HK1198157B - Urease inhibitor formulations - Google Patents

Abstract

There is provided a liquid urease inhibitor formulation comprising an urease inhibitor and a primary solvent selected from the group consisting of dialkyl sulfones, polymethylene cyclic sulfones, and mixtures thereof. A method for inhibiting urease hydrolysis of urea containing fertiliser or waste using said liquid urease inhibitor formulation is also described.

Description

Urease inhibitor formulations

Technical Field

The present invention relates to formulations comprising urease inhibitors. In particular, the present invention relates to formulations comprising urease inhibitors for use on urea-based fertilizers and waste materials containing urea compounds to inhibit the effects of urease activity on such fertilizers and waste materials.

Background

Where a document, act or item of knowledge is referred to or discussed in this specification, this reference or discussion is not an admission that the document, act or item of knowledge or a combination thereof was publicly available, publicly known, part of the common general knowledge at the priority date; or is known to be associated with attempting to solve any problems of interest to this specification.

Nitrogen is an important plant nutrient. Urea (CO (NH)₂)₂) Representing more than 40% of the total nitrogen fertilizer used in crops worldwide. However, urea is readily degraded in soil by the "urease" group of enzymes, which catalyses the reaction of urea and water to produce gaseous ammonia and ammonium ions (referred to as "urea")Hydrolysis (urea hydrolysises) "). Due to this enzymatic hydrolysis, ammonia readily volatilizes from the treated soil; resulting in a loss of up to 60% of the applied urea.

To retard this hydrolysis, "urease inhibitors" have been used in urea-based fertilizers in an attempt to reduce the rate of urea hydrolysis and subsequent loss of ammonia. Examples of such urease inhibitors include N-alkyl thiophosphoric triamides (N-alkylthiophosphoric triamides), such as N- (N-butyl) thiophosphoric triamide (NBPT). However, NBPT is a waxy, viscous, heat-sensitive and water-sensitive material, and therefore requires specific formulations to minimize decomposition during storage and compounding. Examples of such formulations include:

concentrated solutions of N-alkylthiophosphoric triamides in solvent mixtures of glycols (such as propylene glycol) and liquid amides (such as N-methylpyrrolidone) (see, for example, International patent application No. WO 97/22568);

mixtures comprising thiophosphoric triamides and amino group-containing compounds having a boiling point above 100 ℃ (see, for example, international patent application No. WO 2009/079994); and

liquid compositions comprising phosphorus or thiophosphoric triamide derivatives and one or more of hydroxy acids, esters of heterocyclic alcohols, cyclic esters of carbonic acid and esters of dicarboxylic acids (see, for example, international patent application No. WO 2010/072184).

Existing urease inhibitor formulations currently used in agriculture (e.g. called Agrotain)^ＴＭThe commercial product of (trademark of phosphor Resource Limited Partnership registered in some countries) has many disadvantages in use, including:

limited storage stability of the treated urea;

health and safety concerns regarding the solvents used in the formulation; and

ecotoxicological concerns regarding the impact of solvents used in the formulation once they enter aquatic and terrestrial environments.

Accordingly, there is a need for an improved urease inhibitor formulation that overcomes at least one of these disadvantages.

Summary of The Invention

It has been found that novel solvent combinations and/or mixtures of active ingredients overcome at least one of the above disadvantages. The new formulation continuously increases the efficiency of urea-based fertilizers by delaying urea hydrolysis in the soil and reducing the release of ammonia into the atmosphere.

According to a first aspect of the present invention, 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,

wherein X is O or S, R¹Unsubstituted and substituted C₃-C₆Alkyl, unsubstituted and substituted C₅-C₈Cycloalkyl, phenyl and substituted phenyl with nitro, amino, alkyl or halide substituents; and Y H, NO₂Halide, NH₂Or C₁-C₈An alkyl group; 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;

wherein R is²＝C₁-C₆Alkyl radical

R³＝C₁-C₆Alkyl radical

Wherein n is 3-6

Wherein the urease inhibitor is soluble in the primary solvent.

Urease inhibitors for use in formulations according to the invention include:

n-alkyl-thiophosphoric triamide;

n-alkyl-phosphoric triamide;

n-cycloalkyl-thiophosphoric triamide;

n-cycloalkyl-phosphoric triamide;

n-aryl-thiophosphoric triamide; or

An N-aryl-phosphoric triamide,

wherein the alkyl, cycloalkyl or aryl group may be further substituted by chlorine, nitro or amino. Common urease inhibitors include N-butyl phosphoric triamide (NBPT), N-cyclohexyl phosphoric triamide (CHPT) and 2-nitrophenyl phosphoric triamide (2-NPT). It is known to the person skilled in the art that many other urease inhibitors can be used in the formulation according to the invention. Combinations of two or more urease inhibitors may also be used in the formulations according to the invention. Preferably, the urease inhibitor is present in the formulation in an amount in the range of 0.5-51% by weight of the total formulation, more preferably 10-20%.

The primary solvent, selected from the specific sulfones, provides excellent stability and solubility for the urease inhibitor. They also have environmental and occupational health and safety advantages. Preferably, the primary solvent is tetramethylene sulfone, which is readily biodegradable in soil (half-life of 10 days) and is free of ecotoxicological hazards (LC 50 for fish, algae and invertebrates is greater than 1000 mg/l). Tetramethylene sulfone has a high boiling point (284 ℃), is non-flammable and is not classified as a hazardous item or substance.

The use of the principal solvent in the formulation according to the invention has beneficial properties not achieved by prior art solvent systems, including:

the urease inhibitor is stable in concentrated solution even at high temperature (up to 40 ℃) for more than 12 months;

the formulation according to the invention can be applied directly to a liquid fertilizer or liquid waste containing a urea compound;

the preparation according to the invention can be sprayed directly on, and mixed into, the solid waste material containing the urea compound;

the formulation according to the invention has a low viscosity, thus promoting a rapid and uniform diffusion on the surface of the urea granules;

the formulation according to the invention can be applied to the surface of the urea granules that absorb it, penetrating deeply into the solid granules ("impregnated" granular structure);

urea granules coated with the formulation according to the invention remain strong during storage, transport and handling, thus retaining their hardness and crush strength;

urea granules coated with the formulation according to the invention hydrolyse more slowly in the soil than urea granules treated with the formulations of the prior art, thus achieving the desired slow release of ammonia for the most efficient absorption by crops and plants. A slower rate of urea hydrolysis results in a lower pH close to the urea granules, which results in a higher proportion of stable ammonium/ammonia; and

urea granules coated with a formulation according to the invention remain stable and retain their urease-inhibiting activity when stored for more than 3 months in hot climates up to 40 ℃.

The formulations according to the invention impart superior properties and unexpected results not previously obtained with other solvent systems.

Preferably, the amount of primary solvent present in the formulation is in the range of 10-80% by weight of the total formulation, more preferably 40-70%.

In a preferred embodiment, the liquid urease inhibitor formulation further comprises:

(c) a buffer and a stabilizer selected from the group consisting of hydroxyethylamine and hydroxypropylamine according to structure IV, wherein the amine can be a primary, secondary or tertiary amine, and the number of hydroxyethyl or hydroxypropyl groups can be 1, 2 or 3,

wherein

R⁴And R⁵Independently H, C₁-C₆Alkyl or

R⁷H or CH₃。

The buffers and stabilizers further improve the storage stability of the urease inhibitor in the formulation according to the invention. Preferred buffers and stabilizers are triethanolamine, monoethanolamine and mixtures thereof. Preferably, the buffering and stabilising agents are present in the formulation in an amount in the range of 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 nonionic surfactant having humectant properties selected from the group consisting of fatty alcohol alkoxylates, alkylphenol alkoxylates, and mixtures thereof.

The nonionic surfactant improves the wetting and spreading effect of the formulation according to the invention on the surface of the urea granules. An example of a suitable nonionic surfactant is Terwet^ＴＭProducts offered under the brand. Preferably, the amount of nonionic surfactant present in the formulation is in the range of 0.1 to 2.0% by weight of the total formulation.

The formulations according to the invention may further comprise additional components, such as amides, esters, heterocyclic alcohols and glycols.

Examples

Various embodiments/aspects of the present invention will now be described in conjunction with the following non-limiting examples.

Example 1

Formulations were prepared according to the invention.

Components	Volume (gram)
		Sulfolane (tetramethylene sulfone)	690
Triethanolamine	100
		N-butylthio groupPhosphoric triamides	200
Terwet 245 (surfactant)	10
		Total mass	1000

The components were mixed in the order shown and stirred at 50 ℃ for 30 minutes. A clear solution free of insoluble solids was obtained.

Example 2

Formulations were prepared according to the invention.

Components	Volume (gram)
		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.

Example 3

Formulations were prepared according to the invention.

The above formulation was prepared according to the method described in example 1.

Example 4

Formulations were prepared according to the invention.

Components	Volume (gram)
		Sulfolane	440
Triethanolamine	440
		N-butyl thiophosphoric triamide	100
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

Formulations were prepared according to the invention.

Components	Volume (gram)
		Sulfolane	500
Monoethanolamine	290
		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 6

Formulations were prepared according to the invention.

Components	Volume (gram)
		Sulfolane	300
Triethanolamine	640
		N-cyclohexyl phosphoric triamide	50
Terwet245	10
		Total mass	1000

The above formulation was prepared according to the method described in example 1.

Example 7

Formulations were prepared according to the invention.

Components	Volume (gram)
		Sulfolane	390
Triethanolamine	400
		N-butyl thiophosphoric triamide	200
Terwet245	10
		Total mass	1000

The above formulation was prepared according to the method described in example 1.

Example 8

Components	Volume (gram)
		Sulfolane	470
Triethanolamine	470
		2-Nitrophenyl phosphoric triamide	50
Terwet245	10
		Total mass	1000

The above formulation was prepared according to the method described in example 1.

Example 9

This example investigates the amount of ammonium produced by urea granules treated with a formulation according to the invention.

Method of producing a composite material

The incubation experiments were performed by storing the soil-water suspension at 21 ℃ for 14 days. Daily, a small aliquot (0.5ml) of the upper aqueous phase was extracted and analyzed for ammonium ions using Flow Injection Analysis (FIA). The soil-water suspension consisted of:

soil sample, 60% water holding Capacity	40 g
		Water (W)	200 g
Urea	400mg
		N-butyl thiophosphoric triamide	400μg
Solvent(s)	1600μg

The solvents used in this experiment were those used in examples 5 and 7 above.

The test solution contained 400. mu.g NBPT/200ml water. The results are shown in Table 2.

TABLE 2

Test solutions	NH4 +(mg/1)	% inhibition	Urea hydrolysis (mg)
				Control (no inhibitor)	29.9	---	256
AgrotainＴＭ	8.2	73	70
				Example 7	8.4	72	72
Example 5	8.9	70	76

A control solution of urea without urease inhibitor showed 29.9mg/l NH4 after 14 days incubation⁺. The amount of urea hydrolyzed in 200ml of solution after conversion according to the dilution factor (1:20) was calculated to be 256 mg. This represents a loss of 64% of the initial mass (400mg) of urea added to the aqueous phase.

In contrast, the formulations according to the invention only formed 8.4 and 8.9mg/l of NH4⁺. This represents a loss of only 72 and 76mg of urea after 14 days of incubation. Using NH4 in the equation⁺The% inhibition was calculated to be 72% and 70%, respectively:

by comparison, the widely used standard product "Agrotain" as a commercial urease inhibitor^ＴＭ"in the above experiment 73% inhibition was produced。

These results show that the formulations prepared according to the invention (examples 5 and 7) are at least equivalent to the standard formulations Agrotain prepared according to the prior art^ＴＭ。

Example 10

This example investigates the amount of ammonium produced by urea granules treated with a formulation according to the invention.

Method of producing a composite material

The incubation experiments were performed by storing the soil-water suspension at 21 ℃ for 17 days. The ammonium produced was measured as in example 9. The results are shown in Table 3. The incubation mixture comprises:

soil sample	40 g
		Water (W)	200 g
Urea	400mg
		Solvent(s)	1600μg
Urease inhibitors	50-400μg

The solvents and urease inhibitors used in this experiment were those used in examples 5 and 8 above.

TABLE 3

The above results show that example 5 appears to be more Agrotain than the standard product^ＴＭMore effective (84% and 73% inhibition after 17 days, respectively).

The urease inhibitor 2-NPT (2-nitrophenylphosphoric triamide) performs better when compared to NBPT. Even at 50pg/200ml water, (example 8) active 2-NPT produced 72% inhibition, similar to NBPT at 400pg/200 ml. This indicates that 2-NPT is about 8-fold more active than NBPT. Thus, according to current standard practice, 2-NPT can be used at a concentration of 2.5% w/w in commercial formulations, as compared to 20% w/w NBPT.

Example 11

This example investigates the storage stability of formulations according to the invention. The concentrated solution of urease inhibitor was stored at 40 ℃ for 8 weeks. At regular intervals, samples were taken and analyzed by HPLC for urease inhibitor content. The results measured as the storage stability of NBPT concentration in% w/w are shown in Table 4.

TABLE 4

Solutions of	0 week	2 weeks	6 weeks	8 weeks
					AgrotainＴＭ	19.8	19.7	19.6	20.1
Example 1	19.9	19.6	19.3	19.8
					Example 2	19.5	19.6	19.9	20.2

These results show that the concentrate is stable at 40 ℃ for 8 weeks with no change in NBPT concentration within experimental error. These storage conditions correspond to storage at ambient temperature for about 12 months.

Example 12

This example investigates the stability of urea granules treated with a formulation according to the invention.

Method of producing a composite material

The coated urea samples were stored at 40 ℃ for 8 weeks. The results showing NBPT concentration in grams/kg urea are shown in Table 5. Concentrated inhibitor solution (Agrotain) was added at a ratio of 5ml/kg urea^ＴＭExamples 1 and 2) applicationTo urea granules. The remaining inhibitors present in the urea granules are shown in Table 5 in grams NBPT/kg urea.

TABLE 5

Solutions of	0 week	2 weeks	6 weeks	8 weeks
					AgrotainＴＭ	0.93	0.70	0.55	0.54
Example 1	0.89	0.72	0.57	0.50
					Example 2	0.94	0.77	0.69	0.65

Based on the above results, the most stable formulation coated onto urea granules is example 2. After 8 weeks of storage at 40 ℃, only about 35% of the urease inhibitor was lost from example 2, while the other two formulations lost between 46-50% of the urease inhibitor.

Further experiments were performed on urea samples stored at 20 ℃ for 8 weeks. In this experiment, the loss of urease inhibitor from the urea granules was only between 4-10%. The best results are obtained from example 2, which shows only a 4% loss after 8 weeks of storage at 20 ℃.

These results demonstrate the excellent stability of the coated surface of the urea granules of example 2. The shelf life of the treated urea will last at least 12 months under normal industrial storage conditions based on NBPT loss of only 35% after 8 weeks of storage at 40 ℃. According to the prior art (Agrotain)^ＴＭ) Has a half-life of 3 months.

Example 13

This example investigates the crush strength of urea granules treated with a formulation according to the invention.

Substantially spherical urea particles having a uniform size are identified. Individual urea granules were placed between two plates and subjected to increasing pressure on the test plate until the granules broke. The Force required to cause fragmentation is recorded by a Force Gauge (e.g. Digital Force Gauge DFE-050, Chatillon, Ametek). The average of ten tests was recorded for each batch of urea.

The results of the average hardness (expressed in kg/pellet) are shown in table 6.

TABLE 6

Sample (I)	Fresh samples	After 8 weeks at 20 ℃	After 8 weeks at 40 ℃
				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 results show that the urea granules become softer after 8 weeks of storage at 20 ℃ and the average crush strength decreases from about 3.2 to 2.14 kg/g. However, the change in the crush strength was not large after 8 weeks of storage at 40 ℃ and the average value was reduced to 3.0 kg/g.

These results show that the urea granules coated with examples 1 and 2 have no significant loss of mechanical strength compared to the untreated control. This property is important for large-scale storage of processed urea in storage silos or hoppers, where the formation of urea dust is detrimental to human health.

Example 14

This example investigates the water absorption of urea particles treated with a formulation according to the present method. Storage experiments were performed at 30 ℃ with 70% or 75% humidity.

Water absorption was measured as the Critical Relative Humidity (CRH), which is the weight gain% after 3 hours of storage at 70% and 75% relative humidity, respectively. The urea granules were treated with an inhibitor solution at a ratio of 5ml/kg urea.

TABLE 7

These results show that all treated urea granules (Agrotain)^ＴＭExamples 1 and 2) behave similarly with respect to absorbing moisture from air at 70% and 75% humidity. Although these results were higher than the untreated urea control, they were still acceptable under normal industrial storage conditions. Excessive moisture absorption can cause the urea particles to become soft and sticky and thus difficult to transport and handle on a large scale.

Example 15

This example investigates the urease-inhibiting properties of urea granules treated with a formulation according to the invention stored at 40 ℃.

Method of producing a composite material

The use of a catalyst based on ammonium ions (NH) formed in a soil solution by hydrolysis of urea as described in example 9₄ ⁺) The method of (4) to perform a urease inhibition assay. The following samples were tested:

coated with Agrotain^ＴＭUrea of (4) (1.0 g NBPT activity/kg urea);

coated with urea from example 1 (1.0 grams NBPT activity/kg urea); and

coated with urea from example 2 (1.0 gram NBPT activity/kg urea).

The above sample tests were performed using freshly prepared samples as well as samples stored at 20 ℃ and 40 ℃. The same experimental conditions as in example 9 were used. Table 8 gives the ammonium concentration in the soil solution and the results of% inhibition after 20 days incubation.

TABLE 8

These results show that the newly prepared sample of example 1 produced 82% inhibition of urea hydrolysis during 20 days of incubation at 21 ℃. In comparison, the samples stored at 20 ℃ and 40 ℃ produced 81% and 78% inhibition, respectively. This indicates that the inhibitor NBPT is stable and active after this storage period.

Similarly, example 2 produced 82, 82 and 81% inhibition on fresh samples and samples stored at 20 ℃ and 40 ℃ respectively. These stability tests are superior to those of Agrotain^ＴＭ(which produced 77, 72 and 78% inhibition, respectively) obtained (table 8).

Example 16

This example investigates the efficiency of urea granules treated with a formulation according to the invention.

Method of producing a composite material

Random group design, repeated field experiments were performed in order to measure the improvement in dry matter production, N-absorption and N-absorption efficiency of winter rye grass fertilized with control urea and with urea treated with the formulation according to the invention.

The amount of urea applied was 100kg/Ha, corresponding to 46kg nitrogen/Ha. Urea granules were coated with 2, 3 or 5ml of example 1 per kg of urea. Use of Agrotain at a ratio of 5ml/kg Urea^ＴＭ。

The results of one set of experiments are shown in table 9.

TABLE 9

Based on the above results, the example 1 treatment applied at 2 or 5ml produced ryegrass dry matter significantly more efficiently than the urea control. Compared with Agrotain^ＴＭThe treated urea, the treatment of example 1, showed no statistically significant improvement in dry matter yield and N-absorption. However, there is a tendency to favor the treatment of example 1 (even if the proportion added to urea is lower). The treatment of example 1 achieved an N-absorption% efficiency of about 80-90% better than about 50% of the untreated urea. Use of Agrotain^ＴＭHas an efficiency of about 60%.

N-absorption efficiency (sample absorption-blank absorption) × 100/46

These results show that the agent is compatible with Agrotain^ＴＭThe urea treated with the formulation according to the invention has an excellent N-absorption% efficiency compared to conventional treatments.

Example 17

This example investigates the stability of a urease inhibitor formulation according to the invention when applied to urea granules.

An industrial scale production of 15 tons of urea with the standard inhibitor formulation Agrotain was carried out^ＴＭOr with a urease inhibitor formulation according to the invention as described in example 3.

At 3 litres per tonne of ureaProportional application of liquid product Agrotain^ＴＭ(ii) a Whereas the liquid inhibitor of example 3 was applied at a lower rate of 2 litres per tonne.

The two batches of treated urea were stored for a period of 8 weeks at ambient temperature and humidity from 3 months and 17 days 2011 in Wagga, NSW, Charles Sturt university, australia.

The stability tests were carried out on samples stored under the following conditions:

the bulk urea-fourteen (14) tons are placed in the dry area of the manufacturing plant and are deposited in bulk on a concrete floor.

> one ton of bag-processed urea is also stored in one ton of "bulk bags" that are commonly used for storing and transporting bulk urea.

>25Kg bags-treated urea was also stored in 25Kg woven plastic bags commonly used for storing dry manure.

Each sample was analyzed by HPLC for the remaining active ingredient NBPT at regular intervals as shown in table 10.

Table 10: NBPT (% w/w) remaining after storage of treated Urea

These results show the excellent stability of NBPT when applied to urea using the urease inhibitor formulation according to the present invention. After 8 weeks of storage, the bulk urea still showed NBPT of 0.042% + 0.02% compared to the initial value of 0.038% + 0.02%. This demonstrates that there is no loss of active NBPT after 8 weeks of storage in bulk urea when using the urease inhibitor formulation according to the invention.

In contrast, after 8 weeks of storageWith Agrotain^ＴＭThe treated urea lost 21% of the NBPT applied to the bulk urea sample, decreasing from an initial value of 0.062% to a reduced level of 0.049%.

In the case of a one-ton bag, the uremic toxicity treated with the formulation according to example 3 of the invention still maintained 0.035% NBPT (only 3% loss after 8 weeks); and Agrotain^ＴＭThe treated urea contained only 0.025% NBPT (60% loss after 8 weeks).

The loss is higher for a 25Kg bag. Agrotain^ＴＭThe treated urea lost 74% of the applied NBPT; whereas the uremic toxin treated with the formulation according to example 3 of the invention lost only 20% of the active ingredient.

The word "comprising" and forms of the word "comprising" as used in this description and in the claims do not limit the invention claimed to exclude any variants or additions.

Variations and modifications of the present invention will be apparent to those skilled in the art. Such variations and modifications are intended to be within the scope of the present invention.

Claims (21)

1. A liquid urease inhibitor formulation for urea-based fertilizers and wastes containing urea compounds 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,

wherein X is O or S, R is unsubstituted or substituted C₃-C₆Alkyl, unsubstituted and substituted C₅-C₈Cycloalkyl, phenyl and substituted phenyl with nitro, amino, alkyl or halide substituents; and Y H, NO₂Halide, NH₂Or C₁-C₈An alkyl group, wherein the urease inhibitor is not a compound having the structure:

(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;

wherein R is²＝C₁-C₆Alkyl radical

R³＝C₁-C₆Alkyl radical

Wherein n is 3-6

Wherein the urease inhibitor is soluble in the primary solvent; and

(c) a buffering agent and a stabilizing agent selected from hydroxyethylamine and hydroxypropylamine according to structure IV, wherein the amine is a primary, secondary or tertiary amine and the number of hydroxyethyl or hydroxypropyl groups is 1, 2 or 3,

wherein

R⁴And R⁵Independently H, C₁-C₆Alkyl or

R⁷H or CH₃。

2. The liquid urease inhibitor formulation of claim 1 further comprising:

(d) a nonionic surfactant having humectant properties selected from the group consisting of fatty alcohol alkoxylates, alkylphenol alkoxylates, and mixtures thereof.

3. The liquid urease inhibitor formulation of claim 1 wherein the amount of urease inhibitor is in the range of 0.5-51% by weight of the total formulation.

4. The liquid urease inhibitor formulation according to claim 1 wherein the amount of primary solvent is in the range of 10-80% by weight of the total formulation.

5. The liquid urease inhibitor formulation of claim 1 wherein the amount of buffering agent and stabilizing agent is in the range of 1-50% by weight of the total formulation.

6. The liquid urease inhibitor formulation according to claim 2, wherein the amount of the non-ionic surfactant is in the range of 0.1-2.0% by weight of the total formulation.

7. The liquid urease inhibitor formulation of claim 1 wherein the primary solvent is tetramethylene sulfone.

8. The liquid urease inhibitor formulation of claim 1 wherein the buffering agent and stabilizing agent are selected from the group consisting of triethanolamine, monoethanolamine, and mixtures thereof.

9. The liquid urease inhibitor formulation of claim 1, wherein the urease inhibitor is selected from the group consisting of N-butyl phosphoric triamide, 2-nitrophenyl phosphoric triamide, N-cyclohexyl phosphoric triamide (CHPT), and mixtures thereof.

10. A method for inhibiting urease hydrolysis of a urea-containing fertilizer or waste material, the method comprising the step of applying a liquid urease inhibitor formulation to the urea-containing fertilizer or waste material, 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 structure I and mixtures thereof,

wherein X is O or S, R is unsubstituted or substituted C₃-C₆Alkyl, unsubstituted and substituted C₅-C₈Cycloalkyl, phenyl and substituted phenyl with nitro, amino, alkyl or halide substituents; and Y H, NO₂Halide, NH₂Or C₁-C₈An alkyl group, wherein the urease inhibitor is not a compound having the structure:

(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;

wherein R is²＝C₁-C₆Alkyl radical

R³＝C₁-C₆Alkyl radical

Wherein n is 3-6

Wherein the urease inhibitor is soluble in the primary solvent; and

(c) a buffering agent and a stabilizing agent selected from hydroxyethylamine and hydroxypropylamine according to structure IV, wherein the amine is a primary, secondary or tertiary amine and the number of hydroxyethyl or hydroxypropyl groups is 1, 2 or 3,

wherein

R⁴And R⁵Independently H, C₁-C₆Alkyl or

R⁷H or CH₃。

11. The method of claim 10, wherein the liquid urease inhibitor formulation further comprises:

(d) a nonionic surfactant having humectant properties selected from the group consisting of fatty alcohol alkoxylates, alkylphenol alkoxylates, and mixtures thereof.

12. The method of claim 10, wherein the amount of urease inhibitor used in the liquid urease inhibitor formulation is in the range of 0.5 to 51% by weight of the total formulation.

13. The method of claim 10, wherein the amount of primary solvent used in the liquid urease inhibitor formulation is in the range of 10 to 80% by weight of the total formulation.

14. The method of claim 10, wherein the amount of buffer and stabilizer used in the liquid urease inhibitor formulation is in the range of 1 to 50% by weight of the total formulation.

15. The method of claim 11, wherein the amount of the non-ionic surfactant used in the liquid urease inhibitor formulation is in the range of 0.1 to 2.0% by weight of the total formulation.

16. The method of claim 10, wherein the primary solvent for the liquid urease inhibitor formulation is tetramethylene sulfone.

17. The method of claim 10, wherein the buffering agent and stabilizing agent for the liquid urease inhibitor formulation is selected from the group consisting of triethanolamine, monoethanolamine, and mixtures thereof.

18. The process of claim 10, wherein the urease inhibitor used in the liquid urease inhibitor formulation is selected from the group consisting of N-butyl phosphoric triamide, 2-nitrophenyl phosphoric triamide, N-cyclohexyl phosphoric triamide (CHPT), and mixtures thereof.

19. The method of claim 10, wherein the urea-containing fertilizer is a urea granule and the step of applying a liquid urease inhibitor formulation comprises spraying the formulation onto a surface of the urea granule or melting the urea granule and the formulation to form a solid mixture.

20. The method of claim 19, wherein the inhibition of urease hydrolysis of urea in the wet soil is for at least 14 days.

21. Use of a liquid urease inhibitor formulation according to any one of claims 1-9 for inhibiting urease hydrolysis of urea in wet soil.