RU2797320C2 - Improved composition based on urea-ammonium sulphate and method for its manufacturing - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention is related in particular to fertilizers based on urea-ammonium sulphate. Homogeneous particulate fertilizer composition based on urea-ammonium sulphate (UAS) contains urea-ammonium sulphate, a urease inhibitor of the phosphoric acid triamide type and magnesium sulphate, the content of ammonium sulphate in the urea-ammonium sulphate fertilizer composition is from 5 to 30% by weight, the content of magnesium sulphate is from 0.02 to 1% by weight and the content of the urease inhibitor is from 0.0001 to 1% by weight. The fertilizer composition additionally contains an alkaline or alkaline forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and optionally one or more anti-caking and/or water-repellent and/or anti-dust compounds.

EFFECT: proposed fertilizer composition based on urea-ammonium sulphate has improved properties to reduce ammonia losses due to urease activity in the soil.

25 cl, 1 tbl, 5 dwg, 4 ex

Description

SUMMARY OF THE INVENTION

The present invention relates to a homogeneous particulate solid composition based on urea-ammonium sulfate, additionally containing a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), and magnesium sulfate, which improves the properties to reduce loss of ammonia in the soil due to urease activity. In addition, the invention relates to a process for the manufacture of a homogeneous particulate solid composition based on urea-ammonium sulfate, containing urea, ammonium sulfate, a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), and magnesium sulfate. The product is particularly suitable as a fertilizer.

BACKGROUND OF THE INVENTION

Urea is the most common nitrogen-containing fertilizer. Urea has the highest nitrogen content of all commonly used nitrogen fertilizers (46%). Its worldwide consumption has increased significantly from about 20 million tons at the beginning of the seventies to about 100 million tons at the beginning of the twenty-first century. Nitrogen is the main component of any living system as a constituent of protein.

Thanks to intensive farming and the reduction of sulfur emissions from industrial plants and its subsequent release into the soil with rainfall, modern agriculture requires sulfur in addition to nitrogen.

Current agricultural practices typically require nitrogen and sulfur in a ratio of 10/1 to 5/1 to meet crop demand, eg 150 kg N/ha/yr and 30 kg sulphur/ha/yr.

Sulfur deficiency leads to both reduced quantity and quality of crops, and sulfur deficiency often affects the content and type of proteins. Indeed, sulfur is the main element included in the chemical composition of cells in molecules such as amino acids (cysteine, methionine, etc.). It is also a catalyst for photosynthesis and in some cases can improve atmospheric nitrogen fixation.

Typically, sulfur is applied to the soil in the form of elemental sulfur, or as compounds such as ammonium sulfate, ammonium bisulfate, thiosulfates, sulfides or gypsum, or in combination with other fertilizers such as urea, for example, as a physical mixture of urea and ammonium sulfate, or as a combined granulate of urea and ammonium sulfate, the latter hereinafter referred to as urea-ammonium sulfate, abbreviated as UAS.

Like urea itself, the urea that is present in UAS is also hydrolyzed in soil by the action of an enzyme catalyst, commonly referred to as urease, to form ammonia and carbon dioxide. Ureases are found in numerous bacteria, fungi, algae, plants, and some invertebrates, as well as in soils as a soil enzyme. Urease activity tends to increase the pH of its environment as ammonia dissolves in water in the soil, which is taken up by plants as a major source of nitrogen. However, ammonia can also be released into the atmosphere, making it unavailable to plant roots, a process called ammonia volatilization. Depending on the type of soil, water content, pH value, climatic conditions, etc. as a result of volatilization of ammonia, up to 50 wt. % nitrogen.

The availability of nitrogen from urea to the plant root system can be increased by combining (ie, adding or adding) a urease inhibitor with a fertilizer containing urea. Urease inhibitors are compounds that are able to temporarily reduce the activity of the enzyme and slow down the rate of hydrolysis of urea. There are many compounds that can inhibit urease, but only a few are non-toxic, effective at low concentrations, sufficiently chemically stable, and able to combine with fertilizers containing urea.

Among the most effective urease inhibitors known to date are the phosphoric acid triamide compounds first described in US Pat. No. 4,530,714 (Allied Corporation, 1985).

An example of an effective urease inhibitor described in said patent is N-(n-butyl)thiophosphoric acid triamide, which will be referred to in this application as nBTPT. This compound is in fact the precursor of the active compound N-(n-butyl)phosphoric acid triamide (nBPT) obtained by the oxidation of a thio compound, and it is this thio compound that is commonly produced, marketed and used. Throughout this application, when referring to urease inhibitors of the phosphoric acid triamide type, these terms are understood to cover all active compounds, active precursors and active transformation products derived from said phosphoric acid triamides.

When combined with a fertilizer containing urea, phosphoric acid triamides reduce the rate of hydrolysis of urea to ammonia in the soil. Benefits that result from delayed hydrolysis of urea include: (1) nutrient nitrogen is available to plants for a longer period of time, (2) there is no excessive accumulation of ammonia in the soil after the application of fertilizer containing urea, (3) the likelihood of wastage is reduced. nitrogen due to ammonia volatilization, (4) the potential for damage to seedlings and young plants by high levels of ammonia is reduced, (5) nitrogen uptake by plants is increased, and (6) crop yields are increased. Although phosphoric acid triamides do not directly affect the rate of ammonia nitrification, they regulate the levels of ammonia that undergoes nitrification and thereby indirectly regulate the levels of nitrate nitrogen in the soil.

Surprisingly, the inventors have encountered the problem that a phosphoric acid triamide type urease inhibitor, especially when applied as a liquid, which is the most common commercially available form, is not stable when in contact with the urea-ammonium sulfate composition, despite that a urease inhibitor of the phosphoric acid triamide type is generally described for use in urea-ammonium sulfate fertilizers. Moreover, even a phosphoric acid triamide type urease inhibitor in an alkaline organic solvent such as a mixture of propylene glycol and N-methylpyrrolidine, stabilized for long-term storage of the solution, rapidly decomposes after being added to the urea-ammonium sulfate composition. In addition, a phosphoric acid triamide type urease inhibitor, also used in solid form, is unstable when in contact with the urea-ammonium sulfate composition. The problem is most relevant for the storage of said urea-ammonium sulfate composition, where the particulate urea-ammonium sulfate composition and the phosphoric acid triamide type urease inhibitor are in close contact with each other for a long period of time.

This fact was the most unexpected, but it prompted the inventors to find a solution to the problem of stabilizing the urease inhibitor (namely, reducing the degree of its degradation) in the presence of a composition based on urea-ammonium sulfate in the form of particles. In this context, stability refers to the property of a chemical compound, in particular a urease inhibitor compound, to resist chemical degradation in the presence of a particulate urea-ammonium sulfate composition. Increased stability means longer life (or shelf life).

BACKGROUND OF THE INVENTION

The problem of stabilizing a urease inhibitor (namely, reducing its degradation), in particular nBTPT, in the presence of urea and ammonium sulfate is disclosed in international application WO 2017042194 (Yara International, 2017), which describes the addition of an alkaline or alkali-forming inorganic or organic compound selected from groups of oxides, carbonates, hydroxides, acetates and organic bases of metals and mixtures thereof, in particular selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof. However, it was found that, despite their stabilizing effect, the addition of these compounds induced the formation of ammonia as a result of the reaction of urea-ammonium sulfate with an alkaline compound such as CaO. During coating, the release of ammonia can be from 0.1 to 0.2 vol. %. Therefore, there is a need for a better stabilizer which stabilizes a urease inhibitor of the phosphoric acid triamide type in the presence of a urea-ammonium sulfate product, but does not cause the formation of significant amounts of ammonia, in particular by reaction with urea-ammonium sulfate, in particular less than 0.1 vol. . %. Publication CN 106069441 (Xu et al., 2016) describes a solid fertilizer composition containing 20 wt. % urea, 3 wt. % ammonium sulfate, 0.4 wt. % magnesium sulfate and 0.04 wt. %nBPT. Publication CN 103896673 (Li et al., 2014) describes a solid fertilizer composition containing 10 wt. % urea, 40 wt. % ammonium sulfate, 0.5 wt. % magnesium sulfate and 0.5 wt. %nBPT. Publication CN 103896672 (Li et al., 2014) describes a solid fertilizer composition containing 60 wt. % urea, 20 wt. % ammonium sulfate, 5.0 wt. % magnesium sulfate and 1.5 wt. %nBPT.

SUMMARY OF THE INVENTION

Surprisingly, the inventors found that the stability of a phosphoric acid triamide type urease inhibitor in the presence of a urea-ammonium sulfate product can be significantly increased when magnesium sulfate is added to the urea-ammonium sulfate.

In its broadest sense, this invention relates to a homogeneous particulate urea-ammonium sulfate composition containing urea-ammonium sulfate, a phosphoric acid triamide-type urease inhibitor and magnesium sulfate, characterized in that the UAS-based composition contains from 0.02 to 1 wt. % magnesium sulfate, from 0.0001 to 1 wt. % urease inhibitor and from about 5 to about 30 wt. % ammonium sulfate.

By incorporating magnesium sulfate into a urea-ammonium sulfate composition containing urea-ammonium sulfate and a phosphoric acid triamide type urease inhibitor, the stability of the phosphoric acid triamide type urease inhibitor is significantly improved, resulting, among other things, in a reduction in ammonia emission even when the inhibitor phosphoric acid triamide type urease was added to the urea-ammonium sulfate composition long before the actual application in the field as a fertilizer. In addition, it has been found that the stabilizer according to the invention stabilizes the urease inhibitor of the phosphoric acid triamide type in the presence of the urea-ammonium sulfate product and does not cause the formation of ammonia, in particular by reaction with the urea-ammonium sulfate product.

By including a stabilizer in the urea-ammonium sulfate composition containing the phosphoric acid triamide type urease inhibitor, the stability of the phosphoric acid triamide type urease inhibitor is greatly improved, especially during storage, so that smaller amounts of said urease inhibitor can be used.

In accordance with a specific embodiment of the present invention, magnesium sulfate is present in the composition in an amount of from 0.02 to 1 wt. %, preferably from 0.05 to 1 wt. % relative to the total weight of the composition.

In accordance with a specific embodiment of the present invention, magnesium sulfate is selected from the group consisting of anhydrous, mono-, di-, tri-, tetra-, penta-, hexa-, heptahydrates and mixtures thereof.

In accordance with a specific embodiment of the present invention, magnesium sulfate has a purity of > 70%, preferably > 80%, more preferably > 90%, most preferably > 99%.

According to a specific embodiment of the present invention, the phosphoric acid triamide type urease inhibitor is a compound of formula I:

Where:

X represents oxygen or sulfur;

R ₁ is alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl or cycloalkyl;

R ₂ is hydrogen, alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl or cycloalkyl; or R ₁ and R ₂ together may form an alkylene or alkenylene chain, which may optionally include one or more divalent oxygen, nitrogen or sulfur heteroatoms, forming a 4, 5, 6, 7 or 8-membered ring system;

R ₃ , R ₄ , R ₅ and R ₆ each separately represent hydrogen or alkyl containing from 1 to 6 carbon atoms; And

alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl and cycloalkyl refer to compounds containing 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms.

According to a specific embodiment of the present invention, the urease inhibitor is N-(n-butyl)thiophosphoric acid triamide (nBTPT).

In accordance with a specific embodiment of the present invention, the urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), is present in the composition based on a mixture of urea in an amount of from 0.0001 to 1 wt. %, preferably from 0.02 to 0.2 wt. %, most preferably from 0.03 to 0.06 wt. % relative to the total weight of the composition based on a mixture of urea.

In accordance with a particular embodiment of the present invention, the ratio by weight of urease inhibitor of the phosphoric acid triamide type to magnesium sulfate is in the range of 1:20 to 1:1, preferably 1:15 to 1:1, more preferably 1:10 to 1 :1.

According to a specific embodiment of the present invention, the urease inhibitor is incorporated into the urea-ammonium sulfate composition in liquid or particulate form, melt-blended with the urea-ammonium sulfate compound, or a combination of the two.

In accordance with a particular embodiment of the present invention, the urea-ammonium sulfate composition further comprises an alkali or alkali-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof.

According to a specific embodiment of the present invention, the weight ratio of said alkali or alkali forming compound to magnesium sulfate is in the range of 1:20 to 1:2, preferably 1:15 to 1:2, more preferably 1:10 to 1:2 .

According to a preferred embodiment of the present invention, the ammonium urea sulfate composition further comprises an anti-caking agent and/or a moisture repellent and/or an anti-dust agent, preferably coated on the ammonium urea particles.

According to a specific embodiment of the present invention, an anti-caking and/or water-repellent and/or anti-dust coating comprising at least a non-polar compound, in particular a liquid organic compound such as an oil, wax, resin or the like, and any mixture thereof , is present in the composition in the range from 0.0001 to 1 wt. %, preferably from 0.02 to 0.5 wt. %, most preferably from 0.1 to 0.2 wt. % relative to the total weight of the composition.

In accordance with a specific embodiment of the present invention, UAS is a co-granular product, preferably obtained by melt mixing molten urea and ammonium sulfate in the form of solid particles, obtained by pressing finely divided solid powders of urea and ammonium sulfate, or obtained by a chemical process for obtaining urea from dioxide carbon and ammonia, wherein the ammonia is neutralized to form ammonium sulfate (AS) in the urea melt or solution to form the UAS, or where the UAS is a mixture of particulate urea and particulate ammonium sulfate.

In accordance with a specific embodiment of the present invention, the average particle size (dp50) of the particulate urea-ammonium sulfate compound is from 1 mm to 5 cm, as determined by sieve analysis.

In accordance with a specific embodiment of the present invention, the composition based on urea-ammonium sulfate contains from about 5 to about 30 wt. % ammonium sulfate, from 0.03 to 0.06 wt. % nBTPT, 0.05 to 0.1 wt. % magnesium sulfate and from 0.015 to 0.03 wt. % magnesium oxide; adding up to 100 wt. % of the total weight of the composition.

In its broadest sense, the invention also relates to the use of the homogeneous solid particulate urea-ammonium sulfate composition of the invention as a fertilizer, in particular to support the growth of agricultural products on sulfur-deficient soil.

In its broadest sense, the invention also relates to a process for the preparation of a homogeneous, solid, particulate urea-ammonium sulfate composition of the invention, the process comprising the steps of:

1) providing a urea-ammonium sulfate product containing from about 5 to about 30 wt. % ammonium sulfate;

2) providing from 0.02 to 1 wt. % magnesium sulfate relative to the total weight of the composition;

3) providing from 0.0001 to 1 wt. % based on the total weight of the urease inhibitor composition of the phosphoric acid triamide type, preferably N-(n-butyl)thiophosphoric acid triamide (nBTPT);

4) optional, providing from 0.001 to 0.5 wt. % with respect to the total weight of the composition of an alkaline or alkaline-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and

5) optionally, providing a coating that is capable of increasing at least the anti-caking and/or moisture repellency and/or anti-dust properties of said urea-ammonium sulfate composition; And

6) adding the components provided in steps 2), 3), 4) and 5), in any order, to the component provided in step 1).

In the broadest sense, the invention also relates to a set of parts containing a quantity

a) magnesium sulfate;

b) a phosphoric acid triamide type urease inhibitor, preferably N-(n-butyl)thiophosphoric acid triamide (nBTPT);

c) an alkali or alkali forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and

d) optionally, one or more anti-caking and/or moisture-repellent and/or anti-dust compounds.

In the broadest sense, the invention also relates to a method for improving the stability of a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT) in a urea-ammonium sulfate composition containing urea-ammonium sulfate and from 0 .0001 to 1 wt. % urease inhibitor, by adding to the specified composition from 0.02 to 1 wt. % relative to the total weight of the composition of magnesium sulfate and, optionally, by adding from 0.001 to 0.5 wt. % relative to the total weight of the composition of an alkaline or alkaline-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof.

Hereinafter the invention will be described in more detail.

DETAILED DESCRIPTION OF THE INVENTION

In the context of this application, in the form of particles means a physical form, which can also be referred to as granulated, prilled, crystalline, compressed, powdered and the like, in which the corresponding compound is in the form of small particles.

The term "about" in the context of the present description, referring to a measurable value such as a parameter, amount, time duration and the like, means that it covers options of +/-20% or less, preferably +/-10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and even more preferably +/-0.1% or less of the specified value, as far as such options are suitable for performing in the disclosed invention. However, it should be understood that the meaning to which the term "about" refers is also specifically disclosed.

Magnesium sulfate

In accordance with a particular embodiment of the present invention, the present invention relates to a homogeneous, solid, particulate urea-ammonium sulfate composition comprising urea-ammonium sulfate, a phosphoric acid triamide-type urease inhibitor and magnesium sulfate, characterized in that the composition based on UAS contains from 0.02 to 1 wt. % magnesium sulfate, from 0.0001 to 1 wt. % urease inhibitor and from about 5 to about 30 wt. % ammonium sulfate.

In accordance with a specific embodiment of the present invention, magnesium sulfate is present in the composition in the range from 0.02 to 1 wt. %, preferably from 0.05 to 1 wt. % relative to the total weight of the composition. As a result of experiments, it was found that more than 1 wt. % does not produce a proportionally better stabilizing effect.

Magnesium sulfate is an inorganic salt with the chemical formula MgSO ₄ ⋅x(H ₂ O), where 0≤x≤7. It is solid at room temperature and is available as a powder with various average particle sizes (d ₅₀ ), for example from 5 to 1000 µm. Many hydrates are known. MgSO ₄ ⋅ 7(H ₂ O) heptahydrate (epsomite) can be obtained by neutralizing sulfuric acid with carbonate or magnesium oxide, but is usually obtained directly from natural sources. The heptahydrate easily loses one equivalent of water to form the hexahydrate. MgSO ₄ ⋅H ₂ O monohydrate occurs as the mineral kieserite. It can be obtained by heating the hexahydrate to approximately 150°C. Upon further heating to approximately 200° C., anhydrous magnesium sulfate is obtained.

In accordance with a specific embodiment of the present invention, magnesium sulfate is selected from the group consisting of anhydrous, mono-, di-, tri-, tetra-, penta-, hexa-, heptahydrates and mixtures thereof. Preferably the magnesium sulfate is anhydrous magnesium sulfate. The presence of water molecules in magnesium sulfate has been found to adversely affect the hygroscopicity of urea-ammonium sulfate.

In accordance with a specific embodiment of the present invention, magnesium sulfate has a purity of > 70%, preferably > 80%, more preferably > 90%, most preferably > 99%.

Magnesium sulfate can be incorporated into the composition of the present invention by conventional application methods such as coating and mixing methods well known to those skilled in the art such as spray coating and drum coating. Preferably, magnesium sulfate and a phosphoric acid triamide type urease inhibitor are in direct contact with each other so that magnesium sulfate is effective. This can be achieved most preferably by applying a urease inhibitor such as phosphoric acid triamide, magnesium sulfate and optionally an anti-caking and/or moisture repellent coating to the particles either sequentially or simultaneously, for example as a liquid anti-caking and/or moisture repellent coating composition, containing a urease inhibitor such as phosphoric acid triamide and magnesium sulfate.

Urease inhibitor

In accordance with a specific embodiment of the present invention, the present invention relates to a homogeneous particulate solid composition based on urea-ammonium sulfate, containing urea-ammonium sulfate and a urease inhibitor of the phosphoric acid triamide type, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT) wherein the phosphoric acid triamide type urease inhibitor is a compound of formula I:

Where:

X represents oxygen or sulfur;

R ₁ is alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl or cycloalkyl;

R ₂ is hydrogen, alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl, or cycloalkyl, or R ₁ and R ₂ together may form an alkylene or alkenylene chain, which may optionally include one or more divalent oxygen, nitrogen, or sulfur heteroatoms, forming 4, 5, 6, 7 or 8-membered ring system; And

R ₃ , R ₄ , R ₅ and R ₆ individually represent hydrogen or alkyl containing from 1 to 6 carbon atoms. In the present specification and claims, the term "phosphoric acid triamide compounds" is used to refer to compounds of formula I.

The terms alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl and cycloalkyl, as used herein, refer to compounds containing up to 10 carbon atoms, preferably up to 6 carbon atoms. The smallest number of carbon atoms is from 1 to 3, depending on the structure of the substituent.

nBTPT is marketed as the most effective urease inhibitor known and has the following chemical formula II

It should be understood that the term nBTPT in the context of this description refers not only to N-(n-butyl)thiophosphoric acid triamide in its pure form, but also to industrial types of this compound, which can contain up to 50 wt. % impurities depending on the method of synthesis and purification scheme(s), if any, used in the preparation of nBTPT.

To be effective, a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), is present in the urea-ammonium sulfate composition in the range of 0.0001 to 1 wt. %, preferably from 0.02 to 0.2 wt. %, most preferably from 0.03 to 0.06 wt. % relative to the total weight of the composition based on urea-ammonium sulfate.

As generally mentioned in this document and unless otherwise indicated, wt. % refers to the weight percent of an ingredient of a composition relative to the total weight of said composition.

In one embodiment, the weight ratio of the phosphoric acid triamide type urease inhibitor to magnesium sulfate is in the range of 1:20 to 1:1, preferably 1:15 to 1:1, more preferably 1:10 to 1:1. An exemplary weight ratio is 1:10.

In one embodiment, the urease inhibitor may be a liquid at room temperature, a liquid at elevated temperature, or a solid that is dissolved (solution) or suspended (suspension) in a carrier liquid, all of which are various liquid forms of a phosphoric triamide type urease inhibitor. acids, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT).

In embodiments where the phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), is used as a liquid, it is preferably used as a solution in an amount of from 0.1 to 75 wt. %, preferably in the form of a solution in an amount of from 15 to 30 wt. % relative to the total mass of the solution. Industrial solutions are available such as Agrotain® Ultra (Koch, US), N Yield™ (Eco Agro, The Netherlands), Rhodia Ag-Rho™ N Protect B (Solvay, Germany), Iper N-Protect Liquid (Van Iperen, The Netherlands) and BASF Limus (BASF, Germany).

In embodiments where the nBTPT urease inhibitor is used as a liquid dissolved in a carrier, it can be used as a powder dissolved in propylene glycol, for example, in an amount of 17.5 wt. %nBTPT. It is available from Yara International ASA (Norway) as Amiplus® liquid.

Experiments have shown that less of a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), must be used in the compositions of the invention than is commonly used in the prior art. For example, according to the invention, the most preferred amount is 0.05 wt. %, while for the application of Agrotain® Ultra an amount equal to 0.09 wt. %. This established fact, at least in part, can be attributed to the fact that in the compositions of the invention, the urease inhibitor of the phosphoric acid triamide type, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), is stabilized, while in the prior art, an excess dose is needed to compensate for the degradation of the urease inhibitor and increase its shelf life. The discovery of this fact also results in less urease inhibitor of the phosphoric acid triamide type, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), being released into the environment.

In the case of embodiments where the urease inhibitor is applied in solid form, it is applied in powder form, preferably with a purity of 99 wt. % or more. Such an inhibitor is available, for example, from Sunfit Chemical Co. (China).

A phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), can be incorporated into a composition containing urea and ammonium sulfate particles using conventional coating and mixing techniques well known to one skilled in the art. such as spray and drum application.

A phosphoric acid triamide type urease inhibitor, in particular N-(h-butyl)thiophosphoric acid triamide (nBTPT), can also be incorporated into the urea ammonium sulfate composition by hot melt mixing as described in US Patent 5,352,265 (Weston et al., 1994) for urea, which discloses that nBTPT is incorporated into a homogeneous granular fertilizer composition by mixing a concentrated solution of nBTPT in a solvent selected from liquid amides, 2-pyrrolidone and N-alkyl 2-pyrrolidones, directly with molten urea prior to its granulation.

Additional Alkaline or Alkaline Forming Compounds (Co-Stabilizer) According to a specific embodiment of the invention, the urea-ammonium sulfate composition further comprises an alkali or alkali forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof.

Surprisingly, it has been found that adding some amount of one or more of the above compounds improves the stabilizing properties of magnesium sulfate for stabilizing a phosphoric acid triamide type urease inhibitor in the presence of a urea-ammonium sulfate product without the formation of significant amounts of ammonia, in particular by reaction with a urea-ammonium sulfate product. .

In one embodiment, the weight ratio of said alkali or alkali forming compound to magnesium sulfate is in the range of 1:20 to 1:2, preferably 1:15 to 1:2, more preferably 1:10 to 1:2. Illustrative weight ratios are about 1:10 and about 1:3, that is, the amount of alkali or alkali-forming compound is always less than the amount of magnesium sulfate. In one embodiment, the amount of alkali or alkali forming compound is 2, 3, 5, or even 10 times less than the amount of magnesium sulfate. According to one embodiment, the amount of alkali or alkali-forming compound is in the range from 0.001 to 0.5 wt. % relative to the total weight of the composition based on UAS.

Coating

In accordance with a specific embodiment of the present invention, the urea-ammonium sulfate composition of the invention further comprises an anti-caking agent and/or a moisture repellent and/or an anti-dust agent coated on the particulate components of the urea-ammonium sulfate composition. ammonium, where the coating includes at least a non-polar compound, in particular a liquid organic compound such as oil, wax, resin and the like and any mixture thereof, and is present in the composition in the range from 0.0001 to 1 wt. %, preferably from 0.02 to 0.5 wt. %, most preferably from 0.1 to 0.2 wt. % relative to the total weight of the composition.

Examples of suitable anticaking and/or moisture repellent coatings are vegetable oil (eg, from rapeseed or neem), paraffin, and Novoflow anticaking and/or moisture repellent agents (Novochem Fertilizer Additives, The Netherlands).

Preferably, the water-repellent coating is the coating described in EP 0768993 A1 (Norsk Hydro ASA) for nitrogen-containing fertilizers, containing at least wax, oil and resin soluble in oil and miscible with the wax.

Urea-ammonium sulfate

Urea-ammonium sulfate is a co-granular product and can be produced in several ways, such as melt-blending molten urea and ammonium sulfate in particulate form by adding ammonium sulfate in particulate form to the molten urea in a granulation step, e.g., in a drum or boiler, as described in US Patent No. 3,785,796 (Tennessee Valley Authority, 1974), or using a fluid bed granulator, as described, for example, in application WO 99/65845 (SKW StickstofFwerke Piesteritz GmbH, 1999), or as used by Yara on at their factories in Sluiskil (The Netherlands).

Alternatively, the urea-ammonium sulfate product can also be obtained in accordance with the method of WO 92/12633 (FMC Corp., USA) or the like as a compressed material, where fine solid urea and powdered ammonium sulfate are pressed together with microcrystalline cellulose to form lozenges, tablets and the like.

Alternatively, the urea-ammonium sulfate product can be prepared by a chemical process to produce urea from carbon dioxide and ammonia, wherein the ammonia is neutralized to form ammonium sulfate (AS) in a melt or solution of urea to form UAS, as described in WO 2006/004424 A1 (Yara International ASA, Norway), and more specifically when using a tubular reactor at the end of the process in a classic urea plant as described in WO 2006/093413 A1 (Yara International ASA, Norway). According to a specific embodiment, the neutralization of ammonia can be carried out with sulfuric acid in a scrubber and return the product to the urea melt, followed by granulation.

In the above cases, the UAS granules in the composition are homogeneous, that is, each granule consists in principle of the same substances.

Alternatively, the UAS may be a mixture of particulate urea and particulate ammonium sulfate, eg in powder form, applied to the particulate urea. In this case, each granule does not contain the same substances.

Regardless of the method of obtaining UAS may contain from about 5 to about 30 wt. % ammonium sulfate (AS), preferably 10 wt. % or more, based on the total weight of UAS, in which the remaining weight is preferably urea. Preferred product grades contain from about 23 to about 30 wt. % AS [such as YaraVera® Amidas™ (40-0-0 5.5 S), Yara International ASA, which is a homogeneous granular fertilizer containing urea and ammonium sulfate with an N to S ratio of 7.3:1, and YaraVera ® Ureas™ (38-0-0 7.5 S), Yara International ASA, which is a homogeneous granular fertilizer containing urea and ammonium sulfate with a ratio of N to S equal to 5:1].

For use as a fertilizer, the average particle size (dp50) of the urea-ammonium sulfate compound should be between 1 mm and 5 cm, preferably between 1 and 20 mm, preferably between 1 and 10 mm, preferably between 1 and 6 mm, preferably between 2 and 4 mm, most preferably between 3.2 and 3.5 mm as determined by sieve analysis.

In accordance with a specific embodiment of the present invention, the composition based on urea-ammonium sulfate contains from about 5 to about 30 wt. % ammonium sulfate, from 0.03 to 0.06 wt. % nBTPT, 0.05 to 0.1 wt. % magnesium sulfate and from 0.015 to 0.03 wt. % magnesium oxide, with the addition of up to 100 wt. %, which is the total weight of the composition.

Application

In accordance with a specific embodiment of the invention, the present invention further provides for the use of a homogeneous solid composition in the form of particles based on urea-ammonium sulfate as a fertilizer, in particular to support the growth of agricultural products on sulfur-deficient soil. Sulfur-deficient soils are a growing problem: because sulfur is a component of numerous protein enzymes that regulate photosynthesis and nitrogen fixation, when sulfur is limited, less chlorophyll is produced, causing young plant leaves to turn yellow, a symptom sometimes confused with nitrogen deficiency.

Receipt

According to a particular embodiment of the present invention, the invention also relates to a process for the preparation of a homogeneous particulate urea-ammonium sulfate composition comprising urea-ammonium sulfate, magnesium sulfate and a phosphoric acid triamide type urease inhibitor, in particular N-(n -butyl)thiophosphoric acid (nBTPT).

In particular, the invention relates to a process for the preparation of a homogeneous, solid, particulate urea-ammonium sulfate composition according to the invention, the process comprising the steps of:

1) providing a urea-ammonium sulfate product containing from about 5 to about 30 wt. % ammonium sulfate;

2) providing from 0.02 to 1 wt. % magnesium sulfate relative to the total weight of the composition;

3) providing from 0.0001 to 1 wt. % based on the total weight of the urease inhibitor composition of the phosphoric acid triamide type, preferably N-(n-butyl)thiophosphoric acid triamide (nBTPT);

4) optional, providing from 0.001 to 0.5 wt. % relative to the total weight of the composition of a compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof,

5) optionally, providing a coating that is capable of at least increasing the anti-caking and/or water repellency and/or anti-dust properties of said urea-ammonium sulfate composition; And

6) adding the components provided in steps 2), 3), 4) and 5), in any order, to the component provided in step 1).

It was found that the order in which the magnesium sulfate, phosphoric acid triamide type urease inhibitor, stabilizer, co-stabilizer and coating material were added had little effect on achieving the claimed results.

Parts set

In accordance with a specific embodiment of the present invention, the invention further relates to a set of parts containing a quantity

a) magnesium sulfate;

b) a urease inhibitor of the phosphoric acid triamide type, preferably N-(n-butyl)thiophosphoric acid triamide (nBTPT);

c) a compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and

d) optionally, one or more anti-caking and/or moisture-repellent and/or anti-dust compounds.

The components of such a set of parts can then be added to the urea-ammonium sulfate in the form of solid particles in the desired amount to obtain a homogeneous solid composition in the form of particles based on urea-ammonium sulfate, containing urea-ammonium sulfate and a phosphoric acid triamide type urease inhibitor of this invention .

In one embodiment, the components are provided as separate parts. In another embodiment, the components are premixed and provided as a combined portion. Preferably they are premixed in a given weight ratio of urease inhibitor of the phosphoric acid triamide type to ammonium sulfate of 1:20 to 1:1, preferably 1:15 to 1:1, more preferably 1:10 to 1:1.

Finally, this invention relates to a method for improving the stability of a phosphoric acid triamide type urease inhibitor, in particular N-(n-butyl)thiophosphoric acid triamide (nBTPT), in a urea-ammonium sulfate composition containing urea-ammonium sulfate and from 0, 0001 to 1 wt. % urease inhibitor, by adding to the specified composition from 0.02 to 1 wt. % magnesium sulfate relative to the total weight of the composition.

Detailed embodiments have been discussed herein above and in the following examples.

Preferred embodiments of the method of the invention will now be illustrated by means of the following non-limiting examples.

EXAMPLES

Description of Figures

Fig. 1. Ammonia recovery from YaraVera® Amidas product containing 462 ppm (parts per million) nBTPT treated with several stabilizers (see Table 1).

Fig. 2A. Stability of nBTPT in YaraVera® Amidas containing 462 ppm nBTPT in plastic containers exposed to air at room temperature after 40 days [A = no stabilizer; B = CaO (2541 ppm); C = MgSO ₄ , 99.5% pure (4957 ppm)].

Fig. 2B. Stability of nBTPT in YaraVera® Amidas containing 462 ppm nBTPT in bags at 40°C after 8 days [A = no stabilizer; B = CaO (2541 ppm); C = MgSO ₄ , 99.5% pure (4957 ppm)].

Fig. 3. Stability of nBTPT in YaraVera® Amidas containing 462 ppm nBTPT using various grades and forms of MgSO ₄ and Na ₂ SO ₄ stored in open plastic containers at room temperature for 21 days [A = no stabilizer; B = CaO (2541 ppm); C = MgSO ₄ , 99.5% pure (4957 ppm); D = MgSO ₄ , 99.999% pure (4957 ppm); E \u003d MgSO ₄ 7H ₂ O (10163 ppm); F = Na ₂ SO ₄ (5849 ppm)].

Fig. 4. Stability of nBTPT in YaraVera® Amidas containing 462 ppm nBTPT using various combinations of MgSO ₄ /MgO [A = no stabilizer; B = CaO (2310 ppm); C = MgO (212 ppm); D = MgSO ₄ content > 98% (4620 ppm); E = MgSO ₄ content > 98% (924 ppm)/MgO (212 ppm)].

experimental part

1. Volatilization measurements (diffusion kit 2 L for determination of ammonia emission)

200 g of the UAS product treated with nBTPT/stabilizer was placed in a 2 L plastic container. A Dräger tube is placed through the lid to measure volume. % ammonia. The Draeger tube changes color from yellow to cyan/magenta when ammonia is absorbed in the tube. The amount (vol.%) of released ammonia can be tracked over time.

2. nBTPT measurements

For laboratory experiments, 1.2 kg of solid fertilizer was placed in a laboratory drum. In the next step, nBTPT/stabilizer was added slowly. The contact time was 10 minutes, and, accordingly, the speed of rotation of the drum in each experiment was the same. In the case where a hydrophobic coating was added, a sprayer was used and depending on the order of addition, the hydrophobic coating was added before or after the addition of nBTPT. Before use, the hydrophobic coating was preheated to 80°C. Experiments on a large scale, up to 40 kg of fertilizer, were carried out in a concrete mixer.

The samples were stored under various conditions depending on the type of samples:

• Packed in bags, at room temperature (18-25°C);

• Packed in bags, at 40°C;

• With access to air at room temperature (18-25°C).

3. HPLC analysis of nBTPT content

HPLC analysis of nBTPT was performed as described in the method according to the European standard CEN 15688-2007.

4. Products

UAS was obtained from Yara as YaraVera® Amidas 40-0-0 beads (product code PA421X).

Solid N-(n-butyl)thiophosphoric acid triamide was obtained from Sunfit Chemical Co. (China) (CAS-Nr. 94317-64-3) as a white crystalline solid, melting point 58-60°C.

Technical grade MgO was obtained from Mannekus & Co BV, Schiedam, The Netherlands (dp(50) = 27 µm, +/- 90% purity, 2-2.9% CaO, 1.1% SiO ₂ ).

Technical grade CaO was obtained from VWR International, Oud-Heverlee, Belgium (91.3% purity, 2.7% CaCO ₃ and 6% Ca(OH) ₂ , dp(50) = 22 μm).

CaCO ₃ (limestone powder) was obtained from Nordkalk AB, Finland (purity 98.5%, dp(50)=7 µm).

CaSO ₄ , anhydrous, was obtained from Alfa Aesar, Haverhill, USA.

MgSO ₄ , anhydrous, 99.999%, was obtained from Alfa Aesar, Haverhill, USA.

MgSO ₄ , anhydrous, >99.5%, was obtained from Alfa Aesar, Haverhill, USA.

MgSO ₄ , anhydrous, >98%, was obtained from Ekmekciogullari, Turkey.

MgSO ₄ ⋅7H ₂ O >99.5% was obtained from Merck KGaA, Darmstadt, Germany.

Coating: Hydrophobic (MR) coating was prepared in accordance with European patent application EP 0768993 A1 (Norsk Hydro ASA) by mixing about 28 wt. % wax, about 68 wt. % oil and about 4 wt. % resin and applied to the fertilizer in an amount of about 0.1-0.5 wt. %. In this application, this coating is referred to as the NH coating.

EXPERIMENT 1 (ammonia evolution)

Experiment 1 defines a task. On FIG. 1 shows ammonia recovery from YaraVera® Amidas containing 462 ppm nBTPT treated with several stabilizers. The numbers in brackets for each stabilizer compound are the weight ratio of the specified stabilizer compound and nBTPT.

Although compounds such as MgO and CaO are mentioned in the prior art document WO 2017042194 (Yara International, 2017) as the most effective nBTPT stabilizers in the presence of the urea-ammonium sulfate product, these compounds have been experimentally determined to cause ammonia release in the presence of this product. , which is an undesirable effect of these stabilizers. Only without a stabilizer and in the presence of MgSO ₄ and CaSO ₄ does not release ammonia.

EXPERIMENT 2

This experiment was carried out to show the difference between the positive effect caused by the addition of an alkaline or alkali-forming inorganic or organic compound (CaO prior art) and MgSO ₄ (VWR purity 99.5%) to UAS on the stability of nBTPT in the presence of UAS open to access to air at room temperature (Fig. 2A) and bagged at elevated temperature (Fig. 2B). As can be seen, the stabilizing effect of MgSO ₄ is comparable to that of the prior art compound (CaO), but no ammonia is formed (as shown in Fig. 1).

EXPERIMENT 3 (various brands)

This experiment shows the effect of adding different grades and forms of MgSO ₄ as well as another sulfate, Na ₂ SO ₄ , compared to the prior art CaO compound for outdoor storage conditions at room temperature (FIG. 3). All grades of MgSO ₄ show comparable nBTPT stability in YaraVera® Amidas. This experiment shows that the stabilizing effect of MgSO ₄ on nBTPT in UAS is not 100% based on pH determination (alkaline pH 8.5 for MgSO ₄ 99.5% compared to acidic pH 6.1 for MgSO ₄ 99.999%), but also not 100% based on the water-binding capacity of anhydrous MgSO ₄ because MgSO ₄ ⋅7H ₂ O provides similar stability to nBTPT. Na ₂ S04 does have a negative effect on the stability of nBTPT. This shows the unique stabilizing effect of magnesium sulfate.

EXPERIMENT 4 (effect of addition of oxides and synergistic effect of MgSO ₄ and MgO)

This experiment shows the effect of adding a small amount of oxide to a stabilizer. Small amounts of MgSO ₄ , which have little effect, become very effective in combination with MgO (see D versus F). The effect is synergistic (see C + D versus F) and not additive. There is practically no difference in stability depending on the way the components of the stabilizer composition are combined (ie, adding the components sequentially in any order/premixing the components and adding the premix to the UAS). MgO has been found to be more effective than CaO, but any alkali or alkali forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof is believed to be effective.

Claims (41)

1. Homogeneous particulate fertilizer composition based on urea-ammonium sulfate (UAS) containing urea-ammonium sulfate, a urease inhibitor of the phosphoric acid triamide type and magnesium sulfate, characterized in that the fertilizer composition based on UAS contains from 5 to 30 wt. .% ammonium sulfate, from 0.02 to 1 wt.% magnesium sulfate and from 0.0001 to 1 wt.% urease inhibitor. 2. Fertilizer composition based on urea-ammonium sulfate according to claim 1, characterized in that magnesium sulfate is present in the composition in the range from 0.05 to 1 wt.% relative to the total weight of the composition. 3. The composition of the fertilizer based on urea-ammonium sulfate according to any one of paragraphs. 1, 2, in which magnesium sulfate is selected from the group consisting of anhydrous mono-, di-, tri-, tetra-, penta-, hexa-, heptahydrate and mixtures thereof. 4. The urea-ammonium sulfate fertilizer composition of claim 3, wherein the magnesium sulfate is >70% pure. 5. Composition fertilizer based on urea-ammonium sulfate according to any one of paragraphs. 1-4, characterized in that the phosphoric acid triamide type urease inhibitor is a compound of formula I:

where X is oxygen or sulfur, R ₁ is alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl or cycloalkyl; R ₂ is hydrogen, alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl or cycloalkyl or R ₁ and R ₂ together may form an alkylene or alkenylene chain which may optionally include one or more divalent oxygen, nitrogen or sulfur heteroatoms to form 4 -, 5-, 6-, 7- or 8-membered ring system; And R ₃ , R ₄ , R ₅ and R ₆ each separately represents hydrogen or alkyl containing from 1 to 6 carbon atoms; And alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl and cycloalkyl refer to compounds containing from 1 to 10 carbon atoms. 6. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-5, wherein the urease inhibitor is N-(n-butyl)thiophosphoric acid triamide (nBTPT). 7. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-6, in which the urease inhibitor is present in the range from 0.02 to 0.2 wt.% in relation to the total weight of the fertilizer composition based on urea-ammonium sulfate. 8. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-7, wherein the weight ratio of phosphoric acid triamide type urease inhibitor to magnesium sulfate is 1:20 to 1:1. 9. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-8, wherein the urea ammonium sulfate fertilizer composition can be obtained by (i) applying a phosphoric acid triamide type urease inhibitor to the urea ammonium sulfate fertilizer composition in liquid or particulate form, (ii) melt blending with a urea-ammonium sulfate fertilizer compound; or (iii) a combination thereof. 10. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-9, wherein the urea-ammonium sulfate fertilizer composition further comprises an alkali or alkali-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof. 11. A urea-ammonium sulfate fertilizer composition according to claim 10, wherein the weight ratio of alkali or alkali-forming compound to magnesium sulfate is in the range of 1:20 to 1:2. 12. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-11, characterized in that the fertilizer composition based on ammonium sulfate additionally contains an anti-caking and/or water-repellent and/or anti-dust substance. 13. The urea-ammonium sulfate fertilizer composition according to claim 12, wherein the anti-caking and/or moisture-repellent and/or anti-dust substance is applied as a coating to the ammonium urea particles. 14. A urea-ammonium sulfate fertilizer composition according to claim 12 or 13, in which the anti-caking and/or moisture-repellent coating contains at least a non-polar compound and is present in the composition in the range from 0.0001 to 1 wt.% with respect to the total weight of the composition. 15. The urea-ammonium sulfate fertilizer composition of claim 14, wherein the non-polar compound is a liquid organic compound such as an oil, wax or resin and any combination thereof. 16. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-15, where UAS is a co-granular product. 17. The urea-ammonium sulfate fertilizer composition of claim 16, wherein the co-granular product is one obtained by melt-blending molten urea and ammonium sulfate in the form of solid particles, obtained by pressing powders of finely divided solid urea and ammonium sulfate, or obtained by a chemical method for obtaining urea from carbon dioxide and ammonia, wherein the ammonia is neutralized to form ammonium sulfate (AS) in a melt or solution of urea to form UAS, or wherein the UAS is a mixture of particulate urea particulate and ammonium sulfate particulate. 18. Fertilizer composition based on urea-ammonium sulfate according to any one of paragraphs. 1-17, characterized in that the average particle size (dp50) of the particulate urea-ammonium sulfate fertilizer compound is from 1 mm to 5 cm, as determined by sieve analysis. 19. The composition of the fertilizer based on urea-ammonium sulfate according to any one of paragraphs. 10-18, where the fertilizer composition based on urea-ammonium sulfate contains from 5 to 30 wt.% ammonium sulfate, from 0.03 to 0.06 wt.% nBTPT, from 0.05 to 0.1 wt.% magnesium sulfate , from 0.015 to 0.03 wt.% magnesium oxide and urea, added to 100 wt.%, which is the total weight of the composition. 20. The use of a homogeneous solid fertilizer composition in the form of particles based on urea-ammonium sulfate according to any one of paragraphs. 1-19 as fertilizer. 21. Use according to claim 20 to support the growth of agricultural products on sulfur-deficient soil. 22. The method of obtaining a homogeneous solid fertilizer composition in the form of particles based on urea-ammonium sulfate according to any one of paragraphs. 1-19, including the steps: 1) providing a product urea-ammonium sulfate containing from 5 to 30 wt.% ammonium sulfate; 2) providing from 0.02 to 1 wt.%, relative to the total weight of the magnesium sulfate composition; 3) providing from 0.0001 to 1% by weight, based on the total weight of the composition, of a urease inhibitor of the phosphoric acid triamide type; 4) optionally providing from 0.001 to 0.5 wt.%, relative to the total weight of the composition, of an alkali or alkali-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and 5) optionally providing a coating material, wherein the coating material is capable of increasing at least the anti-caking and/or moisture repellency and/or anti-dust properties of said urea-ammonium sulfate fertilizer composition; And 6) adding the components provided in steps 2), 3), 4) and 5), in any order, to the component provided in step 1). 23. The method of claim 22 wherein the phosphoric acid triamide type urease inhibitor is N-(n-butyl)thiophosphoric acid triamide (nBTPT). 24. Kit for adding to urea-ammonium sulfate, to obtain a composition according to any one of paragraphs. 1-19 containing quantity a) magnesium sulfate; b) a urease inhibitor of the phosphoric acid triamide type; c) a compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate and mixtures thereof, and d) optionally one or more anti-caking and/or moisture-repellent and/or anti-dust compounds. 25. The kit of claim 24 wherein the phosphoric acid triamide type urease inhibitor is N-(n-butyl)thiophosphoric acid triamide (nBTPT).

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