Soilless growing media

Abstract

The method comprises separating the petiole base from the palm trunk after drying to provide dry or semi-dry petiole base; defibring the petiole base into particles with reduced size and removing the

Description

Field of the Invention The present invention relates to soilless growing media and more particularly but not exclusively to soilless growing media obtained from palm trees; and more particularly from defibring palm petiole base to provide palm pith. Background The growing media industry has been continuously challenged to source and process growing media in suitable volumes. Many of those challenges emerged from global geopolitical issues, increased regulatory pressures on peat moss extraction and use (which resulted in depletion of natural habitats), unpredictable weather patterns (which affected harvests), transportation costs and labour shortage. The need for more non-peat materials has therefore led to a search for alternative soilless substrates, such as coconut coir pith and wood products. However, as global demand for soilless substrates is expected to increase, driven by increased crop production, the transition of newer crops from soil to soilless production, a booming mushroom industry and an increase in home gardening; the importance of exploring new sources of soilless growing media is becoming ever more critical in the view of future food production and food security. Date palm is the main element of flora in the Middle East and North Africa with global harvested areas typically exceeding 1 million hectares. The estimated annual byproducts of pruning of date palms globally is estimated as 5 million tons (air dry weight), which is often treated as agricultural waste. Previous attempts to extract soilless growing media from date palm residues, have been limited to grinding the entire palm frond excluding the petiole base, which resulted in a grinded biomass very rich in fibres but with a low lignin content. This biomass is unsuitable for use as a soilless growing substrate unless it was mixed with other media. There is therefore a need for a novel soilless growing media which is capable of utilising agricultural residues generated during pruning of plant species such as palms. Some of these previous attempts at providing such soilless media are described in the documents mentioned below. Prior Art United Kingdom patent application GB 2139609 (Chemical Discoveries SA) discloses a growing medium for plants that is prepared by mixing a particulate growing material derived from palm nuts, such as coir fibres, with a highly water absorbent polymer. Canadian patent application CA 1283555 (Cooke) discloses a growing medium for plants which is prepared by mixing a growing material with a highly water-absorbent polymer. The polymer is an acrylamide polymer cross-linked with methylene bisacrylamide which absorbs water to form a sticky gel. The polymer may be supplemented with an additive. Canadian patent application CA 2504227 (Soil Sub Technologies PTY Ltd) discloses a process for treating palm waste comprising the steps of: shredding palm fibrous waste; and blending the shredded palm fibrous waste with a dried plant mill effluent and peat. Japanese patent JP 3400926 (Tosco Corp) discloses a material for a greening base which is obtained by carrying out by compressing a mixture of a grain like fibres of a natural palm or peat moss with a natural palm fibre. The material can include husk chips of natural coconut husk fibre or an active carbon of coconut husk compounded therewith. Japanese patent application JP H08242683 (Central Green KK) discloses a culture soil which is a water-containing mixture of palm powder obtained by cutting palm skin and peat-moss at a specific ratio. The soil assists growth in budding and improves in raising seedlings and may be used for cultivating fruits and vegetables. Chinese patent application CN 107912230 (HUILI TIANZE IND CO LTD) discloses a selenium-rich morchella esculenta culture medium. The medium comprises, by weight, 15-30 parts of peat soil, 0.1-0.3 part of selenium yeast, 45-55 parts of corncobs, 14-18 parts of palm leaves, 4-6 parts of distillers' grains, 5-8 parts of rice straw, 4-7 parts of humus soil,4-8 parts of cow dung, 7-9 parts of moss, 0.5-1 part of morchella esculenta powder, 4-6 parts of magnolia denudata leaves and 1-4 parts of soybean husks. Chinese patent application CN 107912230 (HUILI TIANZE IND CO LTD) relates to compost for radish planting. The compost is mainly prepared from, by mass, 30-40 parts of com cobs, 20-40 parts of rice chaff ash, 10-20 parts of vinegar slough, 2-6 parts of coarse sand, 0.1 -0.3 part of a mould inhibitor, 8-10 parts of peat, 0.5-1.2 parts of dried tangerine or orange peel, 2-6 parts of liquorice roots, 5-8 parts of dried alfalfa grass, 2-4 parts of trace elements, 2-4 parts of black tea residues, 2-6 parts of sisal hemp leaves and 2-4 parts of hemp palm branches and leaves. Shirani, M. and Mohammadi-Ghehsareh, A., 2014 entitled “The effect of composted and un-composted date-palm waste as a media on some microelements of tomato fruit”. Research Journal of Recent Sciences. ISSN, 2277, p.2502. In a paper by Radhouani, A., Benyehia, L, Lechaiheb, B., Mahjoubi, A. and Ferchichi, A., 2021 entitled “Date palm compost versus peat and perlite: a comparative study on germination and plant development of muskmelon and tomato”. Acta Horticulturae et Regiotecturae, 24(2), pp.96-104 discusses In a paper Borji, H., Mohammadi-Ghehsareh, A. and Jafarpour, M., 2012 entitled “Effect of date-palm and perlite substrates on nutrients content and quality of tomato grown in soilless culture”. Resources on Crops, 13(1), pp.258-261 In a paper by Ghehsareh, A.M., Hematian, M. and Kalbasi, M., 2012 entitled “Comparison of date-palm wastes and perlite as culture substrates on growing indices in greenhouse cucumber. International Journal of Recycling of Organic Waste in Agriculture, 1(1), pp.1-4. In a paper by Ghehsareh, A.M., Samadi, N. and Borji, H., 2011 entitled “Comparison of date-palm wastes and perlite as growth substrates on some tomato growing indexes”. African Journal of Biotechnology, 10(24), pp.4871-4878. In a paper Abdolali, H., Saadat, S.K., Fatemeh, A. and Arman, B.K., 2012 entitled “Date-peat as an alternative in hydroponic strawberry production”. African Journal of Agricultural Research, 7(23), pp.3453-3458. In a thesis by Al Marzooqi, K.M., 2020 entitled “Date Palm Wastes as Growth Substrate in Hydroponics to Grow Lettuce” (Lactuca Sativa L.). The present invention arose in an attempt to provide a more reliable method of production of a soilless growing media by defibring palm petiole base to provide palm pith. Summary of Invention According to a first aspect of the present invention, there is provided a method for the production of soilless growing media comprising: separating the petiole base from the palm trunk after drying to provide dry petiole base; defibring the petiole base into particles with reduced size and removing the fibres to provide palm pith; and mechanically processing the palm pith by at least one of the steps comprising: milling, grinding, pulverizing, liquidizing and crushing. It is appreciated that the petiole base from the palm trunk may be semi-dry petiole base. The mechanical processing may be conducted using machine rollers, smooth, fluted or pinned. Optionally the processed palm pith is sieved to provide sieved palm pith. In some methods, the palm pith is compressed into palm pith having defined, predetermined shapes. When suitably sized the palm pith may be used as wood chip substitutes or in smaller form in mulch. The method of the present invention utilises agricultural residues generated by palm plantations. In particular, the palm petiole base (also known as leaf base, basal end, midrib base, or frond base) which remains left on the palm trunk during pruning to be removed after drying (typically removed the following year). The method may further comprise pre-soaking the dry petiole base in water to provide wet petiole base prior to processing of the petiole base. The dry petiole base may for example be pre-soaked in water, in a process also known as retting, for a period of at least 2 weeks, preferably at least 4 weeks, for example at least 5 weeks. Preferably, the dry petiole base is pre-soaked in water for a period of no more than 10 weeks, preferably no more than 8 weeks. In one embodiment, the dry petiole base is pre-soaked in water for a period of between 5 and 7 weeks. The processing step may comprise processing of dry petiole base or wet petiole base to provide dry or wet palm pith. In one embodiment, the method further comprises drying of wet palm pith. The sieving step is configured to remove any undesirable particles, such as for example mud, weed, stones, sand, residual fibres, or any other impurities. The method may further comprise sorting the palm pith according to one or more parameters selected from: moisture content, electrical conductivity (EC) and particle size, or any combination thereof. For example, the palm pith may be sorted according to particle size such that the maximum particle size is no greater than 20 mm, preferably no greater than 15 mm, for example around 12 mm. Palm pith, preferably having a maximum particle size of no more than 12 mm, may be utilised in soilless growing media. Palm pith having a larger maximum particle size (for example greater than 12 mm) may be utilized as mulching materials. Palm pith having large maximum particle sizes, in the form offer example chunks, may be used as growing media for orchids and Anthurium. In one embodiment, palm pith may be washed with for example fresh water to adjust the electrical conductivity of the palm pith as required. Electrical conductivity is a measure of the mineral content of the palm pith. The method may further comprise sterilisation of the palm pith. Sterilization may occur using one or more of the following techniques: autoclaving, dry heat sterilization (for example a hot air oven), radio sterilization, gas sterilization, exposure to hydrogen peroxide, or any combination thereof. The palm pith may be dried by spreading out and exposure to, for example, the sun, air drying or using a drying machine (for example a hot air oven). In one embodiment, the method further comprises mixing the dry palm pith with one or more materials selected from: soilless growing media (organic or inorganic), fibres, pH adjusting agents, microbial inoculums, fertilizer, or any combination thereof. The organic soilless growing media may be selected from: mud, peat moss, coconut coir pith, bark, saw dust, rice hull, straw or any combination thereof. The inorganic soilless growing media may be selected from rockwool, gravel, sand, vermiculite, perlite, pebbles, or any combination thereof. The palm pith may be compressed in the form of blocks, slabs, or pellets. In one embodiment, the method further comprises wrapping the sieved palm pith or compressed palm pith in plastic bags, optionally comprising planting and / or drainage holes. The palm petiole base may be obtained from one or more of: date palm, oil palm, sugar palm, coconut palm or any combination thereof. According to a further aspect, the present invention provides soilless growing media comprising one or more of: palm pith, sieved palm pith, compressed palm pith, or any combination thereof. In one embodiment, the palm petiole base has a fibre volume fraction of at least 5%. Preferably, the palm petiole base has a fibre volume fraction of no more than 30%. In one embodiment, the maximum size of the particles of the soilless growing media is no greater than 12 mm. According to a further aspect, the present invention provides soilless growing media preferably comprises one or more of: palm pith, sieved palm pith, or compressed palm pith obtained by the method as herein described. According to a further aspect, the present invention provides the use of a soilless growing media as claimed in one or more of: horticulture, floriculture, nurseries, gardening, landscaping, indoor farming, hydroponics, lawns or any combination thereof. The invention will now be described, with reference to examples, and the following Figures in which: Brief Description of Drawings Figure 1 schematic illustration of parts of a date palm; Figure 2A is a photograph of a section of a petiole base; Figure 2B shows magnified SEM image of sponge-like parenchyma cells inside a dry petiole base; Figure 3 is a schematic illustration of steps in a method of producing soilless growing media from a date palm according to one embodiment of the present invention; Figures 4A and 4B are magnified images of fibre volume fraction of a petiole base of a palm and a frond of a palm; Figure 5 is a photograph of the soilless growing media obtained by the method of the present invention from a petiole base of a date palm; and Figure 6 is a photograph of palm pith in a form of chunks. Detailed Description of Preferred Embodiments With reference to Figures 1 to 3, the method for the production of soilless growing media according to one embodiment of the present invention comprises separating the petiole base from the palm trunk after drying 2 to provide dry or semi-dry petiole base 4 as shown in Figure 2A. The dry petiole base 4 is then optionally pre-soaked in water, in a process known as retting, to provide wet petiole base 6 prior to processing of the wet or dry petiole base 4, 6. The wet or dry petiole base 4, 6 is then processed to reduce the particle size and to remove fibres to provide palm pith 8 (in a process also known as defibring). The palm pith 8 may then be optionally sieved and sorted to provide sieved and sorted palm pith 10. For example, the palm pith 8 may be sorted according to one or more parameters selected from: moisture content, electrical conductivity (EC) and particle size, or any combination thereof. For example, the palm pith 8 may be sorted according to particle size such that the maximum particle size is no greater than 12 mm. The palm pith 8 may be washed with fresh water in order to provide washed palm pith 12 having the required electrical conductivity. The washed palm pith 12 is then sterilised to provide sterilised palm pith 14. The sterilisation step may comprise the use of one or more of the following techniques: autoclaving, dry heat sterilization (for example a hot air oven), radio sterilization, gas sterilization, exposure to hydrogen peroxide, or any combination thereof. The sterilised palm pith 14 is then dried to provide dry palm pith 16. The drying step may be conducted by exposing to direct sunlight, air drying or by the use of a hot air oven. The dry palm pith 16 is then mixed with one or more materials selected from: further soilless growing media, fibres, pH adjusting agents, microbial inoculums, fertilizer, or any combination thereof. The further soilless growing media is selected from: mud, peat moss, coconut coir pith, bark, rockwool, saw dust or any combination thereof. The mixed palm pith 18 is then compressed to provide compressed palm pith 20 having defined, predetermined shapes. The compressed palm pith may be provided in the form of blocks, slabs, or pellets. The invention includes a method of extracting coarse lignin particles, with high cell rigidity, and minimal amount of cellulose fibre content, from date palm petiole base and one example is shown in Figure 3 which illustrates key steps as a process flow diagram. Referring to Figure 3, the petiole base is left on the palm trunk after the pruning of the fronds and then left to dry. The palm is then trimmed and cuttings are removed during the pruning process in a subsequent year. Retting Retting is optional and involves pre-soaking the petiole bases in water for around 5 to 7 weeks. Defibring Either wet or dry petiole bases are then processed to reduce their size and to remove the fibres. This can be achieved by mechanical processing including but not limited to milling, grinding, pulverizing, liquidizing, and crushing using machine rollers which may be smooth rollers, fluted rollers or pinned rollers. Sieving Dry palm pith is then sieved to remove any undesirable particles such as mud, weed, stones, sand, residual fibres, and any other impurities. The resulting palm pith is then collected for further use as shown in Figure 5. Sorting (optional) Palm pith is then sorted according to moisture content, electrical conductivity (EC), and particle size. Particles smaller than 12 mm are used in most soilless growing media applications. Whereas particles larger than 12 mm are used as mulching material. Further, larger chunks also known as chips are used as special growing media for orchids and anthurium, as shown in Figure 6. Washing (optional) Resulting palm pith may be washed by fresh water to adjust the electrical conductivity (EC) as required. EC is the measure of mineral content of the pith. Sterilizing (optional) Palm pith may be sterilized by one of the following techniques or more, including autoclaving, dry heat sterilization using hot air oven, radiation sterilization, gas sterilization, or using hydrogen peroxide. Drying The extracted palm pith is then dried either by spreading on the land to dry under the sun, air drying or dried using a drying machine, such as hot air oven. Mixing (optional) The dry palm pith could be then mixed with other materials such as but not limited to soil, soilless growing media, organic, inorganic or synthetic (for example, mud, rockwool, perlite (RTM), peat moss, coconut coir pith, saw dust, bark, straw), fibres, pH adjusting agents, microbial inoculums, and / or fertilizers such as perlite, vermiculite, and calcium nitrate. Compressing The dry palm pith is then compressed using a hydraulic or mechanical press (not shown), to densify the material with the requested size and shape for more cost-effective transportation. It can be compressed into blocks or other shapes and sizes such as slab or pellet shapes. Further, the palm pith may be wrapped in plastic bags (any packaging bag) also known as grow bags, with or without planting and drainage holes. Although in the illustrated embodiment, the method includes the steps of sieving, washing, sterilising, drying, mixing, and compressing, it is to be understood that each of these steps is optional, and that the method may include none of these steps, or any one or more of these steps in any combination. The illustrated embodiment relates to the use of petiole base from date palm. It is however to be understood that the palm petiole base is obtained from one or more of: date palm, oil palm, sugar palm, coconut palm or any combination thereof. The petiole base has been found to be very rich in lignin which is characterized by a unique cellular structure provided by spongy parenchyma cells as shown in Figure 2B. This cellular structure is important for growing media to enhance its water holding capacity. The petiole base has also been found to have the least fibre content (typically between 5% and 30% fibre volume fraction) compared to the other parts of the date palm pruning residues. As such, the petiole base has been found to be an excellent source for extracting soilless growing media. The soilless growing media of the present invention, obtained from petiole base of palms, has been found to comprise lignin particles with high cell rigidity and minimal amount of cellulose fibre content. Example of one type of soilless growing media, extracted from date palm petiole base according to one embodiment of the present invention, is shown in Figures 5 and whose properties are in Table 1 below. Parameters Value range Analysis method Particle size (mm) 2-12 Bulk density CEN (Kg / m3) 275 - 375 EN 12580 pH 5,5 - 7,5 EN 13037 EC (mS / m) 0-80 EN 13038 Organic matter (%) 0-35 EN 13039 Dry matter (%) 25-40 EN 130340 WHC (g / 100g DM) 600 - 800 Table 1 10 Figures 4A and 4B illustrate differences in fibre volume fraction obtained from a date palm petiole base and a frond of date palm. The invention has been described byway of examples only, and it will be appreciated that variations may be made to the aforementioned examples, without departing from the scope of protection as defined by the claims.

Claims

1. A method for the production of soilless growing media comprising the steps of: separating the petiole base from the palm trunk after drying to provide dry petiole base; defibring the petiole base into particles with reduced size and removing the fibres to provide palm pith; andmechanically processing the palm pith by at least one of the steps comprising: milling, grinding, pulverizing, liquidizing and crushing.

2. A method according to claim 1 wherein the mechanical processing is performed using a machine roller and / or a smooth roller and / or a fluted roller and / or a pinned roller.

3. A method according to either claims 1 or 2, further comprising drying the palm pith prior to production.

4. A method according to any preceding claim further comprising the step of sieving the processed palm pith prior to production to provide sieved palm pith.

5. A method according to any preceding claim further comprising the step of presoaking the dry petiole base in water to provide wet petiole base prior to processing of the petiole base.

6. A method according to any preceding claim, further comprising the step of: sorting the palm pith according to one or more parameters selected from the group including: moisture content, electrical conductivity (EC) and particle size.

7. A method according to claim 6, wherein the palm pith is sorted according to particle size such that the maximum particle size is no greater than 12 mm.

8. A method according to any preceding claim, further comprising the step of sterilising the palm pith prior to production.

9. A method according to any preceding claim further comprising the step of compressing the palm pith into defined, predetermined shapes.

10. A method according to claim 9, wherein the predetermined shapes are in the form of blocks, slabs or pellets.

11. A method according to any preceding claim, further comprising the step of: mixing the dry palm pith with one or more materials selected from the group including: soilless growing media, fibres, pH adjusting agents, microbial inoculums and fertilizers.

12. A method according to claim 11, wherein the soilless growing media is selected from the group comprising: mud, peat moss, coconut coir pith, bark, saw dust, rice hull, straw, rockwool, gravel, sand, vermiculite, perlite and pebbles.

13. A method according to any preceding claim, further comprising the step of: wrapping the sieved palm pith or compressed palm pith in bags, optionally comprising planting and / or drainage holes.

14. A method according to any preceding claim, wherein the palm petiole base is obtained from the group comprising: date palm, oil palm, sugar palm and coconut palm.

15. A soilless growing media produced according to the method of any preceding claim having a fibre volume fraction of less than 30% of total volume.

16. A soilless growing media according to claim 15 comprising one or more of: palmpith, sieved palm pith, compressed palm pith, or any combination thereof.

17. A soilless growing media according to claim 15 or 16, having a fibre volume fraction of at least 5% by volume.

18. A soilless growing media according to claim 16 or 17, used as chunks or chips.

19. A soilless growing media according to any one of claims 16 to 18, wherein the maximum size of the particles is no greater than 12 mm.

20. A soilless growing media comprising one or more of: palm pith, sieved palm pith, or compressed palm pith obtained by the method of any one of claims 1 to 14.

21. Use of a soilless growing media according to any of claims 16 to 20 in: horticulture, floriculture, nurseries, gardening, landscaping, indoor farming, hydroponics, lawns or any combination thereof.

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