AU2022224713A1 - Nitrogen Fertiliser with Water Soluble Micro-Elements - Google Patents

Abstract

Herein disclosed is a method for preparing a liquid fertiliser comprising a micronutrient. The method comprises the steps of providing a concentrated solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen. The concentrated solution comprises a solvated micronutrient, preferably in nitrate or acetate form and in the range of from about 25 wt% to about 55 wt%. In the method, a solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen can be added to the concentrated solution in order to dilute the solution. The diluted solution comprises the solvated micronutrient in the range of from about 0.04 to about 3 wt%. The concentrated and diluted liquid fertiliser is a substantially clear solution, stable for at least about 30 days. Y-I) 0 C 0U 0 It CN 8 00 z N 8 Co 080 N N z 00 Co 00N 9 N0 N -y N m nct z r 6n'i 00 N o 00 N m o pr Z N m 00 m 0 Nn m N L 0 0 E 00 CLn 00 (UC ) 0)m CL 4-N' V LU o o 00 NU 4-'>- , 0, 00 00 00 ,

Description

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Nitrogen Fertiliser with Water Soluble Micro-Elements

Technical field

The present invention relates to fertilisers which can be used to improve crop growth and yield. In embodiments, the present invention comprises fertilisers modified with micronutrients which play a role in crop nutrition.

Background

As they grow, plants must obtain mineral nutrients to successfully complete a life cycle. The mineral nutrients are obtained from their growing medium, such as soil. Mineral nutrients can be macronutrients including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulphur (S), magnesium (Mg), carbon (C), oxygen (0) and hydrogen (H). Mineral nutrients can be micronutrients, which are required in much smaller amounts than macronutrients, but which are still essential for healthy plant development. Micronutrients (sometimes referred to as trace minerals) include iron (Fe), boron (B), chlorine (CI), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni).

A plant that is unable to obtain enough micronutrients may not show evidence of the limitation until the deficiency is severe. If the plant is unable to obtain enough e.g. zinc during its growth phase, its cells and overall structure in top growth can suffer and the zinc deficiency can be visual in the stunted leaves (small leaves) and weak stems. Furthermore, the yield of a crop can be deleteriously affected by insufficient micronutrients, such as zinc, present in the soil.

It is not uncommon to add micronutrients to soil and crops to optimise plant health and increase yields. Yields have been found to increase by 3 to 12 % by the application of micronutrients in furrow. The amount of micronutrient(s) applied need only be very small. For example, for every tonne of grain produced by a cereal crop only about 14 to 20 grams of the micronutrient zinc and about 3 to 5 grams of the micronutrient copper are removed from the system. Following application, the micronutrient in the soil can have positive effects for up to 5 years.

Zinc helps in the production of a plant hormone responsible for stem elongation and leaf expansion. In addition to assisting in plant growth, micronutrients such as zinc, can be incorporated into the final plant (such as grain), and can become a part of the food chain. A human health aspect of zinc nutrition can therefore be improved by the ingestion of zinc incorporated into plants. According to reports, up to 2 billion human subjects may be deficient in micronutrients such as zinc.

In liquid fertilisers, such as liquid nitrogen fertilisers, the addition of a micronutrient can increase shoot number and or density and grain yields. However, a current challenge is that micronutrients can be difficult to incorporate into liquid fertilisers. A common method for the incorporation of zinc into liquid fertilisers is to grind zinc to a fine nano-powder which is then added to the liquid formulation. The zinc powder in the fertiliser is suspended for a sufficient time period that it can be applied to the soil and crops, but the suspension is not stable over time. This means that long term storage is often not possible and on-farm mixing /incorporation of this material is required, a capability not possessed by all farmers. Furthermore, the addition of the fertiliser comprising particulate matter, although small, has an adverse impact on application equipment which can over time clog due to accumulation of the solid particles.

An additional problem with the addition of micronutrients to liquid fertilisers is that at the concentrations required in field, the amount of liquid that needs to be transported can be commercially cost prohibitive. Liquids are transported in tankers which require diesel fuel to operate. With increasing prices of diesel, the transport of liquid fertilisers containing micronutrients "ready for use" is simply not possible.

Accordingly, there exists a need for an improved liquid fertiliser formulation that comprises micronutrients. In embodiments, the improved liquid fertiliser overcomes or at least ameliorates at least some of the problems associated with the prior art.

Summary of invention

In a first aspect there is provided a method for preparing a liquid fertiliser comprising a micronutrient, the method comprising the steps of providing a concentrated solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein the concentrated solution comprises a solvated micronutrient in the range of from about 25 wt% to about 50 wt%; adding a solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen to the concentrated solution in order to dilute the solution, wherein the diluted solution comprises the solvated micronutrient in the range of from about 0.3 to about 3 wt%.

io The method can further comprise the step of delivering the diluted solution as a liquid fertiliser.

The solvated micronutrient can be a solvated nitrate or acetate micronutrient. By solvated micronutrient, it is meant that the micronutrient is in solution. While solvation is one means for keeping a micronutrient in solution, there may be other means that do not involve the chemical definition of solvation. Solvation is the interaction of a solvent with the dissolved solute-in the case of water, solvation is often referred to as hydration. In the solvation process, typically ionized and uncharged molecules interact strongly with solvent. Solvation involves bond formation including hydrogen bonding, and van der Waals forces. Thus solvation is an interaction of a solute with the solvent which leads to stabilization of the solute species in the solution. Other chemical processes which lead to stabilisation of the micronutrient in the aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen are in spirit and scope. What is important is that the micronutrient is not predominately a solid in the solution.

The concentrated solution can comprise a micronutrient selected from zinc nitrate (in a concentration in the range of from about 34.5 to about 45.3%), zinc acetate (in a concentration in the range of from about 19.8 to about 29.1%), copper nitrate (in a concentration in the range of from about 25.9 to about 53%) and molybdenum (in a concentration in the range of from about 16.7 to about 23.8%).

Presently, it is believed that there are no soluble micronutrient liquid fertilisers in the market. At least one reason for this is the difficulty in getting the micronutrient to dissolve and stay in solution. In the present invention, the concentrated solution comprises a solvated micronutrient. The concentrated solution is preferably stable for at least 30 days to allow for transport and storage. The diluted solution is also preferably stable for at least 30 days to allow for transport of the micronutrient into the soil system and the plant.

Without wishing to be limited by theory, it is thought that the beneficial co-solvation behaviour exhibited by urea and ammonium nitrate solutions in the liquid nitrogen base provided herein extends to the incorporated micronutrient material leading to suppression of the micronutrient salt-out temperature. This improves storability of the urea-ammonium nitrate-micronutrient systems according to the present invention when compared to similar systems used in different nitrogen base formulations.

Another reason for there being no liquid fertiliser with solvated micronutrients on the market is because transport of liquid systems can be cost prohibitive. The present inventors have found that by the use of the disclosed aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, a stable concentrate can be prepared which can reduce transport costs. In embodiments, in order to keep the micronutrient in solution, the concentrated solution can be kept at elevated temperatures. The elevated temperature can be provided by a transport vessel such as a tanker comprising a heated jacket. Furthermore, the inventors have found that a diluted form of the solution can be prepared in situ by the addition of additional aqueous nitrogen solvent to the concentrated solution to prepare a formulation for use. If the additional aqueous solvent is added to the concentrated solution there is sufficient agitation that leads to a more homogenous solution for application.

In another aspect, there is provided a stable liquid fertiliser of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein urea is present in a range of from about 31.2 to about 40.9 wt%, the fertiliser comprising a solubilised nitrate or acetate micronutrient in an amount in the range of from about 0.3 to about 3.0 w/v, wherein the fertiliser is a substantially clear solution, stable for at least about 30 days.

In an embodiment, the micronutrient is selected from the group consisting of zinc, copper and molybdenum. In an embodiment, the micronutrient comprises zinc. The zinc micronutrient can comprise solubilised zinc ions of a zinc nitrate or zinc acetate salt.

The fertiliser is a liquid fertiliser. The liquid comprises a liquid nitrogen solution. The nitrogen solution is a base for the dissolution of the micronutrient ion additive. The nitrogen solution base can comprise nitrogen in the range of from about 32 wt% to io about 42.5 wt%. The nitrogen solution can comprise nitrogen in the form of urea, ammonium and nitrate. In an embodiment, the nitrogen solution comprises a base formulation referred to as Urea/Ammonium Nitrate (UAN) which can be sold under the brand EASY N@. The UAN fertiliser solution can comprise amine nitrogen from urea in the range of from about 19.1 to about 14.5 wt%. The nitrate nitrogen from ammonium nitrate can be in the range of from about 10 to about 13.5 wt%.

In an embodiment, the ammonium nitrate to urea ratio is in the range of from about 0.9 to about 1.6. In an embodiment, the formulation comprises about 2.5 to 3.5 parts urea, 3.5 to 4.5 parts ammonium nitrate and 0.07 to 0.22 parts micronutrient such as zinc and greater than 2 parts water. It should be understood that in any wt% calculation referred to herein, the balance is water.

In an embodiment, the aqueous nitrogen solution comprises 32% UAN (UAN32) comprising about 35% ammonium nitrate, 45% urea and 20% water at the eutectic point.

Where zinc is the micronutrient, the weight ratio of zinc to urea nitrogen can be in the range of 1 : 15 to 1 to 35. It has previously been thought that at urea levels in this high range, a liquid fertiliser formation containing zinc would be prone to manifesting precipitates which would be detrimental to the stability of the formulation. Such precipitates would inevitably remove the zinc from the fertiliser solution and render it unavailable for foliar absorption. However, the present inventors have found that if the liquid nitrogen solution of a co-solvent of urea, ammonium and nitrate forms of nitrogen is used then the disadvantages of the prior art are not observed, or are not observed to the same extent, over a time period.

In an embodiment, the fertiliser comprises a pH greater than about 55. The fertiliser is stable and does not exhibit precipitates at a pH of greater than 5.5. even over an extended storage period e.g. in excess of 30 days. In contrast to other approaches to micronutrient addition to liquid fertilisers, such as chelated metal systems, the stability of the fertiliser prepared as described herein does not have a great dependence on the pH of the liquid fertiliser and the micronutrient can remain soluble in very low (less than 5) and at moderately high (greater than 8) pH systems. It has been previously thought that when e.g. zinc is present in solution along with high levels of urea, the pH should be maintained between about 3.5 and 5 (preferably 3.7 to 4.5) in order to maintain stability and reduce precipitate formation. The ability to have a fertiliser containing a micronutrient at any pH including a pH greater than 5.5 facilitates the mixing and dilution of the material that is common practice during liquid fertiliser use, as well as the possibility to use a great variety of materials as the liquid fertiliser base.

It is thought that with other micronutrient incorporation approaches, the form of the liquid fertiliser base can result in incompatibility and precipitation of the solubilised micronutrient. For example, chelated metal systems involve the pre-solubilisation of the metal by chelation after which the solution is added to the liquid fertiliser to form the final micronutrient system. As the stability of this sort of chelated system is pH dependent (typically only stable in the range of pH 4 to 7) and the pH of the liquid fertiliser can vary, particularly those with urea (including the exemplar mentioned herein) the pH can be upwards of pH 8, the mixing of the chelated system with such a liquid fertiliser can lead to immediate precipitation of the solubilised metal. This is not seen with the present approach as the micronutrient material such as zinc is soluble in a wide range of pH solutions and is incorporated in amounts far below its theoretical solubility of the salts used of >30 g/mL at 0 °C.

The nitrogen fertiliser solution may include therein macronutrients. The micronutrients may comprise one or more of phosphorus (P), potassium (K), calcium (Ca), sulphur (S), magnesium (Mg), carbon (C), oxygen (0) and hydrogen (H). In an embodiment, the nitrogen solution comprises phosphorus (20 % P w/v), sulphur (8 - 26 % S w/v) and potassium (<40 % K w/v).

The nitrogen solution includes therein at least one micronutrient. The nitrogen solution may include more than one type of micronutrient. The micronutrient can be zinc. The micronutrient may comprise one or more of iron (Fe), boron (B), chlorine (CI), manganese (Mn), copper (Cu), molybdenum (Mo), nickel (Ni). The micronutrients may be present in single element form or in a more complex form (e.g., complexes or compounds). In embodiments, the formulation comprises co mixtures of molybdenum and zinc. In embodiments, the formulation comprises co io mixtures of molybdenum and copper.

In addition to macronutrients and micronutrients, the nitrogen-based fertiliser can further comprise one or more additives. The additive can be a corrosion inhibitor. The corrosion inhibitor can be to protect the storage tanks from the fertiliser stored within them. The one or more additive can comprise a nitrification inhibitor. The nitrification inhibitor can be 3,4-dimethylpyrazole (DMP) as described in AU2015227487: Nitrification inhibitors and formulations the entire contents of which are hereby incorporated by reference. The one or more additive can comprise a urease inhibitor. The urease inhibitor can be N-(n-butyl) thiophosphoric triamide (NBPT) as described in AU2013202217: Urease inhibitor formulations the entire contents of which are hereby incorporated by reference.

The micronutrient ions can be provided in the form of a nitrate salt. In an embodiment, the micronutrient ions are provided in the form of an acetate salt. The salts of micronutrient provided can be hydrated. The salt can be added to the nitrogen solution and agitated to effect dissolution. Not all salts provided will be directly soluble in the liquid nitrogen base, and the present invention does not intend to include in scope insoluble micronutrient salts. However, it is an option that an insoluble salt is first dissolved in a solvent such as water and the aqueous solution of that salt can be added to the aqueous nitrogen base.

The concentrated fertiliser can comprise a solubilised micronutrient in an amount in the range of from about 25 wt% to about 50.0 wt%. While up to 50 wt% can be incorporated into solution while remaining substantially clear and stable, less than

5 wt% is all that is required to be agronomically effective. In some embodiments, 0.3 wt% is all that is required to be agronomically effective. The concentrated solution is diluted to achieve these lower amounts of micronutrients. The amount of micronutrient dissolved in the concentrated solution of liquid nitrogen is typically higher than would be used in agricultural application (i.e. higher than 0.3 wt%).

The diluted fertiliser can comprise a solubilised micronutrient in an amount in the range of from about 0.04 to about 0.05 wt%. Alternatively, 1 to about 3 wt%. The concentrates are therefore the maximum salt concentration that can be obtained io based on long term physical stability. Prior to use, the concentrate is diluted for use.

The fertiliser is a substantially clear solution. In order to determine whether the solution is substantially clear, a clarity check can be performed. The clarity check can be to check whether there are insoluble materials in the solution. The solution of fertiliser should be mostly clear and mostly transparent after dissolution of the compounds added including the micronutrient. By substantially clear it is meant that there can be some undissolved material such as about 0.5, 0.75 or 1%, or more if tolerable, of added material that forms undissolved materials that affects the overall clarity. Unless the fertiliser itself is a suspension or emulsion, the clarity inspection method is an extremely sensitive and intuitive test index. A visual method is the first choice for clarity inspection. When the visual method cannot be used for effective judgment, and the solution is not coloured, the instrument method can be used to judge the extent of clarity result. The clarity inspection of coloured solutions needs to be judged by visual method for coloured solutions. In most instances herein, the solution will be coloured, i.e. blue, so a visual inspection is required for clarity.

If the instrument measurement method is used, there are three methods that can be used including: transmitted light, scattered light, and transmitted light-scattered light comparative measurement mode (ratio turbidity mode). The principle is that when the light source illuminates the liquid surface, there is a certain correlation between the transmitted light intensity, scattered light intensity, the ratio between the transmitted light intensity and the scattered light intensity and the turbidity of the test sample. By measuring the transmitted light intensity, the ratio of scattered light intensity, transmitted light intensity and scattered light intensity reflects the turbidity of the test product.

The fertiliser in concentrated form is advantageously stable for at least about 14 days. In an embodiment, the fertiliser is stable for 30 days. In an embodiment, the fertiliser is stable for 60 days. In an embodiment, the fertiliser is stable for 90 days. The stability can be at about 2 to about 4 degrees Centigrade. By stable, it is meant that the micronutrient in the fertiliser does not fully precipitate out of solution. A small percentage of micronutrient can precipitate out of solution whilst still being in scope. This is related to the clarity of the solution since any precipitate (or salt out) will be readily detected by a gradual or sudden change in the clarity of the fertiliser solution.

In use, the concentrated fertiliser can be delivered to the site at which it will be required. The concentrated fertiliser can be transferred to a tank for storage. When required for use, a portion of the concentrated fertiliser can be selected for use. A solution of aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen can be added to the concentrated solution in an amount that dilutes the solution to the required final diluted concentration. The fertiliser can then be applied. In an alternative embodiment, concentrate of the trace elements (micronutrients) are made at a central location and then dispatched to different distribution centres. At the distribution centre, the concentrate is diluted to the desired concentration before dispatch to customers.

The fertiliser can be directly surface applied, applied by fertigation, or applied by foliar spraying. If the fertiliser is surface applied, incorporation (e.g. by cultivation or irrigation) shortly after application can assist in reducing the risk of any volatilisation losses. The solution can be applied by irrigation systems or overhead sprinkler systems. The solution can be diluted with water if necessary. The solution can be applied neat. The naturally high nitrogen content of the fertiliser may allow large areas of e.g. grain and cotton crops to be covered quickly with low volume spray equipment. The fertiliser can be tank-mixed with some crop protection products, but compatibility tests should always be carried out before application as would be appreciated by the person skilled in this technical area. Where the formulation is to be applied to the soil, it will ideally be injected into the root zone or if sprayed onto the soil surface, incorporated by cultivation to ensure that immobile micronutrient e.g. zinc is located in close proximity to emerging root tips.

Small quantities of trace elements or micronutrients such as iron, manganese, zinc, copper, boron and molybdenum are needed by the plant. Trace elements can be applied as coatings to solid/ granular fertilisers or they can be added to liquid fertilisers. For coating applications, the common form of the micronutrients are io oxides; however, oxides are not water soluble. The challenge with the liquid application of the oxide form of a micronutrient is the insolubility in water and other liquid fertilisers. Therefore, prior to use in a liquid, the oxides are normally milled down and used to make an emulsion with liquid fertilisers. The emulsions can cause blockages in the liquid application equipment (also impacting the rate of application), in addition to settling of solids if stored for prolong period. Similarly, chelated metal systems when used with liquids are sensitive to pH resulting in precipitation out of the trace element (micronutrient) over time particularly when multiple products are mixed, as is typical with liquid fertilisers.

In embodiments of the present invention, the formulations described herein can lessen the issues arising from long-term storage of liquid fertilizer material, as the commonly used chelated metal ion systems typically suffer from precipitation issues after a relatively short period of storage. Furthermore, stability tends to be affected during mixing of the fertilizer product with other fertilizers, which is a common on-farm practice. Through the use of water-soluble salts of the desired elements (e.g. zinc), the need for strict conditions to retain solubility of the trace elements may be lessened and hence the long-term stability and mixability of the end product can be retained.

Brief Description of the Figures Embodiments of the invention will now be described with reference to the accompanying drawings which are not drawn to scale and which are exemplary only and in which:

Figure 1 is Table 1 showing sample preparation details for formulations used to exemplify the fertiliser.

Figure 2 is a graph showing storage temperatures across the physical stability monitoring period.

Figure 3A and 3B shows formulation LNZ02-1 (top) and 02-2 (bottom), before (left) and after (right pair) 1 month of storage at ambient (left of each pair) and low (right of each pair) temperatures, showing no physical changes or precipitation.

Figure 4A and 4B shows formulation LNZ03-2 before and after 7, 28 35 and 49 days of storage (from left to right) at ambient (top) and low (bottom) temperatures, showing no precipitation but a colour change of the ambient stored samples. "Before" images not taken of fridge stored sample.

Figure 5 shows formulations LNCoO1-2 before and after 14 days of storage at ambient and low temperatures.

Figure 6 shows formulations LNMoO1-1 before and after 14 days of storage at ambient and low temperatures.

Figure 7A and figure 7B show concentrates that were used to prepare the more dilute formulations analysed.

Detailed Description of Embodiments

The following examples are exemplary of embodiments of the invention, and of comparative embodiments not in the scope of the invention, all of which are not intended to be limiting.

In embodiments, the present invention provides a liquid nitrogen fertiliser that can contain soluble trace elements such as zinc, copper and molybdenum, in single element or combination. The liquid nitrogen fertilisers may contain urea, ammonium and nitrate forms of nitrogen. The soluble forms of trace element are provided such as zinc acetate, zinc nitrate copper sulphate, sodium molybdate in the liquid nitrogen fertiliser. The soluble forms of the trace elements can allow for the application of these fortified fertilisers through liquid and foliar application equipment. In embodiments, the formulations serve to lessen the issues arising from long-term storage of the material, as the commonly used chelated metal ion systems suffer from precipitation issues after a relatively short period of storage and also during mixing of the product with others, which is a common on-farm practice. Through the use of water-soluble salts of the desired elements (zinc, io copper and or molybdenum), the need for strict conditions to retain solubility of the trace elements is lessened and hence the long-term stability and mixability of the end product.

Example 1 - stability of the diluted formulations

The following dilute formulations were made by adding the mineral salts slowly to a nitrogen solution comprising 45% ammonium nitrate and 35% Urea (referred to as UAN32). During adding of the zinc salts, the solution was stirred moderately on a magnetic stirrer. After complete addition of the required amount of zinc compound, the formulation was stirred for a further 20 minutes to ensure complete dissolution.

1. LNZ02-1 - zinc nitrate hexahydrate (lwt%) 2. LNZ02-2 - zinc acetate dihydrate (lwt%) 3. LNZ02-3 - zinc sulfate heptahydrate (comparative) (lwt%) 4. LNZ02-4 - zinc sulfate heptahydrate + water (comparative) (lwt%) 5. LNZ03-1- zinc acetate dihydrate (3wt%) 6. LNZ03-2- zinc acetate dihydrate (5wt%) 7. LNC01-1- copper nitrate trihydrate(lwt%) 8. LNC01-2 - copper nitrate trihydrate (3wt%) 9. LNMoO1-1 - sodium molybdate dihydrate (lwt%)

In experiments 1 to 4 (LNZ02-1, LNZ02-2, LNZ02-3, LNZ03-4), an amount of zinc compound was added to result in a formulation having a wt% of zinc of about 1.00%.

In experiments 5 and 6 (LNZ03-1, LNZ03-2), an amount of zinc compound was added to result in a formulation having wt% of zinc of about 3.00% and 5.00% respectively.

The zinc sulfate heptahydrate (without water LNZ02-3) was found to not be sufficiently soluble in the nitrogen solution to reach the target concentration of 1% zinc. In order to improve solubility, the zinc sulfate heptahydrate was dissolved first in water and stirred for 1 hour (LNZ02-4). The required amount zinc sulfate solution io for LNZ02-4 was then sampled, while stirring to ensure homogeneity, and added to the nitrogen solution as described above.

Table 1 of Figure 1 shows the mass (g) of each Zn component added. The amount of each component required to achieve the targets was based on the theoretical zinc content of the zinc salts calculated from their chemical compositions. For example, for LNZ02-1, 4.5552g of zinc nitrate hexahydrate was added to the nitrogen solution resulting in a % of zinc ions of 1.00% as shown in the Table of Figure 1.

The zinc content of zinc acetate dihydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate are 29.8%, 22.0% and 22.7%, respectively. These are the zinc contents of the different salts (%w/w), for example the acetate and hydrate/water component of the zinc acetate dihydrate salt makes up 70.2% of the weight of the salt and the rest is the zinc. So, to get 1% zinc in the solution we need the formulation to be 3.35% zinc acetate dihydrate (as 29.8% of 3.35% is 1%).

In experiments 7 and 8 (LNC01-1 and LNC02-2, an amount of copper compound was added to result in a formulation having wt% of copper of about 1.00% and 3.00 wt% respectively.

In experiment 9 (LNMo01-1) an amount of molybdenum salt was added to result in a formulation having a wt% of Mo of about 1wt%.

After formulation, an aliquot of each formulation was taken and transferred to a 10 mL vial for storage in the fridge for low temperature stability testing whilst the original formulation vessel served as the sample for ambient storage.

The samples of each formulation were stored at (i) ambient and (ii) low temperatures on the bench or in the fridge, respectively, in the R&D laboratory. Both environments were equipped with a temperature data logger to monitor the conditions throughout the storage. Figure 2 shows the average temperature of the ambient environment to be 25.1 °C and that of the fridge to be 5.3 °C for the 29 days of storage. Notably, the fridge dropped to almost -5 °C around the 25 day io mark.

Stability Some of the samples were stored at ambient or in low temperatures for 29 days, during which no precipitation or physical changes were observed. Figure 3 shows the samples LNZ02-1 and LNZ02-2 before (A) and after (B) the storage period in the two environments.

Figure 4A shows the LNZ03-1 and LNZ03-2 samples after storage for 0, 7, 28, 35 and 49 days in ambient (left to right) and Figure 4B shows low temps on bench (left to right 7, 28, 35, 49).

LNZ02-3 was not included in the physical stability testing as the formulation could not be made due to this observed poor solubility. LNZ02-4 was only stable for 1 day. Crystal formation was observed after one day of storage for both the ambient and low temperature samples.

The successful zinc acetate formulation, LNZ02-2, was analysed for nutrient content. This showed the target of 1% zinc was achieved (Zn 1.4% w/v, N 41.1% w/v)). The pH of the formulations was measured to be 5.69.

For LNZ03-1 and LNZ03-2 where the colour change was observed over time, nutrient analysis was conducted, to ensure the observed colour change did not correspond to a change in nutrient content. The analysis gave 28.5%w/w N and 3.03%w/w Zn for formulation 03-1 and 26.4%w/w N and 5.03%w/w Zn for 03-2, which both closely match the anticipated analysis. This confirms the target of 3% and 5% Zn has been achieved and also that the colour change does not affect the nutrient content of the solutions. With the measured SG values of 1.38 and 1.39 for 03-1 and 03-2, respectively, this leads to 39.8%w/v N and 4.1%w/v Zn for 03-1 and 37.4%w/v N and 7.0%w/v Zn for 03-2. The pH of the solutions were measured to be 5.40 and 5.26, respectively.

The copper and molybdenum samples were stored at ambient or in low temperatures for 14 days, during which no precipitation or physical changes were io observed. Figures 5 and Figure 6 shows the samples LNC01-2 and LNMo1-1 before and after the storage period in the two environments.

Example 2

The procedure outlines methods to produce fully water-soluble trace elements, with a focus on zinc, copper and molybdenum. These instructions are to formulate the concentrate in UAN32 containing ammonium nitrate (36.9 - 49.9%) and Urea (31.2 - 40.9%) with the addition of trace elements, in the form of zinc nitrate (to a concentration of 34.5 - 45.3%), Zinc acetate (to a concentration of 19.8 to 29.1%), copper nitrate (to a concentration of 25.9 - 53%) and molybdenum (to a concentration of 16.7 - 23.8%).

Zinc Nitrate Concentrate:

Approximately 1000 L of the "trace element concentrate solution" (Zinc concentrate solution) can be made following the below instructions. • For these high concentrations, UAN32 must be heated to a temperature of at least about 50 °C before trace element is added to the UAN32, to ensure complete dissolution of trace elements. • Add 468 kg (354 L) of UAN32 to an adequately sized vessel ( 1000 L). • Heat to 50 °C using a heat jacket. • Add 1152 kg of zinc nitrate hexahydrate powder. • Add in small amounts while stirring, adding more zinc nitrate powder once last addition has been incorporate by stirring to avoid hold up and caking above the liquid level (minimises powder lost on vessel walls above liquid level). • After all zinc nitrate powder required has been added, stir for a further 15 minutes to ensure complete dissolution.

Zinc Acetate Concentrate:

Approximately 1000 L of the "trace element concentrate solution" (Zinc concentrate io solution) can be made following the below instructions. • For these high concentrations, UAN32 must be heated to a temperature of at last about 50 °C before trace element is added to the UAN32, to ensure complete dissolution of trace elements. • Add 945 kg (716 L) of UAN32 to an adequately sized vessel ( 1000 L). • Heat to 50 °C using a heat jacket. • Add 505 kg of zinc acetate dihydrate powder. • Add in small amounts while stirring, adding more zinc acetate powder once last addition has been incorporate by stirring to avoid hold up and caking above the liquid level (minimises powder lost on vessel walls above liquid level). • After all zinc acetate powder required has been added, stir for a further 15 minutes to ensure complete dissolution.

Copper Nitrate Concentrate:

Approximately 1000 L of the "trace element concentrate solution" (Copper concentrate solution) can be made following the below instructions. • For these high concentrations, UAN32 must be heated to a temperature of at least about 50 °C before trace element is added to the UAN32, to ensure complete dissolution of trace elements. • Add 565 kg (428 L) of UAN32 to an adequately sized vessel ( 1000 L). • Heat to 50 °C using a heat jacket. • Add 1215 kg of copper nitrate trihydrate powder. • Add in small amounts while stirring, adding more copper nitrate powder once last addition has been incorporate by stirring to avoid hold up and caking above the liquid level (minimises powder lost on vessel walls above liquid level). • After all copper nitrate powder required has been added, stir for a further 15 minutes to ensure complete dissolution.

Molybdenum Concentrate:

Approximately 1000 L of the "trace element concentrate solution" (Moly io concentrate solution) can be made following the below instructions. • For these high concentrations, UAN32 must be heated to a temperature of at least about 50 °C before trace element is added to the UAN32, to ensure complete dissolution of trace elements. • Add 1006 kg (762 L) of UAN32 to an adequately sized vessel ( 1000 L). • Heat to 50 °C using a heat jacket. • Add 314 kg of sodium molybdate dihydrate powder. • Add in small amounts while stirring, adding more sodium molybdate powder once last addition has been incorporate by stirring to avoid hold up and caking above the liquid level (minimises powder lost on vessel walls above liquid level). • After all sodium molybdate powder required has been added, stir for a further 15 minutes to ensure complete dissolution.

Blending of concentrate solution with UAN32 (Easy N):

1000 L of final product, Liquid N + trace elements where trace element concentration can range from 0.04% to 5% trace element can be made following the below instructions utilising the trace element concentrate solutions made in the instructions above. The outlined ratios are for the most typical agronomically used concentrations being 1%w/v for Zn and Cu and 0.04% for Mo, however scaling of the ratios will yield the desired end concentration.

I%w/v zinc from zinc nitrate concentrate: • Add 30.5 L of previously made zinc nitrate concentrate to an adequately sized vessel ( 1000 L). Heating (to 50 °C) the concentrate solution before blending to ensure there are no precipitation or settlements in the concentrate solution which would cause uneven distribution of the trace element. Add 969.5 L of UAN32 on top which will provide mixing, however if available further stirring can be utilised to ensure homogeneity.

1%w/v zinc from zinc acetate concentrate: • Add 51.3 L of previously made zinc acetate concentrate to an adequately sized vessel ( 1000 L). • Heating (to 50 °C) the concentrate solution before blending to ensure there are no precipitation or settlements in the concentrate solution which would cause uneven distribution of the trace element. Add 948.7 L of UAN32 on top which will provide mixing, however if available further stirring can be utilised to ensure homogeneity.

I%w/v copper from copper nitrate concentrate: • Add 24.2 L of previously made copper nitrate concentrate to an adequately sized vessel ( 1000 L). • Heating (to 50 °C) the concentrate solution before blending to ensure there are no precipitation or settlements in the concentrate solution which would cause uneven distribution of the trace element. Add 975.8 L of UAN32 on top which will provide mixing, however if available further stirring can be utilised to ensure homogeneity.

0.04%w/v molybdenum from moly concentrate: • Add 2.4 L of previously made moly concentrate to an adequately sized vessel ( 1000 L). • Heating (to 50 °C) the concentrate solution before blending to ensure there are no precipitation or settlements in the concentrate solution which would cause uneven distribution of the trace element. • Add 997.6 L of UAN32 on top which will provide mixing, however if available further stirring can be utilised to ensure homogeneity.

Figure 7 is a series of table showing that the concentrates from which the samples LNZO2-1 and LNZ02-2 were prepared. These concentrates can present a useful ways of storing the micronutrient prior to use in the field.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Any promises made in the present description should be understood to relate to some embodiments of the invention and are not intended to be promises made about the invention as a whole. Where there are promises that are deemed to apply to all embodiments of the invention, the applicant/patentee reserves the right to later delete them from the description and does not rely on these promises for the acceptance or subsequent grant of a patent in any country.

Claims (20)

1. A method for preparing a liquid fertiliser comprising a micronutrient, the method comprising the steps of providing a concentrated solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein the concentrated solution comprises a solvated nitrate or acetate micronutrient in the range of from about 25 wt% to about 55 wt%; adding a solution of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen to the concentrated solution in order to dilute the solution, wherein the diluted solution comprises the solvated micronutrient in the range of from about 0.04 to about 3 wt%.

2. The method of claim 1, wherein the micronutrient is zinc and the solvated nitrate or acetate micronutrient is zinc nitrate in the range of from about 34.5 wt% to about 45.3% wt%.

3. The method of claim 1, wherein the micronutrient is zinc and the solvated nitrate or acetate micronutrient is zinc acetate in the range of from about 19.8 wt% to 29.1 wt%.

4. The method of claim 1, wherein the micronutrient is copper and the solvated nitrate or acetate micronutrient is copper nitrate in the range of from about 25.9 wt% to about 53 wt%.

5. The method of claim 1, wherein the micronutrient is molybdenum and the solvated nitrate or acetate micronutrient is in the range of from about 16.7 wt% to about 23.8 wt%.

6. The method of any one of claims 1 to 5 further comprising the step of delivering the diluted solution as a liquid fertiliser.

7. A stable liquid fertiliser of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein urea is present in a range of from about 31.2 to about 40.9 wt%, the fertiliser comprising a solubilised nitrate or acetate micronutrient in an amount in the range of from about 25 wt% to about

55 wt%, wherein the fertiliser is a substantially clear solution, stable for at least about 30 days.

8. The stable liquid fertiliser of claim 7, wherein the micronutrient is zinc and the solvated nitrate or acetate micronutrient is zinc nitrate in the range of from about 34.5 wt% to about 45.3% wt%.

9. The stable liquid fertiliser of claim 7, wherein the micronutrient is zinc and the solvated nitrate or acetate micronutrient is zinc acetate in the range of from about 19.8 wt% to 29.1 wt%.

10. The stable liquid fertiliser of claim 7, wherein the micronutrient is copper and the solvated nitrate or acetate micronutrient is copper nitrate in the range of from about 25.9 wt% to about 53 wt%.

11. The stable liquid fertiliser of claim 7, wherein the micronutrient is molybdenum and the solvated nitrate or acetate micronutrient is in the range of from about 16.7 wt% to about 23.8 wt%.

12. The stable liquid fertiliser of any one of claims 7 to 11 wherein the system is heated in order to maintain stability.

13.A stable liquid fertiliser of an aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein urea is present in a range of from about 31.2 to about 40.9 wt%, the fertiliser comprising a solubilised nitrate or acetate micronutrient in an amount in the range of from about 0.04 wt% to about 3.0 wt%, wherein the fertiliser is a substantially clear solution, stable for at least about 30 days.

14. The stable liquid fertiliser of claim 13, wherein the micronutrient is zinc in the range of from about 1 wt% to about 3 wt%.

15. The stable liquid fertiliser of claim 13, wherein the micronutrient is copper in the range of from about 1 wt% to about 3 wt%.

16. The stable liquid fertiliser of claim 13, wherein the micronutrient is molybdenum in the range of from about 0.04 wt% to about 0.05 wt%.

17. The stable liquid fertiliser of any one of claims 7 to 16, wherein the aqueous nitrogen solution comprising a co-solvent of urea and ammonium nitrate forms of nitrogen is UAN32.

18. The stable liquid fertiliser of any one of claims 7 to 17 having a pH greater than 5.

19. Use of the stable liquid fertiliser of any one of claims 7 to 18 as a fertiliser.

20.A method for preparing an aqueous nitrogen liquid fertiliser comprising a micronutrient, the method comprising providing a co-solvent of urea and ammonium nitrate forms of nitrogen, wherein urea is present in a range of from about 31.2 to about 40.9 wt%,, adding a nitrate or acetate micronutrient salt to the liquid nitrogen solution, the salt, allowing or assisting the micronutrient salt to dissolve in the liquid nitrogen solution by applying heat, thereby forming a concentrated solution; wherein the concentrated solution comprises the solvated nitrate or acetate micronutrient in the range of from about 25 wt% to about 55 wt%.

LNZ02-1 LNZ02-2 LNZ02-3 LNZ02-4 LNZ03-01 LNZ03-2 LNC01-1 LNC01-2 LNMo01-1

zinc sulphate heptahydrate (g) 4.3967 4.3970 zinc acetate dihydrate (g) 3.3596 10.0700 16.7866 zinc nitrate hexahydrate (g) 4.5552 copper nitrate trihydrate (g) 3.0000 9.0000 sodium molybdate dihydrate (g) 1.9495 water (g) 13.1910 Easy N (g) 95.4583 96.6373 95.6104 82.4120 89.9316 83.2128 97.0000 91.0000 98.0505 % zinc sulphate heptahydrate 4.4000 4.4000 - - % zinc acetate dihydrate 3.4000 % zinc nitrate hexahydrate 4.6000 % copper nitrate trihydrate (98% pure material not compound) 2.9000 9.0000 % sodium molybdate dihydrate (98% pure material) 1.9000 % Easy N 95.4000 96.6000 95.6000 82.4000 - - 97.0000 91.0000 98.1000 wt% N 30.7300 31.1200 30.7800 26.5400 28.9600 26.7900 31.6000 29.3000 31.6000 wt% S 0.4900 0.4900 - - wt% Zn 1.0000 1.0000 1.0000 1.0000 3.0000 5.0000 wt%Cu 0.8000 3.1000 wt%Mo 0.8000

Figure 1

Figure 2

Figure 3A Figure 3B

Figure 4A

Figure 4B

Figure 6 Figure 5

Figure 7B Figure 7A