

In a further experiment the plant growth substrate of present invention was used as prepared in example 1, with the further addition of a wetting agent saponin (1 wt%) being mixed with the adhesive composition and subsequently included in the growth substrate. As comparison an identical plant growth substrate was prepared, but without wetting agent. It was concluded that the plant growth substrate according to present invention with wetting agent significantly improved water uptake and liquid nutrient uptake into the growth substrate due to the water surface tension being reduced, as determined by visual inspection.

Example 3 - improved biomass yield and seed germination using biostimulant and wetting agent in the biomat

In a further experiment the plant growth substrate of present invention was used as prepared in example 2, comprising a wetting agent and biosimulatory compound mixed with the adhesive composition and subsequently included in the growth substrate. Parsley and Chives were tested for their seed germination and biomass growth. As comparison an identical plant growth substrate was prepared, but without wetting agent and biosimulatory compound (control group).

Figure 2 shows the Parsley (A, B) and Chives (C, D) plants about 40 days after sowing. Figures B and D show plant being cultivated on the plant growth substrate of present invention, and A and C showed the control group. Seeds showed an improved germination and the biomass growth was also improved in the plants using the plant growth substrate of present invention.