Environment-friendly slow-release fertilizer and preparation method thereof

Abstract

The application discloses an environment-friendly slow-release fertilizer and a preparation method thereof, and belongs to the technical field of fertilizer mixture preparation. The preparation method comprises the following steps: mixing, stirring and heating mussel extract-polysaccharide-nitrogen fertilizer complex, inorganic fertilizer and water according to a weight ratio of 1-2:5-7:15-23 to form a dispersion solution heated to 50-60 DEG C, mixing and stirring the dispersion solution with calcium salt according to a weight ratio of 1:0.005-0.01, and cooling to 20-25 DEG C to react for 20-24 hours to obtain a viscous mixture; and drying and crushing the viscous mixture to obtain the environment-friendly slow-release fertilizer. The mussel extract with good adhesion effect and carboxymethyl cellulose or hyaluronic acid with biocompatibility are used as carriers, the nitrogen fertilizer and the inorganic fertilizer are wrapped through the synergistic cooperation of amide structure, imine structure and metal coordination, and finally the environment-friendly slow-release fertilizer is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fertilizer mixture preparation, and particularly relates to an environment-friendly slow-release fertilizer and a preparation method thereof. BACKGROUND

[0002] Although traditional chemical fertilizers can provide nutrients rapidly, their improper use often leads to environmental problems such as soil degradation and water pollution. In order to solve these problems, slow-release fertilizers have emerged. Due to their unique release mechanism and nutrient supply characteristics, slow-release fertilizers have gradually become an indispensable choice of fertilizers in modern agriculture. In the national standard (GB / T 23348-2009), the definition of slow-release fertilizer is: a chemical fertilizer that makes the effective nutrients for crops slowly release over time through chemical complexation or physical action of nutrients. Slow-release fertilizer is a fertilizer that is manufactured by using coating, wrapping and adding inhibitors, etc., and has a slower release speed of effective nutrients absorbed by plants than ordinary fertilizer after being applied to the soil. Once applied, it can slowly release to meet the physiological needs of plant growth and development, improve fertilizer utilization, save labor and fertilizer, and reduce pollution caused by fertilizer loss to the environment, and has good development space in terms of resource utilization, environmental protection, etc.

[0003] Slow-release fertilizers can be divided into the following categories according to their release characteristics and material composition: (1) chemical slow-release fertilizers: this type of fertilizer is made by chemical synthesis, and common ones include slow-release urea, slow-release phosphorus fertilizer and slow-release potassium fertilizer, etc. They usually change the chemical structure of the fertilizer so that the nutrients can be slowly released in the soil. (2) Physical slow-release fertilizers: this type of fertilizer usually controls the release rate of the fertilizer through physical methods such as coating, particle wrapping, etc. For example, polymer-coated granular fertilizers can slowly release nutrients under conditions of changes in moisture or temperature. (3) Biological slow-release fertilizers: biological slow-release fertilizers gradually release nutrients through the action of microorganisms or biological materials. For example, certain microorganisms can decompose organic matter to release the nutrients required by plants.

[0004] Patent CN113582771A discloses a preparation method of a high-molecular slow-release fertilizer. The invention mixes a compound containing a mercapto monomer and a compound containing an acrylate monomer to form a solution; immerses the fertilizer in the above-mentioned solution, then takes out the fertilizer and places it in a triethylamine gas environment, after 1-8 hours, the fertilizer is taken out to obtain a slow-release fertilizer. Through the reaction and crosslinking of the mercapto monomer and the acrylate monomer, a layer of hydrophobic polymer is wrapped on the surface of the fertilizer, so that the fertilizer has the characteristics of slow release.

[0005] Patent CN113816794A discloses a preparation method of lignin-based water-retaining double-layer controlled-release fertilizer. The invention blends polyvinyl alcohol and cellulose derivatives to obtain a mixed liquid for standby; grafts polyacrylic acid-acrylamide copolymer and lignin derivatives to obtain a lignin-based water absorbent; uniformly sprays the mixed solution obtained by blending on the surface of fertilizer particles, and repeats the coating multiple times to obtain a single-layer coated fertilizer; uniformly coats the pre-ground lignin-based water absorbent powder on the outer layer of the single-layer coated fertilizer, and finally dries the fertilizer at 55°C to obtain a double-layer coated slow-release fertilizer.

[0006] Patent CN112624865A discloses a water-retaining slow-release fertilizer and a preparation method thereof. The invention places fertilizer particles in a coating machine, adds a polycaprolactone-polyurethane block copolymer solution, performs coating treatment, dries and cools to obtain a coated material; places the coated material in a coating machine, performs secondary coating treatment, dries and cools to obtain a water-retaining slow-release fertilizer. By coating the fertilizer core, the first coating forms a slow-release layer, and the second coating forms a water-retaining layer, which can have excellent water-retaining performance while ensuring good slow-release speed.

[0007] The above-mentioned invention has made certain progress in slow-release fertilizer, but some polymeric materials may have harmful effects on the environment during the degradation process. Even if it can achieve the function of slow-release fertilizer, it may be relatively persistent in the environment for long-term use, leading to its accumulation in the ecosystem, thereby affecting the ecological balance of soil and water.

[0008] Biological materials derived from animals, plants or microorganisms are renewable and have good degradation performance, so it is of great significance to use biological materials derived from organisms to prepare slow-release fertilizer for environmental protection. SUMMARY

[0009] According to the deficiencies of the prior art, the invention uses mussel extract with good adhesion effect and carboxymethyl cellulose or hyaluronic acid with biocompatibility as a carrier, and realizes the wrapping of nitrogen fertilizer and inorganic fertilizer through the synergistic cooperation of amide structure, imine structure and metal coordination, finally obtaining an environmentally friendly slow-release fertilizer, solving the technical problems raised in the background art. Specifically, the technical scheme of the invention includes the following contents:

[0010] One of the purposes of the invention is to provide a preparation method of an environmentally friendly slow-release fertilizer, which includes the following steps:

[0011] The mussel extract-polysaccharide-nitrogen fertilizer complex, inorganic fertilizer and water are mixed and stirred in a weight ratio of 1-2:5-7:15-23, heated to 50-60°C to form a dispersion solution, the dispersion solution is mixed and stirred with calcium salt in a weight ratio of 1:0.005-0.01, and cooled to 20-25°C to react for 20-24h to obtain a viscous mixture;

[0012] The viscous mixture is dried to remove water and crushed to obtain the environmentally friendly slow-release fertilizer.

[0013] Further, the preparation method of the mussel extract-polysaccharide-nitrogen fertilizer complex comprises the following steps:

[0014] The mussel extract is dissolved in dimethyl sulfoxide, mixed with oxidized polysaccharide and anhydrous sodium sulfate, heated to 30-40°C to react for 10-14h to obtain a mixed solution, the mixed solution, nitrogen fertilizer, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole are mixed to react for 18-24h at a temperature of 15-20°C to obtain the mussel extract-polysaccharide-nitrogen fertilizer complex.

[0015] Further, the preparation method of the mussel extract comprises the following steps:

[0016] The byssus of the mussel is cut and placed in a 0.1mol / L sodium hydroxide solution, stirred at 50-100r / min for 2-3h at 4-10°C, and then hydrochloric acid is added to adjust the pH value to 9-10 to obtain a protein precipitate solution;

[0017] The protein precipitate solution is treated by centrifugation at a speed of 10000-15000r / min for 3-5min to obtain a precipitate, and the precipitate is treated by dialysis with a dialysis bag with a cut-off of 10kDa to obtain the mussel extract.

[0018] Further, the preparation method of the oxidized modified polysaccharide comprises the following steps:

[0019] The water-soluble polysaccharide derivative is mixed and dissolved with water, acid is added to adjust the pH value to 3-4, and stirred for 30-60min to obtain a mixed solution, and the mixed solution is vacuum dried to obtain a water-soluble polysaccharide.

[0020] The water-soluble polysaccharide is mixed and stirred with sodium periodate and reacted in the dark to obtain an oxidized modified polysaccharide.

[0021] Further, the water-soluble polysaccharide derivative includes carboxymethylcellulose sodium or sodium hyaluronate.

[0022] Further, the mass ratio of the water-soluble polysaccharide to sodium periodate is 1:1-2.

[0023] Further, the light-avoiding reaction condition comprises a reaction temperature of 20-25 DEG C and a reaction time of 2-5 hours.

[0024] Further, the nitrogen fertilizer is urea.

[0025] Further, the mass ratio of the mussel extract, oxidized polysaccharide, anhydrous sodium sulfate, nitrogen fertilizer, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 0.1:5-10:0.05-0.1:20-30:3-6:3-6.

[0026] Further, the inorganic fertilizer is potassium fertilizer.

[0027] Further, the calcium salt comprises calcium chloride solution.

[0028] Further, the mass concentration of the calcium salt is 5-10%.

[0029] The second object of the present application provides an environment-friendly slow-release fertilizer prepared by the preparation method of the environment-friendly slow-release fertilizer.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] The present application uses mussel extract with good adhesion effect as one of the carriers, the mussel extract contains a large amount of mussel mucin, the mussel mucin has strong adhesion effect, the mussel mucin has active groups of amino and carboxyl groups, through the activation of the carboxyl group on the mussel mucin by the carboxyl group activation reagent N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide hydrochloride and 1-hydroxybenzotriazole, the carboxyl group on the mussel mucin is activated, so that the mussel mucin is activated and condensed with the amino group in the nitrogen fertilizer to form an amide structure; then carboxymethyl cellulose or hyaluronic acid with biocompatibility is used as the second carrier, the carboxymethyl cellulose or hyaluronic acid has good water absorption and water retention capacity, through acidification treatment of the water-soluble polysaccharide derivative, the water-soluble polysaccharide is obtained by restoring the carboxylic acid structure, the functional group aldehyde group is obtained by oxidation of the water-soluble polysaccharide, on the one hand, the water-soluble polysaccharide is condensed with the amino group in the nitrogen fertilizer to form an amide bond through the action of the carboxyl group activation reagent, on the other hand, the water-soluble polysaccharide is condensed with the amino group of the mussel mucin in the mussel extract through the aldehyde group to form a dynamic imine bond with high temperature resistance, realizing the high temperature resistance protection of the mussel mucin, preventing the degradation of the mussel mucin during high temperature heating and drying. Through the synergistic cooperation of the amide structure and the imine structure, the nitrogen fertilizer is wrapped and the carrier is protected, then the adhesion of the mussel mucin is used to adhere and wrap the inorganic fertilizer, finally, the calcium ion can form a metal coordination effect with the carboxymethyl cellulose or hyaluronic acid to gel, further realizing the wrapping of the inorganic fertilizer, through the synergistic cooperation of the amide bond, the imine bond and the metal coordination effect of the calcium ion, the environment-friendly slow-release fertilizer is finally obtained, which is slowly released by means of microenvironmental conditions such as microorganisms and enzymes contained in the soil after being applied to the soil. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described clearly and completely through the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0033] Unless otherwise specified, the raw materials and reagents used in the present application are commercially available or can be prepared by known methods.

[0034] Preparation Example 1:

[0035] The preparation of mussel extract specifically includes the following processes:

[0036] The fresh purple mussels are washed with water, and then the byssus is cut off with scissors and put into 200 mL of 0.1 mol / L sodium hydroxide solution. Then the stirring controller is started to stir in a low-temperature environment at 4℃, and the stirring speed is set to 50 r / min. After stirring for 2 h, hydrochloric acid is added dropwise while stirring until the pH value of the solution is reduced to 9-10. Then the solution is left to stand for 10 min to obtain a protein precipitate. The protein precipitate is put into a centrifuge and centrifuged at a speed of 10,000 r / min for 3 min to obtain a precipitate. The precipitate is mixed with Tris-hydrochloric acid buffer with a pH value of 7 and then put into a dialysis bag with a 10 kDa cutoff. The dialysis bag is dialyzed against deionized water for 2 days, and then the mussel extract is obtained by freeze-drying.

[0037] Preparation Example 2:

[0038] The preparation method of the mussel extract specifically includes the following processes:

[0039] The fresh purple mussels are washed with water, and then the byssus is cut off with scissors and put into 200 mL of 0.1 mol / L sodium hydroxide solution. Then the stirring controller is started to stir in a low-temperature environment at 6℃, and the stirring speed is set to 70 r / min. After stirring for 2 h, hydrochloric acid is added dropwise while stirring until the pH value of the solution is reduced to 9-10. Then the solution is left to stand for 10 min to obtain a protein precipitate. The protein precipitate is put into a centrifuge and centrifuged at a speed of 12,000 r / min for 4 min to obtain a precipitate. The precipitate is mixed with Tris-hydrochloric acid buffer with a pH value of 7 and then put into a dialysis bag with a 10 kDa cutoff. The dialysis bag is dialyzed against deionized water for 2 days, and then the mussel extract is obtained by freeze-drying.

[0040] Preparation Example 3:

[0041] The preparation method of the mussel extract specifically includes the following processes:

[0042] The fresh purple mussels are washed with water, and then the byssus is cut off with scissors and put into 200 mL of 0.1 mol / L sodium hydroxide solution. Then the stirring controller is started to stir in a low-temperature environment at 8℃, and the stirring speed is set to 90 r / min. After stirring for 3 h, hydrochloric acid is added dropwise while stirring until the pH value of the solution is reduced to 9-10. Then the solution is left to stand for 15 min to obtain a protein precipitate. The protein precipitate is put into a centrifuge and centrifuged at a speed of 14,000 r / min for 4 min to obtain a precipitate. The precipitate is mixed with Tris-hydrochloric acid buffer with a pH value of 7 and then put into a dialysis bag with a 10 kDa cutoff. The dialysis bag is dialyzed against deionized water for 2 days, and then the mussel extract is obtained by freeze-drying.

[0043] Preparation Example 4:

[0044] The preparation method of the mussel extract specifically comprises the following process:

[0045] The fresh purple mussels are washed with water, and then the byssus is cut off with scissors and placed in a 200 mL 0.1 mol / L sodium hydroxide solution. Then, the stirring controller is started in a low-temperature environment of 10°C, and the stirring speed is set to 100 r / min. After stirring for 3 h, hydrochloric acid is added dropwise while stirring until the pH value of the solution is reduced to 9-10. Then, the solution is left to stand for 15 min to obtain a protein precipitate. The protein precipitate is placed in a centrifuge and centrifuged at a speed of 15,000 r / min for 5 min to obtain a precipitate. The precipitate is mixed with a Tris-hydrochloric acid buffer solution with a pH value of 7, and then placed in a dialysis bag with a 10 kDa cutoff. The dialysis bag is dialyzed against deionized water for 2 days, and then freeze-dried to obtain the mussel extract.

[0046] Preparation Example 5:

[0047] The preparation of the oxidatively modified polysaccharide specifically comprises the following process:

[0048] 100 g of sodium carboxymethyl cellulose is dissolved in 500 mL of deionized water, and then the pH value of the dissolved sodium carboxymethyl cellulose solution is adjusted to 3 with acetic acid. After stirring for 30 min, vacuum drying is performed to obtain carboxymethyl cellulose. 50 g of carboxymethyl cellulose is mixed with 50 g of sodium periodate and dissolved in 400 mL of water. Then, the mixture is placed in a water bath environment at 20°C and stirred in the dark for 2 h. After the reaction is completed, 100 mL of ethylene glycol is added to quench the reaction for 2 h to obtain a mixed solution. The mixed solution is then placed in a dialysis bag with a 3.5 kDa cutoff, dialyzed against deionized water for 2 days, and then freeze-dried to obtain the oxidatively modified carboxymethyl cellulose.

[0049] Preparation Example 6:

[0050] The preparation of the oxidatively modified polysaccharide specifically comprises the following process:

[0051] 100 g of sodium carboxymethyl cellulose is dissolved in 500 mL of deionized water, and then the pH value of the dissolved sodium carboxymethyl cellulose solution is adjusted to 3.5 with acetic acid. After stirring for 40 min, vacuum drying is performed to obtain carboxymethyl cellulose. 50 g of carboxymethyl cellulose is mixed with 70 g of sodium periodate and dissolved in 400 mL of water. Then, the mixture is placed in a water bath environment at 20°C and stirred in the dark for 3 h. After the reaction is completed, 100 mL of ethylene glycol is added to quench the reaction for 3 h to obtain a mixed solution. The mixed solution is then placed in a dialysis bag with a 3.5 kDa cutoff, dialyzed against deionized water for 2 days, and then freeze-dried to obtain the oxidatively modified carboxymethyl cellulose.

[0052] Preparation Example 7:

[0053] The preparation of the oxidatively modified polysaccharide specifically includes the following process:

[0054] Dissolve 100 g of sodium hyaluronate in 600 mL of deionized water, then adjust the pH of the dissolved sodium hyaluronate to 4 with acetic acid, and then vacuum dry after stirring for 50 min to obtain hyaluronic acid. Take 50 g of hyaluronic acid and mix with 90 g of sodium periodate and add 400 ml of water to dissolve, then place in a water bath environment at 25°C, stir in the dark for 4 h. After the reaction is completed, 150 ml of ethylene glycol is added to quench the reaction for 4 h to obtain a mixed solution, then the mixed solution is placed in a dialysis bag with a cut-off of 3.5 kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain oxidatively modified hyaluronic acid.

[0055] Preparation Example 8:

[0056] The preparation of the oxidatively modified polysaccharide specifically includes the following process:

[0057] Dissolve 100 g of sodium hyaluronate in 600 mL of deionized water, then adjust the pH of the dissolved sodium hyaluronate to 4 with acetic acid, and then vacuum dry after stirring for 60 min to obtain hyaluronic acid. Take 50 g of hyaluronic acid and mix with 100 g of sodium periodate and add 400 ml of water to dissolve, then place in a water bath environment at 25°C, stir in the dark for 5 h. After the reaction is completed, 150 ml of ethylene glycol is added to quench the reaction for 5 h to obtain a mixed solution, then the mixed solution is placed in a dialysis bag with a cut-off of 3.5 kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain oxidatively modified hyaluronic acid.

[0058] Preparation Example 9:

[0059] The preparation of the oxidatively modified polysaccharide specifically includes the following process:

[0060] Directly mix 100 g of sodium hyaluronate with 100 g of sodium periodate and add 400 ml of water to dissolve, then place in a water bath environment at 25°C, stir in the dark for 5 h. After the reaction is completed, 150 ml of ethylene glycol is added to quench the reaction for 5 h to obtain a mixed solution, then the mixed solution is placed in a dialysis bag with a cut-off of 3.5 kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain oxidatively modified sodium hyaluronate.

[0061] Preparation Example 10:

[0062] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following process:

[0063] The mussel extract obtained in Preparation Example 1 was dissolved in 300 mL of dimethyl sulfoxide, and then 50 g of the oxidized modified carboxymethyl cellulose obtained in Preparation Example 5 was added thereto, and the mixture was stirred to be uniform, and then the temperature was raised to 30°C to react for 10 hours. After the reaction was completed, the obtained mixture was mixed with 200 g of urea, 3 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 3 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 15°C to react for 18 hours. After the reaction was completed, the solution was put in a dialysis bag having a 30 kDa cut-off to be dialyzed to obtain a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0064] Preparation Example 11:

[0065] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex includes the following processes:

[0066] The mussel extract obtained in Preparation Example 2 was dissolved in 300 mL of dimethyl sulfoxide, and then 70 g of the oxidized modified carboxymethyl cellulose obtained in Preparation Example 6 was added thereto, and the mixture was stirred to be uniform, and then the temperature was raised to 30°C to react for 12 hours. After the reaction was completed, the obtained mixture was mixed with 230 g of urea, 4 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 4 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 15°C to react for 20 hours. After the reaction was completed, the solution was put in a dialysis bag having a 30 kDa cut-off to be dialyzed to obtain a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0067] Preparation Example 12:

[0068] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex includes the following processes:

[0069] The mussel extract obtained in Preparation Example 3 was dissolved in 400 mL of dimethyl sulfoxide, and then 90 g of the oxidized modified hyaluronic acid obtained in Preparation Example 7 was added thereto, and the mixture was stirred to be uniform, and then the temperature was raised to 35°C to react for 12 hours. After the reaction was completed, the obtained mixture was mixed with 270 g of urea, 5 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 5 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 20°C to react for 22 hours. After the reaction was completed, the solution was put in a dialysis bag having a 30 kDa cut-off to be dialyzed to obtain a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0070] Preparation Example 13:

[0071] Preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex includes the following processes:

[0072] The mussel extract obtained in Preparation Example 4 was dissolved in 400 mL of dimethyl sulfoxide, and then 100 g of the oxidized modified hyaluronic acid obtained in Preparation Example 8 was added thereto, and 1 g of anhydrous sodium sulfate was mixed and stirred uniformly, and then the temperature was raised to 40°C to react for 14 h. After the reaction was completed, the obtained mixture was mixed with 300 g of urea, 6 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 6 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 20°C to react for 24 h. After the reaction was completed, the solution was placed in a dialysis bag having a 30 kDa cut-off to perform dialysis treatment, thereby obtaining a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0073] Preparation Example 14:

[0074] Preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex includes the following processes:

[0075] The mussel extract obtained in Preparation Example 4 was dissolved in 400 mL of dimethyl sulfoxide, and then 100 g of the oxidized modified hyaluronic acid obtained in Preparation Example 8 was added thereto, and 1 g of anhydrous sodium sulfate was mixed and stirred uniformly, and then the temperature was raised to 40°C to react for 14 h. After the reaction was completed, the obtained mixture was mixed with 300 g of urea, 6 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 6 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 20°C to react for 24 h. After the reaction was completed, the solution was placed in a dialysis bag having a 30 kDa cut-off to perform dialysis treatment, thereby obtaining a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0076] Preparation Example 15:

[0077] Preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex includes the following processes:

[0078] The mussel extract obtained in Preparation Example 4 was dissolved in 400 mL of dimethyl sulfoxide, and then 100 g of the oxidized modified hyaluronic acid obtained in Preparation Example 8 was added thereto, and 1 g of anhydrous sodium sulfate was mixed and stirred uniformly, and then the temperature was raised to 40°C to react for 14 h. After the reaction was completed, the obtained mixture was mixed with 300 g of urea, 6 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 6 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 20°C to react for 24 h. After the reaction was completed, the solution was placed in a dialysis bag having a 30 kDa cut-off to perform dialysis treatment, thereby obtaining a mussel extract-polysaccharide-nitrogen fertilizer complex having a viscous form.

[0079] Example 1:

[0080] Preparation of an environment-friendly slow-release fertilizer, specifically comprising the following processes:

[0081] 1 part by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 10 was dispersed in 15 parts by weight of water, and then heated to 50°C, followed by adding 5 parts by weight of potassium fertilizer and mixing to form a dispersion solution. At a temperature of 50°C, a calcium chloride solution with a mass concentration of 5% was added to the dispersion solution at 0.005 times the weight of the dispersion solution, and stirred uniformly while hot. Subsequently, the temperature was lowered to 20°C and left to stand for 20 h to obtain a viscous mixture, which was dried by an oven to remove water, and then put into a crusher to be pulverized to obtain an environment-friendly slow-release fertilizer.

[0082] Example 2:

[0083] Preparation of an environment-friendly slow-release fertilizer, specifically comprising the following processes:

[0084] 1.2 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 10 was dispersed in 17 parts by weight of water, and then heated to 50°C, followed by adding 5 parts by weight of potassium fertilizer and mixing to form a dispersion solution. At a temperature of 50°C, a calcium chloride solution with a mass concentration of 6% was added to the dispersion solution at 0.006 times the weight of the dispersion solution, and stirred uniformly while hot. Subsequently, the temperature was lowered to 20°C and left to stand for 20 h to obtain a viscous mixture, which was dried by an oven to remove water, and then put into a crusher to be pulverized to obtain an environment-friendly slow-release fertilizer.

[0085] Example 3:

[0086] Preparation of an environment-friendly slow-release fertilizer, specifically comprising the following processes:

[0087] 1.4 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 11 was dispersed in 18 parts by weight of water, and then heated to 55°C, followed by adding 6 parts by weight of potassium fertilizer and mixing to form a dispersion solution. At a temperature of 55°C, a calcium chloride solution with a mass concentration of 7% was added to the dispersion solution at 0.007 times the weight of the dispersion solution, and stirred uniformly while hot. Subsequently, the temperature was lowered to 20°C and left to stand for 22 h to obtain a viscous mixture, which was dried by an oven to remove water, and then put into a crusher to be pulverized to obtain an environment-friendly slow-release fertilizer.

[0088] Example 4:

[0089] Preparation of an environment-friendly slow-release fertilizer, specifically comprising the following processes:

[0090] Take 1.6 parts by weight of mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 12 and disperse in 20 parts by weight of water, then heat to 55°C, and then add 6 parts by weight of potassium fertilizer and mix to form a dispersion solution. At a temperature of 55°C, add a calcium chloride solution with a mass concentration of 8% to the dispersion solution at 0.008 times the weight of the dispersion solution, and stir while hot to make uniform. Then cool to 25°C and stand for 22 hours to obtain a viscous mixture, dry the viscous mixture with a dryer, and then put it into a crusher to obtain an environmentally friendly slow-release fertilizer.

[0091] Example 5:

[0092] An environmentally friendly slow-release fertilizer is prepared, specifically including the following processes:

[0093] Take 1.8 parts by weight of mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 13 and disperse in 22 parts by weight of water, then heat to 60°C, and then add 7 parts by weight of potassium fertilizer and mix to form a dispersion solution. At a temperature of 60°C, add a calcium chloride solution with a mass concentration of 9% to the dispersion solution at 0.009 times the weight of the dispersion solution, and stir while hot to make uniform. Then cool to 25°C and stand for 24 hours to obtain a viscous mixture, dry the viscous mixture with a dryer, and then put it into a crusher to obtain an environmentally friendly slow-release fertilizer.

[0094] Example 6:

[0095] An environmentally friendly slow-release fertilizer is prepared, specifically including the following processes:

[0096] Take 2 parts by weight of mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 13 and disperse in 23 parts by weight of water, then heat to 60°C, and then add 7 parts by weight of potassium fertilizer and mix to form a dispersion solution. At a temperature of 60°C, add a calcium chloride solution with a mass concentration of 10% to the dispersion solution at 0.01 times the weight of the dispersion solution, and stir while hot to make uniform. Then cool to 25°C and stand for 24 hours to obtain a viscous mixture, dry the viscous mixture with a dryer, and then put it into a crusher to obtain an environmentally friendly slow-release fertilizer.

[0097] Comparative Example 1:

[0098] An environmentally friendly slow-release fertilizer is prepared, specifically including the following processes:

[0099] The mussel extract-polysaccharide-nitrogen fertilizer complex in Example 6 is replaced with the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 14, and the remaining conditions are the same as in Example 6.

[0100] Comparative Example 2:

[0101] A preparation of an environment-friendly slow-release fertilizer, specifically comprising the following processes:

[0102] The mussel extract-polysaccharide-nitrogen fertilizer complex in Example 6 is replaced with the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 15, and the remaining conditions remain the same as in Example 6.

[0103] According to GB / T 23348-2009 Slow-Release Fertilizer, the total nutrient (nitrogen and potassium) cumulative release rates of the environment-friendly slow-release fertilizers obtained in Examples 1-6 and Comparative Examples 1-2 at 30℃±5℃ are determined on the 7th day, the 14th day, and the 28th day, and the results are shown in Table 1 below.

[0104] Table 1

[0105] Material Source Cumulative release rate at day 7 Cumulative release rate at day 14 Cumulative release rate at day 28 Example 1 4.87 14.8 38.4 Example 2 4.84 14.7 38.1 Example 3 4.75 14.4 37.6 Example 4 4.62 13.9 37.1 Example 5 4.54 13.6 36.8 Example 6 4.31 13.2 36.3 Comparative Example 1 6.67 35.6 52.5 Comparative Example 2 8.04 42.7 61.3

[0106] According to the cumulative release rates in Table 1 above, it can be seen that:

[0107] (1) Examples 1-6 of the present application use mussel extract with good adhesion effect and carboxymethyl cellulose or hyaluronic acid with biocompatibility as carriers, and through the synergistic cooperation of amide structure, imine structure, and calcium ion metal coordination, slow release of the fertilizer is achieved.

[0108] (2) It is found from Comparative Example 1 that since the sodium ions in sodium hyaluronate are not removed by acidification, the carboxyl structure in hyaluronic acid cannot form amide bonds, which may result in insufficient crosslinking density, and relying on the coordination of calcium ions and covalent crosslinking of imine bonds, the release rate is faster and the slow-release effect is poorer.

[0109] (3) It is found from Comparative Example 2 that since the sodium hyaluronate is not oxidized, it cannot form a high-temperature-resistant dynamic imine bond with mussel mucin in mussel extract, and during high-temperature drying, the mussel mucin is easily denatured and inactivated, losing adhesion, the release rate is faster, and the slow-release effect is poorer.

[0110] The above examples have described the technical solutions and beneficial effects of the present application in detail, and it should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for preparing an environmentally friendly slow-release fertilizer, characterized in that, The preparation method includes the following steps: Mussel extract-oxidized polysaccharide-nitrogen fertilizer complex, inorganic fertilizer and water are mixed and stirred in a weight ratio of 1~2:5~7:15~23 and heated to 50℃~60℃ to form a dispersion solution. The dispersion solution is then mixed and stirred with calcium salt in a weight ratio of 1:0.005~0.01 and cooled to 20℃~25℃ for 20h~24h to obtain a viscous mixture. The viscous mixture is dried, dehydrated, and pulverized to obtain the environmentally friendly slow-release fertilizer. The preparation method of the mussel extract-oxidized modified polysaccharide-nitrogen fertilizer complex includes the following steps: Mussel extract was dissolved in dimethyl sulfoxide and then mixed with oxidized polysaccharide and anhydrous sodium sulfate. The mixture was heated to 30℃~40℃ and reacted for 10h~14h to obtain a mixed solution. The mixed solution, nitrogen fertilizer, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were mixed and reacted at 15℃~20℃ for 18h~24h to obtain the mussel extract-oxidized polysaccharide-nitrogen fertilizer complex. The preparation method of the mussel extract includes the following steps: The byssal threads of the mussels were cut off and placed in a 0.1 mol / L sodium hydroxide solution. The mixture was stirred at 50 r / min to 100 r / min for 2 to 3 hours at 4℃ to 10℃. Then, hydrochloric acid was added to adjust the pH to 9 to 10 to obtain a protein precipitate. The protein precipitate was centrifuged at 10000r / min~15000r / min for 3min~5min to obtain a precipitate, and the precipitate was dialyzed through a dialysis bag with a flow rate of 10kDa to obtain the mussel extract. The preparation method of the oxidized modified polysaccharide includes the following steps: The water-soluble polysaccharide derivative is mixed and dissolved in water, and then acid is added to adjust the pH value to 3-4. The mixture is stirred for 30-60 minutes to obtain a mixed solution. The mixed solution is then vacuum dried to obtain the water-soluble polysaccharide. The water-soluble polysaccharide was mixed with sodium periodate and stirred and reacted in the dark to obtain an oxidized modified polysaccharide; The water-soluble polysaccharide derivatives include sodium carboxymethyl cellulose or sodium hyaluronate; The inorganic fertilizer is a potassium fertilizer; The mussel extract was prepared by the following process: oxidatively modified polysaccharide: anhydrous sodium sulfate: nitrogen fertilizer: N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride: 1-hydroxybenzotriazole in a mass ratio of 0.1:5~10:0.05~0.1:20~30:3~6:3~6.

2. The method for preparing an environmentally friendly slow-release fertilizer according to claim 1, characterized in that, The nitrogen fertilizer mentioned is urea.

3. The method for preparing an environmentally friendly slow-release fertilizer according to claim 1, characterized in that, The calcium salts include calcium sulfate or calcium chloride.

4. An environmentally friendly slow-release fertilizer prepared by the method described in any one of claims 1 to 3.