Improvements in or relating to growing media

Abstract

A growing medium is made, which is rich in microorganisms, especially fungi. The growing medium is made in two stages. First, a starter composition is made by carrying out composting in the presence of one or more added components, namely microorganisms, food for microorganisms, and physical support for microorganisms. Second, after maturation, the starter composition is added to a compost or soil product, for example composted bark fines, to make a growing medium. The growing medium has a diverse microorganism population which promotes healthy plant growth.

Description

IMPROVEMENTS IN OR RELATING TO GROWING MEDIA

[0001] The present invention relates to a growing medium for growing plants; to the production of the growing medium; to the use of the growing medium; to a starter composition for use in the production of the growing medium; to the production of the starter composition from a compostable mixture; and to the compostable mixture itself. The invention relates particularly to arboreal use (for example forests and woodlands) but may also be of application in other fields of field of horticulture and agriculture.

[0002] For reasons of environmental enhancement, the rate of tree planting in the UK is being accelerated. By 2025, the UK Government is seeking to increase tree planting to 10,000 hectares per year in England. Furthermore, the UK Government has set legally binding targets to increase tree and woodland cover to 16.5% of total UK land area by 2050. To meet such planting target, the UK Forestry Commission has launched the Tree Production Innovation Fund (TPIF). Objectives include enhancing the diversity of tree species, and improving germination, propagation, and establishment of trees. Another stated aim relates to the development of growing media to enhance the efficiency of tree production and improve the resilience of trees to a changing climate. Aside from this desired enhancement in the efficiency of tree production there will clearly need to be an increase in the UK production of growing media if the tree planting targets are to be met.

[0003] If the UK Government's stated objectives are to be met the adoption of new techniques and practices will be required.

[0004] The growing environment of trees is very important for their germination, health and rate of growth. Typically, young trees are initially grown in a nursery under conditions where factors such as soil moisture, air humidity, and chemical food source are carefully controlled. Difficulties have been observed when trees are planted out, for example in a garden or arboreal environment. Such environments - especially arboreal environments - may be very different from the environment of the nursery in which they were raised. Frequently, the transplanted trees may fail to thrive or may even die. If they grow at all, this may often be after a period of 1-3 years of stasis, in which they appear to undergo a shock, as if struggling to come to terms with their new environment. We believe, therefore, that there is a need to improve the compatibility between the nursery environment young plants experience and their final growing environment. For example, it would be desirable to produce a growing medium which more closely reflects arboreal conditions.

[0005] Similar considerations apply to other types of plants, for example herbaceous shrubs, and crops. Here, the focus is often on the food content (NPK) of the growing medium without realisation that the compatibility of the nursery growing medium and the soil of the final location of the plant, for example in a garden, may be of importance.

[0006] Peat-based composts have typically provided cheap growing media but peat is a finite resource, and peat-based composts are not sustainable. Accordingly the compost industry has been reducing the use of peat. The advantages of peat-based composts include that they have excellent water retention due to the types of fibrous materials used to form them. Other peat-free alternatives contain a high proportion of brown sterilised media or coir as a base and are not conducive to good root structure development or able to provide sufficient natural nutrients. There is a risk that the dry ingredients of peat-free alternatives become hydrophobic and so become unsuitable as growing media.

[0007] It is known that one of the most important issues with peat-free alternatives for potting / growing media is poor water retention capacity. This leads to lower germination rate and plant stress which causes elevated susceptibility to pests and diseases, and increased cost and labour for irrigation.

[0008] We have sought to make improvements to growing media which are of benefit to the forestation program initiated by the UK Government. In doing so we have sought to mitigate the problems we have described above with peat-based and current peat-free composts.

[0009] It is an object of embodiments of the invention to provide growing media which are rich and diverse in microorganisms and which are produced by processes of microbial colonisation and replication, for example in environments which naturally contain the colonising microorganisms. More specifically, it is an object of embodiments of the invention to provide growing media which are rich and diverse in fungal microorganisms. It is an object of embodiments of the invention to provide growing media which can be considered as grown or gestated, rather than assembled, in the manner of many bacterially-dominated commercial composts.

[0010] Some of the improvements we have made have applications which extend beyond the arboreal environment.

[0011] According to a first aspect the invention there is provided a compostable mixture suitable for use in making a starter composition which can be added to a growing medium to effect improvement, wherein the compostable mixture comprises:(a) a first composting material;(b) optionally, a second composting material;and one or both of the following components (c) and (d);(c) a source of microorganisms added in a predetermined amount, for example having regard to the amount and type of composting material(s);(d) a microorganism support added in a predetermined amount, for example having regard to the amount and type of composting material(s).

[0012] According to a second aspect the invention there is provided a method of forming a compostable mixture of the first invention.

[0013] According to a third aspect of the invention there is provided a method of making a starter composition by retaining a compostable mixture of the first or second aspect of the invention for a maturation period.

[0014] According to a fourth aspect of the present invention there is provided a starter composition resulting from the method of the third aspect.

[0015] The paragraphs which now follow describe features of the first, second, third and fourth aspects of the invention. Of course, the compostable mixture changes over time, as composting proceeds. When we define characteristics of the compostable mixture the reference point is the time it is formed by bringing together the defined components. When we define characteristics of the starter composition the reference point is when it has matured and is ready for use, for example when it can be mixed with a further material.

[0016] In this specification we use the term microorganism, and its synonym microbe, and derivative words such as microbial, in the manner which is conventional in the art, to include all bacteria and fungi irrespective of size, and not just those which are too small to be seen by the naked eye.

[0017] In some embodiments, the first composting material is a material which is often called a green composting material and / or a high nitrogen composting material, in this art.

[0018] In some embodiments, a green composting material may be manure, or manure with light bedding (such as from poultry, horse, sheep, and / or cow). In some embodiments, the green composting material may be coffee grounds. In some embodiments, the green composting material may be hay. In some embodiments, the green composting material may be silage. In some embodiments, the green composting material may be clover and / or other legume residues. In some embodiments, the green composting material may be food waste (such as vegetable scraps / peelings and / or fruit pulps). In some embodiments, the green composting material may be horticultural industry residues (such as root crop tops, fresh leaf prunings, and / or non-consumableproduce). In some embodiments, the green composting material may be fresh grass clippings. In some embodiments, the green composting material may be seaweed. In some embodiments, the green composting material may be wood ash. In some embodiments, the green composting material may be wheat bran. In some embodiments, the green composting material may be milling industry residue (such as grain dust). In some embodiments, the green composting material may be distillery waste (such as grape marc). In embodiments of the invention the first composting material may comprise spoiled silage. Spoiled silage is silage which has become unfit for bovine nutrition, usually due to oxidative processes. In some embodiments the green composting material may be digestate (the material remaining after the anaerobic digestion of a biodegradable feedstock).

[0019] In some embodiments, a green composting material may have a carbon to nitrogen molar ratio of at least 15:1. In some embodiments, the green composting material may have a carbon to nitrogen molar ratio of at least 18:1.

[0020] In some embodiments, the green composting material may have a carbon to nitrogen molar ratio of up to 29:1. In some embodiments, the green composting material may have a carbon to nitrogen molar ratio of up to 23:1.

[0021] A high nitrogen composting material may have a lower carbon to nitrogen molar ratio compared to the green composting material.

[0022] In some embodiments, a high nitrogen composting material may have a carbon to nitrogen molar ratio of at least 3:1. In some embodiments, the high nitrogen composting material may have a carbon to nitrogen molar ratio of at least 6:1. In some embodiments, the high nitrogen composting material may have a carbon to nitrogen molar ratio of up to 15:1. In some embodiments, the high nitrogen composting material may have a carbon to nitrogen molar ratio of up to 12:1.

[0023] In some embodiments, a high nitrogen composting material may be brewery waste (such as spent grain). In some embodiments, the high nitrogen composting material may be distillery waste (such as grape marc). In some embodiments, the high nitrogen composting material may be a residue from fish and / or shellfish (such as mussels, shrimps); or slaughter waste (such as blood, carcasses, and / or hair / fur). In some embodiments, a high nitrogen composting material may be feathers. In some embodiments, a high nitrogen composting material may be hemp seed cake. In some embodiments, the high nitrogen composting material may be a dairy by-product (such as cheese whey). In some embodiments, the high nitrogen composting material may be manure (separated from bedding). In some embodiments, the high nitrogen composting material may bewool (such as from sheep shearing). In some embodiments, the high nitrogen composting material may be green sprout (such as grass in early springtime). In some embodiments, the high nitrogen composting material may be cover crop fresh cuts (such as alfalfa, hairy vetch, amaranth and / or purslane). In some embodiments, the high nitrogen composting material may be activated sludge.

[0024] When the first composting material is composed of a mixture of materials, the C and N molar ratio of the mixture is the calculated mean value.

[0025] In some embodiments, the second composting material is a material which is often called a brown composting material, in this art. Suitably, the second composting material is a high-carbon material, with a higher carbon to nitrogen molar ratio than the first composting material.

[0026] In some embodiments, the second composting material may comprise wood industry residue (e.g. saw dust). In some embodiments, the second composting material may comprise arable land by-product such as straw (e.g. wheat, oat, rye straw), corn cobs, and / or stalks. In some embodiments, the second composting material may comprise forestry / arboriculture by-product such as wood chips, bark (e.g. from soft-and / or hard-wood trees), and / or fern cuttings. Bark components may include uncomposted bark fines and composted bark fines. In some embodiments, the second composting material may comprise garden waste such as leaves, twigs, and pine needles. In some embodiments, the second composting material may comprise animal bedding. In some embodiments, the second composting material may comprise paper waste such as cardboard, shredded paper / newspaper and / or paper pulp. In some embodiments, the second composting material may comprise nut shells. In some embodiments, the second composting material may comprise cotton. In some embodiments, the second composting material may comprise mushroom substrate. In embodiments of the invention the second composting material may comprise fresh wood chips and / or partially composted wood chips.

[0027] In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of at least 30:1 In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of at least 80:1. In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of at least 130:1. In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of at least 180:1.

[0028] In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of up to 400:1. In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of up to 350:1. In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of up to 300:1. In some embodiments, the second composting material may have a carbon to nitrogen molar ratio of up to 250:1.

[0029] When the second composting material is composed of a mixture of materials, the C and N ratio of the mixture is the calculated mean value.

[0030] In embodiments of the invention the compostable mixture contains both a first composting material and a second composting material. In such embodiments of the invention there may suitably be 1 part of the first composting material to 0.5 to 15 parts of the second composting material, suitably 1 part of the first composting material to 1 to 8 parts of the second composting material, suitably 1 part of the first composting material to 1 to 6 parts of the second composting material, weight / weight.

[0031] In some embodiments the compostable mixture may include biochar in particulate form. Biochar is the residue from the carbonisation of any biological material at a high temperature (for example in the range 300-1000°C), in the absence of oxygen or under oxygen-starved conditions. Biochar may comprise up to 30% wt / wt of the compostable mixture, preferably up to 20% wt / wt, more preferably up to 10% wt / wt. Biochar may aid water retention and promote carbon capture.

[0032] It is an object of embodiments of the invention to produce a growing medium which is compatible with an arboreal soil.

[0033] It is an object of embodiments of the invention to produce a growing medium which has significant characteristics of an arboreal soil, especially in terms of its fungal content. Embodiments of the invention could be seen as an attempt to mimic an arboreal soil, is so far as that is possible.

[0034] It is an object of embodiments of the invention to produce a growing medium whose microbiome, preferably its fungal microbiome, as far as possible reflects or even replicates the microbiome of an arboreal soil.

[0035] The source of microorganisms may be fungal and bacterial microorganisms whose habitat is soil or wood, especially those which are characteristic of arboreal environments. An example of soil-living fungi of significance in arboreal environments is the class Deuteromycota, including mycorrhizal fungi. Free-living soil bacteria beneficial to plant growth, usually referred to as plant growth promoting rhizobacteria (PGPR), can promote plant growth by colonizing the plant root. PGPR are also termed plant health promoting rhizobacteria (PHPR) or nodule promoting rhizobacteria (NPR). These are associated with the rhizosphere, which is an important soil ecological environment for plant-microbe interactions. Symbiotic nitrogen-fixing bacteria which may be employed or preferentially grown in the present invention include the cyanobacteria of the genera Rhizobium, Bradyrhizobium, Azorhizobium, Allorhizobium,Sinorhizobium and Mesorhizobium; and free-living nitrogen-fixing bacteria or associative nitrogen fixers, for example bacteria belonging to the species Azospirillum, Enterobacter,Klebsiella and Pseudomonas, which have been shown to attach to the root and efficiently colonize root surfaces.

[0036] In some embodiments a microorganism source used in this invention may be a refined or concentrated compost, a liquid compost, and / or a compost extract. A microorganism source may comprise a portion taken from a previous starter composition made in accordance with the present invention or a liquid extract therefrom. A liquid compost or a liquid compost extract may be made by liquefying a compost with water and draining it to separate liquid and solid phases, and optionally concentrating the liquid phase. When a microorganism source is used as an inoculant in a method of making a new starter composition it is preferred that the inoculant and the new starter composition derive from compatible environments. For example both may be made in the vicinity of sawmills, or both made be made in woodland environments. The fungal and bacterial microorganisms present in the inoculant are more likely to be favoured microorganisms for replicating in the new starter, when the environments are compatible. Beneficially, the inoculant and the new starter composition may derive from substantially the same location.

[0037] When a portion is taken from a previous starter composition and used in the feedstock for a making a new starter composition it is preferred that the portion taken from a previous starter composition provides at least 2% (wt / wt) of the feedstock, preferably at least 4%, and more preferably at least 8%. It is preferred that it provides up to 20% (wt / wt) of the feedstock, preferably up to 15%, and more preferably up to 12%.

[0038] A microorganism support can be of a class which can be digested by a desired microorganism (which we will call microorganism support type (dl)) or of a class which can provide physical support for microorganisms in the compostable mixture (which we will call microorganism support type (d2)). Each such type of microorganism support promotes replication of the microbiome. In embodiments of the invention both types of microorganism support (that is, the digestible type (dl) and the physical support type (d2)), are present and they may work beneficially together in promoting the microbiome.

[0039] A microorganism support of type (dl) which may be digested by a desired microorganism, may include, for example, one or more of the following organic materials: fish protein, including shellfish protein; dried sea algae, including brown seaweed, or kelp; and pressed cakes of plant matter, which may be left after oil or juice extraction; for example the residues from the pressing of hemp, olives, peanuts, coconut, soybeans, flax seed (linseed), cottonseed and sunflower seeds. A microorganism support (dl) may be an omega oil source; and / or a protein source.

[0040] A microorganism support (dl) may suitably be present in embodiments of the invention in a ratio from 2 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (dl) may be present in a ratio from 3 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (dl) may be present in a ratio from 4 kg per 1000 litres of total compostable material.

[0041] A microorganism support (dl) may suitably be present in embodiments of the invention in a ratio of up to 12 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (dl) may be present in a ratio of up to 10 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (dl) may be present in a ratio of up to 8 kg per 1000 litres of total compostable material.

[0042] A microorganism support of type (d2) which may provide physical support in the compostable mixture may be a particulate inorganic material, and may include naturally occurring rock materials in finely divided form; for example in pulverized form. Examples of rocks that can produce suitable particulates include one or more of sedimentary, igneous and metamorphic rocks. Examples of suitable sedimentary rock sources include magnesium carbonate, calcium carbonate (which may be as chalk or limestone), sandstone, clay, shale and gypsum. Examples of suitable igneous rock sources include silica, quartz, silicates, basalt and pumice. Examples of suitable metamorphic rock sources include marble and slate.

[0043] A microorganism support (d2) may suitably be present in embodiments of the invention in a ratio from 2 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (d2) may be present in a ratio from 4 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (d2) may be present in a ratio from 5 kg per 1000 litres of total compostable material.

[0044] A microorganism support (d2) may suitably be present in embodiments of the invention in a ratio of up to 15 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (d2) may be present in a ratio of up to 12 kg per 1000 litres of total compostable material. In some embodiments a microorganism support (d2) may be present in a ratio of up to 10 kg per 1000 litres of total compostable material.

[0045] In embodiments of the invention both types of microorganism support (dl) and (d2) are present, each in the amounts separately defined above. The ratio (wt / wt) is suitably in the range 1 part (dl) to 0.2 - 5 parts (d2); suitably 1 part (dl) to 0.5 - 2 parts (d2); suitably 1 part (dl) to 1 - 3 parts (d2); and preferably 1 part (dl) to 1.1 - 2 parts (d2).

[0046] There may be more than one microorganism support of type (dl) and in such embodiments the amounts and ratios given above denote the total amount of such components.

[0047] There may be more than one microorganism support of type (d2) and in such embodiments the amounts and ratios given above denote the total amount of such components.

[0048] In embodiments of the invention the components - namely the first composting material; the second composting material when present; and 'micro-ingredients' - namely one, two or three of the further components, namely the source of microorganisms, microorganism support of type (dl) and microorganism support of type (d2) - are introduced into the container in layers. However, mixing them before they are introduced into the container is not excluded.

[0049] In some embodiments of the invention the compostable mixture is loaded into a container which has openings in its side walls to promote aeration of the compostable mixture. In some embodiments of the invention the container may be a bulk bag of flexible material, having side walls with perforations. In some embodiments the container may be a rigid framework intended to receive an industrial storage container, for example of the type known as an IBC. The rigid framework may be wrapped in an air- and water-permeable jacket, for example of netting or mesh.

[0050] Suitably a container into which the compostable mixture is loaded has a volume in the range from 400 litres to 3000 litres. In embodiments of the invention the container volume is in the range from 600 litres to 1800 litres. In embodiments of the invention the container volume is in the range from 700 litres to 1300 litres.

[0051] In some embodiments of the invention the compostable mixture is loaded into a container which has openings in its bottom wall, or has no bottom wall at all, the container being located out of doors during the maturation period, and subject to the ambient weather conditions, and preferably in an arboreal environment. In such a situation the compostable mixture may be in direct contact with the arboreal soil to facilitate colonisation by fungal species in the arboreal soil.

[0052] In embodiments of the invention the compostable mixture is formed into a freestanding mass or pile. The pile may be elongate, in the form of windrow. In some embodiments of the invention the pile may be left open to the elements. In other embodiments the pile may be covered with a flexible perforated material.

[0053] Standard horticultural advice is to turn compost to increase aeration. In the method of the present invention the compostable mixture can be turned during the maturation period. However, in embodiments of the present invention the compostable mixture is not turned, so that thedeveloping microbiome is not disturbed. Nevertheless the composting process in the method of the invention is preferably aerobic.

[0054] Different methods are available for carrying out the method of making the starter composition. They include hot composting, vermicomposting and the Johnson-su composting in which a high level of aeration is achieved, without turning the material. The Johnson-su method uses a container which is permeable to air and water transmission. Large channels are formed in the mixture to be composted, for example by drilling into the material or by having tubes in place as the container is filled, and then withdrawing them when the container is full, straight away after the channels have been formed or after an interval, for example of a few weeks. The Johnson-su method is aerobic but without intermediate stages of turning the composition. In some embodiments of the invention a combination of techniques can be employed, for example Johnson-su and vermicomposting. Composting worms can be added to the Johnson-su composting mixture.

[0055] In the third aspect of the invention the compostable mixture is retained for a maturation period, to make the starter composition. The maturation period starts as soon as the components are mixed to form the compostable mixture.

[0056] In some embodiments of the invention the maturation period may be at least 6 months. In embodiments of the invention the maturation period may be at least 8 months. In some embodiments of the invention the maturation period may be at least 10 months.

[0057] In some embodiments of the invention the maturation period may be up to 24 months. In some embodiments of the invention the maturation period may be up to 18 months. In some embodiments of the invention the maturation period may be up to 14 months.

[0058] At the end of the maturation period it has been found that the compostable mixture has matured into a starter composition which may have a very rich microbiome, comprising high levels of bacteria and fungi. A rich microbiome is of benefit because it means that a very wide range of microorganism is present. The richer the microbiome, the more likely it is that microorganisms of particular benefit to plants will be present; and that valuable, mutually beneficial relationships between microorganisms and plants may develop. Certain microorganisms may, for example, be particularly effective in assisting plants to access food sources in the soil, or in retaining moisture. Providing rich fungal biome with a diverse range of microorganisms may be especially important in such respects.

[0059] The microbiome can be assessed by microscopy and by DNA studies. Typically, in the microscopic method a sample is removed at the end of the maturation process and is mixed withfiltered water, and the biomass of each group of microorganisms is assessed. Fungi counts used dilution in water of 5 to 10 to 1 total volume. Bacterial counts are done at 100 to 500 to 1 dilution. One drop of the dilution is transferred onto a slide and observed under a bright field microscope. General morphology is used as a differentiator of the elements of soil food web present. This method was used to generate results set out in the examples. DNA methods identified species by their known genetic information. Specialist institutes such as FERA in York, UK are available to carry out such testing, and were contracted to do the DNA testing described in examples in this specification.

[0060] In embodiments of the invention the concentration of fungi in the starter composition is at least 175 pg / ml, for example at least 400 pg / ml. In some embodiments of the invention the concentration of fungi in the starter composition can be at least 800 pg / ml, and may be at least lOOOpg / ml. In some embodiments of the invention concentrations of fungi in excess of 1400 pg / ml have been achieved.

[0061] In some embodiments of the invention the concentration of bacteria (including actinobacteria) in the starter composition is at least 20 pg / ml. In some embodiments the concentration of bacteria (including actinobacteria) in the starter composition is at least 30 pg / ml. In some embodiments the concentration of bacteria (including actinobacteria) in the starter composition is at least 40 pg / ml.

[0062] Fungi to bacteria biomass ratio affects groups of plants that the soil / compost will best support. The following guideline information is provided as guidance:F:B = 0.1 - weedy stage, or irrigated wheat (not much biomass, or highly bacterial when excessive chemical have been used)F:B = 0.3 - early successional plants (early annuals, dryland wheat). Bromus, bermuda, brassicas, mustard and kale crops as examplesF:B = 0.75 - 0.8 - mid successional grasses, vegetables, herbs and forbs (herbaceous flowering plants that are not graminoids)F:B = 1 - late successional grasses, productive row crops, pastures, turf, prairies (fescues, corn, wheat, lucerne)F:B = 2 - 5 - fruit bushesF:B = 5 - 10 - deciduous trees, orchardsF:B = 10 - 1000 - late successional, old growth, forests, conifer systems

[0063] In some embodiments of the invention the ratio of the concentration of fungi to the concentration of bacteria (including actinobacteria) (F:B ratio) in the starter composition is at least 0.25:1 (pg / ml / pg / ml), or at least 0.5:1. In some embodiments of the invention the ratio of the concentration of fungi to the concentration of bacteria (including actinobacteria) (F:B ratio) in the starter composition is at least 1:1 (pg / ml / pg / ml). Bacteria are needed in the growing media of the invention but in preferred embodiments the concentration of fungi is higher than the concentration of bacteria. In some embodiments the F:B ratio is at least 2:1, and preferably at least 4:1. In some embodiments the F:B ratio is at least 8:1. In some embodiments the F:B ratio is at least 12:1 and may be at least 18:1.

[0064] It will be appreciated that the present invention employs natural biological processes. Variations in fungal and bacterial content in starter compositions cannot be avoided, even when they apparently have undergone the same regime. In reality, no starter composition will have undergone exactly the same process as another - there will be unavoidable variations, for example in composting materials, sun, temperature, wind, rain, shade, worm population and proximity of fungal and bacterial sources.

[0065] The present invention may include a step of assessing starter compositions, for example using a chemical assay, which may lead to determination of optimal uses for the starter compositions, or in some cases to determine if they need modification.

[0066] In embodiments of the invention a modified starter composition may be made by blending a starter composition of the present invention with a microorganism source as defined above, or with a soil or compost, or with another starter mixture, to obtain tailored properties.

[0067] A starter composition with a high fungal content and / or a high F:B ratio may be highly suitable for use in formulating a growing medium for germinating tree seeds and planting trees, including saplings. A starter composition with a lower fungal content and / or a lower F:B ratio may be highly suitable for use in formulating a growing medium for ericaceous plants. A starter composition with a still lower fungal content and / or a still lower F:B ratio may be suitable for use in formulating a growing medium for plants in horticultural or market garden applications.

[0068] According to a fifth aspect of the invention there is provided a growing medium comprising an amount of the starter composition of the fourth aspect of the invention, a larger amount of a compost or soil component and, optionally, trace minerals.

[0069] According to a sixth aspect of the present invention there is provided a method of forming a growing medium by mixing an amount of the starter composition of the fourth aspect of the invention, a larger amount of a compost or soil component and, optionally, trace minerals.

[0070] In describing the starter composition and the compost or soil component of these fifth and sixth aspects of the invention, ratios are given as vol / vol of the total growing medium.

[0071] In some embodiments of these fifth and sixth aspects of the invention the starter composition provides at least 5% of the growing medium. In some embodiments of the invention the starter composition provides at least 10% of the growing medium. In some embodiments of the invention the starter composition provides at least 15% of the growing medium.

[0072] In some embodiments of these fifth and sixth aspects of the invention the starter composition provides up to 40% of the growing medium. In some embodiments of the invention the starter composition provides up to 30% of the growing medium. In some embodiments of the invention the starter composition provides up to 25% of the growing medium.

[0073] In some embodiments of these fifth and sixth aspects of the invention the compost or soil component provides up to 95% of the growing medium. In some embodiments of the invention the compost or soil component provides up to 90% of the growing medium. In some embodiments of the invention the compost or soil component provides up to 85% of the growing medium.

[0074] In some embodiments of these fifth and sixth aspects of the invention compost or soil component provides at least 60% of the growing medium. In some embodiments of the invention the compost or soil component provides at least 70% of the growing medium. In some embodiments of the invention the compost or soil component provides at least 75% of the growing medium.

[0075] In some embodiments of these fifth and sixth aspects trace minerals may not be needed and so are not added. Where they are added they are be added in such small amounts that they do not in substance alter the definitions just given as to the amounts of starter composition and compost or soil component which are present.

[0076] Different trace minerals (which may include compounds and elements) may be added to optimise the growing medium for different intended end uses. A chemical assay may be made and a decision can then be taken, as to mineral additions which would be beneficial. An assay to determine the content of such trace minerals may be of the growing medium, newly formed by mixing the starter composition and the soil or compost component. On completion of the assay the required trace minerals may be added to the growing medium. Alternatively assays to determine the content of such trace minerals may be of the starter composition and of the soil or compost component before they are mixed to form the growing medium. The required trace minerals can be added to either component prior to mixing or, most conveniently, when they are mixed to together to form the growing medium.

[0077] Trace minerals added to support healthy plant function may include salts of boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), aluminium (Al) selenium (Se), phosphorus (P), sulphur (S), as well as nitrate ions, ammonium ions and sugars.

[0078] When trace minerals are added to the growing medium they may be added in very low amounts, for example less than 4% on total growing medium (wt / wt), for example less than 2%, for example less than 1%, preferably less than 0.5%.

[0079] In embodiments of these fifth and sixth aspects the components - namely the starter composition, the compost or soil component and, optionally, trace minerals - are mixed together to form the growing medium, which may be used immediately or may be kept for a dwell time before packaging. The dwell time may be at least 2 weeks, for example at least four weeks, for example at least 6 weeks. A dwell time, in which the soil or compost component is exposed to the microbially 'live' starter composition, may have a rapid growth-promoting effect on the microbiome, in particular the fungal biome.

[0080] In embodiments of the present invention the compost or soil component comprises or consists of a tree bark component.

[0081] A tree bark component used in these fifth and sixth aspects of the invention may comprise or consist of tree bark chippings; suitably fine bark chippings which are quick to compost (or compost further, if they are already part-composted).

[0082] A tree bark component used in these fifth and sixth aspects may comprise or consist of tree bark fines.

[0083] A tree bark component used in these fifth and sixth aspects, for example tree bark fines, may be uncomposted or composted, before mixing with the starter composition.

[0084] In some embodiments of these fifth and sixth aspects the tree bark component comprises or consists of composted tree bark fines or uncomposted tree bark fines or a mixture thereof.

[0085] The presence of peat or a peat derivative, for example in some embodiments up to 40% (by weight on total weight of composition), or in some embodiments up to 20%, or in some embodiments up to 10%, is not excluded in the present invention. Preferably, however, no product or method of any aspect of the present invention includes the addition of peat or a peat derivative.

[0086] The presence of coir, for example in some embodiments up to 40% (by wt on total wt of composition), or in some embodiments up to 20%, or in some embodiments up to 10%, is notexcluded in the present invention. Preferably, however, no product or method of any aspect of the present invention includes the addition of coir.

[0087] The addition of a nitrogen-based fertiliser, a phosphorus-based fertiliser or a potassium- based fertiliser, or any combination thereof, for example an NPK fertiliser, is not excluded in the present invention. Such a fertiliser could be of value in fast-growing food crops, such as lettuces. Such fertilisers are commonly the products of chemical synthesis and may typically comprise compounds such as ammonium nitrate, ammonium sulphate, ammonium phosphate and potassium nitrate. Chemically synthesised fertilisers have a very large carbon footprint, partly because of the manufacture of the fundamental precursor compound ammonia by the Haber- Bosch process. Several other problems arise from the use of chemically synthesised fertiliser. Excess nitrogen in the soil can deplete soil of its richness and microbial biodiversity, cause soil acidification, damage plant growth, contribute to the leaching of nutrients into waterways and release nitrous oxide, a potent greenhouse gas. Excess phosphorus and potassium also cause environmental detriment. The chemical compounds in chemically synthesised fertilisers are highly soluble in water and when applied at a location they are substantially immediately present in the soil. Unless careful assays have been taken of the soil chemistry prior to application and unless careful application to the soil is carried out the result can be uncontrolled excessive use of chemically synthesised fertilisers, with detrimental consequences.

[0088] Growing media of embodiments of the present invention are rich in nutrients and rich in bacteria and / or fungi which may assist plants in accessing nutrients. Together these may be sufficient for the growing needs of plants, such as young trees, without addition of any nutrition.

[0089] In many preferred embodiments of the invention no product or method of any aspect of the present invention includes the addition of a nitrogen-based fertiliser, a phosphorus-based fertiliser or a potassium-based fertiliser, or any combination thereof, for example an NPK fertiliser. In those cases when additional nutrition is needed, the addition of chemically synthesised fertiliser is not excluded but it is preferred to add a biologically-derived fertiliser. A biologically-derived fertiliser will not have many of the problems associated with immediately-soluble chemically synthesised fertilisers. Examples of suitable biologically-derived fertilisers include seaweed, hoof and horn, dried blood, fish blood & bone, bone meal, poultry manure pellets and liquid comfrey or liquid nettle feeds. Such materials may be useful as feed materials for starter compositions but they may also be added at later stages of the production of growing media of the invention to bring the content of N, P or K to a required level, if needed.

[0090] Microorganisms (microbes) in the soil help build the structure of the growing medium by creating micro- and macro-aggregates, which benefit the water retention of the growing medium. Furthermore, the by-products of the microbial activities, e.g. humic acid, also increase the moisture holding capacity. Water usage may thus be reduced by use of growing media of the present invention.

[0091] Advantages of the invention include that growing media of the present invention may have a high content of fungi, and / or high F:B ratio, and may have excellent water retention. In addition they may have good binding properties. Such properties lead to good handling and potting characteristics.

[0092] Growing media of the invention are suitable for use in biodegradable pots, for example pots having a cellulosic band around them but being open at both ends. A biodegradable pot, containing a growing medium and a young plant, may be planted directly into soil. Such biodegradable pots offer several advantages. They can be used in efficient automated horticultural practices, and so have production advantages. There is a substantial environmental benefit in not having to manufacture plastic pots which, ultimately, will be discarded. They allow air pruning. They minimise root disturbance on planting. A further benefit, of particular importance in the present invention, is that such pots facilitate the microbial colonisation of the growing medium in the pots. Both ends of the pots are open, permitting the ingress of microbes. The band, which is designed to degrade quickly in soil, may also allow the ingress of microbes. Examples of such pots are ELLEPOTS (Registered Trade Mark).

[0093] Generally, growing media of the invention may be highly suitable for any tree planting or tree seed germination, for example in a forest, woodland, orchard, park, garden, playground or grass verge. When compared to outcomes from planting in native soil or in composts with lower concentrations of microbes, in particular fungi, growing media of the invention may improve survival rate of saplings and promote faster growth, and may improve the germination rate of tree seeds.

[0094] Tree planting of saplings in sterile ground, following construction of roads, buildings and the like is notoriously problematic. For example, the UK Government agency National Highways has reported that out of 850,000 saplings planted along the new A14 road near Cambridge, UK in 2020, more than 637,000 have died. Lack of water was said to be one issue but the UK Government Highways Agency stated that the main issue was the quality of soil along the planting route. The use of the live growing media of the invention, especially those having a high fungal content and / or high F:B ratio, can improve sapling and tree planting outcomes even in such unpromisingenvironments. In this situation it may be desirable to use a starter composition on its own, without it having been added to a further soil or compost component.

[0095] When used to assist tree planting of saplings in sterile ground a growing medium, or starter composition, may be applied as a solid or in a liquid or slurry form.

[0096] Growing media in accordance with the present invention with a lower fungal content and / or a lower F:B ratio may be highly suitable for other plant-growing situations, for example as growing media for ericaceous plants, or for plants grown in horticultural or market garden applications. A growing medium for ericaceous plants may if necessary have addition of pH adjusting components, for example, sulphur).

[0097] Growing media of the invention may find application in ground cover application, as a mulch or mulch mat. This has the property that it can increase the biological activity in the soil beneath and promote later healthy growth from that area.

[0098] In accordance with a seventh aspect of the invention there is provided a method of producing a growing medium from composted bark fines by mixing composted bark fines with soil from an arboreal environment and retaining the resulting mixture for a maturation period, or by keeping the composted bark fines in an arboreal environment for a maturation period, the maturation period being sufficient in each case for the growing medium to be colonised by fungi to a concentration of at least 175 pg / ml, suitably to a concentration of at least 400 pg / ml, for example to a concentration of at least 800 pg / ml.

[0099] In the seventh aspect of the invention the maturation period may be at least 2 months. In embodiments of the invention the maturation period may be at least 6 months. In some embodiments of the invention the maturation period may be at least 12 months.

[0100] In the seventh aspect of the invention the maturation period may be up to 24 months. In some embodiments of the invention the maturation period may be up to 18 months. In some embodiments of the invention the maturation period may be up to 14 months.

[0101] Suitably in the seventh aspect of the invention the bark fines had been additized by one or both of the following components (c) and (d):(c) a source of microorganisms added in a predetermined amount; and(d) a microorganism support added in a predetermined amount

[0102] The definitions given above in connection with the first aspect of the invention for components (c) and (d), are applicable to this seventh aspect of the invention. Thus, they include the definitions of a microorganism support of type (dl) which may be digested by a desiredmicroorganism, and the definitions of a microorganism support of type (d2) which may provide physical support in the compostable mixture.

[0103] In accordance with the seventh aspect of the invention it is possible to produce a 'live' growing medium similar to the growing medium as defined above in earlier aspects, but without addition of any starter material. The definitions given above in earlier aspects, of preferred features relating to fungal content, bacterial content, F:B ratio, micro-ingredient addition, balancing mineral composition addition and possible uses apply also to the seventh aspect.

[0104] According to an eighth aspect of the invention there is provided the use of a growing medium of the fifth aspect in growing plants. The growing media may be highly suitable for growing trees, including saplings. Growing media employing features of the present invention may be useful in other growing contexts, for example for crops and shrubs. Growing media of the invention may promote germination of plants, including of tree species.

[0105] Starter compositions and growing media of the invention are believed to have particularly diverse microbiome and this is believed to offer significant benefits in terms of plant germination and growth. Growing media of the invention may include fungi from the phyla Ascomycota, Basidomycota and Mucoromycota. The Ascotymotae may include A.Pezizomycetes, A.Sordariomycetes, A.Leotiomycetes, A.Dothideomycetes, A.Eurotiomycetes and A.Orbiliomycetes. The Basidomycota may include B.Agaricomycetes and B.Tremellomycetes. The Mucoromycota may include M.Mortierellomycetes. Growing media of the invention have undergone DNA testing to determine number of fungal species ('Richness') and diversity (Shannon value based on a-diversity distribution). Growing media of the present invention have been shown to have Richness values of at least 120, for example at least 140, or at least 160. Some samples have exhibited Richness values in excess of 190. Such samples have shown Shannon values of at least 4.8, for example at least 5.2. A Shannon value of over 5.8 has been achieved.

[0106] In aspects of the invention a starter composition or a growing medium as defined herein has a fungal biome with one, any two or all three of the following characteristics (A), (B) and (C):(A) it contains all of the following fungal classes: Ascomycota Pezizomycetes, Ascomycota Sordariomycetes, Ascomycota Leotiomycetes, Ascomycota Dothideomycetes, Ascomycota Eurotiomycetes, Ascomycota Orbiliomycetes, Basidomycota Agaricomycetes, Basidomycota Tremellomycetes, Mucoromycota Mortierellomycetes;(B) It has a Richness value of at least 120;(C) it has a Shannon value (a-diversity) of at least 4.8.

[0107] The invention will be described, by way of illustration only, with reference to the following examples.EXAMPLES 1 to 6

[0108] Six starter compositions were prepared, using different compostable materials in differing amounts as described in Table 1. The compostable materials stated for each example were used to fill metal frames for IBC tanks, lm3in volume (lm x lm x lm). The IBC frames had widely separated metal support bars. The frames had been lined before filling with flexible plastic mesh sheets permitting air- and water-flow.TABLE 1

[0109] The fresh wood chip was beech waste which was approximately 6 weeks old. This was sourced from a tree surgeon using a standard chipper. Chip particles were approximately 2cm long. Fresh wood chip is a 'brown' compostable material which typically has a high carbon / nitrogen weight ratio in the range from 30:1 to 400:1.

[0110] Mature composted chip was a pre-composted wood chip with a maturation time of about 18 months. It was tree surgeon waste woodchip from a mixture of trees which was composted in a 3m x 3m x lm (9m3) open-top pile. Mature composted chip is a 'brown' material and typically has a high carbon / nitrogen weight ratio in the range from 30:1 to 400:1.

[0111] Spoiled silage was sourced from a local farm contractor. Spoiled silage is a 'green' compostable material which typically has a moderate carbon / nitrogen weight ratio in the range from 15:1 to 25:1.

[0112] Fresh coppiced willow chip was sourced from recently cut (coppiced) trees. The advantages of using fresh coppiced willow chip include that it provides young wood which will decompose quickly to reduce particle size within the finished product. Fresh coppiced willow chip is a 'brown' compostable material which typically has a high carbon / nitrogen weight ratio in the range from 30:1 to 400:1.

[0113] Leaves were gathered on-site from the woodland floor on Hardwick Estate woodland, Oxfordshire, UK (diverse mixed woodland). Leaves are a 'green' compostable material which typically has a moderate carbon / nitrogen weight ratio in the range from 15:1 to 25:1.

[0114] Hops and malt brewers waste were sourced from Loddon Brewery, Reading, UK. Hops and malt brewers waste are a 'high nitrogen' compostable material having a low carbon / nitrogen weight ratio in the range from 3:1 to 15:1.

[0115] Fresh horse manure (with bedding) was obtained from Hardwick Estate stud farm from horses which were grazed on organic land. Manure bedding is wood shavings and straw. The fresh horse manure contains about 50wt% manure and 50wt% bedding. Fresh horse manure (with bedding) is a 'green' compostable material which typically has a moderate carbon / nitrogen weight ratio in the range from 15:1 to 25:1.

[0116] A mixture of the first and second compostable materials for each composition was used to fill the frame in layers. Between layers, the microorganism support (micro-ingredient composition) with the components listed in Table 2 was applied such that 12 kg of the microorganism support was used for frame.TABLE 2

[0117] Each filled IBC frame was matured for a year as a Johnson-su bioreactor (JSB). The frame contains a plurality of layers of compostable material 20 and of microorganism support 25. The compostable material 20 comprises a mixture of the first and second compostable materials. Themicroorganism support 25 comprises the inorganic and organic components set out in Table 2. A plurality of columnar voids 32 are formed in the compostable material 20 in each IBC frame, to improve aeration. The columnar voids 30 are formed by drilling into the compostable material in the full IBC frame or by placing a plurality of suitable columns in the IBC frame 15 prior to the addition of the compostable material 20 and microorganism support 25 then removing the columns after the IBC frame 15 has been filled, to leave the voids 30.

[0118] Thus, a grid of air-holes was formed in the contents of the filled IBC frames.

[0119] A 10ml sample was removed from each IBC frame at the end of a maturation period of 12 months and was mixed with filtered water, and the ratio was included in calculating biomass of each group of microorganisms. Fungi counts used dilution of 5 to 10 to 1 total volume. Bacterial counts were done at 100 to 500 to 1 dilution. One drop of the dilution was transferred onto a slide and observed under a bright field microscope. General morphology is used as a differentiator of the elements of soil food web present.

[0120] The results obtained are detailed in Table 3 below.TABLE 3

[0121] There is natural variation in the amounts of bacteria and fungi due to uncontrollable ambient biological factors but all the compositions are potentially useful. It should be noted that all these examples of starter compositions have high levels of fungi - at least 182 pg / ml. The presence of fungi is desirable under most growing conditions. Examples 1, 2 and 6 have very high levels of fungi, from 903 to 1650 pg / ml, suggesting that such compositions have the potential to be components of growing media which will support tree growth. Examples 4 and 5 may be suitable as components of growing media for ericaceous plants (if necessary with pH adjustment using, for example, sulphur chips) while Example 3 may be suitable for as a component of growing media for early successional plants, for example lettuces and other leafy crops.

[0122] Examples 1 to 6 can be seen as 'live' composted materials which may be used as starter or inoculant compost compositions in admixture with other materials; the latter may be more inert and not optimised for some plant-growing applications, but useful for others; and with capacity to be improved by addition of the starter compositions.

[0123] A starter composition of any of Examples 1 to 6 may be useful as a component of a feedstock for making further starter compositions by the method of the present invention. The presence of thriving colonies of bacterial and fungi from the very start of the further composting method, introduced by the recycled starter component, aids the development of the bacterial and fungal biome of the further compost compositions.EXAMPLES 7 to 12

[0124] Six growing media according to the invention were obtained by mixing approximately 20% by volume of each of the starter compositions of Examples 1 to 6 with approximately 80% by volume of an additional composition, namely composted bark fines (CBF), and minor amounts of a balancing mineral composition (BMC). The balancing mineral composition, its components, and the amounts thereof, will depend on the requirements of the plants which will ultimately be grown in the growing media and so will vary. The amounts to be added will be decided with the aid of an assay to determine the ambient levels of such compounds within the respective starter composition, before any BMC addition. Typically, the balancing mineral composition, comprising compounds required to support healthy plant function, may be selected from salts of B, Na, K, Fe, Ca, Mg, Mn, Cu, Zn, Mo, Ni, Al, Se, P, Cl, S, as well as nitrate ions, ammonium ions and sugars.TABLE 4

[0125] Examples 7 and 8 were stored for 6 - 8 weeks in an airy environment prior to testing for bacterial and actinobacterial content, and for fungal content, in comparison with composted bark fines (CBF) to which the same Balancing Mineral Compositions (BMCs) had been added. Thepresence of the BMC in the CBF allowed for a true comparison with Examples 7 and 8, which also contained the BMC. The results are given in Table 5 below.TABLE 5

[0126] Table 5 shows that Examples 7 and 8 both have much higher concentrations of fungi, compared with the comparison composition which had CBF and BMC, but no starter composition. Examples 7 and 8 are considered suitable for arboreal uses.

[0127] The fungi values determined for Examples 7 and 8 are substantially at or exceed the expected values which are determined by calculating weighted averages of the respective admixtures, 20% vol / vol of Examples 1 and 2, and 80% vol / vol CBF + BMC. These calculated values are 334 pg / ml for Ex. 7, and 483 pg / ml for Ex. 8.EXAMPLE 13

[0128] The bacterial and high-fungal 'living' growing medium of Example 12 was tested for its ability to bind together in the manner of a peat-based compost, and for its suitability for use in an ELLEPOT (Registered Trade Mark) pot-filling system, and for its moisture retention properties.

[0129] In the ELLEPOT system a broad strip of biodegradable paper is wound around a plug of compost and sealed to form a cylinder. The plug is open at the top and bottom, with the strip functioning as a retaining band. A plant or seed is inserted into the plug at the top. Clearly, the compost must not fall through the bottom when the cylinder is lifted.

[0130] It was found that the Example 12 'living' growing medium has excellent binding and is perfectly suitable for use in the ELLEPOT process.

[0131] Further, the use of the ELLEPOT process offers benefits of lack of damage on planting, and of air pruning. A further important benefit is that there can be fungal permeation through the band following planting and / or as the band decomposes.

[0132] To test water retention two ELLEPOT paper pots were made containing the Example 12 'living' growing medium. Two ELLEPOT paper pots were made containing the commercial compostproduct JIFFY (Registered Trade Mark). JIFFY is a peat-free compost containing coir, wood derivatives and perlite. It is marketed as having "good water retention". At T = 0 days the pots were watered to their maximum capacity. Excess water was allowed to drain away. The pots were then weighed to give the T = 0 days value. Pots and test conditions were identical apart from the growing media.

[0133] The results are shown in Tables 6 and 7 below.TABLE 6

[0134] Weight in grams of each paper pot measured at various time points:TABLE 700135] Calculated water loss in relation to the initial weights:

[0136] It will be seen that the results indicate that the Example 12 high-fungal 'living' composition showed water retention benefits over the JIFFY compost after 2 and 4 days. Given that the JIFFY product is marketed as having good water retention it is of value that the high-fungal 'living' composition offers excellent water retaining properties without the presence of coir, or of peat.EXAMPLE 14

[0137] Much of our work has centred on growing media especially suitable for arboreal applications (tree seeds, seedlings, plantlets, saplings and trees) but in accordance with theinvention we are able to produce growing media suitable for other applications, for example crops, shrubs and other herbaceous plants. Trials were carried out to assess the potential of a growing medium of the invention, Example 7 above, for lettuces, in comparison with other growing media, as set out in Table 8 below. The samples were assayed for bacterial and actinobacterial content, and for fungal content, at the end of the trial unless stated otherwise.TABLE 8

[0138] MELCOURT SC (Melcourt Composted Fine Bark Soil Conditioner) and SYLVAFIBRE (fine, composted wood-fibre growing medium) are commercial products available from Melcourt Industries Ltd, Tetbury, UK. They were selected as useful comparators with Example 7, which is itself a product derived in substantial part from wood products, including bark fines. Peat is an undesirable material for environmental and other reasons but was selected for benchmarking purposes.

[0139] It can be seen that Example 7 showed slightly higher fungal content than the peat-based compost but much higher fungal content than MELCOURT SC and SYLVAFIBRE.

[0140] In this trial lettuce plants Example 7 were successfully grown even without the addition of nutrition.

[0141] In a later trial Example 7 was supplemented by nutrition, in order to provide a comparison with the commercial composts, which contain nutrition in the form of chemically synthesised NPK. However the case of Example 7 the nutrition was provided by biologically-derived fertiliser having as its major nitrogenous components bone meal and hoof and horn materials, fertiliser applied to give a nitrogen level commensurate with that provided in the commercial comparison composts. Lettuces were grown in the compost of the invention and in the commercial composts. Ten seedlings were planted out in pots containing a respective growing medium and the plantparameters of young plants were assessed on the same day. The results are shown in Table 9 below.TABLE 9

[0142] Example 7 with biologically-derived fertiliser was shown to be a viable replacement for peat-based composts.

[0143] Example 7 with biologically-derived fertiliser was assayed for bacterial and actinobacterial content, and for fungal content, at the end of the trial and the values are shown in Table 10 below.TABLE 10EXAMPLE 15

[0144] The bacterial and fungal microbiome of the compositions of Examples 7, 8 and 12 was examined by DNA techniques, and compared with that of composted bark fines (CBF), as-supplied except for addition of a Balancing Mineral Composition (BMC). The latter was added to create the closest possible comparison with Examples 7, 8 and 12; and with that of a commercial peat-free compost containing coir, wood derivatives and perlite, sold under the Registered Trade Mark JIFFY. This is called 'peat-free' below.

[0145] For each growing medium 4 replicates were tested. For the growing media to which a BMC was added 6 weeks were allowed between the BMC additions and microbiome testing.

[0146] DNA metabarcoding was used to measure the underlying microbial biodiversity found in each sample. The a-diversity (within-sample diversity) using richness (that is, number or organismsdetected) and Shannon index metrics (a well-known method of determining diversity within a sample) was determined for each sample.

[0147] The Shannon index is a common way to measure the alpha diversity of a microbial sample. To use the Shannon index, the DNA is sequenced and all the microbes in the sample are separated into 'bins' or categories. This identifies the different species that are present.Bacterial results

[0148] Bacterial community a-diversity results are stated in summary in Table 11 below for each index (Richness, Shannon) and growing medium.TABLE 11

[0149] All of the samples contained Acidobacteriota, Actinobacteriota, Bacteroidota, Chloroflexi, Firmicutes, Planctomycetota, Proteobacteria and Verrucomicrobiota bacteria in varying proportions. The 'peat-free' samples were overall less diverse, characterised by higher relative abundances of Proteobacteria and Actinobacteria, along with lower relative abundances of taxa Bacteroidota, Chloroflexi, and Firmicutes. Examples 7, 8 and 12 all contain Myxococcota, which was absent from the CBF + BMC samples.Fungal results

[0150] Fungal community a-diversity results are stated in summary in Table 12 below for each index (Richness, Shannon) and growing medium. TABLE 12

[0151] The samples of the invention contained fungi from the phyla Ascomycota, Basidomycota and Mucoromycota, including A.Pezizomycetes, A.Sordariomycetes, A.Leotiomycetes, M.Mortierellomycetes, A.Dothideomycetes, A.Eurotiomycetes, A.Orbiliomycetes, B.Agaricomycetes and B.Tremellomycetes, in varying proportions. Several of these classes of fungi were not found or were found only in low proportion in the CBF + CMB or peat-free examples. One further observation is that Ascomycota Sordariomycetes was much more prominent in the examples of the invention, than in the other samples.EXAMPLE 17

[0152] Saplings of oak were grown in the growing media of Examples 7, 8 and 12, and as a comparison, in the commercial compost product JIFFY. When all saplings were at least 10 cm high assessments were made of their growth parameters. The chlorophyll readings were taken using a LEAF (RTM) Chlorophyll Meter from FT Green LLC, Wilmington, US.

[0153] The readings recorded are set out in Table 13 below.TABLE 13

[0154] The oak saplings grown in JIFFY had greater mass but were weakly elongated and were severely unhealthy, unlike the oak saplings grown in growing media of the invention.EXAMPLE 18

[0155] Saplings of cherry were grown in the growing medium of Example 12, and as a comparison, in the commercial compost product JIFFY. When all saplings were at least 6 cm high assessments were made of their growth parameters. The readings recorded were as set out in Table 14 below.TABLE 14

[0156] The cherry saplings grown in JIFFY were larger but were unhealthy, unlike the cherry saplings grown in growing media of the invention.

[0157] The microbial content of the growing media which had been used to grow the cherry saplings was determined and is set out in Table 15 below.TABLE 15EXAMPLE 19

[0158] Use of a bacterial and high-fungal 'living' growing medium of the present invention to germinate seeds of different tree species has been examined. High germination rates have been observed when using the Example 7 high-fungal growing medium to germinate seeds of cherry, oak, Sitka spruce, Douglas fir, small-leaved lime and hazel. Strong healthy growth of resulting seedlings has also been observed.

[0159] Similarly, good results have been obtained when growing hazel plants from seeds germinated in growing media of the invention.

[0160] Table 16 shows the results of growing hazel plants from seeds stratified over four winter months respectively in the growing medium of Example 12, and in standard peat. During this period the two groups of seeds were keep from water and light. At the end of that period they were planted to achieve germination. In each case the germinated plantlets were grown on in the same standard commercial peat-free compost. Root mass and girth of the seedlings were assessed. To facilitate this the plants were cut to separate the above-ground part from the below-ground part. The girth of the stems were measured on the above-ground parts 5 mm above the cutting point.TABLE 16

[0161] The plants grown in the Example 12 growing medium were stronger. The average weight of their roots was slightly greater. Their average stem girth was significantly greater.EXAMPLES 20 to 22

[0162] Further examples of starter compositions were made, using the method described for Examples 1 to 6, but in each with the addition of an inoculum - the starter composition of Example 6. In addition one example included bio-char as a potential soil improver and carbon sequestration agent.

[0163] The bulk materials used as feedstock were as described in Table 17 below.

[0164] Microorganism support materials were added to the layered materials in the amounts and manner as described in Examples 1 to 6.TABLE 17

[0165] A significant difference between Examples 1 to 6 and Examples 20 to 22 is the use in the latter examples of a starter composition of Example 6, with its high microbial content, particularly high and rich in fungal species, as an inoculant component of the feedstocks for Examples 20 to 22.

[0166] The resulting starter material were analysed from microbial content in the manner described in Examples to 6 and the results are as shown below in Table 18.TABLE 18

[0167] Each of the resulting starter compositions is microbially active. As was the case for earlier examples there are differences and these can be attributed to local and environmental factors. However all have a 'live' biome of bacteria and fungi. It will be seen that Example 21 is particularly high in fungal content, and Example 22 is particularly high in bacterial content. In contrast our testing of many different soils from many different locations has shown than many soils are seriously depleted in microbial content; especially in fungal content, which is often found to be substantially zero. This is thought to be due in part to intensive farming practices employing repeated applications of chemical pesticides. If the soil is sterile the arable farmer is heavily dependent on chemically derived nutrition to supply the NPK needs of the growing plants. If a microbially live soil can be developed with the help of microbially live starter composts of the type described a more sustainable and natural way of farming is in prospect.EXAMPLE 23

[0168] Confidential trials were carried out to examine the performance of a growing medium comprising Example 21 in growing winter barley, compared with a conventional farming method, which used chemically synthesised NPK fertiliser.

[0169] A growing medium in accordance with the invention was obtained by mixing 10% by volume of the starter composition of Example 21 with approximately 90% by volume of anadditional composition (namely composted bark fines, CBF) minor amounts of a balancing mineral composition (BMC), and hoof and horn biologically-derived fertiliser, calculated to give an application rate of 168 kg / ha nitrogen. There was no addition of any chemically synthesised NPK fertiliser to the growing medium or to the plot at any stage of the growth.

[0170] A 0.22 hectare plot was treated with 10 m3of the growing medium.

[0171] Adjacent areas were conventionally farmed, using a synthetic chemical NPK fertiliser, applied to give an application rate of 210 kg / ha nitrogen.

[0172] The barley plants in the plots were assayed at intervals to assess their content of elements. The chemically raised barley plants showed problems of nitrogen, manganese, iron, copper and zinc being far in excess of optimal values, but such problems were not found in the plants grown using the growing medium of Example 21 and the hoof and horn biologically-derived fertiliser. The conventionally raised barley plants required further chemical treatments to correct growth problems, including two fungicidal treatments, one treatment by a growth regulator to correct NPK-induced early 'sugar-rush' growth, and magnesium sulphate. In the plot treated using the growing medium of the invention no further treatments were needed, and none were carried out.

[0173] Plant growth appears to be similar between the samples (following the corrective treatments carried out on the conventional control plot) but at the time of writing the plants have yet to go to maturity. Yield data is therefore not available. However I regard it as a finding of high interest that a growing medium of the invention, which provides a live microbiome to the soil around the plants, can enable a biologically-derived fertiliser to be used at a lower nitrogen application rate than the industry standard for a chemical fertiliser. The carbon footprint of synthetic chemical fertilisers is extremely large, both in terms of their production and their use. The Haber-Bosch process for the manufacture of ammonia fixes most of the nitrogen used in agriculture and is estimated to account for 1-2% of the world's total energy consumption and 3-5% of the world's natural gas consumption. In Europe, every ton of synthetic chemical fertiliser produced by this process emits an average of 9.7 tons of CO2 equivalent. The use of a composition of the present invention with a biologically-derived fertiliser, used at a higher equivalent nitrogen rate, suggests that a much lower carbon footprint could be attained.

Claims

CLAIMS1. A method of making a starter composition which can be added to a growing medium to effect improvement, the method comprising steps of: i) assembling a compostable mixture which comprises:(a) a first composting material;(b) optionally, a second composting material; and one or both of the following components (c) and (d):(c) a source of microorganisms added in a predetermined amount;(d) a microorganism support added in a predetermined amount; and ii) retaining the compostable mixture for a maturation period.

2. A method as claimed in claim 1 wherein the first composting material has a carbon to nitrogen molar ratio in the range from 3:1 to 29:1 and the second composting material has a carbon to nitrogen molar ratio in the range from 30:1 to 400:1.

3. A method as claimed in claim 1 or 2 wherein the source of microorganisms comprises a refined compost, a liquid compost, and / or a compost extract (including a portion taken from a previous starter composition made in accordance with the method as claimed in claim 1 or 2, or a liquid extract therefrom) and the microorganism support comprises a material which can be digested by a desired microorganism in the compostable mixture and / or a material which provides physical support for microorganisms in the compostable mixture.

4. A method as claimed in claim 3 wherein: a microorganism support of the type which may be digested by a desired microorganism comprises one or more of the following organic materials: fish protein, including shellfish protein; dried sea algae, including brown seaweed, or kelp; and pressed cakes of plant matter, which may be left after oil or juice extraction, for example the residues from the pressing of hemp, olives, peanuts, coconut, soybeans, flax seed (linseed), cottonseed and sunflower seeds; anda microorganism support of the type which may provide physical support in the compostable mixture comprises a particulate inorganic material derived from one or more of sedimentary, igneous and metamorphic rocks.

5. A method as claimed in any preceding claim wherein, at the start of the maturation period, the compostable mixture is formed into a freestanding mass, for example a windrow, or the compostable mixture is loaded into a container which permits air flow through the walls of the container and the compostable mixture in the container is formed with air channels through its mass; and wherein the compostable mixture is not turned during the maturation period.

6. A starter composition made by the method of any preceding claim.

7. A starter composition as claimed in claim 6 in which the concentration of fungi is at least 175 pg / ml and may be at least lOOOpg / ml.

8. A starter composition as claimed in claim 6 or 7 in which the concentration of bacteria (including actinobacteria) is at least 20 pg / ml.

9. A starter composition as claimed in any preceding of claims 6 to 8 in which the ratio of the concentration of fungi to the concentration of bacteria (including actinobacteria) in the starter composition is at least 1:1 and may be at least 12:1.

10. A growing medium comprising an amount of the starter composition as claimed in any of claims 6 to 9, a larger amount (by volume) of a tree bark component and, optionally, trace minerals.

11. A growing medium as claimed in claim 10 wherein the starter composition provides from 5% to 40% by volume of the growing medium.

12. A growing medium as claimed in claim 10 or 11 wherein the tree bark component comprises tree bark chippings or tree bark fines.

13. A growing medium as claimed in claim 12 wherein the tree bark component comprises composted tree bark fines.

14. A biodegradable pot intended to be planted directly into soil, the pot containing a growing medium as claimed in any of claims 10 to 13.

15. A method of making a growing medium as claimed in any of claims 10 to 13 wherein the components are mixed together to form the growing medium, and kept for a dwell time of at least 2 weeks before being used.

16. A method of making a growing medium as claimed in any of claims 10 to 13 wherein the addition of trace minerals is carried out following an assay to determine the content of such trace minerals in the starter composition and in the tree bark component, before they are mixed, or in the growing medium formed once they have been mixed.

17. A method of producing a growing medium from composted bark fines by mixing composted bark fines with soil from an arboreal environment and retaining the resulting mixture for a maturation period, or by keeping the composted bark fines in an arboreal environment for a maturation period, the maturation period being sufficient in each case for the growing medium to be colonised by fungi to a concentration of at least 175 pg / ml, suitably to a concentration of at least 400 pg / ml, for example to a concentration of at least 800 pg / ml.

18. A starter composition, or a method of making a starter composition, or a growing medium, or a method of making a growing medium, or a method of using a growing medium, respectively as claimed in any preceding claim; not including the addition of peat or a peat derivative, or of coir, or of a synthetic chemical NPK fertiliser.

19. A starter composition, or a method of making a starter composition, or a growing medium, or a method of making a growing medium, or a method of using a growing medium, respectively as claimed in any preceding claim; not including the addition of peat or a peat derivative, or of coir or a coir derivative, or of a chemically synthesised fertiliser.

20. A starter composition, or a method of making a starter composition, or a growing medium, or a method of making a growing medium, or a method of using a growing medium, respectively as claimed in any preceding claim; which includes the addition of a biologically- derived NPK fertiliser.

21. A starter composition as claimed in any of any of claims 6 to 9 or a growing medium as claimed any of claims 10 to 13, wherein the fungal biome has one, any two, or all three of the following characteristics (A), (B) and (C): (A) it contains all of the following fungal classes: Ascomycota Pezizomycetes,Ascomycota Sordariomycetes, Ascomycota Leotiomycetes, Ascomycota Dothideomycetes, Ascomycota Eurotiomycetes, Ascomycota Orbiliomycetes, Basidomycota Agaricomycetes, Basidomycota Tremellomycetes, Mucoromycota Mortierellomycetes; (B) it has a Richness value of at least 120;(C) it has a Shannon value (a-diversity) of at least 4.8.

22. The use of a growing medium as claimed in any of claims 10 to 13 or 21, in germinating seeds or in growing plants, including trees, including juvenile trees, crops and shrubs.

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