HK1234027B - Composition containing n-(n-butyl) thiophosphoric triamide adducts and reaction products - Google Patents

Description

Compositions containing N-(n-butyl)thiophosphoric triamide adducts and reaction products

Cross-reference to related applications

This application claims priority to U.S. Provisional Application No. 62/196,781, filed on July 24, 2015, which is incorporated herein by reference in its entirety.

Technical Field

The present subject matter generally relates to compositions comprising urease inhibitors and methods of making and using the same.

Background Art

Fertilizers have been used for some time to provide nitrogen to the soil. The most widely used and agriculturally important nitrogen fertilizer is urea, CO(NH ₂ ) ₂ . Most urea currently produced is used as a fertilizer in its granular (or granulated) form. After urea is applied to the soil, it readily hydrolyzes to produce ammonia and carbon dioxide. This process is catalyzed by the enzyme urease, which is produced by some bacteria and fungi that may be present in the soil. The gaseous products formed by the hydrolysis reaction (i.e., ammonia and carbon dioxide) may evaporate into the air and, as a result, may result in significant losses from the total amount of nitrogen applied to the soil.

Attempts to reduce the loss of applied nitrogen have used urease inhibitors and/or nitrification inhibitors as additives to fertilizers. Urease inhibitors are compounds that can inhibit the catalytic activity of urease on urea in the soil. Nitrification inhibitors are compounds that can inhibit the bacterial oxidation of ammonium in the soil to nitrates. Urease inhibitors and nitrification inhibitors can be associated with fertilizers in a variety of ways. For example, they can be coated on fertilizer particles or mixed into the fertilizer matrix. Many granulation methods are known, including falling curtain, spherudization-agglomeration drum granulation, spheroidization and fluidized bed granulation techniques.

Examples of urease inhibitors are the thiophosphoric triamide compounds disclosed in U.S. Pat. No. 4,530,714 to Kolc et al., which is incorporated herein by reference. The disclosed thiophosphoric triamide compounds include N-(n-butyl)thiophosphoric triamide (NBPT), the most developed representative of this class of compounds. When incorporated into urea-containing fertilizers, NBPT reduces the rate at which urea is hydrolyzed to ammonia in the soil. Benefits realized as a result of delayed urea hydrolysis include the following: (1) nutritional nitrogen is available to plants over a longer period of time; (2) excessive accumulation of ammonia in the soil after application of urea-containing fertilizers is avoided; (3) the potential for nitrogen loss through ammonia volatilization is reduced; (4) the potential for damage to seedlings and rice plants from high levels of ammonia is reduced; (5) plant uptake of nitrogen is increased; and (6) an increase in crop yield is achieved. NBPT is commercially available for use in agriculture and is sold as a product line called nitrogen stabilizers.

Technical-grade NBPT is a solid, waxy compound that decomposes under the action of water, acid, and/or elevated temperatures. In particular, NBPT is believed to degrade at elevated temperatures into compounds that are unable to provide the desired inhibitory effect on urease. Therefore, combining it with other solid materials to provide materials that can inhibit urease can be challenging, particularly through granulation with urea, which typically utilizes heat. Consequently, a need exists for compositions containing urease inhibitors that can be combined with urea (ideally using current urea manufacturing practices) to produce fertilizer compositions that provide effective urease inhibition.

Summary of the Invention

As disclosed herein, compositions comprising urease inhibitors and methods for preparing the same are provided. Such compositions typically comprise a reaction product between a urease inhibitor (e.g., N-(n-butyl)thiophosphoric triamide, NBPT), urea, and formaldehyde. Such reaction products can be characterized as adducts because the product resulting from the reaction retains at least a portion of two or more reactants (i.e., urease inhibitor, urea, and/or formaldehyde). Compositions resulting from such reactions (including the disclosed reaction products) can be provided independently and, in certain embodiments, can be combined with other ingredients. For example, such adduct-containing compositions can be combined with fertilizer materials comprising a nitrogen source, including, but not limited to, urea, ammonia, ammonium nitrate, and combinations thereof. Advantageously, the adduct-containing compositions disclosed herein, alone or in combination with one or more nitrogen sources, can provide fertilizers that exhibit a considerable degree of urease inhibitory effect and can therefore be characterized by low ammonia volatilization losses during use (i.e., when applied to soil).

In one aspect, the present disclosure provides a composition comprising an adduct of NBPT, urea, and formaldehyde. In another aspect, the present disclosure provides a composition comprising an adduct of NBPT, urea, and formaldehyde, and one or more materials selected from the group consisting of free NBPT, free formaldehyde, a urea-formaldehyde polymer (UFP), water, and combinations thereof. In a further aspect, the present disclosure provides a composition comprising an adduct of NBPT, urea, and formaldehyde, wherein the composition is substantially free of dicyandiamide. In an even further aspect, the present disclosure provides a composition comprising one or more adducts of NBPT, urea, and formaldehyde, wherein the one or more adducts are represented by the following structure:

In some embodiments, the compositions provided herein can be in the form of a solution of the adduct (e.g., using an organic solvent, such as those disclosed below). In certain embodiments, the composition is a synergistic mixture of free NBPT and the adduct. The disclosed compositions, in some embodiments, can be substantially free of dicyandiamide (DCD). In some compositions, at least a portion (including all) of the urea and formaldehyde is in the form of a urea-formaldehyde reaction product comprising dimethylol urea.

In another aspect, the present disclosure provides a fertilizer composition comprising urea and an adduct of NBPT, urea, and formaldehyde. Any of the compositions of NBPT, urea, and formaldehyde adducts disclosed herein can be used in such fertilizer compositions. In certain embodiments, the fertilizer composition can comprise a significant amount of urea, for example, at least about 90% urea by weight, at least about 95% urea by weight, at least about 98% urea by weight, at least about 99% urea by weight, or at least about 99.5% urea by weight.

In a further aspect, the present disclosure provides a method of forming a fertilizer composition, the method comprising combining a composition comprising an adduct of NBPT, urea, and formaldehyde as disclosed herein with a fertilizer material. The method, in certain embodiments, may comprise mixing the adduct-containing composition with solid particles of the fertilizer material, and in other embodiments, may comprise mixing the adduct-containing composition with a molten stream of the fertilizer material. In some embodiments, the method may further comprise combining free NBPT with one or both of the fertilizer material and the adduct-containing composition.

In another aspect, the present disclosure provides a method for preparing a urease-inhibiting fertilizer, the method comprising combining urea, formaldehyde, and NBPT such that an excess of urea is present to form an adduct of NBPT, urea, and formaldehyde, the adduct remaining bound to the remaining urea. In some embodiments, the urea and formaldehyde are in the form of a urea-formaldehyde reaction product comprising dimethylol urea.

In a further aspect, the present disclosure provides a method of reducing the hydrolysis of urea to ammonia in soil, the method comprising applying to the soil a composition comprising an adduct of NBPT, urea, and formaldehyde. Such a method can comprise combining a nitrogen source with the composition before applying, applying the composition to the soil after applying the nitrogen source to the soil, or applying the composition to the soil and then applying the nitrogen source to the soil.

In a further aspect, the present disclosure provides a method for incorporating an adduct of NBPT, urea, and formaldehyde into molten urea, the method comprising combining such an adduct (e.g., including, but not limited to, an adduct in the form of an adduct-containing composition) with molten urea. Additionally, the present disclosure provides a method for forming an adduct of NBPT, urea, and formaldehyde, the method comprising contacting NBPT with a molten urea stream containing formaldehyde and/or a reaction product of urea and formaldehyde.

In one aspect, the present disclosure specifically provides a composition comprising a mixture of: N-(n-butyl)thiophosphoric triamide (NBPT), an adduct of urea and formaldehyde; and free NBPT. The present disclosure also provides fertilizer compositions comprising urea and such a composition. It further provides methods of forming the fertilizer composition, comprising contacting a fertilizer material with such a composition, and methods of reducing the hydrolysis of urea to ammonia in soil, comprising applying such a composition to the soil.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to provide an understanding of the embodiments of the present invention, reference is made to the accompanying drawings, which are exemplary only and should not be construed as limiting the present invention.

Figure 1 is a graph of the effects of various urease inhibitors on ammonia volatilization (measured in ppm); and

FIG2 is a graph of the cumulative N loss (measured in %) from urea and urease inhibitor treated urea.

DETAILED DESCRIPTION

It is noted herein that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. All percentages, parts, and ratios are based on the total weight of the compositions of the present invention, unless otherwise indicated. As they pertain to listed ingredients, all such weights are based on the active level, and, therefore, do not include solvents or by-products that may be included in commercially available materials, unless otherwise indicated. The term "weight percent" may be expressed herein as "wt %." All molecular weights used herein are weight average molecular weights, expressed as grams per mole, unless otherwise indicated.

According to the present disclosure, compositions exhibiting effective urease inhibition and methods for producing such compositions are provided. Surprisingly, it was found that when a higher amount of urease inhibitor was added to a mixture of urea and formaldehyde, the amount of free urease inhibitor present in the final product mixture did not increase proportionally accordingly. Subsequently, it was determined that at least a portion of the urease inhibitor added to urea and formaldehyde reacted under the conditions under which it was carried out to form an adduct comprising the urease inhibitor (thereby reducing the concentration of free urease inhibitor in the final product mixture). Such reaction products and compositions derived therefrom are described in more detail herein.

In particular, a reaction product comprising an adduct formed by one or more urease inhibitors with urea and/or formaldehyde is provided. Such a reaction product can be provided as formed, can be purified to separate one or more components therefrom, or can be provided in combination with one or more other components, such as another urease inhibitor or a fertilizer composition, for example, in the form of a nitrogen source (including, but not limited to, a urea source). In some embodiments, the compositions disclosed herein can exhibit a novel, slow release of one or more urease inhibitors.

As used herein, the term "urease inhibitor" refers to any compound that reduces, inhibits, or otherwise slows the conversion of urea to ammonium ( _NH4 ⁺ ) in soil. Exemplary urease inhibitors include thiophosphoric triamides and phosphoric triamides of formula (I):

X＝P(NH ₂ ) ₂ NR ¹ R ² (I)

wherein X = oxygen or sulfur, and ^R1 and ^R2 are independently selected from hydrogen, _C1 - _C12 alkyl, _C3 - _C12 cycloalkyl, _C6 - _C14 aryl, _C2 - _C12 alkenyl, _C2 - _C12 alkynyl _{, C5} -C14 heteroaryl, _C1 - _C14 heteroalkyl, C2- _C14 heteroalkenyl, _C2 - _C14 heteroalkynyl, or _{C3 - C12} cycloheteroalkyl.

In certain embodiments, the urease inhibitor is an N-(alkyl)thiophosphoric triamide urease inhibitor described in U.S. Patent No. 4,530,714 to Kolc et al., which is incorporated herein by reference. Specific illustrative urease inhibitors may include, but are not limited to, N-(n-butyl)thiophosphoric triamide, N-(n-butyl)phosphoric triamide, thiophosphoric triamide, phenyl phosphorodiamidate, cyclohexylphosphoric triamide, cyclohexylthiophosphoric triamide, phosphoric triamide, hydroquinone, p-benzoquinone, hexaamidocyclotriphosphazene, thiopyridine, thiopyrimidine, thiopyridine-N-oxide, N,N-dihalo-2-imidazolidinone, N-halo-2-oxazolidinone, derivatives thereof, or any combination thereof. Other examples of urease inhibitors include phenylphosphorodiamidates (PPD/PPDA), hydroquinone, N-(2-nitrophenyl)phosphoric triamide (2-NPT), ammonium thiosulfate (ATS) and organophosphorus analogs of urea, which are effective inhibitors of urease activity (see, e.g., Kiss and Simihaian, Improving Efficiency of Urea Fertilizers by Inhibition of Soil Urease Activity. Kluwer Academic Publishers, Dordrecht, The Netherlands, 2002; Watson, Urease inhibitors. IFA International Workshop on Enhanced-Efficiency Fertilizers, Frankfurt. International Fertilizer Industry Association, Paris, France 2005).

In certain embodiments, the urease inhibitor can be or include N-(n-butyl)thiophosphoryl triamide (NBPT). The preparation of phosphoramidite urease inhibitors such as NBPT can be accomplished, for example, by a process starting with thiophosphoryl chloride, a primary or secondary amine, and ammonia, as described, for example, in U.S. Pat. No. 5,770,771, which is incorporated herein by reference. In a first step, thiophosphoryl chloride is reacted with one equivalent of a primary or secondary amine in the presence of a base, and the product is then reacted with an excess of ammonia to obtain the final product. Other methods include those described in U.S. Pat. No. 8,075,659, which is incorporated herein by reference, in which thiophosphoryl chloride is reacted with a primary and/or secondary amine, followed by ammonia. However, this process may result in a mixture. Thus, when N-(n-butyl)thiophosphoric triamide (NBPT) or other urease inhibitors are used, it should be understood that this refers not only to the urease inhibitor in pure form, but also to the various commercial/technical grades of the compound, which may contain up to 50% (or less), preferably no more than 20%, of impurities, depending on the method of synthesis and purification scheme used in its production (if any). Combinations of urease inhibitors are known, for example, using mixtures of NBPT and other alkyl-substituted thiophosphoric triamides.

Representative grades of urease inhibitors may contain up to about 50%, about 40%, about 30%, about 20%, about 19%, about 18%, about 17%, about 16%, about 15%, about 14%, about 13%, about 12%, about 11%, 10%, about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2%, or about 1% by weight of impurities, depending on the method of synthesis and purification scheme used (if any) in the production of the urease inhibitor. A typical impurity in NBPT is PO( _NH2 ) ₃ , which can catalyze the decomposition of NBPT under aqueous conditions. Thus, in some embodiments, the urease inhibitor used has a purity of about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 99.1%, about 99.2%, about 99.3%, about 99.4%, about 99.5%, about 99.6%, about 99.7%, about 99.8%, or about 99.9%.

For simplicity, the present invention may be described with respect to embodiments in which NBPT is a urease inhibitor. Description of the present invention in which NBPT is a urease inhibitor should not be construed to necessarily exclude the use of other urease inhibitors, or combinations of urease inhibitors, unless expressly stated.

The urea used to produce the adducts disclosed herein can be in various forms. For example, urea can be a solid in the form of small particles, flakes, particles, etc., and/or a solution, such as an aqueous solution, and/or a molten urea. At least a portion of the urea can be in the form of animal waste. Urea and combined urea-formaldehyde products can be used according to the present disclosure. Illustrative urea-formaldehyde products can include, but are not limited to, urea-formaldehyde concentrates ("UFCs") and urea-formaldehyde polymers ("UFPs"). These types of products can be as discussed and described in U.S. Patent Nos. 5,362,842 and 5,389,716 to Graves et al., for example, which are incorporated herein by reference. Any form of urea or urea combined with formaldehyde can be used to prepare UFPs. Examples of solid UFPs include PERGOPAK2, available from Albemarle Corporation, and NITAMIN 36S, available from Koch Agronomic Services, LLC. Any of these urea sources can be used alone or in any combination to prepare the reaction products disclosed herein.

As cited above, in some embodiments, the formaldehyde used as a reagent to produce the reaction products disclosed herein can be provided in combination with urea (e.g., as a mixture or as a polymer with urea). In such embodiments, additional formaldehyde need not be added to form the desired adduct, although the present disclosure is not limited thereto and additional formaldehyde may be added to the urea-formaldehyde product.

In some embodiments, formaldehyde is intentionally added as a formulation for preparing the reaction product disclosed herein, and formaldehyde can be in various forms. For example, polyoxymethylene (solid, polymerized formaldehyde) and/or formalin solution (aqueous solution of formaldehyde, sometimes with about 10 weight %, about 20 weight %, about 37 weight %, about 40 weight %, or about 50 weight % methanol based on the weight of the formalin solution) are commonly used forms of formaldehyde. In some embodiments, formaldehyde can be an aqueous solution with a formaldehyde concentration from about 10 weight % to about 50 weight % based on the gross weight of the aqueous solution. Formaldehyde gas can also be used. Formaldehyde partially or completely substituted by substituted aldehydes such as acetaldehyde and/or propionaldehyde can also be used as a formaldehyde source. Any of these forms of formaldehyde sources can be used alone or in any combination to prepare the reaction product described herein.

Methods for preparing the reaction products disclosed herein can vary. Typically, NBPT is combined, mixed, or otherwise contacted with urea and formaldehyde. Thus, in some embodiments, the present disclosure provides methods for preparing adducts comprising combining urea, formaldehyde, and NBPT to form at least one adduct. For example, at least a portion of the NBPT can react with at least a portion of the urea and/or at least a portion of the formaldehyde to form one or more structurally distinct adducts, as further described below.

The reactants (i.e., urea, formaldehyde, and NBPT) can be combined with one another in any order or ranking. For example, in one embodiment, urea and formaldehyde are combined first and NBPT is added thereto. In another embodiment, urea and a urea-formaldehyde product (e.g., a urea-formaldehyde concentrate or a urea-formaldehyde polymer) are combined and NBPT is added thereto. In a further embodiment, the urea-formaldehyde product and formaldehyde are combined and NBPT is added thereto. In yet further embodiments, urea and NBPT are combined and formaldehyde or a urea-formaldehyde product is added thereto. Furthermore, in certain embodiments, other components may be included in any of these stages, either alone or in combination with urea, formaldehyde, or NBPT. For example, in some embodiments, a nitrification inhibitor (such as those disclosed below) may be combined with one or more of the described components, including, but not limited to, embodiments in which a nitrification inhibitor is combined with NBPT and this mixture is combined with the other components.

In these various embodiments, the form of the added NBPT can vary. For example, NBPT can be used in a molten liquid form, in a solution form, or in a suspension/dispersion form. Similarly, the form of the material with which NBPT is combined (i.e., the urea/formaldehyde mixture, the urea/urea-formaldehyde product mixture, or the urea-formaldehyde product/formaldehyde mixture) can vary. For example, in some embodiments, the material with which NBPT is combined can be in the form of a solution, a dispersion/suspension form, or a molten urea liquid form. In either case, the form of NBPT, urea, and formaldehyde should allow for a high degree of contact between the reagents to promote the reaction and formation of the adduct. The most preferred form of NBPT is a solution or a suspension/dispersion form. The most preferred form of the urea/formaldehyde mixture, the urea/urea-formaldehyde product mixture, or the urea-formaldehyde product/formaldehyde mixture is a solution containing formaldehyde or a molten urea liquid form. In another embodiment using MAP, DAP, or AMS catalysts to promote the reaction, the urea/formaldehyde mixture, the urea/urea-formaldehyde product mixture, or the urea-formaldehyde product/formaldehyde mixture can be in the form of a solid (i.e., urea pellets) and a NBPT solution.

Where a solvent is used at any stage of the combination process, the solvent used is generally one that dissolves one or more of NBPT, urea, and/or formaldehyde. Suitable solvents may include, for example, water (including aqueous buffers), N-alkyl 2-pyrrolidones (e.g., N-methylpyrrolidone), glycols and glycol derivatives, ethyl acetate, propylene glycol, benzyl alcohol, and combinations thereof. Representative solvents known to dissolve NBPT include, but are not limited to, those described in U.S. Patent Nos. 5,352,265 and 5,364,438 to Weston, 5,698,003 to Omilinsky et al., 8,048,189 and 8,888,886 to Whitehurst et al., WO 2014/100561 to Ortiz-Suarez et al., WO 2014/055132 to McNight et al., WO 2014/028775 and WO 2014/028767 to Gabrielson et al., and EP 2032589 to Cigler, which are incorporated herein by reference. In certain embodiments, the solvent or mixture of solvents used to combine the components can be selected from the group consisting of water (including buffers, e.g., phosphate buffer), glycols (e.g., propylene glycol), glycol derivatives and protected glycols (e.g., glycerol, including protected glycerols such as isopropylidine glycerol), glycol ethers such as monoalkyl glycol ethers and dialkyl glycol ethers), acetonitrile, DMSO, alkanolamines (e.g., triethanolamine, diethanolamine, monoethanolamine, alkyldiethanolamines, dialkylmonoethanolamines, wherein the alkyl group can be composed of methyl, ethyl, propyl, or any branched or unbranched alkyl chain), alkyl sulfones (e.g., sulfolane), alkylamides (e.g., N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, or any non-cyclic amide), monoalcohols (e.g., methanol, ethanol, propanol, isopropanol, benzyl alcohol), dibasic esters and their derivatives, alkylene carbonates (e.g., ethylene carbonate, propylene carbonate), monobasic esters (e.g., ethyl lactate, ethyl acetate), carboxylic acids (e.g., maleic acid, oleic acid, itaconic acid), Acid), acrylic acid, methacrylic acid), glycol esters, and/or surfactants (e.g., alkyl benzenesulfonates, ligninsulfonates, alkylphenylethoxylates, polyalkoxylated amines) and combinations thereof. Further cosolvents may be used in certain embodiments, including, but not limited to, liquid amides, 2-pyrrolidone, N-alkyl 2-pyrrolidone, and nonionic surfactants (e.g., alkyl aryl polyether alcohols).

Various other additives that do not negatively affect the formation of the adducts disclosed herein can be included in the reaction mixture (i.e., urease, one or more inhibitors, urea, formaldehyde, and optionally one or more solvents). For example, components normally present in urea and/or formaldehyde (e.g., impurities) are typically incorporated into the reaction mixture. In some embodiments, components that are desired to be included in the final product can be incorporated into the reaction mixture (e.g., dyes, as described in more detail below).

In certain embodiments, monoammonium phosphate (MAP), diammonium phosphate (DAP), and/or ammonium sulfate (AMS) can be used to promote the formation of adducts. Although not intended to be limiting, it is believed that MAP, DAP, or AMS can be used as a catalyst to promote the formation of the adducts disclosed herein. In some embodiments, it is possible to reduce the reaction time and/or conduct the reaction at a temperature lower than that otherwise required to form the adducts by including MAP, DAP, and/or AMS (and/or other catalysts). In certain embodiments, mixing particles of NBPT-treated urea with particles of MAP, DAP, or AMS also accelerates the formation of the adducts disclosed herein compared to embodiments in which no catalyst is used. In some embodiments, the use of a particular catalyst can have an effect on the amount and/or type of various adducts formed during the reaction.

Adduct formation can be carried out at various pH values, and in some embodiments, it may be desirable to adjust the pH of the reaction mixture (e.g., by adding an acid and/or base). Representative acids include, but are not limited to, solutions of inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and combinations thereof. Exemplary bases include, but are not limited to, solutions of ammonia, amines (e.g., primary, secondary, and tertiary amines, and polyamines), sodium hydroxide, potassium hydroxide, and combinations thereof. In some embodiments, it may be desirable to use a buffer solution to control the pH of the reaction mixture. Representative buffer solutions include, but are not limited to, solutions of triethanolamine, sodium borate, sodium bicarbonate, sodium carbonate, and combinations thereof.

The conditions under which NBPT, urea, and formaldehyde (and optionally other additives) are combined can vary. For example, the reaction can be carried out at various temperatures, for example, from ambient temperature (about 25°C) to elevated temperatures (above 25°C). In certain embodiments, the reaction is carried out at a temperature of at least about 50°C, at least about 60°C, at least about 70°C, at least about 80°C, at least about 90°C, or at least about 100°C, such as from about 20°C to about 150°C.

Advantageously, in some embodiments, the reaction product can be prepared under conventional urea manufacturing conditions (e.g., as described in Jozeef Meesen, Ullman's Encyclopedia of Industrial Chemistry (2012), Vol. 37, pp. 657-695, which is incorporated herein by reference). Such urea manufacturing conditions typically include temperatures at which urea is in molten form, for example, temperatures of about 130° C. to about 135° C. For example, in such an embodiment, NBPT can be added to a molten mixture of urea and formaldehyde (or urea and urea-formaldehyde (i.e., UF, UFC, or UFP)). The mixture can be combined and subsequently cooled to provide a reaction product comprising a reaction product, i.e., an adduct of NBPT, urea, and formaldehyde. For example, the composition can be cooled by subjecting the reaction mixture to a conventional urea pastille, granulation, or pelletizing process (e.g., fluidized bed granulation, drum granulation, sprouted bed granulation, etc.), which typically includes a cooling step after forming pastilles, granules, and/or pellets. Typically, the drying process provides the reaction product in the form of a solid material (eg, a pastille, granular, or pelletized solid).

NBPT, urea, and formaldehyde (i.e., the reaction mixture) can be maintained together under reaction conditions for varying periods of time. For example, in some embodiments, the reaction can be conducted for a relatively short period of time (e.g., in minutes, e.g., from about 30 seconds to about 30 minutes, from about 1 to about 20 minutes, or from about 1 to about 10 minutes). In some embodiments, the reaction can be conducted for about 1 minute or longer, about 2 minutes or longer, about 5 minutes or longer, about 10 minutes or longer, about 15 minutes or longer, or about 20 minutes or longer. In certain embodiments, the reaction can be conducted for about 2 hours or less, about 1 hour or less, about 30 minutes or less, about 25 minutes or less, about 20 minutes or less, or about 15 minutes or less. In some embodiments, the reaction time is from about 2 hours to about 48 hours, such as from about 4 hours to about 36 hours.

In certain embodiments, the reaction is carried out for an amount of time that is required to convert a given percentage of the NBPT in the reaction mixture to the adduct form. For example, in one embodiment, the reaction mixture is reacted to about 10% or less by weight of free (i.e., unreacted) NBPT based on the total NBPT charged to the reaction mixture, or to about 5% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture. In another embodiment, the reaction mixture is reacted to about 40% or less by weight of free (i.e., unreacted) NBPT based on the total NBPT charged to the reaction mixture, or to about 30% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture, or to about 20% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture. In another embodiment, the reaction mixture is reacted to about 2% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture, or to about 1% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture, or to about 0.1% or less by weight of free NBPT based on the total NBPT charged to the reaction mixture. In further embodiments, the reaction mixture is reacted to produce about 50% by weight (i.e., unreacted) NBPT based on the total NBPT added to the reaction mixture to produce a 1:1 weight % adduct:free NBPT product (as measured by phosphorus content). In still further embodiments, the reaction mixture is reacted to produce a weight ratio of adduct:free NBPT product ranging from about 4:1 to 1:4 (as measured by phosphorus content), including 3:1 to 1:3, 2:1 to 1:2, and 1:1. Thus, in some embodiments, the methods of producing the adducts described herein further comprise monitoring the amount of free NBPT remaining over the course of the reaction and assessing the completion of the reaction based on the amount of free NBPT (as compared to the maximum amount of free NBPT desired by weight to be included in the reaction product).

It is noted that the specific reaction components can affect the reaction conditions required to produce the reaction product. For example, reacting the components in one solvent may be more efficient than reacting those components in a different solvent, and it is understood that, therefore, less time and/or lower temperatures may be required for adduct formation in the former case. Furthermore, where a catalyst is used, adduct formation may require less time and/or lower temperatures. It is also noted that, in some embodiments, using different reaction conditions may have an impact on the amount and/or type of various adducts formed during the reaction.

The reaction products provided according to the methods disclosed above may contain one or more structurally different adducts. For example, a given reaction product may contain at least one adduct, at least two different adducts, at least three different adducts, at least four different adducts, at least five different adducts, at least ten different adducts, at least twenty-five different adducts, at least about fifty different adducts, or at least about one hundred different adducts. The adducts may be in the form of isolated compounds, oligomers, polymers, and combinations thereof. The total amount of adducts formed may vary, and likewise, the amount of each different adduct (where more than one adduct is present in the composition) may vary.

Based on the reaction between urea, formaldehyde and NBPT, certain representative adducts that have been identified in the reaction products are as follows (wherein the designations "Adduct 1," "Adduct 2," and "Adduct 3" are provisional names chosen to distinguish them from each other and from other adducts that may be present in the various reaction products):

In addition to one or more adducts, the reaction product may contain various other components. It will be appreciated that other components that may be present in the reaction product may be a result of the specific method used to produce the reaction product, and in particular, the amounts of the individual reactants included in the reaction mixture. For example, where the reaction conditions are such that one or both reactants are present in excess, the reaction product may contain free reactants (i.e., reactants that are not incorporated into the adduct). In various embodiments, the reaction product may contain at least some weight percentage of one or more components selected from the group consisting of free NBPT, free formaldehyde, free urea, free urea-formaldehyde product (e.g., UFP), catalyst (e.g., MAP, DAP, or MAS), impurities (e.g., resulting from the grade of reactants used), solvent, water, and combinations thereof. The relative amounts of such components may vary, and exemplary amounts and ratios are disclosed below.

The reaction products disclosed herein can include widely varying mole percentages of urea, formaldehyde, and NBPT (including each component in both complexed and free form, e.g., as determined by elemental analysis). Similarly, the reaction products disclosed herein can have widely varying mole ratios, particularly because the method of producing the adduct-containing composition can vary. In some embodiments, the reaction product can have a mole ratio of NBPT:urea (including each component in both complexed and free form, e.g., as determined by elemental analysis) of from about 1:0.5 to about 1:2. In certain embodiments, urea is used in a substantial excess relative to NBPT; consequently, in such embodiments, the mole ratio of NBPT:urea is significantly lower. In some embodiments, the reaction product can have a mole ratio of NBPT:formaldehyde (including each component in both complexed and free form, e.g., as determined by elemental analysis) of from about 1:0.5 to about 1:2. Furthermore, in some embodiments, formaldehyde is present in a substantial excess relative to NBPT; in such embodiments, the mole ratio of NBPT:formaldehyde is significantly lower.

The reaction products disclosed herein can advantageously exhibit effective urease inhibition and, in preferred embodiments, can exhibit a slow release of NBPT, providing extended urease inhibition. Thus, these reaction products can exhibit urease inhibition for a longer period of time than comparative compositions comprising only free (i.e., unreacted) NBPT. Surprisingly, the reaction products, in some embodiments, can exhibit effective urease inhibition even at levels of NBPT that are considered ineffective. In other words, a reaction product prepared using a given amount of NBPT can, in some embodiments, exhibit effective urease inhibition at levels where a comparative composition comprising the same amount of NBPT in free (i.e., unreacted) form does not exhibit significant urease inhibition.

The reaction product obtained according to the methods disclosed herein can be used or stored for later use in the form in which it is provided, can be processed in some way (e.g., to provide it in a different form or to separate one or more components therefrom) before use or storage for later use, and/or can be combined with other components before use or storage for later use. Various compositions comprising at least a portion of the reaction product disclosed herein are disclosed below.

For example, in one embodiment, the reaction product is maintained substantially in the form in which it is provided after the reaction (e.g., in undiluted liquid or solid form, in solution form, in suspension/dispersion form, in the form of urea-based particles comprising an adduct, etc.). As noted above, such form, in some embodiments, may comprise other components, e.g., residual reactants and/or solvents. The specific form of these initially formed reaction products may, in certain embodiments, be further modified to provide a solid form of the reaction product prior to use and/or storage, e.g., by concentrating the solution or suspension/dispersion form therefrom by removing a solvent, by diluting any form by adding one or more solvents thereto, by dissolving the solid form, or by contacting the solid, undiluted liquid, solution, or suspension/dispersion form with a contact solid support. In a specific embodiment, the reaction product is provided in the form of a homogeneous solution.

In another embodiment, the reaction product is treated to separate one or more adducts therefrom. For example, the reaction product can be treated to remove any or all components other than the adducts from the reaction product to obtain a mixture comprising all adducts, a mixture comprising some adducts, or one or more individual, isolated adducts. Such isolated mixtures or individual adducts can be provided in their native form (e.g., solid or liquid, substantially pure form), or can be treated as described with respect to the initially formed reaction product that is modified prior to use or storage (e.g., by adding one or more solvents thereto to provide a solution or suspension/dispersion of one or more adducts, or by contacting the adduct or adduct mixture in solid, undiluted liquid, solution, or suspension/dispersion form with a solid support to provide the adduct or adduct mixture in solid form).

In further embodiments, the reaction product (as initially formed or modified as described above) or one or more isolated adducts (as initially provided or modified as described above) can be combined with one or more other components. For example, certain compositions are provided that include the reaction product in admixture with one or more other components, such as one or more nitrogen sources (e.g., urea or urea-formaldehyde products) or free NBPT. Certain compositions are provided that include one or more isolated adducts in admixture with one or more other components, such as one or more nitrogen sources (e.g., urea or urea-formaldehyde products) or free NBPT. In addition, any of these combinations can be in a modified form (e.g., solid form, undiluted liquid form, solution form, dispersion/suspension form, etc.).

Initial reaction products

As described in detail above, the reaction products provided herein can contain varying amounts of one or more adducts and can also contain varying amounts of other components.The specific configuration of the reaction product can determine the method of use for which the reaction product is particularly suitable.

For example, in the case of providing a reaction product comprising a significant free urea content and/or a significant urea-formaldehyde product content, the reaction product (in a changed physical form, for example, as described above) can be used as a fertilizer composition. For example, although not intended to be limiting, a reaction product comprising at least about 90% urea, at least about 95% urea, at least about 98% urea, or at least about 99% urea can be used as a fertilizer composition. Because the reaction product can contain a varying amount of urea and/or urea-formaldehyde product, the amount of the reaction product applied as a fertilizer composition can change. In some embodiments, the ratio at which the composition is applied to the soil can therefore be identical or proportional to the ratio currently used for a given application of urea (for example, based on the weight percent of the urea contained in the reaction product).

The reaction product comprising high concentrations of urea can be widely used in all agricultural applications currently using urea. These applications include very wide-ranging crops and lawn species, farming systems, and fertilizer placement methods. The compositions disclosed herein can be used for fertilizing a variety of seeds and plants, including seeds for planting human consumption, for silage, or for other agricultural purposes. In fact, any seed or plant can be processed using the composition of the present invention according to the present invention, such as cereals, vegetables, ornamental plants, conifers, coffee, turf grass, feed and fruit, including citrus. The plants that can be processed include cereals such as barley, oats and corn, sunflowers, sugar beets, rapeseed, safflower, flax, canary grass (canary grass), tomatoes, cottonseed, peanuts, soybeans, wheat, rice, alfalfa, sorghum, beans, sugarcane, cauliflower, cabbage and carrots. Applying the reaction product containing considerable urea concentrations to soil and/or plants can increase the nitrogen uptake of plants, enhance crop yield, and minimize nitrogen losses from soil.

Such reaction products can be used to fertilize and inhibit urease in various types of soils. Although not limited thereto, such compositions are particularly useful in very acidic soils in certain embodiments. It is generally understood that acidic soils degrade NBPT; however, the reaction products of the present disclosure have been shown to perform well in acidic soils (e.g., better than urea-based fertilizers combined with an equal amount of free NBPT).

In some embodiments, (in the form of change, for example, as described above, including in the form of an adduct separated) reaction product is used in combination with one or more fertilizer compositions. The method can be used for the reaction product comprising sizable urea concentration and the reaction product comprising lower urea concentration (including the reaction product comprising seldom to not comprising free urea). For example, the reaction product can be applied to soil before, simultaneously with, or after applying the nitrogen-based fertilizer composition. The reaction product can, for example, be in soil, on or near the soil surface or its combination and merge with the fertilizer composition. Urea can include any type of urea disclosed above, such as free urea, urea-formaldehyde product etc. and can include different substituted ureas in addition. Other suitable urea sources can be or can include animal waste such as one or more animals, for example, urine and/or manure produced by cattle, sheep, chicken, buffalo, turkey, goat, pig, horse etc.

In some embodiments, the urea source can be or can comprise animal waste such as urine and/or manure deposited on or in the soil, or the nitrogen source can be or can comprise the fertilizer product applied to soil before.Thus, reaction product can be applied to soil and mixed with animal waste and/or one or more fertilizers applied with animal waste on the soil surface and/or in it.Reaction product can be applied to soil before, during and/or after animal waste and/or one or more fertilizers are deposited on the soil and/or in the soil.In other examples, the urea source can be or can comprise animal waste such as urine and/or manure that can be collected and placed in storage, pond etc., and reaction product can be added in the animal waste to provide mixture.The mixture obtained then can be deposited near the soil to be used as fertilizer therein.

Reaction products + free NBPT

In certain embodiments, the reaction product (in an altered form, e.g., as described above, including in the form of an isolated adduct) can be combined with additional free urease inhibitor (e.g., including, but not limited to, additional free NBPT). The reaction product and free urease inhibitor, in some embodiments, can be combined during use (e.g., the reaction product can be applied to the soil before, simultaneously with, or after application of the free NBPT).

In certain embodiments, the reaction product and the free urease inhibitor can be provided in a single composition. The free urease inhibitor combined with the reaction product can be the same urease inhibitor as that present in the adduct, or a different urease inhibitor, or a combination of the same and different urease inhibitors. In such compositions, the free urease inhibitor (e.g., NBPT) can be present in varying amounts. The adduct and the free urease inhibitor can be provided in approximately equivalent amounts, the amount of NBPT can be greater than the amount of the adduct, or the amount of NBPT can be less than the amount of the adduct. In some embodiments, the molar ratio of NBPT:adduct is from about 1:1 to about 1:10, for example, from about 1:1 to about 1:7. In other embodiments, the molar ratio can be from about 10:1 to about 1:1, for example, from about 7:1 to about 1:1. In other embodiments, the weight ratio of the adduct to the free NBPT product ranges from about 4:1 to 1:4 (as measured by phosphorus content), including 3:1 to 1:3, 2:1 to 1:2, and 1:1. This embodiment can include a solution of the adduct and free NBPT, or a fertilizer (solid or molten) comprising the adduct and free NBPT. The solution of the adduct and free NBPT can contain from about 15% by weight of the adduct and free NBPT to about 50% by weight of the adduct and free NBPT, including from about 20% by weight of the adduct and free NBPT to about 40% by weight of the adduct and free NBPT, and from about 25% by weight of the adduct and free NBPT to about 30% by weight of the adduct and free NBPT.

As described above, the reaction products disclosed herein, in some embodiments, may already contain some percentage of free (unreacted) NBPT, which is added to the reaction mixture (but which does not react to form an adduct under the reaction conditions). Thus, in some embodiments, free NBPT can be added to the reaction product to bring the total amount of free NBPT into the desired range. In other embodiments (e.g., where the reaction product is in the form of isolated adducts), it is understood that little to no NBPT is present in the isolated individual adducts or mixtures thereof; therefore, sufficient free NBPT must be added to bring the free NBPT content of the resulting composition into the above-mentioned ranges.

Surprisingly, the adducts disclosed herein, in combination with free NBPT, can, in some embodiments, produce synergistic activity. For example, when the reaction product is combined with free NBPT, the resulting composition can exhibit greater urease inhibition than would be expected based on the urease inhibition of an equivalent amount of NBPT (all in free (unreacted) form) or than would be expected based on the urease inhibition of an equivalent amount of the adduct alone.

In certain embodiments, the reaction product/free NBPT composition can be used directly as a fertilizer composition (i.e., wherein the reaction product comprises a substantial free urea content and/or a substantial urea-formaldehyde product content). However, more commonly, such reaction product/free NBPT compositions are used in combination with a nitrogen source. In this embodiment, the composition comprising the reaction product and free NBPT can be applied to the soil in a modified form (e.g., in liquid, solution, dispersion/suspension, or solid form) before, simultaneously with, or after application of a nitrogen-based fertilizer composition. The nitrogen-based fertilizer can include, for example, any of the types of urea and urea-formaldehyde products disclosed above. The composition can be combined with the fertilizer composition, for example, within, on, or around the soil, or a combination thereof. The reaction product/free NBPT composition advantageously provides effective urease inhibition with respect to nitrogen-based fertilizer compositions.

Reaction product + urea

The reaction product, in some embodiments, can be combined with a nitrogen source to provide a fertilizer composition containing the adduct. For example, in some embodiments, the reaction product (in various forms, including isolated adduct forms) can be combined (e.g., mixed, blended, or otherwise combined) with one or more nitrogen sources (e.g., urea or urea-formaldehyde products). The relative amounts of the adduct and urea in such a fertilizer composition can vary, and in certain embodiments, the amount of the adduct in the fertilizer composition can be, for example, within the range of about 1 ppm to about 10,000 ppm of adduct, including about 20 ppm to about 1000 ppm, and about 100 ppm to about 800 ppm. In addition, the amount of the adduct in the fertilizer can be measured based on phosphorus (i.e., ppmP from the adduct), and includes a range of about 20 ppmP to about 1000 ppmP, 50 ppmP to about 500 ppmP, and 20 ppmP to 250 ppmP. Combining the reaction product with urea to provide a composition can provide a fertilizer composition comprising up to about 95% by weight urea, up to about 98% by weight urea, up to about 99% by weight urea, up to about 99.5% by weight urea, or up to about 99.9% by weight urea, e.g., from about 95% to about 99.9% by weight urea, from about 98% to about 99.9% by weight urea, or from about 99% to about 99.9% by weight urea, etc.

In certain embodiments, the reaction product can be directly blended with urea for granulation or can be used as an additive to liquid (molten) urea. Combining the reaction product with urea can be carried out at ambient temperature or at an elevated temperature, for example, at least about 50°C, at least about 60°C, at least about 70°C, at least about 80°C, at least about 90°C, or at least about 100°C, such as from about 20°C to about 150°C. Advantageously, in some embodiments, the reaction product can be combined with urea under conventional urea manufacturing conditions, which typically include temperatures at which the urea is in molten form, for example, from about 130°C to about 135°C. In this embodiment, it is advantageous to ensure that sufficient mixing is used during this combination step so that the adduct is substantially uniformly distributed within the molten urea, especially before the urea melt cools and solidifies in the subsequent granulation step.

The reaction product can be combined with urea in various forms, for example, in liquid form, as a solution or suspension/dispersion, or in solid form. The amount of urea added to the reaction product according to this embodiment depends on the adduct content of the resulting fertilizer composition and the adduct content of the reaction product and can be readily calculated by one skilled in the art. It should be noted that in some embodiments, additional free NBPT can be added to the reaction product, urea, or a combination thereof. Other components may be present in the adduct-containing fertilizer composition, which may be intentionally added or may be inherently present in one or more of the composition components. For example, in addition to urea and the reaction product components, the composition may include some moisture, urea synthesis byproducts, one or more solvents, and, as further described herein, may optionally contain other additives such as one or more dyes, one or more NBPT stabilizers, and/or one or more micronutrients.

Other optional ingredients (can be used in all compositions disclosed herein)

Other optional components may be used in the compositions of the present invention. Examples of other such components include, but are not limited to, nitrification inhibitors; conditioners; xanthan gum; various forms of calcium carbonate (agricultural lime) for adding weight and/or raising the pH of acidic soils; metal compounds and minerals such as gypsum, metal silicates, and chelates of various micronutrient metals such as iron, zinc, and manganese; talc; elemental sulfur; activated carbon, which can be used as a "safener" to protect the soil from potentially harmful chemicals; plant protectants; nutrients; nutrient stabilizers; super absorbent polymers; wicking agents; wetting agents; plant stimulants to stimulate growth; inorganic nitrogen, phosphorus, potassium (N-P-K) type fertilizers; phosphorus sources; potassium sources; organic fertilizers; surfactants such as alkyl aryl polyether alcohols; initiators; stabilizers; crosslinking agents; antioxidants; UV stabilizers; reducing agents; dyes such as blue dye (FD&C blue #1); insecticides; herbicides; fungicides; and plasticizers. The additional component(s) disclosed herein can be present in an amount from about 1 to about 75 weight percent of the composition and will depend in part on the desired function of the additional component(s) and the configuration of the composition to which the additional component(s) are added.

Examples of conditioning agents include, but are not limited to, tricalcium phosphate, sodium bicarbonate, sodium ferricyanide, potassium ferricyanide, bone phosphate, sodium silicate, silicon dioxide, calcium silicate, talc, bentonite, calcium aluminum silicate, stearic acid, and polyacrylate powder. Examples of plant protection agents and nutrient stabilizers include silicon dioxide and the like. Examples of nutrients include, but are not limited to, phosphorus and potassium-based nutrients. Commercially available fertilizer nutrients can include, for example, K-Fol 0-40-53, which is a solution containing 40% by weight phosphate and 53% by weight potassium, manufactured and distributed by GBS Biosciences, LLC.

Nitrification inhibitors are compounds that inhibit the conversion of ammonium to nitrate and reduce nitrogen loss in the soil. Examples of nitrification inhibitors include, but are not limited to, dicyandiamide (DCD), and the like. Although the compositions disclosed herein may include DCD, in certain embodiments, the compositions are substantially free of DCD. "Substantially free" means that either DCD is not detectable in the mixture, or, if DCD can be detected, it is (1) present at <1% w/w (preferably, <0.85% w/w, <0.80% w/w, or <0.75% w/w); and (2) does not produce an effect characteristic of DCD at higher proportions. For example, even if trace amounts of DCD can be detected in the mixture, a composition that is substantially free of DCD will not produce the environmental effects of exposure to concentrated or pure DCD. Certain exemplary compositions may have a DCD content of less than about 0.85% by weight, less than about 0.80% by weight, less than about 0.75% by weight, less than about 0.5% by weight, or less than about 0.25% by weight.

Example

In order to provide a better understanding of the above discussion, the following non-limiting examples are provided. Although all examples may be directed to specific embodiments, they are not considered to limit the present invention in any specific way. All parts, ratios and percentages are by weight unless otherwise indicated.

Example 1: Synthesis of adduct

As a representative example, to a solution of NBPT (5.0 g, 29.90 mmol) in N-methylpyrrolidone (NMP, 25 mL) at room temperature was added ACS-grade urea (1.79 g, 29.90 mmol, 1 eq) followed by formalin (50%, 795 μL, 29.90 mmol, 1 eq). The reaction mixture was stirred for 24 h. A homogeneous solution was obtained containing ~10% unreacted NBPT (as assessed by HPLC) and adducts, as well as other substances.

Table 1: Adduct formation observed using different reactants and reaction conditions

^aACS -U is ACS-grade urea identified as formaldehyde and/or UF-free.

^b Reg-U is a commercial grade urea containing approximately 0.4 wt% formaldehyde as UF.

Example 2: Catalyst Effect

Urea (>99% purity) was treated at 260 ppm with a solution of PRIME (i.e., containing NBPT); note that formaldehyde was already present in the urea. One day later, the resulting treated urea (ATU) was blended with either monoammonium phosphate (MAP) at a ratio of 50:50 wt%, diammonium phosphate (DAP) at a ratio of 50:50 wt%, or ammonium sulfate (AMS) at a ratio of 50:50 wt%. The blends were retained for 6 months, with samples withdrawn for analysis at defined time points. ATU was separated from the other blend components, after which NBPT content was analyzed by HPLC and NBPT and adducts were characterized by LC-MS.

Table 2: Adduct formation in the presence of MAP

Table 3: Adduct formation in the presence of DAP

Table 4: Adduct formation in the presence of AMS

Example 3: Determination of urease inhibition

The effectiveness of urease inhibition was measured as follows. One spoonful of water was used to moisten 4 ounces (-100 g) of Tifton, GA soil at pH 7.7. The moistened soil was placed in an 8 ounce plastic cup with a tight fitting lid. Approximately 1 spoonful (-2 g) of NBPT- and/or adduct-treated urea granules was applied to the soil surface and the container was sealed. The container was incubated at room temperature for three days and analyzed for ammonia volatilization by inserting an ammonia-sensitive tube through the lid of the sealed container. In this way, the amount of ammonia present in the headspace of the container was quantified to a maximum of 600 ppm, the limit of the tube. Generally, more effective urease inhibitors are characterized by having lower concentrations of ammonia in the headspace. All tests were performed in duplicate in the presence of a positive control (i.e., untreated urea), which typically exhibited >600 ppm ammonia after 3 days of application.

Various compositions comprising NBPT and/or the adducts disclosed herein were prepared by combining NBPT and/or the adducts with urea particles; and urease inhibition was determined using the method described above. The adduct used in this example was prepared according to entry 14 in Table 1 above.

The data in Figure 1 show the effects of various urease inhibitors, i.e., NBPT and/or the adducts disclosed herein, on ammonia volatilization from treated urea exposed to soil according to the methods described above. For comparison, data for various inhibitors used to treat urea are provided based on phosphorus content (i.e., ppmP as measured by ICP). These data show that increasing the amount of NBPT within the range of 111-196 ppmP relative to urea content has no significant effect on the onset of significant ammonia volatilization. For example, for urea treated with varying amounts of NBPT, the onset of significant ammonia volatilization (temporarily selected as ≥100 ppm) was comparable to approximately 8 days after application, i.e., ATU 111 ppmP = ATU 128 ppmP = ATU 196 ppmP. However, when some NBPT was replaced with the adduct disclosed herein—at the same phosphorus content—a significant delay in the onset of significant ammonia volatilization was observed, for example, ≥100 ppm ammonia no earlier than day 9 after application, i.e., 'NBPT/adduct 42/69 ppmP' > ATU 111 ppmP. Furthermore, when NBPT and the adduct disclosed herein were combined with urea at a 1:1 ratio of NBPT:adduct based on phosphorus content, the onset of significant ammonia volatilization was not observed until after day 10 after application, i.e., 'NBPT/adduct 111/85 ppmP' >> ATU 196 ppmP. Surprisingly, the adduct alone did not outperform a comparable amount of NBPT, i.e., 'adduct 111 ppmP' = ATU 111 ppmP. This demonstrates the synergistic relationship between NBPT and the adduct disclosed herein, as described above.

Example 4: Volatility Analysis

For NBPT- and/or adduct-treated urea granules applied to soil at pH 5.05, the cumulative N loss during volatilization was determined over a period of 14 days. Generally, more effective urease inhibitors are characterized by lower N production. All tests were performed in duplicate in the presence of a control (i.e., unfertilized soil).

Soil (pH 5.05) (representing the top 4 inches of soil from a given location) was obtained and air-dried, passed through a 2-mm sieve, and uniformly mixed with a cement mixer. Portions of the air-dried soil (500 g each) were transferred to individual pots. The soil moisture in each pot was adjusted to 2/3 of its water holding capacity by adding deionized water, and the entire process was mixed to ensure that the soil moisture in each pot was consistent. Once the entire soil moisture was balanced, the pot was placed in a temperature-controlled wooden cabinet for 24 hours to balance the moist soil to 26°C. Three N sources were evaluated, including two experimental urease inhibitor-treated urea and untreated urea. In addition, untreated soil was included to evaluate background ammonia levels. The urea used for all treatments was passed through an 8-mesh sieve and retained on a 10-mesh sieve to ensure uniformity. Nitrogen sources were applied at an equivalent rate of 120 pounds of N/acre based on the surface area of the soil in the pot. Each treatment was repeated 4 times and randomly placed in four separate chambers, each containing four pots.

The air flow rate through the soil chamber was controlled at 1.00 L min ^-1 and the temperature was maintained at 26 ° C. An acid distributor containing 100 mL of 0.02 M orthophosphoric acid was used to capture NH ₃ volatilized in the air stream flowing through the soil surface. The acid distributor was changed 24, 48, 72, 96, 120, 144, 168, 216, 264, 312, and 336 h (2 weeks) after the start of the experiment. The acid distributor was weighed and the total volume of the solution was calculated using the density of 0.02 M phosphoric acid at 25 ° C. The ammonium N concentration in the acid distributor was determined by colorimetry using a Lachat QuickChem automatic ion analyzer (Lachat Instruments, Loveland, CO). The experiment was analyzed according to a randomized group design (grouping) of four replicates. Analysis of variance (ANOVA) was used to analyze each experiment separately using Proc Mixed in SAS (SAS Institute, 2009). Least significant difference (LSD) mean separation was used to determine treatment differences in the accumulated N captured in the acid separator at α = 0.05. The maximum loss rate was calculated by dividing the percentage of _NH3 lost during the sampling interval by the duration of the sampling interval (hours).

Table 2 below provides the results of the study, where soil N source K1 represents urea treated with only a carrier (N-methylpyrrolidone and dye), soil N source K2 represents ATU (111 ppmP), and soil N source K3 represents adduct-treated urea (adduct/NBPT, 55 ppmP/55 ppmP). The adduct-treated urea used in this example was prepared according to entry 14 in Table 1 above.

Table 4: Cumulative N loss during volatilization

^a indicates that the following letters or symbols are not significantly different (P = 0.05, LSD)

^b Comparisons were made only when AOV treatment (P(F)) was significant when comparing mean values to OSL

^c Untreated treatment 4 excluded from analysis

The data presented in Table 5 clearly show that, in this study, starting on day 2 after application to acidic soils, adduct-treated urea (K3) produced significantly less N loss through volatilization than urea treated with either carrier alone (K1) or ATU (K2). After 2 days, adduct-treated urea (K3) provided a 98% reduction in N loss compared to urea treated with carrier alone (K1) and performed 75% better than ATU (K2). After 14 days, adduct-treated urea (K3) provided a 65% reduction in N loss compared to urea treated with carrier alone (K1) and performed 25% better than ATU (K2). Furthermore, even in acidic soils, the maximum N loss through volatilization was delayed by 2-3 days with adduct-treated urea (K3) compared to that exhibited by ATU (K2) (comparing K3 at day 7 to the equivalent N loss for K2, based on the curve generated from this data in Figure 2 on days 4-5).

Claims (21)

1. A composition comprising one or more adducts of N-(n-butyl)thiophosphoric triamine (NBPT), urea, and formaldehyde, wherein the one or more adducts are represented by the following structure: 2. The composition of claim 1, wherein the composition does not contain dicyandiamide. 3. The composition of claim 1, further comprising one or more materials selected from the group consisting of: free NBPT, free formaldehyde, urea-formaldehyde polymer (UFP), water, and combinations thereof. 4. The composition of claim 3, wherein one or more materials are free NBPT. 5. The composition of claim 1, wherein the urea and formaldehyde are in the form of a urea-formaldehyde reaction product comprising dihydroxymethylurea. 6. The composition of claim 1, wherein the composition is a solution containing the adduct in an organic solvent. 7. The composition of claim 1, wherein the composition comprises more than 90% by weight of free urea. 8. The composition of claim 1, wherein the composition comprises more than 98% by weight of free urea. 9. The composition of claim 1, wherein the composition comprises free urea, and wherein the one or more adducts are present in an amount between 20 ppmP and 1000 ppmP based on the total weight of the composition. 10. The composition of claim 1, wherein the composition comprises free urea and further comprises free NBPT, wherein the weight ratio of the composition of claim 1 to free NBPT is in the range of 4:1 to 1:4. 11. A method for forming a fertilizer composition, the method comprising combining fertilizer materials with the composition of claim 1. 12. The method of claim 11, wherein the composition of claim 1 is in the form of a solution containing the adduct in an organic solvent. 13. The method of claim 12, wherein the method comprises mixing the composition of claim 1 with solid particles of the fertilizer material. 14. The method of claim 11, wherein the method comprises mixing the composition of claim 1 with a molten flow of the fertilizer material. 15. The method of claim 14, wherein the molten flow of the fertilizer material comprises formaldehyde or a reaction product of urea and formaldehyde. 16. A method for preparing a urease-inhibiting fertilizer, the method comprising combining urea, formaldehyde, and N-(n-butyl)thiophosphoric triamine (NBPT) such that an excess of urea is present to form an adduct of NBPT, urea, and formaldehyde, represented by the following: The adduct remains bound to the remaining urea. 17. The method of claim 16, wherein the urea and formaldehyde are in the form of a urea-formaldehyde reaction product comprising dihydroxymethylurea. 18. A composition comprising a mixture of the following: An adduct of N-(n-butyl)thiophosphoric triamine (NBPT), urea, and formaldehyde; and Free NBPT, The weight ratio of the adduct to free NBPT is in the range of 4:1 to 1:4. 19. The composition of claim 18, wherein the weight ratio of the adduct to free NBPT is in the range of 2:1 to 1:2. 20. The composition of claim 18, wherein the weight ratio of the adduct to free NBPT is 1:1. 21. The composition of claim 18, wherein the adduct and free NBPT are present in a solution comprising at least one solvent selected from the group consisting of: NMP, glycols, glycol derivatives and protected glycols, acetonitrile, DMSO, alkanolamines, alkyl sulfones, monools, diesters and their derivatives, alkylene carbonates, monoesters, carboxylic acids, and ethylene glycol esters.