NZ624594B2 - Urease inhibitor formulations - Google Patents

Abstract

Provided are liquid urease inhibitor formulations comprising a N-substituted thiophosphoric triamide or a N-substituted phosphoric triamide compound of Structure I as the urease inhibitor, and a dialkyl sulfone of Structure II or a polymethylene cyclic sulfone of Structure III as the solvent. The variables are as defined in the specification. riables are as defined in the specification.

Description

Urease Inhibitor Formulations Field of the invention The invention relates to formulations comprising urease inhibitors. In particular, the invention relates to formulations comprising urease inhibitors for ation to urea—based fertilisers and waste containing urea compounds to inhibit the effect of urease activity on such fertilisers and wastes.

Background of the invention In this specification, where a document, act or item of knowledge is referred to or discussed, this nce or discussion is not an ion that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Nitrogen is an important plant nutrient. Urea (CO(NH2)2) represents more than 40% of the total nitrogen fertiliser d to agricultural crops worldwide. However, urea is readily ed in soil by the “urease” group of enzymes, which catalyses the reaction of urea with water to produce gaseous ammonia and um 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” have been applied to urea based fertilisers in an attempt to reduce the rate of urea hydrolysis and subsequent loss of ammonia. es of such urease tors include the l thiophosphoric triamides such as N—(n— butyl)thiophosphoric triamide (NBPT). However, NBPT is a waxy, sticky, heat—sensitive and water —sensitive material and so particular formulations are required to se decomposition during storage and distribution. es of such formulations include: 0 a concentrated solution of an N—alkyl thiophosphoric triamide in a solvent mixture of glycols (eg propylene glycol) and liquid amides (eg N—methyl idone) (see for example international patent application no WO 97/22568); • a mixture comprising a thiophosphoric acid triamide and a compound containing an amino group having a boiling point of more than 100°C (see for example international patent application no ); and • a liquid composition containing a oric or thiophosphoric triamide derivative and one or more of esters of hydroxyacids, heterocyclic alcohols, cyclic esters of carbonic acid and esters of dicarboxylic acids (see for example international patent application no ).

The ng urease inhibitors formulations currently used in agriculture (e.g. the commercial product called AgrotainTM (trade mark of Phosphate Resource Partners Limited Partnership, registered in some countries)) suffer from a number of antages in use, including: • limited storage stability of the treated urea; • health and safety concerns regarding the solvents used in the formulation; and • ecotoxicology concerns regarding the effect of solvents used in the formulation once in the c and terrestrial environment.

Therefore, there is a need for an improved urease inhibitor formulation which addresses at least one of these disadvantages. [0006a ] Any discussion of documents, acts, als, devices, art icles or the like which has been included in the present specification is not to be taken as an ion that any or all of these matters form part of the prior art base or were common general dge in the field relevant to the present sure as it existed before the priority date of each claim of this application. [0006b] Throughout this specification the word "comprise", or ions such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other t, integer or step, or group of elements, integers or steps.

Summary of the ion It has been ered that new solvent combinations and/or mixtures of active ingredients address at least one of the above antages. The new formulations continue to enhance the efficiency of urea-based isers by delaying urea hydrolysis in soils and reducing liberation of ammonia into the atmosphere.

According to a first aspect of the ion, there is provided a liquid urease inhibitor formulation comprising: (a) a urease inhibitor selected from the group consisting of N-substituted thiophosphoric triamides and N-substituted phosphoric triamides represented by Structure I and mixtures thereof, Structure I wherein X is selected from O or S; R1 is selected from C4-C6 alkyl, C5-C8 cyclo alkyl and phenyl, wherein the alkyl and cyclo alkyl groups are optionally substituted with a group selected from halo, nitro and amino, and wherein the phenyl is optionally substituted with a group selected from nitro, amino, alkyl and halo; and Y is selected from H, NO2, halo, NH2 and C1 to C8 alkyl; and (b) a primary solvent selected from the group consisting of dialkyl sulfones ing to Structure II, polymethylene cyclic sulfones according to Structure III, and mixtures thereof; ure II wherein R2 is alkyl C1 to C6 R3 is alkyl C1 to C6 ure III wherein n is 3 to 6 wherein the urease inhibitor is soluble in the primary solvent. [0008a] A method for inhibiting the urease hydrolysis of urea-containing fertiliser or waste, the method comprising the step of applying a liquid urease inhibitor formulation to the ureacontaining fertiliser or waste, the liquid urease inhibitor formulation comprising: (a) a urease inhibitor selected from the group consisting of N-substituted thiophosphoric triamides and N-substituted phosphoric triamides represented by ure I and mixtures thereof, Structure I wherein X is ed from O or S; R1 is selected from C3-C6 alkyl, C5-C8 cyclo alkyl and phenyl, wherein the alkyl and cyclo alkyl groups are optionally substituted with a group selected from halo, nitro and amino, and wherein the phenyl is optionally substituted with a group ed from nitro, amino, alkyl and halo; and Y is selected from H, NO2, halo, NH2 and C1 to C8 alkyl; and (b) a primary solvent ed from the group consisting of dialkyl es according to Structure II, polymethylene cyclic sulfones according to Structure III, and mixtures thereof; Structure II wherein R2 is alkyl C1 to C6 R3 is alkyl C1 to C6 Structure III wherein n is 3 to 6 wherein the urease inhibitor is soluble in the primary solvent.

The urease inhibitors used in the formulations according to the invention include: • N-alkyl-thiophosphoric triamides; • N-alkyl-phosphoric triamides; • N-cycloalkyl-thiophosphoric triamides 0 N—cycloalkyl—phosphoric triamides; 0 N—aryl—thiophosphoric triamides; or 0 N—aryl—phosphoric triamides, where the alkyl, cycloalkyl or aryl groups may be further substituted with chloro—, nitro— or amino—groups. Commonly available urease tors include N—butyl thiophosphoric triamide (NBPT), N—cyclohexyl oric triamide (CHPT) and 2—nitrophenyl phosphoric triamide (2— NPT). Many other urease inhibitors can be used in formulations according to the invention as known to those skilled in the art. Combinations of two or more urease inhibitors can also be used in formulations according to the invention. Preferably, the urease inhibitor is present in the ation in an amount in the range from 0.5 to 51% by weight of the total formulation, more preferably 10 to 20%.

The primary solvents, selected from the specified sulfones, provide excellent stability and solubility for the urease tors. They also have environmental and occupational health and safety advantages. Preferably, the primary solvent is tetramethylene sulfone which is readily biodegradable in soils (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°C), is non—flammable and is not classified as a Dangerous Good or Hazardous nce.

The use of the primary solvents in formulations according to the invention have beneficial properties not achieved by the prior art solvent systems, including: 0 the urease inhibitors are stable in the concentrated solution even at elevated temperatures (up to 40°C) for more than 12 months; 0 the formulations according to the invention can be applied directly into liquid izer or liquid waste containing urea compounds; 0 the ations ing to the invention can be sprayed directly onto, and mixed into, solid wastes containing urea compounds; 0 the formulations ing to the invention have low viscosity, y facilitating rapid and uniform spreading on the surface of urea granules; 2012/001395 0 the formulations according to the invention can be d to the surface of urea granules, which absorb the formulation, penetrating deep into the solid granule (“impregnating” the granule structure); 0 urea granules coated with the formulations according to the invention remain robust during storage, transport and handling, thereby retaining their ss and crush strength; 0 urea granules coated with the formulations according to 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 hydrolysis leads to a lower pH in proximity to the urea granules which results in a higher ratio of stable ammonium to ammonia; and 0 urea granules coated with the formulations according to the invention remain stable and retain their urease inhibition activity during storage in hot climates up to 40°C for more than 3 months.

The formulations according to the invention give superior performance with cted results not previously obtained with other solvent s.

Preferably, the y solvent is present in the ation in an amount in the range from 10 to 80% by weight of the total formulation, more preferably 40 to 70%.

In a preferred ment, the liquid urease inhibitor formulation further comprises: (c) a buffering agent and stabiliser selected from the group consisting of hydroxyethyl and hydroxypropyl amines according to Structure IV, in which the amine can be a primary, ary or tertiary amine and the number of hydroxyethyl or hydroxypropyl groups can be 1, 2 or 3, R4-N—R5 Structure IV wherein R4 and R5 are independently H, C1 — C6 alkyl or _ —R7 R6 2 — CHg—CH—R7 R7 = H or CH3 The buffering agents and stabilisers further improve the storage stability of the urease inhibitors in the formulations according to the ion. Preferred buffering agents and stabilisers are triethanolamine, monoethanolamine and mixtures thereof. Preferably, the buffering agents and stabilisers are present in the formulation in an amount in the range from 1 to 50% by weight of the total formulation, more preferably 20 to 50%.

In a preferred embodiment, the liquid urease inhibitor formulation further comprises: (d) a non—ionic surfactant having wetting agent ties selected from the group consisting of aliphatic alcohol alkoxylates, alkylphenol alkoxylates and mixtures thereof.

The non—ionic surfactant improves the wetting and spreading effect of formulations according to the invention on the surface of the urea granules. An example of a suitable nonionic surfactant are the products available under the TerwetTM brand. Preferably, the nonionic surfactant is present in the formulation in an amount in the range from 0.1 to 2.0% by weight of the total formulation The formulations according to the invention may r comprise additional components such as amides, , heterocyclic alcohols and s.

Examples s embodiments/aspects of the invention will now be described with reference to the ing non—limiting examples.

Example 1 A formulation was ed according to the invention.

Components Amount (grams) Sulfolane (tetramethylene sulfone) 690 Triethanolamine 100 N—butyl thiophosphoric triamide 200 Terwet 245 (surfactant) 10 Total Mass 1000 The components were mixed in the order shown and stirred at 500C for 30 minutes. A clear on, with no insoluble solids, was obtained.

Example 2 A formulation was prepared ing to the ion.

Components Amount (grams) Sulfolane 690 Monoethanolamine 100 N—butyl thiophosphoric triamide 200 Terwet 245 10 Total Mass 1000 The above formulation was prepared according to the method described in Example 1.

WO 71344 2012/001395 Example 3 A formulation was prepared according to the invention. ents Amount (grams) Sulfolane 400 Triethanolamine 390 N—butyl thiophosphoric triamide 200 Terwet 245 10 Total Mass 1000 The above formulation was prepared according to the method described in Example 1.

Example 4 A formulation was prepared according to the invention. 2—nitrophenyl phosphoric triamide 10 Terwet 245 10 Total Mass 1000 The above formulation was prepared according to the method described in Example 1.

Example 5 A formulation was prepared according to the invention. ents Amount ) Sulfolane 500 Monoethanolamine 290 N— butyl thiophosphoric triamide Terwet 245 Total Mass The above formulation was prepared ing to the method described in Example 1.

Example 6 A formulation was prepared according to the invention.

Components Amount (grams) Sulfolane 300 Triethanolamine 640 N—Cyclohexyl phosphoric triamide 50 Terwet 245 10 Total Mass 1000 The above formulation was prepared according to the method described in Example 1.

Example 7 A formulation was prepared according to the invention.

N—Butyl thiophosphoric de 200 The above formulation was prepared according to the method described in Example 1.

Example 8 A formulation was prepared according to the invention. ophenyl phosphoric triamide 50 The above formulation was prepared according to the method described in Example 1.

Example 9 This example igated the amount of ammonium produced by urea granules treated with formulations according to the invention.

Methodology An incubation experiment was performed by storing a soil—water suspension at 21°C for 14 days. Each day, a small aliquot (0.5 ml) of the supernatant aqueous phase was awn and analysed for ammonium ions using flow injection is (FIA). The soil— water suspension consisted of: soil sample, 60 % water holding capacity 40 grams Water 200 grams Urea 400 mg N— butyl thiophosphoric triamide 400 ug Solvents 1600 pg The solvents used in this experiment were those used in Examples 5 and 7 above.

The test solutions contained 400 ug NBPT per 200 ml water. The results are shown in Table 2.

Table 2 Test Solution NH4+ (mg/l) % Inhibition Urea ysed (mg) Control (no Inhibitor) 29.9 — 256 The control solution of urea, without a urease inhibitor, showed an NH4+ concentration of 29.9 mg/l after 14 days incubation. After converting for a on factor (1:20), the quantity of urea hydrolysed in 200 ml of solution was calculated to be 256 mg. This represents a loss of 64% of the original mass of urea added (400 mg) to the aqueous phase.

By contrast, the formulations according to the invention only formed 8.4 and 8.9 mg/l as NH4+. This represents a loss of only 72 and 76 mg urea after 14 days incubation. The % Inhibition was calculated to be 72 % and 70 % respectively, using the concentrations of NH4+ in the equation: % Inhibition 2 (Control — Test] * 100 Control By comparison, the standard product “AgrotainTM” widely used as a commercial urease inhibitor, gave 73 % tion in the above experiment.

These s trate that the formulations prepared according to this invention (Examples 5 and 7) are at least equivalent to the rd formulation AgrotainTM, prepared ing to the prior art.

Example 10 This example investigated the amount of ammonium produced by urea granules treated with formulations according to the invention.

Methodology An incubation experiment was performed by storing a soil—water suspension at 21°C for 17 days. The ammonium ed was measured as per Example 9. The results are shown in Table 3. The incubation mixture contained: Urease Inhibitor 50 to 400 ug The solvents and urease inhibitor used in this experiment were those used in Examples and 8 above.

WO 71344 Table 3 Test Solution Urease tor amount % inhibition Inhibitor (Hg/200 ml) (17 days) l (Urea only) Nil Nil Nil inTM NBPT 400 73 Example 5 NBPT 400 84 Example 8 2 — NPT 100 80 Example 8 2 — NPT 50 72 The above results show that Example 5 appears to perform more effectively than the standard product AgrotainTM (84 % and 73 % inhibition respectively, after 17 days).

The urease inhibitor 2 — NPT (2— nitrophenyl phosphoric triamide) was superior in performance when compared to NBPT. Even at 50 pig/200 ml water, (Example 8) the active 2— NPT gave 72 % inhibition, similar to NBPT at 400 pig/200 ml. This indicates that 2—NPT is about eight times more active than NBPT. Therefore, in a commercial formulation, 2—NPT could be used at a concentration of 2.5% w/w, compared to 20% w/w for NBPT as per current standard practice.

Example 11 This example investigates the storage stability of formulations according to the invention. Concentrated solutions of urease inhibitors were stored at 40°C for 8 weeks. At regular als, samples were awn and the urease inhibitor content was analysed by HPLC. The results for the storage stability measured as concentration of NBPT as %w/w are shown in Table 4.

Table 4 These results show that the concentrate liquids are stable at 40°C for 8 weeks, with no change in the concentrations of NBPT, within experimental variance. These storage conditions are equivalent to about 12 months e at ambient temperature.

Example 12 This example investigates the stability of urea es treated with formulations according to the invention.

Methodology Samples of coated urea were subjected to storage at 40°C for 8 weeks. The results showing the concentration of NBPT as grams/kg of Urea are shown in Table 5. The concentrated inhibitor solutions (AgrotainTM, Example 1 and Example 2) were applied to urea granules at the rate of 5 ml/kg of urea. The residual inhibitor present on the urea granules are shown in Table 5 as grams g of urea.

Table 5 Based on the above results, the most stable formulation for coating onto urea es was Example 2. After 8 weeks storage at 40°C, only about 35 % of the urease inhibitor was lost from Example 2, while the other two formulations lost between 46 to 50% of the urease inhibitor.

A further ment was conducted in which the urea samples were stored at 20°C for 8 weeks. In that experiment, the urea granules lost only between 4 to 10% of the urease inhibitor. The best result was obtained with Example 2, which showed only 4% loss after 8 weeks storage at 20°C.

These results demonstrate the superior ity of Example 2 on the coated surface of urea granules. Based on the loss of only 35% of NBPT after 8 weeks storage at 40°C, the shelf life of treated urea will be at least 12 months under normal industrial e conditions. The conventional treatment according to the prior art (AgrotainTM), has a half life of 3 months.

Example 13 This example investigates the crush strength of urea granules d with formulations according to the invention Urea granules of a uniform size having a substantially spherical shape are identified.

The individual urea granules are placed between two plates and subjected to sing pressure on a test plate until the granule fractures. The force required to cause the fracture is recorded with a force gauge (eg Digital Force Gauge DFE—050, Chatillon, Ametek). A mean of ten tests is recorded for each batch of urea.

The results for Mean Hardness (expressed as kg/granule) are shown in Table 6.

Table 6 Sample Fresh Sample After 8 weeks at 20°C After 8 weeks at 40°C AgrotainTM 3.01 2.01 2.95 Example 1 3.26 1.99 2.98 Example 2 3.19 2.16 2.78 Urea (untreated) 3.21 2.28 3.02 These s show that the urea granules became softer after 8 weeks storage at 20°C, with a reduction in average crush strength from about 3.2 to 2.15 kg/granule. However, at 40°C storage there was little change in the crush th after 8 weeks, with the mean value falling to 3.0 kg/granule.

These s indicate that the urea es coated with Examples 1 and 2 do not significantly lose mechanical strength compared to the untreated control. This property is important in large scale e of treated urea in storage bins or hoppers, where formation of urea dust is deleterious to human health.

Example 14 This example investigates the water absorption of urea granules treated with formulations according to the invention. The storage experiment was conducted at 30°C, under either 70% or 75% humidity.

The water absorption was measured as the Critical ve Humidity (CRH) being the % weight gain after 3 hours storage at each of ve Humidity 70% and 75%. The urea granules were treated with the inhibitor solutions at the rate of 5 ml per kg of urea.

Table 7 Sample CRH at CRH at 70%/30°C 75 %/30°C AgrotainTM fresh 0.7 AgrotainTM stored 0.3 for 8 weeks at t AgrotainTM stored for 8 weeks at 40°C 0.

Example 2 stored for 8 weeks at 40°C 0.4 These results show that all the treated urea granules (AgrotainTM, es 1 and 2) perform similarly with respect to moisture absorption from the air at 70% and 75% humidity.

While these results are higher than the untreated urea control, they are still acceptable under normal industrial storage conditions. Excessive moisture absorption will cause the urea es to become soft and sticky and therefore difficult to transport and handle on a large scale.

Example 15 This example investigates the urease inhibition properties of urea granules treated with formulations according to the invention stored at 40°C.

Methodology Urease Inhibition tests were performed using the method based on ammonium ion ion (NH4+) in soil solution from the hydrolysis of urea as described in Example 9. The following samples were tested: 0 Urea coated with AgrotainTM (1.0 gram NBPT active/kg urea); 0 Urea coated with Example 1 (1.0 gram NBPT active/kg urea); and 0 Urea coated with Example 2 (1.0 gram NBPT active/kg urea).

Each of the above samples were tested on freshly ed samples and on samples stored at 20°C and 40°C for 8 weeks. The same experimental ions were used as in Example 9. The results for ammonium concentrations in soil solutions and % Inhibition after days incubation are given in Table 8.

Table 8 Test Solution -NH4+ (mg/l) % Inhibition (20 days) Control Urea (no inhibitor) Urea + inTM — fresh sample 77 Urea + AgrotainTM — stored at 20°C for 8 weeks 72 Urea + AgrotainTM — stored at 40°C for 8 weeks 78 Urea + Example 1 — fresh sample 82 Urea + Example 1 — stored at 20°C for 8 weeks “ 81 Urea + Example 1 — stored at 40°C for 8 weeks 78 Urea + Example 2 — fresh sample 82 Urea + e 2 — stored at 20°C for 8 weeks 82 Urea + Example 2 — stored at 40°C for 8 weeks 81 These results show that the freshly prepared sample of Example 1 gave 82% inhibition of urea hydrolysis during 20 days incubation at 21°C. By comparison, the samples stored at °C and 40°C gave 81% and 78% inhibition, respectively. This indicates that the inhibitor NBPT was still stable and active after this storage period.

Similarly, Example 2 gave 82, 82 and 81% inhibition for the fresh sample and the samples stored at 20° and 40°C, respectively. These stability tests compare favorably with the s obtained with AgrotainTM, which gave inhibition results of 77, 72 and 78% respectively (Table 8).

Example 16 This e igates the efficacy of urea granules treated with formulations according to the invention. ology Replicated field tests in a random block design were performed in order to measure improvements in dry matter production, N—Uptake and N—Uptake Efficiency in winter rye grass, fertilised with control urea and urea treated with ations according to the invention.

The urea ation rates were 100 kg/Ha, equivalent to 46 kg Nitrogen/Ha. The urea granules were coated with 2, 3 or 5 ml of Example 1 per kg of urea. AgrotainTM was used at the rate of 5 ml per kg of Urea.

The results from one trial are shown in Table 9.

Table 9 Fertiliser Added Dry Matter ke ke (Inhibitor ml/kg Urea) Kg/Ha Kg/Ha % Efficiency Nil (Blank) 1525 45.5 0 Urea (Control) 2062 68.1 49.1 Urea + 5 ml Example 1 2546 87.7 91.7 Urea + 3 ml Example 1 2411 81.8 78.8 Urea + 2 ml Example 1 2561 81.5 78.3 Urea + 5ml AgrotainTM 2301 74.8 63.7 LSD (P = 0.05) 431 17.3 CV% 14.1 17.8 Based on the above results, the Example 1 treatments applied at 2 or 5 ml were significantly more effective in producing ryegrass dry matter than the urea control. The Example 1 treatments did not deliver statistically significant improvements in the Dry Matter yield and N—Uptake over the AgrotainTM treated urea. There is however a trend which favours the Example 1 treatments (even at lower rates of on to the urea). N—Uptake % ency of approximately 80 — 90% was achieved with Example 1 treatments, which compares favourably with the approximately 50% efficiency with untreated Urea. The conventional treatment with AgrotainTM gave about 60% efficiency. ke Efficiency 2 (Sample Uptake — Blank Uptake) *

Claims (17)

1. The claims defining the invention are as follows: 1 A liquid urease inhibitor formulation for application to urea-based fertilisers and waste containing urea compounds comprising: (a) a urease inhibitor selected from the group consisting of tituted thiophosphoric triamides and N-substituted phosphoric triamides represented by Structure I and mixtures thereof, Structure I wherein X is selected from O or S; R1 is selected from C4-C6 alkyl, C5-C8 cyclo alkyl and phenyl, wherein the alkyl and cyclo alkyl groups are optionally substituted with a group selected from halo, nitro and amino, and wherein the phenyl is ally substituted with a group selected from nitro, amino, alkyl and halo; and Y is selected from H, NO2, halo, NH2 and C1 to C8 alkyl; and (b) a primary t ed from the group consisting of dialkyl sulfones according to Structure II, polymethylene cyclic sulfones according to Structure III, and mixtures f; Structure II wherein R2 is alkyl C1 to C6 R3 is alkyl C1 to C6 23 Structure III wherein n is 3 to 6 wherein the urease inhibitor is soluble in the primary solvent.
2. 2 The liquid urease inhibitor formulation according to claim 1 further comprising: (c) a buffering agent and stabiliser selected from the group consisting of hydroxyethyl and hydroxypropyl amines according to Structure IV, in which the amine can be a y, secondary or tertiary amine and the number of hydroxyethyl or hydroxypropyl groups can be 1, 2 or 3, Structure IV wherein R4 and R5 are ndently H, C1-C6 alkyl or R6 is R7 is selected from H or CH3.
3. 3 The liquid urease inhibitor formulation according to either of claims 1 or 2 further comprising: 24 (d) a non-ionic surfactant having wetting agent properties selected from the group consisting of aliphatic alcohol alkoxylates, alkylphenol alkoxylates and mixtures thereof.
4. 4 The liquid urease tor formulation according to any one of the preceding claims wherein the amount of the urease inhibitor is in the range from 0.5 to 51% by weight of the total formulation.
5. 5 The liquid urease inhibitor formulation according to any one of the preceding claims wherein the amount of primary solvent is in the range from 10 to 80% by weight of the total formulation.
6. 6 The liquid urease inhibitor formulation ing to any one of claims 2 to 4 wherein the amount of buffering agent and stabiliser is in the range from 1 to 50% by weight of the total formulation.
7. 7 The liquid urease inhibitor formulation according to any one of claims 3 to 6 wherein the amount of the nonionic surfactant is in the range from 0.1 to 2.0% by weight of the total formulation.
8. 8 The liquid urease inhibitor formulation for application to urea-based isers and waste containing urea compounds according to any one of the preceding claims wherein the primary solvent is ethylene sulfone.
9. 9 The liquid urease inhibitor formulation according to any one of claims 2 to 8 wherein the buffering agent and stabiliser is ed from the group consisting of triethanolamine, monoethanolamine and mixtures f.
10. 10 The liquid urease inhibitor formulation ing to any one of the preceding claims wherein the urease inhibitor is selected from the group consisting of N-butyl osphoric triamide, 2-nitrophenyl phosphoric triamide, N- cyclohexyl phosphoric triamide and mixtures thereof.
11. 11 A method for inhibiting the urease hydrolysis of urea-containing fertiliser or waste, the method comprising the step of applying a liquid urease inhibitor formulation 25 to the ontaining fertiliser or waste, the liquid urease tor formulation comprising: (a) a urease inhibitor ed from the group consisting of N-substituted thiophosphoric triamides and N-substituted phosphoric triamides represented by Structure I and mixtures thereof, Structure I wherein X is selected from O or S; R1 is selected from C3-C6 alkyl, C5-C8 cyclo alkyl and phenyl, wherein the alkyl and cyclo alkyl groups are ally substituted with a group selected from halo, nitro and amino, and wherein the phenyl is optionally substituted with a group selected from nitro, amino, alkyl and halo; and Y is selected from H, NO2, halo, NH2 and C1 to C8 alkyl; and (b) a primary solvent selected from the group consisting of dialkyl sulfones according to Structure II, polymethylene cyclic sulfones according to Structure III, and mixtures thereof; Structure II wherein R2 is alkyl C1 to C6 R3 is alkyl C1 to C6 26 Structure III wherein n is 3 to 6 wherein the urease inhibitor is soluble in the y solvent.
12. 12 The method according to claim 11 comprising the liquid urease inhibitor formulation according to any one of claims 2 to 10.
13. 13 The method according to claim 11 wherein the urea-containing fertiliser is urea es and the step of applying the liquid urease inhibitor formulation comprises spraying the formulation onto the surface of the urea granules, or melting the urea granules with the formulation to form a solid mixture.
14. 14 The use of a liquid urease inhibitor formulation according to any one of claims 1 to 10 for the inhibition of urease hydrolysis of urea in moist soil.
15. 15 The use according to claim 14 wherein the inhibition of urease hydrolysis of urea in moist soil is for at least 14 days.
16. 16 The liquid urease inhibitor ation according to claim 1, substantially as herein described with reference to the examples and excluding, if any, comparative examples.
17. 17 The method ing to claim 11 or use according to claim 14, substantially as herein bed with reference to the examples and excluding, if any, comparative examples.