A compound formulation for improving the stability of nitration inhibitors, its preparation method and application

Abstract

This invention belongs to the field of nitrification inhibitor technology, specifically disclosing a composite formulation for improving the stability of nitrification inhibitors, its preparation method, and its application. The preparation method includes the following steps: adding wheat gluten powder to water, then adding transglutaminase for enzymatic hydrolysis, followed by enzyme inactivation and sterilization to obtain an enzymatic hydrolysate; inoculating the enzymatic hydrolysate with a microbial agent for fermentation, filtering and freeze-drying the fermentation broth to obtain pretreated wheat gluten powder; adding the pretreated wheat gluten powder to a nitrification inhibitor solution, then adding *Ficus pumila* fruit extract and modified diatomaceous earth, dispersing evenly, and spray-drying to obtain the final product. The composite formulation prepared by this invention can significantly improve the stability of nitrification inhibitors, reduce the loss of nitrification inhibitors during fertilizer production and application to soil, and expand the application range of nitrification inhibitors in fertilizers.

Description

Technical Field

[0001] This invention belongs to the field of nitration inhibitor technology, specifically relating to a compound formulation for improving the stability of nitration inhibitors, its preparation method, and its application. Background Technology

[0002] Nitrogen is one of the most important nutrients for plant growth and is therefore widely used in agricultural production systems. However, only about 50% of the applied nitrogen fertilizer can be absorbed and utilized by plants; the remainder is lost through ammonia (NH3) volatilization and nitrate (NO3) formation. - Nitrate loss occurs through leaching and nitrous oxide (N2O) emissions. Nitrate leaching leads to eutrophication of groundwater, while N2O is a greenhouse gas with a global warming potential 298 times that of carbon dioxide, causing serious pollution to the atmosphere and water bodies.

[0003] Nitrification inhibitors can suppress ammonium nitrogen (NH4+) in the soil. 4+ -N) to nitrate nitrogen (NO 3- The conversion of nitrogen (N-N) prolongs the retention time of ammonium nitrogen in the soil, thereby reducing nitrogen loss caused by nitrification and improving nitrogen use efficiency. Currently, the application of nitrification inhibitors has become an important trend in the development of efficient and environmentally friendly fertilizers, with broad application prospects.

[0004] 3,4-Dimethylpyrazole phosphate (DMPP), as a highly efficient nitrification inhibitor, is characterized by low dosage, high efficiency, and environmental friendliness, with no adverse effects on soil. It has been industrialized and commercialized, and is widely used in the production of stabilized fertilizers, making it the most widely used nitrification inhibitor currently. DMPP appears as white fine crystals or a white powder, readily soluble in water and slightly soluble in methanol. However, it is sensitive to alkaline and high-temperature environments, easily deactivated upon contact with alkaline fertilizers, making it unsuitable for internal addition during fertilizer production. Furthermore, the high-temperature environment during production also affects its stability. In addition, the behavior of DMPP in soil exhibits significant variability. Therefore, improving the stability of DMPP during fertilizer production and application is of great importance.

[0005] Therefore, it is extremely urgent to develop a protective formulation that can improve the stability of DMPP addition and application. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the primary objective of this invention is to provide a method for preparing a compound formulation that improves the stability of nitration inhibitors.

[0007] Another object of the present invention is to provide a compound formulation for improving the stability of nitration inhibitors, which is prepared by the above-described method.

[0008] A third objective of this invention is to provide the application of the above-mentioned compound formulation for improving the stability of nitrification inhibitors in fertilizers.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a compound formulation to improve the stability of nitration inhibitors includes the following steps:

[0011] (1) Add gluten powder to water, then add transglutaminase for enzymatic hydrolysis, and then perform enzyme inactivation and sterilization on the solution after enzymatic hydrolysis to obtain the hydrolysate;

[0012] (2) Inoculate the enzymatic hydrolysate obtained in step (1) with microbial inoculum for fermentation, collect the fermentation liquid and filter it, and freeze-dry the filtrate to obtain pretreated gluten powder;

[0013] (3) Add the pretreated gluten powder obtained in step (2) to the solution of nitrification inhibitor, then add fig fruit extract and modified diatomaceous earth, disperse evenly and spray dry to obtain the product.

[0014] According to the above method for preparing a compound preparation for improving the stability of nitration inhibitors, further, in step (1), the mass ratio of gluten powder to transglutaminase is 1:(0.2-0.4); the concentration of gluten powder in water is 25-35wt%; and the enzyme activity of transglutaminase is 1000 U / g.

[0015] According to the above method for preparing a compound formulation that improves the stability of nitration inhibitors, further, the enzymatic hydrolysis in step (1) is carried out at a temperature of 40-50℃, a pH of 6-7, and a time of 1.5-2.5 h.

[0016] Furthermore, according to the above method for preparing the compound formulation that improves the stability of nitration inhibitors, the temperature of enzyme inactivation and sterilization in step (1) is 80-90℃ and the time is 10-20 min.

[0017] According to the above method for preparing the compound formulation for improving the stability of nitrification inhibitors, further, the microbial agent mentioned in step (2) is Bacillus subtilis, and the inoculum amount is 10. 6 -10 7 CFU / g; the fermentation temperature is 35-38℃, and the time is 3-4 days.

[0018] According to the above method for preparing a compound formulation to improve the stability of nitration inhibitor, further, in step (3), the mass ratio of the nitration inhibitor, pretreated gluten powder, ficus pumila fruit extract and modified diatomaceous earth is 1:(3-8):(4-6):(2-4); the concentration of the nitration inhibitor solution is 15-20 wt%; and the nitration inhibitor is 3,4-dimethylpyrazole phosphate.

[0019] According to the above method for preparing a composite formulation that improves the stability of nitration inhibitors, the preparation process of the modified diatomaceous earth in step (3) is as follows: the diatomaceous earth is added to a nitric acid solution for impregnation, filtered, washed, dried and calcined to obtain the product.

[0020] Further, according to the above-mentioned method for preparing the composite formulation for improving the stability of nitration inhibitors, the concentration of the nitric acid solution is 5-10 wt%; the impregnation temperature is 45-55℃ and the time is 1.5-2.5 h; the calcination temperature is 450-500℃ and the time is 1-2 h.

[0021] According to the above-mentioned method for preparing a compound preparation that improves the stability of nitration inhibitors, the preparation process of the fig fruit extract is as follows: fig fruit is added to water and decocted twice, the two decoctions are combined and concentrated, and then 95% ethanol solution is added to the obtained concentrate until the final ethanol concentration is 80%. After standing, centrifugation, washing, and freeze-drying, the product is obtained.

[0022] According to the above method for preparing a compound formulation that improves the stability of nitration inhibitors, further, the inlet air temperature of the spray dryer in step (3) is 150-170℃, the outlet temperature is 60-70℃, and the feed rate is 1-2 L / h.

[0023] A compound formulation for improving the stability of nitration inhibitors is prepared using the above-described method for preparing a compound formulation for improving the stability of nitration inhibitors.

[0024] The application of the above-mentioned compound formulations that improve the stability of nitrification inhibitors in fertilizers.

[0025] The present invention has the following advantages over the prior art:

[0026] 1. The method for preparing a composite formulation to improve the stability of nitration inhibitors provided by this invention involves pretreating gluten powder by enzymatic hydrolysis with transglutaminase and microbial fermentation. This optimizes the molecular structure and enhances the film-forming properties, enabling the formation of a dense coating layer on the surface of the nitration inhibitor, effectively isolating it from adverse external factors and improving storage stability. The extract of *Ficus pumila* fruit is rich in natural high-molecular-weight polysaccharides and other components, exhibiting good adhesion and encapsulation properties. It adheres tightly to the coating layer, strengthening its integrity and stability, forming a dual protection, while simultaneously slowing down the release rate of the nitration inhibitor in the medium, thus improving utilization efficiency. Modified diatomaceous earth, after being impregnated with nitric acid solution, has an increased specific surface area, rich pore structure, and enhanced adsorption capacity. It can adsorb nitration inhibitor molecules, reducing loss and providing physical protection. The synergistic effect of these three components ensures the stability of nitration inhibitor storage and release from multiple levels, improving the retention rate of the nitration inhibitor.

[0027] 2. The composite formulation prepared by this invention can significantly improve the stability of nitrification inhibitors, reduce the loss of nitrification inhibitors during fertilizer production and application to soil, and expand the application range of nitrification inhibitors in fertilizers. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0029] The Bacillus subtilis strain of this invention is an existing strain, with accession number CICC NO.10071, and was obtained through commercial sales;

[0030] The preparation method of *Ficus pumila* fruit extract is as follows: Ficus pumila fruit is divided longitudinally into 4 parts, dried at 50℃ for 24 h, then soaked in 8 times its volume of 95% ethanol for 15 h. After removing the ethanol solution, the remaining residue is dried and then decocted in 8 times its weight of water for 2.5 h. The filtered residue is then decocted in 6 times its weight of water for 1.5 h. The two decoctions are combined and concentrated under reduced pressure at 50℃. The concentrate is centrifuged at 3500 rpm for 10 min to remove insoluble matter. 95% ethanol solution is added to the concentrate until the final ethanol concentration is 80%. The concentrate is allowed to stand for 12 h, then centrifuged at 4000 rpm for 20 min to separate the precipitate. The precipitate is washed with water and 95% ethanol solution, and then freeze-dried to obtain the final extract.

[0031] Example 1

[0032] A method for preparing a compound formulation to improve the stability of nitration inhibitors includes the following steps:

[0033] (1) Add gluten powder to water to make the concentration of gluten powder in water 30 wt%; add 1000 U / g of transglutaminase to the aqueous solution of gluten powder according to the mass ratio of gluten powder to transglutaminase 1:0.3, and enzymatically hydrolyze for 2 h at 45℃ and pH=6.5; after the enzymatic hydrolysis is completed, inactivate the enzyme and sterilize the solution at 85℃ for 15 min to obtain the enzymatic hydrolysate;

[0034] (2) Inoculate the enzymatic hydrolysate obtained in step (1) with Bacillus subtilis at an inoculation amount of 10. 6 CFU / g, fermented at 37℃ for 3.5 days, the fermentation broth was collected and filtered, and the filtrate was freeze-dried to obtain pretreated gluten powder;

[0035] (3) Diatomaceous earth was added to a nitric acid solution with a concentration of 8 wt%, soaked at 50°C for 2 h, filtered, washed, dried, and then calcined at 480°C for 1.5 h to obtain modified diatomaceous earth; nitrification inhibitor DMPP was added to water to prepare a DMPP solution with a concentration of 18 wt%; then, according to the mass ratio of nitrification inhibitor, pretreated gluten powder, fig fruit extract and modified diatomaceous earth as 1:5:5:3, the pretreated gluten powder obtained in step (2) was added to the DMPP solution, and then fig fruit extract and modified diatomaceous earth were added. After being dispersed evenly, it was spray-dried. The inlet air temperature during spraying was 160°C, the outlet temperature was 65°C, and the feed rate was 1.5L / h, thus obtaining a composite preparation that improves the stability of nitrification inhibitor.

[0036] This embodiment also provides a composite formulation for improving the stability of nitration inhibitors obtained by the above preparation method.

[0037] Example 2

[0038] A method for preparing a compound formulation to improve the stability of nitration inhibitors includes the following steps:

[0039] (1) Add gluten powder to water to make the concentration of gluten powder in water 35 wt%; according to the mass ratio of gluten powder to transglutaminase 1:0.2, add 1000 U / g transglutaminase to the aqueous solution of gluten powder, and enzymatically hydrolyze for 2.5 h at 40℃ and pH=6d; after the enzymatic hydrolysis is completed, inactivate the enzyme and sterilize the solution at 80℃ for 20 min to obtain the enzymatic hydrolysate;

[0040] (2) Inoculate the enzymatic hydrolysate obtained in step (1) with Bacillus subtilis at an inoculation amount of 10. 6 CFU / g, fermented at 35℃ for 4 days, the fermentation broth was collected and filtered, and the filtrate was freeze-dried to obtain pretreated gluten powder;

[0041] (3) Add diatomaceous earth to a 5 wt% nitric acid solution, soak at 45°C for 2.5 h, filter, wash, dry, and calcine at 450°C for 2 h to obtain modified diatomaceous earth; add nitrification inhibitor DMPP to water to prepare a 20 wt% DMPP solution; then add the pretreated gluten powder obtained in step (2) to the DMPP solution according to the mass ratio of nitrification inhibitor, pretreated gluten powder, fig fruit extract and modified diatomaceous earth as 1:3:4:2, and then add fig fruit extract and modified diatomaceous earth. After dispersing evenly, spray dry. The inlet air temperature is 150°C, the outlet temperature is 60°C, and the feed rate is 1 L / h to obtain a composite preparation that improves the stability of nitrification inhibitor.

[0042] This embodiment also provides a composite formulation for improving the stability of nitration inhibitors obtained by the above preparation method.

[0043] Example 3

[0044] A method for preparing a compound formulation to improve the stability of nitration inhibitors includes the following steps:

[0045] (1) Add gluten powder to water to make the concentration of gluten powder in water 25 wt%; add 1000 U / g of transglutaminase to the aqueous solution of gluten powder according to the mass ratio of gluten powder to transglutaminase 1:0.4, and enzymatically hydrolyze for 1.5 h at 50℃ and pH=7; after the enzymatic hydrolysis is completed, inactivate the enzyme and sterilize the solution at 90℃ for 10 min to obtain the enzymatic hydrolysate;

[0046] (2) Inoculate the enzymatic hydrolysate obtained in step (1) with Bacillus subtilis at an inoculation amount of 10. 7 CFU / g, fermented at 38℃ for 3 days, the fermentation broth was collected and filtered, and the filtrate was freeze-dried to obtain pretreated gluten powder;

[0047] (3) Diatomaceous earth was added to a 10 wt% nitric acid solution and soaked at 55°C for 1.5 h. After filtration, washing and drying, it was calcined at 500°C for 1 h to obtain modified diatomaceous earth. The nitrification inhibitor DMPP was added to water to prepare a 15 wt% DMPP solution. Then, according to the mass ratio of nitrification inhibitor, pretreated gluten powder, fig fruit extract and modified diatomaceous earth as 1:8:6:4, the pretreated gluten powder obtained in step (2) was added to the DMPP solution, and then fig fruit extract and modified diatomaceous earth were added. After being dispersed evenly, it was spray-dried. The inlet air temperature was 170°C, the outlet temperature was 70°C, and the feed rate was 2L / h, thus obtaining a composite preparation that improves the stability of the nitrification inhibitor.

[0048] This embodiment also provides a composite formulation for improving the stability of nitration inhibitors obtained by the above preparation method.

[0049] Comparative Example 1

[0050] Comparative Example 1 is basically the same as Example 1, except that steps (1) and (2) of Example 1 are omitted and the pre-treated gluten powder in step (3) is replaced with gluten powder.

[0051] Comparative Example 2

[0052] Comparative Example 2 is basically the same as Example 1, except that the extract of fig fruit in step (3) of Example 1 is omitted.

[0053] Experimental Example 1

[0054] Verification of the effect of adding the compound formulation prepared in this invention to urea-based compound fertilizer on the stability of DMPP.

[0055] The compound preparations prepared in Examples 1-3 and Comparative Examples 1-2, as well as commercially available DMPP (purity >98%), were mixed with 15-15-15 urea-based compound fertilizer powder. The amount added (based on the DMPP content in each sample) was 1% of the mass of the 15-15-15 urea-based compound fertilizer powder. The mixture was then accelerated in a constant temperature oven at 45℃±1 for 5 days. The DMPP content in the fertilizer was detected by high performance liquid chromatography (reference method: Bao Wankui, Huang Junming, Han Yansong, et al. Study on the determination of 3,4-dimethylpyrazole phosphate in fertilizer by high performance liquid chromatography [J]. Chinese Journal of Soil and Fertilizer, 2021, (03):354-358.). The DMPP retention rate was calculated as follows: retention rate = (DMPP content after acceleration / initial DMPP content) × 100%. The results are shown in Table 1.

[0056] Table 1

[0057]

[0058] As shown in Table 1, the retention rate of DMPP in the composite formulations prepared in Examples 1-3 of this invention can reach 90.02%, which is significantly higher than that in Comparative Examples 1-2 and commercially available DMPP. This indicates that the composite formulations of this invention can significantly improve the stability of DMPP mixed with 15-15-15 urea-based compound fertilizer at high temperatures.

[0059] Compared to Example 1, Comparative Example 1 did not pretreat the gluten powder during the preparation of the compound formulation, and Comparative Example 2 omitted the ficus seed extract. The retention rate of DMPP in both examples was not as high as that in Example 1. This indicates that the preparation process of the compound formulation of the present invention can significantly improve the stability of the nitration inhibitor DMPP. The possible reasons are as follows: This invention optimizes the molecular structure of gluten powder through enzymatic hydrolysis with transglutaminase and microbial fermentation, improving its film-forming properties. This allows it to form a dense coating layer on the surface of nitrification inhibitors, effectively isolating them from adverse external factors and improving storage stability. The extract of *Ficus pumila* fruit is rich in natural high-molecular-weight polysaccharides and other components, exhibiting good adhesion and encapsulation properties. It adheres tightly to the coating layer, enhancing its integrity and stability, forming a double protection, while simultaneously slowing down the release rate of nitrification inhibitors in the medium, thus improving utilization efficiency. Furthermore, modified diatomaceous earth, after being impregnated with nitric acid solution, has an increased specific surface area, rich pore structure, and enhanced adsorption capacity. It can adsorb nitrification inhibitor molecules, reducing loss and providing physical protection. The synergistic effect of these three factors ensures the stability of nitrification inhibitor storage and release from multiple levels, improving the retention rate of nitrification inhibitors.

[0060] Experimental Example 2

[0061] Verification of the effect of adding the compound formulation of the present invention to the high-tower granulation of nitro compound fertilizer on the stability of DMPP

[0062] The compound formulations prepared in Examples 1-3 and Comparative Examples 1-2, as well as commercially available DMPP (purity >98%), were mixed with 15-15-15 nitro compound fertilizer raw materials. The amount of each sample added (based on the DMPP content in each sample) was 0.1% of the mass of the 15-15-15 nitro compound fertilizer powder. Compound fertilizer samples were prepared using a high-tower granulation process. The DMPP content before and after granulation was quantitatively analyzed by high-performance liquid chromatography, and the DMPP retention rate was calculated as follows: retention rate = (DMPP content after granulation / DMPP content before granulation) × 100%. The results are shown in Table 2.

[0063] Table 2

[0064]

[0065] As can be seen from Table 2, the compound formulations prepared in Examples 1-3 of this invention can significantly improve the stability of DMPP added in the high-tower granulation of nitro compound fertilizer. The retention rate of DMPP can reach 94.82%, which is significantly higher than that of Comparative Examples 1-2 and commercially available DMPP added to the high-tower granulation of nitro compound fertilizer.

[0066] Experimental Example 3

[0067] Verification of the effect of adding the compound formulation prepared in this invention to the rotary drum granulation of urea-based compound fertilizer on the stability of DMPP.

[0068] The compound formulations prepared in Examples 1-3 and Comparative Examples 1-2, as well as commercially available DMPP (purity >98%), were mixed with 15-15-15 urea-based compound fertilizer raw materials. The amount of each sample added (based on the DMPP content in each sample) was 0.1% of the mass of the 15-15-15 nitro compound fertilizer powder. Compound fertilizer samples were prepared using a rotary drum granulation process. The DMPP content before and after granulation was quantitatively analyzed by high performance liquid chromatography, and the DMPP retention rate was calculated as follows: retention rate = (DMPP content after granulation / DMPP content before granulation) × 100%. The results are shown in Table 3.

[0069] Table 3

[0070]

[0071] As can be seen from Table 3, the retention rate of DMPP in the compound formulations prepared in Examples 1-3 is significantly higher than that in Comparative Examples 1-2 and commercially available DMPP. This indicates that the compound formulations prepared in this invention can significantly improve the stability of DMPP added in the rotary drum granulation of urea-based compound fertilizers.

[0072] Test Example 4

[0073] Verification of the effect of the compound formulation prepared in this invention on the stability of DMPP during application in alkaline soil.

[0074] To simulate the loss of nitrification inhibitors during application in alkaline soils, the compound formulations prepared in Examples 1-3 and Comparative Examples 1-2, as well as commercially available DMPP (purity >98%), were mixed with soil and stored separately. The mixing amount of each sample (based on the DMPP content in each sample) was 0.2% of the soil mass, and the soil moisture was controlled at 60% of the field capacity. The mixed samples were then placed in an environment of 25°C for 28 days. Samples were taken on days 7, 14, 21, and 28, and the DMPP content in the soil was quantitatively analyzed by high performance liquid chromatography. The DMPP retention rate was calculated as (DMPP content in soil at each sampling time / initial DMPP content in soil) × 100%. The results are shown in Table 4.

[0075] Table 4

[0076]

[0077] As can be seen from Table 4, the retention rate of DMPP in the composite formulations prepared in Examples 1-3 of the present invention is significantly higher than that in Comparative Examples 1-2 and commercially available DMPP, indicating that the composite formulations of the present invention can significantly improve the stability of DMPP after application to the soil, prolong the action time of DMPP in the soil, and improve the inhibitory effect of DMPP.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for producing a complex preparation for improving the stability of a nitrification inhibitor, characterized by, It comprises the following steps: (1) adding vital gluten into water, then adding transglutaminase for enzymolysis, and then carrying out enzyme inactivation and sterilization treatment on the solution after the enzymolysis is completed to obtain an enzymolysis solution; (2) inoculating microbial inoculum into the enzymolysis solution obtained in step (1) for fermentation, collecting the fermentation liquor and filtering, and then obtaining pretreated vital gluten through freeze-drying of the filtrate; (3) adding the pretreated vital gluten obtained in step (2) into a solution of nitration inhibitor, then adding bauhinia purpurea fruit extract and modified diatomite, uniformly dispersing, and then spray drying to obtain the composite preparation for improving the stability of nitration inhibitor; The microbial inoculant in step (2) is Bacillus subtilis, and the inoculation amount is 10 6 -10 7 CFU / g; The mass ratio of the nitration inhibitor, the pretreated vital gluten, the bauhinia purpurea fruit extract and the modified diatomite in step (3) is 1:(3-8):(4-6):(2-4); the nitration inhibitor is 3,4-dimethylpyrazole phosphate; The preparation process of the modified diatomite in step (3) is: dipping diatomite into a nitric acid solution, filtering, washing, drying and calcining to obtain the modified diatomite.

2. The method for producing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, The mass ratio of the vital gluten and transglutaminase in step (1) is 1:(0.2-0.4); the concentration of the vital gluten in water is 25-35 wt%; and the enzyme activity of the transglutaminase is 1000 U / g.

3. The method for producing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, The temperature of the enzymolysis in step (1) is 40-50℃, the pH is 6-7, and the time is 1.5-2.5 h.

4. The method for producing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, The temperature of the fermentation in step (2) is 35-38℃, and the time is 3-4 d.

5. The method for producing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, The concentration of the solution of the nitration inhibitor in step (3) is 15-20 wt%.

6. The method for producing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, In the preparation of the modified diatomite, the concentration of the nitric acid solution is 5-10 wt%; the dipping temperature is 45-55℃, and the time is 1.5-2.5 h; and the calcination temperature is 450-500℃, and the time is 1-2 h.

7. The method for preparing a complex preparation for improving stability of a nitrification inhibitor according to claim 1, characterized by, The preparation process of the bauhinia purpurea fruit extract in step (3) is: twice decoction of bauhinia purpurea fruit in water, combining the two decoction liquors and concentrating, then adding 95% ethanol solution to the obtained concentrated liquor until the final concentration of ethanol is 80%, and then standing, centrifuging, washing and freeze-drying to obtain the bauhinia purpurea fruit extract.

8. A complex preparation for improving the stability of a nitrification inhibitor, characterized by, The composite preparation for improving the stability of nitration inhibitor is prepared by the preparation method of the composite preparation for improving the stability of nitration inhibitor according to any one of claims 1-7.

9. The application of the composite preparation for improving the stability of nitration inhibitor in fertilizer according to claim 8.

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