A potassium formate-based fertilizer and a method for its preparation

Abstract

The application provides a potassium formate-based fertilizer and a preparation method thereof, and the method comprises the following steps: step S1: dissolving and dispersing potassium formate and humic acid in water to obtain a first mixed solution; step S2: after the pH of the first mixed solution is adjusted, glutaraldehyde is added to carry out a cross-linking reaction, so that the humic acid is cross-linked and combined with the potassium formate, and a second mixed solution is obtained; and step S3: the second mixed solution is subjected to a spray drying treatment to obtain the potassium formate-based fertilizer. According to the application, the fertilizer obtained by the method has good slow-release effect, can realize long-acting release of potassium elements, and thus improves the utilization rate of the potassium elements by plants and reduces the loss and waste of the potassium elements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical fertilizer production, and particularly relates to a potassium formate-based fertilizer and a preparation method thereof. BACKGROUND

[0002] Potassium formate (chemical formula: HCOOK) is an inorganic compound, usually white crystals or particles, soluble in water. It is the potassium salt of formic acid, commonly used in agriculture, chemical industry and some biological applications. Since potassium formate can provide potassium elements required by plants, and formate has little effect on plant growth, it is often used as a potassium source in chemical fertilizers. Compared with other potassium salt fertilizers, potassium formate has better comprehensive performance, especially suitable for high-value economic crops.

[0003] However, the problem of using it as a potassium fertilizer is that the nutrient speed is fast, which can cause the plant to absorb more potassium elements in a short period of time, but the long-term continuous supply is insufficient. The rapid release of nutrients can make the plant unable to continuously absorb the required potassium elements from the soil for a long time, resulting in an increase in the frequency of application, and the rapid loss of potassium elements also wastes resources, resulting in an increase in cost.

[0004] Therefore, when potassium formate is used as a potassium element in a fertilizer, it is necessary to control the release of potassium formate in the fertilizer, so as to achieve the effect of slow release, promote the full absorption and utilization of potassium elements in the fertilizer by plants, reduce the waste of potassium elements, and achieve the effect of long-term supply of potassium elements.

[0005] Current slow-release fertilizers generally exist in the form of granules, which generally use inert porous materials as carriers to fix pesticides or fertilizers on the surface or porous structure of the carriers; or directly coat the pesticides or fertilizers to achieve the effect of slow release, but these methods are not suitable for the slow release of potassium formate.

[0006] Patent CN119100881A discloses a polydopamine-coated nano slow-release pesticide and fertilizer and a preparation method thereof. The nano slow-release pesticide and fertilizer uses a simple one-pot method to encapsulate the bactericide and the fertilizer in the synthesized zinc-based nano carrier ZIF-90 by coordination assembly between zinc ions and imidazole-2-formaldehyde, and finally coats a layer of polydopamine on the outside of the carrier. The nano slow-release pesticide and fertilizer comprises the following components in mass percentage: 45-60wt% zinc-based nano carrier ZIF-90, 15-30wt% pesticide and fertilizer, and 5-15wt% coating material polydopamine. The nano slow-release pesticide and fertilizer prepared by the patent has the characteristics of small average particle size, good biocompatibility and environmental safety, and has good application prospect.

[0007] Patent 119241305A discloses a slow-release fertilizer for saline-alkali soil and a preparation method thereof, comprising: a granular core formed by co-granulating a base fertilizer composition with biochar powder; a first coating layer formed on the surface of the granular core from a mixture of gamma-polyglutamic acid or its derivative and sodium alginate; a second coating layer formed on the surface of the first coating layer from sulfur; and a third coating layer formed on the surface of the second coating layer from an anti-caking agent. The slow-release fertilizer for saline-alkali soil has strong functionality, good slow-release effect, improves soil aggregate structure, increases water and fertilizer utilization rate, cooperatively reduces saline-alkali soil pH, increases soil nutrient and organic matter content, promotes plant growth and development, and improves soil microecology.

[0008] The above patents all achieve the slow-release effect by loading pesticides or fertilizers on specific inorganic carriers and then coating, but the loading effect of inorganic carriers on potassium formate is poor, so it is difficult to achieve slow release of potassium formate by the above methods.

[0009] Therefore, it is necessary to provide a potassium formate-based fertilizer with good slow-release effect. SUMMARY

[0010] Therefore, the present application provides a potassium formate-based fertilizer and a preparation method thereof, which has good slow-release effect and can achieve long-term release of potassium elements, thereby improving the utilization rate of potassium elements by plants and reducing the loss and waste of potassium elements.

[0011] In a first aspect, the present application provides a method for preparing a potassium formate-based fertilizer, characterized in that it comprises the following steps:

[0012] Step S1: Dissolve and disperse potassium formate and humic acid in water to obtain a first mixture;

[0013] Step S2: After adjusting the pH of the first mixture, add glutaraldehyde for cross-linking reaction to make humic acid cross-link and combine with potassium formate, to obtain a second mixture;

[0014] Step S3: Spray dry the second mixture to obtain a potassium formate-based fertilizer.

[0015] According to the present application, the inventors found that humic acid has good loading effect on potassium formate, and under the action of glutaraldehyde, humic acid is cross-linked, and the obtained fertilizer has good slow-release effect, can achieve long-term release of potassium elements, thereby improving the utilization rate of potassium elements by plants and reducing the loss and waste of potassium elements.

[0016] In some embodiments, in step S1, the mass ratio of potassium formate to humic acid in the first mixture is 1:2-4, and the mass percentage content of potassium formate in the first mixture is 0.5%-3%.

[0017] In some embodiments, after dissolving and dispersing the potassium formate and the humic acid in water in step S1, the method further comprises adding an aqueous solution of an aminopolysaccharide to obtain a first mixture; wherein the aminopolysaccharide comprises chitosan and / or carboxymethyl chitosan.

[0018] In some embodiments, in the first mixture, the mass ratio of the potassium formate to the aminopolysaccharide is 1:1-3 in step S1.

[0019] In some embodiments, the aminopolysaccharide comprises chitosan and carboxymethyl chitosan, and the mass ratio of the chitosan to the carboxymethyl chitosan is 1:0.5-1 in step S1.

[0020] In some embodiments, the degree of deacetylation of the chitosan is 75%-98%, and the degree of substitution of the carboxymethyl group of the carboxymethyl chitosan is 80%-95%.

[0021] In some embodiments, in step S2, the pH adjustment comprises adjusting the pH of the first mixture to 6.5-7.5.

[0022] In some embodiments, in step S2, the cross-linking reaction is performed under conditions comprising: a mass concentration of glutaraldehyde in the reaction system of 0.1%-1%, a reaction temperature of 40-60°C, and a reaction time of 20-60 min.

[0023] In some embodiments, in step S3, the spray drying is performed under conditions comprising: a temperature of the feed liquid of 25-30°C, an inlet air temperature of 120-160°C, an outlet air temperature of 60-90°C, a nozzle diameter of 0.4-1 mm, and a spray pressure of 1.5-2.5 MPa.

[0024] In a second aspect, the present application provides a potassium formate-based fertilizer prepared by the method according to any one of the first aspect. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0026] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the implementation or example are included in at least one implementation or example of the present application. In the description of the specification, the exemplary description of the above terms does not necessarily mean the same implementation or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more implementations or examples as appropriate.

[0027] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0028] In a first aspect, the present application provides a method for preparing a potassium formate-based fertilizer, characterized in that it comprises the following steps:

[0029] Step S1: Dissolve and disperse potassium formate and humic acid in water to obtain a first mixed solution;

[0030] Step S2: After adjusting the pH of the first mixed solution, add glutaraldehyde to carry out cross-linking reaction, so that the humic acid is cross-linked and combined with potassium formate to obtain a second mixed solution;

[0031] Step S3: Spray drying treatment is carried out on the second mixed solution to obtain a potassium formate-based fertilizer.

[0032] According to the present application, the inventors found that humic acid has good loading effect on potassium formate, and under the action of glutaraldehyde, the humic acid is cross-linked, and the fertilizer obtained by spray drying has good slow-release effect, which can realize long-acting release of potassium element, thereby improving the utilization rate of potassium element by plants and reducing the loss and waste of potassium element.

[0033] Specifically, humic acid is a complex natural organic macromolecule mainly composed of aromatic and aliphatic skeleton, and contains various active groups in the molecule, including hydroxyl, carboxyl, phenolic hydroxyl, ether bond, amino and carbonyl, etc. The carboxyl group can be deprotonated to form carboxylate, so that humic acid carries a large number of negative charges, which can adsorb potassium ions through electrostatic interaction, thereby preventing the rapid loss of potassium element. In addition, the formate group in potassium formate can react with the hydroxyl or amino group in humic acid due to its special structure, and can be combined with humic acid through physical (forming hydrogen bond with hydroxyl) or chemical (reacting with hydroxyl or amino to form hemiacetal or imine) to further increase the negative charge of humic acid, so that it has a stronger adsorption effect on potassium element. At the same time, it can be understood that the aromatic structure in the humic acid molecule provides a hydrophobic environment, which can also fix the potassium formate molecules or potassium elements through physical adsorption or chelation. Therefore, through the above effects, humic acid has good loading effect on potassium formate, and the formed complex has strong adsorption and fixation effect on potassium element.

[0034] In step S2, the complex formed in the first mixed solution is further cross-linked under the action of glutaraldehyde. The hydroxyl and amino groups in humic acid can react with the aldehyde group of glutaraldehyde, so that the chain structure of humic acid can be cross-linked to form a more stable three-dimensional cross-linked network. The inventors have found that the cross-linked humic acid has better loading and slow-release effect on potassium element, which can further improve the loading efficiency of the fertilizer on potassium element and achieve longer slow-release effect.

[0035] In step S3, the cross-linked product formed in the second mixed solution is dried by using a spray drying method. Spray drying can obtain a fertilizer with complete structure and uniform particle size distribution, so that the fertilizer has more stable slow-release effect.

[0036] Therefore, the potassium formate-based fertilizer obtained by the above method has good slow-release effect and can achieve long-term release of potassium element, thereby improving the utilization rate of potassium element by plants and reducing the loss and waste of potassium element.

[0037] In some embodiments, in step S1, the mass ratio of potassium formate to humic acid in the first mixed solution is 1:2-4, and the mass percentage content of potassium formate in the first mixed solution is 0.5%-3%.

[0038] In the above embodiments, the mass ratio of potassium formate to humic acid is controlled within the above range, and the mass percentage content of potassium formate in the first mixed solution is controlled within the above range. Appropriate reactant concentration is conducive to the complete dissociation and combination of each component, so that potassium formate can be fully combined with humic acid to form a more stable potassium salt complex, thereby preventing the rapid dissolution and loss of potassium formate in the fertilizer after application, and the obtained fertilizer has better slow-release effect.

[0039] In some embodiments, after the potassium formate and the humic acid are dissolved and dispersed in water in step S1, the method further comprises: adding an aqueous solution of an aminopolysaccharide to obtain a first mixture; wherein the aminopolysaccharide comprises chitosan and / or carboxymethyl chitosan.

[0040] In some of the above embodiments, the inventors have further found that, since the content of amino groups in humic acid is generally low and the reactivity of hydroxyl groups is relatively weak, the cross-linking density of the cross-linked product is relatively low. By further adding the aminopolysaccharide to the first mixture, the amino groups on the aminopolysaccharide can be further cross-linked with the humic acid under the action of glutaraldehyde, and the hydroxyl groups on the aminopolysaccharide can be combined with the humic acid through hydrogen bonds, so that the cross-linking density of the cross-linked product is higher, the adsorption and fixation effect of potassium elements is better, the loading efficiency is improved, and the polysaccharide segments in the cross-linked product gradually decompose after the fertilizer is applied, the cross-linking density gradually decreases, and the long-term release of potassium elements is realized, so that the fertilizer has a better slow-release effect.

[0041] It can be understood that the aminopolysaccharide refers to a polysaccharide compound containing amino groups, and generally includes chitosan and carboxymethyl chitosan. Chitosan is a product formed by removing acetyl groups from part of deacetylated chitin to form amino groups. Carboxymethyl chitosan is a product formed by modifying part of the amino groups and hydroxyl groups of chitosan to carboxymethyl groups.

[0042] In some embodiments, in step S1, the mass ratio of the potassium formate to the aminopolysaccharide in the first mixture is 1:1-3.

[0043] In some of the above embodiments, by controlling the mass ratio of the potassium formate to the aminopolysaccharide in the first mixture within the above range, the cross-linking density of the cross-linked product can be further improved, and the easily degradable aminopolysaccharide can regulate the slow release of potassium elements in the fertilizer, so that the fertilizer has a better slow-release effect.

[0044] In some embodiments, in step S1, the aminopolysaccharide includes chitosan and carboxymethyl chitosan, and the mass ratio of chitosan to carboxymethyl chitosan is 1:0.5-1.

[0045] In some of the above embodiments, the amino polysaccharide comprises both chitosan and carboxymethyl chitosan, and the mass ratio of the two is controlled within the above range. The inventors have found that although chitosan can effectively increase the cross-linking density of the cross-linking product due to its large number of amino groups, the large number of unreacted amino groups in chitosan can balance the negative charge of the humic acid-potassium formate complex, resulting in weaker electrostatic attraction to potassium ions. Thus, the cross-linking product obtained has better slow-release performance but weaker loading performance for potassium ions. Therefore, the fertilizer obtained by spray drying has a too-fast release of non-tightly loaded potassium elements in the early stage of application. Although the fertilizer obtained by further cross-linking of chitosan alone can achieve the effect of long-acting slow release of potassium elements, the release speed is too fast in the early stage due to the weaker loading effect. Therefore, by using a certain proportion of chitosan and carboxymethyl chitosan for cross-linking, the chitosan can effectively increase the cross-linking density of the cross-linking product, and the partial hydroxyl and amino groups on the carboxymethyl chitosan can also participate in the cross-linking reaction. At the same time, the large number of carboxymethyl groups on the carboxymethyl chitosan can increase the negative charge of the cross-linking product, thereby reducing the influence of the unreacted amino groups on the charge of the cross-linking product. Thus, the cross-linking product has good loading efficiency for potassium ions, and the fertilizer obtained has better long-acting slow-release effect.

[0046] In some embodiments, the degree of deacetylation of the chitosan is 75% to 98%, and the degree of substitution of the carboxymethyl group of the carboxymethyl chitosan is 80% to 95%. Based on the above embodiments, when the degree of deacetylation of the chitosan and the degree of substitution of the carboxymethyl group of the carboxymethyl chitosan are within the above ranges, the fertilizer has better slow-release effect.

[0047] In some embodiments, in step S2, adjusting the pH comprises adjusting the pH of the first mixed solution to 6.5 to 7.5. Based on the above embodiments, when the pH of the mixed solution is within the above range, the glutaraldehyde has good reactivity with the amino and hydroxyl groups, which can promote the cross-linking of the components in the mixed solution.

[0048] In some embodiments, in step S2, the conditions of the cross-linking reaction include that the mass concentration of glutaraldehyde in the reaction system is 0.1% to 1%, the reaction temperature is 40 to 60°C, and the reaction time is 20 to 60 min. Based on the above embodiments, under the above cross-linking reaction conditions, a cross-linking product with appropriate cross-linking density can be obtained, and the fertilizer obtained has better slow-release effect.

[0049] In some embodiments, in step S3, the conditions of the spray drying include that the temperature of the feed liquid is 25 to 30°C, the temperature of the inlet air is 120 to 160°C, the temperature of the outlet air is 60 to 90°C, the diameter of the nozzle is 0.4 to 1 mm, and the spray pressure is 1.5 to 2.5 MPa. Based on the above embodiments, under the above conditions of spray drying, a fertilizer with appropriate uniformity and suitable particle size can be obtained, and the fertilizer obtained has stable slow-release effect.

[0050] In a second aspect, the application provides a potassium formate-based fertilizer prepared according to the method of any one of the first aspect.

[0051] According to the application, the fertilizer is prepared according to any one of the first aspect, and thus has the beneficial effects of the first aspect, i.e., the fertilizer has a good slow-release effect, and can achieve long-term release of potassium elements, thereby improving the utilization rate of potassium elements by plants and reducing the loss and waste of potassium elements.

[0052] Humic acid from Xinjiang Shengda Yifang Biological Technology Co., Ltd.;

[0053] Chitosan with a degree of deacetylation of 90% from Hubei Shiteng Chemical Technology Co., Ltd.;

[0054] Carboxymethyl chitosan with a degree of deacetylation of 92% and a degree of carboxymethyl substitution of 90% from Hubei Shiteng Chemical Technology Co., Ltd.

[0055] The scheme of the application will be described below in combination with the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from ordinary commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0056] Example 1

[0057] 120 g of chitosan and 80 g of carboxymethyl chitosan were dissolved in 4800 g of 1 wt% acetic acid aqueous solution to obtain an amino polysaccharide aqueous solution;

[0058] 300 g of humic acid was dispersed in 4600 g of water, and sodium hydroxide was used to adjust the pH to 7. After stirring, a humic acid aqueous solution was obtained. 100 g of potassium formate was added to the humic acid aqueous solution, and stirring was performed for 1 h to obtain a humic acid-potassium formate composite solution;

[0059] The amino polysaccharide aqueous solution was slowly added to the humic acid-potassium formate composite solution, and stirring was performed at 60 rpm until uniformity was achieved to obtain a first mixed solution;

[0060] After the pH of the first mixed solution was adjusted to 6.5, 25 wt% glutaraldehyde aqueous solution was added dropwise to achieve a glutaraldehyde concentration of 0.5 wt% in the system. Stirring was performed at 45°C and 60 rpm for 35 min to obtain a second mixed solution;

[0061] After the second mixed solution was cooled to 25°C, spray drying was performed with an inlet temperature of 135°C, an outlet temperature of 65°C, a nozzle diameter of 0.8 mm, and a spray pressure of 2 MPa to obtain a potassium formate-based fertilizer.

[0062] Example 2

[0063] 300 g humic acid was dispersed in 9600 g water, the pH was adjusted to 7 using sodium hydroxide, and the humic acid aqueous solution was obtained by stirring; 100 g potassium formate was added to the humic acid aqueous solution, and the humic acid potassium formate composite solution was obtained by stirring for 1 h, which was the first mixed solution;

[0064] After the pH of the first mixed solution was adjusted to 6.5, 25wt% glutaraldehyde aqueous solution was added dropwise to make the concentration of glutaraldehyde in the system 0.5wt%. The second mixed solution was obtained by stirring at 45℃ and 60rpm for 35min;

[0065] The second mixed solution was cooled to 25℃ and then spray dried, the inlet air temperature was 135℃, the outlet air temperature was 65℃, the nozzle diameter was 0.8mm, and the spray pressure was 2MPa, to obtain a potassium formate-based fertilizer.

[0066] Example 3

[0067] 200 g chitosan was dissolved in 4800 g 1wt% acetic acid aqueous solution to obtain an amino polysaccharide aqueous solution;

[0068] 300 g humic acid was dispersed in 4600 g water, the pH was adjusted to 7 using sodium hydroxide, and the humic acid aqueous solution was obtained by stirring; 100 g potassium formate was added to the humic acid aqueous solution, and the humic acid potassium formate composite solution was obtained by stirring for 1 h;

[0069] The amino polysaccharide aqueous solution was slowly added to the humic acid potassium formate composite solution, and the first mixed solution was obtained by stirring uniformly at 60rpm;

[0070] After the pH of the first mixed solution was adjusted to 6.5, 25wt% glutaraldehyde aqueous solution was added dropwise to make the concentration of glutaraldehyde in the system 0.5wt%. The second mixed solution was obtained by stirring at 45℃ and 60rpm for 35min;

[0071] The second mixed solution was cooled to 25℃ and then spray dried, the inlet air temperature was 135℃, the outlet air temperature was 65℃, the nozzle diameter was 0.8mm, and the spray pressure was 2MPa, to obtain a potassium formate-based fertilizer.

[0072] Example 4

[0073] 200 g carboxymethyl chitosan was dissolved in 4800 g water to obtain an amino polysaccharide aqueous solution;

[0074] 300 g humic acid was dispersed in 4600 g water, the pH was adjusted to 7 using sodium hydroxide, and the humic acid aqueous solution was obtained by stirring; 100 g potassium formate was added to the humic acid aqueous solution, and the humic acid potassium formate composite solution was obtained by stirring for 1 h;

[0075] Slowly add the aqueous solution of the amino polysaccharide into the humic acid potassium formate complex solution, and stir uniformly at 60 rpm to obtain a first mixed solution;

[0076] After adjusting the pH of the first mixed solution to 6.5, add dropwise a 25wt% aqueous solution of glutaraldehyde to make the concentration of glutaraldehyde in the system 0.5wt%. Stir at 60 rpm at 45℃ for 35 min to obtain a second mixed solution;

[0077] After cooling the second mixed solution to 25℃, spray dry at an inlet temperature of 135℃, an outlet temperature of 65℃, a nozzle diameter of 0.8mm, and a spray pressure of 2MPa to obtain a potassium formate-based fertilizer.

[0078] Comparative Example 1

[0079] Disperse 300g of humic acid in 9600g of water, adjust the pH to 7 using sodium hydroxide, and stir to obtain an aqueous solution of humic acid. Add 100g of potassium formate to the aqueous solution of humic acid, and stir for 1h to obtain a humic acid potassium formate complex solution, which is the first mixed solution;

[0080] After cooling the first mixed solution to 25℃, spray dry at an inlet temperature of 135℃, an outlet temperature of 65℃, a nozzle diameter of 0.8mm, and a spray pressure of 2MPa to obtain a potassium formate-based fertilizer.

[0081] Test Method:

[0082] The fertilizers obtained in Examples 1-4 and Comparative Example 1 were subjected to a simulated soil release test, which specifically included:

[0083] Preparation of soil: Take 500g of air-dried soil and place it in a breathable container.

[0084] Mixing of fertilizer: Mix 5g of fertilizer per 500g of soil uniformly.

[0085] Simulated irrigation: Simulate rainfall or irrigation every 3 days by adding 50mL of water.

[0086] Periodic sampling: Take soil samples at 20d intervals, disperse the soil samples in water for 30min, centrifuge to obtain supernatant, and determine the content of potassium ions in the soil solution to obtain the content of potassium elements in the soil, and calculate the release rate of potassium elements in the fertilizer; release rate = (content of potassium elements in the soil on the nth day - content of potassium elements in the original soil solution) / content of potassium elements in the fertilizer.

[0087] The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] Due to the existence of certain error in the test process, it is generally considered that the release rate greater than 98% can be considered as complete release, in addition, since the uncombined potassium formate will be quickly released in the soil in the first 20 days, therefore, the loading efficiency of the fertilizer to potassium element can be judged according to the size of the 20d release rate.

[0091] According to Table 1, it can be known that the fertilizer obtained by each embodiment has better loading efficiency to potassium element compared with the comparative example, and has better slow-release effect, in the comparative example 1, the fertilizer is obtained by only compounding and drying potassium formate and humic acid, the loading efficiency and fixation effect to potassium element is poor through the compounding of humic acid and potassium formate, and it is easy to dissociate under the action of water and microorganisms, and the slow-release effect is poor.

[0092] According to Examples 1-4, it can be known that the fertilizer obtained by using a certain proportion of chitosan and carboxymethyl chitosan in combination with glutaraldehyde for cross-linking treatment in Example 1 has better loading efficiency to potassium element, and has better slow-release effect; although glutaraldehyde is used for cross-linking treatment in Example 2, the effect is limited, and it is basically completely released in 80d; although chitosan is used in combination with glutaraldehyde for cross-linking treatment in Example 3, it has good slow-release effect, but its 20d release rate is high, which indicates that its loading efficiency to potassium element is poor, and it is easy to cause the loss of potassium element in the early stage of application; although carboxymethyl chitosan is used in combination with glutaraldehyde for cross-linking treatment in Example 4, its loading efficiency to potassium element is good, but the improvement of cross-linking density is small, and the slow-release effect is not as good as that of Example 1.

[0093] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a potassium formate-based fertilizer, characterized in that, Includes the following steps: Step S1: Dissolve and disperse potassium formate and humic acid in water, then add an aqueous solution of amino polysaccharide to obtain a first mixture; wherein, the mass ratio of potassium formate to humic acid in the first mixture is 1:2~4, the mass percentage of potassium formate in the first mixture is 0.5%~3%, the mass ratio of potassium formate to amino polysaccharide in the first mixture is 1:1~3, the amino polysaccharide includes chitosan and carboxymethyl chitosan, and the mass ratio of chitosan to carboxymethyl chitosan is 1:0.5~1; Step S2: After adjusting the pH of the first mixture, glutaraldehyde is added to carry out a cross-linking reaction, so that humic acid cross-links and combines with potassium formate to obtain the second mixture. Step S3: Spray dry the second mixture to obtain a potassium formate-based fertilizer.

2. The method according to claim 1, characterized in that, The degree of deacetylation of the chitosan is 75%~98%; the degree of carboxymethyl substitution of the carboxymethyl chitosan is 80%~95%.

3. The method according to claim 1 or 2, characterized in that, In step S2, adjusting the pH includes adjusting the pH of the first mixture to 6.5~7.

5.

4. The method according to claim 3, characterized in that, In step S2, the conditions for the crosslinking reaction include: glutaraldehyde concentration in the reaction system is 0.1%~1%, reaction temperature is 40~60℃, and reaction time is 20~60min.

5. The method according to claim 1, characterized in that, In step S3, the conditions for spray drying include: feed liquid temperature of 25~30℃, air inlet temperature of 120~160℃, air outlet temperature of 60~90℃, nozzle diameter of 0.4~1mm, and spray pressure of 1.5~2.5MPa.

6. A fertilizer based on potassium formate, characterized in that, Prepared according to the method according to any one of claims 1 to 5.

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