GB2604589A

GB2604589A - Fertilizer particles coated with a micronutrient source

Info

Publication number: GB2604589A
Application number: GB2102929.3A
Authority: GB
Inventors: Ward Stuart; Hathway Laura
Original assignee: Yara UK Ltd
Current assignee: Yara UK Ltd
Priority date: 2021-03-02
Filing date: 2021-03-02
Publication date: 2022-09-14
Also published as: BR112023017257A2; CA3209724A1; EP4301716A1; AR125584A1; GB202102929D0; WO2022185049A1; CN116867754A

Abstract

A liquid composition comprising a micronutrient dissolved in a solvent which is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols, and mixtures thereof. The micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc. Preferably the micronutrient is a salt or a chelate comprising ethylenediaminetetraacetate (EDTA). The micronutrient may alco be boric acid, sodium borate, boron ethanolamine or sodium molybdate. The solvent has a melting point below 15°C and represents 30-90 wt% of the liquid composition. Preferably the solvent is selected from glycerol, ethylene glycol, propylene glycol, diethylene glycol, 2-(2-ethoxyethoxy)ethan-1-ol (diethylene glycol monoethyl ether). The liquid composition may further comprise urea and an acid selected from citric acid, malic acid and lactic acid. In one embodiment the composition is used as a coating agent for fertiliser particles, wherein the core of the fertiliser particle may preferably comprise urea, ammonium salts, nitrate salts, phosphate salts, potassium salts, calcium nitrate and mixtures thereof.

Description

Fertilizer particles coated with a micronutrient source

Field of the invention

The present disclosure relates to the field of fertilizer particles, in particular fertilizer particles coated with a composition comprising a micronutrient.

Background of the invention

In agriculture, micronutrients refer to the group of elements consisting of boron, copper, iron, manganese, molybdenum and zinc. Most crops require one or more of these elements to ensure optimal growth. Some of these elements may be found naturally in the soil, but it is often necessary for the farmer to supply to the crops one or more of these elements via the application of fertilizer products to meet the crop requirements.

Micronutrients may be supplied to crops in a number of different means, for example, micronutrients solids may be distributed to the fields via manual or mechanical spreading; or a solution, often aqueous, containing the micronutrient is sprayed onto the foliage of crops (foliar application); or the micronutrient may be dissolved and applied to the crop in the irrigation water (fertigation).

A convenient way to supply micronutrients to crops is to apply a coating composition comprising the micronutrient to fertilizer particles containing primary or secondary nutrients, such as nitrogen, phosphorus, potassium, calcium, magnesium or sulphur. This method has the advantage to reduce the workload for the farmer who can distribute several nutrients with a single application and reduces the water consumption on the farm. Micronutrients are required by plants in small quantities and the requirement can be met by a thin layer of coating composition on fertilizer particles.

Micronutrients can also be incorporated in fertilizer particles during the prilling or granulation process of the particles but practical considerations in high volume production operations imply that it is difficult to satisfy the widely different nutrient requirements of different crops and different soil types using this approach.

GB25132232 (Yara, 2014) discloses a method to prepare fertilizers coated with a layer of an oil-based composition comprising a micronutrient source. The micronutrient source is suspended in the oil-based composition and uniformly coated on the particles. This method provides an efficient method for delivering micronutrients via solid fertilizers intended to be spread on the soil. However, oil-based compositions are not ideal for fertigation, since the oil-based coatings would not fully dissolve in the water leading to blockages in the irrigation system.

Water-based compositions comprising micronutrients are not suitable to be coated on fertilizer particles since the water impacts negatively the physical properties, such as particle strength and caking tendency, of the particles for handling, transport and storage, and their distribution in the fields.

Thus, there is a need to develop new coating compositions comprising micronutrients that contain minimum amounts of water and oil.

Summary of the invention

Surprisingly it has now been discovered that compositions containing a micronutrient dissolved in a solvent selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, wherein the solvent has a melting point below 15 °C, are highly suitable for fertilizer coating applications, thus providing an easy and flexible method whereby solid fertilizers can be coated with an effective source of one or more micronutrient without negatively affecting fertilizer quality.

In the first aspect of the invention, a fertilizer particle is provided, the particle comprising a core and an outside layer of a conditioning agent covering the core comprising a component which comprises a micronutrient, the compound being dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, the solvent has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the conditioning agent, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.

In another aspect, a method to manufacture a fertilizer particle according to the present invention is provided, wherein the fertilizer particle comprises a layer of a conditioning agent, the method comprising the steps of: (a) providing a fertilizer core particle; and (b) applying an amount of a conditioning agent comprising a compound which comprises a micronutrient, the compound being dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, the solvent has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the conditioning agent, the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc, and the conditioning agent optionally comprises urea and/or an acid.

In another aspect, a liquid composition is provided, the composition comprising a compound which comprises a micronutrient, the compound being dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, the solvent has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the liquid composition, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.

In another aspect, the use of a composition as a coating agent for fertilizer particles is provided, the composition comprising a compound which comprises a micronutrient selected from the group consisting of boron, copper, manganese, molybdenum and zinc, the compound being dissolved in a solvent selected from the group consisting polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, having a melting point below 15 °C, and optionally urea and/or citric acid.

Detailed description of the invention

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

All references cited in this description are hereby deemed to be incorporated in their entirety by way of reference.

As used herein, the following terms have the following meanings: "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

"About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/-20 % or less, preferably +/-10 % or less, more preferably +/-5 % or less, even more preferably +1-1% or less, and still more preferably +/-0.1 % or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

"Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

The expression "weight%", "weight percent", "% w/w", "wt%" or "%wt", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.

In the first aspect of the invention, a fertilizer particle is provided, the particle comprising a core and an outside layer of a conditioning agent covering the core, the conditioning agent comprising a component which comprises a micronutrient, the compound being dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof, the solvent has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the conditioning agent, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.

It was found that it was possible to prepare a fertilizer particle comprising a high amount of micronutrient by coating a fertilizer core, comprising nutrients, with a conditioning agent comprising a micronutrient component dissolved in a solvent.

The solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof and the solvent has a melting point below 15 °C. It was found out that polyhydric alcohols and/or their derivatives were able to dissolve a wide range of micronutrient components and the liquid compositions obtained could be applied to fertilizer particle by standard coating methods.

Polyhydric alcohols refer to the group consisting of molecules comprising a carbon chain, which may be linear or branched, and at least two hydroxy groups. The group of polyhydric alcohols comprise diols, also named glycols such as 1,2-ethanediol, also named ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol; triols, such as 1,2,3-propanetriol, also named glycerol.

Derivatives of polyhydric alcohols comprise the compounds named above, where one of the hydroxy group has been substituted or modified. For example, the hydroxy group may have been tuned unto an ether, an ester, a carbonate. Derivatives of polyhydric alcohols also comprise polymers of the compounds cited above, such as diethylene glycol, triethylene glycol and any polyethylene glycol with a melting point below 15°C. Derivatives of polyhydric alcohols also comprise derivatives of polymers mentioned above, such as mono ethers, and diethers of polyethylene glycol, such as monomethyl diethylene glycol, monoethyl diethylene glycol, monopropyl diethylene glycol, monobutyl diethylene glycol, dimethyl diethylene glycol, diethyl diethylene glycol, dipropyl diethylene glycol, dibutyl diethylene glycol.

The solvent may be of high purity, in particular it may be at least 98% pure, more in particular at least 99% pure. The conditioning agent should comprise from about 30 to about 90 wt% of solvent, so that it is suitable to be coated onto a solid fertilizer core. The solvent may be a single chemical component, but it may also be a mixture of two or more glycols or glycol ethers.

The solvent may be anhydrous or contain a small amount of water, such as less than 2.0 weight%, less than 1.5 weight%, or less than 1.0 weight%. Water is not desirable since it might degrade the fertilizer particle by dissolving some of the nutrients comprised in the fertilizer core, and negatively impacts some physical properties of the particle, such as the particle strength. But anhydrous solvents may be significantly more expensive than solvents comprising a small amount of water, such as less than 2.0 weight%, and a compromise may be acceptable.

In one embodiment, the solvent comprises less than 2.0 weight% of water. In one embodiment, the solvent comprises less than 1.5 weight% of water.

In one embodiment, the solvent comprises less than 1.0 weight% of water.

The amount of solvent that is possible to use may depend on the micronutrient component selected for the conditioning agent and the micronutrient loading desired for the nutritional effect. In one embodiment, the solvent may represent from about 40 to about 80 wt% of the conditioning agent. In particular, it may represent from about 50 to about 80 wt%, or from 45 to 80 wt%, or from to 85 wt% of the conditioning agent. The fertilizer particle comprising the layer of conditioning agent was found to be free-flowing, which is important for handling operations. In addition, the product showed good anti-caking properties and its crushing strength was similar to the uncoated product. Anti-caking and crushing strength are important parameters for fertilizer particles that affect the storability of the particles.

In one embodiment, the outside layer of conditioning agent may cover at least 50, 60, 70, 80, 90, 95, 96, 97, 98 or 99% of the surface of the core. In one embodiment, the layer of conditioning agent may cover 100% of the surface of the fertilizer particle.

In one embodiment, the conditioning agent comprises urea. Surprisingly, it was also found that adding a small amount of urea to the conditioning agent decreased the viscosity of such agents.

When these agents are applied onto solid particles, such as fertilizer particles, it is desirable that the conditioning has a viscosity which enables a good and even coating. Several methods may be used to apply a conditioning agent onto solid particles, e.g. mixing in a blender or in a coating apparatus, such as a coating drum, spraying the agent. In particular, the conditioning agent may have a viscosity at 20 °C in the range from about 0.005 to about 7 Pas (5 to 7000 cP), in particular in the range from about 0.1 to about 5 Pas (100 to 5000 cP). If a spraying method is used and the viscosity is too high, the liquid will not be easy to be sprayed and it might block the spraying equipment. Further, the repartition of the resulting coating on the particles may be uneven due to high viscosity. Since urea is a nutrient source, the addition of urea in the conditioning agent does not reduce the overall nutrient content of the fertilizer particle. Urea may be added as a solid and dissolves readily in the organic solvent. It may be dissolved in a small amount of solvent before mixing with the conditioning agent. To ensure a high quality of the final product, the coated fertilizer particle, the urea may be very pure. In particular, it may be more than 95% pure, more in particular more than 96% pure, even in more in particular more than 97% pure, even in more in particular more than 98% pure, even in more in particular more than 99% pure. Urea may contain water and/or biuret in a low amount, in particular it may contain less than S wt% of water or biuret, more in particular less than 2 wt% of water or biuret. In one embodiment, the conditioning agent comprises about 0.1 to about 5.0 wt% of urea. In particular, it may comprise up to 2.0 wt% of urea. In one embodiment, the solvent is selected from the group consisting of glycerol, also known as propane-1,2,3-triol or glycerine, monoethylene glycol, monopropylene glycol, diethylene glycol, 2-(2-ethoxyethoxy)ethan-1-ol, also known as diethylene glycol monoethyl ether, and mixtures thereof. Glycerol, monoethylene glycol, monopropylene glycol, diethylene glycol and 2-(2-ethoxyethoxy)ethan-1-ol are all well-known glycol-type solvents widely used in the chemical industry. They are well tolerated by plants, although some of these substances are classified as hazardous, such as monoethylene glycol, diethylene glycol. It was found that glycerol and 2-(2-ethoxyethoxy)ethan-1-ol are particularly suitable solvents for the preparation of high micronutrient concentration liquid solutions, since glycerol and 2-(2-ethoxyethoxy)ethan-1-ol are classified as non-hazardous substance. It reduces the risks for the user when manipulating the conditioning agent. In one embodiment, the solvent is 2-(2-ethoxyethoxy)ethan-1-ol. In one embodiment, the solvent is monoethylene glycol. In one embodiment, the solvent is glycerol.

In one embodiment, the conditioning agent comprises at least 30 g/L of the micronutrient, in particular at least 35 g/L of the micronutrient, more in particular at least 40 g/L, even more in particular at least 44 g/L, even more in particular at least 50 g/L of the micronutrient. To supply an amount of micronutrient high enough to the plants, it was found that the conditioning agent should comprise at least 30 g/L of the micronutrient. A high micronutrient loading of the agent allows the farmer or fertilizer supplier to use a lower loading of the conditioning agent on the fertilizer core. This is desirable since a high loading might reduce the physical properties of the final product, such as anti-caking or strength indexes. A high coating loading might also make the product sticky and difficult to store, handle and spread in the field.

The micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc. These elements are well-known elements required in different amounts by a large number of crops.

In one embodiment, the component comprising a micronutrient is a salt thereof or a complex of a micronutrient selected from the group consisting of boron, copper, manganese, molybdenum and zinc, wherein the salt thereof or complex thereof is soluble in the solvent of the conditioning agent.

Elements such as boron, copper, manganese, molybdenum and zinc, need to be provided to the plants as ions, such as Zn2+, Mn2+, Mn3+, Cu*, Cu'', Mo.', or Mo6+, so that the plant can absorb them.

Plants cannot absorb neutral atoms. For each element, several sources, such as salts or complexes, are known to be suitable for agriculture use. A risk for metal ions such as copper, manganese, molybdenum and zinc, is that they react in the soil, for example via oxidation, once they are applied to the crop. Oxidation can occur due to the oxygen in the air or oxidative compounds or organisms, such as bacteria, present in the soil. Crops can usually not absorb oxidized metals, such as zinc oxide ZnO, copper (I) oxide or cuprous oxide Cu20, copper (II) oxide or cupric oxide CuO, manganese (II, Ill, IV, VI, VII) oxides and molybdenum (IV or VI) oxides. Micronutrients can also react with phosphate ions present in the soil and form insoluble phosphate salts or complexes. So, it is important that the micronutrient component is stable long enough after being applied to the crops, so that crops may absorb it. Another risk is that the micronutrient source may react in the irrigation water, which could also render them unavailable to the crop. For example, in high pH conditions, copper, manganese and zinc may precipitate as insoluble hydroxides, or phosphates, resulting in blockages in the pipes and drippers of the irrigation system.

In one embodiment, the compound which comprises a micronutrient is a chelate comprising an element selected from the group consisting of copper, manganese, and zinc. Chelated species comprise an organic molecule, named the chelant or chelating agent, comprising one or more chelating groups such as amine, hydroxyl group or carboxylic acid. A metal atom, such as copper, manganese, or zinc is bound to the organic molecule via non-covalent bounds. The chelated species may comprise additional ions, other than the micronutrient, to be electronically neutral.

Chelated species are usually more stable than other types of salts of the same metal, i.e. the metal ion is protected or caged in by the chelating agent and this allows the metal to stay in his soluble, plant-available form, which is particular important for application in irrigation systems. A known chelating agent is ethylenediaminetetraacetic acid, that forms ethylenediaminetetraacetate (EDTA) complexes with metals such as zinc, copper, manganese and molybdenum. These EDTA complexes are commercially available and are usually some of the cheapest chelates available. Example of EDTA complexes are zinc disodium EDTA (ZnEDTA-Na2), zinc dipotassium EDTA (ZnEDTA-K2), copper disodium EDTA (CuEDTA-Na2), and manganese disodium EDTA (MnEDTA -NA2).

In one embodiment, the chelating agent in the chelate is an amino-alcohol or an aminopolycarboxylic acid, in particular selected from the group consisting of ethylenediamine-N, N'- di[(ortho-hydroxyphenyl) acetic acid], ethylenediamine-N-[(ortho-hydroxyphenyl)acetic acid[-N1- [(para-hydroxyphenyl)acetic acid], ethylenediamine-N,N'-diLortho-hydroxy-methylphenyl]acetic acid], ethylenediamine-Ngortho-hydroxy-methylphenyl]acetic acidkN'-[(para-hydroxy-methylphenyl)acetic acid] or N,N'-di(2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid, and mixtures thereof. Micronutrient chelates are commercially available as a wide range of compounds.

It was found that those comprising an amino-alcohol or an aminopolycarboxylic acid are particularly suitable for the present conditioning agent. They are generally not toxic to plants and they have a high solubility in a wide range of organic solvents, including glycol and glycol ether solvents. They are each stable over a specific range of pH. The chelating agent ensures that the micronutrient cation stays in its soluble form available to plants and does not oxidize to oxide, which is not water-soluble and is not taken up by plants.

In one embodiment, the compound which comprises a micronutrient is selected from the group consisting of boric acid, sodium borate, sodium molybdate, and mixtures thereof. It was found that boric acid, sodium borate and sodium molybdate were soluble in polyhydric alcohols, such as a glycol, a glycol ether or mixtures thereof. These components are also known sources of boron and molybdenum that are suitable for use in agriculture. Boric acid, sodium borate and sodium molybdate are also soluble enough in water so that fertilizer particles coated with a conditioning agent comprising one or more of boric acid, sodium borate and sodium molybdate would solubilize completely in water.

In one embodiment, the conditioning agent comprises an anti-foam agent. A possible method to apply the conditioning agent to solid particles implies spraying the agent onto the particles. The particles may be in a rotating drum or lying on a bed. When spraying composition comprising organic compounds, there is always a risk that the composition will foam. Foam appears when air bubbles are trapped within a layer of organic compound. To prevent that, it is possible to add an anti-foam agent to the composition before the spraying operation. A wide range of anti-foam agents are commercially available from suppliers, for example Synthron. The anti-foam agent are usually added in a very small amount, in particular from 0.001 to about 1.0 weight% compared to the total composition, and do not affect the properties of the composition except for the foaming tendency.

In one embodiment, the mass ratio of the compound which comprises a micronutrient to solvent in the conditioning agent is in the range of from 1:9 to 3:1, in particular in the range of from 1:3 to 3:1. It is desirable to achieve a suitable ratio of micronutrient compound to solvent. If the ratio is too high, the chelate might not be completely soluble in the solvent or the viscosity of the composition might become too high. This creates issues when applying the conditioning agent onto the fertilizer particles. If the ratio is too low, the concentration of micronutrient will be very low. To supply enough micronutrients to the plants will require either to apply more conditioning agent onto the fertilizer particles, which may degrade the physical properties of the particles, or will require a higher application rate of the particles, which increases the operational costs for the farmer. Further, the other nutrients comprised in the particles may be supplied in an excess amount to the crops, which may have negative impact on the environment. For example, if too much nitrates or phosphates are supplied to a soil, these ions will not be retained properly by the soil and will leach in the environment. It was found that a mass ratio of micronutrient compound to solvent in the conditioning agent may be in the range of from 1:9 to 3:1, in particular in the range of from 1:3 to 3:1.

In one embodiment, the conditioning agent is essentially water-free. It may be desirable for the conditioning agent to be essentially water-free, as water may decrease the physical properties, such as particle strength and anti-caking character, of the fertilizer particles. It may be difficult to obtain a completely anhydrous conditioning agent, but the conditioning agent may comprise less than 5 wt% of water, in particular less than 2 wt%, more in particular less than 1 wt%, even more in particular less than 0.5 wt%. The components of the conditioning agent, the solvent, the compound which comprises a micronutrient, and optionally the urea, may each contain a small amount of water, e.g. less than 5 wt% of water. In particular, they may each comprise less than 2 wt% of water, more in particular less than 1 wt% of water.

In one embodiment, the conditioning agent represents 0.1 to 2.0 weight%, in particular 0.1 to 1.0 weight%, of the fertilizer particle. It is important for the conditioning agent to be comprised in the fertilizer particle at the right amount. If the composition comprises too little conditioning agent, the amount of micronutrient supplied to the crops will not be enough to obtain the best yield. But if it contains too much, the overall nutrient content of the composition will be reduced: both the solvent and the ligand do not deliver nutrients to the plants. Further, the physical properties of the fertilizer particle, such as particle strength, stickiness, might be reduced because of the high amount of solvent.

In one embodiment, the fertilizer core comprises a component selected from the group consisting of urea, ammonium salts, nitrate salts, phosphate salts, potassium salts, calcium nitrate and mixtures thereof. It is desirable that the fertilizer core comprises a high percentage of nutrients available to plants. Urea, ammonium salts and nitrate salts are three sources of nitrogen for plants; phosphate salts is the main source of phosphorus for plants; other cations, such as potassium and calcium are also important nutrients for plants. In one embodiment, the fertilizer core comprises urea. In one embodiment, the fertilizer comprises all three primary nutrients, N, P and K. Such a fertilizer is named NPK fertilizer. In addition to primary nutrients, the fertilizer core may comprise at least one source of one or more of the secondary nutrients (calcium, sulphur, magnesium) and micronutrients (boron) manganese, molybdenum, copper and zinc). Suitable sources of these elements for use in agriculture are well known in the field.

In one embodiment, the fertilizer core comprises more than one component selected from the group consisting of urea, ammonium salts, nitrate salts, phosphate salts, potassium salts, calcium nitrate and mixtures thereof. The fertilizer core may comprise two components containing the same nutrient, for example urea and ammonium nitrate, or two components containing different nutrients, for example urea and ammonium sulfate.

In one embodiment, the conditioning agent comprises from about 0.1 to about 10 weight% of urea relative to the weight of the composition. It was found that it was preferable for the conditioning agent to comprise from about 0.1 to about 10 weight% of urea relative to the total composition of the conditioning agent. If too little urea is used, the effect of decreasing the viscosity is not measurable. If too much urea is used, the micronutrient content decreases and may become too low for agricultural purposes. In particular, the conditioning agent may comprise from about 0.1 to about 5.0 weight% of urea relative to the weight of the composition. More in particular, the conditioning agent comprises from about 0.1 to about 3.0 weight% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a CuEDTA complex, such as CuEDTA disodium, or CuEDTA diammonium, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a ZnEDTA complex, such as ZnEDTA disodium, or ZnEDTA dipotassium, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a MnEDTA complex, such as MnEDTA disodium, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a CuEDTA complex, such as CuEDTA disodium, or CuEDTA diammonium, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a ZnEDTA complex, such as ZnEDTA disodium, or ZnEDTA dipotassium, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a MnEDTA complex, such as MnEDTA disodium, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to SO wt% of boric acid, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of sodium borate, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of sodium molybdate, about 40 to about 80 wt% of glycerol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of boric acid, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of sodium borate, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of sodium molybdate, about 40 to about 80 wt% of monoethylene glycol, optionally 0.01 to 1.0 wt% of an anti-foam agent and optionally 0.1 to 5.0 wt% of urea.

In one embodiment, the conditioning agent comprises an acid. In particular, the acid may be organic, i.e. a small molecule. More in particular, the acid may be a polycarboxylic acid, even more in particular it may be selected from the group consisting of citric acid, malic acid, lactic acid and mixtures thereof.

When the conditioning agent was applied onto a fertilizer particle comprising an ammonium source, for example calcium ammonium nitrate, it was noted that the particles emitted a strong and unpleasant smell. Upon analysis via a Drager tube, the smell was identified as being ammonia.

Without being bound by theory, it is supposed that an element in the conditioning agent, for example the solvent or the micronutrient chelate compound, may exhibit a basic character and catalyse the transformation of ammonium to ammonia. It was found that adding a component with an acidic character to the conditioning agent reduced the problem. A suitable acid needs to fulfil several criteria: acidic enough to stop the ammonia emission but not react or interact with the other elements of the fertilizer particle and/or the conditioning agent; preferably soluble in the solvent or solvent mixture used in the conditioning agent; preferably with a low health and safety risk to avoid complicating the use of the conditioning agent; commercially available at reasonable cost; preferably available pure or in an anhydrous solvent, however, it may be available as an hydrate complex. It was found that malic acid, lactic acid and citric acid are three chemicals fulfilling these criteria and are suitable to be added to the conditioning agent. Malic acid is a bis-carboxylic acid with pKas of 3.4 and 5.2, citric acid is a tri-carboxylic acid with pKas of 3.1, 4.8 and 6.4, and lactic acid is a monocarboxylic acid with a pKa of 3.9. It may be an advantage to lower the pH of the conditioning agent to about 7 or below to reduce the ammonia emissions from the fertilizer particles. A conditioning agent wherein citric acid was added to adjust the pH to about 7, was shown to reduce ammonia emissions by about 50% compared to the same conditioning agent without citric acid and possessing a pH of 8.7. The pH of the conditioning agent may be kept above 5. Below pH = 5, the stability of the micronutrient compound, in particular wherein the compound is a chelate, may be affected, and the micronutrient atoms may precipitate and become unavailable for the plant. The conditioning agent may comprise from about 0.5 to about 10 weight% of the acid. In particular, it may comprise from about 0.5 to about 5 weight% of the acid, more in particular from about 1 to about 5 weight% of the acid. In one embodiment, the pH of the conditioning agent may be from 5.0 to 7.0.

It was also observed in some embodiments, that the addition of citric acid, in particular in a conditioning agent comprising glycerine, reduced the viscosity of the conditioning agent.

In one embodiment, the conditioning agent comprises 15 to 50 wt% of a compound which comprises a micronutrient, about 40 to about 80 wt% of a solvent, in particular ethylene glycol or glycerol, 0.1 to 5.0 wt% of urea, and 0.1 to 5.0 wt% of an acid, in particular citric acid.

In one embodiment, the fertilizer core comprises 0.1 to 2.0 weight% of water-insoluble material. The conditioning agent is interesting to apply on fertilizer particles to be used in fertigation, i.e. a method where the fertilizer particles in dissolved in an aqueous solution, such as water, and distributed to the plant via the irrigation system. Fertigation is a powerful fertilization method because it provides nutrients to the plant at the right time in the right amount. Fertigation requires the use of high purity fertilizer products that comprise a low amount of water-insoluble material. The advantage of the conditioning agent according to the present invention is that it may be fully water-soluble: glycol and glycol ethers usually have very good water-miscibility and water-soluble micronutrient compounds, such as chelates, are well known. So a fertilizer particle wherein its core comprises 0.1 to 2.0 weight% of water-insoluble material and comprising a layer of the conditioning agent as disclosed herein is a very good fertilizer product for fertigation. Such particles can be prepared in production plants where the coating can be varied to supply different micronutrients, and then delivered to the farmer who can directly add the particles to its fertigation tank and prepare a solution ready to be used. Alternatively, to achieve the same nutrient solution from a non-coated fertilizer product, the farmer would have to purchase a separate micronutrient product or solution, and measure the right quantity to add to its fertigation tank. There are risks associated with each of these steps, such as incompatibility of the micronutrient product with the fertilizer particle, and risk of mistakes when dosing. So a fertilizer particle combining primary and/or secondary nutrient in its core with the right amount of micronutrient already coated on top of it is a very attractive product for farmers.

In one embodiment, the fertilizer particle comprising the core and the conditioning agent comprises 0.1 to 2.0 weight% of water-insoluble material.

In another aspect, a method to manufacture a fertilizer particle is provided, wherein the fertilizer particle comprises a layer of a conditioning agent comprising a compound which comprises a micronutrient, the method comprising the steps of: (a) providing a fertilizer core particle; and (b) applying an amount of a conditioning agent comprising a compound which comprises a micronutrient dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof and has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the conditioning agent, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.

This aspect may exhibit the same or similar features and technical effects as the first aspect, and vice versa.

In another aspect, a method to manufacture a fertilizer particle according to the present disclosure is provided.

A number of well-established methods can be used to coat a fertilizer particle with a liquid composition, e.g. spraying the composition above the particles sitting on a conveyor, mixing the composition and the particles in a rotating drum. Any coating method known in the art may be used with the present invention.

In one embodiment, the solvent is selected from the group consisting of glycerol, monoethylene glycol, monopropylene glycol, diethylene glycol, 2-(2-ethoxyethoxy)ethan-1-ol, also known as diethylene glycol monoethyl ether and mixtures thereof.

In one embodiment, the conditioning agent comprises at least 30 g/L of the micronutrient, in particular at least 35 g/L of the micronutrient, more in particular at least 40 g/L, even more in particular at least 44 g/L, even more in particular at least 50 g/L of the micronutrient.

In one embodiment, the conditioning agent used in the method described above comprises urea. Surprisingly, it was also found that adding a small amount of urea to the conditioning agent decreased the viscosity of such agents.

In one embodiment, the conditioning agent comprises an anti-foam agent. A possible method to apply a conditioning agent onto solid particles implies spraying the agent onto the particles. The particles may be in a rotating drum or lying on a bed. When spraying composition comprising organic compounds, there is always a risk that the composition will foam. Foam appears when air bubbles are trapped within a layer of organic compound. To prevent that, it is possible to add an anti-foam agent to the composition before the spraying operation. A wide range of anti-foam agents are commercially available from suppliers, for example Synthron. The anti-foam agent are usually added in a very small amount, typically less than 1.0 weight% compared to the total composition and do not affect the properties of the composition except for the foaming tendency.

In one embodiment, the conditioning agent comprises an acid. In particular, the acid may be organic, i.e. a small molecule. More in particular, the acid may be a polycarboxylic acid, even more in particular it may be selected from the group consisting of citric acid, malic acid and mixtures thereof.

In one embodiment, the conditioning agent represents 0.1 to 2 weight%, in particular 0.1 to 1.0 weight%, of the fertilizer particle.

In another aspect, a liquid composition is provided, the composition comprises a compound which comprises a micronutrient dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof and has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the liquid composition, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc. This aspect may exhibit the same or similar features and technical effects as the first aspect, and vice versa.

This composition may be used to coat fertilizer particles to provide an micronutrient source to the particles. Surprisingly, it was found that adding a small amount of urea to the compositions described previously decreased the viscosity of such compositions. When these compositions are applied onto solid particles, such as fertilizer particles, it is desirable that the liquid composition has a suitable viscosity which enables an even coating.

In one embodiment, the solvent in the liquid composition is selected from the group consisting of glycerol, monoethylene glycol, monopropylene glycol, diethylene glycol, 2-(2-ethoxyethoxy)ethan-1-ol, also known as diethylene glycol monoethyl ether and mixtures thereof.

Several examples of glycol and glycol ethers were found to be particularly suitable to prepare a composition with a micronutrient compound, in particular a micronutrient chelate, and optionally urea. Glycerol and diethylene glycol monoethyl ether are classified as a non-hazardous substance so they are particularly suitable as a solvent.

In one embodiment, the liquid composition comprises from about 0.1 to about 10 weight% of urea relative to the weight of the composition. It was found that an amount of urea from about 1.0 to 10 weight% of the total liquid composition is preferable. If too much urea is used, the micronutrient content decreases and becomes too low for agricultural purposes. In particular the liquid composition may comprise from about 0.1 to about 5.0 weight% of urea, more in particular from about 0.1 to about 2.0 weight% of urea.

In one embodiment, the mass ratio of the compound which comprises a micronutrient to solvent is in the range 1:9 to 3:1, in particular in the range 1:3 to 3:1, and more in particular in the range 1:2 to 2:1. The ratio of micronutrient compound to solvent has to be optimized to obtain a composition with the desired characteristics. The composition has to have a suitable viscosity so that it can be applied onto solid particles and the micronutrient content has to be high enough so that it provides enough micronutrient to the plants in a minimum of applications.

In one embodiment, the liquid composition comprises an anti-foam agent.

In one embodiment, the liquid composition comprises an acid. In particular, the acid may be organic, i.e. a small molecule. More in particular, the acid may be a polycarboxylic acid, even more in particular it may be selected from the group consisting of citric acid, malic acid and mixtures thereof.

In one embodiment, the liquid composition has a pH of from 5.0 to 9.0, or from 5.0 to 8.0, or from 5.0 to 7.5.

In another aspect, the use of a composition as a coating agent for fertilizer particles is provided, the composition comprising a compound which comprises a micronutrient selected from the group consisting of boron, copper, manganese, molybdenum and zinc, dissolved in a solvent selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof and has a melting point below 15°C, and optionally urea. This aspect may exhibit the same or similar features and technical effects as the first aspect, and vice versa.

In one embodiment, the composition comprises an anti-foam agent.

In one embodiment, the composition comprises an acid. In particular, the acid may be organic, i.e. a small molecule. More in particular, the acid may be a polycarboxylic acid, even more in particular it may be selected from the group consisting of citric acid, malic acid, lactic acid and mixtures thereof. In one embodiment, the composition has a pH from 5.0 to 7.0.

In another aspect, the use of the composition as described above as a coating agent for fertilizer particles is provided.

The invention will now be further described with reference to the following examples.

Example 1

The following example shows the formulation required to make 1 kg of a liquid copper chelate composition based on copper disodium EDTA: Cu disodium EDTA (15% w/w Cu) 250.0 g Monoethylene glycol 750.0 g Total 1000.0 g The solvent was placed in a glass vessel fitted with an impeller stirrer. The copper chelate powder was added slowly to the stirred solvent, controlling the rate of addition in such a way as to avoid clumping. After completing the addition, stirring was continued for 120 minutes to ensure complete dissolution. The process can be carried out at room temperature or alternatively the solvent/mixture may be heated to 30-40°C in order to speed up the dissolution.

The resultant product was a clear, bright blue, slightly viscous solution with the following physiochemical characteristics: Density: 1.217 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C Cu content: 3.65% w/w (= 44 g/I) The product remained stable for at least 12 weeks when stored at room temperature.

Example 2

The following example shows the formulation required to make 1 kg of a liquid copper chelate composition based on copper disodium EDTA: Cu disodium EDTA (15% w/w Cu) 250.0 g glycerine 750g Total 1000.0 g The product was prepared in a similar manner to Example 1.

The resultant product was a clear, bright blue, slightly viscous solution with the following physiochemical characteristics: Density: 1.351 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) 6700 cP at 20°C Cu content: 3.65% w/w (= 49 g/I) The product remained stable for at 12 weeks when stored at room temperature.

Example 3

The following example shows the formulation required to make 1 kg of a liquid zinc chelate composition based on zinc disodium EDTA: Zn disodium EDTA (15% w/w Zn) 250.0 g Monoethylene glycol 750.0 g Total 1000.0 g The product was prepared in a similar manner to Example 1.

The resultant product was a clear, colourless, slightly viscous solution with the following physiochemical characteristics: Density: 1.232 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C pH 6.8 Zn content: 3.7% w/w (= 46 g/I) The product remained stable for at 12 weeks when stored at room temperature.

Example 4

The following example shows the formulation required to make 1 kg of a liquid copper chelate composition based on copper disodium EDTA: Cu disodium EDTA (15% w/w Cu) 250.0 g Monoethylene glycol 742.5 g Citric acid 7.5 g Total 1000.0 g The product was prepared in a similar manner to Example 1.

The resultant product was a clear, bright blue, slightly viscous solution with the following physiochemical characteristics: Density: 1.272 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) 3240 cP at 20°C Zn content: 3.65% w/w (= 49 g/I) The product remained stable for at 12 weeks when stored at room temperature.

Example 5

The following example shows the formulation required to make 1 kg of a liquid manganese chelate composition: Mn disodium EDTA (13% w/w Mn) 250.0 g Monoethylene glycol 750.0 g Total 1000.0g The product was prepared in a similar manner to Example 1.

The resultant product was a clear, dusky pink, slightly viscous solution with the following physiochemical characteristics: Density: 1.209 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C Mn content: 3.2D% w/w (= 39 g/I) pH 6.6 The product remained stable for at 12 weeks when stored at room temperature.

Example 6

The following example shows the formulation required to make 1 kg of a liquid manganese chelate composition: Mn disodium EDTA (13% w/w Fe) 250.0 g Monoethylene glycol 742.5 g Urea 7.5g Total 1000.0 g The solvent was placed in a glass vessel under a SiIverson high shear rotor/stator mixer. The mixer was started and the manganese chelate powder was added slowly to the mixed solvent, controlling the rate of addition in such a way as to avoid clumping. After completing the addition, mixing was continued for 9 minutes to ensure complete dissolution.

The resultant product was a clear, dusky pink, slightly viscous solution with the following physiochemical characteristics: Density: 1.210 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C Mn content: 3.20% w/w (= 39 g/I) pH 6.6

Example 7

The following example shows the formulation required to make 1 kg of a liquid composition comprising boric acid: Boric acid 250.0 g Glycerine 750.0 g Total 1000.0g Boric acid is a powder. In order to facilitate its dissolution, it may be an advantage to grind the powder to decrease the particle size. The powder can be ground manually.

Alternatively, the SiIverson high shear rotor/stator mixer as described in Example 6 may be used. The resultant product was a clear, colourless, slightly viscous solution with the following physiochemical characteristics: Density: 1.268 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) 400 cP at 20°C B content: 4.40% w/w (= 56 g/l) pH 1.9

Example 8

The following example shows the formulation required to make 1 kg of a liquid composition comprising boric acid and urea: Boric acid 250.0 g Glycerine 742.5 g Urea 7.5g Total 1000.0g The resultant product was a clear, colourless, slightly viscous solution with the following physiochemical characteristics: Density: 1.275 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) 360 cP at 20°C B content: 4.40% w/w (=56 g/l) pH 2.2 The addition of 0.75 wt% of urea lead to a 10% decrease of the viscosity of the solution compared with Example 7.

Example 9

The following example shows the formulation required to make 1 kg of a liquid composition comprising sodium molybdate: Sodium molybdate 250.0 g Monoethylene glycol 750.0 g Total 1000.0g The resultant product was a clear, slightly viscous solution with the following physiochemical characteristics: Density: 1.270 kg/1 at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C Mo content: 10% w/w (= 127 g/1)

Example 10

The following example shows the formulation required to make 1 kg of a liquid composition comprising zinc dipotassium EDTA: Zn dipotassium EDTA (14.5 w/w Zn) 250.0 g Monoethylene glycol 750.0 g Total 1000.0g The resultant product was a clear, slightly viscous solution with the following physiochemical characteristics: Density: 1.217 kg/1 at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) <200 cP at 20°C Zn content: 3.7% w/w (= 45 g/l)

Example 11

The following example shows the formulation required to make 1 kg of a liquid composition comprising a mixture of chelated elements of Mn, Zn and Cu: Mn disodium EDTA (13% w/w Mn) 100.0 g Zn disodium EDTA (15% w/w Zn) 100.0 g Cu disodium EDTA (15% w/w Cu) 100.0 g Glycerine 700.0 g Total 1000.0 g The resultant product was a clear, bright blue, slightly viscous solution with the following physiochemical characteristics: Density: 1.354 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) 9880 cP at 20°C Mn content: 1.30% w/w (= 17.6 WI) Zn content: 1.50% w/w (= 20.0 WI) Cu content: 1.50 % w/w (= 20.0 WI) pH 7.4

Example 12

The following example shows the formulation required to make 1 kg of a liquid composition comprising a copper chelate and a mixture of solvents: Glycerine 375g MEG 375g Cu disodium EDTA (15% w/w Cu) 250 g Total 1000.0 g The resultant product was a clear, bright blue, slightly viscous solution with the following physiochemical characteristics: Density: 1.305 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) >10000 cP at 20°C Cu content: 3.70% w/w (= 48.3 WI) pH 6.8

Example 13

The following example shows the formulation required to make 1 kg of a liquid composition comprising sodium molybdate and a mixture of solvents: Glycerine 375 g MEG 375g Sodium molybdate 300g Total 1000.0 g The resultant product was a clear, colourless, slightly viscous solution with the following physiochemical characteristics: Density: 1.350 kg/I at 20°C Viscosity (Brookfield, Spindle 3, 12 rpm) >10000 cP at 20°C Mo content: 10.00% w/w (= 135.0 g/I) pH 6.8

Example 14

Tests were carried out to assess the effect of a copper chelate composition according to the present application described above on fertilizer quality parameters when coated on to solid particulate fertilizer. A water-based copper chelate solution was prepared and tested for comparison. The strength (= crushing strength, hardness) of fertilizer granules/prills is an important property used in quality control of fertilizer production. The crushing strength is one of the main parameters for evaluation of the physical properties of fertilizers and is significantly influenced by the content of free water in the fertilizer.

Each of the copper chelate composition was applied to NPK particles comprising at least 98.5 weight% of water-soluble material at a rate equivalent to 4 litres per tonne (equivalent to about 0.50 wt% of the final product) using a lab scale conical blender. 1 kg of the NPK particles was added to the blender and the appropriate quantity of copper chelate composition added to the fertilizer as it was mixed in the rotating blender. Blending was continued for 20 seconds after addition to allow thorough distribution and coating of the copper chelate composition over the urea. The treatments used were as follows: 1. Control -Untreated 2. 4L/mt water-based copper chelate composition (25 wt% of Cu disodium EDTA which comprises 15% w/w Cu) 3. 4L/mt Non-aqueous copper chelate composition dissolved in monoethylene glycol (25 wt% of Cu disodium EDTA which comprises 15% w/w Cu and 75 wt% of monoethylene glycol) 4. 4L/mt Non-aqueous composition comprising copper EDTA and urea dissolved in glycerol (25 wt% of Cu disodium EDTA which comprises 15% w/w Cu, 10 wt% of urea and 75 wt% of glycerol) 5. 4L/mt Non-aqueous composition comprising copper EDTA and urea dissolved in monoethylene glycol (25 wt% of Cu disodium EDTA which comprises 15% w/w Cu, 10 wt% urea and 75 wt% of monoethylene glycol) "mt" is the abbreviation for the unit metric tonne, also written metric ton.

The coated particles were bagged, sealed and stored for 24 h at 50°C before the crushing strength of the granules was tested using a Mecmesin DT10 Hardness Gauge according to the following method.

An individual granule was placed on a smooth, solid surface (lab bench top) and the plunger of the tester was placed over the granule. The tester was pressed down until the granule fractured and the reading from the scale noted.

The test was carried out at room temperature (ca. 20°C), repeated 20 times for each treatment and the average value was reported in the table below.

No Treatment Crushing Strength 1 Control -Untreated 20.5 2 4L/mt water-based copper chelate composition (25 wt% of CuEDTA) 19.4 3 4L/mt Non-aqueous copper chelate composition dissolved in monoethylene glycol (25 wt% of CuEDTA and 75 wt% of monoethylene glycol) 20.4 4 4L/mt Non-aqueous composition comprising copper EDTA and urea dissolved in glycerol (25 wt% of CuEDTA, 10 wt% of urea and 75 wt% of glycerol) 20.9 4L/mt Non-aqueous composition comprising copper EDTA and urea dissolved in monoethylene glycol (25 wt% of CuEDTA, 10 wt% urea and 75 wt% of monoethylene glycol) 20.5 The results clearly demonstrate that the composition according to the present invention has less impact on the strength of fertilizer granules than a water-containing composition.

The coated particles were also put through a caking test, where a 1 kg plate was placed on top of a bag of particles. After two weeks at 50 °C, none of the particles with test numbers 3 to 6 showed any caking.

Claims

Claims 1. A fertilizer particle comprising a core and an outside layer of a conditioning agent covering the core, the conditioning agent comprising a compound which comprises a micronutrient; the compound being dissolved in a solvent; wherein -the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols and mixtures thereof; - the solvent has a melting point below 15°C; - the solvent represents from about 30 to about 90 weight% of the conditioning agent; and -the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.
2. The fertilizer particle according to claim 1, wherein the conditioning agent comprises an acid.
3. The fertilizer particle according to claim 1 or 2, wherein the acid is selected from the group consisting of citric acid, malic acid, lactic acid and mixtures thereof.
4. The fertilizer particle according to any one of claims 1 to 3, wherein the conditioning agent comprises urea.
5. The fertilizer particle according to any one of claims 1 to 4, wherein the compound which comprises a micronutrient is a salt thereof or a complex of the micronutrient selected from the group consisting of boron, copper, manganese, molybdenum and zinc, wherein the salt or complex is soluble in the solvent of the conditioning agent.
6. The fertilizer particle according to claim 5, wherein the salt or complex is a chelate comprising an element selected from the group consisting of copper, manganese, and zinc.
7. The fertilizer particle according to claim 6, wherein the chelate comprising an element selected from the group consisting of copper, manganese, and zinc, is an ethylenediaminetetraacetate chelate.
8. The fertilizer particle according to any one of claims 1 to 5, wherein the compound which comprises a micronutrient is boric acid, sodium borate, boron ethanolamine or sodium molybdate.
9. The fertilizer particle according to any one of claims 1 to 8, wherein the solvent is selected from the group consisting of glycerol, monoethylene glycol, monopropylene glycol, diethylene glycol, 2-(2-ethoxyethoxy)ethan-1-ol, also known as diethylene glycol monoethyl ether, and mixtures thereof.
10. The fertilizer particle according to any one of claims 1 to 9, wherein the conditioning agent comprises at least 30 g/L of a micronutrient selected from the group consisting of boron, copper, manganese, molybdenum and zinc, in particular at least 35 g/L of the micronutrient, more in particular at least 40 g/L, even more in particular at least 44 g/L, even more in particular at least 50 g/L of the micronutrient.
11. The fertilizer particle according to any one of claims 1 to 10, wherein the mass ratio of the compound which comprises a micronutrient to solvent in the conditioning agent is in the range of from 1:9 to 3:1, in particular in the range of from 1:3 to 3:1.
12. The fertilizer particle according to any one of claims 1 to 11, wherein the conditioning agent represents 0.1 to 2.0 weight%, in particular 0.1 to 1.0 weight%, of the fertilizer particle.
13. The fertilizer particle according to any one of claims 1 to 12, wherein the fertilizer core comprises a component selected from the group consisting of urea, ammonium salts, nitrate salts, phosphate salts, potassium salts, calcium nitrate, and mixtures thereof.
14. The fertilizer particle according to any one of claims 1 to 13, wherein the fertilizer core comprises 0.1 to 2.0 weight% of water-insoluble material.
15. A method to manufacture a fertilizer particle according to any one of claims 1 to 14, the method comprising the steps of: a. providing a fertilizer core particle; b. applying an amount of a conditioning agent comprising a compound which comprises a micronutrient dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols, and mixtures thereof;, the solvent has a melting point below 15 °C; the solvent represents from about 30 to about 90 weight% of the conditioning agent; the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.
16. A liquid composition comprising a compound which comprises a micronutrient, the compound being dissolved in a solvent, wherein the solvent is selected from the group consisting of polyhydric alcohols, derivatives of polyhydric alcohols, and mixtures thereof, the solvent has a melting point below 15 °C, the solvent represents from about 30 to about 90 weight% of the liquid composition, and the micronutrient is selected from the group consisting of boron, copper, manganese, molybdenum and zinc.
17. The liquid composition according to claim 16, wherein the liquid composition comprises from about 0.1 to about 10 weight% of urea relative to the weight of the composition, in particular 0.1 to 5.0 weight% of urea.
18. The use of a composition according to claim 16 or 17 as a coating agent for fertilizer particles.