An Inhibitor for use in agriculture

Abstract

A formulation is disclosed comprising a solvent system comprising a polar aprotic solvent such as sulfolane; and an ethanolamine compound such as triethanolamine. The solvent system comprising dissolved therein a nitrification inhibitor 3,4-dimethyl pyrazole such as (DMP); and a urease inhibitor N-butyl thiophosphoric triamide such as (NBPT); wherein when the DMP:NBPT weight ratio changes the NBPT is present at less than a given percentage relative to the solvent system. 20 25 20 48 78 27 J un 2 02 5 A B S T R A C T A f o r m u l a t i o n i s d i s c l o s e d c o m p r i s i n g a s o l v e n t s y s t e m c o m p r i s i n g a p o l a r a p r o t i c 2 0 2 5 2 0 4 8 7 8 2 7 J u n 2 0 2 5 s o l v e n t s u c h a s s u l f o l a n e ; a n d a n e t h a n o l a m i n e c o m p o u n d s u c h a s t r i e t h a n o l a m i n e . T h e s o l v e n t s y s t e m c o m p r i s i n g d i s s o l v e d t h e r e i n a n i t r i f i c a t i o n i n h i b i t o r 3 , 4 - d i m e t h y l p y r a z o l e s u c h a s ( D M P ) ; a n d a u r e a s e i n h i b i t o r N - b u t y l t h i o p h o s p h o r i c t r i a m i d e s u c h a s ( N B P T ) ; w h e r e i n w h e n t h e D M P : N B P T w e i g h t r a t i o c h a n g e s t h e N B P T i s p r e s e n t a t l e s s t h a n a g i v e n p e r c e n t a g e r e l a t i v e t o t h e s o l v e n t s y s t e m . A B S T R A C T 2 0 2 5 2 0 4 8 7 8 2 7 J u n 2 0 2 5

Description

This is a divisional of 2024200928 with same title, the contents of which are hereby incorporated by reference in their entirety. However, where there is discrepancy between the specifications the present specification takes precedence. Technical field The present invention relates to nitrification inhibitors and urease inhibitors which are typically used with nitrogen containing fertilisers and urea containing fertilisers, respectively, to improve the efficiency of the fertiliser. Background Nitrogen is an essential plant nutrient. Nitrogen-based fertilisers are commonly used in agriculture, including ammonium-based fertilisers and urea. Ammonium based fertilisers are used world-wide as a primary source of added nitrogen in crop and pasture production. Increasing demands for improved yields and quality require an increase in "nitrogen use efficiency" (NUE). Conversion of ammonium (NH4+) to nitrate (NO3-) by microbial enzyme catalysis causes increased losses of nitrogen from the soil by: • leaching of soluble, mobile nitrate anions into groundwater and water runoff; •  de-nitrification by conversion of nitrate (via nitrite) to gaseous products, such as nitrous oxide (N20), which is a potent greenhouse gas. In the presence of oxygen, warm temperatures, moisture and soil bacteria, ammonium ions are converted to nitrate through a biochemical process of nitrification. A first bacterium Nitrosomonas converts ammonium to nitrite, and a second bacterium Nitrobacter converts nitrite to nitrate, which is readily lost from soils by leaching or denitrification. It is also known that other groups of non-bacterial micro-organisms collectively known as Archaea may also oxidize ammonium nitrogen. This process increases the chance of nitrogen moving out of 1 2025204878   27 Jun 2025 the plant root zone and consequently nitrification inhibitors are used with nitrogenbased fertilisers in situations where such losses are likely. Nitrification inhibitors delay the nitrification process by acting on the bacteria Nitrosomonas when nitrogen is present in the ammonium form. Most "nitrification inhibitors" (NI) block the reactive sites of ammonia oxidising bacteria (AOB). For better utilization of nitrogen-based fertilisers, nitrification inhibitors (NI) are added to the fertilisers, soils or agricultural areas. Known nitrification inhibitor are disclosed in AU2015227487: Nitrification inhibitors and formulations, the contents of which are hereby incorporated by reference in their entirety. As a source of nitrogen, urea (CO(NH2)2) represents more than 40% of the total nitrogen fertiliser applied to agricultural crops worldwide. However, urea is readily degraded in soil by the "urease" group of enzymes, which catalyses the reaction of urea with water to produce gaseous ammonia and ammonium ions (referred to as "urea hydrolysis"). The ammonia is readily volatile from the treated soil; leading to a loss of up to 60% of the applied urea as a result of this enzymatic hydrolysis. In order to delay this hydrolysis, "urease inhibitors" (UI) have been applied to urea based fertilisers in an attempt to reduce the rate of urea hydrolysis and subsequent loss of ammonia. Examples of such urease inhibitors include the N-alkyl thiophosphoric triamides such as N-(nbutyl)thiophosphoric triamide (NBPT). For better utilization of urea-based fertilisers, urease inhibitors (UI) are added to the fertilisers, soils or agricultural areas. Known urease inhibitors are disclosed in AU2013202217: Urease inhibitor formulations, the contents of which are hereby incorporated by reference in their entirety. It is typical for the nitrification inhibitor and the urease inhibitor to be added to the soil separately. Nitrification inhibitors are typically applied at higher rates than urease inhibitors for the desired efficacy, the ratio is usually 2 : 1 (NI : UI). The 2 2025204878   27 Jun 2025 nitrification inhibitor is typically applied as an acid-based solution (less than pH 5.5). The NI in cationic form is thought to assist in binding the NI to the soil infrastructure. As the skilled person will appreciate most urease inhibitors are acid sensitive, accordingly the NI and UI are typically applied at different times to the soil. If the NI and UI are applied together, the acid from the NI reacts with the UI thereby destroying it. In a comparative experiment undertaken by the present inventors to demonstrate the instability of a UI in a NI formulation, an exemplary urease inhibitor NBPT was added to a formulation of a known solution of a nitrification inhibitor 3,4-dimethyl pyrazole (DMP) (refer to comparative experiment 2 in this document). The DMP was provided in a solvent system of glycolic acid and tetramethylene sulfone (sulfolane) (sold commercially under the Brand eNpower®). As expected, due to the acidic nature of the nitrification inhibitor solution, the NBPT urease inhibitor degraded quickly. There exists a need for improved nitrification inhibitors and improved urease inhibitors; and furthermore, improved methods of delivering the inhibitors in formulations for use in agricultural settings. Summary of invention Herein described is a formulation comprising a solvent system comprising: (i) a polar aprotic solvent such as sulfolane; and (ii) an ethanolamine compound such as triethanolamine; the solvent system comprising dissolved therein: (iii) a nitrification inhibitor such as 3,4-dimethyl pyrazole (DMP); and (iv) a urease inhibitor such as N-butyl thiophosphoric triamide (NBPT); wherein the amount of urease inhibitor in grams is present is in the range of above about 18.25% to below about 23.25 % of urease inhibitor (in grams) relative to the solvent (in grams) wherein the total DMP and NBPT is less than 40%. This formulation is charactersed by a relatively high loading of the urease inhibitor (NBPT), in the range of above 18.25% to below 23.25% relative to the solvent 3 2025204878   27 Jun 2025 system, combined with a moderate amount of the nitrification inhibitor (DMP) such that the total solids content (DMP plus NBPT) remains below 40% by weight of the formulation. These formulations are optimised to deliver robust urease inhibition performance while maintaining chemical stability within the solvent system. The relatively low total solids content mitigates the risk of instability associated with acidic or high-concentration environments. The DMP to NBPT ratio is approximately balanced, typically close to 1:1, reflecting a formulation strategy aimed at concurrently managing urease activity and nitrification processes without overwhelming the solvent system's stability limits. The weight ratio of nitrification inhibitor (DMP) to urease inhibitor (NBPT) is a parameter in stable formulations. Commercially, a DMP:NBPT ratio of 2:1 is widely used because nitrification inhibitors are typically applied at higher rates than urease inhibitors to effectively suppress soil nitrification processes. This aligns with the differing modes of action: while urease inhibition requires short-term suppression of enzymatic activity at the soil surface, nitrification inhibition typically requires sustained activity within the soil profile to limit ammonium oxidation over a longer timeframe. The DMP:NBPT ratio does not only influence field efficacy but also directly impacts the chemical environment of the formulation. DMP-containing formulations are typically mildly acidic due to the nature of the solvent system and the acidity of DMP when solubilised. As the proportion of DMP increases relative to NBPT, the formulation’s acidity increases correspondingly. This acidity poses a risk to the stability of NBPT, which is known to be susceptible to acid-catalysed hydrolysis and degradation over time. Therefore, the DMP:NBPT ratio is a key driver in determining both the agronomic balance of inhibitor performance and the chemical stability constraints that must be managed in the formulation. In a first aspect of the present invention there is provided a formulation comprising: a solvent system comprising: (i) a polar aprotic solvent such as sulfolane; and 4 2025204878   27 Jun 2025 (ii) an ethanolamine compound such as triethanolamine; the solvent system comprising dissolved therein: (iii) a nitrification inhibitor such as 3,4-dimethyl pyrazole (DMP); and (iv) a urease inhibitor such as N-butyl thiophosphoric triamide (NBPT); 5       dissolved in the solvent system; wherein: the formulation satisfies either: (i) a weight ratio of DMP to NBPT from about 2.5:1 to about 5:1, with NBPT present at less than about 18% by weight relative to the solvent system, and total 10 solids less than about 45% by weight; or (ii) a weight ratio of DMP to NBPT from about 0.5:1 to about 1.2:1, with NBPT present at about 20% to about 44% by weight relative to the solvent system, and total solids less than about 45% by weight. 15 In an embodiment there is provided a formulation comprising: a solvent system comprising: (i) a polar aprotic solvent such as sulfolane; and (ii) an ethanolamine compound such as triethanolamine; the solvent system comprising dissolved therein: 20       (iii) a nitrification inhibitor such as 3,4-dimethyl pyrazole (DMP); and (iv) a urease inhibitor such as N-butyl thiophosphoric triamide (NBPT); dissolved in the solvent system; wherein a weight ratio of DMP to NBPT from about 2.5:1 to about 5:1, with NBPT present at less than about 18% by weight relative to the solvent system, and 25 total solids less than about 45% by weight. In an embodiment there is provided a formulation comprising: a solvent system comprising: (i) a polar aprotic solvent such as sulfolane; and 30       (ii) an ethanolamine compound such as triethanolamine; the solvent system comprising dissolved therein: (iii) a nitrification inhibitor such as 3,4-dimethyl pyrazole (DMP); and (iv) a urease inhibitor such as N-butyl thiophosphoric triamide (NBPT); dissolved in the solvent system; 2025204878   27 Jun 2025 wherein a weight ratio of DMP to NBPT from about 0.5:1 to about 1.2:1, with NBPT present at about 20% to about 44% by weight relative to the solvent system, and total solids less than about 45% by weight. . The present formulation is stable against degradation of the NBPT over defined circumstances. Previously, the nitrification inhibitor was provided in a first formulation; and the urease inhibitor was provided in a second, separate, formulation. The inventors have found that surprisingly, any degrading effect of the nitrification inhibitor on the urease inhibitor may be prevented or reduced when the present solvent system is used as defined. The present formulation enables the co-formulation of a nitrification inhibitor (DMP) and a urease inhibitor (NBPT) in a single stable product. In embodiments, this can overcome longstanding challenges in the field, where combined formulations have been impractical due to the chemical instability of NBPT in acidic nitrification inhibitor systems. By defining specific and interdependent constraints on the DMP:NBPT ratio, the NBPT concentration relative to the solvent, and the total solids content, the present invention can in embodiments achieve a balance that maintains both chemical and physical stability. At higher DMP:NBPT ratios, where the risk of NBPT hydrolysis is greatest due to acidity and solvation pressure, the formulation imposes a limit on NBPT concentration relative to the solvent to prevent degradation. Conversely, at lower DMP:NBPT ratios, where the chemical environment is less acidic and solubility competition is reduced, the formulation tolerates higher NBPT loadings, enabling broader use-case flexibility. Across both ratio regimes, a total solids cap ensures the formulation remains physically homogeneous and storage stable. This approach can enable the delivery of both nitrification inhibition and urease inhibition from a single liquid formulation without the need for sequential application or separate products. In formulations where the weight ratio of DMP to NBPT is increased beyond typical commercial levels, particularly in the range of about 2.5:1 to about 5:1, the formulation presents significant chemical stability challenges. This is due to the 6 2025204878   27 Jun 2025 cumulative acidity associated with the high concentration of DMP within the solvent system, which increases the risk of acid-catalysed hydrolysis of NBPT. Furthermore, the physical solubility limits of the formulation are strained at these high DMP loadings. NBPT becomes increasingly difficult to stabilise both chemically and physically as its concentration relative to the solvent rises. It has been determined that, within this high ratio regime, NBPT must be limited to less than about 18% urease inhibitor (in grams) relative to the solvent (in grams) in order to maintain chemical stability and prevent degradation. This less than about 18% threshold reflects the maximum NBPT load that the solvent system can stably accommodate in the presence of a high proportion of nitrification inhibitor (DMP), specifically when the DMP to NBPT weight ratio is from about 2.5:1 to about 5:1. Exceeding this threshold can result in either chemical degradation of NBPT, due to acid-catalysed hydrolysis, or physical instability, such as crystallisation or phase separation. In an embodiment there is less than about 20% or 22% urease inhibitor (in grams) relative to the solvent. Additionally, the total solids content in the said formulation with the about 18 % threshold must be constrained to less than about 40, 42 or 45% total solids by weight to avoid precipitation or phase instability. These constraints are believed to be critical to achieving a stable formulation when the DMP:NBPT ratio is within the about 2.5:1 to about 5:1 range. Total solids refers to the combined weight percentage of the active ingredients namely, the nitrification inhibitor (DMP) and the urease inhibitor (NBPT) relative to the total formulation. That is, total solids = total DMP + total NBPT, with the balance comprising the solvent system. The solids content reflects the overall loading of functional actives. Higher solids concentrations can increase the likelihood of chemical interaction or degradation, particularly under acidic or reactive conditions. In formulations where the DMP to NBPT weight ratio is within the range of about 0.5:1 to about 1.2:1, the formulation tolerates substantially higher loadings of NBPT relative to the solvent system. This is because the lower DMP content results in a 7 2025204878   27 Jun 2025 formulation with reduced acidity and lower chemical stress on NBPT. As a result, NBPT can be present at concentrations of about 18, 20 or 22% to about 40, 42, 44 or 46%, such as about 20 to about 44%, relative to the solvent system without risking chemical degradation. In this embodiment, the solvent system, comprising a polar aprotic solvent and an ethanolamine compound, provides sufficient solvency capacity to maintain NBPT in a stable, dissolved state within this ratio range about 0.5:1 to about 1.2:1. However, the total solids content of the formulation must be maintained at less than about 40, 42 or 45% by weight to ensure physical stability. Exceeding this total solids threshold can lead to precipitation, crystallisation or phase separation, even in the absence of chemical instability. The thresholds provided herein may enable the development of formulations with higher NBPT loadings (e.g. 20%-44%), suitable for use cases where enhanced urease inhibition is desired alongside lower nitrification inhibitor content. In a second aspect of the present invention there is described a formulation comprising a solvent system comprising: (i) a polar aprotic solvent such as sulfolane; and (ii) an ethanolamine compound such as triethanolamine; the solvent system comprising dissolved therein: (iii) a nitrification inhibitor such as 3,4-dimethyl pyrazole (DMP); and (iv) a urease inhibitor such as N-butyl thiophosphoric triamide (NBPT); dissolved in the solvent system, wherein: when the DMP:NBPT weight ratio is from about 2.5:1 to about 5:1, NBPT is present at less than about 18% relative to the solvent system; when the DMP:NBPT weight ratio is from about 1.7:1 to about 2.5:1, NBPT is present at less than about 23% relative to the solvent system; when the DMP:NBPT weight ratio is from about 0.2:1 to about 1.7:1, NBPT is present at about 28% or less relative to the solvent system; and the total solids content is less than about 45% by weight It has been determined that the ratio of DMP to NBPT exerts a dominant influence on the chemical stability of the formulation. As the ratio increases, the formulation 8 2025204878   27 Jun 2025 becomes progressively more acidic due to the higher proportion of DMP, which in turn increases the risk of acid-catalysed hydrolysis of NBPT. Furthermore, higher DMP loadings place additional pressure on the solubility balance of the system. To address these interrelated chemical and physical constraints, the inventors have identified three operational ratio bands, each associated with specific stability requirements. These can be broadly defined as follows: In the high ratio band, where the DMP to NBPT ratio is from about 2.5:1 to about 5:1, the formulation must impose the most restrictive NBPT loading. This is less than about 18, 20 or 22% relative to the solvent system to protect NBPT from degradation, while maintaining total solids below about 40, 42, 45% to ensure physical stability. In the intermediate band, where the DMP to NBPT ratio is from about 1.7:1 to about 2.5:1, the acid load is moderate but still significant. This band permits NBPT at a higher level. This is less than about 25 or 23% relative to the solvent system while maintaining the same total solids constraint. This band includes ratios commonly used in commercial formulations but imposes necessary limits to ensure NBPT stability. In the low ratio band, where the DMP to NBPT ratio is from about 0.2:1 to about 1.7:1, the formulation is comparatively chemically benign. Here, the acid burden from DMP is sufficiently low that NBPT can be present at concentrations of up to about 26, 28 or 30% relative to the solvent system without risk of degradation. Nonetheless, even in this low ratio band, the total solids content must still be maintained below about 45% by weight to prevent phase separation, precipitation, or crystallisation. Without wishing to be limited by theory, this banded framework is thought to provide a robust, predictable basis for formulating stable combinations of nitrification and urease inhibitors across a wide range of use cases, overcoming prior limitations associated with NBPT degradation in acidic systems. The present formulation is advantageous because it comprises a stable formulation 9 2025204878   27 Jun 2025 with both the nitrification inhibitor and the urease inhibitor in the same formulation. The formulation is stable to APVMA Guidelines. APVMA “Guidelines for the Generation of Storage Stability Data of Agricultural Chemical Products”. These guidelines suggest the use of the accelerated storage conditions of 40 °C for 8 5 weeks to simulate 2 years of storage. The solvent system comprises solvents that can solubilise DMP and NBPT. The solvent system comprises a polar aprotic solvent. The polar aprotic solvent is a solvent that lacks an acidic proton and is polar. Such solvents typically lack 10 hydroxyl and amine groups. These solvents do not serve as proton donors in hydrogen bonding, although they can be proton acceptors. Many solvents, including chlorocarbons and hydrocarbons, are classifiable as aprotic, but polar aprotic solvents are of particular interest for their ability to dissolve salts. Preferably, the polar aprotic solvent is water soluble. 15 The aprotic solvent should be one which is “agriculturally accepted” and therefore is less likely to be phytotoxic. Agriculturally acceptable aprotic solvents are typically already in use in agriculture. 20 The term "agriculturally acceptable" includes solvents or additives that are suitable for agricultural formulations. For example "agriculturally acceptable excipient" includes but is not limited to water, alcohols such as butanol or glycol as well as their ethers and esters, ketones such as acetone, methyl ethyl ketone, sulfones such as dialkyl sulfones, polymethylene cyclic sulfones, petroleum fractions, 25 mineral or vegetable oils, aliphatic chlorinated hydrocarbons, water-soluble or strongly polar solvents, liquefied gases such as halogenated hydrocarbons as well as butane, propane, nitrogen and carbon dioxide, carboxymethyl cellulose, ethylene glycol, propylene glycol, kaolin, bentonite, dolomite, calcium carbonate, talc, powder magnesia, Fuller's earth, gypsum, diatomaceous earth and China clay. 30 The polar aprotic solvent can be selected from one or more of N-Butyl-2-pyrrolidone (NMP), an organosulphur compound including sulfolane and Dimethyl sulfoxide (DMSO) and dihydrolevoglucosenone (cyrene). 2025204878   27 Jun 2025 In an embodiment, the solvent system comprise an aprotic solvent selected from the group consisting of dialkyl sulfones according to Structure II, polymethylene cyclic sulfones according to Structure III, and mixtures thereof; R» 0=S--R2 Structure II wherein R3 = alkyl Ci to Q R; = alkyl C, to C* Structure III wherein n - 3 to 6 5 In a preferred embodiment, the aprotic solvent is sulfolane. The other solvent in the solvent system is an ethanolamine. The ethanolamine can be viscous, and the aprotic solvent can help to thin the solvent system to be more 10 commercially useful. In an embodiment, the ethanolamine is a pH balancer. The ethanolamine can be basic which means it can be useful as a buffering agent and or stabiliser. In an embodiment, the ethanolamine compound is diethanolamine or triethanolamine 15 (TEA). In an embodiment, the co-solvent fraction comprises both diethanolamine and triethanolamine. Other ethanolamines such as monoethanolamine, N-Isopropylethanolamine, 2-Dimethylaminoethanol, N-Butyldiethanolamine and similar are also in scope 20 In an embodiment, the other solvent fraction is selected from the group consisting of hydroxyethyl and hydroxypropyl amines according to Structure IV, in which the amine can be a primary, secondary or tertiary amine and the number of hydroxyethyl or hydroxypropyl groups can be 1, 2 or 3, 2025204878   27 Jun 2025 R6 rM-r5 Structure IV wherein R^andR' are independently II, Ci -Ct> alkyl or OH OH R«= -CHj-CH—Rt R7 = HorCHj In a preferred embodiment, the ethanolamine is triethanolamine. 5 Described herein is that the nitrification inhibitor compound may be selected from the group consisting of Formulae 1 to 6, as laid out below: Formula 1                Formula 2               Formula 3 Formula 4 Formula 5 Formula 6 Wherein: 10             Formula 1 is a 3,4,5-substituted pyrazole; Formula 2 is a 3,5-substituted 1,2,4-triazole; 2025204878   27 Jun 2025 Formula 3 is a 4,5-substituted 1,2,3-triazole; Formula 4 is a 2,4,6-substituted pyridine; Formula 5 is a 2,4,6-substituted pyrimidine; and Formula 6 is a 2,4,6-substituted 1,3,5-triazine. R1, R2 and R3 (if present) can each be independently selected from hydrogen, hydroxyl, halo, amino, thio, C1-10 alkyl, C1-10 alkylamino, C1-10 alkylhalo, C1-10 alkylthio, C2-10 alkenyl, C2-10 alkenylamino, C2-10 alkenylhalo, C2-10 alkenylthio, C2-10 alkynyl, C2-10 alkynylamino, C2-10 alkynylhalo, C2-10 alkynylthio, C1-10 alkoxy, C1-10 alkoxyhalo, and C1-10 alkylcarbonylamino. When the nitrification inhibitor compound is or comprises Formula 3, R1, R2 and / or R3 may be joined together to form a 3-10 membered monocyclic or fused bicyclic heteroaryl. In a further embodiment, the heteroaryl may further be optionally substituted with one or more of the above substituents. In an embodiment, the compound of formula 3 may be selected from 4-butyl-1H-1,2,3-triazole-1-butanoic acid ethyl ester; 2-[3-[4,5-di(hydroxymethyl)-1H-1,2,3-triazole]propyl]-isoindoline-1,3-dione; 2-[3-[4,5-(methyl ethanoate)-1H-1,2,3-triazole]propyl]-isoindoline-1,3-dione; ethyl 4,5-bis(hydroxymethyl)-1H-1,2,3-triazole-1-butyrate; ethyl 4,5-bis(methyl ethanoate)-1H-1,2,3-triazole-1-butyrate; ethyl 4,5-bis(methyl ethanoate)-1H-1,2,3-triazole-1-acetate; 1-butyl-4-propyl-1H-1,2,3-triazole; 1-(2-methoxyethyl)-4-butyl-1H-1,2,3-triazole; 4-propyl-1H-1,2,3-triazole-1-ethanol; and 1-(3-butyn-1-yl)-4-propyl-1H-1,2,3-triazole; or agriculturally acceptable salts thereof. The inhibitor compound may be selected from the group consisting of 3-methyl pyrazole, 1,2,4-triazole, benzotriazole, 2-ethynyl-pyridine, 2,4-diamino-6-trichloromethyl-1,3,5- triazine, 2-amino-4-methyl-6-trichloromethyl-1,3,5-triazine, 2-chloro-6-trichloromethyl-pyridine and 2-amino-4-chloro-6-methyl-pyrimidine or agriculturally acceptable salts thereof. Combinations of two or more nitrification inhibitors can also be used in formulations according to the invention. The nitrification inhibitor compound is not selected from pyridine citrate, pryridine tartrate, pyridinium tartrate, 1,3,5-triazine-2,4,6-triamine citrate, 1,3,5-triazine-2,4,6-triamine tartrate, or ethenylpyridine glycolate. 13 2025204878   27 Jun 2025 In the present invention, the nitrification inhibitor is 3,4-dimethyl pyrazole (DMP). The urease inhibitor can be selected from the group consisting of N-substituted 5 thiophosphoric triamides and N-substituted phosphoric triamides represented by Structure I and mixtures thereof, X HjN----P----NH2 NH 11----¥ Structure I wherein X = 0 or S, R1 = unsubstituted and substituted C3 -C6 alkyl, unsubstituted and substituted C5 -C8 cyclo alkyl, phenyl and substituted phenyl 10 having a nitro, amino, alkyl, or halide substituent; and Y = H, NO2, halide, NH2 or C to Cs alkyl; The urease inhibitors used in these formulations can include: • N-alkyl-thiophosphoric triamides; 15       • N-alkyl-phosphoric triamides; • N-cycloalkyl-thiophosphoric triamides; • N-cycloalkyl-phosphoric triamides; • N-aryl-thiophosphoric triamides; or • N-aryl-phosphoric triamides, 20 where the alkyl, cycloalkyl or aryl groups may be further substituted with chloro-, nitro- or amino-groups. Commonly available urease inhibitors include N-butyl thiophosphoric triamide (NBPT), N-cyclohexyl phosphoric triamide (CHPT) and 2-nitrophenyl phosphoric triamide (2NPT). Many other urease inhibitors can be used 25 in formulations as known to those skilled in the art. Combinations of two or more urease inhibitors can also be used in formulations. In the present invention, the urease inhibitor is N-butyl thiophosphoric triamide (NBPT). 2025204878   27 Jun 2025 Thus, in one aspect there is provided a formulation comprising a solvent system comprising: (i) sulfolane; and 5        (ii) triethanolamine; the solvent system comprising dissolved therein: (iii) 3,4-dimethyl pyrazole (DMP); and (iv) N-butyl thiophosphoric triamide (NBPT); The formulation has the thresholds as defined herein. 10 The solvent system, including the specified sulfones, may provide excellent stability and solubility for the urease inhibitors. They also have, in embodiments, environmental and occupational health and safety advantages. Preferably, the primary solvent is tetramethylene sulfone which is readily biodegradable in soils 15 (half life is 10 days) and does not present an ecotoxicological hazard (the LC50 is greater than 1000 mg / l for fish, algae and invertebrates). Tetramethylene sulfone has a high boiling point (284 degrees Centigrade), is non-flammable and is not classified as a Dangerous Good or Hazardous Substance. 20 In embodiment, it is thought that: • the formulations according to embodiments of the invention can be applied directly into liquid fertilizer or liquid waste containing urea compounds; • the formulations according to embodiments of the invention can be sprayed directly onto, and mixed into, solid wastes containing urea compounds; 25       • the formulations according to embodiments of the invention have low viscosity, thereby facilitating rapid and uniform spreading on the surface of urea granules; • the formulations according to embodiments of the invention can be applied to the surface of urea granules, which absorb the formulation, penetrating 30          deep into the solid granule ("impregnating" the granule structure); • urea granules coated with the formulations according to embodiments of the invention remain robust during storage, transport and handling, thereby retaining their hardness and crush strength; 2025204878   27 Jun 2025 • urea granules coated with the formulations according to embodiments of the invention hydrolyse more slowly in soils than urea granules treated with the prior art formulation, thereby achieving the desired slow release of ammonia for most efficient uptake by crops and plants. The slower rate of urea 5          hydrolysis leads to a lower pH in proximity to the urea granules which results in a higher ratio of stable ammonium to ammonia; and • urea granules coated with the formulations according to embodiments of the invention remain stable and retain their urease inhibition activity during storage in hot climates up to 40'C for more than 3 months. 10 A surfactant can be added to assist in formation of the coating. A stabiliser could be added to increase the longevity of the coating. The stabiliser could be a magnesium sulfate added into the formulation in an attempt to increase the inhibitor longevity when coated on urea. 15 In one aspect there is provided a method of preparing a formulation for use with a fertiliser, the method comprising the steps of providing a solution of urease inhibitor N-butyl thiophosphoric triamide (NBPT) in a solvent system comprising a polar aprotic solvent such as sulfolane; 20 and a solvent fraction comprising an ethanolamine compound such as triethanolamine; adding a nitrification inhibitor 3,4-dimethyl pyrazole (DMP) to the solution, adjusting or controlling the DMP:NBPT ratio to be within the range disclosed herein, 25          adjusting or controlling the NBPT% by weight relative to the solvent system to be within the threshold defined herein, and adjusting or controlling the total solids content to be within the threshold defined herein. 30 The formulation can be used as a coating. The formulation can be added to a liquid fertiliser. The liquid fertiliser can be a solution of urea and ammonium nitrate in water (UAN). Brief Description of the Figures 2025204878   27 Jun 2025 Embodiments of the invention and other embodiments will now be described with reference to the accompanying drawings which are not drawn to scale and which are exemplary only and in which: 5 Figure 1 is a table showing the sample preparation summary of the three formulations Figure 2 is a calculation of the expected analyte concentration from the 10 known mass of sample added to the volumetric flask. Figure 3a is a graph showing DMP concentrations over time based on HPLC analysis of DIF2-1 and DIF2-2. 15         Figure 3b is a graph showing NBPT concentrations over time based on HPLC analysis of DIF2-2 and DIF2-3. Figure 4 is a table showing the sample preparation summary of the two formulations in experiment 2. 20 Figure 5 are graphs showing HPLC chromatograms of the 50 pg / mL NBPT standard (top) and the DIF3-2 sample (bottom) showing the lack of the NBPT signal at 4.4 minutes in the DIF3-2 sample. 25          Figure 6 is a graph of data from a plurality of stability experiments showing the rations of DMP:NBPT, the amount of solvent to DMP and NBPT respectively, and the % of solids (DMP + NBPT). Detailed Description of Embodiments of the Invention 30 Examples: Experiment 1 Chemical stability of DMP and NBPT in DI water to form a baseline expectation of other formulations stability 2025204878   27 Jun 2025 The aim of this experiment was to assess the chemical stability of 3,4-dimethylpyrazole (DMP) and N-(n-butyl)thiophosphoric triamide (NBPT) in deionised water (DI) water over time to gain an understanding of what is to be 5 expected in terms of chemical stability from other formulations. Secondary aim is to assess if there is any detrimental interaction between DMP and NBPT to inform the potential for e.g. a dual inhibitor coating formulation. The ratio of DMP to NBPT used in this experiment was based on the amount of 10 these inhibitors currently applied to urea and green urea products. DMP as a formulation is currently applied to urea at about 5.3 kg / t of final product and NBPT is currently applied at 2.4 kg / t of urea. As the current nitrification inhibitor formulation comprises about is 17.6 wt% DMP and the current urease inhibitor formulation comprises about 20 wt% NBPT, this leads to an approximate 2:1 ratio 15 of DMP:NBPT required in a dual inhibitor coating to provide an equivalent of the current amounts of DMP and NBPT used for urea and green urea, respectively. Three formulations were made: • DMP in water, 20      • NBPT in water and • DMP and NBPT (dual) in water. DMP (as required) was added to DI water (50 g) and stirred until dissolved. NBPT (as required) was added and stirred until it dissolved. The mixture was stirred for a 25 further 20 minutes to ensure homogeneity before subsampling. Table 1 of Figure 1 shows the sample preparation summaries. An aliquot of each sample (approx. 10 mg; different every time) was added to a volumetric flask and made up to 10 mL with the relevant HPLC solution. The 30 resulting solution was then sonicated to ensure the solution was homogeneous. With the mass of the samples added to the flasks known, the expected concentrations of the analytes in the HPLC sample can be calculated as shown in Table 2 of Figure 2. The graphs of the DMP and NBPT concentrations over time for 2025204878   27 Jun 2025 the sample can be seen in the graphs of Figure 3. As the graphs of Figure 3 show there is no noticeable loss of DMP or NBPT concentration over the monitoring period indicating both that DMP and NBPT are stable over time in solution when there are no other components present and also that DMP and NBPT can be safely added together into future dual inhibitor formulations as they do not interact in solution. In conclusion, DMP and NBPT were seen to display no degradation over upwards of 9 weeks in DI water and further showed no detrimental interactions with each other. The pH of the solutions were between 5 and 8 indicating chemical stability of the inhibitors is not influence by pH within that range. Comparative experiment 2 Chemical stability of NBPT in eNpower (DMPG) to form a dual inhibitor coating The aim of this experiment was to assess the physical and chemical stability of N-(n-butyl)thiophosphoric triamide (NBPT) in a known solution of nitrification inhibitor comprising a DMP glycolate over time to assess its potential as a dual inhibitor coating. The known DMPG is sold under the brand name eNpower. Two sample formulations were made by mixing glycolic acid (46.75 g) and sulfolane (46.75 g). • To one batch was added DMP (31.00 g) and NBPT (15.50 g) with stirring to dissolution after addition of each solid to form DIF3-1. • To the other batch NBPT (15.50 g) alone was added and stirred until dissolution to form DIF3-2. The table of Figure 4 shows the formulation summaries. Immediately after the sample preparation DIF3-2 a strong odour of sulfur was noticeable, more pungent than the typical NBPT odour. Upon resting the sample for a day, the solution separated into two liquid phases. A cloudy, oily liquid formed on top and a clear, less viscous liquid formed on the bottom. For DIF3-1, a lower layer was much smaller and can barely be seen as a clear thin layer. The same behaviour was 19 2025204878   27 Jun 2025 seen with the samples stored in the fridge. As can be seen in the HPLC graph of Figure 5, DIF3-2 showed no signal eluting at 2.8 minutes, indicating no remaining NBPT in the sample and hence complete degradation of the NBPT in the carrier solution. The figure at bottom shows the HPLC chromatograms of one of the NBPT standards showing the expected elution time of the NBPT, and the DIF3-2 chromatogram showing no such signal In conclusion, NBPT is not stable either chemically or physically in a solution comprising DMPG carrier solution as two liquid phases were seen to form soon after preparation of the formulations and no NBPT was detected by HPLC analysis hence there is little to no potential for adding NBPT to a DMPG formulation to form a dual inhibitor formulation. Experiment 3 Physical and chemical stability assessment of dual inhibitors The incorporation of the nitrification inhibitor, DMP, into a solution of a urease inhibitor containing NBPT, was investigated to determine whether the previously observed long-term stability of NBPT in the formulation could be maintained after DMP addition to form a stable dual inhibitor coating. Herein the creation and stability assessment of such formulations is investigated using test methods from the APVMA “Guidelines for the Generation of Storage Stability Data of Agricultural Chemical Products”. (Australian Pesticides and Veterinary Medicines Authority. 2020. “Generation of storage stability data for agricultural chemical products”. apvma.gov.au. Accessed November 19, 2020. https: / / apvma.gov.au / node / 1042). These guidelines suggest the use of the accelerated storage conditions of 40 °C for 8 weeks to simulate 2 years of storage. The formulations were made by first making a base by stirring the solvents of TEA, surfactant and sulfolane for 5 minutes at 500 rpm. NBPT was then added and then the mixture was stirred until clear (approx. 30 minutes at 750 rpm). The DMP was then added, and the formulation stirred again at 750 rpm for 30 minutes. For formulations in which the subsequent dissolution of DMP was not complete after the 30 minutes, the formulations were stirred on a magnetic stirrer overnight. 20 2025204878   27 Jun 2025 Figure 6 is a table showing the ratio of DMP to NBPT used in these formulations as well as other data such as total solids and DMP to solvent and NMBT to solvent. The successful formulations (all from the table of Figure 6 were successful) were 5 split up for physical stability monitoring. For physical stability monitoring the samples were stored in the R&D lab, with half of the retained sample stored at ambient and the other half stored in the fridge. HPLC analysis was conducted at regular intervals from formulation to approximately 8 weeks after to monitor the concentration of the inhibitors. 10 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. 15 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 20 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 25 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

1. A formulation comprisinga solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system, wherein:when the DMP:NBPT weight ratio is from about 2.5:1 to about 5:1, NBPT is present at less than about 18% relative to the solvent system;when the DMP:NBPT weight ratio is from about 1.7:1 to about 2.5:1, NBPT is present at less than about 23% relative to the solvent system;when the DMP:NBPT weight ratio is from about 0.2:1 to about 1.7:1, NBPT is present at about 28% or less relative to the solvent system; andthe total solids content is less than about 45% by weight.

2. A formulation comprisinga solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system, wherein:when the DMP:NBPT weight ratio is from about 2.5:1 to about 5:1, NBPTis present at less than about 18% relative to the solvent system; andthe total solids content is less than about 45% by weight.

3. A formulation comprisinga solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:2025204878   27 Jun 2025(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system, wherein:when the DMP:NBPT weight ratio is from about 1.7:1 to about 2.5:1, NBPT is present at less than about 23% relative to the solvent system; and the total solids content is less than about 45% by weight.

4. A formulation comprisinga solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system, wherein:when the DMP:NBPT weight ratio is from about 0.2:1 to about 1.7:1, NBPT is present at about 28% or less relative to the solvent system; andthe total solids content is less than about 45% by weight.

5. A formulation comprising:a solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system;wherein:the formulation satisfies either:(i) a weight ratio of DMP to NBPT from about 2.5:1 to about 5:1, with NBPT present at less than about 18% by weight relative to the solvent system, and total solids less than about 45% by weight; or(ii) a weight ratio of DMP to NBPT from about 0.5:1 to about 1.2:1, with NBPT present at about 20% to about 44% by weight relative to the solvent system,2025204878   27 Jun 2025and total solids less than about 45% by weight.

6. A formulation comprising:a solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor s 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system;wherein a weight ratio of DMP to NBPT from about 2.5:1 to about 5:1, with NBPT present at less than about 18% by weight relative to the solvent system, and total solids less than about 45% by weight.

7. A formulation comprising:a solvent system comprising:(i)     a polar aprotic solvent such as sulfolane; and(ii) an ethanolamine compound such as triethanolamine;the solvent system comprising dissolved therein:(iii) a nitrification inhibitor 3,4-dimethyl pyrazole (DMP); and(iv) a urease inhibitor N-butyl thiophosphoric triamide (NBPT);dissolved in the solvent system;wherein a weight ratio of DMP to NBPT from about 0.5:1 to about 1.2:1, with NBPT present at about 20% to about 44% by weight relative to the solvent system, and total solids less than about 45% by weight.

8. The formulation according to any one of the preceding claims, wherein the aprotic solvent is sulfolane.

9. The formulation according to any one of the preceding claims, wherein the ethanolamine compound is triethanolamine.

10. The formulation according to any one of the preceding claims, wherein the formulation is stable at 40 °C for 8 weeks to simulate 2 years of storage.2025204878   27 Jun 202511. A nitrogen containing fertiliser coated with the formulation according to any one of claims 1 to 10.

12. The fertiliser of claim 11, wherein the nitrogen containing fertiliser is urea.

13. A nitrogen containing liquid fertiliser comprising therein the formulation according to any one of claims 1 to 10.

14. The liquid fertiliser according to claim 13, wherein the nitrogen containing liquid fertiliser is UAN.

15. A particle when coated with a formulation according to any one of claims 1 to 10.

16. Urea when coated with a formulation according to any one of claims 1 to 10.

17. Applying a fertiliser according to any one of claims 11 to 14 in an agricultural setting.

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