Particle for delayed release of an active ingredient to a plant or seed

Abstract

A particle for delayed release of an active ingredient to a plant or seed, wherein the particle is comprised of a composite material, the composite material comprising an active ingredient component comprising microbial cell extract or a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, and a clay component comprising smectite clay mineral. The clay component forms layered stacks in the composite material and the active ingredient component is intercalated between individual clay layers in the stacks.

Description

[0001] PARTICLE FOR DELAYED RELEASE OF AN ACTIVE INGREDIENT TO A PLANT OR SEED

[0002] TECHNICAL FIELD

[0003] The present disclosure is related to a particle for delayed release of an active ingredient to a plant or seed, the use of such particles for delayed release of an active ingredient to a plant or seed and to a method of producing such particles.

[0004] BACKGROUND ART

[0005] Controlled release of inputs for enhanced vegetative cultivation, such as fertilizers, biostimulants, plant growth regulators and pesticides, formulated with non-biodegradable polymers may create persistent pollution with unknown consequences for animal and human health. Multiple, recurrent applications of such formulations may lead to the accumulation of micro-plastics; affecting local soil biodiversity and function. In the event of fire, these plastics may generate secondary compounds with unknown toxicity profiles.

[0006] In US20060135368A1 is shown controlled release nitrogen pellets that are water dispersible. The pellets may comprise methylene urea and a bentonite binder component. The pellets disperse on contact with moisture from the treated area itself, from irrigation or from natural precipitation. The particle retains its size and shape during handling and application to a desired area and disintegrates or crumbles into small particles upon contact with water within twelve hours.

[0007] CN112409077A, CN107056468B and US2011 / 0296885A1 show various constellations of combining montmorillonite clay with urea for the purpose of making a control release nitrogen fertilizer.lf the release of inputs from pellets / granules can be matched to the plant's demand for nutrition, or if a more optimally timed release can be obtained, a more efficient treatment of plants could be achieved.

[0008] SUMMARY OF THE INVENTION

[0009] It is an object of the present disclosure to provide a particle for delayed release of an active ingredient to a plant or seed. The invention is defined by the appended independent patent claims. Non-limiting embodiments emerge from independent claims, the appended drawings and the following description.

[0010] According to a first aspect, there is provided a particle for delayed release of an active ingredient to a plant or seed, the particle is comprised of a composite material, the composite material comprising an active ingredient component and a clay component, wherein 5 to 99 wt.% of the composite material is constituted by the clay component, wherein 1 to 95 wt.% of the composite material is constituted by the active ingredient component, and a weight ratio of clay component to active ingredient component in the composite material is 1:20 to 99:1, wherein the active ingredient component comprises microbial cell extract or comprises a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, wherein the clay component comprises smectite clay mineral and the composite material comprises at least 5 wt.% of the smectite clay mineral, and wherein the clay component forms layered stacks in the composite material and the active ingredient component is intercalated between individual clay layers in the stacks.

[0011] Clay is a naturally occurring and desirable component of agricultural soil due to its water and nutrient holding capacity.

[0012] Smectite-type clays have a layered structure where each individual clay layer or clay platelet, consists of one aluminium, iron or magnesium dominated octahedral sheet (O) sandwiched between two tetrahedral silica sheets (T). The smectite TOT layers have a negative anionic surface charge and exhibit a common characteristic of swelling and expansion in the normal direction when exposed to water, mainly due to the hydration of the counter-cations residing in-between the negative charged TOT layers. Due to the layered structure and the negative surface charge, smectite-containing clays may be characterised by high specific surface area and high cation exchange capacity.

[0013] The clay component forms layered stacks in the composite material and at least a portion of the active ingredient component is intercalated or interposed between individual clay layers in the stacks. The active ingredient component may also be arranged on the edge of clay layers, on the outer surface of the stacked clay layers etc.

[0014] The stacking of clay layers may be caused by electrostatic forces along with Van der Waals forces.

[0015] The active ingredient component comprises microbial cell extract or comprises a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid. The active ingredient, i.e. the microbial cell extract or the mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, may constitute at least 80%, 85%, 90% or at least 95% of the active ingredient component. The rest may be binder or other substances such as benign inactive ballast.

[0016] The active ingredient component may comprise constituents that are more or less ionic. The active ingredient component comprises constituents that are ionic enough to interact with clay minerals of the clay component.

[0017] Microbial cell extract, such as yeast extract, is a complex mixture of the cell contents of microbial cells, such as yeast cells, including proteins, peptides, amino acids, metabolites, ions, carbohydrates and lipids. It comprises a complex mixture of cations, anions and neutral molecules in both inorganic and organic form. The large majority of the nitrogen is in the form of free amino acids and peptides, which carry both positive and negative charge depending on the different pKa values of the different organic molecules, as well as pH. In turn, the profile of release of the constituent components of yeast extract from the particles will depend on charge and size.

[0018] A mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, is a mixture comprising arginine, lysine and / or histidine, and one or more negatively charged ion, such as phosphate, sulphate, nitrate or phytic acid and / or one or more neutral molecule, such as serine, threonine, glutamine or asparagine. Clay layers may be stacked into primary particles; primary particles may be stacked together to form larger particles. This may be caused by ionic forces along with van der Waals forces. The particle may have any shape, such as spherical-, platelet- or cylinder-shape, and any size such as being on the nanometre, micrometre, millimetre or centimetre scale, and is suitable for being provided at or close to a plant. In one example, the particle may have an average diameter of 0.01-4 mm. The particle may be comprised solely of the composite material or for example 80-100% of the particle may be comprised of the composite material. The rest may for example be a coating layer, a binder, etc.

[0019] It should be noted that embodiments of the invention are not limited to particles and composite material having particular characteristics such as shape, dimension, distances etc.

[0020] The composite material comprising 5 to 99 wt.% of the clay component is calculated as clay component free of active ingredient on the total weight of the composite material. The composite material may comprise 5-99 wt.%, 10-99 wt.%, 20-99 wt.%, 30-99 wt.%, 40-99 wt.%, 50-99 wt.%, 60-99 wt.%, 70-99 wt.%, 80-99 wt.%, 90-99 wt.%, 5-90 wt.%, 5-80 wt.%, 5- 70 wt.%, 5-60 wt.%, 5-50 wt.%, 5-40 wt.%, 5-30 wt.%, 5-20 wt.%, 5-10 wt.%, 10-80 wt.%, or 20- 50 wt.% of the clay component.

[0021] The composite material comprising 1 to 95 wt.% of the active ingredient component is calculated as active ingredient component on the total weight of the composite material. The composite material may comprise 1-95 wt.%, 1-90 wt.%, 1-80 wt.%, 1-70 wt.%, 1-60 wt.%, 1- 50 wt.%, 1-40 wt.%, 1-30 wt.%, 1-20 wt.%, 1-10 wt.%, 10-95 wt.%, 20-95 wt.%, 30-95 wt.%, 40- 95 wt.%, 50-95 wt.%, 60-95 wt.%, 70-95 wt.%, 80-95 wt.%, 90-95 wt.%, 20-90 wt.% or 50-80 wt.% of the active ingredient component

[0022] A ratio of clay component to active ingredient component is 1:20 to 99:1, 1:10 to 99:1, 1:5 to 99:1, 1:2 to 99:1, 1:1 to 99:1; 2:1 to 99:1, 5:1 to 99:1, 10:1 to 99:1, 20:1 to 99:1, 30:1 to 99:1, 40:1 to 99:1, 50:1 to 99:1, 60:1 to 99:1, 70:1 to 99:1, 80:1 to 99:1, 1:20 to 90:1, 1:20 to 80:1, 1:20 to 70:1, 1:20 to 60:1, 1:20 to 50:1, 1:20 to 40:1, 1:20 to 30:1, 1:20 to 20:1, 1:20 to 10:1, 1:20 to 5:1, 1:20 to 2:1, 1:20 to 1:1, 1:20 to 1:2, 1:20 to 1:5, 1:20 to 1:10, 1, 1:10 to 5:1, 1:2 to 2:1, or 1:5 to 1:1. In one embodiment, the particle is comprised of a composite material, wherein 10-80 wt.% of the composite material is constituted by the clay component and 20-90 wt.% of the composite material is constituted by the active ingredient component, and a weight ratio of clay component to active ingredient component in the composite material is 1:20 to 20:1.

[0023] The smectite clay mineral may be montmorillonite, beidillite, nontronite, saponite, laponite, vermiculite, hectorite, stevensite, sauconite or any combination thereof.

[0024] Bentonite clay, which is dominated by montmorillonite, may be used.

[0025] The clay component comprises smectite clay mineral and the composite material comprises at least 5 wt.% of the smectite clay mineral, or the composite material may comprise 5-99 wt.%, 10-99 wt.%, 20-99 wt.%, 30-99 wt.%, 40-99 wt.%, 50-99 wt.%, 60-99 wt.%, 70-99 wt.%, 80-99 wt.%, 90-99 wt.%, 5-90 wt.%, 5-80 wt.%, 5-70 wt.%, 5-60 wt.%, 5-50 wt.%, 5-40 wt.%, 5-30 wt.%, 5-20 wt.%, 5-10 wt.%, 10-80 wt.%, or 20-50 wt.% of the smectite clay mineral.

[0026] At least 50% of the clay component may be comprised of smectite clay mineral, at least 60%, at least 70%, at least 80%, at least 90 %, or 50-100%, 60-100%, 70-100%, 80-100%, or 90-100% may comprise smectite clay mineral. The rest of the clay component may be constituted by non-smectite accessory minerals commonly found in clays, such as silicates, magnesium oxides, aluminium oxides, manganese oxides, iron-oxides, sand and / or silt.

[0027] In one embodiment, the composite material comprises 10-80 wt.% or 20-50 wt.% of the clay component and the rest being the active ingredient component.

[0028] The described particle retains its size and shape during handling and application to a desired area. Upon contact with water or moisture, the clay layers of the clay component of the particle re-swell and exfoliate as water enters the inter-layer space. This allows the active ingredient to dissolve and diffuse out of the particle, such that the active ingredient of the active ingredient component can reach the intended area or plant. A particle comprising a non-layered mixture of clay and an active ingredient has an immediate and near complete release of the active ingredient when contacted with water / moisture. The above described particle with active ingredient intercalated between clay layers in the stack exhibits on the other hand a more delayed, controlled and buffered release of the active ingredient from the particle when contacted with water / moisture / soil, offering an alternative to non- biodegradable polymers. By adjusting the amount of clay component, the amount of active ingredient component and the ratio between clay and active ingredient components in the composite material, the particles may be adapted to different requirements and conditions, such as time for full release of the active ingredient.

[0029] Active ingredient component is fully mixed with the clay in a homogenous phase. Hence, the amount of the active ingredient component intercalated in a clay particle is mainly determined by the ratio of the active ingredient component to clay. The amount of intercalated active ingredient component in the particles is unlimited and may be at least 40, or at least 50 wt.% of the total weight of the particle (as measured by XRD).

[0030] The above-described particle shows a combined effect of delayed and staggered / multi-phased release rate. The nitrogen source in microbial cell extract is largely in organic form as 20 different proteinogenic amino acids. Each amino acid has a unique isoelectric point and therefore will carry a unique charge depending on pH. The 20 different amino acids will each be released according to idiosyncratic rates depending on charge and size. A delayed and staggered / multi-phased controlled release rate is beneficial as it helps to match available nutrition with the nutrient demand needed for healthy and stress tolerant growth, reducing losses and improving efficiency. The delayed and staggered / multi-phased release is compatible with biologically sensitive process such as seed germination where small changes in osmotic potential surrounding the seed can arrest germination, allowing the granule to be precisely placed in close proximity to the seed in the seeding furrow at rates that are reduced compared to broadcast applications.

[0031] An active ingredient component comprising a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid clay particle, would give a similar result because the release rate of organic nitrogen and other nutrients would be delayed and staggered / multi-phased in a similar profile to microbial cell extract, matching plant demand.

[0032] If similar clay particles instead were formed from clay and urea as active ingredient component, this would result in a limited amount of intercalated urea of at most about 35 wt.% of the total weight of the particle (as measured with XRD). Urea is a small charge neutral molecule with a molecular weight of 60.06 g / mol with a nitrogen content of 46%. Urea does not contain phosphate, potassium or any other plant nutrient and the density of urea is no more than 1.3 g / cm3. Excess urea not intercalated will re-crystallize outside the clay particles.

[0033] Using urea as a fertilizer, most of the nitrogen in urea is made available for plant uptake upon hydrolysis and the formation of ammonia by free urease enzymes in the soil. It is well established that the ammonia derived from urea can damage root tips, show characteristic symptoms of leaf tip burn, or arrest seed germination if applied in too close proximity. Therefore, broadcast fertilizer application, i.e. the fertilizer is spread evenly across the soil surface, is practiced to reduce the effective concentration at the seed.. Further, nonintercalated and recrystallized urea outside the clay particle is available for immediate and highly concentrated release to the plant, which may cause harm to the plant as mentioned above rather than improving the growth and germination thereof. The release rate of urea is not influenced by ionic associations, and soil concentration of urea will increase according to a single, acute, release rate function. The release rate of intercalated and non-intercalated urea in this way is not compatible with sensitive biological process such as seed germination if granules are placed in close proximity to the seed, which means such granules cannot be used for precision placement in the seeding furrow and must be broadcast or banded away from the seeding furrow at high overall rates.

[0034] The active ingredient component and / or the clay component may comprise phytic acid.

[0035] Phytic acid is a six-fold dihydrogenphosphate ester of inositol (specifically, of the myo isomer), also called inositol hexakisphosphate (IP6) or inositol polyphosphate. It is found in many seeds and grains and non-rumanant animals lack the necessary enzyme, phytase, to break it down, impeding digestion. Phytic acid also associate with proteins and amino acids, and ions. As such, phytic acid is recognised as an "anti-nutrient" in animal feed and food because it restricts the digestability and absorbtion of nutrition. This property can be exploited as a means to delay the release of organic and inorganic active ingredients in plant production systems such as fertilizers. According to a second aspect, there is provided a use of the particle described above for delayed release of an active ingredient to a plant or seed.

[0036] The particle or aggregates, granules or pellets thereof, can be applied to the soil, incorporated into the soil, incorporated into potting substrate, placed in close proximity of a seed at sowing or placed in close proximity of roots at planting of a tree seedling for delayed release of the active ingredient. The particles could be applied as a powder to seeds. The particles could be sprayed as a suspended powder onto leaves.

[0037] According to a third aspect there is provided a method of producing a particle for delayed release of an active ingredient, the method comprising the steps of:

[0038] - pre-swelling a clay component consisting of at least 50% smectite clay mineral in an aqueous solvent,

[0039] - mixing the pre-swelled clay component with an active ingredient component comprising microbial cell extract or comprises a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, wherein 5 to 99 wt.% of the mixture is constituted by the clay component on a dry weight basis, wherein 1 to 95 wt.% of the mixture is constituted by the active ingredient component on a dry weight basis, and a weight ratio of the clay component to the active ingredient component in the mixture is 1:20 to 99:1,

[0040] - drying the mixture, thereby forming particles comprising layered stacks of clay component wherein individual clay layers in the stacks are intercalated with active ingredient.

[0041] The amount of the clay component and the active ingredient component and the ratio of these components used in the method may be varied as discussed above for the composite material of the particle.

[0042] After mixing the pre-swelled clay component with an active ingredient component the mixture is dried, possibly during or after extrusion of the mixture.

[0043] The active ingredient component may be mixed with phytic acid before being mixed with the clay component. The amount of phytic acid mixed with the active ingredient component may be 1:100 to 1:10 (w / w or mole:mole) of phytic acid relative to the active ingredient component.

[0044] Mixing the active ingredient component with phytic acid may be used as a means to bind the active ingredient and slow the release rate of active ingredient from the particle.

[0045] Alternatively or in addition, the pre-swollen clay component may be mixed with phytic acid before the clay component is mixed with the active ingredient component.

[0046] The amount of phytic acid mixed with the clay component may be 1:1000 to 1:100 (w / w or mole:mole) of phytic acid relative to the clay component.

[0047] Phytic acid can adsorb to the clay, making it more negatively charged, and ensure exfoliation in individual clay layers. Adding phytic acid may act like a thinning agent (decreases viscosity) which may be useful in the production process as a way of decreasing the amount of water required to achieve effective dispersal and mixing, and to reduce drying cost of the mixture.

[0048] According to a fourth aspect there is provided a plant or seed treatment composition comprising the particle described above.

[0049] The composition may comprise the particles as aggregates, granules or pellets. The composition could be in powder form. Alternatively, the composition could be a suspension such as a sprayable suspension. The composition may be applied to the soil, incorporated into the soil, incorporated into potting substrate, placed in close proximity of a seed at sowing or placed in close proximity of roots at planting of a tree seedling for delayed release of the active ingredient. The composition may, apart from the particles, comprise other components, such as binders, e.g. carboxymethyl cellulose. Such components may for example make up less than or about 2% of the composition on a dry weight basis.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Fig. 1 schematically illustrates a possible structure of the composite material of a particle for delayed release of an active ingredient to a plant or seed. The clay component is arranged in stacks of clay layers and the active ingredient component is intercalated between individual clay layers. Fig. 2 schematically illustrates how the active ingredient is intercalated between layers of clay (left part of the figure) in the composite material of particle. The average basal spacing (dooi) being greater than or about 2 nm with a range between 1.2 nm and 4.1 nm. In the right part of Fig. 2 is illustrated layers of clay, wherein active ingredient is not intercalated between layers of clay. The basal spacing (dooi) being, on average, less than 2 nm.

[0052] Fig. 3 shows release rate profiles of two particles, Material 1 and Material 2. Material 1 comprises particles of pre-swelled montmorillonite mixed with yeast extract at a ratio of 1:1. Material 2 comprises particles of non-pre-swelled / dehydrated montmorillonite mixed with yeast extract also at a ratio of 1:1.

[0053] Fig. 4 schematically illustrates the major steps of a method for producing a particle for delayed release of an active ingredient.

[0054] Fig. 5 shows powder XRD data for: (a) montmorillonite clay intercalated with urea, displaying a (001) diffraction peak at 4.9° 20 resulting from ordered and limited layer expansion, with a corresponding dooi of 18 A, (b) montmorillonite clay intercalated with yeast extract, not displaying a (001) diffraction peak due to unlimited and unordered swelling, (c) the native montmorillonite clay, displaying a (001) diffraction peak at 7.4° 20, and a corresponding dooi of approx. 12.4 A due to water uptake at ambient relative humidity, (d) pure urea in powdered form, displaying the (110), (101), (111), (200) diffraction peaks of crystalline urea at 22.2°, 24.6°, 29.3° and 31.6° 20. Peaks indicated by i-iv are minor micaceous phases, montmorillonite (hkO) reflections, quartz and feldspar phases.

[0055] Fig. 6 shows a photograph of corn seeds placed in soil with moisture content of 14%. Five days after sowing a reference seed (with no added fertilizer) (a) showed normal germination, whereas a seed (b) fertilized with montmorillonite clay and urea granules (cl) placed next to the seed (b) failed to germinate.

[0056] Fig. 7 shows a photograph of corn seeds placed in soil with moisture content of 14%. Five days after sowing both a reference seed (with no added fertilizer) (a) and a seed (b) fertilized with montmorillonite clay and yeast extract granules (cl) placed next to the seed (b) showed normal germination. DETAILED DESCRIPTION

[0057] Below is described a method of producing a particle that can be used for delayed release of an active ingredient, such as a fertilizer, a soil nutrient, a biostimulant, and / or a pesticide, to a plant or seed.

[0058] The particle is comprised of a composite material, where the composite material comprises an active ingredient component and a clay component. 5 to 99 wt.% of the composite material is constituted by the clay component, wherein 1 to 95 wt.% of the composite material is constituted by the active ingredient component, and a weight ratio of clay component to active ingredient component in the composite material is 1:20 to 99:1. The clay component comprises smectite clay mineral and the composite material comprises at least 5 wt.% of the smectite clay mineral. As smectite-type clays have a layered structure, the clay component forms layered stacks in the composite material and at least a portion of the active ingredient component, which comprises microbial cell extract or comprises a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, is intercalated or interposed between individual clay layers in the stacks. The active ingredient component may also be arranged on the edge of clay layers, on the outer surface of the stacked clay layers etc. The degree of stacking of the clay layers, i.e. the number of stacks and number of layers per stack, can be determined by means of transmission electron microscopy and / or XRD (X-Ray Diffraction Analysis).

[0059] Fig. 1 schematically illustrates a possible structure of the composite material of such a particle. The clay component is arranged in stacks of clay layers (black lines) and the active ingredient component (dotted areas) is intercalated between individual clay layers. Each individual clay layer may have a thickness of about 1 nm and the other two dimensions being about 30-1000 nm. An average distance between the layers of the clay in a stack in the composition may be of at least 1.0 nm, or at least 3 nm. These thicknesses and distances may, however, deviate from the above and depend on the active ingredient component and active ingredient used, and on the amounts and ratios of clay component and active ingredient component in the composite material. Fig. 2 schematically illustrates how the active ingredient is intercalated between layers of clay (left part of the figure) in the composite material. The average basal spacing (dooi) being greater than or about 2 nm with a range between 1.2 nm and 4.1 nm. In the right part of the figure is illustrated layers of clay, wherein active ingredient is not intercalated between layers of clay. The average basal spacing (dooi) being less than 2 nm. The space between the internal faces of adjacent clay platelets, layers, is the interlayer, which may be occupied by materials, such as the active ingredient. The sum of the distance and platelet thickness is the "dOOl" basal spacing (platelet spacing), which can be measured by X-ray diffraction. The specific surface area of the composite may be greater than 700 m2 / g and there may be a large aspect ratio, such as greater than 50.

[0060] In the composite material a majority, or at least a portion, of the clay layers may not be arranged in stacks, i.e. non-aggregated (dispersed) clay layers, and present as single entities or with edge to face ionic association (house of cards structure) or as no more than two clay layers with face to face contact where the inter-layer space is absent of active ingredient. This house of cards structure may, however, mostly be present in wet / hydrated particles, while this structure might collapse when the particle is dried.

[0061] The number of stacks in the composite material and in the particle is dependent on e.g. the amount of clay in the composition and the size of the particle. There may be a varying number of individual clay layers (also called tactoid / aggregate) in a stack, such as at least 2 up to 100 clay layers or more. The stacks of clay layers in the composite material may be disorganized, bent, and vary in size. The degree of stacking of the clay layers / platelets, i.e. the number of layers per stack, can be determined by means of transmission electron microscopy and / or XRD.

[0062] Generally, the method, schematically illustrated in Fig. 4, comprises to pre-swell a clay component 100 consisting of at least 50% smectite clay mineral in an aqueous solvent. Before pre-swelling, the clay component may be pre-treated in different ways, such as e.g. to enrich sodium in the clay component. Pre-swelling may for example take place in water, distilled water, a buffer or water with a salt content of at most 0.3 M. In the pre-swelling step 100, the clay component, usually added as a dry powder, is mixed with the aqueous solvent at a ratio of 5% to 50% (w / v). Mixing of clay component and solvent may for example take place by stirring or by mixing during incubation or followed by incubation for at least 4 hours or at least 8 hours or up to 48 hours or more to ensure complete swelling and exfoliation of the clay layers.

[0063] To measure if the pre-swelling method used results in a clay component that has reached a completely swollen or sufficiently swollen state, a simple approach would be to measure the volume of the clay component before and after swelling. If the wet volume of the swollen clay is four times larger or more than the volume of the dry clay (before being mixed with the solvent), the pre-swelling step has resulted in a sufficiently swollen clay. Another way to measure the degree of clay swelling could be to spin down the solids as the clay is undergoing swelling and measure the volume. Generally, the clay should swell to an even consistency and have an average basal distance between layers of at least 2 nm. The pre-swelling step 100 may take place at room temperature or at a higher temperature, such as 20-50°C.

[0064] The pre-swelled clay component is thereafter mixed 101 with the active ingredient component using e.g. kneading or stirring. 5 to 99 wt.% of the mixture is constituted by the clay component on a dry weight basis, 1 to 95 wt.% of the mixture is constituted by the active ingredient component on a dry weight basis, and a weight ratio of the clay component to the active ingredient component in the mixture is 1:20 to 99:1. The mixing step 101 may take place at room temperature or at a higher temperature such as 20-80°C. The mixing step may be followed by an incubation step of up to 24 hours or more to ensure adequate diffusion of the yeast extract amongst and between the exfoliated montmorillonite layers. This can be measured using XRD. Adequate diffusion does not necessarily mean complete, homogenous, infiltration of the active ingredient component into the inter-clay-layer spaces. While complete diffusion is ideal, adequate mixing means the active ingredient component sufficiently resides in the interlayer space such that the release rate of active ingredient from the particle is reduced. In a heterogeneous structure some (at least 5% of the total volume of the composite material of the particle) of the active ingredient component is intercalated and the remaining fraction remains as unincorporated active ingredient component in the composite material.

[0065] Thereafter the mixture is possibly extruded, dried 102 and possibly crushed into smaller particles. XRD measurements were used to compare the structure of clay particles with urea and clay particles with yeast extract. The XRD data in Fig. 5 shows powder XRD data for (a) montmorillonite clay intercalated with urea (Material 3), displaying a (001) diffraction peak at 4.9° 20 resulting from ordered and limited layer expansion, with a corresponding dooi of 18 A, (b) montmorillonite clay intercalated with yeast extract (Material 1), not displaying a (001) diffraction peak due to unlimited and unordered swelling, (c) the native montmorillonite clay, displaying a (001) diffraction peak at 7.4° 20, and a corresponding dooi of approx. 12.4 A due to water uptake at ambient relative humidity, (d) pure urea in powdered form, displaying the (110), (101), (111), (200) diffraction peaks of crystalline urea at 22.2°, 24.6°, 29.3° and 31.6° 20.

[0066] Peaks indicated by i-iv are minor micaceous phases, montmorillonite (hkO) reflections, quartz and feldspar phases.

[0067] For the clay-yeast extract composite particles the XRD results show that swelling of the montmorillonite layer is not ordered or limited, since the (001) peak of clay peak is lost in the presence of yeast extract, meaning that massive intercalation of yeast extract is not limited, only determined by the yeast extract to clay ratio.

[0068] The release patterns of active ingredient from such formed layered particles comprising yeast extract were compared to particles comprising a non-layered mixture of the same clay and active ingredient. The release of active ingredient from a non-layered particle with yeast extract was immediate and near complete. In contrast, the release from a clay particle with intercalated yeast extract was delayed.

[0069] This demonstrates that an intercalated active ingredient is retained over time and multiple elution cycles to a greater extent compared to the same amounts of active ingredient and clay as a mere admixture where clay layers are stacked in aggregate with an average basal distance of less than 2 nm. The release of active ingredient held between each single clay layer is delayed because it requires the material to first swell, and then for ions to be released from the cationic and anionic exchange sites on the face and edge of the clay layer respectively.

[0070] The release rate can be modified to make an active ingredient available at optimal levels over time, depending on the intended outcome of application of the active ingredient. Release can be further delayed or peak concentrations reduced, thus extending the efficacy of a treatment, by increasing the ratio of clay to the active ingredient.

[0071] Further, biologically relevant consequences of using clay particles with yeast extract as fertilizer compared to using clay particles with urea as fertilizer were compared. Biologically relevant consequences of using clay particles with yeast extract as fertilizer was also compared to use of no fertilizer at all. After 5 days, the germination status of the seeds was visually checked.

[0072] Fig. 6 shows corn seeds placed in soil with moisture content of 14%. Five days after sowing a reference seed (with no added fertilizer) (a) showed normal germination, whereas a seed (b) fertilized with montmorillonite clay and urea granules (cl) placed next to the seed (b) failed to germinate. It was evident that the clay particle with urea had arrested germination, while all reference seeds germinated normally.

[0073] It is apparent that urea does not interact with charged montmorillonite surfaces or edges via ionic bonding and is released at a rate sufficient to generate stress and arrest germination. Urea loaded in excess of the limit of intercalation is most likely released first, allowing urease- mediated ammonia production and causing associated toxicity. To a degree, plants can detoxify ammonia by metabolic conversion into amino acids. As a seed dormancy breaks and metabolic competence is regained, it is particularly sensitive to ammonia toxicity. Amino acids like those in yeast extract can be taken up directly and metabolised efficiently.

[0074] Fig. 7 shows corn seeds placed in soil with moisture content of 14%. Five days after sowing both a reference seed (with no added fertilizer) (a) and a seed (b) fertilized with montmorillonite clay and yeast extract granules (c2) placed next to the seed (b) showed normal germination. All seeds fertilized with granules of clay and yeast extract germinated normally with similar root radical and cotyledon growth rate as the reference.

[0075] As is seen in Fig. 7, normal seed germination is observed in immediate proximity of granules of yeast extract intercalated within montmorillonite layers. This is due to the combined effect of the delayed and staggered / multi-phased release rate, together with the form of nutrition. The nitrogen source in yeast extract is largely in organic form as 20 different proteinogenic amino acids. Each amino acid has a unique isoelectric point and therefore will carry a unique charge depending on pH. This underlies an important functional distinction between the varied mixture of amino acids in yeast extract when compared to the single source of nitrogen from urea when intercalated between montmorillonite layers. As the release rate of urea is not influenced by ionic associations, soil concentration will increase according to a single, acute, release rate function. The 20 different amino acids, on the other hand, will each be released according to idiosyncratic rates depending on charge and size. A delayed and staggered controlled release rate is beneficial as it helps to match available nutrition with the nutrient demand needed for healthy and stress tolerant growth, reducing losses and improving efficiency.

[0076] The montmorillonite clay then has an ongoing function serving as an exchange surface for charge ions.

[0077] Above is discussed the use of yeast extract as the active ingredient in the active ingredient component of the clay particles. Other microbial cell extracts or an active ingredient component comprising a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid clay particle, would give a similar result because the release rate of organic nitrogen and other nutrients would be delayed and staggered / multi- phased in a similar profile to yeast extract, better matching plant demand.

[0078] EXPERIMENTAL

[0079] Particle formation from pre-swelled clay, Material 1

[0080] A 10 % (w / v) montmorillonite-rich bentonite clay, consisting of at least 50% smectite clay mineral, was pre-swelled by gently mixing the clay with tap water and allowed to stand for >48 hours at room temperature to ensure complete exfoliation of the montmorillonite layers. A pre-swelled clay compound, a viscous gel resulted. Dry yeast extract powder, i.e. the active ingredient component, was added, bringing the mixture to 20% (w / v) with a dry content ratio of 1:1 (clay component:yeast extract powder). The gel was intermittently manually kneaded in a plastic bag and allowed to incubate in a water bath at 65 degrees Celsius for 24 hours to ensure adequate diffusion of the yeast extract amongst and between the exfoliated montmorillonite layers. The gel was then pressed through a hole, 7 mm in diameter, to form a sausage-like shape and dried at 50 degrees Celsius. The dried material was then crushed into smaller particles with a particle size distribution from 1-4 mm.

[0081] Particle formation from non-pre-swel led clay, Material 2 (reference material)

[0082] A reference material was made (Material 2) where the final particle was comprised of a material that consisted of equal amounts of the same yeast extract as used for Material 1 aggregated together with the same clay component as used for Material 1, such that the yeast extract was not intercalated between individual clay layers, which may be confirmed using electron microscopy or XRD. Equal amounts of dry (non-swelled) montmorillonite-rich bentonite and dry yeast extract powder were homogenized. The dry mix was granulated by spraying a fine mist of water to momentarily (minutes) wet the surface and through agitating in a plastic bag by shaking until a particle size distribution of 1-4 mm was achieved. The particles were then immediately dried at 50 degrees Celsius. The amount of water added during the granulation process did not cause any swelling or exfoliation of the montmorillonite layers, and thus did not allow for yeast extract to diffuse between individual layers.

[0083] Particle formation for XRD measurements

[0084] Clay particles with urea were produced (Material 3) by pre-swelling montmorillonite-rich bentonite in the same way as was done for Material 1, but instead of introducing yeast extract, urea was mixed with the clay paste bringing the mixture to 20% (w / v) with a dry content ratio of 1:1 (clay component:urea). The gel was intermittently manually kneaded in a plastic bag and allowed to incubate in a water bath at 65 degrees Celsius for 24 hours to ensure adequate diffusion of the yeast extract amongst and between the exfoliated montmorillonite layers. The gel was then pressed through a hole, 7 mm in diameter, to form a sausage-like shape and dried at 50 degrees Celsius. The dried material was then crushed into smaller particles with a particle size distribution from 1-4 mm.

[0085] Clay particles with yeast extract were produced in the same way as for Material 1.

[0086] XRD measurements

[0087] Standard powder XRD measurements with CuKa X-rays (1.542A) between 3.5-35 20 was used. Samples of both 1:1 (clay component:yeast extract) and 1:1 (clay component:urea) for XRD measurements were prepared by pre-swelling montmorillonite-rich bentonite and then mixing in either dry yeast extract or urea in the same way as was done for Material 1 and Material 3, respectively. Rather than extruding the material to form granules, the paste of either 1:1 (clay component:yeast extract) or 1:1 (clay component:urea) were smeared evenly on glass slides and dried to form an oriented mount. These slides were then placed on a stage and XRD measurement was performed.

[0088] Release rate test

[0089] A release rate test of the active ingredient from Material 1 and Material 2 was performed. This was done to show that the release of an active ingredient from a smectite clay-based nanocomposite material can be delayed if the active ingredient is intercalated between the clay layers.

[0090] The experiment was set as a vertical cylinder of washed and sieved sand in a 50 mL plastic tube with a 1.5 mm diameter hole in the bottom. Equal amounts of Material 1 or Material 2 were mixed evenly into respective tubes. The sand / Material mixture was taken to field capacity with de-ionised water and a series of time points elapsed. At each time point, a 15 mL volume of de-ionised water equivalent to the field capacity of the sand / Material mixture was introduced at the top of the tube and percolated through under gravity allowing for a complete purge and refresh of water in the column. The liquid that drained from the hole in the base of the column (the eluant) was collected and the electrical conductivity of the eluant was measured. A blank tube with sand but no material added was used to measure and correct for the small ion content present in the sand that had the potential to influence electrical conductivity. In series, de-ionised water was run through the tube according to the schedule in Table 1. The electrical conductivity of each successive eluant was measured providing a profile over time and volume.

[0091] Table 1 - Release rate elution volumes in series over time

[0092] The release rate profile of Material 1 and Material 2 (Fig. 3) are distinct. The release of active ingredient from Material 2 is immediate and near complete. In contrast, the release from Material 1, where active ingredient is efficiently integrated between layers of montmorillonite, is delayed. Particle formation for comparison of clay particles with yeast extract as fertilizer and clay particles with urea as fertilizer

[0093] Yeast extract:clay particles with a ratio of yeast extract to clay of 50:50 w / w were prepared in the same way as for Material 1. Urea:clay particles with a ratio of urea to clay of 50: 50 w / w were prepared in the same way as for Material 3.

[0094] Six replicates of each were prepared.

[0095] Comparison of clay particles with yeast extract as fertilizer and clay particles with urea as fertilizer Soil with a moisture content of 14%, which is adequate for normal seed germination, was packed into 12 cm x 12 cm plates. Two corn seeds were evenly spaced in the middle of each plate and pressed into the soil with the same orientation such that the embryo was facing up ensuring soil-seed contact. Equivalent amounts (66mg) of granules of either clay with yeast extract or clay with urea were then placed in direct contact with one of the corn seeds on each plate. A reference seed with no fertilizer granules placed next to the seed was included on each plate. All plates were then wrapped in aluminum foil to exclude light and placed vertically.

[0096] After five days the seeds were visually inspected.

Claims

CLAIMS1. A particle for delayed release of an active ingredient to a plant or seed, the particle is comprised of a composite material, the composite material comprising an active ingredient component and a clay component, wherein 5 to 99 wt.% of the composite material is constituted by the clay component, wherein 1 to 95 wt.% of the composite material is constituted by the active ingredient component, and a weight ratio of clay component to active ingredient component in the composite material is 1:20 to 99:1, wherein the active ingredient component comprises microbial cell extract or comprises a mixture of at least one type of amino acid and one or more negatively charged ion and / or neutral molecule, wherein the mixture comprises at least one type of positively charged amino acid, wherein the clay component comprises smectite clay mineral and the composite material comprises at least 5 wt.% of the smectite clay mineral, and wherein the clay component forms layered stacks in the composite material and the active ingredient component is intercalated between individual clay layers in the stacks.

2. The particle of claim 1, wherein the smectite clay mineral is montmorillonite, nontronite, saponite, hectorite or any combination thereof.

3. The particle of claim 1 or 2 wherein the active ingredient component and / or the clay component comprises phytic acid.

4. Use of the particle of any of claims 1-3 for delayed release of the active ingredient to a plant or seed.

5. Method of producing a particle for delayed release of an active ingredient, the method comprising the steps of:- pre-swelling a clay component (100) consisting of at least 50% smectite clay mineral in an aqueous solvent,- mixing the pre-swelled clay component with an active ingredient component (101) wherein the active ingredient component comprises microbial cell extract or comprises a mixture of at least one amino acid and one or more negatively charged ion or neutralmolecule, wherein the mixture comprises at least one type of positively charged amino acid, wherein 5 to 99 wt.% of the mixture is constituted by the clay component on a dry weight basis, wherein 1 to 95 wt.% of the mixture is constituted by the active ingredient component on a dry weight basis, and a weight ratio of the clay component to the active ingredient component in the mixture is 1:20 to 99:1,- drying the mixture (102), thereby forming particles comprising layered stacks of clay component wherein individual clay layers in the stacks are intercalated with active ingredient.

6. The method of claim 5, wherein the active ingredient component is mixed with phytic acid before being mixed with the clay component.

7. The method of any of claims 5-6, wherein the pre-swollen clay component is mixed with phytic acid before the clay component is mixed with the active ingredient component.

8. Plant or seed treatment composition comprising the particle of any of claims 1-3.

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